CALPUFF 1992-1993 Modeling Analysis of the
Sulfur Dioxide Impacts due to Emissions
from the Portland Generating Station
February 25, 2010
Bureau of Technical Services
Division of Air Quality
New Jersey Dept. of Environmental Protection
Introduction
This report describes a CALPPUFF modeling analysis conducted to predict ambient sulfur dioxide
(SO2) concentrations in the vicinity of the Portland Power Plant using meteorological data that was
used in the New Jersey Department of Environmental Protection's February 25, 2010 validation
study, "Validation of CALPUFF in the Near-Field." The validation study demonstrated that
CALPUFF predicts impacts with better accuracy than the AERMOD model in the vicinity of the
Portland and Martins Creek Power Plants. The local meteorological data, collected between May 1,
1992 through May 19, 1993, and detail on the CALPUFF model setup are described in the validation
study. The key difference between this modeling analysis and the validation study is the modeling
analysis's use of Portland Generating Station's allowable SO2 emission rate to assess its impact as
compared to the use of Portland's actual emissions in the validation study. Other differences in the
current modeling analysis are (1) only one source (Portland Power Plant) was modeled, and (2) SO2
impacts were predicted at many different locations because receptors were placed throughout the
modeling grid, including near the Portland Power Plant. In the validation study, impacts were only
modeled at the eight sites where the monitors were located.
Modeling Platform
Modeling of the Portland Generating Plant was performed with the latest EPA approved version of
the CALPUFF modeling suite; CALMET/CALPUFF Version 5.8, Level 07063 and CALPOST
Version 5.6394, Level 070622.
Meteorology
Meteorological data collected from May 1, 1992 through May 19, 1993 were used. The SODAR and
10 meter tower data from AMS-4 (see Figure 1) were both used in the meteorological preprocessor
programs of CALPUFF. The AMS-4 site is located 2.5 km to the west-southwest of the Martins
Creek Power Plant. AMS-4 is within the Delaware River valley at a base elevation of 320 feet. The
SODAR data consists of wind speed and wind direction at 30 meter height increments from 90 meters
to 420 meters above-ground. The 10 meter tower data consist of 10 meter wind speed, wind
direction, standard deviation of the horizontal wind direction (sigma-theta) and temperature data.
To help capture the three-dimensional local and mesoscale wind fields, wind measurements taken at
the AMS-8 meteorological tower were also input into CALMET. AMS-8 is located 6 km to the
northwest of the Martins Creek Power Plant and 10.6 km southwest of the Portland Power Plant in
Upper Mount Bethel Township, PA (see Figure 1). It is on the valley ridge to the west of the
Delaware River at a base elevation of 810 feet. At AMS-8, tower temperature, wind speed and wind
direction were collected at the 10 meter level.
Concurrent twice daily upper air meteorological soundings from the Albany, NY, Sterling, VA, and
Atlantic City, NJ National Weather Service (NWS) stations provided the remaining data needed for
input into CALMET.
Processing of Meteorological Data for CALPUFF
The CALMET model was used to develop the parameters for the three-dimensional meteorological
grid. The meteorological grid includes meteorological parameters, surface parameters, and terrain
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elevations for each hour. This three-dimensional meteorological grid was calculated by CALMET in
three steps, as discussed in the following subsections.
The SODAR data from AMS-4 was incorporated into CALMET using the subroutine PROF2UP.
PROF2UP constructs a CALMET ready UP.DAT vertical wind and temperature file. The three
additional upper air data sites (Albany, NY, Atlantic City, NJ and Sterling, VA) were also used for
developing the initial guess wind fields of the three-dimensional meteorological grid.
Step1 Wind Fields
The geophysical data, as processed by the TERREL, CTGPROC and MAKEGEO pre-processors
were used to account for the effects of terrain and surface characteristics. TERREL reads raw terrain
data, calculates the elevation of the center of each grid cell in the modeling domain, and writes a
processed data file. The elevation of the center of the grid cells were calculated using sixteen 7.5
minute (24,000:1) DEM terrain data files with a horizontal spacing of 10 meters. CTGPROC reads
land use data, calculates weighted land use for each grid cell in the modeling domain, and writes a
processed data file. USGS National Land Cover Datasets (NLCD 92) which have a 30 meter
resolution were used to calculate the weighted land use for each grid cell.
