Section R. 336.1227 - Demonstration of compliance with health-based screening levelRule 227.
(1) Compliance with the health-based screening level provisions of R 336.1225 shall be determined by any of the following:(a) The emission rate of each toxic air contaminant is not greater than the rates determined from the algorithms in table 21. If table 21 provides 2 allowable emission rates for a screening level specific averaging time, then compliance with both emission rates is required. Table 21. Algorithms for determining allowable emission rates (AER)
Screening Level (SL) Averaging Time | Monthly Emission Rate (pounds per month)1,2 | 24 Hour Emission Rate (pounds per 24 hours)1,3 | 8 Hour Emission Rate (pounds per 8 hours)1,4 | 1 Hour Maximum Emission Rate (pounds per hour)1,5 |
Annual | SL X 40 = AER | SL X 0.54 = AER |
24 hours | SL X 0.12 = AER | SL X 0.05 = AER |
8 hours | SL X 0.02 = AER | SL X 0.02 = AER |
1 hour | SL X 0.001 = AER |
1 All screening levels (SL) are in units of µg / m3.
2 The constant value of 40 is in units of
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3 The constant value of 0.12 is in units of
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4 The constant value of 0.02 is in units of
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5 The constant values of 0.54, 0.05, 0.02, and 0.001 are in units of
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(b) The emission rate of each toxic air contaminant is not greater than the rate determined from the AIR matrix screening methodology in table 22 or determined by any other screening method approved by the department.(c) The maximum ambient impact of each toxic air contaminant is less than the applicable screening level (initial threshold screening level, initial risk screening level, or secondary risk screening level) determined using the maximum hourly emission rate in accordance with the provisions of R 336.1240 or R 336.1241, or both.(2) For intermittent emissions, the average emission rate may be used to determine the allowable emission rate in subrule (1)(b) of this rule or the maximum ambient impact in subrule (1)(c) of this rule, if the average rate is not less than 10% of the maximum hourly rate. An average rate that is less than 10% of the maximum rate may only be used if the applicant can demonstrate, to the satisfaction of the department, that the proposed new or modified emission unit or units will not cause or contribute to peak exposures that may result in a violation of the provisions of R 336.1901. Intermittent emissions are emissions that are not allowed to be emitted continuously for the entire length of the time specified in the averaging time for the appropriate screening level.(3) Table 22 description: (a) The ambient impact ratio (AIR) matrix enables the determination of an emission rate of a toxic air contaminant that would cause a maximum predicted ambient air impact equal to a screening level. This emission rate is derived by multiplying the screening level by the appropriate AIR value. Emission rates that do not exceed that rate are determined to be in compliance with the health-based screening level under R 336.1225.(b) Use of the AIR matrix requires information pertinent to the dispersion characteristics of the emission source, namely, the distance to the nearest secured property line and the height of the stack and the influential building. The AIR matrix shall not be used if any of the following provisions apply: (i) The stack height is less than 10 feet.(ii) The influential building height is more than 100 feet.(iii) There are terrain elevations that are more than 25% of the discharging stack height within a distance of 500 feet from the stack.(iv) The analysis of elevated receptors, for example, hospital air intakes.(c) Instructions for the use of the AIR matrix are as follows:(i) Determine the height of the discharging stack from ground level in feet (Hs).(ii) Determine the height of the influential building in feet (Hb) by first identifying all buildings, including buildings on-site and off-site, located within a distance of 5 times their height from the discharging stack. Next, determine which building is the highest. This is the influential building, with height (Hb) in feet. If the stack is not attached to a building, assume a building height 2.5 times lower than the stack height.
(iii) Determine the ratio of the stack height to the influential building height by dividing the stack height, in feet, by the influential building height, in feet, Hs/Hb.(iv) Determine the minimum distance, in feet, from the discharging stack to the secured property line. If there is no secured property line, then a distance of 25 feet is used.(v) Determine the appropriate value from the AIR matrix by selecting the column with the appropriate influential building height and Hs/Hb ratio, and selecting the row with the appropriate minimum distance to the secured property line. If the influential building height is between values in the column headings, then use the lower value or interpolate between values in the column headings. If Hs is less than Hb, then set the influential building height equal to the stack height and use the 1.25 Hs/Hb column. If Hs/Hb is between 1 and 1.25, then select the 1.25 column. If Hs/Hb is between 1.25 and 1.75, then use the 1.25 column or interpolate between the 1.25 and 1.75 columns. If Hs/Hb is between 1.75 and 2.5, then use the 1.75 column or interpolate between the 1.75 and 2.5 columns. If Hs/Hb is greater than or equal to 2.5, then use the 2.5 column. If the minimum distance to the secured property line is between 2 distances in the row headings, then use the lower value, for example, if the distance is 250 feet, then use the 200 foot distance row in the matrix.(d) The value derived from the body of the matrix is the ratio of the annual averaged hourly emission rate divided by the maximum annual ambient impact, in units of (lbs/hr)/(ug/m3). This value is the annual AIR.(e) The annual AIR is adjusted as necessary for shorter averaging times, consistent with the averaging times for the screening levels. This adjustment is done as follows: 24-hr AIR (lbs/hr)/(ug/m3) = annual AIR x 0.091.
8-hr AIR (lbs/hr)/(ug/m3) = annual AIR x 0.046.
1-hr AIR (lbs/hr)/(ug/m3) = annual AIR x 0.02.
(f) Determine the maximum emission rate that would comply with the health-based screening level and averaging time by multiplying the screening level, in ug/m3, by the AIR value for the appropriate averaging time. The result is the highest emission rate, averaged over the averaging time period, that would be in compliance with the screening level. If a sources maximum hourly emission rate does not exceed this, then the screening level would not be exceeded. If the emission is intermittent, then the emission rate can be averaged over the applicable averaging time as long as the averaged emission rate is not less than 10% of the maximum hourly emission rate, as specified in R 336.1227(2).(g) In the special case of toxic air contaminant emissions from multiple stacks, determine the AIR value for each stack and select the lowest value among them. Then proceed as in subdivision (f) of this subrule. Table 22. Ambient Impact Ratio (AIR) Matrix
Annual Averaged Hourly Emission Rate Ambient Impact Ratios in Units of (lbs/hr)/(µg/m3) for Toxic Air Contaminants wit Annual Averaged Screening Levels
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Mich. Admin. Code R. 336.1227
1998-2000 AACS; 2016 MR 24, Eff. 12/20/2016