DAQ-2024-011571

Section IX Part B page 1
UTAH STATE IMPLEMENTATION PLAN
SECTION IX PART B
CONTROL MEASURES FOR AREA AND POINT SOURCES
SULFUR DIOXIDE
IX.B.1 HISTORY OF NonattAINMENT AREAS DESIGNATION AND SIP SUBMITTALS
In the Federal Register of September 11, 1978, there were three areas in
Utah that were designated as nonattainment for sulfur dioxide (SO2). These
three areas include:
1. Salt Lake County
2. Tooele County
3. Cedar City
The designation of Cedar City as a nonattainment area for SO2, made by
the State, was based on ambient air quality data collected at the State's
monitoring station on the campus of Southern Utah State College (now Southern
Utah State University).
The designation of Salt Lake and Tooele Counties was made by the U.S
Environmental Protection Agency (EPA), based on data collected at the State's
ambient air monitoring stations in Magna and Tooele. The old reverberatory
furnace system at the Kennecott Copper Corporation's Utah Smelter was still in
operation at that time. On March 13, 1981, EPA revised the nonattainment
designation for Tooele County to exclude all areas except those above 5600
feet. The main concern of the SIP for Salt Lake and Tooele Counties as
proposed by the State and EPA's proposed approval was control of emissions
from Kennecott.
On August 16, 1981 the State submitted a State Implementation Plan (SIP)
for the control of SO2 in Salt Lake County, Tooele County, and Cedar City to
the EPA. The primary control measure in the SIP for Salt Lake and Tooele
Counties was the construction of a new smelter at Kennecott Copper Corporation
to replace the old reverberatory furnace system. The only control measure in
the SIP for Cedar City was enforcement of the existing limitation for sulfur
content in fuel oil used at Southern Utah State College. In December of 1983,
Cedar City was redesignated an attainment area for SO2.
On March 23, 1984, in 49 FR 10946-10950, EPA proposed approval of this
implementation plan for control of SO2 from the Kennecott smelter contingent
upon submittal of an approvable good engineering practice stack height
demonstration. Prior to final approval, EPA requested that the State make
several additional commitments as a part of the SIP.
In February 1982, EPA promulgated "stack height" regulations (47 FR
5864). In October 1983, portions of those regulations were overturned by the
U.S. Court of Appeals for the D.C. circuit. The outcome of this decision
affected the Utah SIP because the modeling to demonstrate attainment with the
National Ambient Air Quality Standards (NAAQS) for SO2 considered emissions
Section IX Part B page 2
from Kennecott Copper Corporation's tall stack. If it was determined that the
stack height did not meet "good engineering practices", the results of the
model might be affected. In order to resolve this issue, the Utah Air
Conservation Committee (now the Air Quality Board) committed to the following:
1. When EPA promulgated new regulations applicable to stack heights as
mandated by the courts, the Committee would require Kennecott to prepare
a demonstration of the adequacy of the smelter main stack to assure
attainment of ambient standards when stack height was taken into
account. Upon approval by the Committee of the required demonstration,
the Committee would then submit the demonstration to EPA.
2. If the demonstration required by the Committee showed that
attainment could not be achieved based on any new stack height
requirements promulgated by EPA as a result of the court decision, the
Committee was to revise the SIP consistent with the new height
requirements.
In 1986, after questions concerning the stack height regulations were
resolved, the State submitted Section 17 (since renumbered to Section 16) of
the Utah Implementation Plan, Demonstration of GEP Stack Height, to EPA. This
SIP demonstrated that the height of the Kennecott tall stack met the criteria
for "good engineering practices." EPA was required to approve or disapprove
this SIP within one year of submittal, and to also issue final approval or
disapproval of the SO2 SIP, based on the stack height determination for
Kennecott's tall stack.
