Jul 14, 2016

USGS Study Shows High Potential for Corrosive Groundwater in Half of U.S. States

Primarily northeast, southeast and northwest states are affected

corrosive groundwater, water quality, lead, plumbing, drinking water

A U.S. Geological Survey (USGS) assessment of more than 20,000 wells nationwide showed that untreated groundwater in 25 states has a high prevalence to be potentially corrosive. Primarily northeastern, southeastern and northwestern states have the largest percentage of wells with potentially corrosive groundwater. A press conference was held July 13 to discuss the findings.

Two indicators of potential corrosivity were combined to determine that corrosive groundwater occurs in all 50 states and the District of Columbia. If left untreated, corrosive groundwater can dissolve lead and other metals from pipe and plumbing fixtures.

“The corrosivity of untreated groundwater is only one of several factors that may affect the quality of household drinking water at the tap,” said Stephen Moulton II, chief of the USGS National Water-Quality Assessment Program. “Nevertheless, it is an essential factor that should be carefully considered in testing for water quality in both public and private supplies nationwide.”

The U.S. Environmental Protection Agency (EPA) regulates public water supplies, but homeowners are responsible for the maintenance, testing and treatment of private water supplies. Approximately 44 million people in the U.S. use drinking water from private wells, yet surveys indicate that many homeowners are unaware of basic testing that should be done to help ensure safe drinking water in the home.

“Fortunately, in most areas of the country and with appropriate safeguards, the majority of homeowners can get good-quality drinking water from private wells,” Moulton said. “But this study is a good reminder that prudent routine testing of the water, including its interaction with the water supply system, is an essential first step so homeowners and their families can confidently drink water from their faucets.”

Naturally corrosive water is not dangerous to consume by itself; however, it can cause health-related problems by reacting with plumbing fixtures. If the materials contain lead or copper, these metals may be leached into the water supply by corrosive water. Signs of this leaching may include bluish-green stains in sinks, metallic taste to water and small leaks in plumbing fixtures.

Potential sources of lead in homes include:

  • Lead pipe or fittings used in homes built before 1930;
  • Lead solder used in copper fittings in homes built before the late 1980s;
  • “Lead-free” brass components, which, in all states except for California, may have contained up to 8% lead before 2014; and
  • Galvanized steel that contained 0.5% to 1.4% lead before 2014.

“USGS has consistently monitored the water quality of the nation’s groundwater for over three decades by analyzing representative water samples,” Moulton said. “Recent public health and water quality issues underscore the responsibility for us to report the possibility that regional geologic characteristics of groundwater could potentially affect household water systems, resulting in significant implications for public health.”

For concerns about potential health effects of household drinking water, USGS looks to federal and state agencies to provide an indication of the potential scope of the problem. 

For example, private water sources, such as wells, springs or cisterns, are especially common in Virginia and Pennsylvania. Approximately 1.7 million people in Virginia and 3 million people in Pennsylvania use private water systems.

In these states, the Virginia Household Water Quality Program and the Pennsylvania Master Well Owner Network provide practical information to homeowners about maintaining, testing and protecting private water systems. University researchers at Virginia Tech and Pennsylvania State work with these specialized programs to monitor the quality of drinking water supplied by private water systems and to provide testing and advice to identify and remediate water quality problems caused by contaminated or corrosive groundwater.

“Between 2012 and 2014, we found that 19% of the 2,144 private water systems sampled in Virginia exceeded the EPA lead action level,” said Dr. Kelsey Pieper, USDA-NIFA postdoctoral fellow at Virginia Tech. “We also observed that ‘lead-free’ plumbing components released lead when exposed to more corrosive groundwater supplies.”

“In Pennsylvania, corrosive water is usually associated with certain types of bedrock geology, but can be found across the entire state,” said Bryan Swistock, water resources specialist for Penn State Extension. “Lead levels exceeded the EPA action level in 12% of the 251 drinking water systems monitored in Pennsylvania in 2007.”

The USGS report is unrelated to the drinking water problems in Flint, Mich. The problems in Flint were related to treated surface water from the Flint River, whereas the water analyzed in this report came from untreated groundwater.

The USGS report, Assessing the Potential Corrosivity of U.S. Groundwater, can be accessed online. Additional information on groundwater quality monitoring and modeling is available on the USGS National Water-Quality Assessment project website. And a new USGS online mapper provides a decadal look at groundwater quality.

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