THE JOB
Joints in a 25-foot vertical, 48-inch precast stormwater manhole were leaking. These leaks created a large sinkhole at the surface next to the structure. Homeowners on both sides of the easement worried about the ground’s stability and contacted the municipality. Repairing the manhole from the outside via excavation would have cost more than $50,000.
THE CHALLENGE
Because of the manhole’s depth, the crew performed a confined space entry. The project required a grout that could handle wet soil and affordably fill large empty spaces (voids). Since these voids were likely very large, the grout also needed a low exotherm (low heat release during curing) to stay stable.
High-density geotechnical polyurethane grouting fills the sinkholes adjacent to the structure and seals all points of infiltration.
THE SOLUTION
The CJGeo crew sealed every leak and filled the sinkholes in just one day. We avoided all excavation, keeping the total cost below 20% of a traditional dig-and-replace repair.
The crew chose CJGrout 35NHV, a foam made specifically for buried structures. It reacts at a moderate speed, which lowers the number of injection holes needed. It is also “hydroinsensitive,” meaning it reacts perfectly even in standing water.
After drilling 5/8″ holes through the structure’s walls, 35NHV is injected through mechanical packers. There were two cutoff criteria for this project:
- 35NHV geotechnical polyurethane extruding through the full circumference of each joint in the precast structure
- grout coming to the surface from the bottom of the sinkholes
CJGrout 35NHV sets within two minutes, and reaches 95% cure within 15 minutes.
Speak With An Expert
Facing a similar challenge to this 25VF stormwater manhole sealing project?