MAKEGEO reads the processed data files from CTGPROC and TERREL. MAKEGEO calculates
weighted surface characteristics and writes those data as well as the terrain elevations to a processed
data file, MAKEGEO.DAT. The MAKEGEO.DAT file is used by the CALMET model to modify
the initial guess wind fields in developing the step 1 wind fields. A value of 2.7 kilometers was
selected for TERRAD, the radius of influence of terrain features. This value approximates the
distance from the valley floor to the top of the valley that is used in modifying the initial guess wind
fields to develop the step 1 wind fields of the three-dimensional meteorological grid.
Step 2 Wind Fields
Meteorological observations (surface data, and upper air data) are used to modify the step 1 wind
fields to develop the step 2 wind fields of the three-dimensional meteorological grid. Besides the 10
meter data from AMS-4 and AMS-8, surface meteorological data from the NWS stations at
Allentown/Lehigh Valley PA, Newark NJ, and Wilkes-Barre, PA were input into CALMET. The
combination of on-site SODAR data and surface meteorological stations, NWS Upper Air data and
surface stations, fine-grid terrain data, and fine-grid land use data resulted in an appropriate
representation of the three-dimensional flow in the modeling domain.
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CALMET/CALPUFF Model Setup
CALMET version 5.8 was used to develop the wind fields for the model validation. Table 1 lists the
options selected when making the CALMET run. Predictions at the receptors were done with
CALPUFF version 5.8. Table 2 lists important options selected when making the CALPUFF runs in
this study. CALPOST Version 5.6394, Level 070622 was also used.
Variable
NUSTA
IBYR
IBMO
IBDY
IBHR
IBTZ
IRLG
IRTYPE
LCALGRID
ITEST
MREG
PMAP
NX
NY
DGRIDKM
XORIGKM
YORIGKM
NZ
ZFACE
NOOBS
NSSTA
NPSTA
ICLOUD
IWFCOD
IFRADJ
IKINE
IOBR
ISLOPE
IEXTRP
ICALM
BIAS
RMIN2
IPROG
ISTEPPG
Table1 Important CALMET Control File Variables
Description
Default
Number of upper air stations
NA
Starting Date: Year
NA
Starting Date: Month
NA
Starting Date: Day
NA
Starting Date: Hour
NA
Base Time Zone
NA
Length of run (hours)
NA
Run type 0= compute wind fields only 1= compute
1
wind fields and micrometeorological variables
Compute special data fields required for CALGRID
T
Flag to stop run after setup 1= stop 2= continue
2
Test options to see if they conform to regulatory values
na
Map projection
na
No. of X grid cells
Na
No. of Y grid cells
Na
Grid spacing (km)
Na
X coordinate (km)
Na
Y coordinate (km)
Na
No. Vertical layers
Na
Cell heights in grid
Na
No. observation mode (0 = surface, overwater and
upper air )
No. of surface meteorological stations
No. of precipitation stations (-1 to use MM5)
Gridded cloud fields (0 = not used)
Model selection variable
Compute Froude number adjustment? (0 = no, 1 = yes)
Compute kinematic effects? (0 = no, 1 = yes)
Use O’Brien procedure? (0 = no, 1 = yes)
Compute slope flow effects? (0 = no, 1 = yes)
Extrapolate surface wind observations to upper levels?
