March 12, 2019

Geosyntec to Present at Asset Integrity Management - Pipeline Integrity Management Under Geohazard Conditions

Geosyntec professionals will make technical contributions at Asset Integrity Management - Pipeline Integrity Management Under Geohazard Conditions (AIM-PIMG) at the Norris Conference Center in Houston, Texas on March 25-28, 2019.

Geosyntec staff in attendance will be: Rodolfo Sancio, Tony Rice, Logan Brant, Ali Ebrahimi, and Alex Greene.

Asset Integrity Management – Pipeline Integrity Management Under Geohazard Conditions Conference will present the advances in managing ground movement hazards that have been made in the last decade. Ground movements, such as landslides and subsidence/settlement, can pose serious threats to the integrity of pipelines. Girth welds tend to be the weakest link in the integrity of a pipeline subjected to ground movement hazards. Unfortunately, girth welds made to comply with industry standards such as API 1104 are not guaranteed to have high resistance to longitudinal stresses or strains. In addition, American Society of Mechanical Engineers (ASME) codes such as B31.8 specifies that the maximum permitted longitudinal strain is to 2% without providing any direction on how to ensure that the pipe can meet this strain capacity. The technical presentations will focus on topics addressing design, qualification and construction of new pipelines and integrity management of existing pipelines and identifies any remaining gaps in existing regulations and industry codes. In addition to the technical sessions, two panel sessions are organized for regulators to discuss regulation philosophy and for pipeline operators/owners to discuss safe pipeline management strategies.

The conference is sponsored by the American Society of Mechanical Engineers (ASME), which is a not-for-profit membership organization that enables collaboration, knowledge sharing, career enrichment, and skills development across all engineering disciplines, toward a goal of helping the global engineering community develop solutions to benefit lives and livelihoods. Founded in 1880, ASME has grown to include more than 100,000 members in more than 140 countries.


Title: Guidelines for Managing Geohazards Affecting the Engineering and Construction of New Oil and Natural Gas Pipelines
Authors: Dr. Rodolfo Sancio, Senior Principal, Geosyntec Consultants, Inc.; Mr. Anthony Rice, Senior Principal, Geosyntec Consultants Inc; Dr. Jean Audibert, Independent Consultant, Independent Consultant; Mr. David Morgan, Independent Consultant, Independent Consultant, Ms. Jordan Rattray, Senior Counsel, Geosyntec Consultants, Inc.
Time: 10:00 a.m. – 11:30 a.m., March 25, 2019.

Abstract: Pipelines are inextricably exposed to geohazards given that they are long linear facilities that encounter variable terrain and geologic conditions, including watercourses. As such, reconnaissance, feasibility, and engineering design studies for new or existing pipelines need to include analyses that identify, characterize, and mitigate the potential long-term effects of geohazards on pipeline integrity. Also, there is a growing recognition that potential short-term effects of geohazards during construction, need to be addressed. Developing a pipeline project without considering geohazards early in the project cycle and mitigating them, as appropriate, is likely to lead to greater construction costs, contractor claims, schedule delays, and ultimately higher operational costs. The technical literature includes numerous publications describing approaches, methodologies, and recommendations, for identifying, characterizing, and mitigating geohazards, as well as case histories of pipelines affected by geohazards and how their effects were mitigated. However, these publications are not comprehensive, separately provide information for identification, characterization, and mitigation, do not include all geohazards affecting pipelines, or may not have been developed specifically for pipelines. Under the auspices of the Pipeline Research Council International, Inc. (PRCI), a guidance document has been prepared by the authors to efficiently incorporate geohazard management guidance into a single volume addressing: i) the types of geohazards affecting pipelines, ii) the typical process used in practice to identify and characterize the geohazards throughout the various project stages, iii) the techniques used to mitigate the geohazards, and iv) the approaches and methods recommended to project teams of owners, operators, engineers, and contractors to successfully mitigate project risks. The guidance document is intended for a wide audience that includes technical and nontechnical managers at pipeline owning and operating companies, geoscience and engineering teams involved in studies and assessments of pipeline integrity hazards, and construction staff, regulators, lenders, and other stakeholders involved in executing pipeline projects. This paper presents an abridged version of the PRCI guidance document [1] with updates.