On November 15, 1990, Congress amended the Clean Air Act. Section
107(d)(1)(C)(i) of the Amended Act states that any area designated as
nonattainment on November 15, 1990 is automatically redesignated as
nonattainment. Because the SO2 SIP had not yet been approved, Salt Lake and
Tooele Counties were automatically redesignated as nonattainment areas, even
though no violations of the standard had been recorded since 1980. Section
191(b) of the amended Act requires any state with a nonattainment area lacking
a fully-approved implementation plan for SO2 as of November 15, 1990 to start
over again, and resubmit a new SIP by May 15, 1992. Because of the amendments
to the Clean Air Act, the State was required to resubmit both the GEP Stack
Height SIP, and the SO2 SIP to the EPA.
On December 18, 1991, the State submitted a new GEP Stack Height SIP to
the EPA. Once again, this SIP demonstrated that the height of Kennecott
Copper Corporation's tall stack met "good engineering practices." Based on
this demonstration, the modeling performed in 1981 SIP to demonstrate
attainment of the NAAQS standard for SO2 in Salt Lake and Tooele Counties is
still a valid demonstration.
Section IX Part B page 3
IX.B.2 SULFUR DIOXIDE CONCENTRATIONS
Sulfur dioxide concentrations have been measured at two stations in the
Salt Lake County nonattainment area, at one station in the Tooele County
nonattainment area, and at three stations in the Cedar City nonattainment
area. A summary of the data for Salt Lake City and Cedar City are shown in
Figure IX.B.1.
Sulfur Dioxide (ppm)
Salt Lake Magna Cedar City
2nd High # Greater 2nd High # Greater 2nd High #
Greater
24-Hr Avg. than NAAQS 24-Hr Avg. than NAAQS 24-Hr Avg. than NAAQS
1977 .02 0
1978 .04 0
1979 .05 0 .15 49 .04 0
1980 .11 0 .17 35 .02 0
1981 0
1982 .04 0 .09 0
1983 .03 0 .06 0
1984 .08 0 .07 0
1985 .07 0 .08 0
1986 .09 0 .00 0
1987 .02 0 .01 0
1988 .04 0 .07 0
1989 .07 0 .07 0
1990 .03 0 .07 0
Salt Lake Magna
2nd High # Greater 2nd High #Greater
3-Hr Avg.than NAAQS 3-Hr Avg.than NAAQS
1982 .10 0 .22 0
1983 .08 0 .22 0
1984 .11 0 .17 0
1985 .12 0 .14 0
1986 .13 0 .02 0
1987 .05 0 .20 0
1988 .08 0 .19 0
1989 .13 0 .16 0
1990 .07 0 .15 0

NAAQS Primary =0.03 ppm, annual arithmetic mean
0.14 ppm, 24-hour average concentration
Secondary = 0.5 ppm, 3-hour average concentration
Note: 24-hour and 3-hour NAAQS may be exceeded once each year
FIGURE IX.B.1
Section IX Part B page 4
IX.B.3 CONTROL STRATEGIES
IX.B.3.a. Cedar City.
The State operated an ambient monitoring station which measured
concentrations of SO2, and particulates in Cedar City, Utah from April 1975 to
1980.
Violations of the primary and secondary Ambient Air Quality Standards
for SO2 were observed in 1975 and only the Primary NAAQS was violated in 1976
and 1977. The 1977 maximum 24-hour average concentration was 0.21 ppm and the
second high 24-hour running average was 0.18 ppm. A review of the emission
inventory indicated that there are no major sources of SO2 in Cedar City.
An investigation was conducted to determine the source of SO2 which
resulted in violations of the NAAQS. The State's monitoring station was
located on the campus of the College of Southern Utah (now Southern Utah State
University) and was southwest of and near the college heating plant which is
fired with fuel oil. A review of the monitoring data showed that violations
of the NAAQS occurred during the winter season when easterly winds were
observed. Two special-purpose monitoring units were installed upwind from the
original monitoring site to determine how widespread the high concentrations
might be and to help pin-point the source. Although SO2 was detected by the
new units, the concentrations were well below the NAAQS. The data collected
at the two stations are shown in Figure IX.B.2. As a result, efforts to
locate the source were directed to the vicinity of the original monitoring
unit.
