Three groups are objecting to the tentative $12 million agreement between the state and Kennecott Corp. to settle the state's federal suit that says the copper giant damaged groundwater in southwestern Salt Lake County.

Kennecott officials admit it is responsible for some of the pollution below mining operations in the Oquirrh Mountains. But they add that part of the pollution came from mining before Kennecott moved in, and some is natural contamination in the heavily mineralized region.A 30-day public comment period ended Tuesday. Kenneth L. Alkema, director of the Utah Division of Environmental Health, is considering requests to extend the period.

The legal situation is somewhat murky because U.S. District Judge J. Thomas Greene mistakenly signed his agreement to the consent decree on July 30 - long before the state's public comment period was over.

He did that even though the cover letter submitted with the document says, "The decree should not be signed and entered at this time. Your attention is drawn to Section XI of the decree which calls for a 30-day public comment period."

After the formal notice, "case closed" was entered in the docket for the suit on July 31, the state and Kennecott returned to Greene with a stipulation saying his approval should be rescinded. Greene signed the rescission on Aug. 19 and asked the parties to report to him after the review period ended.

Meanwhile, the Utah Environment Center, the Utah Chapter of the Sierra Club and the Community Action Program of Salt Lake are unhappy over the settlement. In a press release, the groups are calling on the state not to accept the terms.

Karen Denton of the Environment Center charged that the contamination of 77 square miles of the county's underground water table "could be the Superfund site of the universe." Superfund is a federal cleanup program that targets hazardous-waste sites.

The groups fear the contamination is spreading, and that the plume is heading for drinking water supplies of West Jordan, Magna, Copperton, South Jordan and Riverton.

"Additionally, the settlement does not reserve the state's right to sue Kennecott for any future remedial action, no matter how necessary the action may become," said Ivan Weber of the Sierra Club.