by Thomas Seeber, Lead Pipeline Engineer, Atteris
River, road and rail crossings will usually be required in the construction of new pipelines. The Energy Pipelines Cooperative Research Centre has combined with the industry to establish best-practice guidelines to ensure crossings are completed safely, efficiently and with minimal impact on the surrounding environment.
Pipeline shoreline and waterway crossings have traditionally been challenging sections in pipeline routes. The primary objective is to ensure that the pipeline at the crossing will maintain its integrity during the operational lifetime of the entire pipeline system. Just as important is the care for the natural environment.
The geology along shorelines and waterways can be complex. In some cases, a natural waterway has been formed along an ancient geologically active zone. In many cases, gravels and cobbles have been deposited in the bed or banks. Rivers can experience intense flooding events and are usually subject to meandering. Shorelines are often subject to gradual or extreme change under the influence of waves, tidal currents, and weather. Sometimes there is a natural seasonal erosion or accretion process with fluctuating beach levels. Shoreline cliffs are also often subject to catastrophic erosion and collapse. These geomorphology processes can sometimes be difficult to predict, introducing risks for the operation of a pipeline system.
In Australia, shorelines and waterways are almost always pristine environmental habitats for flora and fauna. They are also highly valued by people for a range of purposes. Australian legislation requires that due care is applied when planning, designing, building and operating pipelines across these areas.
The need for better engineering guidance at crossings in pipeline routes has been relevant for decades; not only in Australia, but also globally.
Safe, efficient, reliable
The Energy Pipelines Cooperative Research Centre (EPCRC) enables safer, more efficient, and reliable pipelines to meet Australia’s economic growth. This is achieved by providing the Australian pipeline industry with the technology necessary to extend the life of the existing pipeline network, and to build better, more cost effective networks necessary to support increased demand for utilities.
To address the above concerns in relation to crossings in pipeline routes, the EPCRC Offshore Users Group teamed up with Woodside Energy and Chevron Australia to form the Crossway Joint Industry Project (JIP), together with subsea and pipeline consultancy Atteris.
Selecting Atteris to undertake the work was a logical choice, given their extensive design and engineering expertise in this field. This has included many trenchless river and shoreline crossings in Australia and overseas, including small scale projects as well as large diameter pipelines; such as the Alkimos Ocean Outfall, Gorgon’s HDD shore crossing and Wheatstone’s microtunnelled shore crossing, to name a few recent Australian examples.
Research study and engineering guideline
The objective of the Crossway JIP has been to develop an Engineering Guideline for these challenging areas in pipeline routes. It was proposed to develop the guideline in two phases. The first step was to conduct a research study in order to collate all the existing relevant literature, and identify any gaps in the industry’s knowledge. This formed the basis with which to develop the engineering guideline.
The study has involved the review and assessment of applicable national and international engineering standards, as well as relevant published literature such as books, technical papers, company standards, existing engineering guidelines, and technical articles. In addition, Atteris’ extensive national and international in-house expertise was applied; including lessons learned from a large number of projects in Australia, Asia, Europe, Africa and the Americas. An overview of the regulatory approvals regime in relation to designing, constructing, and operating pipelines at shoreline and waterway crossing locations in Australia has also been provided.
The Engineering Guideline has subsequently been prepared to provide recommended processes and considerations to assist the design of pipelines at shoreline and waterway crossings, from the early concept development through to detailed design. Guidance for the operational phase of a pipeline system at crossings, focusing on inspection, monitoring, maintenance and repair, has also been included. Finally, the topic of decommissioning is addressed in the guideline.
The document presents an overall approach to engineering in relation to pipelines at crossings. A clear process is given, broken down into design steps, for the pipeline route selection and crossing design development. This incorporates the required engineering design data, such that appropriate site data collection can be planned and coordinated for each design step.
A comprehensive pipeline system integrity design section is provided, which outlines all the considerations that require assessment in order to complete the engineering design of a crossing. The topics range from system and mechanical design through to external coatings and cathodic protection design. Pipeline stability and seismic loading are covered, among many other topics. The construction, commissioning and operational considerations that might influence the design are also listed.
In addition to these, specific issues common to shoreline and waterway crossings are presented: environmental preservation and design interface management.
The recommended environmental preservation philosophy at crossings is that it should be an integral component in the development of the design of a crossing, rather than an afterthought. Key decisions in any phase should always consider the impact on the natural environment. Environmental submissions should have appropriate engineering input reflecting the design of a pipeline at a crossing. The timelines for development of a crossing design and the environmental approvals processes should be integrated at an early stage of the design, and regularly updated as the design progresses.
Design interface management is relevant for all engineering design, and can be particularly onerous for pipeline shoreline crossings on very large projects. Internal interfaces are those between the different disciplines within a project or operations team. External interfaces are those between the project or proponent and an external stakeholder. Interfaces can be managed formally or informally, depending on the nature, size, culture, complexity and composition of a crossing. For large scale and complex crossings, a detailed project interface system should be developed in the early project phase.
The work performed under the JIP was completed within a ten-month period. The research study commenced in September 2014; the Engineering Guideline was delivered in its final issue in June 2015. Further work is necessary to refine and add to the guideline, and to close some existing gaps in the knowledge of complex technical issues regarding pipeline shoreline and waterway crossings.
The Engineering Guideline has been presented to the AS2885.4 Standards Review Committee with a recommendation to incorporate the considerations outlined within. The recommendation has been received favourably and work has begun to update the standard. Det Norske Veritas (DNV) of Norway has also expressed interest in the guideline and the JIP partners are working together with DNV to update their submarine pipeline standard DNV-OS-F101.
