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HomeMy WebLinkAbout2007 Remedial Action Plan part 1 REMEDIAL ACTION PLAN San Luis Obispo Tank Farm 276 Tank Farm Road San Luis Obispo, California December 18, 2007 PREPARED FOR Chevron Environmental Management Company 276 Tank Farm Road San Luis Obispo, California 93406 PREPARED BY Avocet Environmental, Inc. 16 Technology Drive, Suite 154 Irvine, California 92618-2327 Robert Van Hyning, P.E. Principal Project No. 1212.001 December 18, 2007 Project No. 1212.001 Mr. Eric Snelling Project Manager PADRE ASSOCIATES, INC. 811 El Capitan Way, Suite 130 San Luis Obispo, California 93401 Remedial Action Plan San Luis Obispo Tank Farm 276 Tank Farm Road San Luis Obispo, California Dear Mr. Snelling: Enclosed is the Remedial Action Plan for the San Luis Obispo Tank Farm. Attached are 12 hard copies for your use. Nine copies are loose, for inclusion in the Project Execution Plan, and three are in binders. We have also included two full-size drawing sets. If you have any questions or require additional information, please do not hesitate to call. Respectfully submitted, AVOCET ENVIRONMENTAL, INC. Robert Van Hyning, P.E. Principal RVH:sh Enclosure S:\Projects\1212 Chevron_Padre_SLOTF\RemedialDesignReport\SupportingDocs\RemedialActionPlan_18Dec2007.doc Remedial Action Plan Chevron San Luis Obispo Tank Farm Page i San Luis Obispo, California December 18, 2007 TABLE OF CONTENTS Page LIST OF TABLES ....................................................................................................................... iv  LIST OF FIGURES ...................................................................................................................... v  LIST OF ABBREVIATIONS AND ACRONYMS .................................................................. vii  1.0 INTRODUCTION ................................................................................................................ 1  1.1 REMEDIAL ACTION PLAN PURPOSE AND FRAMEWORK .................................................. 1  1.2 SCOPE OF THE REMEDIAL ACTION PLAN ........................................................................ 2  1.3 OTHER PLANS ................................................................................................................ 3  2.0 BACKGROUND INFORMATION .................................................................................... 4  2.1 CURRENT CONDITION .................................................................................................... 7  2.1.1 Off-Site Utilities ................................................................................................ 7  2.1.2 Operations Related Pipelines ............................................................................ 8  2.1.3 Potential Land Use ............................................................................................ 8  2.2 SITE HYDROLOGY ........................................................................................................ 10  2.3 WETLANDS AND RARE PLANT HABITAT ...................................................................... 11  2.4 ENVIRONMENTAL SITE CHARACTERIZATION SUMMARY .............................................. 11  3.0 OPERABLE UNITS, AREAS OF CONCERN, AND THE INTEGRATED PREFERRED REMEDY ................................................................................................... 13  3.1 OU #1- FORMER NW OPERATIONS AREA .................................................................... 13  3.1.1 Preferred Remedy OU#1-AOC#1 Groundwater ............................................. 14  3.1.2 Preferred Remedy OU#1-AOC#2 Soil ........................................................... 15  3.2 OU #2- RESERVOIRS 5 AND 7 ....................................................................................... 15  3.3 OU #3- EAST DEVELOPMENT AREA (RESERVOIR 4) .................................................... 16  3.4 OU #4- REMAINING SITE-WIDE TERRESTRIAL AND WETLAND AREAS ........................ 18  3.5 AOC#1 - NORTH MARSH ............................................................................................. 18  3.6 AOC#2 - RESERVOIR 3 ................................................................................................ 19  3.7 AOC#3 - PLIABLE SURFACE EXPRESSIONS OF PETROLEUM ......................................... 20  3.8 OU #5- SITE-WIDE GROUNDWATER ............................................................................ 20  4.0 GENERAL REMEDIAL ACTIONS ................................................................................ 22  4.1 LONG-TERM MONITORING ........................................................................................... 22  4.2 REMOVAL EXCAVATIONS ............................................................................................ 23  4.3 CAPS ............................................................................................................................ 25  5.0 EARTH CONSTRUCTION MATERIALS ..................................................................... 26  5.1 COMMON FILL ............................................................................................................. 26  5.2 STRUCTURAL FILL ....................................................................................................... 26  5.3 GRAVEL ....................................................................................................................... 26  5.4 TOPSOIL ....................................................................................................................... 27  Remedial Action Plan Chevron San Luis Obispo Tank Farm Page ii San Luis Obispo, California December 18, 2007 Page 5.5 EARTH MATERIAL SOURCES ........................................................................................ 27  5.5.1 Flower Mound/OU #3 ..................................................................................... 28  5.5.2 Berms .............................................................................................................. 29  5.5.3 Borrow No. 1 .................................................................................................. 29  5.5.4 Borrow No. 2 .................................................................................................. 29  5.5.5 Borrow No. 3 .................................................................................................. 30  6.0 SITE-WIDE REMEDIAL ACTIONS .............................................................................. 31  6.1 MOBILIZATION, STAGING AREAS, AND SITE ACCESS ................................................... 31  6.2 BUILDING DEMOLITION ............................................................................................... 33  6.3 MISCELLANEOUS CLEANUP ......................................................................................... 34  6.4 PIPELINE ABANDONMENT ............................................................................................ 35  6.4.1 Pipeline Inventory ........................................................................................... 35  6.4.2 Pipeline Flushing and Pigging ........................................................................ 36  6.4.3 Pipeline Grouting ............................................................................................ 37  6.4.4 Pipeline Segment Removal ............................................................................. 37  6.5 MONITORING WELL DESTRUCTION .............................................................................. 37  6.6 HISTORICAL PRODUCTION WELLS ............................................................................... 38  6.7 LAND USE COVENANTS ............................................................................................... 38  6.8 VAPOR BARRIERS ........................................................................................................ 39  7.0 OPERABLE UNIT REMEDIAL ACTIONS ................................................................... 40  7.1 OU #1-NW OPERATIONS AREA ................................................................................... 40  7.1.1 AOC #1 Groundwater ..................................................................................... 40  7.1.2 AOC #2 Soil-Development Scenario .............................................................. 40  7.2 OU #2-RESERVOIRS 5 AND 7 ....................................................................................... 47  7.3 OU #3/FLOWER MOUND/BORROW AREA NO. 2 REGRADING ....................................... 52  7.4 OU#4-REMAINING SITE-WIDE TERRESTRIAL AND WETLAND AREAS ......................... 57  7.4.1 AOC #1-North Marsh ..................................................................................... 57  7.4.2 AOC #2-Reservoir 3 ....................................................................................... 59  7.4.3 AOC #3-Other Sticky Hydrocarbon Surface Expressions .............................. 62  7.5 OU#5-SITE-WIDE GROUNDWATER .............................................................................. 63  8.0 HABITAT IMPACTS AND MITIGATION .................................................................... 64  9.0 LONG-TERM MAINTENANCE ..................................................................................... 65  10.0 SCHEDULE ........................................................................................................................ 67  REFERENCES ............................................................................................................................ 68  TABLES  FIGURES  Remedial Action Plan Chevron San Luis Obispo Tank Farm Page iii San Luis Obispo, California December 18, 2007 Page APPENDIX A: REPORT CD APPENDIX B: MONITORING AND REPORTING PROGRAM 93-120 AND SUPPORTING DOCUMENTS APPENDIX C: REMEDIAL DESIGN DRAWINGS APPENDIX D: REMEDIAL DESIGN SPECIFICATIONS APPENDIX E: EARTH MATERIALS SPECIFICATIONS APPENDIX F: QUANTITY CALCULATIONS APPENDIX G: HYDROLOGY CALCULATIONS APPENDIX H: SETTLEMENT CALCULATIONS APPENDIX I: GEOSYNTHETIC CALCULATIONS APPENDIX J: SOIL LOSS CALCULATIONS APPENDIX K: RETAINING WALL EVALUATION APPENDIX L: PIPELINE QUANTITY ESTIMATE APPENDIX M: VAPOR BARRIER ENGINEERING GUIDELINES Remedial Action Plan Chevron San Luis Obispo Tank Farm Page iv San Luis Obispo, California December 18, 2007 LIST OF TABLES Table No. Title 1 Summary of Operable Units and Preferred Remedies 2 List of Active Monitoring Wells and Wells Proposed for Abandonment 3 Estimated Borrow Source Material Quantities 4 Estimated Remediation Construction Quantities 5 Summary of Habitat Impacts Remedial Action Plan Chevron San Luis Obispo Tank Farm Page v San Luis Obispo, California December 18, 2007 LIST OF FIGURES Figure No. Title 1 Site Location Map 2 Site Map 3 Northwest Operations Area Historic and Current Features 4 Existing Utilities and Easements 5 Chevron Pipelines 6 Detail Plan of Chevron Pipelines in the Northwest Operations Area 7 Existing San Luis Obispo County Land Use Plan 8 City of San Luis Obispo AASP Land Use Plan 9 Constraints to the Proposed City of San Luis Obispo Land Use Plan 10 Proposed Land Use Concept 11 Hydrology Map 12 Wetlands, Fairy Shrimp, and Rare Plant Habitats 13 Summary of Environmental Impacts 14 Overview of Operable Units 15 Proposed Impacted Soil Stockpile Location 16 Borrow Source Location Map 17 Work Areas, Staging Areas, and Site Access 18 Preliminary Traffic Control Improvements 19 Miscellaneous Cleanup Areas 20 Monitoring Well Network Modifications 21 Northwest Operations Area (OU #1/AOC #2) Demolition Plan 22 Northwest Operations Area (OU #1/AOC #2) Cap Grading Plan 23 Northwest Operations Area (OU #1/AOC #2) Section A-A’ 24 Northwest Operations Area (OU #1/AOC #2) Section B-B’ Remedial Action Plan Chevron San Luis Obispo Tank Farm Page vi San Luis Obispo, California December 18, 2007 25 Northwest Operations Area (OU #1/AOC #2) Section C-C’ 26 Northwest Operations Area (OU #1/AOC #2) Section D-D’ 27 Typical Survey Monument 28 Reservoir 5 (OU #2) Demolition Plan 29 Reservoir 7 (OU #2) Demolition Plan 30 Reservoir 5 (OU #2) Cap Grading Plan 31 Reservoir 7 (OU #2) Cap Grading Plan 32 Reservoirs 5 and 7 (OU #2) Typical Section 33 Reservoirs 5 and 7 (OU #2) Typical Cap Details 34 Reservoir 4 (OU #3), Flower Mound, and Borrow No. 2 Work Areas 35 Reservoir 4 (OU #3) Demolition Plan 36 Flower Mound Demolition Plan 37 Reservoir 4 (OU #3) Excavation and Geotextile Placement Plan 38 Reservoir 4 (OU #3) Cap Grading Plan 39 Borrow Area No. 2 Grading Plan 40 Reservoir 4 (OU #3) Typical Cap Section and Details 41 North Marsh (OU #3/AOC #1) Demolition and Excavation Plan 42 Reservoir 3 (OU #3/AOC #2) Demolition and Excavation Plan 43 Reservoir 3 (OU #3/AOC #2) Grading Plan 44 Reservoir 3 (OU #3/AOC #2) Typical Section 45 Other PPSH Impacted Areas 46 Areas of Habitat Impact 47 Preliminary Schedule Remedial Action Plan Chevron San Luis Obispo Tank Farm Page vii San Luis Obispo, California December 18, 2007 LIST OF ABBREVIATIONS AND ACRONYMS AASP San Luis Obispo Airport Area Specific Plan ACM asbestos-containing material amsl above mean sea level AOC area of concern APCD San Luis Obispo County Air Pollution Control District AST aboveground storage tank ASTM ASTM International bgs below ground surface BMP Best Management Practice BTEX benzene, toluene, ethyl benzene, and total xylenes Cal/OSHA California Division of Occupational Safety and Health CD compact disc CEQA California Environmental Quality Act CERCLA Comprehensive Environmental Response, Compensation and Liability Act cfs cubic foot per second DTSC California Department of Toxic Substances Control DWR California Department of Water Resources EPA U.S. Environmental Protection Agency ERWG Ecological Risk Working Group FML flexible membrane liner GIS Geographic Information System GPS Global Positioning System HDPE high density polyethylene LCM lead-containing material LNAPL light nonaqueous-phase liquid M&RP Monitoring and Reporting Program MCL maximum contaminant level NCP National Oil and Hazardous Substances Pollution Contingency Plan NHIS nonhazardous impacted soil NOAA National Oceanic & Atmospheric Administration OSHA U.S. Occupational Safety and Health Administration OU operable unit PAH polynuclear aromatic hydrocarbon pcf pound per cubic foot PDF portable document format PG&E Pacific Gas and Electric Company psf pound per square foot psi pound per square inch PVC polyvinyl chloride RTP Remediation Technology Panel Remedial Action Plan Chevron San Luis Obispo Tank Farm Page viii San Luis Obispo, California December 18, 2007 RWQCB California Regional Water Quality Control Board SERRT Surface Evaluation, Remediation and Restoration Team SLO San Luis Obispo TEPH total extractable petroleum hydrocarbons TIN Triangular Irregular Network TPH total petroleum hydrocarbons TPPH total purgeable petroleum hydrocarbons µg/L microgram per liter USDA U.S. Department of Agriculture USLE Universal Soil Loss Equation UST underground storage tank Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 1 San Luis Obispo, California December 18, 2007 1.0 INTRODUCTION Chevron 1 owns a 340-acre former tank farm property south of the city of San Luis Obispo (Figure 1), in San Luis Obispo County, that was constructed in 1910 to serve as the tidewater accumulation point for the petroleum pipeline from the San Joaquin Valley. This property, commonly referred to as the San Luis Obispo Tank Farm, SLO Tank Farm, or Tank Farm, was slowly withdrawn from operation during the later decades of the twentieth century, and by the late 1990s, was formally decommissioned. Chevron now desires to convert the property to alternative uses that are consistent with local planning, community needs, good environmental stewardship, regulatory requirements, and efficient asset management. A long history of intensive industrial activity on the property, however, has affected its environmental condition. On March 15, 2007, Avocet Environmental, Inc. (Avocet) published the Feasibility Study, Former San Luis Obispo Tank Farm addressing the nature of the environmental impacts and recommending a set of preferred remedial alternatives. This Remedial Action Plan describes how the preferred remedial alternatives will be implemented. 1.1 REMEDIAL ACTION PLAN PURPOSE AND FRAMEWORK This Remedial Action Plan is intended to provide regulatory agencies, the municipalities with jurisdiction over the site, and other stakeholders detailed information on how Chevron will implement the preferred remedial alternative from the Feasibility Study. It presents the detailed engineering, which is the basis for design of the preferred remedial alternative components. It also provides conceptual-level information on habitat restoration to support environmental analysis through the California Environmental Quality Act (CEQA) process, which will be necessary to permit this project. This document is built upon a foundation of cooperative agreements with the regulatory community and local municipalities. As with the Feasibility Study, the Remedial Action Plan has followed the general framework for developing site remediation documents found in the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). It has been adapted, however, to meet the needs of a non-CERCLA (Comprehensive Environmental Response, Compensation and Liability Act) site regulated by local agencies. Working cooperatively with the various agencies to develop this plan has resulted in an approach with broad consensus and support. Nevertheless, it is understood that approvals and permits must be granted by these agencies independent of the cooperative process. Chevron will be working with the regulatory agencies and municipalities to clarify the permitting process, especially identifying the lead agency for environmental review under CEQA, which is 1 This property was originally owned and operated by Unocal. Chevron purchased Unocal, including this property, in August 2005. Chevron is considered synonymous with Unocal for the purpose of this document. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 2 San Luis Obispo, California December 18, 2007 anticipated to include cooperative agreements and memoranda of understanding between those bodies. 1.2 SCOPE OF THE REMEDIAL ACTION PLAN For the purposes of this report, it is assumed that Chevron will pursue development of the site consistent with proposed land use plans. As such, where the Feasibility Study included discussions of open space alternatives for several of the Operable Units (OUs), those discussions are omitted from consideration in this report. However, ecological risks are the basis of remediation in the open space areas. Where remediation coincides with developable areas, the remedial approach ensures compatibility with allowable uses. This report provides the reader with a brief background of the site, its current condition, an overview of the OUs and the associated preferred remedies developed in the Feasibility Study. Subsequent sections of the report describe implementation of those remedies and present the supporting engineering analyses. Detailed engineering drawings and specifications are included in the appendices. The drawings, which are presented as portable document format (PDF) files on the CD in Appendix A, are intended to be printed full-size (i.e., 24” x 36”). Line work quality and legibility will suffer if the full-size drawings are printed smaller (e.g., 11” x 17”). This report also describes important closure activities that were not relevant to the Feasibility Study, such as the approach for abandoning the pipelines or demolishing structures. These and some other minor cleanup issues were not identified as critical for evaluation in the Feasibility Study or previous risk management documents, since they do not pose a direct threat to human or ecological receptors. They do, however, affect implementation of the remedies and how they will be conducted and are, therefore, material to this document. Since publication of the Feasibility Study, there have been further environmental studies as well as an extension of Runway 11-29 at the adjacent San Luis Obispo Regional Airport (Figure 1) that are relevant to future development of the site. Consequently, Chevron has evaluated potential changes to the existing Airport Area Specific Plan (AASP) prepared by the City of San Luis Obispo. The proposed land use plan incorporates the new ecological resource and land use feasibility studies. The Feasibility Study considered remedial activities that supported development consistent with the land use plans available at that time. Similarly, the Remedial Action Plan supports development consistent with the proposed land use plan, although it is recognized that this requires the approval of the City of San Luis Obispo. This report provides a brief overview of the long-term maintenance items. It describes the general activities that will be performed to ensure continued achievement of the remedial objectives. This section also discusses the alternatives under consideration for future management of the open space. If the primary objective of this process has been to protect human and ecological receptors from exposure to potentially harmful substances, a secondary objective has been to maintain and, if Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 3 San Luis Obispo, California December 18, 2007 possible, improve the ecological function associated with the various habitats across the site. Key among these are the wetlands, vernal pool fairy shrimp, and rare plant habitats. The Remedial Action Plan clearly identifies which habitats will be impacted and notes whether the impacts will be temporary, with the habitat being restored after remediation, or permanent, which requires mitigation (i.e., replacement) of the habitat elsewhere onsite. The specific requirements for habitat restoration and mitigation will be developed in concert with the regulatory agencies and will be distributed under separate cover as the Habitat Mitigation Plan. 1.3 OTHER PLANS The Remedial Action Plan has been prepared to accompany the Project Execution Plan, which is an umbrella document for remediation, restoration, and permitting of this site. Other plans that support the Remedial Action Plan are either included as appendices to this report or are incorporated in the Project Execution Plan. One of these, the Habitat Mitigation Plan, has already been mentioned. Other documents that are discussed in the text include the Geotechnical Study, the Soil Management Plan, and Land Use Covenants. The Geotechnical Study supports the engineering basis for the cap designs. The Soil Management Plan will address how contractors must handle impacted soil if its disturbance is unavoidable after remediation is complete. A draft of the plan is included in the appendices to this report. Land Use Covenants document restrictions on the property and record those with the deed, making its requirements binding upon future property owners. It will be developed by Chevron independently of this Remedial Action Plan through their legal department and with the California Regional Water Quality Control Board (RWQCB) and the municipalities. Prior to construction, the contractor will also prepare a site-specific Health and Safety Plan that complies with the requirements of the supervisory jurisdiction as well as the stringent demands of Chevron’s corporate health and safety program. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 4 San Luis Obispo, California December 18, 2007 Construction of Reservoir 4 – August 25, 1910 2.0 BACKGROUND INFORMATION The following is intended to quickly acquaint the reader with the history, operations, and background of the Tank Farm. It is largely taken from the background discussion provided in the Feasibility Study, but has been edited and is a somewhat briefer summary. Readers desiring more detailed information are referred to the Feasibility Study and other background documents listed in the References of this report. Chevron’s 340-acre Tank Farm is located at 276 Tank Farm Road in western San Luis Obispo County, south of the city of San Luis Obispo and northwest of the municipal airport (Figure 1). The site is divided into north and south sections by Tank Farm Road, and is bordered by light commercial and industrial development, the San Luis Obispo County airport, agricultural and pastoral lands, with scattered residences and a trailer park. The existing buildings in the northwest part of the site currently serve as Chevron’s local headquarters for a variety of environmental and remediation operations (Figure 2). From 1910 until the early 1980s, the SLO Tank Farm was used for storing crude oil transported via pipeline from the San Joaquin Valley. Storage facilities at the site included 6 large earthen reservoirs, ranging in capacity between 775,000 and 1,350,000 barrels 2 , and 21 steel aboveground storage tanks (ASTs) capable of holding 55,000 barrels each. The reservoirs were constructed by excavating a circular or elliptical depression, which was then lined with wire- 2 One barrel is equivalent to 42 gallons. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 5 San Luis Obispo, California December 18, 2007 mesh-reinforced concrete. The walls were also reinforced concrete, but were constructed either vertically or integrated into the sloping sides of the depression. The walls and floors of the ASTs were constructed of heavy plate steel secured with rivets. The roofs of both the reservoirs and ASTs were of wood and composition. All told, the site had the capacity to store over 6 million barrels of petroleum. On April 7, 1926, a lightning strike ignited a fire at the Tank Farm. At that time, there were 933,577 barrels of oil stored in the ASTs, and another 5,374,927 barrels of oil were stored in the reservoirs. The total inventory was 6,308,504 barrels of oil of various grades. Eyewitnesses claim that a lightning strike simultaneously ignited the vapors in Reservoirs 5, 6, and 7. The power of the resulting explosion registered on the Weather Bureau barograph in downtown San Luis Obispo, which recorded the time as 7:35 a.m. A second lightning strike ignited Reservoir 3 sometime between 7:50 and 7:55 a.m. Despite suppression efforts by the facility staff, the fire spread to the other reservoirs and to 12 of the existing 15 steel ASTs over the course of the next four days by a combination of burning embers and boil-overs, where the heated oil flowed out of the reservoirs and onto the ground surrounding the tanks. By April 11, 1926, all but a few thousand of the six million barrels in inventory had been burned to coke and spread across the site. This release is considered responsible for most of the numerous surface occurrences (i.e., expressions) of highly weathered and burned petroleum that cover the ground in topographically low areas of the Tank Farm. Morning of April 9, 1926. Reservoir 4 (left) has been extinguished. Reservoir 2 and ASTs (right) are still burning. