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Containment Systems Working Group

Containment Systems Working Group's (CSWG) current remit

The CSWG was set up in 2011 in response to policy and guidance that were developed after the Buncefield incident and which sought to improve the integrity of bulk storage facility operations. The focus is on primary containment in above-ground storage tanks and related secondary and tertiary containment systems. Specifically, its remit is to research and develop technical guidance and tools to meet knowledge gaps in the COMAH Competent Authority Policy on Containment of Bulk Hazardous Liquids at COMAH Establishments (‘Containment Policy’) and its supporting guidance, and PSLG Final report: Safety and environmental standards for fuel storage sites (‘PSLG Final report’). These knowledge gaps formed technical development projects, and CSWG has developed guidance and tools to fill those knowledge gaps using a robust scientific basis, and doing so independently with broad stakeholder input from industry, regulators, trade associations, consultancies and service suppliers. The products developed by CSWG provide a common understanding of how to meet the technical requirements of the policy and guidance.

Technical products delivered

EI Guidance on conceptual design, selection and life cycle assurance of liners intended to improve integrity of bunds to above-ground storage tanks for bulk storage of petroleum, petroleum products or other fuels

This publication provides a practical framework and is a source of information for those involved in the planning, management and operation of bulk storage facilities using above-ground storage tanks (ASTs), where lined bunds are expected as the principal type of secondary containment. It can also be applied to other hazardous liquids stored in ASTs and are subject to the requirements of the GB COMAH CA ‘Containment policy’ and EU Directive on the control of major-accident hazards involving dangerous substances (‘Seveso lIl directive’).

Background information on the regulatory and practical constraints applying to bulk storage sites are compiled and the concept of a staged life cycle process to the design, installation and operation of lined bund containment is introduced. The publication explains the multi-layered aspects of bund design, categorising these aspects on proposed individual bund systems and evaluating them against expected performance specifications. As well as setting out the permeability specifications and known technical and practical constraints, the publication also provides guidance on evaluation methods of bund performance during installation and operation.

Following the principles set out in this publication should enable operating companies to efficiently and effectively design, implement and maintain liner systems to a high degree of integrity, without needing to resort to over-design or over-engineering.

Publication is a available to purchase from the publications website, click here.

EI Guidance on risk assessment and conceptual design of tertiary containment systems for bulk storage of petroleum, petroleum products, or other fuels

This guidance aims to fill a knowledge gap surrounding the review of requirements for tertiary containment at individual sites, and the conceptual design for tertiary containment options. It is primarily for use by process safety specialists, environment risk assessment specialists, designers, operators and owners of installations holding bulk quantities of petroleum, petroleum products or other fuels.

The publication provides practical guidance to assist readers to meet the requirements of the GB COMAH CA ‘Containment policy’.

It also provides guidance on:

  • The completion of risk assessments to determine the need for tertiary containment.
  • Criteria for design of tertiary containment measures.

Whilst the focus of this document is on bulk storage facilities, the information provided here may also provide a useful reference to sites holding smaller quantities of such products, or to sites in related industry sectors storing other dangerous substances.

Publication is available to purchase from the publications website, click here.

EI Guidance on environmental management for facilities storing bulk quantities of petroleum, petroleum products and other fuels (3rd edition)

This publication provides guidance on managing environmental issues involved in the design, construction and commissioning, operation and decommissioning of bulk storage facilities. It provides management, technical and operational guidance to minimise the impact of bulk storage facilities on the environment, and in doing so, to help meet regulatory requirements.

In addition to covering bulk stores at petroleum distribution installations, the guidance contained in this publication can be used as a basis for environmental management at refinery off-sites, authorised distributor depots and bulk stores of LPG, bitumen, aviation fuels and lubricants.

The guidance takes account of new guidance and standards released since the publication of the 2nd edition, including the PSLG Final report and CDOIF guidance: Environmental risk tolerability for COMAH establishments (2013).

The document is structured to assist the reader by aligning with their different needs, which are primarily driven by:

  • Where the facility is in its life cycle (design, construction and commissioning, operation or decommissioning).
  • The COMAH tier of the facility (sub-, lower or top-tier).
  • The site use (e.g. bulk storage only, bulk storage and rail loading/unloading facility, etc.).

Publication is available to purchase from the publications website, click here.

