There is much interest in testing well water to evaluate risk related to oil and gas drilling in our region of the USA. The newer “unconventional” gas and oil development tapping Devonian shale source rocks (Marcellus, Utica, etc.) involves deep and directional drilling, with hydrofracturing (HF) used in completion. Because large volumes (millions of gallons) of water, amended with chemicals, are used in each HF event (often referred to as “fracking”), and because of the risk of penetrating methane-yielding formations, it is widely advised that well owners should conduct relevant testing of the quality of water wells.
As this deep drilling is in its infancy in Ohio, we look to neighboring Pennsylvania, where Marcellus drilling is more advanced, for experience. A study of gas drilling impacts on rural water supplies was recently completed by the Center for Rural Pennsylvania. These tests examined well water quality before and after nearby gas well drilling. Effects of that work are apparently insignificant. The one significant parameter was bromide, which is related to the drilling process itself.
Most significant is that most of the potential risk in the water wells studied is just due to their own characteristics, primarily construction and maintenance deficiencies. Some 31 % were positive for total coliform bacteria. As is repeatedly noted in the report, Pennsylvania is one of two U.S. states that do not have private water well construction standards. Previous reports posted at the Center for Rural Pennsylvania website, (including) document that construction and operation have notable effects in PA, and this is echoed elsewhere in the USA. The more recent data on bacterial contamination in PA are very similar to earlier studies.
The above-linked report documents the effect that simple awareness has on improved water well "health". Penn State University Extension hosts a Master Well Owner Network, which I think is a brilliant concept that should be replicated elsewhere. These more-knowledgeable and better-informed well owners seem to have statistically fewer problems.
We address issues of and managing risk with resource drilling and development in our "Geologic Illiteracy" item.