The goal of Provision C.3 of the Municipal Regional Stormwater Permit (MRP) is to include appropriate source control, site design, and stormwater treatment measures in new development and redevelopment projects. These measures are intended to address both soluble and insoluble stormwater runoff pollutant discharges and prevent increases in runoff flows from new and redevelopment projects. The C.3 goal is to be accomplished primarily through the implementation of low impact development (LID) techniques.
MRP Regulated Projects are defined in the following categories:
Small Projects and Detached Single-Family Home Projects (*New Requirements Effective 12/1/2012)
Projects that create and/or replace at least 2,500 square feet, but less than 10,000 square feet, of impervious surface, and
Individual single-family homes that create and/or replace 2,500 square feet or more of impervious surface must include at least one of the following site design measures:
· Direct roof runoff into cisterns or rain barrels for use and/or onto vegetated areas.
· Direct runoff from sidewalks, walkways, and/or patios onto vegetated areas.
· Direct runoff from driveways/uncovered parking lots onto vegetated areas.
· Construct sidewalks, walkways, and/or patios with permeable surfaces.
· Construct bike lanes, driveways, and/or uncovered parking lots with permeable surfaces.
New development and redevelopment projects that create 10,000 square feet or more of impervious surface (collectively over the entire project site) including commercial, industrial, residential housing subdivisions (i.e., detached single-family home subdivisions, multi-family attached subdivisions (town homes), condominiums, and apartments), mixed-use, and public projects are required to treat the permit-specified amount of stormwater runoff with the following Low Impact Development (LID) methods:
Special Land Use Categories
Projects that create and/or replace 5,000 square feet or more of impervious surface related to the following categories of land use will be required to provide LID stormwater treatment:
• Auto service facilities
• Retail gasoline outlets
• Restaurants, and/or
• Uncovered surface parking (This applies to stand-alone parking, or parking included as part of any other development project. It also applies to the top uncovered portion of a parking structure, unless drainage from the uncovered portion is connected to the sanitary sewer.)
When considered at the watershed scale, certain land development projects characterized as smart growth, high density, or transit-oriented development can either reduce existing impervious surfaces, or create less “accessory” impervious areas and automobile-related pollutant impacts. Incentive LID Treatment Reduction Credits approved by the Water Board may be applied to these Special Projects, which are Regulated Projects that meet the specific criteria.