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 6 San Luis Obispo, California December 18, 2007 Subsequently, Unocal resumed operations at the Tank Farm, including reconstructing ten of the steel ASTs and four of the reservoirs (Reservoirs 3, 4, 5, and 6). Reservoirs 2 and 7 were never again used for petroleum storage. The reconstruction effort included expanding the fire breaks and enlarging the containment areas surrounding the reservoirs, which created numerous hydraulically closed depressions around the site; depressions that subsequently became wetlands. In addition to the 6 reservoirs and 21 ASTs utilized for petroleum storage, the facility included a series of pipelines for oil movement to and from the site and for movement between the onsite tanks and facilities. Regional pipeline operations were also conducted at the site, primarily from the northwest area of the property (Northwest Operations Area; Figure 3). Facilities to support pipeline operations included a pumphouse, boilers (for heating crude oil to reduce viscosity) and an associated blow-down area, a petroleum physical properties testing laboratory, and an electrical equipment house (Figure 3). The Northwest Operations Area also included areas for general equipment storage and maintenance, as well as underground storage tanks (USTs) that contained diesel fuel and gasoline (England, Shahin & Associates, May 11, 1994). The USTs were removed in 1987. Other historical activities at the site include the operation of a fire training school in the unpaved eastern portion of the Northwest Operations Area (Figure 3). The school consisted of several simulated sumps, flares, and tanks where students would practice techniques for extinguishing petroleum-fed fires. Off-specification gasoline and diesel fuel were fed to these fixtures from a set of three ASTs via a system of buried metal pipes. The four reservoirs repaired after the 1926 fire continued in service for several more decades, but were progressively decommissioned beginning in the late 1950s and continuing into the mid- 1970s, according to the following schedule: Reservoir Date Decommissioned 5 1959 3 1961 6 1961 4 1976 Field evidence suggests that decommissioning involved emptying the reservoirs of liquid petroleum and removing the roofs and, at Reservoirs 3 and 4, the vertical walls. The reinforced concrete covering the sloping slides and bottoms was left in place. In Reservoirs 2, 5, and 7, there is evidence that the concrete bottoms were ripped by the shank of a bulldozer in perpendicular directions. The bottoms of the remaining reservoirs have not been directly observed, so it is uncertain whether these have been similarly ripped. It is anecdotally reported that the ripping was done to prevent water from accumulating in the former reservoirs. Reservoirs 3 and 4 were largely backfilled by bulldozing the berms into the center of the reservoirs. Reservoir 4 generally contains 5 to 6 feet of non-engineered fill and construction debris above the concrete bottom, and Reservoir 3 is estimated to contain between 8 and 11 feet Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 7 San Luis Obispo, California December 18, 2007 of non-engineered fill. To provide access, a portion of the berms surrounding Reservoirs 5, 6, and 7 has been pushed into the reservoirs. Approximately 1.5 feet of non-engineered fill and construction debris cover the bottoms of Reservoirs 5 and 6, and in Reservoir 7 the berm debris was not distributed evenly across the reservoir bottom, but rather was left as an apron near the notch. Most of the bottom of Reservoir 7 is covered by several inches of interlayered tar and organic debris. A review of historical aerial photographs shows that the ten steel ASTs remaining or rebuilt after the 1926 fire were decommissioned at various times. AST 522, located in the Northwest Operations Area, was removed sometime between 1959 and 1965. Eight of the nine remaining ASTs were removed in 1994, with the last AST being reserved for fire water storage. The final AST was removed in August 2000. Fire school exercises were suspended at the Tank Farm in the 1970s and transferred to the Richmond refinery. The pumphouse, pipelines, and boilers were taken out of service in the early 1990s and were demolished or decommissioned in the late 1990s. Of the original Tank Farm structures, only three buildings in the operation remain. For several years, approximately 2 acres of land near the center of the property north of Tank Farm Road were leased to a recycling company. The site was used as a transfer station and accumulation point for recyclable materials such as paper, glass, and aluminum. The operation was shut down and removed in mid-2000, when the lease expired, and was not renewed (England Geosystem, April 17, 2001). 2.1 CURRENT CONDITION Aside from the current Chevron office buildings situated in the northwestern portion of the property, the site presently consists of undeveloped land that contains native grasslands and both natural wetlands and wetlands resulting from water accumulating in depressions associated with the former oil storage facility (Figure 2). The site is best characterized as open space, with cattle grazing for the purpose of fire prevention and weed control. Adjacent land uses include light commercial and industrial development, the San Luis Obispo (SLO) County Regional Airport, agricultural and pastoral land with scattered residences, and a trailer park. Some modifications and improvements have been made to the Northwest Operations Area since the last petroleum-dedicated ASTs were decommissioned in 1994. These include upgrades to the front gate, the addition of a modular office building adjacent to the northernmost original building, a new fire water tank to replace the water storage AST decommissioned in 2000, and various upgrades to the electrical and telecommunication systems (Figure 3). 2.1.1 Off-Site Utilities Utility companies provide natural gas, electricity, and telecommunication service to the site or have lines that cross the site. The locations of these lines and easements are shown in Figure 4. The Gas Company owns a 4-inch-diameter gas line located just north of Tank Farm Road. The Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 8 San Luis Obispo, California December 18, 2007 line is buried in the shoulder of the road and terminates approximately 400 feet from the west boundary of the Northwest Operations Area. A 2-inch-diameter gas line tees off the main and runs underground along the western property line for approximately 500 feet. That branch line provides natural gas service to the Northwest Operations area. Aerial lines also run parallel to Tank Farm Road, offset to the north approximately 100 feet from the road centerline. The aerial lines include electrical power provided by Pacific Gas and Electric Company (PG&E), and telecommunications service provided by AT&T. Electricity and telecommunications services also branch off the main lines at the west boundary of the Northwest Operations area, run along the western property line, and serve the ongoing operations. Also shown in Figure 4 is the proposed sewer that is scheduled to be installed by the City of San Luis Obispo in 2008. The City is in the process of obtaining easements and access agreements for construction and maintenance. 2.1.2 Operations Related Pipelines Historical operations at the site were served by approximately 25,125 feet of crude oil pipeline, 47,340 feet of water supply line, and 1,172 feet of other pipeline. The approximate locations of these lines are shown in Figure 5. The analyses supporting the estimated lengths of pipeline are found in Appendix L. It is believed that most of the lines were abandoned in place, although it is reported anecdotally that much of the pipeline serving the ASTs was removed when the tanks were removed. Since there is no record of final cleaning or abandonment procedures, it is presumed that at least some of the lines still contain crude oil. Crude oil pipelines vary in diameter from 8 to 16 inches. It appears that the most common diameter is 8 inches, and using this as a nominal diameter for the entire network suggests that the crude oil pipeline volume is on the order of 16,750 cubic feet. It is unlikely, however, that this volume of oil remains in the lines. Many of the lines are demonstrably empty where they are exposed on the surface. Much of the facility piping is found in the Northwest Operations Area, as shown in Figure 6. This includes nearly 20 percent of the total crude oil pipe network (approximately 4,300 lineal feet). This configuration allowed the operators to direct oil in and out of the facility and to transfer oil between the various storage locations as needed. There are also 4,900 feet of water line, 1,120 feet of dedicated Foamite fire-fighting lines, and leach and drain lines totaling slightly less than 1,200 feet. The estimated volume of the crude oil lines in the Northwest Operations Area is approximately 3,260 cubic feet. 2.1.3 Potential Land Use It is expected that after closure, the site will be converted to new productive uses. These will be consistent with the evolving land use plans for the area, although the final land use configurations have not yet been determined. Chevron is working in concert with the City of San Luis Obispo, San Luis Obispo County, and other stakeholders to ensure that the final disposition of the site is in harmony with community at large. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 9 San Luis Obispo, California December 18, 2007 A key decision will be which local government jurisdiction to place the Tank Farm under. At present, as noted previously in this report, the site is within unincorporated San Luis Obispo County. It has been proposed, however, to annex the Tank Farm into the City as part of the AASP. Chevron has proposed a new land use plan that incorporates new ecological and land use feasibility studies, and conforms to the revised runway protection zones resulting from extending Runway 11-29 at the SLO County Regional Airport. Chevron is evaluating the potential benefits and consequences of each alternative. Since a decision has not been made prior to publication of the Remedial Action Plan, the elements of each land use plan are briefly discussed below. However, remediation has been tailored in this plan to support the proposed land use concept. The SLO County General Plan envisions future development on portions of the Tank Farm (Figure 7). Possible development areas under the County plan are situated on the east and west ends of the northern portion of the property (i.e., north of Tank Farm Road). Anticipated land uses in the eastern area include 17 acres zoned for industrial uses principally within the footprint of former Reservoir 4, and 19 acres zoned for commercial services immediately to the north. Land uses in the western area include 31 acres zoned for light industrial use. The sum of potentially developable land under the County plan is approximately 67 acres. Although the site is presently within unincorporated SLO County, it also lies within the City of SLO’s sphere of influence and the City desires to annex the site in accordance with the Airport AASP, dated January 2005. The central focus of the AASP is to convert the 340-acre site (approximately one-third of the Airport Area) and other surrounding areas to greater beneficial use, including limited commercial development (Business Park) and recreational open space, while enhancing the physical link between the Airport and City areas. The AASP compliments the adjacent Margarita Area Specific Plan, which addresses the area immediately north of the Tank Farm. The proposed land uses, as identified in the AASP, are shown in Figure 8 and include 2.3 acres of available Business Park development, 41.8 acres of Services/Light Manufacturing, and the balance (approximately 296 acres) as open space (43 potentially developable acres). The most obvious difference between the City and County plans is that the City plan includes potential development in the eastern end of the site, south of Tank Farm Road. The site is located beneath the departure pattern for Runway 11-29 of SLO County Regional Airport, which has extended Runway 29 by approximately 500 feet. This had expanded the airport safety zones beyond those originally considered in the AASP. The airport safety zones are shown in Figure 9. These expanded zones render approximately 14.6 acres of the originally proposed building area less suitable for development. Further, environmental studies subsequent to the AASP have identified protected habitat for vernal pool fairy shrimp in several of the former tank rings north of the Northwest Operations Area (discussed further in Section 2.3). Consequently, Chevron has proposed revisions to the existing City land use plan that would be consistent with these post AASP developments. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 10 San Luis Obispo, California December 18, 2007 The proposed land use plan is shown in Figure 10. It trades approximately 9 acres in the northwest portion of the site and on the west edge of the area south of Tank Farm Road for just under 16 acres in the northeast portion of the site. Overall, the developable area relative to the AASP land use plan increases by almost 7 acres but decreases by 16 acres relative to the existing SLO County General Plan. The proposed swap of land use designations also overlaps, to a large degree, with the SLO County General Plan. The proposed plan provides more developable frontage along Santa Fe Road, which is anticipated to see significant traffic when it eventually connects Tank Farm Road with Prado Road. It also avoids 3.28 acres of protected fairy shrimp habitat in the northwest corner of the site. While it has not been decided whether “any or all” of the site will be annexed into the City, the design considered in this Remedial Action Plan envisions that the site is eventually developed as shown in the proposed land use plan (Figure 10). Chevron would perform the remediation necessary for regulatory compliance and potentially for development of those areas of the site identified for Service Commercial/Business Park land use. Chevron may elect to annex developable portions of the site into the City, while the remaining areas may be left as open space within the County for preservation as an ecological preserve. Future residential development of any area of the site is excluded by zoning, airport safety zone restrictions, and future institutional controls. It is anticipated that cattle grazing may continue in selected areas of the site. Cattle are effective at controlling invasive weeds and limiting the fuel available to a potential fire. It is expected that cattle grazing would be limited to grassland areas, and would be excluded from upland and wetland restoration areas. The specific requirements for continued cattle grazing will be coordinated with the California Department of Fish and Game, the RWQCB, and the U.S. Fish and Wildlife Service. 2.2 SITE HYDROLOGY Regionally, the Tank Farm is within the Central Coast Hydrologic Area, a 6,600-square-mile watershed that extends from Santa Barbara to the upper reaches of the Nacimiento River. More specifically, the site is within the San Luis Obispo Hydrologic Subunit, a 44,370-acre component of the larger San Luis Obispo Hydrologic Unit. The boundaries of these watersheds have been defined by the California Department of Water Resources and are illustrated in Appendix G. Locally, the Tank Farm is situated north of the East Fork of San Luis Obispo Creek, which is tributary to San Luis Obispo Creek, and is illustrated in Figure 11. A small portion of the Tank Farm discharges to this creek directly, referred to as Design Point B on Figure 11. However, most of the Tank Farm consists of a closed catchment that retains storm water. This is a legacy of the historical containment structures and other topographic modifications that were made to facilitate operations. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 11 San Luis Obispo, California December 18, 2007 Ditches along Tank Farm Road collect storm water from the frontage properties. A local high point is located approximately 1,000 feet east of Higuera Road. Storm water collected east of this point drains toward the Tank Farm and eventually discharges into the North Marsh wetland complex. A small channel, referred to by the City of San Luis Obispo as Tank Farm Creek, is located on the western side of the property and collects storm water from a catchment approximately 485 acres in size, including about 150 acres that are on the Tank Farm proper. Tank Farm Creek discharges from the site at a concrete outlet works labeled Design Point A on Figure 11. Much of that catchment is located north of the Tank Farm and currently enters the site as sheet flow, or concentrated into natural channels, along the northern property line. Development plans for the Margarita Area will change the upgradient hydrology and will likely concentrate flow at one or possibly a few locations. Remediation and grading on the east side of the property will also affect this drainage. Anticipated changes to the onsite hydrologic system are discussed in subsequent chapters. Remediation and restoration of the North Marsh may require further changes to the site hydrology. The details of these changes will be developed as the Habitat Mitigation Plan is finalized in conjunction with the regulatory agencies. It is believed, however, that the natural retention capacity of the onsite wetland complexes will be more than adequate to address any foreseeable hydrologic changes. Improvements that may be necessary for conveyance of storm water to the wetlands will be made in conjunction with the upstream developers’ habitat restoration activities, as necessary. 2.3 WETLANDS AND RARE PLANT HABITAT The Tank Farm currently hosts wetland and rare plant habitats (Figure 12). Much of the wetland habitat has been established from the closed hydrologic conditions onsite that are artifacts of the containment and fire suppression controls constructed after the 1926 fire. Several delineations of the wetlands have been accompanied by supporting scientific studies. This report focuses on the most current delineation, which encompasses federal as well as state wetlands. This most recent delineation identified 75.95 acres of state wetlands (incorporating 55.8 acres of federal wetlands). This total also includes 32.1 acres of vernal pool fairy shrimp habitat. In addition, the site supports several other rare plant habitats that are identified in Figure 12. It is likely that these current measurements will be revised to reflect recent legal developments relative to wetland delineation. There may also be modifications to the rare plant surveys, which will be conducted in the spring and summer of 2008. Modifications to these surveys and their effect on remediation or grading will be attached to this report as an addendum as the information becomes available. 2.4 ENVIRONMENTAL SITE CHARACTERIZATION SUMMARY Considerable effort has been expended to characterize the site. The following is offered as a brief summary to orient the reader who is not otherwise familiar with that characterization work. It focuses on those portions of the characterization that are most relevant to the remedial action, Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 12 San Luis Obispo, California December 18, 2007 including the key soil and water impacts, wetland and rare plant habitats, and the environmental impacts considered pertinent to risk management. For those readers desiring more detailed information on the site characterization efforts, the documents listed in the reference section are useful, especially the following: • Feasibility Study, Risk Management Summary • Seep Evaluation Trenching Report • Supplemental Site Characterization • Remediation Technology Panel (RTP) Assessment of Off-Site Migration and On-Site Surface Expressions of Hydrocarbons at the San Luis Obispo Tank Farm Site • Surface Hydrocarbon Inspection and Mitigation Plan (recently approved by the California Department of Fish and Game, Office of Spill Prevention) Given that petroleum storage and handling facilities operated on the property for many decades, it is not surprising that environmental issues at the site are generally petroleum-related. Crude oil is found in soil as deep as 60 feet below the ground surface (bgs). It is also seen in surface expressions ranging from solid asphalt-like coke to viscous liquid. The locations and nature of these impacts are shown in Figure 13. Characterization of these impacts has included, in addition to their careful identification and delineation, an evaluation of their importance relative to human and ecological health, and the need for their remediation. Key to this effort has been the cooperative process between Chevron and the regulatory community that has progressively reviewed existing data, evaluated assessments, identified data gaps, established the risk associated with a given impact, and determined which impacts require remediation. Following are the principal impacts identified in the various site studies, RTP report, or Risk Management Plan, that were further evaluated in the Feasibility Study: • Liquid hydrocarbon surface expressions (red areas in Figure 13) impacting the seasonal wetlands in the bottoms of Reservoirs 5 and 7. • Plastic surface hydrocarbon expressions (purple areas in Figure 13) found across the site, but predominantly in low lying areas (e.g., North Marsh, Reservoir 3) that pose an entrapment hazard to small animals. • Groundwater affected by light nonaqueous-phase liquid (LNAPL) and benzene beneath the Northwest Operations area. • Arsenic in the shallow soil of the Northwest Operations Area. • Wetlands impaired by an asphaltic crust. • The potential for methane to affect habitable structures Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 13 San Luis Obispo, California December 18, 2007 3.0 OPERABLE UNITS, AREAS OF CONCERN, AND THE INTEGRATED PREFERRED REMEDY Once a consensus on the objectives of remediation had been reached, it was necessary to evaluate methods for achieving those goals. Chevron elected to generally follow the procedure outlined in the NCP, which establishes the framework for evaluation of remedial actions used by the U.S. Environmental Protection Agency (EPA). This provided a platform for selecting remedial alternatives that was familiar to the regulatory community and would provide a transparent and credible process for their evaluation. Through that process, five operable units (OUs) were developed for the Tank Farm. The four terrestrial operable units are shown in Figure 14 (OU #5, site-wide groundwater, is not depicted). A brief description of each operable unit is provided in the sections below and is accompanied by a discussion of the associated preferred remedy. These descriptions are largely taken from the Feasibility Study but have been edited to reflect the current plan to pursue the development options where applicable, and to reflect refinement of the AASP land use zones. Detailed proposals for implementing the preferred remedies are provided in Sections 4 through 7. A summary list of the operable units, areas of concern, the relevant constituents of concern, and the preferred remedies is provided in Table 1. 3.1 OU #1- FORMER NW OPERATIONS AREA OU #1 encompasses approximately 5 acres in the northwest area of the site. Historically, this area was used to support tank farm and pipeline operations and included equipment and processes not found across the remainder of the site. Consequently, this area is affected, at least in part, by a unique group of contaminants, namely arsenic in shallow soil and LNAPL with a significant lighter fraction, including benzene, toluene, ethyl benzene, and total xylenes (BTEX), in the saturated zone. In addition, this area of the site is designated both by the City and San Luis Obispo County for potential commercial development (Figures 7, 8, and 10). Although the area zoned for commercial development in either land use plan includes all or portions of the northwest corner of the property, including the former AST containment berms, the area of OU #1 excludes the AST berms due to the identified value of the vernal pool fairy shrimp habitat that they support (Figure 12). An additional concern to this operable unit is that it lies within the 100-year floodplain (Figure 9), which affects how development can be implemented. OU #1 includes two media-focused areas of concern (AOCs), groundwater (AOC #1) and soil (AOC #2). As stated previously, due to a set of conditions unique to the Northwest Operations Area, the LNAPL in the saturated zone also contains a light fraction (C5-C20), including benzene. This light fraction is responsible for the Northwest Operations Area being the only area of the site identified by the RTP where groundwater containing dissolved contaminants (total Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 14 San Luis Obispo, California December 18, 2007 petroleum hydrocarbons [TPH] and benzene) at concentrations greater than maximum contaminant levels (or frequently applied action levels) has migrated offsite. The LNAPL impact in the Northwest Operations Area covers an area approximately 600 feet long by 300 feet wide and ranges in depth from 4 to 28 feet bgs (Figure 14). The light fraction co-occurs with, and is dissolved in, the heavier oil. Light-end hydrocarbons, including BTEX, are hundreds of times more soluble in oil than in water. Therefore, this light fraction would be difficult to remove without also removing the heavier residual oil. In the Northwest Operations Area, groundwater typically occurs at depths ranging from 5 to 15 feet bgs. Benzene is the most toxic constituent of BTEX and its presence in soil, groundwater, and soil gas has the potential to pose the greatest potential risk to future users of the site. The Feasibility Study describes the circumstances surrounding the presence and discovery of the BTEX in detail. In summary, it was determined that the BTEX does not pose a significant risk to building occupants, provided adequate institutional controls (e.g., vapor barriers) are in place. AOC #2 includes shallow soil in OU #1, which is impacted by arsenic and, to a more limited extent, by TPH and polynuclear aromatic hydrocarbons (PAHs), and deeper (4 to 28 feet bgs) soil impacted by the above-described LNAPL. Within the operable unit, the arsenic is relatively widespread and limited to shallow (<2 feet) soil, which is consistent with its likely use as an herbicide. Although not relevant to the development plans considered in this report, the metals and PAHs have been identified as potential ecological risks and would be issues if the area were converted to open space3 . The arsenic was identified as a potential human health risk for both open space and commercial development land uses. It is assumed that the entire operable unit is impacted with arsenic, subject to remediation given the available spatial distribution of data. 3.1.1 Preferred Remedy OU#1-AOC#1 Groundwater It has been demonstrated that benzene dissolved in groundwater has historically migrated offsite in the vicinity of Well SLOW-12, but rapidly attenuates and does not appear to threaten downgradient water wells. The remedial action objectives for OU #1/AOC #1 established in the Feasibility Study are intended to prevent human contact with TPH- or benzene-impacted groundwater and ensure that groundwater resources downgradient of existing impacts are not affected. Given that the LNAPL is stable and unrecoverable, the dissolved phase is naturally contained, there is no evidence of hydrocarbon impacts to downgradient groundwater beneficial uses, and groundwater in the airport area is not used for drinking, it was concluded that monitored natural attenuation is sufficiently protective to be adopted as the long-term remedy for groundwater in OU #1/AOC #1. Therefore, the preferred remedial alternative for AOC #1 is monitored natural attenuation with institutional controls and long-term monitoring. Monitored natural attenuation includes semiannual sampling of the existing groundwater monitoring network on and surrounding AOC #1; testing those samples for total extractable petroleum hydrocarbons (TEPH), total 3 In its present condition, the Northwest Operations Area was not considered suitable habitat in the pERA. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 15 San Luis Obispo, California December 18, 2007 purgeable petroleum hydrocarbons (TPPH), BTEX, and natural attenuation parameters; and reporting those findings to the RWQCB in accordance with an approved monitoring and reporting program. Institutional controls will include deed restrictions limiting land use to commercial/industrial purposes, a soil management plan to be implemented in the event contaminated soils are disturbed, and groundwater use restrictions in impacted areas. 3.1.2 Preferred Remedy OU#1-AOC#2 Soil AOC #2 includes shallow soil, which is impacted by arsenic and, to a more limited extent, by TPH and PAHs, and deeper (4 to 28 feet bgs) soil impacted by LNAPL containing a light fraction. The arsenic is relatively widespread and limited to shallow (<2 feet) soil, which is consistent with its probable former use at the site as a herbicide. The arsenic and PAHs have been identified as potential threats to human and ecological receptors (if the area were converted to open space). With regard to the deeper soil, the LNAPL is not considered a direct contact risk, but vapor intrusion by the volatile fraction may pose a risk to future onsite commercial workers. Remedial action objectives are primarily focused on preventing human and eco- receptor contact with arsenic, TPH, PAHs, and volatile hydrocarbons. Since the area is to be developed, it will not support suitable ecological habitat, thereby mitigating the potential for ecological risks. The preferred remedy for OU #1/AOC #2 includes construction of a minimum 4-foot-thick soil cap. The cap will provide a barrier between the impacted soil and potential receptors and also provide a soil layer of sufficient thickness to facilitate foundation construction and utility installation with a low potential of disturbing contaminated soil. The Northwest Operations Area is within the 100-year flood plain associated with Tank Farm Creek. At its current grade, the southernmost structure within the Northwest Operations Area is subject to inundation during periods of moderate to heavy rain. Raising the ground elevation by 4 feet and regrading appropriately would also satisfy the requirements for construction in floodplains and help alleviate the current flooding problems. A geotextile would be placed between the cap and the existing ground surface. It would act as an identifying marker to reduce the likelihood of inadvertently excavating into the impacted soils. The cap will require long-term monitoring and maintenance. Institutional controls will include deed restrictions limiting land use to commercial/industrial purposes, excavation notification requirements, a soil management plan, groundwater use restrictions in impacted areas, and a vapor barrier requirement for any new buildings that are constructed in the OU; which will protect the building occupants from possible vapors from the underlying hydrocarbons. 