By Mary Jo Wagner, freelance writer, Vancouver,
B.C., Canada.
The numbers are disconcerting—11 millimeters, 7 centimeters, 20 feet, 30
feet. While not individually significant, they cumulatively indicate how
much some of the world’s major cities or regions have sunk or are
sinking each year. The city of Shanghai sank an annual average of 16
millimeters from 1991 to 2002 and continues to fall at a rate of 11
millimeters a year. Jakarta loses 7 centimeters of elevation every year.
Terrain west of Phoenix has sunken more than 20 feet during the last 40
years. California’s southern San Joaquin Valley has lost 30 feet of
elevation. Added to the list of well-known sinking cities such as
Venice, Mexico City, Osaka and Los Angeles, one begins to feel a little
uneasy about just how stable, or unstable, the ground is.
Rocketing population growth and demand for
natural resources—particularly groundwater—place tremendous strain on
terrain and underground infrastructure such as wells, pipelines and
cables. These issues, combined with intense precipitation events,
changes in groundwater conditions, erosion, steepening of slopes,
earthquakes, stream scouring and encroachment, can lead to significant
geohazards, including landslides, debris flows, ground settlement,
subsidence and soil heave—all of which can seriously affect underground
systems.
Despite the sizable financial and publicrelations gamble (see
“Geohazards Management Makes Dollars and Sense” at right), the pipeline
industry in general exercises a reactive approach to subsidence and
encroachment risks, deeming them unpredictable and infrequent enough to
manage with minimal technology investments. Although a growing number of
pipeline and extractive companies are adopting new technologies to
better their integrity management systems, several players still live in
denial about potential geotechnical liabilities, much the same as people
who ignore chronic aches and pains because they aren’t prepared to deal
with the consequences of diagnosis.
“That ‘ignorance is bliss’ attitude just isn’t good enough anymore,”
says Brian Young, a civil engineer and consultant in North Vancouver,
B.C. “Particularly when you have viable, advanced technology available
that can tell you what’s happening along your assets, down to the
millimeter.”
The advanced technology to which Young refers
is Interferometric Synthetic Aperture Radar (InSAR). A radar
satellite data processing technique, InSAR is a tool that allows
users to map and monitor subtle—1 centimeter and smaller—changes in
surface position, whether it be vertical movement of the surface or
structural movement through subsidence. Together with traditional
monitoring methods, InSAR data can provide companies with broad,
highly detailed environmental intelligence to help them plan
installations, monitor the integrity of their linear assets,
determine the impact of their operations and devise strategies to
avoid property or environmental damage.
InSAR Options
InSAR is a long-established and proven technique for measuring and
monitoring land subsidence, but only during the last few years has
it escaped its earthquake “pigeon hole” and surfaced as a
less-expensive and more precise alternative to detect and monitor
geohazards. Its increased stature as a strong candidate for
commercial applications is due mainly to recent breakthroughs in
processing techniques—namely corner reflector InSAR (CRInSAR) and
permanent scatterer InSAR (PSInSAR)—that overcome the shortcomings
of conventional InSAR and offer even better precision.
Together, CRInSAR and PSInSAR are heightening the commercial
attractiveness of InSAR to a broad breadth of organizations,
including utilities, engineering companies, pipeline companies,
local government and extractive companies. Of that list, the
pipeline and extractive industries have become heavy targets for
geospatial organizations eager to prove the feasibility of
integrating InSAR intelligence into regular operations.
Since 2001, the European Space Agency (ESA) has launched at least 14
InSAR-related projects to study the technology’s benefits to
monitoring geohazards—three specifically target the pipeline
industry, one of which, PIPEMON, is still ongoing.
Launched in November 2003, the three-year ESA-funded PIPEMON project
is designed to define and develop an integrated service to provide
ground motion information along the routes of existing pipelines and
for pipeline route planning. Led by Nigel Press Associates (NPA), a
satellite mapping company based in Edenbridge, England, that
specializes in InSAR applications for ground displacement and
subsidence detection, the aim is to conduct pre-commercial trials
with market players and potential customers to introduce these
services to Europe’s pipeline industry.
