Brownwood, TX, is considered a pioneer in municipal trenchless construction because for the past seven years, the city has exclusively used static pipe bursting for sewer main replacements, doing all of the work with its own municipal maintenance staff and machinery.
This municipality was also the first to use CertaFlo Greenline, a segmented, restrained-joint PVC pipe designed specifically for trenchless sewer projects.
CertaFlo Greenline is made by North American Specialty Products LLC (NASP), part of the North American Pipe Corporation group. Brownwood has since installed more than eight miles of this product. When NASP developed StraightShot, the industry’s first restrained-joint PVC pipe to offer a smooth, consistent outside and inside diameter, it was no surprise that the city of Brownwood was the first municipality contacted about a test installation.
“We wanted our first real-life installation of StraightShot to be done by a crew that had ample experience in static pipe bursting with our pipe products,” said Robert Eads, regional sales manager for NASP. “Having worked with our pipe as much as they have, they are a well-seasoned crew that knows our products well.”
Featuring NASP’s field-proven Certa-Lok restrained-joint technology, StraightShot offers a smooth, flush pipe joint without the need for the costly, time-consuming process required to connect other types of pipe. StraightShot provides an ideal solution for guided boring and gravity sewer projects where precise grading is critical and can also be used in sliplining and microtunneling applications.
When presented with the opportunity for his crew to be the first to install the groundbreaking product, David Harris, director of utilities for the city of Brownwood, eagerly accepted.
“A lot of municipalities and contractors might be uneasy seeing the word “trial” stamped on a pipe product and knowing that they would be the first to install it but, due to the success we’ve had with the CertaFlo product, I wasn’t worried about it,” Harris said. “Plus, I was able to compare a sample section of StraightShot with CertaFlo beforehand and that added to my confidence.”
The city found a section of six-inch gravity-fed clay sewer main due for replacement and ordered eight-inch StraightShot pipe from NASP for the trial installation. Using its TT Technologies Grundoburst 800G static pipe bursting system, the 10-person crew was able to complete the 440-foot sewer main burst within two hours, despite light rain.
The pipe came in three meter (approximately 10-feet) joints and was lowered into the confined launch pit to be added to the pipe string as pullback continued. To further simplify the pipe assembly process, the crew laid an eight-inch-wide steel I-beam on the bottom of the pit and slid the pipe joints along its groove until the joints butted up against one another. This helped line up the pipe correctly and keep gravel and dirt out of the gaskets. Once two joints were flush, the crew inserted a spline by hand to lock them into place.
Reaping the benefits
During the installation, Harris and his crew saw a variety of advantages with the new pipe. The three-meter joints were perfect for smaller pits and the splines were easily inserted without the use of any tools. Most important, the flush-joint connections served their purpose.
“Since it doesn’t have couplings or a bell, there’s less friction loss and the pipe doesn’t catch on anything when you’re dragging it through the remnants of the host pipe,” Harris said. “It’s a much smoother insertion. The flush joints also allow you to get full pipe capacity with a smaller expanding head.”
The crew also noticed that the new product’s wall thickness was greater than other pipe of the same diameter, making it a great choice for this particular installation.
“This sewer main runs in front of a fire station, with heavy fire trucks driving over it daily,” Harris said. “If a thinner-walled pipe is installed at a shallow depth in such a location, surface pressures will become an issue. The extra wall thickness of this pipe gives it the strength needed to resist this pressure.”
Overall, Harris was pleased with how efficiently the new pipe installed and can see the advantages of using it in future projects