Design sections for shoreline revetments often specify a layer of filter fabric to separate clay or sand subgrade soils from the voids in the overlying rock. Consistent and complete placement of the filter fabric through several feet of water is difficult. The plunger box we developed solves that problem.
The installation process begins on dry land where we lightly attach the fabric to the bottom of the frame on dry land. Once attached, we pickup up the frame and fabric with an excavator and position them above it above the water in the correct location as determined by linework on the GPS machine control system. When the frame is in the correct location we steadily push the frame down through the water column until the fabric is resting on the subgrade. The frame holds the fabric taught and provides even pressure around the perimeter of the fabric during the plunging process. Once the frame is in place, the mast protrudes from the water providing a visual indication of where the fabric is located and how it is oriented. We place a couple of bucket loads of core stone inside the frame to anchor the fabric in place. Once the fabric is anchored, we retrieve the plunger box and swing it back up on shore for the next segment of filter fabric.
This approach was completely the result of a team effort within Edgerton. This would not have happened without the ideas, experience and enthusiastic input of several people each focused on various aspects of design, fabrication, and application. The U.S. Patent Office has now agreed that this approach is worthy of a patent. It’s a great example of Edgerton’s priorities in action! Safety. Quality. Efficiency.