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Home My WebLink AboutPD 2021-0004; NORTH COUNTY ACADEMY; STORM WATER QUALITY MANAGEMENT PLAN; 2022-02-24 CITY 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: 12-31-23 PASCO LARET SUITER & ASSOCIATES, INC. 27127 CALLE ARROYO, SUITE 1904 SAN JUAN CAPISTRANO, CA 92675 PREPARED FOR: NORTH COUNTY ACADEMY 1640 MAGNOLIA CARLSBAD, CA 92008 PREPARED BY: 27127 CALLE ARROYO SAN JUAN CAPISTRANO, CA 92675 858-259-8212 DATE: December 17, 2020 Updated: May 10, 2021 Updated: August 17, 2021 Updated: October 28, 2021 Updated: December 07, 2021 Final: February 24, 2022 PASCO LARET SUITER & ASSOCIATES CIVIL ENGINEERING+ LAND PLANNING+ LAND SURVEYING STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 2 TABLE OF CONTENTS Certification Page Project Vicinity Map FORM E-34 Storm Water Standard Questionnaire Site Information FORM E-36 Standard Project Requirement Checklist Summary of PDP Structural BMPs Attachment 1: Backup for PDP Pollutant Control BMPs Attachment 1a: DMA Exhibit Attachment 1b: Tabular Summary of DMAs and Design Capture Volume Calculations Attachment 1c: Harvest and Use Feasibility Screening (when applicable) Attachment 1d: Categorization of Infiltration Feasibility Condition (when applicable) Attachment 1e: Pollutant Control BMP Design Worksheets / 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 Thresholds and Actions Attachment 3a: Structural BMP Maintenance Thresholds & Actions & BMP Fact Sheet Attachment 3b: Draft Maintenance Agreement Attachment 4: Single Sheet BMP (SSBMP) Exhibit STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 3 CERTIFICATION PAGE Project Name: North County Academy – Campus Consolidation Project ID: PD2021-0004 / GR2020-0004 / 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. ________________________________________________________ William J. Suiter, P.E. RCE 68964 Exp.: 12-31-23 Pasco Laret Suiter & Associates 02/24/2022 Date 'M STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 4 PROJECT VICINITY MAP VICINITY MAP CITY OF OCEANSIDE PACIFIC OCEAN i's CITY OF ENCNITAS STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 5 [Insert City’s Storm Water Standard Questionnaire (Form E-34) here] E-34 Page 1 of 4 REV 03/19 Development Services Land Development Engineering 1635 Faraday Avenue (760) 602-2750 www.carlsbadca.gov STORM WATER STANDARDS QUESTIONNAIRE E-34 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: PROJECT ID: ADDRESS: APN: The project is (check one): New Development Redevelopment The total proposed disturbed area is: ________ ft2 (________) acres The total proposed newly created and/or replaced impervious area is: ________ ft2 (________) 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 ID SWQMP #: Then, go to Step 1 and follow the instructions. When completed, sign the form at the end and submit this with your application to the city. NORTH COUNTY ACADEMY 1640 MAGNOLIA, CARLSBAD, CA 92008 205-220-99 12,834 0.29 9,064 0.21 N/A N/A PD2021-0004 / GR2021-0004 / DWG529-4A X C cityof Carlsbad □ □ E-34 Page 2 of 4 REV 03/19 STEP 1 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 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: a) Designed and constructed to direct storm water runoff to adjacent vegetated areas, or other non-erodible permeable areas; OR b) Designed and constructed to be hydraulically disconnected from paved streets or roads; OR c) 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? 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. X X X X □ □ □ □ □ □ □ □ E-34 Page 3 of 4 REV 03/19 STEP 3 TO BE COMPLETED FOR ALL NEW OR REDEVELOPMENT PROJECTS To determine if your project is a PDP, please answer the following questions (MS4 Permit Provision E.3.b.(1)): YES NO 1. 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, and public development projects on public or private land. 2. 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. 3. 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). 4. 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 development project includes development on any natural slope that is twenty-five percent or greater. 5. 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 a land area or facility for the temporary parking or storage of motor vehicles used personally for business or for commerce. 6. 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, trucks, motorcycles, and other vehicles. 7. 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 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 the project to the ESA (i.e. not commingled with flows from adjacent lands).* 8. 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 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. 9. 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 RGO’s that meet the following criteria: (a) 5,000 square feet or more or (b) a project Average Daily Traffic (ADT) of 100 or more vehicles per day. 10. 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? 11. 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%? (CMC 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. X X X X X X X X X X X □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ X X0 8,973 8,973 52,6009,06417.2STEP4 TO BE COMPLETED FOR REDEVELOPMENT PROJECTS THAT ARE PRIORITY DEVELOPMENT PROJECTS (PDP) ONLY Complete the questions below regarding 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: Existing impervious area {A) = sq. ft. [x] □ Total proposed newly created or replaced impervious area (B) = sq. ft. Percent impervious area created or replaced (B/A)*100 = % If you answered "yes", the structural BMPs 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 BM P's required for PDP apply to the entire development. Go to step 5, check the check the first box statinq "My project is a PDP ... " and complete applicant information. STEP5 CHECK THE APPROPRIATE BOX AND COMPLETE APPLICANT INFORMATION [xi 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. 0 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. D 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,~ Applicant Title: Project Manager Date: 5k45/ZO'L( Applicant Signature: ~ ~ • Environmentally Sensitive Areas Include but are not limited to all Clean Water Act Section 303(d) 1mpa1red water bodies; areas designated as Areas of Special 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 Ci Use On/ YES NO City Concurrence: □ □ By: Date: Project ID: E-34 Page 4 of 4 REV 03/19 -- STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 6 SITE INFORMATION CHECKLIST Project Summary Information Project Name North County Academy – Campus Consolidation Project ID PD2021-0004 / GR2021-0004 / DWG 529-4A 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 Project Watershed (Hydrologic Unit) Hydrologic Unit: Carlsbad Hydrologic Area: Agua Hedionda Hydrologic Sub-Area Name: Los Monos Hydrologic Sub-Area #: 904.31 Parcel Area _4.19____ Acres (_195,787__ Square Feet) Existing Impervious Area (subset of Parcel Area) _0.00____ Acres (_0_______ Square Feet) Area to be disturbed by the project (Project Area) _0.29____ Acres (_12,834___ Square Feet) Project Proposed Impervious Area (subset of Project Area) _0.21____ Acres (_9,064____ Square Feet) Project Proposed Pervious Area (subset of Project Area) _0.08___ Acres (_3,770_____ Square Feet) Note: Proposed Impervious Area + Proposed Pervious Area = Area to be Disturbed by the Project. This may be less than the Parcel Area. STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 7 Description of Existing Site Condition and Drainage Patterns Current Status of the Site (select all that apply): Existing development  Previously graded but not built out 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):  Vegetative Cover 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  NRCS Type D (Per Report of Geotechnical Investigation for Proposed Portable Classrooms North County Academy by NOVA dated December 7, 2020.) Approximate Depth to Groundwater (GW): GW Depth < 5 feet 5 feet < GW Depth < 10 feet 10 feet < GW Depth < 20 feet  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. STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 8 Existing Natural Hydrologic Features (select all that apply): Watercourses Seeps Springs Wetlands  None Description / Additional Information: N/A STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 9 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. STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 10 Description of Proposed Site Development and Drainage 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?  