appendix d air quality calculations

APPENDIX D Air Quality Calculations

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AIR QUALITY CALCULATIONS

Sand and Gravel Processing

The processing of sand and gravel for a specific market involves the use of different combinations of washers, screens, and classifiers to segregate particle sizes; crushers to reduce oversized material; and storage and loading facilities.

After being transported to the processing plant, the wet sand and gravel raw feed is stockpiled or emptied directly into a hopper, which typically is covered with a "grizzly" of parallel bars to screen out large cobbles and boulders. From the hopper, the material is transported to fixed or vibrating scalping screens by gravity, belt conveyors, hydraulic pump, or bucket elevators. The scalping screens separate the oversize material from the smaller, marketable sizes. Oversize material may be used for erosion control, reclamation, or other uses, or it may be directed to a crusher for size reduction, to produce crushed aggregate, or to produce manufactured sands.

Crushing generally is carried out in one or two stages, although three-stage crushing may also be performed. Following crushing, the material is returned to the screening operation for sizing. The material that passes through the scalping screen is fed into a battery of sizing screens, which generally consists of either horizontal or sloped, and either single or multideck, vibrating screens. Rotating screens with water sprays are also used to process and wash wet sand and gravel. Screening separates the sand and gravel into different size ranges. Water is sprayed onto the material throughout the screening process. After screening, the sized gravel is transported to stockpiles, storage bins, or, in some cases, to crushers by belt conveyors, bucket elevators, or screw conveyors.

The sand is freed from clay and organic impurities by log washers or rotary scrubbers. After scrubbing, the sand typically is sized by water classification. Wet and dry screening is rarely used to size the sand. After classification, the sand is dewatered using screws, separatory cones, or hydroseparators. Material may also be rod milled to produce smaller sized fractions, although this practice is not common in the industry. After processing, the sand is transported to storage bins or stockpiles by belt conveyors, bucket elevators, or screw conveyors.

Industrial sand and gravel typically are mined from open pits of naturally occurring quartz-rich sand and sandstone. Mining methods depend primarily on the degree of cementation of the rock. In some deposits, blasting is required to loosen the material prior to processing. The material may undergo primary crushing at the mine site before being transported to the processing plant.

The mined rock is transported to the processing site and stockpiled. The material then is crushed. Depending on the degree of cementation, several stages of crushing may be required to achieve the desired size reduction. Gyratory crushers, jaw crushers, roll crushers, and impact mills are used for primary and secondary crushing. After crushing, the size of the material is further reduced to 50 micrometers or smaller by grinding, using smooth rolls, media mills, autogenous

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mills, hammer mills, or jet mills. The ground material then is classified by wet screening, dry screening, or air classification. At some plants, after initial crushing and screening, a portion of the sand may be diverted to construction sand use.

After initial crushing and screening, industrial sand and gravel are washed to remove unwanted dust and debris and are then screened and classified again. The sand (now containing 25 to 30 percent moisture) or gravel then goes to an attrition scrubbing system that removes surface stains from the material by rubbing in an agitated, high-density pulp. The scrubbed sand or gravel is diluted with water to 25 to 30 percent solids and is pumped to a set of cyclones for further desliming. If the deslimed sand or gravel contains mica, feldspar, and iron bearing minerals, it enters a froth flotation process to which sodium silicate and sulfuric acid are added. The mixture then enters a series of spiral classifiers where the impurities are floated in froth and diverted to waste. The purified sand, which has a moisture content of 15 to 25 percent, is conveyed to drainage bins where the moisture content is reduced to about 6 percent. The material is then dried in rotary or fluidized bed dryers to a moisture content of less than 0.5 percent. The dryers generally are fired with natural gas or oil, although other fuels such as propane or diesel also may be used. After drying, the material is cooled and then undergoes final screening and classification prior to being stored and packaged for shipment.

Emissions from the production of sand and gravel consist primarily of particulate matter (PM) and particulate matter less than 10 micrometers (PM10) in aerodynamic diameter, which are emitted by many operations at sand and gravel processing plants, such as conveying, screening, crushing, and storing operations. Generally, these materials are wet or moist when handled, and process emissions are often negligible. A substantial portion of these emissions may consist of heavy particles that settle out within the plant area.

Emissions from dryers include PM and PM10, as well as typical combustion products including CO and NOx. In addition, dryers may be sources of volatile organic compounds (VOC) or sulfur oxides (SOx) emissions, depending on the type of fuel used to fire the dryer. With the exception of drying, emissions from sand and gravel operations primarily are in the form of fugitive dust, and control techniques applicable to fugitive dust sources are appropriate. Some successful control techniques used for haul roads are dust suppressant application, paving, route modifications, and soil stabilization; for conveyors, covering and wet suppression; for storage piles, wet suppression, windbreaks, enclosure, and soil stabilizers; for conveyor and batch transfer points, wet suppression and various methods to reduce freefall distances (e. g., telescopic chutes, stone ladders, and hinged boom stacker conveyors); and for screening and other size classification, covering and wet suppression.

