Memorandum
To: Bent S. Jorgensen From: Bob Humphries Date: February 23, 2007
Re: Model results of Permit 2001 and Stack Test 2005 emission scenarios
Levelton modelled two emission scenarios for PM2.5 for the Roxul plant in Grand Forks. The modelled scenarios are:
1. Emissions based on the 2001 air permit,
2. Emissions based on the most recent (December 2005) stack test results,
The CALPUFF model was used in a screening mode for this analysis. In the screening mode, the meteorological data from a single surface station is used and the wind field is uniform throughout the domain. CALPUFF divides the emitted plume into a series of distinct puffs, which are dispersed and tracked. CALPUFF can therefore calculate the dispersion of stack emissions during situations of low wind speed or calms.
The model used about 1 year of hourly weather data (8760 hours) and calculated concentrations at each grid point (we call these receptors) for each hour of weather data. Each receptor therefore has 8,760 1-hour concentrations. Figure 1 shows the receptors used in this study. Note the spacing becomes larger with distance from the plant. One can then extract the maximum hourly
concentration at each receptor – the maximum at one receptor can be for a different hour than the maximum at another receptor. One can also go through and calculate 24 hour averages for each day. This yields 365 24-hour average values per receptor. We then extract the maximum 24-hour average at each receptor. These values are what we provided in the plots. The annual average, or for this case because there is an extra day of weather data the period average, is the average at each receptor of all the hourly results. . The values are in micrograms per cubic metre. The 98thpercentile value for the daily concentrations provides the value at each receptor for which 98 percent of the time the concentration is the same or less than the given value.
Therefore after post-processing the model output, each receptor will have (assuming a full non-leap year is modelled) 8,760 1-hour concentrations, 365 daily 24-hour average concentrations, and one annual or period average.
Figure 1 Grid of receptors used by model to calculate concentrations over an area – the X locates the plant site
Summary of Model Results
The current provincial and federal air quality objectives are provided in Table 1. Table 1 Summary of BC and Canada ambient air quality objectives for PM2.5
Parameter BC
Objective (µg/m3)
Federal Objective
(µg/m3) PM2.5
24-hour Maximum - 30*
Annual Mean - -
*Canada Wide Standard – based on 98thpercentile averaged over 3 consecutive years. Table 2 provides a summary of the model results for all scenarios. The table shows the maximum and 98thpercentile concentration of PM2.5for each scenario for the averaging times of 24-hours and the run length (period average). The meteorological data set that is available for Grand Forks runs from Oct 30, 1996 to November 2, 1997 and is 24 hours longer than a year. Hence, the run length average is essentially the annual average. The 2005 stack test case has lower maximum
concentrations of PM2.5, than the 2001 air permit scenario.
The maximum concentration for the permit 2001 scenario occurs on a hill about 1,400 m to the NE of the plant. The maximum concentration for the 2005 stack test case occurs on the northern edge of the
February 23, 2007
Table 2 Maximum concentrations of PM2.5in µg/m3for each scenario for the indicated averaging times.
Pollutant Averaging Period
Permit 2001 Maximum
Permit 2001 98th Percentile
Stack Test 2005 Maximum
Stack Test 2005
98th Percentile
24-hour 30 12.6 15 10.9
PM2.5
Run length 5 n/a 3 n/a
Scenario 1 – 2001 Permit
The model input data for scenario 1 are shown in Table 3. The December 2005 stack test results for moisture content and stack exhaust temperature were used to determine exit velocity. In addition, the stack test results were used to determine the percentage of the total PM attributed to PM2.5. The balance of the data is taken from the 2001 permit. Note: (i) the dust collection-charging plant stack was idle and not modeled. The cooling tower only emits water vapour.
Table 3 Stack Parameters for the 2001 permit case.
