8 foot diameter CMP joint sealing

Northern Virginia

Spraying polyurethane-polyurea hybrid to seal CMP joints.


An 8′ diameter stormwater structure required CMP joint sealing in order to pass an exfiltration test by the municipality for acceptance. The filter assembly is comprised of sections of 8′ diameter corrugated metal pipe, arranged in a rectangle with distribution and, six filter chambers, and a collection end.

In order to pass the water exfiltration test, 38 joints within the distribution and filter chambers needed to be thoroughly sealed.


Many of the pipe ends had been snagged during installation. A compressed construction schedule also forced the connection of the filter to the stormwater drainage system prior to the CMP joint sealing. This resulted in the filter being charged multiple times before the joint sealing could be done, which introduced extensive amounts of silt and trash to the filter, so cleaning was required prior to the application of the sprayed joint sealant.

Cleaning CMP pipe for joint sealing.


CJGeo cleaned and ventilated the structure in order to dry it. 24 hours of negative pressure ventilation thoroughly dried the structure, allowing for proper surface preparation of the filter structure. After drying and surface preparation were completed, all 38 joints in the 8′ diameter CMP were sealed using a polyurethane-polyurea hybrid foam.  

Sprayed application of polyurethane-polyurea hybrid allows for conforming the joint sealant to joints that are too misaligned or deformed to seal using traditional neoprene gasketed bands clamps. Slightly misaligned joints are very common in culvert construction; our CMP repair processes are inherently adaptive for sealing misaligned joints.

The hybrid foam was spray applied, with a combination of supplied air and negative pressure ventilation. CJGeo self-performed confined space permitting, entry, and monitoring for this CMP joint sealing project.