South Windham sewer rates will likely rise in the range of 40 to 80 percent as town councilors look to update the rates in light of the debt created by the Little Falls Wastewater Conveyance, the $6.5 million project connecting South Windham to the Portland Water District’s treatment facility in Westbrook.

The Town Council last week received from the engineering company Woodard & Curran a complete review of the current rate system for South Windham, the only area of town served by a sewer system. Included in the study are options that have the town’s general fund picking up 50, 25 and zero percent, respectively, of the debt service created by the Little Falls Wastewater Conveyance.

The question now is, how much of that debt should be picked by the residents who use the sewer, and how much should be paid for the taxpayers in general.

A public forum on the sewer rate study will be held Monday, Feb. 9, 7-8 p.m., at the South Windham Community Church, located at 31 Main St. At the forum, town officials will explain the results of the study, the recommended method for determining sewer rates, and the various proposals in the study. A public hearing will then be held at the regular Town Council meeting on Tuesday, Feb. 10, at 7 p.m.

According to the study, if sewer users pay all of the debt service, average monthly rates will rise from $26.50 to $48.88. If 25 percent of the debt is picked up by the general fund through town-wide property taxes, the rate would rise to $42.88, and if the debt is split 50-50 between the users and general fund, the monthly rate would be $36.96.

If all the debt service is laid at the feet of the South Windham sewer users, the average annual rate would be around $586, lower than Cape Elizabeth ($612) and Cumberland ($642) but greater than Gorham ($467) and Westbrook ($277).

The number is in line with other communities, said Town Councilor John MacKinnon. But the council has to consider the size of the rate increase as well, he said.

“It’s quite jump. That’s the adjustment we have to keep in mind,” said MacKinnon.

During a workshop on sewer rates in October, Councilor Liz Wisecup said the rates for sewer users, even if they paid 100 percent of the debt, were in line with the costs associated with septic systems that are paid by residents in other areas of town.

“I’d hate to have the rest of town subsidize this if they don’t have to,” she said.

The council will likely make a decision on the sewer rates at their Feb. 24 meeting after taking into account the comments from residents and property owners.

The current rate system, which has not been altered since 1992, is based on water use as measured by meters and offers users a base fee plus a surcharge for additional use. Residents can deduct from their bill all non-wastewater water use, such as that for pool use or watering lawns. The Maine Correctional Center, however, is charged a fee based on sewerage flow, not water use.

To maintain this rate, the town has subsidized through the general fund additional costs forwarded to the town by the Portland Water District. But with the completion of Little Falls Wastewater Conveyance and its accompanying debt, the annual bill to the town has increased from $120,030 in 2007 to $331,848 in 2009. Without a rate change, the study said, the town would need to come up with an additional $166,607 to cover the bill.

To more equitably spread the costs around, the study recommends placing the costs of operating and maintaining the system on the sewer users alone but also figuring into the rate system the 85 condominiums approved, but not yet built, at the old Keddy Mill in South Windham. The study also gives the town options for paying part of the debt service through the general fund.

To determine the rate paid by each property, a number is assigned to each home based on its anticipated wastewater flows. A single-family home would be assigned one Equivalent Dwelling Unit, while an apartment building would get one unit per apartment. The Maine Correctional Center would count as 440 units. In all, South Windham would have 610 units, including the 85 unbuilt condominiums at Keddy Mill not yet using the system.

Property owners who are able to connect to the system but have not would only be responsible for their portion of the debt service, which totals $173,557 annually. They would not have to pay any part of the operation and maintenance costs for the system.