In a recent advisory bulletin (ADB-2022-01,
Potential for Damage to Pipeline Facilities Caused by Earth Movement and Other
Geological Hazards), PHMSA highlighted the importance of proactive integrity
management, to reduce the potential for damage to pipeline facilities caused by
earth movement or other geological hazards, collectively referred to as
“geohazards.”
The bulletin is part of the increased interest by
regulators in proactively managing geohazards, pipeline companies and the
public. The bulletin also demonstrates some of the increased awareness of how
these threats can be identified, assessed and ultimately managed prior to an
incident.
The good news is that geohazards are almost
always identifiable and recognizable prior to an incident — using the right
approach and using integrated data for a complete picture.
Geohazards can also be effectively managed
through a combination of monitoring and mitigation efforts. In this article,
we’ll discuss geohazards threats, the unique challenges associated with
geohazards, the key considerations for building a geohazard management program
and where the industry should concentrate efforts, so we — as an industry — are
able to find the geohazards before the geohazards find us.
Intro to Geohazards
In discussing geohazards, we have to first define
what we mean by the term “geohazard.” In
the context of the PHMSA bulletin, a geohazard can be defined as a naturally
occurring phenomena or human-trigged phenomena that occurs — similar to natural
phenomena that results in the displacement of soil or rock.
Geohazards include landslides, seismicity,
subsidence (such as from karst or collapse of underground mines), growth faults
and other similar phenomena. In some instances, the action of rivers and
streams is also considered a geohazard (also referred to as “hydrotechnical
hazards”), but for this discussion, we will focus on those that result in earth
movement.
An increase in awareness and an improvement in
the capabilities of inspection technology have transformed how we view
geohazards. A review of geohazard incident historical data from the PHMSA
Significant Incident Database reveals that the rate of geohazard incidence does
not appear to be increasing over the long-term; in other words, geohazard
incidents were just as common in the 1980s and 1990s as they are in the 2010s
and 2020s.
Still, the awareness around geohazards has
changed, and technological improvements that allow for pipeline operators to
proactively recognize and identify areas susceptible to geohazard occurrence
prior to an incident. In other words, geohazard events are no longer “Acts of
God” that cannot be predicted or addressed ahead of time.
Fortunately, these technological improvements —
such as lidar and inertial measurement unit (IMU) bending strain — have allowed
operators to identify and evaluate geohazards with far greater accuracy and
precision than was previously possible. This, in turn, greatly improves the
ability of operators to manage them.
How Geohazards Differ
Geohazard threats are inherently different than
other types of integrity threats — like corrosion or cracks — because
geohazards usually involve phenomena that not only extend outside of the
pipeline but also often extend well outside of the ROW and, at the time of
identification, may not even cross or intersect the ROW.
They also encompass a huge range of behavior,
from earthquakes that can happen with no advanced warning, to landslides that
can suddenly reactivate after years or decades of dormancy and which can move
at speeds measured in miles per hour or continuously move or creep at rates as
slow as inches per year.
Geohazards can be small and entirely confined to
a pipeline ROW, or they can be large, with sizes measured in tens of miles. The
approach to the management of geohazard needs to consider five basic
principles:
It is important to remember that there are often considerable uncertainties associated with geohazards, such as those discussed above. Geohazard management programs need to have appropriate conservatism and measures in place to account for and manage these uncertainties. It should also be remembered that with rare exceptions, most pipelines — even newer pipelines built in the 2000s — were not designed to accommodate the effects of geohazards, and thus, all pipelines (of any vintage) can be potentially affected by geohazards.
Threat Management
The integration of geohazards as part of a formal
component of pipeline integrity programs is relatively recent, with most pipeline
operator’s pipeline geohazard management programs dating only from the 2010s
and 2020s.
The field of pipeline geohazard management can be
considered developmental, and at this time, it has few prescriptive regulations
or agreed-upon industry standards. Thus, it is up to each operator to set the requirements
and structure for their geohazard management program.
To assist the operator in this process, the
Interstate Natural Gas Association of America (INGAA) Foundation has released
multiple sets of guidelines, including “Management of Landslide Hazards for
Pipelines”1and “Framework for Geohazard Management”2.
As described in “Framework for Geohazard
Management,” operators are recommended to identify and assess geohazards using
a three-level framework, progressing from an initial assessment (i.e., Level 1)
conducted at desktop level for entire pipeline systems, to a highly detailed,
site-specific assessment (i.e., Level 3).