Yes 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. STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 11 Does the project include changes to site drainage (e.g., installation of new storm water conveyance systems)?  Yes No 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 September 2021. 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 and are considered de-minimus. 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, slope on the south side of BMP-1, and daylight slopes adjacent to the North hardscape are all considered to be self-mitigating areas 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. STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 12 Identify whether any of the following features, activities, and/or pollutant source areas will be present (select all that apply):  On-site storm drain inlets Interior floor drains and elevator shaft sump pumps Interior parking garages Need for future indoor & structural pest control  Landscape/Outdoor Pesticide Use Pools, spas, ponds, decorative fountains, and other water features Food service Refuse areas Industrial processes Outdoor storage of equipment or materials Vehicle and Equipment Cleaning Vehicle/Equipment Repair and Maintenance Fuel Dispensing Areas Loading Docks Fire Sprinkler Test Water Miscellaneous Drain or Wash Water  Plazas, sidewalks, and parking lots STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 13 Identification of Receiving 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 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 STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 14 Trash & Debris X X Oxygen Demanding Substances X X Oil & Grease X X Bacteria & Viruses X X Pesticides X X STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 15 Hydromodification Management Requirements Do hydromodification management requirements apply (see Section 1.6 of the BMP Design Manual)? 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.  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. 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  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 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 8 of the SWQMP. 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: STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 16 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)? No, the low flow threshold is 0.1Q2 (default low flow threshold) Yes, the result is the low flow threshold is 0.1Q2 Yes, the result is the low flow threshold is 0.3Q2 Yes, the result is the low flow threshold is 0.5Q2 If a geomorphic assessment has been performed, provide title, date, and preparer: Discussion / Additional Information: (optional) N/A Other Site Requirements and Constraints 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 STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 17 [Insert City’s Standard Project Requirement Checklist Form E-36 (here)] E-36 Page 1 of 4 Revised 09/16 Development Services Land Development Engineering 1635 Faraday Avenue (760) 602-2750 www.carlsbadca.gov STANDARD PROJECT REQUIREMENT CHECKLIST E-36 Project Information Project Name: Project ID: DWG No. or Building Permit No.: 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-1 Prevention of Illicit Discharges into the MS4 Yes No N/A Discussion/justification if SC-1 not implemented: SC-2 Storm Drain Stenciling or Signage Yes No N/A Discussion/justification if SC-2 not implemented: SC-3 Protect Outdoor Materials Storage Areas from Rainfall, Run-On, Runoff, and Wind Dispersal Yes No N/A Discussion/justification if SC-3 not implemented: North County Academy PD2021-0004 / GR2021-0004 529-4A Proposed inlets within proposed hardscape, drain to BMP-1 prior to offsite discharge, and therefore stenciling not proposed. C cityof Carlsbad Iii □ □ □ □ Iii □ □ Iii E-36 Page 2 of 4 Revised 09/16 Source Control Requirement (continued) Applied? SC-4 Protect Materials Stored in Outdoor Work Areas from Rainfall, Run-On, Runoff, and Wind Dispersal Yes No N/A Discussion/justification if SC-4 not implemented: SC-5 Protect Trash Storage Areas from Rainfall, Run-On, Runoff, and Wind Dispersal Yes No 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 E.1 of BMP Manual for guidance). On-site storm drain inlets Yes No N/A Interior floor drains and elevator shaft sump pumps Yes No N/A Interior parking garages Yes No N/A Need for future indoor & structural pest control Yes No N/A Landscape/Outdoor Pesticide Use Yes No N/A Pools, spas, ponds, decorative fountains, and other water features Yes No N/A Food service Yes No N/A Refuse areas Yes No N/A Industrial processes Yes No N/A Outdoor storage of equipment or materials Yes No N/A Vehicle and Equipment Cleaning Yes No N/A Vehicle/Equipment Repair and Maintenance Yes No N/A Fuel Dispensing Areas Yes No N/A Loading Docks Yes No N/A Fire Sprinkler Test Water Yes No N/A Miscellaneous Drain or Wash Water Yes No N/A Plazas, sidewalks, and parking lots Yes No 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. Native landscaping is proposed for much of disturbed area. Pesticide use is not proposed at this time, and therefore additional BMP treatment is not proposed. Proposed site sidewalk/hardscape is all tributary to BMP-1, dispersed within adjacent landscape area (SRA1), or minor De-minimus areas. Additional BMP treatment is not proposed. □ □ Iii □ □ Iii Iii □ Iii □ □ □ □ Iii □ □ □ Iii □ □ □ Iii Iii □ Iii □ □ □ □ Iii □ □ □ Iii □ □ □ Iii □ □ □ Iii □ □ □ Iii □ □ □ Iii □ □ □ Iii □ □ □ Iii □ □ □ Iii □ □ □ Iii □ □ □ Iii Iii □ Iii □ NC) I) lJ IVI PI N CJ c::_, &~ ~ Dl~AINS TO OCl:AN E-36 Page 3 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? SD-1 Maintain Natural Drainage Pathways and Hydrologic Features Yes No N/A Discussion/justification if SD-1 not implemented: SD-2 Conserve Natural Areas, Soils, and Vegetation Yes No N/A Discussion/justification if SD-2 not implemented: SD-3 Minimize Impervious Area Yes No N/A Discussion/justification if SD-3 not implemented: SD-4 Minimize Soil Compaction Yes No N/A Discussion/justification if SD-4 not implemented: SD-5 Impervious Area Dispersion Yes No N/A Discussion/justification if SD-5 not implemented: I I Iii ID ID I Iii lo lo I Iii lo lo I Iii ID ID I Iii ID ID E-36 Page 4 of 4 Revised 09/16 Site Design Requirement (continued) Applied? SD-6 Runoff Collection Yes No N/A Discussion/justification if SD-6 not implemented: SD-7 Landscaping with Native or Drought Tolerant Species Yes No N/A Discussion/justification if SD-7 not implemented: SD-8 Harvesting and Using Precipitation Yes No N/A Discussion/justification if SD-8 not implemented: I I Iii lo lo I Iii ID ID ID ID I Iii STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 18 SUMMARY OF PDP STRUCTURAL BMPS PDP 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 I-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 I-8. Please refer to Attachment 1d. 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 for surface waters to discharge via underdrain or overflow to the downstream conveyance system. (Continue on next page) STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 19 (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 7 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. STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 20 Structural BMP Summary Information Structural BMP ID No. Basin DWG 529-4A Sheet No. 2 Type of structural BMP: Retention by harvest and use (HU-1) Retention by infiltration basin (INF-1) Retention by bioretention (INF-2) Retention by permeable pavement (INF-3) Partial retention by biofiltration with partial retention (PR-1)  Biofiltration (BF-1) Flow-thru treatment control included as pre-treatment/forebay 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) Detention pond or vault for hydromodification management Other (describe in discussion section below) Purpose:  Pollutant control only Hydromodification control only Combined pollutant control and hydromodification control Pre-treatment/forebay for another structural BMP Other (describe in discussion section below) Discussion (as needed): STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 21 ATTACHMENT 1 BACKUP FOR PDP POLLUTANT CONTROL BMPS This is the cover sheet for Attachment 1. Check which Items are Included behind this cover sheet: Attachment Sequence Contents Checklist Attachment 1a DMA Exhibit (Required) See DMA Exhibit Checklist on the back of this Attachment cover sheet. (24”x36” Exhibit typically required)  Included Attachment 1b Tabular Summary of DMAs Showing DMA ID matching DMA Exhibit, DMA Area, and DMA Type (Required)* *Provide table in this Attachment OR on DMA Exhibit in Attachment 1a Included on DMA Exhibit in Attachment 1a Included as Attachment 1b, separate from DMA Exhibit Attachment 1c Form I-7, Harvest and Use Feasibility Screening Checklist (Required unless the entire project will use infiltration BMPs) Refer to Appendix B.3-1 of the BMP Design Manual to complete Form I-7.  