Yolo-Solano Air Quality Management District

1947 Galileo Court, Suite 103

Davis, CA 95618

(530) 757-3650

www.ysaqmd.org

PROPOSED AMENDMENTS TO

RULE 2.34, STATIONARY GAS TURBINES

FINAL STAFF REPORT

October 24, 2014

Prepared by: Kyle Rohlfing, Associate Air Quality Engineer

Reviewed by: Frank DeMaris, Engineering Manager
Table of Contents Page

I. EXECUTIVE SUMMARY ............................................................................................................. 1

A. BACKGROUND ................................................................................................................ 2

II. DISCUSSION OF PROPOSED RULE 2.34 REQUIREMENTS ................................................... 3

III. COMPARISON TO OTHER APPLICABLE REGULATIONS AND REQUIREMENTS ........... 5

IV. IMPACTS OF THE PROPOSED RULE ...................................................................................... 10

V. ENVIRONMENTAL IMPACTS OF METHODS OF COMPLIANCE ....................................... 11

VI. REGULATORY FINDINGS......................................................................................................... 12

VII. PUBLIC COMMENTS AND STAFF RESPONSES.................................................................... 13

VIII. REFERENCES .............................................................................................................................. 16

ATTACHMENT A PROPOSED AMENDMENTS TO RULE 2.34, STATIONARY GAS 

TURBINES; STRIKE-OUT UNDERLINE VERSION

ATTACHMENT B NOTICE OF EXEMPTION FROM CEQA GUIDELINES 

ATTACHMENT C RESOLUTION NO. 14-08

ATTACHMENT D WRITTEN COMMENTS RECEIVED
Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

I. EXECUTIVE SUMMARY

On November 12, 2014, the Yolo-Solano Air Quality Management District (District) Board of 

Directors will consider the proposed amendments to Rule 2.34, Stationary Gas Turbines. The 

rule applies to all stationary gas turbines rated 0.3 megawatts (MW) and larger.

The main revisions/requirements for Rule 2.34 will be:

1. Definitions have been stricken or added as appropriate.

2. References to efficiency have been removed from the rule as they are no longer required. 

3. Limitations on emissions concentrations in short-term excursions have been added to the 

standards section of the rule.

4. Requirements for emissions control during start-up and shut-down periods have been 

added.

5. The compliance schedule section of the administrative requirements has been stricken as 

all new or currently permitted sources will be immediately subject to rule provisions.

6. The emission control plan section of the administrative requirements has been edited so 

that the section will also apply to proposed sources.

There is currently one permitted source within the District that will be subject to this revised rule. 

The rule revision was prompted by the application for an Authority to Construct for a new 

combined cycle power plant which has since been canceled. The revised rule will apply to any 

future proposals for installation of simple cycle or combined cycle gas turbine power plants. The 

revisions of the rule acknowledge the practical considerations of operating a combined cycle gas 

turbine power plant. The deletion of the efficiency multipliers from the standards section of the 

rule will result in lower permissible limits for oxides of nitrogen (NOx). 

The District does not expect the proposed rule changes to have either a significant or a 

detrimental effect on the environment. Therefore, staff has prepared a Notice of Exemption 

(NOE) to satisfy the California Environmental Quality Act (CEQA) requirements. The NOE 

states that the adoption of these proposed rule amendments is exempt from the requirements of 

CEQA pursuant to Section 15308, Actions by Regulatory Agencies for Protection of the 

Environment.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

A. BACKGROUND

Overview of source category

Stationary gas turbines are engines consuming liquid or gaseous fuels, which produce mechanical 

power that can be used to perform mechanical work or can be converted into electrical power. 

After air is compressed in the compressor section of the engine, fuel is introduced and mixed with 

the air and then the mixture is ignited in the combustor. The expanding combustion gases 

exhaust through the turbine section of the engine, causing the turbine blades to spin and thus 

creating shaft power. The combustion of fuel by the stationary gas turbine results in the emission 

of five of the District’s criteria pollutants: carbon monoxide (CO), oxides of nitrogen (NOx), 

oxides of sulfur (SOx), volatile organic compounds (VOC), and particulate matter with an 

aerodynamic diameter equal to or less than ten microns (PM10). Many stationary gas turbines 

utilize selective catalytic reduction (SCR) as an emissions control technology. This control 

technology results in the emission of ammonia, which can negatively affect the respiratory system 

with acute and chronic exposures.

In the simple cycle gas turbine power plant electrical power is created from the generator driven 

by the gas turbine. A later development in stationary power generation is the combined cycle 

power plant which utilizes additional components. The more complex combined cycle extracts 

useful heat energy from the gas turbine exhaust with a heat recovery steam generator. The heat 

recovery steam generator then channels the steam to drive a steam turbine. The shaft power from 

the steam turbine is used to drive an additional electric generator. The additional equipment of 

the combined cycle power plant results in a greater amount of time necessary to reach steadystate operation compared to the simple cycle process.

