CHAPTER 3 - AIRPORT AND MILITARY EMISSIONS

1996 Emission Inventory for the Alamo Area Council of Governments Region 

Airport & Military Emissions Chapter Contents

 

SAN ANTONIO INTERNATIONAL AIRPORT

Background and Setting

The City of San Antonio Aviation Department operates two municipal airports, San Antonio International and Stinson Field. Scheduled airlines which served San Antonio as of November 1997 consisted of West, American, Continental, Delta, Mexicana, Northwest, Southwest, TWA, United, American Eagle, and regional airlines - Aerolitoral, Aeromar, and Mesa. In addition, five military installations are located in San Antonio: Fort Sam Houston, Brooks Air Force Base, Kelly Air Force Base, Lackland Air Force Base, and Randolph Air Force Base. Stinson Field, one of the oldest continually operated airports in the United States, is the relief airport for San Antonio International Airport and handles general aviation aircraft only.

San Antonio International Airport is located approximately seven miles north of the San Antonio central business district. This area consists primarily of older, fully-developed residential areas with commercial strip development along or near the major arterials.

Dating back to 1915, Stinson Field was the official city airport. Braniff Airlines and Eastern Airlines came into the City in 1935. The original land acquisition began in 1941 for San Antonio International Airport. This was an area generally bounded by Wetmore Road, north Loop Road, Jones-Maltsberger Road, and Bitters Road. In 1942, Eastern and Braniff moved to the present airport site. Additional tracts of land were purchased in the following years as airport expansion occurred.

During World War II, despite limitations on civilian travel, expansion of the Airport occurred in conjunction with Alamo Army Air Field activity (now Fairchild Aviation). On August 1, 1944, an American Airlines DC-3 arrived from Mexico City, making San Antonio a port of entry for the first time. In 1952, the first unit of the present terminal structure was completed and in 1960, the East finger and West finger were added. Also in 1960, Braniff introduced the first jet service to San Antonio using Boeing 707 aircraft. A major terminal building expansion was undertaken in 1967-68, at the time of the HemisFair, when the Satellite (of Terminal 2) was added. Continental and Southwest Airlines additions were made, and the baggage claim area was expanded. The last major terminal expansion at San Antonio International Airport was completed on July 1, 1984, and consisted of the sixteen gates of Terminal 1.

The Federal Aviation Administration (FAA) has developed and promulgated procedures to analyze air quality at airports. These procedures are encapsulated in two primary FAA texts entitled: Air Quality Procedures for Civilian Airports and Military Bases; and, Airport Environmental Handbook. Additional guidance is provided by the Environmental Protection Agency (EPA) in a text entitled, An Air Pollution Impact Methodology for Airports; Phase I. The analysis in this overview has been conducted in accordance with these various requirements and/or methods.

Existing Air Quality

International Airport is located at the edge of the hill country area but still in relatively level terrain. The area experiences many sunny days. The bright sun provides good thermal mixing and is conducive to good wind flow. These characteristics lead to good atmospheric dispersion of pollutants.

Emissions Inventory

For an inventory to be informative, all sources related to any proposed project must be considered. For this project analysis at San Antonio International Airport, the following major sources were identified:

aircraft
ground support equipment
boilers (heating plants)
motor vehicles (parking lots and roadways)
fuel storage
fueling operations

Aircraft Emissions and Ground Support Equipment

Each aircraft type that operates at San Antonio International Airport may be equipped with several different engines, according to year of manufacture, retrofitting, and customer preference. Through a review of published literature, engine types for each aircraft model were determined. Then a comparison was made to the aircraft types included in the Emissions & Dispersion Modeling System (EDMS). The actual aircraft fleet mix was placed in categories with similar engines contained in EDMS.

Ground service equipment must also be considered at an airport. EDMS, dependent upon aircraft evaluated, automatically includes these emissions based on EPA emission factors. Accordingly, no input was required for ground support equipment.

Airport Boilers (Heating Plants)

In 1993, 341,329 cubic meters of natural gas were burned. It was projected that this annual value would increase to 504,000 cubic meters per year in 2015. The 1996 annual value, 363,511 cubic meters, was approximated for use in the inventory by straight-line interpolation. Because natural gas was used, no other control measures were evaluated.

Airport Roadways

Multiple roadways were modeled for this analysis. The roadways, their lengths and peak-hour volumes are shown in this analysis. Peak-hour volumes are approximately 10% of the daily traffic as shown in the Master Plan. Speeds were conservative assumptions made by facility site visit, based on a 1998 study by Ricondo & Associates. It was assumed that any vehicle accessing the terminal idled, and 2 minutes of idle time was included. This assumption was based on a site visit to the airport to review curb-front activity.

Airport Parking

Parking lots were included in the Ricondo & Associates (1998) analysis. These lots included seven surface lots and three parking garages. Both public and employee parking was considered. For employee lots, the reported demand was 730. It was assumed that these lots were filled and emptied 2.5 times in a twenty-four hour setting resulting in 1825 vehicle movements per day. Actual vehicle counts (entry and exits) were made for the public parking lots. An average of 4,523 vehicle movements was measured. It was assumed, based on mapping, that the average trip in a surface lot was approximately 300 feet. In the parking garages it was assumed the average trip in the lot was 600 feet. Accounting for vehicle movements, a total of 483.3 vehicle miles was traveled in the parking lots each day. This mileage, along with a 1-minute idle time per movement was used along with MOBILE5's emission factors to estimate total yearly emissions. A speed of 10 mph was assumed in the parking lots. In addition, the cars were assumed to be evenly split between the hot start mode and cold start mode.

Airport Fuel Storage and Operations

In 1993 (base case), annual fuel throughput at the Airport included Jet A fuel (208,258 kiloliters) and aviation gasoline (55,360 kiloliters). These values are expected to reach 315,846 kiloliters per year and 83,959 kiloliters per year for Jet A fuel and aviation gasoline, respectively. Stage I vapor recovery was assumed for all cases. No Stage II vapor recovery was assumed. The Emissions and Dispersion Modeling System software does not calculate emissions for this category. In this case alone, emission values supplied by the 1998 study by Ricondo & Associates were used as default values.

Emission Inventory Results for San Antonio International Airport.
Tons/year

NAME	CO tons/yr.	VOC tons/yr.	NOx tons/yr.	SOx tons/yr.	PM10 tons/yr.
Aircraft	445.885	105.831	421.502	17.184	0
GSE/AGE/APU*	1417.900	32.400	105.543	2.869	3.326
Roadways	215.602	24.685	17.854	0.746	0.889
Parking Lots	37.491	4.393	1.342	0.036	0.054
Fueling Ops	-	64.320	-	-	-
Stationary Sources	0.256	0.011	3.526	0.004	0.019
Total	2117.134	231.640	549.767	20.839	4.288

*Note: GSE/AGE/APU stands for Ground Support Equipment, Aerospace Ground Equipment and Auxiliary Power Unit, respectively

METHODOLOGY

This document was prepared in accordance with the Federal Aviation Administration (FAA) promulgated guidelines. FAA air quality assessment procedures require an emissions inventory be conducted for the existing airport and for future years.

To assist in the preparation of an accurate emission inventory, the FAA microcomputer model EDMS Version 3.01, was used with all prescribed data input methodologies. All emission factors and estimation techniques are approved EPA methods. However, after careful review and comparison of the models to manual calculations, it was decided that the roadways and parking lots would be calculated external to the EDMS. As such, MOBILE5a was used to estimate motor vehicle emission factors and multiplied by estimated vehicle miles of travel and idle time. Traffic data was collected in 1998 by Ricondo & Associates as the base for planning future airport expansion projects. It is the best available data and accurately reflects airport operations in 1996. This allowed direct calculation of the motor vehicle emissions on the airport property. The methodology and assumptions used to predict each source is discussed in the following sections.

Aircraft Emissions and Ground Support Equipment

The number of aircraft operations was supplied by the FAA control tower in their monthly activity reports. Scheduled Air Carrier data was supplied by the FAA in their annual airport summary. Aircraft types for air taxi and general aviation were obtained from interviews with the tower staff and fixed base operators. However each aircraft type may be equipped with several different engines, according to year of manufacture, retrofitting, and customer preference. Through a review of published literature, engine types for each aircraft model were determined. Then a comparison was made to the aircraft types included in EDMS and the actual aircraft fleet mix placed in categories with similar engines contained in EDMS. The results of this aircraft type determination are presented in the following subsection.

Emission factors for aircraft relate the time the aircraft spends at distinct throttle settings and the amount of fuel used at each setting to predict emissions released to the atmosphere from the aircraft. For this report, EDMS default times-in-mode were used for all modes except idle/taxi. In this case, the best information available was from modeling accomplished by Ricondo & Associates and supplied for this work. The results indicated the following:

Year 1996

Idle/taxi time = 7.4 min

Queue time = 1.2 min

The times shown above were used for the ground movements at SAT. Default values were used for takeoff, cruise, and approach times in mode.

Ground service equipment must also be considered at an airport. EDMS, dependent upon aircraft evaluated, automatically includes these emissions based on EPA emission factors. A survey of ground support equipment used by operators at the airport was completed and a composite set of support vehicles in actual operation servicing aircraft on the flight line was used as input to EDMS for ground support equipment.

