The Pennsylvania Department of Environmental Protection has publicly posted documents revealing official determinations that oil and gas operations have damaged Pennsylvania water supplies since late 2008.
The determination letters, made available for the first time late Thursday afternoon, show 248 incidents where drilling has contaminated water supplies, a number higher than the 209 first tallied by the DEP. In July, state environmental regulators provided the Pittsburgh Post-Gazette an early version of the spreadsheet in response to an open records request.
The highest number of confirmed incidents occurred in 2010, according to DEP records. That year saw 58 occurrences, followed by 39 in 2011 and 37 in 2009.
In 2014 so far, there have been 11 incidents, according to the DEP letters.
Each entry represents one water supply that environmental regulators determined was polluted by drilling operations. That information was compiled from letters and orders issued by the DEP’s regional offices throughout the state, according to DEP spokesman Eric Shirk.
The numbers vary by region. In Southwestern Pennsylvania, the second most heavily drilled portion of the state, saw nine incidents, according to DEP data.
Washington County, which has 1,042 unconventional wells, counts two incidents. Meanwhile, Bradford County in the prolific region of northeastern Pennsylvania has 52 incidents on 1,295 unconventional wells drilled.
Mr. Shirk said the DEP is continuing to review and update the data.
He noted that the list includes both conventional wells, which have been drilled in the state for decades, and unconventional wells.
“Anecdotally, we believe the makeup is about 50-50 [of conventional and unconventional wells],” Mr. Shirk said.
The number of impacts is small relative to the number of new oil and gas wells drilled during the same time period — nearly 20,000 shallow wells and shale wells, according to DEP records.
Mr. Shirk noted that since the DEP has been updating its oil and gas regulations in the wake of the shale boom, the number of incidents has gone down.
“However, even one incident is too much,” he said.
Environmental regulators are required by law to determine within 45 days of getting a drilling-related water complaint if oil and gas operations contaminated a water supply or reduced its flow.
DEP reports its findings in letters to property owners. It also issues orders to companies to fix the damage in cases where oil and gas operations are found to be accountable or are presumed to be the cause because of the proximity between drilling activities and a disrupted groundwater source.
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