One of the oldest power plants in the US Pacific Northwest, the historic Snoqualmie Falls Hydroelectric Project, is once again producing electricity following a three-year, top-to-bottom 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 270ft underground – is also getting a comprehensive makeover. Built in 1898-99, the elder powerhouse is scheduled to resume electric generation in July.

“The Snoqualmie Falls project was an engineering marvel when built in the late 19th century," said Paul Wiegand, PSE senior vice president of Energy Operations. "The redevelopment of its backbone infrastructure truly marks the renewal of a renewable resource for our customers and our region."

Once Plant 1 comes online this summer, Snoqualmie Falls’ generating capacity will be 54MW, compared to about 44MW 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.

Besides the upgrades to Snoqualmie Falls’ power-generating infrastructure, PSE is nearing completion of major improvements to Snoqualmie Falls Park, including a new visitor center that will showcase historical artifacts, documents and photos, and interpretive displays.

Key upgrades made at Plant 2 include:

• A new steel and concrete intake structure along the river’s edge for channeling water into a 1215ft-long underground tunnel that runs beneath the Salish Lodge and the upper portion of Snoqualmie Falls Park;
• Relining of the 12ft-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 1100ft down a steep hillside to the Plant 2 powerhouse;
• One new, 7ft-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, 13.7MW turbine-generator, replacing the plant’s original, 1910 turbine (the plant’s 1957-vintage, 26.5MW 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.