--> Has the Initial Development of the Haynesville Gas Play Impacted the Overlying Carrizo-Wilcox's Water Quality?

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Has the Initial Development of the Haynesville Gas Play Impacted the Overlying Carrizo-Wilcox's Water Quality?

Abstract

Recent development of unconventional hydrocarbon deposits requires millions of gallons of water for hydraulic fracturing plus many compounds that are contaminants. This is a concern because of possible impact on groundwater used for drinking. As a result, a number of states and communities have required baseline testing of groundwater near oil and gas wells that are drilled. Baseline testing can be useful in three different ways: one, it can be used to help resolve or avoid some future disputes involving contamination; two, it can be used improve the base of policy and regulatory decisions; and three it can be used to identify pre-existing water quality problems. This study is an example of the third reason and can be a benefit for two later on. With this mind a baseline of study of groundwater quality was completed prior to any hydraulic fracturing of a permitted oil well in St. Tammany Parish in southeast Louisiana. The study includes sampling from 100 wells, almost all are domestic wells that lie within approximately 4 miles of the oil well. At each of these wells six samples of water were collected for later analytical analysis for approximately 30 analytes including common ions, diesel range organics (DRO), gasoline range organics (GRO), metals, natural gases, nutrients, and specific conductance and TDS. It appears that two wells have been contaminated with DRO with one significantly above the detection limit of 0.15 mg/L and the other slightly over the detection limit, A few others appear that they could be contaminated as indicated by chromatographs that reveal peaks common to the ones with DRO concentrations above the detection limit but were at concentrations below the detection limit which has a high confidence that contamination has occurred. These are probably a result of contamination from the well owner's home heating fuel tank or maybe a neighbors tank nearby. The second possible contaminant source are septic tanks and their associated drain fields. Within the study area the density of residential development differs greatly. Several subdivisions have lot sizes that are typically several acres in size. However, one subdivision has lot sizes that is typical under one acre. The wells within the higher density subdivision have statistically significantly higher concentrations of many analytes including nitrogen which according to many studies is an indicator of groundwater contamination from septic systems.