Extrapolate surface winds even if calm? (0 = no, 1 =
yes)
Layer dependent biases modifying the weights of
surface and upper air stations
Minimum distance from nearest upper air station to
surface station for which extrapolation of surface winds
at surface station will be allowed (set to -1 for IEXTRP
where all surface stations should be extrapolated
Use gridded prognostic wind field model output fields
as input to the diagnostic wind field model (0 = no)
Time step (hours) of the prognostic model input data
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Value
4
1992
5
1
1
5
9239
0
1
F
2
0 No
UTM
189
200
0.200
473.700
4508.700
12
0, 20, 40, 80, 135, 195,
255, 315, 405, 1000,
1500, 2200, 3000
0
Na
na
0
1
1
0
0
1
-4
0
5
0
0
1
1
0
0
1
-4
1
NA
-1 first layer, 0 next
two layers,+1 other 9
4
-1
0
0
1
1
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ISURFT
Table1 Important CALMET Control File Variables
Description
Default
Use varying radius of influence
F
Maximum radius of influence over land (km)
Na
Maximum radius of influence over land aloft (km)
Na
Maximum radius of influence over water (km)
Na
Minimum radius of influence used in the wind field 0.1
interpolation (km)
Radius of influence of terrain features (km)
NA
Relative weighting of the first guess field and NA
observations in the surface layer. (km)
Relative weighting of the first guess field and NA
observations in the layers aloft. (km)
No of surface stations.
NA
Variable
IBYR
IBMO
IBDY
IBHR
Table 2 Important CALPUFF Control File Variables
Description
Default
Starting Date: Year
NA
Starting Date: Month
NA
Starting Date: Day
NA
Starting Date: Hour
NA
Value
1992
5
1
1
IBTZ
IRLG
NSPEC
NSE
METFM
Base Time Zone
Length of run (hours)
Number of chemical species
Number of chemical species emitted
Meteorological data format 1 = CALMET binary
NA
NA
5
3
1
5
9215
1
1
1
MGAUSS
Vertical distribution used in the near field 1 = Gaussian
1
1
MCTADJ
Terrain adjustment method 3 = partial plume path adj.
3
3
MSLUG
Near-field puffs modeled as elongated slugs? 1 = yes
0
0
MTRANS
MTIP
MBDW
Transitional plume rise modeled? 1 = yes
Stack tip downwash modeled? 1 = yes
Method used to simulate building downwash 1 = ISC
1
1
1
1
1
1
MSHEAR
Vertical wind shear modeled above stack top? 0 = no
0
0
MSPLIT
MCHEM
Puff splitting allowed? 0 = no
Chemical mechanism flag 1 = MESOPUFF II scheme
0
1
0
0
MAQCHEM
Aqueous phase transformation 0 = not modeled
0
0
Variable
LVARY
RMAX1
RMAX2
RMAX3
RMIN
TERRAD
R1
R2
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Value
F
2
2
2
0.1
2.7
1
1
5
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Table 2 Important CALPUFF Control File Variables
Description
Default
Method used to compute dispersion coefficients
2 = dispersion coefficients from internally calculated
sigma v, sigma w. 3 = PG and MP dispersion
3
coefficients
2
MCTURB
Method used to compute turbulence sigma-v &sigma-w
using micrometeorological variables 1 = Calpuff
2 = Aermod
1
2
MPARTL
Partial plume penetration of elevated inversion? 1= yes
1
1
MPDF
PDF dispersion under convective conditions? 1=yes
0
1
CSPEC
CSPEC
MOZ
Chemical species modeled
Chemical species emitted
Ozone data input option 1 = hourly ozone conc
na
na
1
SO2
SO2
0
Variable
MDISP
Value
Meteorological Modeling Domain
The 37.8 km by 40 km CALMET/CALPUFF modeling domain is shown in Figures 2 and 3. The
values used in CALMET to define the horizontal and vertical grid resolution within this modeling
domain are listed in Table 3. The selected values provide enough detail to adequately capture the
horizontal and vertical gradients of the complex winds at this location. The modeling grid used a
horizontal resolution of 200 meters. There were a total of 12 vertical layers. The vertical resolution in
the lower levels of the atmosphere was defined with grid cells between 0 – 20m, 20 – 40m, 40 – 80m,
80 – 135m, 135 – 195m, 195 – 255m , 255 – 315m, 315 – 405m, 405 – 1000m, 1000 – 1500m, 1500
– 2200m, and 2200 – 3000m. This level of detail allowed CALPUFF to incorporate the multi-level
SODAR measurements at AMS-4. Table 4 lists the coordinates of the meteorological grid.