3.2 OU #2- RESERVOIRS 5 AND 7 OU #2 includes the former Reservoirs 5 and 7 (Figure 14). Measured from the outside toe of the reservoir containment berms, the reservoirs cover a total area of 9.8 acres. The reservoirs contain about 8.5 acres of wetland, none of which are identified fairy shrimp habitat, although Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 16 San Luis Obispo, California December 18, 2007 Reservoir 5 contains local communities of Congdon’s tarplant. Both reservoirs pond water during the winter, with the amount of water largely dependent on the amount of rainfall. In years of heavy rainfall, it is not unusual for 2 to 3 feet of water to accumulate in the reservoirs. The reinforced concrete bottoms, though ripped, are still present in both of the reservoirs but are covered by 1 to 2 feet of tar, non-engineered fill, and construction debris. In all land use plans, Reservoirs 5 and 7 are in areas designated as Open Space. Reservoirs 5 and 7 are unique in that they are the only areas of the site impacted by liquid-type hydrocarbon surface expressions and these are the only surface expressions that are hydraulically connected to subsurface LNAPL sources. The implication of this is that simple removal of the shallow hydrocarbon-impacted soils will not effectively remediate the sheen that seasonally develops on surface water in the reservoirs. The source of the hydrocarbon sheen is mobile hydrocarbon extending to depths of up to 25 feet below the bottom of the reservoirs, which is displaced vertically upward during periods of a rising water table. Elimination of the sheen will require either removal of the mobile hydrocarbon at depth, making that hydrocarbon immobile, or raising the bottom of the reservoirs to elevations above the seasonal water table highs (RTP, 2006). The preferred remedy caps Reservoirs 5 and 7, mitigates wetland impacts in other onsite areas, and provides institutional controls and long-term monitoring. Cap construction will involve removing existing non-engineered fill down to the existing concrete floor in each reservoir. Gravel will be placed directly on top of the existing concrete floor in each reservoir to a height of 1.5 feet above each reservoir’s historical (1990 to 2005) high water table elevation. The gravel will be covered with a layer of geotextile and a combination of common earth fill and topsoil to create the finished surface. The cap will be graded to encourage runoff, thereby minimizing water infiltration into the gravel reservoir. This approach requires removal of the existing wetlands. Mitigation for these impacts will occur in other suitable areas of the property. Specific institutional controls will depend partially on the degree of public access, but are expected to include fencing, signs, awareness programs, and similar active measures to ensure that access to the site is controlled. Other institutional controls will include deed restrictions and other covenants (as needed) to preserve the land as open space in perpetuity. Long-term monitoring will include periodic inspections and maintenance (as needed) to ensure that the institutional controls and cap remain effective. 3.3 OU #3- EAST DEVELOPMENT AREA (RESERVOIR 4) OU #3 includes approximately 30 acres in the eastern part of the site (Figure 14) and is also zoned for possible future commercial development (Figures 7, 8, and 10). This operable unit includes Reservoir 4, several surface expressions of sticky (“purple-type”) hydrocarbon that collectively cover an area of about 2.3 acres, and the former recycling center. The floor of former Reservoir 4 is covered with 5 to 6 feet of non-engineered, hydrocarbon-impacted soil and construction debris. The Risk Management Summary recommended that soil within Reservoir 4 be left in place with no further action, assuming that the area remains as open space. Due to the Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 17 San Luis Obispo, California December 18, 2007 entrapment hazard posed by the sticky hydrocarbon surface expressions, however, these areas, together with some proximal “blue”- and “green”-type expressions that are not physical hazards, were identified by the Ecological Risk Working Group (ERWG) for remediation. OU #3 contains several small areas of wetlands, none of which are fairy shrimp habitat, and at least two special status plants: Congdon’s tarplant and SLO morning glory. Finally, three areas of relatively low, Level 2 ecological risk were identified in the former recycling center, but because the area is paved and does not provide suitable ecological habitat, the Risk Management Summary recommended no further action as long it does not revert to open space. For purposes of the Feasibility Study evaluation, the development scenario was defined as including all of the activities necessary to leave the operable unit in a condition such that a developer could undertake construction. For OU #3, this is potentially significant since there are several feet of non-engineered fill within Reservoir 4 anticipated to be incapable of supporting a conventional spread footing building foundation without adverse differential settlement. Consequently, the Feasibility Study considered remedial alternatives that would support high foundation loads by removing and replacing the non-engineered, hydrocarbon-impacted fill within Reservoir 4, as well as development alternatives that would require minimal structural support, such as a parking lot. Weathered, high-molecular weight TPH-impacted soil extends to depths of up to 50 feet below Reservoir 4 (Figure 12). As no significant risk has been attributed to the presence of this material, and considering the impracticability of contaminant removal, remedial measures targeting this material were not considered in the Feasibility Study. Subsequent to the Feasibility Study, a refinement of the land uses shown in the AASP has been proposed. Consequently, the grading of the original preferred alternative was augmented to support this land use concept. The approach is at least equally effective, in that surficial hydrocarbon exposures are removed. In addition, the refined preferred alternative provides a soil cover over Reservoir 4 that is at least 4 feet thick, and as much as 11-feet thick .. The cover will provide a barrier between the impacted soil and potential receptors and also sufficient structural support for future onsite construction. A geotextile identifying layer, placed between the cap and the existing ground surface, would serve to reduce the likelihood of inadvertently excavating into the impacted soils. Landscaped areas of the cover would be planted with appropriate shallow- rooted vegetation to prevent erosion without penetrating the cover. Development will still require the installation of vapor barriers below any future foundations or slabs to protect against potential methane intrusion. Construction will unavoidably impact wetlands, which will require mitigation, as well as some Congdon’s tarplant and SLO morning glory communities. Since residual contamination will remain at depth, institutional controls (e.g., restrictions on excavation, development of a Soil Management Plan) will be used to minimize the potential for future onsite exposures. Long- term monitoring will be used to assess compliance and effectiveness. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 18 San Luis Obispo, California December 18, 2007 3.4 OU #4- REMAINING SITE-WIDE TERRESTRIAL AND WETLAND AREAS OU #4 includes all the remaining terrestrial and wetland areas of the Tank Farm not considered in the first three operable units. OU #4 covers an area of about 270 acres, all but 24 acres of which is planned open space. Three areas of concern were defined in the operable unit corresponding to “must-do” areas identified by the Surface Evaluation, Remediation and Restoration Team (SERRT) (Figure 14). These are: • AOC#1 – the North Marsh • AOC#2 – Reservoir 3 • AOC#3 – Other sticky hydrocarbon surface expressions. All three of these areas were identified by the SERRT due to the presence of sticky hydrocarbon surface expressions. However, the conditions surrounding the occurrence of these surface expressions in each area of concern are subtly different, necessitating their separation. Over 70 acres of wetland occur in OU #4, including more than 30 acres identified as fairy shrimp habitat. The operable unit also includes substantial coverage by a variety of special status plants. The Risk Management Summary report also recommended two areas of surface hydrocarbon expressions surrounding Reservoir 3, which were not identified as eco-risks, for ripping to facilitate re-vegetation. These areas, which are also identified in Figure 14, shall be scarified to depths of not less than 15 inches. 3.5 AOC#1 - NORTH MARSH AOC# 1, the North Marsh, consists of approximately 11.9 acres of wetlands without vernal pool fairy shrimp habitat located east of the Northwest Operations Area. The wetlands include the most extensive coverage of pliable plastic (i.e., “blue” and “purple”) hydrocarbon surface expressions at the Tank Farm. When grouped into areas based on proximity, these expressions cover about 7 acres. The extent in the shallow subsurface, however, may be significantly larger. Based on the 1926 topography of the North Marsh, these surface expressions may cover as many as 13 acres. The thickness of the expressions varies but has been estimated to be 2 to 3 feet on average. The North Marsh has not been identified as fairy shrimp habitat. The preferred remedy is to excavate the plastic hydrocarbon surface expressions from the North Marsh, disposing of the impacted material offsite, and improving upon the original wetland function. The area of excavation is estimated to be between 7 and 13 acres, with an average assumed excavation depth of 3.5 feet. Given the areas and thickness, the excavation may generate anywhere from 40,000 to 73,000 cubic yards of material. Any material identified as unimpacted would be stockpiled separately and used later as backfill. It is anticipated that the soil would be disposed of as nonhazardous contaminated soil at an appropriate landfill. Depending on the landfill used, trucks may haul backfill material from the landfill on their return trip. It is assumed that the upper 1 foot of soil would be an appropriate organic-rich topsoil, to be specified in a future restoration plan, consisting either of clean soil from on site or imported to Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 19 San Luis Obispo, California December 18, 2007 the site. The actual amount of topsoil used would be based on the final soil balances, but it is assumed, for the purposes of this analysis, that 1 foot of topsoil will be imported for backfilling. Once the excavation and backfill operations are complete, the marsh would be replanted to restore, and potentially improve, wetland function. Mitigation will likely require that additional wetlands be created elsewhere on the site. Institutional controls may include fencing, signs, awareness programs, and similar active measures to ensure that access to the area is controlled. Other institutional controls might include deed restrictions or other covenants that would maintain the wetlands in perpetuity. Long-term monitoring would include a monitoring and maintenance program to ensure that those controls remain effective. 3.6 AOC#2 - RESERVOIR 3 AOC #2 includes 8.4 acres within the footprint of former Reservoir 3. Much of the ground surface within the former reservoir area is covered by pliable hydrocarbon surface expressions with entrapment hazard potential. Studies have demonstrated that groundwater is not responsible for the hydrocarbon surface expressions in this former reservoir. These studies have determined that viscous oil is being slowly squeezed from the mixed reservoir fill as the soil slowly settles. The reservoir is filled with 8 to 11 feet of non-engineered fill, including berm soils, construction debris, and tar. Approximately 4 acres of precipitation/runoff-supported wetlands hosting fairy shrimp habitat form seasonally along the inside edges of the former reservoir. The preferred remedy consists of constructing a geosynthetic and soil cap that will establish a permanent barrier between contaminated soil and potential human and eco-receptors. The cap will attempt to reestablish wetlands in the same area, thus minimizing the amount of habitat that must be created elsewhere on the site. Conceptually, the cap will be constructed by removing a minimum amount of hydrocarbon-impacted soil so that the cap can be installed without significantly changing the existing grades. Non-hazardous contaminated soil will be disposed of at an appropriate landfill. Since the remaining reservoir fill material is non-engineered and, at best, has poor bearing capacity, it will be necessary to support the cap with various soil and geosynthetic materials. A geotextile will be laid over the exposed work surface and anchored in a trench excavated around the perimeter of the work area. A tri-directional geogrid anchored in a 1-foot-thick gravel layer will be used to distribute loads as evenly as possible and to limit settlement to the cap center. A flexible membrane liner protected above and below by geotextiles will create the impermeable barrier. The primary function of the flexible membrane is to prevent downward migration of water, which may help to support wetland habitat in a manner similar to the current condition. The final component of the cap will be an overlying thickness of common fill and organic-rich topsoil, which will be contoured to mimic the existing topography and wetland hydrology. Remediation may unavoidably impact up to 3.9 acres of wetlands, which has also been identified as habitat for a sensitive species. Even if the original wetland habitat is reestablished within Reservoir 3, additional mitigation may be required elsewhere on the site for the vernal pool fairy shrimp habitat. Institutional controls will include fencing, signs, awareness programs, and Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 20 San Luis Obispo, California December 18, 2007 similar active measures to ensure that access to the site is controlled. Other institutional controls might include deed restrictions or other covenants that would maintain the wetlands in perpetuity. Long-term monitoring will include periodic inspections and maintenance (as needed) to ensure that the institutional controls and cap remain effective. 3.7 AOC#3 - PLIABLE SURFACE EXPRESSIONS OF PETROLEUM AOC #3 includes approximately 3 acres of sticky hydrocarbon surface expressions in six general areas of the south Tank Farm (Figure 14). These surface expressions occur in topographically low areas that accumulated petroleum during the 1926 fire. These expressions are limited in areal extent by surrounding berms and are 2 to 3 feet thick on average. Because these expressions are in topographically low spots, many occur within wetlands, some of which include protected fairy shrimp habitat. The preferred remedy consists of excavating the plastic hydrocarbon surface expressions, disposing of the contaminated material offsite, and restoring the original grade. This alternative would also restore (at a minimum) the existing wetland function, create additional wetlands onsite to reach the expected mitigation requirements, establish institutional controls, and provide long-term monitoring. It is intended that the initial restoration of the impacted wetlands will occur at their current locations. Any further mitigation required in consultation with the regulatory agencies would occur elsewhere on the site. Institutional controls may include fencing, signs, awareness programs, and similar active measures to ensure that access to the site is controlled. Other institutional controls might include deed restrictions or other covenants that would maintain the wetlands in perpetuity. Long-term monitoring will include periodic inspections to ensure that those controls remain effective. 3.8 OU #5- SITE-WIDE GROUNDWATER OU#5 includes site-wide groundwater, exclusive of the Northwest Operations Area. Groundwater flows toward the southwest at an average rate of about 100 feet per year and primarily within sandy interbeds in the largely fine-grained valley fill. The major potential source areas for petroleum impacts to water quality in OU #5 are the LNAPL areas underlying the former reservoirs. Groundwater monitoring of OU#5 has been conducted continuously since 1990, both on and off the property, through a network monitoring wells. The entire network is comprised of more than 80 monitoring wells. However, sufficient data has been collected during the 17-year program that the RWQCB has approved actively monitoring 29 wells. These are located in key positions around the site that ensure any changes in the groundwater conditions could be rapidly addressed. Almost 1,000 groundwater samples have been collected from the entire monitoring network over the 17-year program. For the most part, these samples were tested for TEPH and BTEX, Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 21 San Luis Obispo, California December 18, 2007 although a significant number were also tested for PAHs. With respect to TPH, there is no maximum contaminant level (MCL); the RWQCB regulates this contaminant on a case-by-case basis but often ascribes 1,000 micrograms per liter (µg/L) as a reasonable action level. A study of the OU #5 monitoring record indicates that 43 percent (414) of the samples tested for TEPH contained detectable (>100 µg/L) concentrations. These concentrations range from 100 to 1,600 µg/L, with a median concentration of 220 µg/L. The vast majority of detected concentrations are in the 100 to 400 µg/L range, with many fewer in the 400 to 1,000 µg/L. Only 2 out of the 966 samples tested for TPH have contained concentrations greater than 1,000 µg/L, and neither of these was verified by resampling. Benzene has never been detected (<0.5 µg/L) in an OU #5 monitoring well. Therefore, in OU #5 there is no direct evidence of offsite migration of dissolved contaminants in excess of MCLs or the frequently applied RWQCB TPH action level of 1,000 µg/L. These findings, together with those of the groundwater natural attenuation monitoring program, suggest that any dissolved hydrocarbons generated in OU #5 are being attenuated by natural processes within distances of a few hundred feet from the source. As such, the preferred remedial alternative for OU #5 is monitored natural attenuation with institutional controls and long-term monitoring. Monitored natural attenuation includes semiannual sampling of the existing groundwater monitoring network on and surrounding OU #5, testing those samples for TEPH and natural attenuation parameters, and reporting these findings to the RWQCB in accordance with an approved monitoring and reporting program. Institutional controls will include deed restrictions limiting land use to open space and/or commercial/industrial purposes and groundwater use restrictions in and adjacent to impacted areas. Land use restrictions may also be required on the Betita Property, situated south of the Tank Farm, due to the localized presence of petroleum in the subsurface (Figure 13). Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 22 San Luis Obispo, California December 18, 2007 4.0 GENERAL REMEDIAL ACTIONS Sections 4 through 7 provide detailed descriptions of the proposed remedial design. This section focuses on the general remedial actions. That is, those actions applicable across the site, irrespective of the operable unit. This includes long-term monitoring, excavation, and the general approach used in capping. 4.1 LONG-TERM MONITORING As described in the Feasibility Study, remedial action includes various long-term monitoring activities. The principal monitoring activity is groundwater sampling and reporting. The requirements of the current program are described in Monitoring and Reporting Program (M&RP) 93-120, which is provided in Appendix B along with supporting documentation describing its evolution over the last 15 years. The monitoring program currently requires sampling of onsite and offsite wells according to the list provided in Table 2. Chevron currently samples all of the wells listed on a semiannual basis. Samples are tested for extractable range hydrocarbons, and samples from wells monitoring OU #1 are also tested for purgeable range hydrocarbons and BTEX. A few samples are analyzed for all three constituent types. During remediation, 25 existing monitoring wells, including 4 that are currently monitored (Table 2), will be abandoned (Figure 20). Their abandonment is a direct result of the remedial activities. It is understood, however, that replacement of at least some of these wells will be required by the RWQCB. It is noted that only four of the affected wells are actively monitored under M&RP 93-120 at this time. Nevertheless, the number and location of replacement wells will be as directed by the RWQCB. The details of those requirements will be appended to the Remedial Action Plan once they have been finalized. Another consideration to be discussed with the RWQCB will be future reductions in the monitoring frequency. It is proposed to reduce the overall frequency of monitoring within five years of approval of the Remedial Action Plan. The basis of this proposal is discussed more thoroughly in Sections 7.1.1 and 7.5. As with monitoring well replacement, however, the final requirements of the monitoring and reporting program will be prescribed by the RWQCB. Long-term monitoring will also include periodic inspections of the caps and excavation areas. This will be done to ensure those remedies continue to function properly and are achieving the remedial action objectives. It is anticipated that inspections would occur on a semiannual basis. In particular, one event should occur just prior to the rainy season and the other during or just after the rainy season. Long-term monitoring will also be performed to evaluate habitat restoration and mitigation. This is covered in more detail in the Habitat Mitigation Plan (Padre, 2007b). Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 23 San Luis Obispo, California December 18, 2007 4.2 REMOVAL EXCAVATIONS Some impacted near-surface soils, mostly those affected by petroleum with wildlife entrapment potential, will be excavated. These selective excavations have been chosen to either improve the function of a capping system or to mitigate an identified ecological risk. Where performed in conjunction with construction of a cap, the excavation will remove a limited amount of material defined by an excavation depth (e.g., 2 feet) or by exposure of some existing feature (e.g., a former reservoir bottom). Clean-closure areas are described further in Sections 7.4.1 and 7.4.3, the North Marsh and Other Sticky Hydrocarbon Surface Expression areas of concern, respectively. The clean-closure approach will be limited to pliable hydrocarbon material as originally identified in the Feasibility Study. As a practical matter, it is understood that field determinations may occasionally be required to ascertain the need for removal. There may be field determinations as to the need for removal of some hydrocarbon materials, and that these determinations will be made with the concurrence of the appropriate regulatory agencies. A practical field methodology for making this determination is presented in the Project Execution Plan (Padre, 2007e). Field investigations have shown that the isolated pockets of plastic hydrocarbon identified for removal are the byproducts of the fire or operational spills and appear to be localized to within 3 to 4 feet of the ground surface. In the event that these impacts are determined to extend locally to depths greater than 5 feet, it is proposed that removal excavations will be limited to a depth of 5 feet bgs. Four issues were evaluated in adapting this limitation: worker safety, the potential to encounter groundwater, mitigating risk to burrowing animals, and ensuring that plastic hydrocarbon does not resurface at some later date. Excavations beyond 5 feet require special planning and support for worker safety, based on the requirements of the U.S. Occupational Safety and Health Administration (OSHA) and the California Division of Occupational Safety and Health (Cal/OSHA). In addition, excavations beyond 5 feet in the low-lying areas of the site are likely to encounter groundwater. The Feasibility Study demonstrated that the risks of further environmental impact and the expense associated with the handling and treatment of impacted groundwater did not warrant the effort. One objective of the remedial design is to ensure that future open space uses of the site do not pose an unacceptable risk to potential ecological receptors, which includes burrowing animals. The proposed limit for excavation is below the burrowing depths of most animals that are likely to be encountered at the Tank Farm (DTSC, 1998). Further protection can be provided by using a 0.75-inch gravel for the first 6 inches of backfill to act as a barrier to burrowing animals, if that is deemed necessary. It is also believed that 5 feet of compacted backfill will prevent resurfacing of the plastic materials. The materials are viscous and generally appear to mobilize only when exposed to the warming effects of direct sunlight (England Geosystem, Inc., 2000). By removing material from the near-surface and replacing it with a well-compacted backfill, the likelihood that the material Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 24 San Luis Obispo, California December 18, 2007 will resurface is very low. Soil used for backfill will be compacted to 90 percent of its relative maximum density as determined by ASTM International (ASTM) Method D1557. Remediation will include long-term monitoring and maintenance of the site. In the unlikely event that plastic hydrocarbon were to resurface, it will be detected by the long-term monitoring program and further remedial steps would be taken as part of site maintenance. Clean materials, those not impacted by plastic hydrocarbon, will be segregated during excavation, stockpiled locally, and reused as common earth backfill. Common earth may include solid asphaltic (e.g., green-type) hydrocarbon. Materials that are impacted by plastic hydrocarbon will be disposed of offsite at an appropriate location. It is uncertain, however, at what rate that disposal will be allowed to occur once traffic and air quality impacts are considered during the environmental analysis. Assuming that there are no constraints on truck trips, impacted soils will be loaded directly onto a truck and hauled offsite. An alternative will be to stockpile the impacted material onsite and remove it at a rate that does not unduly burden local streets or air quality. The Northwest Operations Area will be used as a staging area, if needed, to stockpile contaminated soil prior to loading on trucks for offsite disposal (Figure 15). The Northwest Operations Area will be capped and later developed, so a small amount of hydrocarbon residue on the existing surface will not be problematic. It is estimated that remedial actions could generate up to 157,000 cubic yards of impacted soil (Appendix F). If necessary, however, a secondary stockpile could be located on the south side of the Tank Farm, adjacent to the gate on the existing paved slab (Figure 15). It is likely that this area will be used to store equipment or materials. It is potentially available for impacted soil stockpiling if crossing Tank Farm Road to access the central staging area is seen as being problematic. The paved area is slightly more than an acre, and the stockpile would be limited in capacity to approximately 15,000 cubic yards. Access routes to the proposed stockpile location are shown in Figure 17. The routes have been chosen to use existing roads and thereby avoid sensitive habitat. These routes may require widening and drainage improvement, as discussed in Section 6.1. A flagman or other means of traffic control will be provided, as necessary, at the Tank Farm Road crossing. In operating a stockpile for impacted soil, it will be necessary to comply with local air quality and traffic regulations. This will likely require covering the stockpile and periodic monitoring to keep volatile organic compound emissions within regulatory limits. It will also be necessary to control dust and minimize stockpiling during the rainy season. It is anticipated that most hydrocarbon-impacted soils will be disposed of at the nonhazardous impacted soil (NHIS) facility operated by the City of Santa Maria at their landfill. In order to ensure compliance with the appropriate disposal facility’s acceptance criteria, representative samples will be collected of the materials designated for removal.. