Of measured risks: The environmental impacts of the Prudhoe Bay, alaska, oil field

Abstract

AbstractThe 20th anniversary of the filing of the Trans‐Alaska Pipeline System (TAPS) Environmental Impact Statement (EIS) affords an opportunity to assess retrospectively the environmental impacts of the resultant North Slope oil fields, now the largest single source of U.S. domestic oil production. As the oil field expanded, particularly to near‐shore areas such as the Endicott Development, additional EIS documents were prepared to assess impacts not included in the original TAPS EIS. In the ensuing years, numerous agency‐monitored and industry‐sponsored environmental monitoring studies, estimated to average $4 million per year, have been conducted in and around the oil field, making the Alaskan North Slope one of the most studied environments in North America.In this paper, the EIS requirement of the National Environmental Policy Act (NEPA) is examined as a predictive environmental risk assessment. A tabulated summary of the predicted environmental impacts from the original TAPS and offshore Endicott Development EIS documents is compared with the extensive amount of resultant monitoring data. These data confirm localized impacts to air and water quality; however, regulated discharges remain well below criteria established for the protection of human health and the environment. As predicted, some unavoidable habitat losses to resident and migratory wildlife have occurred within the oil field and pipeline corridors. Approximately 2% of the land surface in developed portions of the oil field was actually altered. However, careful monitoring of wildlife populations demonstrates that no species has experienced a measurable decline, and most continue to utilize oil field habitat for breeding, nesting, and summer forage. As habitat does not appear to be limiting the growth of North Slope caribou herds, the Central Arctic Herd has been able to accommodate the incremental habitat loss due to the oil field and has shown a sevenfold increase in numbers since the oil field development began in the early 1970s. Offshore monitoring data for the gravel causeways verify the predicted small, localized effects on water circulation and show the possibility is low that fish are experiencing resulting significant negative effects.The challenge faced in the EIS process is not how to ensure zero impact, as this is not a realistic goal, but instead it is how to predict impacts and describe mitigation measures accurately to ensure that the resultant ecological responses remain within a normal range of ecosystem oscillations that can be used to describe sustainable development. This review demonstrates that in the EIS process, a well‐designed program using the best available field data can indeed provide a relatively accurate prediction of subsequent impacts.