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Corrosivity FAQ
Find answers to your questions about corrosivity here
A U.S. Geological Survey assessment of more than 20,000 wells nationwide shows that untreated groundwater in 25 states has a high prevalence of being potentially corrosive. The states with the largest percentage of wells with potentially corrosive groundwater are located primarily in the Northeast, the Southeast, and the Northwest.
These FAQs were written in conjunction with that study. In addition to information specific to the study, these FAQs include many answers to general corrosivity questions.
► Additional
About the Study
- Are the findings of this study applicable to the recent drinking water problems experienced in Flint Michigan?
- What is the purpose of this study?
- Why assess the potential corrosivity of the Nation’s groundwater?
- How many wells were sampled? When were they sampled?
- What types of wells were sampled?
- Were the samples collected before or after treatment?
- Were analyses of tap water samples done as part of this study?
- What measures of potential corrosivity were used in this study?
- How can I retrieve the data used in this report?
- What are the limitations of this study?
USGS Role Regarding Drinking Water
- Is USGS responsible for monitoring drinking water?
- Does USGS regulate drinking water?
- Where can I learn more about how drinking water from public supplies and private wells is regulated?
Human Health Implications
- What are the potential human-health issues associated with corrosive well water?
- If indicators show that my well water is potentially corrosive and it is untreated, will I also have high levels of lead or other metals in my well water?
- What are the potential sources of lead in private water distribution systems?
Information for Homeowners with private wells
- How do I determine if my well water is corrosive?
- Where can I find information regarding water testing, maintenance, and treatment of my well?
Additional information on USGS assessments
- Where can I learn more about the quality of source groundwater for private wells and public wells across the Nation, natural and human factors that affect the quality of groundwater used for drinking water, and how groundwater-quality is changing over time?
- Where can I learn more about the USGS National Water-Quality Assessment (NAWQA) Project?
- Who do I contact for additional information about this report?
About the Study
Are the findings of this study applicable to the recent drinking water problems experienced in Flint Michigan?
No. The source of corrosive water used for the Flint drinking water supply was the Flint River, a surface-water source whereas the USGS report deals with the potential corrosivity of untreated groundwater. In addition, the high levels of lead in drinking water supplied to residents of Flint were related to inadequate treatment of the corrosive source water pumped from the Flint River by the public water utility. The USGS study is only reporting on the potential corrosivity of untreated groundwater, with the implications of having potentially corrosive water directed primarily at homeowners who rely on private wells for their drinking water supply. Unlike public water supplies like Flint, the quality and safety of drinking water from private wells are not regulated by the Federal government or, in most cases, by state laws. Rather, individual homeowners are responsible for testing, treating, and maintaining their private water systems.
What is the purpose of this study?
The purpose of this study is to present national maps of the distribution of two indicators of the corrosivity of untreated groundwater across the Nation: the Langelier Saturation Index (LSI) and the Potential to Promote Galvanic Corrosion (PPGC). The PPGC is based on chloride-to-sulfate mass ratio (CSMR). For each indicator, two maps are presented: one map shows the values of the indicator at individual groundwater sites and, the other map shows characteristic values for each state. The maps are based on data at about 27,000 groundwater sites obtained from the US Geological Survey’s (USGS) National Water Information System (NWIS). The combined corrosivity index map combines the LSI and PPGC into one general indicator of potentially corrosive groundwater to summarize study results at the state level.
Why assess the potential corrosivity of the Nation’s groundwater?
Corrosive groundwater, if untreated, can dissolve lead and other metals from pipes and other components present in household plumbing. About 43.5 million people rely upon groundwater from private wells and springs for their source of drinking water. The corrosivity of untreated groundwater is only one of several factors that may affect the quality of household drinking water at the tap. Nevertheless, it is an essential factor that should be carefully considered in testing, treating, and maintaining the quality and safety of drinking water obtained from a private water system supplied by groundwater.
How many groundwater sites were sampled? When were they sampled?
Water quality data from about 27,000 groundwater sites across the Nation were obtained from the U.S. Geological Survey’s National Water Information System. The samples were collected from 1991 to 2015.
What types of groundwater sites were sampled?
The study assessed corrosivity in samples from private wells, public supply wells, wells of other types, and springs.
Were the samples collected before or after treatment?
All groundwater samples were collected prior to any treatment or blending that potentially could alter the quality of the source groundwater. USGS personnel collected water samples after the well had been pumped a minimum of three casing volumes and after basic water-quality properties such as temperature, pH, and specific conductance had stabilized from outlets located before any pressure tanks or treatment systems.
Were analyses of tap water samples done as part of this study?
No. Samples were collected to represent the source of the groundwater being used for drinking water, not the quality of water at the tap.
What measures of potential corrosivity of groundwater were used in this study?
Water corrosivity is affected by more than just pH, although pH is a major driver of corrosivity in many cases. The corrosivity of water is characterized by factors such as pH, calcium concentration, hardness, alkalinity, dissolved solids, and temperature. There are several indicators of corrosivity. Two indicators are summarized in this report to provide a national characterization of the potential corrosivity of groundwater: the Langelier Saturation Index (LSI) and the chloride-to-sulfate mass ratio (CSMR). The LSI provides an indication of the extent to which calcium carbonate scale might be deposited inside pipes and other components of a distribution system (Langelier, 1936; Larson and others, 1942). In the absence of a protective scale, lead, if present, can dissolve from plumbing materials into the water (Langelier, 1936; Stumm and Morgan, 1981; Hu and others, 2012). The LSI only indicates the tendency for scaling to occur; it is not a measurement of corrosivity (Singely and others, 1984). Nevertheless, the LSI is commonly used as an indicator of the potential corrosivity of water.
A three-tier classification system based on the chloride-to-sulfate mass ratio (CSMR) developed by Nguyen and others (2010, 2011) is used to assess levels of concern related to galvanic corrosion of lead in water distribution systems. If the source water entering those systems has a relatively elevated CSMR (Gregory 1985; Edwards and Triantafyllidou, 2007; Hu and others, 2012), the potential for galvanic corrosion to occur is elevated, especially in water with low values of alkalinity (Nguyen and others (2011). In this report, untreated groundwater is assessed and the three-tier classification is applied without considering the absence or presence of lead or other metals in the distribution system. Consequently, the three-tier classification system is referred to in this report as the Potential to Promote Galvanic Corrosion (PPGC).
The LSI and PPGC classifications are combined into a Combined Corrosivity Index to classify the potential for corrosive groundwater at the individual state scale. Confidence intervals for these classifications are provided in the report Appendix.
How can I retrieve the data used in this report?
- Langelier Saturation Index – maps and water-quality data
- Chloride-to-sulfate ratio – maps and water-quality data
What are the corrosivity classification uncertainties of this study?
