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HomeMy WebLinkAboutPD 2021-0004; NORTH COUNTY ACADEMY; PRIORITY DEVELOPMENT STORM WATER QUALITY MANAGEMENT PLAN; 2021-05-10CITY OF CARLSBAD PRIORITY DEVELOPMENT PROJECT (PDP) STORM WATER QUALITY MANAGEMENT PLAN (SWQMP) FOR NORTH COUNTY ACADEMY - CAMPUS CONSOLIDATION PD 2021-0004 GR 2021-0004 DWG 529-4A ENGINEER OF WORK: WILLIAM J. SUITER, P.E. RCE 68964 EXP: 12-31-21 PASCO LARET SUITER & ASSOCIATES, INC. 7127 CALLE ARROYO, SUITE 1904 SAN JUAN CAPISTRANO, CA 92675 -Oml No. CE 6964 LiI \EXP .i231V5/ OF C Li1*II1SJ NORTH COUNTY ACADEMY 1640 MAGNOLIA CARLSBAD, CA 92008 PREPARED BY: PAS CO. J R E T S U I'l... or t -1k & ASSOCIATES NG .LN' L A1 SURV'EYNG 27127 CALLE ARROYO SAN JUAN CAPISTRANO, CA 92675 858-259-8212 DATE: December 17, 2020 Updated: May 10, 2021 RECEIVED JUN 2.8 2021 LAND DEVELOPME ENGINEERING STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 TABLE OF CONTENTS ENGINEER'S CERTIFICATION PROJECT VICINITY MAP STORM WATER STANDARD QUESTIONNAIRE SITE INFORMATION SUMMARY OF PDP STRUCTURAL BMPs ATTACHMENT I - Backup for PDP Pollutant Control BMPs Attachment la ...........................................................................................................DMA Exhibit Attachment lb ................ Tabular Summary of DMAs and Design Capture Volume Calculations Attachment 1 c ..................................................................Harvest and Use Feasibility Screening Attachment I d ..................................................Categorization of Infiltration Feasibility Condition Attachment le ... .......................... ....... Pollutant Control BMP Design Worksheets I Calculations ATTACHMENT 2— Backup for PDP Hydromodification Control Measures Attachment 2a ............................. ................................... Hydromodification Management Exhibit Attachment 2b ......................... ............... .Management of Critical Coarse Sediment Yield Areas Attachment 2c.......................................Geomorphic Assessment of Receiving Channels Attachment 2d ..................................................................................Flow Control Facility Design ATTACHMENT 3— Structural BMP Maintenance Plan Attachment 3a......Structural BMP Maintenance Thresholds and Actions and BMP Fact Sheets Attachment 3b ........................................... .................................... Draft Maintenance Agreement ATTACHMENT 4— Single Sheet BMP Site Plan NORTH COUNTY ACADEMY 2 STORM WATER QUALITY MANAGEMENT PLAN MAY2021 CERTIFICATION PAGE Project Name: North County Academy - Campus Consolidation Project ID: PD2021-0004 / GR2020-0004 I DWG 529-4A I hereby declare that I am the Engineer in Responsible Charge of design of storm water BMPs for this project, and that I have exercised responsible charge over the design of the project as defined in Section 6703 of the Business and Professions Code, and that the design is consistent with the requirements of the BMP Design Manual, which is based on the requirements of SDRWQCB Order No. R9-2013-0001 (MS4 Permit) or the current Order. I have read and understand that the City Engineer has adopted minimum requirements for managing urban runoff, including storm water, from land development activities, as described in the BMP Design Manual. I certify that this SWQMP has been completed to the best of my ability and accurately reflects the project being proposed and the applicable source control and site design BMPs proposed to minimize the potentially negative impacts of this project's land development activities on water quality. I understand and acknowledge that the plan check review-of this SWQMP by the City Engineer is confined to a review and does not relieve me, as the Engineer in Responsible Charge of design of storm water BMPs for this project, of my responsibilities for project design. ki. William J:Suiter, P.E. RCE 68964 Exp: 12-31-21 - Date Pasco Laret Suiter & Associates 27127 Calle Arroyo, Suite 1904 San Juan Capistrano, CA 92675 NORTH COUNTY ACADEMY STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 SITE VICINITY MAP CITY OF OCEANSIDE fl! CITY OF SAN MAROS CITY OF ENCINUAS Vicinity Map N.T.S NORTH COUNTY ACADEMY 4 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 SITE INFORMATION CHECKLIST - Project SummayInformation North County Academy - Campus Consolidation Project Name Project ID PD20210004 / GR20210004 I DWG 5294A Project Address 1640 Magnolia Carlsbad, CA 92008 Assessor's Parcel Number(s) (APN(s)) APN: 205-220-99-00 Parcel 4 of Parcel Map 21374 Hydrologic Unit: Carlsbad Hydrologic Area: Agua Hedionda Project Watershed (Hydrologic Unit) Hydrologic Sub-Area Name: Los Monos Hydrologic Sub-Area #: 904.31 Parcel Area (1 Total Parcel) 4.19 Acres ( 195,787 Square Feet) Existing Impervious Area to be disturbed by the project 0.00 Acres ( 0 Square Feet) (subset of Parcel Area) Area to be disturbed by the project (Project Area) 0.36 Acres ( 15,520 Square Feet) Project Proposed Impervious Area (subset of Project Area) 0.21 Acres ( 8,973 Square Feet) Project Proposed Pervious Area 0.15 Acres ( 6,547 Square Feet) Note: Proposed Impervious Area + Proposed Pervious Area = Area to be Disturbed by the Project. This may be less than the Parcel Area. NORTH COUNTY ACADEMY STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Description of Existing Site Condition and Draina Patterns Current Status of the Site (select all that apply): Existing development 11 Previously graded but not built out O Agricultural or other non-impervious use Vacant, undeveloped/natural Description / Additional Information: The existing site is currently vacant and covered with turf vegetation over the entire site. (See further discussion below on-site topography and drainage). Existing Land Cover Includes (select all that apply): Ll Vegetative Cover O Non-Vegetated Pervious Areas Impervious Areas Description / Additional Information: The existing site is currently vacant and covered with turf vegetation over the entire site. (See further discussion below on-site topography and drainage). Underlying Soil belongs to Hydrologic Soil Group (select all that apply): NRCS Type A NRCS Type B NRCS Type C lJ NRCS Type D (Per Report of Geotechnical Investigation for Proposed Portable Classrooms North County Academy by NOVA dated December 7, 200.) Approximate Depth to Groundwater (GW): 0 GW Depth < 5 feet C1 5 feet < GW Depth < 10 feet lo feet <GW Depth <20feet GW Depth > 20 feet Groundwater was not encountered during geotechnical testing per Report of Geotechnical Investigation for Proposed Portable Classrooms, North County Academy by NOVA dated December 7, 2020. NORTH COUNTY ACADEMY STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Existing Natural Hydrologic Features (select all that apply): Watercourses O Seeps Springs O Wetlands tl None Description / Additional Information: N/A NORTH COUNTY ACADEMY 7 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Description of Existing Site Topography and Drainage [How is storm water runoff conveyed from the site? At a minimum, this description should answer (1) whether existing drainage conveyance is natural or urban; (2) describe existing constructed storm water conveyance systems, if applicable; and (3) is runoff from offsite conveyed through the site? if so, describe]: The project site is a part of a larger school campus site for North County Academy at 1640 Magnolia Avenue. The existing site is a vacant turf open field at the southeast corner of the campus that is graded to drain at approximately 5% northwest to an inlet that is a part of the school's storm drain facilities and an 18 inch storm drain within Magnolia Avenue per PD 01-11. The public storm drain system is tributary to Agua Hedionda Lagoon, which is hydromodification exempt, and ultimately to the Pacific Ocean. NORTH COUNTY ACADEMY 8 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Descriotion of Pr000sed Site Develooment and Drainaue Patterns Project Description / Proposed Land Use and/or Activities: The project proposes the construction of three side-by-side modular buildings, including two classrooms and a sensory room, on a level graded pad. Adjacent to the new elementary school aged classrooms is proposed hardscape and playground, shade structure, as well as a smaller turf field play area to the north of the buildings. The developed impervious areas will mostly drain to a single biofiltration basin BMP at the south edge of the project site, which has a discharge pipe that extends north to the existing inlet currently draining the field. The proposed project's drainage infrastructure will not significantly alter the existing site's drainage patterns. The said biofiltration basin BMP will be sized for water quality treatment, as well as mitigation of the 100-year storm event peak runoff. List/describe proposed impervious features of the project (e.g., buildings, roadways, parking lots, courtyards, athletic courts, other impervious features): The proposed project will include the construction of three new modular buildings, hardscape surrounding the proposed buildings, shade structure within said hardscape, and playground surface. List/describe proposed pervious features of the project (e.g., landscape areas): Pervious features of the site in this phase include the biofiltration basin area for pollutant control/detention described in this report, and turf field area to the north of the buildings, and decomposed granite maintenance path to the east of the buildings. Does the project include grading and changes to site topography? El Yes El No Description / Additional Information: The project will include precise grading for placement of the new building and hardscape on site, including two accessible access ramps from the existing school site, along with associated landscape, and underground utilities throughout. NORTH COUNTY ACADEMY STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Does the project include changes to site drainage (e.g., installation of new storm water conveyance systems)? 