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.

Evaluating the impacts
Although most of the pipeline extends through agricultural areas, the alignment also crosses numerous environmentally sensitive areas, including the two rivers, two critical natural areas and a variety of other habitats. As a result, the Line 108 Replacement Project required extensive environmental analysis and careful planning to avoid or minimize environmental impacts.

PBS&J prepared the Project Environmental Assessment for the Line 108 Replacement Project and assisted PG&E in complying with the requirements of the California Environmental Quality Act (CEQA), which requires that state and local agencies identify significant environmental impacts associated with their activities and take steps to avoid or mitigate those impacts, if feasible. In addition to consulting with the various agencies overseeing the project, PBS&J handled such tasks as special status plant surveys, avian surveys, habitat mapping, wetlands delineation and wetland permitting.

Among the more fragile natural areas through which the pipeline passes are the Mokelumne and Cosumnes rivers, the Cosumnes River Preserve and the Stone Lakes National Wildlife Refuge (NWR). The pipeline crosses the two rivers and the Cosumnes River Preserve at its southern terminus, while the Stone Lakes NWR is located near the project’s northern end. Comprising parcels of land owned by several federal and state agencies and nonprofit organizations, the Cosumnes River Preserve is administered by the U.S. Bureau of Land Management. The Stone Lakes NWR is administered by the U.S. Fish & Wildlife Service.

Within the Cosumnes River Preserve, the pipeline crosses riparian forest, riparian scrub, grasslands and seasonal wetlands. Meanwhile, within the Stone Lakes NWR, the pipeline traverses annual grasslands, seasonal wetlands, drainage features and vernal pools. These pools are depressions that remain inundated during the rainy season and provide habitat to a unique assembly of plants and animals, such as the federally listed vernal pool fairy shrimp, that complete their life cycles before the pools dry out during the dry season.

The vernal pool fairy shrimp is one of many sensitive species whose presence had to be accounted for during the design and construction of the project. Other species that are protected by either federal or state mandate and known to inhabit areas along or near the pipeline alignment include the giant garter snake, Swainson’s hawk, western pond turtle, valley elderberry longhorn beetle and burrowing owl, as well as approximately 11 special status plants.