Fracking and well water contamination: what EPA found, and the baseline test to get before drilling nearby

Can fracking contaminate well water? The U.S. EPA's 2016 final assessment found that activities in the hydraulic fracturing water cycle "can impact drinking water resources under some circumstances," but data gaps kept it from estimating how often that happens nationwide.

For a private well owner near a planned oil or gas well, that leaves one practical step: a certified baseline test before drilling starts. Pennsylvania, West Virginia, Colorado, Wyoming and Ohio have rules that have the operator sample nearby water wells, or reward it for doing so.

This page is about oil and gas drilling near your home. Fracturing your own water well to get more water out of it is a different job; see hydrofracking a water well in our flow test guide.

What EPA's 2016 assessment concluded

The final report (EPA-600-R-16-236, December 2016) reviewed "approximately 1,200 cited sources of data and information." Its executive summary states the main finding in two sentences:

"These activities can impact drinking water resources under some circumstances. Impacts can range in frequency and severity, depending on the combination of hydraulic fracturing water cycle activities and local- or regional-scale factors."

EPA lists the combinations it found "more likely than others to result in more frequent or more severe impacts":

• "Water withdrawals for hydraulic fracturing in times or areas of low water availability, particularly in areas with limited or declining groundwater resources;"
• "Spills during the management of hydraulic fracturing fluids and chemicals or produced water that result in large volumes or high concentrations of chemicals reaching groundwater resources;"
• "Injection of hydraulic fracturing fluids into wells with inadequate mechanical integrity, allowing gases or liquids to move to groundwater resources;"
• "Injection of hydraulic fracturing fluids directly into groundwater resources;"
• "Discharge of inadequately treated hydraulic fracturing wastewater to surface water resources;" and
• "Disposal or storage of hydraulic fracturing wastewater in unlined pits, resulting in contamination of groundwater resources."

Identified impacts, the summary says, "generally occurred near hydraulically fractured oil and gas production wells and ranged in severity, from temporary changes in water quality to contamination that made private drinking water wells unusable."

EPA also wrote that "significant data gaps and uncertainties in the available data prevented us from calculating or estimating the national frequency of impacts on drinking water resources," and that they "also precluded a full characterization of the severity of impacts." In cases of alleged impacts, hydraulic fracturing activities "may be one of several causes of impacts, including other oil and gas activities, other industries, and natural processes." This guide takes no side on fracking.

Why a before-test matters: the data EPA could not find

EPA states the gap directly: "local water quality data needed to compare pre- and post-hydraulic fracturing conditions are not usually collected or readily available," and that limited data "reduces the ability to determine whether these activities affected drinking water resources."

A baseline fills that gap for one well, and it shows what was already there. Methane is the clearest case. Penn State Extension cites a 2011 Penn State study of 233 water wells in Pennsylvania's Marcellus region that "found detectable methane concentrations in 24% of the water wells before drilling began at adjacent gas well sites," and a 2012 USGS report on 239 New York wells that found detectable methane in 53% "prior to any drilling of unconventional gas wells."

USGS fact sheet 2006–3011 shows methane is common in West Virginia groundwater too: it "was detected in 131 of 170" wells sampled from 1997 to 2005.

What can reach a well, and why the test list looks the way it does

The parameters follow from what comes up out of an oil or gas well. EPA says produced water has been found to contain "Salts, including those composed from chloride, bromide, sulfate, sodium, magnesium, and calcium"; "Metals, including barium, manganese, iron, and strontium"; "Naturally-occurring organic compounds, including benzene, toluene, ethylbenzene, xylenes (BTEX), and oil and grease"; "Radioactive materials, including radium"; and "Hydraulic fracturing chemicals and their chemical transformation products."

The salt is why chloride, bromide and total dissolved solids (TDS) appear on nearly every list. EPA reports Marcellus Shale produced water ranging "from less than 1,500 milligrams per liter (mg/L) of total dissolved solids to over 300,000 mg/L," against "approximately 35,000 mg/L" for seawater.

Why not test for "fracking chemicals"? EPA identified 1,606 chemicals in fracturing fluid and/or produced water, and operators "claimed at least one chemical as confidential at more than 70% of wells reported to FracFocus 1.0." In our reading, that's why agency lists rely on indicators (salts, metals, gases, hydrocarbons) instead. Texas's Railroad Commission (RRC) requires operators to post ingredients for wells permitted on or after February 1, 2012 on FracFocus; AgriLife notes the exception for chemicals "considered 'trade secrets' or proprietary."

What to test before drilling: the lists side by side

Four columns are what operators must sample under state rules. Two are for homeowners testing on their own: Pennsylvania DEP's "Recommended Basic Oil and Gas Pre-Drill Parameters" (8000-FS-DEP4300, Rev. 4/2014) and Texas A&M AgriLife Extension's fact sheet SC-012. "Minimum" marks what DEP prints in bold with an asterisk as the least a homeowner should order.