Wet suppression techniques include application of water, chemicals and/or foam, usually at crusher or conveyor feed and/or discharge points. Such spray systems at transfer points and on material handling operations have been estimated to reduce emissions 70 to 95 percent. Spray systems can also reduce loading and wind erosion emissions from storage piles of various

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materials 80 to 90 percent. Control efficiencies depend upon local climatic conditions, source properties and duration of control effectiveness. Wet suppression has a carryover effect downstream of the point of application of water or other wetting agents, as long as the surface moisture content is high enough to cause the fines to adhere to the larger rock particles.

In addition to fugitive dust control techniques, some facilities use add-on control devices to reduce emissions of PM and PM10 from sand and gravel processing operations. Controls in use include cyclones, wet scrubbers, venturi scrubbers, and fabric filters. These types of controls are rarely used at construction sand and gravel plants, but are more common at industrial sand and gravel processing facilities.

Air emissions were determined for the operation of the crushed stone processing units. The air emission calculations accounted for the proposed production levels, the number, types, and size of equipment, and the type of material processed and emission controls, if any. The emission factors were determined using the methodology found in Section 11.19 of EPA’s AP-42. Table AQ-1 presents the emission factors for the stone processing operations. A substantial portion of the air emissions from gravel processing consists of heavy particles that may settle out within the plant area.

Fugitive sources include the transfer of sand and aggregate, truck loading, mixer loading, vehicle traffic, and wind erosion from aggregate storage piles. The amount of fugitive emissions generated during the transfer of sand and aggregate depends primarily on the surface moisture content of these materials.

TABLE AQ-1 EMISSION FACTORS FOR STONE PROCESSING

Emission Point

Number of Equipment

Uncontrolled Emission Factor

(lbs/ton of material)

Controlled Emission Factor


Conveyor Belt 41 0.0014 0.000048

Feeder/Hopper 4 0.0055 0.0014

Screens 9 0.015 0.00084

Crushers 3 0.0024 0.00059

Washer/Scrubber 5 NA 0.00010

Truck Loading 3 0.000016 NA

Truck Unloading 3 0.0001 NA

NA = Not applicable. SOURCE: Compilation of Air Pollutant Emission Factors, AP-42, Fifth Edition, Volume I: Stationary Point and Area

Sources, Section 11.19.2 Crushed Stone Processing, January, 1995.

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Air emissions were determined for the operation of the sand and gravel processing. The air emission calculations accounted for the proposed production levels (1,200 tons per hour and 4,000,000 tons per year), the number, types, and size of equipment, and the type of material processed and emission controls, if any. The emission factors were determined using the methodology found in Section 11.19.1 of EPA’s AP-42. Table AQ-2 presents the emission factors for the sand and gravel processing operations. Additional emissions of toxic air pollutants such as formaldehyde, fluoranthane, naphthalane, and phenamthrane can occur as a result of dryer operations.

Fugitive sources include the transfer of sand and aggregate, truck loading, mixer loading, vehicle traffic, and wind erosion from aggregate storage piles. The amount of fugitive emissions generated during the transfer of sand and aggregate depends primarily on the surface moisture content of these materials.

TABLE AQ-2 EMISSION FACTORS FOR SAND AND GRAVEL PROCESSING

Emission Point

PM10 Emission Factor


NOx Emission Factor


Sand Dryer 2.0 0.031

Sand Dryer with Wet Scrubber 0.039 0.031

Sand Dryer with Fabric Filter 0.010 0.031

Sand Handling 0.0013

Sand Screening 0.0083

SOURCE: Compilation of Air Pollutant Emission Factors, AP-42, Fifth Edition, Volume I: Stationary Point and Area Sources, Section 11.19.1 Sand and Gravel Processing, November 1995.

Concrete Batching Operations

Concrete is composed essentially of water, cement, sand (fine aggregate), and coarse aggregate, consisting of crushed stone. Sand, aggregate, cement, and water are all gravity fed from a weigh hopper into the mixer trucks. The cement is transferred to elevated storage silos. The sand and coarse aggregate are transferred to elevated bins. From these elevated bins, the constituents are fed by gravity or screw conveyor to weigh hoppers, which combine the proper amounts of each material.

Air emissions were determined for the operation of the concrete batching plants. The air emission calculations accounted for the proposed production level, the number, types, and size of

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equipment. The emission factors can be calculated using the methodology found in Section 11.12 of AP-42. Table AQ-3 presents the emission factors for the concrete batching operations. The cement unloading and truck loading points have air emission controls applied to them.

