Rain for RentEvery city prides itself on a virtually invisible infrastructure. Residents are happiest when they can go about their daily lives without thinking about the pipelines below. When that peace and tranquility are threatened by deteriorating sewer lines, immediate action must be taken.

A city in Alabama faced this exact situation when severe deterioration was revealed during routine maintenance on a 36-in. trunk sewer line. The deterioration was so bad, the pipeline risked failure at any moment. The deterioration was discovered in the City’s historic district on the eve of the state’s largest music festivals when nearly 200,000 people would come to celebrate.

The city engineer and sewer department determined that the 36-in. trunk line had several upstream and downstream segments with severe deterioration 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 (CIP) liner for the most deteriorated section of the line, requiring the sewer to be bypassed around the section being rehabbed. While the lining process was fairly straight forward, the bypass pumping had several critical hurdles that required solutions for the project to be completed successfully in the quick, one week timeframe.

The Project

The solution to rehabilitate the pipe included relining 750 ft of trunk sewer with a cured-in-place liner that 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-in. 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-ft bypass included six intersection crossings during the quick one week project.

Rain for RentConcerns

First and foremost, the location of the sewer to be rehabbed was in the heart of the downtown historic district with numerous retail stores, restaurants, private businesses and residential housing located in the area that needed street access and specific noise constraints. All work needed to be completed quickly and safely with as little disturbance as possible, especially during a 5k run scheduled during the bypass setup.
Secondly, the streets were very narrow and the city required minimal excavation, which meant that the suction lines for the bypass would have to enter through 24-in. manhole ring.

Third, there was no laydown area available to use during the construction phase, requiring all work to be done in the street.

Lastly, there was an additional 12-in. force main that entered the 36-in. trunk line that would need to be bypassed to complete the cured-in-place pipe (CIPP) work.

The Solution

The contractor chose Rain for Rent because of a long, successful history working together on dozens of pumping projects over the past several years. Rain for Rent, a nationwide company with locations supporting all 50 U.S. states and Canada, has worked in Alabama since 2003, specializing in bypass pumping, filtration projects and liquid storage.

The contractor and the city project manager, working in conjunction with the Rain for Rent engineering department and project manager, developed a comprehensive plan to solve the concerns facing the bypass. According to the Rain for Rent project manager onsite Curt Dykes, “We were in constant communication with the City, CIPP contractor and other subs. It made everything go very smoothly.”

To ensure the project operated safely, Rain for Rent worked with the City’s traffic department head, the police department and an external traffic safety company. By developing an intricate traffic control plan, all construction work could be completed safely and timely. Relying on prior bypass pumping expertise and by using GPS technology, the contractor, City and Rain for Rent were able to identify which streets would need to be closed temporarily and determine the order and timeframe in which they would need to be closed during the initial job walk. This would allow for the majority of the area to be open at all times keeping businesses and retail stores open throughout the construction.

Prior to the start of the project, the Rain for Rent operations team coordinated with businesses and home owners to inform them of the project, eliminating frustration and answering questions. Rain for Rent coordinated with the City and 5k run organizers to delay set up of the project during the actual race.

Rain for Rent’s certified fusion technicians fused the HDPE pipe on the project, ensuring a leak-free system. Daily Job Safety Analyses were also conducted with all contractors onsite to identify any potential hazards before they were an issue. Prior to starting the bypass operation, Rain for Rent confirmed that the system was leak free by hydrostatically testing the entire system.

To alleviate the need to excavate the suction manhole, a single, 18-in,. HDPE suction stinger was manifolded to four 6-in., DV150i sound-attenuated pumps. These pumps were then manifolded through gate valves into a single, 18-in. HDPE discharge pipe that ran the length of the project.

At each intersection, an 18-in. 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-in. force main bypass enough head pressure to break into the existing flow of the 18-in. sewer line bypass, the project used a pump drawing water from a 21,000-gal 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 6-in. DV150i sound-attenuated pump was used to move the liquid from the tank through a gate valve into the 18-in.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.

Conclusion

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 and the festival were unaffected by the bypass. With a total of approximately 15 million gals 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.

Rain for Rent technical service representative Zack Newberry, has worked a variety of liquid handling jobs including bypass projects as large as 64 MGD since joining Rain for Rent in 2007. He said that working with the City was seamless. “They got what we needed when we needed it.” It helped the project run smoothly.
The bypass challenges faced on this project are not uncommon in the day-to-day trenchless rehabilitation market. However, to find all of these on a project that required a single inversion, is unusual and highlights the intricacy of this type of construction. While there is a minimum amount of excavation required on most trenchless rehabilitation scenarios, there can be many above ground challenges required even for projects with small scopes.

This project is an example of how when an owner, contractor and subcontractors work together to find solutions for the challenges on any given project, it only increases the opportunity for cost-effective, environmentally safe and successful projects.

Brian Brandstetter is senior strategic account manager for Rain for Rent.