Included Not included because the entire project will use infiltration BMPs Attachment 1d Form I-8, Categorization of Infiltration Feasibility Condition (Required unless the project will use harvest and use BMPs) Refer to Appendices C and D of the BMP Design Manual to complete Form I-8.  Included Not included because the entire project will use harvest and use BMPs Attachment 1e Pollutant Control BMP Design Worksheets / Calculations (Required) Refer to Appendices B and E of the BMP Design Manual for structural pollutant control BMP design guidelines  Included STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 22 Use this checklist to ensure the required information has been included on the DMA Exhibit: The DMA Exhibit must identify:  Underlying hydrologic soil group  Approximate depth to groundwater  Existing natural hydrologic features (watercourses, seeps, springs, wetlands)  Critical coarse sediment yield areas to be protected (if present)  Existing topography and impervious areas  Existing and proposed site drainage network and connections to drainage offsite  Proposed grading  Proposed impervious features  Proposed design features and surface treatments used to minimize imperviousness  Drainage management area (DMA) boundaries, DMA ID numbers, and DMA areas (square footage or acreage), and DMA type (i.e., drains to BMP, self-retaining, or self-mitigating)  Structural BMPs (identify location and type of BMP) Attachment 1a DMA Exhibit DMA/HMP MAP NORTH COUNTY ACADEMY DRAINAGE MANAGEMENT AREA (OMA) MAP LEGEND OMA BOUNDARY EXISTING STORM DRAIN PROPOSED STORM DRAIN PROPOSED HARDSCAPE-IMPERVIOUS AREA PROPOSED BUILDING PROPOSED DECOMPOSED GRANITE -PERVIOUS AREA PROPOSED LANDSCAPING -PERVIOUS AREA BIOFILTRATION BASIN AREA SITE DESIGN BMPS -SD- -so- MAINTAIN NATURAL DRAINAGE PATHWAYS & HYDRAULIC FEATURES CONSERVE NATURAL AREAS, SOILS, AND VEGETATION MINIMIZE IMPERVIOUS AREA MINIMIZE SOIL COMPACTION IMPERVIOUS AREA DISPERSION RUNOFF COLLECTION LANDSCAPING WITH NATIVE OR DROUGHT TOLERANT SPECIES SITE BMPS BIOFILTRATION (BF-1) (SEE SHEET 2 FOR DETAILS) GROUNDWATER INFORMATION 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 SOURCE CONTROL BMPS PREVENTION OF ILLICIT DISCHARGES INTO THE MS4 STORM DRAIN STENCILING OR SIGNAGE EX. BLDG ISC-11 ISC-21 ISC-61 ADDITIONAL BMPS BASED ON POTENTIAL RUNOFF POLLUTANTS: [Kl ON-SITE STORM DRAIN INLETS [] LANDSCAPE/OUTDOOR PESTICIDE USE [QJ PLAZAS, SIDEWALKS, AND PARKING LOTS ------ \ DMIN1 TOTA I =106 SF IMPV. -105 SF =0 SF ~ -----~,, , __ _ OMA 1 DMASUMMARY DRAINAGE TOTAL TOTAL TOTAL OMA MANAGEMENT AREA IMPV. AREA PERV. AREA TYPE AREA (OMA) (SF/AC) (SF/AC) (SF/AC) OMA 1 11,348 / 0.26 8,824 / 0.20 2,524 / 0.06 DRAINS TO BMP DMIN 1 106 / 0.0 106 / 0.00 0 I 0.00 DE MINIMIS DMIN 2 134 / 0.0 134 / 0.00 0 I 0.00 DE MINIMIS SMA 1 410 / 0.01 0 I 0.00 410 / 0.01 SELF-MITIGATING SMA 2 555 / 0.01 0 I 0.00 555 / 0.01 SELF-MITIGATING SMA 3 281 / 0.01 0 I 0.00 281 / 0.01 SELF-MITIGATING ~ PASCO LARET SUITER I -----■ I ~~~(O)CC~~rrE~ i San Diego I Solana Beach I Orange County ~ Phone 949.661.66951 www.plsaengineering.com BMP BMP BMPAREA TYPE NAME PROVIDED (SF) BIOFIL TRATION BMP-1 624 BASIN (BF-1) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A ·, ',,, ' ' ', \ \ \ \ \ _T_O_TALA:...t3A 9 IMPV. A=134 S PERV. A=0 SF SMA 1 1 TOTAL A=41 I IMPV. A=0 s I PERV. A=410 I ;;,... t-SD-4 SD- ' -I ------• • ---... ----fSs..--..... --------- \ \ \ \ 1 OF 2 I ! I I !I l SMA 3 j / OFFSITE .__ _ ____. --~ I FIELD TOTAL A=281 SF '} DRAINAGE IMPV. A=0 SF I N.A.P. PERV. A=281 SF \ IS□-4IS□-71 ' ' ' ' GRADED SWALE FOR CONVEYANCE OF ADJACENT FIELD (N.A.P) DRAINAGE TO INLET SCALE: 1" = 20' ~~~--=---==--■---1 !!!!!!!!!!I - -I 0 20 40 60 ~ ~7 # CAREX PANSA PLANTING, OR APPROVED OTHER, PER LANDSCAPE PLANS · ~%%'<,, FG PER PLAN 30 MIL IMPERMEABLE LAYE suB-GRADE coMPACTED TO 95% . 11 m m 11 I 111 111 111 I BIORETENTION ENGINEERED SOIL . 111 111 111 111 , . ==w=W=W== LAYER SHALL BE 85-88% SAND, 8-12% FINES (SILT & CLAY), 3-5% ORGANIC MATTER. PERCOLATION RATE 5-10 IN/HR MINIMUM SUSTAINED 1212 BROOKS BOX, TG PER PLAN WSE ~- = 0 co CD ~ ----------~ ~ 3" PVC SCREW CAP Y, 6" ABOVE GRADE ~ "NON PERFORATED STANDPIPE ' · · AND WRAP INER 12" MIN. PAST EDGE OF BERM 0 MIL IMPERMEABLE AYER **NOTE: BACKFILL FOR STORM DRAIN PIPES ENTERING OR EXITING BASIN SHOULD BE BACKFILLED WITH A 2-SACK MIX OF SLURRY 2 OF 2 WASHED PEA GRAVEL FILTER COURSE ~ 0 r'"l~~~~~~~~~i{~.,~~~u ._________:~,,.c;.,....-..,J,:. ·v----WATER TIGHT CAP ON CLASS II PERM PER CLATRANS /,~~ % A'<<('<(«(( TERMINAL END OF PIPE ' . ' /✓/'/.(/'/✓/'/, /, ' t//.<% , . Y-/,)~, . 3" MIN . . . , 3" PERFORATED PVC PIPE PLACE PIPE i I ~ (: SPEC 68-1.025 OUTFALL PIPE BIOFILTRATION BASIN WITH IMPERMEABLE LINER DETAIL NOTTO SCALE STRUCTURAL SOIL PROPERTIES: ORGANIC CONTENT (QC)> 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: ! ~ 1. 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. ! " 9.; 2 ~ . I 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. i j 3. FINES SHOULD PASS A# 270 (SCREEN SIZE) SIEVE. ! 4. H 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 BIOFIL TRATION 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 I NUTRIENTS (HUNT AND LORD 2006). ALL STRUCTURAL SOIL SHOULD BE ANALYZED FOR BACKGROUND LEVELS OF NUTRIENTS. TOTAL o PHOSPHORUS SHOULD NOT EXCEED 15 PPM. ! PASCO LARET SUITER I I ~~~(Q)(C~~f [E:~ ~ San Diego I Solana Beach I Orange County ~ Phone 949.661.66951 www.plsaengineering.com WITH PERFORATIONS AT THE INVERT BSM SHOULD ACHIEVE A LONG-TERM, IN PLACE INFILTRATION 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 SANDY LOAM COMPOSITION SAND SAND SILT CLAY COMPOST VOLUME 65% 20% 15% WEIGHT 75-80% 10% 3% 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 BIOFIL TRATION 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. Attachment 1b Harvest and Use Feasibility (Form I-7) Appendix I: Forms and Checklists I-2 February 2016 Harvest and Use Feasibility Checklist Form I-7 1. Is there a demand for harvested water (check all that apply) at the project site that is reliably present during the wet season? Toilet and urinal flushing Landscape irrigation Other:______________ 2. 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 B.3.2. [Provide a summary of calculations here] 3. Calculate the DCV using worksheet B.2-1. DCV = __________ (cubic feet) 3a. Is the 36 hour demand greater than or equal to the DCV? Yes / No 3b. Is the 36 hour demand greater than 0.25DCV but less than the full DCV? Yes / No 3c. Is the 36 hour demand less than 0.25DCV? Yes Harvest and use appears to be feasible. Conduct more detailed evaluation and sizing calculations to confirm that DCV can be used at an adequate rate to meet drawdown criteria. Harvest and use may be feasible. Conduct more detailed evaluation and sizing calculations to determine feasibility. Harvest and use may only be able to be used for a portion of the site, or (optionally) the storage may need to be upsized to meet long term capture targets while draining in longer than 36 hours. Harvest and use is considered to be infeasible. Is harvest and use feasible based on further evaluation? Yes, refer to Appendix E to select and size harvest and use BMPs. No, select alternate BMPs. x Proposed turf landscape field area to the north of proposed buildings is 3,399 sf. Assuming the grass turfarea is a high plant water use hydrozone (per Table B.3-3), the 36-hour irrigation demand is 2,640 gal/ac). 