Manhole Rehabilitation

Manhole Rehabilitation

Manholes and other underground structures commonly account for 25-30% of infiltration and up to 70% of inflow in sanitary sewer collection systems. Deteriorated manholes can also cause sewer overflows and endanger the nearby surface environment.

Manholes deteriorate for three basic reasons:

	Structural fatigue: Traffic loading, freeze-thaw cycles, soil movement, and hydrostatic pressure weaken and eventually deteriorate the masonry materials commonly used in the construction of manholes.
	Acid attack: Low pH levels of wastes discharged into the sewer system cause materials to deteriorate
	Corrosive gases: Hydrogen Sulfide is corrosive to metal appurtenances and can be converted into sulfuric acid when it comes in contact with bacteria in the environment.

A number of trenchless manhole restoration techniques are available.

The alternatives to complete replacement of manholes can be summarized by four basic categories, including:

	spot repairs
	cementitious coatings
	chemical coatings
	structural form repair