The trenchless industry has located a problem. Now, it is inspecting how toeliminate that problem.
Trenchless leaders have identified cross-bores — the result when a newlyinstalled utility pierces an existing utility — as a focal point in discussionsabout damage prevention and liability. Cross-bores that involve a gas lineintersecting a sewer lateral present the highest risk because the possibility ofexplosion poses a serious danger to the public.
These so-called time bombs have already severely injured people and destroyedproperty. However, as much damage as cross-bores have caused, the problem hasbeen slow to gain industry-wide attention. Part of the problem has been a lackof documentation.
When severe damage occurs involving a cross-bore, rarely is any informationrecorded for others in the industry to know about, says Dan Weaklend, seniorofficer of safety and operations support for NPL Construction Co. in Arizona.Cross-bores are not specifically covered by government regulation orlegislation, he says. Therefore incidents go unreported and the data is lost.
“Nobody gathers this information and looks at the big picture,” Weaklendsays. “They’re considered isolated incidents in each of these regions, but whenyou start putting all of this together, there are a lot of them.”
Weaklend, with help from his colleagues at NPL, has spent the past four yearstrying to get the word out about cross-bores. NPL started to crusade againstcross-bores when the contractor was involved with an incident in 2002. Sincethen, the company has created a presentation about cross-bores that it hasdelivered to various industry organizations. NPL has participated with industryleaders to establish best practices, and it has developed in-house procedures toprevent cross-bores in future construction projects. Also, Weaklend has beeninvolved with cross-bore discussions with associations such as NASTT and theCommon Ground Alliance (CGA). The problem, Weaklend says, is that laterals arenot properly located or not marked at all.
Locating and verification play a fundamental role in solving the cross-boreproblem, says Joe Purtell, CUES Inc. software director and a sub-committeechairman on the NASTT Cross-bore Committee. That role must be one of action, headds.
“Everything we do committee-wide can be a lot of great ideas, concepts andwritten words, but unless there’s some substance behind the words nothing isgoing to get done,” Purtell says. “At our level, with the locating andverification sub-committee, we’re the ones charged with the task of findingconcrete solutions that can be deployed and used.”
By using a combination of different pipeline inspection tools and mappingsoftware, sewer laterals can be better located and information about cross-boresbetter recorded.
However, there is some confusion over which party is responsible for keepingtrack of the laterals in the first place. Is it the homeowner, contractor,utility owner or municipality? No one seems to agree on the answer.
In most states, utility owners and municipalities are not legally responsiblefor maintaining laterals or recording the service lines on utility maps, Purtellsays. Often, the matter is seen as the homeowners’ responsibility.
“The finger-pointing begins about who’s liable to maintain the laterals whenthe homeowner doesn’t have the capability to know that they have a problem,”Purtell says. “And the utility is not responsible and could even be subject toinvasion-of-privacy type of rules if they were to trespass [by inspecting thelateral]. It becomes a no man’s land of who’s responsible.”
Homeowners don’t have the expertise or know-how to locate or maintainlaterals that run from their house to the sewer main, Weaklend says. Themunicipalities and utility owners have the maps of where utility lines lay andshould have some responsibility.
In the end, the problem gets dumped on the contractors because theytechnically created the cross-bore with their equipment, Weaklend says. Instead,he suggests that all the parties should work together and share equalresponsibility.
Confronting cross-bores requires a comprehensive plan, says Mark Bruce, CanClay president and chairman of the NASTT Cross-bore Committee. That plan shouldinclude preventive practices to avoid cross-boring a line and a verificationprogram to ensure that a cross-bore did not happen during construction.
Currently, inspection work needs to be done visually, by camera, Bruce says.Newer technologies that don’t use visual inspection to some degree are notreliable enough yet, but he hopes to incorporate those technologies when thereis a higher confidence level and it is cost-effective.
Locators and other utility inspectors have the same interests at stake as theentire trenchless industry, Purtell says. They must help ensure the safety ofthe people in the field and the consumers, as well as keep the industry’sreputation at the highest level.
Confronting cross-bores requires a comprehensive approach, but Purtell says acomprehensive approach also must be used with pipeline inspection methods.
