University of California, San Diego
IN-15: Stormwater Modeling

The campus retains runoff on-site using LID practices and green infrastructure to the 85th percentile. We use the County Hydrology Manual and State Water Resources Control Board’s water balance calculator to calculate the sizing that will be needed for either volume-based treatment BMPs or flow-based treatment BMPs. Calculations must be done by a registered Civil Engineer and must meet the criteria described below and summarized in the attached checklists: 1. Storm Water BMP Requirements a. All projects that create or replace more than 2,500 SF are required to complete and submit appropriate “Post-Construction Stormwater Management Checklist” and obtain approval from UCSD Civil Engineers as well as Environment Health & Safety staff during the planning phase, Design Development phase, Construction Document phase. Then Part E of the checklist must be completed after the construction. b. Copies of the checklists can be obtained from http://stormwater.ucsd.edu or from EH&S Environmental Affairs at ehsea@ucsd.edu. c. All projects that create or replace less than 2,500 SF of impervious area 1) Complete page 1 & 2 of the checklist for 2,500 SF -5,000 SF and submit for record. See 7. a. below for WPCP requirements. d. All projects that create or replace more than 2,500 SF and less than 5,000 SF of impervious area 1) Complete Post-Construction Stormwater Management Checklist for 2,500 SF to 5,000 SF. 2)Quantify the runoff reduction using State’s Post-Construction Water Balance Calculator, available at http://stormwater.ucsd.edu or request from EH&S Environmental Affair at ehsea@ucsd.edu and attach to the checklist. e. All projects that create or replace 5,000 SF or more of impervious area (“Regulated Projects”) 1) Complete Post-Construction Stormwater Management Checklist for 5,000 SF or Greater. 2) Quantify “Site Design” BMPs using State’s Post-Construction Water Balance Calculator (see d. above) and show that post-construction water balance is achieved. If balancing is not possible, see 3) below. 3) “Treatment Control” BMPs are only required if the Site Design BMPs above cannot fully meet Permit requirements. a) Quantify and explain in the Post-Construction Stormwater Management Checklist and include any attachments as needed. b) Design shall be based on the Flow-Based or Volume-Based criteria specified in Section F.5.g.2.b (Numeric Sizing Criteria) of the Phase II Small MS4 Permit c) Bioretention facilities are preferred, however alternative treatment BMPs can be used if proper documentation and supporting calculations prepared by a Registered Civil Engineer are provided and attached to the checklist. d) An Operations and Maintenance Plan (O&M) for each Post-Construction BMP must be included in the checklist. e) Sources for additional guidance on the design of post-construction BMP and LID measures are listed in the table below (Table 1). Table 1: Guidance Documents for Design of Post-Construction BMP Agency Guidance Document Website Project Clean Water Model BMP Design Manual http://www-ehs.ucsd.edu/Enviro_Affairs/BMP/StormWaterManagementRequirementsConstructionProjectsLessThanOneAcre.pdf County of San Diegohttps://www.sandiegocounty.gov/content/sdc/dpw/watersheds/DevelopmentandConstruction/BMP_Design_Manual.html LID Handbook http://www.sandiegocounty.gov/content/dam/sdc/dpw/WATERSHED_PROTECTION_PROGRAM/susmppdf/lid_handbook_2014sm.pdf CASQA (California Stormwater Quality Association) So Cal LID Manual https://www.casqa.org/sites/default/files/downloads/socallid-manual-final-040910.pdf f. Design of all post-construction BMP shall meet stormwater permit requirements (Section F.5.g of the Phase II Permit and the Construction General Permit as applicable); be consistent with UCSD’s current Stormwater Management Plan (SWMP) at http://www-ehs.ucsd.edu, and conform to the stormwater treatment standards of the time, as listed in the County of San Diego BMP Design Manual.

Other contacts: Ross Kunishige, Eriko Kobayashi, Roland Bartsch