An East End nonprofit has filed suit to block Suffolk County’s first master plan since 1971, arguing that the county failed to follow state environmental law when it adopted the document this year without reviewing the environmental impact.

The lawsuit by Quogue-based environmental group Peconic Baykeeper said state law requires a study “to analyze the cumulative environmental impacts” of the plan. The county master plan includes proposed commercial and residential developments, sewer system expansions, and bus and rail improvements.

An appointed county environmental committee determined that the plan did not have to go through a full environmental study because it was a nonbinding “blueprint.”

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Each project will have to go through its own environmental review and approval, officials said this summer when County Executive Steve Bellone signed the master plan into law.

An attorney for Peconic Baykeeper said the county should look at the full effects of the projects.

“The county failed to consider the overall impact,” said Joel Barkin, a Manhattan-based attorney representing Peconic Baykeeper.

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The Article 78 lawsuit was filed Dec. 15 in State Supreme Court and is set for a hearing Jan. 15. The lawsuit names Suffolk County, the Suffolk County Legislature, the Suffolk County Planning Commission and the Suffolk County Council on Environmental Quality, among others. A judge has yet to be assigned to the case, Barkin said.

Justin Meyers, a county spokesman, said the county does not comment specifically about pending litigation.

But Meyers noted that the plan was passed unanimously by the county legislature.

“It’s a general guideline in how the county can move forward in substantive ways on important issues,” Meyers said.

Bellone signed the “Framework for the Future — Suffolk County Comprehensive Master Plan 2035,” in August, hailing it as the first unified vision for the county’s future in 44 years.

The 59-page document lists more than 100 objectives for the county. They include promoting multifamily developments near transportation hubs, like the proposed Ronkonkoma Hub and Heartland Town Square mixed-use development in Brentwood.

The plan also backs expansion of bus and train service, including new north-south express bus routes to connect train lines.