Q Street Stormwater Infiltration Pond

Notice is hereby given that the City of Washougal is soliciting proposals from consultants to select a design consultant for professional services on the Q Street Stormwater Infiltration Pond Project.

Key components of the project include:

• Installation of a new manhole at the intersection of Q Street and 39th Street.
• New stormwater piping to redirect runoff westward to the infiltration pond and eastward to the existing manhole at W Street and 37th Street.
• Installation of two proprietary pre-treatment units on W Street to remove total suspended solids (TSS) and protect the infiltration capacity of the pond.
• Regrading and replanting of the infiltration facility, including replacement of compacted topsoil if necessary, to restore and enhance infiltration performance.

The upgraded infiltration pond will provide both flow control and water quality treatment. By combining pre-treatment with infiltration into native soils, the facility will meet phosphorus, enhanced, and basic treatment performance standards. It is expected to treat and detain runoff from approximately 20 of the 22 acres during a 100-year storm event. Any excess runoff will overflow through the pond’s existing outlet to the stormwater system in W Street, ultimately discharging to Campen Creek.

Refer to Exhibit A for the Project Fact Sheet.

A large infiltration pond is located on the north side of Q Street between 37th and 39th Streets within the Campen Creek Villa subdivision. Based on available as-built drawings and desktop analysis, the pond currently only captures and infiltrates stormwater from adjacent properties and streets within the subdivision. Stormwater from other areas is conveyed directly to Campen Creek without flow control or treatment.

Following an initial survey and engineering investigation to confirm the drainage boundaries, this project will redirect runoff from approximately 22 acres—assumed to be 70% impervious and 30% pervious—bounded by Q Street to the south, W Street to the north, and between 37th and 41st Streets, to the existing infiltration facility.