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HomeMy WebLinkAbout12/07/2004, B2 - GROUNDWATER PROJECT: PHASE 1 - EVALUATION OF PROJECT ALTERNATIVES AND POTENTIAL IMPACTS council. j acenaa Repoizt CITY OF SAN LUIS O B I S P O FROM: John Moss,Utilities Directo Prepared By: Gary W. Hend son, Water Division Manager &Fw ka SUBJECT: GROUNDWATER PROJECT: PHASE 1 — EVALUATION OF PROJECT ALTERNATIVES AND POTENTIAL IMPACTS CAO RECOMMENDATION 1. Receive and file report. 2.. Direct staff to defer additional work associated with the Groundwater Development Project. 3. Direct staff to pursue the development and use of groundwater to meet non-potable irrigation needs of commercial or institutional customers where feasible. REPORT-IN-BRIEF The City has been evaluating the potential for increasing groundwater production for many years. Stetson Engineers were retained to prepare the Phase 1 Report for the Groundwater Project. The long term project goal was to increase groundwater production to 1,000 acre feet per year. The Phase 1 study evaluates well locations, treatment options, water treatment facility site options, preliminary environmental review, and cost comparison of the alternatives. The main issue continuing to confront the successful implementation of increased groundwater production involves potential impacts to stream flows in the area. This question has been discussed in past reports and has been very difficult to properly evaluate due to limited historical information. With the recent decision for City participation in the Nacimiento Project and the cost and uncertainty of the additional studies necessary to evaluate project impacts, staff is recommending deferral of addition phases of the Groundwater Development Project at this time. DISCUSSION Background The City of San Luis Obispo has been pursuing the opportunity to increase the City's available water resources by increasing the use of groundwater for a number of years. Several studies have been undertaken to determine the additional yield from the groundwater basin as well as the potential impacts associated with increased withdrawals. The previous studies have concluded that additional groundwater production from the San Luis Groundwater Basin is feasible. The potential impacts associated with increased groundwater production, mainly impacts to stream flows in the area, can not be quantitatively evaluated. Historical information on stream flows and groundwater extractions are not adequate to evaluate the potential impacts. Additional studies to provide the necessary evaluation will be extensive and costly and may be questioned by regulatory agencies due a/ Groundwater Development Project Page 2 to the number of assumptions that will need to be made. In light of the recent Council decision to participate in the Nacimiento Project and the uncertainty in successful evaluation of the stream flow impacts, staff recommends deferral of additional Phases of the Groundwater Project at this time. The following sections provide an overview of the findings of the Phase 1 Report. Phase I Report The identified groundwater project goal was to develop the necessary facilities to allow the City to produce 1,000 acre feet of groundwater per year. On August 8, 2003, the City Council approved a contract with Stetson Engineers for a Phase 1 Evaluation of the Groundwater Development Project. The Phase 1 study provides an evaluation of project alternatives and potential impacts and includes the following: ■ Hydrogeologic and well capacity evaluation ■ Groundwater quality evaluation ■ Analysis of alternative treatment methods e Alternative treatment plant sites and pipeline routes e Treatment waste stream impacts to WRF effluent quality&use for irrigation • Cost comparison of alternatives ■ Hydrologic impact analysis ■ Initial consultation with National Marine Fisheries Service • Preliminary environmental review Hydrologic and Well Cayacity The City has utilized a number of wells in the past in the southern portion of the City. The area bounded by Madonna Road, Los Osos Valley Road and South Higuera Street overlies the deepest portion of the groundwater basin and the potential for largest groundwater production wells. While this area has the greatest groundwater production potential, it also has areas that are