When the Oct. 21 rainstorm dumped 3.26 inches of rain in Gardiner, it wasn’t quite enough to give the new combined sewer overflow tank at Waterfront Park a workout.

“The water came to within inches of going into the holding tank,” said Doug Clark, director of Wastewater Treatment. “But the ground is so dry, it just soaked into the ground.”

For about a year, construction has been underway along the waterfront south of downtown Gardiner to complete the final stage of the city’s sewer rehabilitation and system upgrade.

The combined sewer overflow collects stormwater runoff in a holding tank that has been installed at the waterfront. The tank, which acts like a bathtub, catches storm flows that exceed the capacity of the pump station on the waterfront, holding the water until demand on the system subsides. The tank’s contents are cycled through the pump station at a rate it can handle for transport to the water treatment plant.

Now that the project is essentially finished and its capacity has been tested using river water, the system is ready for the next powerful rainstorm.

Reaching this point has taken years and cost millions of dollars, driven by ever stricter regulations at the state and federal levels.

“We came in under budget,” Clark said. “We didn’t even have to touch the contingency.”

Dan Marks, of Hoyle, Tanner and Associates and the city’s project manager, said the $4.5 million project was funded through both a grant and a loan from the U.S. Department of Agriculture’s Rural Development program, with a $2.7 million loan and a $1.8 million grant.

Under the program’s rules, loan money must be spent first, Marks said, and then grant money can be applied. Because some grant money will be left over, the city is allowed to take on some so-called stretch goals — projects that prevent leftover grant money from being lost.

“And the city has some projects it would like to do,” he said, noting that they are primarily sewer improvements in the collection system. One of them is in the stormwater interceptor in the Arcade parking lot, between Water Street and Cobbosseecontee Stream; and the other is the sliplining project on Highland Avenue, which is expected to rehabilitate the sewer lines there.

There are two ways to handle overflows, Marks said. One is installing a tank, as Gardiner has done already; and the other is tightening up the sewer system, which is the goal of the added projects.

The effect of that is expected to be noticed by ratepayers, because for the next year, sewer rates are expected to remain unchanged; earlier, Clark said he thought they would increase.

That, Clark said, is a result of the project coming in under budget and to other debt coming off the books. In addition, after the retirement of a chief operator, the wastewater treatment department is considering a change in the department staffing that might save $20,000 to $30,000.

“We’re exploring a reorganization,” City Manager Scott Morelli said.

Clark said the goal for the 2018 fiscal year is “not to have a sewer rate increase as a result of this project.”

“I don’t know if we can hold off longer than that,” he said.

The area where the 422,000-gallon tank has been installed has been landscaped and restored. The final step will be replacing the waterfront restroom.

Gardiner Public Works Director Tony LaPlante said the slab and underground plumbing are already in place, and the structure will go up sometime this fall. The restrooms are expected to be open to the public for use by the first part of May.

Jessica Lowell — 621-5632

[email protected]

Twitter: @JLowellKJ