Currently, CalPeak Power - Vaca Dixon, LLC (CalPeak) is the only stationary gas turbine source 

subject to this rule operating in the District. This source consists of two simple cycle stationary 

gas turbines controlled with SCR. Because these are simple cycle turbines, the longer start-up 

period proposed for combined cycle units will not apply.

Sources will be allowed temporary departures from emission limit compliance for periods of 

short-term excursions under the proposed rule revisions; however, the turbines will be limited to a 

more restrictive NOx emission concentration limit for periods of steady state operation. Results 

of recently performed source tests show compliance with the revised applicable NOx emission 

concentration limits can be achieved.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

II. DISCUSSION OF PROPOSED RULE 2.34 REQUIREMENTS

Listed below are descriptions of the proposed revisions to Rule 2.34, Stationary Gas Turbines.

Section 100 General

Section 101 - Purpose: The purpose of this rule is to limit NOx emission from stationary gas 

turbines. 

Section 102 - Applicability: Except as provided in sections 110 and 111, this rule shall apply to 

all stationary gas turbines, 0.3 megawatt (MW) and larger.

Section 103 – Severability: If any provision, clause, sentence, paragraph, section or part of this

rule is for any reason judged to be unconstitutional or invalid, such judgment shall not affect or 

invalidate the remainder of the rule.

Section 110 - Exemption - Laboratory, Firefighting/Flood Control, and Chemical Processing

Units: Except for the notification requirement of section 401.3, the provisions of this rule will not 

apply to laboratory gas turbines used for research into the advancement of gas turbine technology, 

turbines used exclusively for firefighting and/or flood control, or chemical processing gas 

turbines.

The revision of this rule will eliminate the exemption for pipeline gas turbines that could have 

been granted at the Air Pollution Control Officer’s determination that emissions control 

technology is not technologically feasible, cost effective, or creates adverse environmental 

impacts.

Section 111 - Exemption - Emergency Standby and Small Units: Except for the notification and 

record-keeping conditions of sections 401.3, 402, and 502.2, the provisions of this rule shall not 

apply to emergency standby stationary gas turbines operating less than 200 hours per calendar 

year, or units rated less than 4 MW operating less than 877 hours per calendar year.

Section 200 Definitions: Twenty-one (21) terms have been defined for rule clarity.

Section 300 Standards

Section 301 - Emission Limits: Except for the start-up period, shut-down period, or up to four (4) 

consecutive fifteen minute periods during short-term excursions, the gas turbine shall not be 

operated under conditions with NOx emissions (averaged over 15 minutes) in excess of the limits 

specified in Table 1. In response to public comments on the compliance ability of gas turbines 

burning alternative gaseous fuels, such as landfill, digester, and refinery gases, the District is 

revising Table 1 to restrict the emission limits associated with gaseous fuels to commercial 

natural and liquefied petroleum gases. As no existing gas turbine subject to the rule is fired on 

any of these alternative gaseous fuels, this revision is not a relaxation of the emission limits. Any 

future gas turbine proposing to fire alternative gaseous fuels will be subject to the requirement to 

use the best available control technology (BACT) under the District’s New Source Review rule, 

which will include a case-by-case emission limit appropriate for that unit and fuel.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

TABLE 1. NOx Emission Concentration Limits

Unit Size Compliance limit

NOx, ppm @ 15% O2

Megawatt Rating (MW) Gas

A

Liquid

B

0.3 to Less Than 2.9 MW

and Units Greater Than or Equal to 4 MW That Operate Less Than 

877 Hour/Year

42 65

2.9 to Less Than 10 MW 25 65

10.0 MW and Over 9 25

A. GAS INCLUDES ONLY COMMERCIAL NATURAL AND LIQUIFIED PETROLEUM GASES.

B. LIQUID INCLUDES KEROSINE, JET, AND DISTILLATE OIL. THE SULFUR CONTENT OF THE OIL SHALL BE LESS THAN 0.05%.

Section 301.1: This rule amendment limits the duration and NOx concentration of short-term 

excursions.

Section 301.2: This rule amendment limits the total amount of time allowed for short-term 

excursions in a year.

Section 302: This section has been added to require operation of emissions control devices during 

periods of turbine start-up and shut-down. This section will require operation of SCR systems 

once the temperature of the catalyst media has increased to the minimum operation temperature 

either specified by the manufacturer or as previously established in source tests for a specific 

source. The EPA requested the rule should specify a minimum temperature at which SCR control 

should be initiated and supplied a range of 475-550°F. The District has agreed to set the 

minimum temperature for SCR control to the upper limit of this range. To determine a practical 

emission limit during start-up periods the District considered recent power plant projects 

reviewed by the California Energy Commission. Comparing maximum hourly emissions 

proposed during start-up periods to the rated heat inputs of the gas turbines the District 

determined that 0.16 lb NOx/MMBtu is an appropriate limit for turbine emissions during startup

for turbines combusting gaseous fuels. The District determined that this emission rate is 

equivalent to a NOx concentration of 43 ppmv @ 15% O2 and proposed to make this limit 

enforceable as an average over the duration of the startup period.

