Groundwater Pollutants from Gas Wells Including Traditional and Marcellus Gas Wells

Pollution of private water supplies from gas well activity has occurred in Pennsylvania. This contamination may occur from absent or corroded gas well casings (on older or abandoned gas wells) or it may originate from flooded or leaking waste fluid holding pits or spills at the drilling site.

Gas well waste fluids usually contain levels of some pollutants that are far above levels considered safe for drinking water supplies. As a result, even small amounts of pollution from waste fluids can result in significant impacts to nearby drinking water supplies. The broad categories of pollutants in gas drilling waste fluids includes:

Salts—most notably sodium and chloride. Gas well waste fluids can have over 100,000 mg/L of these compounds. Other pollutants that can occur as various salts include magnesium, calcium and potassium. These salts cause the “total dissolved solids” in the wastes to be very high.

Metals—including iron, manganese, barium, arsenic and trace amounts of other heavy metals.

Organics—these include both natural and man-made materials that are used during the drilling process such surfactants, detergents, oil, grease, benzene and toluene. Dozens of other man-made organics may be used in small concentrations during hydrofracturing.

Recommended Benchmark Prior to Gas Drilling Testing For A Well

Tier I

Total Dissolved Solids (TDS)





Tier II

Total Suspended Solids

Iron, Manganese, Lead, Sodium, Arsenic

Hardness ( Calcium and Magnesium )

Total Organic Carbon

Oil and Grease



Coliform Bacteria



Tier III

Volatile Organic Compounds (VOC)

Radionuclides, Gross Alpha, radium


And consider adding BTEX

A serious problem that can occur from gas well drilling is methane gas migration from gas wells into nearby water wells. See our video on finding gas in an interior house sump. The methane gas will rapidly escape from the groundwater and may pose an explosion hazard in confined spaces. Methane gas testing in water is difficult but it usually creates obvious symptoms in the home including effervescence and spurting faucets due to gas build-up. To learn more about methane gas problems in private wells, consult the Penn State Extension publication entitled Water Facts #24—Methane Gas and Its Removal from Wells in Pennsylvania available from your local Cooperative Extension office or online at:

A summary of the various relevant components of the Oil and Gas Act are provided here.

1) Permits Before drilling a gas well in Pennsylvania, the operator must submit an extensive permit application for approval from the Pennsylvania Department of Environmental Protection (DEP). Among other things, the permit application must include a map showing the location of the gas well, proximity of the gas well to coal seams, and distances to nearby surface water and water supplies. The map must also include the projected horizontal boreholes, property lines and acreage which will be disturbed during drilling. A bond ranging from $2,500 to $25,000 must be posted with the permit to ensure compliance with environmental regulations related to the well drilling. The permit also requires notification of surface land owners and coal mineral right owners at the well site along with all drinking water supply owners within 1,000 feet of the well. Notification of these various stakeholders is done by certified mail. As a result, homeowners with private water wells or springs which are located within 1,000 feet of the proposed gas well site should receive notification by certified mail during the permit process.

2) Setback Distances Gas wells must be at least 200 feet from any drinking water supplies. This setback may be waived by the water supply owner in a lease agreement. Gas wells must also be 100 feet from any stream, spring or body of water identified on the most current 7.5 minute USGS topographic map. A 100 foot setback is also required from any wetland greater than one acre in size. These setbacks may also be relaxed if additional protection is put in place to protect these natural resources.

3) Protection of Drinking Water Quality Section 208 of the Oil and Gas Act specifically includes language to protect nearby drinking water supplies. This includes a requirement that gas well drilling operators restore or replace any water supply determined by the DEP to be polluted as a result of nearby gas well drilling. The gas well operator is presumed to be responsible for pollution of any drinking water supply within 1,000 feet of the gas well IF it occurs within six months after completion of the gas well. The operator can use any one of five defenses to prove they are not responsible for water contamination including:

The pollution existed prior to the drilling

The landowner or water purveyor refused to allow the operator access to conduct a pre-drilling water test

The water supply is not within 1,000 ft of the well

The pollution occurred more than six months after completion of drilling

The pollution occurred as the result of some cause other than the gas drilling

4) Protection of Water Flows from Wells and Springs Gas well drilling can occasionally change the flow of water from a water well or spring, although these changes are often temporary. Unlike water quality impacts, gas well operators are NOT presumed responsible for water quantity impacts to nearby water supplies. For this reason, water flow data is often not measured during pre-drilling surveys conducted during the permitting process. Instead, impacts to water quantity would need to be investigated by DEP inspectors and/or proven by the water supply or loss of water quantity

IMPORTANT: Who Should Test the Water

Many homeowners question whether they can collect their own water samples and deliver them to an independent laboratory to save on testing costs. While this method will save money, it is important to realize that test results from water samples collected by the homeowner are generally not recognized in legal proceedings because they are not independent.

owner. Concerned water supply owners may wish to hire a well driller or water consultant to document the flow of water from their well or spring prior to the gas drilling activity

Reasons To Test Water After Drilling

There are no requirements for gas well companies to test private water supplies, even those within 1,000 feet of an active gas well, after the gas well drilling has concluded. Therefore, any post-drilling water sampling is a voluntary decision that must be arranged by the homeowner unless the testing is previously stipulated in a lease agreement or part of a complaint to DEP. Obvious changes to your water supply that would warrant a complaint to DEP can include:

Rapid increases in the TDS or conductivity of the water supply based on readings from a meter.

Occurrence of increased severity of sediment in local surface water (streams, ponds, etc.).

Changes in the appearance of drinking water from a well or spring such as sediment, foaming, bubbling or spurting faucets

Changes in drinking water taste including salty or metallic tastes

Changes in water odor such as a rotten egg odor, fuel or oily smell