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 25 San Luis Obispo, California December 18, 2007 4.3 CAPS Caps will be used to separate impacted materials from potential human and ecological receptors. They will be constructed from earthen materials, but may also include various geosynthetic materials for additional strength or material separation. In addition, caps will support either open space or development land uses. A key distinction between the open space and development caps is that the former will include a topsoil layer that will be used to support revegatation. The development caps may be vegetated to minimize erosion, but that will be done directly on the structural fill. The revegetation will also be of a temporary nature, and will be maintained in place only long enough to minimize potential soil loss from the development areas. The development caps are constructed of structural fill with a minimum thickness of 4 feet. Conversely, the open space caps are more varied due to their differing design objectives and individual site constraints. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 26 San Luis Obispo, California December 18, 2007 5.0 EARTH CONSTRUCTION MATERIALS There are four principal types of earth materials used for this project: common fill, structural fill, gravel, and topsoil. Specifications regarding composition, grain size, and other relevant parameters are provided in Appendix E. The following sections provide more detailed information regarding each of these principal soil materials. 5.1 COMMON FILL Common fill will be used for the majority of nonstructural and unspecialized fill needs for the project. It is readily generated from the available onsite soils. It may consist of silt, clay, silty sand, silty clay, clayey sand, or clayey silt. Common fill may have a wide gradation, as shown in Appendix E. One hundred percent of the material must pass a 1-inch screen, and up to 30 percent may pass the No. 200 sieve. The soil must not have any organic or otherwise decomposable or deleterious materials. Common fill will generally be placed in lifts between 8 and 12 inches in thickness and compacted to within 90 percent of its relative maximum density as measured by ASTM D1557. 5.2 STRUCTURAL FILL Structural fill is physically identical to common fill, but will be used in areas where greater soil strength is required, such as the caps that may support future development. The main difference between common fill and structural fill is that it must be placed in lifts with a maximum thickness of 8 inches and must be compacted to 95 percent of its relative maximum density per ASTM D1557. 5.3 GRAVEL Gravel will be primarily used during this remediation project in the caps that will be constructed over Reservoirs 5 and 7. The gravel will provide a structural void space that will provide a low- resistance accumulation space for rising groundwater and LNAPL. Gravel may also be used as a bio-barrier (if needed) in excavations or shallow caps to prevent burrowing animals from exposing contaminated materials. Soil used for this function must be hard, durable, and not susceptible to slaking when immersed in water. An acceptable gradation envelope is provided in Appendix E. One hundred percent of the material must pass a 0.75-inch sieve and no less than 75 percent must be retained on a No. 4 sieve. Further, no more than 5 percent of the soil may pass a No. 200 sieve. The gravel may be placed in lifts of up to 12 inches in thickness and compacted with two passes of a 5,000-pound drum roller or similar piece of equipment. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 27 San Luis Obispo, California December 18, 2007 5.4 TOPSOIL Topsoil will be used to revegetate open space caps and backfilled excavations. Topsoil layers will typically be 1-foot-thick organic-rich soils harvested onsite, amended, or imported to meet the specifications. Topsoil can be any combination of silt-based or clay-based soil found onsite or locally. Onsite topsoil sources will be expected to contain at least 10 percent organic material. Onsite soils not meeting this requirement can be amended by the addition of fertilizers and mulch. Amended soils, however, must contain at least 15 percent organic matter. Topsoil will be placed in lifts no greater than 12 inches thick. It is anticipated that topsoil may be nominally compacted during placement, but will be scarified to a depth of at least 4 inches prior to seeding or planting. Additional soil requirements will be specified in the Habitat Mitigation Plan to ensure that materials used for restoration or mitigation of habitats is compatible with both the flora and fauna served by that habitat. 5.5 EARTH MATERIAL SOURCES It is anticipated that many of the soil materials needed for remediation may be obtained onsite. The following sections discuss the various proposed borrow sources, the types of materials available in each, and the estimated quantity of potential borrow material. Figure 16 shows the location of each of the borrow sources, and Table 3 summarizes the estimated material quantities available from each. A discussion of proposed access routes is provided in Section 6.1. A quick comparison of Table 3 with the earth materials needs of Table 4 shows that there is ample soil for most of the project requirements. This abundance of borrow sources is presented to provide the greatest flexibility to Chevron in creating habitat to mitigate the unavoidable impacts caused by remediation. Borrows No. 1 and 2 are located adjacent to large existing wetland complexes. Borrowing from these areas provides the opportunity to expand those complexes. Further, it is uncertain what constraints may be imposed on construction activities. Redundant borrow sources reduces the likelihood of having to import significant quantities of material from offsite sources. It is important to note, however, that some borrow materials, especially the tank berms, may contain asphaltic materials that are inseparably embedded into the soil matrix. Only the plastic hydrocarbon has been identified as posing a potential hazard or risk, and where these materials are expressed at the surface or exposed during other excavations, they will be removed. Conversely, the asphaltic material does not warrant remediation and its potential incorporation into the common or structural fills is consistent with the findings and recommendations of the Feasibility Study. Notwithstanding this, remediation efforts will attempt to favor borrow materials that are not impacted by asphaltic material. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 28 San Luis Obispo, California December 18, 2007 Use of the borrow sites may result in habitat impacts. The maximum potential impact for each area is summarized in Table 5. It should be noted, however, that while all of the impacts attributed to remediation will occur, only some of the impacts associated with the borrow sources will be realized if a particular borrow source is used. This will be clarified as the project permitting progresses and the habitat mitigation requirements are finalized. 5.5.1 Flower Mound/OU #3 The Flower Mound is an approximately 17.3-acre site located in the northwest corner of the site (Figure 16). It is an outcrop of the basement bedrock complex known as the Franciscan Formation. Typically referred to as the “Franciscan mélange,” the Franciscan Formation is comprised of a complex collection of various rock types. Although the Franciscan Formation found at the Tank Farm includes localized occurrences of coarse to fine-grained clastic sedimentary rocks, it more commonly consists of highly fractured and weathered metavolcanic rocks and serpentinite. It is these latter types of rock that comprise the Flower Mound. Borrow activities at the Flower Mound/OU #3 Area will generate as much as 328,200 cubic yards of material, most of which must be blasted and processed to access. Approximately 73,700 cubic yards are located on adjacent properties. Chevron will negotiate access agreements with each property owner and determine the final disposition of offsite materials. It is expected, though, that at least 26,300 cubic yards, and potentially all, of the offsite material may be available for use by the project. Processing will at least include crushing, and may include sorting, depending upon what materials are required by the project. Material produced from the Flower Mound will be crushed and screened to the material specifications included in Appendix E. It is anticipated that the Flower Mound material will be readily suitable for use as common, structural fill, or road base. However, preliminary testing (Padre, 2007a) suggests that the Flower Mound material may not be sufficiently durable for use as gravel in the caps that will be constructed over Reservoirs 5 and 7 (Section 7.2). Use of the Flower Mound will require abandonment of two monitoring wells, MW-13 and TMW-4. Abandonment will be as described in Section 6.5. Replacement of monitoring wells, if necessary, will be as prescribed by the RWQCB. The Flower Mound/OU #3 area is integral to future development plans for the site. The City of San Luis Obispo’s proposed extension of Santa Fe Road crosses the middle of this work area and its rough grading is incorporated into the design. The final site grade, including the extension of Santa Fe Road, following the completion of borrow and remediation, affects 52.9 acres. As such, there will be permanent habitat impacts requiring mitigation elsewhere on the site. There are approximately 0.26 acre of wetland habitat in the Flower Mound/OU#3 work area and approximately 0.32 acre of rare plant habitat. There is no known vernal pool fairy shrimp habitat within the Flower Mound borrow area. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 29 San Luis Obispo, California December 18, 2007 5.5.2 Berms Numerous berms were erected around the site during its operational life. These were principally constructed to contain oil spills and to isolate the reservoirs in the event of fire. It is proposed to use the berms adjacent to Reservoirs 5 and 7 to supply the common fill required for cap construction. If borrow from the berms is maximized, approximately 71,600 cubic yards will be generated; 38,800 cubic yards at the Reservoir 5 site, and another 32,800 cubic yards at Reservoir 7. Construction of both caps requires 37,000 cubic yards, which will result in approximately 34,600 cubic yards of excess material that can be used for other common or structural fill needs. Excess material will be borrowed on an as-needed basis. This material may be locally contaminated and, therefore, unsuitable for structural fill. Borrow activities will be monitored and the materials segregated, as necessary. Habitat impacts related to borrowing of berm materials are discussed in the relevant remediation discussions later in this report. 5.5.3 Borrow No. 1 Borrow No. 1 is an approximately 8.6-acre site located adjacent to the North Wetland (Figure 16). It includes approximately 2.3 acres that may have been used as a disposal area for demolition debris from the 1926 fire. Anecdotal reports suggest that the disposed materials consist mostly of construction debris, such as concrete and wood. As described in Section 7.4.1, this material will be characterized, removed, and managed at an appropriately permitted facility. It is estimated that the disposal area contains approximately 10,325 cubic yards, assuming an average depth of approximately 4 feet. Soil suitable for use as common and structural fill, and possibly as topsoil, could be removed from the borrow area after removal of the debris. The nominal grading contours for this area would begin at the existing floor of the wetland area and slope back to the east at approximately 0.5 percent. Side slopes would be no greater than 4:1 (horizontal:vertical). This grading approach would generate approximately 36,200 cubic yards of common or structural fill. This borrow source may be used on an as-needed basis. Its main attraction is that after borrowing the available soil the area can be used to create additional wetland. Complete utilization of the borrow source and removal of the historical debris would potentially generate 7.84 acres of additional wetland habitat. This is in excess of the 0.77 acre of wetland that is currently present within the proposed borrow site. It is important to note, though, that the 0.67 acre is also vernal pool fairy shrimp habitat. Full development of the borrow site would also temporarily affect 0.37 acre of rare plant habitat. 5.5.4 Borrow No. 2 Borrow No. 2 is located on the east portion of the site, south of Tank Farm Road (Figure 16). It covers approximately 17.73 acres. This location is anticipated to provide topsoil for revegetation purposes. Most of this borrow site is within a future development area under the City’s AASP and proposed land use plans. Further, its position within the airport safety zones (Figure 9) generally preclude it as a site for habitat mitigation. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 30 San Luis Obispo, California December 18, 2007 It is estimated that at least 20,700 cubic yards of topsoil may be recovered from this location. It is assumed that the topsoil horizon is 2 feet thick, although the Geotechnical Feasibility Study (Padre, 2007a) suggests that as much as 4 feet of suitable material may be available. After borrow operations are completed, the site will be regraded as shown in Figure 39 to support future development. It is estimated that 65,700 cubic yards of topsoil (Table 4) will be required for remedial construction. Any topsoil deficit will need to be closed by manufacturing topsoil from other borrow materials or importing topsoil from offsite sources. Use of the entire Borrow No. 2 area will require abandonment of five monitoring wells, MW-17, MW-18, MW-21, MW-30, and MW-51. Abandonment will be as described in Section 6.5. Replacement of monitoring wells will be as prescribed by the RWQCB. Excavation and restoration of Borrow No. 2 will permanently affect 1.38 acre of rare plant habitat and 0.98 acre of wetland. It will also temporarily affect 0.2 acre of rare plant habitat. 5.5.5 Borrow No. 3 Borrow No. 3 has a similar function to Borrow No. 1. It provides a useful source for common fill and structural fill, and possibly topsoil. It also provides a location that, if utilized, potentially creates additional wetland habitat that can be used to mitigate the habitat that is unavoidably impacted during remediation. The proposed area is approximately 17.5 acres in extent, including approximately 6.59 acres of existing wetland (Figure 16). It is assumed that material will be borrowed from this source starting at the wetland along the south boundary. The existing grade would be lowered to the elevation in the southwest corner and then allowed to slope up at approximately 0.5 percent to the north. This approach will yield approximately 78,950 cubic yards of total borrow (19,700 cubic yards of top soil and 59,250 cubic yards of common earth), and could generate 10.92 acres of new wetland habitat if fully utilized. This is in excess of the 6.59 acres (3.12 acres of which are vernal pool fairy shrimp habitat) of wetland that is currently present within the proposed borrow site. Use of the borrow site may also permanently affect 0.92 acres of rare plant habitat. Use of the entire area could impact several of the active wells in the groundwater monitoring network. Consequently, the use of this borrow area is anticipated to be minimal. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 31 San Luis Obispo, California December 18, 2007 6.0 SITE-WIDE REMEDIAL ACTIONS There are several construction-related remedial actions that are not considered specific to a particular operable unit. Those actions are discussed in this section and include mobilization and staging of equipment and materials, demolition of the existing buildings, miscellaneous cleanup activities, and abandonment of the remaining pipelines. 6.1 MOBILIZATION, STAGING AREAS, AND SITE ACCESS Mobilization is when the contractor prepares the site to begin work. This includes a variety of tasks including moving equipment and support trailers onsite, improving site access, installing storm water and dust control Best Management Practices (BMPs), and habitat protection measures. To successfully accomplish this work, the contractor will require ready access to the work areas with logical and ample traffic routes. At the same time, the contractor must also minimize impacts to non-work areas and avoid sensitive habitat areas that must be preserved. Figure 17 shows the anticipated work areas and the proposed staging areas and access routes. Within the scope of the activities described in this Remedial Action Plan, the contractor shall limit his activities to the areas identified in Figure 17. In the event unforeseen site conditions require access to the off-limit areas, egress shall be coordinated on an as-needed basis with the appropriate regulatory authorities. The work areas are the limits within which remediation activities will be conducted for a given operable unit or area of concern. The work area limit is generally defined by the extent to which a particular site must be cleared and grubbed to properly perform the work and provide the contractor with sufficient room to move equipment and materials. The limits shown in Figure 17 are, however, only approximate. Precise delineations of the work areas are provided in the drawings found in Appendix C. The contractor will use the former recycling area as his primary staging area. It is paved, readily supplied with electrical power and telephone service, and is centrally located on the property with reasonably convenient access across Tank Farm Road. Major maintenance (e.g., engine rebuilds, fluid changes) will only be performed at the primary staging area in specially prepared areas with proper spill control measures in place. Other local staging areas are also shown in Figure 17. These are located directly adjacent to the work areas and would be used to stage materials, park equipment, and other support activities. Vehicles and equipment can be fueled and minor maintenance (e.g., changing tires) can be performed at the local staging areas. Water is available onsite for construction purposes. Water wells are located just north of the Northwest Operations Area, at the southwest corner of the site (south of Tank Farm Road), at the southernmost tip of the site (also south of Tank Farm Road), and on the eastern edge of the site south of Tank Farm Road (Figure 17). The contractor will supply pumps (as necessary), storage Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 32 San Luis Obispo, California December 18, 2007 tanks, and stands to fill water trucks. One storage tank and fill stand is expected be in the primary staging area (Figure 17), and another will likely be located south of Tank Farm Road, adjacent to the entrance. The final locations will be determined by the contractor to best facilitate his work, consistent with the work area constraints show in Figure 17. The contractor is responsible for determining the adequacy of water supply and for making any upgrades to the supply infrastructure. Prior to mobilization, the suitability of the existing water distribution network for conveying water for construction purposes will be evaluated. If feasible, fill stations would be located at readily accessible points such as the fire hydrants. Otherwise fill stations will be supplied by temporary overland pipelines. Bottled water will be used for potable purposes and will be brought onsite and stationed at work and staging areas as needed. The contractor will also supply sanitary facilities at needed locations. Chevron will have relocated its employees and operations prior to starting site remediation. The principal entrance to the site will, therefore, be relocated as shown in Figure 17. This location utilizes the existing entrance to the site south of Tank Farm Road, but is also reasonably close to the Primary Staging Area. It also consolidates access to the site at one point along Tank Farm Road. A traffic study (ATE, 2007) recommended a standard intersection with left-hand turn pockets and right-hand deceleration lanes at the site entrance. The intersection should also include signalization to control traffic during the construction period. A preliminary traffic control plan is shown in Figure 18. The plan will be finalized in concert with the SLO County Public Works Department. The conceptual plan moves the entrance gate back approximately 100 feet from the road. Berms will also be removed to provide deceleration lanes and to ensure adequate site distance. The greater distance from the road will allow trucks to park at the gate without blocking traffic along Tank Farm Road. Other access points will be provided as needed but controlled by the contractor. Access to the site will also be maintained at the Northwest Operations Area, but will not be used as a primary access to the site. The internal routes shown in Figure 17 are intended to provide the contractor with access to all potential work and borrow areas across the site with as little impact to sensitive habitat as possible. The access routes utilize existing dirt tracks. Those shown as solid lines in Figure 17 will be required, while those shown as dashes will only be used if the borrow sources shown at the end of those routes are developed. It is anticipated that most routes must be able to accommodate two-way traffic. Existing dirt tracks will be widened, as necessary, to at least 24 feet in the direction that is least likely to affect adjoining sensitive habitat. Management procedures will be used to minimize impacts from dust and erosion. Where necessary, the contractor will improve the roadway by grooming the subgrade to provide a reasonably smooth and regular surface. In areas potentially subject to inundation or rutting a geotextile will be placed over the subgrade and will be used to provide separation between the subgrade and a 6-inch-thick (minimum) course of compacted crushed miscellaneous base or gravel. As shown Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 33 San Luis Obispo, California December 18, 2007 in Table 5, the improved roadways are expected to temporarily impact 0.1 acre of wetland, 0.04 acre of vernal pool fairy shrimp, and 0.22 acre of rare plant habitat. The contractor shall also provide traffic control to ensure the safe operation of vehicles and equipment. One key component will be controlling traffic crossing Tank Farm Road. It is anticipated that the contractor will at least provide a flagman and signs. It is possible, however, that in consultation with the appropriate municipal agency, a temporary stop sign or traffic light may need to be installed at this location. The contractor may suggest alternative access points onto and across the Tank Farm. It is also possible that alternative routes may be required to mitigate impacts that may be later identified in the environmental analysis. Any alternative routes must be approved by the Construction Manager and the appropriate regulatory agencies prior to use. Access to the borrow areas will be provided on an as-needed basis. As noted previously, some of the borrow sources may be used to facilitate other project needs such as mitigating habitat impacts. The use of these locations, and the associated access routes, will be determined at a later date. 6.2 BUILDING DEMOLITION There are four buildings at the Tank Farm (Figure 3), located in the Northwest Operations Area, that will be demolished during remediation. Three of these buildings were constructed to support historical operations at the site but are now used primarily as office space. The fourth, a modular building installed adjacent to the northernmost original building, was constructed within the last five years to provide additional office space. Chevron personnel and operations will have been removed from the site prior to remediation, and it is possible that building demolition could precede implementation of the final Remedial Action Plan. Given the age of the three older buildings, it must be assumed that lead-containing materials (LCM) and asbestos-containing materials (ACM) are present. Consequently, physical demolition of the buildings will be preceded by surveys and abatement. Asbestos and lead-based paint surveys will be conducted for each building by a California-licensed Asbestos Consultant and California-certified Lead Consultant, respectively. Positive surveys will require abatement. Prior to abatement, a National Emissions Standard for Hazardous Air Pollutants demolition notification form, asbestos survey report, and an asbestos abatement workplan will be submitted to the San Luis Obispo County Air Pollution Control District (APCD). ACM will be abated in accordance with local, state, and federal regulations. Any suspect material not previously identified and found during abatement will be presumed to be ACM unless contradicted by specific laboratory data. Friable asbestos will be managed in air-tight roll-off bins and transported to a hazardous waste facility (e.g., Kettleman Hills) for disposal. Nonfriable asbestos will be managed as required for disposal at suitably permitted solid waste approved by Chevron. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 34 San Luis Obispo, California December 18, 2007 Once abatement activities are completed, recyclable or potentially reusable materials will be removed. The building structure will be demolished using excavators. Some of the buildings have metal structural elements or siding. This will be segregated for recycling, if economic. Other materials will be loaded into haul trucks for disposal. Concrete foundations will be broken apart using a hydraulic hammer and removed. It is possible that concrete will be crushed and used as gravel elsewhere on the site. Utility lines will be disconnected and abandoned. Where lines are aboveground, they will be removed. Where utility service is brought to a building underground, the line will be cut at a point at least 2 feet below grade and capped. Service lines that use pipes or conduits greater than 4I inches in diameter (e.g., water, sewer) will be filled with cement grout. Voids created in the existing grade by demolition will be backfilled with structural fill or gravel. 6.3 MISCELLANEOUS CLEANUP There are four locations onsite that have been identified as requiring cleanup or demolition that are not part of one of the operable units or areas of concern. They are not generally “contaminated” or impacted areas, although they may have some impacted soil associated with them. Rather, they are comprised of debris or abandoned structures that are unsightly or possible physical hazards. These are shown in Figure 19. Three of the locations are found on the parcel north of Tank Farm Road. There are two debris piles along the north property line. They appear to contain mostly concrete debris. As with other concrete debris, the contractor may crush this material and reuse it for gravel elsewhere on the site. Otherwise, the concrete shall be hauled offsite for recycling or disposal. The other area identified on the parcel north of Tank Farm Road is the historical debris disposal area adjacent to the North Wetland. As discussed in Section 5.5.3, the material in this area will be excavated and removed for disposal or recycling as appropriate. It is recommended that the limits and characteristics of the waste be defined prior to excavation and disposal. It is assumed that the debris extends to a depth of 5 feet and that the nominal excavation volume is 18,000 cubic yards. Material removed from the excavation will be segregated on the basis of how it will be managed. Concrete may be recycled, as described previously. Other construction debris will be sent to a solid waste landfill for disposal. Impacted soils will either be sent to the proposed stockpile area for later disposal or directly to the disposal facility as dictated by traffic and air quality requirements. The excavation will not be backfilled in order to accommodate habitat mitigation later in the project. The fourth miscellaneous cleanup location is found south of Tank Farm Road, adjacent to Reservoir 6 (Figure 19). It is a concrete vault of uncertain purpose, approximately 5 feet wide, 12 feet long, and 8 feet deep. The crude oil supply line serving Reservoirs 6 and 7 connected to it, but it is not known if it was a separator, a valve box, or served some other purpose. The vault is, however, open and presents a physical hazard to people and animals and a possible Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 35 San Luis Obispo, California December 18, 2007 entrapment hazard to small animals. The steel hand rail will be removed and the upper 3 feet of the concrete wall will be broken and used to fill the bottom of the vault. A sand-cement slurry will be used to fill the void spaces. The remaining depth of the vault will be backfilled with common fill until the original grade is reestablished. 