All work on the spillway willoccur in non-spill season. One water stop is located at a non-overflow monolith joint 27/28. One water stop islocated at a closure monolith joint C2/3. All work at the non-overflow and closure monoliths shall be completed from theroadway and during spill season.
In general, the contractor shall complete precision angle drilling within precise tolerances to inject a hydrophilic sealant into the upstream spillway monoliths at fours locations in the overflow section and one location on the non-overflow section. There is a site visit schedule for 22 June 2022 from 1300 to 1500 hours.
Army Corps of Engineers (USACE), Seattle District, requires repairs to damaged and eroded concrete on the south side of the spillway, fish ladder and stilling basin. Damage include holes in the spillway monolith ogee surface, missing concrete between the fish ladder structure and spillway apron with exposed native foundation materials and eroded concrete between the sheet pile wall and the fish ladder.
The approach roadway surface is a concrete surface on the top of the concrete dam’s non-overflow monoliths. There are eight non-overflow monoliths to the west of the spillway bridge and eleven non-overflow monoliths to the east of the spillway bridge. seven monoliths that have head gates. Each monolith is 50-feet in length along the centerline of the dam. The width of the roadway surface from curb to curb is 24-feet.
The scope item with the most impactful contractor limitations is the replacement of the chute drains which involves demolishing lateral sections of the spillway and large excavations behind the spillway wall monoliths to construct the drainage gallery.
Roadway work will also include installation of deck joint material on the 22 spans of the spillway bridge.There are seven monoliths that have head gates. Currently storm water sits over the hatches for the head gates, which causes water to sit in the hatch framing and drip on the head gate machinery.
The Recommended Plan approved in the DSMS for PED consists of: A full replacement of the spillway drainage system through selective demolition of the existing chute slab at designated new lateral drain locations, reinforced concrete overlay throughout the entire chute and stilling basin , armoring the area behind the chute walls, raising the spillway abutment monoliths, constructing a deflector beam to deflect the overflow nappe from gates, and modifying
