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GeoInsighter Summer/Fall
2003 Newsletter
Return to the Newsletter Index New Hampshire (NH) regulates
the discharge to air of a substantial number of compounds under rules
codified at NH Administrative Rule Env-A 1400, Regulated Toxic Air
Pollutants. The list of regulated toxic air pollutants (RTAPs) includes
the 189 “hazardous air pollutants” designated by the United States
Environmental Protection Agency under the Clean Air Act Amendments of
1990 and some 750 additional compounds for which the American Conference
of Governmental Industrial Hygienists has established a threshold limit
value (TLV). Collectively, these compounds are those that NH considers
to pose a potential health-based risk to the human population and to be
in common usage by business and industry. Because of the number and type
of compounds regulated under the rule, many businesses will find that
they use and emit listed compounds. Within the context of NH’s statewide permit system for air emissions, business and industry that emit RTAPs above certain thresholds, or in amounts resulting in an exceedance of ambient air limits (AALs) established by the State, are required to obtain a State permit that limits or controls the RTAP emission. Facilities that emit RTAPs, but below applicable thresholds, must maintain and update annual documentation demonstrating compliance with the Env-A 1400 rule. To determine if a permit is required, or to demonstrate compliance, the rule establishes a three tiered test methodology, including a de minimus emission method, an in-stack concentration method, and air dispersion modeling. Generally, the de minimus method, which requires the least data gathering, is evaluated first. For emissions that do not pass the de minimus evaluation, the in-stack method is used to calculate an emission concentration that is compared to AALs to determine compliance. In the last instance, air dispersion modeling, which is more complex and consequently more costly (although the State will perform modeling upon request), may be used to demonstrate compliance with the AALs. Recent rule changes to the method used in calculating the in-stack concentration have resulted in a relaxation of the applicability of the State permit system to many facilities. In comparison of the calculated in-stack concentration to the AAL, an “adjustment” factor is used, dividing the in stack concentration prior to comparison to the AAL. Prior to April 11, 2003, the adjustment factor was 100. The rule change “adjusts” the “adjustment” factor to 400, effectively increasing the allowable RTAP emission under the in-stack concentration method. Facilities should be aware of the change in their permit evaluation or compliance demonstration efforts.
Christopher M. Rawnsley
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