TABLE AQ-3 EMISSION FACTORS FOR CONCRETE BATCHING

Emission Point

Number of Equipment

Uncontrolled Emission Factor


Controlled Emission Factor


Aggregate Transfer 2 0.0033 0.0033

Sand Transfer 2 0.00099 0.00099

Cement Unloading 2 0.46 0.00034

Weigh Hopper Loading 2 0.0024 0.0024

Mixer Loading 2 0.078 0.0038

Truck Loading 2 0.15 0.051

SOURCE: Compilation of Air Pollutant Emission Factors, AP-42, Fifth Edition, Volume I: Stationary Point and Area Sources, Section 11.12 Concrete Batching, October, 2001.

Asphalt Batching Operations

Hot mix asphalt paving materials are a mixture of size-graded, high quality aggregate, and liquid asphalt cement, which is heated and mixed in measured quantities. Hot mix asphalt paving materials can be manufactured by: 1) batch mix plants, continuous mix (mix outside dryer drum) plants, parallel flow drum mix plants, and counter flow drum mix plants. Processing begins as the aggregate is hauled from the storage piles and is placed in the appropriate hoppers of the cold feed unit. The material is metered from the hoppers onto a conveyer belt and is transported into a rotary dryer (typically gas- or oil-fired).

Dryers are equipped with flights designed to shower the aggregate inside the drum to promote drying efficiency. As the hot aggregate leaves the dryer, it drops into a bucket elevator and is transferred to a set of vibrating screens, where it is classified into as many as four different grades (sizes) and is dropped into individual “hot” bins according to size. To control aggregate size distribution in the final batch mix, the operator opens various hot bins over a weigh hopper until the desired mix and weight are obtained. Concurrent with the aggregate being weighed, liquid asphalt cement is pumped from a heated storage tank to an asphalt bucket, where it is weighed to achieve the desired aggregate-to-asphalt cement ratio in the final mix.

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The aggregate from the weigh hopper is dropped into the mixer (pug mill) and dry-mixed for 6 to 10 seconds. The liquid asphalt is then dropped into a pug mill where it is mixed for an additional period of time. Total mixing time is usually less than 60 seconds. Then the hot mix is conveyed to a hot storage silo or is dropped into a truck and hauled to a job site.

Emissions from hot mix plants may be divided into ducted production emissions, pre-production fugitive dust emissions, and other production-related fugitive emissions. Pre-production fugitive dust sources include vehicular traffic generating dust on paved and unpaved roads, aggregate material handling, and other aggregate processing operations. Ducted emissions are usually collected and transported by an industrial ventilation system having one or more fans, eventually to be emitted to the atmosphere through some type of stack. The most significant ducted source of emissions is the rotary drum dryer. The dryer emissions consist of water; PM; product of combust; and small amounts of organic compounds, including hazardous air pollutants. Other potential process sources include the hot-side conveying, classifying, and mixing equipment, which are vented either to the primary dust collector (along with the dryer gas) or to a separate dust collection system.

Emission controls for PM emissions from the dryer and vent lines include dry mechanical collectors, scrubbers, and fabric filters, and the use of primary dust collection equipment such as large diameter cyclones, skimmers, and settling chambers.

Air emissions were determined for the operation of the asphalt batching processing. The air emission calculations accounted for the proposed production levels (400,000 tons per year), the number, types, and size of equipment, and the type of material processed and emission controls, if any. The emission factors were determined using the methodology found in Section 11.1 of EPA’s AP-42. H2S emission factors were based on information contained in a North Caroiline Department of Environmental Quality report entitled Hydrogen Sulfide Study near Petroleum Asphalt Plants. At this time, it is not known whether the asphalt plant will be hot mix or drum mix, thus, both types of facilities are presented in the analysis. Table AQ-4 presents the emission factors for the asphalt processing operations. Additional emissions include benzene, acetaldehyde, ethyl benzene, PAHs, and various metals. Table AQ-5 presents the TAC emission factors for the asphalt processing operations. PM, CO, and VOC emissions also occur during batch mix plant load-out, silo filling, and asphalt storage, based on asphalt volatility, mix temperature, predictive emission factor equations found in AP-42 Section 11.1 (Table 11.1-14), and HAP speciation profiles.

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TABLE AQ-4 EMISSION FACTORS FOR ASPHALT PROCESSING

Emission Point Units PM10 CO SO2 NOx VOC H2S

Dryer, hot screen, mixerab lb/ton 0.4 0.0046 0.025 0.0041d 0.005

Dryer, hot screen, mixerac lb/ton 0.13 0.0034 0.026 0.0022d 0.005

Fabric Filterb lb/ton 0.0098

Fabric Filterc lb/ton 0.0042

Hot Oil Heater lb/MMbtu 0.00745 0.0835 0.00059 0.0980 0.0539

Loadout lb/ton 0.00030 0.00046 0.0133

Silo Filling lb/ton 0.00042 0.00040 0.00390

Storage Tank lb/ton 0.000001 0.00001 0.0049

SOURCE: Compilation of Air Pollutant Emission Factors, AP-42, Fifth Edition, Volume I: Stationary Point and Area Sources, Section 11.1 Hot Mix Asphalt Plants, December 2000.

