Salmon Lake Dam is an earthfill structure 54 feet high, and has a volume of 195,000 cubic yards. The total active reservoir capacity of Conconully Lake is 15,700 acre-feet (active 10,500 acre-feet). The spillway is a siphon type with a capacity of 400 cubic feet per second. The outlet works is a conduit controlled by two gates. A small diversion headwords structure on Salmon Creek diverts the flow into the reservoir through a short feeder canal.
In July 1998, a reservoir operating restriction to elevation 2314 feet was imposed on Conconully Lake as an interim risk reduction measure pending structural modifications to address seismic safety concerns. This reduces the active reservoir capacity to 7,400 acre-feet.
Salmon Lake Dam is founded on the left abutment against rock.The embankment dam across the valley floor and in the right abutment is founded in such materials as silt, sand and gravel, including boulders. The outlet works and spillway are founded on metamorphic sedimentary rock (gneiss).
|Dam Type||Zoned Earthfill|
|National ID Number||WA00291|
|Crest Elevation||2325.5 ft|
|Structural Height||54.0 ft|
|Hydraulic Height (Normal Operating Depth at Dam)||40.0 ft|
|Crest Length||1260.0 ft|
|Top of Active Conservation Pool (Elevation)||2318.68 ft|
|Spillway Crest Elevation||2324.7 ft|
|Top of Dead Storage Pool (Elevation)||2282.10 ft|
|Streambed at Dam Axis||2276.00 ft|
Hydraulics & Hydrology
|Normal Water Surface Elevation||2318.68 ft|
|Spillway Type||Ungated Siphon|
|Total Water Storage at Elevation||10,500 ac-ft|
|Outlet Works Capacity at Elevation||500 cfs|
|Drainage Area||6.4 sq mi|
|Spillway Capacity at Elevation||400 cfs at 2324.7 ft|
|Hydrometeorological Report (HMR)||HMR 57|