Several solutions exist now for locating sewer laterals and findingcross-bores, Purtell says. A combination of different technologies used as onepresents the best approach. Tools such as GPS, an electro-magnetic sonde andreceiver, lateral camera and GIS mapping software used together can give aprecise line trace within 3-ft or sub-meter accuracy.
“There are some solutions that can be used here and now that revolve aroundGIS, GPS and sonde-equipped cameras,” Purtell says. “If we can at least get somebuy-in from our industry to proceed with these tools at hand now, we couldpotentially save some lives in the near future.”
Implementing these tools as a standard throughout the industry will take somecooperation between the different parties, Purtell says. That cooperation willaid in communicating where sewer laterals are.
“We’d like to propose going forward that folks do things with one levelplaying field and that’s with a GIS software program that is widely recognizedor at least has a common file structure that we can all understand andmanipulate,” Purtell says. “GIS gives us an ability to visually map and seewhere we are at any particular point. The sophistication of GIS and the abilityto track and archive is very useful information for people today. Five yearsfrom now, they’ll be able to look back and see a constantly updated file.”
On the Horizon
In addition to the technology that is already used in some capacity in thetrenchless industry, Purtell says CUES and NASTT are seeking new systems to helpwith location and verification in pipelines. Some newer technologies areavailable, but he says the systems are “not ready for prime-time.”
Systems like geophysical diffraction tomography (GDT) and computer-assistedradar tomography (CART) present some of the more intriguing options, Purtellsays. However, adaptability and expense prevent those technologies from beingused right now in trenchless construction.
GDT generates 3-D imagery below the surface by using an array of antennasthat measure how signals pass through the ground, Purtell says. The technologyhas been around for about seven years. GDT provides measurements fromaboveground.
However, GDT is expensive and considerably large, Purtell says. Departmentsof transportation have used GDT, attaching it to a tractor and taking up morethan one lane of roadway. That kind of size is impractical in confined areaswhere trenchless methods are often used.
CART is based on ground penetrating radar (GPR) and allows the user to inputknown parameters, such as soil composition, to paint a picture of a pipeline,Purtell says. However, the technology is not reliable enough yet to provide anaccurate reading for use in infrastructure management.
Purtell says he is always in search of new technologies to be used forlocating and mapping pipelines and welcomes any suggestions. (Contact Purtell email@example.com)
Locating a Solution
Solving the cross-bore problem comes down to cooperation between all thegroups involved with trenchless construction. That means playing by the samerules using similar methods, industry leaders say. However, it all starts withlocating and keeping track of the sewer laterals.
Municipalities and utility owners don’t generally have good records of wherelaterals are, says Walt Kelly, an underground facility damage preventionconsultant and expert witness in court cases involving underground construction.
“The net result is a utility operator without good records that is expectedto suddenly locate its service laterals simply cannot do it within a two- orthree-day locate time,” Kelly says. “They don’t have the records, and they don’thave a process in place to start finding this stuff.”
The lack of good records could be solved by legislation, Weaklend says,adding that some states, such as Minnesota, have passed laws to regulate betterrecord keeping. However, he says the solution will take teamwork.
“It would be great if all the people involved could sit down at the federallevel or in each state and say, ‘This is the problem. Let’s all throw some chipson the table and solve it and move on,’” Weaklend says. “It is a real problem.People are getting hurt. There’s a tremendous amount of damage, but it’s nottracked because there are no regulatory requirements.”
However, legislation could work against advancing the trenchless industry,Bruce says. If regulations are too specific, the industry could be handcuffed.
“Legislation needs not to be technique specific,” Bruce says. “We need tohave broad solutions and broad statements.”
Legislation is better used to mandate that all parties use best practicesthat the industry itself agrees to and puts forth, Bruce adds. Cooperationbetween all groups involved is vital.
The problem of cross-bores can be solved if the industry starts now and workstogether, Purtell says. Cooperation could be as simple as sharing computer filesabout where utilities are buried.
The effort to solve cross-bores, Weaklend adds, needs leadership from theindustry.
“Someone has to stand up and take charge,” Weaklend says. “They need achampion to deliver the message and work with people to solve the problem.Nothing is insurmountable when people cooperate.”
Bradley Kramer is assistant editor of Trenchless Technology.