Pennsylvania DEP also names alkalinity, calcium and turbidity as minimums, and tells homeowners to ask whether a lab is accredited for each test and, if not, whether it will subcontract to an accredited lab.

What the key results tell you

Penn State Extension's table of gas-drilling test parameters (updated October 13, 2025) explains each one:

• Barium "typically occurs naturally in low concentrations but can be found in a variety of waste fluids from gas drilling and other industries"; 94% of the Pennsylvania wells in its data were below 0.5 mg/L.
• Bromide is "Found abundantly in salt waters, brines, and various waste fluids," and in pristine groundwater is "typically below 0.10 mg/L."
• Chloride can rise "from road salt, gas drilling, septic systems and other activities"; 83% of wells were below 20 mg/L.
• BTEX: "Detectable concentrations are rare (less than 1% of water wells)." See VOCs in well water for these compounds.

EPA's maximum contaminant levels (MCLs), which Penn State lists beside these numbers, are legal limits for public water systems, not private wells. For a baseline, the change matters more. Texas AgriLife: "Any change in TDS from the baseline is of concern because it suggests groundwater contamination that may—or may not—be caused by oil or gas development." See our pH and TDS guide.

State rules that make operators test nearby water wells

Pennsylvania and West Virginia: presumptions, and what refusing access does

Under § 3218(c), "it shall be presumed that a well operator is responsible for pollution of a water supply" if, for an unconventional well, the supply is within 2,500 feet and "the pollution occurred within 12 months of the later of completion, drilling, stimulation or alteration." (For other wells: 1,000 feet and six months.) Defenses include that "the pollution existed prior to the drilling, stimulation or alteration activity as determined by a predrilling or prealteration survey," and that "the landowner or water purveyor refused to allow the operator access to conduct a predrilling or prealteration survey." The operator must give written notice that the presumption "may be void" if access is refused. DEP's rule adds that it "is not applicable to pollution resulting from well site construction."

West Virginia works the same way at 1,500 feet, with a request step: "at the request of the surface owner or water purveyor, the operator shall sample and analyze" used wells and developed springs. The operator's notice must say that "refusal to allow the operator to conduct a pre-drilling water well test constitutes a method to rebut the presumption," and must tell owners of their "independent right to sample and analyze any water supply at his or her own expense." The presumption also fails if "the pollution occurred more than six months after completion of drilling or alteration activities."

Colorado, Wyoming and Ohio: sampling with the permit

Colorado and Wyoming require repeat sampling. Colorado: "between 6 and 12 months" and "between 60 and 72 months following completion," then "every 5 years (57 to 63 month interval) for the life of the Well," plus a sample 6 to 12 months after plugging. Wyoming: "between twelve (12) and twenty-four (24) months" and "between thirty-six (36) and forty-eight (48) months after setting the production casing or liner." Both let the operator seek an exception or variance if owners refuse access despite reasonable efforts.

Ohio puts pre-drilling sampling into the drilling permit. In the version of R.C. 1509.06 effective October 3, 2023 (the newest we could read, in an Internet Archive copy of the official page captured April 15, 2026), a horizontal-well application had to carry "the results of sampling of water wells within one thousand five hundred feet of the proposed horizontal wellhead prior to commencement of drilling," plus a list of wells whose owners refused access. The section was amended again effective September 23, 2026, and we could not open that text, so check codes.ohio.gov or ask ODNR's Division of Oil and Gas Resources Management for the current distances. The 2023 text says sampling follows ODNR's "Best Management Practices For Pre-drilling Water Sampling" (September 20, 2012), whose list has no dissolved gases; if methane is a concern locally, you may want to add it to your own test.

Texas: no pre-drill rule in what we read

We found no Texas rule requiring operators to sample nearby water wells before drilling. Texas A&M AgriLife's SC-012 (dated 4-14, still listed on its site) advises owners to "have a water sample tested to serve as a baseline and then test periodically thereafter (typically once a year)." Its Table 1 lists TDS (method SM 2540C), dissolved methane (RSK-175 or 176) and total petroleum hydrocarbons (TX-1005 or 1006); give the lab the method name.

When to test: before, and again after

Pennsylvania DEP recommends that "homeowners test their water prior to well site drilling and earth disturbance activity," and offers an eNOTICE sign-up for "notice of well permit applications DEP has received for wells in the area they choose." Colorado's and Wyoming's operator windows both start within 12 months before drilling.

AgriLife adds: "After hydraulic fracturing, or any oil/gas development activity, in your area, retest your water to compare against the baseline," and retest on "any change in the water's taste, odor, or color." Borrowing Colorado's or Wyoming's windows is our suggestion, not a rule. For routine yearly tests, see when to test well water.

Chain of custody: make the result count later

A sample you collected yourself may not hold up in a dispute. Penn State's page on chain-of-custody testing (updated May 29, 2025) says it is "conducted to legally document water quality before a nearby activity or land use change, such as gas drilling," and that samples "should be collected by professionals and delivered to a state-accredited water laboratory." Pennsylvania DEP is firmer: "To obtain valid results, samples must be collected by a qualified third party." Its rule (25 Pa. Code § 78a.52) lets any person run a predrilling survey "to support a future claim," by an independent Pennsylvania-accredited laboratory.

