What Lies Beneath
by Michael A. Twohig
March 1, 2008

In 2004, five construction workers died through incineration from striking an oil pipeline in Walnut Creek, California. This tragic accident exemplifies the gaping holes in safety and accurate utility location measures that are prevalent in the industry today.

As the tools and technologies in the hands of contractors continue to improve and evolve, it naturally follows that the roles of engineers, surveyors and contractors are changing. Yet in the midst of the technology evolution, some things do not change. Buried utility lines are still a hidden danger on construction sites, and on many construction projects today, the responsibility for locating and mapping buried utilities is blurred.

Traditionally, designers and engineers have relied on surveyors to incorporate all the available utility information into the site plan that is used to document existing site conditions and serve as the basis for the design of a project. These site plans are subsequently used for bidding and estimating. In many cases, however, there are undocumented buried facilities that are not included on the drawings.

Not all site plans are created equal—and the differences can mean life or death to construction crews and the public. Construction safety and damage prevention can be improved when contractors understand and implement procedures to properly investigate subsurface utilities.


Setting Standards 

In the early 1980s the Federal Highway Administration (FHWA) made it a primary concern of a focus group of engineers to find solutions to help identify all the utility lines on FHWA projects. The result of the FHWA study was the creation and use of a new engineering discipline known as Subsurface Utility Engineering (SUE). SUE is an engineering process for accurately identifying the quality of subsurface utility information needed for plans, and for acquiring and managing that level of information during the development of a project.1 The Federal Highway Administration’s pilot studies proved conclusively that SUE could reduce utility breaks, reduce construction claims and reduce utility-related construction accidents.

By the mid-1980s SUE consultants began to spring up across the United States, and today there are hundreds of subsurface utility engineers dedicated to documenting the location of buried facilities. Although the FHWA instituted SUE programs with the help of state highway agencies nationwide, it took many years for other industry professionals to recognize the value of SUE consultants.

In 2002, the American Society of Civil Engineers (ASCE) published a standard known as “ASCE 38-02, Standard Guidelines for the Collection and Depiction of Existing Subsurface Utility Data.” Today many engineers and surveyors incorporate this standard into their utility locating and mapping practices to ensure that all the subsurface utilities are clearly identified on construction plans. However, not all engineers and surveyors use these techniques and technologies when preparing construction plans, and as a result, utility accidents are still prevalent in construction.

Too often, projects proceed without the necessary investigation to protect buried facilities from damage during construction. Instead, owners and engineers rely on notes on plans, disclaimers on the surveyor’s existing condition plan and wording in the special provisions of bid documents. It is all too common to find a contractor who has been awarded a contract and received a “Notice to Proceed” but still faces the daunting task of verifying and locating the buried utilities prior to beginning work. Not only is this inappropriate, it is also unrealistic to entrust any contractor with a utility location project while its crews are mobilizing and preparing to begin work. Moreover, this process overburdens the contractor’s personnel with utility locating services. In turn, the burden is then placed on the utility owners after the contractor obtains a Dig Ticket from its local One Call Center. Thus, the subsurface utility investigation is frequently rushed without a proper engineering review.

Although this process has been the norm for many years, it leaves no room for errors. Any utility discoveries at this stage result in change orders, project claims, utility relocations and project delays. Even worse, utilities not discovered over the first few weeks on a project may result in facility breaks, utility disruptions, bodily injury or sometimes even loss of life.


SUE to the Rescue

The implementation of SUE can avoid all of these accidents and claims. By using SUE in the preliminary phase of a project, contractors and owners can reap overwhelming financial savings and safety benefits. A professional subsurface utility location consultant can work with the surveyor’s team to obtain all the survey information from below the surface. Incorporating the below-grade information with precision can ensure that the project soil sampling and environmental work begin without a facility break. The design team can work with confidence knowing the data on the existing condition plans is precise. And no surprise utility discoveries will occur to sidetrack the team when the contractor is mobilizing. In addition, the owner of a project will not be faced with expensive utility relocation work during the construction phase of a project, and utility owners will not be adversarial when confronted with a utility relocation in the eleventh hour of a job.

To achieve this higher level of confidence in utility information, utility locating engineers and technicians begin the task of tracing and marking the underground infrastructure using locating technologies. The vast majority of utilities are located using electromagnetic and radiofrequent technologies such as pipe locators and ground-penetrating radar (GPR) systems. Other technologies such as acoustic, thermal or X-ray systems are also used. The subsequent survey or markings from this process is known in the SUE industry as ASCE Quality Level B information (utility designation). (See the sidebar on page 21 for more details about SUE quality levels.)

To achieve the highest level of information possible—ASCE Quality Level A—and incorporate it into a site plan, a competent engineer or surveyor obtains accurate X, Y and Z locations for exposed facilities. Many SUE technicians obtain Quality Level A data by “test pitting” or vacuum excavation to produce a single data point with an exact geographic position of a buried line. Quality Level A information is the appropriate level of data required when breaking ground. Today there are many professional engineers and surveyors compiling utility information. Contractors must place great emphasis on their confidence in the quality of the data ultimately provided to them in a composite utility plan.


Accepting Responsibility

Although the FHWA, the Federal Aviation Administration and studies by Purdue University have documented the cost savings of SUE on projects nationwide, SUE is still widely considered a “Cadillac” service to be used only on projects with big design budgets. More construction professionals need to acknowledge and accept the need to locate the buried facilities prior to construction and remove the ambiguity from contract plans. Contractors and owners should hire reputable SUE firms who understand the risk, provide the professional services to manage the risk and produce reliable data for above- and below-ground features. If no one is responsible for untangling the web of confusion below our feet, events like the one at Walnut Creek could make headlines again.


Reference

1. This definition is adapted from the U.S. Department of Transportation Federal Highway Administration Web site on Subsurface Utility Engineering at www.fhwa.dot.gov/programadmin/basicinf.cfm.

Michael A. Twohig
Michael.twohig@woolpert.com
Michael A. Twohig is a Subsurface Utility Engineering consultant providing mapping services throughout the United States.