a Natural gas-fired b Batch Mix Hot Mix Asphalt Plant c Drum Mix Hot Mix Asphalt Plant d Control efficiency of 50 percent

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TABLE AQ-5 TAC EMISSION FACTORS FOR ASPHALT PROCESSING

Pollutant Hot Mix Drum Mix

Loadout Silo Filling & Storage

Acetaldehyde 0.00032 Benzene 0.00028 0.00039 0.05% 0.03% Ethylbenzene 0.0022 0.00024 0.28% 0.04% Formaldehyde 0.00074 0.0031 0.09% 0.69% Hexane 0.00092 0.15% 0.10% Quinone 0.00027 Isooctane 0.00004 0.002% 0.0003% Methyl chloroform 0.000048 Toluene 0.001 0.00015 0.21% 0.06% Xylene 0.0027 0.0002 0.41% 0.20% 2-Methylnaphthalene 7.10E-05 7.40E-05 2.38% 5.27% Acenaphthene 9.00E-07 1.40E-06 0.26% 0.47% Acenaphthylene 5.80E-07 8.60E-06 0.03% 0.01% Anthracene 2.10E-07 2.20E-07 0.07% 0.13% Benzo(a)anthracene 4.60E-09 2.10E-07 0.02% 0.06% Benzo(a)pyrene 3.10E-10 1.10E-07 0.01% 0.01% Benzo(b)flroranthene 9.40E-09 1.00E-07 0.01% Benzo(ghi)perylene 5.00E-10 4.00E-08 0.002% Benzo(k)fluoranthene 1.30E-08 4.10E-08 0.002% Chrysene 3.80E-09 1.80E-07 0.10% 0.21% Dibenzo(ah)anthracene 9.50E-11 0.0004% Fluoranthene 1.60E-07 6.10E-07 0.05% 0.15% Fluorene 1.60E-06 3.80E-06 0.77% 1.01% Indeno(123-cd)pyrene 3.00E-10 7.00E-09 0.0005% Naphthalene 3.60E-05 9.00E-05 1.25% 1.82% Phenanthrene 2.60E-06 7.60E-06 0.81% 1.80% Pyrene 6.20E-08 5.40E-07 0.15% 0.40% Perylene 8.80E-09 0.02% 0.03% Phenol 1.18% Arsenic 4.60E-07 5.60E-07 Barium 1.50E-06 5.80E-06 Beryllium 1.50E-07 0 Cadmium 6.10E-07 4.10E-07 Chromium 5.70E-07 5.50E-06 Chromium VI 4.80E-08 4.50E-07 Copper 2.80E-06 3.10E-06 Lead 8.90E-07 6.20E-07 Manganese 6.90E-06 7.70E-06 Mercury 4.10E-07 2.40E-07 Nickel 3.00E-06 6.30E-05 Selenium 4.90E-07 3.50E-07 Zinc 6.80E-06 6.10E-05 Antimony 1.80E-07 Cobalt 2.60E-08 Phospherous 2.80E-05 Silver 4.80E-07 Thallium 4.10E-09

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Bromomethane 0.01% 0.005% 2-Butanone 0.05% 0.04% Carbon Disulfide 0.01% 0.02% Chloroethane 0.0002% 0.00% Chloromethane 0.02% 0.02% Cumene 0.11% Methylene Chloride 0.0003% MTBE Styrene 0.01% 0.01% Tetrachloroethane 0.01% 1,1,1-Trichloroethane

Handling and Storage

Fugitive particulate matter emissions are expected from the handling and storage of raw materials from quarry processing. The methodology for the calculation of particulate emissions from the handling and storage of raw materials is described in AP-42 Section 13.2.4 for aggregate handling and storage piles. The quantity of dust emissions from aggregate handling and storage operations varies with the volume of aggregate passing through the storage cycle. The emission factor for the quantity of emissions per quantity of material is estimated using the following equation:

4.1

3.1

2

5)0032.0(

⎥⎦⎤

⎢⎣⎡

⎥⎦⎤

⎢⎣⎡

=M

U

kEF

where: EF = emission factor (lb emissions/ton material) k = particulate size multiplier (PM10 = 0.35) U = mean wind speed (7.4 mph) M = material moisture content (0.7 %)

Based on available data, the emission factor for handling and storage activities is 0.0052 pounds of PM10 per ton of material processed (uncontrolled) and 0.0013 pounds of PM10 per ton of material processed (controlled). Weather data (wind speed) from http://www.wrcc.dri.edu/summary for Stockton, California. To account for emission controls, a control efficiency of 75% was applied.

Wind Erosion

In addition to emissions from the handling of storage piles, EPA provides a methodology for calculating emissions from wind erosion of storage piles as documented in AP-42 Section 13.2.5. The emission factor for wind-generated particulate emissions is dependent on the frequency of

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disturbance of the storage pile and is expressed in units of grams per square meter (g/m2) per year. The following equations were used to calculate the emission factor.

