By Brian Oram, Professional Geologist
Keystone Clean Water Team
September 10, 2026

Baseline testing is a way to document drinking-water quality before natural fluctuations, nearby land-use change, or a suspected release make it harder to tell what is new and what was already there. Done well, it can show where extra monitoring is needed and which wells are most vulnerable. It is also a chance for a company, developer, local agency, or regulator to make decisions from evidence rather than from later arguments about missing data.

The same process helps a landowner who relies on groundwater. A documented pre-existing condition is useful before buying a home, renovating, installing treatment, or evaluating a nearby project.

The principles below apply anywhere a private well or spring may later be compared with post-activity results. The examples, legacy issues, and parameter packages are drawn mainly from Pennsylvania—especially the northeast—where unconventional oil and gas, older conventional development, coal-mining legacy, leaking underground storage tanks, and the absence of statewide private-well construction standards all matter.

Why a grab sample is not a baseline

Practices that get called “baseline testing” vary widely. In Dimock, Pennsylvania, EPA’s 2012 investigation of 64 homes was a thorough, documented sampling effort. At the other extreme, a single sampler with little training may purge a private well from a dirty kitchen sink in about 15 minutes, with no field measurements and no gloves.

That range of technique, combined with thin field notes and a hunt for one universal parameter list, produces reports that look official and travel poorly. They make later disputes easier and reliable comparisons harder.

A water-quality baseline is a snapshot of current conditions plus enough documentation to interpret a later test. Without it, a change in taste, odor, appearance, or laboratory results is difficult to place in time. That was one of the central problems with early unconventional gas development around Dimock: much of the groundwater quality in private wells was not adequately documented beforehand.

Pre-existing problems are common

In northeastern Pennsylvania, rainfall, snowmelt, flooding, aging infrastructure, nearby development, agriculture, seasonal change, and naturally occurring minerals all affect well water. Homeowners on private wells are responsible for their own monitoring.

Problems are not rare. A statewide study of 701 Pennsylvania wells found that about 41 percent failed at least one health-based drinking-water standard, and total coliform bacteria were present in 33 to 50 + (Oram, added) percent of the wells. When aesthetic and nuisance issues—iron, manganese, corrosivity, odor, and salt—are included, a majority of private supplies have at least one condition worth documenting.

That vulnerability is compounded by the lack of statewide standards for private-well placement and construction. Some counties and townships have local rules; most of the state does not. Casing, grouting, and sanitary well caps are often omitted unless the owner asks for them.

A common statement from well owners is that the water tastes fine, does not smell, and looks clear and cold, so there is no problem. Many concerns—bacteria, nitrate, arsenic, and other metals—cannot be judged by sight, smell, or taste. Water can look normal and still contain contaminants that only laboratory testing will show.

What effective baseline testing requires

A useful baseline is a process, not simply a DIY testing kit or even an informational water testing kit conducted by a laboratory. The essential pieces are:

1. Parameters chosen for the site. The list should reflect regional geology, the condition of the existing water system, historic or legacy issues, and the proposed activity—industrial development, unconventional oil and gas, urbanization, agricultural expansion, or another local hazard. A generic list from an agency or legislature is a starting point, not a finished plan.
2. Chain-of-custody with quality control. Custody, internal and external QC, and QA should begin and end with a certified laboratory working with a trained third-party professional.
3. Field documentation. Notes, field measurements, and photographs should describe the well and the household plumbing and treatment system as they exist on the sampling day.
4. Trained third-party sampling. Samples should be collected by licensed professionals or by people trained in the laboratory’s standard operating procedures. Those samplers also need a working knowledge of common treatment systems, so they do not sample treated water when the question is raw-well quality, or the reverse.
5. Review before release. The certified laboratory should validate the results. A third-party professional should then check whether the numbers are internally consistent and should provide an interpretation the owner can use.

A homeowner screening test can still be useful for education. It is not a substitute for third-party, chain-of-custody sampling when the results may later be compared with a nearby land-use change. Conversely, a certified analysis from an unpurged kitchen tap, with no field notes, is also not a baseline.

A certified report can still be unusable

Certification of the laboratory is necessary. It is not sufficient.