2,468 sf/(43,560 sf/ac)*(2,640 gal/ac)*(1cf / 7.48 gal) = 20 cf 414 x x x x □ □ □ c::> ~ ~ ~ i Attachment 1c Infiltration Feasibility (Forms I-8 & I-9) Appendix I: Forms and Checklists I-3 February 2016 Categorization of Infiltration Feasibility Condition Form I-8 Part 1 - Full Infiltration Feasibility Screening Criteria Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences that cannot be reasonably mitigated? Criteria Screening Question Yes No 1 Is the estimated reliable infiltration rate below proposed facility locations greater than 0.5 inches per hour? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. 2 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of geotechnical hazards (slope stability, 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: Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Provide basis: The infiltration rate of the existing soils for locations P-1 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. No. See Criterion 1. X X Appendix I: Forms and Checklists I-4 February 2016 Form I-8 Page 2 of 4 Criteri a Screening Question Yes No 3 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. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. 4 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. Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability. Part 1 Result * If all answers to rows 1 - 4 are “Yes” a full infiltration design is potentially feasible. The feasibility screening category is Full Infiltration If any answer from row 1-4 is “No”, infiltration may be possible to some extent but would not generally be feasible or desirable to achieve a “full infiltration” design. Proceed to Part 2 *To be completed using gathered site information and best professional judgment considering the definition of MEP in the MS4 Permit. Additional testing and/or studies may be required by the City to substantiate findings. Provide basis: Provide basis: Proceed to Part 2 No. See Criterion 1. No. See Criterion 1. X X Appendix I: Forms and Checklists I-5 February 2016 Form I-8 Page 3 of 4 Part 2 – Partial Infiltration vs. No Infiltration Feasibility Screening Criteria Would infiltration of water in any appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated? Criteria Screening Question Yes No 5 Do soil and geologic conditions allow for infiltration in any appreciable rate or volume? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D. 6 Can Infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards (slope stability, 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: The infiltration rate of the existing soils for locations P-1 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. 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. X X Appendix I: Forms and Checklists I-6 February 2016 Form I-8 Page 4 of 4 Criteria Screening Question Yes No 7 Can Infiltration in any appreciable quantity be allowed 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. 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. 8 Can infiltration be allowed without violating downstream water rights? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. 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. Part 2 Result* If all answers from row 5-8 are yes then partial infiltration design is potentially feasible. The feasibility screening category is Partial Infiltration. If any answer from row 5-8 is no, then infiltration of any volume is considered to be 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 MEP in the MS4 Permit. Additional testing and/or studies may be required by the City to substantiate findings. Provide basis: Provide basis: No Infiltration Based on the relatively low measured infiltration rates, it is NOVA's judgment that infiltration should not be considered at this site. Based on the relatively low measured infiltration rates, it is NOVA's judgment that infiltration should not be considered at this site. X X Appendix I: Forms and Checklists I-7 February 2016 Factor of Safety and Design Infiltration Rate Worksheet Form I-9 Factor Category Factor Description Assigned Weight (w) Factor Value (v) Product (p) p = w x v A Suitability Assessment Soil assessment methods 0.25 Predominant soil texture 0.25 Site soil variability 0.25 Depth to groundwater / impervious layer 0.25 Suitability Assessment Safety Factor, SA = p B Design Level of pretreatment/ expected sediment loads 0.5 Redundancy/resiliency 0.25 Compaction during construction 0.25 Design Safety Factor, SB = p Combined Safety Factor, Stotal= SA x SB Observed Infiltration Rate, inch/hr, Kobserved (corrected for test-specific bias) Design Infiltration Rate, in/hr, Kdesign = Kobserved / Stotal Supporting Data 1 2 2 1 0.25 0.50 0.50 0.25 1.5 3 2 1 1.5 0.50 0.25 2.25 3.375 P-1=0.03 P-2=0.06 Briefly describe infiltration test and provide reference to test forms: Design Phase Borehole percolation tests were utilized for all percolation borings (P-1 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. P-1=0.01 P-2=0.01 Attachment 1d DMA Design Worksheets Category #Description i ii iii iv v vi vii viii ix x Units 1 Drainage Basin ID or Name DMA 1 unitless 2 85th Percentile 24-hr Storm Depth 0.60 inches 3 Impervious Surfaces Not Directed to Dispersion Area (C=0.90) 8,824 sq-ft 4 Semi-Pervious Surfaces Not Serving as Dispersion Area (C=0.30) 624 sq-ft 5 Engineered Pervious Surfaces Not Serving as Dispersion Area (C=0.10) 1,900 sq-ft 6 Natural Type A Soil Not Serving as Dispersion Area (C=0.10)sq-ft 7 Natural Type B Soil Not Serving as Dispersion Area (C=0.14)sq-ft 8 Natural Type C Soil Not Serving as Dispersion Area (C=0.23)sq-ft 9 Natural Type D Soil Not Serving as Dispersion Area (C=0.30)sq-ft 10 Does Tributary Incorporate Dispersion, Tree Wells, and/or Rain Barrels? No No No No No No No No No No yes/no 11 Impervious Surfaces Directed to Dispersion Area per SD-B (Ci=0.90) sq-ft 12 Semi-Pervious Surfaces Serving as Dispersion Area per SD-B (Ci=0.30)sq-ft 13 Engineered Pervious Surfaces Serving as Dispersion Area per SD-B (Ci=0.10)sq-ft 14 Natural Type A Soil Serving as Dispersion Area per SD-B (Ci=0.10)sq-ft 15 Natural Type B Soil Serving as Dispersion Area per SD-B (Ci=0.14)sq-ft 16 Natural Type C Soil Serving as Dispersion Area per SD-B (Ci=0.23)sq-ft 17 Natural Type D Soil Serving as Dispersion Area per SD-B (Ci=0.30)sq-ft 18 Number of Tree Wells Proposed per SD-A # 19 Average Mature Tree Canopy Diameter ft 20 Number of Rain Barrels Proposed per SD-E # 21 Average Rain Barrel Size gal 22 Total Tributary Area 11,348 0 0 0 0 0 0 0 0 0 sq-ft 23 Initial Runoff Factor for Standard Drainage Areas 0.73 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 unitless 24 Initial Runoff Factor for Dispersed & Dispersion Areas 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 unitless 25 Initial Weighted Runoff Factor 0.73 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 unitless 26 Initial Design Capture Volume 414 0 0 0 0 0 0 0 0 0 cubic-feet 27 Total Impervious Area Dispersed to Pervious Surface 0 0 0 0 0 0 0 0 0 0 sq-ft 28 Total Pervious Dispersion Area 0 0 0 0 0 0 0 0 0 0 sq-ft 29 Ratio of Dispersed Impervious Area to Pervious Dispersion Area n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a ratio 30 Adjustment Factor for Dispersed & Dispersion Areas 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 ratio 31 Runoff Factor After Dispersion Techniques 0.73 n/a n/a n/a n/a n/a n/a n/a n/a n/a unitless 32 Design Capture Volume After Dispersion Techniques 414 0 0 0 0 0 0 0 0 0 cubic-feet 33 Total Tree Well Volume Reduction 0 0 0 0 0 0 0 0 0 0 cubic-feet 34 Total Rain Barrel Volume Reduction 0 0 0 0 0 0 0 0 0 0 cubic-feet 35 Final Adjusted Runoff Factor 0.73 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 unitless 36 Final Effective Tributary Area 8,284 0 0 0 0 0 0 0 0 0 sq-ft 37 Initial Design Capture Volume Retained by Site Design Elements 0 0 0 0 0 0 0 0 0 0 cubic-feet 38 Final Design Capture Volume Tributary to BMP 414 0 0 0 0 0 0 0 0 0 cubic-feet False False Automated Worksheet B.1: Calculation of Design Capture Volume (V2.0) Dispersion Area, Tree Well & Rain Barrel Inputs (Optional) Standard Drainage Basin Inputs Results Tree & Barrel Adjustments Initial Runoff Factor Calculation Dispersion Area Adjustments No Warning Messages Category #Description i ii iii iv v vi vii viii ix x Units 1 Drainage Basin ID or Name DMA 1 --------- unitless 2 85th Percentile Rainfall Depth 0.60 --------- inches 3 Predominant NRCS Soil Type Within BMP Location D unitless 4 Is proposed BMP location Restricted or Unrestricted for Infiltration Activities? Restricted unitless 5 Nature of Restriction Soil Type unitless 6 Do Minimum Retention Requirements Apply to this Project? Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes yes/no 7 Are Habitable Structures Greater than 9 Stories Proposed? No yes/no 8 Has Geotechnical Engineer Performed an Infiltration Analysis? Yes yes/no 9 Design Infiltration Rate Recommended by Geotechnical Engineer 0.010 in/hr 10 Design Infiltration Rate Used To Determine Retention Requirements 0.000 --------- in/hr 11 Percent of Average Annual Runoff that Must be Retained within DMA 4.5% --------- percentage 12 Fraction of DCV Requiring Retention 0.02 --------- ratio 13 Required Retention Volume 8 --------- cubic-feet False False Automated Worksheet B.2: Retention Requirements (V2.0) Advanced Analysis Basic Analysis Result No Warning Messages Category #Description i ii iii iv v vi vii viii ix x Units 1 Drainage Basin ID or Name DMA 1 ---------sq-ft 2 Design Infiltration Rate Recommended 0.000 ---------in/hr 3 Design Capture Volume Tributary to BMP 414 ---------cubic-feet 4 Is BMP Vegetated or Unvegetated?Vegetated unitless 5 Is BMP Impermeably Lined or Unlined?Lined unitless 6 Does BMP Have an Underdrain?Underdrain unitless 7 Does BMP Utilize Standard or Specialized Media?Standard unitless 8 Provided Surface Area 624 sq-ft 9 Provided Surface Ponding Depth 6 inches 10 Provided Soil Media Thickness 24 inches 11 Provided Gravel Thickness (Total Thickness)24 inches 12 Underdrain Offset 3 inches 13 Diameter of Underdrain or Hydromod Orifice (Select Smallest)3.00 inches 14 Specialized Soil Media Filtration Rate in/hr 15 Specialized Soil Media Pore Space for Retention unitless 16 Specialized Soil Media Pore Space for Biofiltration unitless 17 Specialized Gravel Media Pore Space unitless 18 Volume Infiltrated Over 6 Hour Storm 0 0 0 0 0 0 0 0 0 0 cubic-feet 19 Ponding Pore Space Available for Retention 0.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 unitless 20 Soil Media Pore Space Available for Retention 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 unitless 21 Gravel Pore Space Available for Retention (Above Underdrain)0.00 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 unitless 22 Gravel Pore Space Available for Retention (Below Underdrain)0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 unitless 23 Effective Retention Depth 2.40 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 inches 24 Fraction of DCV Retained (Independent of Drawdown Time)0.30 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ratio 25 Calculated Retention Storage Drawdown Time 120 0 0 0 0 0 0 0 0 0 hours 26 Efficacy of Retention Processes 0.31 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ratio 27 Volume Retained by BMP (Considering Drawdown Time)127 0 0 0 0 0 0 0 0 0 cubic-feet 28 Design Capture Volume Remaining for Biofiltration 287 0 0 0 0 0 0 0 0 0 cubic-feet 29 Max Hydromod Flow Rate through Underdrain 0.4800 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 cfs 30 Max Soil Filtration Rate Allowed by Underdrain Orifice 33.23 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 in/hr 31 Soil Media Filtration Rate per Specifications 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 in/hr 32 Soil Media Filtration Rate to be used for Sizing 5.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 in/hr 33 Depth Biofiltered Over 6 Hour Storm 30.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 inches 34 Ponding Pore Space Available for Biofiltration 1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 unitless 35 Soil Media Pore Space Available for Biofiltration 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 unitless 36 Gravel Pore Space Available for Biofiltration (Above Underdrain)0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40 unitless 37 Effective Depth of Biofiltration Storage 19.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 inches 38 Drawdown Time for Surface Ponding 1 0 0 0 0 0 0 0 0 0 hours 39 Drawdown Time for Effective Biofiltration Depth 4 0 0 0 0 0 0 0 0 0 hours 40 Total Depth Biofiltered 49.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 inches 41 Option 1 - Biofilter 1.50 DCV: Target Volume 431 0 0 0 0 0 0 0 0 0 cubic-feet 42 Option 1 - Provided Biofiltration Volume 431 0 0 0 0 0 0 0 0 0 cubic-feet 43 Option 2 - Store 0.75 DCV: Target Volume 215 0 0 0 0 0 0 0 0 0 cubic-feet 44 Option 2 - Provided Storage Volume 215 0 0 0 0 0 0 0 0 0 cubic-feet 45 Portion of Biofiltration Performance Standard Satisfied 1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ratio 46 Do Site Design Elements and BMPs Satisfy Annual Retention Requirements?Yes ---------yes/no 47 Overall Portion of Performance Standard Satisfied (BMP Efficacy Factor)1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 ratio 48 Deficit of Effectively Treated Stormwater 0 n/a n/a n/a n/a n/a n/a n/a n/a n/a cubic-feet Retention Calculations Automated Worksheet B.3: BMP Performance (V2.0) False False BMP Inputs Biofiltration Calculations False False False False Result False False No Warning Messages STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 23 ATTACHMENT 2 BACKUP FOR PDP HYDROMODIFICATION CONTROL MEASURES N/A: Project is HMP exempt [This is the cover sheet for Attachment 2.] Indicate which Items are Included behind this cover sheet: Attachment Sequence Contents Checklist Attachment 2a Hydromodification Management Exhibit (Required)  Included See Hydromodification Management Exhibit Checklist on the back of this Attachment cover sheet. Attachment 2b Management of Critical Coarse Sediment Yield Areas (WMAA Exhibit is required, additional analyses are optional) See Section 6.2 of the BMP Design Manual.  Exhibit showing project drainage boundaries marked on WMAA Critical Coarse Sediment Yield Area Map (Required) Optional analyses for Critical Coarse Sediment Yield Area Determination 6.2.1 Verification of Geomorphic Landscape Units Onsite 6.2.2 Downstream Systems Sensitivity to Coarse Sediment 6.2.3 Optional Additional Analysis of Potential Critical Coarse Sediment Yield Areas Onsite Attachment 2c Geomorphic Assessment of Receiving Channels (Optional) See Section 6.3.4 of the BMP Design Manual.  Not performed  Included Attachment 2d Flow Control Facility Design and Structural BMP Drawdown Calculations (Required) See Chapter 6 and Appendix G of the BMP Design Manual  Included STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 24 Use this checklist to ensure the required information has been included on the Hydromodification Management Exhibit: The Hydromodification Management Exhibit must identify:  Underlying hydrologic soil group  Approximate depth to groundwater  Existing natural hydrologic features (watercourses, seeps, springs, wetlands)  Critical coarse sediment yield areas to be protected (if present)  Existing topography  Existing and proposed site drainage network and connections to drainage offsite  Proposed grading  Proposed impervious features  Proposed design features and surface treatments used to minimize imperviousness  Point(s) of Compliance (POC) for Hydromodification Management  Existing and proposed drainage boundary and drainage area to each POC (when necessary, create separate exhibits for pre-development and post-project conditions)  Structural BMPs for hydromodification management (identify location, type of BMP, and size/detail) STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 25 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. STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 26 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 to be sure the areas are ready for the wet season. However, additional inspection after periods of heavy runoff is recommended. Prior to rainy season & every other month Inspect to ensure grasses, ground covers, vegetation is well established. If not, either prepare soil and reseed or replant with appropriate alternative species. Install erosion control blankets if necessary. Every other month 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 As part of routine, regular landscape maintenance Irrigate biofiltration area(s) during dry season (April through October) and as necessary to maintain vegetation during the rainy season. Physically remove weeds Remove sediment Apply mulch to areas devoid of mulch, especially prior to the wet season Replace damaged or diseased trees and shrubs 