Source
Stack ht (m)
Stack dia (m)
Stack T (C)
Permit Flow Rate (dscm/min)
Velocity (m/s)
Total Filterable
PM (mg/dscm)
Total PM gm/s
PM10 (g/s)
PM2.5 (g/s)
Dust Collection - Charging Plant 250 30 0.13
Spinner/curing oven stack 28.6 2 74.4 2250 14.69 26 0.98 0.531 0.494
Cooling Zone 14 0.69 40 265 12.78 30 0.13 0.131 0.128
Line Dust Collector 10 0.9097 31.1 510 13.73 10 0.085 0.033 0.033
Fume Hood East 11 0.74 47.8 250 10.65 15 0.063 0.042 0.036
Fume Hood West 10.5 0.53 53.5 100 8.50 15 0.025 0.024 0.024
Cooling Tower - Line/water vapour n/a n/a n/a 187
Pipe Curing Stack 27 1.5 36.7 1100 11.15 30 0.55 0.525 0.493
Pipe Dust Collector 11 1 31.1 560 12.44 10 0.093 0.067 0.040
Room Vents (2 of them) 9.8 0.5 24.2 648 56.33 5 0.054 0.038 0.027
Melter Vent-deleted 2001 27.1 0.64 179.4
Model Results Scenario 1
Figure 2 and Figure 3 shows the maximum 24-hour concentrations of PM2.5in µg/m3. Figure 4 and Figure 5 show the 98thpercentile of the maximum 24-hour concentrations of PM2.5. The figures show the contours as filled in with colour and as contour lines.
Figure 2 Permit 2001 PM2.5(with colour) maximum 24 hour average in µg/m3.
Figure 3 Permit 2001 PM2.5 maximum 24 hour average in µg/m3.
February 23, 2007
Figure 4 Permit 2001 PM2.5(with colour) 98thpercentile 24 hour average in (µg/m3)
Figure 5 Permit 2001 PM2.598thpercentile 24 hour average in (µg/m3)
Scenario 2 - December 2005 Stack Test
The model input data for scenario 2, the December 2005 stack test results, are shown in Table 4. The values for moisture content and stack exhaust temperature are shown because these values were used to determine exit velocity for the other cases. In addition, the stack test results show the percentage of total PM attributed to PM2.5. This percentage was used in the other scenario to determine the emission rate for PM2.5.
Model Results Scenario 2
Figure 6 and Figure 7 shows the maximum 24-hour concentrations of PM2.5in µg/m3. These figures show the contours of concentration filled in with colour and as contour lines. In this case, the maximum value occurs on the northern edge of the plant property. Figure 8 and Figure 9 show the 98thpercentile of the maximum 24-hour concentrations of PM2.5.
February 23, 2007
Table 4 Stack parameters for December 2005 stack test case.
Source Date of test
Stack ht (m)
Stack dia
(m) Stack T (C)
Moisture (%vol, total)
Flow Rate (dscm/min)
Velocity (m/s)
Total Filterable
PM (mg/dscm)
Total PM gm/s
PM10/PM (%)
Filterable PM10 (mg/dscm)
PM10 (g/s)
Spinner/curing oven stack 8-Dec-05 28.6 2 39.8 1.3 3083 17.70 31.4 1.61 54% 17.10 0.88
Cooling Zone 25-Aug-05 14 0.69 40.06 1.24 638 30.78 15.4 0.16 99% 15.20 0.16
Line Dust Collector 26-Aug-05 10 0.9097 31.1 1.1 420.8 11.33 1.8 0.013 39% 0.70 0.0049
Fume Hood East 25-Aug-05 11 0.74 47.8 0.4 331 14.11 6.5 0.036 68% 4.40 0.024
Fume Hood West 24-Aug-05 10.5 0.53 53.5 0.9 147 12.49 8.8 0.022 98% 8.60 0.021
Pipe Curing Stack 23-Aug-05 27 1.5 36.7 1.6 1270 12.87 6.7 0.142 96% 6.40 0.14
Pipe Dust Collector 24-Aug-05 11 1 31.1 0.8 176 3.91 0.7 0.0021 71% 0.50 0.0015
Room Vents (2 of them) 23-Aug-05 9.8 0.5 24.2 0.9 170 14.78 1 0.0028 70% 0.70 0.0020
Figure 6 Stack Test 2005 PM2.5(with colour) maximum 24 hour average in µg/m3.
February 23, 2007
Figure 8 Stack Test 2005 PM2.5(with colour) 98thpercentile 24 hour average in (µg/m3)
Figure 9 Stack Test 2005 PM2.598thpercentile 24 hour average in (µg/m3)
