Walla Walla County, WA Environmental Rules: Stormwater Management (2026)

WWCC Chapter 11.05, 'Illicit Discharge Detection and Elimination,' implements the state Water Pollution Control Law, RCW 90.48, and the federal Clean Water Act. WWCC 11.05.020(A) prohibits any person from throwing, draining or otherwise discharging, or allowing anyone under their control to discharge, any material other than stormwater into the county's storm drainage system or into surface and groundwater, and requires existing pollution-generating land uses to implement best management practices drawn from Chapter 8 of the state Stormwater Management Manual for Eastern Washington. The section lists thirty examples of banned contaminants, including trash and debris, construction materials, petroleum products, antifreeze, batteries, paints and solvents, pesticides and fertilizers, pool backwash, domestic animal waste, sewage and lawn clippings.

WWCC 11.05.020(B) separately bans the construction, use, maintenance or continued existence of any illicit connection to the storm drainage system, expressly including connections made in the past regardless of whether they were legal when installed; connecting a sewage line to the storm system, or letting one remain connected, is itself a violation. WWCC 11.05.030 carves out narrow exceptions for things like diverted stream flows, foundation drains and emergency firefighting discharges, and WWCC 11.05.040 conditionally allows discharges such as dechlorinated pool water and street-wash water if they meet stated limits, including a 0.1 ppm chlorine cap.

The county engineer enforces Chapter 11.05 under the procedures in WWCC 11.01.070, which can include a notice of violation, a voluntary correction agreement, civil penalties, and, for the most serious violations, criminal penalties under WWCC Chapter 14.13.