In addition to PIPEMON, ESA’s TerraFirma initiative aims to establish a
pan-European ground motion hazard information service. Also launched in
2003 and led by NPA, TerraFirma partners use hundreds of ESA ERS-1 and
ENVISAT satellite images and apply PSInSAR techniques to map geohazard
risks such as urban subsidence and landslides for a host of European
cities. To date, the group has processed 14 European cities, including
Stoke-on-Trent in the United Kingdom, Berlin, Lisbon, Moscow, Istanbul,
Palermo, Brussels and Haifa, Israel. Initial products have been
delivered and are being used by a variety of end users such as
utilities, urban planners and local authorities to identify problem
areas—often undetected previously—and devise strategies to combat them.
“The recent advancements in InSAR are really opening a new awareness of
land management in that what we’ve assumed is stable ground is actually
moving,” says Ren Capes, NPA’s manager of InSAR application development.
That is a concern for pipeline operators who may feel their pipeline is
safe and sound underground when actually the terrain around it is moving
and shaking. Realizing that too late can be costly.
An InSAR Information Pipeline
Rio de Janeiro-based Transpetro, a fully owned subsidiary of Petrobras,
Brazil’s national petroleum company, paid a hefty price for such an
oversight in 2000 when an undetected crack in a remote pipeline leaked
crude oil into the Iguacu River and the company was fined for
environmental damage. Not surprisingly, the incident greatly changed its
perspective on asset monitoring and integrity management systems.
With Petrobras already an avid user of RADARSAT-1 satellite imagery for
oil monitoring operations, Transpetro thought it might also be of use to
improve its pipeline monitoring operations. That idea led to the launch
of an ambitious initiative to develop an integrated pipeline geohazard
monitoring service (IPGMS) in conjunction with MDA Geospatial Services
International based in Richmond, B.C., and an additional key U.S.
client, GeoEngineers, a Redmond, Wash.-based company that provides
geotechnical, environmental, and technology consulting services to
pipeline companies and other organizations.
Started in April 2005 with seed funding from the
Canadian Space Agency, the two-year project aims to definitively show
pipeline companies that InSAR can provide cost-effective and
complementary intelligence to enhance traditional monitoring systems and
equipment. Most importantly, MDA plans to prove this in regions such as
Brazil and Washington state, where it’s been nearly impossible to apply
conventional InSAR because humid conditions cause too much decorrelation.
“These are challenging areas where traditional InSAR hasn’t worked in
the past,” explains Gordon Rigby, MDA’s international projects manager.
“However, we’re using specific PSInSAR techniques that should enable us
to apply the technology more effectively in wet environments.”
For the IPGMS project, six study sites have been designated, two of
which—one in Rio de Janeiro and one in southwest Washington—are being
studied initially. For the Rio de Janeiro site, the team placed 12
corner reflectors along a 1-kilometer stretch of underground pipeline
well known for its instability and vulnerability to landslides. More
than 30 RADARSAT-1 fine beam mode images (8-meter resolution, 50 x 50
square kilometer swath) have been acquired that clearly reveal the
corner reflector targets. InSAR processing began in mid-January 2006 to
assess the site for any displacements. MDA plans to deliver the first
InSAR product prototype to Transpetro in March.
“We continually adopt new technologies that can help us reduce costs
while improving our asset monitoring,” says Ulisses Dias Amado in
Transpetro’s technical consulting department. “We believe InSAR will
provide us this opportunity, because it will allow us to more
effectively monitor wider areas, particularly remote areas to detect
subtle ground movements along our pipelines. That is a critical
information source for further pipeline engineering analysis, which will
help us make better business decisions.”
“Conventional tools like inclinometers and strain
gauges provide very accurate movement information for specific points
along a pipeline,” adds Adrian McCardle, MDA’s IPGMS project manager.
