Accidental strikes of underground utility lines continue to interrupt essential services, cause millions of dollars in damage, result in serious injuries, and in some cases, loss of life. And as utility easements become more crowded, preventing damage to underground facilities has become increasingly challenging.
"Protecting our buried utilities is of critical importance," says Scott Pollman, a member of the board of Common Ground Alliance (CGA), a private, non-profit organization dedicated to addressing issues to prevent damage to the nation's underground utility infrastructure. Pollman is manager of Subsite electronics.
"Utility damage prevention," continues Pollman, "is a responsibility that involves many diverse public and private organizations, making communication and cooperation essential to reduce the number of underground utility strikes."
The first step in preventing damage to buried facilities is to accurately locate and mark all utilities in a work area before construction. This process is initiated with a call to the local one-call center, providing the exact location of the work site and requesting locates be made. The call must be placed at least 48 hours before work is scheduled to begin. The one-call center then contacts appropriate utility providers, who then locate and accurately mark positions of their buried lines. Some utilities use their own personnel; others employ contract locating specialists.
The next step is "Potholing"--physically uncovering a buried utility to confirm its location--is the surest method of determining its exact position. Because of accelerated efforts to prevent damage to buried utilities, potholing is becoming a standard practice on a growing number of utility jobs. Government agencies are adopting regulations that require potholing, and project owners and contractors are establishing their own policies specifying potholing before excavation or directional drilling begins. The procedure isn't new.
But until recently, potholes were dug with backhoes, and even skilled operators always ran the risk of hitting and damaging the pipe or cable they were attempting to locate. "Soft" excavation has changed all that.
Portable vacuum excavators use high-pressure water or air to quickly dig small, precisely-controlled potholes to uncover buried utilities.
A vacuum excavator uncovers buried pipe or cable without the risk of damage inherent with a backhoe, excavator, or other mechanical tool.
For many utilities and contractors, potholing is standard procedure on horizontal directional drilling projects when the path of a planned pilot bore either crosses or is in close proximity to buried lines.
Careful project planning plays an important role and is another step in damage-prevention efforts. Utility projects today are extremely complex and incorporate many different elements. A comprehensive project plan includes safety and damage-prevention provisions, and segments of projects employing specialized construction techniques such as directional drilling require individual attention.
One of the most significant advances in HDD technology is development of planning-mapping software that works in conjunction with a drill unit's electronic tracking system. Planning-mapping capabilities give HDD crews a powerful damage-prevention tool. The computer plans a bore path to avoid all buried obstacles and, during drilling, allows the drill unit operator to compare the actual path to the planned one, allowing immediate correction if there is any deviation.
To plan a bore, information including bore length and depth, surface terrain, subsurface conditions, and underground and surface obstacles are entered into the computer. The drilling data is stored and can be used to prepare as-drilled maps of completed installations, providing a valuable records of the utilities.
Pollman says CGA efforts focus on implementing best-practice procedures identified in the Common Ground Best Practices Study, recognized as the most effective guidelines yet developed for preventing damage to underground facilities, and one of CGA's primary roles is coordinating information and communications among the various organizations involved in building, maintaining, and operating the utility infrastructure.
"CGA," says Pollman, "encourages the shared responsibility of utility damage prevention and helps achieve this by refining and disseminating best practice recommendations, developing public awareness through educational programs, supporting appropriate research, and serving as an information clearing house."
A "Dig Safely" public awareness campaign, including a damage-prevention brochure and video, is in progress to make construction personnel and the general public aware of the importance of notifying one-call centers before construction begins. More information on CGA programs is available on the CGA web site.
DAMAGE PREVENTION
Construction professionals understand the importance of not damaging buried utilities while performing any type of new construction and maintenance work.
Even so, accidental strikes of underground utility lines continue to interrupt essential services, because millions of dollars in damage, result in serious injuries, and in some cases, loss of life. And as utility easements become more crowded, preventing damage to underground facilities has become increasingly challenging.
"Protecting our buried utilities is of critical importance," says Scott Pollman, a charter member of the board of Common Ground Alliance (CGA), a private organization dedicated to addressing issues to prevent damage to the nation's underground utility infrastructure. Pollman is the Director of Product Planning at The Charles Machine Works, Inc., manufacturer of Subsite Electronics.
