Technical Manual: Conduits through Embankment Dams (FEMA 484)

Chapter 9—Inspection and Assessment of Conduit-Related Problems• Compass.—A compass unit will provide azimuth and inclination readingssuperimposed on the videotape. This will assist in determining conduitalignment. However, a compass unit likely will not work in a steel conduit.• Narration.—All inspection videotapes should include narration by the operator.The operator should describe in detail what is being seen. Narration shouldnote any deposits, changes in the slope of the invert, condition of conduitjoints, areas of deterioration, changes in shape, etc.• Drawings and photographs.—Copies of all available design and/or as-builtdrawings of the embankment dam and conduit should be onsite during theCCTV inspection for immediate reference and confirmation of details andfeatures observed during the inspection.• Measurements and data collection.—The inspection and the technical evaluation willbe greatly enhanced if the following data are collected at the time the CCTVinspection is performed: reservoir water level, any relevant data on nearbypiezometer levels, history of past operations, and time/date.• Videotape library.—The operator and other inspection personnel should reviewall previous inspection videotapes (if available) prior to doing the CCTVinspection. This will provide a baseline reference, so the rate of any continuingdeterioration can be evaluated.An important part of any CCTV inspection is the technical evaluation of theconditions observed during the inspection. A qualified professional engineerexperienced in the design and construction of conduits should perform thisevaluation. Interpretation of the results of the CCTV inspection should not be leftto inexperienced personnel. The correct determination of conditions within theconduit is crucial in understanding potential failure modes involved. Many years maypass before the opportunity to perform another CCTV inspection is available. Theengineer should prepare a report of findings (ROF), which documents all problemareas observed and recommends future actions. The ROF should also includepictures captured off the videotape or DVD showing areas of concern, a drawing orsketch showing the limits of the CCTV inspection, additional informational drawingsif needed, and a detailed summary or log of observations that corresponds with timeand linear footage on the videotape. Figure 132 shows a picture captured fromvideotape.Other innovations in inspection systems are under development for sewers and forthe oil and gas industry. These systems may eventually prove applicable to conduitinspection. These systems involve state-of-the-art laser scanners (digital imaging),and gyroscope technology. Laser scanner systems allow the operator to see the totalconduit surface with color coding of conduit defects on a digital computer image.227