3155R ALASKAN WAY
Aug. 15, 2020:
The King County Wastewater Treatment Division (WTD) proposes to conduct maintenance repairs on the existing Denny Way combined sewer overflow (CSO) regulator. This WTD facility exists mostly on parcel number 7666202251, although the work area will extend onto the adjacent parcel 7666202250 (owned by Seattle Parks and Recreation) and Seattle right-of-way (ROW, owned by SDOT). There is no address associated with these parcels or ROW. The existing concrete pavilion overlays and protects the subterranean outfall gates of the CSO regulator and is surrounded by a protective layer of large diameter seawall rock (riprap) on the shoreline of Elliot Bay. Wave and tidal action against the riprap and pavilion have begun to erode the pavilion structure, putting the outfall gates at risk. The project therefore proposes to stabilize the plaza wall footing subgrade, repair damage in the seawall, and prevent further erosion of the shoreline around the Denny Way Regulator and Plaza. This project includes the removal of existing riprap to expose the plaza wall footings that have been undermined by tidal and wave action. The footing subgrade will be stabilized by pumping low strength concrete or flowable fill into the void spaces created by erosion of granular material from beneath the footings. Upon completion of stabilizing the plaza wall footings, the seawall will be repaired by replacing existing rock removed to repair the footings. Additional large diameter rock import will be placed to build up the shoreline revetment to protect the plaza walls and regulator transition structure. Repair of the seawall will stabilize the shoreline, prevent further erosion around the Denny Way regulator, and restore the integrity of the surrounding plaza walls and concrete hardscape. The project will also increase the safety of staff working at the Regulator after dark and protect the Plaza's integrated artwork.
The project construction will occur above the High Tide Line (HTL) that occurs at 10 feet NAVD88. All project work will be conducted in the dry. Temporary fencing will be erected in the surrounding upland areas to create a high-visibility barrier between the project site and the park-users. For site access a temporary construction access road and construction haul route will be established from the intersection of Broad Street and Alaskan Way along the Elliott Bay Trail. Environmentally critical areas (ECAs) and shoreline occur within or near the project area. No vegetation will be impacted by the project.
Canceled.
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