contaminated with nitrates and tetrachloroethylene (PCE). The consultants reviewed available well information and additional groundwater sampling was undertaken to identify the potential locations for additional production wells. The various wells in the area are shown on Attachment 1 (Figure 2 from the Phase 1 report). Based on the analysis, the study recommends that the City consider using the following four well locations to meet the water production goal: 1. Auto Park Way Well (requires new well) 2. Pacific Beach#1 Well (existing City well) 3. Dennys/Calle Joaquin Well (existing City well) 4. StausbaughBonetti Well (requires new well and acquisition of site) i �7 Groundwater Development Project Page 3 Groundwater Ouality Groundwater samples were obtained from numerous wells in the area to evaluate the levels of contaminants in the groundwater which would need to be removed using available water treatment options. Attachment 2 & 3 provide an overview of the levels of nitrate and PCE contamination which may be expected if the City were to increase groundwater production in the area. It should be noted that nitrate levels in Auto Park Way well exceeded 50 mg/1 nitrate prior to the shutdown of the well in October of 1992. The maximum contaminate level for nitrate is 45 mg/l (as NO3). Increased groundwater withdrawals can lead to increased contaminants being drawn from the surrounding areas. Depending on the wells that are utilized for increased groundwater production, various levels of contamination are possible but it is expected that treatment facilities would be necessary to reduce nitrate levels and remove PCE from the groundwater. Water Treatment Methods Several treatment technologies are available for treatment of groundwater contaminated with PCE and nitrates. PCE contamination can be removed using either Granular Activated Carbon (GAC) treatment or air stripping. During the drought period in the late 1980's and early 1990's, the City utilized GAC facilities to remove PCE from groundwater. These facilities included two large tanks which contained the activated carbon. Air stripping utilizes aeration towers which allow the water to cascade downward, allowing the PCE to volatize and be "stripped" from the water. The contaminated air may need to be treated prior to release to the atmosphere. The likely preferred treatment alternative for PCE removal would be GAC treatment. Nitrate contamination can be removed using ion exchange or reverse osmosis technologies. The ion exchange process involves passing the contaminated groundwater through a solid resin bed which contains chloride ions (salt solution). An exchange of nitrate ions and chloride ions takes place. The contaminate ions are removed from the water and are stored on the resin. Because the resin has a limited capacity for ion exchange, it must be washed with regenerating solution(brine or salt solution) to regain its function. The backwashing creates a waste stream that must be properly disposed of. Waste stream disposal is discussed in more detail later in this report. Use of salt in the ion exchange process does add chloride to the treated water. Since the groundwater in San Luis Obispo is very low in chloride content, addition of chloride to the treated water does not appear to be a significant concern. Reverse osmosis is the other option for removing nitrate and PCE from the groundwater. Reverse osmosis uses membranes with extremely small pores to separate the contaminants from the water. The process requires high pressure to force the water through the membranes leaving the contaminants in the waste stream which must be properly disposed of. The reverse osmosis process is an energy intensive process due to high pumping pressures. While PCE removal is possible with reverse osmosis, the PCE may pass through the filters without being completely removed and could damage the filters. Additional research would be necessary if reverse osmosis was chosen as the preferred treatment alternative. Groundwater Development Project Page 4 Treatment Plant Sites Three potential treatment plant sites were identified and evaluated as part of the study. The three sites are shown on Attachment 4. Site 1 is located within the McBride property located near the northeast end of Calle Joaquin. The property