Acton has stepped into an ongoing legal dispute between Littleton and Concord over the rights to use Nagog Pond as a water supply.

On Jan. 8, Acton filed a motion to intervene in the lawsuit filed by Concord in Massachusetts Land Court to determine whether the 1985 Water Management Act supersedes the Act of 1884.

The two laws give differing interpretations of Concord’s rights to sole use of Nagog Pond for its water supply.

The Act of 1884 stated that while Concord had rights to use the water, Acton or Littleton could also take water from the pond should either town have a need for it. Concord, however, believes  the 1985 Water Management Act nullifies that portion of the agreement.

Although Acton has not made any claim to currently need water from Nagog Pond, the result of the lawsuit would likely be applied to their rights to use Nagog Pond as well, causing them to file their motion.

Acton Town Manager John Mangiaratti said  he was limited in what he could say because it is an ongoing case, but said “the town was working with legal counsel and reviewing the case.”

According to a press release from the Littleton Water Department, Acton’s motion to intervene states “any judicial declaration that nullifies or constrains the rights of Littleton under the 1884 Act will likely be interpreted or applied as also nullifying or constraining the rights of Acton and Acton’s inhabitants.”

Littleton, which filed a motion to dismiss the lawsuit on Jan. 3, arguing land court has jurisdiction over land rights not water rights, welcomed Acton’s motion to intervene.

“Because the Littleton-Acton line equally divides Nagog Pond, the residents of both towns share in the rights to use this natural resource as a drinking water supply. The Town of Concord has enjoyed the use of Nagog Pond for decades, and now that we need the water, Concord is seeking to strip Littleton, and therefore Acton, of rights to the pond,” Nick Lawler, general manager of the Littleton Water Department, said.

Lawler added that while Acton was the most likely community to be impacted by the outcome of this case, many other municipalities could be impacted as well. Since these two laws have never been weighed against each other, the outcome would set precedent for future rulings.

Concord Town Manager Chris Whelan said that given the lawsuit’s impact on Acton he understood why the neighboring town would get involved.

“We were not surprised that Acton was interested in joining the suit and we did not object,” Whelan said.

Whelan said previously that Concord had filed the lawsuit last year after hearing about Littleton’s desire to begin using Nagog Pond to supplement its water supply. Concord had been planning to construct a $20 million water treatment plant at Nagog Pond and did not want that money to be wasted.

“We need to know that we will be able to use the water before we invest in a new treatment facility,” Whelan said.

Wicked Local Multimedia Journalists Matthew Mallio and Joy Hosford contributed to this story