Responding to massive public protests over the nation's contaminated waterways, Congress passed the Federal Water Pollution Control Act of 1972, commonly known as the Clean Water Act.

A novel part of the act is a citizen suit provision that enables citizens to take on the role of law enforcement by suing polluters and the government, should the regulators fall down on the job. According to Leon Billings, former U.S. Senate staff member and the law's co-author, the provision is "absolutely the single most important provision in clean water and air law in the vast narrative of environmental law enacted since," because it introduced accountability to the government -- meaning EPA had to implement the congressional mandate. "If they failed to do so," Billings says, "citizens could go to court and force them to do so."

FRONTLINE interviewed dozens of successful citizens who used the citizen suit provision and other tools to help the environment. They have forced polluters to clean up their act, and in many cases, have changed federal and state law. Below are a few examples:

AGRICULTURAL POLLUTION Rick Dove

A 27-year U.S. Marine Corps veteran who fought in Vietnam, Rick Dove planned to go into commercial fishing with his son in North Carolina upon his retirement. A few years after investing in a store and fishing equipment, however, millions of menhaden began turning belly-up in a series of mysterious fish kills that eroded the state's fishing industry.

Dove suspected North Carolina's large hog industry was polluting the state's waters and signed up with the Waterkeeper Alliance, a national environmental group that operates largely under the citizen suit provision of the Clean Water Act, to fight back.

"We do law enforcement," explains Robert F. Kennedy Jr., chairman of the Waterkeeper Alliance. "There are other groups that do education. There are other groups that do land preservation, that do lobbying on various issues."

Flying in a small Cessna airplane, Dove shot pictures of pollution from the air to build evidence against farms violating pollution laws. He filed suit against Smithfield Foods in North Carolina and won concessions that led the company to improve its environmental stewardship.

Dove went on to become a roving agriculture detective for Waterkeeper from the Carolinas to California, and most recently in the Chesapeake Bay watershed. He's flown over farms on Maryland's Eastern Shore, snapping hundreds of pictures of manure mounds in preparation for lawsuits against farms discharging waste into the watershed. He and his group are slowly making progress.

In 2003 and 2008, Waterkeeper filed suit against the EPA and Maryland, respectively, gaining access to previously private manure management plans to see how farms were accounting for their waste. More recently, Waterkeeper filed lawsuits against both the EPA and the state of Maryland to tighten manure management controls in poultry farm pollution permits.

"When the government fails to do their job, it allows citizens to do enforcement and that is exactly what we're doing here," Dove says. "[Maryland] has not done its job on chicken farms. What we're seeing in some cases, in my opinion, are gross violations."

For more, visit http://www.waterkeeper.org/

WASTEWATER POLLUTION & A SLOW EPA Will Baker

Will Baker is the president of the nonprofit Chesapeake Bay Foundation, which educates citizens in the watershed on how to save the bay.

Frustrated with the EPA's slow bay cleanup progress, the group has become more aggressive: In December 2004, it filed a petition against EPA to place limits on nitrogen -- one of the pollutants that sucks oxygen out of the water and creates dead zones -- in all wastewater treatment permits across the bay watershed. The result was a settlement in which the agency said it would place limits on nitrogen for significant dischargers.

In January 2009, Baker's group filed another lawsuit against the EPA for failing to reduce pollution in the Chesapeake enough to remove the bay from the EPA's "Impaired Waters" list. The EPA first missed Chesapeake pollution reduction goals in 2000 and then reset the deadline to 2010, which it recently announced it would not meet.

"Here on the Chesapeake Bay, EPA has been the lead agency responsible for 25 years," Baker says. "They haven't done their job. … We think the law is on our side. We're going to go to court and we're going to see that the law gets enforced."

For more, visit http://www.cbf.org/

DEVELOPMENT Cheryl Hutchison and Laura TeKrony

Cheryl Hutchison and Laura TeKrony both live in Loudoun County, Va., once a small farming community about 30 miles up the Potomac River from Washington, D.C. Neither had been particularly involved in the community, but in 2004, both became concerned about their quality of life as increasing swarms of developers and residents moved into the area to find cheaper land away from D.C. A developer-friendly County Board of Supervisors had assumed control and began approving amendments to the comprehensive growth plan to allow thousands of new homes.

Concerned about the increase in traffic and taxes to pay for new roads and schools, Hutchison and TeKrony started filing petitions with neighbors against the proposed developments. After a large grassroots campaign, the county's Board of Supervisors ended up rejecting much of the new development. During the next election, the riled community swept in a new smart-growth County Board of Supervisors.

For more about citizen activism success in Loudoun County, visit http://www.pec.org/ or http://www.loudounsfuture.org/

LEGACY CONTAMINANTS B.J. Cummings

B.J. Cummings and her cohorts at the Duwamish River Cleanup Coalition began fighting to restore the river to a fishable and swimmable body of water more than a decade ago. But when the EPA designated a five-mile stretch of the Lower Duwamish a federal Superfund site in 2001, Cummings saw a window of opportunity to get a new cleanup agenda on the table. The DRCC became a formally recognized "community advisory group" within the Superfund cleanup process, and officially became representatives for Seattle's South Park neighborhood.

