Single Family Residential Stormwater Plan

The Phase II Western Washington National Pollutant Discharge Elimination (NPDES) stormwater general permit (permit) implements the federal Clean Water Act. The permit is administered by the Washington State Department of Ecology and requires stormwater management for new development and redevelopment projects (including Single Family Residential [SFR] projects) that create more than 2,000 square feet of new and replaced impervious surface or disturb 7,000 square feet or more of land. For SFR projects, the type and extent of stormwater requirements vary depending primarily on the amount of new and replaced impervious surface area created. Small projects (e.g., projects that create less than 5,000 square feet of new and replaced impervious surface area) will be required to implement certain minimum stormwater requirements, but will not require engineered flow control or water quality treatment facilities. Large SFR projects could potentially require engineered flow control and/or water quality treatment facilities. This document provides guidance on how to determine which stormwater requirements apply to your project, how to meet the requirements, and how to prepare submittals in accordance with the Clark County.

Overview of Stormwater Requirements

The Clark County has nine minimum stormwater requirements, as summarized in Table 1. Relatively small SFR projects (e.g., projects that create less then 5,000 square feet of new plus replaced impervious surface area) will generally only trigger MR #1-5. However, larger SFR projects could potentially trigger all nine Minimum Requirements.

Erosion Control Plans

Wet Weather Erosion Control Plans show the minimization of the areas of disturbed soils and the duration of exposure during construction. This assures grading work on private or public projects does not result in soils or other material being washed from the construction site onto other properties or into water courses. It is imperative to control water at up-slope site perimeters, control water on-site, control sediment on-site, and control sediment at the downslope site perimeters.

Our Services

Engineering NW provides:

  • Single Family Stormwater Plans and Technical Report
  • Erosion Control Plans and Report

Please call (360) 931-3122 for a quote for your stormwater project.