Initial Modelling Review Jan. 31, 2018

MEMORANDUM
DIVISION OF AIR QUALITY
January 31, 2018
TO: Charles McEachern, Environmental Engineer, RRO
Permit Coo · nator, RRO
SUBJECT: Review of Toxics Air Dispersion Modeling-
Dominion Energy Transmissions, Inc. Atlantic Coast Pipeline, LLC
Northampton County Compressor Station
Northhampton County, North Carolina Facility No. 6600169
I have reviewed the dispersion modeling analysis, initially received January 10, 2018 and most
recently updated on January 29, 2018, for the Dominion Energy Transmissions, Inc. Atlantic
Coast Pipeline, LLC Northampton County Compressor Station County, North Carolina. The
owner has submitted a permit application for a greenfield facility. This application triggered
modeling requirements to evaluate those toxics whose rates are expected to exceed the levels
outlined in 15A NCAC 2Q .0700. The modeling adequately demonstrates compliance, on a
source-by-source basis, for all toxics modeled.
Three air toxics were evaluated facility wide in the modeling. Details of the emission rates and
source parameters used in the modeling are attached. AERMOD (16216r) using five years
(2012-2016) of meteorological surface data from Rocky Mount/Wilson and upper air data from
Greensboro was used to evaluate impacts in both simple and elevated terrain.
Direction-specific building dimensions) determined using EPA's BPIP-Prime program (04274),
were used as input to the model for building wake effect determination. Receptors were placed
around the facility's property line at SO-meter intervals and extended outward to 1,500 meters.
Additional receptors were spaced at 100-meter intervals from 1,500 to 2,500 meters, at 250-
meter intervals out to 5,000 meters, and at 500-meter intervals out to 10,000 meters from the
facility.
Maximum Impacts -Dominion Energy Transmissions, Inc. Atlantic Coast Pipeline, LLC
Northampton County Compressor Station, North Carolina
TAP Averaging Max.Cone. AAL o/oofAAL
Period (u2/m 3) (µg!m3)
Benzene Annual 0.006 0.12 5%
Formaldehyde 1-hour 26.4 150 18%
n-Hexane 24~hour 588.6 1,100 54%
1bis compliance demonstration assumes the source parameters and pollutant emission rates used
in the analysis are correct.
cc: Tom Anderson
Nancy Jones
Dominion Energy Transmissions, Inc. Atlantic Coast Pipeline, LLC
N01thampton County, NC Compressor Station Emission Rates
Source BENZENE FORMALDEHYDE HEXANE
(lb/hr) (lb/hr) (lb/hr)
CT0I 6.90E-04 4.70E+00
CT02 3.89E-04 l.17E+00
CT03 3.41E-04 l.16E+00
EGEN 5.0SE-04 l.36E+00 2.06E-03
EGN2 3.97E-05 2.06E-02 1.69E-04
BOIL 7.94E-06 3.97E-04 9.26E-03
BLR2 3.29E-07 7.94E-06 2.82E-04
TNK.l 2.38E-04 2.00E-03
TNK.2 7.94E-06 5.0IE-06
UNTl 14 3.07E-0l
UNT2 14 3.49E-0l
UNT3 14 5.97E-0l
STNl 14 l.51E+00
STN2 14 1.08E+0O
STN3 14 8.58E-0l
CTOlBLDG l.00E-02
CT23BLDG 2.00E-02
Dominion Energy Transmissions, Inc. Atlantic Coast Pipeline, LLC
Northampton County, NC Compressor Station Volume Source Release Characteristics
Initial
Easting Northing Base Release Init. Hor. Vert.
Source ID (X) (Y) Elevation Height Dimension Dimension
(m) (m) (m) (ft) (ft) (ft)
CTOlBLDG 275,698 4,047,188 28.65 22.5 16.5 20.9
CT23BLDG 275,744 4,047,187 28.65 17.7 26.5 16.5
Dominion Energy Transmissions, Inc. Atlantic Coast Pipeline, LLC Northampton County, NC Compressor Station Point Source Release Characteristics Stack Release Easting Northing Base Stack Exit Stack Source ID Type (X) (Y} Elevation Height Temperature Velocity Diameter (m) (m) (m) (ft) (Of) (fps) (ft) CT0l DEFAULT 275,717 4,047,189 28.3S 60 750 83 6 CT02 DEFAULT 275,722 4,047,187 28.04 60 750 59 6 CT03 DEFAULT 275,767 4,047,188 28.35 60 750 so 6 EGEN DEFAULT 275,734 4,047,234 28.96 27 974 184 1.2 EGN2 DEFAULT 275,337 4,047,254 38.1 5 1200 423 0.21 BOIL DEFAULT 275,740 4,047,235 28.96 26 838 247 0.67 BLR2 DEFAULT 275,341 4,047,263 38.1 10 838 247 0.67 TNKl DEFAULT 275,606 4,047,186 28.35 9 Ambient 0 0.33 TNK2 DEFAULT 275,605 4,047,182 28.35 8 Ambient 0 0.33 UNTt 14 RAINCAP 275,719 4,047,130 27.13 19 Ambient 43 1.85 UNT2 14 RAINCAP 275,734 4,047,130 27.13 19 Ambient 49 1.85 UNT3 14 RAINCAP 275,752 4,047,131 27.13 25 Ambient 60 2.19 STNl 14 RAINCAP 275,601 4,047,146 28.35 11 Ambient 48 6.37 STN2 14 RAINCAP 275,601 4,047,143 28.35 11 Ambient 26 7.32 STN3 14 RAINCAP 275,601 4,047,122 28.35 11 Ambient 27 6.37