McKay Dam is located on McKay Creek about 6 miles south of Pendleton, Oregon. It was constructed to furnish a supplementary supply of water to Stanfield and Westland Irrigation Districts. The dam is an earthfill structure with a reinforced concrete paved upstream slope. It is 165 feet high and contains 2,364,000 cubic yards of material. At closure in 1927, the reservoir had a total storage capacity of 73,800 acre-feet (active 73,800 acre-feet). In 1993, a sedimentation survey estimated the total reservoir storage capacity at 71,500 acre-feet (active conservation is 65,534 acre-feet).
McKay Dam was originally constructed during 1923-1927. Modification of the spillway section was made in 1978-1979 to increase the capacity from 10,000 to 26,910 cubic feet per second. In 1991, the needle valves were replaced with the new jet flow gates. Safety of Dams work on the left abutment included the excavation and replacement of low-strength foundation materials, construction of two 700-foot berms on the upstream and downstream sides, and the installation of a drainage system.