The Interior Department has asked the Justice Department to sue an Indiana utility for damaging the Indiana Dunes National Lakeshore, one of the nation's most popular urban parks.

The development is the latest in a drawn-out battle over whether the Indiana Public Service Co. should build a nuclear power plant on the border of the 8,500-acre park, 20 miles from Chicago.

Interior Secretary Cecil D. Andrus said in June that he would not try to stop construction of the plant. However, indications are now that Interior may be having second thoughts.

The suits, if agreed to by the Justice Department, would seek to halt draining of park groundwater now caused by construction of the nuclear plant's foundations.Interior also wants the company to stop flooding park lands with a million gallons of water daily from its coal plant fly ash ponds. The coal plant is on the same site as the proposed nuclear plant.

In a Sept. 14 letter to the Nuclear Regulatory Commission, Assistant Interior Secretary Robert L. Herbst questioned the safety of locating a nuclear plant so close to a public park. "It may well be impossible to develop evacuation plans [in the event of a nuclear accident] that will reasonably assure the health and safety of park visitors" he wrote.

The letter prompted a rebuke from utility Chairman Dean H. Mitchell, who said Herbst's letter was "a distinct surprise, particularly since the Secretary of the Interior indicated previously that he had decided not to pursue further challenges to our construction permit."