Four of the nation's largest homebuilders agreed Wednesday to pay $4.3 million in fines for allegedly polluting streams and lakes with dirt from their construction sites carried in stormwater runoff.

Seventy-one of the sites were in Georgia. Muddy runoff is among the biggest threats to the state's rivers and lakes. It also harms wildlife and vegetation dependent on those waterways, including fish and river otters.

The consent decree, filed in U.S. District Court in Alexandria, Va., and jointly announced by the U.S. Environmental Protection Agency and the U.S. Department of Justice, ended a sweeping, six-year federal investigation of hundreds of subdivision construction sites in Georgia and 33 other states.

The EPA's complaint listed Georgia residential developments by Pulte Homes, based in Bloomfield Hills, Mich.; KB Home, based in Los Angeles; and Centex Homes, based in Dallas. Most are in metro Atlanta. The fourth homebuilder fined — Denver-based Richmond American Homes — did not have property listed in Georgia.

During on-site inspections from 2002 to 2005, EPA investigators found a widespread pattern of Clean Water Act violations, federal officials said. The problems ranged from incomplete paperwork to no pollution controls. Under state and federal laws, builders are required to prevent muddy runoff from leaving construction sites and polluting nearby waterways by using silt fences, hay bales, rock filters, detention ponds and other low-tech devices.

Local governments are generally charged with ensuring construction crews are maintaining the proper pollution controls, and the Georgia Environmental Protection Division serves as a backstop. But the state has fallen far short of a 2002 goal to hire 80 dirt police to inspect sites across the state. Today there are only 24.

The state is also requiring construction crews to be educated on the regulations to stop violations at the source. Under a 2003 law, thousands of construction workers have been certified in erosion and sedimentation control.

During a teleconference call Wednesday with reporters, EPA Assistant Administrator Granta Nakayama estimated the consent decrees against the four homebuilders will keep 1.2 billion pounds of dirt out of the nation's rivers and lakes every year. Together, the companies build more than 100,000 houses a year.

"Too much dirt in waterways can cause major problems for the environment," Nakayama said. "Whatever ends up on the ground at a construction site can end up in the nearest waterway."

Pulte Homes spokesman Mark Marymee said the company started an in-house training two years ago to make sure employees understand the Clean Water requirements. The new program includes spot inspections of its sites to ensure compliance.

"We're pleased with our progress," Marymee said.

The settlement agreement also requires the companies to increase site inspections and train construction managers and contractors.

In a statement, Justine Thompson, executive director of Atlanta-based GreenLaw, said, "This sends a strong message that failure to comply with the law has consequences. Now we need local governments to follow EPA's lead and take similar action. Georgia's water quality is suffering from death by a thousand cuts."

GreenLaw is an environmental legal team that has sued more than a dozen builders for stormwater violations since 2005.

Wednesday's action was the latest in a series by the EPA to enforce stormwater regulations around the country.

In February, the agency reached a similar agreement with Atlanta-based Home Depot, which required the company to pay a fine of $1.3 million and establish a comprehensive stormwater compliance plan to prevent future violations. In 2005, Wal-Mart paid $3.1 million for similar violations.