By Emily Alhadeff

Probably the only thing worse than an aging sewage treatment plant is an aging sewage treatment plant that catches fire.

That’s what happened in 2015 in the sludge-drying facility at the City of Snoqualmie’s water reclamation facility (WRF), where biosolids from wastewater are treated and processed into salable compost. On the bright side, the fire sparked a $12.8 million renovation to the facility that won a 2021 Environmental Best Practices Award from the Washington state chapter of the American Public Works Association (APWA).

“We had antiquated technology,” says Snoqualmie public works project engineer Jeff Hamlin, who notes that the system wasn’t robust enough to keep up with the city’s triple-digit growth.

“Starting back in the late ’90s, we were a city of about 1,500 people. Now we’re a city of almost 15,000. So in 20 years or thereabouts, we’ve essentially grown an order of magnitude.”

All that growth translated into a whole lot of wastewater that needed processing, overloading a system that was straining the city’s budget.

“The old system would essentially run [the sludge] through these gas dryers, which were not very efficient, using enormous amounts of gas, lots of water for cleanup, lots of electricity,” says Hamlin. “You can think of a wastewater treatment facility kind of like a big digestive tract,” he adds, explaining how the process uses bacteria swimming in aerobic oxidation ditches to consume and convert biosolids into a viscous byproduct that, after being treated and dried, yields literally tons of nontoxic, nutrient-rich biosolids.

After the 2015 fire, all that sludge, with nowhere to be processed, ended up in the landfill at a cost of $26,000 a month, underscoring a need to rebuild better, as quickly as possible. In phase one of the project, completed in 2017, the city worked with RH2 Engineering to upgrade the WRF’s ultraviolet disinfection, backup power, and industrial control systems. The award-winning phase two included the construction of modern aerobic digesters, an aeration system, a state-of-the-art biosolids processing plant, and an operations and control center with 3,400 square feet of office space for staff with a flexible configuration for future growth. To manage the more ambitious second phase, RH2 relied on biweekly meetings with city engineers and contractor Prospect Construction, as well as a digital file-sharing system, to tweak the design and keep the project on track.

It’s another revenue generator we sell at a deep discount, obviously, but you know, that golf course would die without it,

Completed on schedule in April 2020, Snoqualmie’s v.2 WRF, the largest construction project in the city’s history, is projected to save $4.2 million in operating costs over the next decade via reductions in staffing and in the consumption of energy and natural resources. Not to mention hauling costs, which dropped from $26,000 to $4,500 a month once the plant went online; as well, treated water that doesn’t recharge the Snoqualmie River is diverted to irrigation clients (like the Golf Club at Snoqualmie Ridge, home of the Boeing Classic) for a small fee that helps offset operating costs.

“It’s another revenue generator we sell at a deep discount, obviously, but you know, that golf course would die without it,” says Hamlin. Those living downwind from the facility also appreciate another perk: Thanks to enclosed biofilters that process ripe off-gassing from the plant’s digesters, the city’s wastewater treatment process is now odorless. And then there’s the ultimate bottom line.

“We appreciate the hard work of the engineers, contractors, and city staff who collaborated on this award-winning project,” says Matt Larson, Snoqualmie’s mayor. “Its innovative design, cost savings, and environmental best practices will benefit our residents for years to come.”