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New York
Pennsylvania
New
Jersey
Figure 2. Location of CALMET/CALPUFF Meteorological Modeling Domain
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Figure 3. CALMET/CALPUFF Meteorological Modeling Domain with CALMET Processed Terrain and Land
Use Data
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Table 3. CALMET Meteorological Domain
DATUM
WGS-84
Southwest Corner
XORIGKM
UTM 473.700 km Zone 18
YORIGKM
UTM 4508.700 km Zone 18
Number of Grid Cells
NX
189
NY
200
Horizontal Grid Spacing
0.200 km
a
Vertical Grid Spacing
1
20 m
2
40 m
3
80 m
4
135 m
5
195 m
6
255 m
7
315 m
8
405 m
9
1,000 m
10
1,500 m
11
2,200 m
12
3,000 m
a. Top of each cell
BIAS
The layer-dependent bias factor (BIAS) settings for each vertical cell determines the relative weight
assigned to the vertically extrapolated surface meteorological observations and upper air soundings.
The initial guess field is computed with an inverse distance weighting of the surface and upper air
data. The bias affects the vertical interpolation of surface and upper air observations. The biases
selected were -1 for the first layer, 0 for the next two layers, and +1 for the remaining 9 layers. Use of
a -1 bias eliminates the influence of the upper air measurements in the ground to 20 meter layer of the
CALMET grid. Use of a +1 bias for the highest 9 layers (80m to 3000m) eliminates the influence of
the surface air measurements in the 80 m to 3000 m layers. A bias of 0 means there will be no bias in
applying the surface and upper air measurements to the 20 m to 80 m layers.
TERRAD
TERRAD is defined as the radius of influence of terrain features. TERRAD is the distance used in
computing the kinematic effects (IKINE), the slope flow effects (ISLOPE), and the blocking effects
(IFRADJ) on the wind field. TERRAD should be set to the approximate distance from the valley
floor to the top of the valley.
The valley near the Martins Creek Generating Station has hills to the east that are about 2.8
kilometers from the valley floor and hills to the west that are about 3.0 kilometers. The valley near
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the Portland Generating Station has hills to the east that are about 1.0 kilometers from the valley floor
and hills to the west that are about 2.0 kilometers. A value of 2.7 kilometers was selected for
TERRAD to account for the terrain variations.
R1, R2, RMAX1, RMAX2
CALMET uses an inverse-distance squared method to determine the influence of observations in
modifying the step 1 wind field. R1 and R2 are the distances from observation stations at which the
observations and the step 1 winds are equally weighted. R1 controls the weighting of the surface
layer and R2 controls the weighting of the upper layers.
RMAX1, and RMAX2 determine the radius of influence over land in the surface layer, and over land
in layers aloft. Therefore, an observation is excluded if the distance from the observation site to a
given grid point exceeds the maximum radius of influence.
Because the terrain is rugged near the sources, relatively small values were appropriate for the
weighting factors for near-field transport. The maximum distances and relative weightings of
observations (i.e., R1, R2, RMAX1, and RMAX2) are presented in Table 5.
PARAMETER
Terrad
RMAX1
RMAX2
R1
R2
Table 4. CALMET Weighting Factors
DESCRIPTION
Radius of Influence of Terrain Features
Maximum Radius of Influence
Over Land (Surface)
Maximum Radius of Influence
Over Land (Aloft)
Relative Weighting (Surface)
Relative Weighting (Aloft)
VALUE (KM)
2.70
2.00
2.00
1.00
1.00
In CALPUFF, the atmospheric chemistry option that would convert SO2 to sulfate was turned off.
