PROVIDENCE — Lawyers filed a consent decree Wednesday to settle a lawsuit filed to persuade Middletown to improve its sewerage system so that heavy rains no longer cause pollution to overflow onto Newport’s most-prized beaches.

John Rumpler, a lawyer for the advocacy group Environment Rhode Island, and two citizen complainants, Ted Wrobel and David Wixted, held a news conference to report that they reached a settlement with the town and filed a proposed consent decree with the U.S. District Court.

Wrobel said the Newport beaches have been valued by vacationers since before the Revolutionary War. But for decades they have repeatedly been contaminated with sewage overflows during heavy rains.

Between August 2003 and March 2008, there were 29 “bypasses” from Middletown’s Wave Avenue pump station onto First Beach, according to one legal exhibit. Some were small — a few thousand gallons of contaminated water. But more than half ranged from hundreds of thousands to several million gallons of contaminated water.

The second major source of pollution is two outfall pipes near Atlantic Beach.

“We’re talking about millions of gallons of sewage-laced wastewater,” said Rumpler. “It’s an extremely serious problem.”

“People should not be swimming in poop,” said Wrobel, one of the so-called “sewer rats” whose complaints resulted in the lawsuit.

Wrobel acknowledged that many of the overflows occurred during storms in the winter, but he said people are using the beach year-round now.

“Three days ago, I counted 24 surfers down there,” he said.

The pollution is subtle, he said. You don’t see toilet paper or smell horrible odors. But tests show high bacteria counts and swimmers are getting infections.

The consent decree requires the town to examine ways to prevent sewer overflows, including increasing storage capacity, rerouting wastewater flows and reducing inflows and infiltration into the sewer system. The town also committed to find ways to reduce storm-water runoff, including creation of a gravel wetland and disconnecting roof drains from the system.

Within three months, the town will submit a report to the state Department of Environmental Management for review. The decree sets a schedule for completion of the report and an implementation schedule.

Should the town fail to maintain the schedule, there are fines escalating from $250 a day to $750. The town also agreed to pay $25,000 for the plaintiff’s legal fees.

Middletown Town Administrator Shawn J. Brown issued a statement saying he was pleased with the settlement.

Since 2004, he said, the town has spent nearly $13 million upgrading the Wave Avenue pump station and force main and on numerous other system improvements to reduce the inflows of storm water.

He said the town has not recorded a wastewater-overflow discharge since last March. And the town continues to identify ways to reduce impacts from storm-water runoff to Easton’s Bay.

“The proposed settlement incorporates and recognizes the town’s ongoing plans and commitments on these wastewater and storm-water issues,” Brown said. “By reaching this proposed settlement, the town will avoid expending unnecessary costs on litigation, and can instead focus and expend its resources on these plans and commitments.”

Two other complainants were Burton Hoffman and Henry Rosemont Jr.

The group has filed a similar lawsuit against the City of Newport, which is installing an ultraviolet-treatment system to reduce some of the pollution and studying other measures. Rumpler said he is “cautiously optimistic” that suit will be settled, too.

plord@projo.com