Inspection

Trunk sewer inspections should be general in nature and should address all components of the system. "First-level" techniques are used at this initial stage of the process. These first-level techniques are sufficiently sophisticated to identify problems that are serious enough to warrant action. But they are basic and cost effective so that an overview of the entire system can be obtained in a safe and timely fashion.

First-level techniques provided by AndrewsInfrastructure include:

• conventional or pan-and-tilt CCTV camera inspection
• advanced, combined CCTV and Sonar inspection
• manhole inspections either with or without camera documentation
• sewage grab samples and pH testing of MH walls to determine corrosion potential
• person-entry inspections where feasible

Sonar technology gives a clear, underwater image of the wetted perimeter of the pipe. High frequency, rotating Sonar equipment provides a continuous series of closely spaced cross-sections along the sewer which clearly documents shape and distortion, structural condition, sediment deposits, and hydraulic roughness. Combined with a pan-and-tilt CCTV camera, simultaneous video and Sonar imagery can be obtained with comprehensive data on the entire cross-section. Typically the equipment can either be towed or floated through a sewer or siphon with results documented on VHS tape or digitally recorded.

Andrews Infrastructure has teamed with OnSite to carry out the inspection of nearly half a million meters of large diameter trunk sanitary sewers. In addition to more routine operations, we have jointly inspected an 1,800m submerged 1500 mm diameter siphon, a 2400 mm trunk with sewage velocity approaching 2.5 m/s and a 3000 mm diameter tunnel with access points up to 900 mm apart. We have also worked closely together on developing techniques to inspect remote, inaccessible work sites.