AUBURN — Great Falls Plaza’s topography is proving to be a challenge as the city tries to build a downtown transportation center and bus station.

The city may have to install a pump to provide sewer service to the transportation center’s two bathrooms, City Planner Eric Cousens said.

“We installed water and electrical utilities last fall, and we planned on installing the sewer then, too,” Cousens said. “But while we were installing the water, we found out the sewer line we were hoping to tie into was dysfunctional to begin with.”

The center sits at the bottom of a slight slope and much of the underground around it is covered in older utility lines or granite ledge.

Cousens briefed city councilors on the issue at the end of Monday’s regular meeting. They’ll take up the matter at a workshop meeting in the next couple of months, he said.

Installing a pump would cost between $70,000 and $140,000. A smaller pump, just enough to serve the transportation center’s needs, would cost $70,000. A bigger pump that could provide sewer service to other developments in the area could cost between $120,000 and $140,000.

“My recommendation would be that we install a sewer line that can serve any future development, and this building,” Cousens said. “That’s been our goal from the beginning, but it’s going to cost a little bit more.”

The cost is further complicated by the Auburn Sewer District’s policy not to assume management of new sewer pumps without a $50,000 payment.

“We operate 25 sewer pumps right now, and they can be expensive to maintain,” said Sid Hazelton, superintendent at the Auburn Sewer District. “So we’ve had a policy for a number of years that we don’t accept any more pump stations. It’s not fair to other sewer ratepayers to have to pay for new pump station service.”

The district made an exception in 2011, accepting three new pump stations from Poland. But Poland paid for that service, giving the district $50,000 for each of the new stations.

“So that is a precedent, that we will take over a pump station as long as we receive the costs of upkeep and depreciation up front,” Hazelton said.

The center is being built with city money and state and federal grants. The Federal Transit Administration has set aside $247,000 and the Maine Department of Transportation has earmarked another $350,000 for the project. Overall, the project was expected to cost $746,000. The additional sewer line costs could be paid with revenues from the city’s downtown Tax-Increment Finance District.

The transportation center could connect to two sewer lines: one along Turner Street and a second near the Hilton Garden Inn.

The Turner Street line is about 10 feet higher than the transportation center’s site.

“That’s a depth problem,” Cousens said. “It looks fairly flat out there, but when you look there is quite a grade change. So you cannot get the 1 to 2 percent slope down that you need to get to gravity-fed sewer.”

Existing water, electrical and other utilities run between the center and the Hilton line at just the height the sewer line would need to go.

“Again, with a gravity-fed sewer, you don’t have a choice of where you want to go,” Cousens said. “You have to go down. You can’t go up and over other utilities, unless you have a pump.”

The city has been working to build a permanent bus station for 10 years. The station would be about 1,500 square feet, with a warm seating area, two public restrooms and a break area for drivers.

Original plans put the center in Great Falls Plaza, alongside a city parking garage, but the garage was never built and the city began looking at a lot near the Hannaford supermarket on Spring Street. Complications with Spring Street land ownership convinced the city to move the center back to Great Falls Plaza in December 2014.

staylor@sunjournal.com