EMISSION INVENTORY SOURCE CATEGORY

METHOD SUMMARY

These categories include 1997 estimates of organic gas emissions resulting from the storage and transfer operations at gasoline dispensing facilities. Emissions from storage and transfer operations include the working losses and breathing losses from underground tanks, vapors displaced through vehicle refueling, and spillage. Gasoline dispensing facilities consist of gasoline retail outlets and private dispensing facilities.

ACTIVITY DATA SOURCE: The California Department of Transportation issues an annual report, "Travel and Related Factors," which contains the throughput of gasoline distributed in the state by county. The total gasoline sales for service stations in the State by County were from the Annual Report from the California State Board of Equalization. The 1997 calendar year report was used for the 1997 gasoline throughput. These gasoline throughputs were estimated using several variables which are strongly correlated with gasoline consumption. The variables included several categories of taxable sales, population, vehicle miles of travel, and the number of registered vehicles. The weighted average share for all the variables was then computed for each county. The above variables were used to divide the total gasoline sales in each county into highway sales and non-highway sales. Highway sales are assumed to be gasoline sales from service stations and non-highway sales are assumed to be gasoline sales from tax exempt gasoline dispensing facilities. Adjustments were made to account for county-specific factors such as business and recreational trips. The air basin splits were divided by the ratio of the 1997 population.

EMISSION FACTOR SOURCE: Total organic gas emission factors (uncontrolled and controlled) are based on the CAPCOA Air Toxics "Hot Spots" Program Gasoline Service Station Industrywide Risk Assessment Guidelines Document and a June 24, 1994 internal memo from Jim Fries to Dale Shimp estimating the benefits of cleaner burning gasoline. The use of control factors versus uncontrolled factors is based on all service stations that pump more than 480,000 gallons per year.

Private gasoline dispensing facilities, which account for about two percent of a given county's throughput each year, are assumed to be exempt from vapor recovery regulations. Since uncontrolled emission factors are up to 20 times as high as controlled factors, these facilities would contribute 15 to 26 percent of the total emissions

TEMPORAL DATA: For underground tank working and breathing losses, the annual, weekly, and daily activities are all uniform. For vehicle refueling and spillage losses, the annual activity is uniform throughout the year. The weekly activity is nearly uniform, with slightly lower activity on the weekend. The daily activity follows a pattern, which peaks during the after-work hours in the evening and bottoms between midnight and 6 a.m.

CHANGES IN METHOD AND EMISSION ESTIMATES: There is a higher activity rate (gasoline throughput) for 1997 than for 1990. With full implementation of the Benzene rule and the introduction of cleaner burning gasoline, emissions were reduced. Thus, the 1997 statewide emissions are lower than the 1990 emissions. The emission factors are lower from the previous years due to the reduced vapor pressure of cleaner burning gasoline.

DATE OF THE LAST UPDATE: May 1999

GROWTH PARAMETER: The growth parameters were developed by Pechan and are based on gasoline and oil expenditures data (in billions of 1992 dollars).


STATEWIDE EMISSIONS SUMMARY (1997 - ANNUAL AVERAGE TONS/DAY)

CES No.	TOG	CO	NOX	SOX	PM
46532	10.90	0.00	0.00	0.00	0.00
46540	16.80	0.00	0.00	0.00	0.00
46557	2.16	0.00	0.00	0.00	0.00
46565	7.98	0.00	0.00	0.00	0.00
Total	37.84	0.00	0.00	0.00	0.00

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This page last revised on November 11, 2003

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