AIRCRAFT TYPES USED IN ANALYSIS

Aircraft from four major groups combine to operate at the airport. The scheduled air carriers are well documented at the airport derives landing fees for each landing. The records were obtained from the FAA in Washington, D.C. The remaining counts were from the FAA Control Tower daily activity records and are divided into Air Taxi, General Aviation, and Military operations. The following tables summarize airport activity by category for the year 1996.

Aircraft Used at San Antonio International Airport.

Aircraft	EDMS Aircraft
72710A	72710A
72720A	72720A
737	737
737300	737300
737400	737400
737500	737500
757?W	757?W
757RR	757RR
767CF6	767CF6
777	777
HS74 8A	HS74 8A
BEC58P	SF340
CNA44 1	Can Air Reg 100
COMJET	COMJET
DC101O	DC101O
DC1O3O	DC1O3O
DC9Q7	DC9Q7
DC9Q9	DC9Q9
DHC8	DHC8
DHC6	DHC6
F10065	F10065
GASEPV	Cessna 150
MD82	MD82
MD83	MD83
SD330	SD330
LEAR 25	LEAR 25

 

Military Activity At the San Antonio International Airport in 1996
(Estimated by type of aircraft).

Aircraft	L/TO Cycles	T&G Cycles	Low Approaches	Totals
T-38	0	468	680	1148
T-43	0	88	542	630
T-37	0	487	560	1778
T-34	37	86	128	251
T-1	0	382	498	880
F-16	0	0	168	1131
C-5	0	0	68	68
C-130	6	0	54	60
UH-1	28	0	84	112
C-21	8	14	88	172
Totals	79	1525	2870	4474

Activity is distributed across the most common aircraft in the San Antonio Area. Emissions data was located for all aircraft except the Navy T-34.

 

General Aviation Activity at the San Antonio International Airport in 1996.

Aircraft Type	Average Taxi Time	1996-Operations**	L/TO Cycles	T&Gs***
Cessna 172*	20 Min	57,108	45,686	11,422

GSE/AGE	Number Used	Minutes/Sortie
Diesel Baggage Tug	0	0
Gasoline Baggage Tug	0	0

* Cessna 150 used in EDMS as the closest aircraft to the Cessna 172.
FAA at SAIA advised the Cessna 172 was the most representative of General Aviation aircraft.
**FAA tower records show 114,216 General Aviation activities (a takeoff is one activity and a landing is a separate activity). One cycle (i.e. touch & go) is composed to two activities.
***Full-stop landings and touch & gos were divided 80% full-stops as most touch & go are accomplished at other airports.

Air Taxi Operations at the San Antonio International Airport in 1996.

Aircraft Type	Average Taxi Time	1996-Operations**
SW-2/3*	10 Min.	20,306
GSE/AGE	Number Used	Minutes/Sortie/Plane
Diesel Baggage Tug	1	50
Gasoline Baggage Tug	2	50

* The FAA advised the Metro 3 was the most representative of the air taxi aircraft utilizing the SAIA. The Metro 2 is the closest aircraft in EDMS and uses the same Garrett TPE-311-11-612G engines.

 

Boilers (Heating Plants)

From past use rates it was estimated that approximately 341,329 cubic meters of natural gas were burned. These values were utilized in this analysis. Because natural gas was used, no other control measures were evaluated.

 

Motor Vehicles

Roadways

Multiple roadways were modeled for this analysis. The roadways included in this analysis are listed in Table 3, below. Roadway lengths and peak-hour volumes as supplied by Ricondo & Associates are included. Peak-hour volumes are approximately 10% of the daily traffic as shown in the Master Plan. Speeds were conservative assumptions made by facility type. In addition, it was assumed that any vehicle accessing the terminal stopped and 2 minutes of idle was included. This assumption was based on a visit to the airport.

Roadways Used in Analysis of San Antonio International Airport.

ROADWAY	LENGTH (M)	PEAK HR. VOL	SPEED
Airport Blvd. Loop	1,448	2,970	25
South Terminal Dr. Entrance	457	2,470	45
Jones Maltsberger	810	1,984	46
Airport Blvd Entrance	488	3,486	35
N. Loop Road	1,270	2,394	45
Starcrest Road	1,016	1,860	45
Wetmore Road	2,570	4,122	45

The EPA promulgated computer model MOBILE5a was used to estimate emission factors. The emission factors were multiplied by the average daily mileage traveled or multiplied by idle time as appropriate. The sum of idle and moving emissions resulted in the total mass emitted for CO, NOx, and VOCs.

Parking

All major parking lots were included in the analysis. These lots included seven surface lots and three parking garages. Both public and employee parking was considered. For employee lots, the reported demand was 730 as reported by Ricondo & Associates. It was assumed that these lots were filled and emptied 2.5 times in a twenty-four hour period resulting in 1825 vehicle movements per day. Actual vehicle counts (entry and exits) were available for the public parking lots. An average of 4,523 vehicle movements were measured. It was assumed, based on mapping, that the average trip in a surface lot was approximately 300 feet. In the parking garages it was assumed the average trip in the lot was 600 feet. Accounting for vehicle movements, a total of 483.3 vehicle miles are traveled in the parking lots each day. This mileage, along with a 1 minute idle time per movement were used along with MOBILE5a emission factors as described in the previous section to estimate total yearly emissions. A speed of 10 mph was assumed in the parking lots. In addition, the cars were assumed to be evenly split between the hot start mode and cold start mode.

Fuel Storage and Operations

Fuel vendors estimated that in 1996 fuel throughput at the Airport included Jet A fuel (208,258 kiloliters) and aviation gasoline (55,360 kiloliters). Stage I vapor recovery was assumed for all cases. No Stage II vapor recovery was assumed. The Emissions and Dispersion Modeling System software does not calculate emissions for this category. In this case alone, emission values supplied by the 1998 study by Ricondo & Associates were used as default values.

Notes:

Federal Aviation Administration, April 1997. Air Quality Procedures for Civilian Airports and Air Force Bases. Washington, D.C.

Federal Aviation Administration, 1985. Airport Environmental Handbook. Washington, D.C.

Environmental Protection Agency, 1973. An Air Pollution Impact Methodology for Airports; Phase I, EPA Report No. APTD-1470, National Technical Information Service, Springfield, VA.

U.S. DOT, FAA, April 1997. Emissions and Dispersion Modeling System (EDMS) Reference Manual. Washington, D.C.

MOBILE5a is an EPA promulgated computer model to estimate emission factors from motor vehicles. The model is available over the Internet at the EPA's Vehicle & Engine Emission Modeling Software website, http://www.epa.gov/oms/models.htm.

Ricondo & Associates, June 1998. San Antonio International Airport Master Plan Study. Correspondence with Ricondo & Associates, Chicago, Illinois and reference 13.

Texas Water Development Board, 1998. Population Projections 1990 - 2050: Most likely Scenario. Austin, Texas.

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Stinson Municipal Airport

Stinson is the San Antonio's commercial airport until the new international airport was constructed on the north side of town. Operations now consist of air taxi and general aviation as the airport is not certified for air carrier flights. The military frequently uses the field to fly visual omni range (VOR) approaches, as the VOR at Stinson is the only remaining operational VOR in the area. USAF aircraft (specifically the T-37) only fly the approach to a low approach, as the runway length is too short to permit touch & go approaches.

The tower reported flight activity at the airport for 1996 on FAA Form 7230-1, Airport Traffic Record. Operations for 1996 are summarized in the following table:

Air Traffic at Stinson Municipal Airport.

Month	Itinerant				Local		Totals
	Air Carrier	Air Taxi	General Aviation	Military	Civil	Military
Jan	0	65	616	223	1,202	38	2,144
Feb	0	65	605	216	1,336	17	2,239
Mar	0	73	726	235	1,580	10	2,624
Apr	0	74	707	239	1,722	8	2,750
May	0	81	641	270	1,553	8	2,553
Jun	3	69	737	159	1,744	0	2,712
Jul	0	81	725	201	1,639	30	2,676
Aug	0	75	630	166	1,306	8	2,185
Sep	0	66	748	156	1,423	35	2,428
Oct	0	69	741	206	1,434	31	2,481
Nov	0	69	598	214	1,199	8	2,088
Dec	0	98	546	160	1,313	12	2,129
TOTALS	3	885	8,020	2,445	17,451	205	29,009

The activity in the above table was next entered into the FAA/USAF developed Emissions Dispersion Modeling System (EDMS) release 3.10 and processed to determine the resulting emissions. The following aircraft are shown with their speciated emissions by phase of flight that were used in the EDMS model:

Aircraft Emissions by Phase of Flight for Stinson Airport.
(Tons/Year)

