Two environmental groups have filed a second lawsuit in federal court in an ongoing battle to halt construction of Interstate 69 in southern Indiana.

The Hoosier Environmental Council and Citizens for Appropriate Rural Roads, or CARR, allege in a lawsuit filed late last week that the U.S. Army Corps of Engineers violated the federal Clean Water Act in issuing a permit for construction of 29 miles of I-69 between Oakland City and Washington, known as Section 2.

The suit in U.S. District Court for the Southern District of Indiana is similar to one the groups filed in February regarding the Corps’ permitting of Section 3, a 26-mile segment between Washington and Crane.

The new case involves a permit the Corps issued allowing 644,802 cubic yards of fill in wetlands in Pike and Daviess Counties, including the Patoka River National Wildlife Refuge and Wildlife management area.

The fill would consist of earth, riprap and concrete as part of a 25-foot-high causeway stretching 2.5 miles. It would connect a White River bridge and two bridges over tributaries.

“This causeway will act as a virtual dam across the river, raising flood levels up to a foot higher than current levels on about 5,900 acres of floodplain land,” including “a lot of good farmland and Indiana bat habitat,” said Tim Maloney, senior policy director of HEC.

The group in April filed an appeal of a permit issued by the Department of Natural Resources involving the section. The appeal is still in the discovery stage.

HEC and CARR assert in the Oct. 14 suit that engineers are required by the Clean Water Act to find practicable alternatives to proposed discharges that would have fewer adverse impacts on aquatic life.

The Corps has not yet filed a response to the latest suit. It denied allegations made by the groups in the similar suit filed last February involving Section 3 of I-69.

The environmental groups seek an injunction stopping Section 2 and the rest of the Evansville-to-Indianapolis I-69 project “until the defendants fully comply with the requirements” of the Clean Water Act.

The groups for years have complained the currently planned I-69 route crosses some of the most environmentally sensitive parts of the state. They prefer a slightly longer route for I-69 consisting of upgrades to I-70 in western Indiana and conversion to interstate standards for the connecting U.S. 41, which runs south to Evansville.

At this point, only 1.8 miles of the proposed 142-mile “new terrain” I-69 between Indianapolis and Evansville is open for traffic. The tiny stretch links I-64, north of Evansville, to State Road 68, to the north.

Currently, 63 miles of I-69 are under construction in southern Indiana, said Indiana Department of Transportation spokeswoman Cher Goodwin.

Goodwin said the agency declined comment about the latest lawsuit filed by HEC and CARR.

“We are confident that INDOT has followed every law,” she said.

The Indianapolis-to-Evansville extension of I-69 has been a top priority of Gov. Mitch Daniels as achieving the optimal time savings for those traveling to southwestern Indiana—perhaps shaving 30 minutes from what is typically a 3.5-hour to 4-hour drive.

Opponents argue it will have adverse environmental effects on a corridor involving more than 7,000 acres of land, including 4,300 acres of farmland, and on 450 karst features such as caves and underground streams.

INDOT has said it’s on track to build the stretch between Evansville and Crane for about $700 million. It points to tweaks in design that slashed costs, and success securing lower material and labor costs during the slow economy.

But there doesn’t appear to be enough money to build the highway between Indianapolis and Bloomington. Total cost of the entire project could exceed $3 billion, a price tag critics say will siphon unacceptable amounts of money from existing state road maintenance and building budgets.