Twisp Public Works Director Andrew Denham, right, tours the town’s new wastewater treatment plant July 14 with Department of Ecology Municipal Unit Supervisor Erik Van Doren.
Earns another ‘Outstanding’ award from state for wastewater
For the state Department of Ecology, last week’s visit to the newly constructed wastewater treatment plant in Twisp was routine. Agency officials filed into the plant’s shiny new control room and lab to review some paperwork.
But for Andrew Denham, Twisp’s public works director, the day felt celebratory. The inspection at the new plant, which is “close to final completion,” Denham said, put a bow on a project that has occupied him since he took the director’s job 12 years ago.
“This is years in the making, to get to this day,” Denham told Ecology officials shortly after they arrived for their inspection on July 14. He recalled knowing the sewer plant needed an upgrade as soon as he arrived in 2014, and he noted that Ecology has been a valued partner in the project since Twisp started working on a new general sewer plan in 2016.
“It’s a big, big, big deal,” Denham enthused.
Denham designed the new plant himself and said he took a risk when he fired a respected engineering firm because they wouldn’t agree to work with his concept. He ended up going with Ardurra, an Idaho-based civil engineering firm the town also hired to help with the Glover Street revitalization.
Denham and his crew are still ironing out a few wrinkles at the new facility, but it is putting out exceptionally clean water. A report sitting on a table in the control room indicated a recent effluent reading of one part per million of total suspended solids. The state requires no more than 30 ppm on average coming out of a sewer plant over a month.
As Twisp’s Public Works team likes to say, the water leaving the plant is cleaner than the river it is going into.
The new plant will do be more effective at removing ammonia and nitrates, Denham said, while also eliminating phosphorus from the waste stream before it enters the Methow River.
The new plant adds a second clarifier tank, giving it more flexibility and redundancy.
More capacity
The plant also added capacity. Denham said a year ago the old plant could handle a population of roughly 1,200, which is close to Twisp’s current population. At the time, he said the new facility should be large enough for a population of 3,000, although its exact capacity hasn’t been determined yet.
The sewer upgrade cost about $14 million, with $9.8 million coming from grants. The rest is covered by a low-interest loan the town will pay off over the next 20 years.
Ecology normally caps grant awards for capital projects at $5 million, Denham said, but the agency found a way to give the town another $5 million or so, making the project possible. If the town would have been required to come up with the additional funding, it would have needed to raise sewer rates so high they would have been unaffordable for the average Twisp resident, Denham said.
The public works director beamed even more when he received some good news from Erik Van Doren, an Ecology supervisor who was part of the inspection team: Twisp won the state agency’s Outstanding Performance Award for achieving perfect permit compliance in 2025.
Van Doren was particularly impressed with Twisp’s award, given that the town earned it during a major renovation.
“That’s hard to do,” Van Doren said, noting that treatment plants often go out of compliance when they are being rebuilt. Even one bad reading out of the thousands recorded each year will disqualify a facility for the award.
Last year, Ecology handed out Outstanding Performance Awards to roughly a third of the wastewater treatment plants in the state. Twisp has received the award nine times in the past 11 years.
“It says so much about the crew and the department,” Denham said after hearing the news. “If you don’t care about your job, you’re not going to receive an Outstanding Performance Award.”
Mayor Hans Smith announced the award that evening at a town council meeting.
Denham reported at the meeting that the inspection earlier that day went well.
“I look forward to giving tours to anybody that wants them,” he said. “It’s a pretty remarkable plant.”