Classification of states with respect to potential corrosivity and the Potential to Promote Galvanic Corrosion (PPGC) was based on estimates of characteristic values for the states, and those estimates are subject to uncertainty. The uncertainty associated with the estimate of the average LSI was computed using the standard confidence interval at a 90 percent confidence level (Ott and Longnecker, 2001). The uncertainty associated with estimating the proportion of groundwater sites with a given classification was computed using the Clopper-Pearson interval (Clopper and Pearson, 1934) at a 90 percent confidence level. Given a 90 percent confidence interval, six states could be given a classification that is different from the one based on the characteristic value for the state: Kentucky, Missouri, Montana, New Hampshire, North Carolina, and Vermont. Refer to the report Appendix for further discussion on the classification uncertainty.
USGS Role Regarding Drinking Water
Is USGS responsible for monitoring drinking water?
No. The U.S. Geological Survey (USGS), and specifically, the National Water-Quality Assessment (NAWQA) Project, does not assess the quality of the Nation’s treated drinking water or conduct regulatory compliance monitoring. Rather, NAWQA assessments focus mainly on the quality of the available, untreated resource (source water), such as water upstream from treatment plants or groundwater pumped from public-supply and domestic wells.
Does USGS regulate drinking water?
No. The USGS is a non-regulatory agency under the U.S. Department of Interior and is the primary federal agency responsible for providing scientific information on the quality of the Nation’s water resources. USGS information is intended to facilitate effective management of water resources and ensure long-term availability of water that is safe for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife.
Where can I learn more about how drinking water from public supplies and private wells is regulated?
The quality of finished (treated) drinking water from the Nation’s public water systems is regulated by the U.S. Environmental Protection Agency (USEPA) under the Safe Drinking Water Act (SDWA) (U.S. Environmental Protection Agency, 2004). The SDWA defines a public water system as one that serves piped drinking water to at least 25 people or 15 service connections for at least 60 days a year (U.S. Environmental Protection Agency, 2003). The SDWA, originally passed by Congress in 1974 and amended in 1986 and 1996, requires many actions to protect drinking water and its sources—rivers, lakes, reservoirs, springs, and groundwater. For example, SDWA authorizes the USEPA to set national health-based standards for drinking water to protect against both naturally occurring and man-made contaminants that may be detected in drinking water (U.S. Environmental Protection Agency, 2004). USEPA oversees the states, localities, and water suppliers who implement the drinking-water standards. Information about how USEPA decides which contaminants to regulate, how drinking water standards are set, and the review of existing regulations is available online at: http://www.epa.gov/safewater/standard/setting.html. EPA established the Lead and Copper Rule to control levels of lead and copper in public water systems. The rule requires systems to monitor drinking water at customer taps. If lead concentrations exceed an action level of 15 ppb or copper concentrations exceed an action level of 1.3 ppm in more than 10% of customer taps sampled, the system must undertake a number of additional actions to control corrosion. If the action level for lead is exceeded, the system must also inform the public about steps they should take to protect their health and may have to replace lead service lines under their control. See https://www.epa.gov/dwreginfo/lead-and-copper-rule for more information about the Lead and Copper Rule
The quality and safety of water from private wells are not regulated by the SDWA or, in most cases, by state laws. Rather, individual homeowners are responsible for maintaining their private well or spring systems. State laws and local regulations, where they exist, typically require a minimum amount of water testing for private wells. Regulations apply primarily at the time of well installation and are limited in scope. Less than half of the states require testing of water from new private wells, typically for bacteria and nitrate. County or other local testing requirements for new wells also may exist. Water-quality testing at the time of home sales is a condition of some home loans and is required by some states. A few states also conduct free voluntary testing programs.
Human Health Implications
What are the potential human-health issues associated with corrosive well water?
Naturally corrosive water is not dangerous to consume by itself. Nevertheless, it can cause health-related problems by reacting with pipes and plumbing fixtures in homes thereby releasing metals or other contaminants that can present a human health concern. If plumbing materials contain lead, copper, or cadmium these metals may be leached into the water supply by corrosive water. Lead exposure can cause behavior problems and learning disabilities in children and can also affect the health of adults. Per EPA drinking water guidelines, short-term exposure to copper can cause nausea and stomach upset whereas long-term exposure may affect the liver or kidneys; long-term exposure to cadmium in drinking water can cause kidney damage.
If indicators show that my well water is potentially corrosive, will I also have high levels of lead or other metals in my well water?
Having potentially corrosive groundwater does not mean that you also have high lead or other metal levels in your tap water. It depends on several characteristics of the groundwater (pH, calcium concentration, hardness, dissolved solids, and temperature) and the materials used throughout your plumbing distribution system and if your water is untreated. The primary source of lead in private water systems are: the well pump, galvanized iron well components, brass fittings in the well and household plumbing, and leaded solder used to connect copper pipes. Knowledge of the date your well was installed and the types of materials used throughout your distribution system can help provide critical information needed to assess if what types of water-quality testing may be warranted, especially if your water is potentially corrosive.
For the issue of the potential health effects of household drinking water, the USGS looks to partner agencies at the federal and state levels to provide an indication of the potential scope of the problem. EPA’s fact sheet “Actions you can take to reduce Lead In Drinking Water http://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=20001R4V.txt” identifies steps you can take to evaluate levels of lead and copper and to reduce your exposure. Virginia and Pennsylvania are examples of two states where private water systems, such as wells, springs, or cisterns, are especially common. Private water systems are used by about 1.7 million people in Virginia and about 3 million people in Pennsylvania.
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 Penn 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 of 15 μg/L,” 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.”(Pieper and others, 2015)
“In Pennsylvania, corrosive water is usually associated with certain types of bedrock geology but can be found across the entire state,” said Bryan Swistock, a water resources specialist with Penn State Extension. “Lead levels exceeded the EPA action level in 12 percent of the 251 drinking water systems monitored in Pennsylvania in 2007”.” (Swistock and others, 1993, 2009; and Swistock and Clemens, 2013)
What are the potential sources of lead in private water systems?
Lead pipe and fittings were used in homes built prior to 1930 and lead solder, which contains up to 50 percent lead and is used to connect copper pipes and fittings, was used in many homes built prior to the late 1980’s. In 1986 EPA began to regulate the amount of lead in plumbing components and lead solder. However, prior to 2014, “lead-free” brass components, in all states, except California, may have contained up to 8 percent lead. Similarly galvanized steel components may have contained from 0.5 to 1.4 percent lead prior to 2014.
Information for Homeowners with private wells
How do I determine if my well water is corrosive?
If plumbing materials contain lead or copper, these metals may be leached into the water supply by corrosive water. Signs of corrosive water causing leaching of metals may include bluish-green stains in sinks, metallic taste to water, and pitting or small, pinhole leaks in plumbing fixtures. You can also have your well water tested for corrosion.
Where can I find information regarding water testing, maintenance, and treatment of my well?
