6.9 Gasoline Filling Station Storage

Categories 67, 68, 69, 70, 71, 72, 73, and 1905

6.9.1 Introduction

Category 67, 68, 69, 70, 71, 72, 73, and 1905 cover organic emissions (TOG and ROG) from Gasoline filling station storage.

Category	Description
67	Breathing, w/o Phase I & II (Point)
68	Breathing, with Phase I & II (Area)
69	Breathing, with Phase I only (Area)
70	Breathing, with Phase II only (Point)
71	Working, w/o Phase I & II (Area)
72	Working, with Phase I & II (Area)
73	Working, with Phase I only (Area)
1905	Breathing, w/o Phase I & II (Area)

Emissions from gasoline dispensing facilities (GDFs) are generated when gasoline vapors in the underground storage tank are displaced to the atmosphere by the gasoline being loaded into the tank. The emissions are due to breathing (vapor expansion and contraction of liquid in the tank) and working (from filling and emptying the tanks). Breathing losses occur as a result of dinural temperature and pressure variations. Working losses occur as fueling from underground storage tanks, fresh air is entered into the tank through the vent. Because this entering air is not at equilibrium with the liquid in the tank, evaporation of liquid occurs. Most gasoline dispensing facilities in the Bay Area were equipped with Phase I and/or Phase II vapor recovery systems. Phase I vapor recovery system employs a dual hose that recovers gasoline vapor back to the tank truck during the filling of underground tanks. The integral part of Phase II vapor recover system is the vapor recovery nozzle and hose that efficiently collect the displaced vapors.

6.9.2 Methodology

Point Sources

Point Sources are operations that emit air pollution into the atmosphere at a fixed location within a facility, for which the Air District has issued a permit to operate, e.g. refinery cooling towers. These could also be a collection of similar equipment / sources located across multiple facilities, e.g. reciprocating engines.

During the permit to operate (PTO) issuance process, the BAAQMD collects information from the operating facility and/or determines from published literature, e.g. EPA’s AP-42, characteristics of a source including maximum throughput, emission factors for emitted pollutants, and control factors associated with downstream abatement devices. These characteristics are then stored for future use in the BAAQMD’s internal database. Facilities that hold a permit to operate are required to renew this permit periodically (this period varies based on facility and source type). Upon renewal, the facilities are requested to provide any updates to source characteristics as well as the source throughput for the last 12 months. This throughput, in combination with the emission factors and controls factors stored in the internal database, are used to estimate annual emissions at the source level. These source level emissions are then sorted and aggregated into categories.

Category 67 and 70 are considered point source categories and follow the above methodology for emissions estimates.

Area Sources

The Gasoline Filling Station Storage categories (68, 69, 1905,71, 72, 73) account for evaporative emissions resulting from Breathing and Working losses at gasoline dispensing facilities. These categories are considered area source categories since they cover facilities / emission sources that are not directly permitted by the District, and hence not systematically cataloged. Emissions for area source categories are determined using the formula:

Current Year Emissions = Base Year Emission X Growth Profile, and,

Base Year Emission = Throughput X Control Factor X Emission Factor

where,

throughput or activity data for applicable base year(s) is determined using a top-down approach (e.g. state-, national-level data);
emission factor is derived from general literature, specific literature and reports, and/or source testing results provided by Air District staff;
control factor (if applicable) is determined by District and state rules and regulations in effect;
and, historical backcasting and forecasting of emissions is based on growth profiles as outlined in the Trends section of this chapter

The Breathing and Working total organic gas (TOG) methodologies were based on CARB’s Miscellaneous Process Methodology, Gas Dispensing Facilities, Section 4.10.¹⁸⁴

More details on throughput, county distribution, emission factors and controls is provided in the following subsections.

(a) Activity Data / Throughput

The estimates of gasoline consumption in the Bay Area were obtained from California Energy Commission (CEC) , California Annual Retail Fuel Outlet Report Results ¹⁸⁵ report.

(b) County Distribution / Fractions

County annual gasoline fuel consumption distributed into the Bay Area counties were based on CEC California Annual Retail Fuel Outlet Report County breakdown. The gasoline consumption throughput for Solano and Sonoma counties is apportioned based upon CEC’s throughput and CARB’s county estimated emissions.

(c) Emission Factors

This base year inventory GDFs Breathing and Working emission factors were derived from CARB’s Revised Emission Factors for Gasoline Marketing Operations at California Gasoline Dispensing Facilities¹⁸⁶.

