Buried Treasure

T H E V O I C E O F P R O F E S S I O N A L S S E R V I N G A M E R I C A ’ S C O M M U N I T I E S / j a N U ar y 2 0 1 0 / w w w . p w mag . com
● Surveying and mapping / By Darlene North
Buried treasure
A transportation department leads utilities in
deploying radio-based marking technology.
L
ike any highway engineer, Matt
McLaughlin dreads coming across
unexpected water, gas, cable, sewer,
and electrical lines.
“It costs more than $1,000/hour to
put an excavator on hold while a buried utility question is resolved,” says
McLaughlin, who oversees construction
of the relocated utilities related to roadway construction in the Northern Virginia District for the Virginia State DOT
(VDOT). “And in the case of a damage
incident, the safety implications, in addition to public safety costs, are even
greater — not to mention the cost of the
repair, possible evacuations, and personal
injury or loss of life.”
In his quest to minimize these challenges on a $70 million reconstruction
project in suburban Washington, D.C.,
McLaughlin made VDOT the first state
transportation department to implement electronic marking intended for
use by all participating utilities. The system combines radio-frequency identification (RFID), GPS, and GIS technologies,
and is being developed by VDOT; the Gas
Technologies Institute; the Virginia Utility Protection Service, which is the state
one-call operation center; and others to
create a single repository for buried utili-
Virginia DOT is using tiny computer chips inside buried plastic spheres to store the location, ownership,
attributes, placement date, orientation, depth, and assets buried nearby with public and private
utilities via a master geodatabase. Photo: 3M
How it works
2. Add marker
data to GIS
mapping database
A
4. Review
stored data
1. Program and
bury marker
3 to 4
feet
3. Locate and
read marker
Varies by
location
Buried utility
ty mapping to which all stakeholders contribute and refer.
It’s being tested at an intersection
where two major routes, each with four
lanes, are being expanded to six lanes
with 28-foot medians. The average distance between pipe crossings along the
60-foot-wide roads is 3 feet, and more
crossings will be added during the threeyear utility-relocation phase. The crossings must be free of grade cuts, drainage
crossings, traffic signals, and other construction elements.
“The relocation work is substantial,
with every utility interest represented, including gas, telephone, power, CATV, two
water authorities, sanitary sewer, and 13
fiber-optic companies, so the accuracy of
the relocated facilities will have a significant impact to the project,” says McLaughlin.
Passive underground markers have
been in use for more than three decades,
but RFID markers have capitalized on
the signal transmitted by an interrogating
device — in this case, a handheld RFID
tag locator — and are designed to last for
s contractors reinstall pipes and cables, they give Matt McLaughlin,
who oversees the construction of the relocated utilities related to
roadway construction in the Northern Virginia District for the Virginia State
DOT, and his crew the elevations for where the markers will be installed.
Inspectors add that information to each marker’s file and transmit all the
information about that marker via the portable locator.
Once programmed, the 4-inch plastic spheres are dropped into the
backfill material of the trench at a selected, pre-recorded depth (generally
3 to 4 feet below grade), taking future grade changes into account. The
spheres are distinguished by colors and interrogation frequencies for each
of the seven utilities. After backfilling, the department takes GPS readings
at each site to include the marker coordinates in addition to the rest of the
data stored on each marker in the master GIS database.
Programming and marker placement can be done without delaying
excavation or utility placement. Daily data entry means that mapping
details are regularly updated and quickly accessible to stakeholders. The
distributed record consists of a PDF file with all GIS data, including pop-ups
for each marker position that list programmed data and GPS coordinates.
Utility employees can view the information on a computer screen merely
by placing the cursor at a specific location.
McLaughlin expects the database to enhance the partnership between
his agency, utilities, the Virginia Utility Protection Service, and the Virginia
State Corporation Commission. The system is now being applied to an
interchange project in Gainesville, Va., as well as other smaller projects in
Northern Virginia.