∑ ==

N

i iPkEF1

10053.0 uu =•

where: EF = emission factor (g/m2/yr) k = aerodynamic particle size multiplier (0.5) dimensionless P = erosion potential (g/m2) N = number of disturbances (366 disturbances per year)

•u = friction velocity (m/s) •tu = threshold friction velocity (1.02 m/s)

10u = wind at reference height of 10 m (19 m/s)

The basis of this methodology is that wind-blown dust from exposed areas will occur only when two conditions are met: the surface of the exposed area is disturbed and winds occur in excess of a threshold wind speed. Once the two conditions have been met, the emission factor is used to determine how much dust is generated. No more wind erosion occurs until the surface is again disturbed and the wind again exceeds the threshold speed. For conservatism, the calculation assumes the storage piles will be disturbed daily and, therefore, N equals 366 disturbances per year.

Based on available data, the emission factor for wind erosion activities is 5.25 pounds of PM10 per square meter of stockpile (uncontrolled) and 1.31 pounds per square meter of stockpile (controlled). Emissions were based on a continuously exposed stockpile area of 50 square meters. To account for emission controls, a control efficiency of 75% was applied.

Unpaved Roads

When a vehicle travels over an unpaved road, the force of the wheels on the road surface causes pulverization of surface material. Particles are lifted and dropped from the rolling wheels, and the road surface is exposed to strong air currents in turbulent shear with the surface. The turbulent wake behind the vehicle continues to act on the road surface after the vehicle has passed. The emission factors were calculated using the methodology found in Section 13.2 of AP-42, Unpaved Roads. The equation for developing the emission factor is:

EF = k (S/12)a(W/3)b [(365-p)/365] (1-CE)

•••••• ≤=−+−= titti uuforPuuuuP 0);(25)(58 2

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where: k (PM10) = 1.5 (empirical constant) S = 10% (silt content) (use whole number value) W = 34 tons (mean vehicle weight, average of empty and full) p = 72 (precipitation days) a = 0.9 (empirical constant) b = 0.45 (empirical constant) CE = 75% (empirical constant) Based on available data, the emission factor for unpaved roads is 0.568 pounds of PM10 per vehicle mile traveled (uncontrolled) and 0.456 pounds of PM10 per vehicle mile traveled (controlled). To account for emission controls, a control efficiency of 75% was applied. Weather data (days of measurable precipitation) from http://www.wrcc.dri.edu/summary for Lodi, California. The project condition provides for 981 and 256,041 (see Transportation and Traffic section) daily and annual round-trip vehicle trips, respectively, each presumed to be traveling a distance of ½ mile on unpaved roads and within the circulation area (per trip).

Nonroad Equipment and Mobile Vehicles

The types of nonroad equipment at the project site include loaders, grader, excavators, off-highway trucks (such as water trucks), scrapers, and haul trucks. Emission factors for all equipment except haul trucks and pickup trucks were obtained from the U.S. EPA’s NONROAD model and documentation and databases prepared in support of NONROAD. The NONOAD model considers the rules of 40 CFR Part 89 that establish standards for emissions of CO, VOC, NOx, and PM on equipment of the type used in the construction and other industries. Emission factors for each equipment type were applied to the anticipated equipment work output (horsepower-hours of expected equipment use). Average horsepower, hours of operations, and load factors were developed based on NONROAD databases, specifically for California.

Emission factors for haul trucks were obtained from the EMFAC2002 model. Haul trucks with a gross vehicle weight greater than 8,500 pounds (heavy trucks). The pickup trucks were conservatively assumed to travel 50 miles each day, although they are mainly used for inspection and supply/personnel transport purposes at the site. The haul trucks were assumed to travel 50 miles each way between the facility and the aggregate markets, a conservative estimate given the distance between the project site and typical markets. Table AQ-6 presents the nonroad usage data. Table A-7 and Table A-8 present the emission factors used of nonroad equipment and motor vehicles for 2007 and 2021, respectively.

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TABLE AQ-6 SUMMARY DATA FOR NONROAD EQUIPMENT

Equipment

Type Numberb Lifetime Load

Factora

Daily Hoursb

Annual Hoursb

Fuel Typeb Average Size

(hp)b

Excavator 2 8 0.70 10 2580 Diesel 454

Haul Trucks (onsite) 7 8 0.57 10 2580 Diesel 400

Front End Loader 3 8 0.55 8 2064 Diesel 475

Dozer 1 8 0.59 4 1032 Diesel 410

Grader 1 10 0.61 4 1032 Diesel 224

Water Pull 1 8 0.57 10 2580 Diesel 450

Bobcat Loader 1 6 0.55 6 1548 Diesel 54

Maintenance Trucks 4 5 0.57 4 1032 Gasoline 300

Lube & Fuel Truck 1 10 0.57 4 2064 Diesel 350

Forklift 1 10 0.59 4 1548 Diesel 100

SOURCE: aNonroad Engine and Vehicle Emission Study. November 1991. b RMC Pacific Materials Response to Questions

