Gas boom, polluted water: 5 things to know

Associated Press

The Pennsylvania Department of Environmental Protection has released details on 243 cases in which regulators determined that oil and gas drilling polluted or diminished private water supplies. The list, posted on the agency’s website last week, represents the most complete look to date at the impact of a natural gas-drilling boom on people’s drinking water.

Here are five things to know about the newly released data:

CONVENTIONAL DRILLING POLLUTES, TOO

The Marcellus Shale, a deep rock formation whose vast energy reserves have spurred a six-year drilling boom, naturally attracts the most attention, because it’s the nation’s most prolific gas field and because drillers use the techniques of horizontal drilling and hydraulic fracturing, or fracking, to reach the gas.

But energy companies continue to drill and frack far more conventional oil and gas wells in Pennsylvania — and those wells are also implicated in contamination cases. An Associated Press analysis of 170 contamination cases in which the type of well could be determined shows that regulators blamed conventional vertical wells in 97 cases, and Marcellus wells in 73.

However, mishaps at Marcellus wells tend to impact a greater number of water supplies. A Penn State University study estimated that 20 shale wells were responsible for all of the contamination attributed to unconventional drilling between 2008 and 2012.

BY THE NUMBERS

Unsurprisingly, the counties with the most drilling endured the largest number of problems. At the same time, confirmed water contamination cases have declined over time, from a high of 43 cases that originated in 2010 to four so far in 2014.

To put that into perspective: Since 2008, energy companies have drilled more than 12,000 conventional wells, and more than 8,000 shale wells. So there have been a relatively small number of serious cases of water contamination.

METHANE MIGRATES

Methane contamination of drinking-water supplies has long troubled drillers and homeowners. In roughly half the 243 cases, state regulators found methane in private water wells and attributed it to gas drilling.

The odorless, colorless, tasteless gas is commonly and naturally found in Pennsylvania groundwater, so energy companies have sometimes disputed DEP findings that drilling caused methane to migrate into a water well or spring.

Nevertheless, the industry recognizes stray gas as an issue. In 2011, the state tightened well-construction standards in a bid to curtail methane migration.

TESTING THE WATERS

The letters that DEP sent to homeowners revealed problems beyond methane. Drilling sediment clouded people’s tap water. Impoundments leaked toxic wastewater from the fracking process into nearby water supplies, rendering them unusable. As recently as April, compounds used in drilling were discovered in a Susquehanna County water supply.

In some cases, the pollution was temporary and the water cleared on its own. In others, the agency required drillers to permanently replace ruined water supplies.

KNOWN UNKNOWN

The exact number of contamination cases is unknowable.

First, because DEP had to search through voluminous paper files scattered in six regional offices, there’s no guarantee its review yielded every single case in which it determined that gas drilling affected a water supply.

Second, state law presumes an energy company is responsible for water contamination within 2,500 feet of an oil or gas well for up to a year after it was drilled — unless the company can prove the water was already bad. Pre-drilling water testing wasn’t universal in the early years of the shale boom, so the industry had no way of defending itself against many contamination claims, said Terry Engelder, a Penn State University geologist and supporter of the shale gas boom. Therefore, drillers might have been held liable for contamination that was already present in the water.