Two DOT-maintained bridges crossing two privately owned dam spillways had to be closed because of extensive undermining of the spillways. The undermining was allowing nearly all of the flow to happen below the spillway slabs, which caused large sinkholes to form adjacent to and under the roadway pavement, and also led to some settlement of the spillway slabs.
There was very little room to work–just under 4′ of clearance below the bridge beams. Also, the velocity of the water through the voids below the structure was quite high.
CJGeo proposed a combination of plural component polyurethane grouting to address the water flows and voids, and hydrophobic chemical grout placed directly into cracks. A single CJGeo grouting crew was able to complete the repairs in a day (roughly 2500sqft of work, and approximately 4500lbs of polyurethane, plus 30 gallons of hydrophobic chemical grout). Dye testing during and after the grouting work confirmed that no more leaks were present under or around the spillway structures.