Ravenna Creek pipe extension

Completed – Fall 2011

This project was completed in three phases from May 2008 to September 2011.

Phase A was implemented in May 2008 and continued until mid-2010. This phase implemented aggressive cleanup measures after an accidental wastewater release into University Slough was discovered on May 23, 2008. Restoration of the cleanup area was coordinated with University of Washington staff.

Learn more: King County response to Ravenna Creek Sewer spill, May 2008

Phase B of the project took place during Summer 2010. This phase consisted of extending the pipeline that conveys Ravenna Creek downstream from Ravenna Park. A section of pipeline was added to isolate the stream and prevent potential sewer overflows into University Slough.

Learn more: construction begins Monday August 23, 2010. Ravenna Park Ball Field, adjacent trails closed to public through October, Aug. 19, 2010

Phase C of the project was constructed in September of 2011. This phase involves the installation of three large logs with root wads (called "large woody debris" or "LWD") in University Slough as mitigation for the temporary rerouting of Ravenna Creek flow to the combined sewer system instead of University Slough during Phases A and B of the project. Placement of LWD in the slough will create fish habitat and promote biological diversity. The LWD consists of three cedar or fir logs with root wads that are placed in the slough and its buffer as shown on the attached site plan. Each of the logs would be approximately 20 ft long and approximately 16 to 20 inches in diameter at breast height. The bank-side end of each log would be embedded in the ground and anchors would be used to permanently secure the logs in place. The construction area would be dewatered during construction to facilitate installation of the LWD and minimize construction impacts to slough water quality and fish. Dewatering would be accomplished by placing temporary sandbag isolation dams in the slough and pumping slough water around and out of the construction area.