DERRY — After a Tuesday night vote of the Derry Town Council, the last of several stakeholders have signed off on a contract approving the rates, responsibilities and liability terms for a major water interconnectivity project that will deliver water from Manchester to multiple southern communities.

“Getting this done was a huge feat. Getting the construction done is equally as large,” said Sen. Chuck Morse of Salem.

Morse has been facilitating the effort between the state Department of Environmental Services and the communities involved.

The expanded drinking water system, funded by $27 million in state trust fund grants, will deliver water from Manchester Water Works from Derry down to Windham and Salem, up through Atkinson and into Plaistow. Morse said the goal is to get water flowing to Salem by May of 2020.

Derry’s Town Council unanimously approved the deal Tuesday night and Town Administrator Dave Caron signed it Wednesday.

Caron said the deal will be “beneficial to the entire region and the town of Derry as well.”

Plaistow signed the agreement at a ceremony Monday night, and Salem and Windham signed it during the day Tuesday. Manchester Water Works, Pennichuck East and the Hampstead Area Water Company (HAWC) also signed off on the deal.

“Now that the agreement is signed, it’s really moved on to the implementation phase,” Caron said.

The next step for Derry is a public hearing on May 7 for a $6 million grant from the state to cover the town’s portion of the construction. The town will be installing new pipeline from Ryan’s Hill on Bypass 28 down to the Windham line, as well as infrastructure upgrades throughout the existing town system to safely and efficiently route water south, according to Caron.

Morse said Salem Municipal Services will be in charge of all the construction in Salem and Windham. Most parties will be working on engineering and putting projects out to bid in the months ahead.

Salem Town Manager Chris Dillon said the town is due to receive $12.65 million from the state to cover its part of the construction work. A public hearing has been tentatively scheduled for May 6.

“I do believe there’s still a lot to do. Now, it leans a lot more to the engineering. And we certainly have easement’s we’ll have to do along the way,” Morse said.

The first project to break ground is a new water tank in Atkinson overseen by HAWC, according to HAWC General Manager Charlie Lanza.

Construction of the 1-million-gallon tank will cost over $2.1 million, he said. The general contractor will be DN Tanks. Morse said the contract needs approval from the Executive Council.

Once the water starts flowing from Manchester, HAWC is expecting to get an additional 250,000 gallons per day in capacity, Lanza said. Today it has a capacity of about 750,000 gallons per day from 30 wells, though not all of its wells will remain active after the conversion.

Morse said he is thankful for all the towns, cities and water companies for their spirit of cooperation throughout the process.

“I don’t think there was a community that didn’t have questions. That’s why it took two months to get it done,” Morse said.

During town meetings in March, Salem and Windham voters agreed to bonds that would be used to fund water rights from Manchester Water Works.

Existing public drinking water systems in Salem, Atkinson and Hampstead will be seeing some changes, such as the introduction of fluoridated water. While Salem and Manchester have already been using chloramine to disinfect the water, HAWC will have to install treatment systems at some of their pumping stations, as it converts from chlorine.

Lanza said the shift to chloramine, a widely-used method, will provide longer-lasting disinfection.

Ultimately, Plaistow will be installing a brand new drinking water system, mostly from scratch. Some water suppression pipes will be converted for drinking water. That part of the project will cost about $7 million and provide public water to about 400 homes, about 14 percent of which are impacted by MtBE contamination.

Morse said getting water to Plaistow was the driving force behind the whole initiative.