Aircraft	Engine	Mode	CO	HC	NOx	SOx	PM1O
**T-1A	DEFAULT	APCH	0	0	0	0	0
**T-1A	DEFAULT	TKOF	0	0	0	0	0
**T-1A	DEFAULT	TAXI	0	0	0	0	0
**T-1A	DEFAULT	TGO	0.349	0.11	0.108	0.008	0
**T-1A	DEFAULT	APU	0	0	0	0	0
**T-1A	DEFAULT	GSE	0	0	0	0	0
**T-34	DEFAULT	APCH	0	0	0	0	0
**T-34	DEFAULT	CLMB	0	0	0	0	0
**T-34	DEFAULT	TKOF	0	0	0	0	0
**T-34	DEFAULT	TAXI	0	0	0	0	0
**T-34	DEFAULT	TGO	0.168	0.015	0.133	0.01	0
**T-34	DEFAULT	APU	0	0	0	0	0
**T-34	DEFAULT	GSE	0	0	0	0	0
Cessna 150	0-200	TAXI	3.956	0.176	0.01	0.001	0
Cessna 150	0-200	TKOF	0.636	0.014	0.003	0	0
Cessna 150	0-200	CLMB	10.596	0.228	0.053	0.001	0
Cessna 150	0-200	APCH	8.75	0.245	0.008	0.001	0
Cessna 150	0-200	TGO	52.644	1.28	0.171	0.005	0
Cessna 150	0-200	APU	0	0	0	0	0
Cessna 150	0-200	GSE	0.288	0.086	0.791	0.018	0.037
Cessna T-37	IO-360-B	TAXI	0	0	0	0	0
Cessna T-37	IO-360-B	TKOF	0	0	0	0	0
Cessna T-37	IO-360-B	CLMB	0	0	0	0	0
Cessna T-37	IO-360-B	APCH	0	0	0	0	0
Cessna T-37	IO-360-B	TGO	5.897	0.06	0.044	0.001	0
Cessna T-37	IO-360-B	APU	0	0	0	0	0
Cessna T-37	IO-360-B	GSE	0	0	0	0	0
Commanche	TIO-540-J252	TAXI	1.56	0.082	0	0	0
Commanche	TIO-540-J252	TKOF	0.333	0.003	0	0	0
Commanche	TIO-540-J252	CLMB	4.468	0.051	0.001	0	0
Commanche	TIO-540-J252	APCH	2.228	0	0.002	0	0
Commanche	TIO-540-J252	APU	0	0	0	0	0
Commanche	TIO-540-J252	GSE	0.009	0.003	0.024	0.001	0.001
EMB-120	PW 118	TAXI	0.007	0	0.002	0	0
EMB-120	PW 118	TKOF	0	0	0	0	0
EMB-120	PW 118	CLMB	0	0	0.001	0	0
EMB-120	PW 118	APCH	.001	0	0.001	0	0
EMB-120	PW 118	APU	0	0	0.002	0	0
EMB-120	PW 118	GSE	0.064	0.001	0.004	0	0
PA-42 Cheyenne	PT6A-41	TAXI	28.033	24.708	0.479	0.131	0
PA-42 Cheyenne	PT6A-41	TKOF	0.083	0.028	0.13	0.009	0
PA-42 Cheyenne	PT6A-41	CLMS	0.489	0.153	0.57	0.041	0
PA-42 Cheyenne	PT6A-41	APCH	2.723	1.777	0.364	0.042	0
PA-42 Cheyenne	PT6A-41	TGO	1.098	0.653	0.355	0.031	0
PA-42 Cheyenne	PT6A-41	APU	0	0	0	0	0
PA-42 Cheyenne	PT6A-41	GSE	0.253	0.076	0.695	0.015	0.032
T-43A	JT8D-9	TAXI	0	0	0	0	0
T-43A	JT8D-9	TKOF	0	0	0	0	0
T-43A	JT8D-9	CLMB	0	0	0	0	0
T-43A	JT8D-9	APCH	0	0	0	0	0
T-43A	JT8D-9	TGO	0.012	0.003	0.091	0.004	0
T-43A	JT8D-9	APU	0	0	0	0	0
T-43A	JT8D-9	GSE	0	0	0	0	0

** Denotes user defined aircraft

The resulting emissions from the above operations are summarized in the following table:

Total Stinson Aircraft Emissions for 1996.
(Tons/Year)

NAME	CO	VOC	NOx	SOx	PM1O
Aircraft*	124.031	29.736	2.526	0.285	0.000
GSE/AGE/APU**	0.614	0.167	1.516	0.034	0.070
Total	124.645	29.903	4.042	0.319	0.070

* Report includes 2 Aircraft and 0 GSE created by the user.
**Ground Support Equipment/Aerospace Ground Equipment/Auxiliary Power Unit

OTHER EMISSION SOURCES

No traffic emissions are included in the inventory since access to most airport areas is from public roads. No fueling emissions are included in this inventory as fueling data for 1996 was not available.

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RANDOLPH AFB EMISSIONS INVENTORY

Purposes of the Airport and Air Base Emissions Inventory

An air emissions inventory (AEI) was conducted at Randolph Air Force Base (AFB) in San Antonio, Texas, in April 1996. This report outlines the steps, methodologies, and results for the mobile sources portion of this AEI. The AEI was conducted for stationary and mobile sources for calendar year 1995. For the purposes of this inventory, mobile sources may encompass either air or ground sources.

The ground mobile sources can be divided into two distinct groups: on-road and off-road mobile sources. On-road sources include motor vehicles which are licensed to be operated on roads and highways. Off-road mobile sources are specialty vehicles such as landscaping, construction, or industrial equipment. For on-road sources, the total vehicle miles traveled (VMT) were estimated, and MOBILE5a, EPA’s emission factor model, was used to estimate the emissions factors for each vehicle. MOBILE5a calculates the emission factors for volatile organic compounds (VOCs), nitrogen oxides (NOx), and carbon monoxide (CO). The methodology outlined in the EPA 1991 study entitled Non-Road Engine and Vehicle Emission Study was used to perform calculations for off-road sources. EPA’s report contains horsepower estimates, activity factors, load factors, and estimates of hours per year equipment usage to calculate the emissions for off-road sources.

The aircraft emissions were determined by obtaining the type of aircraft and number of landings for the aircraft from base personnel. The hours of operation were estimated from the number of landings in a given year. The emission factors were obtained from several sources for aircraft engine emission factors, and the total emissions were calculated. The following sections outline these methodologies and the results in more detail.

On-Road Mobile Sources

Four types of on-road mobile sources were identified during the air emissions inventory at Randolph AFB:

• Military owned and operated vehicles (military vehicles);
• On base privately owned vehicles (dependant vehicles);
• Commuter and visiting vehicles; and
• Commercial vehicles.

The methodology for calculating the emissions for the four vehicle types is very similar. In each case, the vehicle miles traveled in 1995 were obtained from Base records or estimated based on the layout of the base, the number of people working on base, and the counts of vehicles entering the gates in a 24-hour period. The vehicles in each of the four categories were then divided into the eight vehicle classes specified in MOBILE5. These classes are subdivided by the vehicle’s weight and fuel type:

• Light-duty gas vehicles (LDGV)
• Light-duty gas truck 1 (LDGT1)
• Light-duty gas truck 2 (LDGT2)
• Heavy-duty gas vehicles (HDGVs)
• Light-duty diesel vehicles (LDDVs)
• Light-duty diesel trucks (LDDTs)
• Heavy-duty diesel vehicles (HDDVs) and
• Motorcycles (MCs).

In the cases where vehicle records were available, the exact percentage of vehicles within each class was calculated. For other cases, the breakdown by vehicle class was estimated depending on the category of vehicles. For example, there was no information collected about the specific percentage of vehicles in each class for the vehicles owned and operated by people living on base. Instead, it was assumed that this category of vehicles would contain no heavy duty or diesel vehicles. The percentage of miles traveled per year by each vehicle class was estimated for these remaining vehicle classes.

Once the miles per year were identified for each vehicle class, MOBILE5 was used to generate the emission factor estimates in grams per mile, for each of the eight vehicle classes. The vehicles miles traveled (VMT), normally represented in miles per year or miles per days, were multiplied by the emission factors for each vehicle class to obtain the grams per year for each pollutant in 1995. This gave estimates of the total emissions of VOC, NOx, and CO pollutants. The following sections outline this methodology in more detail for each of the four on-road mobile source categories.

Military Vehicles

In order to calculate the yearly VMT for military owned and operated vehicles, a list of the registered and services vehicles for Randolph AFB was obtained. Registered vehicles are those which were purchased by appropriated government funds. There are approximately 400 registered vehicles on the base, of which 300 are on-road vehicles. The “services” vehicles, which include 42 on-road vehicles, were purchased by non-appropriated funds. These lists contained the estimated mileage, fuel type, gross vehicle weight, and vehicle type for each vehicle.

The information from those lists was used to develop specific inputs for the MOBILE5 model. First, the vehicle class corresponding to the eight classes defined in MOBILE5 was determined for each vehicle. These values were entered into a spreadsheet, and the annual vehicle miles traveled (VMT) was estimated for each vehicle. From this information, the VMT mix (the percentage breakdown of vehicles by class) was determined. Below is the total VMT, by vehicle class, which were used in the MOBILE5 model runs for the military vehicles. The vehicle classes LDDV and MC are excluded from this table because the registered and “services” vehicle lists did not include vehicles in these categories. This table also provides the percentage of the total VMT that is attributable to each vehicle class.

VMT for Randolph AFB Military Vehicles.

