I’ve engaged in a number of debates on the merits of performing flow isolation to determine where in-line CCTV should be performed to locate infiltration sources into sanitary sewer systems. Do you have an opinion? I’m interested in your thoughts.
Here’s my position. Flow isolation is no longer the best method for isolating pipelines that contribute excessive infiltration to a sanitary sewer sytem. Flow isolation also requires that manholes must be entered to take the flow measurement. Manholes are confined spaces which creates a risk for the inspector. Flow isolation is performed to determine how much infiltration is entering a pipe segment. To obtain accurate measurements requires careful execution. The potential for erroneous data is great if proper care in taking the measurements isn’t taken. When EPA developed its I/I guidelines during the 70s under PL 92-500, it was recommended to lamp the pipelines to provide a visual assessment of the presence or absence of infiltration. With the development of stationary zoom cameras we can see a substantial distance down the pipelines providing not only visual evidence of infiltration; but, also visual evidence of the maintenance condition, structural condition and operation condition of the sewer system. Isn’t it time to retire flow isolation in lieu of zoom camera inspection? What do you think?
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