Design Approach, Inspection For Manhole Rehabilitation Technologies

3nd In A 3-Part Series
By Gerhard “Gerry” P. Muenchmeyer, P.E., NASSCO Technical Director | November 2011, Vol. 66 No. 11

Carpenetti: “No, coatings that bond need to withstand the stresses, such as freeze thaw cycles, acting on the existing manhole structure. Therefore they need to be flexible so that over time, they do not crack, fracture or break.”

Johnson: “No, dependence on bond strength can be a risky proposition in the sewer environment. Standards such as ASTM F1216 do not assume adhesion and while conservative, minimize the human installation application factor.”

Kampbell: “Taking credit for bonding requires that it can be quantified up front for the purposes of the analysis -- this, I think, would put a challenging burden on a liner system provider to do the testing that can substantiate the value that should be used. Given the many variances in the host material’s competency and the level of attention to preparing the surface for lining that the contractor must be able to ensure would not be wise. Further, the design analysis method I recommended in the previous question demonstrates that the liner is going into a compressive state that ultimately results in a buckling failure. My judgment is that all lining systems should be designed as if there were no bonding taking place.”

We can therefore, assume that if a product bonds or does not bond to the host structure that the acceptance of the product should always be through verifiable quality assurance and testing.

There seems to be some differences of opinion but it would seem that all will agree that whichever approach to design is implemented the criteria used should be consistent and be verified through proper trained, certified inspection and standard testing procedures.

To confirm that a coating or lining has been properly installed several procedures are commonly followed.

First, the manufacturer’s specification sheet and installation requirements for the specific technology, followed by the applicator, should be a guideline to be studied and evaluated and used as inspection criteria for proper installation.

In the case of coatings and linings, that are promoted to bond to the substrate, a trained and certified inspector must enter the structure during the preparation stage as well as after the material is applied. The preparation inspection should include visual and detailed substrate examination. Running a gloved hand over the substrate surface or using a scraper type tool should not result in material becoming loose from the surface. If so, then further cleaning and removal of deteriorated material is required before the coating is applied.