In the largest settlement of its kind, Hooker Chemical Co. agreed yesterday to spend at least $15 million to permanently clean up a hazardous waste disposal site that has been leaking a deadly pesticide residue into an arm of Lake Michigan.

Michigan authorities jubilantly called the settlement "a landmark" and predicted that it would set a precedent for hazardous waste disposal situations around the country. The state sued Hooker over the leaking waste at Montague, Mich., last March.

"This settelement is unprecedented both in the amount of money involved and in the technological safeguards it will provide for the state well into the next century," Michigan Attorney General Frank Kelly said yesterday after Hooker officials handed over a $1 million check to the state to seal the agreement.

Michigan authorities said Hooker dumped more than 30 kinds of chemical -- some of them cancer-causing -- at the Montague site. They called the situation "an environmental time bomb."

Hooker's waste disposal practices around the nation are the target of several other state and federal investigations. Kelly said yesterday's settlement applies only to Montague.

The company still faces the possiblility of a massive federal lawsuit for dumping at the Love Canal and other New York state sites. The Justice Department is expected to decide within a few weeks whether to file the suit.

In a statement yesterday Hooker said it was pleased with the Montague settlement. But a spokesman said the settlement would not be a precedent for any other hazardous waste situations involving Hooker. "Each location will be handled on an individual basis," the spokesman said.

The Sierra Club, which filed as an intervenor in the state lawsuit this week, criticized the settlement yesterday as inadequate.

"Our attorneys tell us that at the very least it would allow Hooker the benefit of a great deal of confusion if it should ever have to go to court for enforcement," said John Goodspeed, chairman of the west Michigan group of the club.

The Montague site is 880 acres at White Lake, just off Lake Michigan northwest of Detroit. Since the early 1950s Hooker has been dumping a variety of chemical wastes there, including C-56, a chemical used in the manufacture of several cancer-causing pesticides.

State officials sued Hooker when they said they found that traces of C-56 has seeped into local water supplies and into White Lake.

Hooker agreed yesterday to seal up about 1.2 million cubic yards of contaminated soil and sludge in a huge trough a quarter-mile wide and lined with 10 feet of clay.

An additional and unusual element in the bargain gives Michigan indefinite control over future use of the site, Officials said this restrictive covenant, which requires written approval from the attorney general for any sale, lease or other use of the site, is designed to prevent situations such as occured at the Love Canal in New York.

In that case Hooker sold the site after burying large numbers of leaking drums filled with dangerous chemicals in the abandoned canal. Years later, the chemicals made their way into homes and a school built nearby, causing harm to residents.

Kelly said an independent monitoring system will be installed in the giant Michiagan trough to warn of any leakage. If that happens, he said, Hooker will be obligated to repair the leak and contain any chemicals that escape, he said.

"We saw what happened at Love Canal and we don't want it to happen here," said Kelly. "We think this settlement will insure that is doesn't happen."