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HomeMy WebLinkAbout2022-12-21 SWCP Avila Ranch_signed STORMWATER CONTROL PLAN For TRACT 3089 - AVILA RANCH PHASES 2, 3, 4, 5 & 6 December 21, 2022 Prepared by: 612 Clarion Court San Luis Obispo, CA 93401 805 544-4011 Job Number: 1493-0007 Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 2 Table of Contents Table of Contents ............................................................................................................ 2 Certification ...................................................................................................................... 4 Introduction and Project Scope ....................................................................................... 5 Project Location and Description ..................................................................................... 6 Existing Site Drainage Characteristics ............................................................................ 7 Existing Site Soil Conditions ............................................................................................ 7 Post-Construction Stormwater Management Requirements ........................................... 9 PCR #1 – Site Design and Runoff Reduction........................................................... 9 PCR #2 – Water Quality Treatment ....................................................................... 10 PCR #3 – Runoff Retention ................................................................................... 10 PCR #4 – Peak Flow Management ........................................................................ 12 Low Impact Development (LID) Design Strategies ........................................................ 13 Roadside Bioswale with Underground Gravel Trench ............................................ 13 Vegetated Basins .................................................................................................. 14 Motorcourt/ Alley Underground Gravel Chambers ................................................. 14 Shallow Retention Basin with Offset Gravel Chamber ........................................... 15 Linear Bioswales with Underground Gravel Trench ............................................... 16 Permeable Pavers with Underground Gravel Retention ......................................... 16 List of Appendices ......................................................................................................... 18 List of Figures Figure 1. Avila Ranch Project Location within the City of SLO ........................................ 6 Figure 2. Avila Ranch Phase Map ................................................................................... 7 Figure 3. PCR #3 Compliance for Phases 2-6 .............................................................. 12 Figure 4. Roadside Bioswales with Underground Gravel Trench Concept ................... 14 Figure 5. Motorcourt/ Alley Underground Gravel Chamber Concept ............................. 15 Figure 6. Shallow Retention Basin with Offset Gravel Chamber Concept ..................... 16 Figure 7. Permeable Pavers with Underground Gravel Retention Concept .................. 17 List of Tables Table 1: Onsite SCM Separation to Groundwater ........................................................... 8 Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 3 List of Appendices A. Site Information and Exhibits · City of San Luis Obispo SWCP Form · Watershed Management Zone Exhibit B. Soils, Infiltration, and Geotechnical Information · Excerpts from geotechnical documentation - Soils Engineering Report Update Avila Ranch Development, Phases II-VI, GeoSolutions, dated 1/26/2022 - Infiltration Testing Report for Avila Ranch Development, GeoSolutions, dated 2/9/2022 - Infiltration Testing Report – Avila Ranch Development, GeoSolutions Inc., dated 9/4/2015 · Porchet Infiltration Rate Calculations (2015 tests) · Avila Ranch Groundwater Information matrix · Stormwater Post-Construction Requirement SCM Separation from Groundwater Levels for Phases 2-6 Memo · Avila Ranch Groundwater Exhibit · Avila Ranch Infiltration Exhibits - Linear Infiltration exhibit - Porchet method Infiltration exhibit C. Existing Drainage Map D. Proposed Stormwater Control Drainage Management Area Exhibit E. Structural Control Measures (SCM) Exhibit Design · SCM Exhibit · Phases 2-6 Land Use Data · SCM Sizing Calculations · Central Coast Region SCM Sizing Calculator results - Phase 2 + 3 - Phase 4 - Phase 5 - Phase 6 F. Phases 2 & 3 – PCR #3 Attachment E Compliance · Ten Percent Adjustment to Retention Requirement calculation · Excerpts from RWQCB Resolution R3-2013-0032; Attachment 1 G. Structural Control Measures (SCM) Concepts · Roadside Bioswale with Underground Gravel Trench · Motorcourt/ Alley Underground Gravel Chamber · Shallow Retention Basins with Offset Gravel Chamber · SLO County LID Handbook detail 103 – Gravel Check Dams · SLO County LID Handbook detail 150 – Impermeable Layer Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 5 Introduction and Project Scope The purpose of this Stormwater Control Plan (SWCP) is to provide a summary of the strategies and design concepts for complying with the Central Coast Regional Water Quality Control Board’s Post-Construction Stormwater Requirements for Development Projects, Resolution No. R3-2013-0032, Attachment 1 (PCRs) for Phases 2, 3, 4, 5 & 6 of the Tract 3089 Avila Ranch development. This report will discuss PCR compliance strategies and design concepts relative to the project site’s stormwater infiltration capabilities and proximity to groundwater. Please refer to Figure 2 which shows the areas within Tract 3089 that are included in this analysis. This stormwater control plan includes the public right-of-way improvements, single family residential lots, Park E, Park D, Park I, and open space areas within Phases 2-6 of Tract 3089. The Phase 4 medium high density residential areas, Park F, Park G, Park H, and the commercial lots have been included in this report on a conceptual level only. It is expected that final stormwater control plans will be submitted with the individual improvement plans for these future developments. Lots 185, 186, and 188 are excluded from this analysis and will require a separate stormwater control plan to be prepared at the time of development of the onsite multifamily residential improvements. The Avila Ranch project (Phases 2-6) will meet the regulatory requirements for stormwater control, quality, and management in the final developed conditions. Post- Construction Stormwater Requirements (PCR) #1, #2 and #3 will be satisfied with on- site measures while PCR #4 is satisfied by facilities constructed in the Phase 1. Compliance with PCR #3 in Phases 4 and 5 will be achieved through onsite retention facilities. Onsite retention facilities are proposed on each commercial lot within Phase 6 to comply with PCR #3. Corresponding retention calculations and structural control measure designs can be found in Appendix E and Appendix G. In Phases 2 and 3, the size of retention-based facilities will consist of underground motorcourt gravel chambers and linear roadside bioretention facilities has been maximized where feasible. Based upon geotechnical testing and observation, there is relatively high ground water within portions of Phases 2 and 3 which is limiting the depth of retention-based structural control measures and ability to comply fully with PCR#3. The design of the motorcourts with a monolithic curb, gutter, and sidewalk without a parkway along the residential roadways allows for higher density housing and reduces the area available for bioswales to the collector road, Venture Drive. In addition to the underground motorcourt gravel chambers and linear roadside bioretention facilities, 2.10 acres or 20% of the equivalent impervious surface area (EISA) has been dedicated to retention-based facilities which exceeds the requirements of the 10% EISA in Attachment 1, Section 4) e) Attachment E. Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 6 The Phase 1 detention basin has been designed and constructed to meet PCR #4 requirements for Phases 1-6 of the Avila Ranch development. For further information, please see the Avila Ranch Development – Phase 1 Drainage Report prepared by RRM, dated 9/17/2018 and the Stormwater Control Plan for Avila Ranch prepared by RMM, dated 3/22/2022. Project Location and Description Avila Ranch is a housing development project located within the City of San Luis Obispo, California (see Figure 1). The project includes 149 acres of proposed mixed- use development including single and multi-family homes (R-1 to R-4), commercial areas (C-N), parks, and agricultural open space. The project property is bounded by Vachell Lane to the west, Buckley Road to the south, industrial land uses to the north, and agricultural space to the east. The project site is bisected by Tank Farm Creek, which runs from the north edge of the site to the southwest corner. The project has been divided into six phases. The project phase map is shown in Figure 2, below. Figure 1. Avila Ranch Project Location within the City of SLO Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 7 Figure 2. Avila Ranch Scope and Phase Exhibit Existing Site Drainage Characteristics The site is located between Vachell Lane to the west, Buckley Road to the south, industrial parcels to the north, and agricultural land to the east. The project receives run-on from several existing off-site tributary watersheds. To the north, there are two primarily light industrial watersheds and to the east there is a watershed used for agricultural activities. These historic flows travel across the project site toward Tank Farm Creek which bisects Avila Ranch. The existing Avila Ranch site slopes toward Tank Farm Creek from the east and west. Run-off flows in shallow channels across the agricultural land and into Tank Farm Creek. A map of the existing watersheds is included in Appendix C. Existing Site Soil Conditions GeoSolutions, Inc. prepared a site-specific geotechnical report (Soils Engineering Report Update Avila Ranch Development, Phases II-VI, dated 1/26/2022) for the project, along with an infiltration testing report (Infiltration Testing Report for Avila Ranch Development – dated 2/9/2022). Four other geotechnical reports were referred to throughout the stormwater control design for infiltration capabilities and historic groundwater depth. These reports are listed below, and further information can be found in Appendix B. Precedence was given to the most current geotechnical information for sizing of stormwater control facilities while the other reports provided context and project site historical information. Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 8 Below is a list of the geotechnical report references: · Soils Engineering Report Update Avila Ranch Development, Phases II-VI, GeoSolutions, dated 1/26/2022 · Infiltration Testing Report for Avila Ranch Development, GeoSolutions, dated 2/9/2022 · Soils Engineering Report – Avila Ranch Development Bridges, GeoSolutions Inc., dated 2/17/2022 · Soils Engineering Report – Avila Ranch Lift Station, GeoSolutions Inc., dated 4/6/2021 · Infiltration Testing Report – Avila Ranch Development, GeoSolutions Inc., dated 9/4/2015 · Results of Percolation Tests Report & Map, Earth Systems, dated 12/12/2001 Based on the existing geotechnical reports, soils on the site are primarily comprised of older alluvium and varying shades of black sandy fat clays. Groundwater was also encountered across the site at varying depths. For Phases 2-6, separation between groundwater and proposed infiltration facilities has been considered in the design and analysis of the stormwater control measures for the project. Below are the separation requirements utilized in the project design. Table 1: Onsite SCM Separation to Groundwater For more information on groundwater conditions and design separation, refer to the Avila Ranch Groundwater Information Matrix (dated 4/21/2022) and the SCM Separation from Groundwater Memo (prepared by Wallace group, dated 5/15/2022) in Appendix B. The current geotechnical report identifies the soils as Hydrologic Soil Group C and D (mostly clay and loams), which are associated with moderate-to-low infiltration rates usually due to the existence of clays within the soil complexes. Perforated pipe shallow infiltration tests were performed at a combined 24 on-site locations as part of the GeoSolutions geotechnical reports dated 2/9/2022 and 9/4/2015. The percolation rates across the site range from 0.04 to 5.52 in/hr. and are directly applicable to the design of infiltration trenches and similar deep. For shallow facilities with more bottom area than sidewall area, the Porchet conversion is applied to the test data to determine the applicable infiltration rate. Using the Porchet conversion method, 3.0 3.0 Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 9 infiltration rates ranged from 0.03 to 0.74 in/hr. See Appendix B for additional data and exhibits related to onsite groundwater and infiltration. Post-Construction Stormwater Management Requirements The Avila Ranch project site falls within the Central Coast Region Watershed Management Zone (WMZ) #1, on the southern edge of the City of San Luis Obispo. See Appendix A for WMZ Location Exhibit. This project has been designed to comply with the Central Coast Regional Water Quality Control Board’s (RWQCB) Resolution R3-2013-0032; Attachment 1: Post-Construction Stormwater Management Requirements for Development Projects in the Central Coast Region. Because the new or replaced impervious area for the project exceeds 22,500-SF, the project must comply with performance requirements (PCR’s) #1 through #4. The following sections describe the approach for compliance of each PCR. PCR #1 – Site Design and Runoff Reduction The proposed project will increase the impervious area on the property by more than 2,500 SF and is therefore subject to the Site Design and Runoff Reduction Performance Requirement. Optimization of Site Layout: · Limitation of development envelope: the project minimizes excessive land disturbance and site improvements given the required project conditions. · Preservation of natural drainage features: Disturbance to Tank Farm Creek and surrounding wetlands on site have been minimized. Offsite run-on that historically crossed the project to reach Tank Farm Creek will be routed via swales to the creek. · Setbacks from creeks, wetlands, and riparian habitats: a minimum 35’ setback will be held from Tank Farm Creek consistent with the conditions of approval and mitigation measures for Avila Ranch. · Minimization of imperviousness: the nature of the development requires impervious areas to accommodate new residential lots, new roads and streets, sidewalks and hardscapes, and new community facilities. New impervious areas have been minimized where possible. In addition, parks and areas of open space are proposed for the development. · Use of drainage as a design element: drainage and Low Impact Development (LID) elements have been considered during the entire design process. LID facilities proposed on this project included roadside and linear bioswales with underground gravel trenches, motorcourt/ alley underground gravel chambers, vegetated basins, shallow vegetated basins with underground gravel chambers, and permeable pavers with underground retention. Dispersal of Runoff to Pervious Areas: · Impervious surfaces will drain to landscaped and LID facilities when possible and open space areas are included throughout the project. Basins will be vegetated and designed for infiltration. Roads and sidewalks will be designed Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 10 to allow for flow to drain into dispersed stormwater treatment and/ or retention facilities (bioswales, biofiltration gravel trenches and infiltration basins, etc.) Stormwater Control Measures (SCMs): · Several different SCMs have been designed for implementation across the site, depending on proposed surface drainage conditions and subsurface retention requirements. Roadside/ linear bioswales with underground gravel trenches, motorcourt/ alley underground gravel chambers, vegetated basins, shallow vegetated basins with underground gravel chambers, and permeable pavers with underground retention will all be utilized. More information on these different facilities can be found in the Low Impact Development Design Strategies section of this report. See Appendix E and Appendix G for further SCM details and information. PCR #2 – Water Quality Treatment The proposed project (Phases 2-6) will increase the impervious area on the property by more than 5,000 SF and is therefore subject to the Water Quality Treatment Performance Requirement, PCR #2. For Phases 2-3, the primary treatment method will be the proposed bypass channel that will run parallel to Tank Farm Creek. This vegetated, mildly sloped wide channel runs the length of Phases 2-3 and will receive stormwater flow from the project’s storm drain network outlets east of Earthwood Lane. This onsite vegetated bypass channel will also receive and treat offsite stormwater run-on from the northern properties adjacent to Avila Ranch. This offsite run-on will be collected in a perimeter concrete swale along the northern boundary of Phase 3, be conveyed through separate storm drain pipes through the development and outlet south of Venture Drive into the vegetated bypass channel. Additionally, surface bioswales and underground gravel chambers are proposed where feasible in Phases 2 and 3. In Phases 4-6, vegetated bioswales, vegetated open space and park areas, infiltration and retention basins, linear retention facilities, and underground gravel chambers will serve as the compliance mechanisms for PCR #2 stormwater treatment. Refer to the SCM Exhibits and corresponding SCM sizing calculations for information on proposed treatment areas across the site (Appendix E). PCR #3 – Runoff Retention The proposed project will increase the impervious area on the property by more than 15,000 SF and is therefore subject to the Runoff Retention Performance Requirement (PCR #3). For sizing of the retention-based facilities such as underground gravel infiltration trenches, linear roadside bioretention facilities and basins, site-specific infiltration rates were assigned to individual SCMs based upon the infiltration exhibits and infiltration testing data found in Appendix B. For shallow facilities with more bottom Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 11 area than sidewall area, the Porchet conversion is applied to the test data to determine the applicable infiltration rate. Proposed retention and infiltration based SCM facilities have been maximized in depth, volume, and quantity relative to soil infiltration capability and appropriate separation from groundwater. In Phases 2 and 3, the size of retention-based facilities consisting of underground motorcourt gravel chambers and linear roadside bioretention facilities has been maximized where feasible. Based upon geotechnical testing and observation, there is relatively high ground water within portions of Phases 2 and 3 which is limiting the depth of retention-based structural control measures and ability to comply fully with PCR#3. The design of the motorcourts with a monolithic curb, gutter, and sidewalk without a parkway along the residential roadways allows for higher density housing and reduces the area available for bioswales to the collector road, Venture Drive. In addition to the underground motorcourt gravel chambers and linear roadside bioretention facilities in Phases 2 and 3, 20% of the equivalent impervious surface area (EISA), 2.10 acres, has been dedicated to retention-based facilities which exceeds the requirements of the 10% EISA (1.03 acres) in Attachment 1, Section 4) e) Attachment E. The Ten Percent Adjustment calculation can be found in Appendix F. The EISA was calculated assuming a correction factor of 0.22, consistent with hydrologic group C. Compliance with PCR #3 in Phases 4 and 5 will be achieved with onsite retention facilities. Phase 5 will include retention facilities in the north and east drainage management areas (DMA’s H and I) to offset retention deficiencies in the west drainage management area (DMA J). Placement and sizing of SCM facilities is included in Appendix E with SCM details included in Appendix G. Final sizing and onsite placement is anticipated to be included with final improvement plans for these phases. Phase 6 will comply with PCR #3 by providing minimum retention requirements outlined in the SCM calculations in Appendix E are met. It is anticipated that a final SWCP for the tow commercial lots within Phase 6 will be provided with the final improvement plans for each commercial lot. Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 12 Figure 3. PCR #3 Compliance for Phases 2-6 PCR #4 – Peak Flow Management The proposed project will increase the impervious area on the property by more than 22,500 SF and is therefore subject to the Peak Management Performance Requirement. Compliance with this requirement is addressed through the design and construction of the detention basin as part of the Phase 1 improvements for the Avila Ranch project. The Phase 1 Basin design by RRM basin considers the added impervious area from Phases 2-6 and over-detains discharges from the Phase 1 improvements such that the total peak flows leaving the Avila Ranch site into Tank Farm Creek in the developed condition do not exceed pre-project peak flows for the 2-year through 100-year storm events. Refer to the Avila Ranch Development – Phase 1 Drainage Report prepared by RRM, dated 9/17/2018, for additional details about the Phase 1 detention basin. In addition to the peak flow management by the Phase 1 basin, direct discharges or storm drain outlets to Tank Farm Creek have been avoided. Within Phases 2-6, there are a total of sixteen storm drain pipe networks which convey stormwater flow to Tank Farm Creek. Nine of these storm drain networks have outlet structures within the bypass channel. Approximately 40% of the total stormwater runoff from Ph. 2-3 is delivered to the bypass channel which runs parallel to Tank Farm Creek through Phases 2-6. The bypass channel is a wide, flat-bottomed channel with minimal longitudinal slope that will be vegetated with grasses allowing for low velocity flow and infiltration of stormwater. Energy dissipation in the form of rock slope protection is provided at each pipe outlet within the bypass channel and where the bypass channel converges with Tank Farm Creek. PCR #3 Compliance by Onsite Retention & Attach. E (10% Adjustment) PCR #3 Compliance by Onsite Retention Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 13 There are four storm drain networks that have pipe outlets located upstream vegetated swales. These four networks convey approximately 40% of the total runoff from Ph. 2-3 to Tank Farm creek via vegetated swales. Similar to the bypass channel, these flat-bottomed vegetated swales have minimal longitudinal slopes allowing low velocities for flow to the creek. Each pipe outlet also has rip rap to dissipate energy upstream of the vegetated swale. Two of the storm drain networks deliver approximately 20% of the Ph. 2-3 stormwater runoff to the existing agricultural drainage channel tributary to Tank Farm Creek. At each storm drain pipe outlet there is an energy dissipation device. The existing agricultural drainage channel will be vegetated and has longitudinal slope less than 0.50 percent. The storm drain network for DMA A conveys flow to the Phase 1 detention basin. Additional information on the flows within Tank Farm Creek can be found in the flood analysis for the Ph 2-6 CLOMR submitted to FEMA and the Avila Ranch 2-6 Drainage Design Report dated December 2022 and prepared by Wallace Group. Low Impact Development (LID) Design Strategies Low Impact Development design strategies for this project include the use of the following SCMs: · Roadside Bioswale with Underground Gravel Trench · Vegetated Retention Basins · Motorcourt/ Alley Underground Gravel Chambers · Shallow Retention Basin with Offset Gravel Chamber · Linear Bioswales with Underground Gravel Trench · Permeable Pavers with Underground Gravel Retention To manage, treat and retain the on-site stormwater runoff in a well distributed manner, these SCM/ LID features will be strategically located across the project site (see Appendix D for the overall Drainage Management Area Exhibit). Roadside Bioswale with Underground Gravel Trench The right-of-way between the roadside vertical curb and sidewalk allows for the construction of vegetated bioswales along Venture Drive in Phases 2 and 3, residential streets in Phase 5, and Jespersen Road in Phase 4. These vegetated bioswales with bioretention soil media (BSM) will be implemented to manage and treat the 95th percentile storm from surrounding lots and streets, where site infiltration rates allow. Larger storm events will flow back into the roadside curb/gutter and continue downstream to another series of SCMs or a storm drain inlet. This approach allows large flow events that exceed the capabilities of the SCMs to be conveyed by the flood control and storm drain systems. The bioswales will be sloped to match the longitudinal street grades to maintain low velocities suitable for vegetative filtering. Gravel check dams are to be spaced uniformly along the bioswale flowline and follow requirements set by the San Luis Obispo County LID Handbook (construction detail Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 14 103). Underground gravel retention facilities will accompany the bioswales. See Appendix G for SCM conceptual details. Figure 4. Roadside Bioswales with Underground Gravel Trench Concept Vegetated Basins In Phase 5, three vegetated infiltration basins are proposed. Each basin has been designed to maintain a retention depth of 0.6’ and an additional 1.0’ of freeboard. These vegetated basins provide infiltration area and stormwater quality treatment. Low flow storm drain facilities will be included in the Phases 2-6 public improvement plans to convey stormwater to vegetated basins in developed conditions. Motorcourt/ Alley Underground Gravel Chambers Motorcourt/ alley underground gravel chambers are proposed in Phases 2, 3 and 5. These underground gravel chambers beneath the road section will be parallel to the motorcourt or alley storm drain systems. Each gravel chamber will be supplied with stormwater in smaller storm events by a 4” perforated pipe connected to the storm drain network inlet boxes. Larger stormwater flows are conveyed by the primary storm drain piping system to Tank Farm Creek. See Appendix G for SCM conceptual details. 