The District received public comments questioning the feasibility of the proposed startup limit for 

smaller gas turbines. These comments from a turbine manufacturer indicated that a higher limit of 

70 ppmv should be an attainable standard. As the purpose of the startup limit is to avoid a 

perceived loophole in the rule’s emission limits, the District has revised the proposed rule to 

include a startup limit of 70 ppmv NOx at 15% O2.

The District found less recent data available for emissions during startup from turbines 

combusting liquid fuel. To avoid setting an unrealistically low limit for startup emissions the 

District started with a NOx emissions factor of 0.88 lb NOx/MMbtu from the fifth edition of U.S. 

EPA AP-42, Compilation of Air Pollutant Emission Factors as a maximum value. This value was 

substituted in the equation to calculate the startup emissions exhaust concentration limit for liquid 

fueled turbines along with the F factor for crude, residual, and distillate oils at 9,190 scf/MMBtu.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

0.88 lb

MMBtu

× 106 ÷ 46 lb

mole × 385 scfmole ÷ 9,190 scfMMBtu

× �20.9%-15%�

(20.9%) = 226 ppm@15% O2

Section 303: This section has been added to specifically require a stationary gas turbine 

owner/operator to install and operate continuous monitoring equipment. For units with ratings 

equal to or greater than 10 MW, the owner/operator will be required to install equipment that 

measures and records exhaust gas NOx concentrations.

Section 304: This section has been added to require regular third-party testing of emissions from 

affected turbines to determine compliance with NOx emission concentration limits. For units 

with ratings equal to or greater than 10 MW, the owner/operator will also be required to conduct a 

regular Relative Accuracy Test Audit (RATA) to determine the reliability of measurements made 

by the continuous emissions monitoring system.

Section 400 Administrative Requirements

Section 401 – Exemption Applicability: The owner/operator shall submit support documentation 

for any units exempt from the provisions of the rule per Sections 110 and 111 of the rule.

Section 402 - Emergency Standby and Small Units: The owner or operator of an exempt

emergency standby or small unit shall notify the APCO in writing within seven days if the hourper-year limit is exceeded. If the limit is exceeded the exemption shall be permanently 

withdrawn and within 30 days of the exceedance, an application for an Authority to Construct 

shall be submitted detailing a plan to meet the applicable limit of Section 301. This section shall 

not apply to public service units operating during a state of emergency declared by the Governor 

of the State of California.

Section 500 Reporting and Recordkeeping

Section 501 - Reporting: The owner or operator shall maintain records for a period of five years. 

The owner or operator shall also submit to the APCO information demonstrating that the CEMS 

has data gathering and retrieval capability. Prior to the issuance of a Permit to Operate, the owner 

or operator shall submit information correlating the control system operating parameters to the 

associated NOx output. Source test information shall be provided annually regarding the exhaust 

gas NOx concentration.

Section 502 - Recordkeeping: Gas turbine operating logs shall be maintained that include, on a 

daily basis, the actual start-up and stop time and total hours of operation. The information shall 

be retained for a period of five years and shall be made available for inspection.

Section 600 - Test Methods:

Section 601: Oxides of Nitrogen (NOx) shall be determined in accordance with U.S. 

Environmental Protection Agency (EPA) Method 7E or EPA Method 20.

Section 602: Oxygen (O2) shall be determined in accordance with California Air Resources 

Board (ARB) Method 100 or EPA Method 3A.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

III. COMPARISON TO OTHER APPLICABLE REGULATIONS AND REQUIREMENTS

California Health and Safety Code (CH&SC) Section 40727.2 requires districts to perform a 

comparative alternative analysis of any new control standard. Specifically, the District is 

required to prepare a written analysis that identifies all existing federal air pollution control 

requirements, including, but not limited to emission control standards constituting best available 

control technology (BACT) that applies to the same equipment or source type as the rule or 

regulation proposed for adoption or modification by the District. In addition, the analysis shall 

identify any other District rule or regulation that applies to the same equipment or source type. 

The analysis shall compare the following specific elements:

A. New Source Performance Standards

Stationary gas turbines with a 10 Million Btu per hour heat input rate at peak load (based on the 

higher heating value of the fuel fired) are subject to the requirements of the EPA’s New Source 

Performance Standards (NSPS) contained in 40 CFR Part 60, Subpart KKKK. Table 2 below 

presents a comparative analysis between specific elements of the proposed revised rule and the 

corresponding elements of the existing federal regulation.