National Hotlines
Environmental Protection Agency Safe Drinking Water Hotline
1-800-426-4791 (10am - 4pm ET, M-F)
National Ground Water Association Private Well Owner Hotline
855-420-9355 (10am – 4pm ET, M-F)
Federal Agencies
Environmental Protection Agency
Basic Information about Lead in Drinking Water
Additional Information on Private Wells
Drinking Water From Household Wells
Drinking Water in New England--Private Well Owners
Centers for Disease Control
Safe Water for Community Health (SafeWATCH)
National Institute of Health
National Institute of Environmental Health Sciences
Drinking Water Organizations
National Groundwater Association: Well Owner Information
Water Systems Council: Well Owners' Manual
American Groundwater Trust: The American Well Owner
Groundwater Protection Council: Water Quality
National Rural Water Association: Quality on Tap
Water Quality Association: Improve Your Water
State Information
Alabama
Alabama Department of Public Health: Well Water
Alabama Extension: Drinking Water / Human Health
Alaska
Alaska Division of Environmental Health: Drinking Water Protection
Arizona
Arizona Department of Water Resources: Wells
Arizona Extension: Private Wells
Arkansas
Arkansas Department of Health: Private Water Testing. Original link. Organization home.
University of Arkansas Division of Agriculture: Drinking Water
California
California State Water Resources Control Board: A Guide for Private Domestic Well Owners
California Environmental Protection Agency: Well Owners - Water Quality in Private Domestic Wells
Colorado
Colorado Department of Public Health and Environment: Drinking Water: Private Wells
Colorado State University Extension: Private Wells for Home Use
Connecticut
Connecticut Department of Health: Private Wells
Deleware
Deleware Health and Social Services: Drinking Water - Private Well Owners
Florida
Florida Department of Health: Private Well Testing
Georgia
Georgia Department of Public Health: Individual Private Wells
University of Georgia Extension: Publications in the Household Water Quality Series
Hawaii
Hawaii Department of Health: Safe Drinking Water
Idaho
Idaho Department of Environmental Quality: Private Wells
Idaho Department of Health and Welfare: Well Water Safety
Illinois
Illinois Environmental Protection Agency: Private Well Users
Illinois Department of Public Health: Water Wells
University of Illinois: The Private Well Class
Indiana
Indiana Department of Environmental Management: Private Wells and Compliant Response
Indiana Department of Natural Resources: Water Well Record Database
Iowa
State Hygienic Laboratory at The University of Iowa: Private Well Water
Iowa Department of Natural Resources: Private Well Program Hot Topics
Kansas
Kansas Department of Health and Environment: Water Well Program
Kentucky
Kentucky Department of Environmental Protection: Groundwater Awareness
University of Kentucky College of Agriculture, Food, and Environment: Kentucky Well Education
Louisiana
Louisiana Department of Natural Resources: For Water Well Owners
Louisiana Department of Health and Hospitals: Private Well Initiative
Maine
Maine Center for Disease Control & Public Health: Well Water Maine
Maryland
Maryland Department of the Environment: Residential Wells
University of Maryland Extension: Wells
Massachusetts
Massachusetts Energy and Environmental Affairs: Private Wells
Michigan
Minnesota
Minnesota Department of Health: Water Well Information
University of Minnesota Extension: Safe Drinking Water for Minnesotans Original link. Organization home
Mississippi
Mississippi State University Extension: Protecting Your Private Well
Missouri
Missouri Department of Natural Resources: Water Wells
University of Missouri Extension: Drinking Water Well Management
Montana
Montana Division of Public Health and Human Services: Private Well Testing Program
Montana Department of Environmental Quality: Private Well Information
Nebraska
Nebraska Department of Health and Human Services: Water Well Standards
University of Nebraska-Lincoln: Drinking Water Testing
Nevada
Nevada Division of Environmental Protection: Private Wells
New Hampshire
New Hampshire Department of Environmental Services: Be Well Informed
New Hampshire Department of Environmental Services: Private Well Testing Program
New Jersey
New Jersey Department of Environmental Protection: General Information on Wells
New Mexico
New Mexico Environmental Public Health Tracking: Private Wells Water Quality
New Mexico Environment Department: Private Well Owners
New York
New York State Department of Health: Individual Private Water Supply Wells
Cornell University Cooperative Extension: Water Quality Information for Consumers
North Carolina
North Carolina Health and Human Services: Well Water and Health
North Dakota
Ohio
Ohio Department of Health: Private Water Systems
Ohio Watershed Network: Know Your Well Water
National Center for Water Quality Research: Well Water Testing
Oklahoma
Oklahoma Department of Environmental Quality: Home Water Testing FAQ
Oklahoma Water Resources Center: Drinking Water
Oregon
Oregon Health Authority: Well Testing and Regulations
Oregon State University: Well Water Program
Oregon Department of Environmental Quality: Resources for Private (Domestic) Well Owners
Pennsylvania
Pennsylvania Department of Environmental Protection: Private Water Wells
Penn State Extension: Drinking Water Interpretation Tool
Penn State Extension: Master Well Owner Network
Rhode Island
URI Home*A*Syst: Private Well Testing and Protection
South Carolina
South Carolina Department of Health and Environmental Control: Residential Wells
South Dakota
South Dakota Department of Environment and Natural Resources: Private Well Sampling
South Dakota Department of Health: Testing Private Wells
Tennessee
Tennessee Department of Health: Private Water Supply
Tennessee Department of Environment and Conservation: Well Water
Texas
Texas Groundwater Protection Committee: Water Wells
Texas Water Resources Institute: Texas Well Owner Network
Utah
Utah State University Extension: Water Testing
Vermont
Vermont Department of Health: Testing Your Drinking Water Supply
Virginia
Virginia Department of Health: Private Well Water Information
Washington
Washington State Department of Health: Drinking Water
West Virginia
West Virginia Department of Health & Human Resources: Wells, Cisterns, and Springs Original link. Organization home
Wisconsin
Wisconsin Department of Natural Resources: Information for homeowners with private wells
University of Wisconsin Stevens Point: Homeowner Testing
Wyoming
Wyoming Department of Environmental Quality: Know Your Well
Additional information on USGS assessments
Where can I learn more about the quality of source groundwater for private wells and public wells across the Nation, natural and human factors that affect the quality of groundwater used for drinking water, and how groundwater-quality is changing over time?
Public Supply Wells—About 105 million people—more than one-third of the Nation’s population—receive their drinking water from one of the 140,000 public water systems across the United States that rely on groundwater pumped from wells. USGS scientists assessed water quality in source (untreated) water from 932 public-supply wells (referred to as public wells), and in finished (treated) and source water from 94 of these wells. The USGS study focused primarily on “source” water before treatment or blending and describes the occurrence of naturally occurring and man-made contaminants in source water from public wells and their potential significance to human health. USGS Circular 1346, Quality of Water from Public-Supply Wells in the U.S.