19 Yes 0 N Description /Additional Information: Associated project storm water conveyance will be installed onsite through the use of catch basins, underground piping, and biofiltration basin for water quality and peak flow mitigation as required by the City of Carlsbad BMP Design Manual, San Diego Region, dated February 2016. Storm water runoff from the developed project site is routed to the existing inlet at the northwest corner of the project site. Prior to discharging from the project site, storm water is routed through a proposed biofiltration basin BMP-1. The BMP-1 is responsible for handling storm water quality and 100-year storm event peak flow mitigation. Site runoff from a portion of the site's south access ramp, and the site's north access ramp landing is unable to flow to the receiving biofiltration basin or adjacent self mitigating area, and are considered de-minimus. Site runoff from the north access ramp first drains to the adjacent pervious turf area and is considered self-mitigating. However, the proposed biofiltration basin has been oversized to account for the water quality of these impervious areas as well. A portion of landscape area between the proposed westerly retaining wall and the existing parking lot adjacent sidewalk and area between the top of BMP-1 to daylight is unable to drain to the proposed biofiltration basin and are considered to be self-mitigating area per Chapter 5 Section 5.2.1 of the BMP Design Manual. Disturbed slopes will be amended and/or aerated and planted with native or drought tolerant landscaping to promote water retention. Decomposed granite path on the west side of the proposed building drains to an adjacent landscaped swale area and is considered a self-retaining area. NORTH COUNTY ACADEMY 10 STORM WATER QUALITY MANAGEMENT PLAN MAY2021 Identify whether any of the following features, activities, and/or pollutant source areas will be present (select all that apply): 19 On-site storm drain inlets Interior floor drains and elevator shaft sump pumps Interior parking garages O Need for future indoor & structural pest control !l Landscape/Outdoor Pesticide Use Pools, spas, ponds, decorative fountains, and other water features O Food service O Refuse areas O Industrial processes O Outdoor storage of equipment or materials O Vehicle and Equipment Cleaning Vehicle/Equipment Repair and Maintenance O Fuel Dispensing Areas O Loading Docks O Fire Sprinkler Test Water O Miscellaneous Drain or Wash Water lI Plazas, sidewalks, and parking lots NORTH COUNTY ACADEMY Ii STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Identification of Receivinq Water Pollutants of Concern Describe path of storm water from the project site to the Pacific Ocean (or bay, lagoon, lake or reservoir, as applicable): The existing site is a vacant turf open field at the southeast corner of the campus that is graded to drain at approximately 5% northwest to an inlet that is a part of the school's storm drain facilities and an 18 inch storm drain within Magnolia Avenue per PD 01-11. The public storm drain system is tributary to Agua Hedionda Lagoon, which is hydromodification exempt, and ultimately to the Pacific Ocean. List any 303(d) impaired water bodies within the path of storm water from the project site to the Pacific Ocean (or bay, lagoon, lake or reservoir, as applicable), identify the pollutant(s)/stressor(s) causing impairment, and identify any TMDLs for the impaired water bodies: 303(d) Impaired Water Body Pollutant(s)/Stressor(s) TMDLs Agua Hedionda Creek Benthic Community Effects TMDL Required Bifenthrin TMDL Required Chlorpyrifos TMDL Required Cypermethrin TMDL Required Indicator Bacteria TMDL Required Malathion TMDL Required Manganese TMDL Required Nitrogen TMDL Required Phosphorus TMDL Required Selenium TMDL Required Total Dissolved Solids TMDL Required Total Nitrogen as N TMDL Required Toxicity TMDL Required Agua Hedionda Lagoon Toxicity TMDL Required Identification of Project Site Pollutants Identify pollutants anticipated from the project site based on all proposed use(s) of the site (see BMP Design Manual Appendix B.6): Pollutant Not Applicable to the Project Site Anticipated from the Project Site Also a Receiving Water Pollutant of Concern Sediment X X Nutrients X X Heavy Metals X X Organic Compounds X X NORTH COUNTY ACADEMY 12 STORM WATER QUALITY MANAGEMENT PLAN MAY2021 Trash & Debris X X Oxygen Demanding Substances OiI& Grease X X Bacteria & Viruses X X Pesticides X X NORTH COUNTY ACADEMY 13 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Hydromodification Ma nement Requirements Do hydromodification management requirements apply (see Section 1.6 of the BMP Design Manual)? O Yes, hydromodification management flow control structural BMPs required. No, the project will discharge runoff directly to existing underground storm drains discharging directly to water storage reservoirs, lakes, enclosed embayments, or the Pacific Ocean. No, the project will discharge runoff directly to conveyance channels whose bed and bank are concrete-lined all the way from the point of discharge to water storage reservoirs, lakes, enclosed embayments, or the Pacific Ocean. 1J No, the project will discharge runoff directly to an area identified as appropriate for an exemption by the WMAA for the watershed in which the project resides. Description / Additional Information (to be provided if a 'No' answer has been selected above): The proposed site will drain to an existing storm drain inlet on-site that is tributary to existing school's storm drain facilities and an 18 inch storm drain within Magnolia Avenue per PD 01-11. This public storm drain system is tributary to Agua Hedionda Lagoon, which is hydromodification exempt, and ultimately the Pacific Ocean. NORTH COUNTY ACADEMY 14 STORM WATER QUALITY MANAGEMENT PLAN MAY2021 Critical Coarse Sediment Yield Areas* *This Section only required if hydromodification management requirements apply Based on the maps provided within the WMAA, do potential critical coarse sediment yield areas exist within the project drainage boundaries? Yes (See discussion below) 19 No, No critical coarse sediment yield areas to be protected based on WMAA maps If yes, have any of the optional analyses presented in Section 6.2 of the BMP Design Manual been performed? 6.2.1 Verification of Geomorphic Landscape Units (GLUs) Onsite 6.2.2 Downstream Systems Sensitivity to Coarse Sediment Li 6.2.3 Optional Additional Analysis of Potential Critical Coarse Sediment Yield Areas Onsite No optional analyses performed, the project will avoid critical coarse sediment yield areas identified based on WMAA maps If optional analyses were performed, what is the final result? No critical coarse sediment yield areas to be protected based on verification of GLUs onsite Critical coarse sediment yield areas exist but additional analysis has determined that protection is not required. Documentation attached in Attachment 2B of the SWQMP. EL. Critical coarse sediment yield areas exist and require protection. The project will implement management measures described in Sections 6.2.4 and 6.2.5 as applicable, and the areas are identified on the SWQMP Exhibit. Discussion / Additional Information: NORTH COUNTY ACADEMY 15 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Flow Control for Post-Project Runoff* *This Section only required if hydromodification management requirements apply _ List and describe point(s) of compliance (POCs) for flow control for hydromodification management (see Section 6.3.1). For each POC, provide a POC identification name or number correlating to the project's HMP Exhibit and a receiving channel identification name or number correlating to the project's HMP