3. 0 0 ’ 3. 0 0 ’ Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 15 Figure 5. Motorcourt/ Alley Underground Gravel Chamber Concept Shallow Retention Basin with Offset Gravel Chamber In Phases 3 and 4, multiple shallow retention basins with offset gravel chambers are proposed in park areas for onsite stormwater retention and infiltration. The shallow retention basins will be constructed within managed turf areas within the parks. The retention depth is limited to 6” to provide for 72-hour drain times compatible with the basin’s dual-use and infiltration rates, required by the City of San Luis Obispo (Uniform Design Criteria 1010, section 5.1.5). Concrete box inlets with grates (24” by 24”) will be constructed within each shallow retention basin to allow for 6” of ponding and serve as connections to the underground gravel chambers. To provide additional retention storage, gravel chambers are proposed below or adjacent to the basins. Runoff enters the gravel chambers via 4" solid and perforated pipes. The gravel chamber depths are designed to maintain the groundwater separation criteria described above. See Appendix G for SCM conceptual details. 3. 0 0’ Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 16 Figure 6. Shallow Retention Basin with Offset Gravel Chamber Concept Linear Bioswales with Underground Gravel Trench Similar to the designs of the roadside bioretention facilities, additional linear bioretention facilities are proposed in Phases 3-5 parks and Phase 6 commercial lots. These facilities have been identified in size and depth and preliminarily placed based on current site projections for these lots. Further information on the preliminary placement of these linear bioretention facilities can be found on the SCM Exhibit in Appendix E. Final SCM design will be included in future park and commercial lot improvement plans. Permeable Pavers with Underground Gravel Retention In Phase 4, permeable pavers with underground gravel chambers are proposed in multiple parking areas. These underground gravel chambers are beneath the permeable paver section. Localized storm drain inlets connected to the onsite storm drain networks will accompany these facilities to capture stormwater from large storm events when the underground gravel chambers are at maximum retention capacity. Permeable paver system designs will occur with the final designs of the Phase 4 onsite improvement plans. Further information on the concepts of the permeable paver designs can be found on the SCM Exhibit in Appendix E and in the SCM Details in Appendix G. Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 17 Figure 7. Permeable Pavers with Underground Gravel Retention Concept Tract 3089 – Avila Ranch – Phases 2, 3, 4, 5 & 6 – Stormwater Control Plan December 21, 2022 Page 18 List of Appendices A. Site Information and Exhibits · City of San Luis Obispo SWCP Form · Watershed Management Zone Exhibit B. Soils, Infiltration, and Geotechnical Information · Excerpts from geotechnical documentation - Soils Engineering Report Update Avila Ranch Development, Phases II-VI, GeoSolutions, dated 1/26/2022 - Infiltration Testing Report for Avila Ranch Development, GeoSolutions, dated 2/9/2022 - Infiltration Testing Report – Avila Ranch Development, GeoSolutions Inc., dated 9/4/2015 · Porchet Infiltration Rate Calculations (2015 tests) · Avila Ranch Groundwater Information matrix · Stormwater Post-Construction Requirement SCM Separation from Groundwater Levels for Phases 2-6 Memo · Avila Ranch Groundwater Exhibit · Avila Ranch Infiltration Exhibits - Linear Infiltration exhibit - Porchet method Infiltration exhibit C. Existing Drainage Map D. Proposed Stormwater Control Drainage Management Area Exhibit E. Structural Control Measures (SCM) Exhibit Design · SCM Exhibit · Phases 2-6 Land Use Data · SCM Sizing Calculations · Central Coast Region SCM Sizing Calculator results - Phase 2 + 3 - Phase 4 - Phase 5 - Phase 6 F. Phases 2 & 3 – PCR #3 Attachment E Compliance · Ten Percent Adjustment to Retention Requirement calculation · Excerpts from RWQCB Resolution R3-2013-0032; Attachment 1 G. Structural Control Measures (SCM) Concepts · Roadside Bioswale with Underground Gravel Trench · Motorcourt/ Alley Underground Gravel Chamber · Shallow Retention Basins with Offset Gravel Chamber · SLO County LID Handbook detail 103 – Gravel Check Dams · SLO County LID Handbook detail 150 – Impermeable Layer APPENDIX A Site Information and Exhibits · City of San Luis Obispo SWCP Form · Watershed Management Zone Exhibit Stormwater Control Plan for Post Construction Requirements Exhibit 4 Application Submittal Where directions state “Done” that means no additional information or forms below that point needs to be filled out or furnished. See Exhibits for Watershed Management Zones, Basins, & Urban Sustainability Areas Use “n/a” where information requested is not applicable. If you are unsure regarding how to fill out any of the information, please come in and request assistance from a staff person. Project Information Step 1 Applicant Name: Application No: Project Name: Location Address: Location APN: Site Zoning: Project Type:  Commercial Detached Single Family Residential Industrial Multi-unit Residential Mixed Use Public Project Phase: Project Description: Total Project Site Area = (a) Total New Impervious Surface Area = (b) Total Replaced Impervious Surface Area = (c) Total Existing Impervious Area = (d) Total Impervious Area of Completed Project = (e) Net Impervious Area: (a+b) – (c-d) = OR where (c-d) is a negative number: (a+b) = Your project is NOT subject to Post Construction Requirements if… Step 2  Area (a+b) of project is < 2,500 square feet – Done OR  Area (a+b) of project is > 2,500 square feet, and is a project type listed below ( type) – Done  Road & parking surface repair – slurry & fog & crack seal, pothole & spot patching, overlay & resurfacing & other damage repair with no expansion  Road & parking shoulder grading  Road & parking cleaning, repairing, maintaining, reshaping, regarding drainage systems  Sidewalk & bike path / lane project – no other impervious surface created and runoff is directed to vegetated area  Curb & gutter improvement or replacement – no other impervious created  Underground utility project – surface replaced in kind  Utility vaults – Ex: lift stations, backflows  Fuel storage – above ground with spill containment  Photovoltaic systems – on existing impervious surface, over pervious surface with vegetated cover, buffer strip at the most down gradient row of panels  Second story – no increase in building footprint  Decks & stairs & walkways – raised with space below for drainage  Temporary structures – in place less than 6 months  Trails and pathways, where no other impervious surfaces are replaced or created, and built to direct stormwater runoff to adjacent vegetated areas. Form revised: July 12, 2016 APPENDIX A     Stormwater Control Plan for Post Construction Requirements    Otherwise, your project is subject to the Post Construction Requirements   Project Site Details Step 3    Watershed Management Zone:   Urban Sustainability Area Name:   Meet USA Conditions     See Area calculations in Step 1 to compare to thresholds in each Step below   Where directions state “Go To”, fill out and attach the referenced Form and any supporting documents    Step 4  Project is > 2,500 square feet      Yes ‐ Go To Requirement 1 – Site Design & Runoff Reduction  ‐ Form 1  AND THEN   Go To Step 5    Step 5  Detached single family residential project where Area (e) is > 15,000 square feet OR   Project where Area (e) > 5,000 square feet     Yes ‐ Go To Requirement 2 – Water Quality Treatment ‐ Form 2  AND THEN   Go To Step 6     No ‐ Done    Step 6  Detached single family residential project where Area (e) > 15,000 square feet OR   Project where Area (a+b) > 15,000 square feet     AND is in Watershed Management Zone 4,7,10 over a ground water basin OR in Zone 1,2,5,6,8,9      Yes ‐ Go To Requirement 3 – Runoff Retention  ‐ Form 3  AND THEN   Go To Step 7     No ‐ Done    Step 7  Project where Area (a+b) > 22,000 square feet AND is in Watershed Management Zone 1,2,3,6,9      Yes ‐ Go To Requirement 4 – Peak Management ‐ Form 4       No ‐ Done    Exhibits 1. Watershed Management Zones  2. Groundwater Basin Location  3. Watershed Management Zone Revision Request  4. Urban Sustainability Conditions and Maps of Approved Areas        APPENDIX A Stormwater Control Plan for Post Construction Requirements Form 1 Requirement 1 – Site Design and Runoff Reduction: Identify the strategies used to reduce runoff through site design. Strategies 1-5 required. Describe or attach simple plan details for 1. – 5. 1.Limit disturbance of creeks and natural drainage features and setback development from these features. 2.Minimize compaction of highly permeable soils 3.Minimize clearing of native vegetation and grading, conserving natural areas and maximizing undisturbed areas, and developing along natural landforms. 4.Minimize impervious surfaces including roadways and parking lots 5.Do one of the following:  Direct roof run off into cistern, rain barrel, or vegetated area Direct driveway, walkways, patios, and/or parking area into vegetated area Construct surfaces (bike lanes, walks, driveways, parking areas,patios) with permeable surfaces 6.Other (Optional): Identify strategy(s) and describe or show how it will be done in the project. Open space and preservation of ag land will be a priority - as well as maintaining existing riparian environment APPENDIX A Stormwater Control Plan for Post Construction Requirements Form 2 Requirement 2 – Water Quality Treatment: (Reference Post Construction Stormwater Management Requirements for Development Projects in the Central Coast Region – Adopted July 12, 2013 California Regional Water Quality Control Board Central Coast Region – for details regarding requirements – Section B.3 and Section C. Alternative Compliance.) Treatment Location   On Site  Off Site - Alternative Compliance Measure Used   1. Harvesting, infiltration, evapotranspiration  2. Bio-filtration Treatment (Document inability to use 1.)  3. Non-Retention Based Treatment (Document inability to use 1. or 2.) Description of structural controls: Alternative compliance measures: Attachments  Attach treatment/sizing calculations, including any volume treated with off-site compliance.  Attach construction and planting details and specifications for bio-filtration options  Attach documentation regarding Treatment Measure selection  Attach infeasibility analysis where alternative compliance is proposed. Certification I certify that the systems selected and sized, as demonstrated in the attached calculations, meet the Water Quality Treatment required for this project per the Post Construction Requirements adopted by the Central Coast Regional Water Quality Control Board. Where identified in the attached documentation, Water Quality Treatment will be met through alternative compliance. Signature Date APPENDIX A Stormwater Control Plan for Post Construction Requirements Form 3 Requirement 3 – Runoff Retention: (Reference Post Construction Stormwater Management Requirements for Development Projects in the Central Coast Region – Adopted July 12, 2013 California Regional Water Quality Control Board Central Coast Region – for details regarding requirements – Section B.4 and Section C. Alternative Compliance.)  If a revision to the site’s Watershed Management Zone is being requested, attach Watershed Management Revision Request Form (Exhibit) and supporting documentation.  Rainfall maps are available from the Regional Water Quality Control Board Site Assessment Measures Summary  Attach documentation of the following information:  Site topography  Development envelope  Hydrologic features including natural areas, wetlands, watercourses, seeps, springs, and required setbacks  Vegetative cover including trees  Open space requirements  Location of groundwater wells used for drinking water  Depth to seasonal high groundwater  Soil types and hydrologic soil groups  Depth to impervious layer such as bedrock  Presence of unique geology (e.g. karst)  Geotechnical hazards  Existing structures, utilities, and drainage infrastructure including municipal storm drain system components  Existing easements and covenants  Documented soil or groundwater contamination  Source and estimated stormwater run-on from offsite, coming to project area  Drainage Management Areas (B.4.d.iii)  Drainage management strategies by Drainage Management Area  Runoff reduction measures and any structural control measures by Drainage Management Area (or full site as appropriate)  Technical infeasibility limits on-site compliance  10% of equivalent impervious surface area is dedicated to retention based stormwater control measures – No alternative compliance for retention Runoff volume - compliance not achieved on-site:  Alternative compliance for retention proposed Runoff volume – compliance not achieved onsite: Runoff volume – alternative compliance used: Analysis and Sizing  Attach calculated Tributary Areas and Design Volumes per the Post Construction Stormwater Management Requirements – Attachment D  Adjustment made for redevelopment  Adjustment made for being in, and meeting requirements of, an Urban Sustainability Area Note: 10% EISA for Phases 2-3 due to groundwater. Retention volume maximized where possible APPENDIX A Stormwater Control Plan for Post Construction Requirements Form 3 Control Mechanism Site in Zone 1, 4, 7, and/or 10 and over groundwater basin  95th percentile event retained via infiltration  Finding of technical infeasibility – Structural Stormwater Measure proposed Site in Zone 2  95th percentile event retained via storage, harvesting, infiltration, and/or evapotranspiration  Finding of technical infeasibility – Structural Stormwater Measure proposed Site in Zone 5 and/or 8  85th percentile event retained via infiltration  Finding of technical infeasibility – Structural Stormwater Measure proposed Site in Zone 6 and/or 9  85th percentile event retained via storage, harvesting, infiltration, and/or evapotranspiration  Finding of technical infeasibility – Structural Stormwater Measure proposed Attachments  Attach Attachment D calculations for hydrologic analysis and stormwater control measure sizing  Attach discussion of technical infeasibility for structural stormwater measure, where proposed in lieu of preferred storage, harvesting, infiltration, and/or evapotranspiration, include justification for any non- retention based controls  Attach documentation of technical infeasibility for on-site compliance, including a site specific hydrologic and/or design analysis supporting findings  Attach description of alternative compliance project including a summary description of pollutant and flow reduction comparing the expected aggregate results of the alternate project to the results that would otherwise have been achieved by meeting the numeric performance requirements onsite.  Attach Attachment E calculations for retention requirement adjustment for technical infeasibility  Attach Attachment F calculations for off-site retention requirements  Attach agreement for alternative compliance site use, for purposes of achieving compliance  Attach Operations and Maintenance Plan for all stormwater control measures (include any Peak Management facilities) Post-Construction Owner Identification At the time of completion of the construction work, and the shift to post-construction stormwater controls, the below listed owner is responsible for Operations and Maintenance of stormwater control measures: (If responsibilities are divided, list all responsible owners and associated measures.) Certification I certify that the systems selected, sized, and designed as demonstrated in the attached calculations, meet the Runoff Retention Performance Requirement for this project per the Post Construction Requirements adopted by the Central Coast Regional Water Quality Control Board. Where identified in the attached documentation, Runoff Retention will be met through alternative compliance. Signature Date Phases 2 & 3: Underground gravel chambers in motorcourts = HOA // Roadside bioretention swales within city right-of-way = CFD // Underground gravel chamber in parks = CFD // Retention-based Bypass Channel = CFD Phase 4: retention-based facilities within city right-of-way and within parks = CFD // Retention-based facilities located on privately-owned residential lots = Private Homeowner or Landowner Phase 5: Roadside bioretention swales within city right-of-way and within parks = CFD // Vegetated surface retention basins along creek = CFD // Underground gravel chambers in Alley = CFD APPENDIX A Stormwater Control Plan for Post Construction Requirements Form 4 Requirement 4 – Peak Management (Reference Post Construction Stormwater Management Requirements for Development Projects in the Central Coast Region – Adopted July 12, 2013 California Regional Water Quality Control Board Central Coast Region – for details regarding requirements – Section B.5) Show any stormwater control measures used to meet the requirements of this section, in the documentation and attachments required for Retention (Form 3), including in all mapping and Operations and Maintenance materials. Peak Management Compliance  Post-development peak flows, discharged from the site, do not exceed pre-project peak flows for the 2 through 10 years storm events.  Technical infeasibility limits on-site compliance  Alternative compliance for retention proposed Runoff volume – compliance not achieved onsite: Runoff volume – alternative compliance used: Attachments  Attach calculations showing pre-project discharge and post-project discharge for the 2 through 10 year storm events  Attach documentation of technical infeasibility for on-site compliance, including a site specific hydrologic and/or design analysis supporting findings  Attach description of alternative compliance project including a summary description of pollutant and flow reduction comparing the expected aggregate results of the alternate project to the results that would otherwise have been achieved by meeting the numeric performance requirements onsite.  Attach agreement for alternative compliance site use, for purposes of achieving compliance Post-Construction Owner Identification At the time of completion of the construction work, and the shift to post-construction stormwater controls, the below listed owner is responsible for Operations and Maintenance of the peak management control measures: (If responsibilities are divided, list all responsible owners and associated measures.) Certification I certify that the systems selected, sized, and designed as demonstrated in the attached calculations, meet the Peak Management requirements for this project per the Post Construction Requirements adopted by the Central Coast Regional Water Quality Control Board. Where identified in the attached documentation, Peak Management will be met through alternative compliance. Signature Date See the Avila Ranch Development – Phase 1 Drainage Report prepared by RRM, 9/17/2018. APPENDIX A Stormwater Control Plan for Post Construction Requirements Exhibit 1 Watershed Management Zones Avila Ranch Project Site APPENDIX A Stormwater Control Plan for Post Construction Requirements Exhibit 2 Ground Water Basin Avila Ranch Project Site APPENDIX A APPENDIX B Soils, Infiltration, and Geotechnical Information · Excerpts from geotechnical documentation - Soils Engineering Report Update Avila Ranch Development, Phases II-VI, GeoSolutions, dated 1/26/2022 - Infiltration Testing Report for Avila Ranch Development, GeoSolutions, dated 2/9/2022 - Infiltration Testing Report – Avila Ranch Development, GeoSolutions Inc., dated 9/4/2015 · Porchet Infiltration Rate Calculations (2015 tests) · Avila Ranch Groundwater Information matrix · Stormwater Post-Construction Requirement SCM Separation from Groundwater Levels for Phases 2-6 Memo · Avila Ranch Groundwater Exhibit · Avila Ranch Infiltration Exhibits - Linear Infiltration exhibit - Porchet method Infiltration exhibit RFI # 1 – GROUNDWATER CONTOUR MAP Avila Ranch Developers, Inc.: Background: GeoSolutions, Inc. was contacted regarding groundwater levels for Phase II-VI of the residential and commercial portions the Avila Ranch Development at Buckley Road and Vachell Lane, APN's: 053-259-004, -005 & -006 in San Luis Obispo, California. The map was created by Wallace Group, using data collected from 2001 to 2021. When plotted the data shows a strong gradient moving from east to west and north to south. The shallowest water is at the low point of the development, nearest Buckley Road and Higuera Street. Summary The data plots model an expected groundwater gradient in the valley sediments. Given the models predictions, it is possible to set 3 to 5 piezometers to verify depths and investigate any possible seasonal or long-term variations in the data. This would enhance future design and construction methods for the subdivision. If you have any questions or require additional assistance, please feel free to contact the undersigned at (805) 614-6333. Sincerely, GeoSolutions, Inc. Patrick B. McNeill, PE Principal \\192.168.1.100\s\SL09000-SL09499\SL09304-9 - Avila Ranch, Phase II-VI Residential Dev\Construction\SL09304-9 - Avila Ranch, Phase II-VI Residential Dev RFI # 1.doc Reference: Percolation Testing, Avila Ranch Subdivision, Tentative Tract 2452, Buckley Road, San Luis Obispo, California, by Easrth Systems Pacific, File No SL-10632-SC, dated December 18, 2001. Soils Engineering Report, Avila Ranch Lift Station. Avila Ranch Development, Buckley Road and Vachell Lane, APNs: 053-259-004, 005, & 006, San Luis Obispo, California, by GeoSolutions, Inc., Project SL09304-8, dated April 6, 2021. Soils Engineering Report Update, Avila Ranch Development Phase II-VI, Buckley Road and Vachell Lane, APNs: 053-259-004, 005, & 006, San Luis Obispo, California, by GeoSolutions, Inc., Project SL09304-10, dated January 26, 2022. DATE: December 6, 2022 PROJECT NUMBER: SL09304-9 CLIENT: Avila Ranch Developers, Inc. c/o Wathen Castonos Homes 735 Tank Farm Road, Suite 290 San Luis Obispo, California 93401 PROJECT NAME: Phase II-VI at Avila Ranch Development, at Buckley Road and Vachell Lane APN's: 053-259-004, - 005 & -006 San Luis Obispo, California APPENDIX B SOILS ENGINEERING REPORT UPDATE AVILA RANCH DEVELOPMENT PHASE II - VI, BUCKLEY ROAD AND VACHELL LANE APN’S: 053-259-004, 005 & 006 SAN LUIS OBISPO, CALIFORNIA PROJECT SL09304-10 Prepared for Avila Ranch Developers, Inc. c/o Wathen Castonos Homes 735 Tank Farm Road, Suite 290 San Luis Obispo, California 93401 Prepared by GEOSOLUTIONS, INC. 1021 TAMA LANE, SUITE 105 SANTA MARIA, CALIFORNIA 93454 (805) 614-6333 © January 26, 2022 APPENDIX B SOILS ENGINEERING REPORT UPDATE Avila Ranch Developers, Inc: This Soils Engineering Report Update has been prepared for Phases II-VI of the Avila Ranch Development at Buckley Road and Vachell Lane, APN's: 053-259-004, - 005 & - 006 in San Luis Obispo, California. Geotechnically, the site is suitable for the proposed development provided the recommendations in this report for site preparation, earthwork, foundations, slabs, retaining walls, and pavement sections are incorporated into the design. The results of our on-site investigation show poor soil conditions (expansive clays). The client has selected to use post tension foundations as a method of support. This report provides both post tension and deepened footing and grade beam type foundation system recommendations. It is critical that uniform moisture contents be maintained during construction as verified by GeoSolutions, Inc. Thank you for the opportunity to have been of service in preparing this report. If you have any questions or require additional assistance, please feel free to contact the undersigned at (805) 614-6333. Sincerely, GeoSolutions, Inc. Patrick B. McNeill, PE Principal DATE: January 26, 2022 PROJECT NUMBER: SL09304-10 CLIENT: Avila Ranch Developers, Inc. c/o Wathen Castonos Homes 735 Tank Farm Road, Suite 290, San Luis Obispo, California 93401 PROJECT NAME: Avila Ranch Development Buckley Road, between South Higuera and Vaschell Lane, San Luis Obispo, California California APPENDIX B Avila Ranch Phases II-VI January 26, 2022 Project SL09304-10 TABLE OF CONTENTS 1.0 INTRODUCTION .............................................................................................................................. 1 1.1 Site Description ................................................................................................................... 1 1.2 Project Description .............................................................................................................. 1 2.0 PURPOSE AND SCOPE ................................................................................................................. 2 3.0 FIELD AND LABORATORY INVESTIGATION ................................................................................ 3 4.0 SEISMIC DESIGN CONSIDERATIONS .......................................................................................... 