Department of Civil and Environmental Engineering
Pennsylvania State University
The development of unconventional oil & gas (O&G) resources has fundamentally changed energy production in the United States. This development has led to increased demands for fresh water and increased volumes of O&G wastewater. This talk will present two case studies in Pennsylvania: #1 will focus on disposal of wastewater from Marcellus Shale gas wells to surface water, and #2 will focus on disposal of conventional O&G wastewater onto roads. In case study #1, we evaluated the impact of O&G wastewater from two centralized waste treatment (CWT) plants upstream of the Conemaugh River Lake (dam controlled reservoir) in western Pennsylvania. Regulatory compliance data for the CWTs were collected to calculate annual contaminant loads [Ba, Cl, total dissolved solids (TDS)] and document historical industrial activity. Sediment cores were sectioned for the collection of paired samples of sediment and porewater. Sediment layers corresponding to the years of maximum O&G wastewater disposal contained higher concentrations of salts, alkaline earth metals, and organic chemicals. Isotopic ratios of 226Ra/228Ra and 87Sr/86Sr identified that peak concentrations of Ra and Sr were likely sourced from wastewaters from Marcellus Shale. These two CWT plants were 10 and 19 km upstream of the reservoir and left geochemical signatures corresponding to peak industrial activity that occurred 5 to 10 years earlier. In case study #2, we characterized O&G wastewaters that were spread on dirt and gravel roads in Pennsylvania in 2017. Based upon a regulatory review, up to 17 U.S. states allow the “beneficial use” of O&G wastes for road maintenance, dust suppression, or de-icing. In Pennsylvania, more O&G wastewater is disposed of by CWT plants (180 million liters in 2016) than road spreading (40 million liters in 2016). However, effluents from CWT plants contain lower radium concentrations (14.5 pCi/L) compared to the O&G wastewaters spread on roads (1,230 pCi/L). Spreading conventional O&G wastewaters on roads in Pennsylvania could release more radium to the environment than any other O&G wastewater disposal option. Environmental and human health impacts associated with these disposal practices will be discussed.