A sewer plant renovation expected to cost tens of millions of dollars will be outlined next week for townspeople — who will eventually have to vote on it, probably in fall of 2018.

The project includes upgrading the village area’s District I sewage treatment plant on South Street, and also closing the District II plant that serves the area around the intersection of Route 7 and 35, then piping that sewage to the South Street plant for treatment.

The last time the town’s District I sewer plant was renovated, more than 20 years ago, the cost was about $13 million — and the new renovation is expected to cost more.

“This could be three times that amount. It’s premature to say in detail,” First Selectman Rudy Marconi said.

“We have a preliminary design concept,” said Water Pollution Control Authority chairwoman Amy Siebert. “We haven’t gotten into any detailed design at this point. The detailed design is what really lets you firm up the your costs.”

The public hearing on the Phase I and Phase 2 Wastewater Facilities Plan is scheduled for Wednesday, May 3, at 7 p.m. in the conference room of the Town Hall Annex, by the Yanity gym off Prospect Street.

The project, which already been under study for a couple of years, is targeted for construction in 2019.

The project will have several aspects:

  •  To upgrade treatment capability at the District I sewer plant, serving the village and town center, to meet higher state environmental standards for the treatment of both nitrogen and phosphorous;
  • To close the District II sewer plant, near the intersection of Routes 7 and 35, and pipe the effluent currently handled by there to the upgraded District I plant off South Street for treatment;
  • To modernize treatment facilities that are old, and have been relentlessly used.

The plant will continue to be used for treatment of septic system waste from Ridgefield properties, delivered by commercial septic pumping services after they pump tanks in town.

The renovation must meet standards set by the state Department of Energy and Environmental Protection (DEEP), which issues the discharge permit for the plant.

“We have stricter nitrogen and phosphorus limits,” Siebert said. “Those drive the technology that you use, the treatment process that you use to achieve those limits, and those treatment technologies become more complex — and they’re also not what we have in place right now, so we have to get them in place so we can meet our permit limits.”

Getting older

Sewer plants are supposed to be upgraded every 20 years, and it’s been 24 or 25 years for District I; but the town has been working with the DEEP.

Another problem the project will address is aging facilities.

“You’ve got two treatment plants. It’s kind of the end of their useful life,” said Siebert. “We’ve been keeping them going. But when you think Route 7 was 1985 approximately, and when I was looking over the plant at South Street, some of the facilities are from 1968, original equipment ...

“When you have equipment from a 24-7, 365-days-a-year tough environment, it comes time to replace it. Some of our big drivers for this are certainly condition …”

“Motors, pipes, general infrastructure,” said Marconi.

“Instrumentation,” added Siebert.

“You even have to look at the building,” she said. “When you do a facilities plan you have to do everything from soup to nuts — your building, HVAC, roof structures. You want to look at the integrity of your tankage.

“You really give everything a good hard look because, clearly, that the kind of infrastructure you don’t want to fail,” Siebert said. “You want to keep that stuff working.”

Plant capacity

The South Street plant’s current capacity is 1 million gallons a day, and it’s running at about 850,000 gallons per day — when the weather is dry.

“It’s quite variable when it rains,” Siebert said. “It depends on how wet it’s been and how big the storm is.”

“It could be up into the millions of gallons per day,” Marconi said the volume that goes through the plant. “We could go from 850,000 up to 3.5 million. We’ve hit 3.4 million.”

With the addition of the District II plant’s 120,000 gallons per day capacity, the renovated plant will have a capacity of 1,120,000 gallons per day — just what the two plants handle today.

“We’re not expanding capacity,” said Siebert.

“Not beyond what we currently have, for in-town, and Route 7,” Marconi added.

Efficient treatment

The project is being designed to improve the quality of treatment, not add capacity in order to handle more development — a possibility that was hotly debated when the Planning and Zoning Commission was barraged by 8-30g affordable housing applications. Those were halted by a moratorium granted by the state, but that four-year moratorium ends in the fall of 2018.

“We’re building it to handle current build-out assumptions,” Marconi said. “That doesn’t include any 8-30g assumptions.”

To keep the needed capacity — and project cost — down, the town has had a continuing initiative to reduce “infiltration and inflow” into the village area sewer system, which dates back to the early 1900s.

That meant replacing cracked pipes and the like, but also searching out illegal connections where properties pump storm drainage and water from basement sump pumps into the sanitary sewer system — pushing up the needed treatment capacity with what is essentially rainwater.

“We’ve also done a lot of work over the last several years to the wastewater collection system,” Siebert said. “If you have a pipe that is older and you have a crack, that allows groundwater to get in. We’ve made a number of improvements to the system: We’ve address pipes, manholes, we’re addressing the illegal sump pumps.

“It was important work to be done before designing a treatment plant upgrade, because it’s work that removed the extraneous flow,” Siebert said.

“We wanted to make the plant more efficient, first,” Marconi added.

Efficiency was also part of the decision to close the District II plant at 7 and 35, and pump that waste down Route 35 to the center of town for treatment at South Street.

“Long-term cost benefits,” said Marconi.

“We did try to look at it on the 20-year basis, to look at both the capital costs and operating costs over that period — and in that case the analysis showed it certainly is cost-effective to bring Route 7 over,” Siebert said.

The approach will push up the initial design and construction costs, however.

“The cost estimates include the pipelines, the pump station and decommissioning of the Route 7 plant,” Marconi said.

Paying for it

With the cost potentially is the $30-million vicinity, another issue that will eventually have to be tackled is how to share paying for it.

In the previous upgrade of the village sewer system, all town property owners shared in a portion of the cost through general taxes — although properties on the sewer system, which clearly get more benefit, carried another portion of the cost by themselves, through increased hook-up and use fees.

When the Route 7 plant was done, the vast bulk of the cost was put on the users.

One argument for having all taxpayers share some of the cost is that the plant treats the waste generated when properties off the sewer lines have their septic tanks pumped. Another is that sewer system benefits the entire town by allowing there to be a more densely developed area, with commercial and multifamily buildings that create a town center — and pay a lot of taxes.

“Those discussion haven’t taken place yet,” Marconi said.

The preliminary facilities plan for the sewer plant project is available in the town’ clerk’s office of town hall, the Water Pollution Control Authority office in the town hall annex, at the library, and the plans will be posted on the town website under the Water Pollution Control Authority (WPCA).