A city in Alabama discovered severely deteriorated sewer lines, which could fail at any moment, during routine maintenance on a 36-inch trunk sewer line. The city engineer and sewer department determined that the 36-inch trunk line had several upstream and downstream segments with severe weakening due to age. A quick point repair would not alleviate the issue. A permanent repair needed to be completed on several hundred feet of the trunk line quickly and safely. 
During the sewer main repair, the streets had to remain open and the sewer had to continue flowing so residents would be unaffected and could continue to use their services. The ideal solution for the repair included installing a single cured in place liner for the most deteriorated section of the pipe, requiring the sewer to be bypassed around the section being rehabbed.
The solution to rehabilitate the pipe included relining 750-feet of trunk sewer with a cured in place liner which ran the complete length of the pipe. The main bypass required 2.7 million gallons a day (MGD) for peak dry flows and 11 MGD for peak wet weather conditions. A second bypass was necessary for a 12-inch force main that entered the trunk line in the section that was to be rehabbed. It handled flows of 0.5 MGD for normal conditions and 3.5 MGD for wet conditions. The 1,200-foot bypass included six intersection crossings during the quick one week project.
The contractor chose Rain for Rent because of a long, successful history working together on dozens of pumping projects over the past several years. Relying on prior bypass pumping expertise and by utilizing GPS technology , the contractor, city and Rain for Rent were able to minimize road closures by identifying the order and timeframe to close each street during the initial job walk.
Rain for Rent’s certified fusion technicians fused the HDPE pipe on the project, ensuring a leak-free system. Prior to starting the bypass operation, Rain for Rent confirmed the pipeline’s integrity by hydrostatically testing the entire system.
To alleviate the need to excavate the suction manhole, a single 18-inch HDPE suction stinger was manifolded to four 6-inch DV150i sound attenuated pumps. These pumps were then manifolded through gate valves into a single 18-inch HDPE discharge pipe that ran the length of the project.
At each intersection, an 18-inch steel road crossing was placed to allow for traffic to continue without disturbance. Each road crossing was smoothed out with cold patch asphalt to minimize the bump for traffic flow. Sound attenuated pumps ran 24/7 during the installation of the liners, keeping the operation quiet.
To give the 12-inch force main bypass enough head pressure to break into the existing flow of the 18-inch sewer line bypass, the project utilized a pump drawing water from a 21,000 gallon reservoir tank to pressurize the system. Because the tank is portable and only 8-ft wide, cross street traffic continued to flow. The contractor installed a temporary connection at the force main and flanged high pressure hose was used to plumb the force main into the tank. An additional six-inch DV150i sound attenuated pump was used to move the liquid from the tank through a gate valve into the 18-inch HDPE bypass line.
The CIPP contractor installed a direct inversion liner to repair the aging sewer lines. This solution was the fastest, least obtrusive solution to rehabilitate the lines, quickly getting the pipelines back into service.
The city averted an emergency situation by taking action when the initial damage was discovered, collaborating with the CIPP contractor and Rain for Rent, completing the project within the one week timeframe. The 200,000 residents of the city were unaffected by the bypass. With a total of approximately 15 million gallons pumped, the bypass was completed safely without incident during the nearly 210 man hours worked during set up and tear down on the project with an additional 96 hours for 24 hour-a-day pump watch.
Written by Brian Brandstetter. Photo courtesy of Rain for Rent.