“The laser data revealed and quantified corrosion above the water line that the conventional CCTV did not. Seven of the eighteen segments had maximum corrosion depths of greater than 1.0-in.  For areas below the water surface, the sonar data provided additional information on changes in the wall material (i.e., gain or loss) resulting from corrosion, siltation, or deformation (ovality and deflection). Evaluation of pipe below the water surface was not possible by CCTV or the other technologies evaluated.”

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EPA report