Section 18 AAC 50.215 - Ambient air quality analysis methods(a) A person who submits meteorological or ambient air monitoring data under AS 46.03, AS 46.14, or this chapter shall obtain the data in accordance with (1) the department's Quality Assurance Project Plan for the State of Alaska Air Monitoring & Quality Assurance Program, adopted by reference in 18 AAC 50.030, for PM-2.5, PM-10, total suspended particulates (TSP), lead, carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, and ammonia;(2) a reference method or an equivalent method described in 40 C.F.R. Part 50, Appendices D and P, adopted by reference in 18 AAC 50.035(b), for ozone;(3) EPA's Meteorological Monitoring Guidance for Regulatory Modeling Applications, adopted by reference in 18 AAC 50.035(a), EPA 's Quality Assurance Handbook for Air Pollutant Measurement Systems; Volume IV; Meteorological Measurements Version 2.0, adopted by reference in 18 AAC 50.035(a), and the department's Quality Assurance Project Plan for the State of Alaska Air Monitoring & Quality Assurance Program, adopted by reference in 18 AAC 50.030, for meteorological data; or(4) an alternative method that is representative, accurate, verifiable, capable of replication, and approved by the department.(b) Except as provided in (c) of this section, a person who submits an analysis performed to predict ambient air quality conditions shall(1) ensure that estimates of ambient concentrations and impairment to visibility are based on applicable air quality models, databases, and other requirements specified in 40 C.F.R. Part 51, Appendix W (Guideline on Air Quality Models), adopted by reference in 18 AAC 50.040(f); and(2) for comparing predicted or measured ambient concentrations of an air pollutant to a maximum allowable increase established under 18 AAC 50.020, exclude (A) concentrations attributable to a temporary construction activity for a new or modified source; and(B) the concentrations described under 40 C.F.R. 51.166(f), adopted by reference in 18 AAC 50.040(h).(c) A person may substitute or modify a refined air quality model referenced in (b)(1) of this section only after (1) demonstrating, consistent with 40 C.F.R. Part 51, Appendix W (Guideline on Air Quality Models), Section 3.2 (Alternative Models), adopted by reference in 18 AAC 50.040(f), that the alternative air quality model is more appropriate than a preferred air quality model; and(2) obtaining approval from the regional administrator and the commissioner's designee.(d) A stationary source or modification will be considered to cause or contribute to a violation of an ambient air quality standard or maximum allowable increase for a Class II area if the source or modification would, at a minimum, exceed a significant impact level listed in Table 5 of this subsection at any locality that does not or would not meet the applicable ambient air quality standard or maximum allowable increase for a Class II area. A person shall conduct the comparison of a modeled impact to the significant impact level as follows: (1) for the PM-2.5 significant impact level, the annual average PM-2.5 significant impact level, the one-hour nitrogen dioxide significant impact level, or the one-hour sulfur dioxide significant impact level, the person shall compare (A) the highest modeled concentration when using either one year of meteorological data or screening meteorological data; or(B) the highest multi-year average concentration when using a multi-year meteorological data set;(2) for all other pollutants and averaging periods, the person shall use the highest modeled concentration. Table 5
Significant Impact Levels (SILs)
Pollutant Significant impact level (micrograms per cubic meter) Averaging period Annual 24 hours 8 hours 3 hours 1 hour Sulfur dioxide 1.05 N/A 258 PM-101.05 N/A N/A N/A PM-2.5.0 31.2 N/A N/A N/A Nitrogen dioxide 1.0 N/A N/A N/A 8 Carbon monoxide N/A N/A 500 N/A 2,000 Note to Table 5:
In this table, "N/A" means not applicable.
Eff. 1/18/97, Register 141; am 6/21/98, Register 146; am 10/1/2004, Register 171; am 7/25/2008, Register 187; am 4/1/2010, /Register 193; am 10/29/2010, Register 196; am 9/17/2011, Register 199; am 9/14/2012, Register 203; am 1/4/2013, Register 205; am 4/17/2015, Register 214, July 2015; am 8/20/2016, Register 219, October 2016; am 9/15/2018,Register 227, October 2018Authority:AS 46.03.020
AS 46.14.030
AS 46.14.140
AS 46.14.180
Sec. 30, ch. 74, SLA 1993