Table 2. Comparison of Proposed Rule Revision Emission Limits with NSPS 40 CFR, 

Part 60, Subpart KKKK

Turbine Rating District Rule 2.34 NOx Emission Limits, 

ppmv@15% O2

Federal Regulation 40 CFR Part 60, Subpart 

KKKK NOx Emission Limits, ppmv@15% O2

˂ 10 MW fired on 

Natural Gas 25 or 42 42, 100, or 150

˂ 10 MW fired on fuel 

other than Natural Gas 25, 42, or 65 96 or 150

≥ 10 MW fired on 

Natural Gas 9 or 42* 15, 25, 42, 100, or 150

≥ 10 MW fired on fuel 

other than Natural Gas 9, 25, 42, or 65* 42, 74, 96, 100, or 150

* The 42 and 65 ppmv NOx limits in these categories only apply to turbines which are limited to operating for less than 877 

hours/year

The standards for sulfur dioxide of 40 CFR Part 60, Subpart KKKK requires either that the 

emission of sulfur dioxide (SO2) from any stationary gas turbine not exceed 0.90 pounds per 

megawatt-hour or that the fuel burned not contain potential sulfur emissions in excess of 0.060 

pounds of SO2 per million BTU. The subpart also contains alternative compliance limits for 

turbines in a non-continental area or if the EPA administrator finds both that the turbine is located 

in an area where natural gas is not available and that the removal of sulfur compounds would 

cause more environmental harm than benefit. District Rule 2.34 currently does not contain any 

restrictions on sulfur oxides and the proposed amendments will not add any restrictions. 

Emissions of sulfur oxides from stationary gas turbines will be limited by other District rules and 

regulations as well as state-level regulations on fuel sulfur content.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

Table 3. NOx Emission Monitoring Conditions

District Rule 2.34 Federal Regulation 40 CFR Part 60, Subpart KKKK

Requirement Application Requirement

- Monitoring system which continuously 

monitors and records:

a. Control system operating parameters;

b. Elapsed time of operation;

c. For units of 10 MW or greater, the 

exhaust gas NOx concentrations corrected to 

ISO conditions at 15 percent oxygen on a dry 

basis. The NOx monitoring system shall meet 

requirements of 40 CFR Part 60, Appendix B, 

Spec. 2 or other systems that are acceptable to 

the EPA.

- Turbines with water or steam 

injection for NOx control

- Continuous monitoring system 

for fuel consumption and ratio of 

water/steam to fuel

OR

- Continuous emissions monitoring 

system (CEMS) with NOx and O2

(or CO2) monitors and fuel and 

watt meters

Also 

- For combined heat and power 

turbines equipped with CEMS 

monitoring, meters for useful 

recovered energy flow rate, 

temperature, and pressure

Turbines without water or steam 

injection for NOx control

- Annual performance test (may be 

reduced to once every 2 years if 

results show NOx emissions equal 

to or less than 75% of limit

OR

- Continuous emissions monitoring 

system (CEMS) with NOx and O2

(or CO2) monitors and fuel and 

watt meters

OR 

- Continuous parameter monitoring 

(parameters to be monitored 

dependent upon turbine design and 

control equipment)

Stationary gas turbines with a 10 Million Btu per hour heat input rate at peak load (based on the lower 

heating value of the fuel fired) and not regulated under Subpart KKKK are subject to the requirements of 

NSPS contained in 40 CFR Part 60, Subpart GG. Table 3 below presents a comparative analysis between 

specific elements of the proposed revised rule and the corresponding elements of the existing federal 

regulation.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

Table 4. Comparison of Proposed Rule Revision Emission Limits with NSPS 40 CFR, 

Part 60, Subpart GG

Turbine Rating District Rule 2.34 NOx Emission Limits, 

ppmv@15% O2

Federal Regulation 40 CFR Part 60, Subpart GG

NOx Minimum Emission Limits, ppmv@15% O2

0.3 to Less Than 2.9 

MW

And Units Greater 

Than or Equal to 4 

MW That Operate 

Less Than 877 

Hour/Year

42 or 65 75 or 150

2.9 to Less Than 10.0 

MW 25 or 65 150

10.0 MW and Over 9 or 25 75 or 150

The NOx emission limits presented for Subpart GG reflect the most stringent emission limits which can 

be increased to higher levels with an adjustment factor calculated from the manufacturer’s rated heat rate 

at the manufacturer’s rated peak load and a NOx emission allowance for fuel-bound nitrogen.

The federal regulation requires that if a nonzero emission allowance for fuel-bound nitrogen is used in the 

calculation of the applicable NOx emission limit in Subpart GG, the owner or operator of the turbine shall 

monitor the nitrogen content of the fuel combusted by the approved methods.

The standards for sulfur dioxide of 40 CFR Part 60, Subpart GG require that the emission of sulfur 

dioxide from any stationary gas turbine not exceed 0.015 percent by volume at 15 percent excess oxygen 

on a dry basis. The regulation also requires the fuel fired in a stationary gas turbine shall not contain 

sulfur in excess of 0.8 percent by weight. District Rule 2.34 currently does not contain any restrictions on 

sulfur oxides and the proposed amendments will not add any restrictions. Emissions of sulfur oxides 

from stationary gas turbines will be limited by other District rules and regulations as well as state-level 

regulations on fuel sulfur content.