Exhibit. Has a geomorphic assessment been performed for the receiving channel(s)? si No, the low flow threshold is 0.1Q2 (default low flow threshold) ri Yes, the result is the low flow threshold is 0.102 Yes, the result is the low flow threshold is 0.302 .1 Yes, the result is the low flow threshold is 0.502 If a geomorphic assessment has been performed, provide title, date, and preparer: Discussion / Additional Information: (optional) N/A Other Site Requirements and Constraints NORTH COUNTY ACADEMY 16 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 When applicable, list other site requirements or constraints that will influence storm water management design, such as zoning requirements including setbacks and open space, or City codes governing minimum street width, sidewalk construction, allowable pavement types, and drainage requirements. N/A Optional Additional Information or Continuation of Previous Sections As Needed - This space provided for additional information or continuation of information from previous sections as needed. N/A NORTH COUNTY ACADEMY 17 STANDARD PROJECT REQUIREMENT CHECKLIST E-36 Development Services Land Development Engineering 1635 Faraday Avenue (760) 602-2750 www.carlsbadca.gov Project Information Project Name: North Cou Project ID: P02021-0004 I GR2021-0004 DWG No. or Buildinq Permit No,: 529-4A Source Control BMPs All development projects must implement source control BMPs SC-1 through SC-6 where applicable and feasible. See Chapter 4 and Appendix E.1 of the BMP Design Manual (Volume 5 of City Engineering Standards) for information to implement source control BMPs shown in this checklist. Answer each category below pursuant to the following. "Yes" means the project will implement the source control BMP as described in Chapter 4 and/or Appendix E.1 of the Model BMP Design Manual. Discussion/justification is not required. "No" means the BMP is applicable to the project but it is not feasible to implement. Discussion/justification must be provided. Please add attachments if more space is needed. "N/A" means the BMP is not applicable at the project site because the project does not include the feature that is addressed by the BMP (e.g., the project has no outdoor materials storage areas). Discussion/justification may be provided. - Source Control Requirement Applied? SC-I Prevention of Illicit Discharges into the MS4 j il Yes 0 No 0 N/A Discussion/justification if SC-1 not implemented: SC-2 Storm Drain Stenciling _orSignage 0 Yes LJ No 0 N/A Discussion/justification if SC-2 not implemented: Proposed inlets within proposed hardscape, drain to BMP-1 prior to offsite discharge, and therefore stenciling not proposed. SC-3 Protect Outdoor Materials Storage Areas from Rainfall, Run-On, Runoff, and Wind -------------- DYes 1 0 N MN/A Dispersal Discussion/justification if SC-3 not implemented: E-36 Page 1 of 4 Revised 09116 Source Control Requirement (continued) SC-4 Protect Materials Stored in Outdoor Work Areas from Rainfall, Run-On, Runoff, and Wind Dispersal D Yes Applied? U No !l N/A Discussion/justification if SC4 not implemented: SC-5 Protect Trash Storage Areas from Rainfall, Run-On, Runoff, and Wind Dispersal :10 Yes 0 No IJ N/A Discussion/justification if SC-5 not implemented: SC-6 Additional BMPs based on Potential Sources of Runoff Pollutants must answer for each source listed below and identify additional BMPs. (See Table in Appendix El of BMP Manual for guidance). On-site storm drain inlets 0 Yes Ill No 0 N/A O Interior floor drains and elevator shaft sump pumps U Yes 1 0 No !J N/A 0 Interior parking garages 0 Yes 0 No 9 N/A O Need for future indoor & structural pest control 0 Yes 0 No Ill N/A !J Landscape/Outdoor Pesticide Use 9 Yes 0 No 0 N/A Pools, spas, ponds, decorative fountains, and other water features 0 Yes i_0 No M N/A Food service 0 Yes 0 No lJ N/A O Refuse areas 0 Yes 0 No 01 N/A O Industrial processes 0 Yes 0 No 01 N/A Outdoor equipment or materials _storage _of 0 Yes j 0 No LII N/A El Vehicle and Equipment Cleaning 0 Yes 0 No Ill N/A Vehicle/Equipment Repair and Maintenance 0 Yes 0 No LII N/A Fuel Dispensing Areas 0 Yes 0 No LII N/A Loading Docks 0 Yes 0 No III N/A E] Fire Sprinkler Test Water 0 Yes 0 No 01 N/A Miscellaneous Drain or Wash Water 0 Yes 0 No j LII N/A LII Plazas, sidewalks, and parking lots ii Yes 0 No F 0 N/A For "Yes" answers, identify the additional BMP per Appendix E.1. Provide justification for "No' answers. Proposed inlets within proposed hardscape, drain to BMP-1 prior to offsite discharge, and therefore stenciling not proposed. E-36 Page 2 of 4 Revised 09/16 Site Design BMPs All development projects must implement site design BMPs SD-1 through SD-8 where applicable and feasible. See Chapter 4 and Appendix E.2 thru E.6 of the BMP Design Manual (Volume 5 of City Engineering Standards) for information to implement site design BMPs shown in this checklist. Answer each category below pursuant to the following. "Yes" means the project will implement the site design BMPs as described in Chapter 4 and/or Appendix E.2 thru E.6 of the Model BMP Design Manual. Discussion /justification is not required. "No" means the BMPs is applicable to the project but it is not feasible to implement. Discussion/justification must be provided. Please add attachments if more space is needed. "N/A" means the BMPs is not applicable at the project site because the project does not include the feature that is addressed by the BMPs (e.g., the project site has no existing natural areas to conserve). Discussion/justification may be provided. Site Design Requirement Applied? SID-1 Maintain Natural Drainage Pathways and Hydrologic Features WYes 0 No ON/A Discussion/justification if SD-1 not implemented: SD-2 Conserve Natural Areas, Soils, and Vegetation I iii Yes 0 No 1 0-N/A Discussion/justification if SD-2 not implemented: SD-3 Minimize Impervious Area I Ii Yes 0 No 0 N/A Discussion/justification if SD-3 not implemented: SD-4 Minimize Soil Compaction I Yes 0 No 0 N/A Discussion/justification if SD-4 not implemented: SD-5 Impervious Area Dispersion I ii Yes I 0 No i 0 N/A Discussion/justification if SD-5 not implemented: E-36 Page 3 of 4 Revised 09116 Site Design Requirement (continued) SD-6 Runoff Collection Applied? LI Yes 0 No 0 N/A Discussion/justification if SD-6 not implemented: SD-7 Landscaping with Native or Drought Tolerant Species L!1 Yes D No 0 N/A Discussion/justification if SD-7 not implemented- SD-8 Harvesting and Using Precipitation 0 Yes 0 No J 101 N/A Discussion/justification if SD-8 not implemented: E-36 Page 4 of 4 Revised 09/16 STORM WATER QUALITY MANAGEMENT PLAN MAY2021 SUMMARY OF PDP STRUCTURAL BMPS POP Structural BMPs All PDPs must implement structural BMPs for storm water pollutant control (see Chapter 5 of the BMP Design Manual). Selection of PDP structural BMPs for storm water pollutant control must be based on the selection process described in Chapter 5. PDPs subject to hydromodification management requirements must also implement structural BMPs for flow control for hydromodification management (see Chapter 6 of the BMP Design Manual). Both storm water pollutant control and flow control for hydromodification management can be achieved within the same structural BMP(s). PDP structural BMPs must be verified by the City at the completion of construction. This may include requiring the project owner or project owner's representative to certify construction of the structural BMPs (see Section 1.12 of the BMP Design Manual). PDP structural BMPs must be maintained into perpetuity, and the City must confirm the maintenance (see Section 7 of the BMP Design Manual). Use this form to provide narrative description of the general strategy for structural BMP implementation at the project site in the box below. Then complete the PDP structural BMP summary information sheet for each structural BMP within the project (copy the BMP summary information page as many times as needed to provide summary information for each individual structural BMP). Describe the general strategy for structural BMP implementation at the site. This information must describe how the steps for selecting and designing storm water pollutant control BMPs presented in Section 5.1 of the BMP Design Manual were followed, and the results (type of BMPs selected). For projects requiring hydromodification flow control BMPs, indicate whether pollutant control and flow control BMPs are integrated together or separate. The types of structural BMPs chosen for the project were based on the flow chart presented in Figures 5-1 and 5-2 of the City of Carlsbad BMP Design Manual. Using Form 1-7 (Worksheet B.3-1) to gauge the feasibility of implementing capture and use techniques for the project site, it was determined that harvest and use BMPs are considered infeasible. A feasibility study was then conducted for infiltration and if infiltration is fully