Public-Supply-Well Vulnerability—The USGS investigated public-supply-well vulnerability to contamination in 10 major metropolitan areas across the Nation to assess which contaminants in an aquifer might reach a well and when, how, and at what concentration they might arrive. Three measures are particularly useful for understanding public-supply-well vulnerability: the sources of recharge that contribute water to a well and the contaminants associated with the recharge; the geochemical conditions in the aquifer tapped by a well; and the groundwater-age mixture of the water pumped from a well. Factors Affecting Public-Supply-Well Vulnerability to Contamination
Private Wells—About 43.5 million people - or 15 percent of the Nation’s population - use drinking water from private wells, which are not regulated by the USEPA via the Safe Drinking Water Act. The USGS sampled about 2,100 private wells in 48 states from 1991 to 2004 in 30 of the Nation’s principal aquifers used for water supply. As many as 219 properties and contaminants, including pH, major ions, nutrients, radionuclides, trace elements, pesticides, volatile organic compounds, and microbial contaminants, were measured. Sampled water was taken from private wells before any home treatment. The large number of contaminants assessed and the broad geographic coverage of the study provides a foundation for an improved understanding of the quality of water from the major aquifers tapped by private wells in the United States. USGS Circular 1332, Quality of Water from Domestic Wells in Principal Aquifers of the U.S.
Water Quality in Aquifers Across the Nation—USGS scientists assessed water quality in source (untreated) water from 6,600 wells in regionally extensive aquifers that supply most of the groundwater pumped for the Nation’s drinking water, irrigation, and other uses. The comprehensive sampling, along with detailed information on geology, hydrology, geochemistry, and chemical and water use, can be used to explain how and why aquifer vulnerability to contamination varies across the Nation. By knowing where contaminants occur in groundwater, what factors control contaminant concentrations, and what kinds of changes in groundwater quality might be expected in the future, we can ensure the future availability and quality of this vital natural resource. USGS Circular 1360, Quality of the Nation’s Groundwater
Decadal Look at Groundwater Quality— An online interactive mapping tool that provides summaries of decadal-scale changes in groundwater quality across the Nation is now available for use by the public, water-resource managers, and policy makers. The mapper shows how concentrations of 24 contaminants, such as nutrients, pesticides, metals, and volatile organic compounds, are changing over decadal periods in 67 groundwater networks across the Nation. Each network consists of about 20 to 30 wells selected to represent water-quality conditions in a given geographical area, aquifer, and in some cases, a specific land use.
Where can I learn more about the USGS National Water-Quality Assessment (NAWQA) Project?
Look online for recent NAWQA headlines, activities, and publications.
Examples of How USGS Science is Informing Groundwater Quality Management Decisions
Who do I contact for additional information about this report?
Kenneth Belitz
Chief, Groundwater Assessment
National Water-Quality Assessment Project
kbelitz@usgs.gov
References:
Clopper, C.J., and Pearson, E.S., 1934, The use of confidence intervals or fiducial limits illustrated in the case of the binomial: Biometrika, v. 26, no. 4, p. 404–413.
Edwards, M., and Triantafyllidou, S., 2007, Chloride-to-sulfate mass ratio and lead leaching to water: Journal of American Water Works Association, v. 99, no. 7, p. 96–109.
http://www.awwa.org/publications/journal-awwa/abstract/articleid/15699.aspx
Gregory, R., 1985, Galvanic corrosion of lead in copper pipework—Phase I, measurement of galvanic corrosion potential in selected waters: Swindon, England, Water Research Centre Engineering, 74 p.
Hu, J., Gan, F., Triantafyllidou, S., Nguyen, C.K. and Edwards, M.A., 2012, Copper-induced metal release from lead pipe into drinking water, Corrosion, 68(11), p.1037-1048. http://dx.doi.org/10.5006/0616
Langelier, W.F., 1936, The analytical control of anti-corrosion water treatment, Journal (American Water Works Association), 28(10), p. 1500-1521.
Larson, T.E., Buswell, A.M., Ludwig, H.F. and Langelier, W.F., 1942. Calcium Carbonate Saturation Index and Alkalinity Interpretations [with Discussion]. Journal American Water Works Association, 34(11), pp.1667-1684.
Nguyen, C., Stone, K., Clark, B., Edwards, M., Gagnon, G., and Knowles, A., 2010, Impact of chloride—Sulfate mass ratio (CSMR) changes on lead leaching in potable water: Denver, Water Research Foundation, 198 p.
Nguyen, C.K., Stone, K.R., and Edwards, M.A., 2011, Chloride-to-sulfate mass ratio—Practical studies in galvanic corrosion of lead solder: Journal of the American Water Works Association, v. 103, no. 1, p. 81–92. http://www.awwa.org/publications/journal-awwa/abstract/articleid/26682.aspx
Ott, R.L., and Longnecker, M., 2001, An introduction to statistical methods and data analysis (5th ed.): Pacific Grove, Calif., Duxbury Press, 1,152 p.
Pieper, K.J., Krometis, L.A.H., Gallagher, D.L., Benham, B.L., and Edwards, M., 2015, Incidence of waterborne lead in private drinking water systems in Virginia: Journal of Water and Health, v. 13, no. 3, p. 897–908, accessed April 6, 2016, at http://dx.doi.org/10.2166/wh.2015.275
Singley, J.E., Beaudet, B.A. and Markey, P.H., 1984. Corrosion manual for internal corrosion of water distribution systems (No. ORNL/TM-8919; EPA-570/9-84-001). Environmental Science and Engineering, Inc., Gainesville, FL (USA).
Stumm, W. and Morgan, J.J., 1981, Aquatic chemistry: an introduction emphasizing chemical equilibria in natural waters, John Wiley, New York, 780 p.
Swistock, B.R., and Clemens, S., 2013, Water quality and management of private drinking water wells in Pennsylvania: Journal of Environmental Health, v. 75, no. 6, p. 60.
Swistock, B.R., Clemens, S., and Sharpe, W.E., 2009, Drinking water quality in rural Pennsylvania and the effect of management practices: Harrisburg, Pa., Center for Rural Pennsylvania, 24 p., accessed May 10, 2016, at http://www.rural.palegislature.us/drinking_water_quality.pdf.
Swistock, B.R., Sharpe, W.E., and Robillard, P.D., 1993, A survey of lead, nitrate and radon contamination of private individual water systems in Pennsylvania: Journal of Environmental Health, v. 55, no. 5, p. 6–13.
U.S. Environmental Protection Agency, 2003, Water on tap: what you need to know: U.S. Environmental Protection Agency, Office of Water EPA 816-K-03-007, October 2003, 36p. Available at https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1008ZP0.TXT
U.S. Environmental Protection Agency, 2004, Understanding the safe drinking water act: U.S. Environmental Protection Agency, Office of Water EPA 816-F-04-030, June 2004, 4p. Available at https://www.epa.gov/sites/production/files/2015-04/documents/epa816f04030.pdf
Explore the web pages below for topics related to corrosivity.
