Stormwater Pond Outlet Structure Grouting

By applying unique solutions to increase the safety and longevity of our environment.


The stormwater pond in a neighborhood was not holding water.  Geotechnical investigations of the lining material showed that it was adequate.  The developer determined that outlet structure grouting may be required to address water loss around the buried structures.

Due to a very tight site, the pond was designed to release water through two structures feeding manifolds.  While the pond was equipped with a well and pump to make up for water loss, the pond would still not stay at level.  The inlet and two outlet structures were identified as potential flow paths for water exiting the pond, causing the level to drop.

The township engineer told the developer that if they could not get the pond to hold water, they were going to have to install a liner system, which was very expensive.


The repair had to be done without impacting water quality, well operations, or create large disruptions to the residents. Because the exact pathway of water flow around the structures could not be determined, the repair had to address water flows through various seepage paths around the structures.

The repair had to be done in the winter, so could not be affected by cold temperatures. Additionally, one of the structures was beyond the cold weather reach of plural component polyurethane grouting equipment.


Chemical grouting using prepolymer chemical grouting.

The equipment used for chemical grouting is easily carried in a pickup truck. Because the equipment is mobile, it can be moved around isolated sites easily after being unloaded from the pickup truck.

A very low prepolymer chemical grout was selected. This would allow for sealing leaks in the structures themselves, and seeking out and sealing water passages around the outside of the structures.


Prepolymer chemical grout was injected through the walls of the three structures to seal cracks in failed parging and fill extensive voids. The chemical grout expanded to show at the surface, which confirmed completeness of fill. Additionally, chemical grouting was performed below grade using injection pipes to block water flows through the stone beds under the discharge manifold pipes.

This outlet structure grouting project was completed in one day. There was no disruption to the surrounding residents.