"Utility damage prevention," continues Pollman, "is a responsibility that involves many diverse public and private organizations, making communication and cooperation essential to reduce the number of underground utility strikes."
Locating Is The First Step
The first step in preventing damage to buried facilities is to accurately locate and mark all utilities in a work area before construction. This process is initiated with a call to the local one-call center, providing the exact location of the work site and requesting locates be made. The call must be placed at least 48 hours before work is scheduled to begin.
The one-call center then contacts appropriate utility providers, who then locate and accurately mark positions of their buried lines. Some utilities use their own personnel; others employ contract locating specialists.
The basic tool used by locating personnel is the electronic locator, says John Bieberdorf, product manager over Subsite Electronics.
"One of our locator products," says Bieberdorf, "is the Subsite Electronics 950 R/T locator package. It is designed to help make locating buried cable and pipe easier and to provide more accurate results."
The 950 R/T system consists of a lightweight hand-held receiver and compact transmitter unit.
"The 950 Receiver," explains Bieberdorf, "uses different frequencies and modes to find locations of different types of utilities by detecting magnetic fields created by electrical current passing through the lines."
In some situations, the receiving unit is all that is necessary to locate electrical and television cable signals. To find telephone cable and metallic pipe, the 950 Transmitter unit is connected to cable or pipe and a current is sent through the line, creating a signal that is detected by the receiver.
For PVC pipe with tracer wire, the wire is energized by the transmitter to provide a signal that the receiver can read.
The receiver processes information and displays an estimate of depth and other data on an easy-to-read screen.
Bieberdorf says that some utilities also mark positions of buried facilities with 3M electronic markers which are buried with pipe or cable. Markers are passive resonate circuits with no internal power source to run down; their polyethylene shells are impervious to minerals, chemicals, and temperature extremes. They are located using a Subsite 950 Receiver equipped with an Electronic Marker Locator (EML) attachment that transmits a signal to the buried marker which resonates it back to the EML. Markers, Subsite locators, and EML attachments are available at Subsite dealerships.
Bieberdorf says that "Ground-penetrating radar technology also has been adapted for utility locating purposes. One of our new Subsite products is the 2150 GR Radar and can be used to detect and locate both metallic and non-metallic pipes and cables, but the method is dependant on soil conditions and antenna selection. Radar products are not effective in all types of soils, but can be helpful in locating some previously unknown facilities."
Potholing
"Potholing"—physically uncovering a buried utility to confirm its location—is the surest method of determining its exact position. Because of accelerated efforts to prevent damage to buried utilities, potholing is becoming a standard practice on a growing number of utility jobs. Government agencies are adopting regulations that require potholing, and project owners and contractors are establishing their own policies specifying potholing before excavation or directional drilling begins.
The procedure isn't new.
But until recently, potholes were dug with backhoes, and even skilled operators always ran the risk of hitting and damaging the pipe or cable they were attempting to locate.
"Soft" excavation has changed all that.
Portable vacuum excavators use high-pressure water or air to quickly dig small, precisely-controlled potholes to uncover buried utilities.
A vacuum excavator uncovers buried pipe or cable without the risk of damage inherent with a backhoe, excavator, or other mechanical tool.
"Vacuum excavators," says Smith, "are capable of digging much deeper, but utility potholes seldom need to be more than six feet deep. The vacuum function of the dual-purpose machine picks up soil displaced during excavation to use later as fill or to be removed from the job site. Soft excavation causes less surface damage and reduces disruption of traffic and other surface activities. The small excavation is easier, faster, and less expensive to repair."
For many utilities and contractors, potholing is standard procedure on horizontal directional drilling projects when the path of a planned pilot bore either crosses or is in close proximity to buried lines.
"A vacuum excavator's usefulness isn't limited to HDD operations," adds Smith. "It is the ideal tool any time a small, carefully-controlled excavation is necessary. Vacuum excavators also are used to clean up drilling fluids that escape from bore holes during drilling, backreaming, and product installation and can be used as a powerful, portable vacuum for just about any type of clean-up need."
Project Planning
Careful project planning plays an important role in damage-prevention efforts.
Utility projects today are extremely complex and incorporate many different elements. A comprehensive project plan includes safety and damage-prevention provisions, and segments of projects employing specialized construction techniques such as directional drilling require individual attention.