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 BF-1 Biofiltration Design Adaptations for Project Goals Biofiltration Treatment BMP for storm water pollutant control. The system is lined or un-lined to provide incidental infiltration, and an underdrain is provided at the bottom to carry away filtered runoff. This configuration is considered to provide biofiltration treatment via flow through the media layer. Storage provided above the underdrain within surface ponding, media, and aggregate storage is considered included in the biofiltration treatment volume. Saturated storage within the aggregate storage layer can be added to this design by raising the underdrain above the bottom of the aggregate storage layer or via an internal weir structure designed to maintain a specific water level elevation. Integrated storm water flow control and pollutant control configuration. The system can be designed to provide flow rate and duration control by primarily providing increased surface ponding and/ or having a deeper aggregate storage layer above the underdrain. This will allow for significant detention storage, which can be controlled via inclusion of an outlet structure at the downstream end of the underdrain. Recommended Siting Criteria Siting Criteria □ □ □ Placement observes geotechnical recommendations regarding potential hazards (e.g., slope stability, landslides, liquefaction zones) and setbacks (e.g., slopes, foundations, utilities). An impermeable liner or other hydraulic restriction layer is included if site constraints indicate that infiltration or lateral flows should not be allowed. Contributing tributary area shall be ~ 5 acres (~ 1 acre preferred). E-110 Intent/Rationale Must not negatively impact existing site geotechnical concerns. Lining prevents storm water from impacting groundwater and/ or sensitive environmental or geotechnical features. Incidental infiltration, when allowable, can aid in pollutant removal and groundwater recharge. Bigger BMPs require additional design features for proper performance. Contributing tributary area greater than 5 acres may be allowed at the discretion of the City Engineer if the following conditions are met: 1) incorporate design features (e.g. flow spreaders) to minimizing short circuiting of flows in the BMP and 2) incorporate additional design features requested by the City Sept.2021 Siting Criteria BF-1 Biofiltration Intent/Rationale Engineer for proper performance of the regional BMP. □ Finish grade of the facility is S 2%. Flatter surfaces reduce erosion and channelization within the facility. Recommended BMP Component Dimensions BMP Component Free board Surface Ponding Ponding Area Side Slopes Mulch Dimension :::: 6 inches for earth basin :::: 2 inches for concrete planter/box structure :::: 6 and S 12 inches 3H: 1 V or shallower :::: 3 inches E-111 Intent/Rationale Freeboard provides room for head over overflow structures and minimizes risk of uncontrolled surface discharge. Surface ponding capacity lowers subsurface storage requirements. Deep surface ponding raises safety concerns. Surface ponding depth greater than 12 inches (for additional pollutant control or surface outlet structures or flow-control orifices) may be allowed at the discretion of the City Engineer if the following conditions are met: 1) surface ponding depth drawdown time is less than 24 hours; and 2) safety issues and fencing requirements are considered (typically ponding greater than 18" will require a fence and/ or flatter side slopes) and 3) potential for elevated clogging risk is considered. Gentler side slopes are safer, less prone to erosion, able to establish vegetation more quickly and easier to maintain. Mulch will suppress weeds and maintain moisture for plant growth. Aging mulch kills pathogens and Sept.2021 BMP Component Dimension 2 18 inches BF-1 Biofiltration Intent/Rationale weed seeds and allows the beneficial microbes to multiply. Media Layer 1: 1 slope maximum for edge condition A deep media layer provides additional filtration and supports plants with deeper roots. Standard specifications shall be followed. For non-standard or proprietary designs, compliance with F.1 ensures that adequate treatment performance will be provided. Underdrain Diameter 2 6 inches Cleanout Diameter 2 6 inches Design Criteria and Considerations Smaller diameter underdrains are prone to clogging. Properly spaced cleanouts will facilitate underdrain maintenance. Bioretention with underdrain must meet the following design criteria. Deviations from the below criteria may be approved at the discretion of the City Engineer if it is determined to be appropriate: Design Criteria Surface Ponding □ Surface ponding is limited to a 24-hour drawdown time. Vegetation Plantings are suitable for the climate and Intent/Rationale Surface ponding limited to 24 hours for plant health. Surface ponding drawdown time greater than 24-hours but less than 96 hours may be allowed at the discretion of the City Engineer if certified by a landscape architect or agronomist. □ Plants suited to the climate and ponding expected ponding depth. A plant list to aid in depth are more likely to survive. selection can be found in Appendix E .21. □ An irrigation system with a connection to water supply should be provided as needed. Mulch (Optional) E-112 Seasonal irrigation might be needed to keep plants healthy. Sept.2021 Design Criteria □ A minimum of 3 inches of well-aged, shredded hardwood mulch that has been stockpiled or stored for at least 12 months is provided. Media Layer □ □ □ Media maintains a minimum filtration rate of 5 in/hr over lifetime of facility. An initial filtration rate of 8 to 12 in/hr is recommended to allow for clogging over time; the initial filtration rate should not exceed 12 inches per hour. Media is a minimum 18 inches deep, meeting either of these two media specifications: Section F.3 Bioretention Soil Media (BSl\1) or specific jurisdictional guidance. Alternatively, for proprietary designs and custom media mixes not meeting the media specifications, the media meets the pollutant treatment performance criteria in Section F.1. Media surface area is 3% of contributing area times adjusted runoff factor or greater. Unless demonstrated that the BMP surface area can be smaller than 3%. E-113 BF-1 Biofiltration Intent/Rationale Mulch will suppress weeds and maintain moisture for plant growth. Aging mulch kills pathogens and weed seeds and allows the beneficial microbes to multiply. A filtration rate of at least 5 inches per hour allows soil to drain between events. The initial rate should be higher than long term target rate to account for clogging over time. However an excessively high initial rate can have a negative impact on treatment performance, therefore an upper limit is needed. A deep media layer provides additional filtration and supports plants with deeper roots. Standard specifications shall be followed. For non-standard or proprietary designs, compliance with F.1 ensures that adequate treatment performance will be provided. Greater surface area to tributary area ratios: a) maximizes volume retention as required by the MS4 Permit and b) decrease loading rates per square foot and therefore increase longevity. Adjusted runoff factor is to account for site design BMPs implemented upstream of the BMP ( such as rain barrels, impervious area dispersion, etc.). Refer to Appendix B.1 guidance. Sept.2021 Design Criteria □ Where receiving waters are impaired or have a Tl\IDL for nutrients, the system is designed with nutrient sensitive media design (see fact sheet BF-2). Filter Course Layer □ □ □ A filter course is used to prevent migration of fines through layers of the facility. Filter fabric is not used. Filter course is washed and free of fines. Filter course calculations assessing suitability for particle migration prevention have been completed. Aggregate Storage Layer □ □ Class 2 Permeable per Caltrans specification 68-1.025 is recommended for the storage layer. Washed, open-graded crushed rock may be used, however a 4-6 inch washed pea gravel filter course layer at the top of the crushed rock is required. The depth of aggregate provided (12-inch typical) and storage layer configuration is adequate for providing conveyance for underdrain flows to the outlet structure. In.iow, Underdrain, and Outflow Structures □ □ Inflow, underdrains and outflow structures are accessible for