Construction of Gas Pipeline Relied Heavily on HDD to Minimize Environmental Impacts

Minimal Impact, Maximum Outcome
By Ron Walker | November 2009 Vol. 64 No. 11
Successful hammerjack bore connecting to area previously trenched. Photo: Travis King.

Given the protected status of several landforms and species along the alignment, extensive evaluations of potential environmental impacts were required to secure the necessary permits and approvals from various resource agencies, including the California State Land Commission, the U.S. Army Corps of Engineers, the California State Water Resources Control Board, the California Department of Fish & Game, the U.S. Fish & Wildlife Service, the California Office of Historic Preservation and the Sacramento Metropolitan Air Quality Management District.

Avoiding the impacts

Key issues addressed as part of the planning and permitting for the project included minimizing environmental impacts associated with the pipeline’s route and the temporary use areas in which pipe sections are connected before installation. During consultations with the various regulatory agencies, several mitigation measures were developed to avoid disturbing wetlands and other waters under the jurisdiction of the Clean Water Act that are located on or adjacent to the construction area.

By far, the main technique used to avoid impacts to wetlands and other jurisdictional waters of the United States involved installing pipeline in sensitive areas by means of HDD. This technique was used to install pipeline beneath the two rivers, portions of the Cosumnes River Preserve and Stone Lakes NWR, and other sensitive areas.

A bore of approximately 2,600 feet was used to pass beneath the rivers and related riparian habitat, requiring a pull back area of the same length along agricultural land south of the Mokelumne River. Within the Cosumnes River Preserve, HDD was used to install approximately 3,300 feet of pipe beneath freshwater marsh, annual grassland, seasonal wetlands, and riparian habitat. Elsewhere along the pipeline alignment, another 1,400 feet of pipe were installed by HDD underneath an unnamed tributary to Snodgrass Slough, while a 1,500 foot long section of pipeline was placed by HDD beneath a dairy.

The project’s longest pipeline section installed by means of HDD occurred within the Stone Lakes NWR. Here, approximately 6,500 feet of pipe were installed in this manner to avoid disturbing vernal pools and seasonal wetlands. A pullback area of the same length extended to the north of the Elk Grove Station between an existing sound wall and the UPRR line.