In one pre-drill case, a non-professional sampler collected the water, a certified laboratory analyzed it, and a natural-gas company gave the packet to the well owner a few weeks before drilling. The report included raw data, spike-and-recovery results, surrogates, a field sheet, methods, and certifications. It still failed basic checks:

1. Field conductivity was about 250 µS/cm, while laboratory total dissolved solids were reported as 1,500 mg/L.
2. The cation–anion balance was off by more than 25 percent.
3. Some “total” metal results were lower than the corresponding dissolved results.
4. Arsenic exceeded the primary drinking-water standard by more than a factor of ten and was never flagged for the owner.

That data was not scientifically valid. There was no time to collect another pre-activity sample. Professionals have an obligation to screen results before they are handed to a family as “the baseline.”

How to choose parameters

Parameter selection depends on the water source, regional geology, current and past land use, and the specific hazard of concern. Northeastern Pennsylvania has a long list of legacy issues: leaking underground storage tanks, older conventional oil and gas, coal-mining legacy, nonpoint-source pollution, landfills, and poorly managed wastewater systems.

The lists below are starting points for that region, not statewide or national checklists. Add or drop parameters after a site- and activity-specific hazard review. Extra analytes that cannot be tied to a documented local source usually add cost without making the baseline more defensible.

Larger project proposing land-based wastewater management

pH, conductivity, total coliform, E. coli, nitrate, nitrite, ammonia, phosphate, total dissolved solids, surfactants, chloride, sulfate, iron, manganese, turbidity, alkalinity, and total hardness.

Unconventional oil and gas

The wastewater list, plus methane, ethane, propane, bromide, gross alpha and beta, aluminum, arsenic, barium, lithium, strontium, sodium, volatile organic compounds including MTBE, oil and grease, and PFAS. Add other constituents only when a documented local source exists.

Data centers and large industrial projects

pH, conductivity, total coliform, heterotrophic plate count, E. coli, nitrate, nitrite, total dissolved solids, surfactants, sodium, chloride, sulfate, glycols, volatile organic compounds, iron, manganese, turbidity, alkalinity, total hardness, and PFAS where a local source is plausible.

PFAS belong on a list when military sites, fire-training areas, industrial facilities, or other known sources are nearby. They do not automatically belong on every rural well. A Penn State study of 167 Pennsylvania private wells detected PFAS in 65 percent of sampled wells and found 18 percent above EPA maximum contaminant levels, with the highest concentrations in the southeast. That is a reason to consider PFAS in the right setting, not a reason to treat every baseline as a full forensic scan.

A neighborhood hazard review for the individual well or community is usually a better first step than buying the longest package on a price sheet.

Well construction and yield are companion work, not the same task

Baseline testing often stops at chemistry. Construction and yield still matter when the later question is “did this well change?” or “can this well support the house?”

Most homeowners do not have a drilling log or as-built drawing. A downhole camera inspection can document casing, joints, water-bearing zones, and obvious defects.

A controlled pumping test—recording pumping rate, water-level drawdown, and recovery—is useful when yield, well interference, or future demand is part of the decision. A four-hour pumping period plus a recovery test is more informative than a short VA-loan-style test. It is a separate scope item. It is not required for every water-quality baseline.

How owners should use the results

The value of a baseline is not the PDF. It is a reference point that can save time and money when taste, odor, staining, treatment performance, or a nearby project later raises questions.

Ask for the field notes, unique sample identifiers, and an interpretation that flags results against drinking-water standards and against whether the numbers internally agree. If conductivity, dissolved solids, and the ion balance cannot be reconciled, do not treat the report as a finished baseline.

Establishing that record today is one of the few steps a well owner, buyer, or project sponsor can take while conditions are still the “before” picture.

Need a practical reference for the next step? Order our Drinking Water Guide for Well Water and City Water.

About this article

Brian Oram, P.G., is a professional geologist with B.F. Environmental Consultants and works with the Keystone Clean Water Team and the KnowYourH2O education program. This article is educational and is not a site-specific sampling and analysis plan.

Resources

KnowYourH2O; B.F. Environmental Consultants; Carbon County Groundwater Guardians; Keystone Clean Water Team.

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