Introduction

This Fact File provides guidance to aide sources in defining when a scenario is (or is not) a risk management program “process.” This determination is one of the more complicated pieces, yet critical in the program. Linking that decision with threshold quantity will then provide a clear picture on when risk management program does apply.

Background

The EPA risk management program exists to prevent accidental releases of extremely hazardous toxic and flammable substances that can cause serious harm to the public and the environment. Stemming from the federal Clean Air Act (CAA), EPA developed the “Chemical Accident Prevention Provisions,” to regulate stationary sources that have processes with listed substances above the threshold quantity (TQ). An important distinction in the risk management program, and different from most other chemical regulations, is the applicability determination at the process level. Understanding the definition of “process” is therefore critical for sources to evaluate their need for compliance with the program. However, even with the included definition of process there is often confusion around its intent.

Confusion comes from two causes:

1. EPA’s use of the term does not correspond with general engineering use of the term, and
2. The concept of co-location is left open to a high level of interpretation

Determining co-location

Unfortunately, there is no single rule or distance that defines when to consider vessels as one or separate processes. This determination has to be made on a case-by-case basis, considering factors such as distance, chemical, surroundings, and worst-case risks. EPA suggests consulting with the local fire department to assist in making these decisions. Beyond that, using informed professional judgment to answer the following questions will help define when processes are co-located:

• Could an event external to the containers (fire, explosion, collapse, collision, etc.) potentially release the regulated substance from multiple containers?
• Could a release from one vessel lead to a release from the other?
• Are there non-covered containers in the area that could affect both processes in the event of a release (i.e., compressed gas cylinders)?

Scenario interpretation

Interpreted as one process:

• More than one (2 or more) connected vessels same regulated substance above TQ
• More than one connected vessels different substances each above TQ
• More than one vessels co-located, but not connected, different substances each above TQ
• One series of interconnected vessels substances (same or different) above TQs plus a co-located storage vessel containing flammables

Interpreted as more than one process:

• More than one vessels, located so they won’t be involved in a single release substances (same or different) each above TQ
• More than one location with regulated substances each above TQ

Applicable laws & regulations

• 40 CFR 68 – Chemical accident prevention provisions
• Clean Air Act (CAA) Section 112(r)(1) – General Duty Clause
• 29 CFR 1910.119 – Process safety management of highly hazardous chemicals

Related definitions

Process: “[A]ny activity involving a regulated substance including any use, storage, manufacturing, handling, or on-site movement of such substances, or combination of these activities. For the purposes of this definition, any group of vessels that are interconnected, or separate vessels that are located such that a regulated substance could be involved in a potential release, shall be considered a single process.” (40 CFR 68.3)

Key to remember

1. There is no hard and fast rule on how far apart containers must be to be considered separate processes.
2. Single vessels and interconnected vessels (even if not permanent connections) don’t need to be evaluated for process implications – they are always in and need to only be evaluated for chemical thresholds

Real world example

As an example, a stationary source has two independent ammonia refrigeration systems, together the volume of ammonia exceeds the risk management program trigger quantity but separate they do not. The refrigeration systems share a water diffusion tank, and because of this, the two systems should be considered one process. Should something affect that shared diffusion tank or the piping from it to the ammonia tanks, it is reasonable to assume both systems could be affected.