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TABLE AQ-7 EMISSION FACTORS (2008) FOR NONROAD EQUIPMENT AND MOTOR VEHICLES

Equipment Type

Model Year

Units ROG CO NOx PM10

Excavator 2008 g/hp-hr 0.16 0.97 2.53 0.12

Haul Trucks (onsite) 2004 g/hp-hr 0.42 1.15 5.04 0.18


Front End Loader 2004 g/hp-hr 0.36 1.11 4.89 0.17


Dozer 2008 g/hp-hr 0.13 0.94 2.48 0.12

Grader 2004 g/hp-hr 0.36 3.07 5.11 0.26

Water Pull 2004 g/hp-hr 0.42 1.15 5.04 0.18

Bobcat Loader 2008 g/hp-hr 0.14 3.18 2.95 0.21

Maintenance Trucks 2008 g/hp-hr 4.20 54.1 10.1 0.04

Lube & Fuel Truck 2008 g/hp-hr 0.15 0.96 2.52 0.12

Forklift 2004 g/hp-hr 0.72 3.89 6.44 0.61

Pickup Trucks (onsite) g/mile 0.272 6.554 0.460 0.041

Haul Trucks (offsite) g/mile 0.817 5.956 7.940 0.284

SOURCE: California Air Resource Board. 2002. EMFAC2002 Version 2.2 and Environmental Protection Agency. 1991. Nonroad Engine and Vehicle Emission Study.

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TABLE AQ-8 EMISSION FACTORS (2020) FOR NONROAD EQUIPMENT AND MOTOR VEHICLES

Equipment Type

Model Year

Units ROG CO NOx PM10

Excavator 2016 g/hp-hr 0.42 1.15 2.86 0.05





Dozer 2016 g/hp-hr 0.23 1.01 2.61 0.03

Grader 2014 g/hp-hr 0.28 3.22 2.63 0.05

Water Pull 2020 g/hp-hr 0.16 0.97 2.53 0.03

Bobcat Loader 2020 g/hp-hr 0.14 3.18 2.95 0.05

Maintenance Trucks 2018 g/hp-hr 1.88 36.7 5.18 0.04

Lube & Fuel Truck 2018 g/hp-hr 0.25 1.03 2.65 0.04

Forklift 2014 g/hp-hr 0.37 3.93 3.30 0.09

Pickup Trucks (onsite) g/mile 0.063 2.169 0.140 0.040

Haul Trucks (offsite) g/mile 0.286 1.798 1.830 0.137

SOURCE: California Air Resource Board. 2002. EMFAC2002 Version 2.2 and Environmental Protection Agency. 1991. Nonroad Engine and Vehicle Emission Study.

Dispersion Modeling

Dispersion is the process by which atmospheric pollutants disseminate due to wind and vertical stability. The results of a dispersion analysis are used to access pollutant concentrations at or near an emission source. The results of an analysis allow a direct comparison of predicted concentrations of pollutants to air quality or exposure standards.

A rising pollutant plume reacts with the environment in several ways before it levels off. First, the plume’s own turbulence interacts with atmospheric turbulence to entrain ambient air. This mixing process reduces and eventually eliminates the density and momentum differences that cause the plume to rise. Second, the wind transports the plume during its rise and entrainment process. Higher winds mix the plume more rapidly, resulting in a lower final rise. Third, the plume interacts with the vertical temperature stratification of the atmosphere, rising as a result of

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buoyancy in the unstable-to-neutrally stratified mixed layer. However, after the plume encounters the mixing lid and the stably stratified air above, its vertical motion is dampened.

Dispersion modeling uses hourly averaged meteorological data, terrain elevation data, and emissions and source release data to compute downwind pollutant concentrations over averaging periods ranging from one hour to one year. This section presents the methodology used for the dispersion modeling analysis. The methodology is consistent with procedures documented in the EPA Guideline on Air Quality Models (Revised, 1993) and SJVUAPCD’s Guide for Assessing Air Quality Impacts.

Molecules of gas or small particles injected into the atmosphere will separate from each other as they are acted on by turbulent eddies. The Gaussian mathematical model simulates the dispersion of the gas or particles within the atmosphere. The formulation of the Gaussian model is based on the following assumptions:

• The predictions are not time dependent (all conditions remain unchanging with time); • The wind speed and direction are uniform, both horizontally and vertically throughout the

region of concern; • The rate of diffusion is not a function of position; and • Diffusion in the direction of the transporting wind is negligible when compared to the

transport flow. The Gaussian dispersion model algorithm provides a simple analytical method of estimating downwind concentrations, where concentration is a function of several basic elements:

• Initial plume height (sum of the physical stack height and the plume rise); • The source emission rate; • The horizontal and vertical plume distribution (based on atmospheric stability); • The wind speed at source height; • The height of the receptor; • The off-centerline of the receptor; and • The downwind distance from the source to the receptor.

