In its last day at work, the Carter administration yesterday signed a $16.5 million settlement with the Hooker Chemical & Plastics Co. in the first of four toxic-waste dump lawsuits involving Niagara Falls, N.Y. But it left the problem of the Love Canal for the Republicans to solve.

Environmental Protection Agency Deputy Administrator Barbara Blum called the agreement over the Hyde Park site "the most comprehensive and technically advanced remedial program ever undertaken" in a dump site case. "The settlement should serve as a model for industry," she said.

Clearly hoping that the model will also apply to Love Canal, one of the other three cases pending, Blum said Hooker will clean up the 16-acre Hyde Park landfill between Niagara and Lewiston, N.Y., at its own expense, while EPA and New York State keep watch.

Hooker dumped 80,000 tons of at least 82 chemicals there between 1953 and 1974. Under the 159-page agreement, which still must win approval from the U.S. District Court in Buffalo, Hooker and its parents, Occidental Petroleum Co., will guarantee up to $10 million for the cleanup and another $5 million for monitoring and maintenance costs for 35 years. Another $1.5 million will set up a fund to reimburse the state and federal governments for environmental studies and for their costs in the watchdog process.

EPA officials said their portion would be turned over to state and is expected to be used in part for follow-up health studies on the Hyde Park area population.

If the agreement is approved, Hooker is released from a total of $300 million in state, federal and local suits pending in the Hyde Park case. $3At the Justice Department, outgoing Assistant Attorney General James Moorman called the pact "one of the most complex and sophisticated environmental settlements ever reached."

A Hooker spokesman said from the company's Houston headquarters that the settlement was "the final stage of a voluntary progam begun by Hooker in 1974." The $15 million, he said, is probably "far in excess" of what the cleanup actually will cost. The steps to be taken, he said, "are what we wanted to do all along" but were delayed in doing by the lawsuit filing in December 1979.

That suit, still the biggest environmental protection action ever filed, asked $124 million.

The Hyde Park site was opened when Hooker stopped using the Love Canal site in 1953. Hooker has also agreed:

To test all soils, water and sewer lines in and near the area to trace all chemical migration, and to clean and replace any sewer lines if needed.

To expand the drainage and discharge barrier system down to bedrock.

To lay an impermeable clay cap over contaminated areas, excavating Bloody Creek to clean it and to put a layer of seeded topsoil over the caps.

To follow up with detailed studies and monitoring for 35 years, correcting whatever doesn't work, doing everything with the latest technology and according to top safety standards.

EPA and state officials will determine when the area is sufficiently clean.