5 5.0 LIQUEFACTION HAZARD ASSESSMENT ..................................................................................... 6 6.0 GENERAL SOIL-FOUNDATION DISCUSSION .............................................................................. 6 7.0 CONCLUSIONS AND RECOMMENDATIONS................................................................................ 6 7.1 Preparation of Building Pad ................................................................................................ 7 7.2 Preparation of Paved Areas ................................................................................................ 8 7.3 Pavement Design ................................................................................................................ 8 7.4 Conventional Foundations .................................................................................................. 9 7.5 Post-Tensioned Slabs ....................................................................................................... 11 7.6 Slab-On-Grade Construction ............................................................................................ 13 7.7 Exterior Concrete Flatwork- Bike Paths ............................................................................ 14 7.8 Retaining Walls ................................................................................................................. 14 8.0 ADDITIONAL GEOTECHNICAL SERVICES ................................................................................. 17 9.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS ................................................................... 18 REFERENCES APPENDIX A Field Investigation Soil Classification Chart Boring Logs (GeoSolutions, Inc., 2015) APPENDIX B Laboratory Testing Soil Test Reports (GeoSolutions, Inc., 2015) APPENDIX C Seismic Hazard Analysis Design Map Summary (SEAOC, 2019) APPENDIX D Preliminary Grading Specifications Key and Bench with Backdrain APPENDIX E Volflo V1.5 APPENDIX B Avila Ranch Phases II-VI January 26, 2022 Project SL09304-10 LIST OF FIGURES Figure 1: Site Location Map .......................................................................................................................... 1 Figure 2: Site Plan ......................................................................................................................................... 2 Figure 3: Google Earth Image (Boring Locations) ........................................................................................ 3 Figure 4: Regional Geologic Map ................................................................................................................. 4 Figure 5: Setback Dimensions – Slope Gradients Between 3-to-1 and 1-to-1 .......................................... 11 Figure 6: Center Lift Diagram ...................................................................................................................... 12 Figure 7: Edge Lift Diagram ........................................................................................................................ 12 Figure 8: Sub-Slab Detail ............................................................................................................................ 13 Figure 9: Retaining Wall Detail .................................................................................................................. 15 Figure 10: Retaining Wall Active and Passive Wedges .............................................................................. 16 LIST OF TABLES Table 1: Engineering Properties - (GeoSolutions, Inc., 2015) ...................................................................... 5 Table 2: Seismic Design Parameters ............................................................................................................ 6 Table 3: Native Subgrade (R-Value of 5) ...................................................................................................... 9 Table 4: Type II Biaxial Geogrid (R-Value of 25) .......................................................................................... 9 Table 5: Minimum Footing and Grade Beam Recommendations ............................................................... 10 Table 6: Post-Tension Foundation Criteria ................................................................................................. 11 Table 7: Minimum Slab Recommendations ................................................................................................ 13 Table 8: Retaining Wall Design Parameters .............................................................................................. 15 Table 9: Required Verification and Inspections of Soils ............................................................................. 18 APPENDIX B SOILS ENGINEERING REPORT UPDATE AVILA RANCH DEVELOPMENT, PHASE II TO VI BUCKLEY ROAD AND VACHELL LANE APN’S: 053-259-004, 005 & 006 SAN LUIS OBISPO, CALIFORNIA PROJECT SL09304-10 1.0 INTRODUCTION This report presents the results of the geotechnical investigation for Phases II-VI of the residential and commercial portion the Avila Ranch Development at Buckley Road and Vachell Lane, APN's: 053-259- 004, - 005 & -006 in San Luis Obispo, California. See Figure 1: Site Location Map for the general location of the project area. Figure 1: Site Location Map was obtained from the website application TopoView (USGS, 2013. This report serves as an update to the referenced Soils Engineering Report dated September 3, 2015 by GeoSolutions, Inc. (GeoSolutions, Inc., 2015). It is intended to address the applicable changes to the referenced report (GeoSolutions, Inc., 2015) required by the adoption of the 2019 California Building Code (CBSC, 2019). 1.1 Site Description Avila Ranch is located at 35.239 degrees north latitude and 120.669 degrees west longitude at a general elevation of 115 feet above mean sea level. The property is approximately 149.96 acres in size. The nearest intersection is where Buckley Road intersects Vachell Lane at the southeast corner of the property. The Site is vacant of structures and undeveloped. The Site was being actively farmed during our field investigation. Currently, the fields are left tilled and planted in grass. The surrounding area is primarily industrial/commercial or agriculture. There is a small creek that runs from the northeast along the center of the property that requires several crossings. The specific recommendations for the crossings (bridge piers) are addressed under a separate report. 1.2 Project Description The proposed development is to consist of multiple residential housing types, commercial buildings, parks and open space. The structures are anticipated to range between one and three stories in height. To provide access across the site, given the presence of a creek, two bridges are expected to be constructed. The Figure 1: Site Location Map APPENDIX B Avila Ranch Phases II-VI January 26, 2022 Project SL09304-10 2 project property will hereafter be referred to as the “Site.” See Figure 2: Site Plan for the general layout of the Site. At the time of the preparation of this report, it is assumed the proposed structures may be constructed using light wood framing, masonry, steel, or concrete tilt-up type construction. Retaining walls are expected to be constructed as part of this project. It is anticipated that the proposed residential and commercial development areas will utilize slab-on-grade lower floor systems. Dead and sustained live loads are currently unknown. They are anticipated to be for continuous footing and column loads to be approximately 1.5 to 3.0 kips per linear foot and 15 to 50 kips, respectively. 2.0 PURPOSE AND SCOPE The purpose of this study was to explore and evaluate the surface and sub-surface soil conditions at the Site and to develop geotechnical information and design criteria. The scope of this study includes the following items: 1. A literature review of available published and unpublished geotechnical data pertinent to the project site including geologic maps, available on-line or in-house aerial photographs, and review of previous GeoSolutions, Inc., report dated September 3, 2015. 2. A review of the previous field study which consisted of site reconnaissance and subsurface exploration including exploratory borings in order to formulate a description of the sub-surface conditions at the Site. Figure 2: Site Plan APPENDIX B Avila Ranch Phases II-VI January 26, 2022 Project SL09304-10 3 3. A review laboratory testing performed on representative soil samples that were collected during our field study. 4. A review of engineering analysis of the data gathered during our literature review, field study, and laboratory testing. 5. Development of recommendations for site preparation and grading as well as geotechnical design criteria for building foundations, retaining walls, pavement sections, underground utilities, and drainage facilities. 3.0 FIELD AND LABORATORY INVESTIGATION The field investigation, as described in the referenced report (GeoSolutions, Inc., 2015), was conducted on July 29 and 30, 2015 utilizing a Mobile B-24 drill rig. Six six-inch borings were advanced to a maximum depth of 25 feet below ground surface (bgs) at the approximate locations indicated on Figure 3: Google Earth Image. Sampling methods included the Standard Penetration Test utilizing a standard split-spoon sampler (SPT) without liners and a Modified California sampler (CA) with liners. The Mobile B-24 drill rig was equipped with a safety hammer, which has an efficiency of approximately 60 percent and was used to obtain test blow counts in the form of N-values Data gathered during the field investigation suggest that the soil materials at the Site consist of alluvial soil (expansive clays) overlying formational material. The surface material at the Site generally consisted of varying shades of black sandy fat CLAYs (CH) encountered in a stiff condition to approximately 10.0 feet bgs. The soils were generally dry at the surface. On the north side of the creek, the soils become wet at 6 to 9 feet in depth. Shallow water was encountered during grading for the Phase 1 development and was detected from 6 to 10 feet bgs near Tango, Bravo, and Earthwood (B-1, B-2, and B-3 and the boring for the wet well, GeoSolutions, Inc. 2021). Shallow groundwater was encountered on the south side of the creek during boring operations for the bridge crossings near B-4. Figure 3: Google Earth Image (Boring Locations) APPENDIX B Avila Ranch Phases II-VI January 26, 2022 Project SL09304-10 4 Regional site geology was obtained from United States Geological Survey MapView internet application (USGS, 2013) which compiles existing geologic maps. Figure 4: Regional Geologic Map presents the geologic conditions in site vicinity as mapped on the Geologic Map of the Pismo Beach Quadrangle (Dibblee, 2006). The CLAY and the majority of all underlying material at the Site was interpreted as older alluvium. Groundwater was encountered in borings B-1 and B-2 at 18 feet bgs and 10 feet bgs, respectively. A review of borings completed in 2001 (Earth Systems Pacific, 2001) groundwater was 7 to 9 feet deep on the east property line, 5 to 7 feet deep along the creek, and 4 to 9 feet deep along the northern property line. During the boring operations of the referenced report (GeoSolutions, Inc., 2015), the soils encountered were continuously examined, visually classified, and sampled for general laboratory testing. A project engineer has reviewed a continuous log of the soils encountered at the time of field investigation. The Boring Logs from the referenced report (GeoSolutions, Inc., 2015) are attached in Appendix A. Figure 4: Regional Geologic Map APPENDIX B Avila Ranch Phases II-VI January 26, 2022 Project SL09304-10 5 Table 1: Engineering Properties - (GeoSolutions, Inc., 2015) As part of the preparation of the referenced report (GeoSolutions, Inc., 2015), laboratory tests were performed on soil samples obtained from the Site during boring operations. The results of these tests are listed in Table 1: Engineering Properties - (GeoSolutions, Inc., 2015). Laboratory data reports and detailed explanations of the laboratory tests performed during this investigation are provided in Appendix B. 4.0 SEISMIC DESIGN CONSIDERATIONS Estimating the design ground motions at the Site depends on many factors including the distance from the Site to known active faults; the expected magnitude and rate of recurrence of seismic events produced on such faults; the source-to-site ground motion attenuation characteristics; and the Site soil profile characteristics. According to section 1613 of the 2019 CBC (CBSC, 2019), all structures and portions of structures should be designed to resist the effects of seismic loadings caused by earthquake ground motions in accordance with the ASCE 7: Minimum Design Loads for Buildings and Other Structures, hereafter referred to as ASCE 7-16 (ASCE, 2016). The Site soil profile classification (Site Class) can be determined by the average soil properties in the upper 100 feet of the Site profile and the criteria provided in Table 20.3-1 of ASCE 7-16. Spectral response accelerations and peak ground accelerations, provided in this report were obtained using the computer-based Seismic Design Maps tool available from the Structural Engineers Association of California (SEAOC, 2019). This program utilizes the methods developed in ASCE 7-16 in conjunction with user-inputted Site location to calculate seismic design parameters and response spectra (both for period and displacement) for soil profile Site Classes A through E. Sa m p l e N a m e Sample Description US C S S p e c i f i c a t i o n Ex p a n s i o n I n d e x Ex p a n s i o n Po t e n t i a l Ma x i m u m D r y De n s i t y , γd (p c f ) Op t i m u m M o i s t u r e (% ) An g l e o f I n t e r n a l Fr i c t i o n , φ (d e g . ) Co h e s i o n , c ( p s f ) Pl a s t i c i t y I n d e x Fi n e s C o n t e n t ( % ) Co m p r e s s i o n In d e x , C C Re c o m p r e s s i o n In d e x , C r A Very Dark Grayish Brown Sandy Fat CLAY CH 100 High - - - - 47 - - - B Light Yellowish Brown Sandy Fat CLAY CH 110 High - - - - 47 - - - C Very Dark Gray Sandy Fat CLAY CH 87 Medium - - - - 33 - - - E Light Brown Silty CLAY SC 41 Low - - - - 41 - - - F Olive Brown Silty SAND SM 27 Low - - - - N/A - - - G Very Dark Gray Sandy Fat CLAY CH 106 High - - - - 35 - - - B-2 @ 5’ Very Dark Grayish Brown Sandy CLAY SC - - - - 10.5 400 - - 0.091 0.009 B-6 @ 5’ Black Sandy CLAY CL - - - - 18.2 308 - - 0.081 0.008 APPENDIX B INFILTRATION TESTING REPORT INTRODUCTION GeoSolutions, Inc. has been contracted to perform infiltration testing at the development known as Avila Ranch in San Luis Obispo County, California. See Figure 1: Site Location Map for the general location of the project area. The property will hereafter be referred to as the “Site”. A total of thirteen infiltration test wells were placed at the end of November and early December 2021. Prior to drilling operation each site (storm water control measure- SCM) was located and a stake was placed by a survey crew indicating the bottom elevation of the proposed SCM. The test holes were drilled to the approximate bottom elevation indicated on the stake and an approximate 2-foot sample was obtained at the bottom and returned to the laboratory (driven CAL - no rings). An Atterberg limit (PI) and sieve (#200 wash) result was obtained from each site. Shortly after the wells where placed, a series of winter storms arrived with approximately ten inches of rain falling over a two-week period. The following rain gauge data was taken from the “Gas Company” site located near the airport. Table 1: Gas Company Rain Data Figure 1: Site Location Map DATE: February 9, 2022 PROJECT NUMBER: SL09304-9 CLIENT: Avila Ranch Developers, Inc. c/o Wathen Castonos Homes 735 Tank Farm Road, Suite 290, San Luis Obispo, California 93401 PROJECT NAME: Avila Ranch Development Buckley Road, between South Higuera and Vaschell Lane, San Luis Obispo, California California APPENDIX B Avila Ranch- Residential February 9, 2022 Project SL09304-9 2 FIELD EXPLORATION The approximate locations of the thirteen test wells are indicated on Figure 2: Infiltration Test Locations. Three- inch diameter perforated PVC pipe was placed in the infiltration test borings on a few inches of bedding pea gravel and the annular spaces were filled with clean pea gravel. In addition, each pipe was wrapped with a filter sock. The following field soil classifications for the borings are in accordance with the Unified Soils Classification System (USCS). The material at the Site generally consisted of varying shades of brown fat CLAY (CH) in a moist to wet condition typical of alluvial soils. I-13 encountered a sand, clay gravel mix that is typical of stream deposits. This material was not encountered in an extensive area and is likely discontinuous. LABORATORY TEST RESULTS In general, the test results indicate the soils are typically plastic clays with high fine contents. I-13 was an exception at 8 percent fines and I-20 at 30 percent fines. See attached laboratory results for further detail. Figure 2: Infiltration Test Locations APPENDIX B Avila Ranch- Residential February 9, 2022 Project SL09304-9 3 HISTORIC GROUNDWATER READINGS See the attached Plate 1 for historical borings locations and groundwater depths (ESP, 2001 and GeoSolutions, Inc., 2015 & 2021). INFILTRATION TESTING Prior to infiltration testing, each infiltration test boring was presoaked to a stabilized percolation rate. Infiltration testing consisted of maintaining a constant head (gallons per minute) for 30 minutes, with the total volume (ft3) recorded. The depth to water was measured immediately following the pre-saturation cycle. Measurements were then performed for a determined period of time of 30 minutes. Testing was terminated after an elapsed time of 240 minutes. The infiltration rates (in inches per hour) were calculated by dividing the time period of the last reading obtained by the recorded water elevation drop. The infiltration test results for the Site are presented below in Table 2: Infiltration Test Results. Table 2: Infiltration Test Results Dates Test Location Infiltration Rate (inches/hour) Infiltration Rate (inches/hour) Porchet Method February 7, 2022 I-12 0.96 0.02 submerged I-13 - - submerged I-14 - - January 15, 2022 I-15 1.92 0.09 February 4, 2022 I-16 5.52 0.74 January 21, 2022 I-17 2.88 0.10 January 24, 2022 I-18 1.68 0.11 January 21, 2022 I-19 1.92 0.13 January 21, 2022 I-20 3.84 0.26 February 4, 2022 I-21 2.16 0.25 Inaccessible I-22 - - February 6, 2022 I-23 1.68 0.10 February 6, 2022 I-24 0.24 0.03 CONCLUSIONS Above are results of a four-hour infiltration test. The infiltration test results indicate that infiltration rates of the materials can be categorized for hydrologic purposes utilizing the Hydrologic Soil Group (HSG) classification ranging from group C to D (Part 630, Hydrology, National Engineering Handbook, 2007). Based on the clay content “Passing #200 Sieve”, the soils generally classify as Group D. For long duration saturated conditions, the soils will behave as a Group D. Based on the information available today we would recommend the use of 0.02 to 0.06 inches per hour for D soils and to 0.14 inches per hour for C soils where it is required that the SCM fully empty prior to the next storm event. Group C-Soils in Group C have moderately high runoff potential when the thoroughly wet. Water transmission through the soil is somewhat restricted. Group C soils typically have between 20 percent and 40 percent clay and less than 50 percent sand and have loam, silt loam, sandy clay loam, clay loam, and silty clay loam textures. APPENDIX B Avila Ranch- Residential February 9, 2022 Project SL09304-9 4 Some soils having clay, silty clay, or sandy clay textures may be placed in this group if they are well aggregated, of low bulk density, or contain greater than 35 percent rock fragments. The limits on the diagnostic physical characteristics of Group C are as follows. The saturated hydraulic conductivity in the least transmissive layer between the surface and 20 inches is between 0.14 inches per hour and 1.42 inches per hour. The depth to any water impermeable layer is greater than 20 inches. The depth to the water table is greater than 24 inches. Soils that are deeper than 40 inches of the surface exceeds 0.06 inches per hour but is less than 0.57 inches per hour. Group D-Soils in Group D have high runoff potential when thoroughly wet. Water movement through the soil is restricted or very restricted. Group D soils typically have greater than 40 percent clay, less than 50 percent sand, and have clayey textures. In some areas, they also have a high shrink-swell potential. All soils with a depth to a water impermeable layer less than 20 inches and all soils with a water table within 24 inches of the surface are in this group, although some may have a dual classification, if they can be adequately drained. The limits on the diagnostic physical characteristics of Group D are as follows. For soils with a water impermeable layer at a depth between 20 and 40 inches, the saturated hydraulic conductivity in the least transmissive soil layer is less than or equal to 0.14 inches per hour. For soils that are deeper than 40 inches to a restriction or water table, the saturated hydraulic conductivity of all soil layers within 40 inches of the surface is less than or equal to 0.06 inches per hour. (Part 630, Hydrology, National Engineering Handbook, 2007) LIMITATIONS Changes in the location of the proposed storm water control measures will render our findings invalid unless our staff reviews such changes. Subsurface exploration of any site is not necessarily confined to selected location and conditions may, and often do, vary between and around these locations. If varied conditions are encountered during installation, additional exploration and testing may be required. If the installer should discover field conditions that are different from those described in this letter, GeoSolutions, Inc. should be notified immediately for further evaluation. Thank you for the opportunity to have been of service for Infiltration testing and reporting. If you have any questions or require additional assistance, please feel free to contact the undersigned at (805) 614-6333. Sincerely, GeoSolutions, Inc. Patrick B. McNeill, PE Principal Attachments: Plate 1 Groundwater Exhibit, Infiltration Boring Logs, Infiltration Test Results, Laboratory Test Results, Appendix D Sections 1 and 4 of San Luis Obispo County Grading and Stormwater Management New Storm Water Post Construction Requirements Handbook. \\192.168.1.100\s\SL09000-SL09499\SL09304-9 - Avila Ranch, Phase II-V Residential Dev\Environmental\SL09304-9 - Avila Ranch, Residential Dev Infiltration Report.doc APPENDIX B APPENDIX B GeoSolutions, Inc.(805) 543 - 8539 Boring Hole Depth (ft)Sample LL PI γd_max (pcf) ωc_opt (%) C (psf) ø (deg) C (psf) ø (deg) I-12 13'Very Dark Gray Fat CLAY CH 34.6 94.0 65 44 I-13 6'Grayish Brown Well Graded SAND with Clay and Gravel SW-SC 8.0 I-14 5'Very Dark Grayish Brown Fat CLAY CH 38.3 86.6 83 66 I-15 8'Very Dark Grayish Brown Fat CLAY CH 36.1 98.6 63 43 I-16 8'Light Olive Brown Fat CLAY CH 35.8 93.5 53 32 I-17 10'Olive Brown Sandy Fat CLAY CH 20.6 68.4 50 36 I-18 6'Olive Brown Sandy Fat CLAY CH 23.2 69.7 54 33 I-19 7'Olive Brown Sandy Lean CLAY CL 21.9 56.6 36 24 I-20 8'Dark Grayish Brown Clayey SAND with Gravel SC 30.4 I-21 5'Light Olive Brown Fat CLAY CH 31.2 99.6 64 42 I-22 3'Very Dark Grayish Brown Fat CLAY CH 36.6 99.6 80 60 I-23 6'Very Dark Grayish Brown Sandy Lean CLAY CL 19.2 65.1 48 36 I-24 3'Olive Brown Fat CLAY with Sand CH 17.8 74.6 50 36 LABORATORY SUMMARY REPORT SHEET Sample ID Material Description Dr y D e n s i t y (p c f ) Mo i s t u r e Co n t e n t ( % ) Direct Shear (Ultimate) % F i n e s Atterberg Limits Compaction Curve Direct Shear (Peak) 11549 1/7/22 AE US C S Sp e c i f i c a t i o n s Project: Client: Job #: 1 Ex p a n s i o n In d e x R- V a l u e Checked By: Lab #: Date: Avila Ranch Development - Infiltration SL09304-9 Avila Ranch Developers, Inc. APPENDIX B   County of San Luis Obispo   Post Construction Requirements Handbook (Version 1.1 – March 2014) D1‐ 5  ATTACHMENT 1 Shallow Quick Infiltration Testing Methodology 1. For small sites with limited areas for infiltration-based SCMs, drill 1 profile boring and 2 infiltration test borings in each potential SCM area. 2. For acreage and unconstrained sites:  Up to 5 acres: drill 1 profile boring and 2 infiltration test borings per acre potentially usable for SCMs.  Over 5 acres: drill 1 profile boring and 2 infiltration test borings per geologic unit that may be usable for SCMs, with 2 to 4 infiltration test borings associated with each profile boring. 3. Profile borings should be 6” to 12” diameter. Where the planned SCMs will be constructed near the site’s existing grade, borings should be 10’ to 15’ deep. If significant cuts will be necessary to install the SCMs, the borings should extend 5’ to 10’ below the invert of the planned SCM. The boring cuttings should be observed and the soils in the borings sampled as necessary to allow accurate logging. Where excavations are utilized to determine the profile, they should be no wider than necessary to facilitate logging of the strata with the same level of detail as for borings. 4. All soil strata should be identified on the logs as to USCS classification, consistency, presence of moisture or free water, color, impermeable and permeable zones, and any other characteristics that may be pertinent to infiltration potential. All logs should include the boring identification, date of drilling, auger type and diameter, sampling methods, and surface elevation (known or assumed). 