Both 40 CFR Part 60, Subpart GG and District Rule 2.34 require monitoring of the emission unit to 

demonstrate compliance with the applicable emissions standards. The federal regulation requires 

monitoring of the total sulfur content of the fuel combusted in the turbine. This monitoring becomes 

elective if the owner or operator can demonstrate by approved means that the fuel being fired in the 

turbine meets the definition of natural gas given in the regulation. District Rule 2.34 has not contained,

and the rule revision will not add, any limitations on sulfur dioxide emissions, so the District rule includes

no requirement to monitor the fuel sulfur content.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

Table 6. NOx Emission Monitoring Conditions

District Rule 2.34 Federal Regulation 40 CFR Part 60, Subpart GG

Requirement Application Requirement

- Monitoring system which continuously 

monitors and records:

a. Control system operating parameters;

b. Elapsed time of operation;

c. For units of 10 MW or greater, the 

exhaust gas NOx concentrations corrected to 

ISO conditions at 15 percent oxygen on a dry 

basis. The NOx monitoring system shall meet 

requirements of 40 CFR Part 60, Appendix B, 

Spec. 2 or other systems that are acceptable to 

the EPA

- Turbines with water or steam 

injection for NOx control

- Continuous monitoring system 

for fuel consumption and ratio of 

water/steam to fuel

- Construction, reconstruction, or 

modification after Oct 3, 1977 but 

before July 8, 2004

- May as alternative install 

continuous emissions monitoring 

system (CEMS) with NOx and O2

(or CO2) monitors

- Construction, reconstruction, or 

modification after Oct 3, 1977 but 

before July 8, 2004 without water

or steam injection

- CEMS not requried

- Turbine constructed after July 8, 

2004 with water or steam injection

- Either continuous monitoring of 

fuel consumption and ratio of 

water/steam injection or use of 

NOx CEMS

- Turbine constructed after July 8, 

2004 without water or steam 

injection

- May elect to, but not required to, 

operate NOx CEMS

- May elect to, but not required to, 

perform continuous parametric 

monitoring

- Periodic testing is an another 

acceptable monitoring system

- Parameters to be continuously monitored to show compliance with 

acceptable emission rates shall be monitored during the initial source test 

to establish acceptable values and ranges

B. Reasonably Available Control Technology

The revisions to this rule would establish for steady-state operation the same NOx emission limits 

as those currently established for stationary gas turbines by the Sacramento Metropolitan Air 

Quality Management District, which are equal to or lower than the applicable standards 

established by the federal government under 40 CFR 60 Subpart KKKK and well below the 

lowest applicable standards required by Subpart GG. Many determinations of Best Available 

Control Technology (BACT) made by other districts in California and by state agencies in other 

states of the country have shown that the application of various control technologies, including 

low-NOx combustors and SCR, result in emissions well in compliance with the proposed rule 

revision. These determinations demonstrate that the proposed rule emission limits are achievable. 

The District showed the existing rule satisfies RACT in a 2006 RACT State Implementation Plan 

and the proposed revised rule will be as stringent in controlling emissions. The CalPeak peaking 

power plant in Vacaville complies with the rule to satisfy RACT. The Permit to Operate for 

CalPeak includes two limits on the emission concentration of NOx. This source is limited to emit 

NOx in no higher concentration than 3.0 ppmv corrected to 15% O2 on a 3 hour rolling average 

and 12 ppmv corrected to 15% O2 for 15 minute averages except for certain periods of operation 

when the source is exempt from one or both of these limits. This source has demonstrated ability 

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

to operate in compliance with the lower emission limits of the proposed revision accepting that a 

source will be exempt from compliance with the rule emissions concentration standards during 

periods of shutdown and short-term excursions as defined in the rule and that separate limits have 

been established for periods of startup.

C. Best Available Retrofit Control Technology

The Sacramento Federal Non-Attainment Area is classified by the EPA to be in severe 

nonattainment of the 8-hour national ambient air quality standard for ozone. According to 

Section 40920 of the California Health and Safety Code, a district with severe air pollution shall, 

to the extent necessary to meet the requirement that a district design a plan to achieve and

maintain air quality standards by the earliest practicable date, include in the district plan all 

measures required for moderate and serious nonattainment areas. One of the measures for 

districts with serious air pollution is the use of the Best Available Retrofit Control Technology 

(BARCT) for existing permitted stationary sources. The only existing stationary gas turbines 

subject to the rule are operated by CalPeak Power and have the potential to emit 0.06 tons per day 

of NOx. The Yolo-Solano Air Quality Management District has not relied on the application of 

BARCT for stationary gas turbines as a means to achieve ambient air quality standards in the 

2012 Triennial Assessment and Plan Update. BARCT is not required and this rule does not 

establish BARCT.