“But what they may not indicate is the source of the shift. InSAR
supplements those points by providing sub-centimeter measurements over a
large area, helping users find the point of origin.”
The process for the Washington site was similar.
The team placed reflectors along a known, unstable stretch of pipeline
owned by one of GeoEngineers customers. The reflectors complement
existing inclinometers that already have been indicating recent ground
movement along this particular pipeline segment. More than 30 RADARSAT-1
scenes were gathered, revealing the artificial targets, and InSAR
processing is under way. GeoEngineers also will receive its first
prototype product in March.
“Pipelines often run for long distances through remote, inaccessible
areas, and it is expensive to use traditional methods to monitor those
problematic sites,” explains Richard Duncan, a geologist and geospatial
analyst at GeoEngineers. “For pipeline companies often faced with aging
assets and tight maintenance budgets, InSAR presents a far more
practical and less expensive alternative to dispatching personnel into
the field.”
A New Perspective on Route Planning
Another facet of the IPGMS project is to test the feasibility of InSAR
for pipeline route planning using a study site in the remote Amazon, an
area where Transpetro plans to build a pipeline. MDA’s Rigby says
engineers know there is tectonic activity there, but they aren’t sure
how much geohazard risk the area presents. InSAR data of this
challenging area will provide detailed environmental knowledge to help
them plan their route.
By using InSAR data as a pre-planning tool, operators stand to avoid
significant cost by first choosing routes in stable areas and then
installing cost-effective tools to monitor the line, according to
Bernhard Rabus, a leading InSAR expert in MDA’s Research and Development
department. Says Rabus, “If you use InSAR to plan a suitable route—
particularly in remote areas—and then strategically set additional
reflectors along the pipeline during construction, the cost of adding
the reflectors is totally negligible, and it will be far cheaper to
monitor the pipeline over time.”
Digging for the Truth
Because PSInSAR requires users to acquire stacks
of data, there’s great potential to use the information for other
applications such as encroachment or mining. According to the U.S.
Department of Transportation Office of Pipeline Safety, more than 60
percent of natural gas distribution pipeline incidents were caused by
outside force damage, including third-party excavation, in 2002-2003.
Operators have much to gain from adopting a more holistic approach to
maintaining pipelines.
“Pipeline companies are responsible for their
pipeline right of ways, but there are many forces outside that narrow
swath, such as urban development, that can seriously affect their
structures,” says MDA’s McCardle. “Both Transpetro and GeoEngineers’
clients have a real need to monitor encroachment risks. Near the
Washington study site, for example, there is a subdivision built on a
slope that has already shown signs of movement—a newly paved road has a
sizable crack in it. Although this development isn’t directly on the
pipeline, it would affect it should there be a landslide. It’s important
for companies to understand how parallel activity can affect their
lines.”
Excavating activities such as mining stand to benefit from InSAR
information as well—some work already has garnered positive results.
International engineering firm AMEC used InSAR to assess subsidence
around the closed Hollinger gold mine near Timmins, Ontario, Canada, for
mining giant Placer Dome. Processing archived data from 1992 to 2003,
AMEC detected subsidence ranging from 25-55 millimeters within an area
previously deemed stable based on results from conventional geological
instruments and survey techniques. The company is translating that
success to other mines, including South Africa’s Palabora copper mine,
where it uses ERS-1 and RADARSAT-1 imagery to study ground subsidence.
Young sees great potential for InSAR in mine decommissioning monitoring.
When a mine is decommissioned, companies are required to monitor the
area to ensure its safety. InSAR could be an effective, routine tool to
monitor the integrity of the structure remotely.
Stopping the Slide
A proven remote surveillance tool, PSInSAR also has been found to be an
equally impressive monitoring tool in urban settings, providing ground
movements of an individual building down to the millimeter. The fact
that an urban environment sank 2 millimeters last year may not induce
panic, but all those little slumps eventually lead to sizable drops,
like those of Phoenix and Jakarta. InSAR won’t be the rubber stopper to
plug the drain, but it may help planners and engineers stem the size of
the drop.
