Pipe diameter, condition, depth, length, new pipe diameter, soil conditions, and service connections dictate whether pipe bursting is appropriate for rehabilitating a failed line. Photos: Vermeer Corp.
More departments are requiring contractors to bid rehab and new infrastructure projects based on using trenchless methods.
The patents on some aspects of some trenchless techniques have expired, opening up these markets to more contractors and giving infrastructure managers more options for less-disruptive utility improvements. With greater opportunity, however, comes greater potential exposure.
“As an industry, we've done a pretty good job educating people about alternatives,” says Gerry Muenchmeyer, PE, technical director for the National Association of Sewer Service Companies and principal of Muenchmeyer Associates. “What we haven't done is educate people who are responsible for determining if a quality product has been installed.”
If you've successfully specified a particular technique in the past, the task is relatively straightforward. If state rules allow it, you may even be able to offer the bid to a select group of contractors, in effect exercising a pre-screening process. Or you can learn from managers who've learned the hard way.
Overland Park, Kan., Right-of-Way Coordinator Murv Morehead says that bids for the city's utility installations sometimes are written on a performance basis in which the bid specifies the expected result of the project but leaves implementation in the contractor's hands.
“We don't force contractors to use a specific method, but we do reserve the right to encourage them to look at alternatives to open-cut, especially if digging up a street is involved,” Morehead says. “We can withhold the permit until we're convinced that the contractor has done due diligence and has proved to us why there's no other method available than open-cut.”
Some departments write bids specifying only that the project be done “by a means other than open-cut” without actually selecting the technique, according to Ray Sterling, PE, director of the Trenchless Technology Center at Louisiana Tech University.
“If you approach bidding in this way, you must be in a position to approve the method that you allow to be used, and you must have a consistent design basis for the various methods approved,” he says. The department also must have established quality control procedures and a method for asses sing the experience level of contractors.
Quality control was Overland Park's impetus for developing the Horizontal Directional Drilling Guidelines Handbook that outlines expectations for items like jobsite safety, calibration of tracking equipment, and containment of drilling fluid. The International Pipe Bursting Association also offers detailed specification guidelines for classifying project difficulty, assessing contractor experience, and controlling various aspects of the process.
The National Association of Sewer Service Companies' Muenchmeyer recommends writing specifications “at a high level for quality control and inspection in the field.” If they're silent regarding inspection and testing, your authority may be significantly impaired.
Large projects may require more than one trenchless method as well as sections of open-cut. While Roselle, Ill., uses horizontal directional drilling (HDD), coupled with other methods, for certain aspects of water-system maintenance and installation of streetlight cable, Public Works Director Rob Burns points out that open cutting is still sometimes the most viable option. The point is to avoid the assumption that a 14-foot backhoe solves every sewer or water problem.