Last Sunday, the county celebrated completion of its raingarden/stormwater-diversion project in Sunrise Heights and Westwood (formally known as the Barton CSO Control Project). Now, the city is announcing it’s almost done with its two Delridge-area CSO (combined-sewer overflow) reduction projects – the two that also were affecting traffic in the work zones at times in recent months. From Seattle Public Utilities:

Seattle Public Utilities (SPU) is wrapping up work at CSO 2 and CSO 3, two sewer improvement project sites in the Delridge neighborhood. Crews are finishing construction next month and both sites will be fully operational by the end of the year. Thanks for your patience during construction!

WHAT WE DID
Over the past year, we installed:
* A “smart” system, including valves and sensors to better monitor and control the amount of stormwater and sewage that is allowed to enter the downstream sewer system
* A new ventilation fan to improve air quality and safety for workers in the large storage tank
* Roadside cabinets to transmit flow information to SPU
* Pedestrian and landscaping improvements

WHY WE DID IT
During heavy rainstorms, combined sewer overflow (CSO) storage tanks hold excess storm water and sewage until there is capacity in the downstream system to carry it away, reducing the chance of sewage overflows into Longfellow Creek. As CSO 2 and CSO 3 aged, they became less efficient, resulting in more frequent overflows. This project increased the efficiency of these storage tanks, which will reduce overflows of untreated stormwater and sewage into Longfellow Creek.

WRAP-UP ACTIVITIES
* Landscaping at both sites (through fall 2015)
* Installation of permanent public art at CSO 3, commissioned through the city of Seattle Percent-for-Art program (2016)
* Ongoing equipment testing at both sites and the diversion structure

Details of the art project are in our coverage of last May’s Westwood-Roxhill-Arbor Heights Community Council meeting.