CHESTERFIELD, MO, Aug. 10, 2004 -- The Sacramento Regional County Sanitation District has awarded Affholder Inc. a $44 million contract to bore tunnels at two points under the Sacramento River.
The tunnels are part of the new Lower Northwest Interceptor, a 19-mile sewer line that will transport wastewater from West Sacramento and rapidly growing north Sacramento County to the Sacramento Regional Wastewater Treatment Plant near Elk Grove, California. The northern river crossing will be located east of the I-80 Interstate Bridge; the southern crossing will be north of Sacramento's Freeport Bridge.
"When the District looked at the region's sewer needs for the next 50 years, it was clear that significant growth would occur in the northern part of Sacramento County," explains Bill Moler, lead tunnel engineer for The Lower Northwest Interceptor Program. "This new interceptor is needed to support the previously planned general growth in that area."
When completed in 2006 the Lower Northwest Interceptor is expected to serve about 200,000 households and carry peak wet weather flows of up to 200 million gallons a day.
Affholder's contract calls for the company to begin each set of tunnels by excavating 25-foot by 150-foot access shafts on both sides of the river, where it will launch and receive its tunnel boring machines. Working from these shafts, workers will then bore tunnels, each about 15 feet in diameter and 2,000 feet in length, at each of the two crossings. During the excavation of the tunnel, Affholder will line each tunnel with a 13 ½-foot diameter precast concrete, watertight, segmental tunnel liner. Upon completion of the tunnels, twin steel pipes will be installed inside the tunnels as the sewer line.
The tunnels will connect on both sides of the river crossings with pipelines that are being constructed under separate construction contracts. "It will take a work crew of 45 to 50 persons about two years to bore and line the tunnels," according to Bob Stier, area manager for Affholder. Work on the project is expected to begin in August and continue through the summer of 2006.
Affholder Inc., a subsidiary of Insituform Technologies Inc., uses tunneling methods to perform trenchless installations of new pipelines throughout North America.
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