Focus on Best Practices
Pollman says CGA efforts focus on implementing best-practice procedures identified in the Common Ground Best Practices Study, recognized as the most effective guidelines yet developed for preventing damage to underground facilities, and one of CGA's primary roles is coordinating information and communications among the various organizations involved in building, maintaining, and operating the utility infrastructure.
"CGA," says Pollman, "encourages the shared responsibility of utility damage prevention and helps achieve this by refining and disseminating best practice recommendations, developing public awareness through educational programs, supporting appropriate research, and serving as an information clearing house."
A "Dig Safely" public awareness campaign, including a damage-prevention brochure and video, is in progress to make construction personnel and the general public aware of the importance of notifying one-call centers before construction begins. More information on CGA programs is available on the CGA web site.
GROUND PENETRATING RADAR
Damage prevention is still not an exact science, but locating strategies, tools and processes are helping to reduce the possibility of damage during utility installations. One of the technologies for identifying and locating utilities is ground-penetrating radar (GPR).
"GPR represents damage prevention for municipalities and utility companies," says to John Bieberdorf, product manager for The Charles Machine Works, Inc., manufacturer of Subsite® electronic equipment. "A lot of utility maps are outdated, so when it comes time to dig near infrastructure, GPR can save these companies a lot of trouble. GPR essentially can pay for itself by preventing one ruptured pipe or gas line."
Unlike standard cable and line locators, which only detect metallic objects, GPR systems locate both metallic and non-metallic obstructions. This is why GPR is becoming a more popular tool among subsurface utility engineering (SUE) firms, which create facility maps or plans for construction crews to follow.
GPR is not without limitations. Some soil has clay content that doesn't allow a clear reading of underground objects. To identify precisely where buried utilities are, Bieberdorf recommends using a vacuum excavation system to expose pipe and cable.
Reducing Risk Step By Step
In addition to employing the right locating equipment for the task, damage prevention also requires thorough jobsite preparation and detailed planning. Recent advancements in software and communications technology have simplified these steps.
Before drilling or excavating begins, it is essential to first study the existing facility maps and then verify the information by calling either the facility owner or the local One-Call center. In March, the Federal Communications Commission (FCC) adopted a new national Call Before You Dig number, 811, in an effort to streamline the process of contacting the local One-Call center.
Detailed planning is another vital step in preventing damage to existing utilities, and Bieberdorf says a number of excellent new planning and mapping software packages are making this process easier. "Most of these systems allow the user to enter information on topography, aboveground features, and both aboveground and underground obstacles, including existing utilities," he says. "Planning and mapping systems can be integrated with guidance electronics, enabling the operator to view the bore as it progresses in real-time and recalculate the plan after each locate."
For both excavating and horizontal directional drilling, Bieberdorf strongly recommends adhering to the best-practice techniques that are detailed in the Common Ground Study developed by the Common Ground Alliance (CGA). CGA efforts focus on implementing best-practice procedures identified in the Common Ground Best Practices Study, recognized as the most effective guidelines yet developed for preventing damage to underground facilities, and one of CGA's primary roles is coordinating information and communications among the various organizations involved in building, maintaining, and operating the utility infrastructure. "CGA," says Bieberdorf, "encourages the shared responsibility of utility damage prevention and helps achieve this by refining and disseminating best practice recommendations, developing public awareness through educational programs, supporting appropriate research, and serving as an information clearing house." A "Dig Safely" public awareness campaign, including a damage-prevention brochure and video, is in progress to make construction personnel and the general public aware of the importance of notifying one-call centers before construction begins. More information on CGA programs is available on the CGA web site.
"Thorough jobsite preparation, planning, and taking advantage of the latest equipment, software systems, and operational techniques will significantly reduce the risk of underground pipe and cable damage," says Bieberdorf.
Three Steps Toward Damage Prevention
The following checklist will help ensure success for your next excavation or HDD project.
