Mud Mountain Dam
30525 S.E. Mud Mountain Rd.
Enumclaw, WA 98022

Our office hours are from 7:30 a.m. to 4 p.m. If you need additional information, please feel free to call us. (360) 825-3211 or (206) 764-3717.  For Water Management information, you may call (206) 764-3750.

For Recreation information or to reserve a large group shelter please contact the Park Ranger at (206) 316-3019.

Mud Mountain Dam

Mud Mountain DamMud Mountain Dam is a flood control dam protecting the lower White and Puyallup River valleys from flooding by holding back water from heavy rains and melting snow in its reservoir. Water managers from the U.S. Army Corps of Engineers, Seattle District, slowly release water back into the river. The photo on the left is what the dam looks like when it isn't being used for flood control.  Visitors to the facility, located on the White River near Mt. Rainier in Washington State, can view the dam, picnic, hike, bike or ride their horses in a scenic woodland setting.

The U.S. Army Corps of Engineers built the dam on the White River in the 1940s. The Corps also made channel improvements and built levees on the lower Puyallup River. Together, these structures have saved an estimated $308 million in flood damages. The project currently helps protect the homes and businesses of about 400,000 people. The dam regulates flooding by holding back water from heavy rains and melting snow in the reservoir, then releasing it slowly back into the river. The reservoir is usually empty, except for the normal flow of the White River.  Completely filled, the reservoir would stretch 5.5 miles and cover 1,200 acres.

Mud Mountain Dam holding a pool

Congress authorized construction of Mud Mountain Dam with the Flood Control Act of June 22, 1936. Work began on August 25, 1939, but was halted by World War II. Construction resumed in 1947, and the dam was completed in 1948. At that time, it was the highest rock and earth-filled dam in the world. Fishway facilities in Buckley were finished in 1949, and the Rim Trail and picnic areas were added in 1980.

The core of the dam is a compacted blend of sand, gravel and glacial till. Upstream and downstream sides of the dam are crushed rock covered by large quarry rocks. The massive weight of the rock holds the core firmly in place. Two tunnels channel the river around and under the dam. A 9-foot-wide tunnel passes normal flows. A 23-foot-wide tunnel is used during periods of high flows and during floods.

The photo on the right shows the dam holding a pool, which is only done when it's being used for flood protection.  The dam has a spillway near the right bank of the White River that will allow excess floodwaters to be released. This will prevent water from reaching the top of the dam, which could possibly damage or destroy it.

Mud Mountain Dam Fish Passage Facility Video

MMD Historical Construction Video

Flip the River Video

The U.S. Army Corps of Engineers began construction on the new $112 million Mud Mountain Dam Fish Passage Facility in June. It will be the nation’s largest trap-and-haul facility, transporting Endangered Species Act-listed and other fish around the dam near Buckley, Washington. The Corps’ contractor, Kiewit Infrastructure West Company, provided this video of them diverting the White River to isolate the left bank for demolition of the existing barrier dam to begin construction of the new project.

The Corps is pursuing an aggressive schedule to minimize risk to ESA-listed species. Recent years have seen large increases in the White River Chinook run. The 2017 count was 16,271, a 174 percent increase over 2016’s 9,347 total, which was the best seen in 71 years of return records.