is immediately adjacent to Highway 101. Site 1 would require acquisition of approximately 1-2 acres within the property for the treatment plant facilities. Site 2 is located immediately adjacent to the proposed Marketplace Project on the Dalidio property. Locating the facilities to the rear of the proposed commercial development may minimize the visual impacts of the treatment plant facilities and provide vehicle access to the facility from the adjacent paved access routes. Site 3 is located on City owned property to the south of the City's Water Reclamation Facility. Installation of pipelines from the proposed well locations to the site may be difficult due to creek crossings. In addition, access to the facilities would need to be improved to provide for chemical deliveries and other activities. Waste Stream Disposal There are two options available for disposal of the waste stream from the water treatment facilities. The first would be to dispose the waste stream to the City sewer system. The second alternative would involve trucking the waste to an approved disposal site. The disposal of the waste stream to the sewer system could impact the effluent which is discharged from the Water Reclamation Facility to San Luis Obispo Creek. The addition of the waste products could increase the Total Dissolved Solids (TDS) in the effluent to a level above our permit limits. There may be an opportunity to work with the Regional Water Quality Control Board relative to the permit terms or the City could implement a "salts" management plan throughout the city to reduce the TDS levels in the effluent. Offsite disposal of the waste products would involve trucking the wastes to a facility that could handle the increased TDS impacts. This would likely require trucking the waste to a wastewater treatment plant facility that has an ocean outfall. Further evaluation of the costs associated with trucking waste would be necessary if this alternative were pursued. Phase 1 Study Recommended Alternative and Cost The study's recommended alternative for increasing the City's groundwater production to 1,000 acre feet per year would require the construction of two new wells, pipeline installations for delivery of raw groundwater to the treatment plant site (McBride property) and treated water from the site to the existing water distribution system,treatment facilities for removal of nitrate and PCE (ion exchange and GAC), and chlorination, fluoridation, and hauling of brine waste. The total estimated initial cost is approximately$3,232,000 which does not include property acquisition. The operations and maintenance (O&M) cost for the project are estimated at approximately $532,000 per year which does not include additional staff which may be required for facility operations. It should be noted that more than half of the annual O&M costs are for brine hauling and disposal. Groundwater Development.Project Page 5 Hydrologic Analysis The potential reduction in stream flows in the area due to increased groundwater production has been extremely difficult to quantify. While past groundwater analyses have identified estimates for potential annual reduction in stream flows associated with various groundwater withdrawal scenarios, lack of sufficient creek flow records prevents a comprehensive analysis of the stream flow impacts on a daily or monthly basis. While the City has hired several consultants to investigate this issue, it is now apparent that quantifying the stream flow impacts would be very difficult and costly and the results would likely be questioned by the regulatory agencies (i.e. National Marine Fisheries Service, Department of Fish & Game, etc.). Based on the limited historic information, an alternative strategy was developed to minimize potential impacts to stream flows. Increasing groundwater production could be accomplished through an exchange of recycled water with agricultural groundwater users or over time as agricultural groundwater use is reduced. This strategy would provide a"net zero'impact to the groundwater basin. National Marine Fisheries Service Consultation As part of the Phase 1 Study, the consultants contacted the National Marine Fisheries Service (NMFS) regarding the Groundwater Development Project. Based on the potential stream flow impacts, the National