Solutions – Sonic Drilling, Permeation Grouting
Service – SOE Closure Grouting
The Job
This SOE closure grouting project is part of Archer Western’s work on the Belmont Pump Station for Prince William Water. It is located in Prince William County Virginia, which is a suburb of Washington, DC. Archer Western is constructing an additional pump station adjacent to an existing pump station. This will significantly increase capacity from 8MGD to 12MGD to service rapid population growth in the area.
Manchette tube installation.
The Challenge
The existing pump station sits just above a 4-foot-thick layer of natural open-graded stone, with the groundwater elevation at grade. The design places the new building immediately adjacent, dropping its floor elevation about 3 feet below the existing structure. Because the existing building obstructs the 4th side of the sheet pile SOE, the contractor worried about potential water infiltration from beneath it. To control the water and ensure a safe excavation, the crew had to seal the open-graded stone layer.
The Solution
CJGeo proposed a multi-step process to close the gap in the SOE. First, sonic drill down to the existing pump station footing, through it, through the gravel layer, and into the underlying fat clay. Next, install Manchette tubing at each of the approximately 30 drilling locations. Then, CJGeo pumped acrylic grout to permeate the stone layer and cohesionless soils to make them impermeable. After completion of the TAM grouting, the contractor excavated to the top of the footing. CJGeo returned to install additional permeation grout under the existing pump station. This helps facilitate traditional underpinning of the pump station, and completion of the new pump station excavation to grade.
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