Vehicle Class	Total VMT(miles/year)	VMT Mix(% of total VMT)
LDGV	228,932	12.7%
LDGT1	493,564	27.3%
LDGT2	533,079	29.5%
HDGV	32,248	1.8%
LDDT	202,305	11.2%
HDDV	316,768	17.5%
Total	1,806,896	100%

The registration fractions, the percentage of vehicles, by vehicle class, in each model year, were also determined. The range of model years used in MOBILE5 is 25 (1971 - 1995). The mileage accumulation rates for each vehicle class were also calculated based on the specific vehicle records. This rate is the number of miles accumulated in one year by the average vehicle in a certain vehicle class and model year. The driving patterns for these vehicles were also estimated to determine the operating mode fractions, the percentage of hot and cold starts of the vehicles, required by MOBILE5. A vehicle is considered in hot-start mode if it has not been left sitting (since it was last driven) for more than an hour. It is assumed that most of the driving for the military vehicles will consist of short trips within the base. Therefore, most of the vehicle starts would be in the hot-start mode.

The calculated VMT mix, registration fractions, and mileage accumulation rates were entered into MOBILE5. MOBILE5 uses this information to calculate the emission factors for VOC, CO, and NOX. Using the outputs from MOBILE5, the total emissions for these three pollutants were calculated by season. The estimated temperature ranges for each season was included in the MOBILE5 input files. The estimated temperature ranges for the model runs were obtained from the Alamo Area Council of Governments (AACOG) in San Antonio, Texas. The AACOG provided the MOBILE5 input files used for the city inventory. Using the same parameters as the city provides consistency among the emissions inventory efforts.

In order to obtain the emissions for these vehicles, the total VMT for each class of vehicles was multiplied by the emission factor (in grams per mile) for that class. The grams per year estimate was then converted into tons per year for inventory purposes. The table below shows the emission estimates for each of the vehicle classes and the total emissions by season for these vehicles. For each of the emissions estimates tables in this section, the total tons of pollutants per year is provided in the bottom right hand corner of the table in bold type. Again, only 6 of the 8 vehicle classes are included in this table because Randolph’s records did not contain any motorcycles (MC) or light duty diesel vehicles (LDDV).

Total Emissions of VOC, NOX, and CO by Season
Military Vehicles.

Vehicle Class	Summer Emissions (tons/yr.)			Fall Emissions (tons/yr.)			Winter Emissions (tons/yr.)			Spring Emissions (tons/yr.)
	VOC	NOx	CO	VOC	NOx	CO	VOC	NOx	CO	VOC	NOx	CO
LDGV	0.078	0.047	0.334	0.074	0.052	0.602	0.079	0.055	0.738	0.069	0.049	0.430
LDGT1	0.230	0.143	1.170	0.214	0.116	1.961	0.230	0.178	2.364	0.205	0.155	1.473
LDGT2	0.276	0.151	1.188	0.247	0.167	1.995	0.260	0.182	2.403	0.239	0.159	1.485
HDGV	0.048	0.044	0.121	0.030	0.042	0.140	0.028	0.046	0.143	0.031	0.044	0.125
LDDT	0.031	0.074	0.080	0.031	0.074	0.080	0.032	0.078	0.080	0.032	0.078	0.080
HDDV	0.192	1.219	0.898	0.192	1.219	0.898	0.195	1.268	0.903	0.195	1.268	0.903
Total	0.855	1.678	3.791	0.788	1.670	5.676	0.824	1.807	6.631	0.771	1.753	4.496

Vehicle Class	Total Emissions (tons per year)
	VOC	NOx	CO
LDGV	0.30	0.20	2.10
LDGT1	0.88	0.64	6.97
LDGT2	1.02	0.66	7.07
HDGV	0.14	0.18	0.53
LDDT	0.13	0.30	0.32
HDDV	0.77	4.97	3.60
Total	3.24	6.95	20.59

Dependant Vehicles

There are approximately 1,000 housing units on Randolph AFB. For the vehicles owned by people living in these housing units, the records including vehicle type and registration were not readily available. The information was not kept in one central file, and, according to the base security police, compiling this information might take a significant amount of time. In the interest of time, the number of vehicles and registration fractions were estimated. Base personnel indicated that there is approximately 1 vehicle per housing unit at the base. Therefore, the number of dependant vehicles is 1,000.

In order to obtain estimates of the mileage accumulation, the number of trips per day was calculated for each vehicle using Modified Trip Generation equations. For typical apartment units, the number of trips per day from the household is calculated using the equation:

T =	exp[1.024 * ln (x) + 1.71] 2

where T = number of entering trips and x = number of dependant vehicles.

From this equation, the number of round trips (exiting and entering the base) was estimated as 6,526 trips per day. Once the number of trips per day is estimated, the configuration and layout of the base was examined to estimate the number of miles per trip for these vehicles. The base is about 2 miles wide and, using this estimate, it is assumed that the average vehicle would travel one mile on base before leaving the base and would travel one mile on return. This estimate of one mile per trip is assumed throughout the mobile source calculations for the on-road vehicles. Since these vehicles are owned and operated by people living on the base, the estimated number of days that the vehicles will travel this pattern is 365. This makes the total number of vehicle miles traveled equal to the number of trips per day times the number of days times the number of miles per trip. For the VMT mix, it was assumed that there would be no heavy-duty vehicles but only light-duty vehicles, light-duty trucks, and motorcycles.

It was assumed that the percentage of vehicle miles traveled by each of the vehicle categories would be similar to the percentages (VMT mix) used in the inventory for the San Antonio. Therefore, the VMT mix in the input files from AACOG was used. The fraction of VMT for each vehicle was taken from these input files, and the classes not represented by this fleet were omitted. The remaining percentages were then re-calculated to determine the VMT mix shown below.

VMT for Randolph AFB
Dependant Vehicles.

Vehicles Miles Traveled (VMT)
Number of Vehicles		1,000
Miles/day		6,526
VMT/year		2,381,990
Vehicle Class	VMT	VMT Mix
LDGV	1,608,864	67.5%
LDGT1	519,954	21.8%
LDGT2	239,219	10.0%
MC	16,333	0.7%

The estimated VMT mix was used as a model input to MOBILE5. However, since specific information about these vehicles was not collected, the MOBILE5 default values for registration fractions and mileage accumulation rates were used. The following table shows the estimated emissions for the dependant vehicles.

Total Emissions of VOC, NOX, and CO by Season
Dependant Vehicles.

Vehicle Class	Summer Emissions (tons/yr.)			Fall Emissions (tons/yr.)			Winter Emissions (tons/yr.)			Spring Emissions (tons/yr.)
	VOC	NOx	CO	VOC	NOx	CO	VOC	NOx	CO	VOC	NOx	CO
LDGV	1.250	0.714	9.657	1.295	0.807	13.128	1.423	0.869	14.879	1.184	0.763	10.605
LDGT1	0.490	0.259	3.968	0.506	0.291	4.913	0.559	0.311	5.562	0.470	0.277	4.081
LDGT2	0.297	0.147	2.400	0.314	0.167	2.910	0.343	0.176	3.239	0.291	0.158	2.475
MC	0.027	0.003	0.114	0.016	0.004	0.104	0.017	0.004	0.115	0.017	0.004	0.095
Total	2.064	1.123	16.139	2.131	1.269	21.055	2.342	1.360	23.795	1.962	1.202	17.256

Vehicle Class	Total Emissions (tons/year)
	VOC	NOx	CO
LDGV	5.152	3.153	48.269
LDGT1	2.025	1.138	18.524
LDGT2	1.245	0.648	11.024
MC	0.077	0.015	0.428
Total	8.499	4.954	78.245

 

Commuter and Visiting Vehicles

Two sources were used to determine the number of vehicles entering the base per day. First, the number of people working on the base (approximately 10,200) was obtained from Base personnel. Assuming that the average vehicle occupancy is 1.1, which is common for large metropolitan areas which do not have a car pool program, the number of vehicles entering the base each day for workers who live off base is 9,270. It was assumed that the vehicles would travel one mile after entering base and then another mile before exiting the base. It was also assumed that 30% of these vehicles would leave and return, traveling one mile each, during the lunch break. The total number of commuter trips per day was calculated based on these assumptions and data.

The Visitor Center provided figures representing the average number of vehicle passes issued per day and the average duration of each pass. From these estimates, the number of visiting vehicles that entered and left the base each day was determined. In order to calculate the total VMT per year, the number of days per year the commuter and visiting vehicles would drive in this pattern was assumed to be 240 working days. This number includes 5 days a week for 52 weeks (260 days), taking out 20 days for vacation and holidays. Below are the estimated number of vehicles, trips, and VMT per year for the commuter and visiting vehicles. It also shows the VMT mixes assumed for these vehicles. It also shows the VMT mixes assumed for these vehicles. The VMT percentages were determined again from the AACOG input files for the city of San Antonio. It was assumed that the commuting and visiting vehicle fleet would not contain any heavy duty or diesel vehicles. The methodology used was the same as for the dependant vehicles.

VMT for Randolph AFB Commuter and Visiting Vehicles.

