Preventing damage to underground utility infrastructure is a priority for utility operators and contractors who excavate, drill and bore in areas where there are existing utilities.
Even so, accidental strikes of underground utility lines continue to interrupt essential services, cause millions of dollars in damage every year, result in serious injuries and sometimes loss of life.
As utility easements become more crowded, preventing damage to underground facilities has become increasingly challenging.
Typically, utility locates are initiated through the nation’s one-call system. Local one-call agencies notify member utility owners who are responsible for marking locations of their pipe or cable on construction sites, either with their own personnel or contract locating companies.
However, there are instances where one-call locates cannot be made, leaving the responsibility to project owners, planners and often the contractor who will do the project.
During the Damage Prevention & Safety Program at the 2011 UCT show last January, Kevin Miller, president of Miller Pipeline LLC., conducted a session about circumstances when contractors may need to make underground utility locates.
Miller said the primary driver for contractors to do their own locates is to identify unmarked sewer laterals in order to prevent crossbores — drilling through an unmarked lateral while installing gas lines or power cable by horizontal directional drilling.
Only occasionally do Miller Pipeline crews need to do locates on projects not related to crossbores, such as when working in areas where the utilities belong to property owners that don’t utilize the one-call system.
“Examples might be a large factory, commercial complexes or mobile home parks,” he said. “The contractor may face the need either to locate the existing utilities or hire a third party to locate and mark them. Some contract locating companies that serve the utilities will also make locates for contractors in these situations. Pricing for this type of work usually is done on an hourly basis, instead of lump sum per locate as it is for their big utility clients. If the job requires that utilities be accurately marked within the 24-inch ‘window’ accepted as a standard by One-
Call, most of these contractors will do a good job. There also are smaller locating specialists who do not serve one-call utilities, but who will make private locates.”
Miller stated that all Miller Pipeline crews are equipped with electromagnetic locators, the industry’s basic locating tool.
“We have the ability to locate some utilities, particularly gas lines, as several of our gas distribution contracts require us to locate the customers’ facilities,” said Miller “but locating other types of utilities happens only on rare occasions. If we are digging on private property, we will try to locate water lines or small electric lines running to a barn or outbuilding, as the cost of making such locates and the consequences of missing them are not too significant. However, if the job is near anything dangerous, such as a primary or secondary power line, high-pressure lines of any type, or critical communication lines, we would hire a locator.”
For larger projects, such as bringing gas to a trailer park, the gas company probably would pay for the cost of necessary locates, and blanket contracts usually cover the cost of any locates that have to be made.
Locates to prevent crossbores of sewer laterals is another story.
“The debate continues over whether laterals are the responsibility of the utility or the property owner,” said Miller. “With most utilities taking the position that laterals belong to property owners, the locating responsibility ultimately falls on the contractor crew doing the project.”
In its work across the United States, Miller Pipeline has found no sewer system owners that provide accurate sewer lateral locates.
To make sure company crews do not inadvertently bore through a sewer lateral, Miller Pipeline personnel do their own lateral locates and inspections using several methods.
The basic procedure is to send a crew with a sewer camera to the job site before directional drilling begins. The two-man crew will operate the sewer camera via a remote-controlled tractor lowered into the sewer main which then tracks down the sewer, allowing inspection of sewer-lateral connections.
The process is expensive.
“Cost of equipment can be more than $100,000 per crew, significant training is required and the electronic equipment needs constant maintenance,” Miller said. “There are not many third-party companies that offer this service, so we have taken on the responsibility.”
An alternative is to send an employee to each house in a project area to search for sewer clean outs. A fiberglass push rod with a locating beacon is pushed into the lateral, allowing crews to locate the sewer line all the way to the street, using a walk-over locator.
“If clean-outs can’t be found,” Miller said, “we try to gain entry to the house and research the actual location where the sewer lateral leaves the building. Special tools can be inserted into the lateral from the house, allowing contractor personnel to find the lateral in the yard. In some cases we are able to determine from site investigations that the laterals will not be in conflict with our bore path; for example, the line may come out of a basement at an eight-foot depth, or it exits at the back of the house to a sewer main in an alley, instead of in front where the drilling is taking place. Tooling can be acquired for less than $10,000, and training necessary for this method is minimal.”
The cost to locate or inspect a lateral depends on several factors, with the average between $100 and $200 per locate, said Miller. Making locates can add $2 to $4 per linear foot to the cost of a project. In addition, some companies now require locates of sewer laterals on all of their projects, and some require post-installation inspections to confirm no damage or crossbore has occurred.
All parties agree that crossbores pose a serious safety issue, but exactly how to avoid them remains a controversy with no immediate prospects for resolution. Few would disagree that accurately locating and marking existing sewer laterals is a key element in preventing crossbores.
Miller believes that the industry recognizes the need to investigate sewer laterals before directional drilling. If all utilities would start requiring their drilling contractors to have laterals located, it will become a common practice, and companies will come to the market that will provide this service in a cost effective manner.
“In the meantime,” he concluded, “Miller Pipeline is taking steps to avoid crossbores. At the end of every work day we want each crew to leave the job without having damaged any utilities and without anyone being hurt.”
FOR MORE INFO:
Miller Pipeline Corp., (800) 428-3742, www.millerpipeline.com