Problem: Sinkholes had developed around storm drainage manholes in grassy areas of a military housing subdivision in Richmond, Virginia. Besides being unsightly, they posed a danger to neighborhood children. Flooding the sinkholes identified infiltration points further up the structure. The connection of the inlet pipe from the surface catch basin and the connection of the storm main near the bench were the source of most leaks. These connections have brick aprons that had been surface sealed. There were no rubber boots present. Water leaked between the bricks through cracks in the surface seal. 

Solution: The crew injected Prime Resins Prime Flex 920 through the manhole wall to fill voids and create a watertight curtain. Prime Flex 920 is an expansive hydrophobic polyurethane resin that forms a watertight mass. The grouting was done from inside the manhole because the repair locations were so deep ­— as much as 20 feet from the surface. Technicians repaired wide gaps around the main connection by soaking oil-free oakum with hydrophilic Prime Flex 900 XLV and pushing it into the gaps to seal the openings with a bond to the wet concrete. 

Result: The crew tested their repair by flooding the sinkhole again and saw no infiltration. The contractor completed the repairs with 8 gallons of material. 

800-321-7212; www.primeresins.com