The Environmental Protection Agency Tuesday proposed to add 229 sites, including Richardson Flat Tailings in Summit County, Utah, to the "Su-perfund" priority list for toxic waste cleanups and to drop 30.

The Richardson Flat site, located 31/2 miles east of Park City, is owned by United Park City Mines and has been used by some of its leases as a milling site, said Ed Osika, company vice president.

Osika said Tuesday the EPA had not notified the company of its proposal to add the Richardson Flat mill site to the Superfund list. "We have been working with them in several of the studies and have been taking a lot of action ourselves," he said. Osika questioned whether conditions at the site warranted its being added to the EPA's list. "We feel some of the test results may not be reflective of what may have occurred."

Brent Bradford, director of the Utah Bureau of Solid and Hazardous Waste, said about 7 million tons of tailings cover 160 acres at the site, where the milling of silver and other precious metals has taken place until about 1981.

EPA has proposed no immediate action but has plans to conduct a remedial investigation feasibility study within the next year. The role United Park would play in any cleanup activity has not been determined, Bradford said.

EPA's announcement brings the Superfund priority list to 1,177 sites, of which 378 are still proposals and 799 have been formally designated.

Eventually, the agency has said, the list could grow to about 2,500 sites.

Fourteen of the new sites announced Tuesday are owned by other federal agencies, 12 of them either related to nuclear weapons manufacture or a military base. Last week, EPA announced agreement with the Defense Department on penalties to be imposed if the department fails to live up to cleanup agreements.

The 30 sites being proposed for deletion have not been cleaned up, but "do not satisfy any of the criteria" for listing, EPA said. Three other sites were deleted from the list in April on the grounds that all work had been completed or that they posed no threat, EPA said.

Designations for the "National Priority List" means the site is eligible for 90 percent federal financing of the cleanup under EPA's supervision, unless a federal agency owns it. Federal agencies are responsible for cleaning up their sites using money from their own budgets.