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Stormwater Management
BACKGROUND INFORMATION
The City of San Jose is responsible for ensuring compliance with Federal and State laws that regulate how stormwater runoff is managed prior to its entry to the storm drain system, streams, rivers and/or the San Francisco Bay.
Specifically, the City operates under the Regional Water Quality Control Board’s Municipal Regional Stormwater NPDES Permit (MRP). Provision C.3 (pages 17- 49, Attachment A, and Attachment L) of the MRP requires new and redevelopment projects to include appropriate measures to treat urban runoff and to prevent increases in runoff flows.
The City implements Provision C.3 through City Council Policy 6-29: Post-Construction Urban Runoff Management and City Council Policy 8-14: Post Construction Hydromodification Management. These policies emphasize the use of Low Impact Development (LID) measures in line with Provision C.3.
C.3 STORMWATER HANDBOOK
The C.3 Stormwater Handbook was written to help project applicants, developers and builders create stormwater control plans that include appropriate post-construction site design, source control and treatment control measures in their projects that meet City of San Jose requirements and the requirements of the Municipal Regional Permit (MRP)
When using this program-wide handbook keep in mind that some requirements may vary from one local jurisdiction to the next. Contact your planning project manager if you have any questions about how these requirements will apply to your project. In the case of conflicting information between this handbook and the MRP, the MRP requirements prevail.
LOW IMPACT DEVELOPMENT (LID)
“Regulated Projects” must provide a Stormwater Control Plan that describes and illustrates the exclusive use of Low Impact Development (LID) measures. Provision C.3.c of the MRP requires each Regulated Project to treat 100% of a project’s stormwater runoff with LID treatment measures as of December 1, 2011.
LID measures include: preserving existing open space areas and reducing the amount of impervious surfaces (Site Design); preventing stormwater runoff from coming into contact with pollutants (Source Control); removing pollutants from stormwater runoff (Treatment); and retaining or detaining runoff (Hydromodification).
LID Treatment Measures include: Infiltration; Harvest and Use; Evaportranspiration; and Biotreatment. Infiltration and Harvest and Use are the preferred methods. Biotreatment is only permitted if Infiltration and/or Harvest and Use are infeasible. There is no separate evapotranspiration treatment measure because this process occurs naturally in infiltration, harvest and use, and biotreatment.
The standards for determining if infiltration and/or harvesting and use, are feasible or infeasible are based on a report by Geosyntec Consultants: BASMAA Harvest and Use, Infiltration and Evapotranspiration Feasibility/Infeasibility Criteria Report. The process to determine which Treatment Measure is appropriate to use is described under Application Requirements.
For more information about these using these techniques, refer to the C.3 Stormwater Handbook.
REGULATED PROJECTS
Projects that fall into one of the following three categories must submit a Stormwater Control Plan that includes Site Design Measures, Source Control Measures and hydraulically sized Low Impact Development (LID) Treatment Measures.
Special Land Use Categories
- Special Land Use Categories are any auto service facilities, retail gasoline stations, restaurants, and/or uncovered or stand alone (or part of a larger project) parking areas that creates, replaces, or expands the amount of impervious areas by 5,000 square feet (or more).
Other Development & Redevelopment Projects
- New development or redevelopment projects are projects that create, replace, or expand the amount of impervious surface by 10,000 square feet (or more). Redevelopment is any land-disturbing activity that results in the creation, addition, or replacement of exterior impervious surface area on a site which some past development has occurred.
Hydromodification Management Projects (HMP)
- HMP projects are located in a green area of the Hydromodification Applicability Map that create and/or replace one acre or more of impervious surface and increases the amount of impervious areas above the pre-project conditions. Projects that meet this criteria must submit a Hydromodification Plan that meets the requirements of the MRP as detailed in City Council Policy 8-14, Post Construction Hydromodification Management
50% Rule – Applies to Special Land Use Categories, Other and Redevelopment Projects and Hydromodification Management Projects
When a project results in an alteration of more than 50 percent of the total amount of impervious area from a previously approved project/existing area then runoff from the entire project must be included in the treatment system design. Where a project results in an alteration of less than 50 percent of the total amount of impervious area from a previously approved project/existing area then only the new or replaced impervious surface of the project must be included in the treatment system design.
Refer to City Council Policy 6-29; Post Construction Urban Runoff Management, City Council Policy 8-14, Post Construction Hydromodification Management and the C.3 Stormwater Handbook for specific sizing requirements and other information.
Land Uses of Concern
A Stormwater Control plan that includes specific Source Control Measures (not numerically sized) and an Installation, Operation & Maintenance plan are required for Land Uses of Concern regardless of project size or amount of new impervious area.
Land Uses of Concern are uses that can potentially create contaminate stormwater runoff. These include, but are not limited to:
- Any industrial use
- Car washing and detailing facilities
- Construction/corporation yards
- Automotive uses including but not limited to dismantling, parts recovery, and vehicle repair
- Material recycling facilities (processing, transfer and large collection facilities)
- Outdoor Storage
- Gas stations or equipment fueling
- Uncovered parking lots
- Loading docks
- Restaurant activities
- Trash and recycling areas
Refer to City Council Policy 6-29, the Project Data Form, and the C.3 Stormwater Handbook for the specific source control measures that must be included on the Stormwater Control Plan.
APPLICATION REQUIREMENTS
All Regulated Projects must complete the following forms and worksheets. These forms must be submitted with the Permit Application and copied onto the Stormwater Control Plan. Refer to the application instructions for all remaining information that must be included throughout the plan set.
Required Forms
The purpose of the Project Data Form is to describe and document a Regulated Project’s compliance with Provision C.3 of the MRP, including the listing of its specific stormwater-related site design, source control, and treatment measures, treatment system sizing requirements, hydromodification management applicability, and operation and maintenance data.
The purpose of the Infiltration/Harvesting and Use Feasibility Screening Worksheet is to determine if Infiltration, and/or Rainwater Harvesting and Use might be feasible Low Impact Development treatment measures.
Additional supplemental worksheets must be completed if the Screening Worksheet indicates that Infiltration and/or Harvest and Use might be feasible (see below).
Supplemental Feasibility Worksheets
If the Screening Worksheet indicates that Infiltration might be feasible, complete the following form:
If the Screening Worksheet indicates that Harvest and Use might be feasible, complete the following form:
The criteria and procedures for determining whether if Infiltration and/or Harvesting and Use, are feasible or infeasible are based on a report by Geosyntec Consultants: BASMAA Harvest and Use, Infiltration and Evapotranspiration Feasibility/Infeasibility Criteria Report.
SPECIAL PROJECTS
The Municipal Regional Permit allows certain types of Smart Growth development to use non LID methods in addition to Low Impact Development (LID) practices of infiltration, harvest and use and biotreatment to manage stormwater runoff.
Qualifying projects, known as Special Projects, can apply for reduction credits based on location and density criteria that allow non-LID treatment for a portion of the project’s runoff, but only after the use of onsite and offsite LID is evaluated.
The LID reduction credits are intended to allow Smart Growth projects greater flexibility in meeting stormwater treatment requirements, based on the inherent environmental benefits of Smart Growth and potential technical challenges of implementing LID treatment exclusively on high-density sites.
Complete the Special Projects Worksheet and refer to Appendix J (Section J.7) of the C.3 Stormwater Handbook to determine if your project meets the specific criteria that allows treatment reduction credits. The final determination to allow non LID treatment measures is based on whether or not onsite and/or offsite LID treatment is feasible or infeasible, subject to the Planning Division’s review and approval. Site design and source control measures are still required.
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