The New York Times' Charles Duhigg reports today that the violations - which include dangerous bacteria or illegal concentrations of toxic or radioactive substances - affected water delivered to more than 49 million people.
While many violations were one-time events, posing little risk, for hundreds of other systems illegal contamination persisted for years, with no penalty.
Created in 1974 to regulate the nation's public drinking water supply (and later amended in 1986 and 1996), the Safe Drinking Water Act mandates the Environmental Protection Agency to create water quality standards to be applied to more than 160,000 water systems nationwide. The EPA has ultimate authority in enforcing violations.
The law covers treatment and disinfection of water systems, and contaminants (including improperly disposed-of chemicals, pesticides, animal and human wastes, bacteria and naturally-occurring substances) that can contaminate drinking water sources, treatment or distribution systems.
Studies have linked contaminants in drinking water to millions of instances of illness each year.
The Times' analysis of EPA data (which included only situations where residents were exposed to contaminants, rather than, say, violations involving paperwork) showed that Safe Drinking Water Act violations have occurred in every state. The majority occurred at water systems which serve fewer than 20,000 residents.
For example, drinking water tests in Ramsey, N.J., have, since 2004, detected illegal concentrations of arsenic (a carcinogen) and the dry cleaning solvent tetrachloroethylene.
Data showed that since 2004 there have been 205 cases of water systems in New York State providing tap water containing illegal amounts of bacteria. Only three water systems were penalized, according to federal data.
Find Water Polluters Near You (New York Times Interactive)
In response to inquiries by Sen. Barbara Boxer, D-Calif., EPA reported that, since 2005, more than three million Americans have been exposed to illegal concentrations of arsenic and radioactive elements in their drinking water.
Federal data showed that, in some areas, radium was detected at 2,000 percent the legal limit. But less that eight percent of water systems that violated EPA standards for arsenic and radioactive substances were fined or punished. The EPA said that in the majority of cases, state regulators offered help to violators (such as by providing technical assistance) but many systems were still out of compliance afterwards. And for more than a quarter of cases, paperwork notifying systems of violations were sent by regulators but never followed up.
In September an Associated Press investigation found drinking water at thousands of schools across the country had. Many of those schools had their own water supply, from wells, which are also subject to Safe Drinking Water Act protections.
Last year, the EPA.
On Tuesday, the Senate Environment and Public Works committee will hold an oversight hearing on the enforcement of federal drinking water quality laws. EPA officials are expected to announce new policies for overseeing water systems.
Earlier this year EPA administrator Lisa Jackson announced an overhaul of enforcement of the Clean Water Act (which regulates waterway pollution).
In interviews with the Times some current and past EPA enforcement officials said there was little support by their overseers for prosecuting drinking water violations.
"I proposed drinking water cases, but they got shut down so fast that I've pretty much stopped even looking at the violations," an anonymous EPA enforcement official told the Times. "The top people want big headlines and million-dollar settlements. That's not drinking-water cases."
"This administration has made it clear that clean water is a top priority," EPA spokeswoman Adora Andy told the Times. "The previous eight years provide a perfect example of what happens when political leadership fails to act to protect our health and the environment."
One mid-level EPA regulator was skeptical of change actually occurring, telling the Times, "The same people who told us to ignore Safe Drinking Water Act violations are still running the divisions. There's no accountability, and so nothing's going to change."