How frequently are volatile organic compounds (VOCs) detected in groundwater?

Volatile organic compounds (VOCs), which are widely used in the manufacture of many products including refrigerants, plastics, adhesives, paints, and petroleum products, have been detected in about one-third of the wells sampled by the National Water-Quality Assessment (NAWQA) Program of the USGS. 

  • Chloroform and other trihalomethanes, the most commonly detected compounds, were found in about 9 percent of the sampled wells.
  • Solvents, particularly chlorinated solvents, were found in about 8 percent of sampled wells.

VOCs predominantly occur in urban areas, often in mixtures; specifically, 2 or more compounds were found in about one quarter of the sampled urban wells.

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Why does my drinking water look cloudy sometimes?

Once in a while you get a glass of water that looks cloudy; maybe milky is a better term. After a few seconds, it miraculously clears up! The cloudiness is due to tiny air bubbles in the water. Like any bubbles, the air rises to the top of the water and goes into the air, clearing up the water. The water in the pipes coming into your house might...

Where can I find information about my local drinking water supply?

The best way to learn about your local drinking water quality is to read the annual drinking water quality report/consumer confidence report that water suppliers now send out by July 1 of each year. The reports are often sent out with water bills, but they may be sent separately. The reports tell where drinking water comes from, what contaminants...

What can cause our water to have an earthy odor or to smell like rotten eggs?

Naturally-occurring organic compounds are created when plant material decays in lakes and reservoirs. Those organic compounds frequently cause musty, earthy odors, especially toward the end of summer. The odors can be objectionable, but generally are not harmful to health. However, odors can be caused by other constituents as well, so you might...

Where can I find information about bottled water?

Bottled water is regulated by the U.S. Food and Drug Administration and by individual states. For general information about bottled water, sources include the International Bottled Water Association and NSF International .

What can be causing our drinking water to have a reddish color?

Your water might be affected by iron, which is a commonly-occurring constituent of drinking water. Iron tends to add a rusty, reddish-brown (or sometimes yellow) color to water. If the color is more black than red, your water might contain a combination of iron and manganese. Both of these metals can cause staining of plumbing fixtures or laundry...

Where can I get my well water tested?

Contact your county or state health department or check with your State Certification Officer for a list of state certified laboratories in your area that do water testing. The cost will vary, depending on the laboratory and the test(s), but people usually consider the cost to be reasonable. Also try using your browser's search engine to do a...

Where can I find detailed sampling methods for surface water and groundwater?

The National Field Manual for the Collection of Water-Quality Data (National Field Manual) provides guidelines and standard procedures for USGS personnel who collect data used to assess the quality of the Nation’s surface water and groundwater resources. The manual is published as separate chapters. Learn more: Techniques of Water-Resources...

If the ground filters water, is groundwater always clean?

Water drawn from a well was once precipitation that fell onto Earth's surface. It seeped into the ground and, over time, occupied the porous space in some subsurface material. Big particles that are in surface streams, such as leaf chunks, will not be seen in groundwater. So, yes, big particles are filtered out by the ground, along with some...

How important is groundwater?

Groundwater, which is in aquifers below the surface of the Earth, is one of the Nation's most important natural resources. Groundwater is the source of about 37 percent of the water that county and city water departments supply to households and businesses (public supply). It provides drinking water for more than 90 percent of the rural population...
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Date published: December 7, 2017

The Quality of the Nation’s Groundwater: Progress on a National Survey

The U.S. Geological Survey makes progress on a complex undertaking to survey the quality of the nation’s largest drinking-water sources.

New reports assess the quality of drinking-water supplies in three Western and Southwestern regional aquifers, adding to 15 previously assessed across the nation.

Current website:

Date published: October 18, 2017

Study Estimates about 2.1 Million People using Wells High in Arsenic

Most Arsenic Presumed to be From Naturally Occurring Sources

Date published: May 11, 2017

High Levels of Radon Found in Some Wells Across Pennsylvania

A new U.S. Geological Survey study has discovered high levels of radon in wells across certain areas of Pennsylvania.

Date published: March 6, 2017

USGS Finds Elevated Levels of Arsenic, Radon, Methane in Some Private Wells in Lycoming County, Pennsylvania

Tests of 75 private drinking water wells in Lycoming County, in north-central Pennsylvania, found water from most of the sampled wells contained concentrations of radon that exceeded a proposed, nonbinding health standard for drinking water. Smaller percentages of the wells contained concentrations of arsenic or methane that exceed existing drinking water standards.

Date published: July 13, 2016

New Study Shows High Potential for Groundwater to be Corrosive in Half of U.S. States

An analysis of more than 20,000 wells nationwide shows 25 states have groundwater that has either high or very high potential to be corrosive...

Filter Total Items: 11
USGS scientist sampling groundwater at recharge site 6
December 9, 2016

USGS scientist sampling groundwater at recharge site 6

USGS scientist sampling groundwater at recharge site 6 

Photo of USGS scientists collecting groundwater samples to determine water quality.
December 31, 2015

USGS scientist collects groundwater samples to determine water quality

USGS scientist, Rick Arnold collects groundwater samples to determine water quality. 

The USGS is near the midpoint of a complex undertaking to survey the quality of the nation’s largest drinking-water resource. From 2012 – 2023, the USGS is assessing groundwater throughout the country through extensive sampling. The latest results from five regional aquifers are

woman filling gw sample bottle from plastic encased box made from pvc pipes
October 7, 2015

305(b) groundwater quality sampling

305(b) groundwater quality sampling 

March 6, 2015

Quality of Our Nation's Groundwater

USGS will describe the occurrence of contaminants in groundwater, how natural features and human activities can affect groundwater quality, and how models are being used to predict contaminant concentrations in unmonitored areas and inform water-resource management decisions.

Photo of USGS staffer collecting groundwater sample
July 8, 2011

Groundwater sampling - Long Island

USGS staffer collecting groundwater sample on Long Island

Tech sampling groundwater next to a table of sensors
October 13, 2010

Sampling groundwater

USGS Scientist Lisa Carper testing groundwater samples

man under pop-up tent leaning over pumping equipment on table

Collecting Groundwater Samples - Long Island, New York in July 2017

Collecting Groundwater Samples from a Well on Long Island: The image above shows USGS scientists pumping a deep Lloyd aquifer observation well in Long Beach, NY.  To ensure that water-quality samples represent the formation water, the well is pumped for an extended period of time or until at least three casing volumes are removed and measured field

USGS employee sampling surface water and groundwater photo

USGS employee sampling surface water and groundwater photo

Claire Rose filling out paper work while conducting ground water/surface water sampling on the Steele Bayou River in MS Delta.