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Home My WebLink AboutSDP 2018-0007; VALLEY VIEW; STORM WATER QUALITY MANAGEMENT PLAN (SWQMP); 2020-02-27TABLE 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 1 a: DMA Exhibit Attachment 1 b: Tabular Summary of OMAs 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 4: Single Sheet BMP (SSBMP) Exhibit ( City of Carlsbad STORM WATER STANDARDS QUESTIONNAIRE Development Services Land Development Engineering 1635 Faraday Avenue (760} 602-2750 www.carlsbadca.gov E-34 I 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: VALLEY VIEW PROJECT ID: GPA 2018-0001 ADDRESS: Palmer Way, Carlsbad CA 92010 APN: 209-040-43-00 The project is (check one): !ll New Development D Redevelopment RELATED PROJ. 10; MS 2018-0007, SOP 2018-0007 The total proposed disturbed area is: 30,745 ft2(0.71 ) acres The total proposed newly created and/or replaced impervious area is: 24,234 ft2 ( 0.56 ) 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. E-34 Page 1 of 4 REV 02/16 _, --,,.,-.. ....... -· -.... ~ --z:-•·-· .-.•~----'sTEP}it ;{ ',: -. ·- TO f}E CQ"41PLETJ;D FQR ALI,; PRO~ECTS . -- 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 □ Ill 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. 11 '~ _,, ... '"'"' " ,,.,. --"''STESf2 11: "' ---·---- ,--·-~TO BE C:OMP-LETEP FO,~,.~li.L D~VELQPMENT PRQ_JECT$ ·---= To determine if your project is exempt from PDP requirements pursuant to MS4 Permit Provision E.3.b.(3), please answer the following questions: ts 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; □ Ill b) Designed and constructed to be hydraulically disconnected from paved streets or roads; c) Designed and constructed with permeable pavements or surfaces in accordance with USEPA Green Streets Quidance? 2. Retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constructed in □ Ill accordance with the US EPA Green Streets guidance? 3. Ground Mounted Solar Array that meets the criteria provided in section 1.4.2 of the BMP manual? □ Ill If you answered ·yes" to one or more of the above questions, provide discussion/justification below, then go to Step 5, mark the second box stating "my project is EXEMPT from PDP .. ." and complete applicant information. Discussion to justify exemption ( e.g. the project redeveloping existing road designed and constructed in accordance with the USEPA Green Street guidance): If you answered "no" to the above questions, your project is not exempt from PDP, go to Step 3. E-34 Page 2 of 4 REV 02/16 -":i ··-----·, '.C'i .iJj;_ ---STEP 3 • "" --- TO §.E COptlPLETl;D FOR rtt.t. Neyl 0R,~DEV~t.p PMsNT PR~JE&T~,: • ---... 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, Ill □ 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 □ Q] 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 □ Ill 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 Ill □ development project includes development on any natural slope that is twenty-five percent or Qreater. 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 Ill □ 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 surface collectively over the entire project site and supports a street, road, highway Ill □ freeway or driveway? A street, road, highway, freeway or driveway is any paved impeNious 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 □ Ill 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 □ Ill 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 □ Ill 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 □ Ill 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 □ Ill 21.203.040) If you answered "yes" to one or more of the above questions, your project is a POP. 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 statinc::i "My project is a 'STANDARD PROJECT' ... " and complete aoolicant information. E-34 Page 3 of 4 REV 02/16 SITE INFORMATION CHECKLIST '·· lP roject Summ$.rv Information -~ ·-~ C --- Project Name VALLEY VIEW Project ID GPA 2018-0001 Project Address Palmer Way, Carlsbad CA 92010 Assessor's Parcel Number(s) (APN(s)l 209-040-43-00 Project Watershed (Hydrologic Unit) Carlsbad 904 Parcel Area 6.34 Acres ( 276,170 Sauare Feet) Existing Impervious Area 0.00 Acres ( 0 Square Feet) (subset of Parcel Area) Area to be disturbed by the project 0.71 Acres ( 30,927 Square Feet) (Project Area) Project Proposed Impervious Area 0.61 Acres ( 26,759 Square Feet) (subset of Project Area) Project Proposed Pervious Area 0.10 Acres ( 4,168 Square Feet) (subset of Project Area) Note: Proposed Impervious Area + Proposed Pervious Area = Area to be Disturbed by the Project. This may be less than the Parcel Area. 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 existing drainage conveyance is natural. The existing site has a relatively flat pad along Palmer Way that drains to the north into the Agua Hedionda Creek, only approximately 0.20 acres of the site drain to the south into Palmer Way. There is no off-site contributing to the on-site basins. . . Des~riptionA of P[Qposed Site.Development anc[ Draioage eatterris Project Description / Proposed Land Use and/or Activities: The proposed construction of an office building about 1 O' higher than the street level with parking at street level, landscape areas and court yard. In addition to the proposed bio-retentions for water quality purposes and installation of a Bio-Clean curb filter insert on the existing public curb inlet at the NW side of Palmer Way. List/describe proposed impervious features of the project (e.g., buildings, roadways, parking lots, courtyards, athletic courts, other impervious features): Building, parking, walkways and trash enclosure List/describe proposed pervious features of the project (e.g., landscape areas): Landscape areas Does the project include grading and changes to site topography? ,tJYes □No Description / Additional Information: The proposed project includes minor grading for the parking lot at street level. Does the project include changes to site drainage (e.g., installation of new storm water conveyance systems)? ¢Yes □No Runoff generated drains to proposed bio-filtrations for cleansing purposes then will be conveyed to proposed underground vault for detention and hydromodification. then the runoff will be connected to the existing 36" public storm drain in Palmer Way. There is a small increase of runoff due solely to increase "C" value from vacant lot to office land, this increase in flow will not have a negative impact to the existing downstream storm drain system since it will be detained on-site to release the same amount of Q as the ex. condition. Identify whether any of the following features, activities, and/or pollutant source areas will be present (select all that apply): .ft On-site storm drain inlets D Interior floor drains and elevator shaft sump pumps □ Interior parking garages $Need for future indoor & structural pest control ri Landscape/Outdoor Pesticide Use D Pools, spas, ponds, decorative fountains, and other water features D Food service D Refuse areas D Industrial processes D Outdoor storage of equipment or materials o Vehicle and Equipment Cleaning C Vehicle/Equipment Repair and Maintenance D Fuel Dispensing Areas D Loading Docks {I Fire Sprinkler Test Water fl Miscellaneous Drain or Wash Water VJ Plazas, sidewalks, and parking lots -l_denti{icatiQn of R~ceiving Water Ppl_lutants of Concii n -,, ,,. -,,_, Describe path of storm water from the project site to the Pacific Ocean (or bay, lagoon, lake or reservoir, as applicable): The proposed runoff from the project drain to Agua Hedionda Creek then to Agua Hedionda Lagoon 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 Lagoon Toxicity Required Agua Hedionda Creek Enterococcus, Fecal Coliform, Required TDS, Heavy Metals, Toxicity ·-~ ld~_ptificc(tjQ.n of Project Site Pollytan~ '" ~---Identify pollutants anticipated from the project site based on all proposed use(s) of the site (see BMP Desion Manual Appendix 8.6): Also a Receiving Not Applicable to Anticipated from the Water Pollutant of Pollutant the Project Site Project Site Concern Sediment ✓ ✓ Nutrients ✓ ✓ Heavv Metals ✓ Oroanic Compounds Trash & Debris ✓ Oxygen Demanding ✓ Substances Oil & Grease ✓ Bacteria & Viruses Pesticides ✓ ~· ·"" -Qthe.r. Site ,Re,q-uir,.ements and ConJtralnis - 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. Due to zoning limitations and restriction we can not grade within the 40% slope areas, and the proposed site has been designed to meet the minimum width necessary without putting on risk the public safety. ,,, €)ption.~JAddJtiona.l lrifor;ijiati~jf;or..~0 ontinuatioo of Pr~vlouJ~Sections As .Nee~ed This space provided for additional information or continuation of information from previous sections as needed. 11 ( City of Carlsbad - '•· ··~ Project Name: VALLEYVIEW Project ID: GPA 2018-0001 DWG No. or Building Permit No.: - ,. - -·- STANDARD PROJECT REQUIREMENT CHECKLIST E-36 ,,, Projic~.lntormatio~. ' -· "'source Control BMPs --- - Development Services Land Development Engineering 1635 Faraday Avenue (760) 602-2750 www.carlsbadca.gov --_, ----.. -----· --~· ••, ·--- ·----·· ,c,·,·~ --··- ·~ 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. • "NIA" 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. ~ Sou_r~e Cot!trol Requir~Jnent ... "' __ ;;, ---•> -Applie<J? SC-1 Prevention of Illicit Discharges into the MS4 1iJ Yes 0 No □ NIA Discussion/justification if SC-1 not implemented: SC-2 Storm Drain Stenciling or Signage li]Yes 0 No □ NIA Discussion/justification if SC-2 not implemented: SC-3 Protect Outdoor Materials Storage Areas from Rainfall, Run-On, Runoff, and Wind □Yes □No 111 N/A Dispersal Discussion/justification if SC-3 not implemented: E-36 Page 1 of 4 Revised 09/16 -· Source Control Reauirement (continued) Applie<f? SC-4 Protect Materials Stored in Outdoor Work Areas from Rainfall, Run-On, Runoff, and □Yes 0 No Iii N/A Wind Dispersal Discussion/justification if SC-4 not implemented: SC-5 Protect Trash Storage Areas from Rainfall, Run-On, Runoff, and Wind Dispersal Iii Yes 0 No 0 NIA 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 Aooendix E.1 of BMP Manual for quidance). Iii On-site storm drain inlets Ill Yes 0 No □ N/A D Interior floor drains and elevator shaft sump pumps □Yes ONo lil N/A □ Interior parking garages □Yes D No 111 NIA Iii Need for future indoor & structural pest control □Yes D No 0 N/A Iii Landscape/Outdoor Pesticide Use D Yes 0 No 0 N/A D Pools, spas, ponds, decorative fountains, and