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Mud Mountain Inlet

Mud Mountain Inlet

Protecting the Lower White and Puyallup River Valleys
Location
Enumclaw, Washington
Client
U.S. Army Corps of Engineers
Designer
Jacobs Engineering
Contract Value
$33.5 Million
Completion Date
1995
Market Sector
Dam & Hydro

Fifty years after completing the Mud Mountain Dam, Atkinson returned to the site to make major modifications to the flow control facilities. The scope of work consisted of the construction of new intake works for the 9-foot and 23-foot-diameter tunnels, which are used to control the flow of the White River during potential flood periods. 

The new intake structure, containing 29,000 cubic yards of concrete, replaced the two existing structures. Short connecting tunnels were driven to the existing tunnels. Radial gates at the new intake replaced the Howell Bunger valves at the outlet of the 23-foot-diameter tunnel as well as the gate at the intake of the 9-foot diameter tunnel. 

The 9-foot-diameter tunnel's invert was relined with T-1 high-strength steel to reduce scouring by the large amount of gravel that is carried through the tunnel with each flood. Atkinson crews demolished the outlet works as well as the old intakes when the new intake structure connecting the tunnels was completed. 

Additionally, Atkinson constructed new pedestrian and vehicle bridges to provided operations personnel with ready access to the new inlet structure.

 
 
 

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