NATOMAS CROSS CANAL LEVEE IMPROVEMENT PROGRAM
Great Lakes E&I continued a history of award-winning performance, receiving the American Society of Civil Engineers (ASCE) 2010 Outstanding Project of the Year Award for the Natomas Levee Improvement Program. The Natomas Basin is part of the Sacramento River Flood Control Project (SRFCP), an integrated system of levees, nearby bass channels and dams, constructed to protect communities in the Sacramento Valley from flooding. The levees were constructed with unsuitable materials that proved to be extremely porous when subjected to sustained high flows.
In 2007, the Sacramento Area Flood Control Agency (SAFCA) initiated the Natomas Levee Improvement Program. This program was designed to correct levee seepage and to bring the 42-mile Natomas Basin perimeter levee system into compliance with applicable standards for urban area protection. Great Lakes E&I team members have participated in four phases of this program dating back to the program’s inception. The most recent two phases (2009 and 2010) are described below.
NATOMAS CROSS CANAL SOUTH LEVEE
Great Lakes E&I was subcontracted to construct a 547,500 sf soil-bentonite cutoff slurry wall to a depth of 75 ft below the crown of the Natomas Cross Canal South Levee. The cutoff slurry wall was built along 7,300 lf of the levee with a maximum specified permeability of 1×10-7 centimeters per second. Excavated soils and imported sand were utilized to meet a maximum fine content of 60 percent. Great Lakes E&I constructed the cutoff slurry wall using a company-owned Komatsu PC 1250 excavator equipped with a custom built boom and stick capable of excavating to a depth of 85 ft. The wall was completed on an accelerated schedule between June and August 2009 to ensure that the general contractor could complete the larger scale levee rehabilitation by the stipulated completion date of October 31, 2009. Great Lakes E&I worked around the clock, six days per week to meet the schedule, completing the project within budget and without incident.
SACRAMENTO RIVER EAST LEVEE
In the fourth phase of SAFCA’s multiyear levee improvement project in the Natomas Basin, Great Lakes E&I constructed an 18,300 lf soil-bentonite cutoff slurry wall along the Sacramento River East Levee adjacent to the Garden Highway. The wall was excavated to depths between 27 ft and 63 ft below grade. All excavated soils were placed along work padding adjacent to the trench for use in the soil-bentonite backfill mixture. Excavated soils containing fine content greater than 60 percent were amended with imported sand. Amendment ratios were carefully controlled to maintain specified design permeability and to eliminate the need for further bentonite addition. The project was completed on time, within budget, and without incident between July and September 2010.