inspection and maintenance. Inflow velocities are limited to 3 ft/ s or less or use energy dissipation methods. (e.g., riprap, level spreader) for concentrated inflows. E-114 BF-1 Biofiltration Intent/Rationale Potential for pollutant export is partly a function of media composition; media design must minimize potential for export of nutrients, particularly where receiving waters are impaired for nutrients. Migration of media can cause clogging of the aggregate storage layer void spaces or subgrade. Filter fabric is more likely to clog. Washing aggregate will help eliminate fines that could clog the facility and impede infiltration. Gradation relationship between layers can evaluate factors (e.g., bridging, permeability, and uniformity) to determine if particle sizing is appropriate or if an intermediate layer is needed. Washing aggregate will help eliminate fines that could clog the aggregate storage layer void spaces or subgrade. Proper storage layer configuration and underdrain placement will minimize facility drawdown time. Maintenance will prevent clogging and ensure proper operation of the flow control structures. High inflow velocities can cause erosion, scour and/ or channeling. Sept.2021 BF-1 Biofiltration Design Criteria Intent/Rationale □ □ □ □ □ □ Curb cut inlets are at least 12 inches wide, have a 4-6 inch reveal (drop) and an apron and energy dissipation as needed. Underdrain outlet elevation should be a minimum of 3 inches above the bottom elevation of the aggregate storage layer. Minimum underdrain diameter is 6 inches. Underdrains are made of slotted, PVC pipe conforming to ASTM D 3034 or equivalent or corrugated, HDPE pipe conforming to AASHTO 252M or equivalent. An underdrain cleanout with a minimum 6- inch diameter and lockable cap is placed every 250 to 300 feet as required based on underdrain length. Overflow is safely conveyed to a downstream storm drain system or discharge point Size overflow structure to pass 100-year peak flow for on-line infiltration basins and water quality peak flow for off-line basins. Inlets must not restrict flow and apron prevents blockage from vegetation as it grows in. Energy dissipation prevents erosion. A minimal separation from subgrade or the liner lessens the risk of fines entering the underdrain and can improve hydraulic performance by allowing perforations to remain unblocked. Smaller diameter underdrains are prone to clogging. Slotted underdrains provide greater intake capacity, clog resistant drainage, and reduced entrance velocity into the pipe, thereby reducing the chances of solids migration. Properly spaced cleanouts will facilitate underdrain maintenance. Planning for overflow lessens the risk of property damage due to flooding. Conceptual Design and Sizing Approach for Storm Water Pollutant Control Only To design bioretention with underdrain for storm water pollutant control only (no flow control required), the following steps should be taken: 1. Verify that siting and design criteria have been met, including placement requirements, contributing tributary area, maximum side and finish grade slopes, and the recommended media surface area tributary ratio. 2. Calculate the DCV per Appendix B based on expected site design runoff for tributary areas. 3. Use the sizing worksheet presented in Appendix B.3 to size biofiltration BMPs. E-115 Sept.2021 BF-1 Biofiltration Conceptual Design and Sizing Approach when Storm Water Flow Control is Applicable Control of flow rates and/ or durations will typically require significant surface ponding and/ or aggregate storage volumes, and therefore the following steps should be taken prior to determination of storm water pollutant control design. Pre-development and allowable post-project flow rates and durations should be determined as discussed in Chapter 6 of the manual. 1. Verify that siting and design criteria have been met, including placement requirements, contributing tributary area, maximum side and finish grade slopes, and the recommended media surface area tributary ratio. 2. Iteratively determine the facility footprint area, surface ponding and/ or aggregate storage layer depth required to provide detention storage to reduce flow rates and durations to allowable limits. Flow rates and durations can be controlled from detention storage by altering outlet structure orifice size(s) and/ or water control levels. Multi-level orifices can be used within an outlet structure to control the full range of flows. 3. If bioretention with underdrain cannot fully provide the flow rate and duration control required by this manual, an upstream or downstream structure with significant storage volume such as an underground vault can be used to provide remaining controls. 4. After bioretention with underdrain has been designed to meet flow control requirements, calculations must be completed to verify if storm water pollutant control requirements to treat the DCV have been met. Maintenance Overview Normal Expected Maintenance. Biofiltration requires routine maintenance to: remove accumulated materials such as sediment, trash or debris; maintain vegetation health; maintain infiltration capacity of the media layer; replenish mulch; and maintain integrity of side slopes, inlets, energy dissipators, and outlets. A summary table of standard inspection and maintenance indicators is provided within this Fact Sheet. Non-Standard Maintenance or BMP Failure. If any of the following scenarios are observed, the BMP is not performing as intended to protect downstream waterways from pollution and/ or erosion. Corrective maintenance, increased inspection and maintenance, BMP replacement, or a different BMP type will be required. • The BMP is not drained between storm events. Surface ponding longer than approximately 24 hours following a storm event may be detrimental to vegetation health, and surface ponding longer than approximately 96 hours following a storm event poses a risk of vector (mosquito) breeding. Poor drainage can result from clogging of the media layer, filter course, aggregate storage layer, underdrain, or outlet structure. The specific cause of the drainage issue must be determined and corrected. • Sediment, trash, or debris accumulation greater than 25% of the surface ponding volume within one month. This means the load from the tributary drainage area is too high, reducing E-116 Sept.2021 BF-1 Biofiltration BMP function or clogging the BMP. This would require pretreatment measures within the tributary area draining to the BMP to intercept the materials. Pretreatment components, especially for sediment, will extend the life of components that are more expensive to replace such as media, filter course, and aggregate layers. • Erosion due to concentrated storm water runoff flow that is not readily corrected by adding erosion control blankets, adding stone at flow entry points, or minor re-grading to restore proper drainage according to the original plan. If the issue is not corrected by restoring the BMP to the original plan and grade, the City Engineer shall be contacted prior to any additional repairs or reconstruction. Other Special Considerations. Biofiltration is a vegetated structural BMP. Vegetated structural BMPs that are constructed in the vicinity of, or connected to, an existing jurisdictional water or wetland could inadvertently result in creation of expanded waters or wetlands. As such, vegetated structural BMPs have the potential to come under the jurisdiction of the United States Army Corps of Engineers, SDRWQCB, California Department of Fish and Wildlife, or the United States Fish and Wildlife Service. This could result in the need for specific resource agency permits and costly mitigation to perform maintenance of the structural BMP. Along with proper placement of a structural BMP, routine maintenance is key to preventing this scenario. E-117 Sept.2021 BF-1 Biofiltration Summary of Standard Inspection and Maintenance The property owner is responsible to ensure inspection, operation and maintenance of permanent BMPs on their property unless responsibility has been formally transferred to an agency, community facilities district, homeowners association, property owners association, or other special district. Maintenance frequencies listed in this table are average/ typical frequencies. Actual maintenance needs are site-specific, and maintenance may be required more