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Final report
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166 While priority should be given to preventing a loss of primary containment, adequate
secondary and tertiary containment remains necessary for environmental protection and safety
of people in the event of a loss of primary containment of hazardous substances. The failure of
secondary and tertiary containment at Buncefield contributed significantly to the failure to prevent
a major accident to the environment (MATTE).
167 The final report of the MIIB on the Buncefield Incident of 11 December 2005 provides two
recommendations covering engineering against loss of secondary and tertiary containment. These
are detailed below.
168 The COMAH CA Containment Policy was issued in February 2008 and Containment Policy
Supporting Guidance was issued in April 2008. These can be accessed at the following website
http://www.environment-agency.gov.ukor the direct web page link: Environment Agency –
COMAH containment policy. The sector has been reviewing its measures in relation to secondary
and tertiary containment and implementing improvement programmes to ensure that the minimum
standards of control are in place and that the risk to the environment and associated risks to
people (for example, preventing uncontrolled flows of flammable liquids) are as low as reasonably
practicable (ALARP).
Part 4 Engineering against loss of
secondary and tertiary containment
MIIB Recommendation 17
The Competent Authority and the sector should jointly review existing standards for secondary
and tertiary containment with a view to the Competent Authority producing revised guidance by
the end of 2007. The review should include, but not be limited to the following:
(a) Developing a minimum level of performance specification of secondary containment (typically
this will be bunding).
(b) Developing suitable means for assessing risk so as to prioritise the programme of
engineering work in response to the new specification.
(c) Formally specifying standards to be achieved so that they may be insisted upon in the event
of lack of progress with improvements.
(d) Improving firewater management and the installed capability to transfer contaminated
liquids to a place where they present no environmental risk in the event of loss of secondary
containment and fires.
(e) Providing greater assurance of tertiary containment measures to prevent escape of liquids
from site and threatening a major accident to the environment.
MIIB Recommendation 18
The Competent Authority and the sector should jointly review existing standards for secondary
Revised standards should be applied in full to new build sites and to new partial installations.
On existing sites, it may not be practicable to fully upgrade bunding and site drainage. Where
this is so operators should develop and agree with the Competent Authority risk based plans for
phased upgrading as close to new plant standards as is reasonably practicable.