injecting CJGrout 35NHV for manhole sealing on a stormwater structure in Virginia

25VF stormwater manhole sealing

Northern Virginia


Leaks throughout the joints on a 25VF, 48″ precast stormwater manhole were leaking. This caused a large sinkhole to open up at the surface, adjacent to the structure, requiring manhole sealing. Homeowners on either side of the easement were concerned about the stability of the area and reached out to the municipality. The estimated cost for excavating the structure to repair it from the outside exceeded $50,000.



Due to the depth of the manhole, a confined space entry had to be used. Additionally, the grout had to tolerate high moisture levels in the adjacent soil, and economically fill the extensive voids. Due to the presumed large size of voids, the grout had to also below heat.

High-density geotechnical polyurethane grouting fills the sinkholes adjacent to the structure and seals all points of infiltration.  


CJGeo polyurethane grouting crew sealed all of the infiltration points and filled the sinkholes in a single day. No excavation was required. The cost of the manhole sealing was less than 20% of that of open excavation.

The CJGeo crew used CJGrout 35NHV, which is specifically formulated for use around buried structures. It has a moderate reaction speed to helps reduce the number of injection holes. It’s hydroinsensitive, meaning even when injected directly into standing water, it reacts the same as in a dry environment. Hyrdoinsensitivity is important for water intrusion repair applications.

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.

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