Failed roadside raingardens a lesson for the city

Seattle Public Utilities (SPU) is continuing its $500,000 project to remove some of the roadside raingardens and restore the planting strips to their original look.

One of the bulb-out raingardens that has been filled in with grass.

Earlier this week the Department of Planning and Development released SPU’s proposal to remove ten of the 13 bulb-outs. The proposal states that SPU will “restore the curb-line, roadway surfaces, and planting/parking strips to their former condition. The project also would install under-drains in some of the raingardens on 28th Avenue Northwest to eliminate surface ponding.” Information on how to appeal this plan or make comments can be found here. The project is expected to start late next month.

One of the failed roadside raingardens that has been filled in with dirt.

Mike Eagan with SPU tells us that while one-third of the raingardens failed, two-thirds are either working or will be working as soon as the retrofit is complete. “Although the results were not what SPU expected, it succeeded as a ‘pilot project’ in that it provided some important lessons, including the development (again, with community input) of designs that will help reduce Combined Sewer Overflows (CSOs) throughout the city,” Eagan says.

A look at one of the roadside raingardens from May

Ballard is a high priority for CSO reduction. “State and federal laws now require Seattle to reduce CSOs to no more than once a year per drainage basin,” says Eagan. “Ballard’s two drainage basins experienced 93 CSOs last year, dumping over 43 million gallons of combined stormwater and raw sewage into Salmon Bay.” Those numbers are about 25-percent or more of the city’s entire CSO volume in 2010, Eagan tells us. “For example, in December more than 23.5 million gallons overflowed into Salmon Bay. Even this past June, we saw six storm-related CSOs and four of those were in Ballard, spilling over half a million gallons of combined stormwater and raw sewage into Salmon Bay – 95% of Seattle’s total CSO volume for the month.”