The Sad State of Our Buried Infrastructure Knowledge

As a civil engineer with site and utility design experience, it amazes me to think about how little we actually know about what is buried just beneath our feet. Specifically, the quality of our engineering knowledge about existing buried infrastructure - water lines, sewers, telecommunication, gas and electric utilities - does not nearly reflect just how critical this infrastructure is to the very fabric of our society. The problem is both widespread and systemic. As engineers and facility managers, we simply do not have a good history of utility-related record-keeping - a fact which profoundly affects our ability to manage, maintain and expand our engineering infrastructure today. In engineering and construction practice, uncertainty about utility locations can easily lead to budget overruns, project delays, and construction change orders. In the worst-case scenarios, it can result in unwanted legal action, costly damage to existing utilities, and safety risks to excavating contractors.

From a historical perspective, there are many reasons why our buried infrastructure records are in such an unfortunate state. Much of our infrastructure was designed and constructed decades ago - perhaps even over a century ago, in our older cities. Computer-Aided Drafting (CAD) and Geographic Information Systems (GIS) had not yet been invented, and the importance of standardization, centralized records storage and construction oversight were not widely understood or valued. Moreover, these buried assets changed ownership and management hands over time.  Thus, the personal knowledge about the utility construction and maintenance history was often lost, along with many of the physical records. As our cities and suburbs grew and the reference topography changed over the decades, the problems only became more complex and difficult to remedy.

Use of Radio Frequency Identification (RFID) for Locating Underground Pipes and Cables

At this point in time, we can only look to the future and try to implement more intelligent long-term solutions for these age-old problems. Modern day surveying techniques, 3-D CAD, GIS and subsurface utility engineering (SUE) practices have all helped considerably. Overall, these are exellent tools for addressing the issues of generally locating existing utilities, organizing known utility data geospatially, and aiding in visualization. What is still missing from the picture, however, is a complementary technology that would allow facility managers to proactively tag buried assets - either during installation or when exposed during periodic excavation - so that they may be more accurately sensed and uniquely identified in the field. In this article, we will discuss an exciting and growing technology called Radio Frequency Identification (RFID), which is well-suited for just such a purpose.

Without going too much into detail about the inner workings, RFID is a broad-term that describes any system that consist of RFID tags and readers.   A typical RFID tag consists of a microchip attached to a radio antenna, which allows the tag to broadcast data over radio waves to the readers.  The tags can generally store up to 2 kilobytes of data, and are therefore suitable for storing the unique identification or serial number of whatever object is tagged.  Tags can come in varying sizes and shapes and are already being integrated into many common objects, including credit cards, clothing labels,  and shipping packages.  RFID readers, on the other hand, are used to retrieve the data from RFID tags.  A typical reader is a device that has one or more antennas that emit radio waves and receive signals back from the tag. The reader then passes the information in digital form to a back-end computer system, which are used for long-term storage of data, analysis and interactiion with the user.    The diagram above illustrates a typical RFID system.

RFID is arguably one of the fastest growing markets in the information technology sector, and a wealth of information is available online and is published about how RFID will soon transform the manufacturing, retail, healthcare sectors, as well as the military.  Much less has been written about the potential applications of RFID in civil engineering and infrastructure management.  Overall, the construction industry currently seems most poised to take advantage of RFID technology, primarily for supply chain management and site inventory control.  This is an important application and will undoubtedly be a topic for future Advanced-Infrastructure posts.  However, I personally think that utility marking and buried asset management are equally attractive uses for RFID technology, both in terms of life cycle cost benefits, and short-term feasibility.

Benefits of Using RFID for Utility Marking and Buried Asset Management.

For utility locating and management purposes, RFID offers several significant features and advantages to facility owners:

• Able to Operate in Challenging Environments: RFID tags for utility marking can be easily designed to withstand a variety of challenging environmental operating conditions.  Factors such as temperature variations, moisture and dirt have little or no impact on their ability to function and, assuming that passive RFID tags are used, the tags do not even require an on-board battery.  They are instead powered by the reader - a very important factor for long-term underground installation.
• Enables Flexible Stategies for Locating Assets:  Depending on the type of tags and readers used and future advances in RFID technology, field-locating utilities using RFID has the potential to be useful on multiple levels.  The most common scenario may be to use handheld readers to locate utilities horizontally and mark them in the field.  However, in theory, readers may also be installed on excavating and construction equipment, in order to proactively warn the operator, in real-time, that utilities are in close proximity to the excavation area.
• Implements Database Back-End Storage:  As mentioned earlier, RFID tags typically are able to store only 2 kilobytes of data on-board - just enough to store a unique identification code and not much else.  Some extended-capability RFID tags are capable of storing up to 64 kilobytes of data; however, it is much more common to implement a back-end database for additional storage.  This makes RFID a powerful tool indeed, as the database can be designed to be as simple or as extensive as the user desires.  The database records are associated with the individual tags using the unique identification number and the database can be used to store all of the information that is pertinent to the tagged asset.  The database can store information about the contractor, installation conditions, installation date, installation depth, dimensions, specifications, CAD drawings, shop drawings, installation photographs, and maintenance records.  Maintenance records are discussed in more depth below.
• Facilitate Maintenance Tasks:  A technology such as RFID would not only facilitate location of utilities, it would also ensure that regular maintenance and replacement tasks are more accurately associated with specific assets, over their entire lifetime.  Because each RFID tag has a unique identification number associated with it, these tags can be used to mark specific pipe sections, splices, valves, or other appurtenances within the utility network.  These different parts may have varying expected life spans, and will likely be serviced individually, over time.   With RFID, facility owners would be able to more easily maintain part-specific maintenance records than existing practices permit.
• Serve as a Basis for Future Decision Support Tools:  In addition to the uses mentioned above, RFID has the potential to be leveraged as a basis for a variety of innovative decision support tools.  The data can easily be integrated into GIS systems, served over the Internet, or manipulated through handheld devices. 

Implementation Strategies for RFID Utility Marking

The following diagrams, obtained from a 3M presentation on the topic, demonstrate RFID implementation strategies for several different types of utilties.  In the illustrations below, the colored balls are representative of the RFID tag markers, which are typically installed alongside or directly on top of the underground utilities.  Typically, a good implementation strategy involved marking utilities at any changes in alignment or geometry, at major appurtenances, at crossings with other utilities, roadways, streams or railroads, and at other signficant feature locations.

Case Study - Use of RFID-enabled Utility Markers at Hartsfield-Jackson Atlanta International Airport

In 2006, the U.S. Federal Aviation Administration (FAA) buried more than 1,000 RFID-enabled marker balls around a new runway at the Hartsfield-Jackson Atlanta International Airport. The marker balls, supplied by 3M's Communication Markets Division, allowed the FAA, airport employees and contractors to use handheld RFID interrogators to locate utility cables and pipes buried five (5) feet underground, to determine what type of infrastructure they represent and who owns that infrasructure.   The following is an excerpt from the 2006 article on the topic, published by RFID Journal:

"The Dynatel 2200MiD Series Locating and Marking system uses 4-inch-wide, high-density polyethylene plastic marker balls, each containing a coil antenna and a passive RFID chip floating in a liquid combining water and biodegradable propylene glycol. This ensures that the liquid does not freeze. Since the RFID tag floats, it can automatically align itself in the best orientation for receiving and transmitting RF signals. The RFID chip's 256-bit memory includes the ball's unique serial number and also allows users to program additional data on the chip. The FAA is using that feature to program each marker ball with details as to which kind of cable is located in what location, whose cable it is and whether it is fiber, copper or another material. The ball can be positioned up to 5 feet underground. The FAA deployed the balls approximately every 200 feet along cables—every 10 feet in more congested areas with multiple cables in close proximity or with cable bends. After the ball is buried, a 3M RFID handheld interrogator can energize the RFID tag and receive the chip's RF signal. There are seven different frequencies, ranging between 66 kHz and 169 kHz, for telephone, power, gas, water, wastewater, CATV and general-purpose applications. The company opted for markers operating at different frequencies so utilities could differentiate between each type of underground infrastructure, says Dynatel product manager Corey Willson. 'Depending on the resonant frequency, the electronic markers mark a wide range of facilities,' he says."

As a final note, although this post is not intended to be an endorsement of any particular product, it is worth noting that the company 3M is something of a pioneer in the RFID utility-marking field - one of the first to commercialize an entire product line, in fact.  The photograph below shows their entire product lines, which consists of markers that function at varying installlation depths, between 2 and 8 feet.

Conclusion

One of the important thing to note about the Atlanta airport case study is that airports are, by nature, extremely busy and dynamic environments - both above and below ground.  Buried utilities are typically very densely distributed throughout the airport grounds, which itself is constantly under construction with the addition of terminal expansions, new taxiways, and runway extensions.  This fact makes RFID a very attractive solution for underground utility marking at airports, with an exceptionally good Return-on-Investment (ROI).  It should be noted, however, that other types of facilities can similarly benefit from RFID utility marking.  For example, college and university campuses, amusement parks, concert venues, commercial and industrial complexes, and public parks all share the same utility infrastructure management challenges as are found at a typical airport.   

References

1. RFID-Based 3-D Buried Asset Location System
2. 3M Dynatel Locating and Marking Technology Presentation
3. Applying Subsurface Utility Engineering to Highway and Road Projects
4. RFID Markers Track Buried Cables at Atlanta Airport