or partially feasible for the project's structural BMPs. The negative impacts associated with infiltration were identified and substantiated through the completion of Form 1-8. Please refer to Attachment ld. Based on site geologic conditions, it has been determined that full or partial infiltration of storm water is considered infeasible. Since infiltration is considered infeasible, biofiltration (BF-1) was selected as type of structural BMP for the DMA. Biofiltration was selected for treatment control for the project site and integrated as storm water flow control (detention facility) by including outlet control at the downstream outlet of the facilities. With infiltration infeasible at the BMP location, the facility will be lined in order for surface waters to discharge via underdrain or overflow to the downstream conveyance system. nued on next NORTH COUNTY ACADEMY 19 STORM WATER QUALITY MANAGEMENT PLAN MAY2021 (Continued from previous page) The biofiltration basin for this project has been integrated into the drainage design to meet pollutant control requirements for the site. The proposed building roof area and hardscape associated with the project drain to the proposed biofiltration basin using roof drain downspouts and piping, which allow runoff to flow directly into the biofiltration basin for water quality treatment. Rip rap energy dissipaters will be located at points where concentrated flow enters the biofiltration basin from pipe outfalls to minimize erosion from occurring. The biofiltration system is designed to allow ponding to occur. In developed conditions, the basin will have a total ponding depth of 6 inches and an internal outlet structure. Flow will infiltrate through amended soil and low flow orifice or discharge through the outlet structure. The riser structure will act as a spillway such that peak flows can be safely discharged to the receiving storm drain system. The basin is comprised of a 3-inch layer of mulch, a 24-inch layer of amended soil (a highly sandy, organic rich composite with an infiltration capacity of at least 5 inches/hr) and a 24-inch reservoir layer of gravel. An underdrain pipe with low flow orifice will be provided at the bottom of the basin to carry away filtered runoff to the receiving storm drain system. The underdrain pipe will be located 3 inches above the gravel layer invert. The bottom of the basin will be lined with an impermeable liner to prevent storm water infiltration. A riser structure will be constructed within the BMP with an emergency overflow weir, such that peak flows can be safely discharged to the private storm drain system. The biofiltration basin area will be landscaped with a combination of ground covers, shrubs and/or trees as selected by the project's landscape architect. The biofiltration basin will provide water quality treatment for the DCV and mitigation of the 100-year storm event peak flow rate. NORTH COUNTY ACADEMY 20 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 Structural BMP Summary Information Structural BMP ID No.: Basin Sheet No. 2, DWG 529-4A Type of structural BMP: • Retention by harvest and use (H U-1) O Retention by infiltration basin (INF-1) o Retention by bioretention (lNF-2) O Retention by permeable pavement (INF-3) o Partial retention by biofiltration with partial retention (PR-1) 19 Biofiltration (BF-1) o Flow-thru treatment control included as pre-treatmentlforebay for an onsite retention or biofiltration BMP (provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in discussion section below) o Detention pond or vault for hydromodification management O Other (describe in discussion section below) Purpose: t1 Pollutant control only o Hydromodification control only O Combined pollutant control and hydromodification control o Pre-treatmentlforebay for another structural BMP O Other (describe in discussion section below) Discussion (as needed): NORTH COUNTY ACADEMY 21 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 ATTACHMENT I BACKUP FOR PDP POLLUTANT CONTROL BMPS Attachment Contents Checklist Sequence Attachment la DMA Exhibit (Required) E1 Included See DMA Exhibit Checklist on the back of this Attachment cover sheet. (24"x36" Exhibit typically required) Attachment lb Tabular Summary of OMAs Showing 0 Included as Attachment lb DMA ID matching DMA Exhibit, DMA separate from DMA Exhibit Area, and DMA Type (Required)* *Provide table in this Attachment OR on DMA Exhibit in Attachment 1 a Attachment Ic Form 1-7, Harvest and Use Feasibility El Included Screening Checklist (Required unless 0 Not included because the the entire project will use infiltration entire project will use infiltration BMPs) BMPs Refer to Appendix 13.3-1 of the BMP Design Manual to complete Form 1-7. - Attachment 1 d Form 1-8, Categorization of Infiltration 11 Included Feasibility Condition (Required unless 0 Not included because the the project will use harvest and use entire project will use harvest and BMPs) use BMPs Refer to Appendices C and D of the BMP Design Manual to complete Form 1-8. Attachment le Pollutant Control BMP Design lJ Included Worksheets / Calculations (Required) Refer to Appendices B and E of the BMP Design Manual for structural pollutant control BMP design guidelines NORTH COUNTY ACADEMY 22 DMA Exhibit I PROP. INLET 1 SD-6I - I -'INLET I TOTAL A=552 SF IMPV, A=O SF PERV. A552 SF 50-71 DMA PROP INLET :fl \ TOTAL A= 163 SF IMPV. A=163 SF PERV. A=O SF TOTAL A2.363 SF IMPV, A222 SF PERV. A2.341 SF ---- SUBGRADE INLETS UNDER RELOCATABLE BUILDING (T FOR NUISANCE DRAINAGE. NOT TO BE TREATED. JSRA2 TOTAL A=1.i31 SF IMPV A=O SF PERV. A=1,131 SF SD-2 SD-3 [SD-4[SD-5 TOTAL A=243 SF B%IP-1 IMPV. A=O SF PERV. A=243 SF I SCALE: 1"= 20' 0 20 40 60 DMA MAP NORTH COUNTY ACADEMY DRAINAGE MANAGEMENT AREA (DMA) MAP EXISTING /SD --.-, EXISTING SD6 / 24"X24' 1 OF 2 LEGEND DMA BOUNDARY SITE BMPS BIOFILTRATION (BF-1) (SEE SHEET 2 FOR DETAILS) EX. BLDG TOTAL A56 SF PROP IMPV. A56 SF I PERV A=O SF EXISTING STORM DRAIN PROPOSED STORM DRAIN PROPOSED HARDSCAPE- IMPERVIOUS AREA GROUNDWATER INFORMATION GROUNDWATER WAS NOT ENCOURNTERED PROPOSED BUILDING DURING GEOTECHNICAL TESTING PER REPORT OF GEOTECHNICAL INVESTIGATION PROPOSED DECOMPOSED GRANITE - PERVIOUS AREA I I FOR PROPOSED PORTABLE CLASSROOMS, NORTH COUNTY ACADEMY BY NOVA DATED PROPOSED LANDSCAPING - PERVIOUS AREA DECEMBER 7, 2020 BIOFILTRATION BASIN AREA SITE DESIGN BMPS MAINTAIN NATURAL DRAINAGE PATHWAYS & HYDRAULIC FEATURES FS iI CONSERVE NATURAL AREAS, SOILS. AND VEGETATION SD-3 MINIMIZE IMPERVIOUS AREA ii4I MINIMIZE SOIL COMPACTION FS D75 IMPERVIOUS AREA DISPERSION FS-D RUNOFF COLLECTION 50-7 LANDSCAPING WITH NATIVE OR DROUGHT TOLERANT SPECIES SOURCE CONTROL BMPS PREVENTION OF ILLICIT DISCHARGES INTO THE MS4 Eii1 STORM DRAIN STENCILING OR SIGNAGE FS C76 ADDITIONAL BMPS BASED ON POTENTIAL RUNOFF POLLUTANTS: LII ON-SITE STORM DRAIN INLETS LANDSCAPE/OUTDOOR PESTICIDE USE FQJ PLAZAS SIDEWALKS. AND PARKING LOTS DMA SUMMARY DRAINAGE TOTAL TOTAL TOTAL DMA BMP BMP BMP MANAGEMENT AREA IMPV. AREA PERV AREA TYPE TYPE NAME AREA AREA (DMA) (SF/AC) (SF/AC) (SF/AC) PROVIDED (SF) DMA-1 10,562/ 8532/ 2030/ DRAINS BIOFILTRATION BMP-1 624 0.24 0.19 0.05 TO BMP BASIN (BF-1) PASCO LARET SUITER & San Diego I Solana Beach I Orange County Phone 949.661.6695 1 www.plsaengineering.com DRAINAGE MANAGEMENT AREA (DMA) TOTAL AREA (SF/AC) TOTAL IMP. AREA (SF/AC) TOTAL PERV. AREA (SF/AC) DMA TYPE BMP TYPE BMP NAME BMP AREA PROVIDED (SF) DMA-1 10,086/013 1 8,056/0.18 2,030/0.05 DRAINS TO BMP BIOFIL. BASIN (BF-1) BMP-1 624 OUTFALL PIPE BIOFILTRATION BASIN WITH IMPERMEABLE LINER DETAIL NOT TO SCALE CAREX PANSA PLANTING, OR APPROVED OTHER, PER LANDSCAPE PLANS FG PER PLAN j", 30 MIL IMPERMEABLE LAYER BIORETENTION ENGINEERED SOIL LAYER SHALL BE 85-88% SAND, 8-12% FINES (SILT & CLAY), 3-5% ORGANIC MATTER. PERCOLATION PERCOLATION RATE 5-10 IN/HR \4&.<I 11,Hi=HI. MINIMUM SUSTAINED J=L=i.. SUB-GRADE COMPACTED TO 95% . \< TRIAXIAL GEOGRID (TRIAX OR SIMILAR) .\ NON-WOVEN GEOTEXTILE (TENCATE HP-570) CLASS II PERM PER CLATRANS SPEC .• 1212 BROOKS BOX, TG PER PLAN WSE 2 OF 2 ""NOTE: BACKFILL FOR STORM DRAIN PIPES 3" PVC SCREW CAP / ENTERING OR EXITING BASIN SHOULD BE r f 6" ABOVE GRADE BACKFILLED WITH A 2-SACK MIX OF SLURRY EXTEND AND WRAP LINER 12"M.PAST EDGE OF BERM MIN 6' ç- ORFICE PLATE MIN SQUARE 30 MIL IMPERMEABLE 3" I 1 / DIMENSIONS 1.0 FT GREATER I=LIU- LAYER / THAN PIPE DIA HOT DIP 0 0 GALVANIZED PLATE AFTER IF 11 EXCAVATED SLOPE '. HOLES HAVE BEEN DRILLED INFLOW PIPE 3" DRILLED ORFICE AS REQUIRED )ELO 1/2" MAX BY APPROVEMENT STORMWATER MANAGEMENT PLAN 3/8" DIA. HOLE FLOW CONTROL ORFICE PLATE 1111 w, 3" NON PERFO,11~TED 06 TANDPIPE 4P, \ •..