Highway 99 Water Quality Retrofit

The water quality of streams around Northeast Highway 99 is poor. Updates to the area’s stormwater treatment facilities will improve water quality. Public Works will install stormwater catch basin retrofits in summer 2023. 


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About the project


Several potential project areas were identified after study of the Cougar Creek basin. The study assessed water quality and flow control needs. Northeast Highway 99 is the most used roadway among the primary arterials maintained by the County. The project area includes Northeast Highway 99 between Northeast 78th Street and Northeast 68th Street. This segment was selected due to the urgency of its needs for water quality improvement. Stormwater facility updates in this area are not likely to be impacted by future road improvement projects.

Click here for a map of drainage areas with little to no stormwater treatment infrastructure.


The project area includes Northeast Highway 99 between Northeast 68th Street and Northeast 78th Street. The project will retrofit 18 catch basins and curb inlets, adding water quality treatment components. Northeast Highway 99, which is one of the county’s busiest primary arterials, is traveled by more than 20,000 vehicles daily . Common pollutants from such high traffic roadways include total suspended solids, metals and petroleum hydrocarbons. Retrofit of these catch basins is an effective way to prevent pollutants from being discharged into Cougar Creek.

Click here for a map of the project location.


The goal of the project is to increase treatment of stormwater running off of Highway 99 before it reaches Cougar Creek.

Storm drain inlets, often referred to as catch basins or curb inlets, are the most widely used structures for capturing runoff from roads and parking lots. These inlets typically include a  a sump to capture sediment, debris and pollutants. There are an estimated 12,000+ storm drain inlets currently owned and maintained by Clark County. Catch basins treat runoff that enters water bodies. Some water bodies in the county are included in Ecology’s 303(d) list of impaired water bodies because of high levels of various pollutants, high turbidity, high temperature, and/or low dissolved oxygen levels. Many of these catch basins lack pretreatment devices or downstream treatment facilities. This contributes to untreated stormwater decreasing water quality in streams, lakes and rivers.

Water quality is poor in many streams throughout Clark County. Catch basin retrofits are cost-effective stormwater treatment options in areas where space limits the use of larger treatment facilities. 


Clark County recently completed a study of Cougar Creek basin. The study assessed water quality and flow control needs. During the study, the county evaluated water quality along several high traffic roadways. Highway 99 was identified as high need for water quality treatment. Highly polluted runoff is currently directly discharged to Cougar Creek without treatment.

Project timeline

Design: spring 2023
Construction: summer 2023


The total cost of the project is $724,000. The count received a grant from the Department of Ecology grant for $543,000. The remaining balance of $181,000 being paid by the Clean Water Fund.


Comments or Questions

Please contact the project manager.

More information:

Scott Fakler
Project manager
Clark County Public Works