Pipe Bursting Proves Successful at California GM Plant 

by Jim Schill

Ask just about any good business and they will tell you that time is money. General Motors is a good business and they know all too well the value of time. So when Al Brown, facility engineer at the Advanced Technology Vehicles Division of GM in Torrance, California, realized that something was drastically wrong with the company's sewer system, the potential for disruption of the plant and loss of man hours did not sit well.

The Advanced Technology Vehicles Division in Torrance is a 172,000 square foot research and design facility. It has the capability to produce engineering quantities of actual product. The Torrance facility produced the first electric car built from the ground up. The plant's 180 employees work on everything from specs and design to actual product testing. The loss of even one day or a major disruption at the plant would be very costly.

Problems with the plant's sewer system had been going on for quite some time. GM purchased the building in September of 1991. Back then, calls to the local sewer and drain service happened once a year. Over the next few years the frequency increased from once a year to once every six months, eventually to every three or four weeks. Restroom facilities were backing up. Sometimes blockages were caught early enough to prevent damage. Other times they were not so lucky.

Brown knew that something needed to be done. In November of 1996, a video was shot of the plant's 4 inch VCP sewer. Using a small fiber optic camera, a drainage contractor was able to look inside the pipe. At that time, the pipe was getting to a point where replacement was warranted. A year later when a second video was taken, it was determined that the pipe would have to be replaced. The video revealed tree roots, blockage and a deteriorating pipe that would not last much longer. The video also showed severe pipe displacement that Brown attributes to seismic activity over the years. "After all," Brown says, "it's California."

A coffee room was the scene of one of the last encounters with the failing sewer pipe in the fall of 1997. According to Brown, the coffee room was originally a small restroom with a commode and a sink. It was later converted into a coffee room. One afternoon, an employee noticed that the coffee he had just poured into the sink was not going down the drain. In fact, it was backing up. The employee also noticed that there was a considerable amount of water around the base of one of the cabinets in the room. The lateral sewer line was completely blocked.

Replacing a pipe in that situation is no small task, but there are options that can reduce the enormity of such a project. The existing 4 inch VCP sewer needed to be replaced with a 6 inch polyethylene pipe. The new pipe had to be 330 feet long with 5 service lines. A 330 foot trench through the plant was not feasible. A trenching application would necessitate a completely different route for the pipe, besides, the idea did not appeal very much to Brown. After some consideration with their facility plumber, Doty Bros. Equipment Company of Norwalk, California, was contacted.

After doing a cost and site analysis, Doty Bros. project manager Bernie Monette and Al Brown decided to use a trenchless applicationpipe bursting. The pipe bursting process has become a popular method of pipe rehab. It effectively displaces a fracturable host pipe, while simultaneously guiding in a replacement pipe. In this particular case, a pipe bursting job would keep disturbance around the plant to a minimum and let the replacement pipe follow the same path as the old pipe. It would also allow the job to be completed within the plant's small window of opportunity (December 24 - January 5) and maybe most importantly, cost about 50% less than a trenching job.

Torrance is a suburb of Los Angeles. Located just a few miles from the Pacific Ocean, the soil is loamy clay, very soft and silty and some of the area is just plain sand. Monette was thankful that they did not run into any seriously sandy conditions on this job. What they did run into was extremely tight working conditions. The layout of the plant resembles a letter "L" rotated clockwise 90 degrees (see diagram). Throughout the 330 foot run, the Doty Brothers crew needed to avoid Melaleucas trees, the parking lot, medians and landscaping obstacles.

Monette planned to pull the pipe into the short corner of the "L", around the trees, into the launch pit and underground, 7 to 11 feet deep. The pipe would then travel the length of the building, to the exit pit where the pipe would be attached to the sewer main 25 feet underground. An HDPE replacement pipe, teamed with a pneumatic pipe bursting tool, was the perfect choice for working in such tight quarters.

Before the project could even begin, it needed approval from Torrance's Building and Safety Department. Senior plumbing inspector Jon McClannahan was familiar with the pipe bursting method, however the 1994 Uniform Plumbing Code did not have any specific language regarding the pipe bursting process. After receiving written materials, including job specifications, from Doty Bros. and GM, the plan was approved under section 301.2 of the Uniform Plumbing Code.

McClannahan explains, "That section covers new and alternative methods and materials. While there is nothing specifically related to pipe bursting in the code, this provision allows for the use of new types of technology. We certainly do not want to inhibit the advancement of technology or the use of that technology by certified and qualified individuals."

After the city's approval, Monette consulted the gas and electric utility associations to make sure they would not encounter any surprises. With the help of Brown, Monette and his crew identified the location of the sewer pipe, as well as launch and exit pits. The project was now underway.

After small launch and exit pits were dug, the actual pipe burst was a breeze. The Doty Bros. crew used a Grundocrack PCF 145 5.7 inch diameter pneumatic pipe bursting tool from TT Technologies of Aurora, Illinois. The Grundocrack was guided along the 330 foot burst by a 10-ton, constant-tension Grundowinch, also from TT Technologies. This type of winch supplies hydrostatic constant tension to ensure that a constant speed is maintained no matter what the pipe bursting tool encounters while traveling through the old host pipe.

The actual burst at the GM plant took a mere six hours. The new 6-inch SDR 17 HDPE pipe easily made all corner bends and went in without a hitch. The new pipe was connected to a chimney drop into the main sewer line 25 feet underground. The blocked lateral from the coffee room in the plant was eventually cleared. According to Brown, when the line was flushed, a host of interesting items vacated, including years of coffee grounds and a 4-foot-long tree root.

The new pipe needed to pass a water test after it was installed. According to McClannahan, the test is designed to check the integrity of the new pipe and the integrity of the lateral joints. The pipe is capped and then filled with water. After it's filled, it must maintain a constant level of water. This ensures that there are no leaks and that the lateral joints are also leak free. The new pipe passed without a problem.

The Doty Bros. crew had been working with TT product specialist Collins Orton for some time and had successfully completed four other pipe bursts with the Grundocrack system before this one. Monette, who has been in the pipeline rehab business for 20 years, says the technology is impressive as well as cost efficient.

McClannahan was impressed by the project as well and says pipe bursting and other trenchless applications look to be the wave of the future, especially for public entities that deal with water and sewer lines on a regular basis.

After the pipe passed the tests, the launch pits were refilled and the plant was operational by the January 5 deadline. Al Brown received a letter of commendation on the project from GM and was happy to be part of another pipe bursting success story.

Cleaner, May 1998