As more and more utility companies place their facilities underground, damage prevention has become paramount to all stakeholders. Groups such as the Common Ground Alliance (CGA) and the National Utility Locating Contractor’s Association (NULCA) have initiated programs aimed at preventing damage to our vital underground infrastructure. “Call 811,” “Dig Safely” and “Locate Accurately” are just a few of the initiatives that have had an impact on damage prevention.
One area that could have a dramatic impact on damage prevention is accurate utility mapping. For years, locators have been taught that utility maps and prints are only a guide and that their accuracy should not be trusted. In many cases, maps provided showed only a vague representation of where the facility was located and in some cases maps did not exist at all. Updates were slow to be added and as-built drawings may have been missed along the way. Processes may not have been in place to allow for corrections when discovered in the field. With our rights of way quickly becoming overcrowded, it is more important than ever to have accurate maps and records of what lies beneath the ground.
The law in Virginia requires utility operators to mark underground utility lines within 2 ft of their location in response to a notice of excavation. The law further requires utility operators to prepare “reasonably accurate” maps of utility infrastructure during installation. The Virginia State Corporation Commission (Commission) is the enforcement authority in the state of Virginia with regard to utility damage prevention laws. The Commission staff, which assists the Commission in carrying out enforcement actions, has interpreted the law to provide that when utility lines cannot be located through conventional methods and utility operators or their locators, rely on maps as the method of field marking their facilities, they still must be able to locate those lines in accordance with state statutes.
In other words, utility maps must be accurate enough to facilitate marking within the 2-ft tolerance zone specified in the state statute. Virginia has been a leader in the area of damage prevention for many years and many states will follow its lead. Unfortunately, most utility maps don’t meet this level of accuracy. Facilities may have been placed years ago with no thought of how to locate them in the future and non-metallic lines further complicate the situation.
One solution to this mapping issue is to combine all available technologies to produce a suite of services designed to meet and exceed the mapping needs of any utility or municipality. Subsurface utility engineering (SUE) techniques are employed to determine exact locations of underground facilities. Metallic lines can be located with traditional electromagnetic instruments. When nonmetallic facilities are involved, a number of options are available including acoustical locators, ground penetrating radar (GPR) and radar tomography (RT). Combining these technologies with GPS will allow most underground utilities to be located, providing X and Y coordinates. Vacuum excavation is then utilized to provide exact X, Y and Z coordinates.
In situations involving nonmetallic conduits or pipes, a number of technologies can be deployed. Small gauge wire, such as phone service lines, can be inserted into the ducts. Locatable rods are a similar solution. Sondes can also be run through these ducts and traced using electromagnetic locators when the ducts or pipes are not extremely deep.
While not applicable in all situations, there is a new technology that can be utilized when deep lines are involved. For example, the Smart Probe can accurately locate and map pipes and conduits regardless of depth. This technology consists of two main components. The first is an array of data collection instruments that include accelerometers, gyroscopes and odometers located within each of the probe bodies. The second is a proprietary software package that extracts and interprets the collected data and allows for the seamless transfer of the collected data into various GIS data bases. The probe is autonomous, meaning that it is not tethered via a data cable to the surface. In fact, the probe does not communicate with the surface at all. This means that there is no restriction by the depth of ground cover over the pipeline nor is it subject to possible interference derived from other pipelines or metals located within the soil. There is no requirement to “trace” the movement of the probe from above ground. It is designed to run through conduits and pipes as small as 1 ½ in. in diameter and it can be walked through very large pipes — up to 96 in. in diameter.
Regardless of the method of collection, once the field data is acquired, it must be placed into a mapping system. GIS systems can provide not only the mapping solution, but can also store nearly unlimited amounts of data. Line segments can be “clicked on,” revealing data such as genetic make up of the line, date installed, GPS coordinates and much more. This information can be critical in the field as more and more lines are replaced in the ground. If the contractor knows that the field technician has located a PVC line and in the course of exposing it finds a steel line, they will know to continue looking or at a minimum, call the utility for clarification.
Utilities and their locators, whether in-house or outsourced, should develop lines of communication so that there is a method to relay errors or omissions involving existing maps. This is an area that is commonly overlooked. On a daily basis, locators discover these problems, but without a way to communicate with the GIS department, these damage prevention opportunities are not realized.
Use of Utility Mapping
One example of mapping as a damage prevention tool occurred on a major Midwest construction site. During the first six months of their project, the general contractor utilized the one-call system and followed the local laws. However, despite their best efforts, the general contractor accumulated more than $500,000 in utility damages. During the next year and a half, the contractor still followed all one-call laws, but when the field technicians completed the locates, the marked lines were mapped and added to the construction plans. The plans were copied and given to each equipment operator. When the operator checked his plans and saw a discrepancy between the plans and the site, he knew to call the locator for clarification. During the next three phases of the project, the total cost of utility damages was less than $3,000. This represented one damage to an exposed line that occurred when a chain failed, dropping a large pipe on a small phone line.
This example shows that when employed during the construction process, utility mapping can have a significant positive effect on damage prevention.
By utilizing state-of-the-art technology, utility lines, both newly installed and existing, can be mapped with great precision. Industry stakeholders across the country agree that communication is the key to damage prevention. Accurate maps and records are one of the most effective methods of communication. With this information, engineers will more effectively design their projects, locators will provide more accurate marks and contractors will dig safely. Accurate underground utility mapping will save the industry time, money and ultimately it will save lives.
Ron Peterson is central region operations manager with Geospatial Corp., based in Kansas City, Mo. He is also executive director of the National Utility Locating Contractor’s Association (NULCA).