The complexities of locating underground utilities and performing subsurface utility engineering (SUE) are attracting more attention than ever before due to the financial and safety impacts related to these activities. Almost every construction and transportation project that involves digging below the earth’s surface could potentially hit oil or gas transmission pipelines, water or sewer lines, telecommunications cables, or electrical conduit. Breaks in any of these lines very often cause costly delays and major inconvenience, as well as injuries to people and damage to property.
Historically the placement of underground features of any kind has been recorded rather loosely, if at all. Records for legacy utilities are not comprehensive nor detailed or accurate enough for project engineering purposes. An “as-built” drawing might refer to the underground locations based on the distance from a visual object on the surface, such as a fire hydrant, but generally do not include an accurate measurement of the feature’s depth underground. It was understood that surveyors and engineers were absolved of responsibility for the accuracy or completeness of utility information because there were no widely accepted or enforced standards. As time went by, the uncertainty about utility locations increased, along with the possibility of an accident.
Also, prior to 1980 there were few devices for finding underground utilities, few firms were mapping utilities, and utility owners did “locating” only for their own maintenance and repair purposes. Incomplete and inaccurate maps of underground utilities between structures often led to project construction surprises, delays, re-design costs, damages, claims and change orders.
The Need for Standards and Training
In the keynote speech at the MAPPS 2015 Summer Conference, James Anspach, director of utility market and practice development at Cardno, an international engineering and surveying firm, addressed the very timely issues of standards for mapping underground utilities and specialized training in SUE. Anspach is a long-time member of the American Society of Engineers (ASCE), leading the development of standards for utility mapping, and has been instrumental in several research projects for the Transportation Research Board (TRB) with the goal of bridging the technology gap between utilities and project owners to establish timely, safe and cost-effective best practices.
Standards such as the ASCE 38-02 (Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data) have been developed to assist owners and engineers in more clearly documenting the risks presented by utilities. By standardizing how utilities are portrayed, engineers can design better plans to work within the existing conditions, and most importantly, be clear about the reliability and quality of the utility information available. The ASCE also supports the development of specialized training and certificates for surveyors and engineers who work with subsurface utilities due to the complexity of the topic and the high potential for encountering dangerous situations.
Quality Levels to Support Utility Engineering
Today utility maps are rated by quality level (QL) to let users know to what degree they may rely on the information.
- Quality Level D (least reliable): Plotted on plans from records. Sometimes involves a field visit to look for utility indications on the site. Sometimes “verbal recollections” are plotted.
- Quality Level C (traditional utility depiction): Surface appurtenances are surveyed and accurately plotted on a current site plan. Utility data from records (QL D) are correlated to the appurtenances.
- Quality Level B: Surface geophysical methods are used to search for and trace existing utilities. Designated utilities are then surveyed and plotted on site plan.
- Quality Level A (includes physical and visual verification): Utilities exposed via non-destructive air-vacuum means. Exposed utilities are then surveyed and plotted on the site plan. Elevations, size, condition, materials, and precise horizontal positions are measured and documented.
Clear definitions of quality levels are very helpful to utility engineers responsible for planning and designing new underground features; however, the perception of how to incorporate this information into projects has changed over the years, perhaps not for the best. According to Anspach, “The process has become linear instead of holistic. You are expected to work your way up from QL D, to C, to B, to A, when it would often be more efficient to start early on with QL B. A linear process creates duplication of effort, loss of continuity, and higher costs.”
Anspach continues, “Some projects might benefit from a linear approach, but many could make use of comprehensive utility mapping in the first stages, such as projects that are uncertain due to financial or environmental reasons, or if the project is likely to change significantly over time. Each project should be looked at individually and the most appropriate QL should be prepared right from the start.”
Teamwork: Surveying, Engineering and Geophysics
Although the three professions of surveying, engineering, and geophysics have some knowledge overlap, they must often work together to complete a utility map. Engineers are allowed to do engineering surveys if they are competent to do so, such as measuring distances between fixed objects on the earth’s surface. However, engineers are not allowed to determine easements or property boundaries, or metes and bounds, so if any utility depiction requires these, a surveyor must be engaged.
For years surveyors have produced drawings that include utilities, by surveying physical features they could see and incorporating utility records. With SUE, geophysical technology is also incorporated to reference where the utility might be, and added to a survey reference to make a map. Most surveyors are not trained in geophysical technology, so they are not able to produce these maps without assistance. A partnership between engineers, geophysicists, and surveyors must exist to produce a utility map that meets the ASCE standard.
For example, in Texas a utility map receives an engineer’s “seal” with the help of a surveyor. Typically the engineer decides the quality level of the depiction, and the surveyor decides where the depiction goes on the map. If there is a question of negligence, it needs to be clear who was responsible for what and was the activity performed correctly based on the standards.
Future Direction for SUE
There are a number of initiatives underway that will improve the availability of utility information for use in future projects.
The ASCE Utility “as-built” standard is currently being developed and is on track to be published in 2016/17 as the first “as-built” standard in the U.S. With new survey technologies, such as GPS and CAD, we are capable of producing much more accurate “as-builts” than ever before. Anspach explains, “Utility owners are usually installing the lines, so they record information that will help them with maintenance and operations functions. The references are typically visual, like the edge of the road or the corner of a building. The lines are not surveyed so they might be off by +/- 10 feet, which is not adequate for future projects that require digging in the vicinity. The standards will provide minimum requirements for recording the installation of new utilities going forward.”
To aid in the locating and documenting of utilities, the development of SHRP Tools (Strategic Highway Research Program) has been ongoing for 15 years. The research is completed and the tools are available to anyone. Anspach says, “Now we’re identifying opportunities to implement the new tools that have been developed. There is a new utility database and 3D visualization tool, a utility conflict identification and procedure tool, and updated geophysical tools to find existing utilities.”
Another major trend is specialized SUE training and certifications. “Since the 1940s utilities have been identified as one of the top three reasons why highway projects are delayed,” Anspach says. “Research shows our education method teaches engineers how to design systems — transportation networks, buildings — but not take into account the existing hidden utilities; utilities are looked at as someone else’s problem. Engineers must know about the utility constraints as well as regular engineering challenges. Utilities are an integral part of engineering design.”
To address this knowledge gap, the Utility Engineering and Surveying Institute, in conjunction with several universities, is developing new certifications that may require two-week classes or a series of short courses, in person or via webinars and e-learning opportunities.
And last but not least, the concept of “utility risk envelopes” is being developed to enhance the ability of CAD programs to perform more advanced clash detection by moving beyond hard clash (actual physical interference) and soft clash (putting a buffer zone around the two elements and notifying the user if the buffer is violated). Anspach explains, “A high pressure gas line shouldn’t be very close to something that is subject to strain, so we need a larger ‘risk envelope’ or buffer around it. Or a 24-inch water line with a 90-degree bend has thrust blocks to keep the pipe from shifting, but we don’t know where the block is after it is covered up so a larger buffer is advisable. We are trying to develop enhancements to the software and to engineers’ knowledge to make the buffers more effective and avoid design problems.”
The Importance of SUE
The need for improved documentation for subsurface features will only continue to expand as the volume and complexity of our utilities increases along with the earth’s population. In the long run, carefully thought-out standards will reduce project costs and prevent damage and injuries, while utility specialists trained in all aspects of utility design will enhance the efficiency and safety of our systems.