Pipe-bursting work 8 feet below ground on S. 21st
To those driving by, the Colorado Springs Utilities project on South 21st Street is a continuing obstacle, with occasional stoppages because of construction equipment
on the roadway. In that regard, the good news is that completion is still slated for mid-December.
What most people can't see - and which will be covered with eight feet of dirt and pavement when work is done between Lower Gold Camp Road and Villa de Mesa Drive - is a modern water-line replacement process that actually is saving Utilities customers money.
According to Kristin Flannery, part of the city enterprise's issues management group, the process is called “pipe-bursting,” in which a pipe can replace one of smaller diameter without having to dig the old one out. Although she did not have the specific costs for the 21st Street work (it's part of an ongoing multi-million-dollar Utilities water-main replacement program), she said that typically, based on national averages, pipe-bursting “can save 50 to 75 percent in total construction costs.”
The contractor on the 21st Street work is Global Underground, an international company based in Colorado Springs.
The 21st Street bursting work is occurring in three “pulls,” according to Mike Lovato, a construction maintenance specialist with Utilities who is serving as project supervisor. This is requiring the digging of four trenches, one at each end of the line-replacement area and two in the middle. The longest of these pulls, accomplished this week between trenches across from Patsy's and Skyway Lane, respectively, was 670 feet, he said. The entire length of all three pulls will be 1,500 feet.
In each trench, a hole is being dug to expose the old line, a 16-inch-diameter ductile iron pipe. The new 20-inch pipe is made of a more modern material, high density polyethylene (HDPE), which is slightly more flexible and thus more impervious to line breaks than the ductile, Lovato said.
The hope is that the HDPE can last up to 100 years, he added. The ductile pipe was installed 42 years ago, and has suffered frequent line breaks in recent years.
Adding to the HDPE's strength is that it's several inches thick, so that the actual flow through it will be the same as the 16-inch it's replacing, he said. Also, a special heat process is used in fusing each segment of the HDPE together so that units that have been fused together are actually stronger than unbroken sections, Lovato said.
The only uncertainty about HDPE is that it has not been around long enough to truly know how long it can last. Colorado Springs Utilities has only been using that material for a few years, although it has been used in the industry for 20 years or so, according to one of the workers on the site.
In the bursting process, the new pipe is fed behind a steel head which is lubricated and pulled through - bursting the old pipe as it goes - behind connected 700-pound rods controlled by powerful machinery at 22,000 pounds per square inch (PSI).
Asked to illustrate that amount of force, Lovato said, “Imagine a fire hydrant running water through a fire hose at full power, which produces only 120 psi. So 22,000 psi is the equivalent of approximately 180 fire hoses flowing at the same time.”
The 21st Street work started in September. The project is actually installing two lines in place of the old one. Phase 1, completed in November put in a new 12-inch- wide service line for the 14 businesses along that part of 21st. The 20-inch pipe will be a transmission line only.
Westside Pioneer article