Corrosivity
Chloride, Salinity, and Dissolved Solids
A U.S. Geological Survey assessment of more than 20,000 wells nationwide shows that untreated groundwater in 25 states has a high prevalence of being potentially corrosive. The states with the largest percentage of wells with potentially corrosive groundwater are located primarily in the Northeast, the Southeast, and the Northwest.
These FAQs were written in conjunction with that study. In addition to information specific to the study, these FAQs include many answers to general corrosivity questions.
► Additional
About the Study
- Are the findings of this study applicable to the recent drinking water problems experienced in Flint Michigan?
- What is the purpose of this study?
- Why assess the potential corrosivity of the Nation’s groundwater?
- How many wells were sampled? When were they sampled?
- What types of wells were sampled?
- Were the samples collected before or after treatment?
- Were analyses of tap water samples done as part of this study?
- What measures of potential corrosivity were used in this study?
- How can I retrieve the data used in this report?
- What are the limitations of this study?
USGS Role Regarding Drinking Water
- Is USGS responsible for monitoring drinking water?
- Does USGS regulate drinking water?
- Where can I learn more about how drinking water from public supplies and private wells is regulated?
Human Health Implications
- What are the potential human-health issues associated with corrosive well water?
- If indicators show that my well water is potentially corrosive and it is untreated, will I also have high levels of lead or other metals in my well water?
- What are the potential sources of lead in private water distribution systems?
Information for Homeowners with private wells
- How do I determine if my well water is corrosive?
- Where can I find information regarding water testing, maintenance, and treatment of my well?
Additional information on USGS assessments
- Where can I learn more about the quality of source groundwater for private wells and public wells across the Nation, natural and human factors that affect the quality of groundwater used for drinking water, and how groundwater-quality is changing over time?
- Where can I learn more about the USGS National Water-Quality Assessment (NAWQA) Project?
- Who do I contact for additional information about this report?
About the Study
Are the findings of this study applicable to the recent drinking water problems experienced in Flint Michigan?
No. The source of corrosive water used for the Flint drinking water supply was the Flint River, a surface-water source whereas the USGS report deals with the potential corrosivity of untreated groundwater. In addition, the high levels of lead in drinking water supplied to residents of Flint were related to inadequate treatment of the corrosive source water pumped from the Flint River by the public water utility. The USGS study is only reporting on the potential corrosivity of untreated groundwater, with the implications of having potentially corrosive water directed primarily at homeowners who rely on private wells for their drinking water supply. Unlike public water supplies like Flint, the quality and safety of drinking water from private wells are not regulated by the Federal government or, in most cases, by state laws. Rather, individual homeowners are responsible for testing, treating, and maintaining their private water systems.
What is the purpose of this study?
The purpose of this study is to present national maps of the distribution of two indicators of the corrosivity of untreated groundwater across the Nation: the Langelier Saturation Index (LSI) and the Potential to Promote Galvanic Corrosion (PPGC). The PPGC is based on chloride-to-sulfate mass ratio (CSMR). For each indicator, two maps are presented: one map shows the values of the indicator at individual groundwater sites and, the other map shows characteristic values for each state. The maps are based on data at about 27,000 groundwater sites obtained from the US Geological Survey’s (USGS) National Water Information System (NWIS). The combined corrosivity index map combines the LSI and PPGC into one general indicator of potentially corrosive groundwater to summarize study results at the state level.
Why assess the potential corrosivity of the Nation’s groundwater?
Corrosive groundwater, if untreated, can dissolve lead and other metals from pipes and other components present in household plumbing. About 43.5 million people rely upon groundwater from private wells and springs for their source of drinking water. The corrosivity of untreated groundwater is only one of several factors that may affect the quality of household drinking water at the tap. Nevertheless, it is an essential factor that should be carefully considered in testing, treating, and maintaining the quality and safety of drinking water obtained from a private water system supplied by groundwater.
How many groundwater sites were sampled? When were they sampled?
Water quality data from about 27,000 groundwater sites across the Nation were obtained from the U.S. Geological Survey’s National Water Information System. The samples were collected from 1991 to 2015.
What types of groundwater sites were sampled?
The study assessed corrosivity in samples from private wells, public supply wells, wells of other types, and springs.
Were the samples collected before or after treatment?
All groundwater samples were collected prior to any treatment or blending that potentially could alter the quality of the source groundwater. USGS personnel collected water samples after the well had been pumped a minimum of three casing volumes and after basic water-quality properties such as temperature, pH, and specific conductance had stabilized from outlets located before any pressure tanks or treatment systems.
Were analyses of tap water samples done as part of this study?
No. Samples were collected to represent the source of the groundwater being used for drinking water, not the quality of water at the tap.
What measures of potential corrosivity of groundwater were used in this study?
Water corrosivity is affected by more than just pH, although pH is a major driver of corrosivity in many cases. The corrosivity of water is characterized by factors such as pH, calcium concentration, hardness, alkalinity, dissolved solids, and temperature. There are several indicators of corrosivity. Two indicators are summarized in this report to provide a national characterization of the potential corrosivity of groundwater: the Langelier Saturation Index (LSI) and the chloride-to-sulfate mass ratio (CSMR). The LSI provides an indication of the extent to which calcium carbonate scale might be deposited inside pipes and other components of a distribution system (Langelier, 1936; Larson and others, 1942). In the absence of a protective scale, lead, if present, can dissolve from plumbing materials into the water (Langelier, 1936; Stumm and Morgan, 1981; Hu and others, 2012). The LSI only indicates the tendency for scaling to occur; it is not a measurement of corrosivity (Singely and others, 1984). Nevertheless, the LSI is commonly used as an indicator of the potential corrosivity of water.
A three-tier classification system based on the chloride-to-sulfate mass ratio (CSMR) developed by Nguyen and others (2010, 2011) is used to assess levels of concern related to galvanic corrosion of lead in water distribution systems. If the source water entering those systems has a relatively elevated CSMR (Gregory 1985; Edwards and Triantafyllidou, 2007; Hu and others, 2012), the potential for galvanic corrosion to occur is elevated, especially in water with low values of alkalinity (Nguyen and others (2011). In this report, untreated groundwater is assessed and the three-tier classification is applied without considering the absence or presence of lead or other metals in the distribution system. Consequently, the three-tier classification system is referred to in this report as the Potential to Promote Galvanic Corrosion (PPGC).
The LSI and PPGC classifications are combined into a Combined Corrosivity Index to classify the potential for corrosive groundwater at the individual state scale. Confidence intervals for these classifications are provided in the report Appendix.
How can I retrieve the data used in this report?
- Langelier Saturation Index – maps and water-quality data
- Chloride-to-sulfate ratio – maps and water-quality data
What are the corrosivity classification uncertainties of this study?
