Systemic Analyses and Indicators for Assessing Risks to Drinking Water Resources from Hydraulic Fracturing Chemicals
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Abstract
Hydraulic fracturing (HF) is a disruptive technology that has unlocked a vast amount of hydrocarbon resources, but presents risks to drinking water resources. Applying systemic risk assessment approaches to environmental and public health risks created by onshore unconventional oil and gas development (OUOGD) has not been explored and there are research gaps in system dynamics related to HF chemical transparency, variety, and hazard levels.
The first objective of this research is to advance the application of systemic causation models to assess environmental and public health risks associated with OUOGD. A critical review of systemic causation models and their application for assessing these is presented. Holistic conceptual OUOGD process and control structure models are elucidated to provide a catalyst for future research.
The second objective is to improve techniques and metrics used to measure and monitor systemic HF chemical transparency and feedback loops. After a comprehensive review of existing transparency indicators, two new metrics are developed and applied. The percent of wells with publicly disclosed ingredients increased from ~0% to 95%, and the average percent of HF fluid mass withheld on chemical disclosure forms decreased ~46.8%.
The third objective is to provide context and analyze changes in HF chemical variety and influencing factors. A methodology for processing public HF chemical disclosure data into an updated unique HF chemical list is provided. The annual unique HF chemical counts were found to have dropped 32.3%. Identified HF chemicals are compared with reference chemical lists, including known food, cosmetics, and water-related additives and contaminants, for system and risk context. Approximately 70.0% of the HF chemicals are found in the reference chemical list.
The last objective is to develop and apply a repeatable methodology for reporting relative HF chemical hazard levels to drinking water resources and characterize system dynamics. New individual parameter and aggregated risk indicators with associated approaches are provided. The aggregated metric indicated a 42.6% risk reduction. Overall, this research reveals past progress and methods for fostering future improvements related to HF chemical stewardship that can potentially be applied toward safer chemicals and transparency across all industries.