Southeastern Connecticut’s casino-owning Indian tribes, now in the process of forming a joint venture to pursue a commercial casino project north of Hartford, have a little more breathing room.

The tribes’ target, the $800 million resort casino MGM Resorts International is building in Springfield, Mass., won’t open until September 2018, about a year later than had been expected.

In correspondence this week, Blue Tarp redevelopment, MGM’s development arm, informed the Massachusetts Gaming Commission that MGM is pushing back the Springfield casino’s opening to accommodate the Massachusetts Department of Transportation’s Interstate 91 viaduct project. The highway work, being undertaken in connection with the casino, is scheduled to begin next month and could involve ramp and lane closures from late this year until the summer of 2018, according to Blue Tarp’s “final project schedule.”

MGM now anticipates the Springfield casino’s opening will be Sept. 5, 2018.

While the Mashantucket Pequot and Mohegan tribes, owners of Foxwoods Resort Casino and Mohegan Sun, respectively, had expected the Springfield opening to be delayed, recent research into the MGM project’s likely effect on Connecticut jobs and gaming revenue was based on a 2017 opening. The timetable for a resort casino approved in Everett, Mass., also is likely to be pushed back.

A bill considered this spring by the Connecticut legislature would have authorized the tribes to operate up to three satellite casinos. An amended version of the bill, calling for one satellite and a two-step approval process that will require further legislative action, was ultimately approved. Gov. Dannel P. Malloy signed the measure into law this week.

Once they’ve formed a subsidiary to pursue the casino project, the tribes are expected to file a request for proposals from municipalities willing to host the casino. Several north central Connecticut towns are expected to respond.

The City of Springfield recommended the gaming commission accept Blue Tarp’s revised construction schedule, which will require changes in MGM’s “host community agreement” with the city. As a result, MGM will have to make an additional $4 million in payments to the city in the fall of 2017.

b.hallenbeck@theday.com

Twitter:@bjhallenbeck