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A Meteorologist’s Look at the Polar Vortex and Boiler MACT

Posted: February 28th, 2014

Author: All4 Staff 

As a Certified Consulting Meteorologist (CCM), I am actively engaged with colleagues in the American Meteorological Society (AMS) regarding the interaction of weather and climate on industry. At this year’s AMS annual meeting in Atlanta, I co-chaired the CCM Forum, which was focused on consulting opportunities for CCMs related to hazard planning. Hazard planning, in a general sense, consists of three phases: prior to an event, during an event, and after an event. An event, from a meteorologist’s perspective for this forum, usually is related to a situation such as a severe thunderstorm, flash flood, blizzard, or hurricane. For this particular session, which happened to fall just one week after a winter storm literally shut down the Atlanta area, much of the chatter (both technical and good-natured fun) was focused on this year’s buzz word, “polar vortex.” Following our discussions, I began to think about how weather (particularly long duration cold snaps) can impact facilities regulated by Boiler MACT, which most of the regulated community would agree is a hazard on multiple levels! Along with the usual environmental compliance challenges of Boiler MACT is the matter of dealing with operational challenges, in particular, natural gas supply curtailments.

So how does weather (and forecasting the weather, or in the spirit of the recent CCM forum, “pre-planning” for an event such as a natural gas curtailment) impact your Boiler MACT compliance? It will hit home most likely for facilities with dual fuel boilers (those that primarily fire natural gas, but have retained the ability to burn fuel oil as a backup fuel). Natural gas boilers will typically be considered gas 1 units under both the area source and major source Boiler MACT rules. Within the definition of a gas 1 boiler is an allowance to fire fuel oil for up to 48 hours per year while maintaining the advantageous gas 1 boiler classification (i.e., gas 1 units are not subject to numerical emission limits). Those 48 hours are limited to non-curtailment periods only, whereas fuel oil usage is unlimited under a curtailment scenario.

The nuance of what is considered curtailment is contained within its definition in the rule, which states that “a period of gas curtailment or supply interruption means a period of time during which the supply of gaseous fuel to an affected boiler is restricted or halted for reasons beyond the control of the facility.” The definition goes on to state that “the act of entering into a contractual agreement with a supplier of natural gas established for curtailment purposes does not constitute a reason that is under the control of the facility.”  In other words, having a contractual agreement with curtailment provisions is typically considered a reason that is beyond the control of the facility – the hours of oil usage during a gas curtailment would not count against the 48 hours per year threshold.

However, the definition further states that “an increase in the cost or unit price of natural gas due to normal market fluctuations not during periods of supplier delivery restriction does not constitute a period of natural gas curtailment or supply interruption.” Furthermore, “on-site gaseous fuel system emergencies or equipment failures qualify as periods of supply interruption when the emergency or failure is beyond the control of the facility.” Therefore, switching to fuel oil solely because the price of gas exceeds the price of oil is not a reason that is beyond the control of the facility – the hours of oil usage under this scenario would count against the 48 hours per year threshold.

Prior to the winter of 2013-14, many facilities that we consulted with regarding Boiler MACT had not experienced more than a handful of gas curtailments over the past several years. This winter alone has resulted in the same number of curtailment orders as during the past several years. While one season of harsh winter weather does not a trend make, facilities are encouraged to revisit their natural gas and fuel oil firing plans for the near future. If a facility does not have a contractual arrangement with its gas supplier, an extended curtailment order could result in burning enough fuel oil to move your boiler into a less desirable liquid fuel subcategory. 

How has the winter of 2013-14 impacted your facility’s operations? Did you experience a gas curtailment period? What changes are you evaluating at your facility to minimize impacts of extreme weather in the future? As we all wait patiently (or not) for winter to come to an end, I’d like to think that we are in phase three of hazard planning…for now.

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