PT Notes
New Jersey TCPA Risk Tolerance Criterion
The first process safety regulation enacted in the United States was in the state of New Jersey under the Toxic Catastrophe Prevention Act (TCPA). The current regulation that implements the TCPA contains a numerical risk tolerance criterion. Unfortunately, the criterion and the procedure for using it are seriously flawed. They should be revised for those companies subject to the TCPA regulation. Furthermore, they should not be used as a precedent by companies or regulators seeking to establish numerical criteria, for example, in conducting Layers of Protection Analysis (LOPA) studies or complying with industry practices and standards such as IEC 61511 / ISA 84.
The TCPA criterion can be faulted on multiple grounds including:
- Technical foundation and validity.
- Suitability for the regulation of catastrophic accident risk in process plants.
- Comparability with other established regulatory precedents and frameworks.
The TCPA criterion and the approach specified for its use are flawed in multiple ways, including:
- No valid reference point.
- No consideration of group (societal) risk.
- ALARP principle is not employed.
- No relation to overall tolerable facility risk.
- No allocation of overall tolerable facility risk to scenarios.
- No limit is imposed on the total risk posed by a facility.
- Risk to the public from different facilities can vary significantly.
- Facility risk can significantly exceed the values of criteria established by regulators elsewhere in the world.
- Endpoint criteria should result in equivalent consequence severities which is not clearly the case.
- Endpoint criteria are not defined in meaningful and relevant terms.
- Level of causality used in PHA studies that provide scenarios is not addressed.
- Geographic TCPA risk criterion does not match the actual risk calculated from PHA scenarios.
- No account taken of complex scenarios.
- No account taken of uncertainties in risk estimates.
These issues can result in more or less risk being tolerated than is appropriate and the inconsistent regulation of risk from one facility to another.
The risk assessment approach used by the TCPA regulation can be modified and corrected by addressing these issues. In particular, appropriate and justifiable reference points for overall tolerable facility risk should be employed using the ALARP principle, meaningful and appropriate scenario endpoint criteria should be used, both individual and group (societal) criteria should be considered, and uncertainties in risk estimates should be addressed. Harmonization of the TCPA approach with the tolerability of risk framework that has become established and accepted in other locations and jurisdictions around the world would be beneficial.
Further details, including ways to correct the approach used for the TCPA, can be found in the paper:
Paul Baybutt, Numerical Risk Tolerance Criteria in the United States: A Critique of the Risk Criterion Used for the New Jersey Toxic Catastrophe Prevention Act, Journal of Loss Prevention in the Process Industries, 32 (2014), pp. 428-435, DOI: 10.1016/j.jlp.2014.10.015.
This paper may be accessed for free on ScienceDirect until December 23, 2014 using the click and read link:
http://authors.elsevier.com/a/1Pzlw3O6UQ8inC
No sign up or registration is needed.
