MDN recently highlighted a new study of several hundred water wells by Penn State researchers which found no evidence of chemical or methane contamination related to nearby Marcellus gas drilling (see this MDN story). The study did announce one oddity in the data: increased levels of bromide in seven wells. That oddity has now been explained—it was a lab error. Oops. Bottom line conclusion from the study? Shale gas drilling does not lead to either methane or chemical contamination of nearby water wells.
A study by Penn State researchers is being revised after test results apparently linking increased bromide in some water wells to Marcellus Shale gas drilling were traced instead to a lab error.
An error notice was published on Nov. 22 on the website of the Center for Rural Pennsylvania, which funded the study and released it in late October.
According to the notice, an accredited laboratory contracted by the researchers incorrectly reported the bromide concentration data that were used in the original report. Updated data showed that increased bromide levels were recorded in one of 42 water wells, not seven wells as originally reported.
The one affected water well also showed increased levels of chloride, hardness and other parameters days after a Marcellus well about a quarter-mile away was hydraulically fractured, but "nearly all" of the increased parameters, including bromide, "had nearly returned to pre-drilling concentrations" after 10 months, according to the notice and the original report.
The study of 233 water wells in 20 Pennsylvania counties did not find any statistically significant increases in methane after drilling or evidence of contamination from the most prominent pollutants found in the wastewater that flows out of natural gas wells after hydraulic fracturing.
According to the error notice, all of the study’s research findings are being reviewed and a revised report will be issued "in the coming weeks."*
*The Scranton Times Tribune (Nov 29, 2011) – Increased bromide caused by lab error not drilling, researchers say