Manhole Rehabilitation

Wade, Mark G.; ,

Manhole Rehabilitation

by Mark G. Wade, (M.ASCE), Pres.; Wade and Associates, Inc., Lawrence, KS,

Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 10, Pg. 58-60

Document Type: Feature article

Abstract:

Manholes are frequently the forgotten element in infrastructure renewal. When they aren't properly maintained they allow excess water into the sewer system, and structural damage can prevent them from performing their primary function�allowing personnel to inspect and maintain the sewer system. The first step toward preventing manhole problems is a comprehensive inspection plan. This requires standardized methods to maintain objectivity and uniformity, a form that records data pertinent to the rehab program and trained field technicians. A two-member field team is best. Once the engineers have determined the rehab needs for a sewer system, there are four basic methods of restoration: coating systems, chemical grouting, replacement and nondestructive reconstruction. Coatings work best in brick structures that show little or no evidence of movement or subsidence, since the coatings have little ability to resist shear and tension. Chemical grouting is a relatively inexpensive way to reduce I/I, but it does not improve the manhole's structural integrity. Pressure grouts are typically applied to brick manholes that have relatively tight joints or active I/I; that are structurally sound or in cohesive soils with optimum moisture content. Non-destructive reconstruction methods are superior to coating and pressure-grouting systems when the manhole is 48-72 in. in diameter, structural degradation is substantial, the manhole is inaccessible, or H2S control is necessary. Also, according to life-cycle cost analysis, the present-worth value of in situ reconstruction is competitive with other methods.

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