IV. IMPACTS OF THE PROPOSED RULE

Emissions Impacts

As previously stated, there is currently only one permitted source within the District that will be 

subject to the provisions of the revised rule. CalPeak has demonstrated ability to meet the NOx 

emission concentration standard of the revised rule. Although an exemption for short-term 

excursions will allow the NOx emission concentration to be exceeded for short periods of time, 

additions to the rule require that the average emissions for any six hour period containing a shortterm excursion comply with the NOx emission limitation, and short-term excursions will be 

limited to no more than ten hours per year. The limitations to the short-term excursions provision 

will ensure that NOx emissions will not increase as a result of the revisions to this rule. The 

longer start-up period for combined cycle stationary gas turbine power plants will not result in 

higher NOx emissions from a relaxation of regulation of such sources since the longer start-up 

period reflects the practical limitations of operating combined cycle power plants. The 

elimination of the thermal stabilization period emissions limits exemption has been replaced by 

exemptions for periods of start-up and shut-down; however, with the added requirement to 

operate control equipment during such periods and an added start-up limit the proposed revisions 

will not result in a relaxation of the emissions control from the existing version of the rule

currently in the State Implementation Plan.

Cost Effectiveness

CH&SC Section 40703 requires the District, in the process of adopting any regulation, to 

consider and make public its findings related to the cost effectiveness of a control measure. Cost 

effectiveness for rulemaking purposes is calculated by dividing the cost of air pollution controls 

required by the rule by the amount of air pollution reduced.

Since there are no reductions expected from the proposed amendments to this rule and no 

additional air pollution controls are expected, no cost effectiveness calculations are required.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

Socioeconomic Impacts

CH&SC Section 40728.5(a) requires the District, in the process of adopting any rule or 

regulation, to consider the socioeconomic impact if air quality or emission limits may be 

significantly affected. However, districts with a population of less than 500,000 persons are 

exempt from the provisions of Section 40728.5(a). The District’s population is estimated to be 

approximately 331,600, well below the 500,000 person threshold. Therefore, a socioeconomic 

analysis for this rulemaking is not required. 

Incremental Cost Effectiveness

CH&SC Section 40920.6 requires an assessment of the incremental cost-effectiveness for 

proposed regulations related to ozone, Carbon Monoxide (CO), Sulfur Oxides (SOx), Nitrogen 

Oxides (NOx), and their precursors. Incremental cost-effectiveness is defined as the difference in 

control costs divided by the difference in emission reductions between two potential control 

options that can achieve the same emission reduction goal of a regulation. Rule 2.34 only 

contains limitations on NOx emissions. Since the revised rule does not require any additional air 

pollution controls not already required by other District rules and regulations, no cost 

effectiveness calculations are required.

Impacts to the District

The currently operating source has already demonstrated emissions that will be in compliance 

with the applicable NOx emission limitation of the rule. Additional record-keeping will be 

required of sources to demonstrate compliance with rule provisions for periods of short-term 

excursions from NOx emission compliant operation. It is anticipated that the proposed rule will 

have little to no impact on staff workload at the District. It is expected that any additional work 

load can be absorbed within the District’s engineering division.

V. ENVIRONMENTAL IMPACTS OF METHODS OF COMPLIANCE

California Public Resource Code Section 21159 requires the District to perform an environmental 

analysis of the reasonably foreseeable methods of compliance. The analysis must include the 

following information for the proposed amendments to Rule 2.34:

1. An analysis of the reasonably foreseeable environmental impacts of the methods of 

compliance.

2. An analysis of the reasonably foreseeable mitigation measures.

3. An analysis of the reasonably foreseeable alternative means of compliance with the rule 

or regulation.

Table 1 lists all reasonably foreseeable compliance methods, the environmental impacts of those 

methods, and measures that could be used to mitigate the environmental impacts. 

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

TABLE 7. Environmental Impacts, Mitigation Measures, and Alternatives

Compliance 

Methods

Reasonably Foreseeable Environmental 

Impacts

Reasonably Foreseeable Mitigation 

Measures

Water/Steam 

Injection, Low 

NOx Combustion, 

and Selective 

Catalytic 

Reduction

Air Quality Impacts: Reduced NOx 

emissions but potential for ammonia

emissions from use of selective catalytic 

reduction

Installation of Continuous Emissions 

Monitoring System (CEMS) and 

regular source testing to ensure rule 

compliance and minimize ammonia

emission

Water Impacts: Potential for increased 

consumption of water for water/steam 

injection as emissions control

Human Health Impacts: Improved human 

health in the District by reduction in 

emission of precursor to ground level 

ozone

Solid Waste Disposal Impacts: Small 

increase in solid waste from SCR 

catalysts that cannot be reactivated or 

otherwise recycled 

This analysis demonstrates the adoption of amendments to Rule 2.34 will not have a significant 

effect on the environment or humans due to unusual circumstances. In addition, the proposed 

amendment of Rule 2.34 is an action taken to protect the environment. Therefore, staff has

determined that the project is categorically exempt from the requirements of the California 

Environmental Quality Act (CEQA) pursuant to Section 15308, Actions by Regulatory Agencies 

for Protection of the Environment. Staff has prepared a Notice of Exemption (NOE) to meet the 

CEQA Guidelines (Attachment B) for submittal to the County Clerk for Yolo County, and the 

Clerk of the Board of Supervisors for Solano County. 

