The development of a multicriteria, GIS-based model provides a systematic tool for assessing comprehensive risk for Permian Basin tank-battery facilities. Input variables include maximum saturated soil hydraulic conductivity, surface-water proximity, water-well proximity, depth to groundwater, public-road proximity, maximum HsS concentration, maximum reading of naturally occurring radioactive materials (NORM), total tank capacity, and average daily oil production. Raw values for these variables are derived from many different source datasets that undergo a wide range of formatting and geoprocessing.

Through a weighted linear combination (WLC) method coupled with the Analytic Hierarchy Process (AHP), raw variable scores are converted to a common, normalized scale and weighted according to relative importance. The weighted, normalized criteria scores are then summed to yield the overall risk score for each facility. The intention of the model is to identify facilities for which HSE incidents may have greater negative impact so that proactive measures can be taken in ensuring these higher-risk facilities receive additional inspections, maintenance, etc.

We apply the model to 122 facilities in a study area straddling Midland and Glasscock Counties in West Texas. Preliminary results yield a low overall risk range and suggest heavier weights on environmental criteria may produce a more useful score range while also recognizing spills as the most prevalent hazard associated with these facilities. Regardless of the overall score range, the model can be useful in defining relative risk among facilities for relative prioritization. Testing and expansion of the model into other areas and adding new criteria will continue to improve its applicability to current and future risk-based projects in the Permian Basin.

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