Challenge

Located at the bottom of the drainage basin for the downtown core of Forest Grove and the headwaters to Council Creek, Hawthorne Avenue experienced frequent flooding and suffered from a lack of pretreatment of stormwater runoff.

Solution

By using property vacated by Portland & Western Railroad (a former railroad depot), this project constructed a water quality swale that treats half a million square feet of impervious area and develops overflow storage and conveyance for the large storm events that frequently overtopped the road.

The overflow and conveyance aspect of the project required coordination with an active railroad line, removing and reinstalling track to install 5′ 30″ Cooper E-80 rated culverts. Parallel to the railroad, the narrow, highly incised ditch was widened to take advantage of the 60′ railroad right-of-way. This widened channel continued under Hawthorne Street to a second channel connecting to Council Creek. The existing 48″ culvert under Hawthorne Street, albeit in deteriorating condition, was repurposed as an overflow during extreme events.