Walla Walla County, WA Environmental Rules: Erosion Control (2026)

WWCC 11.07.030 sets the county's construction and post-construction stormwater standards, and subsection C, 'Construction Site Runoff Control,' is where erosion and sediment control during building activity is addressed. Any construction site disturbing one acre or more, and any smaller site that is part of a common plan of development or sale exceeding one acre, must prepare a stormwater site plan and a stormwater pollution prevention plan (SWPPP) following Chapters 3 and 7 of the Stormwater Management Manual for Eastern Washington before work begins. Construction operators must provide erosion and sediment control BMPs and implement source control BMPs during construction to protect water quality, reduce pollutant discharge, and satisfy the state's AKART standard, all known, available and reasonable methods of prevention, control and treatment, with those BMPs selected, designed, installed, operated and maintained to the manual's standards.

Under WWCC 11.07.030(C)(1)(b), a project disturbing between one and five acres between June 15 and October 15 may instead apply for a state erosivity waiver, which excuses it from the SWPPP requirement for that certified period; work that runs past the waiver window needs either a revised waiver or a full stormwater site plan for the remaining work. Every qualifying site must also obtain coverage under the state Department of Ecology's construction stormwater general permit. Plans and SWPPPs are filed with and reviewed by the county engineer under WWCC 11.07.040, and the developer bears responsibility for construction inspection, staking and record drawings under WWCC 11.07.050.

Failure to control erosion is enforced through the civil and criminal process WWCC 11.01.070 applies to the rest of Title 11, since Chapter 11.07 violations fall under that section's enforcement scheme.