Pacific Gas and Electric (PG&E) needed to replace an old corroded gas pipeline that crossed Georgiana Slough in the Sacramento-San Joaquin Delta.

PG&E chose to install the new pipe using directional drilling methods. GEI was retained to provide geotechnical design consultation, and construction observation.

GEI recommended that the new alignment be at least 70 feet below the slough and include entry and exit angles as flat as 8 degrees. Using these criteria, the total length of directionally drilled pipe was 1,250 feet, and the entry and exit points were 300 to 500 feet behind levees on either side of the slough.

GEI provided recommendations regarding casing, drilling fluids, jetting pressures, instrumentation and emergency contingency plans. During construction, GEI observed the contractor’s operation and monitored pore pressures. The 16-inch diameter steel pipeline was successfully installed across a 220-ft.-wide delta area.