The U.S. Department of Transportation, Research and Special Programs Administration (RSPA), Office of Pipeline Safety (OPS) is required to identify areas unusually sensitive to environmental damage in the event of a hazardous liquid pipeline accident. Pipeline segments where a release could impact an USA are subject to additional prevention, mitigation, and response measures than what has previously been implemented by pipeline operators. Ecological USAs have been identified and mapped for the entire United States using data and expertise from many different sources. The final mapping product was completed at Research Planning, Inc, Columbia, South Carolina and was sent to OPS for distribution to the pipeline operators. USAs are selected from a set of candidate resources that include federally threatened and endangered species, imperiled species (generally 20 or fewer known populations world-wide), depleted marine mammals, and high concentration areas for migratory waterbirds. Final USAs include all critically imperiled species (generally 5 or fewer known populations world-wide), multi-species assemblages (three or more overlapping candidate resource types), Ramsar sites (areas designated under the Convention on Wetlands of International Importance Especially as Waterfowl Habitat), Western Hemisphere Shorebird Reserve Network (WHSRN) sites, high quality candidate occurrences (condition or viability of a species occurrence as determined by the Natural Heritage Programs) and candidate species that are aquatic dependent or terrestrial with limited home range sizes. RSPA's Geographic Information System (GIS) model integrates state Natural Heritage Program data, Environmental Sensitivity Index (ESI) data, Ramsar and WHSRN data and maps, hydrography, and species habitat and range classifications assigned by project ecologists. A summary map of all ecological USAs is presented at a nation-wide scale. The map provides specific examples as given by OPS, of regions: Southern, Southwest, Central, Eastern, and Western. States with high concentrations of liquid pipelines are also presented. This project and its results are unique in that they represent one of the first nation-wide compilations of ecological data for the purposes of a standardized pipeline risk assessment.

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