The Sierra Club is suing federal environmental regulators to block construction of the Ridge Road extension through a 6,533-acre nature preserve in Pasco County.

The suit was not unexpected. The environmental group had pledged a legal challenge to the U.S. Army Corps of Engineers permit, and Pasco County already had retained outside legal counsel for the court fight.

The suit, filed Thursday in U.S. District Court in Tampa, names U.S. Army Corps Commander Lt. Gen. Todd T. Semonite and Col. Andrew Kelly, of the corps’ Jacksonville district as defendants. Dan Rametta of Land O’ Lakes, a longtime opponent of the road project, joined the Sierra Club as a plaintiff.

The 59-page suit contends the corps issued the environmental permit Dec. 20 without requiring sufficient wildlife studies, a public hearing and inclusion of public comments prior to 2011. The permit, which Pasco County first applied for in the late 1990s, allowed the four-lane road to extend eight miles from its terminus at Moon Lake Road to the Suncoast Parkway and on to U.S. 41 in Land O’ Lakes.

The state acquired the Serenova Preserve — a former ranch earmarked for a massive residential subdivision and commercial development — in the 1990s to offset the environmental damage from construction of the Suncoast Parkway. As part of the acquisition, the state’s water management district did not object to Ridge Road’s path through the preserve.

The county has said the route is needed for hurricane evacuations, but opponents contend the road’s true mission is to further development in hard-to-access rural land.

The route east of the parkway goes through Lennar’s planned Angeline residential and commercial project that includes an 800-acre commerce park that already has attracted a proposed H. Lee Moffitt Cancer Center expansion as its lead occupant.

Separately, Rametta and the Sierra Club are seeking an emergency injunction to halt the ongoing construction, saying gopher tortoise habitat on site is in imminent danger.

"I derive professional, aesthetic, spiritual, recreational, economic, informational and education benefits from observing the wildlife and their habitat within the Serenova Preserve,'' Rametta said in an affidavit.

Rametta said he has the gate code and permission to use a four-wheel drive on the Serenova property and said he encourages others to make use of the preserve.

Map of the planned Ridge Road Extension in Pasco County.

In an emailed statement, county spokesman Brendan Fitterer said the county does not comment on pending litigation but said "the Ridge Road Extension is a critically needed, additional east-west thoroughfare that has the potential to save lives during an emergency evacuation while providing enhanced connectivity and accessibility.

"Pasco County has taken great care with the design and environmental considerations of this project, including extensive bridging and numerous wildlife crossings designed to maintain habitat continuity,'' he said.