other water features □Yes □No Ml N/A D Food service D Yes D No 111 NIA D Refuse areas □Yes 0 No 111 N/A D Industrial processes □Yes 0 No Iii N/A □ Outdoor storage of equipment or materials □Yes □No (I] N/A D Vehicle and Equipment Cleaning D Yes 0 No (I] N/A D Vehicle/Equipment Repair and Maintenance D Yes □No lil N/A D Fuel Dispensing Areas □Yes 0 No Ill N/A D Loading Docks D Yes D No lil N/A Iii Fire Sprinkler Test Water □Yes 0 No 0 NIA Iii Miscellaneous Drain or Wash Water □Yes O No 0 N/A lil Plazas, sidewalks, and parkinq lots □Yes O No 0 N/A For "Yes" answers, identify the additional BMP per Appendix E.1. Provide justification for "No" answers. E-36 PaQe 2 of 4 Revised 09/16 .... --Site Design BMPs ~ - All development projects must implement site design BMPs SD-1 through SD-8 where applicable and feasible. See Chapter 4 and Appendix E.2 thru E.6 of the BMP Design Manual (Volume 5 of City Engineering Standards) for information to implement site design BMPs shown in this checklist. Answer each category below pursuant to the following. • "Yes" means the project will implement the site design BMPs as described in Chapter 4 and/or Appendix E.2 thru E.6 of the Model BMP Design Manual. Discussion / justification is not required. • "No" means the BMPs is applicable to the project but it is not feasible to implement. Discussion/justification must be provided. Please add attachments if more space is needed. • "N/A" means the BMPs is not applicable at the project site because the project does not include the feature that is addressed by the BMPs (e.g., the project site has no existing natural areas to conserve). Discussion/justification may be provided. ,;: , .. Si{e Design Reqy!rem,!{t, '" -I . I < .:,,· ·------Applied"? SD-1 Maintain Natural DrainaQe Pathways and HvdroloQic Features I □Yes l Ill No I D NIA Discussion/justification if SD-1 not implemented: PER SOILS ENGINEER RECOMMENDATION, NO RUNOFF CAN BE DIRECTED TO THE NORTH SIDE (STEEP SLOPE) DUE TO POSSIBLE SLOPE LANDSLIDES. ALL RUNOFF FROM THE PROPOSED CONDITION WILL NEED TO BE DIRECTED TO PALMER WAY. A DETENTION BASIN IS PROVIDED ON THE PROPOSED CONDITION TO ONLY RELEASE THE SAME "Q" AS THE EXISITNG CONDITION. SD-2 Conserve Natural Areas, Soils, and Vegetation I lil Yes I D No ID N/A Discussion/justification if SD-2 not implemented: WHERE POSSIBLE. SD-3 Minimize Impervious Area I lil Yes I D No ID NIA Discussion/justification if SD-3 not implemented: SD-4 Minimize Soil Compaction I □Yes I lil No I D NIA Discussion/justification if SD-4 not implemented: DUE TO SLOPE STABILITY CONSTRAINTS. SD~s Impervious Area Dispersion I □Yes I lil No I D NIA Discussion/justification if SD-5 not implemented: DUE TO SLOPE STABILITY CONSTRAINTS. E-36 Paoe 3 of 4 Revised 09/16 Site.Design Requirement (continued) c,rl I -. Applied? -~ ~ SD-6 Runoff Collection I (j] Yes I D No I D N/A Discussion/justification if SD-6 not implemented: SD-7 Landscaping with Native or Drought Tolerant Species I Ill Yes I 0 No I D NIA Discussion/justification if SD-7 not implemented: SD-8 HarvestinQ and UsinQ Precipitation I □Yes I Ill No I D NIA Discussion/justification if SD-8 not implemented: DUE TO SLOPE STABILITY CONSTRAINTS. E-36 Paae 4 of 4 Revised 09/16 SUMMARY OF PDP STRUCTURAL BMPS _ ~· ~DP 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 proposed project consist's of 2 proposed bio-filtration basins where the stormwater will be treated, addressing water quality requirements before exiting the site. At a different location an underground vault will be provided for hydromodification and detention. Regarding the Management of Critical Coarse Sediment Yield Areas the proposed development is not within the CCSYA This SWQMP has shown LID design, source control and treatment BM P's that should satisfy the requirements identified in the order and standards by treating and mitigating runoff to the most extent practicable, and it is anticipated that the downstream water will not be affected by the proposed development. The bio-retention basi ns will be lined and have a perforated storm drain system, as [Continue on next page as necessary.] [Continued from previous page -This page is reserved for continuation of description of general strategy for structural BMP implementation at the site.) recommended by the Soils Engineer to prevent landslides due to the proximity of the steep slopes of more than 100' vertically. Also, in addition to the Self Treatment Green Street Design for the new meandering public sidewalk we are installing a Bio-clean inlet filter insert for treatment purposes. Filter insert will be installed by the project property owner and maintained by the City of Carlsbad. Structural BMP Silmmafy Information [Copy this page 11s needed to provide information for Etach individual proposed _ structuraliBMP] ~ Structural BMP ID No. BMP-1 DWG Sheet No. Type of structural BMP: O Retention by harvest and use (HU-1) D Retention by infiltration basin (INF-1 ) D Retention by bioretention (INF-2) D Retention by permeable pavement (INF-3) D Partial retention by biofiltration with partial retention (PR-1) q'Biofiltration (BF-1) D 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) D Detention pond or vault for hydromodification management D Other (describe in discussion section below) Purpose: ¢'Pollutant control only D Hydromodification control only D Combined pollutant control and hydromodification control D Pre-treatment/forebay for another structural BMP D Other (describe in discussion section below) Discussion (as needed): The bio-filtration basin 1 will be receiving surface runoff from the uncovered parking stalls, hardscape and driveway areas to be treated for pollutants generated on the site. Then the runoff will be directed o the proposed vault that will take care of the hydro-modification and detention control after confluencing with the runoff from basin 2. The proposed vault will have an orifice control to release equal or less runoff than the existing condition, see hydrology and hydraulic report for additional information. ' •• ,. Str.uctural BMP Summary Information 11 [Copy tfiis pag~ as needed to provide information for each individual proposed ·~ structural BMP]. ~ _ Structural BMP ID No. BMP-2 DWG Sheet No. Type of structural BMP: D Retention by harvest and use (H U-1) '.J Retention by infiltration basin (INF-1) '.J Retention by bioretention (INF-2) D Retention by permeable pavement (INF-3) D Partial retention by biofiltration with partial retention (PR-1) q'Biofiltration (BF-1) D 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) D Detention pond or vault for hydromodification management D Other (describe in discussion section below) Purpose: ¢'Pollutant control only D Hydromodification control only D Combined pollutant control and hydromodification control D Pre-treatment/forebay for another structural BMP D Other (describe in discussion section below) Discussion (as needed): The bio-filtration basin 2 will be receiving runoff from the building roof that covers part of the parking and driveway area, the downspouts will be directed to basin 2 for pollutant control. Then the runoff will be directed o the proposed vault that will take care of the hydro-modification and detention control after confluencing with the runoff from basin 1. The proposed vault will have an orifice control to release equal or less runoff than the existing condition, see hydrology and hydraulic report for additional information. • 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 Contents Checklist Senuence Attachment 1 a OMA Exhibit (Required) ' ~ Included See DMA Exhibit Checklist on the back of this Attachment cover sheet. (24"x36" Exhibit typically required) Attachment 1 b Tabular Summary of OMAs Showing I~ Included on OMA Exhibit in OMA ID matching OMA Exhibit, OMA Attachment 1 a Attachment 1 c Attachment 1 d Area, and OMA Type (Required)* Included as Attachment 1 b. separate from OMA Exhibit *Provide table in this Attachment OR on OMA Exhibit in Attachment 1a Form 1-7, Harvest and Use Feasibility I .fJ Included Screening Checklist (Required unless __ Not included because the entire the entire project will use infiltration project will use infiltration BMPs BMPs) Refer to Appendix B.3-1 of the BMP Design Manual to complete Form I-7. Form 1-8, 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 1-8. per soils engineer recommendations no infiltration is allowed on this project _ Included C Not included because the entire project will use harvest and use BMPs per soils engineer recommendations no infiltration is allowed on this project. Attachment 1e Pollutant Control BMP Design ;t'lncluded Worksheets / Calculations (Required) Refer to Appendices B and E of the BMP Design Manual for structural pollutant control BMP design guidelines - Use this checklist to ensure the required information has been included on the DMA The OMA Exhibit must identify: .l"Underlying hydrologic soil group {/J Approximate depth to groundwater Exhibit: ~ Existing natural hydrologic features (watercourses, seeps, springs, wetlands) $ Critical coarse sediment yield areas to be protected (if present) ,/1 Existing topography and impervious areas JJ Existing and proposed site drainage network and connections to drainage offsite ,t Proposed grading $ Proposed impervious features .t. Proposed design features and surface treatments used to minimize imperviousness ~Drainage management area (OMA) boundaries, OMA ID numbers, and OMA areas (square footage or acreage), and OMA type (i.e., drains to BMP, self-retaining, or self-mitigating) /le Structural BMPs (identify location and type of BMP) Attachment 1 c Appendix I: Forms and Checklists Harvest and Use Feasibility Checklist Form 1-7 1. Is there a demand for ha.n·esred water (check all clrnt apply) ar cl1e project site rhat is relrnbly present du1-:ing the ,,·er seiison? IZl ·1 oiler and urinal flushu1g (;21 Landscape 1rngation O Other: ______ _ 2. If there is a demand: estimate the anticipated a\·erage wet season demand 0Yer a period of 36 hours. Guidance for planrung le\'el demand calculatiom for toiler/urinal flushing and landscape u-rigarion is pro,~ided in Section B.3.2. Land type (Table B 3-1) = Office T&U = ~ • 55 persons x 1.5 days = 84 93 day 7.48 g;il/ft3 Total Use per employee and v1sttor (Table B 3-1) = 7 • 1 1 = 7 7 Plant water use (Table B 3·2) " Moderate 36hr lmga11on demand (Table B 3-3) = 1 470 gal/ac per 36 hr penod Total employee and 111s11ors = 55 persons LI = 0.53 acres" 1,470 gal • 0.53 • 1.5 day= 1S6.24 day acre 7 48 gal/ft3 landscape area = 23 082 sf = o 53 acres 3. Calculate the DC\" using worksheet B-2.1. Total 36hr Demand= T&U +LI= 84.93 + 156.24 = 0 31 DC\"= __ 1_n ___ (cubic fcer) 3a. Is the 36 hour demand greater dum or e9ual co the DC\'? Ye~ / ✓No ~ -0. HarYest an<l use appears to be fea$ible. Conducr more detailed e,·aluacion and sizing calculation:; to confirm Lime D CV can be used at an adequate rare to meet drnwdown criteria. ~ 777 3b. Is the 36 hour demand greater than 0.25DC\' bur le~s than the full DC\? Yes / ✓ No ~ t Har\'est and use ma, be feasible. Conduce more derailed en1luauon and s1zmg calculations to determine feasibility. Harvest and use may only be able to be used for a porrion of Lhe site. or (optionally) the srornge may need co be upsized to meet long rerm capture rargecs while dnuning m longer than 36 hours. ls han·esr and use feasible based on further e,·aluation? Yes, refer to .