Vehicles Miles Traveled (VMT)
Number of Vehicles		12,167
Miles/day		28,358
VMT/year		6,805,896
Vehicle Class	VMT	VMT Mix
LDGV	4,596,897	67.5%
LDGT1	1,485,630	21.8%
LDGT2	683,506	10.0%
MC	46,670	0.7%

MOBILE5 was then run using default registration fractions and mileage accumulation rates to generate the grams per mile emission factor estimates for these vehicles. The only difference between the MOBILE5 input files for the dependant vehicles and the commuter and visiting vehicles is the percentage of cold and hot starts for each of the vehicle categories. The commuter vehicles are assumed to arrive in a hot stabilized mode and leave in a cold start mode. This assumes that the commuter and visiting vehicles have driven at least a short distance (at least 4 miles) before arriving at the base, and the vehicles are started again (at the end of the day, usually) after sitting for more than an hour. The dependant vehicles use MOBILE5's default operating modes. The defaults are used for the dependant vehicles because it is assumed that a portion of the driving for the dependant vehicles will be between destinations on base (for example, from home to the BX or to work on base). Therefore, the dependant vehicles will have more hot starts than the commuter and visiting vehicles. Once the MOBILE5 emission factor estimates were obtained, the miles per year VMT estimate was multiplied by the grams per mile emission factor to obtain the emissions estimates for commuter and visiting vehicles for the 1995 calendar year. Below are the calculated total emissions of VOC, NOx, and CO for the commuter vehicles and visiting vehicles by season.

Total Emissions of VOC, NOX, and CO by Season
Commuter and Visiting Vehicles.

Vehicle Class	Summer Emissions (tons/yr.)			Fall Emissions (tons/yr.)			Winter Emissions (tons/yr.)			Spring Emissions (tons/yr.)
	VOC	NOx	CO	VOC	NOx	CO	VOC	NOx	CO	VOC	NOx	CO
LDGV	3.902	2.141	30.606	4.484	2.394	44.693	5.308	2.559	53.586	3.889	2.293	35.369
LDGT1	1.519	0.786	13.019	1.773	0.872	17.740	2.096	0.921	21.011	1.552	0.839	14.456
LDGT2	0.915	0.433	7.798	1.089	0.494	10.463	1.273	0.510	12.066	0.947	0.469	8.732
MC	0.077	0.010	0.313	0.054	0.011	0.381	0.059	0.011	0.445	0.053	0.011	0.328
Total	6.413	3.370	51.736	7.400	3.771	73.277	8.736	4.001	87.108	6.441	3.612	58.885

Vehicle Class	Total Emissions (tons/year)
	VOC	NOx	CO
LDGV	17.583	9.387	164.254
LDGT1	6.940	3.418	66.226
LDGT2	4.224	1.906	39.059
MC	0.243	0.043	1.467
Total	28.990	14.754	271.006

 

Commercial Vehicles

There are no records kept of the number of commercial vehicles entering the base per day. Commercial vehicles may include those delivering food or supplies to different areas of the base. However, using the number of the total vehicles entering the base and subtracting estimates already calculated for commuter, visiting, and base-owned vehicles the number of vehicles that were unaccounted for each day was determined. It was assumed that half of these vehicles would be commercial vehicles.

As discussed previously, because of the size and configuration of the base, the estimated number of miles per trip is one mile after entering the base and one-mile before leaving the gate. The methodology is also the same. MOBILE5 was used in order to obtain the emissions factor estimates. However, heavy-duty vehicles were included in the VMT mix for commercial vehicles. The next table shows the estimated VMT and the assumed VMT mix for the commercial vehicles. There are only 5 vehicle classes included because it was assumed that commercial traffic would not consist of motorcycles or light duty diesel trucks.

VMT for Randolph AFB Commercial Vehicles.

Vehicles Miles Traveled (VMT)
Number of Vehicles		5,345
Miles/day		10,689
VMT/year		2,565,560
Vehicle Class	VMT	VMT Mix
LDGV	513,072	10.0%
LDGT1	769,608	30.0%
LDGT2	769,608	30.0%
HDGV	256,536	20.0%
HDDV	256,536	20.0%

After the emissions factors were generated in MOBILE5, these numbers were used to calculate the total amount of emissions. The next table shows the estimates of the total emissions of VOC, NOX, and CO for the commercial vehicles.

On-Road Emissions Results

The following table shows the combined results for the four types of on-road vehicles: military vehicles, dependant vehicles, commuter and visiting vehicles, and commercial vehicles. It also shows the overall results and percent contribution by each of the four types of on-road vehicles. These emission values are annual estimates for all five pollutants in only the vehicle classes that were in the fleets of vehicles considered, which excludes only the LDDV class. The total tons of pollutant are provided in the bottom right hand corner of the table.

Total Emissions of VOC, NOX, and CO by Season
Commercial Vehicles.

Vehicle Class	Summer Emissions (tons/yr.)			Fall Emissions (tons/yr.)			Winter Emissions (tons/yr.)			Spring Emissions (tons/yr.)
	VOC	NOx	CO	VOC	NOx	CO	VOC	NOx	CO	VOC	NOx	CO
LDGV	0.376	0.221	2.890	0.356	0.250	3.687	0.362	0.274	3.939	0.342	0.235	3.038
LDGT1	0.685	0.371	5.260	0.634	0.420	5.951	0.649	0.454	6.375	0.621	0.397	5.035
LDGT2	0.908	0.460	6.961	0.859	0.530	7.656	0.874	0.568	8.159	0.842	0.498	6.634
HDGV	0.690	0.371	7.984	0.527	0.400	6.397	0.555	0.418	6.949	0.538	0.399	6.395
HDDV	0.177	0.989	0.850	0.177	0.989	0.850	0.181	1.027	0.858	0.181	1.027	0.858
Total	2.836	2.412	23.945	2.553	2.589	24.541	2.621	2.741	26.280	2.524	2.556	21.960

Vehicle Class	Total Emissions (tons/year)
	VOC	NOx	CO
LDGV	1.44	0.98	13.56
LDGT1	2.59	1.64	22.62
LDGT2	3.48	2.06	29.41
HDGV	2.31	1.59	27.73
HDDV	0.72	4.03	3.41
Total	10.54	10.30	96.73

 

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Total Emissions and Percent Contribution
All On-Road Vehicles.

On-Road Source Category	Emissions
	PM Emissions		SOx Emissions		NOx Emissions		CO Emissions		VOC Emissions
	TPY	%	TPY	%	TPY	%	TPY	%	TPY	%
Military	0.312	17.6%	0.368	17.2%	6.908	18.7%	20.594	4.4%	3.238	6.3%
Dependant	0.400	22.6%	0.560	26.0%	4.954	13.4%	78.245	16.8%	8.499	16.6%
Commuter	0.480	27.1%	0.760	35.4%	14.75	40.0%	271.01	58.1%	28.99	56.6%
Commercial	0.580	32.7%	0.460	21.4%	10.30	27.9%	96.276	20.7%	10.53	20.5%
Total	1.77	100%	2.15	100%	36.91	100%	466.71	100%	51.26	100%

 

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OFF-ROAD MOBILE SOURCES

The methodology used for calculating the off-road mobile source emissions is outlined in EPA’s 1991 study entitled Non-road Engine and Vehicle Emission Study. This report details the equation used to calculate the mass of emissions produced for a certain type of off-road vehicle. This equation is:

Emissions (grams/yr.) for VOC, CO, and NOx
M = N × HRS × HP × LF × EF

Where

M   = mass of emissions; N   = number of vehicles; HRS = annual hours of use; HP   = average rated horsepower; LF   = typical load factor; EF   = average emissions of pollutant per unit of use (emission factor).

These values were obtained for each of these parameters from the Randolph registered vehicle records and from interviews with several non-road vehicle fleet managers. The list of registered vehicles contained about 100 off-road vehicles. Information was also obtained from interviews with fleet managers for the golf course maintenance equipment, the stables grounds equipment, and the landscaping equipment. It was assumed, for these calculations, that the vehicles contained in the registered vehicles list are different from the ones mentioned in each of the interviews. Therefore, if any of the vehicles described in the interviews with fleet managers were already included in the registered vehicle list, the off-road numbers may overestimate the total emissions slightly because some vehicles may be counted twice.

Registered Vehicles

The registered vehicle records contained information about the vehicle type, number of vehicles, fuel type, model year, and number of hours of operation. This list, however, did not include information about the loading factors, horsepower ratings, or emission factors for these vehicles. One way to obtain the horsepower ratings would be to visually inspect almost 100 off-road vehicles contained in the registered list and record the engine type for each vehicle. This task could take a considerable amount of time, considering that these vehicles are operated and stored at locations all across the base. In the interest of time, the default value assumptions from EPA’s 1991 report were used. EPA’s report contains tables of average horsepower ratings, typical load factors, and typical emission factors for the different types of off-road vehicles. The equation from EPA’s report, on page 3-1 of this report, was used to calculate the mass of emissions per year.

The following table shows the total emissions (in tons) calculated for the registered off-road vehicles. It includes the vehicle type, number of vehicles, load factors, and average horsepower rating used in the calculation. Note that all five pollutants are in this table. Because the 1991 EPA report includes emission factors for each of the pollutants, no computer modeling was required to obtain the emission estimates.

Other Off-Road Vehicles

The information about the other off-road vehicles was obtained through interviews with fleet managers at Randolph. These other off-road vehicles include golf course maintenance equipment, stables grounds equipment, and contracts/landscaping equipment. In each case, the fleet manager estimated the number of each type of unit in the fleet, determined the horsepower rating and the fuel type, and estimated the number of hours per day that each unit operated.