It was believed that the station had been fumigated by the plume from
the college heating plant. A sample of the fuel oil used in the plant was
analyzed; the sulfur content (8.1% by weight) was substantially higher than
that allowed by the Utah Air Conservation Rules (1.5% by weight).
The college was informed of the violation of the sulfur content of fuels
requirement. They immediately acquired a supply of fuel oil which met the
requirements. That change is the control strategy and resulted in attainment
of the NAAQS for SO2 in Cedar City. The original monitoring station was left
in operation until 1978 to determine the attainment status. One of the
special-purpose monitoring stations was also left in operation until 1980.
Maintenance of the NAAQS for SO2 in Cedar City will be achieved through
enforcement of the sulfur content of fuels regulations. (See Subsection R307-
1-4.2, Utah Air Conservation Rules).
IX.B.3.b Salt Lake and Tooele Counties.
A careful review of the emissions inventory and diffusion modeling which
was coordinated by the State indicated that the emissions from one point
source, Kennecott Copper Corporation, resulted in violations of the NAAQS for
SO2 which were observed in both counties.
Ambient measurements taken by the Department of Health in Salt Lake
Section IX Part B page 5
County indicated that the NAAQS were violated only at the site in Magna, Utah.
Based on this information, the Magna monitoring site was used as the control
point for development of the control plan. No violations of the NAAQS have
been observed at any of the monitoring stations since 1980.
To attain and maintain the ambient air quality standards in Salt Lake
and Tooele Counties, it was and continues to be necessary to control SO2
emissions from the Kennecott operation. In 1981, the Utah Air Conservation
Rules were revised to include emission limitations and control requirements
for the following Kennecott operations:
1. Smelter Main Stack
2. Fugitive Emissions
3. Power Plant
4. Molybdenite Heat Treaters
5. Refinery
As part of the approval process for the 1981 submittal by the State, the
EPA performed a modeling analysis. Figure IX.B.3 shows the distribution and
expected concentrations of SO2 as determined by diffusion modeling, using the
CDMQC model. The highest predicted concentration of SO2 was at Lake Point,
which is on the property of Kennecott Copper Corporation. Figure IX.B.4 shows
the location of Lake Point as well as the 5600-foot level contour of the
Oquirrh Mountains and the Kennecott Utah Copper property boundary. In 1979,
Kennecott established a monitor at Lake Point to measure SO2 concentrations.
On August 15, 1991 the State promulgated a State Implementation Plan for
the control of PM10 in Salt Lake County. Because SO2 is a precursor of PM10,
the SIP relied heavily on reductions of SO2 emissions to control PM10 in the
Salt Lake/Davis County nonattainment areas. As part of the PM10 SIP,
Kennecott Copper Corporation agreed to install double-contact acid plant
technology as well as other control measures that would result in SO2 emission
reductions from the facility. As required to protect the 3-hour NAAQS for
SO2, a 3-hour emission limit has been included in Section IX, Part H, Emission
Limits. The discussion in IX.B.3.c below details the development of that
limit.
By comparing the ratio of Kennecott Copper Corporation's 1981 SO2
emissions limitations and the 1991 PM10 SIP emissions limitations, and using
the modeling/monitoring ratio established in the 1981 SO2 SIP, the State is
able to demonstrate that the SO2 NAAQS will not be exceeded in Salt Lake
County or Tooele County as detailed in IX.B.3.d below.
IX.B.3.c. Development of the 3-hour Tall Stack Emission Limit.
One of the principle requirements of the 1992 SO2 SIP revision is the
establishment of a 3-hr emission limit for the tall stack at the Kennecott
smelter. This limit will reflect the new levels of control agreed upon as
part of the PM10 SIP which resulted in new emission limits for both 24-hour
and annual averaging periods. This new level of control will be achievable
through the application of available double contact acid plant technology.
