The PIPES Act 2016 calls for increased use of data and technology to improve pipeline safety, and contractors are acting quickly to fulfill this. But first they need to find the pipelines!
WITH THE RENEWED EMPHASIS on improving and rebuilding the U.S. infrastructure comes a major challenge: gaining accurate information on the locations and conditions of existing utility assets. In addition to identifying and planning needed repairs to pipelines and other equipment, buried pipelines also must be protected against accidental damage. One of the first steps in meeting this challenge is determining the location of underground natural gas pipelines.
There are nearly 1.9 million miles of gas distribution mains and service pipelines in the country, according to the US Pipeline and Hazardous Materials Safety Administration. On top of that, there are roughly 300,000 miles of large collection and transmission lines that carry gas from production fields to a distribution center.
Some of the most vulnerable pipelines are in developed and municipal areas including commercial, residential and industrial settings. It is often difficult to locate miles of gas pipelines in these regions. Where data exists, the locations may not be in an easily retrievable and shareable format. For example, paper maps are not always tied to accurate coordinate systems so it often comes down to the knowledge of the aging workforce. In many instances, workers nearing retirement age often may be the only ones who know the (sometimes approximate) location of the lines.
Not knowing where or how deep gas pipelines are creates many hazards. Without accurate, readily- available location data, pipeline operators, construction companies, farmers, land owners and other stakeholders face the risk of accidental and potentially catastrophic damage to a buried gas pipeline.
The PIPES Act 2016 (Protecting our Infrastructure of Pipelines and Enhancing Safety) requires increased use of data and technology to improve pipeline safety. The legislation is strongly supported by industry members and calls for ways to prevent damage by third parties, such as accidental contact with a buried line.
There are two ways this is being addressed. First, a new technology has been introduced that can accurately detect the depth of buried pipelines. Second, locating technologies combined with geospatial solutions produce accurate position information tied to known coordinate systems. The resulting survey-quality data forms the basis for GIS-based approaches for planning, asset management, operations and emergency response.
Finding the Pipelines
Woolpert is a U.S. architecture, engineering and geospatial firm. Its surveyors sometimes use a subsurface utility locating system in conjunction with survey-grade GNSS to locate and georeference underground utility lines. One of their first projects took place on a client’s property in northern Ohio.
“We used a a utility surveying unit coupled with a GNSS receivers to detect buried gas lines,” says Dave Kuxhausen, Woolpert discipline leader for surveying and geomatics. “The scale of the project was sufficient to demonstrate that we had the capabilities to perform this type of work.”
The utility surveying system uses magnetic field sensors to determine the distance to a buried pipe or other asset capable of carrying an electric current. The sensors can be integrated with GNSS receivers or total stations connected to software running on a field controller.
The system locates buried pipes in three dimensions. The controller indicates when a pipe has been located and aids the crew in following the pipe. The system provides horizontal and vertical offsets from the sensor to the pipe while the GNSS receiver supplies precise geographic positioning.
When the surveyors want to capture a measurement, the field software automatically combines the data and stores the resulting positions into its database. In addition to a 3D coordinate on the pipeline itself, the solution also produces coordinates for points on the surface directly above the pipe.
The surveyors can detect and mark the pipe as well as capture survey-grade positions in a single pass. The resulting locations approach the accuracy of Level A excavations. (Level A locations require the pipe to be physically exposed, usually by digging or hydro excavation.) Kuxhausen says that the system enables his crews to capture pipe depths accurate to roughly 8cm, depending on the integrity of the tracer wire. Crews can work with the speed and flexibility associated with handheld electromagnetic sensors not capable of determining a pipe’s depth.
The field data is then transferred to software. “We run the data through a QA/QC process and then export the data and look at them in an Esri-type environment to check for gaps or overlaps,” Kuxhausen explains. “We take advantage of the fact that the data comes with a depth and a surface elevation. In many instances, we’ll turn it into a profile view to make sure that the depths look consistent and there are no spikes or obvious issues.”
Mapping is Key
Keeping the systems in use is easy. Kuxhausen says that his clients quickly recognize the value of the mapping solution. In addition to mapping mandated by the PIPES Act, demand for their mapping services is coming from large and small construction companies. The work includes locating utilities for new construction as well as maintenance and update projects.
There isn’t a lot of flexibility when working on these projects so the accurate locations are important for efficient design and construction. “In a lot of places, clients are forced to do Level A excavation just to locate a pipe,” Kuxhausen says. “They may need data every 10 feet along the road. We are able to use this system to reduce the frequency of the Level A excavations to, say, every 50 feet. It’s a faster and more cost-efficient approach.”
The aviation sector, such as airports, is another source of business for utility locations. Airfield operators need accurate data on the complex web of underground pipes, wires and conduits. “We repeatedly receive requests to perform mapping and subsurface utility engineering services to support the redesign or relocation of navigation equipment,” Kuxhausen says. “For instance, we’ve completed work for airports where they might be deconstructing a control tower or some other site. Our crews will go out and locate the existing utilities, both active and decommissioned, so that no lines are damaged when the deconstruction takes place.”
Other opportunities come from public works and roads departments that need to see existing utilities in their transport corridors for design mapping. The information enables the departments to develop comprehensive GIS datasets on the myriad of structures and facilities that lay beneath the roadways. The efforts may not be connected to current construction projects, but they provide significant value in support of long-term planning.
“WE USED A UTILITY SURVEYING UNIT COUPLED WITH A GNSS RECEIVERS TO DETECT BURIED GAS LINES,” SAYS DAVE KUXHAUSEN, WOOLPERT DISCIPLINE LEADER FOR SURVEYING AND GEOMATICS . “THE SCALE OF THE PROJECT WAS SUFFICIENT TO DEMONSTRATE TH AT WE HAD THE CAPABILITIES TO PERFORM THIS TYPE OF WORK .”
Kuxhausen’s goal is productivity and the ability to meet the needs of clients. “It comes down to how can we streamline our processes,” he says. “We can quickly, safely and accurately locate utility data and add it into the larger infrastructure mass. Coupling the information from the system with the GIS database can be invaluable for clients that have large inventories of underground assets.”
Erik Dahlberg is a writer specializing in the geomatics, civil engineering and construction industries. Drawing on extensive training and industry experience, Dahlberg focuses on applications and innovation in equipment, software and techniques.