Classification of states with respect to potential corrosivity and the Potential to Promote Galvanic Corrosion (PPGC) was based on estimates of characteristic values for the states, and those estimates are subject to uncertainty. The uncertainty associated with the estimate of the average LSI was computed using the standard confidence interval at a 90 percent confidence level (Ott and Longnecker, 2001). The uncertainty associated with estimating the proportion of groundwater sites with a given classification was computed using the Clopper-Pearson interval (Clopper and Pearson, 1934) at a 90 percent confidence level. Given a 90 percent confidence interval, six states could be given a classification that is different from the one based on the characteristic value for the state: Kentucky, Missouri, Montana, New Hampshire, North Carolina, and Vermont. Refer to the report Appendix for further discussion on the classification uncertainty.
USGS Role Regarding Drinking Water
Is USGS responsible for monitoring drinking water?
No. The U.S. Geological Survey (USGS), and specifically, the National Water-Quality Assessment (NAWQA) Project, does not assess the quality of the Nation’s treated drinking water or conduct regulatory compliance monitoring. Rather, NAWQA assessments focus mainly on the quality of the available, untreated resource (source water), such as water upstream from treatment plants or groundwater pumped from public-supply and domestic wells.
Does USGS regulate drinking water?
No. The USGS is a non-regulatory agency under the U.S. Department of Interior and is the primary federal agency responsible for providing scientific information on the quality of the Nation’s water resources. USGS information is intended to facilitate effective management of water resources and ensure long-term availability of water that is safe for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife.
Where can I learn more about how drinking water from public supplies and private wells is regulated?
The quality of finished (treated) drinking water from the Nation’s public water systems is regulated by the U.S. Environmental Protection Agency (USEPA) under the Safe Drinking Water Act (SDWA) (U.S. Environmental Protection Agency, 2004). The SDWA defines a public water system as one that serves piped drinking water to at least 25 people or 15 service connections for at least 60 days a year (U.S. Environmental Protection Agency, 2003). The SDWA, originally passed by Congress in 1974 and amended in 1986 and 1996, requires many actions to protect drinking water and its sources—rivers, lakes, reservoirs, springs, and groundwater. For example, SDWA authorizes the USEPA to set national health-based standards for drinking water to protect against both naturally occurring and man-made contaminants that may be detected in drinking water (U.S. Environmental Protection Agency, 2004). USEPA oversees the states, localities, and water suppliers who implement the drinking-water standards. Information about how USEPA decides which contaminants to regulate, how drinking water standards are set, and the review of existing regulations is available online at: http://www.epa.gov/safewater/standard/setting.html. EPA established the Lead and Copper Rule to control levels of lead and copper in public water systems. The rule requires systems to monitor drinking water at customer taps. If lead concentrations exceed an action level of 15 ppb or copper concentrations exceed an action level of 1.3 ppm in more than 10% of customer taps sampled, the system must undertake a number of additional actions to control corrosion. If the action level for lead is exceeded, the system must also inform the public about steps they should take to protect their health and may have to replace lead service lines under their control. See https://www.epa.gov/dwreginfo/lead-and-copper-rule for more information about the Lead and Copper Rule
The quality and safety of water from private wells are not regulated by the SDWA or, in most cases, by state laws. Rather, individual homeowners are responsible for maintaining their private well or spring systems. State laws and local regulations, where they exist, typically require a minimum amount of water testing for private wells. Regulations apply primarily at the time of well installation and are limited in scope. Less than half of the states require testing of water from new private wells, typically for bacteria and nitrate. County or other local testing requirements for new wells also may exist. Water-quality testing at the time of home sales is a condition of some home loans and is required by some states. A few states also conduct free voluntary testing programs.
Human Health Implications
What are the potential human-health issues associated with corrosive well water?
Naturally corrosive water is not dangerous to consume by itself. Nevertheless, it can cause health-related problems by reacting with pipes and plumbing fixtures in homes thereby releasing metals or other contaminants that can present a human health concern. If plumbing materials contain lead, copper, or cadmium these metals may be leached into the water supply by corrosive water. Lead exposure can cause behavior problems and learning disabilities in children and can also affect the health of adults. Per EPA drinking water guidelines, short-term exposure to copper can cause nausea and stomach upset whereas long-term exposure may affect the liver or kidneys; long-term exposure to cadmium in drinking water can cause kidney damage.
If indicators show that my well water is potentially corrosive, will I also have high levels of lead or other metals in my well water?
Having potentially corrosive groundwater does not mean that you also have high lead or other metal levels in your tap water. It depends on several characteristics of the groundwater (pH, calcium concentration, hardness, dissolved solids, and temperature) and the materials used throughout your plumbing distribution system and if your water is untreated. The primary source of lead in private water systems are: the well pump, galvanized iron well components, brass fittings in the well and household plumbing, and leaded solder used to connect copper pipes. Knowledge of the date your well was installed and the types of materials used throughout your distribution system can help provide critical information needed to assess if what types of water-quality testing may be warranted, especially if your water is potentially corrosive.
For the issue of the potential health effects of household drinking water, the USGS looks to partner agencies at the federal and state levels to provide an indication of the potential scope of the problem. EPA’s fact sheet “Actions you can take to reduce Lead In Drinking Water http://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=20001R4V.txt” identifies steps you can take to evaluate levels of lead and copper and to reduce your exposure. Virginia and Pennsylvania are examples of two states where private water systems, such as wells, springs, or cisterns, are especially common. Private water systems are used by about 1.7 million people in Virginia and about 3 million people in Pennsylvania.
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 Penn 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 of 15 μg/L,” 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.”(Pieper and others, 2015)
“In Pennsylvania, corrosive water is usually associated with certain types of bedrock geology but can be found across the entire state,” said Bryan Swistock, a water resources specialist with Penn State Extension. “Lead levels exceeded the EPA action level in 12 percent of the 251 drinking water systems monitored in Pennsylvania in 2007”.” (Swistock and others, 1993, 2009; and Swistock and Clemens, 2013)
What are the potential sources of lead in private water systems?
Lead pipe and fittings were used in homes built prior to 1930 and lead solder, which contains up to 50 percent lead and is used to connect copper pipes and fittings, was used in many homes built prior to the late 1980’s. In 1986 EPA began to regulate the amount of lead in plumbing components and lead solder. However, prior to 2014, “lead-free” brass components, in all states, except California, may have contained up to 8 percent lead. Similarly galvanized steel components may have contained from 0.5 to 1.4 percent lead prior to 2014.
Information for Homeowners with private wells
How do I determine if my well water is corrosive?
If plumbing materials contain lead or copper, these metals may be leached into the water supply by corrosive water. Signs of corrosive water causing leaching of metals may include bluish-green stains in sinks, metallic taste to water, and pitting or small, pinhole leaks in plumbing fixtures. You can also have your well water tested for corrosion.
Where can I find information regarding water testing, maintenance, and treatment of my well?
