THE JOB
This RCP pipe sealing project is located in Wake Forest, North Carolina. The asphalt parking lot over a 300′ run of 54″ RCP culvert kept collapsing. The locality’s public works department determined that the installation crew had not properly gasketed or seated the joints between the 4′ sticks of pipe. The pipe saw the continuous flow of a small stream. Flow enters at an end wall and discharges into a box culvert that crosses a public street. The drop inlet at the downstream junction between the RCP culvert and box culvert also had a failed 18″ RCP culvert feeding it. This had been repaired multiple times using open trench excavation.
THE CHALLENGE
The municipality was looking for an affordable, proven, and non-disruptive solution. Replacement would have required removal of a structure, and prevented adjacent businesses from using their parking lot during the work. Relining was not practical due to multiple sewers and water utility lines crossing through the pipe. Significant joint offsets would have also made lining difficult.
Extensive voids were identified around the pipe through an inspection. Much of the water flow from the stream was passing under/outside of the pipe, causing the erosion and collapse of the overhead parking lot, and the floor of a storage building built over the pipe. Previous attempts at sealing the joints and filling voids around the pipe with concrete had failed.
THE SOLUTION
Polyurethane grouting fill voids around the pipe and seal the joints between the individual pieces of pipe, end wall and drop inlet. And, chemical grouting to treat a curtain at the upstream end to reduce subsurface flow, and at the downhill end to stabilize a joint in the failed small diameter RCP culvert entering the drop inlet.
CJGeo polyurethane grouting crews placed 50 cubic yards of CJGrout 35NHV61, hydro insensitive polyurethane and 45 gallons of polyurethane resin chemical grout for an upstream grout curtain over a period of three days to complete the repair. The repairs were all completed without disruption to the adjacent businesses or streets.
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