6.4 PIPELINE ABANDONMENT When operational, the Tank Farm required numerous pipelines to move oil between the pump house, boilers, tanks, and reservoirs. The site was also served by water, natural gas, and septic lines. Figure 5 shows pipeline locations based on historical facility drawings. It is estimated that more than 25,000 feet of oil pipeline were installed onsite; approximately 4,500 feet are found in the Northwest Operations Area (Figure 6). Much of that pipeline remains in place, as indicated on Figure 5. Chevron intends to abandon most of the pipeline in place. Portions of the line that are within work areas will be removed for disposal, except for the Northwest Operations Area, where the pipelines may be closed in place by pressure-grouting. If a pipeline crosses an environmentally sensitive area (e.g., wetland) and would not otherwise be disturbed by remediation activities, it will also be closed in place by pressure-grouting. All pipelines will be flushed and, if possible, pigged to remove residual hydrocarbon and vapors prior to abandonment. If a section of pipeline is in such poor condition that it cannot be adequately cleaned, it will be excavated and removed in its entirety. 6.4.1 Pipeline Inventory The positions of the pipelines shown in Figure 5 and Figure 6 have not been field verified. While these figures (and the similar engineering drawings found in Appendix C) are reasonable approximations of their locations, final remediation will require more accurate information. It is, therefore, expected that prior to abandonment, a detailed field survey will be performed to locate the lines and characterize their contents. Potholes will be dug at key locations (e.g., ends, transitions, junctions, valves) to expose the pipe and determine its diameter and materials of construction. Line tracing will be performed using an appropriate geophysical instrument operated by a trained technician. The alignment of the pipeline will be flagged every 5 feet. Pothole and flag locations will be recorded using a high-precision Global Positioning System (GPS) unit and entered into a Geographic Information System (GIS) database. A detailed pipeline inventory, noting location, depth, size, materials of construction, and condition, will be created to guide abandonment activities. Given the interconnected, and possibly deteriorated, web of pipelines within the Northwest Operations Area, Chevron may elect to cut the lines at the operable unit boundary and Abandoned concrete vault adjacent to Reservoir 6-to be abandoned Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 36 San Luis Obispo, California December 18, 2007 completely remove them from its interior. In this case, the lines will be removed in accordance with Section 6.4.4 after their positions have been confirmed. 6.4.2 Pipeline Flushing and Pigging Water trucks attached to portable pumps would be connected via hose to each petroleum pipeline segment within the facility. Additionally, several portable storage tanks or vacuum trucks would be stationed and attached to the pipelines to receive and collect the flush water. Each pipeline segment will be flushed with an adequate volume of water to remove residual oil from the pipelines. Pipeline flushing operations will continue until flush water containing total petroleum hydrocarbons of less than 100 parts per million is achieved. The pipeline segments that may be suitable for pigging will be identified by Chevron during the initial potholing activities. The pigging operations will be basically the same for each pigging run segment. Each segment will have a beginning location where the pig is “launched,” and an end section where the pig is “received.” The pigging operation procedures are presented below. First, the launching/receiving locations will be prepared for the procedure. Buried ends of the pipeline will be excavated. The excavations will vary depending on the depth of the pipe, but should not typically exceed an area larger than 7 feet wide by 12 feet long (84 square feet) and no more than 5 feet in depth. A trench box may be used to minimize the area affected by the excavation. The pipeline fluids will be drained from the pipe and the pipe will then be cold-cut to gain access to the pipe. The pig launcher/receiver will then be attached to the exposed pipe end. Once the pig launcher and receiver are attached to the pipeline, the subject pipe segment will be pigged. The pigging operation will involve the use of scraper-type or foam pigs. The scraper pig is constructed to help remove any remaining hydrocarbons from the inside walls of the pipeline as it moves down the pipe. The pigs will be pushed through the piping segment using liquefied nitrogen gas or compressed air. At the receiving end, vacuum trucks will be used to remove any liquids from the pipe as the liquids are pushed ahead of the pigs. Carbon filtration canisters will treat any vapor emissions generated during pipeline purging operations, in accordance with APCD requirements. Chevron will obtain approval from APCD for the proposed activities. Recovered hydrocarbons and water from the pigging operation will be properly disposed of or recycled by Chevron. There is the possibility that a pig may become lodged in the pipe by an obstruction. If the pig becomes obstructed along a pipe segment, these locations will be identified by the field crews. Excavation activities may be required to remove the pig and the damaged/obstructed section of pipe. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 37 San Luis Obispo, California December 18, 2007 6.4.3 Pipeline Grouting Pipelines that are scheduled for abandonment and have diameters greater than 4 inches will be grouted with a cement-slurry to prevent any future ground subsidence from pipe wall collapse. A portable grout pump will be used to pump grout into the pipeline segments. Grout will be pumped until grout exits the other end of the pipe segment. Following grouting, the pipeline segment ends will be backfilled with soil and the soil compacted. 6.4.4 Pipeline Segment Removal Chevron proposes to remove intra-facility petroleum piping that may be affected by project remediation activities or is determined to be in poor condition. If practical, the pipeline segments will be flushed or pigged prior to removal. The pipeline segment endpoints will be isolated and cut. The pipeline segment will then be uncovered by excavating a trench to the existing pipeline depth. As the pipeline is removed from the trench, a spill containment device will be placed under the pipeline end to catch any residual fluids in the containment. All liquids drained from the piping into the containment device will be removed using a vacuum truck and hauled to an approved facility for disposal or recycling. The pipe segments will then be cut into manageable pieces, the pipe ends wrapped in plastic to prevent spillage, the segments removed from the trench, and the trench backfilled. Scrap pipe will be temporarily stored in bins and transported offsite for recycling. 6.5 MONITORING WELL DESTRUCTION Remediation will require the destruction of 25 monitoring wells across the site. These wells are listed in Table 2 and shown in Figure 20. Each of the affected monitoring wells is in an area that will be excavated or over which a cap will be constructed. Even if retention of the monitoring wells was desired, it would be costly and difficult to protect the wells in place, and it is likely that several would be inadvertently lost. The number and location of replacement wells will be as directed by the RWQCB. The details of those requirements will be appended to the Remedial Action Plan once they have been finalized. Well abandonment will be performed in accordance with California Department of Water Resources Bulletin No. 74-81 and the applicable requirements of the San Luis Obispo County Department of Environmental Health. Permits for this activity will be obtained from the San Luis Obispo County Department of Environmental Health. Monitoring well monuments will be removed and disposed of offsite. The wells will be drilled out using an auger slightly larger than the original boring. Most of the wells consist of 4-inch casing in an 8-inch boring. In this case, a 10-inch-diameter auger would be used to drill out the well. Cuttings will be stored in drums and disposed of offsite. The boring will be backfilled with hydrated bentonite. The boring will be checked 24 hours after the initial abandonment. Additional hydrated bentonite will be added if settlement of the initial fill is observed. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 38 San Luis Obispo, California December 18, 2007 A completion report for the abandonment will be submitted to the San Luis Obispo County Department of Environmental Health and to the RWQCB within ten days of abandoning the final boring listed on Table 2. 6.6 HISTORICAL PRODUCTION WELLS Review of historical operational records and facility drawings has identified the approximate locations of three water wells. These locations are shown in Figure 19. Inspection of these areas has not revealed any surface features associated with the wells. It is likely that the wells were abandoned many years ago and any other record of them has long since been lost. It is desirable, however, to ensure that the wells were properly abandoned. It is, therefore, proposed to conduct a thorough field investigation to verify the location and condition of the wells. It is probable that the wells were constructed with steel casings, and if they are still present, they should be detected by a magnetometer. A licensed geophysical contractor will sweep the approximate well sites and will map and stake any magnetic detections. A backhoe will be used to expose the detections and identify them. If the wells are located, the method of abandonment will be ascertained, and if the method does not meet modern standards, the well will be abandoned according to the requirements of California Department of Water Resources (DWR) Bulletin 74-81. 6.7 LAND USE COVENANTS Land use covenants will be prepared for the various parcels that the site may be subdivided into. This will include not only potentially developable parcels, but also the open space areas . A land use covenant is a legal document that will accompany a parcel’s deed. It will be signed by representatives of Chevron and the lead agencies (e.g., RWQCB), and will be notarized and recorded with the County Clerk/Recorder. It is intended to ensure that future owners of the properties understand what mechanisms are in place at the site to protect human health and the environment, and to identify for future property owners their responsibilities in maintaining those protections. The specifics of the land use covenants for the Tank Farm will vary depending on which parcel is under consideration. It will, however, identify the allowed land uses and will exclude uses that might be allowed under current or future land use planning but are inappropriate for the site. The land use covenants will list the various caps and other containment features that must be maintained. It will be accompanied by various documents, such as the guidelines for vapor barriers (Appendix M), Habitat Mitigation Plan (Padre, 2007b), and Soil Management Plan (Padre, 2007c). The land use covenant will also restrict the use of groundwater in areas of impacted soil on the Tank Farm property. Chevron will work with adjacent land owners to establish covenants regarding soil and groundwater on adjacent properties affected by historical site activities. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 39 San Luis Obispo, California December 18, 2007 Draft land use covenants (as required) will be prepared by Chevron for review by the RWQCB and the lead municipality once the Remedial Action Plan has been approved. 6.8 VAPOR BARRIERS The Feasibility Study identified the need for vapor barriers as an engineering control in habitable structures erected in the potential development areas. Decomposition of the underlying hydrocarbons generates methane. Accumulation of methane within buildings would be unacceptable. A series of conceptual engineering approaches to control methane migration are presented in Appendix M. These range from simple passive systems, where a liner is constructed directly beneath a slab constructed on grade, to active systems that can be used to vent a parking structure that is slightly below grade. The examples provided in Appendix M are reasonable illustrations of the general approaches used to construct vapor barriers. These diagrams have been used on other projects subject to methane or volatile organic compound intrusion, and have been approved by other regulatory agencies and municipalities. These are not, however, construction documents. It is expected that a developer will use these as guides in preparing his plans and specifications. The final version of these guidelines, which will accompany the land use covenant, will be approved by the RWQCB and the lead municipality. The land use covenant will also include provisions requiring approval by those agencies of the construction documents to ensure compliance with the final vapor barrier guidelines. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 40 San Luis Obispo, California December 18, 2007 7.0 OPERABLE UNIT REMEDIAL ACTIONS This section presents the remedial actions specific to each operable unit. It provides detailed descriptions of how the remedial actions will be implemented, as well as the engineering and regulatory bases behind their design. This section includes numerous figures meant to illustrate the remedial actions, and while they are based on the engineering drawings found in Appendix C, they should still be considered only diagrams. 7.1 OU #1-NW OPERATIONS AREA As described in Section 3.0, OU#1 (the Northwest Operations Area) consists of two media-based areas of concern. The first, AOC #1, is groundwater, and the second, AOC #2, is soil. The preferred remedy for AOC #1 is monitored natural attenuation with long-term monitoring and institutional controls. The preferred remedy for AOC #2 is construction of a soil cap, with a minimum thickness of 4 feet, and institutional controls to manage soil that may be exposed during development or maintenance of the site. 7.1.1 AOC #1 Groundwater Monitored natural attenuation will be implemented using the same parameters and methods as specified in Monitoring and Reporting Program 93-120 (Appendix B). However, remediation will require abandonment of several monitoring wells (Table 2). Replacement will be determined in concert with the RWQCB, which will also approve a revised M&RP.. At a minimum, monitoring groundwater for TPH and BTEX (consistent with M&RP 93-120) will be performed at the remaining perimeter monitoring wells MW-49, MW-50, MW-56, and SLOW-17, and the off-site production wells 11Ea and 11Eb. Currently, monitoring is performed on a semiannual basis. After three years, the RWQCB will evaluate the semiannual groundwater data to determine if a reduction in the monitoring frequency is warranted. A land use covenant will be prepared for the operable unit that includes restrictions on the use of groundwater. Those restrictions will prohibit installation of groundwater wells within or immediately downgradient of petroleum-impacted soils. 7.1.2 AOC #2 Soil-Development Scenario It has been presumed in this plan that AOC #2 will be developed at some point in the future and will not be considered suitable habitat for flora or fauna. As such, the remedial objectives are to prevent human contact with the arsenic, TPH, and PAHs that are found in the shallow soil in this area. Construction of a 4-foot-thick soil cap was selected as the preferred remedial alternative in that it not only satisfied the remedial objective, but also made future development feasible by raising the grade out of the 100-year flood plain. Prior to building the cap, unnecessary existing features must be removed and the site must be prepared for construction. Figure 21 illustrates the demolition plan and subgrade preparation Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 41 San Luis Obispo, California December 18, 2007 proposed for AOC #2. It is assumed that prior to demolition, building surveys have been completed for LCM and ACM, the pipelines within AOC #2 have been either abandoned in place or have been removed as described in Sections 6.2 and 6.4, respectively, and the monitoring wells within the AOC will have been abandoned per Section 6.5. The first component of remedial action for AOC #2 will be demolition of the four existing buildings. As more fully discussed in Section 6.2, three of these buildings supported the historical petroleum handling operations and are likely affected by LCM and ACM. After surveys and abatement have been completed, the buildings will be demolished and managed in an appropriate manner. Demolition will also include removal of the existing fences and gates along the south and west boundaries of AOC #2. Future development of the region around the San Luis Obispo Airport envisions widening Tank Farm Road to a 100-foot-wide right-of-way (City of San Luis Obispo, 2005). This will necessitate moving the southern boundary of the Northwest Operations Area north approximately 30 feet (Figure 21). To ensure that the historical infrastructure does not interfere with future road widening, Chevron will remove any existing features from this area, including pipelines and concrete foundations. Prior to any significant demolition work, the site must be cleared and grubbed within the limits shown in Figure 21 and more thoroughly defined on the construction drawings provided in Appendix C. Clearing and grubbing will consist of removing all vegetation from the site. Brush and small trees are cleared by cutting them down and pulling up the roots. The site is then grubbed to a depth of at least 3 inches using a tractor or small dozer to remove grasses and other low-lying vegetation. There are two underground pipelines along the west boundary of the Northwest Operations Area. One is a 2-inch-diameter natural gas line and the other is a 4-inch-diameter water supply line. The gas line is fed by the 4-inch-diameter gas main located in Tank Farm Road and owned by Southern California Gas Company. The water line is fed by the existing water well located adjacent to the southwest-most former tank ring, but is also connected to other water lines across the property. A series of timber poles support both electrical and telecommunication lines. Along that western boundary are drops to electrical panels that feed service to the buildings. Chevron will Northwest Operations Area along Tank F Road - looking west arm Northwest Operations Area along west property boundary – looking north. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 42 San Luis Obispo, California December 18, 2007 Northwest Operations Area - fire water tank Northwest Operations Area - existing water well remove the utilities along this property line prior to constructing the cap. The gas line will be cut and capped at the 4-inch main under Tank Farm Road. It will be necessary to coordinate this work with The Gas Company. Similarly, the aerial utilities will be disconnected at Tank Farm Road in coordination with AT&T and PG&E. Underground electrical and telecommunication conduits supplying service to the demolished buildings will also be removed. Excavations to remove buried conduits and pipelines will be backfilled with structural fill. It is likely that Chevron will retain the existing water well located Two septic tanks with leach fields manage wast tank serves the southern build water tank stores water for firefighting at AOC #2. Once the buildings are adjacent to the southwest-most former tank ring (Figure 21). The well is also shown in the digital image below. Electrical service will be provided to the well after construction of the cap via an underground conduit. The location and specifications for the conduit are provided in the design drawings found in Appendix C. The conduit will be made of 4-inch- diameter PVC and will be buried at a depth of 5 feet, in accordance with applicable local rules and regulations for providing electrical service. ewater at the Northwest Operations Area. One ing and the other serves the northern building, as shown in Figure 21. The tanks and leach lines will be abandoned in place in accordance with the standards of San Luis Obispo County (SLOCo, 2006). This will require emptying the tank contents with a vacuum truck, supplying a receipt of the work to the County Inspector, and then filling the tank with a cement slurry or concrete. There are six overhead light standards located around the paved portion of AOC #2. These will be removed and recycled or disposed of as appropriate. Concrete foundations for the lights will be broken apart to a depth of at least 2 feet bgs. The resulting hole will be backfilled with structural fill. Conduits providing electrical power to the lights will be cut at least 2 feet below the existing grade and capped. Conductors will be pulled and recycled. A 10,000-gallon polyethylene Northwest Operations Area - typical light standard Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 43 San Luis Obispo, California December 18, 2007 demolished, the tank will no longer be needed and will be removed from the site. Water is supplied to the tank by the 2-inch-diameter water line that enters near the top of the tank. The larger 4-inch-diameter line connects to a booster pump and then to the water distribution system that feeds various hydrants surrounding the site. Water level in the tank is maintained by electronic sensors that ensure that a minimum depth of water is present at all times. The tank sits on a 4-inch-thick cast-in-place concrete slab and is protected by four bollards. Once the tank has been removed, the bollards will be pulled and the holes backfilled with a cement slurry or concrete. The concrete slab will be broken apart and recycled onsite along with other concrete debris for use as gravel. Water lines and conduits will be cut 2 feet below the existing grade, capped, and any excavations backfilled with structural fill. Electrical conductors will be removed from the conduit and recycled. As can be seen from the above images and as indicated on Figure 21, AOC #2 is partially paved. It is readily apparent on viewing Figure 21 that AOC #2 is cluttered with the concrete vestiges of The pavement will be left in place. Any valve boxes or other similar types of subterranean vaults not otherwise removed during demolition activities will be filled with cement slurry. Detachable parking curbs will be removed for recycling, and asphalt edge curbs will removed. The former fire school used a concrete-and-asphalt- lined pit for teaching and training techniques for extinguishing petroleum-fed fires (Figure 21). The remains of the pit are shown in the adjacent image. It may be difficult to place and compact structural fill within the pit, which might result in unwanted differential settlement. It is, therefore, proposed to remove the loose debris in the bottom of the trench until a firm surface has been exposed. The trench will then be backfilled with cement slurry to the existing grade. The loose material will be drummed, profiled, and managed at an appropriately permitted facility. the historical petroleum operations. Some of these foundations are flush with the ground surface, or nearly so, and can be abandoned in place, such as the one shown in the top image on the next page. Other concrete structures that project more than 6 inches above the ground surface will protrude above the subgrade preparation layer described below and will interfere with construction of the cap. Consequently, the contractor may leave in place any concrete structure that projects above the existing ground surface less than 6 inches. Concrete structures that project more than that distance must be removed. The concrete may be broken up and recycled onsite for use as gravel. The contractor may elect to remove the Northwest Operations Area - burn trench used by former fire school Northwest Operations Area - typical concrete slab requiring removal Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 44 San Luis Obispo, California December 18, 2007 low-lying concrete structures, as well, if that proves more economic for gravel production. Voids produced during removal of the concrete structures will be replaced by structural fill to the existing ground surface. Once the work area has been cleared and grubbed and the demolition and abandonment activities have been completed, the subgrade will be prepared. This will include compacting the existing ground surface to the specifications of structural fill. In addition, a 6-inch-thick layer of common earth will be placed over the entire work area and compacted to the specifications of structural fill. The intent of this effort is to provide a uniform surface over which to place the geotextile fabric described later in this section. A retaining wall will be constructed along the south boundary of AOC #2, as shown in Figure 22. The purpose of the retaining wall is to ensure the maximum amount of developable land along the south boundary. Illustrations of the typical cap profile are shown in Figures 23 and 24. Additional illustrations showing both the retaining wall and sloped edge detail are shown in Figure 25 and Figure 26, respectively. The retaining wall will be constructed of reinforced cast-in-place concrete with a minimum compressive strength of 3,000 pounds per square inch. A footing for the retaining wall will be excavated along the alignments shown in the figures and design drawings. The excavation shall be inspected and approved by the Engineer prior to placing any steel reinforcement. Weak or otherwise unsuitable soil shall be removed to a depth of at least 24 inches below the footing. If the removed soil meets the requirements of common earth it may be used for backfill. Otherwise, the soil shall be properly disposed and replaced with suitable material. All backfill associated with the retaining wall shall be placed as structural fill. The retaining wall design is a standard configuration taken from the Standard Plans for Public Works Construction (1997), and the basis for its configuration is provided in Appendix K. The wall along the south boundary will be approximately 495 feet long and will vary in height between 3 feet and 6 feet 5 inches. A 12-ounce geotextile will be used to identify the contact between the cap and former ground surface. It is intended to warn future construction workers that the underlying soil layers are potentially contaminated. Specific warnings and instructions will be provided in the land use covenants and Soil Management Plan. Along the retaining wall, the geotextile will be placed on the concrete footing and anchored by the overlying soil layers. Along the sloped soil boundaries, an anchor trench will be cut beneath the location of the slope break, which is the point on the cap surface where the grade switches from a gentle slope to a steeper slope that eventually meets the existing grade. The anchor trench will be at least 1 foot wide and 3 feet deep, and will be backfilled with structural fill. These end details are illustrated in Figure 26. The cap itself covers approximately 6.4 acres and will be constructed of structural fill. To promote proper drainage across the site, the cap thickness varies from a minimum of 4 feet to a maximum of approximately 7 feet towards the center. It is estimated that 53,400 cubic yards of Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 45 San Luis Obispo, California December 18, 2007 common earth will be necessary to achieve the lines and grades depicted in Figure 22. It is anticipated that this material will be obtained from the Flower Mound borrow source (Figure 16) by crushing run-of-pit material to meet the specifications for common earth provided in Appendix E. The cap will be thicker, on average, than the nominal thickness specified in the Feasibility Study. This is primarily to provide adequate flexibility for future development layouts. The proposed grading allows for surface runoff. A thinner cap could be constructed using dedicated subsurface storm drains, but would require substantial expense to modify in the future. A future developer can also modify the surface grade without importing materials and still be assured that the required minimum thickness of the cap is maintained. The Geotechnical Feasibility Study identified potentially soft soils typically between 6 and 25 feet bgs, although the depth varies, beneath the Northwest Operations Area. The settlement analysis (Appendix H) estimates that settlement due to the load of the cap could be on the order of 4 to 6 inches. The Geotechnical Feasibility Study estimated that additional settlement due to foundation loads could be on the order of 1 to 2 inches. In general, it is not considered practical to remove the soil for recompaction. Groundwater is relatively shallow (on the order of 10 to 15 feet bgs). As was discussed in Section 7.1.1, groundwater in this area is affected by LNAPL, benzene, as well as TPH in the soil. The site would require significant dewatering, with treatment of the resulting effluent, and disposal of contaminated soils. Some recompaction of the soils beneath the pipelines will occur as they are removed. To the degree possible during remediation, soils will be stockpiled over the Northwest Operations Area to promote settlement. Prior to construction of the cap, it may be necessary to temporarily stockpile petroleum-impacted