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Stormwater Management

Stormwater Control

Stormwater runoff from urbanized areas is a major source of pollution to local creeks and San Francisco Bay. To comply with the Municipal Regional Stormwater Permit (MRP 3.0), reissued by the Regional Water Quality Control Board in 2022 and amended in 2023, the City of Walnut Creek requires development projects to incorporate appropriate stormwater controls. These may include site design measures, source controls, low impact development (LID) techniques and Hydromodification Management (HM).

Updates are effective as of July 1, 2023.

2023 UPDATES HIGHLIGHT

  • Impervious surface threshold for most projects will drop from 10,000 to 5,000 sq ft, including for new roads and the addition of a travel lane to an existing road

  • New categories of regulated projects include:

    • Road and sidewalk repair projects ≥ 5,000 contiguous sq ft     

    • Road reconstruction and pavement widening ≥ 1 contiguous acre

    • Detached single family home that creates or replaces ≥ 10,000 sq ft

BAHM model is used for flow control only, so the IMP Calculators is still needed for design of treatments

For more details please see:

Clean Water Guide

Stormwater Management C.3 Review Process

 Regulated projects   Not regulated projects 
Analyze the feasibility of infiltrating, evapotranspirating, or harvesting/reusing runoff. Where none of these are feasible, runoff from impervious areas may be routed to Bioretention facilities  Determine the applicability of the MRP Section C.3.i, “Small Projects”  
 In-ground vault filters or tree-well type of biofilters may be used only in specific, narrowly defined Special Projects categories of “Smart Growth” projects Where neither C.3.b “Regulated Projects” nor C.3.i is applicable, the City of Walnut Creek encourages applicants to assess stormwater runoff and provide discussion of planned efforts to implement the best practices and goals outlined in the MRP
 The CCCWP Stormwater C.3 Guidebook (C.3 Guidebook) summarizes the policies, procedures, design and submittal requirements for projects in Contra Costa County   

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