AIR EMISSIONS REGULATIONS:

Air Quality Status	Marginal nonattainment under the 8-hr ozone standards (AQMD includes Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, western portion of Solano and the southern portion of Sonoma counties EPA's Nonattainment Areas
Major Source Threshold	100 tons of NOx, VOCs or PM triggers NSR. 250 tons of any other criteria pollutant triggers PSD
Minor Source Permitting Exemption	Based on size, emissions and type
Minor Source Treatment	BACT, opacity, SO2, NOx and CO limits
Emergency Generating Limits	BACT

DE MINIMIS EXEMPTIONS (Must meet 1298)

In general, internal combustion engines and gas turbines less than 50 hp are exempt from obtaining a District permit, however there are several conditions that apply. A detailed flow chart outlining exemptions is outlined in the permit handbook and may be accessed using the following link.

MINOR SOURCE PERMITTING

Sources with potential emissions of 10 pounds per day of any criteria pollutant are subject to BACT (See Reg. 2-2-301). The air district uses its own BACT workbook to determine levels of control.

Sources that do not trigger BACT must still meet limitations for SO2, NOx, CO and opacity. Opacity is limited to 20% (an opacity limit of 40% applies to IC engines of less than 25 liters displacement, See Regulation 6-303), SO2 emissions cannot exceed 300 ppm and CO emissions are limited to 2,000 ppm. NOx limits are listed below (please see the BACT workbook for a more comprehensive list of limits, and Regulation 9-8-301 and 9-8-302 which outline NOx and CO limits that generally apply to all stationary internal combustion engines. A for a list of NOx limits outlined in the BACT workbook is as follows -

Technology	Size	Limit
Gas Turbines	Simple Cycle < 2.0 MW	* 5.0 ppm@15% O2 for a catalytic combustor, or high temperature SCR; *9.0 ppm @15% O2 with combustion modifications (i.e. dry low-NOx combustor)
	Combined Cycle >/= 2MW and < 40 MW	* 2.5 ppm @15% O2 with SCR + water or steam injection; or SCONOx; *5.0 ppm @ 15% O2 for SCR + water or steam injection
Internal Combustion Engines (natural gas-fired)	Rich-burn >/= 50 hp	* 4 ppm @15% O2 with a 3-way catalyst + air/fuel ratio controller; * 9 ppm with NSCR, 3-way catalyst
	Lean-burn >/= 50 hp	*6 ppm @ 15% O2 with SCR; *12 ppm @15% O2 with SCR

Section 2.3.2 from the Permit Handbook provides an overview of requirements for stationary natural gas engines.

Sources with potential emissions less than 25 pounds per day of all criteria pollutants may receive limits based on the permitting official's discretion.

The permitting process can take up to 180 days. A public comment period of 30 days is required.

TREATMENT OF EMERGENCY ENGINES

Emergency engines must obtain a permit, install run hour meters to measure usage, and will be required to log usage. All new engines will be subject to BACT. Operators of these units must also choose between Emergency Standby status, and typical permitting. Emission limits for spark ignition, natural gas-fired emergency engines can be found here.