“Buried utilities are critical to public services, and
we’re protecting these high-value assets during the
highway construction operation.”
— Matt McLaughlin
the life of the buried asset. Power is provided by the signal from the interrogating
device signal, and information is read as a
reflective radio frequency response.
Accuracy is another benefit. It helps
eliminate the interference and false
marking common to standard locators,
particularly in areas as congested as
McLaughlin’s project site.
Although GPS is an important component of asset management for utilities and
road departments, it provides only submeter accuracy, not the accuracy needed in
real-world environments. An RFID tag
identifies an asset within inches.
Likewise, conventional tracking provides only approximate position and
depth; and when there are high-voltage lines overhead, a high water table,
or other pipes or metal objects in close
proximity, it can be difficult to pinpoint
and accurately identify specific buried
assets. Radio waves can distinguish not
only between utilities but also between
the specific assets of a particular utility when adjacent markers are tuned to
the same frequency. This information is
conveyed by the data programmed into
the RFID tag.
What McLaughlin needed was a primary physical marking and locating
method that would deliver accurate and
reliable point location despite soil conditions, nearby utilities, or the temperature extremes normally found underground. He also needed a system that
would translate his department’s GPS
language — station numbers and offsets
— into the GPS language of latitude and
longitude coordinates that utilities use.
His contacts at the Virginia Utility
Protection Service told him about a pro-
grammable electronic marking system
that 3M Track and Trace Solutions introduced in 2002. The system is composed of a waterproof device — the 3M
EMS 1400 Series iD ball marker — that
houses an RFID chip that can be found
easily from aboveground using the portable Dynatel 2200M Series ID marker locator.
Buried next to an underground asset, the marker’s antenna transmits its
location as a reflective radio frequency
response to the locator along with the
marker’s unique identification number,
information about who owns the asset,
the asset’s function (splice, valve, service
tee, direction change), and its depth.
McLaughlin’s team decided that
about 600 marker balls would be needed to identify the relocated utilities at a
cost of $15/marker — or about $10,000
total including installation.
Then McLaughlin developed a master utility relocation plan that includes
entering marker data immediately into
a master GIS database to be delivered
to participating utilities. So although
each party owns the data on its assets,
it can share the information with other
stakeholders via a single-point repository that’s still being developed and will
be password-protected for security. The
Virginia Underground Protection System will host the combined database.
According to agreed-upon protocol,
utilities must install markers on relocated assets every 50 feet for metallic pipes
and every 25 feet for nonmetallic pipes;
at points of horizontal and vertical direction change; at critical utility crossings;
appurtenances that are important to the
utility; service connections; and abandoned facilities. To quickly locate service
connections, the facility’s address and
other specific data can be programmed
into the RFID tag to enhance accuracy.
Using a template provided by 3M,
McLaughlin’s construction managers or
inspectors enter the data for each utility’s
assets — a unique 10-digit serial number, as well as the name of utility owner,
item description (gas, water, or cable TV),
item details (valve; splice; service tap; horizontal and vertical change in direction),
placement date, depth below grade, orientation, elevation, and information about
adjacent items (for example, that a pipe or
cable lies below) — into the master database. Each utility owns the data it collects.
The department developed a compressed code for this purpose that fits
within the available 256-bit RFID tag’s
memory capacity and is useful across
utility categories. Construction managers also worked with 3M to modify templates to maximize the amount of information that can be programmed into the
tag.
“Our pilot program confirmed the
usefulness of these markers to improve
both the accuracy and efficiency of locating underground utilities and minimized the potential for costly damage,”
McLaughlin says. “This is a ‘safety first’
initiative.” PW
— North is a product manager for 3M
Track and Trace Solutions in Austin, Texas.
Posted with permission from the January 2010 issue of Public Works magazine. © Hanley Wood.
#1-27335846 Managed by The YGS Group, 717.505.9701. For more information visit www.theYGSgroup.com/reprints.