\ppcndix E to select and size hat-Yest and u~e BI\IP~. o. select alremate Bi\£Ps. I-26 3c. Is the 36 hour demand le:::: ilian 0.2SDC\T? ✓ Yes .0. I Ian-est and use 1s considered to be infea~ible. February 2016 Attachment 1 c Appendix I: Forms and Checklists Harvest and Use Feasibility Checklist Form 1-7 I. Is there a demand for h:uyested water (check all that apply) at the project site that ts reliably presenr dunng rhe ,vet season? QI Toilet and urinal fluslung QI J .and~capc 1.rt1gaaon O Other: _____ _ 2. If there is a demand: estimate the anticipated an·rage wet season demand o,·er a period of 36 hours. (1uidance for planning level demand calculations for rotlet/urinal flushing and land~cape imgaoon is provided 111 Secuon B.3.2. Land type (Table B 3-1)"' Office T&U = 7 7 gal • 55 persons x 1.5 days = 84 93 dav 7 48 gal/ft3 Total Use per employee and visitor (Table B 3-1) = 7 • 1 1 = 7 7 Plant water use (Table B 3·2) = Moderate 36hr lrngauon demand (Table B 3-3) = 1 470 gal/ac per 36 hr penod Total employee and v,s,tors = 55 persons LI= 0 53 acres= 1,470 gal• 0.53 • 1.5 day= 156.24 day-acre 7 48 gal/ft3 Landscape area= 23.082 sf= 0.53 acres 3. Calculate the DC\' usmg worksheet B-2.1. DC\'= __ 3_84 ___ (cubtc feet) Total 36hr Demand = T&U + ll = 84.93 + 156.24 = 0.63 ocv 384 3a. ls the 36 hour demand greater than or equal to the DC\'? Ye::: / ✓No ¢ JJ. I lar,est and use appears to be foasiblc. Conduct more detailed e\'aluauon and stzmg calculations co confirm that DC\' can be used at an adequate rate to meet drawdown criteria. 3b. fa the 36 hour demand greater than 0.25DC\' but less rhan the full DCV? Yes / ✓ l\:o ~ D. H:uTcst and use ma,· be feasible. Conduct more detailed evaluation and sizing calculaaons ro deremune feasibility. H:unst and use may only be able co be used for :i poraon of the site, or (opuonally) the srorage may need robe upsized to meet long term caprure targets while draining in longer than 36 hours. Is han·c:.t and use fea:.ible based on further e,·aluation? Yes. refer to \ppendix L to select and size hru,·est and u~e B:'-rPs. :'\:o. select alrematc Bt\fPs. 1-26 3c. Is the 36 hour demand less than 0.25DC\'? ✓ Yes l). Han-est and use is considered to be infeasible. February 2016 Attachment ld Appendix I: Forms and Checklists C . . f I fil • • F .b .li C d . . Form 1-8 ategonzauon o n trauon east 1 ty on 1t10n Part 1-Full InftJtration Feasjbiliey Screenioe 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 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 Appendi.x C.2 and .-\ppendix D. Yes No X Provide basis: Per Geotechnical Report dated 23 February 2018, prepared by Geotechnical Exploration Inc. any infiltration of storm water at the site would result in an unmitigateable geotechnical hazard with regard to the stability of the steep natural slopes which descend down from the building development area along the north and east and therefore should not be allowed. Summarize findings of studies; provide reference ro studies, calculations, maps, data sources, ere. Provide narrative discussion of study/ data source applicability. 2 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of geotecbnical 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: Per Geotechnical Report dated 23 February 2018, prepared by Geotechnical Exploration Inc. any infiltration of storm water at the site would result in an unmitigateable geotechnical hazard with regard to the stability of the steep natural slopes which descend down from the building development area along the north and east and therefore should not be allowed. X Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide oarrarive discussion of study/ data source applicability. 1-27 February 2016 Appendix I: Forms and Checklists ~-. ~ ' .., .. . __ _ Form 1-8 Page 2 of 4 Criteria 3 Screening Question 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. Yes Provide basis: No infiltration is allowed, see above statement per Geotechnical Report recommendations No X Summarize findings of studies; provide reference ro studies. calculations, maps, data sources, ere. Provide narrative discussion of study/data source applicability. 4 Can infiltration g reater 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. PrO\.;de basis: No infiltration is allowed, see above statement per Geotechnical Report recommendations X Swnmarize findings of studies; provide reference ro smilies, calculations, maps, data sources, ere. Provide narrative discussion of studr/dara source apphcability. Part 1 Result * If all answers to rows 1 -4 are "Yes" a full infilrration design is potentially feasible. The feasibility screening category is Full Infiltration If any answer from row 1-4 is "No", infiltration may be possible ro some extent but would not generally be feasible or desirable to achieve a "full infiltration" design. Proceed to Part 2 "To be completed usmg gathered site information and besr professional Judgment cons1deong the de6nit:1on of MEP Ill the MS4 Permit. Additional testing and/or studies may be required by Agency/Jurisdictions to substantiate findings 1-28 February 2016 Appendix I: Forms and Checklists -... • • •• \ ---•..;,,;.4; ~ -I'!'"• .... • ... ·-... -'L 1 .,. • • -" ·rForm 1-8 Page· 3 of 4· Part 2 -Partial Infiltration vs. No Infilmtion Feasibility Screenine Criteria Would infiltration of water in any appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated? Criteria 5 Screening Question Do soil and geologic conditions allow for infiltration in any appreciable rate or volume? The response to tlus Screening Question shall be based on a comprehensive evaluation of the factors presented in .-\ppeod.i.-..i: C.2 and .-\ppendix D . Yes Provide basis: No infiltration is allowed, see above statement per Geotechnical Report recommendations No X 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 mmgate low infiltration rates. 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 Q uestion shall be based on a comprehensive e,·aluation of the factors presented in Appendix C.2. Provide basis: No infiltration is allowed, see above statement per Geotechnical Report recommendations X 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 nor feasible to mitigate low infiltration rates. 1-29 February 2016 Appendix I: Forms and Checklists -. -.... ~ •i .... .,..--... ,. -·--• .~ .:-!' ·~ • Form 1-8 Page 4 of 4 •-• 1 --•: - Cateria 7 Screening Question 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 rhis Screening Question shall be based on a comprehensive evaluation of rhe factors presented in Appendix C.3. Yes Provide basis: No infiltration is allowed, see above statement per Geotechnical Report recommendations No X Summarize findmgs of studies; provide reference to srudies, calculations, maps, data sources, etc. Provide narrative discussion of srudy/data source applicability and why it was not feasible ro mitigate low infiltration rates. 8 Can infiltration be allowed without vio lating downstream water rights? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3. X Pro,ide basis: No infiltration is allowed, see above statement per Geotechnical Report recommendations 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 u,filtracion 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 categorJ 1s No Infiltration . ... To be completed using gathered site information and best professional judgment considering the defininon of MEP in the ~1S4 Permit .. -\ddinonal resting and/or studies may be required by Agencr/Jurisdictions to substantiate findings 1-30 February 2016 ATTACHMENT 2 BACKUP FOR PDP HYDROMOOIFICATION CONTROL MEASURES [This is the cover sheet for Attachment 2.] Indicate which Items are Included behind this cover sheet: Attachment Contents Checklist Seauence Attachment 2a Hydromodification Management .(Included Exhibit (Required) See Hydromodification Management Exhibit Checklist on the back of this Attachment cover sheet. Attachment 2b Management of Critical Coarse .fJ Exhibit showing project drainage Sediment Yield Areas (WMAA Exhibit boundaries marked on WMM is required, additional analyses are Critical Coarse Sediment Yield optional) Area Map (Required) See Section 6.2 of the BMP Design Optional analyses for Critical Coarse Manual. Sediment Yield Area Determination D 6.2.1 Verification of Geomorphic Landscape Units Onsite □ 6.2.2 Downstream Systems Sensitivity to Coarse Sediment O 6.2.3 Optional Additional Analysis of Potential Critical Coarse Sediment Yield Areas Onsite Attachment 2c Geomorphic Assessment of Receiving ,i!Not performed Channels (Optional) C Included See Section 6.3.4 of the BMP Design Manual. Attachment 2d Flow Control Facility Design and ,jll Included Structural BMP Drawdown Calculations (Required) See Chapter 6 and Appendix G of the BMP Desian Manual Use this checklist to ensure the required infonnation 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) /J Existing topography ./J Existing and proposed site drainage network and connections to drainage offsite ;if 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) TO: FROM: DATE: RE: R·E·C TECHNICAL MEMORANDUM Land Development, LLC Luis Parra, PhD, PE, CPSWQ, ToR, D.WRE. David Edwards, PE. April 6, 2018 Summary of SWMM Modeling for Hydromodification Compliance for Valley View, Carlsbad, CA. INTRODUCTION This memorandum summarizes the approach used to model the proposed commercial site in the City of Carlsbad using the Environmental Protection Agency (EPA) Storm Water Management Model 5.0 {SWMM). SWMM models were prepared for