Section IX Part B page 6
The total emissions from the tall stack are composed of two distinct
sources: 1) fugitive smelter emissions captured by the secondary ducting, and
2) tail-gas emissions from the acid plant(s).
Kennecott Utah Copper (KUC), in a meeting held January 10, 1992,
proposed to the State a 3-hour emission limit of 6,900 lbs/hr. This limit
contains a 4,500 lb/hr contribution from the ducted fugitive emissions, which
is the same estimated contribution used to establish the 24-hr limit of 5,700
lbs/hr which was used in developing the PM10 SIP. This is based on an
assumption that fluctuations in these fugitive emissions should be negligible
when comparing a 3-hr period with a 24-hr period. The remainder of the 6,900
lb/hr limit would then be 2,400 lbs/hr from the acid plant(s). The
contribution from the acid plant(s) would correlate to a tailgas SO2
concentration of 1,300 ppm. In a subsequent letter, dated 1/14/92, KUC
presented its' rationale for the selection of this tailgas concentration.
That letter is contained in the technical support document, and is summarized
below.
KUC has based their proposal of 1,300 ppm on certain sections of an EPA
document titled 'Review of New Source Performance Standards for Primary Copper
Smelters' (1984). They begin with Table I-2 (from appendix I of that
document, and herein referred to as Fig. IX.B.5) which summarizes SO2
concentration data collected (in 1973) every 15 minutes from the tailgas of a
double contact acid plant at the ASARCO copper smelter in El Paso, Texas. The
table compares the probability of exceeding various concentration levels (from
150 to 750 ppm) with the effect of different averaging times used to calculate
the measured concentration (from 15 minutes to 10 hrs). As the averaging time
increases, and as the reference concentration level increases, the probability
of exceeding that reference level decreases significantly. For a 3-hour
averaging period, the probability of exceeding a tailgas concentration of 750
ppm is reported by the study as 0.5%.
From that point, KUC looked at the highest concentration reported for
the representative averaging period (also reported in Table I-2), which for
the 3-hour period was 1,238 ppm, and averaged the two. This procedure yielded
a value of: (750 ppm + 1,238 ppm)/2 = 994 ppm.
The next step was to account for the effects of normal catalyst
deterioration with a "safety" factor of 30%. Thus: 994 ppm X 1.3 = 1,292
ppm, and this number was finally rounded up to the 1,300 ppm which KUC
proposed.
During the review of the KUC proposal, the State determined the origin
of the 30% deterioration level. Table G-3 of the same EPA document summarizes
tailgas SO2 concentrations from a different study - one which compared the
tailgas concentration of Kennecott's No.6 acid plant with the tailgas
concentration of their No.7 acid plant. The data for this study was collected
over a three day period in 1972, and during that time the average
concentration of the No.7 plant exceeded that of the No.6 plant by roughly
30%. This difference in performance was attributed entirely to the
deterioration of the catalyst in the No.7 plant, even though the two plants
are of different age, design and manufacture. Both plants, however, routinely
Section IX Part B page 7
clean their catalysts over a 12-month cycle, and while the No.7 plant was in
its twelfth and final month, the No.6 plant was in only the second month of
its cycle. The assumption was that because catalyst deterioration (primarily
a function of pressure drop across the catalyst bed) should occur
exponentially, and should become a factor only during the latter stages of the
cleaning cycle, this was the only difference in the performance of the two
acid plants. Thus, said the KUC study, it would be reasonable to apply a 30%
deterioration factor when establishing a regulatory emission factor for a new
double contact sulfuric acid plant.
There is no question as to whether or not the catalyst in an acid plant
will deteriorate and thereby diminish the performance of the plant.
Therefore, it is the responsibility of the State to verify that a proposed 30%
is a reasonable performance reduction estimate. When the ASARCO study was
further analyzed, it was pointed out that the data collection took place
during what was considered to be the second and third quarters of the plant's
24-month cleaning cycle. Thus, making the same "exponential" assumption,
there would have been little if any adverse effect due to catalyst
deterioration for that double contact acid plant. Recognizing that such
effects should be accounted for when establishing an emission limit, the study
team posed the question of how much deterioration could reasonably be
expected, and their "discussions with the designers of the ASARCO acid plant
indicated that up to a 10% increase in emissions was expected before renewal
of the catalyst."
