Culmback Dam
| Culmback Dam | |
|---|---|
The reservoir, Spada Lake, seen from the air, with the dam on the left end of the lake
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| Location | Snohomish County, Washington |
| Coordinates | 47°58′31″N 121°41′11″W / 47.9753°N 121.6865°WCoordinates: 47°58′31″N 121°41′11″W / 47.9753°N 121.6865°W |
| Construction began | 1960 |
| Opening date | 1965 |
| Operator(s) |
Snohomish County PUD City of Everett |
| Dam and spillways | |
| Impounds | Sultan River |
| Height | 262 ft (80 m) |
| Length | 640 ft (200 m) |
| Elevation at crest | 1,450 ft (440 m) |
| Reservoir | |
| Creates | Spada Lake |
| Total capacity | 165,774 acre·ft (204,479,000 m3) |
| Catchment area | 84 sq mi (220 km2) |
| Surface area | 1,870 acres (760 ha) |
| Power station | |
| Commission date | 1983 |
| Hydraulic head | 1,165 ft (355 m) |
| Turbines | 2x 47.5 MW Pelton 2x 8.4 MW Francis |
| Installed capacity | 112 MW |
| Annual generation | 418 million KWh |
The Culmback Dam (also known as the George Culmback Dam or the Snoqualmie National Forest Dam) is a large rockfill hydroelectric and water supply dam on the Sultan River, a tributary of the Skykomish River, in Washington. Built in 1965, the dam is 640 feet (200 m) long at the crest and 262 feet (80 m) high. Its reservoir, Spada Lake, provides water for 70 to 75 percent of Snohomish County, and the powerhouse downstream of the dam produces 112 megawatts. Some critics charge that the dam has strongly impacted the runs of salmon and other migratory fish in the Sultan River by depleting gravel and sediment needed to line the riverbed. The dam’s operator counters that Culmback Dam dramatically reduces flooding events, benefiting fish populations and the surrounding communities. The dam was named in honor of George Culmback, a former mayor of Everett.
The Dam is co-owned by the Snohomish County PUD and the City of Everett and is operated by the PUD. Water from Spada Lake is diverted through a pipeline to a powerhouse further downstream on the Sultan River. From the powerhouse, some water is returned to the river, and some is diverted to Lake Chaplain, where the water enters the Everett water supply system.
Prior to 1917 the City of Everett received its water supply from Woods Creek, a tributary of the Snohomish River. Because of increasing water needs of large paper mills and factories, the city switched its water supply to the Sultan River basin via the tributary Chaplain Creek. The Chaplain Reservoir was created in 1929 with the completion of an earthfill dam, and later raised in 1942. This supply proved insufficient as well, so engineers looked to tap the main stem of the Sultan River, where an excellent dam site had been identified.
The Culmback Dam was built in two stages, or phases. Phase 1, which began in 1960 and ended in 1965, involved building the dam to a height of 200 feet (61 m), impounding a 40,000-acre-foot (49,000,000 m3) reservoir. The construction done during this phase served to replace the smaller, 22-foot (6.7 m) diversion dam 6.5 miles (10.5 km) downstream on the Sultan River. Phase 2, completed in 1984, involved raising the dam 62 feet (19 m) to its present height, quadrupling the reservoir capacity. The second phase also included the pipeline connecting Spada Lake to a new hydroelectric powerhouse and from there to the Chaplain Reservoir.
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