An excavation crew uses non-destructive vacuum equipment to obtain critical horizontal and vertical utility information.

Surveyors, for the most part, are an analytical and systematic bunch, perhaps more so than other professions. I, on the other hand, work in an industry that is comprised of a smorgasbord of professionals ranging from scientists, geophysicists, engineers, contractors, locating technicians and a few bureaucrats. With this variety of professionals, it is often difficult to define any standards of care to our work. And in our industry--the subsurface utility engineering industry--standards are much needed.

A survey crew locates utility markings on Julian Street in San Jose, Calif., producing ASCE Quality Level B information.

Standards for SUE

Subsurface utility engineering, or SUE, is an engineering process for accurately identifying the quality of subsurface utility information needed for highway plans, and for acquiring and managing that level of information during the development of a highway project.1 For years, this sector of engineering has had its standards and guidelines driven by the decision makers in each SUE provider’s office. The result is that the overall accuracy and precision of many jobs has been inconsistent. There were no documented traverses, no bench marks to check into, no level runs to review. It was not at all an analytical approach.

Fortunately, in 2002, the American Society of Civil Engineers (ASCE) published C1/ASCE 38-02, “Standard Guidelines for the Collection and Depiction of Existing Subsurface Utility Data.” After working in the utility location and mapping industry for more than a decade, I was optimistic that a new dawn had broken with the development of these guidelines. For the most part, it has. But there is still room for important improvements such as defining a universal standard of care. And surveyors can help.

The author and a locating technician expose electric line casing with a vacuum excavator.

Improving the Benchmark

Many large design firms still feel that a utility plan signed by a licensed professional engineer, which states that the document plan is in compliance or conformance with the ASCE 38-02 standard, is an accurate and true plan that represents the below-ground infrastructure. Nothing could be further from the truth. In actuality, insurance certificates and indemnification clauses provide the closure that contract managers need to satisfy their requirements for risk management and utility damage prevention. Unfortunately, as witnessed in the 2004 Walnut Creek, Calif., accident where five construction workers died tragically through incineration from striking an oil pipeline, gaping holes in safety and accurate utility location measures still exist. Since the Walnut Creek incident, California has enacted new legislation to prevent such accidents but no definitive change is evident in the standards of care for the utility location industry, nor have I seen any notable revamping of industry trends to prevent such reoccurrences.

A locating technician traces a gas line in Lake Tahoe, Calif.

Redefining the Process

Most construction projects today have a site plan, either topographic or planimetric, that has been compiled by a qualified surveyor. These plans began as a traverse, a level run, a GPS network or a site survey location and culminate into a graphic representation in a two-dimensional plan. This is an analytical and systematic process that is most likely accurate and precise just about all of the time, to a high degree of certainty.

Then the utility compilation begins. Typically, a survey firm researches all the sources of underground utility information and correlates that data into the site plan based on surface features such as gates, valve boxes, manholes, etc. A compiled Composite Utility Plan at this level by a qualified surveyor is what meets ASCE 38-02 Quality Level C and D. This Composite Utility Plan is a valuable document that can be used on any project, but it should only be considered for preliminary design purposes. For final design, a higher confidence level of utility information should be considered.

To achieve this higher level of confidence, 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 GPR (ground-penetrating radar) systems. But other technologies such as acoustic, thermal or X-ray systems are also used. The subsequent survey or markings from this process are known in the SUE industry as ASCE Quality Level B information (utility designation).

ASCE Quality Level A data--the highest level of information possible to incorporate into a site plan--is when a competent engineer or surveyor obtains accurate X, Y and Z locations for exposed facilities. For many, Quality Level A data is obtained by “test pitting” or vacuum excavation and produces 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; a great emphasis needs to be placed on labeling and qualifying what quality and confidences an owner and contractor places on Composite Utility Plan data. Moreover, not addressing the ASCE quality levels when labeling linework on utility drawings in survey contracts−be it in hard copy or electronic format−may leave many surveying professionals with a liability exposure.