Technical products under development

Above Ground Storage Tank – Base System Guidance – Title TBC
In press

This publication provides a practical framework that should enable operating companies to efficiently and effectively design, implement and maintain liner systems with a high degree of integrity, without the need to resort to over-design or over-engineering. In addition, these principles should serve to assist the value engineering process, helping to drive efficiency and ensure compliance with the COMAH CA’s requirements.

This is a complimentary publication to EI Guidance on conceptual design, selection and life cycle assurance of liners intended to improve integrity of bunds to above-ground storage tanks for bulk storage of petroleum, petroleum products or other fuels

The guidance explains the multi-layered aspects of below tank secondary containment design, and categorises these aspects in such a way that proposed individual system can be gauged against expected performance specifications. The aim is to provide a method for applying secondary containment and leak detection system design criteria, the appraisal of options, planning and managing the installation, and the operation and decommissioning of the secondary containment and leak detection features. In particular, consideration has been given to permeability specifications and known technical and practical constraints. Methods for the evaluation of bund performance (during both installation and operation) are also provided.


Bund wall pipe penetration and expansion/construction joint sealant fire resistance testing
Project under development

This project aims to test the fire resistance properties of commercially available sealants against a suitable performance standard. There is a gap in current knowledge on the performance of sealants however they fall under the GB COMAH CA 'Containment policy' promotes increased standards for bunding and requires ‘fire resistant ….. joints and pipework penetrations’. The PSLG Final report provides guidance on fire resistance and integrity of pipe penetrations, and guidance on bund wall expansion and construction joints. A critical element is the fire resistance of the sealant used to keep the pipe penetrations or expansion and construction joints leak tight.

The current industry view is that products that are tested to a standard such as BS476-20, ISO 834 etc. would offer up to four hours fire resistance.  However the industry has formed an opinion that it would be desirable for bund sealant systems to offer periods of fire resistance well in excess of this. The primary aim of this project is to furnish potential end users of the products, and the industry as a whole, with independently assessed information relating to the fire resistance and integrity of the sealants for situations where extended periods of fire resistance are required; such as in large, long duration pool fires in bunds.

Failure mode analysis assessment tool for AST - Phase 1
Project under development

The failure mode analysis assessment tool for aboveground storage tanks (ASTs) that is being developed aims to improve the predictive risk assessments for catastrophic AST failure that are undertaken when preparing COMAH safety reports. Using this tool will provide consistency in those predictive risk assessments and clarity in the required risk reduction measures, both for preventative measures (e.g. storage tank foundation integrity) and mitigation measures (e.g. liquid volume retention requirements following loss of primary containment).

The project intends to address a gap that is not fully addressed in PSLG Final report  and, nor in other supporting publications from CIRIA, EI, EEMUA or the COMAH CA. For example, EEMUA 159 Above ground flat bottomed storage tanks - a guide to inspection, maintenance and repair provides little information regarding failure modes, and whilst EI Research report: Catastrophic storage tank failure (in press) sets out six major AST failure modes, it doesn’t provide a basis for determining which one is more likely given a set of circumstances.

This project focuses on catastrophic primary containment failure modes and the factors that affect vulnerability to failure. It would provide a basis for assessing the significance of those factors on the likelihood of particular catastrophic AST failure modes on an AST-by-AST basis. The tool is applicable to bulk storage facilities storing other dangerous substances (like petrochemicals).

Further development of failure mode analysis assessment tool for aboveground storage tanks – effects of catastrophic failure on secondary containment
New project for 2016

Phase 2 would use the output from phase 1 to determine the effects of catastrophic tank failure from ASTs on secondary containment bunds. This will be done by calculating hydrodynamic loads on a bund wall to determine whether a bund will be subject to a breach or overtopping scenario, taking into account factors such as their configuration, construction material, and ongoing structural integrity. The type of liquid release, geography and ambient conditions may also be considered.

Phase 3 of this project would calibrate the Phase 2 deliverable ‘methodology for calculating hydrodynamic loads’ using 3 diverse test cases, which would require site measurements, analysis and modelling.

Phase 4 of this project would focus on foreseeable bund breach and/or overtopping fractions from those hydrodynamic loads, and onward liquid flow to tertiary containment systems (e.g. other bunds, drainage systems, emergency response, etc.) or offsite.