the pre and post-developed conditions at the site in order to determine if the proposed HMP facilities have sufficient volume to meet Order R9-2013-001 requirements of the California Regional Water Quality Control Board San Diego Region (SDRWQCB), as explained in the Final Hydromodification Management Plan (HMP), dated March 2011, prepared for the County of San Diego by Brown and Caldwell. SWMM MODEL DEVELOPMENT The Valley View project site consists of a proposed commercial development. Two (2) SWMM models were prepared for this study: the first for the pre-developed and the second for the post-developed conditions. The project site drains to two (2) Points of Compliance {POC) located to the north and south of the project site. Per Section Gl.2 in Appendix G of the 2016 City of Carlsbad BMP Design Manual, the EPA SWMM model was used to perform the continuous hydrologic simulation. For both SWMM models, flow duration curves were prepared to determine if the proposed HMP facilities are sufficient to meet the current HMP requirements. The inputs required to develop SWMM models include rainfall, watershed characteristics, and BMP configurations. The Oceanside Gage from the Project Clean Water website was used for this study, since it is the most representative of the project site precipitation due to elevation and proximity to the project site. Per the California Irrigation Management Information System "Reference Evaporation Zones" (CIMIS ETo Zone Map}, the project site is located within the Zone 4 Evapotranspiration Area. Thus evapotranspiration vales for the site were modeled using Zone 4 average monthly values from Table G.1-1 from the 2016 BMP Design Manual. Per the site specific geotechnical investigation, the project site is situated upon Class D soils. Soils have been assumed to be uncompacted in the existing condition to represent the current natural condition of the site, while fully compacted in the post developed conditions. Other SWMM inputs for the subareas are discussed in the appendices to this document, where the selection of parameters is explained in detail. Valley View HMP Memo April 6, 2018 HMP MODELING PRE DEVELOPED CONDITIONS In current existing conditions, runoff from the development site discharges via overland flow to two (2) points of compliance located at the northern boundary of the project site and the adjacent curb and gutter to the south of the project site. In developed conditions, all runoff from the project site is drained to the southern curb and gutter due to the fact the geotechnical consultant had concerns in regards to draining concentrated flows to the northern discharge location. As such, given that no developed flow will drain to the northern POC, only the southern POC will be analyzed for this study. Table 1 below illustrates the southern POC pre-developed area tributary and impervious percentage accordingly. TABLE 1-SUMMARY OF PRE-DEVELOPED CONDITIONS POC .OMA Tributary Area, A Impervious Percentage, -(Ac) lp(l) POC-1 DMA-1-D 0.2 0% TOTAL .. 0.2 .. Notes: (1)-Per the 2013 RWQCB permit, existing condition impervious surfaces are not to be accounted for in existing conditions analysis. DEVELOPED CONDITIONS In developed conditions, runoff from the project site is drained to three (3) onsite receiving HMP detention facilities. Once flows are routed via the proposed detention basins, onsite flows are then discharged to the adjacent storm drain at POC-1. Table 2 summarizes the post-developed area and impervious percentage accordingly. TABLE 2 -SUMMARY OF POST-DEVELOPED CONDITIONS " Tributary Area, A Impervious POC OMA .. . -(Ac) Percentage, Ip DMA·l-D 0.419 85.44% DMA-BR-1 0.013315 0.0% POC-1 DMA-2-D 0.218 91.18% DMA-BR-2 0.013659 0.0% DMA-DEMIN 0.052 47.98% TOTAL --0.715 N/A Runoff from the developed project site drains to two (2) surface LID bio-filtration BMP facilities prior to then discharging to an underground detention vault for additional HMP storage. The two (2) LID treatment basins have a surface ponding depth of 0.6 feet and 1 foot which then overflows into the underground detention vault. Flows will discharge from the surface basins via a low flow orifice outlet within the gravel layer or the riser outlet structure to the underground detention basin. The riser structure will act as a spillway such that peak flows can be safely discharged to the receiving POC. 2 W.0.7006-24 Valley View HMP Memo April 6, 2018 Beneath the LID basins' invert lays the proposed LID biofiltration portion of the drainage facility. This portion of the basin is comprised of a 3-inch layer of mulch, an 18-inch layer of amended soil (a highly sandy, organic rich composite with an infiltration capacity of at least 5 inches/hr), a 6-inch sand and pea gravel filter layer and an 12-inch layer of gravel for additional detention and to accommodate the French drain system. These systems are to be located beneath the biofiltration layers to intercept treated storm water and convey these flows to a small diameter lower outlet orifice. Once flows have been routed by the outlet structure, flows are then drained to the receiving underground detention vault. The underground detention vault has a width of 20 feet, length of 200 feet and a depth of 4 feet, providing additional HMP detention volume. Flows from the surface LID bio-filtration basins discharge to this receiving vault for additional routing, draining from the vault via an outlet structure constructed at the discharge location of the basin. Water Quality BMP Sizing It is assumed all storm water quality requirements for the project will be met by the BMPs included within the site design. However, detailed water quality requirements are not discussed within this technical memo. The BMPs have been designed in accordance with City of Carlsbad smng criteria. For further information in regards to storm water quality requirements for the project (including sizing and drawdown) please refer to the site specific Storm Water Quality Management Plan (SWQMP). BMP MODELING FOR HMP PURPOSES Modeling of dual purpose Water Quality/HMP BMPs Two (2) HMP LID BMP biofiltration basins with an underground overflow detention basin are proposed for hydromodification conformance for the project site. Tables 3, 4 and 5 illustrate the dimensions required for HMP compliance according to the SWMM model that was undertaken for the project. TABLE 3 -SUMMARY OF DEVELOPED HMP LID BMPS: BMP BR-1 BR-2 DIMENSIONS '' . Tributary BMP Gravel Area (Ac) Area<1> Depth12l LowerOrlf. Depth Riser Weir Perimeter Total Surface (tt2) (in) D (in)13l Invert (ft)14' Lemrth1s' (ft) Depth16l (ft) 0.419 580 18 0.5 0.5 8 0.6 0.218 595 18 0.5 0.8 8 1.0 Notes: (1): Area of amended soil equal to area of gravel (2): Includes filter gravel layer and 3-lnch dead storage layer beneath French Drain. (3): Diameter of orifice in gravel layer with invert at bottom of layer; tied with hydromod min threshold (0.1·~). (4): Depth of ponding beneath spillway. (S}: Overflow length of riser box opening (2' K 2' = 8') (6): Total surface depth of BMP from top crest elevation to surface invert. 3 W.O.7006-24 Valley View HMP Memo April 6, 2018 TABLE 4-SUMMARY OF HMP DETENTION VAULT DIMENSIONS BMP ' Tributary Vault Vault Area (Ac) Area 141 Depth Storage Volume (ft2) (ft) (ft3) Basin 1 0.663 4,000 4.0 16,000 TABLE 5 -SUMMARY OF RISER DETAILS: BASIN Lower Orifice Lower Slot Diam. Number Elev. 111 (ft) Width Height Elev.111 (in) -(ft) (ft) (ft) BR-1 NA ---NA --- BR-2 NA ---NA --- DET BASIN 0.4 1 0.0 0.75 0.083 2.9 Notes: (1): Invert of the basins assumed to be 0.0 elevation. FLOW DURATION CURVE COMPARISON Emergency Weir Width Elev .111 (ft) (ft) - 8 0.5 8 0.8 4 3.5 The Flow Duration Curve (FDC) for the site was compared at the POC by exporting the hourly runoff time series results from SWMM to a spreadsheet. Oi and 0 10 were determined with a partial duration statistical analysis of the runoff time series in an Excel spreadsheet using the Cunnane plotting position method (which is the preferred plotting methodology in the HMP Permit). As the SWMM Model includes a statistical analysis based on the Weibull Plotting Position Method, the Weibull Method was also used within the spreadsheet to ensure that the results were similar to those obtained by the SWMM Model. The range between 10% of Oi and 010 was divided into 100 equal time intervals; the number of hours that each flow rate was exceeded was counted from the hourly series. Additionally, the intermediate peaks with a return period "i" were obtained (Q; with i=3 to 9). For the purpose of the plot, the values were presented as percentage of time exceeded for each flow rate. FDC comparison at the POC is illustrated in Figure 1 in both normal and logarithmic scale. Attachment 5 provides a detailed drainage exhibit for the post-developed condition. As can be seen in Figure 1, the FDC for the proposed condition wit h the HMP BMPs is within 110% of the curve for the existing condition in both peak flows and durations. The additional runoff volume generated from developing the site will be released t o the existing point of discharge at a flow rate below the 10% Q2 lower threshold for POC-1. Additionally, the project will also not increase peak flow rates between the Oi and the 0 10, as shown in the peak flow tables in Attachment 1. 4 W.0.7006-24 Valley View HMP Memo April 6, 2018 Discussion of the Manning's coefficient (Pervious Areas) for Pre and Post-Development Conditions Typically the Manning's coefficient is selected as n = 0.10 for pervious areas and n = 0.012 for impervious areas. Due to the complexity of the model carried out in pre and post-development conditions, a more accurate value of the Manning's coefficient for pervious areas has been chosen. Taken into consideration the "Handouts on Supplemental Guidance-Handout #2: Manning's "n" Values for Overland Flow Using EPA SWMM V.5" by the County of San Diego (Reference [6]) a more accurate value of n = 0.05 has been selected (see Table 1 of Reference [6] included in Attachment 7). An average n value between pasture and shrubs and bushes (which is also the value of dense grass) has been selected per the reference cited, for light rain (<0,8 in/hr) as more than 99% of the rainfall has been measured with this intensity. BMP DRAWDOWN TIME , To ensure compliance with the 96 hour drawdown requirements per Section 6.4.6 of the Final HMP dated March 2011 for surface detention basins, drawdown calculations are provided in Attachment 4 of this report. Per the drawdown calculations, the drying time of the basins area as follows; BMP 1 is 11.4 hours and BMP 2 is 20.3 hours satisfying drawdown time requirements. SUMMARY This study has demonstrated that the proposed HMP BMPs provided for the Valley View project site is sufficient to meet the current HMP criteria if the cross-section areas and volumes recommended within this technical memorandum, and the respective orifice and outlet structure are incorporated as specified within the proposed project site. KEY ASSUMPTIONS 1. Type D Soils is representative of the existing condition site. ATTACHMENTS 1. Ci to Q10 Comparison Tables 2. FDC Plots (log and natural "x" scale) and Flow Duration Table. 