5. Infiltration test borings should also be 6” to 12” diameter. They should be of depths such that the zone tested will range from about the elevation of SCM invert, to about 2’ below the elevation of the invert. 6. Infiltration test excavations should be dug by any means to approximately the elevation of the top of the planned SCM. From the elevation of the top of the planned SCM to 2’ below the elevation of the invert of the SCM, a hand auger or hand shovel should be used to excavate the actual test zone. Preferably, the test zone should be 6” to 12” in diameter; if conditions mandate a larger diameter, it should be as close to 12” as is practicable. APPENDIX B   County of San Luis Obispo   Post Construction Requirements Handbook (Version 1.1 – March 2014) D1‐ 6  7. A perforated pipe, of a diameter that will facilitate the taking of the test measurements should be placed in each test boring or in the test zone of each test excavation. 8. The annulus between each perforated pipe and the boring sidewall should be filled with fine gravel. 9. A suitable elevation datum should be established from which each measurement can be taken. The elevation of the datum relative to the elevation of the top of the SCM should be noted. 10. Using a hose equipped with a water meter, a graduated water tank, or other suitable means of measuring water volume, add water to the approximate elevation of top of the planned SCM and maintain the head for 30 minutes. 11. At the end of the 30-minute period, shut off water and record volume of water that entered the test boring. 12. As the water level falls, measure from the datum to the water level at suitable intervals. Measurements should be to the degree of precision practicable (usually 1/8-inch or 0.01 foot) for a period of 2 hours. Depending upon the rate of fall, intervals between measurements may need to be from 1 minute to 30 minutes. Intervals should be as uniform as is practicable, however, as the water level falls and the head is reduced, the infiltration rate may decrease and the measurement intervals may need to be incrementally lengthened. 13. If a test boring runs dry within 2-hour measurement period, refill the boring and continue measuring the falling head to end of original 2-hour period. If it runs dry again, refill and continue measurements to the end of the original 2-hour period. If it runs dry a third time, do not refill, the testing of that boring is complete. 14. If the fall recorded in any test boring is less than 6” in 2 hours, continue taking measurements for an additional 2 hours (4 hours total). 15. See Attachment 4 for a discussion of how to report the test results. APPENDIX B   County of San Luis Obispo   Post Construction Requirements Handbook (Version 1.1 – March 2014) D1‐ 10  ATTACHMENT 4 Reporting of Test Results 1. Reporting of test results, whether quick or extended, shallow or deep, should contain essentially the same information. 2. For each test boring, tabulate the test data showing: a. Test identification b. Date drilled c. Date tested d. Test boring diameter e. Perforated pipe diameter f. Test boring depth g. Stratum present in the test zone h. Elevation of top of SCM (known or assumed) i. Elevation of invert of SCM (known or assumed) j. Test duration k. Volume introduced between commencement of filling and the end of the 30-minute constant head period, typically in units of cubic feet l. Head during initial 30-minute period m. Time of the first falling head measurement and depth to the water surface n. Time of each subsequent measurement and depth to the water surface o. Intervals between measurements p. Incremental drop between measurements q. Infiltration rate between measurements, typically in units of inches per hour 3. Provide a map showing the approximate locations of all profile and test borings, as well as property lines, landmarks, planned improvements and SCM locations (if known), and other pertinent features that will help the user better understand the boring and testing program. 4. Provide log of each profile boring 5. Provide report summarizing data and discussing the potential for use of infiltration based SCMs on the site or area(s) tested. APPENDIX B September 4, 2015 Project No. SL09304-2 Avila Ranch, LLC Attn: Andy Mangano 735 Tank Farm Road, Suite 240 San Luis Obispo, California 93401 Subject: Infiltration Testing Avila Ranch Development, Buckley Road and Vachell Lane APN's: 053-259-004, -005 & -006 San Luis Obispo, California INTRODUCTION GeoSolutions, Inc. performed infiltration testing using the shallow quick test methodology on July 31, August 3 and 4, 2015 for the mixed use development referred to as Avila Ranch located north of Buckley Road and East of Vachell Lane, APN's: 053-259-004, -005 & -006, in San Luis Obispo County, California. See Figure 1: Site Location Map. The property will hereafter be referred to as the “Site”. Infiltration testing was performed for design of storm water control measures (SCM’s) at the site. Project designers intend to use a system of shallow swales and basins. The areas tested had been previously staked with control elevations noted. The property is approximately 150 acres in size. The nearest intersection is where Buckley Road intersects Vachell Lane at the southeast corner of the property. The elevation of the site is approximately 115 feet above mean sea level. Typical storm water control measures are planned to be located near existing surface elevations. The site is not currently under construction. Figure 1: Site Location Map 1 APPENDIX B Avila Ranch September 4, 2015 Project SL09304-2 2 FIELD EXPLORATION Eleven (11) 6-inch diameter infiltration test borings were drilled on July 29 and July 30, 2015, to varying depths of no greater than 5 feet bgs. Three-inch diameter slotted PVC pipe was placed in the infiltration test borings and annular space was filled with clean pea gravel. Data gathered during the field investigation suggest that the soil materials at the Site consist of alluvial soil (expansive clays) overlying formational material. The surface material at the Site generally consisted of varying shades of black sandy fat CLAY (CH) encountered in a stiff condition to approximately 10.0 feet bgs. The soils were generally dry at the surface. On the north side of the creek, the soils become wet at 6 to 9 feet in depth. The sub-surface materials consisted of varying shades of brown clayey SAND (SC) encountered in a moist and very dense condition to the termination of borings. Regional site geology was obtained by using the Geologic Map of the Pismo Beach Quadrangle (Dibblee, 2006) and the MapView internet application (USGS, 2013); the later application is available from the United States Geological Survey website (USGS, 2013) and compiles existing geologic maps. The Clay and the majority of all underlying material at the Site was interpreted as older alluvium. Groundwater was encountered in borings B-1 and B-2 at 18 feet bgs and 10 feet bgs during our soil investigation, respectively. A review of borings completed in 2001 (Earth Systems Pacific, 2001) groundwater was 7 to 9 feet deep on the east property line, 5 to 7 feet deep along the creek, and 4 to 9 feet deep along the northern property line. INFILTRATION TESTING Prior to infiltration testing, each infiltration test boring was presoaked to a stabilized Infiltration rate. Infiltration testing consisted of maintaining a constant head (gpm) for 30 minutes, with a total volume (ft3), measuring the depth to the water immediately following. Measurements were then performed for a determined period of time of 30 minutes. Testing was terminated after an elapsed time of 120 minutes. The Infiltration rates (in inches per hour) were calculated by dividing the time period of the last reading obtained by the recorded water elevation drop. Stabilized Infiltration test results are presented below in the attached infiltration test results sheets. Figure 2: Infiltration Test Locations APPENDIX B Avila Ranch September 4, 2015 Project SL09304-2 CONCLUSIONS The infiltration test results indicate that infiltration rates of the surface materials can be categorized for hydrologic purposes utilizing the Hydrologic Soil Group (HSG) classification ranging from group B, C, and D (Part 630, Hydrology, National Engineering Handbook, 2007). An inspection of Figure 3, Infiltration Test Results, shows that the soils on the north and west side of the creek tend to have better infiltration rates. Soils in localized areas adjacent to the creek tend to be very low permeable soils. Although the recent drought condition has lowered the water table since the 2001 borings (ES 2001) groundwater is still present at relatively shallow depths on the southwest section of the property. In addition, soils are generally wet at depth throughout the site. Project designers should consider the groundwater elevation reported above from the 2001 event in design. Group B-Soils in Group B have a moderately low runoff potential when thoroughly wet. Water transmission through the soil is unimpeded. Group B soils typically have between 10 and 20 percent clay and 50 to 90 percent sand and have loamy sand or sandy loam textures. Some soils having loam, silt loam, silt, or sandy clay loam textures may be placed in this group if they are well aggregated, of low bulk density, or contain greater than 35 percent rock fragments. The limits on the diagnostic physical characteristics of Group B are as follows. The saturated hydraulic conductivity in the least transmissive layer between the surface and 20 inches ranges from 1.42 to 5.67 inches per hour. Figure 3: Infiltration Test Results 3 APPENDIX B APPENDIX B  CountyofSanLuisObispo PostConstructionRequirementsHandbook(Version1.1–March2014)D1Ͳ5 ATTACHMENT 1 Shallow Quick Infiltration Testing Methodology 1. For small sites with limited areas for infiltration-based SCMs, drill 1 profile boring and 2 infiltration test borings in each potential SCM area. 2. For acreage and unconstrained sites: x Up to 5 acres: drill 1 profile boring and 2 infiltration test borings per acre potentially usable for SCMs. x Over 5 acres: drill 1 profile boring and 2 infiltration test borings per geologic unit that may be usable for SCMs, with 2 to 4 infiltration test borings associated with each profile boring. 3. Profile borings should be 6” to 12” diameter. Where the planned SCMs will be constructed near the site’s existing grade, borings should be 10’ to 15’ deep. If significant cuts will be necessary to install the SCMs, the borings should extend 5’ to 10’ below the invert of the planned SCM. The boring cuttings should be observed and the soils in the borings sampled as necessary to allow accurate logging. Where excavations are utilized to determine the profile, they should be no wider than necessary to facilitate logging of the strata with the same level of detail as for borings. 4. All soil strata should be identified on the logs as to USCS classification, consistency, presence of moisture or free water, color, impermeable and permeable zones, and any other characteristics that may be pertinent to infiltration potential. All logs should include the boring identification, date of drilling, auger type and diameter, sampling methods, and surface elevation (known or assumed). 5. Infiltration test borings should also be 6” to 12” diameter. They should be of depths such that the zone tested will range from about the elevation of SCM invert, to about 2’ below the elevation of the invert. 6. Infiltration test excavations should be dug by any means to approximately the elevation of the top of the planned SCM. From the elevation of the top of the planned SCM to 2’ below the elevation of the invert of the SCM, a hand auger or hand shovel should be used to excavate the actual test zone. Preferably, the test zone should be 6” to 12” in diameter; if conditions mandate a larger diameter, it should be as close to 12” as is practicable. APPENDIX B  CountyofSanLuisObispo PostConstructionRequirementsHandbook(Version1.1–March2014)D1Ͳ6 7. A perforated pipe, of a diameter that will facilitate the taking of the test measurements should be placed in each test boring or in the test zone of each test excavation. 8. The annulus between each perforated pipe and the boring sidewall should be filled with fine gravel. 9. A suitable elevation datum should be established from which each measurement can be taken. The elevation of the datum relative to the elevation of the top of the SCM should be noted. 10. Using a hose equipped with a water meter, a graduated water tank, or other suitable means of measuring water volume, add water to the approximate elevation of top of the planned SCM and maintain the head for 30 minutes. 11. At the end of the 30-minute period, shut off water and record volume of water that entered the test boring. 12. As the water level falls, measure from the datum to the water level at suitable intervals. Measurements should be to the degree of precision practicable (usually 1/8-inch or 0.01 foot) for a period of 2 hours. Depending upon the rate of fall, intervals between measurements may need to be from 1 minute to 30 minutes. Intervals should be as uniform as is practicable, however, as the water level falls and the head is reduced, the infiltration rate may decrease and the measurement intervals may need to be incrementally lengthened. 13. If a test boring runs dry within 2-hour measurement period, refill the boring and continue measuring the falling head to end of original 2-hour period. If it runs dry again, refill and continue measurements to the end of the original 2-hour period. If it runs dry a third time, do not refill, the testing of that boring is complete. 14. If the fall recorded in any test boring is less than 6” in 2 hours, continue taking measurements for an additional 2 hours (4 hours total). 15. See Attachment 4 for a discussion of how to report the test results. APPENDIX B  CountyofSanLuisObispo PostConstructionRequirementsHandbook(Version1.1–March2014)D1Ͳ10 ATTACHMENT 4 Reporting of Test Results 1. Reporting of test results, whether quick or extended, shallow or deep, should contain essentially the same information. 2. For each test boring, tabulate the test data showing: a. Test identification b. Date drilled c. Date tested d. Test boring diameter e. Perforated pipe diameter f. Test boring depth g. Stratum present in the test zone h. Elevation of top of SCM (known or assumed) i. Elevation of invert of SCM (known or assumed) j. Test duration k. Volume introduced between commencement of filling and the end of the 30-minute constant head period, typically in units of cubic feet l. Head during initial 30-minute period m. Time of the first falling head measurement and depth to the water surface n. Time of each subsequent measurement and depth to the water surface o. Intervals between measurements p. Incremental drop between measurements q. Infiltration rate between measurements, typically in units of inches per hour 3. Provide a map showing the approximate locations of all profile and test borings, as well as property lines, landmarks, planned improvements and SCM locations (if known), and other pertinent features that will help the user better understand the boring and testing program. 4. Provide log of each profile boring 5. Provide report summarizing data and discussing the potential for use of infiltration based SCMs on the site or area(s) tested. APPENDIX B Porchet Method calculations of the GeoSolutions Infiltration Testing data from 2015 (prepared by Wallce Group, dated October 2021)May 2022 Porchet Method calculations of the GeoSolutions Infiltration Testing data from 2015 (prepared by Wallace Group, dated May 2022) APPENDIX BAPPENDIX B WG 1493-0007 Avila Ranch Phases 2-6 Stormwater Control Plan 5/4/2022 Infiltration Testing Summary *Tested Infiltration Rate Porchet Infiltration Rate in/hr in/hr I-1 1.68 0.30 I-2 1.68 0.08 I-3 0.96 0.07 I-4 0.04 0.01 I-5 0.12 0.02 I-6 2.4 0.63 I-7 3.6 0.68 I-8 3.36 1.87 I-9 1.68 1.47 I-10 0.96 0.07 I-11 0.96 0.13 0.48 0.13 0.01 1.87 * Infiltration Testing occurred on 8/3/2015 5 5 5 Boring MAX 1 Phase MEAN MEDIAN MIN 3 2 1 1 5 6 4 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-1 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:4.0 Feet Date Tested:7/31/2015 Test Duration:0.5 Hours Technician:AR Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:2.9 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.57 Cubic Feet Volume of Gravel in Test Boring:0.51 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.06 Cubic Feet Gallons Cubic Feet Initial Meter Reading:42 --- Meter Reading at 30 Minutes:39 --- Volume Required to Maintain Head for 30 Minutes:3 0.40 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 1:20 PM ---2.91 --------- 1:50 PM 30 3.18 0.27 9.26 6.48 2:20 PM 30 3.32 0.14 17.86 3.36 2:50 PM 30 3.40 0.08 31.25 1.92 3:20 PM 30 3.47 0.07 35.71 1.68 3:50 PM ------------- 4:20 PM ------------- 4:50 PM ------------- 1.68 Page 1 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. Range used for Porchet conversion APPENDIX B Test I-1 delta H 0.84 inches First Reading 3.4 ft User Input delta T 30 minutes Last Reading 3.47 ft Calculated Values effective radius 3 inches Hole Depth 4 ft H start 7.20 inches Riser Height 0 H end 6.36 inches H ave 6.78 inches It 0.30 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-2 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:5.0 Feet Date Tested:8/4/2015 Test Duration:0.5 Hours Technician:SP Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:3 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.59 Cubic Feet Volume of Gravel in Test Boring:0.52 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.07 Cubic Feet Gallons Cubic Feet Initial Meter Reading:40 --- Meter Reading at 30 Minutes:38 --- Volume Required to Maintain Head for 30 Minutes:2 0.27 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 9:15 AM ---2.85 --------- 9:49 AM 34 2.94 0.09 31.48 1.91 10:24 AM 35 3.04 0.1 29.17 2.06 11:03 AM 39 3.14 0.1 32.50 1.85 11:33 AM 30 3.21 0.07 35.71 1.68 12:33 PM 60 3.28 0.07 71.43 1.68 1:33 PM 60 3.35 0.07 71.43 1.68 2:03 PM 30 3.42 0.07 35.71 1.68 1.68 Page 2 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. Range used for Porchet conversion APPENDIX B Test I-2 delta H 3.36 inches First Reading 3.14 ft User Input delta T 180 minutes Last Reading 3.42 ft Calculated Values effective radius 3 inches Hole Depth 5 ft H start 22.32 inches Riser Height 0 H end 18.96 inches H ave 20.64 inches It 0.08 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-3 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:5.0 Feet Date Tested:7/31/2015 Test Duration:2.5 Hours Technician:AR Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:2.85 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.56 Cubic Feet Volume of Gravel in Test Boring:0.50 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.06 Cubic Feet Gallons Cubic Feet Initial Meter Reading:46 --- Meter Reading at 30 Minutes:42 --- Volume Required to Maintain Head for 30 Minutes:4 0.53 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 1:00 PM ---2.9 --------- 1:30 PM 30 3.21 0.31 8.06 7.44 2:00 PM 30 3.29 0.08 31.25 1.92 2:30 PM 30 3.37 0.08 31.25 1.92 3:00 PM 30 3.41 0.04 62.50 0.96 ------------ ------------ ------------ 0.96 Page 3 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. Range used for Porchet conversion APPENDIX B Test I-3 delta H 0.48 inches First Reading 3.37 ft User Input delta T 30 minutes Last Reading 3.41 ft Calculated Values effective radius 3 inches Hole Depth 5 ft H start 19.56 inches Riser Height 0 H end 19.08 inches H ave 19.32 inches It 0.07 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-4 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:4.0 Feet Date Tested:8/4/2015 Test Duration:3.5 Hours Technician:AR Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:3 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.59 Cubic Feet Volume of Gravel in Test Boring:0.52 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.07 Cubic Feet Gallons Cubic Feet Initial Meter Reading:38 --- Meter Reading at 30 Minutes:35 --- Volume Required to Maintain Head for 30 Minutes:3 0.40 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 9:47 AM ---2.94 --------- 10:27 AM 40 2.96 0.02 166.67 0.36 11:05 AM*38 2.96 0.0017 1862.75 0.03 11:35 AM*30 2.96 0.0017 1470.59 0.04 12:05 PM*30 2.96 0.0017 1470.59 0.04 12:35 PM*30 2.96 0.0017 1470.59 0.04 1:05 PM*30 2.96 0.0017 1470.59 0.04 1:35PM*30 2.97 0.0017 1470.59 0.04 0.04 Page 4 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. * 30 minute reading equal to zero - assumed one half of following 30 minute reading- following 30 minute reading recorded in the field as twice the assumed value. Range used for Porchet conversion APPENDIX B Test I-4 delta H 0.12 inches First Reading 2.96 ft User Input delta T 150 minutes Last Reading 2.97 ft Calculated Values effective radius 3 inches Hole Depth 4 ft H start 12.48 inches Riser Height 0 H end 12.36 inches H ave 12.42 inches It 0.01 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-5 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:4.0 Feet Date Tested:7/31/2015 Test Duration:4.5 Hours Technician:AR Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:2.8 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.55 Cubic Feet Volume of Gravel in Test Boring:0.49 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.06 Cubic Feet Gallons Cubic Feet Initial Meter Reading:50 --- Meter Reading at 30 Minutes:48 --- Volume Required to Maintain Head for 30 Minutes:2 0.27 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 11:40 AM ---2.73 --------- 12:10 PM*30 2.73 0.005 500.00 0.12 12:40 PM 30 2.74 0.005 500.00 0.12 1:10 PM 30 2.75 0.01 250.00 0.24 1:40 PM*30 2.75 0.005 500.00 0.12 2:10 PM 30 2.76 0.005 500.00 0.12 2:40 PM*30 2.76 0.01 250.00 0.24 3:10 PM 30 2.77 0.005 500.00 0.12 0.12 Page 5 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. * 30 minute reading equal to zero - assumed one half of following 30 minute reading- following 30 minute reading recorded in the field as twice the assumed value Range used for Porchet conversion APPENDIX B Test I-5 delta H 0.12 inches First Reading 2.76 ft User Input delta T 30 minutes Last Reading 2.77 ft Calculated Values effective radius 3 inches Hole Depth 4 ft H start 14.88 inches Riser Height 0 H end 14.76 inches H ave 14.82 inches It 0.02 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-6 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:5.5 Feet Date Tested:8/4/2015 Test Duration:2.5 Hours Technician:AR Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:4 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.79 Cubic Feet Volume of Gravel in Test Boring:0.70 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.09 Cubic Feet Gallons Cubic Feet Initial Meter Reading:33 --- Meter Reading at 30 Minutes:30 --- Volume Required to Maintain Head for 30 Minutes:3 0.40 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 11:00 AM ---4.1 --------- 11:30 AM 30 4.5 0.4 6.25 9.60 12:00 PM 30 4.74 0.24 10.42 5.76 12:30 PM 30 5.10 0.36 6.94 8.64 1:00 PM 30 5.2 0.1 25.00 2.40 ------------ ------------ ------------ 2.4 Page 6 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. Range used for Porchet conversion APPENDIX B Test I-6 delta H 1.2 inches First Reading 5.1 ft User Input delta T 30 minutes Last Reading 5.2 ft Calculated Values effective radius 3 inches Hole Depth 5.5 ft H start 4.80 inches Riser Height 0 H end 3.6 inches H ave 4.2 inches It 0.63 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-7 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:3.5 Feet Date Tested:8/4/2015 Test Duration:2.5 Hours Technician:AR Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:3 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.59 Cubic Feet Volume of Gravel in Test Boring:0.52 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.07 Cubic Feet Gallons Cubic Feet Initial Meter Reading:35 --- Meter Reading at 30 Minutes:33 --- Volume Required to Maintain Head for 30 Minutes:2 0.27 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 10:22 AM ---2.22 --------- 11:06 AM 44 2.58 0.36 10.19 5.89 11:36 AM 30 2.72 0.14 17.86 3.36 12:06 PM 30 2.89 0.17 14.71 4.08 12:36 PM 30 3.04 0.15 16.67 3.60 ------------ ------------ ------------ 3.6 Page 7 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. Range used for Porchet conversion APPENDIX B Test I-7 delta H 1.8 inches First Reading 2.89 ft User Input delta T 30 minutes Last Reading 3.04 ft Calculated Values effective radius 3 inches Hole Depth 3.5 ft H start 7.32 inches Riser Height 0 H end 5.52 inches H ave 6.42 inches It 0.68 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-8 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:4.0 Feet Date Tested:8/3/2015 Test Duration:2.5 Hours Technician:SP Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:3 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.59 Cubic Feet Volume of Gravel in Test Boring:0.52 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.07 Cubic Feet Gallons Cubic Feet Initial Meter Reading:40 --- Meter Reading at 30 Minutes:38 --- Volume Required to Maintain Head for 30 Minutes:2 0.27 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 10:40 AM ---3.01 --------- 11:10 AM 30 3.44 0.43 5.81 10.32 11:40 AM 30 3.65 0.21 11.90 5.04 12:10 PM 30 3.83 0.18 13.89 4.32 12:40 PM 30 3.97 0.14 17.86 3.36 ------------ ------------ ------------ 3.36 Page 8 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. Range used for Porchet conversion APPENDIX B Test I-8 delta H 1.68 inches First Reading 3.83 ft User Input delta T 30 minutes Last Reading 3.97 ft Calculated Values effective radius 3 inches Hole Depth 4 ft H start 2.04 inches Riser Height 0 H end 0.36 inches H ave 1.2 inches It 1.87 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-9 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:3.5 Feet Date Tested:8/3/2015 Test Duration:2.8 Hours Technician:SP Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:3 