Emergency Situation: New Sewer Line Needed Stat

Texas contractor installs new sewer line at hospital using a static pipe bursting system in just three weeks.

Emergency Situation: New Sewer Line Needed Stat

John Newell, owner of No-DigTec in Dallas, stands next to his company’s New Holland backhoe loader.

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No-DigTec has tackled challenging jobs throughout its history, but one job in fall 2003 proved to be unusually more challenging for the contractor.

The Dallas-based contractor was hired to replace 200 feet of a collapsed 6-inch sewer line running underneath the Children’s Medical Center of Dallas.

Faced with a tight workspace and deadline, No-DigTec decided to tackle the job using pipe bursting. Crews finished the work in just three weeks.

TIGHT SPACE AND TIME

The main challenge was accessibility; the hospital’s central outdoor courtyard offered the best access to the collapsed line, but its tight, narrow confines made it impossible to bring in conventional heavy equipment — except by helicopter, which wasn’t an option because of the intense noise it would generate. Fortunately, crews were able to hand-carry No-DigTec’s lightweight, collapsible and portable equipment into the courtyard.

But the project took on added drama because in one month (Oct. 12, to be exact), craniofacial surgeons at the hospital were scheduled to separate conjoined, 2-year-old Egyptian twins Ahmed and Mohamed Ibrahim. The high-profile operation was attracting worldwide attention, and a press conference to update a large media contingent was going to be held in the same courtyard where the work was occurring.

The short timeline required No-DigTec crews to work around the clock for weeks. Crews first removed the courtyard landscaping, then hand-dug two 20-foot-deep pits in heavily compacted soil because there was no way to bring in excavation equipment. Furthermore, the pits required shoring, which took even more time. And because there was no room for an excavator, workers had to instead build a gantry to hold a 1-ton electric lift that removed soil from the pit as workers dug deeper and deeper, Newell explains.

“It was a very labor-intensive process,” says John Newell, the owner of the company. “On a stress scale from one to 10, this job was every bit an eight or a nine. There was nothing easy about it. But we got it done.”

BURSTING THE PIPE

No-DigTec used a static pipe bursting system from HammerHead Trenchless that was lowered into the pit via the electric lift. The static system was used because it can punch a length of interconnected metal rods through collapsed lines. Then those rods get connected to an expander head on the other end of the project. The rig then uses the rods to pull the expander head — with the new pipe connected to it — back through the space vacated by the fractured host pipe.

No-DigTec does both pneumatic and static pipe bursting. The former method is used primarily for replacing gravity-feed pipes and the latter mainly for replacing pressurized pipes. Pneumatic bursting relies on a percussion hammer action to help the expander head break the host pipe. A winch located at ground level maintains constant tension on the bursting head via a thick metal cable. In static pipe bursting, a downhole unit pulls the expander head through the host pipe with a series of interconnected rods. 

Pipe bursting offers many advantages compared to open-cut installations. First and foremost, the new pipe follows the path of the host pipe, so there’s rarely a problem with hitting other kinds of lines. Other advantages include:

  • About 85 percent less excavation required. (The process still requires some excavation — an insertion pit on one end and a receiving pit on the other, plus pits for service reconnections.)
  • Significantly faster and more cost-effective installations.
  • Minimal chance of damage to landscapes and things such as trees, patios, buildings and so forth.
  • The ability to upsize pipes for additional flow capacity, sometimes up to five times larger than the host pipe’s diameter.
  • No long-term lane/road closures.
  • Less carbon dioxide emissions from excavation equipment and hauling materials.

PROJECT COMPLETED

The project took three weeks to complete, and workers finished about one week before the 34-hour-long surgery took place, Newell says. Both operations were a complete success. 



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