VI. REGULATORY FINDINGS

Section 40727(a) of the CH&SC requires that prior to adopting or amending a rule or regulation, 

an air district’s board makes findings of necessity, authority, clarity, consistency, nonduplication, 

and reference. The findings must be based on the following:

1. Information presented in the District’s written analysis, prepared pursuant to CH&SC 

Section 40727.2;

2. Information contained in the rulemaking records pursuant to CH&SC Section 40728; and

3. Relevant information presented at the Board’s hearing for adoption of the rule.

The required findings are:

Necessity: The rule amendment is required in order to limit emissions of NOx from stationary gas 

turbines while accepting the additional technical difficulties in achieving emissions compliance at 

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

startup for combined cycle gas turbine power plants versus simple cycle power plants. (CH&SC 

Section 40727(b)(1)).

Authority: The District is authorized to adopt rules and regulations by CH&SC, Sections 40001, 

40702, 40716, 41010 and 41013. (CH&SC Section 40727(b)(2))

Clarity: District staff have reviewed the proposed rule and determined that it can be easily 

understood by the affected industry. In addition, the record contains no evidence that the persons 

directly affected by the rule cannot understand the rule. (CH&SC Section 40727(b)(3)).

Consistency: The District has compared the proposed rule to federal New Source Performance 

Standards (40 CFR Part 60) Subparts GG and KKKK for stationary turbines as well as possible 

revisions to Subpart KKKK for which implementation is pending. The proposed rule does not 

conflict with, and is not contradictory to, existing statutes, court decisions, or state or federal 

regulations. (CH&SC Section 40727(b)(4)).

Non-Duplication: The proposed rule does not duplicate any state laws or regulations regarding 

the attainment and maintenance of state and federal air quality limits. (CH&SC Section 

40727(b)(5)).

Reference: The District is not implementing, interpreting, or making specific any statute, court 

decision, or other provision of law by amending Rule 2.34. (CH&SC Section 40727(b)(6)).

VII. PUBLIC COMMENTS AND STAFF RESPONSES

Staff held a public workshop on January 15, 2014, to discuss the proposed amendments to Rule 

2.34. Notification was sent to surrounding Air Districts, City Managers within the District, 

building/planning/community development departments within the District, all city and county 

libraries within the District, all Board members, and all permitted/proposed sources. The 

workshop notice was published in The Davis Enterprise, The Woodland Daily Democrat, and the 

Vacaville Reporter newspapers on January 8, 2014. A copy of the public workshop notice, the 

draft staff report, and draft rule language, was posted on the District’s web page.

A. Public Workshop - January 15, 2014

No comments pertaining to the proposed rule revisions were received during the public workshop

or during the public comment period that ended on January 29, 2014. On February 6, 2014, the 

U.S. EPA submitted two comments pertaining to the rule.

Comment 1. Nicole Law of the U.S. EPA commented that the definition of “short-term 

excursions” in the draft rule language creates a less stringent exemption from 

NOx emission limit compliant operation than the exemption given in the 

Sacramento Metropolitan Air Quality Management District’s Rule 413, and 

asked that the District consider further limiting the exemption for such 

excursions.

Response 1. The definition of “short-term excursions” was revised to state that such 

excursions are short term departures from compliant operation for turbines with a 

rated output greater than 100 MW, which are part of a combined cycle process, 

due to specified causes.

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

Comment 2. Nicole Law of the U.S. EPA also commented that the rule needed to place 

emission limits on turbines during periods of start-up and shut-down, either with 

numerical emission limits or a requirement that control equipment be operational 

during periods of start-up and shut-down. As part of the comment she provided a 

link to an EPA proposed rule addressing start-up, shut-down, and malfunction 

provisions of rules included in State Implementation Plants (SIPs) at: 

http://www.epa.gov/oar/urbanair/sipstatus/emissions.html.

Response 2. The District notes that the proposed rule is a call for SIP revisions from certain 

specified regions not including any air district in California. EPA did not provide 

in the comment any suggestions for specific emission limits during periods of 

start-up and shut-down. Although this rule does not propose specific emission 

limits for stationary gas turbines during start-up and shut-down events, any unit 

subject to this rule will also be subject to the daily, quarterly, and annual 

emission limits of its Permit to Operate, including all startup/shutdown 

emissions. District permits include emission limits which are determined by the 

type of emission unit permitted, the proposed operation of the source, and the 

requirements of however many different District rules the source is subject to. 

No revision to the rule language is proposed.

B. Additional Regulatory Notice

After receiving written comments from U.S. EPA resulting from the notice performed prior to the 

public workshop, the District revised the proposed rule language. Before moving to a public 

hearing the District sent the revised rule language and updated staff report to U.S. EPA for 

another review period on March 6, 2014. On April 18, 2014 the U.S. EPA submitted additional 

written comments pertaining to the rule.

Comment 1. Andrew Steckel of the U.S. EPA commented on the District’s contention that 

even if the rule did not contain specific emission limits for period of start-up and 

shut-down, emissions units subject to the rule would still have permit limits 

which restrict emissions from such units on a daily, quarterly, and annual basis. 

Mr. Steckel stated that while such permit limits might fulfill Clean Air Act 

requirements they are not approved into the SIP. He suggested revising rule 

provisions to require controls during start-up and shut-down either with 

numerical emission limits or operational requirements.

