Environmental impacts of pipeline corridors in the Mojave Desert, California

Abstract

Three recently-built gas and oil pipelines that cross the Mojave Desert have graded constructed zones averaging 107 feet wide (range 68--200) on terrain of low relief, and 135 feet (range 77--273) on steeper terrain. Where corridors overlap, the graded width of two pipelines combined averages 157 feet (range 100--388). Right Of Way (ROW) Grants stipulate ROWs 50 feet wide, with an extra 25 feet allowed for construction. Pre- and post-construction measurements on one pipeline show that the width of the graded corridor exceeds the surveyed width by about 21%. A moderate rainstorm of 4 hr duration in the Tehachapi Mtns. eroded about 120 tons/ac to 250 tons/ac of soil from one pipeline corridor, measured on 3 transects across steep slopes. Especially in the western Mojave Desert, the pipeline corridors remain vulnerable to wind erosion for at least 5 years, and thus pose hazards to traffic on nearby highways. Pipeline corridors that pass through areas of stable eolian deposits are undergoing active erosion that expands by undercutting roots and sandblasting plants on downwind sides of the corridors, and by burial of plants beneath drifts. Techniques used to clear vegetation from construction corridors range from deep bulldozing to those designed to removemore » foliage while leaving root systems intact; the former technique guarantees long-term impacts, but the latter technique may have been defeated by final grading. Problems arise from failure to implement existing mitigations, inadequacies in environmental stipulations, and inadequacies in engineering oversight. Environmental benefits can be achieved by reducing or eliminating the practice of mechanical grading of the corridor, and by placing ditch lines of subsequent pipelines within existing 50 ft. ROWs and limiting construction disturbance to the existing disturbed zone.« less