3. List of the "n" largest Peaks: Pre-Development and Post-Development Conditions 4. Elevations vs. Discharge Curves to be used in SWMM 5. Pre & Post Development Maps, Project plan and section sketches 6. SWMM Input Data in Input Format (Existing and Proposed Models) 7. SWMM Screens and Explanation of Significant Variables 8. Geotechnical Documentation 9. Summary files from the SWMM Model 5 W.0.7006-24 Valley View HMP Memo April 6, 2018 REFERENCES [1] -"Review and Analysis of Son Diego County Hydromodificotion Management Pion (HMP}: Assumptions, Criteria, Methods, & Modeling Tools -Prepared for the Cities of Son Marcos, Oceanside & Vista", May 2012, TRW Engineering. [2] -"Final Hydromodificotion Management Pion (HMP) prepared for the County of Son Diego", March 2011, Brown and Caldwell. [3] -Order R9-20013-001, California Regional Water Quality Control Board San Diego Region (SDRWQCB). [4] -"Handbook of Hydrology", David R. Maidment, Editor in Chief. 1992, McGraw Hill. [SJ-"City of Carlsbad BMP Design Monuof', February 2016. (6] ~ "Improving Accuracy in Continuous Hydro/ogle Modeling: Guidance for Selecting Pervious Overland Flow Manning's n Values in the Son Diego Region", 2016, TRW Engineering. 6 W.0.7006-24 Valley View HMP Memo April 6, 2018 ATTACHMENT 1. 0 2 to 010 Comparison Table -POC 1 Return Period Existing Condition (cfs) 2-year 0.107 3-year 0.116 4-year 0.133 5-year 0.137 6-year 0.138 7-year 0.147 8-year 0.151 9-year 0.158 10-year 0.172 8 Mitigated Condition (cfs) Reduction, Exist • Mitigated (cfs) 0.006 0.101 0.010 0.106 0.012 0.121 ' 0.013 0.124 0.014 0.125 0.017 0.131 0.017 0.133 0.018 0.140 0.019 0.153 W.Q.7006-24 ATTACHMENT 2 FLOW DURATION CURVE ANALYSIS 1) Flow duration curve shall not exceed the existing conditions by more than 10%, neither in peak flow nor duration. The figures on the following pages illustrate that the flow duration curve in post-development conditions after the proposed BMP is below the existing flow duration curve. The flow duration curve table following the curve shows that if the interval 0.10°'2 -Q10 is divided in 100 sub- intervals, then a) the post development divided by pre-development durations are never larger than 110% (the permit allows up to 110%); and b) there are no more than 10 intervals in the range 101%-110% which would imply an excess over 10% of the length of the curve (the permit allows less than 10% of excesses measured as 101-110%). Consequently, the design passes the hydromodification test. It is important to note that the flow duration curve can be expressed in the "x" axis as percentage of time, hours per year, total number of hours, or any other similar time variable. As those variables only differ by a multiplying constant, their plot in logarithmic scale is going to look exactly the same, and compliance can be observed regardless of the variable selected. However, in order to satisfy the City of Carlsbad HMP example, % of time exceeded is the variable of choice in the flow duration curve. The selection of a logarithmic scale in lieu of the normal scale is preferred, as differences between the pre-development and post-development curves can be seen more clearly in the entire range of analysis. Both graphics are presented just to prove the difference. In terms of the "y" axis, the peak flow value is the variable of choice. As an additional analysis performed by REC, not only the range of analysis is clearly depicted (10% of 0 2 to 0 10) but also all intermediate flows are shown (Oi, 03, ~, Os, CG, 01, Qg and 0 9) in order to demonstrate compliance at any range Ox-Ox+1. It must be pointed out that one of the limitations of both the SWMM and SOHM models is that the intermediate analysis is not performed (to obtain Q; from i = 2 to 10). REC performed the analysis using the Cunnane Plotting position Method (the preferred method in the HMP permit) from the "n" largest independent peak flows obtained from the continuous time series. The largest "n" peak flows are attached in this appendix, as well as the values of O, with a return period "i", from i=2 to 10. The Q; values are also added into the flow-duration plot. Flow Duration Curve Data for Valley View POC-1 , City of Carlsbad CA Q2 = 0.11 ds Fraction 10 % QlO = 0.17 cfs Step = 0.0016 ds Count= 499679 hours 57.00 years Existing Condition Detention Optimized Pass or Interval Q (cfs) Hours> Q %time Hours>Q %time Post/Pre Fail? 1 0.011 977 l.96E-01 1016 2.03E-01 104.0% Pass 2 0.012 855 l.71E-01 833 l.67E-01 97% Pass 3 0.014 803 1.61E-01 668 1.34E-01 83% Pass 4 0.016 725 1.45E-01 408 8.17E-02 56% Pass 5 0.017 677 1.35E-01 300 6.00E-02 44% Pass 6 0.019 647 1.29E-01 238 4. 76E-02 37% Pass 7 0.020 608 1.22E-01 189 3.78E-02 31% Pass 8 0.022 570 1.14E-01 158 3.16E-02 28% Pass 9 0.024 552 1.lOE-01 133 2.66E-02 24% Pass 10 0.025 498 9.97E-02 114 2.28E-02 23% Pass 11 0.027 483 9.67E-02 103 2.06E-02 21% Pass 12 0.029 444 8.89E-02 92 l.84E-02 21% Pass 13 0.030 403 8.07E-02 84 1.68E-02 21% Pass 14 0.032 374 7.48E-02 79 1.58E-02 21% Pass 15 0.034 340 6.80E-02 70 l.40E-02 21% Pass 16 0.035 310 6.20E-02 66 l.32E-02 21% Pass 17 0.037 301 6.02E-02 58 l.16E-02 19% Pass 18 0.038 290 5.80E-02 56 1.12E-02 19% Pass 19 0.040 278 5.56E-02 49 9.81E-03 18% Pass 20 0.042 271 5.42E-02 43 8.61E-03 16% Pass 21 0.043 243 4.86E-02 40 8.0lE-03 16% Pass 22 0.045 234 4.68E-02 38 7.60E-03 16% Pass 23 0.047 221 4.42E-02 37 7.40E-03 17% Pass 24 0.048 205 4.lOE-02 36 7.20E-03 18% Pass 25 0.050 193 3.86E-02 33 6.60E-03 17% Pass 26 0.051 175 3.50E-02 31 6.20E-03 18% Pass 27 0.053 151 3.02E-02 30 6.00E-03 20% Pass 28 0.055 142 2.84E-02 28 5.60E-03 20% Pass 29 0.056 131 2.62E-02 25 5.00E-03 19% Pass 30 0.058 127 2.54E-02 25 5.00E-03 20% Pass 31 0.060 123 2.46E-02 23 4.60E-03 19% Pass 32 0.061 118 2.36E-02 22 4.40E-03 19% Pass 33 0.063 117 2.34E-02 22 4.40E-03 19% Pass 34 0.064 110 2.20E-02 21 4.20E-03 19% Pass 35 0.066 103 2.06E-02 20 4.00E-03 19% Pass 36 0.068 98 l.96E-02 19 3.80E-03 19% Pass 37 0.069 91 1.82E-02 19 3.80E-03 21% Pass 38 0.071 84 1.68E-02 19 3.80E-03 23% Pass Exist.ing Condition Detention Optimized Pass or Interval Q (ds) Hours> Q %time Hours>Q %time Post/Pre Fail? 39 0.073 76 1.52E-02 19 3.80E-03 25% Pass 40 0.074 69 1.38E-02 19 3.80E-03 28% Pass 41 0.076 66 1.32E-02 19 3.80E-03 29% Pass 42 0.077 64 l.28E-02 19 3.80E-03 30% Pass 43 0.079 61 1.22E-02 17 3.40E-03 28% Pass 44 0.081 61 1.22E-02 14 2.80E-03 23% Pass 45 0.082 58 1.16E-02 14 2.80E-03 24% Pass 46 0.084 57 1.14E-02 14 2.80E-03 25% Pass 47 0.086 51 1.02E-02 14 2.80E-03 27% Pass 48 0.087 50 1.00E-02 14 2.80E-03 28% Pass 49 0.089 48 9.61E-03 13 2.60E-03 27% Pass 50 0.091 42 8.41E-03 13 2.60E-03 31% Pass 51 0.092 42 8.41E-03 13 2.60E-03 31% Pass 52 0.094 42 8.41E-03 13 2.60E-03 31% Pass 53 0.095 40 8.0lE-03 13 2.60E-03 33% Pass 54 0.097 40 8.0lE-03 13 2.60E-03 33% Pass 55 0.099 40 8.0lE-03 12 2.40E-03 30% Pass 56 0.100 38 7.60E-03 11 2.20E-03 29% Pass 57 0.102 38 7.60E-03 11 2.20E-03 29% Pass 58 0.104 36 7.20E-03 11 2.20E-03 31% Pass 59 0.105 36 7.20E-03 10 2.00E-03 28% Pass 60 0.107 33 6.60E-03 10 2.00E-03 30% Pass 61 0.108 31 6.20E-03 10 2.00E-03 32% Pass 62 0.110 30 6.00E-03 8 1.60E-03 27% Pass 63 0.112 30 6.00E-03 8 1.60E-03 27% Pass 64 0.113 27 5.40E-03 8 l .60E-03 30% Pass 65 0.115 22 4.40E-03 7 1.40E-03 32% Pass 66 0.117 22 4.40E-03 6 l .20E-03 27% Pass 67 0.118 21 4.20E-03 6 1.20E-03 29% Pass 68 0.120 21 4.20E-03 6 1.20E-03 29% Pass 69 0.121 21 4.20E-03 6 l.20E-03 29% Pass 70 0.123 21 4.20E-03 6 l .20E-03 29% Pass 71 0.125 21 4.20E-03 4 8.0lE-04 19% Pass 72 0.126 21 4.20E-03 3 6.00E-04 14% Pass 73 0.128 21 4.20E-03 3 6.00E-04 14% Pass 74 0.130 20 4.00E-03 3 6.00E-04 15% Pass 75 0.131 16 3.20E-03 2 4.00E-04 13% Pass 76 0.133 16 3.20E-03 2 4.00E-04 13% Pass 77 0.134 13 2.60E-03 2 4.00E-04 15% Pass 78 0.136 12 2.40E-03 2 4.00E-04 17% Pass 79 0.138 11 2.20E-03 2 4.00E-04 18% Pass 80 0.139 9 1.80E-03 2 4.00E-04 22% Pass 81 0.141 9 1.80E-03 2 4.00E-04 22% Pass 82 0.143 9 1.80E-03 1 2.00E-04 11% Pass 83 0.144 9 l.80E-03 1 2.00E-04 11% Pass Existing Condition Detention Optimized Pass or Interval Q (cfs) Hours > Q %time Hours>Q %time Post/Pre Fail? 84 0.146 9 1.80E-03 0 O.OOE+OO 0% Pass 85 0.148 8 1.60E-03 0 O.OOE+OO 0% Pass 86 0.149 7 1.40E-03 0 O.OOE+OO 0% Pass 87 0.151 7 l.40E-03 0 0.00E+OO 0% Pass 88 0.152 7 l.40E-03 0 0.00E+OO 0% Pass 89 0.154 6 l.20E-03 0 O.OOE+OO 0% Pass 90 0.156 6 1.20E-03 0 0.00E+OO 0% Pass 91 0.157 6 l.20E-03 0 O.OOE+OO 0% Pass 92 0.159 6 1.20E-03 0 O.OOE+OO 0% Pass 93 0.161 6 l.20E-03 0 O.OOE+OO 0% Pass 94 0.162 6 1.20E-03 0 O.OOE+OO 0% Pass 95 0.164 6 1.20E-03 0 O.OOE+OO 0% Pass 96 0.165 6 1.20E-03 0 O.OOE+OO 0% Pass 97 0.167 6 1.20E-03 0 0.00E+OO 0% Pass 98 0.169 6 1.20E-03 0 O.OOE+OO 0% Pass 99 0.170 6 1.20E-03 0 O.OOE+OO 0% Pass 100 0.172 6 1.20E-03 0 0.00E+OO 0% Pass Peak Flows calculated with Cunnane Plotting Position Return Period Pre-dev. Q·(cfs) Post-Dev. Q Reduction (years) (cfs) (cfs) _,_, 10 0.172 0.019 0.153 9 0.158 0.018 0.140 8 0.151 0.017 0.133 7 0.147 0.017 0.131 6 0.138 0.014 0.125 5 0.137 0.013 0.124 4 0.133 0.012 0.121 3 0.116 0.010 0.106 2 0.107 0.006 0.101 ATTACHMENT 3 List of the "n" Largest Peaks: Pre & Post-Developed Conditions Basic Probabilistic Equation: R = 1/P R: Return period (years). P: Probability of a flow to be equaled or exceeded any given year (dimensionless). Cunnane Equation: p = i~0.4 n+0.2 Weibull Equation: P=-'-n+1 i: Position of the peak whose probability is desired (sorted from large to small) n: number of years analyzed. Explanation of Variables for the Tables in this Attachment Peak: Refers to the peak flow at the date given, taken from the continuous simulation hourly results of the n year analyzed. Posit: If all peaks are sorted from large to small, the position of the peak in a sorting analysis is included