1. Engineer the Project for Success
Know the jobsite specifications
Existing utilities
Easements
Soil conditions
Get a geological survey
Allow for proper setup space
Be flexible in design
Vary installation depths when necessary
Allow left-to-right variations
Revise installation method due to rock or variable soil conditions
Provide accurate data and communication
Existing utility maps
Blueprints for projects
All project specifications
Project information meeting
Complete the design before the project starts
Provide job locations two weeks prior to work starting
Know the proper agencies and contacts
Formulate a contamination action plan
2. Complete Pre-Excavation Planning
Review blueprints with contractors
Walk jobsite in advance; make adjustments if needed
Call One-Call services
Complete locating three days prior to work starting
Expose all known utilities; verify location and depth
Complete a proposed excavation path plan
Review product to be installed
Notify residents, landowners of the project
Review job-safety requirements
Traffic: signs, vests, flag person, etc.
Soil classifications
Pit depths, etc.
3. Provide a Knowledgeable Inspector
Monitor project progress
Be sensitive to contractor needs
PREVENTING DAMAGE TO UNDERGROUND FACILITIES
Buried beneath our city streets and in easements and rights-of-way is a maze of buried cables and pipes that provide businesses, industrial facilities, and residences with electrical power, telecommunications connections, natural gas, clean drinking water, and sewer services.
Underground infrastructure is protected from storms and other risks, but it can be accidentally cut or damaged when excavations are made by construction and maintenance personnel and equipment, or even individuals digging holes in their backyards. Utility hits interrupt vital services, abruptly halting routine activities.
Preventing damage to underground utilities is a complex task, and it is the shared responsibility involving many organizations and agencies. To most effectively protect buried facilities, it is essential that representatives of utility providers, contractors, one-call agencies, and other stakeholders develop and sustain relationships based on mutual understanding, respect, and cooperation.
The Common Ground Alliance (CGA) plays a vital role in fostering positive relationships among these diverse interests.
CGA is a private, non-profit organization supported by more than 120 organizations representing utility owners and providers of utility services, one-call centers, utility contractors, industry manufacturers and suppliers, and government agencies, and much of the CGA's work is done on a volunteer basis by representatives of member organizations. CGA has accomplished much in a relatively short period of time thanks to the many hours contributed by volunteer representatives of CGA members who have developed working relationships with one another in order to direct their combined efforts to the shared goal of preventing damage to underground facilities.
CGA was established to implement provisions of the Common Ground Best Practices Study, authorized by the Transportation Equity Act for the 21st Century (TEA-21), and completed in 1999.
The study concluded that communication is the single most important element of underground utility damage prevention and provides comprehensive best-practice recommendations to reduce utility strikes, including one-call membership for all utility owners and operators; contacting appropriate one-call centers before excavation or trenchless construction begins; timely notification to utility owners by one-call centers; accurate locating and marking of all utilities; and the implementation of safe excavation and trenchless construction methods.
Much of CGA's activities are directed toward coordinating information and communications among stakeholders and making the general public aware of the importance of protecting buried cable and pipe. The alliance refines and disseminates best-practice recommendations, develops public awareness through educational programs, supports industry research, and serves as an information-clearing house.
One of the most recent developments is establishment of the CGA Regional Partners Program, which extends CGA efforts at state and local levels and communicates local issues and problems to the national CGA organization. The regional program encourages cooperation among existing damage-prevention organizations and creation of new partnerships new partnerships where none exist.
Now being planned is the establishment of a nationwide, three-digit dialing system for one-call notification centers in the United States. The new system will operate similar to "911" for emergencies: a call placed to the three-digit one-call number--no matter where the caller is--will be answered by the one-call center nearest the caller, even in states with multiple one-call agencies. The one-call center then contacts member organizations to locate and mark their utilities before construction begins.
CGA always welcomes new sponsors. For information about membership and CGA programs, visit the CGA web site or call CGA headquarters, (703) 818-3274.
PROTECTING THE NATION'S UNDERGROUND INFRASTRUCTURE
Protecting the nation's vast underground utility infrastructure and ensuring the safety of those who live and work near buried facilities is a complex task encompassing many organizations and individuals.
"Accidents involving strikes of buried facilities cause interrupted services, millions of dollars in damages, serious injuries, and in some instances loss of life," says Scott Pollman, a member of the board of directors of the Common Ground Alliance (CGA) and director of Subsite electronics at The Charles Machine Works, Inc., Perry, Oklahoma.
