GARDINER -- In an effort to reduce sewage and stormwater runoff from flowing into the Kennebec River, the city is taking steps mandated by the state.

The city completed a $7.2 million treatment plant upgrade last year that helped eliminate 80 percent of the combined sewer overflows.

"Now we're working on the remaining 20 percent," City Manger Jeff Kobrock said Thursday. "This is not unique to Gardiner. Every treatment plant is going through the same process. We're just more aggressive than some plants."

Gardiner's treatment plant also serves Farmingdale and Randolph.

A combined sewer is a type of sewer system that provides partially separated channels for sanitary sewage and stormwater runoff. This allows the sanitary sewer system to provide backup capacity for the runoff sewer when runoff volumes are unusually high. But it is an antiquated system that is vulnerable to combined sewer overflows during peak rainfall events or snow melts.

Kobrock said several projects were presented to the city council Wednesday prior to an initial discussion with the Maine Department of Environmental Protection. Every licensed permitted treatment plant in the state is obligated to reduce its combined sewer overflow, he said.

Projects include optimizing pumping capacity at the treatment plant and maximizing storage. Those projects will cost $100,000 each.

An infrastructure construction project will include sewer main replacement and cost $500,000, he said. The projects will be paid for through grants and low interest loans and rate payers.

"We project our rates many years in advance," he said. "What we try to do is take advantage of falling debt services. As it falls off, it's replaced with new debt services so it's a steady line. We try to keep it a 1.5 percent annual increase in that rate projection so we are adjusting for inflation, but also trying to plan these large projects that are mandated."

The last project, construction of an underground storage tank at the Maine Avenue Pump Station, will cost $1 million.

Councilors also considered, but didn't act upon, an agreement with the Maine Turnpike Authority to provide sewer services to the planned travel plaza just over the city line in West Gardiner.

"That was a little more complicated, so they looked at the agreement but didn't take final action," Kobrock said.

In other business, councilors voted unanimously to allow the American Wind Symphony to use the waterfront and provide city service support for the event.

The symphony, led by orchestra conductor and boat skipper Robert Boudreau, is planning a trip to several Maine ports this summer.

The symphony plays on a self-contained floating concert shell built from a barrage dubbed the Point Counterpoint II.

The event, tentatively to be held in mid-July, would be organized as a regional effort. Private fundraising is underway. The cost of bringing the symphony would be $30,000.

"Many people thought there would be challenges with the waterfront not finished and that there may be some construction down there," Mayor Andrew MacLean said. "But this is an opportunity and we would like to see it happen."

Councilors also got an update on the proposed Interstate 295 reconstruction project. The state Department of Transportation has proposed reconstruction of the southbound lanes this summer, possibly closing those lanes to traffic between Topsham and Gardiner.

"We spent a lot of time hearing from the DOT folks," MacLean said. "There were some questions from the council about the timing. Was it necessary for the project to go from mid June to the end of August, right in the middle of tourism season? But DOT concerns are being able to have decent paving weather and also the school bus traffic."

Mechele Cooper -- 623-3811, Ext. 408

mcooper@centralmaine.com