Title: Example of a Semi-Quantitative Stream Crossing Hydrotechnical Hazard Assessment for a New Pipeline
Authors: Dr. Rodolfo Sancio, Senior Principal, Geosyntec Consultants, Inc.; Mr. David Vance, Senior Geologist, Geosyntec Consultants, Inc.
Time: 8:00 a.m. – 9:30 a.m., March 27, 2019
Abstract: Industry guidance and recommended practice documents, such as CEPA's 2014 "Pipeline Watercourse Management - Recommended Practices", and the more recent version of API RP 1133 "Managing Hydrotechnical Hazards for Pipelines Located Onshore or Within Coastal Zone Areas", provide helpful information related to conducting hydrotechnical hazard and/or risk assessments for stream crossings. However, little direction is provided in these documents, or in other readily available published literature, on specific steps or processes that may be followed to semi-quantitatively estimate the hydrotechnical hazard level of a stream crossing. This paper describes the steps that were followed in a Phase 1 hydrotechnical hazard desktop study to estimate the hazard level for a proposed new gas pipeline that traverses various physiographic provinces in mountainous terrain in the eastern US. The Phase 1 work comprised the compilation and analysis of stream channel and watershed characteristics and geomorphic attributes at each stream crossing along the pipeline, together with susceptibility to flood flows and other geologic hazards (e.g., debris flows) that affect the likelihood for vertical and horizontal movement of the stream bed, as well as potential pipeline exposure. Threshold values and scores were assigned to each attribute, the data was analyzed in a GIS platform, and then streams were sorted into three semi-quantitative hydrotechnical hazard levels according to their scores: 1) low hazard stream crossings, which could be addressed through commonly used industry rules of thumb such as 5 feet of cover below thalweg and 15 feet of sag-bend set-back beyond the ordinary high water mark, 2) moderate hazard stream crossings, which would require additional engineering assessment, design and mitigation such, as additional cover, greater sag-bend set-backs and/or bank protection, and 3) high hazard stream crossings, which would require specialized engineering assessment, design, and mitigation, or specialized construction methods such as horizontal directional drilling (HDD). The results of the Phase 1 study were used to support selection of sites requiring later field verification (Phase 2). Data from the field verification was then used to support the design of hydrotechnical hazard mitigation including specific recommendations for burial depth, sag-bend setbacks, bank or bed protection, and other measures.

Title: Performance-based Approach for Stabilizing Steep Slopes on Pipeline Right of Way
Authors: Dr. Logan Brant, Senior Engineer, Geosyntec Consultants, Inc.; Dr. Rodolfo Sancio, Senior Principal, Geosyntec Consultants, Inc.
Time: 8:00 a.m. – 9:30 a.m., March 27, 2019
Abstract: Pipelines around the world are built through rough terrain that includes natural slopes that can be marginally stable. The standard of practice is that the stability of the slopes along the pipeline route is rarely formally evaluated to calculate the factor of safety or likelihood of landslide triggering. An evaluation that would render reliable values of factors of safety (FOS) would require a degree of characterization that cannot be achieved for these long linear structures given that subsurface conditions along the slope prior to pipeline construction are spatially and seasonably variable and can be affected by weathering over the design life of the project. Best practice is to conduct geomorphological evaluations to identify areas that are prone to landslides, such as steep slopes or gentler slopes with relatively weak soil or rock formations. Where it is practical, areas that are subject to landslides before pipeline installation are avoided. When steep areas cannot be avoided, the pipeline is typically installed with best management practices that are intended to mitigate the landslide hazard. These include minimizing ground disturbance during pipeline construction and application of surface water diversions and subsurface drainage, along with other stabilization measures, such as re-establishing vegetation and soil compaction. When enough of these mitigation measures are applied to steep slopes disturbed by pipeline construction the result can generally offset soil strength losses attributed to ground disturbance. In steep slope environments, such as in Appalachia, some natural slopes become unstable following periods of intense precipitation and ground saturation. When slope instability does occur, shallow landslides and soil creep are among the most common mechanisms of permanent ground displacement (PGD). Mitigating these natural processes from occurring on the pipeline right of way (ROW) is not always practical, particularly where they may have occurred naturally regardless of pipeline construction. Emphasis should be placed on the overall risk to the integrity of the pipeline and addressing those with appropriate mitigation measures, such a burying the pipe deeper than the minimum requirement, if needed, to reach stable soil or rock formations and maintaining the stability of the trench backfill. Since the computation of a FOS is highly uncertain and may not reflect the likelihood of initiation of instability, a performance-based criterion is therefore considered to be a more appropriate approach for the design and construction of pipelines along natural steep slopes. Using this approach, the risk of landslides occurring and their possible effects on pipeline integrity, although unknown, is tolerable to the pipeline operators because the slope is expected to perform in a way that is similar to its performance prior to the installation of the pipeline. This paper discusses the technical challenges facing construction of new pipelines on steep soil-covered slopes and provides recommendations for implementation of a performance-based design criterion to mitigate instability of steep slopes on pipeline ROWs.

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