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Envirocon served as a subcontractor to a Small Business Prime Contractor on the last phase of construction on the Sacramento River Flood Control projects. The U. S. Army Corps of Engineers identified sites along 4 miles of levee that performed poorly during a flood event. The scope of work for the Phase 5 contract included improving a 2 ½-mile section of the existing levee by constructing a soil-cement-bentonite cutoff wall that was over 400,000 square feet to a depth of 40 feet. The project also included replacement and temporary bypass of multiple utility lines, and maintenance of public and vehicle access though areas of the site. A road that bordered the cutoff wall was also paved.
Envirocon constructed the cutoff wall using two long reach excavators capable of excavating to a depth of 40 feet. The cutoff wall, with a maximum permeability of 5x10-7 cm/sec and minimum unconfined compressive strength of 30 psi, protects the existing levee and its foundation from potential groundwater under seepage. The existing levee is an active county road, and Envirocon had to construct a 2-mile detour road to maintain safe traffic during construction activities. The detour road was constructed in the adjacent farmland.
Envirocon faced numerous challenges when completing this project including:
- Experiencing a shortage of domestic cement and having to propose and utilize foreign-made cement;
- Adjusting the alignment of the slurry wall to minimize the risk of levee failure during construction;
- Reducing the levee height because the material that the levee was constructed out of in the early 1800s had the potential for hydraulic fracturing;
- Coordination with adjacent property owners in order to set up a batch plant receiving numerous cement and bentonite trucks;
- Consideration of unseasonable rainstorm events during construction which could cause possible water releases from the Shasta and Keswick Dams causing significant flooding;
- Sequencing the work as to avoid the Swainson Hawks which were nesting near the site and also avoiding the Elderberry Beetle; and
- Performing work around a high-pressure gas main.
- Envirocon successfully performed this high visibility project resulting in the Small Business Prime Contractor being selected as Contractor of the Year – Civil Works for work performed under this contract. This project was nominated and won the ASCE Sacramento Section 2005 Outstanding Engineering Project of the Year.
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