Agency Valley Dam is located on the North Fork of the Malheur River near Beulah, Oregon, The dam is a 110-foot-high zoned earthfill structure that contains 646,000 cubic yards of material. The total capacity of the reservoir is 59,200 acre-feet (active 59,200 acre-feet). The needle valves in the outlet works were replaced by jet flow gates in 1990 as part of the operation and maintenance modifications program.
The foundation consists of Columbia River Basalts with interbeds of basaltic tuff, tuff-breccia, and volcanic ash overlying shale in the right abutment. Shales form the left abutment and channel section foundation.