New Transportation Projects Include Stormwater Features

It’s no surprise that Tualatin receives a lot of rain each year. Just ½-inch of rainfall in Tualatin results in 71 million gallons of water. In a natural environment, soil and plants absorb most of that. But when streets, buildings and parking lots cover the ground, rain washes over these hard surfaces and becomes stormwater. Much of that will be intercepted, infiltrated, or detained in our existing stormwater facilities. However, some of that water ends up directly in our streams – Hedges Creek, Nyberg Creek, Saum Creek, or Basalt Creek, and eventually flows into the Tualatin and Willamette Rivers. 

On February 8, the Tualatin City Council adopted a new Stormwater Master Plan – the City’s first since 1972! An educational video introduced the Master Plan, which addresses the challenges and prioritizes solutions for stormwater quantity, quality, and velocity.  

The City has also made it a priority to include stormwater management features in its new transportation projects, in an effort to capture and treat the volumes of stormwater runoff from new pavement – whether roadway, bike path, or sidewalk. Using best practices, the runoff is captured in detention basins and treated before being slowly returned to a stream. 

An example is the Garden Corner Curves project, where construction is underway at 105th Avenue/Blake Street/108th Avenue between Willow Street and Morotoc Drive. Here, the roadway is being narrowed to slow traffic, and reconstructed with a raised crosswalk at 108th Avenue and Blake Street and a shared-use path to enable pedestrians and bikes to safely move through the corridor.  

This is an environmentally sensitive site, with Hedges Creek flowing through a culvert underneath the roadway. Stormwater runoff is being captured during construction to prevent erosion into the stream. Meanwhile, crews are simultaneously installing new stormwater facilities. Project Engineer David Brokaw explains this will include two stormwater planters to buffer the area between the roadway and new sidewalk, a large water quality facility, an upgrade to the existing culvert, a new conveyance system to capture and route stormwater to these facilities, and shared-use pathways constructed with porous asphalt to reduce runoff volumes.  

The City is planning a combined facility to collect and treat stormwater on behalf of projects funded by Tualatin Moving Forward, the City’s bond-funded transportation improvement program.