Furthermore, in an effort to apply the results of their findings to
other acid plants, the study team made the following statement in their
conclusion: "To account for situations of increased emissions due to higher
inlet (SO2) concentrations of up to 9%, the results of Table I-2 require
prorating upward a maximum of 200 ppm".
Therefore, based on the above analysis, it was the decision of the State
to adopt the conclusions of the ASARCO study for the purposes of establishing
a 3-hour emission limit for the tailgas SO2 concentration of KUC's new acid
plant. As a result of this position, the State: 1) accepted KUC's starting
point of 750 ppm as corresponding to a 99.5% confidence level (even though
Table I-2 showed the same degree of certainty associated with 700 ppm); 2)
added 200 ppm to that figure to account for possible differences in or
fluctuations of the inlet SO2 concentration; and 3) allowed a 10% margin of
"safety" to account for the effects of catalyst deterioration, thereby
arriving at a 3-hour SO2 limit as follows:
(750 ppm + 200 ppm) X 1.1 = 1,045 ppm
which would correlate to a lb/hr figure as:
1,045 ppm X (2,400 lbs/hr / 1,300 ppm) = 1,929 lbs/hr
which could be rounded to 1,950 lbs/hr, and, added to the 4,500 lbs/hr
contribution from the ducted fugitive emissions, to arrive at a 3-hour average
emission limit of 6,450 lbs/hr.
Section IX Part B page 8
IX.B.3.d Analysis of Control Strategy.
The SO2 emission limits as required for the control of PM10 and SO2 for
the annual, 24- and 3-hour averages for the main smelter stack are, therefore,
respectively, 3,240, 5,700 and 6,450 lb/hr. The annual and 24-hour limits
represented RACT for the development of the PM10 SIP. The 3-hour limit
represents the amount of control sufficient for the attainment of the 3-hour
SO2 standard in the nonattainment area. Low level emissions (low stack and
fugitive emissions) are not considered in evaluating the impacts on the
elevated terrain (i.e., Lake Point) for three reasons: 1) The exact quantities
of fugitive emissions are unknown; 2) Low level emissions have not caused any
violations at low level monitors since 1980, and their impacts on the high
level terrain would appear even lower or probably insignificant; and 3)
Ignoring low level emissions and attributing impacts solely to the main stack
will be more conservative for the control of main stack emissions.
(1) Evaluation of 24-hour Impacts on Lake Point
Using Previous Modeling Results
EPA previously used the Valley model to estimate impacts at different
distances and elevations. The model evaluated annual impacts using an annual
emission rate of 2,293 g/sec or 18,200 lb/hr. The model then converted the
annual impacts to 24-hour averages. The modeling results are contained in the
technical support document.
Both Lake Point and a site [designated as "Point A"] which is the point
closest to the main stack on elevated terrain outside Kennecott property, are
about 4.5 km distance from the main stack, and are shown on a map contained in
the technical support document. The previous EPA modeling results did not
include impacts at 4.5 km distance. Use of a linear interpolation gives a 24-
hour impact of 570 g/m3 at Lake Point.
Using the new annual emission rate of 3,240 lb/hr, the 24-hour impact is
then estimated as
(3,240 lb/hr)x(570 ug/m3)/(18,200 lb/hr) = 102 ug/m3 = 0.039 ppm.
To be more conservative in estimating the 24-hour impact, the new 24-
hour emission rate of 5,700 lb/hr is used as an annual emission rate. The 24-
hour impact is evaluated as
(5,700 lb/hr)x(570 ug/m3)/(18,200 lb/hr) = 179 ug/m3 = 0.068 ppm,
which is lower than the 24-hour standard of 0.14 ppm.