under the variable Posit. Date: Date of the occurrence of the peak at the outlet from the continuous simulation Note: all peaks are not annual maxima; instead they are defined as event maxima, with a threshold to separate peaks of at least 12 hours. In other words, any peak Pin a time series is defined as a value where dP/dt = O, and the peak is the largest value in 25 hours (12 hours before, the hour of occurrence and 12 hours after the occurrence, so it is in essence a daily peak). List of Peak events and Determination of Q2 and Ql0 (Pre-Development) Valley View· POC-1 T Cunnane Weibull Peaks Period of Return (Year) (rul (ds) (cfs) (Years) 10 0.17 0.18 Date Posit Weibull Cunnane 9 0.16 0.16 0.076 8/17/1977 57 1.02 1.01 • 0.15 0.15 0.078 12/24/1983 56 1.04 1.03 7 0.1S 0.15 0.079 2/12/2003 55 1.05 1.05 6 0.14 0.14 0.081 2/6/1969 54 1.07 1.07 5 0.14 0.14 0.081 2/22/1998 53 1.09 1.09 4 0.13 0.13 0.082 2/8/1993 52 1.12 1.11 3 0.12 0.12 0.083 4/27/1960 51 1.14 1.13 2 0.11 0.11 0.084 1/16/1972 so 1.16 1.15 0.084 4/28/2005 49 1.18 us 0.085 3/19/1981 48 1.21 1.20 Note: 0.087 3/1/1991 47 1.23 1.23 Cunnane is the preferred 0.088 12/22/1982 46 1.26 1.25 method by the HMP permit. a.ass 3/15/1986 45 1.29 1.28 0.089 3/17/1963 44 1.32 1.31 0.089 2/15/1986 43 1.35 1.34 0.089 2/27/1991 42 1.38 1.38 0.089 2/12/1992 41 1.41 1.41 0.09 1/29/1980 40 1.45 1.44 0.09 2/14/1998 39 1.49 1.48 0.094 1/16/1978 38 1.53 1.52 0.095 3/11/1995 37 1.57 1.56 0.099 1/18/1993 36 1.61 1.61 0.1 2/4/1994 35 1.66 1.65 0.102 12/2/1961 34 1.71 1.70 0.102 2/17/1998 33 1.76 1.75 0.106 11/15/1952 32 1.81 1.81 0.106 11/11/1985 31 1.87 1,87 0.106 10/20/2004 30 1.93 1.93 0.107 2/18/1993 29 2.00 2.00 0.108 2/23/1998 28 2.07 2.07 0.11 2/16/1980 27 2.15 2.15 0.112 12/19/1970 26 2.23 2.23 0.113 2/3/1998 25 2.32 2.33 0.114 11/22/1965 24 2.42 2.42 0.114 2/10/1978 23 2.52 2.53 0.114 1/29/1983 22 2.64 2.65 0.114 2/27/1983 21 2.76 2.78 0.114 12/30/1991 20 2.90 2.92 0.118 3/2/1980 19 3.05 3.08 0.13 4/1/1958 18 3.22 3.25 0.13 3/1/1978 17 3.41 3.45 0.131 1/16/1952 16 3.63 3.67 0.133 2/20/1980 15 3.87 3.92 0.133 3/17/1982 14 4.14 4.21 0.135 2/18/2005 13 4.46 4.54 0.137 10/29/2000 12 4.83 4.93 0.138 1/14/1993 11 5.27 5.40 0.138 10/27/2004 10 5.80 5.96 0.146 2/2S/1969 9 6.44 6.65 0.149 2/4/1958 8 7.25 7.53 0.153 2/25/2003 7 8.29 8.67 0.175 9/23/1986 6 9.67 10.21 0.183 1/4/1995 5 11.60 12.43 0.19 1/15/1979 4 14.50 15.89 0.202 10/1/1983 3 19.33 22.00 0.211 1/4/1978 2 29.00 35.75 0.225 4/14/2003 1 58.00 95.33 List of Peak events and Determination of Q2 and Ql0 (Post-Development) Valley View -POC-1 T Cunnane Weibull Period of Return (Year) (cfs) (cfs) Peaks (cfs) {Years) 10 0.02 0.02 Date Posit Weibull Cunnane 9 0.02 0.02 0.0056 1/23/1952 57 1.02 1.01 8 0.02 0.02 0.0056 1/23/1952 56 1.04 1.03 7 0.02 0.02 0.0056 1/23/1952 55 1.05 1.05 6 0.01 0.01 0.0056 1/26/1952 54 1.07 1.07 5 0.01 0.01 0.0057 11/14/1952 53 1.09 1.09 4 0.01 0.01 0.006 1/21/1952 52 1.12 1.11 3 0.01 0,01 0.006 1/21/1952 51 1.14 1.13 2 0.01 0,01 0.0061 1/21/1952 so 1.16 1.15 0.0061 1/21/1952 49 1.18 1.18 0.0062 1/25/1954 48 1.21 1.20 Note: 0.0063 1/19/1952 47 1.23 1.23 Cunnane is the preferred 0.0063 1/19/1952 46 1.26 1.25 method by the HMP permit. 0.0063 1/19/1952 45 1.29 1.28 0.0063 1/19/1952 44 1.32 1.31 0.0063 1/19/1952 43 1.35 1.34 0.0063 1/19/1952 42 1.38 1.38 0.0063 1/19/1952 41 1.41 1.41 0.0063 1/19/1952 40 1.45 1.44 0.0063 1/19/1952 39 1.49 1.48 0.0063 1/19/1952 38 1.53 1.52 0.0063 1/19/1952 37 1.57 1.56 0.0063 1/20/1952 36 1.61 1.61 0.0063 1/20/1952 35 1.66 1.65 0.0063 1/20/1952 34 Ul 1.70 0.0063 1/20/1952 33 1.76 1.75 0.0063 1/20/1952 32 1.81 1.81 0.0063 1/20/1952 31 1.87 1.87 0.0063 1/20/1952 30 1.93 1.93 0.0063 1/20/1952 29 2.00 2.00 0.0065 4/10/1952 28 2.07 2.07 0.0066 12/20/1952 27 2.15 2.15 0.0069 3/22/1954 26 2.23 2.23 0.0073 3/12/1952 25 2.32 2.33 0.0074 1/24/1954 24 2.42 2.42 0.0077 3/16/1952 23 2.52 2.53 0.0088 12/11/1951 22 2.64 2.65 0.009 11/23/1952 21 2.76 2.78 0.0097 1/25/1952 20 2.90 2.92 0.0101 3/23/1954 19 3.05 3.08 0.0112 1/13/1952 18 3.22 3,25 0.0115 12/30/1952 17 3.41 3.45 0.0121 3/25/1954 16 3.63 3.67 0.0123 3/1/1953 15 3.87 3.92 0.0125 3/8/1952 14 4.14 4.21 0.0126 11/23/1951 13 4.46 4.54 0.0131 3/7/1952 12 4.83 4.93 0.0134 3/30/1954 11 5.27 5.40 0.0138 12/29/1951 10 5.80 5.96 0.0164 1/18/1952 9 6.44 6.65 0.017 3/16/1954 8 7.25 7.53 0.0177 1/19/1954 7 8.29 8.67 0.019 11/30/1952 6 9.67 10.21 0.0193 2/13/1954 5 11.60 12.43 0.0205 12/2/1952 4 14.50 15.89 0.0235 3/15/1952 3 19.33 22.00 0.0326 11/15/1952 2 29.00 35.75 0.0391 1/16/1952 1 58.00 95.33 ATTACHMENT 4 AREA VS ELEVATION The storage provided by the LID BMP is entered into the LID Module within SWMM -please refer to Attachment 7 for further information. For verification, a stage storage relationship for the facilities is provided on the following pages. DISCHARGE VS ELEVATION The orifices have been selected to maximize their size while still restricting flows to conform with the required 10% of the Q2 event flow as mandated in the Final Hydromodification Management Plan by Brown & Caldwell, dated March 2011. While REC acknowledges that these orifices are small, to increase the size of these outlets would impact the basin's ability to restrict flows beneath the HMP thresholds, thus preventing the BMP from conformance with HMP requirements. In order to further reduce the risk of blockage of the orifices, regular maintenance of the riser and orifices must be performed to ensure potential blockages are minimized. A detail of the orifice and riser structure is provided in Attachment 5 of this memorandum. A stage-discharge relationship is provided on the following pages for the surface outlet structure. The LID low flow orifice discharge relationship is addressed within the LID Module within SWMM -please refer to Attachment 7 for further information. DRAWDOWN CALCULATIONS Drawdown calculations are provided on the following page assuming the only discharge outlet is the low flow orifice and the basin is full to the emergency spillway {an extremely conservative assumption). Based on these assumptions, the LID facilities are dry within 11.4 hours and 20.3 hours respectively. Outlet structure for Discharge of Detention Basin 1 Discharge vs Elevation Table Low orifice: 0.4" Lower slot Emergency Weir Number: ' Invert: 2.90 ft Invert: 3.S00 ft Cg-low: 0.52 B 0.75 ft B 4 ft Middle orifice: ' " h 0.083 ft number of orif: 0 Upper slot Cg-middle: 0.52 Invert: 0.000 ft invert elev: 0.17ft B 0.00 ft h 0 000 ft h H/0-low H/D-mid Qlow-arlf Qlow-welr Qtot-low Qm1d·Orif Qmid-wel, Qtot-med Qslot-low Qslot-upp Qemer Qtot (ft) . . (ds) Id<) !ck) (cbl (cb) (c:fs) (ch) {ch) (ck) (dsl 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.0000 0.100 3.000 0.000 0.001 0.001 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.0013 0.200 6.000 0.400 0.002 0.019 0.002 0.000 0.000 0.000 0.000 0.000 0.000 0.0019 0.300 9.000 1.600 0.002 0023 0.002 0.000 0.000 0.000 0.000 0.000 0.000 0.0023 0.400 12.000 2.800 0.003 0.027 0.003 0.000 0.000 0.000 0.000 0.000 0.000 0.0027 0.500 15,000 4.000 0,003 0.030 0.003 0.000 0.000 0.000 0.000 0.000 0.000 0.0030 0.600 18.000 5.200 0.003 0.033 0.003 0.000 0.000 0.000 0000 0.000 0.000 0.0033 0.700 21.000 5.400 0.004 0.036 0.004 0.000 0.000 0.000 0.000 0.000 0.000 0.0036 0.800 24.000 7.600 0.004 0.038 0.004 0.000 0.000 0.000 0.000 0.000 0.000 0.0038 0.900 27.000 8.800 0.004 0.041 0.004 0.000 0.000 0.000 0.000 0.000 0.000 0.0041 1.000 30.000 10.000 0.004 0.043 0004 0.000 0.000 0.000 0.000 0.000 0.000 0.0043 1.100 33.000 11.200 0.005 0.045 0.005 0.000 0.000 0.000 0.000 0.000 0.000 0.0045 uoo 35.000 12.400 0.005 0.047 0.005 0.000 0.000 0.000 0.000 0.000 0.000 0.0047 1.300 39.000 13.600 0.005 0.049 0.00S 0.000 0.000 0.000 0.000 0.000 0.000 0.0049 1.400 42.000 14.800 0.005 0.051 0.00S 0.000 0000 0.000 0.000 0.000 0.000 0.0051 1.500 45.000 16.000 0.005 0.053 0.005 0.000 0.000 0.000 0.000 0.000 0.000 0.0053 1.600 48.000 17.200 0.005 0.055 0.005 0.000 0.000 0.000 0.000 0.000 0.000 0.0055 1.700 s1.000 18.400 0.006 0.055 0.006 0.000 0.000 0.000 0.000 0.000 0.000 0.0056 1.800 S4.000 19.600 0.006 0.058 0.006 0.000 0.000 0.000 0.000 0.000 0.000 0.0058 1.900 57.000 20.800 0.006 0.050 0.006 0.000 0.000 0.000 0.000 0.000 0.000 0.0050 2.000 50.000 22.000 0.006 0.061 0.006 0.000 0.000 0.000 0.000 0.000 0.000 0.0061 2.100 63.000 23.200 0.005 0.063 0.006 0.000 0.000 0.000 0.000 0.000 0.000 0.0063 2.200 66.000 24.400 0.005 0.064 0.005 0.000 0.000 0.000 0.000 0.000 0.000 0.0064 2.300 69.000 25.600 0.007 0.065 0.007 0.000 0.000 0.000 0.000 0.000 0.000 0.0066 2.400 72.000 26.800 0,007 0.057 0.007 0.000 0.000 0.000 0.000 0.000 0.000 0.0057 2.500 7S.000 28.000 0.007 0.068 0.007 0.000 0.000 0.000 0.000 0.000 0.000 0.0068 2.600 78.000 29.200 0.007 0.070 0.007 0.000 0.000 0.000 0000 0.000 0,000 0.0070 2.700 81.000 30.400 0.007 0.071 0.007 0.000 0.000 0.000 0.000 0.000 0.000 0.0071 2.800 84.000 31.600 0.007 0.072 0.007 0.000 0.000 0.000 0.000 0.000 0.000 0.0072 2.900 87.000 32.800 0.007 0.074 0.007 0.000 0.000 0.000 0.000 0.000 0.000 0.0074 3.000 90.000 34.000 0.007 0.075 0.007 0.000 0.000 0.000 0.074 0.000 0.000 0.0810 3.100 93.000 35.200 0.008 0.075 0.008 0.000 0.000 0.000 0.122 0.000 0.000 0.1294 3.200 96.000 36.400 0.008 0.077 0.008 0.000 0.000 0.000 0.156 0.000 0.000 0.1533 3.300 99.000 37.600 0.008 0.079 0.008 0.000 0.000 0.000 0.183 0.000 0.000 0.1910 3.400 102.000 38.800 0.008 0.080 0.008 0.000 0.000 0.000 0.207 0.000 0.000 0.2151 3.500 105.000 40.000 0.008 0.081 0.008 0.000 0.000 0.000 0.229 0.000 0.000 0.2367 3.500 108.000 41.200 0.008 0.082 0.008 0.000 0.000 nooo 0.248 0.000 0.392 0.6480 3.700 111.000 42.400 0.008 0.083 0.008 0.000 0.000 0.000 0.266 0.000 1.108 1.3830 3.800 114.000 43.500 0.008 0.084 0.008 0.000 0.000 0.000 0.283 0.000 2.037 2.3284 3.900 117.000 44.800 0.009 0.086 0.009 0,000 0.000 0.000 0.300 0.000 3,136 3.4439 4.000 120.000 46.000 0.009 0.087 0.009 0.000 0.000 0.000 0.315 0.000 4,383 4.7052 ATTACHMENT 5 Pre & Post-Developed Maps, Project Plan and Detention Section Sketches ATTACHMENT 6 SWMM Input Data in Input Format (Existing & Proposed Models) [TITLE] [OPTIONS) FLOW UNITS INFILTRATION FLOW ROUTING START DATE START TIME REPORT START DATE REPORT START_TIME END DATE END_TIME SWEEP START S\1/EEP END DRY_DAYS REPORT STEP WET_STEP DRY_STEP ROUTING STEP ALLOW PONDING INERTIAL_DAMPING VARIABLE_STEP LENGTHENING_STEP MIN_SURfAREA NORMAL fL0\11 LIMITED SKIP STEADY_STATE fORCE MAIN EQUATION LINK OFFSETS MIN_SLOPE cm GREEN_AMPT KINWAVE 10/17/1948 00:00:00 10/17/1948 00:C0:CC 10/17/~0(5 23:C0:0C 01/01 12/31 0 01:00:00 00:15:00 04:00:00 0: 01' co ,o PARTIAL 0. 