CEI was retained to provide geotechnical engineering and utility location services as part of multiple design assignments for the MDC Clean Water Project.
The scope of services included 19 soil borings and 5 monitor wells, laboratory soil testing, analysis and 15 test pits to locate utilities which may be in conflict with the proposed design. The design includes a new sanitary sewer, new water main, new drain line (storm water) and new storm and sanitary laterals.
The geotechnical testing and analysis included undisturbed soil sampling, shear testing, consolidation testing, and atterberg limits.The soils encountered ranged from clean sands to soft clay deposits of extensive depth.
CEI’s analysis indicated significant settlement would occur from the sanitary sewer construction.CEI provided recommendations for mitigating the settlement and preserving the integrity of the new facilities.
These recommendations included steepening the pipe slopes to provide for the two to three inches of settlement or utilizing light weight trench backfill material to eliminate any settlement.
The owner preferred the use of lightweight fill due to the tight slope tolerances on the project. CEI provided specifications and mix ratios to limit any settlements after completion of construction.
In addition, because of the soft clay, issues were raised about the use of vibratory equipment to place the sheeting for temporary trench support and the concern it would cause damage to the adjacent homes. This was initially prohibited for use by the contractor. But the contractor proposed the use of an untested variable speed vibratory hammer that would avoid the resonant frequency which would be detrimental to the nearby house foundations.
CEI was present for the testing of the equipment, and observed that the vibrations were within acceptable tolerances for use of the equipment.
CEI is provided shop drawing review and construction observation for the piping installations throughout the completion of the project.