The ability to flush away unseemly substances comes with a cost and, for Oak Harbor residents, that cost will inevitably balloon because of the new sewage treatment plant.
The exact numbers are hard to determine at this point, but a contractor working for the city came up with new projections of sewer rates based on the latest estimates of the cost of constructing the plant downtown.
Shawn Koorn of HDR Engineering presented the numbers during a lengthy workshop Wednesday. He said the monthly rate could grow to between $108.98 and $135.90 by 2021, depending on the final cost of the project.
The residential monthly rate for sewer service is currently at $57.50.
The bulk of the cost of the new sewage treatment plant will be borne by the monthly fees residents and businesses pay for sewage treatment. City officials years ago decided to gradually increase rates to finance the plant.
Two firms working on the project came up with separate estimates for the construction costs now that the project is at the 60-percent design phase. Carollo Engineers pegged the number at $91.3 million, which is down from the company’s $98-million estimate set during the 30-percent design phase.
Hoffman Construction’s estimate is significantly higher at $110.2 million, but it is down from its previous estimate of $113 million.
Koorn previously presented estimates for necessary rate increases in 2012, just after the City Council decided to build the facility on property behind the bank building on City Beach Street. At that time, the monthly sewer rate was $36.52 a month.
The rates have been gradually increasing to build up a reserve, which is currently at $8 million after the purchase of the property; the rates will grow to about $64 a month in December.
Koorn presented estimates for three scenarios based on what construction costs might be — $90 million, $98 million and $110 million.
Under the low estimate, monthly sewer rates will be $108.98 in 2021. Under the medium estimate, the rate will be $118.62. Under the high estimate, the rate will be $135.90.
City Engineer Joe Stowell said the city has “a great team” working on the project and the members are focusing on keeping costs down. He said they still have a lot of work to do.
“Bid prices are the ultimate determination of the cost,” he said.