75 0 0 BOTH ,o a-, DEPTH 0 [EVAPORATION] ; ;Type Parameters '' ---------- MONTHLY 0. 06 0. 08 0. 11 DRY_ONLY NO [RAINGAGES] Rain Time ; ;Name Type Intrvl ----------------------- OCEANSIDE INTENSITY 1:CO [ SUBCATCHMENTS J ; ;Name Raingage , ; -------------- DMA-1 OCEANSIDE [SUBAREAS] 0. 15 Snow Catch LO Outlet POC-1 PRE_DEV 0.17 0.19 0.19 0.18 Data Source ---------- TIMESERIES OCEANSIDE Total Area 0.2 Pent. Imperv 0 0.15 Width 0. 11 Pent. Slope 0.08 0.06 Curb Length 0 ; ;Subcatchrnent N-Imperv N-Perv S-Imperv S-Perv Pct:Zero RouteTo PctRouted DMA-1 O.GS C.02 !INfrLTRATlON] ; ; Subcatchrnent Suction HydCon IMCma>< DMA-1 9 C.0225 Ct.33 {ODTFALLS) ; ;Kame Invert Elev. Outfall Type Stage/Table Time Series Tide Gate POC-1 0 fREE NO [TIMESERIES) ; ;Name Date T~me llalue OCEANSIDE FILE "OsideRain.prn" [REPORT) INPOT NO OUTLET Snow Pack CONTROLS NO SUBCATCHMENTS ALL NODES ALL LINKS ALL [TAGS] [MAP] DIMENSIONS 0.000 0.000 10000.coo lCOOO oco L'ni ts None [COORDINATES] ; ;Nocie ; ;----- FOC-J. [VERTICES] ;,:-coord Y-Coord 2500.00C 270C.0GO ; ; Link X-Coord Y-Coord [ Polygons] ;;Subcatchment x-coord Y-Coord DMA-1 DMA-1 [SYMBOLSj 2427.184 2427.184 5983.010 5983.010 ; ;Gage X-Coord Y-Cocrd OCEANSIDE 1525.~24 6864.407 PRE_OEV ' [TITLE] [OPTIONS] FLOW UNITS INFILTRATION FLOW ROUTING START DATE START_TIME REPORT START DATE REPORT START TIME END_DA'TE END_TIME SWEEP START SWEEF_END CRY DAYS REPORT_STEP WET_STEP DRY_STEP ROUTING STEP ALLOW PONDING INERTIAL_DAMPING VARIABLE_STEP LENGTHENING_STEP MIN SIJRFAREA NORMAL_FLOW LIMITED SKIP STEADY STATE FORCE_MAIN_EQUATION LINK_OFFSETS MIN SLOPE css GREEN_AMPT KI NW AVE 10/17/1948 00:00:00 10/17/1948 00:00:0C 1G/17/2CC5 23:00:CO 01/0~ ~~/3: C 01:00:00 00:15:00 04:00:00 o,o~,oo "° PARTIAL 0. 75 0 0 BOTH ,c ,_, DEPTH C !EVAPORATION) ; ;Type Parameters ,,---------- MONTHLY 0. 06 0. 08 0 .11 DRY ONLY NO [RAINGAGES] Time POST_DEV 0.15 0.17 0. 19 0 .19 0.18 Snow Data ; ; Name Rain Type Intrvl Catch Source OCEANSIDE INTENSITY 1:GO 1.0 TIMESERIES OCEANSIDE [SUBCATCHMENTS] Total Pent. ; ; Name Raingage Outlet Area Imperv -------------------------------------------------------------- DMA-1 OCEANSIDE BR-1 0 . 419 ss. " BR-1 OCEANSIDE "' _VAULT 0 .013315 0 DMr,,-.'.' OCEANSIDE BR-2 o. ns SL '" BR-2 OCEANSIDE DET VAULT 0 .013659 0 OMA-DE-MIN OCEANSIOE POC-1 0 .IJ52 " 9S [SUBAREASj ; ;Subcatchment N-Imperv N-Perv 5-Irnperv 5-Perv PctZero 0. 15 0. 11 0.08 0. 06 Pent. Curb Width Slope Length ------------------------ " 1 0 rn 0 0 5S ' 0 10 0 0 4S 1 0 RouteTo Pct Routed ;,-------------------------------------------- DMA-1 BR-1 OMA-: BR-2 DMA-DE-t-!IN [INFILTRATION) ; ; Subcatchment --------------., CMA-1 BR-1 DMA-2 BR-2 OMA-DE-MIN [LID_ CONTROLS] o. 012 0 . 01 0. 01' 0. 01: 0 .01: Suction ---------- 9 9 9 9 s 0 .0, 0 . 1 0 .OS o. 05 0. 05 HydCon ---------- C . Cl875 0 .01875 0. 01875 0 .01875 0 .01875 0.02 0.05 0.02 0. 02 0.02 IMDmax ----------o . " 0 .33 0 . 33 0. 33 0. 33 o. 0.05 0.1 0. o., '5 25 " ,s 25 OIJTLET OUTLET OUTLET OUTLET OUTLET Snow Pack -------- - - Type/Layer Parameters ---------------------------------- BR< " BR-1 SURFACE 7.5~ 0. BR-1 soi:, 18 0. CR-1 STORAGE 18 o. Be\-1 DRAB 0. ~4 35 0. BR-~ " BR-2 SURFACE C BR-2 sen " C. BR< STORAGE lS C. B~-2 DRAIN c.~399 C . [LID_USAGEJ POST_ 05 0 ' 0 . 2 6, 0 5 ' cs 0 C 8 0 " C 5 s DEV 0 0 . 0 6 0 C c. C C 5 5 s 5 . 5 ; ; Subcatchrnent LID Process Number Area Widtr. 0 InitSatur Fromim?rv ~oPerv Report File BR-1 BR-2 [OUTFALLS] ; ;Name BR-1 BR-~ Invert Elev. Outfall Type Stage/Table Tin-,e Series 0 Tide Gate ;;-------------------------------------------------- POC-1 0 FREE NO [STORAGE] ; ; Name Parameters ;,---------- DET_VAULT [OUTLSTSJ ; ;Name OUTLET (CURVES] ; ;Name ;;-------------- Ouc Vault ouc Vault Ouc Vault Ouc Vault -Ouc Vault -OuC Vault -Ouc Vault -ouc Vault -ouc _Val..lt Out Vai.:l t Cut_ Vai.:l t OuC Vault -Ouc Vault Ouc Vault Out_ Vault ouc Vault Ouc Vault ouc Vault ouc Vault ouc Vau:t -ouc Va,1lt -ouc Vault -ouc Vault -ouc _vault OuC Vai.:lt -Que Vault ouc Vault Out Vault Invert Elev. 0 Inlet Node "' VAULT Type Ma;-:. Depth Init. Depth 0 Outlet Node e'OC-1 Storage Ci.:rve TABULAR X-Value Y-Value ------------------------------ Rat.ing 0. oco 0 ,0000 0. :oo 0 0013 0. ::oo 0 0019 0 . 300 0 .00~3 0 .400 0 .00~7 0. 500 0 . 0030 0. 600 0. 0033 0 ,700 0. 0036 C.80C 0. C038 C.9CC 0 .cc~: 1.oco 0 .00~3 1.~co 0 0045 1. 200 o. 0047 ' . 300 0 . 0049 . q O 0 0 .C051 L 500 0 .0053 L 600 0. 0055 ,00 0.0056 ' .800 0.0056 .soc C, 0060 " .ooc C. OGC . lOC 0 . OOE3 2 . 200 0. OOE4 2 .300 0 .0066 2 . 400 0 . 0067 2 . 500 0 . 0068 2. 600 0 .Q070 ' .700 0 .007l Curve Pa rams Basin l Outf:ow Heigl".t 0 0 0 Outlet Type TABULAR/DEPTH mo 1IJ0 0 0 Pended Area 0 Qcoeff/ QTable Out Vault Evap. Frac. Infi:tration Qe:-:pon flap Gate '°' Vault 2 .800 0 .001: -o"' Vault 2 . 9CO o. 0014 Out_ Vault 3. 000 o. 0810 Out Vault 2 ,co o. l.'.'94 -o"' Vault 2 .200 0. 1613 '"' Vdult 3. 200 o. 191 O -O"o Vdult 3 . 400 0 2151 o"' Vault 2. 900 0 2367 o", Vault 2. oOO 0. 648G Cut Vault 2 ,00 1. 38 3C Ci..:t Vat.:~t 2 .BOC . 3.'.'8 4 -Oc.;t Vau:t 3. 9CC 2. 4439 -c·~t Vae<~ t 4.00C ' .ICC - Basin . Storage 0 40GG -Basin ' ' 4000 jTIMESERIES] ;;Na.me Date Time Value OCEANSIDE [REPORT) INPUT NO CONTROLS NO SUBCATCHMENTS ALL NODES ALL LINKS ALL [TAGS] [MA?J FILE "OsideRain.prn" DIMENSIONS 0.000 0.000 10000.000 10000.000 Units None [COORDINATES) ; ; Node , ,-------------- POC-1 DET VAULT [VERTICES] ; ; Link (Polygons] X-Coord 4146.734 4329.983 X-Cocrd Y-Coorct 536.013 242e. SL Y-Coorc ; ;Subca.tchment X-Coord Y-Coorct DMA-1 DMA-1 BR-1 CMA-2 ER-2 DMA-DE-MlN [SYMBOLS) 3400. 000 3400. 000 3400. coo 5167. 5" 5234. 506 812.395 6500.000 6500.000 50011.000 6599. 665 5041. 876 3936. 348 ; ;Gage X-Coord Y-Coorct OCEANSIDE 15~5.424 6864.407 POST DEV - ATTACHMENT 7 EPA SWMM FIGURES AND EXPLANATIONS Per the attached, the reader can see the screens associated with the EPA-SWMM Model in both pre-development and post-development conditions. Each portion, i.e., sub-catchments, outfalls, storage units, weir as a discharge, and outfalls (point of compliance), are also shown. Variables for modeling are associated with typical recommended values by the EPA-SWMM model, typical values found in technical literature (such as Maidment's Handbook of Hydrology). Recommended values for the SWMM model have been attained from Appendix G of the 2016 City of San Diego BMP Design Manual. Soil characteristics of the existing soils were determined from the Geotechnical Investigation and the NRCS Web Soil Survey (located in Attachment 8 of this report). A Technical document prepared by Tory R Walker Engineering for the Cities of San Marcos, Oceanside and Vista (Reference [11) can also be consulted for additional information regarding typical values for SWMM parameters. Manning's roughness coefficients have been based upon the findings of the "Improving Accuracy in Continuous Hydrologic Modeling: Guidance for Selecting Pervious Overland Flow Manning's n Values in the San Dfego Region" date 2016 by TRW Engineering (Reference [61). LID Control Editor: Explanation of Significant Variables Storage Depth: The storage depth variable within the SWMM model is representative of the storage volume provided beneath the surface riser outlet and the surface of the bio filtration facility. In those cases where the surface storage has a variable area that is also different to the area of the gravel and amended soil, the SWMM model needs to be calibrated as the LID module wilt use the storage depth multiplied by the BMP area as the amount of volume stored at the surface. let ABMP be the area of the BMP (area of amended soil and area of gravel). The proper value of the storage depth SD to be included in the LID module can be calculated by using geometric properties of the surface volume. let~ be the surface area at the bottom of the surface pond, and let A; be the surface area at the elevation of the invert of the first row of orifices (or at the invert of the riser if not surface orifices are included). Finally, let h; be the difference in elevation between/¼) and Ai. By volumetric definition: A S -(A,+A,) h· BMP' D -z l (1) Equation (1) allows the determination of SD to be included as Storage Depth in the LID module. It should be noted that the effective depth includes an additional 1.2 inches to account for the volume of solids present in the 3-inch mulch layer (void ratio of 60%). Porosity: A porosity value of 0.4 has been selected for the model. The amended soil is to be highly sandy in content in order to have a saturated hydraulic conductivity of approximately 5 in/hr. REC considers such a value to be slightly high; however, in order to comply with the HMP Permit, the value recommended by the Copermittees for the porosity of amended soil is 0.4, per Appendix A of the Final Hydromodification Management Plan by Brown & Caldwell, dated March 2011. Such porosity is equal to the porosity of the gravel per the same document. Void Ratio: The ratio of the void volume divided by the soil volume is directly related to porosity as n/{1-n). As the underdrain layer is composed of gravel, a porosity value of 0.4 has been selected {also per Appendix A of the Final HMP document), which results in a void ratio of 0.4/(1-0.4) = 0.67 for the gravel detention layer. Conductivity: Per the site specific geotechnical investigation for the project site, no infiltration is allowable on the project site as such a value of 0 has been applied. Clogging factor: A clogging factor was not used {O indicates that there is no clogging assumed within the model}. The reason for this is related to the fairness of a comparison with the SOHM model and the HMP sizing tables: a clogging factor was not considered, and instead, a conservative value of infiltration was recommended. Drain (Flow) coefficient: The flow coefficient C in the SWMM Model is the coefficient needed to transform the orifice equation into a general power law equation of the form: q = C(H -H0 )" (2) where q is the peak flow in in/hr, n is the exponent (typically 0.5 for orifice equation), Ho is the elevation of the centroid of the orifice in inches (assumed equal to the invert of the orifice for small orifices and in our design equal to O} and His the depth of the water in inches. The general orifice equation can be expressed as: Q _ IT D2 z (H-HD) -c -9 -4fl144 12 (3) where Q is the peak flow in cfs, Dis the diameter in inches, Cg is the typical dfscharge coefficient for orifices (0.61-0.63 for thin walls and around 0.75-0.8 for thick walls), g is the acceleration of gravity in ft/s2, and Hand Ho are defined above and are also used in inches in Equation (3). It is clear that: (ill) X ABMP f ) q hr 12X3600::::: Q (c 5 (4) Cut-Off Flow: Q (cfs) and q {in/hr) are also the cutoff flow. For numerical reasons to insure the LID is full, the model uses cut-off= 1.01 Q. ATTACHMENT 8 Geotechnical Documentation ATTACHMENT 9 Summary Files from the SWMM Model PRE_DEV EPA STORM WATER MANAGEMENT MODEL -VERSION 5.0 (Build 5.0.022) NOTE; The sununary statistics displayed ir. this report are based on results found at every computat~onal time step, not just on results frorr, each reporting time step. Ar,alysis Opt~ons •••••••••••••••• Flow Units Process Models: Rainfall/Runoff Snowmelt Groundwater .. Flow Routing . Water Quality Infiltration Method Starting Date Ending Date Antecedent Dry Days Report Time Step Wet Time Step Dry Time Step .. Runoff Quantity Continuity •••••••••••••••••••••••••• Total Precipitation Evaporation Loss Infiltration Loss Surface Runoff ... Final Surface Storage Continuity Error (%) CFS "' '° '° '° "° GREEN AMPT OCT-17-1948 00:00:00 OCT-17-2005 23:00:00 0.0 0~:00:00 00: 15:00 04:CO:OC Volume acre-feet 608.455 1. 