The Environmental Protection Agency yesterday named 244 new sites to the priority list for "Superfund" cleanup, bringing to 786 the number of toxic-waste sites that the agency believes may pose an imminent threat to public health.

The new sites, in more than 30 states, including Maryland and Virginia, represent a 45 percent increase in sites deemed to be the nation's "most hazardous."

"We have consistently said that the national priority list was going to grow, and grow fast," EPA Superfund chief Lee M. Thomas told a news conference. "I think within two years that list is going to be up within about 1,400 to 2,000 sites."

Hours after the EPA announcement, the Senate voted, 59 to 38, that a proposal to quadruple the $1.6 billion Superfund could not be added as an amendment to the omnibus spending bill under consideration. The action came after a group of environmental lobbyists took to the streets in a last-ditch effort to move an expanded Superfund bill through the Senate.

With banners hiding their three-piece suits and a bullhorn calling out chants ("Two, Four, Six, Eight. Come on, Senate. Legislate!"), more than three dozen representatives of eight environmental and public-interest groups staged an hour-long demonstration on Capitol Hill that looked more like Earth Day than coat-and-tie Washington.

"We don't have any choice," said Diane MacEachern, a Sierra Club representative who came to tote a placard. "You can only be intellectual about this for so long."

"We want to make sure we don't look back and say we didn't do everything we could," said Rick Hind of the U.S. Public Interest Research Group.

EPA officials acknowledge that the current Superfund, most of which has been spent or obligated, will not be adequate to clean up the rapidly expanding list of hazardous sites. The final figure, the EPA estimates, could be as high as $16 billion.

Legislation that would expand the fund to more than $10 billion has passed the House, but the Senate's $7.5 billion renewal is bottled up in the Finance Committee.

It appeared that the bill's only hope for enactment this year rested on its sponsors' ability to attach it to a passing freight train -- either the continuing resolution or a bill to raise the debt ceiling.

An aide to Senate Environment and Public Works Committee Chairman Robert T. Stafford (R-Vt.) said Stafford was prepared to offer his panel's Superfund bill as an amendment to the continuing resolution, which must pass if the federal government is to keep operating. New Jersey's two Democratic senators have vowed to make the effort if Stafford doesn't.

But with time running short and the Senate stalemated, some congressional aides said the Superfund extension, like the original legislation, might have to take its chances on there being a lame-duck session.

"The likelihood of that is growing," said one key Republican aide.

The EPA's new list, meanwhile, suggested that estimates of cleanup costs might continue to rise. Six of the new sites are on the Hawaiian island of Oahu, where pesticides from pineapple fields have contaminated the ground water.

The EPA never has listed sites involving pesticide contamination. If the Hawaiian sites survive a period of public comment and reevaluation, the EPA probably will be under pressure to consider similar sites in California, Florida and New York.

Yesterday's list also included, for the first time, 36 federally owned or operated facilities. While federal sites are not eligible for Superfund money, the agency said it expected that including them would "focus public attention" on cleanups that are supposed to be paid for by the federal agencies responsible. Nearly all the sites are Defense Department installations, including the Defense General Supply Center in Chesterfield County, Va.

The other Maryland sites are the Kane & Lombard Street Drums site in Baltimore; Mid-Atlantic Wood Preservers Inc. in Harmans and Southern Maryland Wood Treating in Hollywood. In Virginia they are Avtex Fibers Inc. in Front Royal; Culpeper Wood Preservers Inc. in Culpeper; IBM Corp. in Manassas; L.A. Clarke & Son in Fredericksburg, and the Rhinehart Tire Fire Dump in Winchester.