Cold Springs Dam is a zoned earthfill type with a structural height of 115 feet and a volume of 793,000 cubic yards. Cold Springs Reservoir is located offstream about 6 miles northeast of Hermiston, Oregon. Water is diverted to the reservoir from the Umatilla River by the Feed Canal Diversion Dam and Canal. The reservoir’s total active capacity is 39,260 acre-feet (active 38,646 acre-feet).
Safety of Dams work in 1994-1995 included the construction of an interceptor trench and drain at the downstream toe of the embankment, a downstream stability berm, extension of the wing dikes, replacement of the spillway with an enlarged roller compacted concrete structure, and a new Feed Canal backflow structure.
A few large exposures of basaltic lave bedrock (Columbia River basalt) can be seen on the valley sides downstream from the dam; alluvium and/or windblown silt cover hut throughout most of the area bedrock. The alluvium appears to be chiefly sand, but beds of gravel and numerous cobbles and boulders can be seen at various places. The alluvium is thick, widespread deposit from a tremendous flood, which covered the area in late glacial times. In the spillway area bedrock is exposed only near the downstream end of the chute along the left wall. In this exposure the basalt is rather soft, crumbly and closely jointed. It is not highly resistant to erosion. Small exposures of basalt can be found at several places in the right hillside between the creek and spillway, but no rock was recognized on the right side of the spillway except at the downstream end. In a cliff along the right canyon wall about 300 feet left (east) of the spillway a considerable thickness of hard, fresh highly resistant basalt also occurs.