96: 591.986 15. 759 0.000 -0.~06 Depth inches 650.290 2.095 632.689 16.842 0.000 Volume Clow Routing Cont~nuity Volu:me acre-feet 10"6 gal •••••••••••••••••••••••••• Dry Weather Inflow wet Weather Inflow Groundwater Inflow RDII Inflow External Inflow External Outflow Internal Outflow Storage Losses Initial Stored Volume Final Stored Volume Continuity Error 1%) Subcatchment Runoff Summary *••························ Subcatchment DMA-1 Total Precip rn 650.29 0.000 15. 759 0.000 0.000 0.000 15.759 0.000 0.000 0.000 0.000 o.ooc o.oo Analys~s begun on: Analysis er.ded on: Total elapsed time: Tue Mar 06 ~3:44:24 2018 Tue Mar 06 13:44:40 2018 OC:00:16 0.00:J 5.135 0.000 0.000 0.000 5.135 0.000 0.000 o.oco o.oco Total Evap '" 2.10 Tctal Ir.ti~ in 632. 69 Total Runoff ic 16.84 Tot;,l Runoff :c'6 gal 5 .13 Peak Rur.cff Runoff C,S 10.98 Coe ff 0. 0'.'.6 POST_DEV EPA STORM WATER MANAGEMENT MODEL -VERSION 5. 0 (Bui:d 5. 0. 0~2: -------------------------------------------------------------- NOTE: The surrunary statistics displayed in tr.is report are based on results found at every computationa: time step, not just on results from each reporting time step Analysis Opt~ons •••••••••••••••• rlow Uni ts Process Models: Rainfall/Runoff Snowmelt Groundwater .. now Routing Ponding Allowed Water Quality ..... Infiltration Method flow Routing Method Starting Date Ending Date Antecedent Dry Days Report Time Step Wet Time Step Dry Time Step Routing Time Step R .. moff Quantity Cont~nuity Total Precipitation Evaporation Loss Infiltration Loss Si..;rface Runoff Final Surface Storage Contir.uity Error (i) Flow Routing Continuity .......................... Dry Weather Inflow Wet Weather Inflow Groundwater Inflow RDil Inflow External Inflow External Outflow lnterna~ Outflow Storage Losses Initial Stored Volume Final Stored Volume Conti~u1ty Error 1%) CFS '" ,o ,o HS ,o ,o GREEN_AMPT KINiiAVE OCT-17-1948 00:00:00 OCT-17-2005 23:00:CO 0.0 Oi:00:00 OC:i5:GO 04:0IJ:GO 60.00 sec Volume acre-feet 38.799 6.046 4 .134 29. :26 O.OC9 329 Volume Uepth inches 650.290 lOl.333 69.283 4E8 .16E C.146 Volume acre-feet 10'6 gas ------------------ 0.000 0. OGO ~9.126 9. '" 0.000 0. 000 0 .000 0. 000 0 . C00 0. 000 29. U3 9 .487 0 . 000 0. 000 0 . 000 0. 000 0.000 0 .000 0.013 0. 00, o.ooc Highest Flow Ir.stability Indexes **•················~············ All lin,.s are stable. Routing Time Step Summary Minimum Time Step Average Time Step 60.00 sec 60.00 sec Maximum Time Step Percent ~n Steady State Average Iterations per Step Subcatchment Runoff Su.Wlary 60.00 sec 0.00 1. 00 POST_DEV Tc1::a: Total Rur.or. Tctal Ir.f~l ir. Total Runoff lr. Subcatchrr.ent Precip ir. 650. cs 0. cc 6, .~8 67. 45 522.21 650. ,s :6433 .,S :059. 6' 0.00 16069.89 DMA-~ BR-~ DMA-: 650 . ::?9 0 . co 6,. 06 40.63 551. 25 BR-2 DMA-DE-MIN 650. 650. LID Performance Summary Subcatchment BR-1 BR-2 Node Depth Summary Node rnc-1 DET VAllLT LID Control BR-1 BR-2 Type OUTFALL STORAGE Node Inflow Summary ••*••·············· Nocie POC-1 DET VAOLT Type OllTFALL STORAGE Node Surcharge Summary •••••••••••••••••••••• ·s C9 8798. °' 0 cc Total Inf:ow i, 17083.48 9448.31 986. 88 42.2::? Evap Loss 1059.65 986.89 C.00 240.11 Infi~ Loss i.r. 0.00 0.00 8485.22 377.80 Surface Outflow '" 4257.23 417.02 Average Depth Feet Maximum Depth Feet Maximum >Ge Feet Time of Max Occurrence days hr:min o.oc 0.12 Maximum Latera: Inflow c,s 0.06 0. 7':: C.00 3. 17 Max~mum Total Ir.flow ccs 0.00 3.17 Time o, 0 11448 "'' Occurrence a'ays hr :min 0.15 11448 22:38 0.79 19902 17:00 00:00 22:38 Lateral Inf~ow vo:ume 1 O' 6 ,., 0.533 8.957 Surct-.arg~ng occurs when water rises above the top of the higl",est conduit. Node Type DET VAULT STORAGE Hours Surcharged 499679. O.:' Max. Height Above Crown Feet 3. 170 Min. Depth Below Rim Feet 0.830 Tota~ Runoff ~c··6 ga:!. 5.9~ 5. 81 3. 26 3 . 15 0.53 Drain Cut flow ir, 11813.28 8068.31 'rotal Inflow Volume ~OA6 ga~ 9,486 8.957 Peal'. RU"1Cff Runoff Cceff C,S C. SC 0. SC C . 26 0 0. I nit. storage in 0. 00 0. 00 '8 06 0.803 0.941 0.848 0.898 C . 581 Fina: Storage rn 4.38 3. 39 Pent. E:rror -o. 30 -0.2".I Node Flooding Summary T·············••++T++ No nodes were flooded. Stcrage Vc:urr.e s,,mmary ·················T···· Storage Unit DET VAllLT Average ·volume 1000 ft3 C. 487 Outfall Loading Summary ....................... Outfall Node POC-1 System Link Flow Summary Flow Freq. Fent. 21. 33 21 . 3 3 •••••••••••••••••••• OUTLET Type DUMMY Conduit Surcharge summary ••••••••••••••••••••••••• No conduits were surcharged. Analysis begun on: Analysis ended on: Total elapsed time: Thu Apr 05 Thu Apr 05 00:00:26 POST_DEV Avg E&I Pent Pent Full Loss Maxi:nurn Volume 1000 ft3 Avg. Flow '" 0.00 0. 00 3 Max~rnum 1cowl '" 0 Max. Flow '" 0.15 0.15 Time cf Max Occurrence days hr:m:Cn 12.ESl Total Volume 10~6 ga: 9.486 9. 486 Maximum IVeloCI '.:t/sec C.15 11448 22·38 13:53:21 13:53:47 2018 2018 """ Pent Full Max/ FuL Flow Time of Max Occurrence days hr:min 11448 21:37 Max/ Fu!l Depth Maximurr, Outflow '" 0 .15 ATTACHMENT 3 Structural BMP Maintenance Information Use this checklist to ensure the required information has been included in the Structural BMP Maintenance Information Attachment: Preliminary Design/Planning/CEQA level submittal: Attachment 3 must identify: ,1J Typical maintenance indicators and actions for proposed structural BMP(s) based on Section 7.7 of the BMP Design Manual Final Design level submittal: Attachment 3 must identify: O Specific maintenance indicators and actions for proposed structural BMP(s). This shall be based on Section 7.7 of the BMP Design Manual and enhanced to reflect actual proposed components of the structural BMP(s) :J How to access the structural BMP(s) to inspect and perform maintenance ~ Features that are provided to facilitate inspection (e.g., observation ports, cleanouts, silt posts, or other features that allow the inspector to view necessary components of the structural BMP and compare to maintenance thresholds) ~ Manufacturer and part number for proprietary parts of structural BMP(s) when applicable □ Maintenance thresholds for BMPs subject to siltation or heavy trash(e.g., silt level posts or other markings shall be included in all BMP components that will trap and store sediment, trash, and/or debris, so that the inspector may determine how full the BMP is, and the maintenance personnel may determine where the bottom of the BMP is . If required, posts or other markings shall be indicated and described on structural BMP plans.) c Recommended equipment to perform maintenance u When applicable, necessary special training or certification requirements for inspection and maintenance personnel such as confined space entry or hazardous waste management Attachment 3 Chapter 7: Long Term Operation and Maintenance TABLE 7-2. Maintenance Indicators and Actions for Vegetated BMPs Typical Maintenance Maintenance Actions lndicator(s) for Vegetated BMPs Accumulation of sediment, litter, or Remove and properly dispose of accumulated materials, without debris damage to the vegetation. Poor vegetation establishment Re-seed, re-plant, or re-establish vegetation per original plans. Overgrown vegetation Mow or trim as appropriate, but not less than the design height of the vegetation per original plans when applicable (e.g. a vegetated swale may require a minimwn vegetation height). Erosion due ro concentrated irrigation Repair/ re-seed/ re-plant eroded areas and adjust the irrigation flow system. Erosion due to concentrated storm Repair/ re-seed/ re-plant eroded areas, and make appropriate \Vater runoff flow 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. Standing water in vegetated swales used Make appropriate corrective measures such as adjusting irrigation for pretreatment and/or site design system, removing obstructions of debris or im·asive vegetation, BMPs loosening or replacing top soil to allow for better infiltration, or minor re-grading for proper drainage. If the issue is not corrected br restoring the BMP to the original plan and grade, the G ty Engineer shall be contacted prior to any additional repairs or reconstruction. Standing water in bioretention, Make appropriate corrective measures such as biofilrrarion with partial retention, or inspecting/unclogging orifice opening, adjusting irrigation system, biofiltration areas, or flow-through removing obstructions of debris or invasive vegetation, clearing planter boxes• for longer than 96 hours underdrains (where applicable), or repairing/replacing clogged or following a storm event""" compacted soils. Obstructed inlec or outlet structure Clear obstructions. Damage to structural components such Repair or replace as applicable. as weirs, inlet or outlet structures *~hese BMPs typically include a surface ponding layer as part of their function which may take 96 hours ro drain following a storm event. • Vegetated swales and !low-through planter boxes in regards to llow-thru treatment control BMPs are not options as structural BMPs. Carlsbad has not adopted an Alternative Compliance Program. February 2016 ATTACHMENT 4 City standard Single Sheet BMP (SSBMP) Exhibit [Use the City's standard Single Sheet BMP Plan.]