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.59 Cubic Feet Volume of Gravel in Test Boring:0.52 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.07 Cubic Feet Gallons Cubic Feet Initial Meter Reading:50 --- Meter Reading at 30 Minutes:42 --- Volume Required to Maintain Head for 30 Minutes:8 1.07 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 9:27 AM ---3 --------- 10:06 AM 39 3.38 0.38 8.55 7.02 10:44 AM 38 3.52 --------- 11:14 AM 30 3.59 --------- 11:44 AM 30 3.66 --------- ------------ ------------ ------------ 1.68 Page 9 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. APPENDIX B Test I-9 delta H 7.92 inches First Reading 3 ft User Input delta T 137 minutes Last Reading 3.66 ft Calculated Values effective radius 3 inches Hole Depth 3.5 ft H start 6.00 inches Riser Height 0 H end -1.92 inches H ave 2.04 inches It 1.47 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-10 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:4.5 Feet Date Tested:7/31/2015 Test Duration:2.8 Hours Technician:AR Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:2.2 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.43 Cubic Feet Volume of Gravel in Test Boring:0.38 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.05 Cubic Feet Gallons Cubic Feet Initial Meter Reading:48 --- Meter Reading at 30 Minutes:46 --- Volume Required to Maintain Head for 30 Minutes:2 0.27 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 12:15 PM ---2.21 --------- 12:45 PM 30 2.68 0.47 5.32 11.28 1:15 PM 30 2.82 0.14 17.86 3.36 1:45 PM 30 2.86 0.04 62.50 0.96 2:15 PM 30 2.9 0.04 62.50 0.96 ------------ ------------ ------------ 0.96 Page 10 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. Range used for Porchet conversion APPENDIX B Test I-10 delta H 0.96 inches First Reading 2.82 ft User Input delta T 60 minutes Last Reading 2.9 ft Calculated Values effective radius 3 inches Hole Depth 4.5 ft H start 20.16 inches Riser Height 0 H end 19.2 inches H ave 19.68 inches It 0.0680 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Project: Avila Ranch Project No.:SL09304-2 Infiltration Test: I-11 Test Hole Diameter:6 Inches Date Drilled:7/30/2015 Test Hole Depth:3.5 Feet Date Tested:8/3/2015 Test Duration:4.8 Hours Technician:AR Test Hole Type:Standard 3" PVC TEST METHODOLOGY:Shallow Quick CONSTANT HEAD Time of Constant Head:30 Minutes Constant Head Utilized for Test:3 Feet Gross Volume of Test Boring, Bottom to Constant Head:0.59 Cubic Feet Volume of Gravel in Test Boring:0.52 Cubic Feet Net Volume of Test Boring, Bottom to Constant Head:0.07 Cubic Feet Gallons Cubic Feet Initial Meter Reading:42 --- Meter Reading at 30 Minutes:40 --- Volume Required to Maintain Head for 30 Minutes:2 0.27 FALLING HEAD TIME ELAPSED TIME (Minutes) READING (Feet) INCREMENTAL FALL (Feet) INFILTRATION RATE (Minutes/Inch) INFILTRATION RATE (Inches/Hour) 10:02 AM ---2.88 --------- 10:42 AM 40 2.98 0.1 33.33 1.80 11:12 AM 30 3.03 0.05 50.00 1.20 11:42 AM 30 3.07 0.04 62.50 0.96 12:12 PM 30 3.12 0.05 50.00 1.20 12:42 PM 30 3.16 0.04 62.50 0.96 1:12 PM 30 3.2 0.04 62.50 0.96 1:42 PM 30 3.24 0.04 62.50 0.96 0.96 Page 11 of 11 INFILTRATION TEST RESULTS (805) 543-8539 (805) 614-6333 AVERAGE INFILTRATION RATE (Inches/Hour) GeoSolutions, Inc. Range used for Porchet conversion APPENDIX B Test I-11 delta H 1.44 inches First Reading 3.12 ft User Input delta T 90 minutes Last Reading 3.24 ft Calculated Values effective radius 3 inches Hole Depth 4 ft H start 10.56 inches Riser Height 0 H end 9.12 inches H ave 9.84 inches It 0.1270 inches/hour "Porchet Method" Source: Riverside County Low Impact Development BMP Design Handbook, 2011 APPENDIX B Tract 3089 - Avila Ranch Avila Ranch Groundwater Information Matrix Project:1493-0007 Avila Ranch Date:April 21, 2022 By:ZKP Avila Ranch Groundwater Information Boring Date ID GW Depth (ft) Test Date Surface Elevation (ft) GW Elevation (ft) Design Surface Elevation* (ft) GW Depth to Design FG (ft) Boring Depth (ft) FG to Relative Bore Depth (ft) Notes 20 2 1 Li f t St a t i o n 3/2021 B-1 (LS) 6.0 105.00 99.00 105.0 6.00 - - 12/2021 B-12 7.5 114.10 106.60 117.0 10.4 -- Creek - Venture Crossing 12/2021 B-13 9.5 113.71 104.21 115.0 10.8 -- Creek - Venture / Wright Bros. Crossing 12/2021 B-14 7.5 101.48 93.98 101.5 7.5 -- Creek - Phase 1/ Ph5 Bike Path Crossing 12/2021 B-15 15.0 96.09 81.09 - - -- Creek - Offsite 12/2021 B-16 10.0 96.64 86.64 - - -- Creek - Offsite 11/2021 I-12 none 121.54 - 114.6 - 13.0 6.1 No GW found. 11/2021 I-13 none 113.04 - 110.0 - 6.0 2.9 No GW found. 11/2021 I-14 none 109.43 - 113.0 - 5.0 8.6 No GW found. 11/2021 I-15 none 115.47 - 115.5 - 8.0 8.0 No GW found. 11/2021 I-16 none 120.70 - 119.0 - 8.0 6.3 No GW found. 11/2021 I-17 none 121.88 - 119.0 - 10.0 7.1 No GW found. 11/2021 I-18 none 119.67 - 120.7 - 6.0 7.0 No GW found. 11/2021 I-19 none 114.45 - 114.5 - 7.0 7.0 No GW found. 11/2021 I-20 none 106.40 - 106.4 - 8.0 8.0 No GW found. 11/2021 I-21 none 116.58 - 117.8 - 5.0 6.2 No GW found. 11/2021 I-22 none 112.95 - 116.7 - 3.0 6.8 No GW found. 11/2021 I-23 none 114.34 - 120.4 - 6.0 12.0 No GW found. 11/2021 I-24 none 115.97 - 122.3 - 3.0 9.3 No GW found. 7/2015 B-1 18.0 107.0 89.0 107.0 18.0 -- Phase 1 7/2015 B-2 10.0 106.5 96.5 106.5 10.0 -- Phase 1 7/2015 B-3 none 113.5 - 113.5 - 13.0 13.0 Phase 1. 7/2015 B-4 none 126.5 - 122.2 - 10.0 5.7 Phase 5. 7/2015 B-5 none 111.5 - 112.3 - 10.0 10.8 Phase 3. 7/2015 B-6 none 115.5 - 116.0 - 10.5 11.0 Phase 3. 7/2015 I-1 none 117.5 - 116.5 - 4.0 3.0 No GW found. 7/2015 I-2 none 115.0 - 119.0 - 5.0 9.0 No GW found. 7/2015 I-3 none 120.0 - 123.0 - 5.0 8.0 No GW found. 7/2015 I-4 none 112.5 - 117.5 - 4.0 9.0 No GW found. 7/2015 I-5 none 105.5 - 105.5 - 4.0 4.0 No GW found. 7/2015 I-6 none 113.5 - 110.0 - 5.5 2.0 No GW found. 7/2015 I-7 none 110.0 - 106.0 - 3.5 -0.5 No GW found. 7/2015 I-8 none 108.0 - 111.0 - 4.0 7.0 No GW found. 7/2015 I-9 none 99.0 - 99.0 - 3.5 3.5 No GW found. 7/2015 I-10 none 118.5 - 124.5 - 4.5 10.5 No GW found. 7/2015 I-11 none 106.5 - 103.0 - 3.5 0.0 No GW found. 8/1997 B-3 15.0 118.4 103.4 123.5 20.15 -- 5/2001 B-4 6.9 111.4 104.5 111.4 6.90 -- Outside of Ph2-6 grading 5/2001 B-5 5.0 110.0 105.0 105.9 0.86 -- 5/2001 B-6 6.6 115.5 108.9 115.5 6.60 -- Outside of Ph2-6 grading 5/2001 B-7 6.0 117.0 111.0 123.0 12.00 -- 5/2001 B-8 none 127.0 - 127.0 - 15.0 15.0 Outside of Ph2-6 grading 5/2001 B-9 9.0 124.5 115.5 124.5 9.00 -- Outside of Ph2-6 grading 5/2001 B-10 9.7 124.0 114.3 124.0 9.70 -- Outside of Ph2-6 grading 11/2001 B-11 19.5 114.5 95.0 114.5 19.50 -- Outside of Ph2-6 grading 11/2001 B-12 25.0 128.5 103.5 118.0 14.50 -- 11/2001 B-13 none 127.0 - 120.4 - 15.0 8.4 No GW found. 11/2001 B-14 none 126.5 - 121.7 - 15.0 10.2 No GW found. 11/2001 B-15 none 117.5 - 117.7 - 15.0 15.2 No GW found. 11/2001 B-16 none 118.8 - 118.5 - 15.0 14.7 No GW found. 11/2001 B-17 none 126.5 - 118.8 - 15.0 7.3 No GW found. 11/2001 B-18 none 121.5 - 118.8 - 15.0 12.3 No GW found. 11/2001 B-19 none 124.5 - 117.8 - 15.0 8.3 No GW found. 11/2001 B-20 none 123.0 - 117.8 - 15.0 9.8 No GW found. 11/2001 B-21 none 123.3 - 120.2 - 16.0 12.9 No GW found. 11/2001 B-22 none 121.5 - 117.1 - 16.0 11.6 No GW found. 11/2001 B-23 none 117.0 - 120.8 - 15.0 18.8 No GW found. 11/2001 B-24 none 124.0 - 124.5 - 16.0 16.5 No GW found. Outside of Ph2- 6 grading 11/2001 B-25 none 113.0 - 110.6 - 15.0 12.6 No GW found. 11/2001 B-26 8.0 112.0 104.0 114.6 10.60 -- 11/2001 B-27 4.0 111.5 107.5 117.0 9.50 -- 11/2001 B-28 7.0 114.0 107.0 118.5 11.50 -- 11/2001 B-29 13.0 116.0 103.0 113.0 10.00 -- 11/2001 B-30 9.0 114.0 105.0 112.0 7.00 -- 11/2001 B-31 8.0 115.0 107.0 117.2 10.20 -- * Report Date 4/6/2021 2/17/2022 2/9/2022 1/26/2022 9/4/2015 12/12/20012001 Percolation Testing/ Boring 2015 Infiltration Testing Report Title Avila Ranch Subdivision- Results of Percolation Tests Report & Map Avila Ranch Development - Infiltration Testing Report Soils Engineering Report Update - Avila Ranch Development Phases II - VI Infiltration Testing Report Soils Engineering Report - Avila Ranch Development Bridges Soils Engineering Report - Avila Ranch Lift Station Design Elevation: If the boring location is inside the Ph2-6 grading area, the Finished Design Grade for Ph2-6 was used. If the location is outside of the Ph2-6 grading area, the "existing aerial topo" OR the "EG-Post-Ph1" topo was used (depending on the date of the boring/ test). 20 1 5 I n f i l t r a t i o n T e s t i n g Locations where groundwater was NOT encountered 20 2 1 I n f i l t r a t i o n T e s t i n g 20 2 1 B r i d g e Bo r i n g 20 0 1 P e r c o l a t i o n T e s t i n g / B o r i n g 20 1 5 B o r i n g 2015 Boring 2021 Infiltration Testing 2021 Bridge Boring 2021 Lift Station References GeoSolutions Company Earth Systems GeoSolutions GeoSolutions GeoSolutions GeoSolutions APPENDIX B MEMORANDUM Wathen Castanos Avila Ranch Phases 2-6 1493-0007 Date: May 15, 2022 To: Craig Campbell, Zac Powell, Dylan Goodwin From: Rachel Hawthorne Subject: Stormwater Post Construction Requirement Structural Control Measures Separation from Groundwater Levels for Phase 2-6 of Tract 3089 The purpose of this memo is to establish a design criterion for the vertical separation of measured groundwater levels to the bottom of proposed structural control measures for post construction stormwater structural control measures for Tract 3089 Avila Ranch, Phases 2-6. The following sources were taken into consideration for this memo: · Resolution No. R3-2013-0032, Attachment 1, Section 1.c.1 – “Technical infeasibility may be caused by site conditions, including: depth to seasonal high groundwater limits infiltration and/or prevents construction of subgrade stormwater control measures6” · 6 “According to the CASQA Frequently Asked Questions about LID, “some MS4 permits and BMP guidance manuals require anywhere from 3-10 feet of separation from the groundwater level for infiltration practices.” · County of San Luis Obispo Subsurface Stormwater Injection Requirements – the minimum separation distance for underground storage from groundwater is based upon infiltration rate. For infiltration rates of 2 inches per hour or less, a 5-foot clearance to groundwater is required. · Table 6-2: BMP Selection Matrix – Site Suitability from the City of Santa Barbara Storm Water BMP Guidance Manual indicates a minimum separation of 5-feet to groundwater for infiltration based BMPs and minimum 2-foot separation for retention basins. · Wallace Group contacted Hal Hannula with Engineering Development Review for the City of San Luis Obispo. Hal responded that the City did not have local provisions for groundwater separation and contacted Lucas Sharkey with the Regional Water Quality Control Board. The Water Board did not have additional requirements for groundwater separation and the 3-10 feet separation recommended by CASQA would be acceptable. The Water Board also noted that 1 to 2 feet of separation could be allowed for infiltration basins. APPENDIX B May 15, 2022 Page 2 of 2 Separation from groundwater was more of a concern for dry wells or underground infiltration devices such as StormTech chambers due to potential groundwater contamination. · Infiltration Testing Report and Soils Engineering Report Update Avila Ranch Development Phase II-VI, Buckley Road and Vachell Lane, San Luis Obispo , California prepared by Geosolutions, January 2022 This report shows that the infiltration rates for vertical or linear facilities (dry wells, vegetated swales infiltration trenches, infiltrators, etc) are generally 2 inches per hour or less with the exception of test locations I-16 and I-20. Based on the above a minimum separation to groundwater of 3 feet is recommended for the vertical or linear facilities at Avila Ranch, Phases 2-6. The report also shows that the infiltration rates for flat facilities (infiltration basins, retention basins with infiltration) are generally 0.1 inches per hour or less. Considering the low infiltration rate, a minimum separation to groundwater of 3 feet is recommended for the vertical or infiltration and retention basins at Avila Ranch Phases 2-6. Based upon the above information, Wallace Group will use the following vertical separation from groundwater for design of stormwater structural control measures: Structural Control Measure Type Minimum Vertical Separation from Groundwater Level (feet) Vertical or Linear Facilities Dry Wells 3.0 Vegetated Swales/Bioswales Infiltrators/Infiltration Trenches Flat Facilities Bioretention Basins 3.0 Infiltration Basins APPENDIX B Resolution No. R3-2013-0032 ATTACHMENT 1 -13- Off-site compliance with Water Quality Treatment, Runoff Retention, or Peak Management Performance Requirements may be allowed when technical infeasibility limits or prevents use of structural Stormwater Control Measures. a) To pursue Alternative Compliance based on technical infeasibility, the Regulated Project applicant, for Regulated Projects outside of Urban Sustainability Areas, must submit a site-specific hydrologic and/or design analysis conducted and endorsed by a registered professional engineer, geologist, architect, and/or landscape architect, demonstrating that compliance with the applicable numeric Post-Construction Stormwater Management Requirements is technically infeasible b) The Regulated Project applicant must submit a description of the project(s) that will provide off-site mitigation. The proposed off-site projects may be existing facilities and/or prospective projects that are as effective in maintaining watershed processes as implementation of the applicable Post-Construction Stormwater Requirements on-site. The description shall include: i) The location of the proposed off-site project(s) must be within the same watershed as the Regulated Project. Alternative Compliance project sites located outside the watershed may be approved by the Central Coast Water Board Executive Officer ii) A schedule for completion of offsite mitigation project(s), where the off-site mitigation project(s) has not been constructed. c) Technical infeasibility may be caused by site conditions, including: i) Depth to seasonal high groundwater limits infiltration and/or prevents construction of subgrade stormwater control measures6 ii) Depth to an impervious layer such as bedrock limits infiltration iii) Sites where soil types significantly limit infiltration iv) Sites where pollutant mobilization in the soil or groundwater is a documented concern v) Space constraints (e.g., infill projects, some redevelopment projects, high density development) vi) Geotechnical hazards vii) Stormwater Control Measures located within 100 feet of a groundwater well used for drinking water viii) Incompatibility with surrounding drainage system (e.g., project drains to an existing stormwater collection system whose elevation or location precludes connection to a properly functioning treatment or flow control facility) 2) Approved Watershed or Regional Plan An approved Watershed or Regional Plan as described below (Section C.2.a.), may be used to justify Alternative Compliance for a Regulated Project’s numeric Runoff Retention and Peak Management Performance Requirements without demonstrating technical infeasibility. a) The Permittee must submit the proposed Watershed or Regional Plan to the Central Coast Water Board Executive Officer for approval. W atershed and Regional Plans must take into consideration the long-term cumulative impacts of urbanization including existing and future development and include, at minimum: 6 According to the CASQA Frequently Asked Questions about LID, “some MS4 permits and BMP guidance manuals require anywhere from 3-10 feet of separation from the groundwater level for infiltration practices. This distance depends on the soil type, pollutants of concern, and groundwater use. In some cases, however, where there may be groundwater or soil contamination, LID infiltrative practices may be restricted completely. (p. 7 in https://www.casqa.org/Portals/0/LID/CA_LID_FAQ_06- 28-2011.pdf) APPENDIX B APPENDIX B Chapter 6: Stormwater Runoff BMP Options Introduction 6-6 Storm Water BMP 7/16/2013 Guidance Manual Report Section Treatment BMP Category Treatment BMP Site Suitability Considerations Applicability for Special Design Districts Drainage Area (Acres)1 Site Slope (%) Depth to Seasonally High Groundwater (ft) Hydrologic Soil Group Horizontal Setback Water Wells (ft) Coastal Bluff Areas Hillside Design District 6.5 Biofiltration BMPs Bioretention < 2 < 15; planter boxes are generally more suitable for steep slopes 2,3 > 2 with underdrains; > 5 without underdrains Underdrains may be provided for "C" and "D" soils 100 6 Acceptable if underdrains are included and if the site slope meets the criteria provided in this matrix table. Acceptable if site slope meets the criteria of this matrix table. If site slopes exceed 7%, underdrains should be included regardless of the hydrologic soil group condition of the site. Vegetated Swale Filter < 5 < 10 site slope; 1.5 to 6 longitudinal slope of swale 2,3 > 2 with underdrains; > 5 without underdrains Any 6 100 Vegetated Strip Filter < 2 < 5 site slope; 2 to 15 longitudinal slope of strip > 2 Any N/A 6.6 Infiltration and Filtration BMPs Infiltration Trench & Basin < 5 < 7 2 > 5 May not be feasible in "C" soils. Not suitable in "D" soils. 100 Infiltration BMPs not permissible in Coastal Bluff Areas. Acceptable if a geotechnical investigation proves that the facility does not comprise the stability of the site slope or surrounding slopes. Dry Well < 5 < 7 2 > 5 May not be feasible in "C" soils. Not suitable in "D" soils. 100 Sand Filter < 10 < 15 4 > 2 with underdrains Any N/A Acceptable if criteria for site slope is met. 6.7 Permeable Pavement BMPs Includes pervious concrete and asphalt concrete (AC), permeable pavers, subsurface reservoir beds, and granular materials Drainage Area is equal to area of pervious pavement < 5 2,5 > 2 with underdrains; > 5 without underdrains Underdrains may be provided for "C" and "D" soils 100 6 Acceptable if underdrains are included and if the site slope meets the criteria provided in this matrix table. Acceptable if site slope meets the criteria of this matrix table. If site slopes exceed 7%, underdrains should be included regardless of the hydrologic soil group condition of the site. 6.8 Building BMPs Cistern/Rain Barrel Depends on system size Any > 2 if tank is underground Any N/A Acceptable if criteria for site slope is met. Planter Box Equal to roof drainage area 4,5 < 15 > 2 with underdrains; > 5 without underdrains Underdrains may be provided for "C" and "D" soils 100 6 Vegetated Roof Equal to roof drainage area N/A N/A N/A N/A 6.9 Retention and Detention BMPs Constructed Treatment Wetland > 10 < 8 2 > 2 "A" soils may require pond liner; "B" soils may require infiltration testing N/A Acceptable if criteria for site slope is met. Wet Retention Basin > 10 < 15 2 > 2 "A" soils may require pond liner; "B" soils may require infiltration testing N/A Dry Extended Detention Basin > 10 < 15 2 > 2 Any N/A 6.10 Proprietary Devices Includes hydrodynamic devices, media filters, and biotreatment devices The site suitability requirements for specific proprietary devices must be provided by the manufacturer and should be verified by independent third- party sources and data or assessed by a professional consultant. Table 6-2: BMP Selection Matrix - Site Suitability Important Note to Users: Site suitability can vary widely for individual BMPs. This table should be used to provide general BMP comparisons only and should not replace the evaluation performed by a professional consultant. For greater accuracy, only compare site suitability considerations within each of the Treatment BMP Categories. from Drinking 1 Drainage areas should be used as a general guideline only. Drainage areas can be larger or smaller in some instances. 2 If slope exceeds given limit or is within 200 feet from the top of a hazardous slope or landslide area, a geotechnical investigation is required. 3 If system is located within 50 feet of a sensitive steep slope on the uphill side or 10 feet from a structure, underdrains should be incorporated. 4 If system is fully contained and includes a liner, underdrain system, and overflow to a storm drain system, then slopes can exceed 15%. 5 If a gravel base is used for storage of runoff: (1) slopes should be restricted to 0.5% (steeper grades reduce storage capacity) and (2) underdrains should be used if within 50 feet of a sensitive steep slope. 6 Setbacks apply to systems without underdrains or systems underlain by "A" or B" hydrologic soil groups. APPENDIX B Avila Ranch- Residential February 9, 2022 Project SL09304-9 2 FIELD EXPLORATION The approximate locations of the thirteen test wells are indicated on Figure 2: Infiltration Test Locations. Three- inch diameter perforated PVC pipe was placed in the infiltration test borings on a few inches of bedding pea gravel and the annular spaces were filled with clean pea gravel. In addition, each pipe was wrapped with a filter sock. The following field soil classifications for the borings are in accordance with the Unified Soils Classification System (USCS). The material at the Site generally consisted of varying shades of brown fat CLAY (CH) in a moist to wet condition typical of alluvial soils. I-13 encountered a sand, clay gravel mix that is typical of stream deposits. This material was not encountered in an extensive area and is likely discontinuous. LABORATORY TEST RESULTS In general, the test results indicate the soils are typically plastic clays with high fine contents. I-13 was an exception at 8 percent fines and I-20 at 30 percent fines. See attached laboratory results for further detail. Figure 2: Infiltration Test Locations APPENDIX B Avila Ranch- Residential February 9, 2022 Project SL09304-9 3 HISTORIC GROUNDWATER READINGS See the attached Plate 1 for historical borings locations and groundwater depths (ESP, 2001 and GeoSolutions, Inc., 2015 & 2021). INFILTRATION TESTING Prior to infiltration testing, each infiltration test boring was presoaked to a stabilized percolation rate. Infiltration testing consisted of maintaining a constant head (gallons per minute) for 30 minutes, with the total volume (ft3) recorded. The depth to water was measured immediately following the pre-saturation cycle. Measurements were then performed for a determined period of time of 30 minutes. Testing was terminated after an elapsed time of 240 minutes. The infiltration rates (in inches per hour) were calculated by dividing the time period of the last reading obtained by the recorded water elevation drop. The infiltration test results for the Site are presented below in Table 2: Infiltration Test Results. Table 2: Infiltration Test Results Dates Test Location Infiltration Rate (inches/hour) Infiltration Rate (inches/hour) Porchet Method February 7, 2022 I-12 0.96 0.02 submerged I-13 - - submerged I-14 - - January 15, 2022 I-15 1.92 0.09 February 4, 2022 I-16 5.52 0.74 January 21, 2022 I-17 2.88 0.10 January 24, 2022 I-18 1.68 0.11 January 21, 2022 I-19 1.92 0.13 January 21, 2022 I-20 3.84 0.26 February 4, 2022 I-21 2.16 0.25 Inaccessible I-22 - - February 6, 2022 I-23 1.68 0.10 February 6, 2022 I-24 0.24 0.03 CONCLUSIONS Above are results of a four-hour infiltration test. The infiltration test results indicate that infiltration rates of the materials can be categorized for hydrologic purposes utilizing the Hydrologic Soil Group (HSG) classification ranging from group C to D (Part 630, Hydrology, National Engineering Handbook, 2007). Based on the clay content “Passing #200 Sieve”, the soils generally classify as Group D. For long duration saturated conditions, the soils will behave as a Group D. Based on the information available today we would recommend the use of 0.02 to 0.06 inches per hour for D soils and to 0.14 inches per hour for C soils where it is required that the SCM fully empty prior to the next storm event. Group C-Soils in Group C have moderately high runoff potential when the thoroughly wet. Water transmission through the soil is somewhat restricted. Group C soils typically have between 20 percent and 40 percent clay and less than 50 percent sand and have loam, silt loam, sandy clay loam, clay loam, and silty clay loam textures. APPENDIX B 95 95 100 105 110115 100 100 10 5 1 0 5 1 0 5 1 0 5 105 110 115 115 115 110 110 110 110 110 110 110 1 1 5 11 5 115 11 5 1 1 5 115 115 1 2 0 120 120 1 2 0 120 120 125 125 11 0 11 0 110 110 110 110 115 115 115 115 120 120 125 125 12 5 1 2 5 130 130 110110 110 11 0 115 115 115 115 115 120120 120120 120 120 120 120 1 2 0 120 12 0 1 2 0 12 0 120 120 120 125 125 130 130 115 1 1 5 115115 115 115 12012 0 120 1 2 0 120 1 2 0 120 120 120 115 115 115 115 115 120 120 120 120 120 125 125 125 125 115 115 11 5 120 120 120125 125 125 125 125 125 12 5125125 125 1 2 5125 13 0 1 3 013 0 1 3 0 95 95 95 95 100 105 11 0 115 120 115115115 11 5 1 1 5 11 5 11 5 11 5 1 1 5 11 5 1 1 5 115 1 1 5 1 1 5 11 5115115 11 5 11 5 11 5 1 2 0 T 805 544-4011 F 805 544-4294 612 CLARION COURT SAN LUIS OBISPO, CA 93401 www.wallacegroup.us PLANNING CIVIL AND TRANSPORTATION ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PUBLIC WORKS ADMINISTRATION SURVEYING / GIS SOLUTIONS WATER RESOURCES DESIGNERS: DRAWING NO. DATE: DRAWN BY: JOB #: OF ® DATE SIGNED SIGNATURE These plans and specifications, and the ideas and designs incorporated herein, are instruments of service prepared for the construction of work shown hereon and shall not be used in whole or in part for any other project without written authority of Wallace Group, a California Corporation. Copyright © 2022 Wallace Group, a California Corporation. All rights reserved. Copies of this drawing shall have this notice. 