soils prior to disposal. After construction of the cap, it may be used as a location for temporary stockpiling of material from the Flower Mound or other borrow sites. Construction of the cap will include installation of three survey monuments at the locations shown in Figure 22. An illustration of a typical survey monument is shown in Figure 27. Should low spots develop following construction, they would be repaired as part of the long-term maintenance program until the property is sold. Future building foundations will require consideration of the soil conditions. Specific and detailed geotechnical studies must be prepared for any work subsequent to cap construction. It is anticipated that future foundation design over the site will require geogrid reinforcement or the use of piles. Any work below the bottom of the cap must be in accordance with the Soil Management Plan. Storm water management features for this cap are designed to handle a 100-year recurrence storm. Runoff is handled as sheet flow off the cap surface. It is directed from a high point near the mid-point of the site to ditches along the perimeter. It is carried in ditches to hardened drop points at the locations shown in Figure 22. Drop structures have rip-rap reinforced energy Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 46 San Luis Obispo, California December 18, 2007 dissipaters to prevent erosion. The calculations used to size the storm water management features are found in Appendix G. Run-on occurs at two locations and is diverted away from the cap at each. Currently, storm water drains from the north toward where the cap will be constructed. Although the amount of flow is relatively small, it is undesirable to allow this water to pond at the cap toe. Consequently, a flow line will be established along the toe of slope that drains toward the existing ditches and wetlands to the east. Ditches along the toe of slope are hardened with gravel and cobbles to minimize erosion at the transition between the slope and the existing wetlands. The other principal source of run-on is from the west, along Tank Farm Road. A local high point is located on Tank Farm Road approximately 1,000 feet west of the Tank Farm. Surface runoff from the surrounding properties is directed toward the Tank Farm in the swale that runs on the north side of the road. At present, the runoff drains onto the agricultural property adjacent to the Tank Farm. During heavy precipitation, the attenuation capacity of that land is exhausted and water drains onto the Northwest Operations Area as sheet-flow. Run-on then flows across the property, collecting in numerous local low points (including the southernmost building) until reaching the wetland complex. The cap will cut off this route for storm water flow, and as such, a new drainage ditch is proposed at the toe of the southern retaining wall. The flow line of the new ditch will start at the existing grade at the western edge of the property and drop to the floor of the wetland complex to the east and will be sized to accommodate up to 17.2 cubic feet per second of flow (Appendix G). Rip-rap will provide erosion protection at the entrance to the wetland complex. The ditch will include a culvert to allow access from Tank Farm Road onto the site. The alignment and slope of the ditch are illustrated in Figure 22, and a typical cross- section is shown in Figure 23. In addition to the erosion control measures previously described, additional BMPs will be provided to minimize the potential for erosion from the cap to the wetland. Unmitigated, soil erosion could be as much as 0.2 ton per year (Appendix J). It is anticipated that the recommended BMPs will substantially lower this total. The ditches along the top of slope of the cap will be provided with sandbag chevrons to slow water flow and allow sediment to drop out of suspension. Further, the surface and slopes of the cap will be covered with a spray-applied mulch/seed, which will be maintained until the property is developed. As discussed in Section 2.2 this portion of the site is within the 100-year flood plain of Tank Farm Creek. Construction of the pad is anticipated to locally remove approximately 12.4 acre- feet of flood storage capacity. It is estimated, however, that further downstream (south of Tank Farm Road) there is an additional 27.9 acre-feet of available storage capacity. Further, it is unknown how restoration of the North Marsh will affect flood storage capacity. However, it will likely be augmented by expansion of the wetland complex. As described in Sections 6.7 and 6.8, institutional controls will be adopted to protect the integrity of the cap. The land use covenant will strictly define appropriate uses for the property. Excavation depths will be controlled, and excavations deeper than the bottom of the cap will be Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 47 San Luis Obispo, California December 18, 2007 Reservoir 5 - typical protective enclosures conducted under the requirements of the Soil Mitigation Plan (Padre, 2007c). Prior to development of the site, access will be controlled through fences and gates. Additional fences will be installed around the interior boundary of the operable unit with a locking gate, as shown in Figure 22, to control access between the development area and the adjacent open space. Prior to development, the cap will be periodically inspected and maintained, as necessary. 7.2 OU #2-RESERVOIRS 5 AND 7 The primary remedial action objective for Reservoirs 5 and 7 (i.e., OU #2) is to prevent the emergence of liquid hydrocarbon on the open water that accumulates at these locations. The sheen produced by the liquid hydrocarbon may adversely affect ecological receptors such as water fowl. The Feasibility Study determined that the most feasible way to prevent contact is to cap the reservoirs in a manner that allows groundwater (and the overlying hydrocarbon) to fluctuate naturally and not try to find alternative (i.e., lower resistance) flow paths. This will necessitate reconstruction of the existing wetlands at another location onsite. Prior to constructing the cap, it will be necessary to clear the work area. The demolition plans for Reservoirs 5 and 7 are illustrated in Figure 28 and Figure 29, respectively. The detailed engineering drawings for demolition are included in Appendix C. A work area boundary has been established for each reservoir. This boundary establishes where the contractor may operate his equipment, disturb habitat, and where cleanup and construction will take place. The contractor will identify this line in the field and provide protective measures to prevent impacts outside of the boundary. These will include cones, caution tape, temporary fencing (if appropriate), silt fences, and other dust and erosion control BMPs. One of the first demolition tasks will be the removal of the protective enclosures, an example of which is shown in the adjacent image. These were installed to ensure that small animals, such as birds, are not entrapped in sticky plastic hydrocarbon surface expressions. They occur both inside and outside of the tank rings. Every location with a protective enclosure is presumed to overlie a surface expression of plastic hydrocarbon that requires removal. Those within the limits of the former reservoir berm are addressed as part of the cap construction. Outside of the berm limits, however, soil beneath the protective enclosures will be removed as described in Section 4.2. Note that there are some plastic hydrocarbon surface expressions outside of the Reservoir 5 work area (Figure 28). Excavation and impacted soil removal at this location is addressed in Section 7.4.3. The enclosure materials will be removed from the site by the contractor and recycled (if feasible) or disposed of in a solid waste landfill. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 48 San Luis Obispo, California December 18, 2007 Reservoir 7 – overview of existing bottom and concrete-lined slopes Reservoir 5 – former oil pipeline Other site preparation activities will include the removal of any pipeline remnants in the work area. The old 8-inch-diameter crude oil distribution line is nearly tangent to the southwest edge of the Reservoir 5 berm. A lateral from this line appears to branch into Reservoir 5. The remains of the lateral can be seen ending within the reservoir in the above image. The remains of the 12-inch and 8-inch lines that served Reservoir 7 may also still be present underground. The concrete superstructure that supported those lines is still visible in the reservoir (see adjacent image). It is expected that the 4-inch-diameter fire water line shown surrounding Reservoir 5 is still present. Since Reservoir 7 was abandoned after the 1926 fire, an upgraded fire water line was never installed at that location. If a pipeline is exposed or is encountered in grubbing, scarifying, or obtaining borrow soil, it will There is a lot of concrete and concrete debris within cled to create crushed gravel for use on Five monitoring wells in OU #2 will be destroyed. Two of the monitoring wells are found in be removed and disposed of as described in Section 6.4.4. Those portions of existing lines that lie outside of the work area will be cut, flushed, pigged (if possible), and capped as described in Section 6.4.2. the work boundary of each reservoir. This includes old pump and lightning tower foundations, valve boxes, vaults, and other supports that were used during historical operations. There are also several small piles of broken concrete on the floor of Reservoir 5 (Figure 28). It also includes the concrete walls of the reservoirs that were cast on the berm slopes. The approximate extent of the walls for Reservoirs 5 and 7 is illustrated in Figure 28 and Figure 29, respectively. Although there appears to be little of the original walls left in Reservoir 5, much of the original walls remain in Reservoir 7 (see adjacent photograph). Concrete debris will be removed from the work area. If practical, it will be recy this project. Otherwise, it will be hauled offsite for recycling. Concrete that is too impacted by petroleum will be hauled away for disposal at an appropriate facility. Reservoir 5 and three are found in Reservoir 7 (see Figure 28 and Figure 29, respectively). The monitoring wells are within the proposed cap boundaries. The procedures described in Section 6.5 will be used to abandon the monitoring wells. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 49 San Luis Obispo, California December 18, 2007 Reservoir 7 – accumulated debris in reservoir bottom It will also be necessary to remove the seepage study equipment that was installed to determine the process by which sheen formed on the open water of the reservoirs and which contributed to the design of the caps proposed in this Remedial Action Plan. The structures were constructed by excavating holes into the reservoir bottoms and installing large-diameter corrugated metal pipes on end. The annular space between the corrugated metal pipes and the soil was sealed with grout. The interiors were partially filled with clean sand and were instrumented to monitor water levels. Observations of water and LNAPL levels within the structures and the surrounding monitoring wells provided our current understanding on sheen formation. Any remaining instrumentation will be removed from the structures and returned to Chevron for final disposition. Any remaining PVC sounding tubes will be pulled from the ground and disposed. The corrugated metal pipes will then be pulled from the ground using a backhoe or similar large piece of equipment. Any resulting void space will be filled during placement of the gravel layer, as described below. Other debris, concrete, or metal that is discovered within the work area will also be removed. This will include the metal posts that are encountered at various locations, wire, fire hydrants, and other debris. Metal and concrete will be recycled where practical. Other materials will be disposed of as appropriate to their characteristics. The last step prior to constructing the cap will be to expose the original concrete floor of the reservoirs. As can be seen in the adjacent image, there is a variable thickness of accumulated soil and organic matter. It is estimated that Reservoir 5 will generate 15,300 cubic yards and Reservoir 7 a further 11,000 cubic yards, for a total of 26,300 cubic yards. This will be stripped and disposed of at an appropriately permitted facility. Implementation of this part of the remediation will be most successful if accomplished in the summer, fall, and possibly early winter if there is little precipitation that year. Remediation may be postponed during periods of high groundwater levels and water in storage in the reservoirs. Once construction has begun, it should be finished as quickly as possible to prevent having to manage petroleum-impacted water. The proposed grading plans for Reservoirs 5 and 7 are illustrated in Figure 30 and Figure 31, respectively. A diagram of the cap profile is shown in Figure 32. The engineering drawings (Appendix C) include the detailed designs for the caps. Once the floor has been exposed, the reservoir bottom can be backfilled with gravel. As described in Section 5.3, this material will be selected and placed so that it provides a low-resistance pathway for groundwater and LNAPL to move into during their seasonal fluctuations. Consequently, it is desirable to have a relatively uniform material with little to no Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 50 San Luis Obispo, California December 18, 2007 fine material (i.e., particle size less than No. 200 sieve). This will create large void spaces with little resistance to flow and a low likelihood of future clogging. The gravel will be placed in lifts no greater than 12 inches thick and will be nominally compacted by one pass of a steel drum roller. Placement of the gravel will be controlled by the nominal top-of-layer elevation. These elevations, 119.20 feet above mean sea level (amsl) for Reservoir 5 and 123.50 feet amsl for Reservoir 7, are based on the relative differences between the known concrete floor elevations and the highest observed local groundwater elevation plus a 1.5-foot factor-of-safety. The top of the gravel is above the downgradient ground surface of the reservoirs. Water cannot rise above this elevation within the reservoir without daylighting outside the reservoir, thereby controlling water levels within the reservoirs. The floor elevation of Reservoir 5 is 115.50 feet amsl, and the highest measured groundwater elevation between 1999 and 2002 was 117.70 feet amsl. Similarly, the floor elevation of Reservoir 7 is known to be 116.50 feet amsl, and the highest recorded groundwater elevation was 122.00 feet amsl. The top of the gravel layer can be no less than the specified design elevations, and results in a minimum thickness of 3.7 and 7 feet for Reservoirs 5 and 7, respectively. It will be acceptable for the contractor to allow the gravel layer to be thicker, but the final surface cannot have depressions or low spots that dip below the nominal top-of-layer elevations. As shown in Table 4, it is estimated that 20,100 cubic yards of gravel will be needed to fill Reservoir 5, and another 39,000 cubic yards will be needed for Reservoir 7. A 12-ounce 4 geotextile will be placed over the gravel to prevent migration of fine soil particles into the void spaces from the overlying soil layers. The geotextile will be anchored in a trench dug around the original concrete floor. The trench will be dug into a shelf cut into the existing berm. The shelf will be approximately 3 feet wide. It is anticipated that the trench will be dug by a small pocket-size excavator with an arm that can be offset from the machine’s centerline. The trench will be centered in the shelf and will be approximately 1 foot wide and 3 feet deep. The configuration of the shelf and anchor trench is illustrated in Figure 33. The trench locations for Reservoirs 5 and 7 are shown in Figure 30 and Figure 31, respectively. The geotextile will be placed as required by the manufacturer. This will include trimming the edges that go into the anchor trench and sewing adjacent rolls together at their overlapped edges. Pro-forma calculations have been included in Appendix I that demonstrate the selected geotextile will prevent soil migration, has adequate tensile strength, and that the anchor trench is sized appropriately to prevent pull-out. The final grades shown in Figure 30 and Figure 31 will be achieved by placing common fill with a 1-foot surface veneer of topsoil over the geotextile. The objective with these grading plans is to produce as natural-looking landform as possible. The final grade will be nominally controlled by grading from a control contour established near the top of the cap. The surface will slope at 4 Geotextile is typically identified by its weight per square yard. Therefore, an 8-ounce fabric weighs 8 ounces per square yard. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 51 San Luis Obispo, California December 18, 2007 no more than 4:1 (horizontal:vertical). Ditches will be established around the perimeter of the cap to ensure proper runoff of storm water. The final configuration of the slopes and ditches will be developed in the field to best integrate with the surrounding topography within the other parameters of the design. It is estimated that Reservoir 5 will require 12,500 cubic yards of common fill and 12,600 cubic yards of topsoil. As shown in Figure 30, the berm borrow around Reservoir 5 could generate another 26,300 cubic yards of common earth that could be used for fill around the site. This material will only be removed if needed elsewhere onsite. Reservoir 7 is expected to require 24,500 cubic yards of common earth and 11,000 cubic yards of topsoil for cap construction. An additional 8,300 cubic yards of soil are potentially available from the local berm borrow if needed elsewhere onsite. The slopes and ditches are designed to minimize potential erosion. The ditch slopes will vary between 0.5 and 2 percent and are designed to accommodate the 100-year return period storm. The discharge points of each ditch are provided with some type of energy dissipation. Where velocities are less than 2 feet per second, a simple gravel mat is supplied. If the exit velocities are greater than 2 feet per second, a reinforced rip-rap energy dissipater will be installed. The hydrology and hydraulic calculations supporting the ditch dimensions and energy dissipaters are found in Appendix G. The U.S. Soil Conservation Service recommends limiting soil erosion to less than 2 tons per acre per year. The calculations in Appendix J show that the estimated annual soil loss from the caps is 0.53 ton per acre and 0.77 ton per acre for Reservoirs 5 and 7, respectively. The surfaces of the Reservoir 5 and 7 caps will be revegetated with an approved native plant seed mix. The specifications for this seed mix will be developed in conjunction with the forthcoming Habitat Mitigation Plan. The surface of the cap will be scarified to a depth of at least 3 inches. Prior to the onset of the rainy season, and preferably as close as possible to the season’s first rain, the seed mix will be applied. The caps will be protected after application of the seed with jute net or spray-applied mulch that will minimize erosion until the vegetation can take root. As noted previously, remediation of the Tank Farm results in unavoidable impacts to existing wetlands, some of which include desirable vernal pool fairy shrimp habitat. The demolition plans depict the wetlands on and around Reservoirs 5 and 7. Impacted wetlands are shown in blue, while wetlands not affected by construction are shown in green. Some of the wetland impacts will be temporary and the existing wetlands will be reestablished after remediation is complete. Those impacts that are permanent will be mitigated at another location onsite to be selected as the Habitat Mitigation Plan evolves in concert with the environmental analysis for the project. A summary of the estimated habitat impacts is provided in Table 5. It is estimated that 4.83 acres of wetland habitat in and around Reservoir 5 will be affected by remediation. Of this total, 3.59 acres will be permanent impacts requiring mitigation at another location onsite. Approximately 1.21 acres of the affected wetlands are also vernal pool fairy shrimp habitat, although only 0.04 acre of that habitat is permanently removed from service. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 52 San Luis Obispo, California December 18, 2007 Due to their similar size and configuration, the amount of habitat affected by remediation of Reservoir 7 is similar to that for Reservoir 5. The total wetland impact is estimated to be approximately 4.22 acres with a permanent impact of 3.65 acres. Of the total wetland impact, 0.90 acre has been identified as vernal pool fairy shrimp habitat, and 0.35 acre will require mitigation at another location onsite. Both caps are expected to affect the habitat for rare plants onsite. The Reservoir 5 cap will affect 0.31 acre of habitat, but only 0.03 acre will be a permanent impact. Similarly, the Reservoir 7 cap will affect 0.28 acres of rare plant habitat, of which 0.15 acre will require mitigation at a different location. Settlement is not anticipated to be a significant issue for the Reservoirs 5 and 7 caps. The caps will be constructed over the original concrete floors, which will tend to evenly distribute the overlying soil loads. The cap is further reinforced by the geotextile, which, within limits, will also distribute loads and provide a bridging support over localized weak spots. In addition, it is likely that the soils directly beneath the reservoir are overconsolidated; that is, they have experienced greater bearing stress than they currently experience. The reservoirs were loaded with a 20-foot or more thickness of oil for many decades. That historical load will have worked to compress the soils, and it is expected that additional settlement should be minimal. To ensure proper performance of the caps, future settlement will be monitored. Three monuments will be placed on and around the cap, as shown on the grading plans for each of the caps. The monuments will be of a standard design acceptable to the City or County. Typically, a survey monument will consist of a 5/8”-diameter steel or aluminum rod between 3 and 5 feet in length. The rod is driven into the ground and then topped with a domed cap that threads onto the rod. One monument will be located on the top of the cap, another near the edge, and a third at a location adjacent to the cap on native ground. Monitoring of the cap will be as described in Section 9.0 7.3 OU #3/FLOWER MOUND/BORROW AREA NO. 2 REGRADING OU #3 is located on the eastern side of the Tank Farm north of Tank Farm Road (Figure 14). As noted in the Feasibility Study, this area includes the remains of Reservoir 4, and has several plastic hydrocarbon surface expressions that pose potential entrapment hazards. Chevron has elected to implement a closure approach for this OU that supports future development in accordance with the proposed land use plan (Figure 10). This entails excavation of the surface expressions and construction of a cap over the former reservoir. It also includes grading of the Flower Mound and Borrow Area No. 2 to support future development. The work area boundaries for OU #3 and the Flower Mound, and Borrow Area No. 2 are shown in Figure 34. Site disturbance associated with remediation of OU #3 grading of the east end of the property will be confined to this area. Preparation of the site for remediation will include clearing, grubbing, removal of the protective enclosures and monitoring wells, and demolition and removal of concrete debris and pipeline remnants. A demolition plan for the Reservoir 4 Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 53 San Luis Obispo, California December 18, 2007 Abandoned concrete lightening stand foundation area is shown in Figure 35, and a demolition plan for the Flower Mound area is shown in Figure 36. Clearing and grubbing will remove vegetation from the work area. Grubbed vegetation will be managed as allowed by San Luis Obispo County, the RWQCB, and the APCD. A chainlink fence secures the property along Tank Farm Road and along the eastern property line. A barbed-wire fence separates the Reservoir 4 area from other portions of the site. The barbed-wire fences are used by ranchers to create paddocks suitable for cattle grazing. The chainlink fence will be maintained, except that minor modifications will be made in its alignment to maximize the working area. The barbed-wire fence will be removed. Five monitoring wells will be abandoned within OU #3. These are SP-6, SP-7, TMW-2, TMW-8, and TMW-9. These wells are included on the list in Table 2. The wells will be abandoned as described in Section 6.5. Replacement of the monitoring wells will be as prescribed by the RWQCB. There are four protective enclosures clustered adjacent to the northwest boundary of Reservoir 4. These will be removed and recycled or disposed of as appropriate. It is presumed that plastic surface expressions are beneath each of these enclosures. The underlying soil will be excavated in accordance with Section 4.2 and the more specific descriptions found later in this section. Concrete foundations for the lightning towers and pumps are still found surrounding the reservoir (Figure 35). These will be removed from the work area and crushed for use as gravel elsewhere on the site, or will be sent offsite for recycling. In addition, frames constructed of wood and concrete (believed to be test plots from a previous study) are found on the west side of the reservoir. These will be removed for disposal at a permitted facility. The remains of the foundations for the reservoir roof and interior wall can be seen in the field and are shown in Figure 35. The contractor can abandon these foundations in place as long as they do not interfere with achieving the lines and grades shown in Figure 38. The contractor will also have the option of recovering the foundations to create gravel for use elsewhere onsite if it can be shown that the cost would be less than importing material from offsite. Crude oil and water lines historically served Reservoir 4 (Figure 5). It appears that most of the crude oil line has been removed (see adjacent image), or is possibly buried within the reservoir. There are exposed portions of the water line, but it is believed to be substantially intact due Reservoir 4 – abandoned oil pipeline Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 54 San Luis Obispo, California December 18, 2007 to the hydrants that still surround the reservoir (Figure 34 Reservoir 4 (OU #3), Flower Mound and Borrow Area No. 2 Work Areas Figure 35). The remains of the crude oil line will be exposed and removed to a point outside of the work area. Some of the water line is exposed at the surface; other portions are within the area that will be used as common earth borrow for the cap construction. As such, the water line will be cut at the three locations where it appears to enter the work area. Those portions within the work area will be removed, while those sections outside of the work area will be capped and managed as described in Section 6.4. Figure 37 shows the areas where soil has been impacted by plastic hydrocarbon. This area is approximately 8.35 acres and is estimated to contain as much as 40,400 cubic yards of impacted soil. The contractor shall segregate asphaltic material and clean soil during the excavation. Those materials can be incorporated into the structural fill for the cap. Excavation shall be performed as described in Section 4.2. The remaining subgrade will be compacted to at least 95 percent of its relative maximum density per ASTM D1557. Geotextile will be used to identify the cap bottom and to provide some structural support in the event of differential settlement. The potential for settlement is discussed later in this section. Approximately 342,900 square feet of geotextile will be anchored in a trench positioned around the former reservoir as shown in Figure 37. The trench will be 1 foot wide and 3 feet deep. Calculations estimating the resistance to pull-out for this trench (including potential strain induced by differential settlement) are provided in Appendix I. The proposed grading plan for the Reservoir 4 cap and the Flower Mound is shown in Figure 38. The grading plan ensures a minimum of 4 feet of cover over the former reservoir bottom. The maximum thickness is approximately 11 feet, and the average thickness is just over 6 feet. The primary feature of the grading plan is the extension of Santa Fe Road. From Tank Farm Road, the rough climbs along gently sweeping curves for approximately 1,200 feet at slopes ranging between approximately 1 and 3 percent. It reaches a high point at approximately elevation 164, and then slopes downward approximately 400 feet to elevation 160, where it ties into the existing grade at the northern property boundary. The highest point of the grading area is at the northwest corner of the Flower Mound. From that point, most of the grade slopes between approximately 1 and 3 percent to the southwest. A portion of the northwest corner of the grading area slopes to the northwest, generally following the northern down slope of the Santa Fe Road extension. A small collector road connects with Tank Farm Road approximately 1,200 feet west of the future Santa Fe Road intersection. The collector road rough grade runs generally north approximately 900 feet at a slope of approximately 1 percent. At this point the collector road turns to the east and intersects the Santa Fe Road extension about 800 feet away. The slope of the eastern leg varies from approximately 3 to 10 percent. West and north of the collector road the grade slopes generally westward until it ties into the existing grade. On the east side of the grading area, approximately 900 feet north of Tank Farm Road is a small drainage basin that collects run-off from the entire grading area. