Mud Mountain Inlet


U.S. Army Corps of Engineers

Completion Date



Jacobs Engineering Group


Enumclaw, Washington

Delivery Method

General Contractor



Contract Value

$33 million
Mud Mountain Inlet

Mud Mountain Inlet project includes significant modifications to this dam to enhance the flow control facilities. The project's primary aim was to create novel intake works for both the 9-foot and 23-foot-diameter tunnels, critical for regulating the flow of the White River during potential flood scenarios.

The newly developed intake structure, containing 29,000 cubic yards of concrete, served as a replacement for the pre-existing structures. To seamlessly integrate the new intake, short connecting tunnels were driven to link with the existing ones. Radial gates were introduced at the new intake, effectively replacing the Howell Bunger valves situated at the outlet of the 23-foot-diameter tunnel and the gate at the intake of the 9-foot diameter tunnel. To mitigate the effects of erosion caused by the substantial gravel flow during floods, the invert of the 9-foot-diameter tunnel underwent re-lining with T-1 high-strength steel. Upon the successful completion of the new intake structure connecting the tunnels, crews proceeded to dismantle the outdated outlet works and old intakes. Additionally, Atkinson built new pedestrian and vehicle bridges to provide operations personnel with ready access to the newly installed inlet structure.