321 4 6 321 4 6 B A ORIGINAL SCALE IS IN INCHES FOR REDUCED PLANS 0 1 2 3 5 5 C 7 7 D E F SHEET WA T H E N C A S T A N O S H O M E S AV I L A R A N C H D E V E L O P E M E N T GR O U N D W A T E R E X H I B I T 1493-0007-00 -- ZKP 3-29-2022 1 1 B-1 (2015) B-2 (2015) B-3 (2015) B-5 (2015) B-6 (2015) B-4 (2015) B-11 (2001) B-3 (2001) B-4 (2001) B-12 (2001) B-13 (2001) B-14 (2001)B-15 (2001)B-16 (2001) B-10 (2001) B-9 (2001) B-17 (2001) B-18 (2001) B-19 (2001) B-20 (2001) B-21 (2001) B-8 (2001) B-24 (2001) B-7 (2001) B-23 (2001) B-29 (2001)B-30 (2001)B-31 (2001) B-28 (2001) B-27 (2001)B-26 (2001) B-25 (2001) B-6 (2001) B-22 (2001) B-5 (2001) N 00 100 200 (IN FEET) 50 GRAPHIC SCALE 1 IN = 100 FT EARTHWOOD LANE BUCKLEY ROAD HUGHES LANE DOOLITTLE DRIVE CO L E M A N L A N E WRIGHT BROTHERS WAY VENTURE DRIVE LA N G L E Y S T R E E T JE S P E R S E N R O A D VENTURE DRIVE EA R T H W O O D L A N E VENTURE DRIVE VA C H E L L L A N E BUCKLEY ROAD JE S P E R S E N R O A D MEMPHIS BELLE WAY PI P E R L A N E FOXTROT COURT KITTY HAWK COURT BRAVO LANE TANGO WAY DE L T A D R I V E BASIN EXCAVATED TO ELEV 93.0' B-1 (2021, LIFT) B-15 (2021)B-16 (2021) B-14 (2021) B-13 (2021) B-12 (2021) LEGEND: SOILS ENGINEERING REPORT UPDATE, GEOSOLUTIONS, INC. AVILA RANCH DEVELOPMENT DATED JUNE 11, 2018 (BORING DATE JULY 2015) RESULTS OF PERCOLATION TESTS REPORT, EARTH SYSTEMS PACIFIC AVILA RANCH SUBDIVISION DATED DECEMBER 18, 2001 (BORING DATE 2001) SOILS ENGINEERING REPORT, GEOSOLUTIONS, INC. AVILA RANCH DEVELOPMENT BRIDGES DATED FEBRUARY 17, 2022 (BORING DATE DECEMBER 2021) SOILS ENGINEERING REPORT, GEOSOLUTIONS, INC. AVILA RANCH DEVELOPMENT LIFT STATION DATED APRIL 6, 2022 (BORING DATE MARCH 2021) RACH E L A . H AWTH O R N E C I V I L No. 73686 NOT FOR CONSTRUCTION FOR PLAN REVIEW ONLY A L A T T S OF E C A O NRFI I REGISTE R E D P R O F E SSIONAL E N G I N E E R 94 RELATIVE GROUNDWATER ELEVATION 104 81 87 89 97 103 95 104 CLEAR TO 103 CLEAR TO 104 114 116CLEAR TO 106 CLEAR TO 109.5 CLEAR TO 108 CLEAR TO 107 CLEAR TO 106 109 105 107 CLEAR TO 102 104 107 105 103 107 CLEAR TO 105 107 CLEAR TO 110 CLEAR TO 111 CLEAR TO 112 111 CLEAR TO 100 99 90 100 105 107 110 115 115 110 10090 105 104 105 104 105107 12/21/2022 APPENDIX B 95 95 100 105 110115 100 100 10 5 1 0 5 1 0 5 1 0 5 105 110 115 115 115 110 110 110 110 110 110 110 1 1 5 11 5 115 11 5 1 1 5 115 115 1 2 0 120 120 1 2 0 120 120 125 125 11 0 11 0 1 1 0 110 110 110 115 115 115 115 120 120 125 125 12 5 1 2 5 130 130 110110 110 11 0 115 115 115 115 115 120120 120120 120 120 120 120 1 2 0 120 12 0 1 2 0 12 0 120 120 120 125 125 130 130 115 1 1 5 115115 115 115 12012 0 120 1 2 0 120 1 2 0 120 120 120 115 115 115 115 115 120 120 120 120 120 125 125 125 125 115 115 11 5 120 120 120125 125 125 125 125 125 12 5125 125 125 1 2 5125 13 0 1 3 013 0 1 3 0 95 95 95 95 100 105 11 0 115 120 115115115 11 5 1 1 5 11 5 11 5 11 5 1 1 5 11 5 1 1 5 115 1 1 5 1 1 5 11 5115115 11 5 11 5 11 5 1 2 0 T 805 544-4011 F 805 544-4294 612 CLARION COURT SAN LUIS OBISPO, CA 93401 www.wallacegroup.us PLANNING CIVIL AND TRANSPORTATION ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PUBLIC WORKS ADMINISTRATION SURVEYING / GIS SOLUTIONS WATER RESOURCES DESIGNERS: DRAWING NO. DATE: DRAWN BY: JOB #: OF ® DATE SIGNED SIGNATURE These plans and specifications, and the ideas and designs incorporated herein, are instruments of service prepared for the construction of work shown hereon and shall not be used in whole or in part for any other project without written authority of Wallace Group, a California Corporation. Copyright © 2022 Wallace Group, a California Corporation. All rights reserved. Copies of this drawing shall have this notice. 321 4 6 321 4 6 B A ORIGINAL SCALE IS IN INCHES FOR REDUCED PLANS 0 1 2 3 5 5 C 7 7 D E F SHEET WA T H E N C A S T A N O S H O M E S AV I L A R A N C H D E V E L O P E M E N T IN F I L T R A T I O N E X H I B I T - L I N E A R / R A W D A T A 1493-0007 -- ZKP 3-29-2022 1 1 LEGEND: RESULTS OF INFILTRATION TESTING, GEOSOLUTIONS, INC. AVILA RANCH DEVELOPMENT DATED SEPTEMBER 4, 2015 RESULTS OF INFILTRATION TESTING, GEOSOLUTIONS, INC. AVILA RANCH DEVELOPMENT DATED FEBRUARY 9, 2022 N 00 100 200 (IN FEET) 50 GRAPHIC SCALE 1 IN = 100 FT EARTHWOOD LANE BUCKLEY ROAD HUGHES LANE DOOLITTLE DRIVE CO L E M A N L A N E WRIGHT BROTHERS WAY VENTURE DRIVE LA N G L E Y S T R E E T JE S P E R S E N R O A D VENTURE DRIVE EA R T H W O O D L A N E VENTURE DRIVE VA C H E L L L A N E BUCKLEY ROAD JE S P E R S E N R O A D MEMPHIS BELLE WAY PI P E R L A N E FOXTROT COURT KITTY HAWK COURT BRAVO LANE TANGO WAY DE L T A D R I V E I-9 1.68 IN HR I-11 0.96 IN HR I-5 0.12 IN HR I-8 3.36 IN HR I-7 3.60 IN HR I-4 0.04 IN HR I-6 2.40 IN HR I-2 1.68 IN HR I-1 1.68 IN HRI-3 0.96 IN HR I-10 0.96 IN HRI-20 3.84 IN HR I-12 0.96 IN HR I-13 NOT TESTED I-14 NOT TESTED I-15 1.92 IN HR I-16 5.52 IN HR I-17 2.88 IN HR I-18 1.68 IN HR I-19 1.92 IN HR I-21 2.16 IN HR I-22 NOT TESTED I-23 1.68 IN HR I-24 0.24 IN HR RAC H E L A . H AWTH O R N E C I V I L No. 73686 NOT FOR CONSTRUCTION FOR PLAN REVIEW ONLY A L A T T S OF E C A O NRFI I REGISTE R E D P R O F E SSIONAL E N G I N E E R CR E E K CR E E K CREE K 1.00 2.00 2.00 0.14 3.00 2.00 2.00 1.00 0.141.001.68 1.68 1.00 1.00 1.00 2.00 2.00 0.14 0.14 GENERAL INFILTRATION TESTING NOTES: Stabilized Tests: I-1, I-2, I-3, I-4, I-5, I-7, I-10, I-11, I-12, I-15, I-17, I-18, I-19, I-20, I-23, I-24 Non-Stabilized Tests: I-6 (inconclusive), I-8 (inconclusive), I-9 (incomplete), I-13 (incomplete), I-14 (incomplete), I-16 (inconclusive), I-21 (inconclusive), I-22 (incomplete) 12/21/2022 APPENDIX B 95 95 100 105 110115 100 100 10 5 1 0 5 1 0 5 1 0 5 105 110 115 115 115 110 110 110 110 110 110 110 1 1 5 11 5 115 11 5 1 1 5 115 115 1 2 0 120 120 1 2 0 120 120 125 125 11 0 11 0 1 1 0 110 110 110 115 115 115 115 120 120 125 125 12 5 1 2 5 130 130 110110 110 11 0 115 115 115 115 115 120120 120120 120 120 120 120 1 2 0 120 12 0 1 2 0 12 0 120 120 120 125 125 130 130 115 1 1 5 115115 115 115 12012 0 120 1 2 0 120 1 2 0 120 120 120 115 115 115 115 115 120 120 120 120 120 125 125 125 125 115 115 11 5 120 120 120125 125 125 125 125 125 12 5125 125 125 1 2 5125 13 0 1 3 013 0 1 3 0 95 95 95 95 100 105 11 0 115 120 115115115 11 5 1 1 5 11 5 11 5 11 5 1 1 5 11 5 1 1 5 115 1 1 5 1 1 5 11 5115115 11 5 11 5 11 5 1 2 0 I-20 0.26 IN HR I-12 0.02 IN HR I-15 0.09 IN HR I-16 0.74 IN HR I-17 0.10 IN HR I-18 0.11 IN HR I-19 0.13 IN HR I-21 0.25 IN HR I-23 0.10 IN HR I-24 0.03 IN HR EARTHWOOD LANE BUCKLEY ROAD HUGHES LANE DOOLITTLE DRIVE CO L E M A N L A N E WRIGHT BROTHERS WAY VENTURE DRIVE LA N G L E Y S T R E E T JE S P E R S E N R O A D VENTURE DRIVE EA R T H W O O D L A N E VENTURE DRIVE VA C H E L L L A N E BUCKLEY ROAD JE S P E R S E N R O A D MEMPHIS BELLE WAY PI P E R L A N E FOXTROT COURT KITTY HAWK COURT BRAVO LANE TANGO WAY DE L T A D R I V E T 805 544-4011 F 805 544-4294 612 CLARION COURT SAN LUIS OBISPO, CA 93401 www.wallacegroup.us PLANNING CIVIL AND TRANSPORTATION ENGINEERING CONSTRUCTION MANAGEMENT LANDSCAPE ARCHITECTURE MECHANICAL ENGINEERING PUBLIC WORKS ADMINISTRATION SURVEYING / GIS SOLUTIONS WATER RESOURCES DESIGNERS: DRAWING NO. DATE: DRAWN BY: JOB #: OF ® DATE SIGNED SIGNATURE These plans and specifications, and the ideas and designs incorporated herein, are instruments of service prepared for the construction of work shown hereon and shall not be used in whole or in part for any other project without written authority of Wallace Group, a California Corporation. Copyright © 2022 Wallace Group, a California Corporation. All rights reserved. Copies of this drawing shall have this notice. 321 4 6 321 4 6 B A ORIGINAL SCALE IS IN INCHES FOR REDUCED PLANS 0 1 2 3 5 5 C 7 7 D E F SHEET WA T H E N C A S T A N O S H O M E S AV I L A R A N C H D E V E L O P E M E N T IN F I L T R A T I O N E X H I B I T - P O R C H E T 1493-0007-00 -- ZKP 5-06-2022 1 1 N 00 100 200 (IN FEET) 50 GRAPHIC SCALE 1 IN = 100 FT RAC H E L A . H AWTH O R N E C I V I L No. 73686 NOT FOR CONSTRUCTION FOR PLAN REVIEW ONLY A L A T T S OF E C A O NRFI I REGISTE R E D P R O F E SSIONAL E N G I N E E R I-13 NOT TESTED I-14 NOT TESTED I-22 NOT TESTED I-9 I-11 0.13 IN HR I-5 0.02 IN HR I-8 1.87 IN HR I-7 0.68 IN HR I-4 0.01 IN HR I-6 0.63 IN HR I-2 0.08 IN HR I-1 0.30 IN HRI-3 0.07 IN HR I-10 0.07 IN HR LEGEND: RESULTS OF INFILTRATION TESTING, GEOSOLUTIONS, INC. AVILA RANCH DEVELOPMENT DATED SEPTEMBER 4, 2015 RESULTS OF INFILTRATION TESTING, GEOSOLUTIONS, INC. AVILA RANCH DEVELOPMENT DATED FEBRUARY 9, 2022 CR E E K CR E E K CREE K 0.20 0.20 0.10 0.10 0.10 0.10 0.30 0.30 0.03 0.03 0.02 0.02 0.10 0.10 0.200.20 0.60 0.60 BASIN J BASIN H-2 BASIN H-1 SHALLOW PARK BASIN SHALLOW PARK BASIN 0.10 GENERAL INFILTRATION TESTING NOTES: Stabilized Tests: I-1, I-2, I-3, I-4, I-5, I-7, I-10, I-11, I-12, I-15, I-17, I-18, I-19, I-20, I-23, I-24 Non-Stabilized Tests: I-6 (inconclusive), I-8 (inconclusive), I-9 (incomplete), I-13 (incomplete), I-14 (incomplete), I-16 (inconclusive), I-21 (inconclusive), I-22 (incomplete) 12/21/2022 APPENDIX B APPENDIX C Existing Drainage Map A E R O D R M A D O N N A R D CREEKSIDEST AIRPORT DR O CEANAIRE DR VIA SANBLAS CEDAR CT CENTER ST MAPLESTREDWOOD ST UNNAMED ST UNNAMED ST DEL ORO CT A LY S S U M C T C O R A L S T 101 N RAMP M U I R F I E L DSTCALLE JOAQUIN SEQUOIA DR CALLE JAZMIN KENTWOOD DR SPOONER DR VIA E S T E B A N SAWLEAFCT F R O O M R A N C H W A Y L A P O S A D A D R H U M B E R T S T W NE W PO RT ST FONTANAAVE BRIARWOODDR TANK FARM RD TANGLEWOOD DR C A N T E R B E R R Y S T U N N A M E D S T GRANADA DR CHUPARROSA DR BAY LEAF DR UNNAMED ST BEECH ST FENNEL ST J A M I L E E C T LAS PRADERAS DR S O L ACT CHUMASH ST GREGORYCT T O N I N I D R MIT CHE LLDR L A W R E N C E D R G O L D E N R O D L N M A R I N E R S C O V E W O O D SID E D R F U L L E R R D BLUEBELL WAY VILLA CT MELLO LN C A Y U C O S D R MCMILLAN AVE SUNFLO W ER W AY A T A S C A D E R O S T VISTA LAGO L A K E VIE W S T BONETTI DR PIN E C O V E D R PROSPECT ST ROYAL W AY G ALLEO N W AY SNAPDRAGON WAY EL M IRADO R CT FELICIA WAY LIL Y L N BALB O A ST SACRAMENTO DR MORRISONST CROSS ST HOLLYHOCK WAY F R A N C IS S T MARGARITAAVE HIND LN R O C K VIE W P L A Z A L E A C T SISQUOC ST LAWNWOOD DR D A H L I A L N K E N D A L L R D GAIL PLLA D E R A C T H U A S N A D R CHANDLER ST MEADOW ST F A R R I E R C T IRONBARK ST R O C K VIE W C T D E V A U L R A N C H R D WILLO W CIR ROSEMARY CT LAUREL LN T A N G L E W O O D D RFERNWOOD D R BOXWOOD CT I N D U S T R I A L W A Y 101 N ON BUTTONMWOOD WAY B L U E R O C K D R CUCARACHA CT C O R A L S T TULIP CT LOMA BONITA DR CALLE LUPITA SUELDO ST ACCESS ROAD ASHMORE ST SOUTHWOOD DR DRAKE CIR RIC A R D O ST RUSTIC WAY S W E E N E Y L N A C C ES S R O A D L O S O S O S V A L L E Y R D THREAD LN P U R P L ESAGE L N STONERIDGE DR ACCESS ROAD A U T O P A R K W A Y BARRANCA CT VACHELL LN EMPLEO ST LOS PALOS DR ACCESS ROAD S W EETB AY LN BUCKLEY RD OLD WINDMILL LN LEXINGTON CT VENTURE DR C A P I T O L I O W A Y M A D O N N A R D U N N A M E D S T FARMHOUSE LN SHORT ST LAWRENCE DR M A S O N D R S PIT FI R E S T A C C E S S R O A D ACCESS ROAD A C C E S S R O A D F I E R O L N M A D O N N A R D ZACA LN UNNAMED ST A C C E S S R O A D P OIN S E T TIA S T SANTA FE RD E L C A P I T A N W A Y R OYAL CT UNNAMEDST LARKSPUR ST101 N ON S HIGUERA ST SANTA FE RD HARMONY WAY MARIPOSA DR JESPERSON RD 101 S ON LONG ST S H I G U E R A S T V I A L A P A Z A L L E N E W A Y A VA L O N ST A C C ES S R O A D B O U G A I N V I L L E A S T M O R A BIT O P L A C C E S S R O A D GARIBALDI AVE B R O A D S T 101 N OFF A C C ES S R O A D L O S V E R D E S D R VIC E N T E D R M A D O N N A R D ALDER LN 101 N OFF 101 S OFF ACCESS ROAD CRESTVIEW CIR A C C E S S R O A D S A N S I M E O N S T M A D O N N A R D C A L L E C R O T A L O A C C E S S R O A D TIBURON WAY A C C E S S R O A D DALIDIO DR C H A P A R R A L C I R A E R O VIS T A P L 101 S OFF DRIVEWAY UNNAMED ST DRIVEWAY ESPERANZA LN OCTAGON WAY 101 N OFF CAVALIER LN H W Y 1 0 1 HOPKINS LN 1 0 1 S O N A C C E S S R O A D B U L L O C K L N EL MERCADO ST SUBURBAN RD PRADO RD DIRT ROAD A C C E S S R O A D MEISSNER ST ELKS LN 9 3 21 EX1 4 6 7 5 8 EX1 10 11 Phase 1 EX3 EX2 EX4 BUCKLEY ROAD 1 EXHIBIT NOTES:WALLACE GROUP DID NOT PERFORM SURVEY SERVICES FOR THIS MAP. NOT A LEGAL DOCUMENT. AV I L A R A N C HEXISTING W AT E R S H E D SFIGURE 31 inch = 1,200 Feet 0 2,4001,200 O JOB NO: 1493-0007-00MAP DOC: EXISTING WATERSHEDSCREATED BY: DJGDATE: 05/11/2022 !!Exisiting Contours (5 ft) Tank Farm Creek Parcels SLO City Limits CIVIL ENGINEERINGCONSTRUCTION MANAGEMENTLANDSCAPE ARCHITECTUREMECHANICAL ENGINEERINGPLANNINGPUBLIC WORKS ADMINISTRATIONSURVEYING/GIS SOLUTIONSWATER RESOURCESWALLACE SWANSON INTERNATIONAL612 CLARION COURTSAN LUIS OBISPO, CA 93401T 805 544-4011 F 805 544-4294www.wallacegroup.us APPENDIX C APPENDIX D Proposed Stormwater Control Drainage Management Area Exhibit SD SD SD SD SS SS SD SD SD SDSD SS SD SS SD SS SS SS SD SD SD SD SS SS SD SD SD SD SD SS SS SD SS SD SS SS SD SS SD SD SD SD SD SD SD SD SD SD SS SD SD SS SS SS SD SD SD SS SS SD SD SD SS SS SD SS S D SD SD SS SS SD SD SD SDSD SD SD SD SD SD SD SD SD SD SD SD SD SS SS SD SDSD SD SD SD SD SSSS SD SD SD SD SD SD SD SD SD SD SD SD SD SS SS SD SD SD SD SD SD SD SS SD SS SD SS SDSD SD SD SD SD SS SS SD SD SD SD SD SD SDSD SD SD SD SD SD SD SD PAGE 1 OF 1 Avila Ranch - Phases 2-6 Proposed Drainage Management Area (DMA) Exhibit BUCKLEY ROAD WATERSHED 1BUCKLEY ROAD WATERSHED 2B BUCKLEY ROAD WATERSHED 2A RAC H E L A . HAWTH O R N E C I V I L No. 73686 A L A T T S OF E C A O NRFI I REGISTER E D P R O F E SSIONAL EN G I N E E R 100 200 1 IN = 100 FT 50001493-0007 Avila Ranch BY: RAH/ ZKP Date: 12/21/2022 DMA A OUTLET "A" OUTLET "B" OUTLET "D" DMA B DMA B DMA C OUTLET "C" OUTLET "E" OUTLET "F" D M A G OUTLET "G" DMA H DMA I DMA J OUTLET "J" OUTLET "I" OUTLET "H" DMA F DMA E-ROW DMA H-PH4 DMA E-PH4a DMA E-4b PARK I PARK H PARK G COMM. 1 COMM. 2 VEG. C H A N N E L PARK F (SOUTH) PARK F (NORTH) PARK E DMA D BYPASS CHANNEL BYP A S S CHA N N E L JE S P E R S E N R O A D HUGHES LANE DOOLITTLE DRIVE FOXTROT CT. VEN T U R E D R I V E MEMPHIS BELLE VENTURE DRIVE WRIGHT BROTHERS WAYWRIGHT BROTHERS WAY EA R H A R T W A Y PH 0 5 A L L E Y BUCKLEY ROAD YE A G E R C T . DMA L DMA K DMA M EA R T H W O O D L A N E ( P H A S E 1 ) DMA N SEE IMPROVEMENT PLANS FOR BUCKLEY ROAD WIDENING FOR OFFSITE WATERSHEDS THAT FLOW TO STORM DRAIN SYSTEM APPENDIX D APPENDIX E Structural Control Measures (SCM) Exhibit Design · SCM Exhibit · Phases 2-6 Land Use Data · SCM Sizing Calculations · Central Coast Region SCM Sizing Calculator results - Phase 2 + 3 - Phase 4 - Phase 5 - Phase 6 SD SD SD SD SS SS SD SD SDSD SD SD SS SS SD SS SD SD SD SD SD SD SD SD SD SS SD SD SS SS SS SD SD SD SD SS S D SD SS SS SD SD SDSD SD SD SD SD SD SD SD SD SD SDSD SD SD SSSS SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SS 115 115 120 115 12 0 120 120 119 118 119 12 0 1 1 8 11 9 12 1 117 118 1 2 1 11 6 1 1 7 1 1 9 11 9 SD SD SD SD SD SDSD SD SD SD SD SD SD SD COMM #1 H (#3) H (#4) H (#5) H (#9) H (#8) H (#10)H (#11) H (#12) H (#13)H (#14)H (#15) H (#16) H (#17) H (#19) H (#18) E-PH4b (#6) E-PH4b (#5) E-PH4a (#1) E-PH4a (#2) E-PH4a (#3) E-PH4a (#4) E (#2) E (#1) E (#4) E (#3) A (#1) B (#1) B (#2) B (#3)B (#4) B (#5) B (#6) B (#7) B (#8) B (#9) B (#10) C (#1) C (#2) C (#3)C (#4) C (#5) D (#1)D (#2) D (#3) D (#4) D (#5)D (#6) D (#7) D (#8) G (#1) G (#2) G (#3) G (#4) B (#11) COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK DMA E-PH4a & E-PH4b STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK H (#20) 5-89 5-80 5-67 5-88 5-81 5-66 5-655-825-87 5-86 5-83 5-64 5-635-845-85 5-62 5-61 5-60 5-59 5-58 5-57 5-56 5-98 5-99 5-100 5-101 2-28 2-27 2-24 2-23 2-222-252-262-29 2-1 2-2 2-5 2-4 2-3 2-8 2-7 2-6 2-11 2-10 2-9 2-14 2-13 2-12 2-17 2-16 2-15 2-18 2-19 2-21 2-20 3-1 3-6 3-53-2 3-7 3-8 3-93-43-3 3-10 3-11 3-13 3-12 3-15 3-14 3-16 3-17 3-18 3-21 3-20 3-19 3-24 3-23 3-22 3-27 3-26 3-25 3-28 3-29 3-30 3-33 3-32 3-31 3-34 3-35 3-36 3-37 3-38 3-39 3-40 3-43 3-42 3-41 3-44 3-45 3-46 3-49 3-48 3-47 3-50 3-51 3-52 3-54 3-53 3-55 3-56 3-57 3-58 3-59 3-60 3-64 3-63 3-62 3-61 3-76 3-75 3-74 3-73 3-77 3-78 3-79 3-80 3-90 3-89 3-88 3-87 3-91 3-92 3-93 3-94 3-65 3-66 3-67 3-70 3-71 3-72 3-83 3-82 3-81 3-84 3-85 3-86 193 200 2-30 3-95 3-96 3-97 3-98 3-99 3-100 202 6-2 6-3 COMM #2 60 120 1 IN = 60 FT 3000 VENTURE DRIVE EA R T H W O O D L A N E JE S P E R S E N R O A D PAGE 1 OF 4 BASIN B BOT. ELEV ≈ 113.50 GW ELEV = 105.00 Avila Ranch - Phases 2-6 Stormwater Control Measures (SCM) Exhibit WRIGHT BROTHERS BASIN H-1 POND = 0.6' + 1.0' FB BOT. ELEV = 112.00 GW ELEV = 105.00 BASIN H-2 POND = 0.6' + 1.0' FB BOT. ELEV = 110.00 GW ELEV = 105.00 DRAWN BY: RAH/ ZKP 12-21-2022 1493-0007 PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). LEGEND: PHASE BOUNDARY DRAINAGE MANAGEMENT AREA BOUNDARY BIOSWALE WITH UNDERGROUND GRAVEL TRENCH MOTORCOURT/ ALLEY GRAVEL CHAMBER OFFSET GRAVEL CHAMBER VEGETATED RETENTION BASIN RETENTION-BASED TREATMENT AREA (REFER TO APPENDIX F, ATTACHMENT E COMPLIANCE) PERMEABLE PAVERS WITH GRAVEL CHAMBER PROPOSED STORM DRAIN NETWORK SCM IDENTIFICATION (REFER TO PHASES 2-6 SCM SIZING CALCULATIONS). PHASE 2, 3, 5, 6 LOT NUMBERS PHASE 4 LOT NUMBERS SD A (#1) 0-00 199 MULTI-FAMILY LOTS NOT INCLUDED MULTI-FAMILY LOTS NOT INCLUDED MULTI-FAMILY LOTS NOT INCLUDED RAC H E L A . H AWTH O R N E C I V I L No. 73686 A L A T T S OF E C A O NRFI I REGISTE R E D P R O F E SSIONAL E N G I N E E R 12/21/2022 APPENDIX E SD SD SD SD SS SS SD SDSD SD SS SS SD SD SDSD SD SD SS SD SS SD SD SD SD SD SD SD SD SS SD SD SS SS SS SD SD SD SD SD SD SS S D SD SS SS SD SDSD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SS SS SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD COMM #1 H (#4) H (#5) H (#9) H (#10)H (#11) H (#12) H (#13)H (#14)H (#15) H (#17) H (#19) H (#18) H-PH4 (#1) H-PH4 (#2) H-PH4 (#3) H-PH4 (#4) H-PH4 (#5) H-PH4 (#6) H-PH4 (#7) E-PH4b (#1) E-PH4b (#2) E-PH4b (#3) E-PH4b (#4) E-PH4b (#6) E-PH4b (#5) E-PH4b (#7) F (#1) F (#2) F (#3) F (#4) F (#5) E-PH4a (#1) E-PH4a (#2) E-PH4a (#3) E-PH4a (#4)E-PH4a (#5) E-PH4a (#6) E (#2) E (#1) E (#4) E (#3) B (#2) C (#1) C (#2) C (#3)C (#4) C (#5) D (#3) D (#4) D (#7) D (#8) G (#1) G (#2) G (#3) G (#4) H-PH4 (#8) DMA H-PH4 STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK DMA F STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK DMA E-PH4a & E-PH4b STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK H (#20) 5-655-825-87 5-86 5-83 5-64 5-635-845-85 5-62 5-61 5-60 5-59 5-58 5-57 5-56 5-100 5-101 3-37 3-38 3-39 3-40 3-43 3-42 3-41 3-44 3-45 3-46 3-49 3-48 3-47 3-50 3-51 3-52 3-54 3-53 3-55 3-56 3-76 3-75 3-74 3-73 3-77 3-78 3-79 3-80 3-90 3-89 3-88 3-87 3-91 3-92 3-93 3-94 3-70 3-71 3-72 3-83 3-82 3-81 3-84 3-85 3-86 192 193 197 194 195 196 199 200 201 2-30 3-100 202 6-2 6-3 201 COMM #2 VENTURE DRIVE JE S P E R S E N R O A D WRIGHT BROTHERS WAY PAGE 2 OF 4 BASIN E-4b BASIN H-PH4 Avila Ranch - Phases 2-6 Stormwater Control Measures (SCM) Exhibit BASIN H-1 POND = 0.6' + 1.0' FB BOT. ELEV = 112.00 GW ELEV = 105.00 BASIN H-2 POND = 0.6' + 1.0' FB BOT. ELEV = 110.00 GW ELEV = 105.00 PROPOSED VEGETATED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). PROPOSED CONCRETE-LINED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). LEGEND: PHASE BOUNDARY DRAINAGE MANAGEMENT AREA BOUNDARY BIOSWALE WITH UNDERGROUND GRAVEL TRENCH MOTORCOURT/ ALLEY GRAVEL CHAMBER OFFSET GRAVEL CHAMBER VEGETATED RETENTION BASIN RETENTION-BASED TREATMENT AREA (REFER TO APPENDIX F, ATTACHMENT E COMPLIANCE) PERMEABLE PAVERS WITH GRAVEL CHAMBER PROPOSED STORM DRAIN NETWORK SCM IDENTIFICATION (REFER TO PHASES 2-6 SCM SIZING CALCULATIONS). PHASE 2, 3, 5, 6 LOT NUMBERS PHASE 4 LOT NUMBERS SD A (#1) 0-00 199 60 120 1 IN = 60 FT 3000 DRAWN BY: RAH/ ZKP 12-21-2022 RAC H E L A . H AWTH O R N E C I V I L No. 73686 A L A T T S OF E C A O NRFI I REGISTE R E D P R O F E SSIONAL E N G I N E E R 12/21/2022 1493-0007 APPENDIX E SD SD SD SD SS SS SD SS SS SS SDSD SD SS SS SDSD SS SS SS SD SS SD SD SD SDSD SS SS SD SD SS SS S D SD SS SS SD SD SD SD SD SD SD SD SD SD SD SS SS SD SDSD SD SD SD SD SD SD SD SD SD SD SDSD SD SD SD SD SD SD SD SD SD SD SD SD SS SD SS SD SS SDSD SD SD SD SS 115 120 120 120 12 0 115 12 0 120 12 0 11 7 11 7 11 8 11 9 12 1 12 1 12 2 12 2 12 0 11 7 11 8 11 9 12 1 12 2 11 6 11 7 120 119 121 121 121 121 120 118 119 12 0 1 1 8 11 9 12 1 12 2 120 1 1 9 1 2 1 118 119 1 1 4 114 1 2 0 115 120 1 1 6 11 7 1 1 0 11 0 110 11 511 5 98 1 0 0 10 5 12 1121 1 2 1 1 2 1 12 1 11 6 1 1 7 11 9 11 8 SD SD SD SD SD COMM #1 J (#1) J (#2)J (#3)J (#4)J (#5) J (#6) J (#7)J (#8)J (#9) J (#10)J (#11)J (#12)J (#14) J (#15) J (#16)J (#17 J (#18)J (#19)J (#20) I (#1) I (#3) I (#4)I (#5) I (#2) I (#6) I (#7) I (#8) I (#9) I (#10) I (#11) H (#1) H (#2) H (#3) H (#4) H (#5) H (#9) H (#8) H (#7) H (#6) H (#10)H (#11) H (#12) H (#13)H (#14)H (#15) H (#16) H (#17) H (#18)B (#7) B (#8) D (#6) I (#12)I (#13) PARK I NO ONSITE RETENTION PARK H PARK STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK J (#21) STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK J (#13) H (#20) 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 5-13 5-14 5-15 5-16 5-17 5-18 5-19 5-20 5-21 5-22 5-23 5-24 5-51 5-52 5-53 5-54 5-55 5-25 5-26 5-27 5-50 5-49 5-48 5-47 5-46 5-28 5-29 5-30 5-45 5-44 5-31 5-32 5-43 5-42 5-33 5-34 5-41 5-40 5-35 5-36 5-39 5-38 5-37 5-95 5-94 5-93 5-76 5-75 5-74 5-73 5-72 5-71 5-705-775-92 5-91 5-78 5-69 5-685-795-90 5-89 5-80 5-67 5-88 5-81 5-66 5-655-825-87 5-86 5-83 5-64 5-635-845-85 5-62 5-61 5-60 5-58 5-57 5-56 5-96 5-97 5-98 5-99 5-100 5-101 2-28 2-27 2-24 2-23 2-222-252-262-29 2-1 2-2 2-5 2-4 2-3 2-8 2-7 2-6 2-11 2-10 2-9 2-14 2-13 2-12 2-17 2-16 2-15 2-18 2-19 2-21 2-20 2-30 6-2 6-3 5-102 5-104 5-105 5-106 COMM #2 BUCKLEY ROAD EA R T H W O O D L A N E JE S P E R S E N R O A D DOOLITTLE DRIVE HUGHES LANE PAGE 3 OF 4 BASIN J POND = 0.6' + 1.0' FB BOT. ELEV = 105.40 GW ELEV = 101.00 BASIN H-1 POND = 0.6' + 1.0' FB BOT. ELEV = 112.00 GW ELEV = 105.00 BASIN H-2 POND = 0.6' + 1.0' FB BOT. ELEV = 110.00 GW ELEV = 105.00 PROPOSED VEGETATED SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). LEGEND: PHASE BOUNDARY DRAINAGE MANAGEMENT AREA BOUNDARY BIOSWALE WITH UNDERGROUND GRAVEL TRENCH MOTORCOURT/ ALLEY GRAVEL CHAMBER OFFSET GRAVEL CHAMBER VEGETATED RETENTION BASIN RETENTION-BASED TREATMENT AREA (REFER TO APPENDIX F, ATTACHMENT E COMPLIANCE) PERMEABLE PAVERS WITH GRAVEL CHAMBER PROPOSED STORM DRAIN NETWORK SCM IDENTIFICATION (REFER TO PHASES 2-6 SCM SIZING CALCULATIONS). PHASE 2, 3, 5, 6 LOT NUMBERS PHASE 4 LOT NUMBERS SD A (#1) 0-00 199 60 120 1 IN = 60 FT 3000 DRAWN BY: RAH/ ZKP 12-21-2022 RAC H E L A . H AWTH O R N E C I V I L No. 73686 A L A T T S OF E C A O NRFI I REGISTE R E D P R O F E SSIONAL E N G I N E E R 12/21/2022 1493-0007Avila Ranch - Phases 2-6 Stormwater Control Measures (SCM) Exhibit APPENDIX E SD SD SD SD SDSD SS SS SD SS SD SD SD SS SS SS SD SS SD SD SD SDSD SD S D SS SS SD SD SD SD SD SD SD SD SD SD SD SD SD SD SD SS SS SD SS SD 120 120 120 12 0 115 12 0 12 0 120 12 1 12 1 12 2 12 2 12 1 12 2 120 119 121 121 121 121 120 118 119 12 0 1 1 8 11 9 12 1 12 2 120 1 1 9 1 2 1 118 119 1 2 0 120 12 0 12 5 12 5 1 1 6 11 7 11 8 11 9 12 1 12 2 12 3 12 4 12 4 11 511 5 12 1121 1 2 1 1 2 1 12 1 11 6 1 1 7 11 9 120 11 8 11 8 11 9 121 122 123 124 13 0 12 7 12 8 12 9 SD SD SD COMM #1 J (#5) J (#9) J (#14) J (#18)J (#20) I (#1) I (#3) I (#4)I (#5) I (#2) I (#6) I (#7) I (#8) I (#9) I (#10) I (#11) H (#1) H (#2) H (#3) H (#4) H (#5) H (#9) H (#8) H (#7) H (#6) H (#10)H (#11) H (#12) H (#13)H (#14)H (#15) H (#16) H (#17) H (#18) H-PH4 (#1) H-PH4 (#2) H-PH4 (#4) H-PH4 (#5)F (#4) F (#5) I (#12)I (#13) PARK H PARK STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK PARK G PARK STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK DMA H-PH4 STORMWATER TO BE COLLECTED BY FUTURE ONSITE DRAINAGE SYSTEM WHICH WILL BE CONNECTED TO PH. 2-6 SD NETWORK J (#13) H (#20) 5-13 5-14 5-15 5-16 5-17 5-18 5-19 5-20 5-21 5-22 5-23 5-24 5-42 5-34 5-41 5-40 5-35 5-36 5-39 5-38 5-37 5-95 5-94 5-93 5-76 5-75 5-74 5-73 5-72 5-71 5-705-775-92 5-91 5-78 5-69 5-685-795-90 5-89 5-80 5-67 5-88 5-81 5-66 5-655-825-87 5-86 5-83 5-64 5-635-845-85 5-62 5-61 5-60 5-58 5-57 5-56 5-96 5-97 5-98 5-99 5-100 5-101 197 196 198 2-30 201 6-2 6-3 5-102 COMM #2 BUCKLEY ROAD JE S P E R S E N R O A D DOOLITTLE DRIVE PAGE 4 OF 4 BASIN H-1 POND = 0.6' + 1.0' FB BOT. ELEV = 112.00 GW ELEV = 105.00 BASIN H-2 POND = 0.6' + 1.0' FB BOT. ELEV = 110.00 GW ELEV = 105.00 PROPOSED VEGETATED PERIMETER SWALE (SEE AVILA RANCH PHASES 2-6 MASS GRADING PLAN). 