On Feb. 10, 2018, at a large Midwestern city’s wastewater treatment plant on the Great Lakes, operators noticed what appeared to be wastewater coming out of the ground near the high-level junction structure. The structure consists of 48-, 60-, 78- and 90-in.-diameter inlet pipes and a 90-in.-diameter outlet to the wastewater treatment plant. The plant declared an emergency and obtained the services of a local contractor to start investigating the issue.
The contractor mobilized with pumps to control any leakage during exploration and began excavating around the inlet pipes. By Feb. 22, the site was stabilized with all high-level siphon inlet pipes exposed. The high-level siphon junction structure and piping consisted of a steel pipe connection into the structure and a transition to a prestressed concrete cylinder pipe slip joint outside of the structure. This slip joint was observed to be leaking on the 48-, 60- and 78-in. pipes. To stop the leakage, a Cretex HydraTite internal joint seal was proposed. The seals can withstand up to 300 psi of internal pressure and completely span the leaking slip joint. By the end of February, a diversion plan was successfully tested prior to the seal installation.
The first seal was installed March 9 on the 60-in. inlet pipe joint. Once the seal had been installed, the leakage was completely stopped. On March 14, the 48-in. pipe was repaired, and on March 16 the 78-in. pipe was repaired. By March 16, no further leaks were observed from any pipes.
The determination was made to install the seals on all similar high-level and low-level siphon inlet and outlet pipe joints as a preventative measure and the final seal was installed April 25. A total of 19 seals ranging from 42 to 90 in. in diameter were installed to complete the repairs. All high-level and low-level siphon pipes, as well as the junction structures, were inspected and shown to be in good condition after the repairs had been completed.
