First the Farthest East. Now the Farthest West. This Operator's Career Spans the Continent.

Mark Descoteaux has operated the easternmost and westernmost clean-water plants in the U.S. His current facility lies on an Aleutian island in the Bering Sea.

First the Farthest East. Now the Farthest West. This Operator's Career Spans the Continent.

Mark Descoteaux, left, shown with operator Trever Shaishnikoff, faces challenges that include challenging logistics in delivery of supplies to his plant’s remote location.

Not many clean-water operators can watch orca and humpback whales while doing plant rounds.

That privilege belongs to Mark Descoteaux and his five-member team at the Unalaska Wastewater Treatment Facility, on an Aleutian island in the Bering Sea some 800 miles west of Anchorage, Alaska.

Their chemically enhanced primary treatment plant (1.0 mgd design, 0.4 mgd average) handles wastewater from some 4,200 residents and four major fish and seafood processing facilities in what Descoteaux calls the largest fishing port in the nation.

Commercial fishing enterprises capture king crab, halibut and cod from the Bering Sea; the king crab boats featured on the Discovery Channel TV show The Deadliest Catch operate out of the island’s Dutch Harbor.

Descoteaux has been supervisor of wastewater for the City of Unalaska since June 2019. Earlier in his career, he operated the clean-water plant in the town of Lubec, Maine, the easternmost plant in the country, facing the vast expanse of the Atlantic Ocean.


Descoteaux grew up in a small town in Massachusetts. After graduating from Berkshire Community College in Pittsfield with a degree in environmental science, he went to work at clean-water plants in Concord and Leominster.

In 1995, at age 35, he heard a call from Downeast. “I wanted to move to Maine, and a friend who was born there said, ‘If you like the ocean, stop by Lubec. You might like it.’”

He became the sole operator, “chief cook and bottle washer,” at Lubec’s 30,000 gpd Imhoff tank primary treatment plant. The Imhoff tank process uses a V-shaped settling compartment over a tapering compartment with gas vents where settled solids are anaerobically digested, generating biogas.

“I was in Lubec for about five years,” Descoteaux recalls. “It was beautiful. I lived in the easternmost house in the country at a place on the ocean called Quoddy Head. My dog loved it, and I loved it.”

After leaving Lubec, Descoteaux worked at a 1 mgd secondary treatment plant on the Loring Air Force Base in Northeast Maine, and spent 2016-17 in water and wastewater operations for the U.S. military installation on Wake Island, in the Pacific Ocean some 2,300 miles west of Hawaii.

Later he wanted to experience Alaska. Browsing the Indeed job website, he noticed an opening in Unalaska and applied. “They flew me out here for a week for an interview and to see if I would like the area,” he recalls. “I came back with an offer letter.”

He soon found life on the remote island to his liking. The weather at 54 degrees latitude is not as extreme as one might imagine — he remembers Maine as being colder. Ocean currents tend to moderate the cold; temperatures stay around 30 degrees in winter and reach the 50s in summer. Winds as strong as 100 miles per hour do arise; the treatment plant facilities are hardened against them and all processes are enclosed.


The Unalaska Wastewater Treatment Facility came on line in 2015. The state license requires a minimum BOD and TSS removal of 30% for each parameter. Chemical flocculants, process control and constant SCADA monitoring (Boreal Controls) help meet those standards consistently.

The plant discharges to the Bering Sea. The fish processors have their own outfalls for process water regulated by the state Department of Environmental Conservation, but their domestic wastewater makes up a meaningful share of treatment plant flow.

The plant is fed by 10 duplex pump lift stations (Flygt, a Xylem brand). The headworks has two mechanical bar screens (Kusters Water), a rag compactor (SEW EURODRIVE), an aerated influent channel for chemical dosing and a Grit Snail cyclone (Hydro International).

The two enclosed primary clarifiers, each with 200,000-gallons capacity, provide enhanced settling with aluminum chlorhydrate as the flocculant. “The other chemical used to aid settling is a plant-based polymer,” says Descoteaux. “The two chemicals are dosed according to flow. Dosage can also be formulated in the lab.”  

