The City of Austin, Texas contracted with J.F. White's Diving Group to inspect an 8.5-mile long, 96 inch diameter sewer tunnel. Because of the complexity of the project, the project was broken into two phases:
(1) lateral system inspection and (2) main tunnel inspection.
Lateral inspection required the Diving Group to evaluate the flume shafts, drop shafts, splash pools, and service laterals. Several specialized techniques were required including manned inspection, video/still photography, pH readings, and concrete core sampling. This phase of the project was particularly challenging because laterals from 40 to 280 feet in length were as deep as 129 feet and had to be inspected during active sewage flow.
In the second phase of the project, the Diving Group inspected the main body of the tunnel. This proved challenging because the distance between the access points was as great as 17,000 linear feet. A customized inspection system was fabricated and used to provide real-time inspection, communication, and rescue capabilities. In addition, flow diversion, submersible pump systems, and HDPE bypass piping were utilized in concert to control sewage flows so that the work could be done safely.