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 55 San Luis Obispo, California December 18, 2007 The layout of the cap and grading supports future development within the bounds of the proposed land use plan. It also includes the rough grading necessary to construct the extension of Santa Fe Road, and provides access to a land-locked parcel along the east property line. In addition, the grading improves the utility (and consequently the value) of the surrounding properties. It also provides a reasonably smooth transition to the former recycling area, which will be used as the contractor’s primary staging area. It is estimated that this grading plan will require approximately 262,800 cubic yards of structural fill. However, the Flower Mound borrow area is expected to generate at least 328,200 cubic yards, and up to 402,000 cubic yards if Chevron has access to the off-site material Some of the excess may be used to regrade Borrow Area No. 2. After topsoil removal, structural fill will be placed as shown in Figure 39. As noted previously, the limits shown in the figure are proposed for development in both the AASP and proposed land use plans. A portion of the grading establishes the rough grade for the Santa Fe Road extension south of Tank Farm Road. The remaining grading establishes contours that will support future development of the site. Enhancement of existing drainages and the construction of new channels and detention features are required to adequately manage storm water. However, the features shown in this Remedial Action Plan are temporary, though they may be used for several years. Development of the area will include construction of a storm drain system, which will replace much of the overland system. Since even the first phase of development may follow remediation by several years, a properly designed and functioning overland system is necessary to prevent excess erosion and transporting unwanted sediment to the North Marsh wetland complex, to which this area is ultimately tributary. Supporting hydrology and hydraulics calculations for the overland system are provided in Appendix G. The hydrologic design point for the area north of Tank Farm Road is identified on Figure 38. Overall, the peak flow to this point has been reduced, mostly due to the longer travel path that water must flow over, which results in a longer time of concentration. The existing peak flow at this point during the 100-year storm is estimated to be 67 cubic feet per second. The peak flow for the same storm after grading is estimated to be approximately 51 cubic feet per second. Most of the graded areas will drain by sheet flow to the roads. The rough graded interior roads collect storm water and direct it to large, over-sized swales along Tank Farm Road and the north property boundary. The larger swale along Tank Farm Road discharges to an even larger swale along the toe of the collector road slope. That swale and the swale along the northern property line discharge to a small sediment removal basin just before the design point. The swales are broad and will be roughened and vegetated to reduce flow velocities, minimize erosion, and limit sediment transport. Regrading of Borrow Area No. 2 will alter the hydrology. At present, precipitation is trapped in a closed catchment. Rough grading of the Santa Fe Road extension will permit 2.9 acres to discharge directly to the East Fork of San Luis Obispo Creek. The peak flow of this discharge during the 100-year storm is estimated to be 5.1 cubic feet per second. This is a relatively minor Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 56 San Luis Obispo, California December 18, 2007 contribution to the overall flow of the creek, and is unavoidable if Santa Fe Road is to be extended as described in the Airport Area Specific Plan. In addition to the erosion control measures previously described, additional BMPs will be provided to minimize the potential for erosion from the cap to the wetlands. Unmitigated, soil erosion could be as much as 1.38 tons per acre per year (Appendix J). It is anticipated that the BMP regime will substantially lower this total. The ditches along the top of slope of the cap will be provided with sandbag chevrons to slow water flow and allow sediment to drop out of suspension. Further, the surface and slopes of the cap will be covered with spray-applied mulch, which will be maintained until the property is developed. Remediation activities in OU #3 and the Flower Mound will affect wetland and rare plant habitat, which is summarized in Table 5. Two acres of wetland habitat will be impacted, although this is a permanent impact requiring mitigation elsewhere onsite. None of the impacted wetland is considered vernal pool fairy shrimp habitat. Remediation will also permanently affect 3.4 acres of rare plant habitat. Regrading of Borrow Area No. 2 will permanently affect 1 acre of wetland of which 0.67 acres is vernal pool fairy shrimp habitat. It will also permanently affect 1.4 acres and temporarily affect 0.2 acres of rare plant habitat. It was noted previously in this section that there is a potential for settlement to occur. It is believed that decommissioning of Reservoir 4 included pushing berm material over the concrete floor. Field inspections of this material indicate that it has not been compacted. The Geotechnical Feasibility Study (Padre, 2007a) estimated that settlement may be on the order of 3 to 4 inches. During construction, the upper few feet of existing material will be compacted. It is not intended, however, to expose and recompact petroleum impacted soils. Since the planned grading is much thicker than the previously envisioned cap (11 feet versus 4 feet), it is expected to provide improved support. In addition, a 12-ounce geotextile will be used to provide additional tensile strength and load distribution capacity. However, development will require lot- and building-specific geotechnical studies. Future foundations may require geogrid support or the use of piles if the thicker fill has not adequately compressed the underlying layers.. This latter approach would require handling spoils and other excavated materials in accordance with the Soil Management Plan and will be specified in any land use covenants attached to future parcels in this area. Potential settlement of the cap will be monitored through the use of survey monuments. It is proposed that five monuments be installed in and around this operable unit. Their locations are shown in Figure 38. A typical survey monument detail is shown in Figure 27. The survey monument consists of a 5/8-inch-diameter steel or aluminum rod driven to a depth of between 4 to 6 feet bgs. The rod is topped with a threaded cap mounted flush with the ground that identifies the monument. The monuments will be periodically surveyed as part of the long-term maintenance requirements for the site. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 57 San Luis Obispo, California December 18, 2007 In addition to possible high-load foundation requirements, the land use covenant will specify the various institutional controls that will accompany title to the property. These will include prohibitions on groundwater use in impacted areas, limitations on excavation, impacted soil management requirements, as well as general guidelines on the use of vapor barriers for habitable structures. An example of these guidelines is provided in Appendix M. 7.4 OU#4-REMAINING SITE-WIDE TERRESTRIAL AND WETLAND AREAS The remaining site-wide impacted terrestrial and wetland areas are addressed as OU #4. It includes three areas of concern. The first, AOC #1, is the North Marsh adjacent to the Northwest Operations Area. The second, AOC #2, is Reservoir 3, and AOC #3 is the remaining plastic (“sticky”) hydrocarbon surface expressions. 7.4.1 AOC #1-North Marsh The North Marsh is a large (approximately 11.9-acre) wetland complex adjacent to the Northwest Operations Area. The SERRT identified this area as requiring remediation as a result of the numerous surface expressions that posed potential entrapment hazards to small animals. After careful consideration, Chevron determined, and documented in the Feasibility Study, that the preferred approach to remediation would be to excavate the hydrocarbon material and restore the wetland in place with improved function and environmental utility. The work area for OU #3/AOC #1 is defined by the clear and grub line shown in Figure 41. The contractor will, to the extent possible, stockpile and protect cleared wetland vegetation. Greater detail regarding selecting, segregating, stockpiling, and maintaining vegetation will be provided in the Habitat Mitigation Plan. One possible stockpile location is shown adjacent to the North Marsh in Figure 41. Other locations can be used, as necessary, as long as they minimize impacts to existing and otherwise unaffected habitat. Every attempt will be made to minimize working outside of the excavation limits. However, it is also recognized that the excavation areas may expand in order to fully capture the hydrocarbon materials within the wetland. There are three protective enclosures within the work area. These will be dismantled and removed for disposal or recycling, as appropriate. Since they are each within the wetland, the presumption that they enclose plastic hydrocarbons is addressed by the excavation described later in this section. A small pile of concrete debris was identified on the east side of the wetland (Figure 41). This material will be removed for disposal. It may be recycled into gravel for use elsewhere on the site (if feasible), or it may be removed from the site for recycling, depending on the project economics. As discussed in Section 5.5.4, the facility used a location adjacent to the wetland for debris disposal following the 1926 fire. Field observations indicate that inert materials, such as wood Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 58 San Luis Obispo, California December 18, 2007 posts, fencing, and concrete, were the principal materials discarded at this location. The area covers approximately 2.3 acres and is estimated to be on the order of about 5 feet deep. This suggests that there may be around 18,000 cubic yards of debris present. In the near term, Chevron will characterize the materials interred at this location so that they can be properly managed during remediation. At a minimum, the site will be cleared of debris when remedial activities for the North Marsh begin. It is also possible that Chevron might expedite the work if it would facilitate other remedial activities. There are two monitoring wells in the work area that will be abandoned, B-36 and SP-4. They are more fully described in Table 2 and their locations are shown in Figure 41. The wells will be abandoned as described in Section 6.5. There are three other monitoring wells (B-33, B-35, and MW-16) that are immediately adjacent to the work area. These will be protected in place if possible. PG&E and AT&T have utilities (power and telecommunications, respectively) that cross the work area adjacent to Tank Farm Road (Figure 41). The contractor will be responsible for protecting those utilities in place. Several of the old facility pipelines intrude into the excavation area, as shown in Figure 41. The historical records indicate that there are a water line and two foamite lines in the north part of the excavation limits crossing in an east-west direction (approximately 400 lineal feet each in the work area, approximately 1,200 lineal feet total). These lines appear to have been used for fire suppression purposes at the 55,000-barrel ASTs. There are two former crude oil lines that cross the excavation area in an east-west direction almost at the midpoint (approximately 860 lineal feet each in the work area, 1,720 feet total). A water line and natural gas line (the latter is reported to have been abandoned) run parallel to Tank Farm Road in the unpaved shoulder area (approximately 270 lineal feet each in the work area). Another water line is found at the southwest end of the excavation area crossing in a north-south direction. A stub off that line protrudes into the excavation area approximately 60 feet in an easterly direction. It is likely that pipeline abandonment will occur prior to remediation in the North Marsh. As such, the lines will have been flushed and the larger lines pigged. If the lines are not exposed during excavation, they will be abandoned in place as described in Section 6.4. If the lines are exposed during excavation of the North Marsh, they will be removed for disposal. The lines will be cut approximately 10 feet outside the work area. The exposed pipeline end will be capped and the local excavation will be backfilled with common fill. A preliminary excavation boundary is shown in Figure 41. It is believed that this boundary includes all of the hydrocarbon expressions that affect the North Marsh. The boundary is delineated in this way mostly for permitting purposes so that the potential maximum impact is quantified in the environmental analysis. The entire excavation boundary, as shown in Figure 41, covers over 13 acres. The Feasibility Study estimated the average thickness of impacted soil to be 3.5 feet. Excavating to this depth within the boundary would generate 75,300 cubic yards of soil, most of which will require offsite management. The mapped hydrocarbon surface Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 59 San Luis Obispo, California December 18, 2007 expressions, in contrast, are only 7 acres (including the protective enclosures). Excavation limited to this area would result in a correspondingly lower volume (approximately 40,000 cubic yards). The actual volume is anticipated to be somewhere between these extremes, but the larger quantity will be used for planning purposes. Excavation is expected to proceed from the north to the south. This allows haul trucks to most readily access either Tank Farm Road for offsite disposal or the temporary impacted soil stockpile in the Northwest Operations Area. The potential haul routes are shown in Figure 17. The access point from Tank Farm Road shown on the figure is preferred since the Remedial Action Plan envisions some form of active traffic control at this location while work is in progress. Although remediation of the North Marsh will create the single largest wetland impact (11.9 acres) for the entire Tank Farm project, it does not affect any vernal pool fairy shrimp habitat, and the impacts are only temporary. In fact, remediation is expected to increase the size of the habitat by approximately 2.3 acres when the historical debris disposal area is cleaned up. Remediation may also temporarily impact up to 0.76 acre of rare plant habitat. The specifics for restoration of the North Marsh and other protected onsite habitats are currently being developed. The forthcoming Habitat Restoration Plan will provide the conceptual approach to be used in restoration and mitigation. The final plan, however, will be developed in consultation with the City, County, and regulatory agencies such as U.S. Fish & Wildlife Service, U.S. Army Corp of Engineers, the RWQCB, and the California Department of Fish & Game as the project proceeds through permitting and environmental analysis. 7.4.2 AOC #2-Reservoir 3 Reservoir 3 was one of the largest reservoirs and one of the last to be decommissioned. Although it contains a large wetland complex, it is unlike Reservoirs 5 and 7 in that the wetland is not of the open water type. Rather, it is generally a wet-marsh-type, with substantial pockets of plastic hydrocarbon exposed at the surface where it poses a physical, and possibly chemical, hazard to ecological receptors. Further, the wetland does not appear to be fed by groundwater, again distinctly different from the wetlands in Reservoirs 5 and 7. The preferred remedial alternative for this area of concern is to remove a limited amount of impacted material and replace it with the cap components, which will include geosynthetics that will create an impermeable barrier and help to support the overlying cap materials. This is anticipated to allow replacement, and possibly expansion, of the existing wetlands. The work area for Reservoir 3 is shown in Figure 42. This work boundary includes the adjacent wetland complex to the northwest that is impacted by plastic hydrocarbon surface expressions. Preparation of this work area will include clearing, grubbing, removal of concrete debris for recycling or disposal, dismantling and removal of the protective enclosures, and removal of exposed pipelines. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 60 San Luis Obispo, California December 18, 2007 Reservoir 3 – former concrete wall foundation There appears to be less concrete debris surrounding this reservoir than the others across the Tank Farm. There are a couple of lightning tower stands and some other loose concrete debris that will be removed for recycling. The remains of the original concrete that lined the reservoir berm slopes can also be observed at the ground surface (see image to left). Those portions that are within the excavation limits (Figure 42) will be removed for recycling as well, assuming that they are not heavily stained with hydrocarbon. Heavily stained concrete will be removed for disposal at an appropriately permitted facility. Reservoir 3 also contains the single largest protective enclosure on the Tank Farm. This enclosure and the one just outside the berm to the north of the reservoir will be dismantled and removed from the work area. If practical, the materials will be salvaged or recycled. If this proves impractical, the contractor will dispose of the materials in an appropriately permitted facility. Reservoir 3 – protective enclosure A single abandoned pipeline approaches the reservoir from the north (Figure 42). It is uncertain if the line even continues into the reservoir. The line will be flushed, pigged (if practical), and abandoned in place (as described in Section 6.4), assuming that it does not interfere with excavation or construction of the cap. If this assumption proves incorrect, the pipeline will be cut outside the work area, capped, and the portion inside the work area will be removed for disposal. The water supply line that served Reservoir 3 appears to be well out of the proposed work area and is not expected to affect the work in this area of concern. It does appear, however, that the water line crosses several of the other plastic hydrocarbon surface expressions adjacent to the reservoir. Managing the water line at these locations is described in Section 7.4.3, below. Monitoring well MW-34, located on the southwest quadrant of the work area (Figure 42), will be abandoned. It will be abandoned as described in Section 6.5. Two other monitoring wells, MW-20 and MW-42, are adjacent to the work area and will be protected in place. The preferred remedy developed in the Feasibility Study recommended removing approximately 2 feet of existing material and replacing it with the components of the cap. Nominally, this would be effective in that the work area is essentially flat, though slightly higher in the center and the east. The resulting depression supports the wetland habitat in this area. The refined approach in this Remedial Action Plan is to remove the minimum 2 feet of material at the outer edge of the excavation, but to deepen the excavation in the center of the reservoir so that the Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 61 San Luis Obispo, California December 18, 2007 excavated bottom has a 0.5 percent slope toward the interior. It is anticipated that this excavation will generate approximately 26,700 cubic yards of hydrocarbon-impacted soil that will require removal and disposal. The excavation will start at elevation 134, which is also the elevation that the top of the cap ties into the existing ground along the outer edge of the reservoir. The entire surface of the cap will then be approximately the same elevation as the existing wetland complex, which should allow restoration and expansion of the existing habitat. The subgrade surface will be compacted to a depth of 6 inches to 90 percent of its relative maximum density per ASTM D1557. Construction equipment may require decontamination after compaction of the subgrade. Depressions in the subgrade resulting from compaction will be restored to the lines and grades of the design with common fill. A liner system will be installed over the subgrade to prevent the remaining hydrocarbon materials from migrating to the surface. The liner system will consist of (from bottom to top): 12-ounce geotextile; a 12-inch layer of gravel with a triaxial geogrid installed mid-thickness; 12-ounce geotextile; 40-mil high density polyethylene (HDPE) liner; 12-ounce geotextile; variable thickness (0-18 inch) common fill; and 1-foot thickness of topsoil. An illustration of the liner section and the anchor trench detail is shown in Figure 44. The lower portion of the liner system is intended to bridge potentially soft portions of the remaining soils in the reservoir. A 12-ounce non-woven geotextile will be installed to ensure that fine soil particles do not migrate into the gravel layer. A 6-inch thickness of gravel will be placed over the geotextile. The initial 6-inch layer will be nominally compacted by at least one pass of a steel drum roller. A triaxial geogrid (Tensar TX-160, or equivalent) will be installed per manufacturer’s specifications and secured in an anchor trench around the perimeter of the original reservoir bottom (Figure 43). The geogrid will be covered with an additional 6-inch layer of gravel. As noted above, the purpose of this component of the liner system is support. For design purposes, it has been assumed that the center of the cap tries to settle by approximately 2 feet, equivalent to a 50 percent consolidation of the original impacted soil remaining between the excavation bottom and the original reservoir bottom. While each of the geosynthetic materials can readily accept the resulting strain, it is expected that the strain will be taken up first by the geogrid, which is designed for this type of application. Further, the geogrid will better distribute loads across the foundation, lessening the potential for differential settlement. This type of geogrid is a relatively new product, but is better at locking aggregate materials and provides superior load distribution than bi-axial geogrids. Supporting calculations for the geosynthetics are provided in Appendix I. Three additional geosynthetic components will be placed on the compacted gravel. These will consist of a 40-mil HDPE flexible membrane liner (FML) over an 12-ounce non-woven geotextile and beneath an 12-ounce non-woven geotextile. The FML creates an impermeable barrier to future migration of hydrocarbon-impacted soils. It also will minimize infiltration losses from the overlying wetland. The primary purpose for the geotextiles is to protect the FML from punctures and abrasions due to angular particles in the common fill. A secondary purpose Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 62 San Luis Obispo, California December 18, 2007 for the geotextiles is to assist in distributing soil loads and bridging soft soils. Since the subgrade slope is so mild (0.5 percent), the use of smooth rather than a textured FML will be acceptable. A variable thickness of common fill will be used to create a nominally level surface across the reservoir. It will be as much as 18 inches thick in the center of the reservoir and will taper out as it reaches the anchor trench bench (Figure 44). The common fill will be pushed onto the geosynthetics from a minimum 1-foot-thick layer. Equipment will not be allowed to operate directly on the geosynthetics. A 1-foot-thick layer of topsoil will be used to complete the cap. The topsoils will only be nominally compacted, and will be scarified prior to revegatation. Restoration of the wetland habitat will be performed in accordance with the Habitat Mitigation Plan. A primary design objective of this remedial alternative has been to facilitate restoration and improvement of the existing wetlands while removing the potential for contact with the hydrocarbon-impacted soils. The liner system provides separation, and the design grades are intended to direct water within the catchment of the reservoir (approximately 11.5 acres) to accumulate in the wetland complex. Seasonally, approximately 12.5 acre-feet of water will accumulate within the new 6.5-acre wetland complex. Remediation at Reservoir 3 will have a temporary impact to the entire existing 4.23-acre wetland complex, which is also vernal pool fairy shrimp habitat. Once remediation is complete, however, the entire habitat will be restored, and it is expected that an additional 2.27 acres of habitat will have been added (that is the entire area covered by the cap for Reservoir 3). Remediation will also affect 0.38 acre of existing rare plant habitat that will be mitigated elsewhere onsite. Some settlement is anticipated (and considered desirable) after construction of the cap. The various geosynthetic elements of the cap are capable of withstanding the likely strains that may be imposed during settlement and are reinforced with a geogrid designed to limit excessive settlement. The excavation plan is designed to provide some additional weight over the center of the reservoir and encourage the greatest relative amount of settlement at that location. This is intended to encourage water to pool towards the center of the reservoir. Settlement will be monitored by three settlement monuments, as shown in Figure 43. One will be located as near to the center of the reservoir as practical, a second will be installed over the cap towards the perimeter, and a third will be installed locally on undisturbed ground. These monuments will consist of the typical cap section but will be cast into concrete blocks approximately 12 inches on a side. 7.4.3 AOC #3-Other Sticky Hydrocarbon Surface Expressions There are an additional 12 areas affected by plastic hydrocarbon surface expressions. These are shown in Figure 45. It is proposed to excavate these areas as described in Section 4.2, and backfill them with common fill and 1 foot of topsoil at the surface. Several of these areas are adjacent to or within the work areas for other remedial activities, such as Reservoir 5 and Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 63 San Luis Obispo, California December 18, 2007 Reservoir 3. As a practical matter, those sites will be excavated in conjunction with preparing the work areas for the larger remedial activities. The 12 locations comprise 5.90 acres and are estimated to generate approximately 28,700 cubic yards of potentially hydrocarbon-impacted soil requiring offsite disposal. Backfilling the excavations will require 19,200 cubic yards of common earth and 9,500 cubic yards of topsoil. Generally, the upper 3 inches of topsoil will be scarified after placement and seeded with a mix to be specified in the Habitat Mitigation Plan. Approximately 0.97 acre of wetland habitat, including 0.93 acre of vernal pool fairy shrimp habitat, will be temporarily impacted by the excavations. Wetland habitat will be restored as described in the Habitat Mitigation Plan. Remediation will also temporarily affect 0.19 acre of rare plant habitat. In addition to the excavations, there are approximately 2.18 acres of wetland habitat that also supports vernal pool fairy shrimp that will be ripped to a depth of no less than 15 inches on at least a 24-inch grid. The upper 3 inches of soil will be scarified; that is, broken up into small pieces (Figure 43). This habitat is impacted by asphaltic hydrocarbon that, while not an ecological risk or physical hazard, still impairs the function of the wetland. It is believed that scarifying the surface will encourage improved plant growth. 