Abstract

The Kern River Pipeline transmits natural gas from southwest Wyoming to southern California in a 36-inch diameter pipe. The alignment of the pipeline bisects Utah and passes within one mile southeast of Newcastle in Iron County. Interstate pipelines arc regulated by the Federal Energy Regulatory Commission, and hazards from surface-fault rupture must be considered in design. The Antelope fault is located at the western base of the Antelope Range, and is crossed by the Kern River Pipeline near Newcastle. Three fault traces were identified based on engineering-geologic reconnaissance. One trace was clearly recognizable from its geomorphic expression, and two traces were inferred from geologic mapping. An exploratory trench was excavated at one of the inferred fault traces and a test pit was excavated at the other. One of the inferred faults was dismissed as being too old to consider for treatment on the basis of the subsurface information. Heavy-wall pipe and select sand backfill were used to mitigate possible surface-fault hazards where the pipeline crossed the other inferred fault and the definite trace.