National Hotlines
Environmental Protection Agency Safe Drinking Water Hotline
1-800-426-4791 (10am - 4pm ET, M-F)
National Ground Water Association Private Well Owner Hotline
855-420-9355 (10am – 4pm ET, M-F)
Federal Agencies
Environmental Protection Agency
Basic Information about Lead in Drinking Water
Additional Information on Private Wells
Drinking Water From Household Wells
Drinking Water in New England--Private Well Owners
Centers for Disease Control
Safe Water for Community Health (SafeWATCH)
National Institute of Health
National Institute of Environmental Health Sciences
Drinking Water Organizations
National Groundwater Association: Well Owner Information
Water Systems Council: Well Owners' Manual
American Groundwater Trust: The American Well Owner
Groundwater Protection Council: Water Quality
National Rural Water Association: Quality on Tap
Water Quality Association: Improve Your Water
State Information
Alabama
Alabama Department of Public Health: Well Water
Alabama Extension: Drinking Water / Human Health
Alaska
Alaska Division of Environmental Health: Drinking Water Protection
Arizona
Arizona Department of Water Resources: Wells
Arizona Extension: Private Wells
Arkansas
Arkansas Department of Health: Private Water Testing. Original link. Organization home.
University of Arkansas Division of Agriculture: Drinking Water
California
California State Water Resources Control Board: A Guide for Private Domestic Well Owners
California Environmental Protection Agency: Well Owners - Water Quality in Private Domestic Wells
Colorado
Colorado Department of Public Health and Environment: Drinking Water: Private Wells
Colorado State University Extension: Private Wells for Home Use
Connecticut
Connecticut Department of Health: Private Wells
Deleware
Deleware Health and Social Services: Drinking Water - Private Well Owners
Florida
Florida Department of Health: Private Well Testing
Georgia
Georgia Department of Public Health: Individual Private Wells
University of Georgia Extension: Publications in the Household Water Quality Series
Hawaii
Hawaii Department of Health: Safe Drinking Water
Idaho
Idaho Department of Environmental Quality: Private Wells
Idaho Department of Health and Welfare: Well Water Safety
Illinois
Illinois Environmental Protection Agency: Private Well Users
Illinois Department of Public Health: Water Wells
University of Illinois: The Private Well Class
Indiana
Indiana Department of Environmental Management: Private Wells and Compliant Response
Indiana Department of Natural Resources: Water Well Record Database
Iowa
State Hygienic Laboratory at The University of Iowa: Private Well Water
Iowa Department of Natural Resources: Private Well Program Hot Topics
Kansas
Kansas Department of Health and Environment: Water Well Program
Kentucky
Kentucky Department of Environmental Protection: Groundwater Awareness
University of Kentucky College of Agriculture, Food, and Environment: Kentucky Well Education
Louisiana
Louisiana Department of Natural Resources: For Water Well Owners
Louisiana Department of Health and Hospitals: Private Well Initiative
Maine
Maine Center for Disease Control & Public Health: Well Water Maine
Maryland
Maryland Department of the Environment: Residential Wells
University of Maryland Extension: Wells
Massachusetts
Massachusetts Energy and Environmental Affairs: Private Wells
Michigan
Minnesota
Minnesota Department of Health: Water Well Information
University of Minnesota Extension: Safe Drinking Water for Minnesotans Original link. Organization home
Mississippi
Mississippi State University Extension: Protecting Your Private Well
Missouri
Missouri Department of Natural Resources: Water Wells
University of Missouri Extension: Drinking Water Well Management
Montana
Montana Division of Public Health and Human Services: Private Well Testing Program
Montana Department of Environmental Quality: Private Well Information
Nebraska
Nebraska Department of Health and Human Services: Water Well Standards
University of Nebraska-Lincoln: Drinking Water Testing
Nevada
Nevada Division of Environmental Protection: Private Wells
New Hampshire
New Hampshire Department of Environmental Services: Be Well Informed
New Hampshire Department of Environmental Services: Private Well Testing Program
New Jersey
New Jersey Department of Environmental Protection: General Information on Wells
New Mexico
New Mexico Environmental Public Health Tracking: Private Wells Water Quality
New Mexico Environment Department: Private Well Owners
New York
New York State Department of Health: Individual Private Water Supply Wells
Cornell University Cooperative Extension: Water Quality Information for Consumers
North Carolina
North Carolina Health and Human Services: Well Water and Health
North Dakota
Ohio
Ohio Department of Health: Private Water Systems
Ohio Watershed Network: Know Your Well Water
National Center for Water Quality Research: Well Water Testing
Oklahoma
Oklahoma Department of Environmental Quality: Home Water Testing FAQ
Oklahoma Water Resources Center: Drinking Water
Oregon
Oregon Health Authority: Well Testing and Regulations
Oregon State University: Well Water Program
Oregon Department of Environmental Quality: Resources for Private (Domestic) Well Owners
Pennsylvania
Pennsylvania Department of Environmental Protection: Private Water Wells
Penn State Extension: Drinking Water Interpretation Tool
Penn State Extension: Master Well Owner Network
Rhode Island
URI Home*A*Syst: Private Well Testing and Protection
South Carolina
South Carolina Department of Health and Environmental Control: Residential Wells
South Dakota
South Dakota Department of Environment and Natural Resources: Private Well Sampling
South Dakota Department of Health: Testing Private Wells
Tennessee
Tennessee Department of Health: Private Water Supply
Tennessee Department of Environment and Conservation: Well Water
Texas
Texas Groundwater Protection Committee: Water Wells
Texas Water Resources Institute: Texas Well Owner Network
Utah
Utah State University Extension: Water Testing
Vermont
Vermont Department of Health: Testing Your Drinking Water Supply
Virginia
Virginia Department of Health: Private Well Water Information
Washington
Washington State Department of Health: Drinking Water
West Virginia
West Virginia Department of Health & Human Resources: Wells, Cisterns, and Springs Original link. Organization home
Wisconsin
Wisconsin Department of Natural Resources: Information for homeowners with private wells
University of Wisconsin Stevens Point: Homeowner Testing
Wyoming
Wyoming Department of Environmental Quality: Know Your Well
Additional information on USGS assessments
Where can I learn more about the quality of source groundwater for private wells and public wells across the Nation, natural and human factors that affect the quality of groundwater used for drinking water, and how groundwater-quality is changing over time?
Public Supply Wells—About 105 million people—more than one-third of the Nation’s population—receive their drinking water from one of the 140,000 public water systems across the United States that rely on groundwater pumped from wells. USGS scientists assessed water quality in source (untreated) water from 932 public-supply wells (referred to as public wells), and in finished (treated) and source water from 94 of these wells. The USGS study focused primarily on “source” water before treatment or blending and describes the occurrence of naturally occurring and man-made contaminants in source water from public wells and their potential significance to human health. USGS Circular 1346, Quality of Water from Public-Supply Wells in the U.S.
