SEWER SEAL INSTALLATION
PROJECT TITLE: Sewer Seal Installation
PROJECT LOCATION: Major Municipality in New Jersey
CLIENT: Sewer Lining Contractor
Problem
A newly installed liner was leaking at several joints in a 72-inch diameter sewer line. After the new liner was installed, a CCTV inspection showed several joints were still leaking. Multiple East Coast dive companies were called, but due to the complexity of the project, none wanted the job. Bulldog Diving was called in from the Midwest to attempt a repair. Based on our experience and expertise, we felt confident we could affect a successful solution. Every aspect of this job was a challenge, but we had faith in our proven problem-solving abilities.
Solution
In general, and especially on large-diameter lines, sewers do not have valves. Therefore, regular flows to our required work area could not be stopped, and bypassing 80 million gallons per day to install an interior seal was not practical. As often is the case in our work, we were left with an incredibly difficult job, due to limited access and technology options available.
Consulting with the utility, we determined that active sewer flow could be stopped, but only for 90 to 120 minutes once each 24-hour period, for the dive team to access the repair location, up to 690 feet into the sewer line. Making the most of a low-flow window from 10:00 pm to 2:00 am, we installed two 72-inch inflatable plugs a mile upstream, to stop flow long enough to make the repair.
Miller Pipeline Weko-Seal internal pipe seals were chosen as the repair technology. Divers had to wear heavy dive helmets, even though the flow water itself was only 12 inches deep, due to the potential presence of H2S gas and the possibility of a plug blowout. This was another experience that led us to develop our lightweight, topside MK3 Air Helmet.
In fact, a plug blowout was almost a certainty, as sewage would be backing up behind it, exerting enormous pressure. Prior to actual installation, we didn’t know how long the two 72-inch plugs would stop flow before being overcome. As it turned out, after 90 minutes of blockage, sewage buildup would push by the plugs.
We had to learn quickly how to work within this window. A 72-inch Weko-Seal has multiple parts that are very heavy, requiring two men per each install. This physical challenge meant some teams were more efficient than others, presenting a constant need for our topside crew to closely monitor conditions to keep our divers safe.
Divers penetrated the line and were able to install the Weko-Seal and interior seal.
Result
All seals were successfully installed at our quoted price. Our customer, the liner company, was able to receive their project completion retainer.