Also, there was no wet or dry deposition calculated. The option that produces “ISCST3-like” plume
dispersion with the Pasquill-Gifford dispersion coefficients was not used. Instead, the option that
utilized similarity theory based dispersion coefficients (MISP=2) and probability density function
convective boundary layer conditions (MPDF=1) were selected. Selection of these options results in
CALPUFF using a plume dispersion methodology similar to AERMOD.
Receptor Grid
A Cartesian grid with 5,780 receptors with 500 meter spacing spanning the extent of the modeling
domain was used. In addition, a 5 km by 5 km (2,500 receptors) Cartesian receptor grid with 100m
spacing was placed over the Portland Generating Plant facility.
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Emission Rates and Stack Parameters
The allowable hourly SO2 emission rates (lbs/hour) used in the modeling were taken from the Title V
air permit for the facility and are listed in Table 5. Stack parameters for the two sources modeled are
listed in Table 6. The UTM coordinates of the stacks reflect WGS-84 datum, not North American
Datum 1927 (NAD-27).
Table 5. Emission Rates
Sulfur Dioxide
Unit
(lb/hr)
5,820
1
8,900
2
Table 6. Stack Parameters
UTM Coordinates
Source
Unit 1
X (km)
493.383
Y (km)
4528.717
Stk.
Base (ft
amsl)
294
Unit 2
493.369
4528.766
294
Stack
Height (m)
121.92
Stack
Diameter (m)
2.84
Exit
Velocity
(m/s)
43.31
Temp.
K)
403.15
121.72
3.79
36.26
405.93
SO2 Modeling Results
Table 7 lists the maximum annual and highest, second-high 3-hour and 24-hour SO2 predicted
impacts. The model results show violations of the 3 and 24-hour SO2 NAAQS. Figure 4 shows the
area surrounding the plant where the 3-hour SO2 NAAQS is violated. Figure 5 shows the area
surrounding the plant where the 24-hour SO2 NAAQS is violated. Without the inclusion of
background SO2, the modeling shows violations of the 3-hour NAAQS at 207 receptors and
violations of the 24-hour NAAQS at 57 receptors. Violations of the 3-hour SO2 NAAQS are
predicted to occur on 38 days. A maximum of 18 separate violations occur at a single receptor.
Violations of the 24-hour SO2 NAAQS are predicted to occur on 17 days. A maximum of 8 separate
violations occur at a single receptor.
Table 7. Sulfur Dioxide Concentrations (a)
Averaging
Portland Impact(b)
NAAQS
time
(ug/m3)
(ug/m3)
38.9
Annual
80
738
24-hour
365
2171
3-hour
1300
a. Only values in New Jersey listed.
b. Values represent predicted highest, second-high 3 and 24-hour average concentration and highest annual.
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4531
4530.5
4530
4529.5
3-hr Max.
Impact
(2,171 ug/m3)
4529
SO2 3-hour high, 2nd-high impacts
at each receptor (ug/m^3)
Reliant Portland
Generating Station
Represents predicted violations
of the secondary 3-hr SO2 NAAQS
of 1,300 ug/m^3
4528.5
Minimum Contour = 1,300 ug/m^3
Contour Interval = 100 ug/m^3
No Background Air Quality
Data Included
4528
4527.5
4527
491
0km
491.5
0.5km
492
1km
492.5
493
1.5km
493.5
494
494.5
495
2km
Figure 4. 3-hour SO2 Violations in the Vicinity of the Portland Generating Station
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4531
4530.5
4530
4529.5
4529
SO2 24-hour high, 2nd-high impacts
at each receptor (ug/m^3)
24-hr Max.
Impact
(738 ug/m3)
Reliant Portland
Generating Station
Represents predicted violations
of the primary 24-hr SO2 NAAQS
of 365 ug/m^3
4528.5
Minimum Contour = 365 ug/m^3
Contour Interval = 25 ug/m^3
No Background Air Quality
Data Included
4528
4527.5
4527
491
0km
491.5
0.5km
492
1km
492.5
493
1.5km
493.5
494
494.5
495
2km
Figure 5. 24-hour SO2 Violations in the Vicinity of the Portland Generating Station
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