frequently. Maintenance must be performed whenever needed, based on maintenance indicators presented in this table. The BMP owner is responsible for conducting regular inspections to see when maintenance is needed based on the maintenance indicators. During the first year of operation of a structural BMP, inspection is recommended at least once prior to August 31 and then monthly from September through May. Inspection during a storm event is also recommended. After the initial period of frequent inspections, the minimum inspection and maintenance frequency can be determined based on the results of the first year inspections. rfhreshold/ilndicator Maintenance Action Accumulation of sediment, litter, or debris Remove and properly dispose of • Inspect monthly. If the BMP is 25% full* accumulated materials, without damage to or more in one month, increase inspection the vegetation or compaction of the media frequency to monthly plus after every 0.1-layer. inch or larger storm event. • Remove any accumulated materials found at each ins ection. Obstructed inlet or outlet structure Clear blockage. • Inspect monthly and after every 0.5-inch or larger storm event. • Remove any accumulated materials found at each ins ection. Damage to structural components such as Repair or replace as applicable • Inspect annually. weirs, inlet or outlet structures • Maintain when needed. Poor vegetation establishment Re-seed, re-plant, or re-establish vegetation • Inspect monthly. per original plans. • Maintain when needed. E-118 Sept. 2021 -, II~ mmfA.Iiiill'eoRIIO rt Dead or diseased vegetation Overgrown vegetation 2/3 of mulch has decomposed, or mulch has been removed Erosion due to concentrated irrigation flow Erosion due to concentrated storm water runoff flow Standing water in BMP for longer than 24 hours following a storm event Surface ponding longer than approximately 24 hours following a storm event may be detrimental to vegetation health BF-1 Biofiltration Ill ffifil(;,j HI.I HiI;lri t"lli[I) I~ 'it ■¢ f!.lUif;JiJ!.lffl[;a iff~ITT~ .. ,....~ Remove dead or diseased vegetation, re-1 • Inspect monthly. seed, re-plant, or re-establish vegetation per • Maintain when needed. original plans. Mow or trim as appropriate. I • Inspect monthly. Remove decomposed fraction and top off with fresh mulch to a total depth of 3 inches. Repair/ re-seed/ re-plant eroded areas and adjust the irrigation system. Repair/re-seed/re-plant eroded areas, and make appropriate corrective measures such as adding erosion control blankets, adding stone at flow entry points, or minor re-grading to restore proper drainage according to the original plan. If the issue is not corrected by restoring the BMP to the original plan and grade, the City Engineer shall be contacted prior to any additional repairs or reconstruction. Make appropriate corrective measures such as adjusting irrigation system, removing obstructions of debris or invasive vegetation, clearing underdrains, or repairing/ replacing clogged or compacted soils. E-119 • Maintain when needed. • Inspect monthly. • Replenish mulch annually, or more frequently when needed based on inspection. • Inspect monthly. • Maintain when needed. • Inspect after every 0.5-inch or larger storm event. If erosion due to storm water flow has been observed, increase inspection frequency to after every 0.1-inch or larger storm event. • Maintain when needed. If the issue is not corrected by restoring the BMP to the original plan and grade, the City Engineer shall be contacted prior to any additional repairs or reconstruction. • Inspect monthly and after every 0.5-inch or larger storm event. If standing water is observed, increase inspection frequency to after every 0.1-inch or larger storm event. • Maintain when needed. Sept. 2021 -, II~ mmfA.Iiiill'eoRIIO rt Presence of mosquitos/larvae For images of egg rafts, larva, pupa, and adult mosquitos, see http:/ /www.mosquito.org/biology U nderdrain clogged Ill ffifil(;,j HI.I HiI;lri t"lli[I) I~ If mosquitos/larvae are observed: first, immediately remove any standing water by dispersing to nearby landscaping; second, make corrective measures as applicable to restore BMP drainage to prevent standing water. If mosquitos persist following corrective measures to remove standing water, or if the BMP design does not meet the 96-hour drawdown criteria due to release rates controlled by an orifice installed on the underdrain, the City Engineer shall be contacted to determine a solution. A different BMP type, or a Vector Management Plan prepared with concurrence from the County of San Diego Department of Environmental Health, may be required. Clear blockage. BF-1 Biofiltration 'it ■¢ f!.lUif;JiJ!.lffl[;a iff~ITT~ .. ,....~ • Inspect monthly and after every 0.5-inch or larger storm event. If mosquitos are observed, increase inspection frequency to after every 0.1-inch or larger storm event. • Maintain when needed. • Inspect if standing water is observed for longer than 24-96 hours following a storm event. • Maintain when needed. "25% full" is defined as ¼ of the depth from the design bottom elevation to the crest of the outflow structure (e.g., if the height to the outflow opening is 12 inches from the bottom elevation, then the materials must be removed when there is 3 inches of accumulation -this should be marked on the outflow structure). E-120 Sept. 2021 BF-1 Biofiltration Blank Page for 2-sided formattingpurposes E-121 Sept. 2021 SD-F Amended Soils chemical properties of the soil. Sand can be used as an amendment to improve the drainage rates of amended soils. Native soil samples may need to be analyzed by a lab to determine the specific soil amendments needed to achieve the desired infiltration, retention, and/ or filtration rates. Amending soil per these guidelines is not the same as preservation of naturally occurring topsoil and vegetation. However, amending soil will improve on-site management of storm water flow and water quality. Design Criteria and Considerations Soil amendments must meet the following design criteria and considerations. Deviations from the below criteria may be approved at the discretion of the City Engineer if appropriate: Siting and Design □ □ □ □ □ □ □ □ When mulch is used as an amendment, it is applied at grade over all planting areas to a depth of 3". When shavings or compost is used as an amendment, it is rototilled into the native soil to a minimum depth of 6" (12 inches preferred). Compost meets the criteria in Appendix F Soil amendments are free of stones, stumps, roots, glass, plastic, metal, and other deleterious materials. Mixing of soils are done prior to planting Care is taken around existing trees and shrubs to prevent root damage during construction and soil amendment application. Soil amendments are applied at the end of construction Soil amendments are compatible with planned vegetation E-43 Intent/Rationale Mulch should be applied on top and not mixed into underlying soils If soil is not completely mixed the overall benefit will be reduced. If poor quality compost is used, it will have negative impact to water quality. Large debris in amended soils can cause localized eros10n. Trash/harmful materials can result in personal injury or contamination. Soil mixing before planting results in a more homogeneous mixing and will reduce the stress on plants. Preservation of existing established vegetation is an important part of site design and erosion control. Soil amendments applied too soon in the construction process may become over compacted reducing effectiveness. The soil amendments impact the pH and salinity of the soil. Some plants have sensitive pH and/ or salinity tolerance ranges. Sept.2021 SD-F Amended Soils Conceptual Design and Sizing Approach for Site Design • When soil amendments are used a runoff factor of 0.1 can be used for DCV calculation for the amended area. • Amended soils should be used as part of SD-A Tree Well and SD-B Impervious Area Dispersion, and to increase the retention volume in other BMPs. Maintenance Annual maintenance may be required to determine reapplication requirements of amended soils. Amended soils should be regularly inspected for signs of compaction, waterlogging, and unhealthy vegetation. E-44 Sept.2021 STORM WATER QUALITY MANAGEMENT PLAN FEBRUARY 2022 NORTH COUNTY ACADEMY 27 ATTACHMENT 4 City standard Single Sheet BMP (SSBMP) Exhibit [Use the City’s standard Single Sheet BMP Plan.]