\ L; MIN 64 PERFORATED PVC PIPE PLACE PIPE \row CONTROL ORIFICE WITH PERFORATIONS AT THE INVERT PLATE PER DETAIL DMA SUMMARY STRUCTURAL SOIL PROPERTIES: ORGANIC CONTENT (OC)> 5 PERCENT, PH BETWEEN 6-8, CATION EXCHANGE CAPACITY (CEC) > 5 MILLIEQUIVALENT (MEQ)/100 G SOIL, INFILTRATION RATES OF 0.5 IN/HR OR GREATER. SOIL MEDIA MUST HAVE AN APPROPRIATE AMOUNT OF ORGANIC MATERIAL TO SUPPORT PLANT GROWTH (E.G., LOAMY SAND MIXED THOROUGHLY WITH AN ORGANIC MATERIAL), IF THE EXISTING SOILS MEET THE CRITERIA, IT CAN BE USED AS THE SOIL MEDIA. IF THE EXISTING SOILS DO NOT MEET THE CRITERIA, A SUBSTITUTE MEDIA MUST BE USED. SOIL MEDIA THAT IS BROUGHT TO THE SITE MUST MEET THE STANDARDS SET FORTH IN COUNTY OF SAN DIEGO BMP DESIGN MANUAL AS WELL AS THE FOLLOWING CRITERIA: SOIL MEDIA CONSISTS OF 85 PERCENT WASHED COURSE SAND, 10 PERCENT FINES (RANGE: 8-12 PERCENT; 8 PERCENT = 2 IN/HR INFILTRATION RATE, 12 PERCENT = 1 IN/HR INFILTRATION RATE), AND 5 PERCENT ORGANIC MATTER, THE SAND PORTION SHOULD CONSIST OF CONCRETE SAND PASSING A ONE-QUARTER-INCH SIEVE). MORTAR SAND (PASSING A ONE-EIGHTH-INCH SIEVE) IS ACCEPTABLE AS LONG AS IT IS THOROUGHLY WASHED TO REMOVE THE FINES. FINES SHOULD PASS A # 270 (SCREEN SIZE) SIEVE. 4, ORGANIC MATTER IS CONSIDERED AN ADDITIVE TO ASSIST VEGETATION IN INITIAL ESTABLISHMENT AND CONTRIBUTES TO SORPTION OF POLLUTANTS BUT GENERALLY SHOULD BE MINIMIZED (5 PERCENT). ORGANIC MATERIALS WILL OXIDIZE OVER TIME CAUSING AN INCREASE IN PONDING THAT COULD ADVERSELY AFFECT THE PERFORMANCE OF THE BIOFILTRATION AREA. ORGANIC MATERIAL SHOULD CONSIST OF AGED BARK FINES, OR SIMILAR ORGANIC MATERIAL. ORGANIC MATERIAL SHOULD NOT CONSIST OF MANURE OR ANIMAL COMPOST. STUDIES HAVE ALSO SHOWN NEWSPAPER MULCH TO BE AN ACCEPTABLE ADDITIVE (KIM ET AL. 2003; DAVIS 2007). ? 5, HIGH LEVELS OF PHOSPHORUS IN THE MEDIA HAVE BEEN IDENTIFIED AS THE MAIN CAUSE OF BIOFILTRATION AREAS EXPORTING NUTRIENTS (HUNT AND LORD 2006). ALL STRUCTURAL SOIL SHOULD BE ANALYZED FOR BACKGROUND LEVELS OF NUTRIENTS. TOTAL fl PHOSPHORUS SHOULD NOT EXCEED 15 PPM. PASCO LARET SUITER & ASSOCIIATES San Diego I Solana Beach I Orange County Phone 949.661.6695 IwwwpIsaonginocring.com BIORETENTION SOIL MEDIA (BSM) PROPERTIES: BSM SHOULD ACHIEVE A LONG-TERM, IN PLACE INHLIRAIION RATE OF 5 IN/HR. BSM SHOULD HAVE AN APPROPRIATE AMOUNT OF ORGANIC MATERIAL TO SUPPORT PLANT GROWTH (E.G., LOAMY SAND MIXED THOROUGHLY WITH AN ORGANIC MATERIAL). THE BSM SHOULD BE A MIXTURE OF SAND, FINES, AND COMPOST. THE FOLLOWING COMPOSITION INCLUDES THE MEASUREMENTS FOR DETERMINING THE BSM BY VOLUME AND WEIGHT: BSM COMPOSITION SANDY LOAM SAND SAND SILT I CLAY COMPOST VOLUME 65% 20% 15% WEIGHT 75-80% 10% 13% MAX. 9% MAX' "9% COMPOST BY WEIGHT RESULTS IN APPROXIMATELY 5% ORGANIC MATTER BY WEIGHT. IN ADDITION, THE BSM SHOULD MEET THE FOLLOWING STANDARDS: ORGANIC CONTENT (OC) 2-5%, PH BETWEEN 6.0-8.0, CARBON:NITROGEN RATIO BETWEEN 10:1-20:1, CATION EXCHANGE CAPACITY (CEC) > 5 MILLIEQUIVALENT (MEQ)/100 G SOIL, IF THE EXISTING SOILS MEET THE CRITERIA, IT CAN BE USED AS THE SOIL MEDIA. IF THE EXISTING SOILS DO NOT MEET THE CRITERIA, A SUBSTITUTE MEDIA MUST BE USED. SOIL MEDIA THAT IS BROUGHT TO THE SITE MUST MEET THE STANDARDS SET FORTH IN THE COUNTY OF SAN DIEGO BMP DESIGN MANUAL: APPENDIX F.3- BIOFILTRATION SOIL MEDIA COMPOSITION, TESTING, AND INSTALLATION (NOV 2018), ALSO CONTAINED IN THE COUNTY OF SAN DIEGO LOW IMPACT DEVELOPMENT HANDBOOK: APPENDIX G- BIORETENTION SOIL SPECIFICATION (JULY 2014, UNLESS SUPERSEDED BY MORE RECENT EDITION). NUTRIENT SENSITIVE MEDIA DESIGN: IN CASES WHERE THE BMP DISCHARGES TO RECEIVING WATERS WITH NUTRIENT IMPAIRMENTS OR NUTRIENT TMDLS, THE BSM SHOULD BE DESIGNED TO MINIMIZE THE EXPORT OF NUTRIENTS FROM THE MEDIA. HIGH LEVELS OF PHOSPHORUS IN THE MEDIA HAVE BEEN IDENTIFIED AS THE MAIN CAUSE OF BIOFILTRATION AREAS EXPORTING NUTRIENTS. ALL BSM SHOULD BE ANALYZED FOR BACKGROUND LEVELS OF NUTRIENTS. TOTAL PHOSPHORUS SHOULD NOT EXCEED 15 PPM, THE CARBON:NITROGEN RATIO OF BSM SHALL BE BETWEEN 15 AND 40 TO REDUCE THE POTENTIAL FOR NITRATE LEACHING. IN ADDITION TO ADHERING TO THE COUNTY MEDIA SPECIFICATIONS, THE GUIDELINES SET FORTH IN THE COUNTY OF SAN DIEGO BMP DESIGN MANUAL: APPENDIX E.20- BF-2 NUTRIENT SENSITIVE MEDIA DESIGN (NOV 2018) SHOULD BE FOLLOWED. Harvest and Use Feasibility (Form 1-7) Appendix I: Forms and Checklists me r iir I Is there a demand for harvested water (check all that apply) at the project site that is reliably present during the wet season? O Toilet and urinal flushing El Landscape irrigation o Other:_________________ If there is a demand; estimate the anticipated average wet season demand over a period of 36 hours. Guidance for planning level demand calculations for toilet/urinal flushing and landscape irrigation is provided in Section 13.3.2. [Provide a summary of calculations herd Proposed turf landscape field area to the north of proposed buildings is 3,399 sf. Assuming the grass turf area is a high plant water use hydrozone (per Table 6.3-3), the 36-hour irrigation demand is 2,640 gal/ac). 2,468 sfl(43,560 sf/ac)*(2,640 gal/ac)*(lcf/ 7.48 gal) = 20 ci Calculate the DCV using worksheet T3.21. DCV = 414 (cubic feet) 3a. Is the 36 hour demand greater 3b. Is the 36 hour demand greater than 3c. Is the 36 hour demand than or equal to the DCV? 0.25DCV but less than the full DCV:1 less than 0.25DCV? LJYes / No LJYes / No X Yes Harvest and use appears to be Harvest and use may he feasible. Harvest and use is feasible. Conduct more detailed Conduct more detailed evaluation and considered to be infeasible. evaluation and sizing calculations sizing calculations to determine to confirm that DCV can be used feasibility. Harvest and use may, only be at an adequate rate to meet able to be used for a portion of the site, drawdown criteria, or (optionally) the storage may need to he upsized to meet long term capture targets while draining in longer than 36 hours, Is harvest and use feasible based on further evaluation? U Yes, refer to Appendix E to select and size harvest and use I3MPs. X No, select alternate BMPs. 1-2 February 2016 Infiltration Feasibility (Forms I-S & 1-9) Appendix I: Forms and Checklists Part I - Full In 1 Itratiun Fcaohil t, Screen n Criteria Would infiItrtion uf the full dcin olume he kaihlc from a phvu. al pci pccti\ c witfwut 11) un&sirahlc cuncqiicncc that cannot he reai nabl\ mitiatcd? Criteria Iv, ri!1:,ii. Yes No Is the estimated reliable infiltration rate below proposed facility locations greater than 0.5 inches per hour? The response 1 to this Screening Question shall be based on a comprehensive X evaluation of the factors presented in Appendix C.2 and Appendix D. Provide basis: The infiltration rate of the existing soils for locations P-I and P-2, based on the on-site infiltration study was calculated to be less than 0.5 inches per hour (0.01 inches per hour) after applying a factor of safety (FS) of FS= 3.375. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of geotechnical hazards (slope stability, 2 groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2. Provide basis: No. See Criterion 1. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 1-3 February 2016 Appendix I: Forms and Checklists c wir fUI' 11 CS No Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of groundwater contamination (shallow water table, storm water pollutants or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C,3. Provide basis: Water contamination was not evaluated by NOVA Services. Summarize findings of studies; provide reference to studies, calculations, traps, data sources, etc. Provide narrative discussion of study/data source applicability. Can infiltration greater than 0.5 inches per hour be allowed without causing potential water balance issues such as change of seasonality of ephemeral streams or increased discharge of contaminated groundwater to surface waters? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: The potential for water balance was not evaluated by NOVA Services. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applical)ihty. f all answers to rows 1 4 are "Yes" a full infiltration design is potentially feasible. Part The feasibility screening category is Full Infiltration Result Proceed to if any answer from row 1-4 is "No", infiltration may be possible to some extent but Part 2 would not generally he feasible or desirable to achieve a "full infiltration" design. Proceed to Part 2 To be completed using gathered site information and best professional judgment considertn E_P g the definition of .M in the MS4 Permit. Additional testing and/or studies may be required by the City to substantiate findings. 14 February 2016 Appendix I: Forms and Checklists -7790-7 Part - Partiil Infiltratio n vs. No I fiItrattn Fcii-JhilitY Scrccniiig Critcria \' ould ituiltrjdon of water in my ippruciablcarl1uunt bc ph\'.ic.11lv fca.ib!e S ithuut tfl\ n(gJti\ CDO iC(jU&1IlU-' hit 1lflflnt he tttUflJt)Iy n ittcd? Yc" No Do soil and geologic conditions allow for infiltration in any appreciable rate or volume? The response to this Scr fling Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. Provide basis: The infiltration rate of the existing soils for locations P-i and P-2, based on the on-site infiltration study was calculated to be 0.01 inches per hour, after applying a factor of safety (FS) of FS=3.375. Infiltration rates equal to or less than 0.01 inches per hour indicate that the soil and geologic conditions do not allow for infiltration in any appreciable rate or volume. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates. Can Infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) X that cannot be mitigated to an acceptable level.-'Me response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2. C2.1 A geologic investigation was performed at the subject site. C2.2 Settlement and volume change due to stormwater infiltration is not a concern with: (i) low expansive soils,(ii) no potential for liquefaction, and (iii) no potential for hydro collapse. C2.3 Infiltration has the potential to cause slope failures. BMPs are to be sited a minimum of 50 feet away from any slope. C2.4 Infiltration can potentially damage subsurface and underground utilities. As planned, BMPs are not located within 10 feet of underground utilities. C2.5 Stormwater infiltration can result in damaging ground water mounding during wet periods. Mounding is not considerd to be a hazard of infiltration at this site due to the depth of groundwater. C2.6 BMPs are not anticipated to be located near foundations or retaining walls. Infiltration has the potential to increase lateral pressure and reduce soil strength which can impact foundations and retaining walls. C2.7 Other Factors: NOVA is not aware of all subsurface conditions on nearby sites and cannot address the potential effects of added saturation to geotechnical hazards like saturation, heave, settlement or hydrocollapse, liquefaction, etc. Accordingly, NOVA recommends potential for lateral migration of water from stormwater BMP's be limited by siting any such structures away from property lines. 1-5 February 2016 Appendix I: Forms and Checklists r 'asirr tnruun WIPCOP ___ Can Infiltration in any appreciable quantity be allowed \c without posing significant risk for groundwater related concerns (shallow water table, storm water pollutants or other factors)? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. Provide basis: Water contamination was not evaluated by NOVA Services. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and. why it was not feasible to mitigate low infiltration rates. Can infiltration be allowed without violating downstream 8 water rights? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix (.;.3. Provide basis: The potential for water balance was not evaluated by NOVA Services. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates. If all answers from row 58 are yes then partial infiltration design is potentially feasible. Part The feasibility screening category is Partial Infiltration. No Result* If any answer from row 5$ is no, then infiltration of any volume is considered to be Infiltration infeasible within the drainage area. The feasibility screening category is No Infiltration. 'TO be completed using gathered site information and best professional judgment considering the definition of MEPin the .MS4 Permit. Additional testing and/or studies may be required by the City to substantiate findings. 1-6 February 2016 Appendix I: Forms and Checklists - -_ l Soil assessment methods 0.25 1 0.25 Predominant soil texture 0.25 2 0.50 Suitability Site soil variability 0.25 2 0.50 Assessment Dcpth to groundwater / impervious 0.25 1 0.25 laver Suitability Assessment Safety Factor, S = Zp 1.5 Level of pretreatment! expected sediment loads 0.5 3 1.5 B l)esi&n Redundancy/resiliency 0.25 2 0.50 Compaction during construction 0.25 1 0.25 Design Safety Factor, S14 = 1p 2.25 Combined Safety Factor, S 1 x St 3.375 Observed infiltration Rate, inch/br, P10.03 (corrected for test.-specific bias) P20.06 P-I =0.01 Design Infiltration Rate, in/hr. = lbwd /S P--2=0.01 Supporting Data Briefly describe infiltration test and provide ix f:rence to test forms; Design Phase Borehole percolation tests were utilized for all percolation borings (P-i and P.2) at the bottom of the prospective infiltration BMP structure accompanied by an exploratory engineering boring (B-4) to depths of at least 10 feet below the bottom elevation of the BMP structure. In coordination with the design engineer, a factor of safety of FS = 3.375 was determined following the guidance in the BMP Manual. 1-7 February 2016 DMA Design Worksheets 3403 North County Academy 5/6121 Appendix B: Stormwater Pollutant Control Hydrologic Calculations and Sizing Methods Worksheet 13.2-1. DCV DMA j* 85s percentile 24-hr storm depth from Figure B.1-1 d= 0.6 inches 2 Area tributary to I3MP (s) A= 0 26 acres 3 Area weighted runoff factor (estimate using Appendix 13.1.1 and B.2.1) * See calculation below C 0.73 u,nniess 4 Street trees volume reduction TCV= 0 cubic-feet 5 Rain barrels volume reduction (1 cubic foot7.48 gallons) RCV= 0 cubic-feet 6 Calculate DCV (3630 x a d A) - TCV - RCV DCV= 423 cubic-feet lmperviou5 Landscape DG Basir Iota Area(sqft) Runoff Factor AxRF Weighted RF 187 8,973 0,9 8,076 1,406 0.1 141 531 0.1 53 624 0.3 11,534 8,457 0.73 *Design. Capture Volume calculation for DMA, is oversized to account for impervious surfaces within DM IN i (56 sf), D:MIN 2 (163 sf'), and SMA. 1. (222 sf). Worksheet B,5-1: DMA 1 Simple Sizing Method for Biofiltration BMPs 1 lRemaining DCV After implementing retention BMP 423.0 j cu-ft Partial Retention 2 Infiltration rate from 1-9 if partial infiltration is feasible 0.00 in/hr 3 Allowable drawdown time for aggregate storage below the underdrain 36 hours 4 Depth of runoff that can be infiltrated [Line 2 x Line 3] 0.00 inches 5 Aggregate pore space 0.40 in/in 6 Required depth of gravel below the underdrain [Line 4/Line 5] 0.00 inches 7 Assumed surface area of the biouiltration BMP 624.0 sq-ft 8 Media retained pore storage 0.1 in/in 9 Volume retained by BMP [[Line 4 + (Line 12 x Line 8)]/12] x Line 7 140.40 cu-ft 10 DCV that requires biofiltration [Line 1 - Line 9] 282.6 cu-ft BMP Parameters 11 Surface Ponding [6 inch minimum, 12 inch maximum] 6 inches 12 Media Thickness [18 in Mm], also add mulch layer thickness to this line 27 inches 13 Aggregate Storage above underdrain invert (12 inches typical) - Use 0 inches for sizing if the aggregate is not over the entire bottom surface area 13 inches 14 Freely drained pore storage 0.2 in/in 15 Media filtration rate to be used for sizing (5 in/hr. with no outlet control; if the filtration rate is controlled by the outlet, use the outlet controlled rate which will be less than 5 in/hr.) * 5 in/hr Baseline Calculations 16 Allowable Routing Time for sizing 6 hours 17 Depth filtered during storm [Line 15 x Line 161 30 inches 18 Depth of Detention Storage [Line 11 + (Line 12 x Line 14) + (Line 13 x Line 5)] 16.60 inches 19 Total Depth Treated [Line 17 + Line 18] 46.60 inches Option 1 - Biofdter 1.5 times the DCV 20 Required biofiltered volume [1.5 x Line 10] 424 cu-ft 21 Required Footprint [Line 20 /Line 191 x 12 109.2 sq-ft Option 2 - Store 0.75 of remaining DCV in pores and podng 22 Required Storage (surface + pores) Volume [0.75 x Line 10] .212 cu-ft 23 Required Footprint [Line 22 /Line 18] x 12 153 sq-ft Footprint of the BMP 24 Area draining to the BMP 11,534 sq-ft 25 Adjusted Runoff Factor for drainage area (Refer to Appendix B.1 and 8.2) 0.70 26 BMP Footprint Sizing Factor (Default 0,03 or an alternative minimum footprint sizing factor from Worksheet B.5-2, Line 11) 0.03 27 1 Minimum BMP Footprint [Line 24 x Line 25 x Line 26] 242 sq-ft 28 IFootprint of the BMP = Maximum (Minimum(Line 21, Line 23), Line 27) 242 sq-ft J:\ACTIVE JOBS\3403 North County Academy\ClVlL\REPORTS\SWQM P\ATTACH M ENTS\3403_Worksheet B-5.1_Biofiltration.xlsx STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 ATTACHMENT 2 BACKUP FOR PDP HYDROMODIFICATION CONTROL MEASURES Attachment Contents Checklist Sequence Attachment 2a Hydromodification Management D Included Exhibit (Required) N/A NORTH COUNTY ACADEMY 23 STORM WATER QUALITY MANAGEMENT PLAN MAY2021 ATTACHMENT 3 Structural BMP Maintenance Information OWNERSHIP AND MAINTENANCE FOR STRUCTURAL BMPs The operations and maintenance of the treatment control BMPs will be the responsibility of the owner. The current contact information for the responsible party is: North County Academy 1640 Magnolia Carlsbad, CA 92008 A training program will be administered and implemented by North County Academy and shall occur at a minimum of once annually. The training program shall consist of, at a minimum: the disbursement of the brochures and flyers included in this SWQMP and a copy of the maintenance plan to all operation and maintenance staff associated with the project. A training log shall be filled out at each training session and kept for a minimum of five (5) years. North