To be even more conservative in estimating the 24-hour impact, the new
3-hour emission rate of 6,450 lb/hr is used as an annual emission rate. The
24-hour impact is then evaluated as
(6,450 lb/hr)x(570 ug/m3)/(18,200 lb/hr) = 202 ug/m3 = 0.076 ppm,
which is still lower than the 24-hour standard of 0.14 ppm.
Section IX Part B page 9
(2) Evaluation of 24-hour Impacts on Lake Point
Using Previous Monitoring Data
Another method to estimate the impact of the main stack emissions using
the new emission limits is to use previous monitoring data at Lake Point and
stack emission rates. The monitoring and emission data for the worst case
episode of 0.33 ppm of 24-hour average on 11/30/79 is contained in the
technical support document.
The 24-hour average emission rate at the hour of the maximum running 24-
hour average concentration of 0.33 ppm was 38,228 lb/hr. Because the plume
from the stack took an unknown time to reach Lake Point, the maximum
concentration observed at the monitor was caused by emissions prior to the
hour when the measurements were taken. Since the emission data showed that
the emission rates prior to the highest concentrations were higher than 38,228
lb/hr, using an emission rate of 38,228 lb/hr results in a more conservative
approach. The 24-hour impact of the new 24-hour emission rate is estimated as
(5,700 lb/hr)x(0.33 ppm)/(38,228 lb/hr) = 0.049 ppm,
which is also lower than the 24-hour standard.
(3) Evaluation of 3-hour Impacts on Lake Point
The monitoring data at Lake Point and emission data can be utilized to
evaluate the 3-hour impact from the new emission rates. From the monitoring
data for running half-hour contained in the Technical Support Document, the
maximum 3-hour average concentration during the episode period on 11/30/79 was
conservatively estimated as 1.0 ppm.
The exact 3-hour average emission rate causing the 1.0 ppm impact is
unknown. Since the emission data in the technical support document indicates
that the emission rate of 24-hour average was lower than that of the 3-hour
average, using the 24-hour emission rate of 38,228 lb/hr as the 3-hour
emission rate will give more conservative results. The 3-hour impact from the
new 3-hour emission rate is evaluated as
(6,450 lb/hr)x(1.0 ppm)/(38,228 lb/hr) = 0.17 ppm,
which is also below the 3-hour standard.
Section IX Part B page 10
(4) Summary
The estimate results for maximum impacts from the new stack emissions on
Lake Point are summarized in Table IX.B.1.
Estimated impacts on Lake Point
Average Emission rate (lb/hr)NAAQS (pm)Impact (ppm)Evaluation method
24-hr 5,700 0.14 0.068 modeling
0.049 monitoring
3-hr 6,450 0.5 0.27 modeling
0.17 monitoring
IX.B.3.e Protection of the 3-hour SO2 Standard.
The EPA has required the State to ensure that the 3-hour SO2 NAAQS will
be protected, as well as the 24-hour and annual NAAQS.
The emission limitation for the tall stack at Kennecott Copper
Corporation was established using a 3-hour average and a multi-point formula
in the 1981 SO2 SIP. The 1991 PM10 SIP revised this limitation to establish a
24-hour standard for SO2 emissions and eliminated the multi-point limitations
allowed in the 1981 SIP. The EPA accepted the new SO2 limitation as a control
strategy for the PM10 SIP, but required the State to develop a 3-hour emission
limit for the tall stack as part of the new SO2 SIP. Section IX, Part H,
Emission Limits, has been revised to include a 3-hour emission limitation for
the smelter tall stack as detailed in IX.B.3.d above.
The EPA also required the State to revise the sulfur content of fuels
requirement in it's regulations. The existing rules specified a limit for the
sulfur content of fuels, but did not specify an averaging time or specific
ASTM methods. Subsection R307-1-4.2 of the Utah Air Conservation Rules have
been revised to include a 24-hour averaging period for the sulfur content of
coal, fuel oil, and fuel mixtures, and to specify the ASTM methods to be used
to demonstrate compliance with the limitations and reporting requirements. It
is the state's position that, because there is no high-sulfur natural gas in
Utah, there is no need for a rule which specifies testing methods for deter-
mining sulfur content of natural gas or fuel mixtures containing natural gas.
