The purpose of this project was to construct a Soil-Bentonite cutoff wall for the Ramona Municipal Water District as part of the San Vicente WRP Pond 1 Rehabilitation Project located in Ramona, California. Geo-Solutions conducted a bench scale mix design and value engineering with regards to various installation methods, ultimately providing a single pass (continuous) trenching option that best fit the challenging site characteristics. The work platform was prepared by degrading the existing embankment while Geo-Solutions furnished supervision, labor, materials, equipment and supplies necessary to construct the low permeability barrier.
Geo-Solutions used our Geo-Trencher to complete the installation which entailed in-situ trenching with fresh water and dry bentonite. Bentonite powder was added to a shallow pre-trench and distributed throughout the depth of the wall using the trencher chain or “blade”. Geo-Solutions collected frequent quality control samples for evaluation and testing.
The in-situ mixed cutoff wall was installed from the prepared work platform through overburden, coarse alluvial and weathered bed rock until competent bedrock (granite) was encountered. This continuous operation where in-situ soils were mixed vertically along the alignment used an assortment of cutting teeth to achieve an 18-inch wide wall through the center of the embankment.
- Following degrade, Geo-Solutions only had approximately 14 feet of work platform to utilize for trenching operations. The ability to operate the Geo-Trencher with a narrow footprint greatly benefited Geo-Solutions throughout the installation process.
- Refusal conditions encountered when trenching to the top of bed rock (granite) proved difficult on the equipment. Increased wear and repairs were required throughout construction in order to ensure a tight seal at the base of the wall.