The Common Ground Alliance is a private, non-profit organization that has emerged as a leader in efforts to implement a comprehensive damage-prevention program to protect underground utilities. CGA is dedicated to developing and implementing programs to prevent damage to buried pipe and cable, educating the construction industry and the general public about the dangers of such accidents, and fostering the shared responsibility of all organizations with a mutual interest in protecting underground facilities.
CGA efforts focus on implementing best-practice procedures identified in the Common Ground Best Practices Study, recognized as the most effective guidelines yet developed for preventing damage to underground and protecting construction workers, the general public, and the environment.
"The study found that communication is the single most important element of underground utility damage prevention," says Pollman.
"For that reason," Pollman continues, "much of CGA's activities are directed toward coordinating information and communications among the various stakeholders and making the general public aware of the importance of protecting buried cable and pipe."
Educational programs include a "Dig Safely" public awareness campaign designed to make the general public and construction personnel aware of the importance of notifying one-call centers before construction begins. The "Dig Safely" logo, including the toll-free number to call to obtain telephone numbers of local one-call centers, is available at no cost for use in advertising, printed material, and inclusion on web pages.
CGA also offers an informative brochure explaining damage-prevention issues and solutions, and has produced an informative damage-prevention video, "Get the Dirt." Representatives of CGA-member organizations staff exhibits at industry trade shows and make presentations as part of the educational programs at many events. CGA participated in the 2001 ICUEE show in Louisville, Kentucky, the most recent Damage Prevention Convention in Dallas, and the 2002 UCT show. CGA speakers also are available for civic and public presentations.
In addition to communications, the Common Ground study concluded other best-practices steps that will help reduce utility strikes include one-call membership for all utility owners and operators; contacting appropriate one-call centers before excavation or trenchless construction begins; timely notification to utility owners by one-call centers; accurate locating and marking of all utilities prior to construction; and the implementation of safe excavation and trenchless construction procedures.
The Common Ground Best Practices Study was authorized by the Transportation Equity Act for the 21st Century (TEA-21). The study was completed in 1999. During the transition between that time and formation of the CGA in 2000, the U.S. Department of Transportation's Office of Pipeline Safety administered Common Ground initiatives and assisted in the organization of CGA.
CGA is supported by more than 90 organizations representing utility owners and providers of utility services, one-call centers, utility contractors, industry manufacturers and suppliers, and government agencies. It is governed by a board of directors who last year named Robert Kipp as executive director. Much of the CGA's work is done on a volunteer basis by representatives of member organizations.
"CGA," says Pollman, "encourages the shared responsibility of utility damage prevention and helps achieve this by refining and disseminating best-practice recommendations, developing public awareness through educational programs, supporting appropriate research, and serving as an information clearing house."
CGA actively continues to seek new sponsor members.
For information about CGA activities, details about the "Dig Safely" program, to order brochures, to order the "Get the Dirt" video, and for information about CGA sponsorships, visit the CGA web site.
SUBSURFACE UTILITY ENGINEERING PLAYS IMPORTANT ROLE
SUE—subsurface utility engineering—is playing an increasingly important role on a variety of construction projects by identifying and mapping existing utility infrastructure before construction begins.
"SUE is a revolutionary engineering process that has evolved in the United States over the past two decade," says Nicholas Zembillas, senior vice president of the TBE Group, a leading provider of SUE services. "The use of SUE enables designers to prepare plans with thorough and comprehensive knowledge of the exact locations of underground utilities, and enables excavators to avoid damaging underground assets, historical and archaeological sites, and other underground items."
Recognizing the importance of the SUE process, the American Society of Civil Engineers (ASCE) has adopted a standard for classifying the quality level of subsurface utility data to allow project owners, engineers and contractors to develop strategies to reduce risks or allocate risks in a defined manner. The standard closely follows concepts already in place in the SUE profession.
"SUE technology can provide accurate information about underground utilities so that utility owners and project designers and engineers can make informed design decisions during the design phase of projects," says Gary Frazho, TBE Group National Field Operations Manager. "Having this information helps avoid costly conflicts, damage, delays, service disruptions, redesigns, claims, and even injuries and lost lives."
Based in Clearwater, Florida, the TBE Group has been serving clients in the private and public sectors since 1984 and has been providing SUE services for the past 12 years.