DRCC's legal backing derives from the Comprehensive Environmental Response, Compensation, and Liability Act, commonly called "Superfund," which Congress passed in 1980 to tackle the most environmentally contaminated sites across the nation. The CERCLA framers were wary that federal bureaucrats might be too disconnected from the distinct nature of each locale, and wanted to give power to the people most affected by these poisonous sites -- the citizens living adjacent to them. By providing an official role as well as funding for local community advisory groups, CERCLA established a system of checks and balances, and nurtured citizen engagement and advocacy.

The DRCC's tenacity has produced stunning results. In 2006, Cummings successfully rallied South Park to engage the Port of Seattle over its cleanup plans for the Malarkey Asphalt facility, which contained PCBs, a legacy pollutant banned by the EPA in the 1970s. "People in South Park, particularly people with families, with small children, got incredibly nervous," Cummings told FRONTLINE. At public meetings, hundreds of South Park residents demanded their voices be heard, as citizens emotionally appealed for the health of their children. In the end, the port sided with the community and changed its cleanup plan from the industrial level of 10 parts per million to the residential level of 1 part per million.

Learn more about the Duwamish River Cleanup Coalition: http://www.duwamishcleanup.org/

FISHING RIGHTS Billy Frank Jr.

Billy Frank Jr. has spent his lifetime protecting the Nisqually River. His family and his tribe, the Nisqually people, have lived and fished along the river's banks for generations. A Native American rights activist since his early teens, Frank came of age in a tumultuous climate characterized by protest. "We never got no share of anything," Frank told FRONTLINE, "so we started fighting the state of Washington in the '60s." Attempting to reclaim treaty rights and restore the devastated salmon population, Frank practiced acts of civil disobedience that got him thrown in jail, beaten and even shot at by the white establishment.

In 1974, he got a burst of momentum, when Federal District Judge George Boldt delivered a historic ruling entitling Indian tribes to a 50-percent share of the salmon catch -- 10 times what they were allotted at the time -- plus the power to co-manage the local fisheries and watersheds with the state of Washington. The Boldt decision represented a sea change in tribal rights and set legal precedent across the Pacific Northwest.

Yet defiance and resistance to the decision were rampant. Washington state Attorney General Slade Gorton openly told commercial fishermen and state courts to ignore Boldt's ruling while it was on appeal. Not until the U.S. Supreme Court upheld the Boldt decision in 1979 were the wheels set in motion to officially turn the tribes and state into co-managers of the fishery.

Empowered by the Supreme Court ruling, Billy Frank took the lead for the tribes as the head of the Northwest Indian Fisheries Commission. He recalls Judge Boldt telling him that the tribes would have to step up and take on new responsibilities: "You 20 tribes are going to be self-sufficient. You will write your own regulations. You will be co-managers with the state of Washington. And you will have your own judicial system. You will have the infrastructure. You will have your science, your policy and your legal people."

But back on the Nisqually River, numbers of salmon were still nose-diving. With the court prodding for action, the state legislature set up the Nisqually River Task Force in the mid-80s with the hope of bringing together all local stakeholders to develop a plan to restore the river and its precious salmon.

The issues were thorny and the parties clashed. Large landowners like Weyerhaeuser Timber, Wilcox Farms, Tacoma Power, and the Army's Fort Lewis wanted to go about their business as usual. But the tribe and environmentalists wanted wide natural buffers along the Nisqually's banks to protect the river. No logging, no clearing, no cows. With tempers flaring, the group found itself deadlocked.

Learning from the bitter "fish wars" that characterized the 1970s, Frank took charge and pushed the task force toward resolution. Farmer Jim Wilcox remembers Frank well. "I'll never forget the night, … it was a particularly stormy session," said Wilcox, "Billy Frank got up, and I'll never forget this. He said, 'We've got to stop this right now.' He said: 'I want everybody to know that we want Weyerhaeuser Timber Company to continue to operate and own the land along the river. We want Wilcox Farms to keep farming. We don't want to do anything that's going to put them out of business.'"

In one fell swoop, Frank had broken the deadlock, calmed the landowners, and changed the tone of the dialogue. Understanding that cooperation could work, Frank offered a compromise on the buffer issue -- from the ridge of one bank to the ridge on the other shore, sometimes narrow, sometimes wide. It sold. With that agreement came trust. A sense of community and cooperation was born within the group of old rivals.

In the 20 years since, the Nisqually tribe and its neighbors along the river have secured 70 percent of the Nisqually River corridor in permanently protected status and are shooting for a goal of 90 percent. The Nisqually Task Force, which has met monthly ever since its conception, has become a model across the Puget Sound region and the country for mediation and resolution of environmental conflicts -- and the payoff can be seen on the river.

"The eagles, the beavers are coming back, the little animals that lived on this watershed, they're coming back and you know these are very important estuary life on the estuary and the ecosystem," Frank told FRONTLINE correspondent Hedrick Smith, "We need these animals. We need each other. Everyone that's living on this watershed has got to be proud to be here, to be proud to be taking part in protecting the water of the Nisqually watershed."

Read more about the Nisqually River: http://www.nisquallyriver.org/