60 120 1 IN = 60 FT 3000 DRAWN BY: RAH/ ZKP 12-21-2022 RAC H E L A . H AWTH O R N E C I V I L No. 73686 A L A T T S OF E C A O NRFI I REGISTE R E D P R O F E SSIONAL E N G I N E E R 12/21/2022 1493-0007 LEGEND: PHASE BOUNDARY DRAINAGE MANAGEMENT AREA BOUNDARY BIOSWALE WITH UNDERGROUND GRAVEL TRENCH MOTORCOURT/ ALLEY GRAVEL CHAMBER OFFSET GRAVEL CHAMBER VEGETATED RETENTION BASIN RETENTION-BASED TREATMENT AREA (REFER TO APPENDIX F, ATTACHMENT E COMPLIANCE) PERMEABLE PAVERS WITH GRAVEL CHAMBER PROPOSED STORM DRAIN NETWORK SCM IDENTIFICATION (REFER TO PHASES 2-6 SCM SIZING CALCULATIONS). PHASE 2, 3, 5, 6 LOT NUMBERS PHASE 4 LOT NUMBERS SD A (#1) 0-00 199 Avila Ranch - Phases 2-6 Stormwater Control Measures (SCM) Exhibit APPENDIX E Tract 3089 - Avila Ranch Phases 2-6 Land Use Data Project:1493-0007 Avila Ranch Date:December 20, 2022 By:ZKP Phases 2-6 Land Use Data 95th 1.92 inches 50% R-1 Low Density Phase 5 50% R-2 Medium Density Phases 2+3 60% R-3 Med. High Density Phase 4 60% R-4 High Density Phase 2+3 75% C-N Commercial Phase 6 20% Park Parks Phases 2-6 Motorcourt/ Alley DMA Total Area (SF) Total Area (AC) Lot Area (SF) % Impervious Impervious Area (SF) Pervious Area (SF)Area (SF)ROW Area (SF) Impervious Area (SF) Pervious Area (SF)Area (SF)% Impervious Impervious Area (SF) Pervious Area (SF) Total Impervious (SF) Total Pervious (SF)Area Check Phase 2+3 27,551 50% 13,776 13,776 7,109 10,468 10,468 - - 20% - - 31,352 13,776 79,123 60% 47,474 31,649 - - - - 10,843 100% 10,843 - - - 279,125 50% 139,563 139,563 40,727 111,023 110,041 982 35,561 20% 7,112 28,449 297,443 168,993 92,547 60% 55,528 37,019 - - - - - - - - - C 169,367 3.89 102,229 50% 51,115 51,115 15,403 34,940 33,495 1,445 16,795 100% 16,795 116,808 52,560 169,367 D 35,561 0.82 - - - - 35,561 28,649 6,912 - - - 28,649 6,912 35,561 Bypass 148,673 3.41 - - - - - - - 148,673 9500 139,173 9,500 139,173 148,673 Phase 4 - Onsite Residential & Right-of-Way E-ROW 74,651 1.71 - - - - 74,651 63,862 10,789 - - - - 63,862 10,789 74,651 E-PH4a 142,167 3.26 142,167 60% 85,300 56,867 - - - - - - - - 85,300 56,867 142,167 E-PH4b Lot 44,315 1.02 44,315 60%26,589 17,726 - - - - - - - 26,589 17,726 44,315 E-PH4b Park F 20,123 0.46 - - - - - - - 20,123 20% 4,025 16,098 4,025 16,098 20,123 F 132,462 3.04 102,547 60% 61,528 41,019 - 29,915 29,915 - - - - 91,443 41,019 132,462 H-PH4 234,998 5.39 202,171 60% 121,303 80,868 - - - - 32,827 25% 8,207 24,620 129,509 105,489 234,998 Veg. Channel 22,767 0.52 - - - 22,767 0%- 22,767 - 22,767 22,767 G 21,042 0.48 - - - - 21,042 16,992 4,050 - - - 16,992 4,050 21,042 K 653,119 14.99 - - - - - - - 653,119 - 653,119 - 653,119 653,119 M 1,326,622 30.46 - - - - - - - 1,326,622 - 1,326,622 - 1,326,622 1,326,622 N 107,721 2.47 - - - - - - - 107,721 - 107,721 - 107,721 107,721 Phase 5 - Residential, Parks I and H, and Onsite Right-of-Way (including adjacent Phase 4 Right-of-Way areas that flow onto Phase 5) Park G 408,921 9.39 - - - - - - - 408,921 25% 102,230 306,691 102,230 306,691 408,921 Park I 19,124 0.44 - - - - - - - 19,124 20% 3,825 15,299 3,825 15,299 19,124 H alley 85,050 1.95 77,497 50% 38,749 38,749 7,553 - - - - - - 46,302 38,749 85,050 H yeager 45,650 1.05 31,234 50% 15,617 15,617 - 14,416 12,578 1,838 - - - 28,195 17,455 45,650 H east 55,487 1.27 - - - - 55,487 51,075 4,412 - - - 51,075 4,412 55,487 H 180,462 4.14 92,416 50% 46,208 46,208 - 80,096 65,742 14,354 7,950 15% 1,193 6,758 113,143 67,320 180,462 J 344,823 7.92 243,896 50% 121,948 121,948 2,528 95,549 84,083 11,466 2,850 950 1,900 209,509 135,314 344,823 I park H 74,103 1.70 - - - - - - - 74,103 20% 14,821 59,282 14,821 59,282 74,103 I alley 46,569 1.07 37,861 50% 18,931 18,931 4,556 - - - 4,152 15% 623 3,529 24,109 22,460 46,569 I 107,938 2.48 39,018 50% 19,509 19,509 - 64,769 58,043 6,726 4,151 25% 1,038 3,113 78,590 29,348 107,938 L 262,099 - - - - - - - 262,099 - 262,099 - 262,099 262,099 Phase 6 - Commercial Comm 1 40,041 0.92 40,041 75% 30,031 10,010 - - - - - - - 30,031 10,010 40,041 Comm 2 36,320 0.83 36,320 75% 27,240 9,080 - - - - - - - 27,240 9,080 36,320 For use in SCM Calculator 45,128 135,093 3.10 A 12.83 558,983 B 466,436 Rainfall Event Data Watershed Information Land Use Information Residential Right-of-Way Park/ Paseo/ Misc Land Use Impervious Data 2022_AVR_SWCP Calculations_update Page 1 of 2 APPENDIX E Tract 3089 - Avila Ranch Phases 2-6 Land Use Data Name Eqiv. Area FB Depth Total Depth Volume Basin B 3,387 - 0.50 0.50 1,694 Basin J 9,415 1.00 0.60 1.60 5,649 Comm 1 771 1.00 1.00 2.00 771 Comm 2 771 1.00 1.00 2.00 771 Basin H-1 8,896 1.00 0.60 1.60 5,338 Basin H-2 1,562 1.00 0.60 1.60 937 Basin H-PH4 1,632 - 0.50 0.50 816 Basin E-4b 1,900 - 0.50 0.50 950 Basin Volume-Depth Calculations 2022_AVR_SWCP Calculations_update Page 2 of 2 APPENDIX E Tract 3089 - Avila Ranch Stormwater Control Measures (SCM) Sizing Calculations Project:1493-0007 Avila Ranch Phases 2-6 Date:December 20, 2022 By:ZKP Stormwater Control Measures (SCM) Sizing Calculations Post-Construction Stormwater Requirements #3 - Runoff Retention *Required Retention 3.00 ft 3.00 ft Proposed Retention (cf) *Required Retention (cf) 20,441 63,496 43,802 43,683 56,684 56,496 3,420 2,843 DMA SCM # Location SCM Description Width (ft) Length (ft) Area (sf) FG Elevation (ft) GW Elevation (ft) GW Separation Elevation (ft) Depth to Top-of- Gravel from FG (ft) Max. Gravel Depth (ft) Max. SCM Depth (ft) Max. Ret. Volume (cf)Notes Depth to Top-of- Gravel from FG (ft)Gravel Depth (ft)Total SCM Depth from FG (ft) Retention Volume (cf) A 1 Lots 3-4 to 3-6 Motorcourt/ Alley Gravel Chamber 6.00 126.60 759.60 119.50 106.00 109.00 3.25 7.25 10.50 2,203 3.25 5.25 8.50 1,595 Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 760 2,203 TOTAL 1,595 4,203 TOTAL B 1 Lots 3-65 to 3-67 Motorcourt/ Alley Gravel Chamber 6.00 124.00 744.00 116.25 105.00 108.00 3.25 5.00 8.25 1,488 3.25 5.00 8.25 1,488 B 2 Lots 3-41 to 3-43 Motorcourt/ Alley Gravel Chamber 6.00 123.30 739.80 116.75 105.00 108.00 3.25 5.50 8.75 1,628 3.25 5.25 8.50 1,554 B 3 Lots 3-16 to 3-18 Motorcourt/ Alley Gravel Chamber 6.00 129.30 775.80 115.25 105.00 108.00 3.25 4.00 7.25 1,241 3.25 4.00 7.25 1,241 B 4 Lots 3-34 to 3-36 Motorcourt/ Alley Gravel Chamber 6.00 121.40 728.40 115.25 105.00 108.00 3.25 4.00 7.25 1,165 3.25 4.00 7.25 1,165 B 5 Venture Drive at Piper (NW) Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 112.50 104.00 107.00 2.50 3.00 5.50 270 2.50 3.00 5.50 270 B 6 Venture Drive at Piper (SW) Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 112.50 104.00 107.00 2.50 3.00 5.50 270 2.50 3.00 5.50 270 B 7 Lots 2-24 to 2-25 Motorcourt/ Alley Gravel Chamber 6.00 74.00 444.00 114.00 104.00 107.00 3.25 3.75 7.00 666 3.25 3.75 7.00 666 B 8 Lots 2-3 to 2-5 Motorcourt/ Alley Gravel Chamber 6.00 78.00 468.00 114.30 104.00 107.00 3.25 4.05 7.30 758 3.25 4.00 7.25 749 B 9 Basin B/ Park E Offset Gravel Chamber 8.00 110.00 880 115.00 105.00 108.00 2.50 4.50 7.00 1,584 2.50 4.50 7.00 1,584 B 10 Park E Shallow Basin B - - 3,260 113.50 105.00 108.00 0.50 - 0.50 1,630 0.50 - 0.50 1,630 BASIN B (depth = 0.5') B 11 Lots 3-57 to 3-60 Motorcourt/ Alley Gravel Chamber 6.00 148.50 891.00 114.25 105.00 108.00 3.25 3.00 6.25 1,069 3.25 3.00 6.25 1,069 Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 9,381 11,770 TOTAL 11,686 40,841 TOTAL C 1 Lots 3-81 to 3-83 Motorcourt/ Alley Gravel Chamber 6.00 124.00 744.00 118.50 105.00 108.00 3.25 7.25 10.50 2,158 3.25 5.25 8.50 1,562 C 2 Lots 3-87 to 3-90 Motorcourt/ Alley Gravel Chamber 6.00 148.50 891.00 117.35 105.00 108.00 3.25 6.10 9.35 2,174 3.25 5.25 8.50 1,871 C 3 Venture Dr/ Lot 3-55 Narrow - Roadside Bioswale + Gravel 4.50 60.00 270.00 116.75 105.00 108.00 2.50 6.25 8.75 675 2.50 5.50 8.00 594 C 4 Venture Dr/ Lot 3-54 Narrow - Roadside Bioswale + Gravel 4.50 30.00 135.00 116.50 105.00 108.00 2.50 6.00 8.50 324 2.50 5.50 8.00 297 C 5 Venture Dr/MemphisBell (SW) Narrow - Roadside Bioswale + Gravel 4.50 60.00 270.00 116.75 105.00 108.00 2.50 6.25 8.75 675 2.50 5.50 8.00 594 Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 2,310 6,006 TOTAL 4,919 17,194 TOTAL D 1 Venture Dr/ Lot 3-30 Narrow - Roadside Bioswale + Gravel 4.50 40.00 180.00 112.50 104.00 107.00 2.50 3.00 5.50 216 2.50 3.00 5.50 216 D 2 Venture Dr/ Lot 3-31 Narrow - Roadside Bioswale + Gravel 4.50 40.00 180.00 112.50 104.00 107.00 2.50 3.00 5.50 216 2.50 3.00 5.50 216 D 3 Venture Dr/ Lot 3-39 Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 113.90 105.00 108.00 2.50 3.40 5.90 306 2.50 3.25 5.75 293 D 4 Venture Dr/ Lot 3-50 Narrow - Roadside Bioswale + Gravel 4.50 40.00 180.00 116.75 105.00 108.00 2.50 6.25 8.75 450 2.50 5.50 8.00 396 D 5 Venture Dr/ Lot 2-20 Narrow - Roadside Bioswale + Gravel 4.50 40.00 180.00 112.50 104.00 107.00 2.50 3.00 5.50 216 2.50 3.00 5.50 216 D 6 Venture Dr/ Lot 2-19 Narrow - Roadside Bioswale + Gravel 4.50 40.00 180.00 112.50 104.00 107.00 2.50 3.00 5.50 216 2.50 3.00 5.50 216 D 7 Venture Dr/Lot 3-39 (opposite) Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 113.90 105.00 108.00 2.50 3.40 5.90 306 2.50 3.25 5.75 293 D 8 Venture Dr/Lot 3-50 (opposite) Narrow - Roadside Bioswale + Gravel 4.50 40.00 180.00 116.75 105.00 108.00 2.50 6.25 8.75 450 2.50 5.50 8.00 396 Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 1,530 2,376 TOTAL 2,241 1,258 TOTAL Bypass -- Bypass Channel Maintained Vegetation - - 148,673 - - - - - - - Self-Treating - - - - Self-Treating, not included Watershed Retention (cf) *Required Retention (cf) A 1,595 4,203 B 11,686 40,841 C 4,919 17,194 D 2,241 1,258 20,441 63,496 TOTAL PCR #3 Retention Requirement - Summary Multi-family omitted from calc Phase 2+3 4 5 6 (Comm.) Notes Phase 2 & 3 Summary of Phase 4 - Onsite Residential & Right-of-Way Notes & Assumptions Data from Central Coast Region SCM Sizing Calculator Linear Facility-Groundwater Separation Basin-Groundwater Separation SCM notes SCM Description SCM Footprint SCM Sizing Calculation Compliance through Attachement E (10% EISA Adjust.) YES --- --- --- Internal Calculations (hide) Maximum SCM Sizing CalculationFG vs. Groundwater Comparison Notes APPENDIX E Tract 3089 - Avila Ranch Stormwater Control Measures (SCM) Sizing Calculations Project:1493-0007 Avila Ranch Phases 2-6 Date:December 20, 2022 By:ZKP Stormwater Control Measures (SCM) Sizing Calculations Post-Construction Stormwater Requirements #3 - Runoff Retention *Required Retention 3.00 ft 3.00 ft Proposed Retention (cf) *Required Retention (cf) 20,441 63,496 43,802 43,683 56,684 56,496 3,420 2,843 DMA SCM # Location SCM Description Width (ft) Length (ft) Area (sf) FG Elevation (ft) GW Elevation (ft) GW Separation Elevation (ft) Depth to Top-of- Gravel from FG (ft) Max. Gravel Depth (ft) Max. SCM Depth (ft) Max. Ret. Volume (cf)Notes Depth to Top-of- Gravel from FG (ft)Gravel Depth (ft)Total SCM Depth from FG (ft) Retention Volume (cf) PCR #3 Retention Requirement - Summary Multi-family omitted from calc Phase 2+3 4 5 6 (Comm.) Notes Notes & Assumptions Data from Central Coast Region SCM Sizing Calculator Linear Facility-Groundwater Separation Basin-Groundwater Separation SCM notes SCM Description SCM Footprint SCM Sizing Calculation Compliance through Attachement E (10% EISA Adjust.) YES --- --- --- Internal Calculations (hide) Maximum SCM Sizing CalculationFG vs. Groundwater Comparison Notes H-PH4 1 Lot 4-6 Pervious Pavers + Gravel - - 1,876 122.50 109.00 112.00 2.50 8.00 10.50 6,003 2.50 6.00 8.50 4,502 H-PH4 2 Lot 4-6 Linear Bioswale + Gravel 4.00 140.00 560 121.50 109.00 112.00 2.50 7.00 9.50 1,568 2.50 5.50 8.00 1,232 H-PH4 3 Lot 4-6 Pervious Pavers + Gravel - - 690 120.25 109.00 112.00 2.50 5.75 8.25 1,587 2.50 5.50 8.00 1,518 H-PH4 4 Lot 4-6 Linear Bioswale + Gravel 4.00 140.00 560 119.40 108.00 111.00 2.50 5.90 8.40 1,322 2.50 5.50 8.00 1,232 H-PH4 5 Lot 4-6 Pervious Pavers + Gravel Trench - - 2,877 117.50 108.00 111.00 2.50 4.00 6.50 4,603 2.50 4.00 6.50 4,603 H-PH4 6 Lot 4-3/ Park F (south) Offset Gravel Chamber 8.00 105.00 840 121.50 109.00 112.00 2.50 7.00 9.50 2,352 2.50 5.50 8.00 1,848 H-PH4 7 Lot 4-3/ Park F (south) Wide - Roadside Bioswale + Gravel 6.00 40.00 240 120.25 109.00 112.00 2.50 5.75 8.25 552 2.50 5.50 8.00 528 H-PH4 8 Lot 4-3/ Park F (south) Shallow Basin H-PH4 - - 1,900 121.00 109.00 112.00 0.50 - 0.50 950 0.50 - 0.50 950 BASIN H-PH4 (depth = 0.5') Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 7,643 Not Including shallow basin 18,937 TOTAL 16,414 14,132 TOTAL E-PH4a 1 Lot 4-1 Linear Bioswale + Gravel 8.00 35.00 280 117.00 106.00 109.00 2.50 5.50 8.00 616 2.50 5.50 8.00 616 E-PH4a 2 Lot 4-1 Linear Bioswale + Gravel 8.00 44.00 352 117.50 106.00 109.00 2.50 6.00 8.50 845 2.50 5.50 8.00 774 E-PH4a 3 Lot 4-1 Linear Bioswale + Gravel 8.00 64.00 512 119.00 106.00 109.00 2.50 7.50 10.00 1,536 2.50 5.50 8.00 1,126 E-PH4a 4 Lot 4-1 Linear Bioswale + Gravel 8.00 95.00 760 118.50 106.00 109.00 2.50 7.00 9.50 2,128 2.50 5.50 8.00 1,672 E-PH4a 5 Lot 4-1 Linear Bioswale + Gravel 8.00 60.00 480 121.25 107.00 110.00 2.50 8.75 11.25 1,680 2.50 5.50 8.00 1,056 E-PH4a 6 Lot 4-1 Linear Bioswale + Gravel 8.00 60.00 480 121.25 107.00 110.00 2.50 8.75 11.25 1,680 2.50 5.50 8.00 1,056 Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 2,864 8,485 TOTAL 6,301 5,901 TOTAL E-PH4b 1 Lot 4-3/ Park F (north) Linear Bioswale + Gravel 6.00 27.00 162 120.00 109.00 112.00 2.50 5.50 8.00 356 2.50 5.50 8.00 356 E-PH4b 2 Lot 4-3/ Park F (north) Linear Bioswale + Gravel 6.00 32.00 192 119.50 109.00 112.00 2.50 5.00 7.50 384 2.50 5.00 7.50 384 E-PH4b 3 Lot 4-3/ Park F (north) Offset Gravel Chamber 8.00 60.00 480 120.50 109.00 112.00 2.50 6.00 8.50 1,152 2.50 5.50 8.00 1,056 E-PH4b 4 Lot 4-3/ Park F (north) Shallow Basin E-4b - - 1,632 118.50 109.00 112.00 0.50 - 0.50 816 0.50 - 0.50 816 BASIN E-PH4 (depth = 0.5') E-PH4b 5 Lot 4-2 Pervious Pavers + Gravel Trench - - 1,187 118.50 108.00 111.00 2.50 5.00 7.50 2,374 2.50 5.00 7.50 2,374 E-PH4b 6 Lot 4-2 Linear Bioswale + Gravel - - 597 116.50 108.00 111.00 2.50 3.00 5.50 716 2.50 3.00 5.50 716 E-PH4b 7 Vegetated Channel/ Flowline Maintained Vegetation - - 22,767 - - - - - - - Self-Treating - - - - Self-Treating, not included Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 2,618 Not Including shallow basin or channel 5,799 TOTAL 5,703 2,962 TOTAL F 1 Lot 4-8 Pervious Pavers + Gravel Trench - - 1,434 122.50 110.00 113.00 2.50 7.00 9.50 4,015 2.50 5.50 8.00 3,155 F 2 Lot 4-8 Linear Bioswale + Gravel 4.00 140.00 560 123.00 110.00 113.00 2.50 7.50 10.00 1,680 2.50 5.50 8.00 1,232 F 3 Lot 4-8 Linear Bioswale + Gravel 6.00 60.00 360 125.50 110.00 113.00 2.50 10.00 12.50 1,440 2.50 5.50 8.00 792 F 4 Lot 4-8 Linear Bioswale + Gravel 4.00 140.00 560 125.50 110.00 113.00 2.50 10.00 12.50 2,240 2.50 5.50 8.00 1,232 F 5 Lot 4-8 Pervious Pavers + Gravel Trench - - 2,672 127.00 110.00 113.00 2.50 11.50 14.00 12,291 2.50 5.50 8.00 5,878 Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 5,586 21,666 TOTAL 12,289 13,232 TOTAL E-ROW 1 North of Jesperson RAB Wide - Roadside Bioswale + Gravel 5.00 50.00 250 117.75 106.00 109.00 2.50 6.25 8.75 625 2.50 5.50 8.00 550 E-ROW 2 Lot 4-1 Wide - Roadside Bioswale + Gravel 5.00 50.00 250 118.80 106.00 109.00 2.50 7.30 9.80 730 2.50 5.50 8.00 550 E-ROW 3 Lot 4-1 Wide - Roadside Bioswale + Gravel 5.00 50.00 250 117.75 106.00 109.00 2.50 6.25 8.75 625 2.50 5.50 8.00 550 E-ROW 4 Lot 4-1 Wide - Roadside Bioswale + Gravel 5.00 50.00 250 118.80 106.00 109.00 2.50 7.30 9.80 730 2.50 5.50 8.00 550 Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 1,000 2,710 TOTAL 2,200 6,327 TOTAL G 1 Jespersen Rd/ near Lot 6-2 Wide - Roadside Bioswale + Gravel 5.00 27.00 135.00 116.60 107.00 110.00 2.50 4.10 6.60 221 2.50 4.00 6.50 216 G 2 Jespersen Rd/ near Lot 6-2 Wide - Roadside Bioswale + Gravel 5.00 37.00 185.00 116.60 107.00 110.00 2.50 4.10 6.60 303 2.50 4.00 6.50 296 G 3 Jespersen Rd/ near Lot 4-6 Wide - Roadside Bioswale + Gravel 5.00 20.00 100.00 116.60 107.00 110.00 2.50 4.10 6.60 164 2.50 4.00 6.50 160 G 4 Jespersen Rd/ near Lot 4-6 Wide - Roadside Bioswale + Gravel 5.00 28.00 140.00 116.60 107.00 110.00 2.50 4.10 6.60 230 2.50 4.00 6.50 224 Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 560 918 TOTAL 896 1,129 TOTAL Phase 4 - Onsite Residential & Right-of-Way APPENDIX E Tract 3089 - Avila Ranch Stormwater Control Measures (SCM) Sizing Calculations Project:1493-0007 Avila Ranch Phases 2-6 Date:December 20, 2022 By:ZKP Stormwater Control Measures (SCM) Sizing Calculations Post-Construction Stormwater Requirements #3 - Runoff Retention *Required Retention 3.00 ft 3.00 ft Proposed Retention (cf) *Required Retention (cf) 20,441 63,496 43,802 43,683 56,684 56,496 3,420 2,843 DMA SCM # Location SCM Description Width (ft) Length (ft) Area (sf) FG Elevation (ft) GW Elevation (ft) GW Separation Elevation (ft) Depth to Top-of- Gravel from FG (ft) Max. Gravel Depth (ft) Max. SCM Depth (ft) Max. Ret. Volume (cf)Notes Depth to Top-of- Gravel from FG (ft)Gravel Depth (ft)Total SCM Depth from FG (ft) Retention Volume (cf) PCR #3 Retention Requirement - Summary Multi-family omitted from calc Phase 2+3 4 5 6 (Comm.) Notes Notes & Assumptions Data from Central Coast Region SCM Sizing Calculator Linear Facility-Groundwater Separation Basin-Groundwater Separation SCM notes SCM Description SCM Footprint SCM Sizing Calculation Compliance through Attachement E (10% EISA Adjust.) YES --- --- --- Internal Calculations (hide) Maximum SCM Sizing CalculationFG vs. Groundwater Comparison Notes Watershed Retention (cf) *Required Retention (cf) H-PH4 16,414 14,132 E-PH4a 6,301 5,901 E-PH4b 5,703 2,962 F 12,289 13,232 E-ROW 2,200 6,327 G 896 1,129 43,802 43,683 TOTAL J 1 Coleman Drive (north west) Narrow - Roadside Bioswale + Gravel 4.50 65.00 292.50 113.50 102.00 105.00 2.50 6.00 8.50 702 2.50 5.50 8.00 644 J 2 Doolittle Dr./ Lot 5-52 Narrow - Roadside Bioswale + Gravel 4.50 20.00 90.00 115.74 103.00 106.00 2.50 7.24 9.74 261 2.50 5.50 8.00 198 J 3 Doolittle Dr./ Lot 5-104 Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 116.34 103.00 106.00 2.50 7.84 10.34 706 2.50 5.50 8.00 495 J 4 Doolittle Dr./ Lot 5-105 Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 117.10 104.00 107.00 2.50 7.60 10.10 684 2.50 5.50 8.00 495 J 5 Doolittle Dr./ Lot 5-105 Narrow - Roadside Bioswale + Gravel 4.50 70.00 315.00 119.00 105.00 108.00 2.50 8.50 11.00 1,071 2.50 5.50 8.00 693 J 6 Coleman Dr./ Lot 5-50 Narrow - Roadside Bioswale + Gravel 4.50 56.00 252.00 113.50 102.00 105.00 2.50 6.00 8.50 605 2.50 5.50 8.00 554 J 7 Doolittle Dr./ Lot 5-48 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 115.35 103.00 106.00 2.50 6.85 9.35 543 2.50 5.50 8.00 436 J 8 Doolittle Dr./ Lot 5-44 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 117.35 104.00 107.00 2.50 7.85 10.35 622 2.50 5.50 8.00 436 J 9 Doolittle Dr./ Lot 5-40 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 119.50 105.00 108.00 2.50 9.00 11.50 713 2.50 5.50 8.00 436 J 10 Coleman Dr./ Lot 5-25 Narrow - Roadside Bioswale + Gravel 4.50 91.00 409.50 113.50 102.00 105.00 2.50 6.00 8.50 983 2.50 5.50 8.00 901 J 11 Hughes Ln./ Lot 5-26 Narrow - Roadside Bioswale + Gravel 4.50 26.57 119.57 115.70 103.00 106.00 2.50 7.20 9.70 344 2.50 5.50 8.00 263 J 12 Hughes Ln./ Lot 5-28 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 116.70 103.00 106.00 2.50 8.20 10.70 649 2.50 5.50 8.00 436 J 13 Hughes Ln./ Lot 5-30 Narrow - Roadside Bioswale + Gravel 4.50 26.00 117.00 120.84 104.00 107.00 2.50 11.34 13.84 531 2.50 5.50 8.00 257 J 14 Hughes Ln./ Lot 5-34 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 119.85 105.00 108.00 2.50 9.35 11.85 741 2.50 5.50 8.00 436 J 15 Coleman Drive (south west) Narrow - Roadside Bioswale + Gravel 4.50 70.00 315.00 113.50 102.00 105.00 2.50 6.00 8.50 756 2.50 5.50 8.00 693 J 16 Hughes Ln./ Lot 5-5 Narrow - Roadside Bioswale + Gravel 4.50 35.66 160.47 114.72 102.00 105.00 2.50 7.22 9.72 463 2.50 5.50 8.00 353 J 17 Hughes Ln./ Lot 5-7 Narrow - Roadside Bioswale + Gravel 4.50 42.27 190.22 116.00 103.00 106.00 2.50 7.50 10.00 571 2.50 5.50 8.00 418 J 18 Hughes Ln./ Lot 5-9 Narrow - Roadside Bioswale + Gravel 4.50 44.62 200.79 121.00 105.00 108.00 2.50 10.50 13.00 843 2.50 5.50 8.00 442 J 19 Hughes Ln./ Lot 5-11 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 118.00 104.00 107.00 2.50 8.50 11.00 673 2.50 5.50 8.00 436 J 20 Hughes Ln./ Lot 5-15 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 120.00 105.00 108.00 2.50 9.50 12.00 752 2.50 5.50 8.00 436 J 21 Lots 5-1 to 5-3 Motorcourt/ Alley Gravel Chamber 6.00 90.00 540.00 114.75 101.00 104.00 3.25 7.50 10.75 1,620 3.25 4.75 8.00 1,026 J Basin J West of Coleman Drive Basin - - 9,415.00 107.00 102.00 105.00 1.60 - 1.60 5,649 Basin J 1.60 - 1.60 5,649 BASIN J (depth = 0.6' + 1' FB) Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 4,838 Linear bioretention 20,481 TOTAL 16,131 21,190 TOTAL 9,415 Basin J I 1 Ph05 Alley/ Lots 5-70 to 5-73 Motorcourt/ Alley Gravel Chamber 6.00 193.00 1,158.00 119.50 106.00 109.00 3.25 7.25 10.50 3,358 Alley 3.25 4.75 8.00 2,200 ALLEY I 2 Hughes Ln./ Lot 5-74 Narrow - Roadside Bioswale + Gravel 4.50 70.00 315.00 120.00 106.00 109.00 2.50 8.50 11.00 1,071 2.50 5.50 8.00 693 I 3 Hughes Ln./ Lot 5-73 Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 118.77 106.00 109.00 2.50 7.27 9.77 654 2.50 5.50 8.00 495 I 4 Hughes Ln./ Lot 5-21 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 120.30 106.00 109.00 2.50 8.80 11.30 697 2.50 5.50 8.00 436 I 5 Hughes Ln./ Lot 5-24 Narrow - Roadside Bioswale + Gravel 4.50 34.80 156.60 118.30 106.00 109.00 2.50 6.80 9.30 426 2.50 5.50 8.00 345 I 6 Jespersen Rd/ Lot 5-102 Wide - Roadside Bioswale + Gravel 5.00 50.00 250.00 121.00 107.00 110.00 2.50 8.50 11.00 850 2.50 5.50 8.00 550 I 7 Jespersen Rd/ Lot 5-102 Wide - Roadside Bioswale + Gravel 5.00 50.00 250.00 118.30 107.00 110.00 2.50 5.80 8.30 580 2.50 5.50 8.00 550 I 8 Jespersen Rd/ Lot 5-24 Wide - Roadside Bioswale + Gravel 5.00 30.00 150.00 117.25 107.00 110.00 2.50 4.75 7.25 285 2.50 4.75 7.25 285 I 9 Jespersen Rd/ Lot 6-1 Wide - Roadside Bioswale + Gravel 5.00 50.00 250.00 120.40 107.00 110.00 2.50 7.90 10.40 790 2.50 5.50 8.00 550 I 10 Jespersen Rd/ Lot 6-1 Wide - Roadside Bioswale + Gravel 5.00 50.00 250.00 117.90 107.00 110.00 2.50 5.40 7.90 540 2.50 5.50 8.00 550 I 11 Jespersen Rd/ Lot 6-1 Wide - Roadside Bioswale + Gravel 5.00 50.00 250.00 117.25 107.00 110.00 2.50 4.75 7.25 475 2.50 4.75 7.25 475 I 12 Jespersen Rd/ Lot 6-1 Wide - Roadside Bioswale + Gravel 5.00 50.00 250.00 119.00 107.00 110.00 2.50 6.50 9.00 650 2.50 5.50 8.00 550 I 13 Jespersen Rd/ Lot 6-1 Wide - Roadside Bioswale + Gravel 5.00 50.00 250.00 119.00 107.00 110.00 2.50 6.50 9.00 650 2.50 5.50 8.00 550 I Park H Park H (overall) Linear Bioswale + Gravel 4.50 330.00 1,485.00 119.00 107.00 110.00 2.50 6.50 9.00 3,861 Park 2.50 5.50 8.00 3,267 MINIMUM FOR PARK Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 1,158 Alley 3,358 Alley 2,200 1,994 Alley 4,280 ROW, Lot, Park 11,529 ROW, Lot, Park 9,295 5,095 ROW, Lot, Park 5,438 TOTAL 14,887 TOTAL 11,495 7,089 TOTAL Phase 5 - Residential, Parks I and H, and Onsite Right-of-Way (including adjacent Phase 4 Right-of-Way areas that flow onto Phase 5) Summary of Phase 4 - Onsite Residential & Right-of-Way APPENDIX E Tract 3089 - Avila Ranch Stormwater Control Measures (SCM) Sizing Calculations Project:1493-0007 Avila Ranch Phases 2-6 Date:December 20, 2022 By:ZKP Stormwater Control Measures (SCM) Sizing Calculations Post-Construction Stormwater Requirements #3 - Runoff Retention *Required Retention 3.00 ft 3.00 ft Proposed Retention (cf) *Required Retention (cf) 20,441 63,496 43,802 43,683 56,684 56,496 3,420 2,843 DMA SCM # Location SCM Description Width (ft) Length (ft) Area (sf) FG Elevation (ft) GW Elevation (ft) GW Separation Elevation (ft) Depth to Top-of- Gravel from FG (ft) Max. Gravel Depth (ft) Max. SCM Depth (ft) Max. Ret. Volume (cf)Notes Depth to Top-of- Gravel from FG (ft)Gravel Depth (ft)Total SCM Depth from FG (ft) Retention Volume (cf) PCR #3 Retention Requirement - Summary Multi-family omitted from calc Phase 2+3 4 5 6 (Comm.) Notes Notes & Assumptions Data from Central Coast Region SCM Sizing Calculator Linear Facility-Groundwater Separation Basin-Groundwater Separation SCM notes SCM Description SCM Footprint SCM Sizing Calculation Compliance through Attachement E (10% EISA Adjust.) YES --- --- --- Internal Calculations (hide) Maximum SCM Sizing CalculationFG vs. Groundwater Comparison Notes H 1 Earhart Way/ Lot 5-37 Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 120.66 106.00 109.00 2.50 9.16 11.66 824 West side 2.50 5.50 8.00 495 H 2 Earhart Way/ Lot 5-38 Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 119.90 106.00 109.00 2.50 8.40 10.90 756 West side 2.50 5.50 8.00 495 H 3 Earhart Way/ Lot 5-97 Narrow - Roadside Bioswale + Gravel 4.50 28.00 126.00 117.90 105.00 108.00 2.50 7.40 9.90 373 West side 2.50 5.50 8.00 277 H 4 Earhart Way/ Lot 5-99 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 116.80 105.00 108.00 2.50 6.30 8.80 499 West side 2.50 5.50 8.00 436 H 5 Earhart Way/ Lot 5-101 Narrow - Roadside Bioswale + Gravel 4.50 78.00 351.00 115.50 105.00 108.00 2.50 5.00 7.50 702 West side 2.50 5.00 7.50 702 H 6 Earhart Way/ Lot 5-94 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 120.20 106.00 109.00 2.50 8.70 11.20 689 West side 2.50 5.50 8.00 436 H 7 Earhart Way/ Lot 5-90 Narrow - Roadside Bioswale + Gravel 4.50 26.00 117.00 118.45 105.00 108.00 2.50 7.95 10.45 372 West side 2.50 5.50 8.00 257 H 8 Earhart Way/ Lot 5-88 Narrow - Roadside Bioswale + Gravel 4.50 22.00 99.00 117.30 105.00 108.00 2.50 6.80 9.30 269 West side 2.50 5.50 8.00 218 H 9 Earhart Way/ Lot 5-87 Narrow - Roadside Bioswale + Gravel 4.50 44.00 198.00 116.25 105.00 108.00 2.50 5.75 8.25 455 West side 2.50 5.50 8.00 436 H 10 Wright Bros/ Lot 5-63 Narrow - Roadside Bioswale + Gravel 4.50 70.14 315.63 118.10 106.00 109.00 2.50 6.60 9.10 833 East side 2.50 5.50 8.00 694 H 11 Wright Bros/ Lot 5-84 Narrow - Roadside Bioswale + Gravel 4.50 60.00 270.00 116.85 106.00 109.00 2.50 5.35 7.85 578 East side 2.50 5.25 7.75 567 H 12 Wright Bros/ Lot 5-85 Narrow - Roadside Bioswale + Gravel 4.50 46.00 207.00 115.75 105.00 108.00 2.50 5.25 7.75 435 East side 2.50 5.25 7.75 435 H 13 Wright Bros/ Lot 5-62 Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 118.40 106.00 109.00 2.50 6.90 9.40 621 East side 2.50 5.50 8.00 495 H 14 Wright Bros/ Lot 5-57 Narrow - Roadside Bioswale + Gravel 4.50 33.00 148.50 116.85 106.00 109.00 2.50 5.35 7.85 318 East side 2.50 5.25 7.75 312 H 15 Wright Bros/ Lot 5-56 Narrow - Roadside Bioswale + Gravel 4.50 64.00 288.00 115.75 105.00 108.00 2.50 5.25 7.75 605 East side 2.50 5.25 7.75 605 H 16 Ph05 Alley/ Lots 5-78 to 5-80 Motorcourt/ Alley Gravel Chamber 6.00 143.00 858.00 120.30 106.00 109.00 3.25 8.05 11.30 2,763 Alley 3.25 4.75 8.00 1,630 ALLEY H 17 Ph05 Alley/ Lots 5-81 to 5-84 Motorcourt/ Alley Gravel Chamber 6.00 193.00 1,158.00 118.25 106.00 109.00 3.25 6.00 9.25 2,779 Alley 3.25 4.75 8.00 2,200 ALLEY H 18 Yeager Ct west Narrow - Roadside Bioswale + Gravel 4.50 93.00 418.50 115.75 106.00 109.00 2.50 4.25 6.75 711 Yeager 2.50 4.25 6.75 711 H 19 Yeager Ct east Narrow - Roadside Bioswale + Gravel 4.50 50.00 225.00 115.75 106.00 109.00 2.50 4.25 6.75 383 Yeager 2.50 4.25 6.75 383 H 20 Wright Bros/ Lot 5-63 Narrow - Roadside Bioswale + Gravel 4.50 28.37 127.67 118.12 106.00 109.00 2.50 6.62 9.12 338 East side 2.50 5.50 8.00 281 H Basin H-1 Yeager Ct/ near Lot 5-56) Basin - - 8,896.00 112.00 105.00 108.00 1.60 - 1.60 5,338 Basin H-1 1.60 - 1.60 5,338 BASIN H-1 (depth = 0.6' + 1' FB) H Basin H-2 near Lot 5-101 Basin - - 1,562.00 110.00 105.00 108.00 1.60 - 1.60 937 Basin H-2 1.60 - 1.60 937 BASIN H-2 (depth = 0.6' + 