Builders, environmentalists and government officials have reached a compromise in a looming legislative fight that threatened to weaken Maryland's new storm-water pollution rules, they said Monday.

The deal, hammered out over more than a week of negotiations, would head off a move by lawmakers in Annapolis to soften or delay by up to a decade the requirements for controlling runoff from development, which are supposed to take effect May 4.

Environmentalists were girding for a major battle to defend the rules, which were written to tackle a significant and growing source of pollution that is fouling streams, rivers and the Chesapeake Bay.