Screening Dispersion Modeling A screening dispersion modeling technique was used to initially estimate health risks due to increases in DPM impacts. The screening dispersion modeling analysis used a dispersion model to predict DPM impacts at sensitive receptors from haul trucks along roadways; the CALINE4 model. The CALINE4 dispersion models are conservative (tend to overpredict).

The CALINE4 model is the most recent in a series of line source air quality models developed by the California Department of Transportation (Caltrans). It is based on the Gaussian diffusion equation and employs a mixing zone concept to characterize pollutant dispersion over the roadway. The purpose of the model is to assess air quality impacts near transportation facilities. Given source strength, meteorology and site geometry, CALINE4 can predict pollutant concentrations for receptors located within 500 meters of the roadway. In addition to predicting concentrations of relatively inert pollutants such as CO and particle concentrations; it also has

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special options for modeling air quality near intersections, street canyons and parking facilities. CALINE4 used the EMFAC2002 emission factors as part of its analysis.

In general, the transport and concentration of pollutants from vehicular sources are influenced by three principal meteorological factors: wind direction, wind speed, and atmospheric stability, which accounts for the effects of dispersion or mixing in the atmosphere. Wind direction, which influences the accumulation of pollutants at a particular receptor location, was chosen to maximize pollutant concentrations at the receptor. In applying the CALINE4 modeling, the wind angle was varied to determine the worst-case wind direction resulting in the maximum concentrations. For short-term average impacts, computations was performed using a wind speed of 1 meter/second, stability class F “very stable”, representing a worst case assumption of conditions and an aerodynamic roughness coefficient of 400 cm, typical of the environment surrounding the Proposed Project.

The SJVQMD has a significance threshold for health risk exposure to diesel emissions of 10 cancers per million for 70-year exposure. Accordingly, the SJVAQMD CEQA Guidelines indicate the primary concern from diesel engine exhaust emissions is a potential long-term health risk to sensitive receptors. Receptors were placed at distances of 1090, 1190, and 1500 meters from the source (designated as the center of the Project site). Annualized average emissions from 2007 and 2021 from onsite equipment were determined. A generalized emission area source with dimensions of 300 by 300 meters with a height of 5 meters was used. Rural dispersion coefficients were used.

Refined Dispersion Modeling This section presents the methodology used for the refined dispersion modeling analysis. This section addresses all of the fundamental components of an air dispersion modeling analysis including:

• Model selection and options; • Receptor spacing and location; • Meteorological data; and • Source release characteristics.

The dispersion modeling analysis estimated ambient DPM concentrations as a result of incremental project emission increases and then determined differential cancer risk. The dispersion modeling included onsite equipment.

MODEL SELECTION AND OPTIONS

The AERMOD dispersion model (Version 99351) was used for the modeling analysis. AERMOD is the U.S. EPA preferred dispersion model for general industrial purposes. The

17

AERMOD model is the appropriate model for this analysis based on the coverage of simple, intermediate, and complex terrain. It also predicts both short-term and long-term (annual) average concentrations. The model was executed using the regulatory default options (stack-tip downwash, buoyancy-induced dispersion, final plume rise), default wind speed profile categories, default potential temperature gradients, and no pollutant decay. Building wake effects were also addressed. The model is based on the Industrial Source Complex-3 (ISC3) model and PRIME downwash algorithm.

Special features of AERMOD include its ability to treat the vertical inhomogeneity of the planetary boundary layer, special treatment of surface releases, irregularly-shaped area sources, a three plume model for the convective boundary layer, limitation of vertical mixing in the stable boundary layer, and fixing the reflecting surface at the stack base. A treatment of dispersion in the presence of intermediate and complex terrain is used that improves on that currently in use in ISCST3 and other models.

The selection of the appropriate dispersion coefficients used in the modeling depends on the land use within three kilometers (km) of the Port of Stockton. The land use typing was based on the classification method defined by Auer (1978); using pertinent United States Geological Survey (USGS) 1:24,000 scale (7.5 minute) topographic maps of the area. If the Auer land use types of heavy industrial, light-to-moderate industrial, commercial, and compact residential account for 50% or more of the total area, the Guideline on Air Quality Models recommends using urban dispersion coefficients; otherwise, the appropriate rural coefficients were used. Based on observation of the area surrounding the Vernalis, rural dispersion coefficients were applied in the analysis.

RECEPTOR LOCATIONS

Receptors were placed at locations within residential areas surrounding the Proposed Project. Receptor base elevations were determined based on USGS mapping programs. Receptors were also positioned as flagpole receptors at a height of 1.8 meters above the ground (breathing height).

