I & I Background In the United States during the 70s and 80s, billions of dollars worth of water treatment plants were built to solve discharge problems. However, those plants only add treatment capacity. It was soon realized that despite this additional capacity, the plants were still filling up with water they were unable to treat. In many cases, building a treatment plant is just a band-aid. Failing sewer pipes and improperly configured sump pumps and downspouts are to blame for unbelievable amounts of groundwater and stormwater entering sewer systems and treatment plants. Treating water that does not need treatment is not only costly, it pushes treat facilities to their limits and can cause back-ups and ultimately environmental hazards. Civil engineers are now looking upstream to solve their treatment problems. TT Technologies pipe bursting specialist Collins Orton said, "They’re replacing big diameter and small diameter mains. Eventually they’re going to work all the way back to the house. One of the most efficient methods to replace and upsize these lines is pipe bursting."
Contractor Background J. Fletcher Creamer and Son has a long and distinguished history as a multifaceted contractor. Over the last 75 years the company developed into one of the most respected contractors in the United States. With over 1,100 employees and offices throughout the country, J. Fletcher Creamer has developed a reputation for dependability, progressiveness and innovation. One area in particular that demonstrates the company’s progressive nature is the use of new technologies. According to California based Area Manager George Mallakis, J. Fletcher Creamer and Son has been on the forefront of new construction equipment and methods throughout its history. He said, "Creamer has always been a leader in new technology, specifically trenchless technology. We have been employing trenchless methods like cleaning and cement mortar lining, epoxy lining, sliplining jacking, boring, pipe ramming and directional drilling from their onset." For the project in Ojai Valley, the method of choice was pipe bursting, another trenchless method Creamer has a great deal of experience with. The scope of the project and a tight timeline tested the Creamer crews and their bursting equipment.
Bursting Background Pipe bursting was developed in Europe from the concepts found in pneumatic piercing tools. These tools have been widely used since the 1960s. Orton explained, "In the late 1970s German and British contractors tried using piercing tools to break cast iron pipe and pull in new pipe. In Europe at that time, there was a great need for trenchless pipe replacement, specifically for cast iron pipe in the gas industry. The results of those early experiments eventually evolved into pipe bursting as we know it today." While static pipe bursting equipment is common, a majority of pipe bursting done in the United States is done with pneumatic tools. During pneumatic pipe bursting, the pipe bursting tool is guided through a fracturable host pipe by a constant tension winch. As the tool travels through the pipe, its percussive action effectively breaks apart the old pipe and displaces the fragments into the surrounding soil. Depending on the specific situation, the tool is equipped with an expander that displaces the host pipe fragments and makes room for the new pipe. As the tool makes its way through the host pipe, it simultaneously pulls in the new pipe, usually High Density Polyethylene pipe (HDPE). In the early 1980s, the pneumatic pipe bursting tools were straight barrel, reversible. Once a run was completed, the expander was removed through the manhole and the tool reversed out through the newly installed pipe. Today most pneumatic pipe bursting is done with rear expander configured tools. With the use of expanders, one tool can be used to burst several different size host pipes and replace them with new HDPE of the same size or larger. Pipe bursting is the only trenchless method of rehabilitation and replacement that allows for the upsizing of the existing pipe. According to Mallakis pipe bursting is really emerging as an important rehabilitation technology. He said, "Pipe bursting is definitely becoming more known among the utilities as a trenchless option to replace failing infrastructure. But more important than just replace, is the upsize, taking a existing line and replacing it with a larger one."
Ojai Valley Project The Ojai Valley Project included bursting approximately 5,400 lf of 6-inch and 8-inch VCP and replacing it with 8-inch HDPE. Mallakis chose an 8.5-inch diameter Grundocrack Hercules with a 10.8-inch rear expander for the job. Under a tight deadline, Creamer crews needed to achieve a high level of production in order to stay on schedule. According to Orton the Creamer pipe bursting crews were a model of pipe bursting efficiency. He said, "The crews were extremely well organized. Launch and exit pits were strategically positioned and dug for easy access and minimal disruption. They really approached this project as a high production job. Once a burst was completed, crews set to work tying services laterals back, while another started the next run. Very efficient." Pipe bursting runs averaged between 400 and 500 feet in length in mostly residential areas. Bursting times were greatly affected by soil conditions. Creamer crews encountered saturated soils, heavy with groundwater, in certain locations. Other areas contained dense, compacted cobble. In order to create the least amount of disruption possible, Creamer crews committed themselves to restoring service connections within a single day. Mallakis said, "We needed to tie in house laterals quickly because we decided not to bypass pump over night. We had a tight schedule to keep, so we worked each day until every lateral was tied back in. It also affected the way we divided up the bursting runs. We had to work in manageable lengths so we could each section within a day’s time." Throughout the 5,400 lf of pipe bursting, Creamer crews replaced over 80 service laterals with electro-fusion couplings. Results The Ojai Valley project was completely successfully within the specified time frame. Mallakis said, "Everyone was really pleased with the results of the project. The residents were extremely pleased about the project and even more when they learned its trenchless aspect. It all boils down to really good planning, an experienced crew and good tools." Equipment Today,
May 2002
|