Using these estimates and the load factors and emissions factors from EPA’s report for these vehicles, the total annual emissions were calculated. The following three tables show the vehicle types and total emissions calculated for the landscaping equipment, the golf course maintenance equipment, and the stables grounds equipment. The total emissions for these vehicles are, in some cases, larger than the estimates for the registered off-road vehicles. This is primarily due to discrepancies between the hourly usage data given in the registered vehicle list.

Total Emissions for All Pollutants - Off-Road Registered Vehicles.

Equipment Type	Fuel Type	Number	HP Rating	Load Factor	Emissions (tons/year)
					PM	SOx	NOx	CO	VOC
2-Wheel Tractor	G	21	7	62%	0.01	0.01	0.07	6.95	0.59
Aerial Lifts	G	2	17	62%	0.00	0.00	0.00	0.52	0.04
Cranes	D	4	194	43%	0.03	0.02	0.23	0.10	0.03
Forklifts	D	14	83	30%	0.22	0.13	1.96	0.85	0.22
Graders	D	1	194	54%	0.02	0.02	0.22	0.09	0.04
Off-Highway Truck	D	23	658	25%	2.28	2.54	27.39	7.99	2.46
Off-Highway Tractor	D	16	214	65%	2.84	1.30	16.65	20.80	3.51
Rollers	D	1	99	59%	0.00	0.00	0.03	0.01	0.00
Sweepers/Scrubbers	D	1	97	68%	0.02	0.01	0.14	0.06	0.02
Tractors/Loaders/Backhoes	D	4	71	38%	0.02	0.02	0.21	0.14	0.03
Total					5.44	4.05	46.90	37.51	6.94

 

Total Emissions for All Pollutants - Off-Road Landscaping Equipment.

Equipment Type	Fuel Type	Number	HP Rating	Load Factor	Emissions (tons/year)
					PM	SOx	NOx	CO	VOC
Chain Saws	G	5	33	50	0.21	0.03	0.06	78.51	39.13
Chippers/Stump Grinders	G	1	22.5	39	0.00	0.00	0.01	2.93	0.86
Lawnmowers	G	5	5	30	0.02	0.00	0.01	5.85	0.73
Leaf Blowers/Vacuums	G	5	5	36	0.01	0.00	0.01	9.32	0.70
Rear Engine Riding Mowers	G	1	10.2	38	0.00	0.00	0.00	3.10	0.13
Shredders	G	1	8	36	0.00	0.00	0.00	2.77	0.13
Tillers	G	1	4	40	0.01	0.00	0.00	0.72	0.35
Trimmers/Edgers/Brush Cutters	G	10	1.3	50	0.03	0.00	0.01	11.81	4.22
Lawn and Garden Tractor	D	5	13.3	38	0.02	0.02	0.19	0.12	0.03
Rear Engine Riding Mowers	D	1	10.2	38	0.00	0.00	0.04	0.02	0.01
Total					0.30	0.05	0.33	115.15	46.29

 

Total Emissions for All Pollutants - Off-Road Golf Course Maintenance Equipment.

Equipment Type	Fuel Type	Number	HP Rating	Load Factor	Emissions (tons/year)
					PM	SOx	NOx	CO	VOC
Chain Saws	G	2	3.2	50%	0.00	0.00	0.00	1.46	0.73
Front Mowers	G	2	22	38%	0.00	0.00	0.01	5.79	0.37
Lawnmowers	G	1	5.5	30%	0.00	0.00	0.00	0.15	0.02
Leaf Blowers/Vacuums	G	2	2	50%	0.00	0.00	0.00	0.47	0.16
Pumps	G	1	21	69%	0.00	0.00	0.00	0.56	0.03
Rear Engine Riding Mowers	G	2	16	38%	0.00	0.00	0.00	3.51	0.15
Sweepers/Scrubbers	G	1	16	71%	0.00	0.00	0.00	0.05	0.01
Trimmers/Edgers/Brushcutters	G	2	1.3	50%	0.00	0.00	0.00	0.02	0.01
Trimmers/Edgers/Brushcutters	G	2	3	50%	0.00	0.00	0.00	0.15	0.05
Trimmers/Edgers/Brushcutters	G	7	1.3	50%	0.01	0.00	0.00	4.81	1.72
Lawn and Garden Tractor	D	4	13.3	38%	0.02	0.02	0.16	0.10	0.02
Rear Engine Riding Mowers	D	1	38	38%	0.00	0.00	0.03	0.02	0.00
Tractors/Loaders/Backhoes	D	1	28	38%	0.00	0.00	0.03	0.02	0.00
Total					0.03	0.02	0.23	17.11	3.27

 

Total Emissions for All Pollutants - Off-Road Stables Grounds Equipment.

Equipment Type	Fuel Type	Number	HP Rating	Load Factor	Emissions (tons/year)
					PM	SOx	NOx	CO	VOC
Trimmers/Edgers/Brushcutters	G	5	1.3	50%	0.00	0.00	0.00	0.43	0.15
Rear Engine Riding Mowers	G	1	10.2	38%	0.00	0.00	0.00	0.25	0.01
Lawn & Garden Tractors	D	2	13.3	38%	0.00	0.00	0.01	0.00	0.00
Total					0.00	0.00	0.01	0.68	0.16

And the estimates given by the fleet managers. In some cases, the fleet managers may have overestimated the hourly usage of the equipment.

Off-Road Emissions Results

The results from each of the off-road vehicle categories were combined to obtain overall annual estimates for the five pollutants. The first table shows these combined results. The results were also combined by each fleet of off-road vehicles. The next table shows these totals and the percentage of emissions contributed to the total by each of the off-road vehicle fleets.

Total Emissions for All Pollutants - All Off-Road Equipment.

Equipment Type	Emissions (tons/year)
	PM	SOx	NOx	CO	VOC
2-Wheel Tractor	0.01	0.01	0.07	6.95	0.59
Aerial Lifts	0.00	0.00	0.00	0.52	0.04
Chain Saws	0.21	0.03	0.06	79.97	39.86
Chippers/Stump Grinders	0.00	0.00	0.01	2.93	0.86
Cranes	0.03	0.02	0.23	0.10	0.03
Front Mowers	0.00	0.00	0.01	5.79	0.37
Forklifts	0.22	0.13	1.96	0.85	0.22
Graders	0.02	0.02	0.22	0.09	0.04
Lawn and Garden Tractor	0.04	0.04	0.36	0.22	0.05
Lawnmowers	0.02	0.00	0.01	6.00	0.75
Leaf Blowers	0.01	0.00	0.01	9.79	0.86
Off-Highway Truck	2.28	2.54	27.39	7.99	2.46
Off-Highway Tractor	2.84	1.30	16.65	20.80	3.51
Pumps	0.00	0.00	0.00	0.56	0.03
Rear Engine Riding Mowers	0.00	0.00	0.07	6.90	0.30
Rollers	0.00	0.00	0.03	0.01	0.00
Shredders	0.00	0.00	0.00	2.77	0.13
Sweepers/Scrubbers	0.02	0.01	0.14	0.11	0.03
Tillers	0.01	0.00	0.00	0.72	0.35
Tractors/Loaders/Backhoes	0.02	0.02	0.24	0.16	0.03
Trimmers/Edgers/Brush Cutters	0.04	0.00	0.01	17.22	6.15
Total	5.77	4.12	47.47	170.45	56.66

 

Total Emissions and Percent Contribution - All Off-Road Vehicles

Off-Road Source Category	Emissions
	PM		SOx		NOx		CO		VOC
	(tons /yr.)	%	(tons /yr.)	%	(tons /yr.)	%	(tons /yr.)	%	(tons /yr.)	%
Registered	5.44	94.3%	4.05	98.3%	46.90	98.8%	37.51	22.0%	6.94	12.2%
Landscaping	0.30	5.2%	0.05	1.2%	0.33	0.7%	115.15	67.6%	46.29	81.7%
Golf Course	0.03	0.5%	0.02	0.5%	0.23	0.5%	17.11	10.0%	3.27	5.8%
Industrial	0.00	0.0%	0.00	0.0%	0.01	0.0%	0.68	0.4%	0.16	0.3%
Total	5.77	100%	4.12	100%	47.47	100%	170.45	100%	56.66	100%

 

Aircraft Sources

Methodology

The methodology used for calculating the emissions for aircraft is similar to the method used to calculate the on-road emissions. Aircraft engine emission factors are generally listed with units of pounds or kilograms per hour (lbs./hr or kg/hr). Therefore, the only other information necessary in order to calculate the total mass of emissions per year is the number of hours per year the particular aircraft was in operation.

The aircraft considered in the calculations for Randolph AFB can be divided into two categories. The first is all aircraft that belong in Randolph’s fleet and are maintained and operated by base personnel. These are the fleet aircraft. The other group of aircraft is the transient aircraft. This group contains any airplanes that landed at the base during 1995 but are not owned or operated by the base. For each group of aircraft, the base provided information about the type of aircraft and its number of landings in 1995.

The number of hours of operation per year had to be estimated from this information. An aircraft takeoff and landing sequence is divided into five separate engine “modes” for the purposes of gathering emission factor data during aircraft engine testing. These five “modes” are approach, taxi (idle), takeoff, climbout, and afterburn. The taxi, or idle, mode happens during takeoff and landing. Each of these modes will last for a different amount of time, depending on the type of aircraft in operation. The average time in each operation mode for typical aircraft types is provided in a draft of an emission calculation manual prepared by Armstrong Laboratory in 1994. These average times are shown in the next table and were used in the calculations for fleet and transient aircraft to estimate the number of hours of operation in each mode per year.