METEOROLOGICAL DATA

The rate at which emissions are dispersed in the atmosphere depends upon the intensity of the ambient turbulence, the velocity of the wind, the position relative to obstacles in the flow field, and any dilutions attributable to the source itself. The most important factor leading to plume spread in the atmosphere is the amount of ambient turbulence. In a stable atmosphere, the horizontal and vertical turbulence is very limited. The plume remains near its emission height and undergoes minimal mixing. This situation is common during the nighttime and early morning hours. If the layer below the plume height becomes neutral to unstable, the plume mixes rapidly to the surface. This is known as a fumigation condition and can cause high concentrations. This occurs for short duration during the early morning. As heating of the

18

surface persists, a fully unstable mixing layer develops, and the plume loops up and down in response to large-scale convective eddies. A neutral stability atmosphere yields moderate amounts of turbulence and results in a cone-shaped plume. Finally, if an inversion is present below the emission height, a lofting condition exists and the plume is cut off from ground level impacts.

Stability class frequencies were calculated from the deviation of the horizontal wind direction (sigma theta). The Sigma Theta method was used to categorize stability class as a function of wind speed and time of day. Stability classes range from extremely unstable (A) to moderately stable (F). These classes are used in dispersion models to estimate how much a plume will spread over time and space. In general, the more stable the atmosphere is, the less potential for plume spread, creating higher plume concentrations.

Surface meteorological data and upper air meteorological (mixing height) data from Fresno and Sacramento, California, respectively, were used for the modeling analysis (http://www.valleyair.org/busind/pto/Tox_Resources/toxics_resources.htm). Meteorological data were obtained from SJVUAPCD and used for modeling impacts of the Proposed Project. Data from 1986 through 1990 was used and the worst case year of analysis was reported.

SOURCE RELEASE CHARACTERISTICS

Onsite equipment was treated as area sources located within the phases of operations. The area source was modeled with a release height of 3 meters. Table AQ-9 provides the exhaust parameters (based on engineering judgment and other similar facilities) for the asphalt batch operations. The loadout, silo filling, and storage tank sources were treated as a volume source with a height of 4.5 meters and a length of 20 meters.

TABLE AQ-9 ASPHALT BATCH EXHAUST PARAMETERS

Height Diameter Velocity Temperature

Source (m) (m) (m/s) (K) Dryer/Heater 12.2 1.44 17.4 422

m = meters. m/s = meters per second. K = Kelvin.

Health Risk Assessment

The SJVUAPCD has a significance threshold for health risk exposure to diesel emissions of 10 cancers per million for 70-year exposure; indicating the primary concern from diesel engine exhaust emissions is a potential long-term health risk to sensitive receptors.

19

CANCER RISKS

The cancer risks from DPM occur exclusively through the inhalation pathway; therefore the cancer risks can be estimated from the following equation:

CRDPM = CDPM • URFDPM • LEA

where,

CRDPM Cancer risk from DPM; the probability of an individual developing cancer as a result of exposure to DPM.

CDPM Annual average DPM concentration in µg/m3.

URFDPM Unit risk factor for DPM; estimated probability that a person will contract cancer as a result of inhalation of a DPM concentration of 1 µg/m3 continuously over a period pf 70 years.

LEA Lifetime exposure adjustment; values range from 0.14 to 1.0.

The inhalation unit risk factor for diesel particulate was established by CARB as 300 in one million per continuous exposure of 1 µg/m3 of DPM over a 70-year period. In order to protect public health, and in accordance with the recommendations of the State of California Office of Environmental Health Hazard Assessment (OEHHA), a 70-year lifetime exposure is assumed for receptor locations. The LEA for most residential or sensitive receptors is 1.0. However, exposure adjustments can be made based on the exposure duration (ex., schools and industrial workers).

NON-CANCER RISKS

The relationship for the non-cancer health effects of DPM is given by the following equation:

HIDPM = CDPM/RELDPM

where,

HIDPM Hazard Index; an expression of the potential for non-cancer health effects.

CDPM Annual average DPM concentration (µg/m3).

RELDPM Reference exposure level (REL) for DPM; the DPM concentration at which no adverse health effects are anticipated.

The chronic REL for DPM was established by OEHHA as 5 µg/m3.

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21

References

Auer, 1978. "Correlation of Land Use and Cover with Meteorological Anomalies", August H. Auer, Jr., American Meteorological Society, Journal of Applied Meteorology, Vol. 17, pp. 636-643, May 1978. EPA, 1985. Guideline for Determination of Good Engineering Stack Height (Technical Support Document For the Stack Height Regulations), EPA-450/4-80-023R, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina, June 1985. EPA, 1993. Guideline on Air Quality Models (Revised, including Supplements), EPA-450/2-78-027R, U.S. Environmental Protection Agency, Office of Air and Radiation, Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina, February 1993.

appendix d air quality calculations

Documents