By Zane Hood, Principal/Senior Engineer
The Spill Prevention, Control, & Countermeasure (SPCC) Rule has a long and storied history reaching all the way back to 1974—a nearly 50 year history! SPCC regulations were revised in 2002 with amendments made in 2006, 2008 and 2009. Furthermore, EPA has issued some interpretive iterations along the way with various levels of clarification issued in the form of memorandums and guidance documents. Almost all of this can be found in EPA’s massive SPCC Guidance for Regional Inspectors, dated December 16, 2013.
In a nutshell, it seems as though spill prevention should be a simple thing, unfortunately there are many topics, issues and interpretation of the rule which are often misinterpreted due to the “gray areas”. Over the coming weeks, PPM will provide some brief insight into some of these myths and truths.
“The secondary containment system for my bulk storage area contains 110% of the volume of the largest tank so my facility is in compliance.”
The rule states that the system should contain the capacity of the largest tank plus sufficient freeboard for precipitation. This rule does not specifically define what “sufficient freeboard” is, so that puts the engineer in a position of making an educated guess. The Preamble to the rule is published for the purpose of memorializing the agency’s various interpretations to provide guidance to facilities and their certifying engineers.
Without going too far in the weeds, EPA stated that a general rule of thumb would be the 25-year, 24-hour storm. Since this isn’t a “rule” – it puts the engineer in a position to interpret this based on the industry standard. Obviously in arid climates, 110% of the largest container may be more than enough, however, in the southeast where tropical storms and hurricanes are prevalent, not so much. Where the rule clearly leaves room for engineering judgement (the one truth that is very clear) is that sufficient freeboard is not about percentages, but rather about regional precipitation expectations.
In the event that a facility is being constructed new, or is being modified, the 25-year 24-hour rainfall should be the prevailing design parameter. When it comes to evaluating existing containments for compliance, if the containment capacity is 30% short of sufficient freeboard, a capital expense is in order to modify the facility to mitigate a nonconformance.
Myth # 2
“My ethanol offloading area is required to have secondary containment volume equivalent or greater than the volume of the largest compartment that loads or unloads.”
EPA differentiates between “loading areas” and “loading racks”. The difference is very subtle. From the SPCC Rule (Part 112.2), the definition of a loading rack is:
…a fixed structure (such as a platform, gangway) necessary for loading or unloading a tank truck or tank car, which is located at a facility subject to the requirements of this part. A loading/unloading rack includes a loading or unloading arm, and may include any combination of the following: piping assemblages, valves, pumps, shut-off devices, overfill sensors or personnel safety devices.
The loading arm (usually indicated by swiveling fixed components) is the defining difference. If a facility has a loading arm, then it is subject to the aforementioned sized-secondary containment requirements.
However, if there is no loading arm, and hoses are used to connect for loading or offloading of tanks, then there are no “sized-secondary containment requirements”, but rather they are subject to “general secondary containment requirements” which allow the engineer to use judgement regarding active or passive means of containment.
For instance, if ethanol is offloaded (not at a rack) at a rate of 250 gallons per minute, and the emergency stop is directly adjacent to the offloading area, the engineer can evaluate the potential of the spill. Let’s assume the emergency stop can be engaged after one minute resulting in a release of 250 gallons. If it can be contained on site and removed with sorbents or either some form of passive secondary containment, either of these meets general secondary containment requirements. Needless to say, this is much easier than construction a containment holding 8,000 gallons!
Separating Fact from Fiction
The coming issues in this series will cover other topics that often get misinterpreted, misconstrued or just missed altogether. Stay tuned!
If you have any questions or want to reach out with questions always feel free to reach out directly to me at firstname.lastname@example.org.