Typically, the length of pipeline or number of
sites being assessed decreases with each increasing level of assessment. The
Level 1 Geohazard Assessment can be considered a screening-level assessment,
used to preliminarily identify areas susceptible to geohazard occurrence and to
target areas for the more detailed Level 2 and Level 3 assessments as needed.
The Level 1 Assessment is most reliable when
conducted using an integrated combination of IMU bending strain, geomorphic
assessment from lidar, and prior geologic and hazard mapping from public
agencies.
By integrating these multiple datasets, the
pipeline operator can perform complimentary assessments to identify areas
potentially susceptible to geohazard occurrence, and they can also evaluate if
the geohazard(s) may have already impacted a pipeline and the degree of that
impact (such as evaluating if a landslide that crosses a pipeline centerline
may have resulted in pipe strain).
While these tools can be used independently
(i.e., only lidar or only IMU bending strain), doing so can create gaps in the
identification and assessment of geohazards, which can increase the likelihood
of geohazards not being proactively recognized and addressed.
Where to Start
For the pipeline operator without a current in-house geohazard
management program or a relatively immature program, it can be daunting to know
where to start. The INGAA Foundation’s “Framework for Geohazard Management”
provides some good advice on this subject. These recommendations can be
summarized as follows:
Identify
someone to manage geohazards. Ideally,
this would be an employee or team inside the pipeline operator’s pipeline
integrity department, but this can also be an external contractor, if the
operator does not have the resources to staff it internally.
Establish
a preliminary process for Level 1 Assessment. This
should include reviewing the availability of data within the pipeline operator,
such as previously collected lidar and IMU bending strain, as well as past
records or databases of prior geohazard incidents.
Operations
staff should be consulted when starting a geohazard management program, as they
will often be aware of past locations of landslides and other geohazards.
Establish
how the data will be stored. Ideally,
the data management system will be a Geographic Information Systems (GIS)
database, such as the ESRI suite of ArcGIS products.
Conduct
a pilot assessment. Use a pipe segment or
system likely to have geohazards. The gold standard for conducting the Level 1
includes collecting lidar — specifically for the area being assessed — and
performing an IMU bending strain assessment to reflect the current condition.
However,
if lidar cannot be collected by the operator, there is an increasing
availability of reasonable quality lidar maintained by the United States
Geological Survey (USGS), although the data is of mixed resolution and age.
Similarly,
if an IMU bending strain analysis cannot be performed specifically for the
Level 1 Assessment, prior ILI runs may be analyzed (as long as IMU data was
collected) for bending strain — even if the ILI run occurred several years
previously.
Refine
the assessment process. Also,
establish classification and decision-making (CDM) criteria based on the
lessons learned during the pilot.
Continue
with the Level 1 assessment process. Do this
for the remaining areas of the pipeline system, then proceed to Level 2 and 3
assessments at targeted locations, based on the results of the Level 1
assessment. Further refine these approaches and the CDM as needed.
Establish
threat management approaches.
These should be based on the results of the leveled assessment process.
Implement
threat management measures. These
will include monitoring and mitigation to manage the geohazard threat.
Transition
the program to continue this cycle. Emphasize
monitoring, reassessment and response going forward. Additional assets that are
built, acquired or constructed should also be subjected to this process, too.
Integrated Approach
As a closing thought, operators are recommended
to have a comprehensive geohazard program that integrates information about the
pipe condition and information about the geological landscape. Both types of
data are required for a complete picture.
While IMU data might provide information on the
impact to a pipeline from a geohazard, it does not provide information on
threats that may not currently impact the pipeline but have the potential to do
so. Similarly, lidar may not be able to identify sites that have been
historically regraded or repaired, and it is not a reliable tool to evaluate
past impacts to a pipeline from a geohazard.
Ideally, using an approach with integrated data provides
operators with the most robust and reliable approach to prioritize threats and reduce
their exposure to geohazards.
As a final note for those operators with more
mature or established geohazard programs, combating complacency will be key.
Staying involved with pipeline industry forums and conferences and contributing
to research will be vital to the continuous improvement of these programs. P&GJ
REFERENCES
Rhett Dotson is chief engineer at D2 Integrity, a pipeline
integrity management consulting firm. With over 18 years of experience in the
pipeline industry, he has used his expertise to transform data collected from
in-line inspection, analysis, and full-scale testing to manage threats associated
with mechanical damage, geohazards, and vintage pipe materials.
Alexander McKenzie-Johnson is senior principal engineering geologist at
Geosyntec Consultants. He specializes in geohazard management and has 22 years
of experience, primarily as a consulting geologist, with additional time spent
implementing and running operations for a geohazard management program for a
large pipeline operator.