32nd Ave W to 23rd Ave W (conveyance and underground storage)

32nd Ave W to 23rd Ave W (conveyance and underground storage)

Updated May 10, 2010

Project elements

• Diversion structure at 32nd, gravity sewer line in right-of-way through hill, underground storage adjacent to 23rd Ave W south of Garfield St. W.
• Odor control and electrical facilities
• In-tank pump station and force main to convey flows back to system on Port of Seattle property north of the Magnolia Bridge.

Benefits

• Single facility located outside of shoreline zone
• Transfer all flows out of basin
• Similar to other King County operating facilities
• Limits facilities in steep slope areas

Challenges

• Trenchless drilling technique will be required to construct gravity sewer
• Use of Parks property required for diversion structure.
• Narrow street will require management of residential access during construction
• Steep slopes may require special construction techniques
• Some potential for cultural resources issues.
• Use of either Seattle Parks or Port of Seattle property for storage tank.
• Design of ventilation systems and underground electrical facilities will be a complex issue, due to code requirement