Bumping Lake Dam


Bumping Lake Dam is an earthfill structure on the Bumping River about 29 miles northwest of Naches. The dam, completed in 1910, is 60 feet high and contains 253,000 cubic yards of material. In 1973, the road crossing the spillway was replaced and a new concrete T-beam bridge was installed to replace a wood-truss bridge. Situated at the lower end of a natural lake, the dam formed a reservoir with an active capacity of 33,700 acre-feet constructed over a natural lake having unknown dead storage capacity.

Modifications to Bumping Lake Dam were undertaken in 1994-1997 under the Bureau of Reclamation’s Safety of Dams Program. These modifications included the installation of an interceptor drain at the downstream toe of the dam, construction of downstream and upstream stability berms, replacement of the concrete spillway, installation of a steel liner in the outlet tunnel, and replacement of the outlet channel lining. The outlet gates, gate house, and gate operators were replaced in the early 1990s.


The stratigraphy at Bumping Lake consists of Evans Creek Glacial drift (Qde), overlain by the Bumping Lake lahar (Qm) and alluvium (Qal).  The alluvium present at the site is composed of reworked drift and lahar materials and is contained to the lowest portion of the valley.  The shells of the dam are founded on the alluvium, between approximately stations 13+00 and 15+00.  Tumac Mountain is located approximately 11 miles south of the dam.  Recent tephra studies near the Tumac Plateau indicate the most recent major eruption occurred between 20,000 to 30,000 years ago.  Observations during the excavation of the test pits indicate the materials overlying the glacial drift were volcaniclastic in nature.  The material also exhibits an interbedded ash layer, indicating multiple emplacements of the Bumping Lake lahar.  The lahar materials mantle the glacial drift to a depth of up to 13 feet near the center of the valley floor and decrease to a thickness of approximately 4 feet at the ends of the dam.  The lahar underlies the shells of the embankment, and appears to be continuous for the entire length of the structure, except in the lowest portion of the valley where the shells are founded on alluvium.  The cutoff trench appears to have fully penetrated the lahar and was terminated in glacial drift.  The thickest portion of the lahar occurs near the outlet works, believed to be the location of the natural channel at the outlet of the ancestral Bumping Lake.  The lahar mainly consists of sand with lesser amounts of silt, gravel and basalt cobbles.  The lahar contains a large amount of organic debris composed mostly of charred wood.  The lahar is classified as silty sand with gravel and cobbles.  The uppermost portion of the unit is composed mostly of silty sand to silty sand with gravel.  The interbedded volcanic ash, approximately 5 to 10 mm thick, occurred at depths ranging from .4 feet in the upstream test pits to 1.4 feet near the downstream toe of the dam.  Just below the ash, the coarseness of the lahar material increases gradually from silty sand with gravel to silty sand with gravel and cobbles.  The Evans Creek drift is composed of gravel sand and silt with cobbles and boulders.  The gradation of the drift deposit varies greatly, but ranges in classification from poorly graded gravel to poorly graded sand with varying amounts of silt.

RegionFacilities in Pacific Northwest | Pacific Northwest Home Page
Dam TypeZoned Earthfill
ReservoirBumping Lake
WatercourseBumping River
Original Construction1909-1910
Modified Construction
National ID NumberWA00263
Hydrologic Unit Code

Structural Height61.0 ft
Hydraulic Height (Normal Operating Depth at Dam)36.0 ft
Top Parapet (Elevation)
Spillway Crest Elevation3429.0 ft
Crest Elevation3435.0 ft
Crest Length3425.0 ft
Crest Width
Base Width
Volume of Dam Construction Materials
Streambed at Dam Axis3391.3 ft
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)
Top of Active Conservation Pool (Elevation)3426.2 ft
Top of Inactive Conservation Pool (Elevation)
Top of Dead Storage Pool (Elevation)3389.6 ft

Hydraulics & Hydrology
Total Water Storage at Elevation33,700 ac-ft
Maximum Water Surface Elevation
Normal Water Surface Elevation3426.2 ft
Spillway TypeUngated overflow, wood chute
Auxiliary SpillwayNo
Spillway Capacity at Elevation3,400 cfs at 3429.0 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation1,500 cfs at 3426.2 ft
Diversion Capacity at Elevation
Drainage Area68.0 sq mi
Hydrometeorological Report (HMR)HMR 57
Probable Maximum Flood (PMF) Report

Contact Information
TitleArea Office Manager
OrganizationColumbia-Cascades Area Office
Address1917 Marsh Road
CityYakima, WA 98901-2058
Phone (Fax)509 454-5611
Phone (Office)509 575-5848 x202
TitleArea Office Manager
OrganizationColumbia-Cascades Area Office
Address1917 Marsh Road
CityYakima, WA 98901-2058
Phone (Fax)509 454-5611
Phone (Office)509 575-5848 x202

Last updated: Oct 25, 2012