Marine Fisheries Service recommended a significant number of studies and analyses be undertaken to more fully evaluate the impacts. These additional studies would be very difficult and costly to prepare and their outcome relative to project implementation and regulatory agency acceptance is uncertain. Preliminary Environmental Review A preliminary environmental review for the project was included in the Phase 1 study. The main focus of the preliminary assessment was for the purpose of determining which alternative site to carry forward for further review. Based on the initial assessment, the preferred site alternative is the McBride property followed by the Dalidio site and the Water Reclamation facility site. Future Groundwater Direction There are many issues which will need to be resolved prior to implementation of the Groundwater Development Project. In light of the recent City Council decision relative to participation in the Nacimiento Project, moving forward with the development of a project to significantly increase groundwater production at this time may not be warranted. The project uncertainties, additional studies, and significant costs warrant reconsideration of the approach to utilization of available groundwater resources. As an alternative to construction of treatment facilities and large increases in groundwater production and the potential associated project impacts, staff would recommend a modified strategy for modestly increasing groundwater use in the City. The City should allow the use of groundwater to meet non-potable irrigation uses in commercial projects and developments such -s i ( I Groundwater Development Project. Page 6 as condominiums and seek to offset potable water use where reasonable opportunities exist. In addition, staff would like Council concurrence for further evaluation of the following two alternatives: 1. Mission Prep School — The Mission Prep School currently receives water at no charge from the City due to a historic agreement between the City and the school. The City acquired property from the school for street right-of-way purposes and the well which served the school irrigation needs was lost to the school's use. As such, the agreement between the City and the school requires that the City provide water for irrigation purposes at no cost. There may be an opportunity to construct a new well for irrigation purposes for the school's use, thereby eliminating the use of potable water for site irrigation. It is estimated that the school uses approximately 6.5 acre feet per year for landscape/sports fields irrigation. 2. Mitchell Park Well — The City has a well located at Mitchell Park which has provided limited groundwater for potable use in the vicinity of the park. Due to the limited capacity of the well, there have been issues with continuous operation of the well (i.e. air entrainment problems, etc.). An option to further evaluate would be to offer the use of the well to the Public Works Parks Division for irrigation of the park. There would be modifications required for use of the well for park irrigation and the pay back period would need to be evaluated to determine the benefit of pursuing this idea. Mitchell Park currently utilizes approximately 5.8 acre feet per year of potable water for irrigation purposes. Summary While previous studies have indicated that additional groundwater could be available from the San Luis Groundwater Basin, there remain impacts that are difficult to quantify. The evaluation of potential stream flow impacts due to increased groundwater withdrawal, will be very difficult to quantify. The capital and O&M costs associated with groundwater treatment facilities are relatively high. Since the City has agreed to participate in the Nacimiento Project which will significantly increase our available water resources, staff recommends deferral of the Groundwater Development Project at this time. FISCAL IMPACT There is no fiscal impact associated with the recommendation. ALTERNATIVES 1. Proceed with additional studies for project implementation - The Council could direct staff to develop the scope of work associated with the additional studies (Phase 2) and analysis to move forward with the Groundwater Development Project. There is no guarantee that the additional studies will adequately