County Academy will complete and maintain operation and maintenance forms to adequately document all maintenance performed on the project's treatment control BMPs. These records should be kept on file for a minimum of five (5) years and shall be made accessible to the City of Carlsbad, the State Water Resources Control Board or any other authority regulating storm water discharges for inspection upon request at any time. All waste generated from the North County Academy project site is ultimately the responsibility of North County Academy. Disposal of sediment, debris, and trash will comply with applicable local, county, state, and federal waste control programs. Suspected hazardous waste will be analyzed to determine proper disposal methods. The following Operation and Maintenance Plan has been developed for each type of pollutant control BMP used on this project. These are minimum requirements only. Their frequency and/or scope may be increased, if necessary, to meet and/or maintain the level of storm water quality treatment required of this project. All costs associated with the operation and maintenance of the pollutant control BMP will be funded by North County Academy in perpetuity or until the project is sold to another entity where the responsibility would transfer with the sale of the property or an individual parcel. The project's owner, North County Academy, will enter into a Stormwater Facility Maintenance Agreement as required by the City of Carlsbad, which will be executed prior to grading permit issuance. The biofiltration basin overflow structure will be a 2'x2' concrete brooks box, which will be accessible for maintenance in the event of clogging. NORTH COUNTY ACADEMY 24 STORM WATER QUALITY MANAGEMENT PLAN MAY 2021 • Biofiltration System Inspection Activities Recommended Frequency Inspect biofiltration system - Before/after rainy season - Bi-weekly during the rainy season - After a rainfall event of 0.5" or more Inspect soil and repair eroded areas Monthly Inspect for erosion or damage to vegetation, preferably at the end of the wet season to schedule dry season maintenance and before major wet season runoff Prior to rainy season to be sure the areas are ready for the wet season. However, additional inspection & every other month after periods of heavy runoff is recommended. Inspect to ensure grasses, ground covers, vegetation is well established. If not, either prepare soil and reseed or replant with appropriate alternative species. Every other month install erosion control blankets if necessary. Check for debris and litter, areas of sediment accumulation Every other month Inspect health of trees and shrubs and vegetation Every other month Inspect system cleanouts and outfall structures Every other month Inspect for standing water and vectors Every other month Biofiltration System Maintenance Activities Recommended - Frequency Remove litter and debris in conjunction with regularly scheduled landscape maintenance Irrigate bioflitration area(s) during dry season (April through October) and as necessary to maintain vegetation during the rainy season. Physically remove weeds Remove sediment As part of routine, Apply mulch to areas devoid of mulch, especially prior to the wet season regular landscape Replace damaged or diseased trees and shrubs maintenance Mow turf areas, if any Repair erosion at inflow points Unclog under drain system Remove and replace dead and diseased vegetation. - Replace tree stakes and wires, if any Mulch should be replaced every 2 to 3 years or when bare spots appear Every 2-3 years, or as needed Rototill or cultivate the surface if the system does not draw down in 48 hours As needed NORTH COUNTY ACADEMY 25 PARTY RESPONSIBLE FOR MAINTENANCE: ADDRESS CONTACT P0014550. - PLAN PREPARED Sr. NYME COMPANY ADDRESS_ PHONE NO eERTPIC.onoH EMP NOTES: I. TN EBMPDAIEIEANDATCRYTO ES INSTALLED PER MARSPACTUANTES BECOMMENDATONSOB THESE ELMS. 2. NO CR404055 TOTES PROPOSES SlAPS ON THIS SHEET WITHOUT PRIM APPROVAL FROM THE CITY ENGINEER- 1 NO SUBSTITUTIONS TO THE MA.TERTAL OR TYPES OR PlANTING TYPES LNTTHOUT PRIOR APPROVAL FROM THE CT'YENGIBEBR 4. NOOUPANGYMOLNE GRANTED UNTIL THE EiTY INSPECT ION STAPP HAS INSPECTED THIS PROJECT =09 APPROPRIATE SlAP CONSTRUCTION AND INSTALLATION S REFER TO MAINTENANCE AOREBMEBTSGCUMSAT. 6. 566 PROJECT STATE FOR ADDITIONAL. TIFOSSMS'TTON, SlAP CONSTRUCTION AND INSPECTION NOTES: THE =Qw'MLLVEFUFYTS4ATPSRMANER1TRMPTARE CONSTRUCTED AND OPERATING TI CONIPEANCE WITH THE APPIJCABLE REGUBTEMENT& PRONTO OCCUPANCY THU SOW MUST PROVIDE: T. PHOTOGRAPHS OF THE INSTAU.AT1ON OF PERMANENT BRATS PEON TO CONSTRUCTION. DURING COW., RIJCTLON ASSAY FINAL INSTALLATION AWET STAURPES LETTER VERIEVNG THAT PEHURSESRIT BTSPSARE CONGIRSCTBCI AND OPERATING PER THE REQIJIREMENYSOF THE APPROVED RIMS. S. PHOTOGRAPHS TO VERIFY THAT PERMANENT WATER MALTY TREATTSENTSISIIAGE HAS BEEN INSTALLED. PRIOR TO RELEASE OF SECURSTES, THE DEVELOPER IS RESPONSIBLE FOR ENSURING THE PERMANENT SNIPS HAVE HOT BEEN REMOVED OR MOSLPISO ST THE NEW ASIMEOWNER OR ROY ETTTNOUT THE AAWROVA.L OF THE CITY ENGINEER MAGNOLIA AVENUE/ / PASCO LARET SUITER :20' /-1 & ASSOCIATES San Diego Solana Beach I Orange County Phone 94966L6698 Iwww BMP TABLE BMPLO SLAPTYPE j, SYMBOL ] CR505 140 QUANTITY j DRAWIING 140.1 SESETROVSLJ - EHESUENCY .1 , TREATMENT CONTROL UIOFILTRSTON 1 AREA - . BE-I 024 SF. 525-OH 2 QUARTERLY SEMI-ANNUALLY HYDROMODIFICATION & TREATMENT CONTROL I HYDROMODIFICATION LOW IMPACT DESIGN (LID.) (j MAIT1RAL SO-I SSAOA 2 ANNUALLY ANNUALLY ® SOLAVEG,- ET2 ANNUALLY ACONSEMNATURAL IINSALLY 01. ERIWESJE4RATESO SC-S SW-IA 2 ANNUALLY ANNUALLY SO-N 5W-IA 2 ANNUALLY ANNUALLY ERA SOS - 520-BA 2 ANNUALLY ANNUALLY cL) IESLTO0 - P.2ELEA 2 ANNUALLY SANLALLY TINTED SOT 2 ANNUALLY MN— SOURCE CONTROL iFNSNWRILUW ® 4sSTQBE Ccitv of G?_ f1s6w d STORM WATER STANDARDS QUESTIONNAIRE E-34 Development Services Land Development Engineering 1635 Faraday Avenue (760) 602-2750 www.carlsbadca.gov INSTRUCTIONS: To address post-development pollutants that may be generated from development projects, the city requires that new development and significant redevelopment priority projects incorporate Permanent Storm Water Best Management Practices (BMPs) into the project design per Carlsbad BMP Design Manual (BMP Manual). To view the BMP Manual, refer to the Engineering Standards (Volume 5). This questionnaire must be completed by the applicant in advance of submitting for a development application (subdivision, discretionary permits and/or construction permits). The results of the questionnaire determine the level of storm water standards that must be applied to a proposed development or redevelopment project. Depending on the outcome, your project will either be subject to 'STANDARD PROJECT' requirements or be subject to 'PRIORITY DEVELOPMENT PROJECT' (PDP) requirements. Your responses to the questionnaire represent an initial assessment of the proposed project conditions and impacts. City staff has responsibility for making the final assessment after submission of the development application. If staff determines that the questionnaire was incorrectly filled out and is subject to more stringent storm water standards than initially assessed by you, this will result in the return of the development application as incomplete. In this case, please make the changes to the questionnaire and resubmit to the city. If you are unsure about the meaning of a question or need help in determining how to respond to one or more of the questions, please seek assistance from Land Development Engineering staff. A completed and signed questionnaire must be submitted with each development project application. Only one completed and signed questionnaire is required when multiple development applications for the same project are submitted concurrently. PROJECT INFORMATION PROJECT NAME: NORTH COUNTY ACADEMY PROJECT ID: PD2021-0004 / GR2021-0004 / ADDRESS: 1640 MAGNOLIA, CARLSBAD, CA 92008 APN: 760-252-0500 The project is (check one): New Development N Redevelopment The total proposed disturbed area is: 15,520 ft2 (_0.36 ) acres The total proposed newly created and/or replaced impervious area is: 8,973 ft2 (0.21_) acres If your project is covered by an approved SWQMP as part of a larger development project, provide the project ID and the SWQMP # of the larger development project: Project IDN/A SWQMP #: N/A Then, go to Step I and follow the instructions. When completed, sign the form at the end and submit this with your application to the city. E-34 Page 1 of 4 REV 03/19 STEP I TO BE COMPLETED FOR ALL PROJECTS To determine if your project is a "development project', please answer the following question: YES NO Is your project LIMITED TO routine maintenance activity and/or repair/improvements to an existing building El or structure that do not alter the size (See Section 1.3 of the BMP Design Manual for guidance)? If you answered 'yes" to the above question, provide justification below then go to Step 5, mark the third box stating "my project is not a 'development project' and not subject to the requirements of the BMP manual" and complete applicant information. Justification/discussion: (e.g. the project includes only interior remodels within an existing building): If you answered "no" to the above question, the project is a 'development project', go to Step 2. STEP 2 TO BE COMPLETED FOR ALL DEVELOPMENT PROJECTS To determine if your project is exempt from PDP requirements pursuant to MS4 Permit Provision E.3.b.