1' FB) Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 2,016 Alley 5,542 Alley 3,830 4,010 Alley 9,540 ROW east of Jesp + Yeager Ct 7,369 ROW east of Jesp + Yeager Ct 6,432 11,585 ROW east of Jesp + Yeager Ct 4,753 ROW + Lots 8,329 ROW + Lots 7,796 5,842 ROW + Lots 16,309 TOTAL 21,240 TOTAL 18,058 21,437 TOTAL Park G 1 Park G/ Lot 4-6 Linear Bioswale + Gravel (combined) - - 5,000.00 119.00 108.00 111.00 2.50 5.50 8.00 11,000 combined 2.50 5.50 8.00 11,000 Offsets Park I Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 5,000 11,000 TOTAL 11,000 5,874 TOTAL Park I 1 Park I/ Lot 5-104 Flows Offsite - - - - - - - - - - - - - - Flows offsite Retention (cf)Retention (cf) *Required Retention (cf) - TOTAL - 906 TOTAL Watershed Retention (cf) *Required Retention (cf) J 16,131 21,190 I 11,495 7,089 Includes Park H H 18,058 21,437 Park G 11,000 5,874 Offsets Park I Park I - 906 Flows offsite 56,684 56,496 TOTAL Comm 1 1 Lot 6-2 (overall) Linear Bioswale + Gravel (combined) - - 1,550 119.00 107.00 110.00 2.50 2.50 5.00 1,550 Linear faciltities 2.50 3.00 5.50 1,860 Minimum for Linear facilitities Comm 2 2 Lot 6-3 (overall) Linear Bioswale + Gravel (combined) - - 1,300 118.00 107.00 110.00 2.50 2.50 5.00 1,300 Linear faciltities 2.50 3.00 5.50 1,560 Minimum for Linear facilitities Subtotal (sf)Retention (cf)Retention (cf) *Required Retention (cf) 2,850 1,550 Lot 6-2 1,860 1,544 Lot 6-2 1,300 Lot 6-3 1,560 1,299 Lot 6-3 2,850 TOTAL 3,420 2,843 TOTAL Phase 6 - Onsite Commercial Lots Summary of Phase 5 - Residential, Parks I and H, and ROW APPENDIX E Central Coast Region Stormwater Control Measure Sizing Calculator 1. Project Information Project name: Project location: Tier 2/Tier 3: Tier 3 - Retention Design rainfall depth (in): 1.9 Total project area (ft2): 865166 Total DMA area (ft2): 865166 Total new impervious area (ft2): 474252 Total replaced impervious within a USA (ft2): 0 Total replaced impervious not in a USA (ft2): 0 Total pervious/landscape area (ft2): 390914 Total SCM area (ft2): 13213 2. DMA Characterization DMA Type Area (ft2) Surface Type New, Replaced? Connection Drains to SCM 31352 Concrete or asphalt New A (combined) Drains to SCM 13776 Landscape New A (combined) Drains to SCM 297443 Concrete or asphalt New B (combined) Drains to SCM 168993 Landscape New B (combined) Drains to SCM 116808 Concrete or asphalt New C (combined) Drains to SCM 52560 Landscape New C (combined) Drains to SCM 28649 Concrete or asphalt New D (combined) Drains to SCM 6912 Landscape New D (combined) Self-Treating 148673 Total assigned DMA area (ft2): 865166 New impervious area (ft2): 474252 Replaced impervious within a USA (ft2): 0 Replaced impervious not in a USA (ft2): 0 Total pervious/landscape area (ft2): 390914 3. SCM Characterization SCM Type Safety Factor SCM Soil Type Infilt. Rate (in/hr) Area (ft2) Direct Infiltration 2 Site-Specific 1.75 780 Direct Infiltration 2 Site-Specific 1.5 8548 Direct Infiltration 2 Site-Specific 1.5 2355 Bioretention 1 Site-Specific 2 1530 4. Run SBUH Model 5. SCM Minimum Sizing Requirements Min. Required Storage Vol. (ft3) Depth Below Underdrain (ft) Drain Time (hours) Orifice Diameter (in) 4206 13.48 61.6 40841 11.94 63.7 17197 18.26 97.3 1259 2.06 0.0 6. Self-Retaining Area Sizing Checks Self-Retaining DMA Area (ft2) Tributary DMA Name(s) Eff. Tributary DMA Area (ft2) Effective Tributary / SRA Area Ratio end_SRA end_Output Self-Retaining DMA Name D (combined) A (combined) Avila Ranch - Phases 2+3 Buckley Road, San Luis Obispo, CA DMA Summary Area Check end_DMA Name DMA A (Pervious) DMA B (Impervious) DMA B (Pervious) DMA C (Impervious) DMA C (Pervious) DMA A (Impervious) DMA D (Impervious) DMA D (Pervious) Bypass Channel C (combined) A (combined) B (combined) Name SCM Name end_SCM D (combined) C (combined) B (combined) APPENDIX E Central Coast Region Stormwater Control Measure Sizing Calculator 1. Project Information Project name: Project location: Tier 2/Tier 3: Tier 3 - Retention Design rainfall depth (in): 1.9 Total project area (ft2): 2779978 Total DMA area (ft2): 2779978 Total new impervious area (ft2): 417720 Total replaced impervious within a USA (ft2): 0 Total replaced impervious not in a USA (ft2): 0 Total pervious/landscape area (ft2): 2362258 Total SCM area (ft2): 20271 2. DMA Characterization DMA Type Area (ft2) Surface Type New, Replaced? Connection Drains to SCM 63862 Concrete or asphalt New E-ROW (combined) Drains to SCM 10789 Landscape New E-ROW (combined) Drains to SCM 85300 Concrete or asphalt New E-PH4a (combined) Drains to SCM 56867 Landscape New E-PH4a (combined) Drains to SCM 30614 Concrete or asphalt New E-PH4b (combined) Drains to SCM 33815 Landscape New E-PH4b (combined) Drains to SCM 61528 Concrete or asphalt New F (combined) Drains to SCM 41019 Landscape New F (combined) Drains to SCM 29915 Concrete or asphalt New F (combined) Drains to SCM 129509 Concrete or asphalt New H-PH4 (combined) Drains to SCM 105489 Landscape New H-PH4 (combined) Self-Treating 22767 Drains to SCM 16992 Concrete or asphalt New G (combined) Drains to SCM 4050 Landscape New G (combined) Self-Treating 653119 Self-Treating 1326622 Self-Treating 107721 Total assigned DMA area (ft2): 2779978 New impervious area (ft2): 417720 Replaced impervious within a USA (ft2): 0 Replaced impervious not in a USA (ft2): 0 Total pervious/landscape area (ft2): 2362258 3. SCM Characterization SCM Type Safety Factor SCM Soil Type Infilt. Rate (in/hr) Area (ft2) Bioretention 1 Site-Specific 1.68 1000 Bioretention 1 Site-Specific 1.68 2864 Direct Infiltration 2 Site-Specific 1 2618 Direct Infiltration 2 Site-Specific 0.65 5586 Direct Infiltration 2 Site-Specific 1 7643 Bioretention 1 Site-Specific 1.68 560 4. Run SBUH Model end_SCM E-PH4a (combined) E-PH4b (combined) DMA H-PH4 (Impervious) DMA H-PH4 (Pervious) H-PH4 (combined) Vegetated Channel DMA G (Impervious) DMA K DMA M DMA N F (combined) G (combined) E-ROW (combined) DMA G (Pervious) Name Avila Ranch - Phase 4 Buckley Road, San Luis Obispo, CA DMA Summary Area Check end_DMA Name DMA E-ROW (Pervious) DMA E-PH4a (Impervious) DMA E-PH4a (Pervious) DMA E-PH4b (Impervious) DMA E-PH4b (Pervious) DMA E-ROW (Impervious) DMA F (Impervious) DMA F (Pervious) DMA F-ROW (Impervious) APPENDIX E 5. SCM Minimum Sizing Requirements Min. Required Storage Vol. (ft3) Depth Below Underdrain (ft) Drain Time (hours) Orifice Diameter (in)Results are out of date. 6327 15.82 45.2 Click 'Launch Model' to update. 5901 5.15 13.5 2962 2.83 27.1 13232 5.92 72.9 14132 4.62 44.4 1129 5.04 12.8 6. Self-Retaining Area Sizing Checks Self-Retaining DMA Area (ft2) Tributary DMA Name(s) Eff. Tributary DMA Area (ft2) Effective Tributary / SRA Area Ratio SCM Name end_SRA end_Output Self-Retaining DMA Name E-ROW (combined) G (combined) H-PH4 (combined) F (combined) E-PH4b (combined) E-PH4a (combined) APPENDIX E Central Coast Region Stormwater Control Measure Sizing Calculator 1. Project Information Project name: Project location: Tier 2/Tier 3: Tier 3 - Retention Design rainfall depth (in): 1.9 Total project area (ft2): 1630227 Check Total DMA and SCM areas to ensure they match total project area Total DMA area (ft2): 1630227 Total new impervious area (ft2): 933898 Total replaced impervious within a USA (ft2): 0 Total replaced impervious not in a USA (ft2): 0 Total pervious/landscape area (ft2): 696329 Total SCM area (ft2): 40923 2. DMA Characterization DMA Type Area (ft2) Surface Type New, Replaced? Connection Drains to SCM 102230 Concrete or asphalt New Park G (combined) Drains to SCM 306691 Landscape New Park G (combined) Drains to SCM 46302 Concrete or asphalt New H-alley (combined) Drains to SCM 38749 Landscape New H-alley (combined) Drains to SCM 28195 Concrete or asphalt New H-Yeager (combined) Drains to SCM 17455 Landscape New H-Yeager (combined) Drains to SCM 51075 Concrete or asphalt New H-East (combined) Drains to SCM 4412 Landscape New H-East (combined) Drains to SCM 113143 Concrete or asphalt New H (combined) Drains to SCM 67319 Landscape New H (combined) Drains to SCM 146656.3 Concrete or asphalt New J-west (combined) Drains to SCM 94719.8 Landscape New J-west (combined) Drains to SCM 14821 Concrete or asphalt New I-Park H (combined) Drains to SCM 59282 Landscape New I-Park H (combined) Drains to SCM 24109 Concrete or asphalt New I-alley Drains to SCM 22460 Landscape New I-alley Drains to SCM 78590 Concrete or asphalt New I (combined) Drains to SCM 29348 Landscape New I (combined) 3825 Concrete or asphalt 15299 Landscape Drains to SCM 62852.7 Concrete or asphalt New J-east (to Basin J) Drains to SCM 40594.2 Landscape New J-east (to Basin J) Self-Treating 262099 Total assigned DMA area (ft2): 1611103 New impervious area (ft2): 667974 Check DMA table areas against plan sheet areas Replaced impervious within a USA (ft2): 0 Replaced impervious not in a USA (ft2): 0 Total pervious/landscape area (ft2): 943129 Check DMA table areas against plan sheet areas 3. SCM Characterization SCM Type Safety Factor SCM Soil Type Infilt. Rate (in/hr) Area (ft2) Bioretention 1 Site-Specific 2 5000 Direct Infiltration 2 Site-Specific 2 2016 Bioretention 1 Site-Specific 2 643 Direct Infiltration 2 Site-Specific 0.1 8897 Bioretention 1 Site-Specific 2 4865 Bioretention 1 Site-Specific 2 4671 Avila Ranch - Phase 5 (plus Park H, I, G) Buckley Road, San Luis Obispo, CA DMA Summary Area Check end_DMA Name DMA Park G (Pervious) DMA H-alley (Impervious) DMA H-alley (Pervious) DMA H-Yeager (Impervious) DMA H-Yeager (Pervious) DMA Park G (Impervious) DMA H-East (Impervious) DMA H-East (Pervious) DMA H (Impervious) DMA I-Park H (Pervious) DMA I (Impervious) DMA J-west (Impervious) J-west (combined) DMA I-alley (Pervious) DMA H (Pervious) H (combined) H-alley (combined) H-Yeager (combined) H-East (combined) DMA J-west (Pervious) DMA I-Park H (Impervious) Park G (combined) Name DMA I-alley (Impervious) DMA J-Park I (Impervious) DMA J-Park I (Pervious) DMA I (Pervious) DMA J-east (Impervious) DMA J-east (Pervious) DMA L APPENDIX E Bioretention 1 Site-Specific 2 1485 Direct Infiltration 2 Site-Specific 2 1158 Bioretention 1 Site-Specific 2 2773 Direct Infiltration 2 Site-Specific 0.1 9415 4. Run SBUH Model 5. SCM Minimum Sizing Requirements Min. Required Storage Vol. (ft3) Depth Below Underdrain (ft) Drain Time (hours) Orifice Diameter (in) 5874 2.94 5.4 4010 4.97 23.7 2221 8.64 20.2 9364 2.63 210.2 5842 3.00 3.5 9190 4.92 10.0 594 1.00 0.0 1994 4.31 20.3 4501 4.06 6.9 12000 3.19 254.3 6. Self-Retaining Area Sizing Checks Self-Retaining DMA Area (ft2) Tributary DMA Name(s) Eff. Tributary DMA Area (ft2) Effective Tributary / SRA Area Ratio H-alley (combined) I-Park H (combined) J-west (combined) H (combined) H-East (combined) H-Yeager (combined) end_SRA end_Output Self-Retaining DMA Name Park G (combined) J-east (to Basin J) I (combined) I-alley I-Park H (combined) I-alley SCM Name end_SCM J-east (to Basin J) I (combined) APPENDIX E Central Coast Region Stormwater Control Measure Sizing Calculator 1. Project Information Project name: Project location: Tier 2/Tier 3: Tier 3 - Retention Design rainfall depth (in): 1.9 Total project area (ft2): 76361 Check Total DMA and SCM areas to ensure they match total project area Total DMA area (ft2): 76361 Total new impervious area (ft2): 57271 Total replaced impervious within a USA (ft2): 0 Total replaced impervious not in a USA (ft2): 0 Total pervious/landscape area (ft2): 19090 Total SCM area (ft2): 2850 2. DMA Characterization DMA Type Area (ft2) Surface Type New, Replaced? Connection Drains to SCM 30031 Concrete or asphalt New Commercial 1 (combined) Drains to SCM 10010 Landscape New Commercial 1 (combined) Drains to SCM 27240 Concrete or asphalt New Commercial 2 (combined) Drains to SCM 9080 Landscape New Commercial 2 (combined) Total assigned DMA area (ft2): 76361 New impervious area (ft2): 57271 Replaced impervious within a USA (ft2): 0 Replaced impervious not in a USA (ft2): 0 Total pervious/landscape area (ft2): 19090 3. SCM Characterization SCM Type Safety Factor SCM Soil Type Infilt. Rate (in/hr) Area (ft2) Bioretention 1 Site-Specific 1.68 1550 Bioretention 1 Site-Specific 2 1300 4. Run SBUH Model 5. SCM Minimum Sizing Requirements Min. Required Storage Vol. (ft3) Depth Below Underdrain (ft) Drain Time (hours) Orifice Diameter (in) 1544 2.49 2.8 1299 2.50 1.1 6. Self-Retaining Area Sizing Checks Self-Retaining DMA Area (ft2) Tributary DMA Name(s) Eff. Tributary DMA Area (ft2) Effective Tributary / SRA Area Ratio Commercial 2 (combined) end_SRA end_Output Self-Retaining DMA Name Commercial 1 (combined) Avila Ranch - Phases 6 (Commercial) Buckley Road, San Luis Obispo, CA DMA Summary Area Check end_DMA Name Commercial 1 (Pervious) Commercial 2 (Impervious) Commercial 2 (Pervious) Commercial 1 (Impervious) Commercial 1 (combined) Name SCM Name end_SCM Commercial 2 (combined) APPENDIX E APPENDIX F Phases 2 & 3 – PCR #3 Attachment E Compliance · Ten Percent Adjustment to Retention Requirement calculation · Excerpts from RWQCB Resolution R3-2013-0032; Attachment 1 PHASES 2 & 3 SUMMARY - (Including Bypass Channel Area) Resolution No. R3-2013-0032 - Attachement E Ten Percent Adjustment to Retention Requirement Calculation 43,560 -- 865,165 SF 19.86 AC 91,535 SF 2.10 AC DMA's Impervious Factor, C Equivalent Impervious Surface Area (AC) Provided SCM Treatment Area (AC) 8.25 1 8.25 2.10 - 9.51 0.22 2.09 Total 19.86 10.34 1.03 1.03 2.10 Total Equivalent Impervious Surface Areas --Required Retention Based Treatment Area (10% of EISA) Compare Required vs. Provided Treatment Areas Total SCM Area Sub Area (AC) Area Description A, B, C, D, Bypass Channel New Impervious 2.10 Retention based SCMs New Pervious Drainage Management Area Information SF to ACRE Total WSHD Area SCM Data Total SCM Area 2022_AVR_SWCP Calculations_update Page 1 of 6 APPENDIX F WATERSHED A:Phase 3 Resolution No. R3-2013-0032 - Attachement E Ten Percent Adjustment to Retention Requirement Calculation 43,560 -- 0.50 0.60 omitted from calcs 45,128 SF 1.04 AC Offset Gravel Length 126.6 LF Offset Gravel Width 6.00 LF 760 SF 0.02 AC DMA Impervious Factor, C Equivalent Impervious Surface Area (AC) Provided SCM Treatment Area (AC) 0.16 1 0.16 omitted - 1 - 0.16 1 0.16 0.25 1 0.25 0.02 - 0.45 0.22 0.10 Total 1.04 0.67 0.07 0.07 0.02 Total SCM Area Total SCM Area SCM Data --Required Retention Based Treatment Area (10% of EISA) 0.02 Compare Required vs. Provided Treatment Areas Sub Area (AC) Area Description A New Impervious (R-2 Lots) Retention based SCMs New Pervious New Impervious (ROW/ Motorcourt) New Impervious (R-4 Lots) New Impervious (Misc.) Total Equivalent Impervious Surface Areas Drainage Management Area Information SF to ACRE R-4 Lot Impervious % Total WSHD Area Total WSHD Area R-2 Lot Impervious % 2022_AVR_SWCP Calculations_update Page 2 of 6 APPENDIX F WATERSHED B:Phase 2 & 3 Resolution No. R3-2013-0032 - Attachement E Ten Percent Adjustment to Retention Requirement Calculation 43,560 -- 0.20 -- 0.50 -- 0.60 omitted from calcs 466,436 SF 10.71 AC Bioswale Length 100 LF Bioswale Width (Typical)5.50 LF Motorcourt Gravel Length 798.50 LF Motorcourt Gravel Width 6.00 LF 110.00 LF Offset Gravel Width 8.00 LF 3,514 SF 9,735 SF 0.22 AC DMA Impervious Factor, C Equivalent Impervious Surface Area (AC) Provided SCM Treatment Area (AC) 1.60 1 1.60 omitted - 1 - 3.46 1 3.46 0.03 1 0.03 0.22 - 5.39 0.22 1.19 Total 10.71 6.28 0.63 0.63 0.22 --Required Retention Based Treatment Area (10% of EISA) 0.22 Compare Required vs. Provided Treatment Areas Total SCM Area Sub Area (AC) Area Description B New Impervious (R-2 Lots) New Impervious (R-4 Lots) New Impervious (ROW/ Motorcourt) New Impervious (Park) Retention based SCMs New Pervious Total Equivalent Impervious Surface Areas SCM Data Total SCM Area Offset Gravel Length Retention Basin Total WSHD Area Total WSHD Area Park Impervious % Drainage Management Area Information SF to ACRE R-2 Lot Impervious % R-4 Lot Impervious % 2022_AVR_SWCP Calculations_update Page 3 of 6 APPENDIX F WATERSHED C:Phase 3 Resolution No. R3-2013-0032 - Attachement E Ten Percent Adjustment to Retention Requirement Calculation 43,560 -- 0.50 -- 169,367 SF 3.89 AC 150 LF 5.50 LF 285.00 LF Offset Gravel Width 6.00 LF 2,535 SF 0.06 AC DMA Impervious Factor, C Equivalent Impervious Surface Area (AC) Provided SCM Treatment Area (AC) 0.59 1 0.59 1.12 1 1.12 0.39 1 0.39 0.06 - 1.74 0.22 0.38 Total 3.89 2.48 0.25 0.25 0.06 --Required Retention Based Treatment Area (10% of EISA) 0.06 Compare Required vs. Provided Treatment Areas Total SCM Area Sub Area (AC) Area Description C New Impervious (R-2 Lots) New Impervious (ROW/ Motorcourt) Retention based SCMs New Pervious Total Equivalent Impervious Surface Areas New Impervious (Misc.) Total SCM Area Drainage Management Area Information SF to ACRE R-2 Lot Impervious % Total WSHD Area Total WSHD Area SCM Data Bioswale Length Bioswale Width (Typical) Offset Gravel Length 2022_AVR_SWCP Calculations_update Page 4 of 6 APPENDIX F WATERSHED D:Phase 2 & 3 Resolution No. R3-2013-0032 - Attachement E Ten Percent Adjustment to Retention Requirement Calculation 43,560 -- - n/a 35,561 SF 0.82 AC 348 LF 5.50 LF 1,914 SF 0.04 AC DMA Impervious Factor, C Equivalent Impervious Surface Area (AC) Provided SCM Treatment Area (AC) - 1 - 0.66 1 0.66 0.04 - 0.11 0.22 0.03 Total 0.82 0.68 0.07 0.07 0.04 Total Equivalent Impervious Surface Areas --Required Retention Based Treatment Area (10% of EISA) Compare Required vs. Provided Treatment Areas Sub Area (AC) Area Description D New Impervious (R-2 Lots) New Impervious (ROW) Retention based SCMs New Pervious 0.04 Total SCM Area Drainage Management Area Information SF to ACRE R-2 Lot Impervious % Total WSHD Area Total WSHD Area SCM Data Bioswale Length Bioswale Width (Typical) Total SCM Area 2022_AVR_SWCP Calculations_update Page 5 of 6 APPENDIX F BYPASS CHANNEL AREA:Phase 2 & 3 Resolution No. R3-2013-0032 - Attachement E Ten Percent Adjustment to Retention Requirement Calculation 43,560 -- 148,673 SF 3.41 AC 76,591 SF 76,591 SF 1.76 AC DMA Impervious Factor, C Equivalent Impervious Surface Area (AC) Provided SCM Treatment Area (AC) - 1 - 0.22 1 0.22 1.76 - 1.44 0.22 0.32 Total 3.41 0.53 0.05 0.05 1.76 Total Equivalent Impervious Surface Areas --Required Retention Based Treatment Area (10% of EISA) Compare Required vs. Provided Treatment Areas Area Description Bypass Channel New Impervious (Lots) 1.76 New Impervious (Bike path & Park D) Retention based SCMs New Pervious Bypass Channel Area Total SCM Area Total SCM Area Sub Area (AC) Drainage Management Area Information SF to ACRE Total WSHD Area Total WSHD Area SCM Data 2022_AVR_SWCP Calculations_update Page 6 of 6 APPENDIX F Resolution No. R3-2013-0032 ATTACHMENT 1 -31- ATTACHMENT E: Ten Percent Adjustment to Retention Requirement – Calculation Instructions Where technical infeasibility, as described in Section C.1.c., prevents full on-site compliance with the Runoff Retention Performance Requirement, on-site retention of the full Retention Volume per Section B.4.d.vi. is not required and the Regulated Project is required to dedicate no less than ten percent of the Regulated Project’s Equivalent Impervious Surface Area to retention-based Stormwater Control Measures. The W ater Quality Treatment Performance Requirement is not subject to this adjustment, i.e., mitigation to achieve full compliance is required on- or off-site. Calculating Ten Percent of a Project’s Equivalent Impervious Surface Area The area of the project that must be dedicated to structural SCMs to waive off-site compliance with the Runoff Retention Requirement is equal to ten percent of the project’s Equivalent Impervious Surface Area, defined as: Equivalent Impervious Surface Area (ft2) = (Impervious Tributary Surface Area (ft2) + (Pervious Tributary Surface Area (ft2)) Impervious Tributary Surface Area is defined as the sum of all of the site’s conventional impervious surfaces. When calculating Impervious Tributary Area: • Do include: concrete, asphalt, conventional roofs, metal structures and similar surfaces • Do not include: green roofs Pervious Tributary Surface Area is defined as the sum of all of the site’s pervious surfaces, corrected by a factor equal to the surface’s runoff coefficient. When calculating Pervious Tributary Surface Area: • Do include surfaces such as: unit pavers on sand; managed turf14; disturbed soils; and conventional landscaped areas (see Table 1 for correction factors). Example: Project Site includes 500 ft2 of unit pavers on sand. Pervious Tributary Surface Area = 500 ft2 x C = 50 ft2 Where C = Correction Factor for unit pavers, 0.1, from Table 1. • Do not include: Infiltration SCM surfaces (e.g., SCMs designed to specific performance objectives for retention/infiltration) including bioretention cells, bioswales; natural and undisturbed landscape areas, or landscape areas compliant with the Model Water Efficient Landscape Ordinance (California Code of Regulations, Title 23. Waters, Division 2. Department of Water Resources, Chapter 2.7.), or a local ordinance at least as effective as the Model Water Efficient Landscape Ordinance. 14 Managed Turf includes turf areas intended to be mowed and maintained as turf within residential, commercial, industrial, and institutional settings. APPENDIX F Resolution No. R3-2013-0032 ATTACHMENT 1 -32- TABLE 1: Correction Factors15 for Use in Calculating Equivalent Impervious Surface Area Pervious Surface Correction Factor Disturbed Soils/Managed Turf (dependent on original Hydrologic Soil Group) A: 0.15 B: 0.20 C: 0.22 D: 0.25 Pervious Concrete 0.60 Cobbles 0.60 Pervious Asphalt 0.55 Natural Stone (without grout) 0.25 Turf Block 0.15 Brick (without grout) 0.13 Unit Pavers on Sand 0.10 Crushed Aggregate 0.10 Grass 0.10 15 Factors are based on runoff coefficients selected from different sources: Turf and Disturbed Soils from Technical Memorandum: The Runoff Reduction Method. Center for Watershed Protection & Chesapeake Stormwater Network. p.13, April 18, 2008. http://town.plympton.ma.us/pdf/land/scheuler_runoff_reduction_method_techMemo.pdf. All other correction factors from C.3 Stormwater Handbook, Santa Clara Valley Urban Runoff Pollution Prevention Program, Appendix F, p. F-9., May 2004. http://www.sanjoseca.gov/planning/stormwater/pdfs/appendices_files/Appendix_F_Final.pdf APPENDIX F APPENDIX G Structural Control Measures (SCM) Concepts · Roadside Bioswale with Underground Gravel Trench · Motorcourt/ Alley Underground Gravel Chamber · Shallow Retention Basins with Offset Gravel Chamber · SLO County LID Handbook detail 103 – Gravel Check Dams · SLO County LID Handbook detail 150 – Impermeable Layer ® AVILA RANCH - PHASES 2-6 SWCP CONCEPTS TYPICAL ROADSIDE BIOSWALES WITH GRAVEL TRENCH 1493-0007 NOT TO SCALE DATE: 5/23/2022 5.00' SIDEWALK 6.00' PARKWAY 1.50' 0. 5 0 ' 2. 0 0 ' VA R I E S 0.50' 3. 0 0 ' M I N SE P A R A T I O N T O GR O U N D W A T E R 2. 5 9 ' VARIES 5.50' TO 6.00' 30 MIL PVC LINER (BOTH SIDES) CALTRANS CLASS 3 PERMEABLE MATERIAL DO NOT USE FILTER FABRIC BETWEEN BSM AND AGGREGATE LAYERS BIORETENTION SOIL MEDIA (BSM) LEGEND: DESIGN FINISHED GRADE REFERENCE TO RECORDED GROUNDWATER MAX. PONDING ELEVATION CITY OF SLO 18" C&G ROADSIDE BIOSWALE WITH UNDERGROUND GRAVEL TRENCH FOR PLAN REVIEW ONLY. NOT FOR CONSTRUCTION 4" CURB 2.00' GRAVEL CHECK DAM WHERE SHOWN ON PLANS ROCK SPLASH PAD AT CURB OPENINGS (BOTH SIDES) 0. 2 5 ' 3 4" (NO. 4) OPEN GRADED AGGREGATE PAGE 1 OF 4 0.50' APPENDIX G ® AVILA RANCH - PHASES 2-6 SWCP CONCEPTS TYPICAL MOTORCOURT/ ALLEY GRAVEL CHAMBER 1493-0007 DATE: 12/21/2022 FOR PLAN REVIEW ONLY. NOT FOR CONSTRUCTION PAGE 2 OF 4 20.00' ALLEY 0.50' ZERO HEIGHT CURB 0.50' ZERO HEIGHT CURB 2.00' 3. 0 0 ' DR Y U T I L I T I E S GAS 12" HDPE STORM DRAIN PIPE 4" PVC PIPE4" PVC PIPE 4" PVC PIPE 1. 5 0 ' MI N . 1. 0 0 ' 18" x 18" CONCRETE BOX INLET 5.00' 6.00' 4" PERF. PVC PIPE VA R I E S 3. 0 0 ' M I N SE P A R A T I O N T O GR O U N D W A T E R 0.50%0.50% PAVERS ON-SITE LATERALS 2.33' MOTORCOURT/ ALLEY UNDERGROUND GRAVEL CHAMBER CALTRANS CLASS 3 PERMEABLE MATERIAL APPENDIX G ® AVILA RANCH - PHASES 2-6 SWCP CONCEPTS RETENTION BASIN WITH OFFSET GRAVEL CHAMBER 1493-0007 DATE: 5/23/2022 FOR PLAN REVIEW ONLY. NOT FOR CONSTRUCTION PAGE 3 OF 4 2. 5 0 ' M I N CO V E R DE P T H V A R I E S PE R P L A N 3. 0 0 ' M I N SE P A R A T I O N T O GR O U N D W A T E R 0. 5 0 ' M A X PO N D I N G D E P T H MANAGED TURF 24" x 24" CONCRETE BOX WITH GRATE INLET 4" PERF. PVC PIPE CALTRANS CLASS 3 PERMEABLE MATERIAL HORIZONTAL LOCATION VARIES PER PLAN 8.00' 4" PVC PIPE (2.00% MIN) APPENDIX G ® AVILA RANCH - PHASES 2-6 SWCP CONCEPTS PERMEABLE PAVERS WITH UNDERGROUND RETENTION - CONCEPTS 1493-0007 DATE: 5/23/2022 FOR PLAN REVIEW ONLY. NOT FOR CONSTRUCTION PAGE 4 OF 4 2" 4" *V A R I E S ASTM No. 2 ASTM No. 57 ASTM No. 8 STRUCTURAL DESIGN AND SIZE OF CONCRETE CURBS, SIDEWALLS WILL BE COMPLETED WITH ONSITE IMPROVEMENT PLANS VA R I E S 6" ADJACENT FINISH GRADE SEE DETAIL A FOR PAVER SECTION Scale: NTS PERVIOUS PAVER SECTIONA Scale: NTS 6" FLUSH CURBB GEOTEXTILE FABRIC MAY NEED TO ELIMINATED OR REPLACED WITH A FABRIC THAT DOES NOT INTERFERE WITH INFILTRATION PERMEABLE PAVERS PREPARE SUBGRADE, CUT NEATLY TO GRADE AND LIGHTLY ROLL, NO COMPACTION TO PROMOTE INFILTRATION PROPERLY PREPARE SUBGRADE, COMPACT TO 95% MAXIMUM DENSITY PER COUNTY OF SAN LUIS OBISPO STANDARDS VA R I E S ADJACENT FINISH GRADE SEE DETAIL A FOR PAVER SECTION Scale: NTS 6" VERTICAL CURB (AT PAVERS)C PROPERLY PREPARE SUBGRADE, COMPACT TO 95% MAXIMUM DENSITY PER COUNTY OF SAN LUIS OBISPO STANDARDS *DEPTH OF NO. 2 GRAVEL WILL VARY TO ALLOW FOR A FLAT SUBGRADE AND TO MEET THE DESIGNED DEPTH FOR STORMWATER CONTROL RETENTION REQUIREMENTS. VA R I E S VA R I E S ASTM No. 8 AGGREGATE BETWEEN PAVERS GEOTEXTILE FABRIC MAY NEED TO ELIMINATED OR REPLACED WITH A FABRIC THAT DOES NOT INTERFERE WITH INFILTRATION STRUCTURAL DESIGN OF CONCRETE CURBS AND SIDEWALLS WILL BE COMPLETED WITH ONSITE IMPROVEMENT PLANS GEOTEXTILE FABRIC MAY NEED TO ELIMINATED OR REPLACED WITH A FABRIC THAT DOES NOT INTERFERE WITH INFILTRATION APPENDIX G APPENDIX G APPENDIX G