Replacing failing water pipelines across North America is not an attractive option on any level, not just economically. With the environmental and technical aspects, plus the complexity associated with excavating, removing and replacing existing pipelines will create havoc on our daily lives.
Globally, the rise of trenchless technologies has been at the heart of efforts to maintain and refurbish existing buried systems. Essentially, the concept is to reduce excavation to the absolute minimum and launch the renewal technology from the surface. In relation to water pipelines, one of the most effective trenchless methods has been the introduction of technology that retrofits HDPE pipe into existing pipelines in order to renew them back to fully operational status — and give it an extended lease of life for another century.
Swagelining, also referred to as compressed fit HDPE lining, dates back to the 1970s, when U.K.-based British Gas began the research, development and implementation of many of the trenchless technologies that are in use today. They did so out of necessity to replace and rehabilitate their ageing pipeline systems with the aim of cutting costs and increasing efficiency.
The method of Swagelining specifies an HDPE pipe with an outside diameter larger in size than the inside of the host pipe to be renewed. After the HDPE is butt fused to correspond to the pull distance, the pipe is pulled through a reduction die immediately before entering the host pipe. This reduces the HDPE pipe temporarily below the ID of the host pipe allowing it to be inserted. While the towing load keeps the HDPE under tension during the pull, the pipe remains in its reduced size. The HDPE remains fully elastic throughout the reduction and installation process. After installation, the pulling load is removed. The HDPE pipe naturally expands until it is halted by the inside diameter of the host pipe resulting in a tight compressive fit. The tight fit maximizes the final ID compared to slip lining with a smaller size pipe.
The Big Easy
New Orleans was settled by the French in 1718 on the high ground adjacent to the Mississippi River, only 14 ft above sea level. Many sections of the city are as much as 6 ft below sea level. As a result of its unusual topography, the City was subject to periodic flooding from the Mississippi River and Lake Pontchartrain, as well as frequent inundation from the high intensity rainfall.
Water for drinking or general use was either collected in large cypress cisterns that stored rain water from the roof tops or taken from the river and allowed to settle in large earthenware jars. At this time, there were no purification or sterilization procedures.
The Sewerage and Water Board of New Orleans (S&WB) has been serving citizens and protecting the environment since 1899. Originally formed to combat disease by providing safe drinking water and eliminating the health hazards of open sewer ditches, today the S&WB continues its mission using 21st century technology.
Once formally organized, the S&WB set out to fulfill its goals of providing the city with adequate drainage, sewerage collection, and drinking water. Between 1879 and 1915, $27.5 million was spent on the construction of water, sewerage, and drainage facilities. Such extensive construction was a bold step for a city at that time. The Louisiana Engineering Society, in honor of its 75th anniversary in 1973, selected the water, drainage, and sewerage systems of New Orleans as among the ten most outstanding engineering achievements in the state.
Reducing Customer Impact
With a large replacement program in the works and seeking a solution geared toward reducing customer impact, minimizing capital spending, and reducing operational costs; S&WB selected the Swagelining technology to install new HDPE pipe to replace existing cast iron water transmission mains. Each project has been located in a sensitive urban environment requiring a fast construction completion.
Wallace C. Drennan, a third generation construction company founded in Louisiana in 1953 and Murphy Pipelines, which specializes with the Swagelining technology, were awarded the projects. To date, work has progressed replacing 3,100 ft of 16-in. and 1,800 ft of 30-in. water main.
The 16-in. water main was located on Calhoun Street, adjacent to both Tulane University and Loyola University New Orleans. With a history of water main breaks and some occurring in late summer, S&WB made the decision in early August to replace the 3,100 ft of water main before both Universities started school in September.
“We looked into traditional open cut, directional drill, CIPP, and ultimately Swagelining. After putting all the options on the table and comparing costs, schedule, and the impact to the neighborhood — residents, two universities, and an elementary school all within the project site, we opted to go with Swagelining. Traditional open-cut would have taken several months and cost S&WB a significant amount of more money. This technology allowed the S&WB to replace a deteriorating main quickly and with substantially less inconvenience to the general public — not to mention, saving several hundred thousands of dollars.” Carmelo Gutierrez, P.E., project manager, Wallace C. Drennan
With only a few weeks allotted for the project before the fall semester began, crews mobilized onsite, developed the Swagelining installation plan and using McElroy equipment fused three sections of HDPE pipe for the pull lengths of 1,300, 1,000 and 800 ft. While insertion/receive pits were being excavated, the HDPE lengths were pre-chlorinated. After the pits were shored, Swagelining operations began. Each pull was installed in less than four hours on subsequent days. In addition to replacing the 16-in. main, cross connections, valves and end connections were made. Within a few weeks the project was complete, in time before fall semester began.
The 30-in. water main was located in the Central City District, and one of the main transmission lines that supplies water to the Superdome, Smoothie King Center, downtown New Orleans, and the French Quarter. The 1,800 ft of 30-inch ran down the middle of Magnolia Street through a congested urban residential and business setting, crossing many busy roads. It was imperative to get the line back in service quickly.
“Swagelining, when compared to traditional open-cut replacement, presents a unique opportunity to rehabilitate a large amount of water or sewer main in a very short amount of time. Traditional open-cut excavation would have taken approximately two months to complete this 30-in. project.” says Bart Peak, vice president of operations with Wallace C. Drennan.
The plan was to pull in the entire section of HDPE in one continuous pull to minimize excavations and reduce impact to the residents, business and traffic flow. While installing the HDPE in one continuous pull would optimize the economics and timing of the project, the one challenge was fusing this length of pipe without blocking major roadways. Martin Luther King Jr. Blvd, located four blocks from the Superdome could not be closed to string out the long section of HDPE. To counter this problem, Wallace C. Drennan and Murphy Pipeline crews fused two 900-ft sections of HDPE.
During Swagelining installation, the majority of the first 900 ft was pulled through the swage die and into the existing 30-in. host pipe. As the end of the first HDPE pipe string was nearing the insertion pit, the pull was stopped and the next 900-ft HDPE pipe string was fused on. During this process, the first section of HDPE that already entered the host pipe remained in its reduced state as constant tension pull equipment from TT Technologies was used. Set up and fusion of the second string of HDPE to the first took around two hours. Once the HDPE fusion joint was made, Swagelining operations resumed until the entire length of HDPE pipe was installed. While the Swagelining installation was completed in one day, from mobilization to project completion took 10 working days.
“Reducing customer impact is a top priority for our water and sewer construction projects. Replacing utilities in congested neighborhoods and business districts, coupled with heavy pedestrian and vehicle traffic is challenging. We also have another element with our restaurants, universities, major events, festivals and parades. Each Swagelining project was completed in a few weeks compared to a few months with open cut, which tremendously reduced our customer impact.” Mark Bear Child, S&WB project manager.