(3), please answer the following questions: Is your project LIMITED to one or more of the following: YES NO 1. Constructing new or retrofitting paved sidewalks, bicycle lanes or trails that meet the following criteria: Designed and constructed to direct storm water runoff to adjacent vegetated areas, or other non- erodible permeable areas; OR Designed and constructed to be hydraulically disconnected from paved streets or roads; OR Designed and constructed with permeable pavements or surfaces in accordance with USEPA Green Streets guidance? 2. Retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constructed in accordance with the USEPA Green Streets guidance? 3. Ground Mounted Solar Array that meets the criteria provided in section 1.4.2 of the BMP manual? LI 91 If you answered "yes" to one or more of the above questions, provide discussion/justification below, then go to Step 5, mark the second box stating "my project is EXEMPT from PDP .....and complete applicant information. Discussion to justify exemption (e.g. the project redeveloping existing road designed and constructed in accordance with the USEPA Green Street guidance): If you answered "no" to the above questions, your project is not exempt from PDP, go to Step 3. E-34 Page 2 of 4 REV 03/19 ST!P3 TO BE COMPLETED FOR ALL NEW ORREDEVELOPMENT PROJECTS To determine if your project is a PDP, please answer the following questions (MS4 Permit Provision E.3.b.(1 )): YES NO Is your project a new development that creates 10,000 square feet or more of impervious surfaces collectively over the entire project site? This includes commercial, industrial, residential, mixed-use, LI EI and public development projects on public or private land. Is your project a redevelopment project creating and/or replacing 5,000 square feet or more of impervious surface collectively over the entire project site on an existing site of 10,000 square feet or more of impervious surface? This includes commercial, industrial, residential, mixed-use, and public development projects on public or private land. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface collectively over the entire project site and supports a restaurant? A restaurant is a facility that sells prepared foods and drinks for consumption, including stationary lunch counters and refreshment stands selling prepared foods and drinks for immediate consumption (Standard Industrial Classification (SIC) code 5812). Is your project a new or redevelopment project that creates 5,000 square feet or more of impervious surface collectively over the entire project site and supports a hillside development project? A hillside El 21 development project includes development on any natural slope that is twenty-five percent or greater. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface collectively over the entire project site and supports a parking lot? A parking lot is E] 129 a land area or facility for the temporary parking or storage of motor vehicles used personally for business or for commerce. Is your project a new or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious street, road, highway, freeway or driveway surface collectively over the entire project site? A street, road, highway, freeway or driveway is any paved impervious surface used for the transportation of automobiles, othervehicles. _trucks, _motorcycles, _and Is your project a new or redevelopment project that creates and/or replaces 2,500 square feet or more of impervious surface collectively over the entire site, and discharges directly to an Environmentally Sensitive Area (ESA)? "Discharging Directly to" includes flow that is conveyed overland a distance of LI I 200 feet or less from the project to the ESA, or conveyed in a pipe or open channel any distance as an isolated flow from to_ the commingled with Iands).* _the _project _ESA _(i.e._not _flows _from _adjacent Is your project a new development or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious surface that supports an automotive repair shop? An automotive repair El ZI shop is a facility that is categorized in any one of the following Standard Industrial Classification (SIC) codes: 5013, 5014, 5541, 7532-7534, or 7536-7539. Is your project a new development or redevelopment project that creates and/or replaces 5,000 square feet or more of impervious area that supports a retail gasoline outlet (RGO)? This category includes El N RGO's that meet the following criteria: (a) 5,000 square feet or more or (b) a project Average Daily Traffic (AD T) of 100 or more vehicles per day. Is your project a new or redevelopment project that results in the disturbance of one or more acres of land and are expected to generate pollutants post construction? Is your project located within 200 feet of the Pacific Ocean and (1) creates 2,500 square feet or more of impervious surface or (2) increases impervious surface on the property by more than 10%? (CIVIC LI LI 21.203.040) If you answered "yes" to one or more of the above questions, your project is a PDP. If your project is a redevelopment project, go to step 4. If your project is a new project, go to step 5, check the first box stating "My project is a PDP and complete applicant information. If you answered "no" to all of the above questions, your project is a 'STANDARD PROJECT.' Go to step 5, check the second box stating "My project is a 'STANDARD PROJECT'.....and complete applicant information. E-34 Page 3 of 4 REV 03/19 STEP 4 TO BE COMPLETED FOR REDEVELOPMENT PROJECTS THAT ARE PRIORITY DEVELOPMENT PROJECTS (POP) ONLY Complete the questions below legarding your redevelopment project (MS4 Permit Provision E.3.b.(2)): YES NO Does the redevelopment project result in the creation or replacement of impervious surface in an amount of less than 50% of the surface area of the previously existing development? Complete the percent impervious calculation below: 52,600 Existing impervious area (A) = sq. ft. . fl Total proposed newly created or replaced impervious area () = 8,973 sq ft. Percent impervious area created or replaced (B/A)*100 = 17.06 If you answered yes", the structural BM Ps required for PDP apply only to the creation or replacement of impervious surface and not the entire development. Go to step 5, check the first box stating 'My project is a PDP .....and complete applicant information. If you answered 'no,' the structural BMP's required for PDP apply to the entire development. Go to step 5, check the check the first box stating "My proiect is a PDP .....and complete applicant information. STEP 5 CHECK THE APPROPRIATE BOX AND COMPLETE APPLICANT INFORMATION j My project is a PDP and must comply with PDP stormwater requirements of the BMP Manual. I understand I must prepare a Storm Water Quality Management Plan (SWQMP) for submittal at time of application. U My project is a 'STANDARD PROJECT' OR EXEMPT from PDP and must only comply with 'STANDARD PROJECT' stormwater requirements of the BMP Manual. As part of these requirements, I will submit a "Standard Project Requirement Checklist Form E-36" and incorporate low impact development strategies throughout my project. Note: For projects that are close to meeting the PDP threshold, staff may require detailed impervious area calculations and exhibits to verify if 'STANDARD PROJECT' stormwater requirements apply. El My Project is NOT a 'development project' and is not subject to the requirements of the BMP Manual. Applicant Information and Signature Box Applicant Name: Ryan WAuffe Applicant Title: Project Manager i f I Applicant Signature.:_ / . Date:. . J ; Environmentally Seftbye A?ea ir,cluda but are not limited to all Clean Water Act Section 303(d) impaired water bodies; areas designated as Aren of Specrai Biological Significance by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); water bodies designated with the RARE beneficial use by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); areas designated as preserves or their equivalent under the Multi Species Conservation Program within the Cities and County of San Diego; Habitat Management Plan; and any other equivalent environmentally sensitive areas which have been identified by the City. This Box for City Use Only YES NO City Concurrence: El El By: Date: Project ID: 03 (0 -.4 () E-34 Page 4 of 4 REV 03/19