If any doubts lingered about the clout of Heal the Bay, the events of recent days may have dispelled them.

Increasingly, the environmental group's simple message that the pollution of Santa Monica Bay must stop is being heard in the corridors of power.

Last week, for example, after Heal the Bay had threatened to sue to force a decision, the U.S. Environmental Protection Agency tentatively denied the county's request for a waiver that would have allowed continued ocean dumping of waste water that fails to meet pollution standards.

Two of the group's founders have been appointed recently to influential environmental posts by Mayor Tom Bradley.

And late last month, two candidates for governor, Sen. Pete Wilson and Atty. Gen. John K. Van de Kamp, appeared at Heal the Bay's annual meeting in Brentwood to present their environmental agendas for the state. Their presence was a testament to the group's influence. "We've come of age," said Dorothy Green, one of Heal the Bay's founders.

In less than five years, the organization has grown from half a dozen activists concerned about sewage pollution to a full-blown cause. It now has 7,500 members, a budget of $430,000, an educational museum in the Santa Monica Place shopping mall and a multifaceted environmental agenda.

Heal the Bay's call to action, forcefully delivered in slick television ads and splashy graphics, has attracted 2,500 new members in each of the last two years.

Their numbers and outspoken advocacy has caught the attention of elected officials and government bureaucrats from City Hall to the nation's Capitol.

"They have come very far, very fast," said Rep. Mel Levine (D-Santa Monica), whose congressional district hugs the bay. "They have become one of the premier environmental organizations in Southern California. They have focused very needed attention very effectively on Santa Monica Bay. They have highlighted the problems in a focused, credible, substantive fashion."

The nonprofit organization got its start in the summer of 1985 when the city of Los Angeles' sewage spills and bay pollution became front-page news.

At the time, the EPA was pressing a long-standing lawsuit against the city for failing to meet federal water quality standards. And Gov. George Deukmejian, in a prelude to the 1986 governor's race, was attacking Bradley for presiding over pollution of the bay.

Heal the Bay stepped into the breach by organizing at the beach.