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Many options, but no cheap fix for Bainbridge's beach sewer mains
Sewer repairs have been costly across the Puget Sound.
Last month’s sewage spill released an estimated 287,000 to 493,000 gallons of untreated sewage and effluent into Eagle Harbor.
Since the spill one thing has become clear – a fix on the aging beach sewer lines won’t come easy or cheap.
On Monday, city Public Works employees offered their first preliminary prognosis of costs and alternatives to fix the city’s beach sewer mains.
Targeted are three sewer mains that run about 5,700 feet along the north side of Eagle Harbor. All three were installed between 1978 and 1979.
“The expected life service of these pipes is between 15 and 30 years,” said interim Public Works Director Bob Earl. “So we’re not surprised by the corrosion. Now it’s about getting this project on the table and getting it funded.”
There are three alternatives the city is considering; slip-lining existing pipes; replacing lines with high-density polyethylene (HDPE) pipe; and rerouting the pipe off the shore.
Slip-lining, while low in capital costs, would require the existing pipe to be structurally sound, and have enough capacity to meet future demand.
Replacing the existing pipe with HDPE pipe is expensive and could cost between $500,000 and $2 million, to replace only a portion of one of the three sewer mains. Earl said estimates broad “to give some idea of scale” of the cost of an overhaul.
The third option, moving the mains upland, would require excavation, paving, pump station upgrades and securing easements, possibly making it the most expensive option, Earl said.
Across the region, repairing beach sewer mains has been costly.
The Town of Friday Harbor in San Juan County is one municipality which is finishing up a retrofit of its beach sewer mains.
The town had to replace a 1969 10-inch Ductile Iron Pipe, similar but smaller than the one on the north shore of Eagle Harbor. Like Bainbridge, the pipe had corrosive problems.
“The only thing that was holding in the sewage was the mud because the pipe wasn’t there anymore, it just disintegrated,” said King Fitch, town administrator for Friday Harbor.
The town struck a deal with the Department of Ecology for a $2.6 million grant, with the provision that a majority of the pipe be moved inland. About two-thirds of the 7,226 feet of pipe is now inland.
The entire project cost $4.3 million, which would have been leveraged against a small number of Friday Harbor utility ratepayers if it weren’t for the DOE grant.
“We only have 858 sewer customers, and our sewer utility is not healthy financially,” Fitch said. “Rates being already high were going to go tremendously higher... fortunately we received a grant.”
On Bainbridge, any repairs will be paid by roughly 1,800 sewer utility ratepayers, and according to Earl, grant possibilities are scarce.
“Financing it could be problematic,” he said. “There is little grant money available from my vantage point at the moment.”
Mercer Island is another city working to overhaul aging sewer lines. Construction is currently underway to replace a 9,000-foot asbestos-cement sewer line.
The project has been in the works for more than eight years, said Anne Tonella-Howe, the lead on the project for the city.
The cost to replace the line was bid out at $14.8 million. However, a new pump station ($4.3 million) and administrative and contingency allocations give the entire project a price tag of $26.7 million.
Unlike Bainbridge, Mercer Island’s sewer utility includes all residences, which means the cost will be dispersed across its population.
Other experiences in the region indicate a Bainbridge fix will not be cheap.
“It’s going to be new meat to chew on,” council member Barry Peters said. “It doesn’t make it any easier to find the major funding of the kind were going to need for this project.”
The city is also dealing with some time constraints.
Although the life expectancy of the pipe is already past, Earl believes it may last for another five years.
“It may require repair or replacement well before that,” Earl said. “That is the chief concern that we will have a repeated number of failures.”
The city is now talking with the DOE to dye test beach sewer mains to seek out any other holes like the ones that caused last month’s spill.
“The leak we had appeared to be the kind that develops from a pinhole over time and finally, when enough metal is lost, you get a large penetration,” Earl said.
Dye testing could prevent another unexpected break, but it is only a temporary fix until the City Council finds a way to fund a permanent solution, Earl said.
“We’re working on this and there certainly is a sense of urgency it to,” Earl said.