Time in Operation by Aircraft Type for Randolph AFB.

Aircraft Type	Operating Mode Time (Hrs)
	Approach	Taxi (Idle)	Takeoff	Climbout	Afterburn
Transport (B-52 & KC135)	0.087	0.795	0.012	0.027	0.012
Transport (General)	0.085	0.265	0.007	0.020	0.012
Combat	0.058	0.496	0.007	0.013	0.012
Trainer (T-38)	0.063	0.320	0.007	0.015	0.012
Trainer (General)	0.067	0.186	0.008	0.023	0.012

Once the hours of operation were calculated, the emission factors (in lbs/hr) were needed to complete the emission calculations. Emission factors for several of the aircraft were listed in sources such as the draft emission calculation manual from Armstrong Laboratory, a Federal Aviation Administration (FAA) database, and a report outlining the Air Quality Utility Information System (AQUIS). All of the emission factors, however, were listed by type of aircraft engine. This information was not collected from base personnel. Therefore, the sources containing the emission factors were also used to determine what type of engine would typically be in a certain aircraft type, and these engines were matched with the aircraft types provided by the base. The number of hours per year were multiplied by the emission factors for each operation mode in order to determine the total emissions per year. The following sections detail the calculations for the fleet aircraft and the transient aircraft.

Results

Randolph AFB personnel provided information about the number of takeoffs by type of aircraft for the fleet aircraft and the transient aircraft. The engines and respective emission factors were found for each of these aircraft, and the number of hours were estimated based on the information provided about time in operation for training aircraft (T-37 and T-43) and transport aircraft (C-21). The following table shows the total emissions of VOC, NOx, CO, SOx, and PM for the fleet aircraft in 1995.

Total Annual Emissions for Fleet Aircraft - Randolph AFB.

Aircraft	Fleet Landings	Emissions (tons/year)
		VOC	NOx	CO	SOx	PM
T-37	42,332	44.49	8.64	368.09	3.94	1.27
T-43	5,661	11.82	41.71	60.62	3.93	1.62
C-21	3,953	2.24	4.95	13.54	0.00	0.00
Total	51,946	58.55	55.30	442.25	7.87	2.89

The total emissions produced by the transient aircraft were calculated using this same method. The aircraft type and number of landings were the known factors. The emission factors were determined by matching the aircraft type with the type of engine typically in this aircraft. For this extensive list of transient aircraft information was not available on the engine typically used in each type of aircraft. In many cases, there was no information in the sources on that type of aircraft at all. Occasionally, the aircraft engine type might be listed, but the emission factors were not available. Therefore, not every transient airplane was able to be included in this analysis. The next table shows the total transient aircraft emissions, and the following table shows the totals for both the transient and fleet aircraft.

Total Annual Emissions for Transient Aircraft - Randolph AFB.

Aircraft	Transient Landings	Emissions (tons/year)
		VOC	NOx	CO	SOx	PM
T-1	161	0.30	0.06	0.92	0.00	0.00
T-37	579	0.61	0.12	5.03	0.05	0.02
T-38	792	2.40	0.49	19.55	0.26	0.01
T-43	21	0.04	0.15	0.22	0.01	0.01
T-44	43	0.09	0.32	0.46	0.03	0.01
T-45	24	0.05	0.18	0.26	0.02	0.00
C-9	11	0.06	0.07	0.29	0.01	0.00
KC-10	3	0.25	0.14	0.45	0.01	0.00
KC-135	24	0.05	0.57	1.02	0.08	0.00
A-10	99	0.27	0.12	0.91	0.02	0.01
F-4	11	0.27	0.12	0.89	0.03	0.06
F-15	232	0.60	2.13	4.71	0.37	0.04
F-16	305	0.40	1.40	3.10	0.24	0.00
F-111	11	0.36	0.05	0.50	0.01	0.00
B-1	2	0.02	0.02	0.16	0.00	0.00
E-3	1	0.09	0.01	0.12	0.00	0.00
Total	2,319	5.89	5.95	38.59	1.14	0.16

 

Total Annual Emissions for Fleet and Transient Aircraft - Randolph AFB.

Aircraft Type	Emissions (tons/year)
	VOC	NOx	CO	SOx	PM
Fleet	58.55	55.30	442.25	7.87	2.89
Transient	5.89	5.95	38.59	1.14	0.16
Total	64.44	61.25	480.84	9.01	3.05

 

RESULTS AND RECOMMENDATIONS

Results

The table below shows the overall mobile source emissions results in tons of pollutant per year. The table also shows the total emissions by pollutant for the three categories of mobile sources and the percent of the total emissions contributed by each category. The total number of on-road vehicles considered in this analysis is almost 20,000. This number includes visiting vehicles, commuting vehicles, dependant vehicles, and military-owned vehicles. The total number of off-road vehicles is less than 1,000. This includes all of the off-road equipment owned by the base.

Randolph AFB Total Annual Emissions for All Pollutants - On-Road, Off-Road, Aircraft, and All Sources.

Mobile Source Category	Emissions
	PM		SOx		NOx		CO		VOC
	(tons /yr.)	%	(tons /yr.)	%	(tons /yr.)	%	(tons /yr.)	%	(tons /yr.)	%
On-Road	1.77	16.7	2.15	14.1	36.91	25.3	466.71	41.7	51.26	29.7
Off-Road	5.77	54.5	4.12	27.0	47.47	32.6	170.45	15.2	56.66	32.9
Aircraft	3.05	28.8	9.01	58.9	61.25	42.1	480.84	43.1	64.44	37.4
Total	10.59	100%	15.28	100%	145.63	100%	1,118.0	100%	172.36	100%

Considering that the population of on-road vehicles is much larger than the off-road equipment, the total pollution generated by each of these categories is imbalance. Even though the number of on-road vehicles is more than 20 times the number of off-road vehicles, the VOC and NOx on-road totals are comparable to the off-road totals, and the CO value is only four times larger. For PM and SOx, the off-road totals are larger than those for the on-road vehicles.

The first reason for the high off-road numbers has to do with the equipment. In the past several years, regulation has become stricter concerning emission controls for on-road motor vehicles. Therefore, many of the on-road vehicles have advanced emission control systems designed for more stringent emissions control, while most of the off-road vehicles have no emission controls. Therefore, the emission factors for the off-road vehicles are much higher.

Another reason for the higher off-road emissions is the hours of operation. Many of the on-road vehicles considered in this study (such as the commuter and visiting vehicles) were assumed to only drive two miles a day on the base. The off-road vehicles, such as the lawn and garden equipment, was in some cases operated four to eight hours a day. This higher number of hours of use and the higher emission factors for the off-road vehicles account for the proportionately high emissions for the off-road mobile sources.

The aircraft emissions are comparable to the other categories in all pollutants except for SOx, where the aircraft emissions are 4 times larger than either the off-road and the on-road total emissions. This result is due to the higher sulfur content in the jet fuel than in the fuels used in on- and off-road vehicles.

Recommendations

The calculation of the emissions for this analysis was based on many assumptions. This is because the records were not available to provide all of the information necessary to complete the mobile source inventory. To aid in future mobile source air emission inventories, it is recommended that the base keep more detailed records for the mobile sources.

The only records that the base has is a list of the mileage or hourly usage for all of the military owned (registered and “services”) vehicles. This includes both on-road and off-road equipment. All of the off-road vehicles considered in this analysis were those owned by the base. However, it is not clear whether or not the list of military-owned vehicles includes all of the base-owned off-road vehicles. For this air emissions inventory, it was assumed that the registered vehicle list did not include all of the off-road vehicles. To obtain the rest of the information, managers of the various off-road equipment fleets were interviewed, and they provided numbers of vehicles and hourly usage per year. They did not have records of hourly usage, so the hourly data are all estimated.

Because the off-road equipment is often a sizable source of pollution, it is recommended that the base develop a more centralized, more accurate system of record keeping for the off-road vehicles. The fleet managers could record hourly usage for each piece of equipment on a weekly or monthly basis. This information could be included in the registered vehicle list and updated periodically. This would ensure that the hourly usage estimates for each piece of equipment is accurate. It would also provide a central list of all of the off-road equipment and would eliminate any double counting of equipment.

Another recommendation is that the base attempt to obtain an accurate estimate of the number of vehicles entering the base and the miles accumulated by each vehicle while on the base. These values were all estimated for this analysis based on a 1987 driving patterns study, the total base population, and the layout of the base, and are a conservative estimate of these values. If the base could collect data for these values, it would increase the accuracy of the mobile sources inventory.

The last recommendation is to keep accurate fuel records for each vehicle. This would increase the accuracy of the inventory for two reasons. First, for vehicles where hourly or mileage data do not exist, the fuel records would be another means of accurately determining the vehicle usage. If any of the vehicles at Randolph AFB are being converted to bi-fuel vehicles, these vehicles can run on either natural gas or gasoline. However, there are no records of how many of the total miles are run on natural gas and how many are run on gasoline. The natural gas fuel records would help in the calculation of the total miles run on natural gas. Since natural gas emission factors are generally lower than gasoline emission factors, this would reduce the total yearly emissions estimates.

