Preston — With the cleanup of the former Norwich Hospital hitting a snag because more contamination has been discovered, town and Mohegan tribal officials are working to extend the date anticipated for the cleanup to be completed in the agreement between the two parties.

The Preston Redevelopment Agency on Wednesday night unanimously approved authorizing Chairman Sean Nugent to sign an extension, subject to approval by the Board of Selectmen, which approved the extension Thursday.

The Mohegan tribe already has approved the extension.

The timeline for completing the cleanup in the development agreement already has been extended once, last year, to an anticipated cleanup completion date of July 17 of this year. But cleanup crews have discovered more extensive coal ash contamination in the ground beneath former roadways through the campus, with some areas containing pockets of contaminated ash beneath layers of clean dirt.

The PRA estimates it needs another $4 million to finish the cleanup, including a $2 million low-interest loan already approved by the state to the town. Town and tribal officials are working with local legislators to seek a $2 million state grant for the remainder of the needed funds.

In the extension agreement approved this week, Preston and the tribe agreed that the town would not begin spending the $2 million contingency loan "unless and such additional grant funding is secured."

The cleanup completion extension at this point does not name a new date. Nugent said Wednesday once all parties sign the agreement, the tribe and town will work to obtain the new funds needed and then propose a formal extension agreement with a new completion date.

The formal agreement would need approval at a town meeting, Nugent said.

Nugent said the town has enough funding remaining in the $10 million state grant approved by the state Bond Commission in February 2017, two months before the town and tribe signed the development agreement in which Mohegan Gaming & Entertainment proposed a major mixed use development on the 393-acre former Norwich Hospital property.

While the PRA still hopes to complete the cleanup by the end of 2019 and transfer the property to the tribe shortly afterward, the PRA on Wednesday received a request from the tribe for permission to use the property May 31 to June 2, 2020, in conjunction with an ATV show.

The request is to use land already disturbed by the cleanup and demolition of former hospital buildings to display 20 to 30 vehicles and for a track that would allow riders to try vehicles for 20 to 25 minutes.

PRA officials will research deed restrictions on the property imposed by the state, including a prohibition on racetracks, to see if the ATV show would be allowed, before agreeing to the tribe’s request.

c.bessette@theday.com