CHARLOTTESVILLE -- Despite objections from environmentalists, a state board has approved new rules aimed at curbing pollution from storm-water runoff from more than 100 localities, hospitals and schools.

The state Soil and Conservation Board last week approved new regulations for permits for storm-sewer systems. The permits are valid for five years, and were last updated in 2003.

A coalition of seven environmental groups had asked Gov. Timothy M. Kaine to delay action on the proposal to toughen the regulations. The groups said the rules should specify limits for different types of pollution.

In response, Virginia Secretary of Natural Resources L. Preston Bryant Jr. told the groups that the new regulations were stronger than the old ones, saying in a letter that they "will significantly advance protection of Virginia's waterways."

William H. Street, executive director of the Richmond-based James River Association, said urban storm water is the fastest-growing threat to Virginia's waterways and the primary reason Chesapeake Bay cleanup efforts have stalled.

"While pollution from wastewater discharges and agriculture have been decreasing, pollution from urban storm water, the third major source of pollution to the Chesapeake Bay and its tributaries, has been increasing," he said in an e-mail.

Joe Tannery, an attorney for the Chesapeake Bay Foundation, one of the groups that had urged Kaine to intervene, said a court challenge is possible. The groups have 30 days to decide whether to file a lawsuit.

Rainfall sends millions of gallons of runoff tainted with oil, fertilizers, dirt and toxins into storm drains that empty directly into creeks, streams and rivers. Owners of storm systems are required to obtain a state environmental permit, which outlines what steps should be taken to reduce pollution.

"We all want to get to the same place," said Gary Waugh, a spokesman for the state Department of Conservation and Recreation, but it's "almost impossible to get there from here right now."

Municipal officials contend no state has gone as far as environmentalists want Virginia to go by writing specific limits into these permits. If Virginia did so, they say, homeowners and businesses would face huge increases in utility bills.

"I sympathize with their goal," said John Carlock, an environmental manager with the Hampton Roads Planning District Commission. "But if cleaning up the bay was that easy, we would have done so years ago."