TBE has expanded its geographic reach from a local Florida presence to a national and international presence, with offices throughout the U.S., as well as Canada and Puerto Rico.
Subsurface utility engineering combines the disciplines of geophysics, surveying, and civil engineering to accurately map existing underground utilities.
There are three primary steps in the subsurface engineering process:
Designating--using geophysical methods to confirm the existence and horizontal position of underground utilities.
Locating--determining the exact position of each utility by using "soft" excavation equipment such as vacuum excavators to uncover each utility at critical points along its path to determine the exact horizontal and vertical positions--what most utility company and contractor personnel call potholing.
Data Management--entering data into a computer-aided design and drafting (CADD) system which allows planners to identify and evaluate project options and develop a plan that eliminates conflicts with existing utilities.
Using SUE data, engineers can design projects with reduced risk of damage to cable and pipe already in place and eliminate their unnecessary relocation. SUE specialists can make a project go more smoothly at several levels.
For example, says Frazho, highway projects frequently require relocating existing utility facilities. TBE's Utility Coordination Professionals manage all of the utility processes and procedures associated with utility relocating, negotiating highway plan adjustments to minimize utility relocations. These utility coordination and negotiation efforts result in fewer on-site construction conflicts, delays and utility relocations.
Locating existing utilities is a basic element in the SUE process.
"A basic SUE locating tool is compact electromagnetic equipment," says Frazho. "We also use GPR (ground penetrating radar) and 3-D imaging, but electromagnetic locators are used for much of the work because of their versatility, ease of use, and light weight."
An electromagnetic locator system has two basic components: a hand-held receiver and compact transformer transmitter. Both are battery powered, relatively light, and housed in weather resistant cases. The receiver locates underground lines by detecting magnetic fields created by electrical current passing through pipes, cables or tracer wires. Information is displayed in a window at the top of the receiving unit.
Receivers use different frequencies and modes to identify different types of utilities. The receiver unit is all that is needed to locate live electrical cable and in some instances, the receiver alone may be able to locate passive signals of communications cable, although the transmitter unit may be connected to induce a stronger signal.
Currently TBE uses Subsite Model 950RT locating systems consisting of transmitter and receiving units and 970T transmitters, a new model transmitter used with 950R receivers.
Controls of the 950R receiver are positioned for convenient one-hand operation, and simplified left/right arrow configurations help improve productivity. It has active, passive, and beacon locating modes and a target identification feature helps the operator locate lines in congested areas. The 950R receiver weighs only 4.5 pounds (2.0 kg) and is ergonomically designed to make it easy to carry throughout the day. The 3-watt 950T transmitter weighs 7.25 pounds (3.3 kg) and operates on 8 D-cell alkaline batteries which provide approximately 40 hours of continuous use at power level 2.
The 5-watt Subsite 970T transmitter is the most advanced in the Subsite line with more power, more frequencies, and longer battery life. The Live Power Adapter is designed to safely connect the transmitter unit to live power lines up to 440 Volts AC.
Because of the importance of the locating process, Frazho says that TBE conducted head-to-head field tests of seven popular multi-frequency locating systems.
"The site was located in the right-of-way of a highly traveled state highway that contained many subsurface utilities of differing materials, sizes and depths," says Frazho of the testing. "A checklist of important traits and characteristics was developed to rate each unit's effectiveness at the test site. Some of the characteristics thoroughly evaluated in the analysis were responsiveness, horizontal and vertical accuracy, signal strength, gain function, transmitter/receiver design, battery consumption, and available frequencies."
Overall performance ratings for the units were calculated based on a combination of checklist scores and more subjective criteria such as operator feel and confidence level.
"The results of the head-to-head comparison indicated that the Subsite 950RT best met our requirements to standardize TBE's significant inventory of multi-frequency electronic designating equipment," Frazho says. "In the few years since performing the field comparison TBE has been able to observe the performance, reliability and durability of the Subsite 950RT as well as the responsiveness and high service level from the manufacturer. Subsequent head-to-head comparisons continue to point us in the direction of the Subsite multi-frequency unit as our standard model in this class."
Subsite locating and electronic tracking system for horizontal directional drilling (HDD) equipment is manufactured by The Charles Machine Works, Inc., Perry, Oklahoma.
