Boysen Dam is a zoned earthfill structure having a structural height of 220 feet. An overflow, weir-type spillway controlled by radial gates is located on the right abutment and surcharges immediately upstream and left of the powerplant.
Design discharge through the spillway is 25,000 cubic feet per second at elevation 4725.00 The Boysen Reservoir has a total controlled storage capacity of 802,000 acre-feet at water surface elevation 4725.00
The outlet works is on the right abutment of the dam. Discharge is through a 66-inch-diameter steel pipe located above the power penstock and a 57-inch-diameter steel pipe joined to the 10-foot-diameter power penstock serving Unit 1 in the powerhouse.
The powerplant has an installed capacity of 15,000 kilowatts developed by two units operating under an average head of 99 feet. Each unit is served by a 10-foot-diameter steel penstock joined to a common 15-foot-diameter steel penstock immediately upstream from the powerplant. The 15-foot-diameter penstock leading from the intake structure to the units was located to utilize the bore of an existing railroad tunnel made available through relocation of the CB&Q railroad.
Other features of the construction activity were the relocation of 13.5 miles of the railroad track, which required a tunnel 1.25 miles long, seven bridges, two sidings, and other construction features.Folded and faulted shales and sandstones lying over pre-Cambrian diorites, with up to 70 feet of alluvium in the riverbed.