It seems as though technologies advancement is jumping forward by leaps and bounds in many areas, including the Utility Mapping Industry. There are millions of dollars of utilities installed every day in highly congested roadways and easements. The actual construction of these facilities is getting more and more difficult, but it’s even harder to perform field locates to find the utilities. The underground utility construction industry
has struggled for many years to find solutions to the ever increasing demand to create a tool to develop accurate as-built plans to enhance damage prevention. One tool that has proven itself is the combined use of RFID, GPS and Mapping Software (RGMS) to create utility as-built plans that have an accuracy level as close as sub-centimeter.
This RGMS process stores, records and retrieves underground utility data to enhance other damage prevention devises such as field locates and test pitting. The Radio Frequency Identification (RFID) marker has specific frequencies for all of the different utility types, including power, telephone, communications, water, gas and sanitary sewer. We use the general purpose frequency to identify abandoned facilities as well as R/W lines. The locating device sends the radio waves into the ground looking for a specific utility. This avoids the issues that are created with locators who are looking for a metallic signal in the ground, which is susceptible to bleed-off from other underground metallic systems and even guardrails. Critical information is stored within the memory of the RFID marker, including the facility owner, elevation, size, type, installation date and so on.
The markers are placed above the installed utility system in established increments, usually 25 feet in tangent sections and at every change of vertical or horizontal direction. This creates a kind of “underground voice mail” that can convey information that is obtained during the construction of the system to field locators and contractors, construction management staff, utility company designers and highway engineers.
Communication is an important role in damage prevention and this technology has been, and continues to be, used successfully on many large-scale utility relocation projects.
After the RFID markers are installed and the trench is backfilled, the marker is found with a locator. During this part of the process, the information that was programmed into the RFID marker is downloaded into the GPS unit and the latitudinal and longitudinal
coordinates are established at the specific spot. If the locator is not directly above the RFID marker, the information can’t be read. We use a GPS unit with sub-foot accuracy because this is about the thickness of the line weight of the as-built plan and it speeds up the field process. The mapping software takes this information and draws lines between the dots, which create an electronic layer of the specific utility system. These layers are then combined and overlaid on the highway design files to create a Master Utility As-built Plan in an electronic format. It can also be overlaid to show the roadway features,
which have been very helpful with the utility locating industry since this information can then be viewed with a tablet in the field. Locating underground facilities in congested areas can be very difficult and subject to error; this system has helped locators become more accurate and efficient.
The RGMS process uses RFID marker balls for open cut installations and to provide a future reference point on performed test pits. The pendant-style RFID marker is used for directional drilling operations. This is accomplished by utilizing the information from the directional drill logs and programming this information into the RFID pendant. A pilot hole is created at the end of every other drilling rod location for the pendant to be installed. This creates a horizontal running line of the drilled-in utility system and the elevation is programmed into the RFID marker to provide information to create a 3D model. This information is obtained from the driller’s log, which has been proven to be very accurate. During the construction operations, these drilled-in utilities have to be test-pitted to comply with Miss Utility Laws and the information provided has been accurate to within a couple tenths of a foot. So a utility system can be drilled in at excessive depths, but the information about the utility is stored very shallow so it can be found during the subsequent locating operations. This is a very valuable tool in damage prevention for directional drilling operations because metallic locators are not going to find a signal 20- plus feet in the ground. So the locator can find it, the highway engineer can use it to design other systems, and the contractor can use the stored information to decide how to perform the test pit, which establishes how the designed highway system is constructed.
All of this information is stored in an ArcGIS system that is username and password protected. Specific information is embedded in the as-built plan and is viewed by the click of a button. In the past, the utility as-built information was lost because it was stored in file cabinets and construction trailers. Now it can be found by computer, tablet and smart phones. A cost analysis was performed on several projects and after the initial startup investment, it adds less than 1% of the cost to construct the facility.
The individual technologies function very well but they have their limitations that are mostly driven by functionality and resources. You can put RFID markers in the field but how do you know they are there unless the as-built plan points you in the right direction? The GPS system works well but when a utility has to be found in the field, it’s done by locating the RFID markers. We have had many experiences where the utility company only
used GPS to map their facility but we installed the RFID markers and they were used to find their mains and valves. The RFID markers are pre-programed and given to the contractor for installation while the utility inspector is doing other tasks in an effort to maximize resources. After several boxes of RFID markers are installed, then the GPS
mapping is performed. This helped us manage our inspection resources and expedited the creation of the as-built plan. The post processing of the information is very important to validate the quality of the data before it becomes of record. The combination of the technologies has given “life” to process, has avoided utility damages and possibly saved some lives. The RGMS process is not the answer to all of our utility problems, but it sure has helped a lot of them.
This process has been in use since 2008 and it continues to evolve with the advancement of technologies to enhance damage prevention.
Matthew D. McLaughlin is a Certified Construction Manager and has worked within the utility and construction industry for more than 35 years. He developed this process with the assistance of a dedicated group of construction managers and utility inspectors
during his years of service as a Utility Inspector for the City of Manassas, Utility Construction Engineer for the VirginiaDOT, and now as a Director of Utility Management Services for CES Consulting, LLC. He can be reached at email@example.com.