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Surface Water Management

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Water resources are crucial to San Mateo County. Water provides recreation to San Mateo County residents and visitors. It is also home to many types of wildlife, including endangered species like salmon, steelhead trout, and California red-legged frog. Water pollution degrades the quality of surface waters, making them unsafe for drinking, fishing, swimming, and other activities. Excessive surface water runoff from private properties could flood the public right of way and adjacent properties, impacting intactness of natural resources, public safety, and property.

Water resource protection and flood prevention are everyone's responsibility. For all the projects in the County’s unincorporated area that require building and planning permits, the San Mateo County Planning and Building Department enforces the following stormwater-related policies:

  1. For all projects requiring a demolition, grading, or building permit that involves site disturbance, the submittal of an Erosion and Sediment Control Plan for County review and approval is required. Also see the Erosion and Sediment Control Plan requirements.
  2. For all projects requiring a planning or building permit that would result in any new/replaced area(s) of impervious surface, the following policies apply:
    1. San Mateo County Planning and Building Department, together with, the San Mateo Water Pollution Prevention Program (SMCWPPP), enforces the State requirements for stormwater quality control and provides guidance resources.
    2. San Mateo County Planning and Building Department enforces the surface water runoff flow control, or drainage, on private properties with detailed requirements and applicable forms.
  3. For coastal projects, ASBS requirements are enforced. The State Water Resources Control Board adopted the California Ocean Plan on July 6, 1972 with the latest revisions adopted in 2009. The Ocean Plan prohibits the discharge of waste to designated Areas of Special Biological Significance (ASBS). ASBS are designated by the State Water Board as ocean areas requiring protection of species or biological communities to the extent that alteration of natural water quality is undesirable.
  4. For all projects disturbing the public right of way, San Mateo County Department of Public Works enforces Encroachment Permit requirement.

Surface Water Drainage Review

In addition to NPDES/stormwater treatment requirements, all projects resulting in an increase in impervious surface must also comply with the County's Drainage Policy.... View moreView Surface Water Drainage Review

Stormwater Treatment Requirements

The San Mateo Water Pollution Prevention Program (SMCWPPP) is a partnership of the City/County Association of Governments (C/CAG), each incorporated city and town in the county, and the County of San Mateo, which share a common National Pollutant Discharge Elimination System (NPDES) permit.... View moreView Stormwater Treatment Requirements

Operation & Maintenance (O&M) of Private Stormwater Treatment Measures

The stormwater treatment measure on your property is one of many in San Mateo County that help reduce the amount of pollutants entering the bay or ocean through the storm water system.... View moreView Operation & Maintenance (O&M) of Private Stormwater Treatment Measures

Erosion and Sediment Control

The San Mateo County Planning and Building Department requires certain types of projects to submit an erosion and sediment control plan for review and approval prior to the issuance of any building permit... View moreView Erosion and Sediment Control

Pollution Prevention in the Areas of Special Biological Significance

Areas of Special Biological Significance (ASBS) are designated by the State Water Board as ocean areas requiring protection of species or biological communities to the extent that alteration of natural water quality is undesirable. The Ocean Plan prohibits the discharge of waste to these areas.... View moreView Pollution Prevention in the Areas of Special Biological Significance
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