Public-Supply-Well Vulnerability—The USGS investigated public-supply-well vulnerability to contamination in 10 major metropolitan areas across the Nation to assess which contaminants in an aquifer might reach a well and when, how, and at what concentration they might arrive. Three measures are particularly useful for understanding public-supply-well vulnerability: the sources of recharge that contribute water to a well and the contaminants associated with the recharge; the geochemical conditions in the aquifer tapped by a well; and the groundwater-age mixture of the water pumped from a well. Factors Affecting Public-Supply-Well Vulnerability to Contamination
Private Wells—About 43.5 million people - or 15 percent of the Nation’s population - use drinking water from private wells, which are not regulated by the USEPA via the Safe Drinking Water Act. The USGS sampled about 2,100 private wells in 48 states from 1991 to 2004 in 30 of the Nation’s principal aquifers used for water supply. As many as 219 properties and contaminants, including pH, major ions, nutrients, radionuclides, trace elements, pesticides, volatile organic compounds, and microbial contaminants, were measured. Sampled water was taken from private wells before any home treatment. The large number of contaminants assessed and the broad geographic coverage of the study provides a foundation for an improved understanding of the quality of water from the major aquifers tapped by private wells in the United States. USGS Circular 1332, Quality of Water from Domestic Wells in Principal Aquifers of the U.S.
Water Quality in Aquifers Across the Nation—USGS scientists assessed water quality in source (untreated) water from 6,600 wells in regionally extensive aquifers that supply most of the groundwater pumped for the Nation’s drinking water, irrigation, and other uses. The comprehensive sampling, along with detailed information on geology, hydrology, geochemistry, and chemical and water use, can be used to explain how and why aquifer vulnerability to contamination varies across the Nation. By knowing where contaminants occur in groundwater, what factors control contaminant concentrations, and what kinds of changes in groundwater quality might be expected in the future, we can ensure the future availability and quality of this vital natural resource. USGS Circular 1360, Quality of the Nation’s Groundwater
Decadal Look at Groundwater Quality— An online interactive mapping tool that provides summaries of decadal-scale changes in groundwater quality across the Nation is now available for use by the public, water-resource managers, and policy makers. The mapper shows how concentrations of 24 contaminants, such as nutrients, pesticides, metals, and volatile organic compounds, are changing over decadal periods in 67 groundwater networks across the Nation. Each network consists of about 20 to 30 wells selected to represent water-quality conditions in a given geographical area, aquifer, and in some cases, a specific land use.
Where can I learn more about the USGS National Water-Quality Assessment (NAWQA) Project?
Look online for recent NAWQA headlines, activities, and publications.
Examples of How USGS Science is Informing Groundwater Quality Management Decisions
Who do I contact for additional information about this report?
Kenneth Belitz
Chief, Groundwater Assessment
National Water-Quality Assessment Project
kbelitz@usgs.gov
References:
Clopper, C.J., and Pearson, E.S., 1934, The use of confidence intervals or fiducial limits illustrated in the case of the binomial: Biometrika, v. 26, no. 4, p. 404–413.
Edwards, M., and Triantafyllidou, S., 2007, Chloride-to-sulfate mass ratio and lead leaching to water: Journal of American Water Works Association, v. 99, no. 7, p. 96–109.
http://www.awwa.org/publications/journal-awwa/abstract/articleid/15699.aspx
Gregory, R., 1985, Galvanic corrosion of lead in copper pipework—Phase I, measurement of galvanic corrosion potential in selected waters: Swindon, England, Water Research Centre Engineering, 74 p.
Hu, J., Gan, F., Triantafyllidou, S., Nguyen, C.K. and Edwards, M.A., 2012, Copper-induced metal release from lead pipe into drinking water, Corrosion, 68(11), p.1037-1048. http://dx.doi.org/10.5006/0616
Langelier, W.F., 1936, The analytical control of anti-corrosion water treatment, Journal (American Water Works Association), 28(10), p. 1500-1521.
Larson, T.E., Buswell, A.M., Ludwig, H.F. and Langelier, W.F., 1942. Calcium Carbonate Saturation Index and Alkalinity Interpretations [with Discussion]. Journal American Water Works Association, 34(11), pp.1667-1684.
Nguyen, C., Stone, K., Clark, B., Edwards, M., Gagnon, G., and Knowles, A., 2010, Impact of chloride—Sulfate mass ratio (CSMR) changes on lead leaching in potable water: Denver, Water Research Foundation, 198 p.
Nguyen, C.K., Stone, K.R., and Edwards, M.A., 2011, Chloride-to-sulfate mass ratio—Practical studies in galvanic corrosion of lead solder: Journal of the American Water Works Association, v. 103, no. 1, p. 81–92. http://www.awwa.org/publications/journal-awwa/abstract/articleid/26682.aspx
Ott, R.L., and Longnecker, M., 2001, An introduction to statistical methods and data analysis (5th ed.): Pacific Grove, Calif., Duxbury Press, 1,152 p.
Pieper, K.J., Krometis, L.A.H., Gallagher, D.L., Benham, B.L., and Edwards, M., 2015, Incidence of waterborne lead in private drinking water systems in Virginia: Journal of Water and Health, v. 13, no. 3, p. 897–908, accessed April 6, 2016, at http://dx.doi.org/10.2166/wh.2015.275
Singley, J.E., Beaudet, B.A. and Markey, P.H., 1984. Corrosion manual for internal corrosion of water distribution systems (No. ORNL/TM-8919; EPA-570/9-84-001). Environmental Science and Engineering, Inc., Gainesville, FL (USA).
Stumm, W. and Morgan, J.J., 1981, Aquatic chemistry: an introduction emphasizing chemical equilibria in natural waters, John Wiley, New York, 780 p.
Swistock, B.R., and Clemens, S., 2013, Water quality and management of private drinking water wells in Pennsylvania: Journal of Environmental Health, v. 75, no. 6, p. 60.
Swistock, B.R., Clemens, S., and Sharpe, W.E., 2009, Drinking water quality in rural Pennsylvania and the effect of management practices: Harrisburg, Pa., Center for Rural Pennsylvania, 24 p., accessed May 10, 2016, at http://www.rural.palegislature.us/drinking_water_quality.pdf.
Swistock, B.R., Sharpe, W.E., and Robillard, P.D., 1993, A survey of lead, nitrate and radon contamination of private individual water systems in Pennsylvania: Journal of Environmental Health, v. 55, no. 5, p. 6–13.
U.S. Environmental Protection Agency, 2003, Water on tap: what you need to know: U.S. Environmental Protection Agency, Office of Water EPA 816-K-03-007, October 2003, 36p. Available at https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1008ZP0.TXT
U.S. Environmental Protection Agency, 2004, Understanding the safe drinking water act: U.S. Environmental Protection Agency, Office of Water EPA 816-F-04-030, June 2004, 4p. Available at https://www.epa.gov/sites/production/files/2015-04/documents/epa816f04030.pdf
Explore the web pages below for topics related to corrosivity.