How to Fix a Flooded Manhole

A precaster’s tried-and-true method for sealing a sump hole.

By Gary K. Munkelt, P.E.

Problem: A utility manhole is installed in an area with an unexpected high water table. The sump hole through the bottom slab allows a constant 2 ft (0.6 m) of water inside the manhole, preventing installation of equipment. How can the hole be sealed?

• Step #1: Drive pipe into ground. The pipe’s inner diameter must be larger than the outer diameter of the gel line.
• Step #2: Inject hydrophilic gel into the ground. Hardened gel will prevent movement of water; the gel hardens in soil when exposed to water.
• Step #3: Inside the manhole, pump water level down to underside of bottom slab.
• Step #4: Roughen surface of concrete around inside of sump hole with chisel and hammer.
• Step #5: Apply a bonding agent to the dry surface of the roughened sump-hole edges.
• Step #6: Use expansion-type grout to close up the hole.

Gary Munkelt is a consulting engineer with Gary K. Munkelt & Associates in North Wales, Pa. Contact him at [email protected].