(d) Control Factors

Emissions were reduced due to the effect of the District’s Regulation 8, Rule 7: Gasoline Dispensing Facilities ¹⁸⁷, Phase II requirements and the following actions:

In July 1976, California Health & Safety Code required CARB certified 90% Phase II gasoline dispensing facilities.
In August 1978, CARB amended Phase II GDFs to 95% efficiency.
In July 1986, CARB issued “Rectification Orders”.
In October 1990, District adopted pressure-vacuum valve requirements for GDFs.
In March 2000, California Air Resources Board (CARB) adopted a series of new Enhanced Vapor Recovery (EVR) amendments to its gas station vapor recovery regulations (Phase I and Phase II). In addition, CARB adopted new standards to make vapor recovery system compatible with on-board vapor recovery (ORVR) systems on motor vehicles, to reduce gasoline spillage, liquid retain in the nozzles, and pressure-related fugitive emissions. The adopted amendments also include mandatory In-Station-Diagnostics (ISD), which require electronic monitoring of vapor recovery system operation and performance.
In December 2013, CARB revised the emission factors for Gasoline Marketing Operations at California Gasoline Dispensing Facilities.

(e) Speciation

The total organic gas emissions from the Gasoline Filling Station Storage categories are considered all reactive organic gas(ROG). The ROG:TOG ratio is equal to 1.

6.9.3 Changes in Methodology

There are two major changes in the methodology for the current base year emissions inventory (EI) as compared to previous inventories:

Estimates for the gasoline consumption (Annual throughput) related to these Gasoline Filling Station Storage categories were obtained from CEC.
The emission factors were based on the revised CARB emission factors for the Gasoline Dispensing Facilities.

6.9.4 Emissions

A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.

6.9.5 Trends

(a) Historical Emissions/History

Emissions for these categories had been reduced due to Phase I and II vapor balance system requirements since 1975. Prior to 1990 Base Year, taxable gasoline sales for California obtained from the Board of Equalization were assumed to distribute to all gasoline filling stations in the California. CARB estimated that the Bay Area consumed 20.01% of the state total. Emissions for this category were determined according to this estimated throughput. Gasoline consumption in 2007 reached record levels. However, the gasoline consumption decreased slightly during the economic recession in 2008. In 2014, the emissions dropped significantly and have been projected to continue to decline in future years based on the revised CARB emission factors for Gasoline Dispensing Facilities.

(b) Future Projections/ Growth

Projections are based on CARB’s Emission Factor (EMFAC) model, EMFAC2021¹⁸⁸, which includes estimates of gasoline consumption in the Bay Area. Due to the coronavirus pandemic impact on the economy, gasoline consumption dropped significantly in 2020. With the new requirements of the California Executive order ¹⁸⁹ to phase out gasoline powered cars and passenger trucks by 2035, the GDF categories’ emissions are expected to be further reduced for forecasted emission years.

6.9.6 Uncertainties

The gasoline consumption estimates for Solano and Sonoma counties may contribute to an increased uncertainty of the Bay Area gasoline consumption for the base year emission inventory.

6.9.7 Contact

Author: Minh Nguyen

Reviewer: Ariana Husain

Last Update: November 06, 2023

6.9.8 References & Footnotes

CARB. 2018. Miscellaneous Process Methodology, Gas Dispensing Facilities, https://ww3.arb.ca.gov/ei/areasrc/fullpdf/full_4-10_april_2018_methodology.pdf ↩︎
CEC. 2021. California Annual Retail Fuel Outlet Report Results (CEC-A15), https://www.energy.ca.gov/data-reports/energy-almanac/transportation-energy/california-retail-fuel-outlet-annual-reporting ↩︎
CARB. 2013. CARB Monitoring and Laboratory Division, Revised Emission Factors for Gasoline Marketing Operations at California Gasoline Dispensing Facilities, https://ww3.arb.ca.gov/vapor/gdf-emisfactor/gdfumbrella.pdf ↩︎
BAAQMD. 2021. Regulation 8, Rule 7 - Gasoline Dispensing Facilities, https://www.baaqmd.gov/~/media/dotgov/files/rules/reg-8-rule-7-gasoline-dispensing-facilities/documents/rg0807.pdf?la=en&rev=55e12318cc9f47c1bd38690a14c85540 ↩︎
CARB. 2022. EMFAC2021 emissions inventories of on-road mobile sources in California, https://arb.ca.gov/emfac/↩︎
CA Executive order. 2020. Governor Newsom Announces California Will Phase Out Gasoline-Powered Cars & Drastically Reduce Demand for Fossil Fuel in California’s Fight Against Climate Change, https://www.gov.ca.gov/2020/09/23/governor-newsom-announces-california-will-phase-out-gasoline-powered-cars-drastically-reduce-demand-for-fossil-fuel-in-californias-fight-against-climate-change/ ↩︎