7.5 OU#5-SITE-WIDE GROUNDWATER Monitored natural attenuation will be implemented using the same parameters and methods as specified in Monitoring and Reporting Program 93-120 (Appendix B). However, remediation will require abandonment of several monitoring wells (Table 2). Replacement will be determined in concert with the RWQCB, which will also approve a revised Monitoring and Reporting Program. At a minimum, monitoring groundwater for TPH and BTEX (consistent with M&RP 93-120) will be performed at the remaining perimeter monitoring wells MW-49, MW-50, MW-56, and SLOW-17, and the off-site production wells 11Ea and 11Eb. Currently, monitoring is performed on a semiannual basis. After three years, the RWQCB will evaluate the semiannual groundwater data to determine if a reduction in the monitoring frequency is warranted. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 64 San Luis Obispo, California December 18, 2007 8.0 HABITAT IMPACTS AND MITIGATION The remedial actions described in this Remedial Action Plan will ultimately reduce potential human health and ecological risks. It will also improve the function and ecological value of various types of habitat found on the site. While these actions are being implemented, however, wetland and rare plant habitats will be impacted. Throughout the previous sections describing the remedial actions, collateral habit impacts have been identified. These are summarized in Table 5 and illustrated in Figure 46. In total, it is anticipated that remediation will affect 29.0 acres of wetland, 9.5 acres of vernal pool fairy shrimp habitat, as well as 4.8 acres of rare plant habitat. Most of the habitat will only be temporarily affected and will be restored following remediation. However, 7.8 acres of wetland, 0.4 acre of vernal pool fairy shrimp, and 1.08 acres of rare plant habitat will be permanently removed from service and will require mitigation elsewhere onsite. It should be noted that remediation will expand existing wetland habitat areas by approximately 5 acres, irrespective of other mitigation efforts. Some of the potential mitigation areas are shown in Figure 46. In general, the locations are found in areas that can expand upon existing habitat such as the North Marsh or the wetland complex in the southwest portion of the site. Restoration, improvement, and mitigation of impacted habitats will be described in the Habitat Mitigation Plan. A conceptual version of this plan is provided in . It provides additional detail on the delineation of wetland and rare plant habitats, opportunities and constraints related to mitigation, and proposed mitigation ratios for discussion. Habitat mitigation will be an ongoing point of discussion through the environmental analysis and permitting of this project. It is understood that the Habitat Mitigation Plan, as well as this Remedial Action Plan, will be revised as comments are received from external stakeholders such as the regulatory community. As the particulars of the mitigation ratios and acceptable mitigation areas are developed, the plans will be revised. It is expected that this will include detailed drawings showing the mitigation areas, specifications on planting and grading, and a habitat maintenance plan describing the frequency of watering, inspections, and procedures to follow to replace unsuccessful plantings. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 65 San Luis Obispo, California December 18, 2007 9.0 LONG-TERM MAINTENANCE Once the caps and other short-term remedial actions have been implemented, the long-term monitoring and maintenance phase of site closure will begin. Long-term monitoring is, in itself, considered a remedial action for various groundwater impacts. These have been previously discussed in Section 4.1. Long-term maintenance, however, is intended to ensure that those actions taken under this plan (e.g., excavations, cap construction) continue to achieve their remedial objectives. This is important, in that most of the impacted materials onsite will remain after remediation is complete, especially in the former reservoirs. Periodic inspection and, as necessary, maintenance are, therefore, necessary components of remediation. Inspection will primarily cover excavations, habitat restoration and mitigation areas, and the open space caps and development caps. In general, it is anticipated that inspections will occur periodically after a given remedial action is completed. The frequency of inspections will be established in concert with the appropriate regulatory agencies. It is tentatively proposed to conduct inspections quarterly for the first five years after construction and semiannually after that. Inspections will, at a minimum, look at the following: • signs of erosion or burrowing by animals • recurrence or new surface expressions of plastic hydrocarbon • successful revegetation • integrity of fencing and other onsite institutional controls • settlement Most of these activities will be visual inspections by trained technicians or subject experts (e.g., wetland habitat biologist). Settlement will be measured by properly trained technicians under the supervision of a surveyor or civil engineer licensed to practice in the state of California. Settlement measurements will monitor movement in the various caps. Inspections will look for resurfacing of plastic hydrocarbon expressions at the excavation locations, especially if material at depths greater than 5 feet was left in place. Inspections will also include other areas of the site overlying impacted soils and will look for new surface expressions. In either case, resurfaced material will be removed using the standards and protocols described in this plan. Further recurrence of a surface expression will prompt evaluation and a focused remedial action. The degree to which settlement is considered unacceptable will vary between caps. It is expected that significant settlement may occur at the Reservoir 3 cap. The geosynthetics are designed to accept strains of up to 2 feet. The caps to be built for Reservoirs 5 and 7 are somewhat more sensitive to settlement, in that it could compromise the void space available for Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 66 San Luis Obispo, California December 18, 2007 groundwater to occupy. These caps can accept settlements up to 1 foot, measured at the former reservoir centers before remedial activity would need to be considered. The development area caps are not expected to experience significant settlement prior to subsequent construction activities. It is anticipated, however, that any structures built on these caps will include careful geotechnical engineering that incorporates the limits and constraints of the caps. Over time, the caps may require maintenance. It is expected that this will be minor in nature and would include activities such as repairing drainages or discouraging bioturbation. It may also be necessary to replace topsoil if erosion is greater than expected or vegetation is slow to establish itself. Frequent maintenance, however, will be necessary for the storm water management features in the development areas. These include the surface mulching, cleaning of desilting basins, and periodic cleaning of the culverts located at the Northwest Operations Area. More significant repairs would be made as needed, and would be based on observations made during the periodic inspections. This would include regrading if low spots were to develop in caps other than Reservoir 3. While Chevron is committed to ensuring the long-term maintenance of this project, the mechanism for implementation has not yet been determined. Chevron may utilize its own forces or out-source the work to a third party with experience in habitat maintenance. The specifics of implementing long-term site maintenance will be developed in concert with the project stakeholders, including the lead municipalities, to ensure the long-term success of the project. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 67 San Luis Obispo, California December 18, 2007 10.0 SCHEDULE A preliminary project schedule is shown in Figure 47. It provides a high-level view of the anticipated timeline of the principal project components. The schedule shows the Remedial Action Plan being submitted to SLO County as part of a grading permit application on December 20, 2007. As discussed in the introduction, it is understood that a CEQA-compliant environmental review will be necessary for this project and that the lead agency will be the County. The CEQA process will be triggered by a request for a discretionary approval from a governmental agency. It is also understood that RWQCB approval of the Remedial Action Plan will be essential to any other project approval. The project schedule anticipates slightly more than one year for this process, but recognizes that time will also be necessary for the proposed land use changes and potentially annexation. Once the project is approved, remediation will begin. At present, it is anticipated that two years will be necessary to complete all of the remedial actions. This nominally avoids work during the rainy seasons. It is also understood that this schedule may be lengthened due to mitigation measures stemming from the environmental analysis, or as a practical limitation of available manpower and equipment resources. Nominally, construction is seen being completed near the end of 2011. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 68 San Luis Obispo, California December 18, 2007 REFERENCES American Public Works Association, Southern California Chapter, 1997, “Standard Plans for Public Works Construction,” BNI Building News. Associated Transportation Engineer, November 9, 2007, Chevron San Luis Obispo Remediation Project, Traffic and Circulation Study. Avocet Environmental, Inc., March 15, 2007, Feasibility Study, Former San Luis Obispo Tank Farm, 276 Tank Farm Road, San Luis Obispo, California. BBL Sciences, December 12, 2005, Risk Management Summary, Former Unocal San Luis Obispo Tank Farm, San Luis Obispo, California (Version 2.0). California Department of Toxic Substances Control (DTSC), Human and Ecological Risk Division (HERD), May 15, 1998, HERD Ecological Risk Assessment Note Number 1, http://www.dtsc.ca.gov/AsessingRisk/upload/econote1.pdf California Department of Transportation, 2003, Caltrans Storm Water Quality Handbooks, Project Planning and Design Guide, April 2003. Cleath & Associates, 2002, Well Construction and Testing, Groundwater Exploration, San Luis Obispo Tank Farm Property, San Luis Obispo, California, September 30, 2002. City of San Luis Obispo, 2005, San Luis Obispo Airport Area Specific Plan, City of San Luis Obispo Community Development Department, August 2005. Duncan, J. Michael, and Bingzhi Yang, 2002, Retaining Wall Stability Workbook Documentation, Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University England Geosystem, Inc., November 1, 2000, Seep Evaluation Trenching Report, Unocal San Luis Obispo Tank Farm, San Luis Obispo County. England Geosystem, Inc., April 17, 2001, Limited Site Assessment, Former SLOCO Recycling Center, Former San Luis Obispo Tank Farm, San Luis Obispo County, California. England Geosystem, Inc., October 15, 2001, Supplemental Site Characterization, Unocal San Luis Obispo Tank Farm, 276 Tank Farm Road, San Luis Obispo, California. England, Shahin & Associates, May 11, 1994, Supplemental Ground Water Investigation, Unocal Tank Farm Facility, 276 Tank Farm Road, San Luis Obispo, California. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 69 San Luis Obispo, California December 18, 2007 Fifield, J.S., 2004, Designing for Effective Sediment and Erosion Control on Construction Sites, Forester Communications, Inc., Santa Barbara. Frederick R.H., and J.F. Miller, 1979, Short Duration Rainfall Frequency Relations for California, Proceedings from the Third Conference on Hydrometrology, August 20-24, 1979, page 67. Goldman, S.J., K. Jackson, and T.A. Bursztynysky, 1986, Erosion and Sediment Control Handbook, McGraw-Hill, New York. ICBO, 1994, Uniform Building Code Volume 2, International Conference of Building Officials. Koerner, R.M., 1990, Designing with Geosynthetics, Prentice Hall, New Jersey. Padre Associates, Inc., 2007a, Geotechnical Feasibility Study, Tank Farm Property Tank Farm Remedial Action Project San Luis Obispo, San Luis Obispo County, California, October 23, 2007 Padre Associates, Inc., 2007b, Habitat Mitigation Plan, December 20, 2007. Padre Associates, Inc., 2007c, Soil Management Plan, December 20, 2007. Padre Associates, Inc., 2007d, Hydrocarbon Typing Methodology, December 20, 2007. Padre Associates, Inc., 2007e, Project Execution Plan, December 20, 2007. Prussing, G. F., L.C. Hampton, and C.F. Lienesch, 1926, San Luis Obispo and Stewart Tank Farm Fires, April 7 to 11, 1926: Union Oil Company of California, Los Angeles, California, Engineering Department Report Dated November 1, 1926. Remediation Technology Panel (RTP), May 9, 2006, Remediation Technology Panel (RTP) Assessment of Off-Site Migration and On-Site Surface Expressions of Hydrocarbons at the San Luis Obispo Tank Farm Site, prepared by Dr. David Huntley, San Diego State University; Dr. Paul Johnson, Arizona State University; and Dr. Kent Udell, University of California at Berkeley. Ratified May 9, 2006. Renard, K.G., 1997, Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Soil Loss Equation (RUSLE), USDA Agricultural Handbook No. 703. U.S. Department of Agriculture, Washington, DC. Schroeder, P.R., T.S. Dozier, P.A. Zappi, B.M. McEnroe, J.W. Sjostrom, and R.L. Peyton, September 1994, The Hydrologic Evaluation of Landfill Performance (HELP) Model: Engineering documentation for Version 3, EPA/600/9-94, U.S. Environmental Protection Agency Risk Reduction Engineering Laboratory, Cincinnati, Ohio. Remedial Action Plan Chevron San Luis Obispo Tank Farm Page 70 San Luis Obispo, California December 18, 2007 San Luis Obispo County (SLOCo), 2006, Private Sewage Disposal System, San Luis Obispo County Department of Planning and Building Department, July 6, 2006 U.S. Department of Transportation, 2001, Urban Drainage Design Manual, Hydraulic Circular No. 22, Second Edition, August 2001. Viessman W., and G.L. Lewis, 1996, Introduction to Hydrology, Fourth Edition, Page183. Tables Table 1 Summary of Operable Units and Preferred Remedies Chevron San Luis Obispo Tank Farm AOC #1 - LNAPL/BTEX-Impacted Groundwater Natural Attenuation + ICs + LTM AOC #2 - Surface Soils Capping + ICs + LTM OU #2 Reservoirs 5 & 7 -Capping + ICs + LTM OU #3 Reservoir 4 - Capping/Excavation + ICs + LTM AOC #1 - North Marsh Area Excavation + ICs + LTM AOC #2 - Reservoir 3 Capping + ICs + LTM AOC #3 - PPSH Areas Excavation + ICs + LTM OU #5 Site-Wide Groundwater -Natural Attenuation + ICs + LTM Operable Unit Area of Concern Preferred Remedy OU #1 Northwest Operations Area OU #4 Remaining Site-Wide Surface and Subsurface Soils Table 2 List of Active Monitoring Wells and Wells Proposed for Abandonment Chevron San Luis Obispo Tank Farm San Luis Obispo, California Active Monitoring Well ID Northing (feet) Easting (feet) Ground Elevation (feet) Total Depth (feet) Proposed for Abandonment 11Ea 2,286,403.33 5,766,242.72 120.12 11Eb 2,285,788.14 5,765,801.69 118.48 11Ec 2,285,291.33 5,765,508.27 116.83 11Ed 2,284,934.66 5,765,842.84 120.62 11La 2,284,552.74 5,766,755.02 114.77 MW-17 2,286,370.00 5,770,908.56 142.51 20.0 X MW-18 2,286,168.77 5,770,163.88 142.48 21.5 X MW-19 2,285,775.94 5,769,634.88 138.72 21.0 MW-26 2,285,032.40 5,766,234.06 117.84 21.0 MW-27 2,285,626.38 5,766,432.64 119.38 22.5 MW-29 2,284,254.39 5,768,615.77 132.06 23.0 MW-35 2,284,544.36 5,769,095.02 132.93 30.0 MW-38 2,284,771.55 5,767,041.29 113.77 30.0 MW-39 2,284,782.44 5,766,583.53 114.57 30.0 MW-40 2,286,140.64 5,766,491.67 117.04 30.0 MW-41 2,286,496.67 5,766,672.93 118.48 30.0 MW-43 2,284,257.98 5,768,184.71 130.61 25.0 MW-45 2,284,500.98 5,767,405.38 127.51 31.0 MW-46 2,284,071.49 5,767,817.56 131.14 30.0 MW-47 2,284,997.98 5,766,065.13 118.12 100.0 MW-48D 2,285,438.75 5,766,297.58 119.40 40.0 MW-48S 2,285,438.75 5,766,297.58 119.50 20.0 MW-49 2,286,660.91 5,766,079.56 122.55 40.0 MW-50 2,286,893.20 5,766,084.77 121.40 40.0 MW-53D 2,285,863.52 5,766,440.08 118.00 40.0 MW-53S 2,285,863.52 5,766,440.08 118.20 20.0 MW-56 2,286,751.61 5,766,088.21 120.67 41.5 SLOW-12 2,286,835.65 5,766,153.13 120.39 15.0 X SLOW-17 2,286,602.27 5,766,284.93 120.46 28.0 SLOW-18 2,286,728.07 5,766,212.88 120.21 26.0 X Table 3 Estimated Borrow Source Quantities Chevron San Luis Obispo Tank Farm San Luis Obispo, California Area Topsoil (cy) Common Earth (cy) Gravel (cy) Off-Site Cut (cy) Borrow Area - 1 9,000 27,200 0 0 Borrow Area - 2 20,700000 Borrow Area - 3 19,700 59,250 0 0 Borrow Area - Flower Mound 0 262,850 65,400 73,700 Reservoir 5 & 7 Berms 0 71,600 0 0 Total 49,400 420,900 65,400 73,700 Note: The Flower Mound borrow volume consists of on-site material only. The grading will generate approximately 73,700 cy of material outside of the property boundary. Table 4 Estimated Remediation Construction Quantities Chevron San Luis Obispo Tank Farm San Luis Obispo, California Grading Area(1) (sf) Work Area(2) (sf) Geotextile 12oz. (sf) Geomembran e (sf) Geogrid (sf) OU #1 - Northwest Operations Area 280,300 280,300 - - - - 53,400 - - - - 280,300 - - - - OU #2 - Reservoir 5 340,239 453,190 15,300 12,500 - - 20,100 12,600 340,239 - - - - OU #2 - Reservoir 7 295,939 349,815 11,000 24,500 - - 39,000 11,000 160,460 - - - - OU #3 and Flower Mound Borrow Area 2,290,570 2,290,570 - - - - 262,800 - - - - 342,886 - - - - OU #4 - North Marsh Area 580,800 678,988 75,300 53,800 - - - - 21,500 - - - - - OU #4 - Reservoir 3 300,161 581,436 26,700 5,100 - - 10,500 11,100 871,002 290,334 290,334 OU #4 - Remaining PPSH 256,873 155,860(3). 28,700 19,200 - - - 9,500 - - - Borrow Area 2 527,389 527,389 - - 57,900 - - - - - - - - - Total 4,872,271 5,317,548 157,000 115,100 374,100 69,600 65,700 1,994,887 290,334 290,334 Notes: (1) The grading area is defined by the cut or fill boundary of any given excavation or cap. (2) The work area, which is the entire area affected by remediation activities, includes all of the area within the identified clear and grub line. (3) Some of the work area for Remaining PPSH has already been accounted for in the work areas corresponding to Reservoirs 5, 7, and 3. Topsoil (cy) Geosynthetics Area Estimated Areas Estimated Impacted Soil Volumes (cy) Common Fill (cy) Structural Fill (cy) Gravel (cy) Table 5 Summary of Habitat Impacts Chevron San Luis Obispo Tank Farm San Luis Obispo, California Temporary (acres) Permanent (acres) Temporary (acres) Permanent (acres) Temporary (acres) Permanent (acres) Northwest Operations Area - - - - - - - - - - 0.26 Reservoir 5 1.24 3.59 1.17 0.04 0.28 0.03 Reservoir 7 0.57 3.65 0.55 0.35 0.13 0.15 OU-3 and Flower Mound Borrow Area - - 1.99 - - - - - - 3.35 North Marsh Area 11.92 - -- -- -0.76 - - Reservoir 3 4.23 - -4.23 - -0.38 0.40 Areas to be Ripped 2.18 - -2.18 - -1.78 - - Sitewide PPSH Areas 0.97 - -0.93 - -0.19 - - Access Roads 0.1 - -0.04 - -0.22 - - Staging Areas - -- -- -- -0.01 - - Total 21.21 9.23 9.1 0.39 3.75 4.19 Borrow Area No. 1 0.77 - -0.67 - -0.37 - - Borrow Area No. 2 - -0.98 - -0.67 0.20 1.38 Borrow Area No. 3 6.59 - -3.12 - -0.92 - - Borrow Areas Remediation Areas Area Wetland Impacts VPFS Impacts Rare Plant Impacts Figures CITY OF SAN LUIS OBISPO BOUNDARY TANK FARM ROADTANK FARM ROAD HIG U E R A S T R E E T HIG U E R A S T R E E T HIG U E R A S T R E E T SAN LUIS OBISPOSAN LUIS OBISPO COUNTY AIRPORTCOUNTY AIRPORT SAN LUIS OBISPO COUNTY AIRPORT REFERENCE: 7.5 MINUTE U.S.G.S. TOPOGRAPHIC MAPS OF OF PISMO BEACH AND SAN LUIS OBISPO, CALIFORNIA DATED: 1965 PHOTOREVISED: 1994 V: \ 1 2 1 2 _ P a d r e - C h e v r o n _ S L O T F \ 1 2 1 2 . 0 0 1 _ R e m e d i a l _ D e s i g n \ 0 0 3 - 1 2 1 2 . 0 0 1 _ S i t e _ L o c a t i o n _ M a p . a i \ 0 8 / 1 2 / 0 7 0 2,000 4,000 FEET APPROXIMATE SCALE N FIGURE 1 PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM SITE LOCATION MAP EXPLANATION TANK FARM SITE TANK FARM ROAD RESERVOIR 4 NORTHWEST AREA RESERVOIR 5 RESERVOIR 6 RESERVOIR 7 RESERVOIR 3 RESERVOIR 2 FORMER RECYCLING AREA FIRE SCHOOL AREAEXISTING BUILDINGS TANK FARM ROAD NORTH MARSH SAN LUIS OBISPO COUNTY REGIONAL AIRPORT TRAILER PARK FLOWER MOUND Tan k F a r m C r e e k East For k Sa n L u i s Ob i s p o Cre e k SAN T A F E R O A D Ac a c i a C r e e k S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 1 9 _ 1 2 1 2 . 0 0 1 _ S i t e _ M a p . m x d \ 1 2 / 1 8 / 0 7 FIGURE 2 SITE MAP REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA EXPLANATION PROJECT AREA BOUNDARY APPROXIMATE SCALE FEET 0 500 1,000250 REFERENCE: AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007. RESERVOIR 4 NORTHWEST AREA RESERVOIR 5 RESERVOIR 6 RESERVOIR 7 RESERVOIR 3 RESERVOIR 2 FORMER RECYCLING AREA T A N K F A R M R O A D NORTH MARSH OCCUPIED OFFICE STUCTURES FORMER FIRE SCHOOL LOCATION AERIAL ELECTRICAL SERVICE (PG&E) AERIAL ELECTRICAL SERVICE (PG&E) AND TELECOMM SERVICE (ATT) AERIAL ELECTRICAL SERVICE (PG&E) AND TELECOMM SERVICE (ATT) UNDERGROUND 4" DIA. H.P. GAS SERVICE (THE GAS CO.) UNDERGROUND ELECTRICAL SERVICE (PG&E) SEWER LIFT STATION S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 0 5 _ 1 2 1 2 . 0 0 1 _ E x i s t i n g _ U t i l i t i e s _ E a s e m e n t s . m x d \ 1 2 / 1 7 / 0 7 FIGURE 4 EXISTING UTILITIES AND EASEMENTS REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA APPROXIMATE SCALE FEET 0 500 1,000250 EXPLANATION PROJECT AREA BOUNDARY OVERHEAD AT&T LINES OVERHEAD PG&E LINES PG&E UNDERGROUND LINE NATURAL GAS LINE PROPOSED SEWER ALIGNMENT REFERENCE: AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007 RESERVOIR 4 NORTHWEST AREA RESERVOIR 5 RESERVOIR 6 RESERVOIR 7 RESERVOIR 3 RESERVOIR 2 FORMER RECYCLING AREA T A N K F A R M R O A D NORTH MARSH OCCUPIED OFFICE STUCTURES FORMER FIRE SCHOOL LOCATION S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 0 4 _ 1 2 1 2 . 0 0 1 _ C h e v r o n _ P i p e l i n e s . m x d \ 0 8 / 1 2 / 0 7 FIGURE 5 CHEVRON PIPELINES REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA EXPLANATION PROJECT AREA BOUNDARY CRUDE OIL PIPELINES OTHER UNDERGROUND PIPELINES APPROXIMATE SCALE FEET 0 500 1,000250 REFERENCES: 1. AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007 2. GENERAL ARRANGEMENT SAN LUIS OBISPO TANK FARM, PRODUCERS PIPELINE, UNION OIL COMPANY OF CALIFORNIA, DRAWING No. UNKNOWN, DATED APRIL 3, 1950. GENERAL ARRANGEMENT SAN LUIS OBISPO TANK FARM NORTHERN DIVISION PIPELINE UNION OIL COMPANY OF CALIFORNIA, DRAWING No. D2A180, DATED JULY 30, 1981. SEE FIGURE 6 FOR DETAIL NOTE: LEACH LINES AND DRAIN LINES ARE SHOWN AS CRUDE OIL LINES ON THIS FIGURE FOR CLARITY. SIMILIARLY FOAMITE LINES ARE SHOWN AS WATER LINES DUE TO THEIR SIMILIAR FUNCTIONS DURING OPERATIONS. SUMMARY OF PIPELINE LENGTHS LENGTH (FEET) 25,125 258 914 38,263 9,177 TYPES CRUDE OIL LEACH LINE (SANITATION) DRAIN LINES WATER LINE FOAMITE RESERVOIR 4 NORTHWEST AREA RESERVOIR 5 RESERVOIR 6 RESERVOIR 7 RESERVOIR 3 RESERVOIR 2 FORMER RECYCLING AREA 16.85 ACRES 19.13 ACRES 258.19 ACRES 30.65 ACRES 15.18 ACRES S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 0 6 _ 1 2 1 2 . 0 0 1 _ E x i s t i n g _ S L O _ C o u n t y _ L a n d _ U s e _ P l a n . m x d \ 1 2 / 1 7 / 0 7 FIGURE 7 EXISTING SAN LUIS OBISPO COUNTY LAND USE PLAN REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA APPROXIMATE SCALE FEET 05001,000250 EXPLANATION PROJECT AREA BOUNDARY RESIDENTIAL AGRICULTURAL COMMERCIAL SERVICES INDUSTRIAL PUBLIC FACILITY RECREATION REFERENCE: AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007 RESERVOIR 4 NORTHWEST AREA RESERVOIR 5 RESERVOIR 6 RESERVOIR 7 RESERVOIR 3 RESERVOIR 2 FORMER RECYCLING AREA 295.90 ACRES 7.8 ACRES 2.3 ACRES13.6 ACRES COLLECTOR ROAD UN O C A L C O L L E C T O R R O A D S A N T A F E R O A D ( E X T E N S I O N ) 18.2 ACRES 2.2 ACRES REFERENCE: AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007. SOURCE: AIRPORT AREA SPECIFIC PLAN, SAN LUIS OBISPO, JANUARY 2005 EXPLANATION PROJECT AREA BOUNDARY RESIDENTIAL BUSINESS PARK SERVICE & MANUFACTURING PUBLIC OPEN SPACE APPROXIMATE SCALE FEET 05001,000250 S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 0 7 _ 1 2 1 2 . 0 0 1 _ P r o p o s e d _ C i t y _ S L O _ L a n d _ U s e _ P l a n . m x d \ 1 2 / 1 7 / 0 7 FIGURE 8 CITY OF SAN LUIS OBISPO AASP LAND USE PLAN REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA PROPOSED ROAD RESERVOIR 4 NORTHWEST AREA RESERVOIR 5 RESERVOIR 6 RESERVOIR 7 RESERVOIR 3 RESERVOIR 2 FORMER RECYCLING AREA S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 0 8 _ 1 2 1 2 . 0 0 1 _ C o n s t r a i n t s _ P r o p o s e d _ S L O _ L a n d _ U s e . m x d \ 0 8 / 1 3 / 0 7 FIGURE 9 CONSTRAINTS TO THE PROPOSED CITY OF SAN LUIS OBISPO LAND USE PLAN REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA REFERENCE: AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007. SOURCE: AIRPORT AREA SPECIFIC PLAN, SAN LUIS OBISPO. DATED: JANUARY 2005 APPROXIMATE SCALE FEET 0 500 1,000250 EXPLANATION RESIDENTIAL BUSINESS PARK SERVICE & MANUFACTURING PUBLIC OPEN SPACE LAND USE RUNWAY ADDITION RUNWAY PROTECTION S-1a S-1b S-1c 100 YEAR FLOODPLAIN AVIATION SAFETY ZONES PROJECT AREA BOUNDARY 5 ACRES 274 ACRES 15 ACRES 5 ACRES 5 ACRES 4 ACRES 21 ACRES 1 ACRE 2 ACRES 8 ACRES COLLECTOR ROAD S A N T A F E R O A D ( E X T E N S I O N ) S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 2 1 _ 1 2 1 2 . 0 0 1 _ P r o p o s e d _ L a n d _ U s e . m x d \ 1 2 / 1 8 / 0 7 FIGURE 10 PROPOSED LAND USE CONCEPT REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA REFERENCE: AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007. EXPLANATION PROJECT AREA BOUNDARY BUSINESS PARK SERVICE & MANUFACTURING RECREATION OPEN SPACE APPROXIMATE SCALE FEET 05001,000250 V: \ 1 2 1 2 _ P a d r e - C h e v r o n _ S L O T F \ 1 2 1 2 . 0 0 1 _ R e m e d i a l _ D e s i g n \ 0 2 9 _ 1 2 1 2 . 0 0 1 _ H y d r o l o g y _ M a p . a i \ 0 8 / 1 3 / 0 7 Small Tributary Creek SITE DESIGN POINT A DESIGN POINT B 2-30” DIAMETER2-30” DIAMETER CMP CULVERTSCMP CULVERTS B 5,476 Acres A 485 Acres EXPLANATION FLOW PATH HYDROLOGIC BOUNDARY CLOSED CATCHMENTS SITE Ac a c i a C r e e k 2-30” DIAMETER CMP CULVERTS BOX CULVERTSBOX CULVERTSBOX CULVERTS 2-30” DIAMETER2-30” DIAMETER CMP CULVERTSCMP CULVERTS 2-30” DIAMETER CMP CULVERTS CLOSED CATCHMENTSCLOSED CATCHMENTS APPROXIMATELY 150 Ac OFAPPROXIMATELY 150 Ac OF TANK FARM DISCHARGE OFFSITETANK FARM DISCHARGE OFFSITE APPROXIMATELY 150 Ac OF TANK FARM DISCHARGE OFFSITE Orc u t t Creek Or c u t t Creek East F o r k S a n Lu i s O b i s p o Creek Tank Far m C r e e k 0 2,000 4,000 FEET APPROXIMATE SCALE N FIGURE 11 PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM HYDROLOGY MAP REFERENCE:REFERENCE: 7.5 MINUTE U.S.G.S. TOPOGRAPHIC MAPS OF7.5 MINUTE U.S.G.S. TOPOGRAPHIC MAPS OF ARROYO GRANDE, LOPEZ MOUNTAIN, PISMO BEACH,ARROYO GRANDE, LOPEZ MOUNTAIN, PISMO BEACH, AND SAN LUIS OBISPO, CALIFORNIA.AND SAN LUIS OBISPO, CALIFORNIA. REFERENCE: 7.5 MINUTE U.S.G.S. TOPOGRAPHIC MAPS OF ARROYO GRANDE, LOPEZ MOUNTAIN, PISMO BEACH, AND SAN LUIS OBISPO, CALIFORNIA. RESERVOIR 4 NORTHWEST AREA RESERVOIR 5 RESERVOIR 6 RESERVOIR 7 RESERVOIR 3 RESERVOIR 2 FORMER RECYCLING AREA S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 1 3 _ 1 2 1 2 . 0 0 1 _ W e t l a n d s _ F a i r y _ S h r i m p _ R a r e _ P l a n t . m x d \ 1 2 / 1 7 / 0 7 FIGURE 12 WETLANDS, FAIRY SHRIMP, AND RARE PLANT HABITATS REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA 0 500 1,000250 Feet Approximate Scale NOTE: CRLF = CALIFORNIA RED LEGGED FROG SOURCE: BIOLOGICAL RESOURCES MAPPING CONDUCTED BY RINCON CONSULTANTS INC., 2003. FIELD STUDIES PERFORMED MAY THROUGH SEPTEMBER 2003. REFERENCE: AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007 EXPLANATION PROJECT AREA BOUNDARY EPHEMERAL WATER DELINEATED WETLAND PROTECTED FAIRY SHRIMP NOT PRESENT PROTECTED FAIRY SHRIMP PRESENT PROTECTED FAIRY SHRIMP NOT PRESENT (75.95 acres) PROTECTED FAIRY SHRIMP PRESENT (32.125 acres) SMALL AREAS WITH LESS THAN 100 INDIVIDUALS LARGE AREAS WITH GREATER THAN OR LESS THAN 1000 INDIVIDUALS HOOVER'S BUTTON CELERY CONGDON'S TARPLANT PURPLE NEEDLEGRASS SAN LUIS OBISPO MORNING GLORY CONGDON'S TARPLANT HOOVER'S BUTTON CELERY SAN LUIS OBISPO MORNING GLORY PURPLE NEEDLEGRASS !( !( !( RESERVOIR 4 NORTHWEST AREA RESERVOIR 5 RESERVOIR 6 RESERVOIR 7 RESERVOIR 3 RESERVOIR 2 FORMER RECYCLING AREA BETITA PROPERTY 801 mg/kg 1,151 mg/kg 488 mg/kg WETLANDS IMPACTED BY ASPHALTIC CRUST T-8-0.5 T-2-0.5 T-17-0.5 S: \ G I S \ 1 2 1 2 _ C h e v r o n _ P a d r e _ S L O T F \ 0 0 1 _ R e m e d i a l _ D e s i g n \ A r c M a p D o c u m e n t s \ 0 1 4 _ 1 2 1 2 . 0 0 1 _ S u m m a r y _ E n v i r o n m e n t a l _ I m p a c t s . m x d \ 1 2 / 1 7 / 0 7 FIGURE 13 SUMMARY OF ENVIRONMENTAL IMPACTS REMEDIAL ACTION PLAN SAN LUIS OBISPO TANK FARM PREPARED FOR CHEVRON EMC SAN LUIS OBISPO, CALIFORNIA 0 500 1,000250 Feet Approximate Scale EXPLANATION TPH IN SOIL > 100 mg/kg EXTENT OF BTEX LIQUID CRUDE OIL. CAPABLE OF GENERATING "FREE" DROPLETS OF OIL. (EVALUATED FOR REMEDIATION IN FEASIBILITY STUDY) PLIABLE, HIGHLY WEATHERED CRUDE OIL. EVIDENCE OF RECENT PLASTIC FLOW. (EVALUATED FOR REMEDIATION IN FEASIBILITY STUDY) SOLID, FORMER CRUDE OIL PLIABLE, HIGHLY WEATHERED CRUDE OIL. NO EVIDENCE OF PLASTIC FLOW LNAPL OCCURANCE PROJECT AREA BOUNDARY TPH IN SOIL > 1,000 mg/kg !(SOIL SAMPLE SHOWING LEAD CONCENTRATION IN mg/kg REFERENCE: AERIAL PHOTOGRAPH BY CENTRAL COAST AERIAL MAPPING. DATED MARCH 2, 2007 AREA OF ASENIC IMPACT (EVALUATED FOR REMEDIATION IN THE FEASIBILITY STUDY)