WINDHAM – Windham moved to the next phase of its exploration of a possible sewer system by approving a $42,500 expenditure Tuesday night that, among other things, aims to narrow the overall cost estimate of creating a sewer.

With the economy tight for both Windham businesses and residents, the narrowing of the estimate, officials say, will help voters and town leaders decide whether the sewer is worth the cost. Any system would need to be approved by voters.

The engineering work will be paid for in part by $10,500 from the Maine Department of Environmental Protection. The remaining $32,500 will be paid for by North Windham development district TIF funds, a pot of money sheltered from the state education subsidy funding formula that pays for North Windham-specific infrastructure ventures.

The concept of a sewer is being touted by supporters due to rising levels of nitrates in North Windham’s groundwater, as evidenced by 15 years of test well data collected by the United States Geological Survey.

Those results were presented to the Town Council in the fall by hydrogeologist Bob Gerber, who has been tracking pollution in the North Windham aquifer for about a decade. He says the studies show increased nitrates and nitrogen levels, which has spurred some councilors to conclude that North Windham needs a sewer to flush the estimated 700,000 gallons of sewage that North Windham residents and businesses daily produce, effluent that now is stored in septic systems which eventually seep into the groundwater.

As part of the $42,500 expenditure, Woodard & Curran engineers will conduct survey work and produce a schematic design of a possible sewer focused on the “backbone” of the system. The sewer, as envisioned so far, would run from North Windham down Route 302 to Westbrook.

This “backbone,” which is a downsized version of what councilors had been previously discussing, would cost an estimated $29 million and include the major pollution contributors, such as the businesses along Route 302, and bits of routes 35 and 115 in North Windham. The backbone system would also include the Windham school campus on Route 202 as well as town hall in Windham Center.

The system would extend down Route 302 into Westbrook before finally connecting into the Portland Water District’s waste treatment plant on East Bridge Street. While estimated to cost $29 million, Woodard & Curran’s lead project engineer Barry Sheff said once the surveying is complete, he’ll be able to whittle the margin of error on that figure from the current minus-30 percent/plus-50 percent to minus-25 percent/plus-30 percent.

For the next 12 weeks, Sheff will collect data such as where pumping stations would need to be built to compensate for uphill sections of the sewer, where ledge is situated, and how many miles of pipe and what size of pipe would be required for the sewer. Sheff will conduct interviews with local landowners and developers familiar with soils conditions in the corridor, as well as determining elevation along the entire route.

“We’ll be focusing on the core of the project, bringing a level of refinement for the cost estimate,” Sheff said Wednesday. “This is the beginning. The town is not rushing. It’s a long, deliberate process, which it needs to be.”

Despite opposition from members of the public who questioned the manner in which the town presented questions on the public sewer survey and the ramifications of a sewer on taxpayers and businesses, councilors were enthusiastic to get the next phase under way.

Newly appointed councilor Peter Anania, who made his support of a sewer known prior to his appointment, said, “We need some accurate numbers so we can make some decisions, that’s what this is all about. You can’t make a decision unless you know what the numbers are.”

Echoing the concerns many in the public have expressed, either through speaking at the podium during public comment or through written comments on the sewer survey, Anania also said the initial cost estimates per resident were “outrageous, and we need to get those down, and this is the first step for us to do that.”

Councilor Tommy Gleason echoed Anania’s sentiments, saying, “I understand we need a sewer in North Windham, but who’s going to pay for it?”

Though most people who have heard of the sewer project want to know the project’s bottom line, councilors avoided that line of discussion, saying a more refined cost estimate is needed before those detailed discussions can take place.

“This sewer project isn’t going to happen overnight. This is a long, long, drawn-out process,” Chairman Scott Hayman said.

Town Manager Tony Plante said, “When we go through this preliminary engineering and construction-estimating series of tasks, we will have a more precise number for that core. We will be able to develop a business plan that is more precise, that will more accurately tell people what the impact will be for their household, for their personal budget, for their business. Right now, we can’t.”