In summary, the recommendations are:

• Keep more accurate and centralized off-road vehicle records;
• Obtain information on the numbers of vehicles entering the base;
• Obtain information on the mileage traveled by visiting vehicles; and
• Keep accurate fuel records for each vehicle.

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LACKLAND AFB EMISSIONS INVENTORY

The Lackland Air Force Base air emissions inventory was conducted for stationary and mobile sources for calendar year 1995. This section outlines the methodology and results for the mobile source portion of this air emissions inventory. Mobile sources may encompass air or ground sources. Lackland Air Force Base did not have any operational aircraft in calendar year 1996. The only airmobile sources operated on base during 1996 were some military and nonmilitary helicopters landing at Wilford Hall, the hospital at Lackland. There is insufficient information to complete a calculation of the emissions produced by these helicopters. It is assumed that due to small hours of usage per year, the total tons of emissions produced by these craft would amount to a small percentage of the total mobile source emissions for the base. Therefore, only ground mobile sources are included in this report.

The ground mobile sources can be divided into two distinct groups: on-road and off-road mobile sources. On-road Sources include motor vehicles, which are licensed to be operated on roads and highways. Off-road mobile sources include specialty vehicles such as landscaping, construction, or industrial equipment. For on-road sources, the total vehicle miles traveled (VMT) were estimated, and then MOBILE5, EPA's emission factor model, was used to estimate the emission factors for each vehicle. MOBILE5 calculates the emission factors for volatile organic compounds (VOC), oxides of nitrogen (NOx), and carbon monoxide (CO).

The methodology outlined in the EPA 1991 study entitled Non-Road Engine and Vehicle Emission Study was used to perform calculations for off-road sources. EPA's report contains horsepower estimates, activity factors, load factors, and estimates of hours per year equipment usage to calculate the emissions for off-road sources. The following sections describe these methodologies and the results in more detail.

On-Road Mobile Sources

Four types of on-road mobile sources were identified during the air emissions inventory at Lackland Air Force Base:

• Military owned and operated vehicles (military vehicles);
• On base privately owned vehicles (dependant vehicles);
• Commuter and visiting vehicles; and
• Commercial vehicles.

The methodology for calculating the emissions for the four vehicle types is very similar. In each case, the vehicle miles traveled in 1995 were obtained from Lackland's records or estimated based on the layout of the base; the number of people working on base, and the counts of vehicles entering the gates in a 24-hour period. The vehicles in each of the four categories were then divided into the eight vehicle classes specified in MOBILE5. These classes are subdivided by the vehicle's weight and fuel type:

• Light-duty gas vehicles (LDGV);
• Light-duty gas truck 1 (LDGT1);
• Light-duty gas truck 2 (LDGT2);
• Heavy-duty gas vehicles (HDGVs);
• Light-duty diesel vehicles (LDDVs);
• Light-duty diesel trucks (LDDTs);
• Heavy-duty diesel vehicles (HDDVs); and
• Motorcycles (MCs).

In the cases where vehicle records were available, the exact percentage of vehicles within each class was calculated. For other cases, the breakdown by vehicle class was estimated depending on the category of vehicles considered in the calculations. For example, there was no information collected about the specific percentage of vehicles in each class for the vehicles owned and operated by people living on base. Instead, it was assumed that this category of vehicles would contain no heavy duty or diesel vehicles. The percentage of miles traveled per year by each vehicle class was estimated for these remaining vehicle classes.

Once the miles per year were identified for each vehicle class, MOBILE5 was used to generate the emission factor estimates in grams per mile, for each of the vehicle classes. The vehicles miles traveled (VMT), normally represented in miles per year or miles per days, were multiplied by the emission factors for each vehicle class to obtain the grams per year total for each pollutant. This gave estimates of the total emissions of VOC, NOx, and CO pollutants. The following sections describe this methodology in more detail for each of the four on-road mobile source categories.

Military Vehicles

In order to calculate the yearly VMT for military owned and operated vehicles, a list of the registered and "services" vehicles for Lackland Air Force Base was obtained. Registered vehicles are those that were purchased by appropriated government fluids. There are approximately 800 registered vehicles on the base, of which 650 are on-road vehicles. Non-appropriated fluids purchased the "services" vehicles, 85 on-road vehicles. These lists contained the mileage, fuel type, gross vehicle weight, and vehicle type for each vehicle.

The information from those lists was used to develop specific inputs for the MOBILE5 model. First the vehicle class corresponding to the eight classes defined in MOBILE5 was determined for each vehicle. These values were entered into a spreadsheet, and the annual VMT was estimated for each vehicle. From this information, the VMT mix (the percentage breakdown of vehicles by class) was determined. The next table shows the total VMT, by vehicle class, which were used in the MOBILE5 model runs for the military vehicles. The vehicle classes LDDV and MC are excluded from this table because the registered and "services" vehicle lists did not include any vehicles in these categories. This table also provides the percentage of the total VMT that is attributable to each vehicle class, known as the VMT mix.

VMT for Lackland AFB Military Vehicles.

Vehicle Class	Total VMT(miles/year )	VMT Mix(% of total VMT)
LDGV	637,532	16.4%
LDGT1	802,015	20.6%
LDGT2	1,223,927	31.5%
HDGV	35,801	0.9%
LDDT	291,449	7.5%
HDDV	890,264	22.9%
Total	3,880,988	100%

The registration fractions, the percentage of vehicles, by vehicle class, in each model year, were also determined. The range of model years used in MOBILE5 is 25 (1971 -1995). The mileage accumulation rates for each vehicle class were also calculated based on the specific vehicle records. This rate is the number of miles accumulated in one year by the average vehicle in a certain vehicle class and model year. The driving patterns for these vehicles were also estimated to determine the operating mode fractions, the percentage of hot and cold starts of the vehicles, required by MOBILE5. A vehicle is considered in hot-start mode if it has not been left sitting (since it was last driven) for more than an hour. It is assumed that most of the driving for the military vehicles will consist of short trips within the base. Therefore, most of the vehicle starts would be in the hot-start mode.

The calculated VMT mix, registration fractions, and mileage accumulation rates were entered into MOBILE5. MOBILE5 uses this information to calculate the emission factors for VOC, CO, and NOx. Using the outputs from MOBILE5, the total emissions for these three pollutants were calculated by season. The estimated temperature ranges for each season was included in the MOBILE5 input files. The estimated temperature ranges for the model runs were obtained from the Alamo Area Council of Governments (AACOG) in San Antonio, Texas. The AACOG provided the MOBILE5 input files used for the city inventory. Using the same parameters as the city provides consistency among the emissions inventory efforts.

In order to obtain the emissions for these vehicles, the total VMT for each class of vehicles was multiplied by the emission factor (in grams per mile) for each class. The grams per year estimate was then converted into tons per year for inventory purposes. Shown next is the emission estimates for each of the vehicle classes and the total emissions by season for these vehicles. For each of the emissions estimates tables in this section, the total tons of pollutants per year is provided in the bottom right hand corner of the table in bold type. Again, only 6 of the B vehicle classes are included in this table because Lackland's records did not contain any motorcycles (MC) or light duty diesel vehicles (LDDV).

Total Emissions of VOC, NOX, and CO by Season - Military Vehicles.

Vehicle Class	Summer Emissions (tons/year)			Fall Emissions(tons/year)			Winter Emissions (tons/year)			Spring Emissions (tons/year)
	VOC	NOX	CO	VOC	NOX	CO	VOC	NOX	CO	VOC	NOX	CO
LDGV	0.27	0.12	0.87	0.24	0.14	1.60	0.26	0.15	1.98	0.23	0.13	1.14
LDGT1	0.54	0.32	3.30	0.51	0.35	4.56	0.57	0.39	5.30	0.49	0.34	3.75
LDGT2	0.70	0.44	4.37	0.71	0.49	6.54	0.78	0.52	7.60	0.66	0.45	5.24
HDGV	1.84	0.05	0.78	0.70	0.06	0.58	0.68	0.06	0.59	0.77	0.06	0.58
LDDT	0.05	0.13	0.12	0.05	0.13	0.12	0.05	0.13	0.12	0.05	0.13	0.12
HDDV	0.58	3.92	2.61	0.58	3.92	2.61	0.59	3.97	2.61	0.59	3.97	2.61
Total	3.98	4.98	12.05	2.79	5.09	16.01	2.93	5.22	18.20	2.79	5.09	13.44

Vehicle Class	Total Emissions (tons/year)
	VOC	NOx	CO
LDGV	1.00	0.54	5.59
LDGT1	2.11	1.40	16.91
LDGT2	2.85	1.91	23.75
HDGV	3.99	0.23	2.53
LDDT	0.20	0.52	0.48
HDDV	2.34	15.78	10.44
Total	12.49	20.38	59.70

 

Dependant Vehicles

There are approximately 750 housing units on Lackland Air Force Base. For the vehicles owned by people living in these housing units, the records including vehicle type and registration were not readily available. Compiling this information would take a significant amount of time, so in the interest of time and budget, the number of vehicles and registration fractions were estimated. Base personnel indicated that there is approximately 1 vehicle per housing unit at the base. Therefore, the number of dependant vehicles is 750.

In order to obtain estimates of the mileage accumulation, the number of trips per day was calculated for each vehicle using Modified Trip Generation equations. For typical apartment units, the number of trips per