Separate chlorine contact chambers provide disinfection with sodium hypochlorite produced on site by MIOX generators. Sodium bisulfite is used for dechlorination. “This is very important because the city has strict chlorine limits imposed by the DEC,” Descoteaux says. “The chlorine limit is 0.34 mg/L.”

In the pump gallery, double-disc pumps (Penn Valley Pump), centrifugal pumps (Gorman-Rupp Co.), FLEXFLO peristaltic pumps (Blue-White Industries) and diaphragm pumps (Lutz-JESCO America Corp.) operate around the clock and are constantly monitored for process control.

A 75,000-gallon glass-lined storage tank holds and thickens biosolids. Two pneumatic Fournier presses dewater the material. Hydrated lime is added during dewatering to raise the pH, kill pathogens and limit vector attraction.  

“Typical solids content from the presses is 40%, a lot higher than from other dewatering equipment,” Descoteaux reports. “Solids are automatically bagged and hauled to the landfill.”

The plant has a state-of-the-art lab complete with deionized water production for analysis. It is staffed by a lab manager constantly monitoring the process. The facility has a $4 million annual budget. New in 2022 is a Vactor truck used to maintain the collection system. 

“Compliance is what this team has a passion for, and we do it 24/7/365,” says Descoteaux. “Our operators have achieved awards from the city for their performance.” 


That’s in keeping with the state’s strong environmental ethic, which extends to the state government and its regulatory approach. Descoteaux isn’t sure why the state requires only primary treatment for Unalaska.

“Nobody nowadays builds a primary plant; they’re all secondary activated sludge or something similar. The plant that was here before was very primitive. This new place is technically more advanced and has a lot more bells and whistles for getting to the point of clean effluent.

Helping to sustain effective treatment are team members Lauren Sevilla, lab manager and holder of a chemical engineering degree; and operators Brian Brown, James Esnardo and Miguel Cristobal, holder of an electrical engineering degree. In most years, engineering students fill a temporary summer position.  

Challenges do exist. For one thing, supplies of all kinds, for the plant and for island life in general, must arrive by barge, most often from Seattle, or by small plane. “Everything I order comes in by barge,” Descoteaux says.

“It takes about 10 weeks to get anything. If the barge is delayed by bad weather, or if a tug breaks down pulling a barge, the plant can be out of state compliance. And then we have to hope the generator stays on that produces the electricity for the island.” Descoteaux notes that the city is exploring the capture of geothermal energy by tapping into the heat source of a nearby active volcano.


All in all, Descoteaux is happy with the choice he made to move as far west as anyone in his position can while remaining a United States resident. “It’s God’s country,” he says. “It’s beautiful. My dog catches two-foot salmon in the stream when the salmon are running.

“There are plenty of hiking places. If you have a little dirt bike like I do, that opens up other avenues. I’ve got a boat, and I go out whale watching. Once you’re on the water, it’s a whole different perspective. It’s like you’re on vacation.”

At the far northern latitude, the lengths of day and night require some adjustment. “During the winter, the sun usually comes up at about 10 a.m.,” Descoteaux says. “You don’t go home in the dark after work, but you come to work in the dark for about three months. In summer the sun sets about midnight.”

The island is remote enough to discourage tourism. Occasionally a cruise ship stops by for a visit of a couple of days before steaming off to another location. “As for this being on a tourist brochure or a travel agency’s destination list, probably not, but I kind of like it that way,” Descoteaux says.

“I feel very fortunate to live and work here. I feed Arctic fox and eagles by hand right out of my mud room. The eagles land right on the whiskey barrel. I hold out a piece of raw-boned chicken, and they’ll take it right out of my hand.”

As for retirement, “Nothing set in stone. I think I’ll retire here. I like the water, the mountains, the lifestyle, the people. It’s just beautiful here. When the sun is out on a winter day, the snow-capped mountains are the whitest white you’ve ever seen, and the sky is the bluest blue. I’ve been in a lot of beautiful places in Maine, but this is a totally different chapter on beauty.”  


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