Subsection R307-1-4.6 was revised to include a 3-hour averaging time for
Sulfur Burning Production Sulfuric Acid Plants.
IX.B.4 EMISSION LIMITATIONS.
See Section IX, Part H of the Utah Implementation Plan for the new
emissions limitations for Kennecott Copper Corporation.
See Subsection R307-1-4.2 of the Utah Air Conservation Rules for
limitations on the sulfur content of fuels.
Section IX Part B page 11
IX.B.5 ADEQUACY DEMONSTRATION.
Monitoring performed in Cedar City, Magna, and Salt Lake City has shown
no violations of the NAAQS for SO2 from 1981 to 1992. The control measures
proposed in this SIP have already been shown through actual measurements over
the recent past 10-year period to be adequate to maintain the standards.
______________________________________________________________________________
SULFUR DIOXIDE (ppm)
# GREATER # GREATER
ANNUAL 2ND HIGH THAN NAT'L THAN NAT'L
MEAN 24-HR. AVG.PRIMARY 24-HR.SECONDARY 24-HR.
Cedar City
(1st East)
1977 .009 .02 0 0
1978 .00*.04 0 0
1979 .00*.04 0 0
1980 .00*.02 0 0
Cedar City
(High School)
1977 .005 .01 0 0
______________________________________________________________________________
NAAQS - Primary - 0.03 ppm annual arithmetic mean, 0.14 ppm 24-hour average
concentration; Secondary - 0.5 ppm 3-hour average concentration
______________________________________________________________________________
NOTE: 24-hour and 3-hour NAAQS may be exceeded once each year.
* Annual mean is less than .005 ppm SO2
Figure IX.B.2
Section IX Part B page 12
Figure IX.B.3
Section IX Part B page 13
Figure IX.B.4
Section IX Part B page 14
The Effect of Reference Concentration Level and Averaging Time on the Percentage of Excursions
Averaging
Time
Number of
Readings 150 200 250 300 350 400 450 500 550 600 650 700 750
Maximum
Concentra-
tion ppm
15 min 14,612 20.00 15.00 10.00 7.50 5.00 4.00 3.00 2.30 1.60 1.35 1.15 1.05 1.05 2,920
1 hr 3,628 20.00 15.00 10.00 7.10 4.10 3.15 2.65 2.10 1.75 1.40 1.00 0.90 0.80 1,982
2 hr 3,702 20.00 15.00 10.00 5.00 3.00 2.50 2.00 1.75 1.50 1.25 1.00 0.90 0.70 1,261
3 hr 3,758 20.00 15.00 10.00 5.00 2.20 2.00 1.60 1.25 0.85 0.80 0.55 0.50 0.50 1,238
4 hr 3,803 20.00 8.15 6.10 3.06 2.20 1.40 1.05 0.80 0.75 0.50 0.45 0.30 0.25 935
5 hr 3,841 20.00 10.00 5.00 2.75 1.75 1.25 1.00 0.75 0.55 0.40 0.30 0.25 0.15 935
6 hr 3,876 20.00 10.00 5.00 2.45 1.75 1.20 0.90 0.45 0.35 0.30 0.15 0.05 0.05 752
7 hr 3,901 20.00 10.00 5.00 2.15 1.40 1.00 0.55 0.30 0.20 0.10 0.05 0.00 0.00 662
8 hr 3,935 15.00 10.00 5.00 2.15 1.40 0.80 0.50 0.25 0.10 0.05 0.00 0.00 0.00 662
10 hr 3,988 15.00 10.00 5.00 2.05 1.20 0.55 0.25 0.10 0.05 0.00 0.00 0.00 0.00 576
Figure IX.B.5