One of the Pacific Northwest's oldest power plants, the historic Snoqualmie Falls Hydroelectric Project, is once again producing electricity for local homes and businesses following a three-year overhaul.
Puget Sound Energy's 102-year-old Plant 2 powerhouse at Snoqualmie Falls, idled in June 2010, last week restarted commercial generation of electricity. Located about a quarter mile downstream from the falls, the plant underwent near-total reconstruction under a new, 40-year federal operating license.
The energy site's Plant 1 powerhouse — just upstream from the falls in a bedrock cavity almost 270 feet underground — also is getting a comprehensive makeover. Built in 1898-99, the older powerhouse is scheduled to resume generating hydropower in July.
Once Plant 1 comes online this summer, Snoqualmie Falls' generating capacity will be 54 MW, compared to about 44 MW previously. The increased output, enough to serve about 40,000 homes, is being achieved through greater plant efficiencies; no additional water will run through the project's seven turbines.
Upgrades made at Plant 2 include:
- A new steel and concrete intake structure along the river's edge for channeling water into a 1,215-foot-long underground tunnel that runs beneath the Salish Lodge and the upper portion of Snoqualmie Falls Park;
- Relining of the 12-foot-diameter, underground tunnel;
- A new Gate House that controls water flow from the tunnel to large, above-ground pipes, or "penstocks," which carry the water more than 1,100 feet down a steep hillside to the Plant 2 powerhouse;
- One new, 7-foot-diameter penstock and one upgraded penstock for delivering water to Plant 2;
- A completely rebuilt powerhouse building, reflecting the original structure's design;
- A new, 13.7 MW turbine-generator, replacing the plant's original, 1910 turbine (the plant's 1957-vintage, 26.5-MW turbine-generator remains in use); and
- A new bypass flow-control system, housed inside the new powerhouse, for ensuring public safety and maintaining consistent downstream flows for fish if an emergency shutdown of power generation were to occur.
This article was originally published on Electric Light & Power/POWERGRID International. It was republished with permission.