1. Find a certified lab accredited for every parameter you want. Penn State warns that "Not all state-accredited laboratories offer chain of custody services."
2. Have the lab, or a consultant, collect the sample. DEP recommends "a qualified third party (a consultant or the laboratory)."
3. Bypass treatment. Ohio's guidelines say to "verify treatment equipment and that filters have been by-passed," and that "Property owners should be present when a sample is collected."
4. Ask about gas. AgriLife warns methane "could degas from the water during shipment and collect in air bubbles," invalidating the result. DEP suggests asking about a headspace test for methane at the same visit.
5. Keep the custody form with the report; see our guide to reading a well water test report.

Bottles and holding times are in our guide to collecting a well water sample. VOC-certified labs: Pennsylvania, West Virginia, Ohio, Colorado, Texas.

Methane: the result that is a safety question

The Minnesota Department of Health (MDH) says methane "is not known to be a health hazard when ingested." The risk is gas leaving the water. Penn State gives the explosive range in air as "5 to 15 percent by volume"; MDH says "between 5 percent and 14 percent," adds that methane can "displace oxygen if released into a confined space," and warns that "A spark from a control switch in a well house, or a flame from a water heater in a basement could ignite the methane."

MDH's signs: a "sputtering" or "spitting" faucet, a gurgling well, or water that looks "clear with bubbles, milky, frothy, or have a bluish tint," though bubbles "may not be due to methane." Penn State says the sample "must be collected by lab personnel, not by the homeowner."

USGS explains the 28 mg/L line: "the solubility of methane in water is between 28 and 30 mg/L," so water above 28 mg/L "could liberate potentially explosive or flammable quantities of gas inside the well or in confined spaces."

Operators have their own triggers, which are not homeowner limits. In a Pennsylvania gas migration investigation, the operator must notify DEP if sustained dissolved methane is "Equal to or greater than 7 mg/l" (25 Pa. Code § 78a.89). In Colorado and Wyoming, methane at or above 10 mg/L, a rise of more than 5.0 mg/L between sampling periods, or a result showing "thermogenic or a mixture of thermogenic and biogenic gas" triggers notice to the regulator and the well owner. Both require gas composition and isotope analysis "to determine gas type" above a set level: 1.0 mg/L in Colorado, 5.0 mg/L in Wyoming.

For fixes, MDH says methane "should be vented to the atmosphere, outside of enclosed spaces such as well houses or homes," and "will not be removed by common water treatment devices such as sediment filters, water softeners, or carbon filters." Penn State says in-home detectors "should be installed near the ceiling," and: "Contact a water-well professional to determine the best method to vent your water well."

If your water changes after drilling starts

• Pennsylvania. Notify a DEP regional office or call the statewide toll-free number, (800) 541-2050. The request must include "Available background quality and quantity data regarding the water supply, if known," which is where your baseline goes. DEP investigates within 10 calendar days and decides within 45.
• West Virginia. Under § 22-6A-18(f), the secretary may order the operator to provide "an emergency drinking water supply within twenty-four hours" and a "temporary water supply within seventy-two hours."
• Ohio. ODNR works "with the property owner and the oil and gas company to resolve the problem," a service "provided without cost to the property owner."
• Texas. Contact the RRC district office. For a domestic well, an inspector "will meet the water well owner to inspect the water well and any nearby oil and gas operations," and "water samples typically are collected."

A result alone doesn't prove a cause, as EPA's note on several possible causes makes clear. For any health concern, talk to your doctor or local health department.

Worked example: a baseline, then a change

Your Pennsylvania home sits about 2,000 feet from a proposed unconventional well. Before drilling, a lab sampler collects your water under chain of custody using DEP's list: methane 3 mg/L, chloride 15 mg/L, TDS 220 mg/L. Ten months after the well is completed, the faucet starts to sputter. A new test shows methane at 12 mg/L, with chloride and TDS unchanged.

• 12 mg/L falls in the "greater than 10 but less than 28" row: USGS says owners might contact the county health department and remove ignition sources. Ask a water-well professional about venting.
• The rise is 9 mg/L. In Colorado or Wyoming, a rise of more than 5.0 mg/L in the operator's sampling would require notice to the regulator; that isn't Pennsylvania's rule.
• You are within 2,500 feet and inside 12 months of completion, so if DEP finds pollution, § 3218(c) presumes the operator responsible unless it proves a defense. Both sides will look at your 3 mg/L baseline.
• Report to DEP with the baseline report attached.

Fracking a water well for more water is a different thing

The phrase also means opening rock fractures in a low-yield water well to raise its flow. For that, see hydrofracking a water well in our flow test guide.

Ready to set your baseline? Check which tests your well needs, then find a state-certified lab that offers sampling and chain of custody, starting from our Pennsylvania, West Virginia, Ohio, Colorado, Wyoming and Texas lab lists.

Questions people ask