address regulatory agency concerns and allow project implementation. Staff does not recommend this alternative at this time. Groundwater Development Project Page 7 ATTACHMENTS 1. Study Area Wells 2. Nitrate Concentrations in the Vicinity of the Study Area 3. PCE Concentrations in the Vicinity of the Study Area 4. Treatment Plant and Well.Sites AVAILABLE FOR REVIEW IN THE COUNCIL OFFICE 1. Groundwater Development Project: Phase 1 — Evaluation of Project Alternatives and Potential Impacts, September 30,2004. Prepared by Stetson Engineers, Inc. a-� Attachment 1 S Maaanrna® 01 Legurte Lake k/aaoma Inn i0 O. caararu yT• ,1 F -,. B13 N4 r o shee wens Media wm15 • station 44 KayaM • AQ. CA 4) ab N a Padfia Beach a ' Paafic Beach Park(ABN wRFO S.N 8 ( ) Park 0 0 0 aaeuln .f • h/BMMM / & a Tank Farm OTIC Udall Prbp.0 , • co Padfic8eo • 6 • (aro • • L 141 suburban • Road Water t - Fmie Ban water W. , e 7e • •�urtlet Water Supply o, - • (.� Ventas Btmktma Parkac �.aP�ana6 `�Im„lata water , APara+tenta Otetr a N -------- --------- Mavash City Owned Water Supply Well 0 City Test Hole or Test Well 0 Private Well NTownship/Range Boundary N I Section Boundary(dashed where approximate) IN e Approximate Study Area Boundary NSan Luis Groundwater Basin Boundary a _ 0 0.125 NIBS City Owned Property(Source:SLO County) C STUDY AREA AND WELLS STETSON STETSENGINEERN ,;2— Attachment Z ro kStreet Laguna Lake Madanna Inn © • 3.2 ns - _ rtro2 - IOOf Cemeta — T acro Iks- 5 s— t2/l12 i. US .o` Madonna Embassy S Laguna lake Q• Shelf Wells Dalidlo Wens 12 9.2 10 ` 10 f 3189 1/04 1/04 �MAb .i 5/02 1/04• � .. O Hayashi l Dalkllo 8.5 7_ each#1 Ag.Wells 1/04 1104 Beach I � ,5 3794 2B'7 S. era G - (ABN) 13 -----------— Park(ABN) O q L — — • FroorRanch I Z/ 9Is J� 0000 90 J� Cook Bus. 5 Quin/ 11043 O Q 0 Q Arm 1 s augh onet0 86 WR & �TA,NK RD. v'^ union Prop Ind. 1 Snell Union b Ind. _2 ( T ) 11ro2 OP �en 0 Hill op,O TI Co. H 2.2 r 0( 1 141 Suburban 01-13 C>�b. i 2003® b2 45 1 BaI _ 2003• _ 10F QQ Kunden 2003 ®11102 Verdes BusPark CopeldRd'a I �{orbw Lane Dlstr 0.5 gDan Trot 11 403 'O 1 51 11/02 11ro2 ----------- - ----- IHayasba2 n N Section Boundary(dashed where approximate) City Owned Water Supply Well N f Approximate Study Area Boundary O City Test Hole or Test Well , W E Approtdmate Groundwater Basin Boundary Q Private Well Nitrate Concentrations in Wells S 11" NO3 Concentration(mg/L) w Nro2 Date of Sample(month/year) 0 0.125 0.25 Miles >45 mgfL a 30-44 mg/L 20-M mg& • 10-19 mg/L NITRATE CONCENTRATIONS IN THE • <10mg/Lornot detected STETSON VICINITY OF THE STUDY AREA * Note: Sample Taken From Irrigation Pipe ENGrN rPK. ** Note: Sample Taken Near Feeding Tank Attachment 3 Bm k Street , 1 J Laguna Lake Madonna Inn • 0.9 v ns 2003 _ 100F -2R Cemem Cleaner • 58 p W I� a103 0.5-3 4/03 .6 8103 Madonna • EmbassySu _ Shell • Wells Dalidic Wells 23 4192 •Mobil S 5101 G) ard '^= ' .� O Hayashi/Dalidio Ag. 0.6 10192 . <0. 91 5101pacific Beach 8/93 ;14 7.3 .S. ague &G (ASN) --._____ 219 � --- "- Pack(ABN) O O 0 O G 7 (V Froom Ftarch � J e oaquin I .•? Cook Susi s Park 00 Q O 3. s O ghl�BOnettl W 8 TANK FARM RD Union PropO Whitson Intl • <0.5 • • 4/87� t Bell ill pers • vCo' • QHd grater 2 LO 1 OH3 y 0( ) 141 Subu¢ran Ernie Ball l s W 10F O• Verdes Bus.Park Co Q Q ND Distr Hor mn lane • Higue Apart 7/02 �� p1 I � I -- --- ;Hayashi.#2 • 1401 Section Boundary(dashed where approximate) City Owned Water Supply Wel r W E ^6* Approximate Study Area Boundary O City Test Hale or Test Well / V Approximate Groundwater Basin Boundary Q Private Well S Tetrachloroethylene(PCE)Concentrations in Wells tt PCE Concentration(ug/L) a 0 0.125 0A5 Miles t1Al2 pate of Sample(rnonthtyear) >10 ug/L S-10 ug/L 7 UWL PCE CONCENTRATIONS IN THE 0 us R VICINITY OF THE STUDY AREA • <0.5ug/L ornot deteaed = STETSON EPIONEms UW— r _ Attachment 4 Laguna Lake i r / r0, < ja / SLO Corp Yard Fi S ion P�® � / - *Pacific each#1 Auto Park Way M Well Sit ro;-0. F S/�3p s Ile Joaq Stra ugh/Bonetti Well Site Denny's N � Existing City Well d Z W e 10 Proposed Project Well Location U vA ' � / Water Main S r 'V WRF Pant and Pond Boundaries 0 500 1000 Feet IV Approximate Study Area Boundary ® City Owned Property M ® Proposed Water Treatment Plant Site(190'x 170') PROPOSED WATER ENC;WEE STETSRS iNONG. TREATMENT PLANT AND WELL SITES � -