It is my opinion, after spending the last two decades on construction sites, that fewer utilities are damaged during the construction phase due to improvements by utility owners marking buried lines prior to construction. Better communication using the new 811 hotline2 to coordinate activities prior to breaking ground and the experience of machine operators to “feel their way through the underground” also improve statistics. Unfortunately, no agency tracks accidents and utility disruptions to know whether there has been improvement in the utility construction arena. But many contractors believe better location, marking and damage prevention awareness are reducing the number of accidents.

It is time that all surveying firms study the ASCE 38-02 standards, the “best practice” guidelines used by organizations like the Common Ground Alliance,3 and start addressing the risk, liabilities and damage prevention measures of utility location into their daily practices. Surveyors can bring several hundred years of analytical skills to incorporate the best of today’s locating technologies, the best surveying skills and the best mapping technologies, and ensure that every site plan can be read and understood for what it is or is not. The immediate benefits of implementing ASCE 38-02 may not be fully appreciated for some time, but the ultimate result will be improved construction safety and damage prevention measures.

Meanwhile, SUE providers need to learn that the analytical and systematic approach to preparing plans is the only way to consistently produce accurate documents, and using the latest surveying technologies and this group’s analytical approach of preparing documents will make tremendous improvements in the future. Contract managers and owners need to sign on reputable firms who understand the risk, provide the professional services to manage the risk and produce reliable data for above- and below-ground features. If these two groups don’t make these changes, events like the one at Walnut Creek could make headlines again.

SUE Quality Levels

Highway plans typically contain disclaimers as to the quality of utility information. The use of quality levels in the SUE process allows designers to certify on the plans that a certain level of accuracy and comprehensiveness has been provided. There are four quality levels:

Quality Level Dinformation comes solely from existing utility records. It may provide an overall “feel” for the congestion of utilities, but it is often highly limited in terms of comprehensiveness and accuracy. Its usefulness should be confined to project planning and route selection activities.

Quality Level Cinvolves surveying visible above-ground utility facilities, such as manholes, valve boxes, posts, etc., and correlating this information with existing utility records. When using this information, it is not unusual to find that many underground utilities have been either omitted or erroneously plotted. Its usefulness, therefore, should be confined to rural projects where utilities are not prevalent, or are not too expensive to repair or relocate.

Quality Level Binvolves the use of surface geophysical techniques to determine the existence and horizontal position of underground utilities. This activity is called “designating.” Two-dimensional mapping information is obtained. This information is usually sufficient to accomplish preliminary engineering goals. Decisions can be made on where to place storm drainage systems, footers, foundations, and other design features in order to avoid conflicts with existing utilities. Slight adjustments in the design can produce substantial cost savings by eliminating utility relocations.

Quality Level Ainvolves the use of nondestructive digging equipment at critical points to determine the precise horizontal and vertical position of underground utilities, as well as the type, size, condition, material and other characteristics. This activity is called “locating.” It is the highest level presently available. When surveyed and mapped, precise plan and profile information are available for use in making final design decisions. By knowing exactly where a utility is positioned in three dimensions, the designer can often make small adjustments in elevations or horizontal locations and avoid the need to relocate utilities. Additional information such as utility material, condition, size, soil contamination, and paving thickness also assists the designer and utility owner in their decisions.

The end product (the CADD file or project plans) may contain any or all of these quality levels.


1. This definition is from the U.S. Department of Transportation Federal Highway Administration Web site on Subsurface Utility Engineering at

2. The national toll-free number 811 is used to locate underground lines on jobsites or dig locations (large or small) before breaking ground. The 811 number connects callers to their local One Call Center, a service that contacts local utility companies to come onsite to visibly mark the approximate locations of utility lines for any digging project. In order for the request for marked utility lines to be processed, all 811 calls must be placed at least 72 hours prior to digging.

3. As the national organization responsible for promoting effective damage prevention practices for all underground facilities in North America, the Common Ground Alliance (CGA) was designated by the Federal Communications Commission as the organization responsible for promoting awareness and use of the new national 811 number.