Response 1. Proposed Rule 2.34 has been revised to add start-up/shut-down operating

standards. This section requires Selective Catalytic Reduction control systems

operate once the temperature of the catalyst media reaches the minimum 

temperature for operation recommended by the manufacturer or as demonstrated 

in source tests. The section also requires other emissions control devices to

operate continuously during start-up and shut-down events.

Comment 2. Mr. Steckel also recommended that the District demonstrate the revised rule 

fulfills Clean Air Act requirements regarding continuous emission limitations, 

RACT, and SIP relaxations.

Response 2. The District feels the addition of operational standards for periods of start-up and 

shut-down adequately addresses the requirement for continuous emission 

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Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

limitations and the concern over SIP relaxations. The requirement for RACT has 

been previously addressed in this staff report.

The District made further revisions to the proposed language and staff report and returned them to 

U.S. EPA for review on May 19, 2014. On June 4, 2014 the U.S. EPA submitted additional 

written comments pertaining to the rule.

Comment 3. Andrew Steckel again commented on the proposed language for start-up/shutdown periods and suggested that some type of numerical limit should be 

established for emissions during start-up periods and for initiation of SCR 

emissions control.

Response 3. The District reviewed recent power plant projects reviewed by the California 

Energy Commission to develop a practical limit for start-up emissions. The 

District also accepted the upper limit of a range of temperature values supplied 

by EPA as the minimum temperature to activate SCR control.

Comment 4. Mr. Steckel also asked for the staff report to explain how the replacement of a 

thermal stabilization period exemption to emission limits by the start-up/shutdown exemption would not relax the State Implementation Plan.

Response 4. This explanation is given in a discussion of the potential emissions impacts of the 

rule revisions in Section IV of this report.

C. Public Hearing Notice Period

Subsequent to the public workshop and addressing the comments, District staff released the 

amended rule language and prepared a public hearing notice for the hearing which will be held 

November 12, 2014. The notice was sent to all the same parties which received the public 

workshop notice. The hearing notice was also published in The Davis Enterprise, The Woodland 

Daily Democrat, and the Vacaville Reporter newspapers. A copy of the public hearing notice and 

updated documents (proposed staff report and proposed rule language), were posted on the 

District’s web page. In response to the notice, the District received the following comments:

Comment 1. Nicole Law of US EPA indicated that the proposed rule was acceptable and EPA 

had no further comments.

Response 1. Comment noted.

Comment 2. Mr. Anthony Pocengal with Solar Turbines Inc. submitted a comment letter 

stating that the proposed 43 ppmv NOx limit during startup may not be attainable 

for all turbines, particularly the smaller units manufactured by Solar. He 

proposed that the startup limit by revised to 70 ppmv.

Response 2. The District notes that the proposed startup limit is derived from mass-based 

limits associated with larger turbines and agrees that smaller units may not follow 

the same emissions profile during startup as a larger unit. Furthermore, the 

District recognizes that data regarding actual NOx concentrations during startup 

of turbines are extremely limited and that, in establishing an emission limit that 

will apply during startups, care must be taken to ensure that an unattainable 

standard is not established. The District is enacting a numerical limit on startup 

Page 15
Final Staff Report – Rule 2.34, Stationary Gas Turbines October 24, 2014

NOx emissions to close a perceived loophole in the rule, rather than with the 

intention of producing any actual emission reductions. Therefore, the District will 

revise the proposed NOx startup limit to 70 ppmv at 15% O2 as suggested.

Comment 3. Mr. Pocengal also commented that the requirement to begin operating SCR as 

soon as it will be effective, and no later than 550 °F, will be sufficient to ensure 

startup emissions are minimized, so a numerical limit is not necessary.

Response 3. See comments 1 and 3 from the additional regulatory notice and the associated 

responses. The District has previously argued that emissions will be minimized 

by operational requirements like the minimum SCR activation temperature 

requirement. Recent litigation has led EPA to begin requiring the closure of 

perceived loopholes in SIPs created by startup and shutdown exemptions from 

emission limits. Therefore, some sort of numerical cap on NOx emissions during 

startup is required for SIP approval of the rule.

Comment 4. Mr. Pocengal also commented that the proposed rule defines “gas” fuels to 

include natural gas, landfill gas, and digester gas, but that landfill and digester 

gases have compositions and qualities that can vary substantially. As the fuel 

characteristics can vary substantially from natural gas, the resulting emissions 

can potentially be much higher, especially if contaminants in the fuel gas will 

interfere with common emission reduction and control devices. Mr. Pocengal 

proposes that such alternative gaseous fuels be subject to separate, higher 

emission limits or evaluated on a case-by-case basis.

Response 4. The District agrees that it can be inappropriate to subject a unit fired on such 

alternative gaseous fuels to the same emission limit that the same unit can meet 

when fired on a commercially-available gaseous fuel of consistent quality and 

properties. Since there are no turbines in the District subject to this rule and 

operating on alternative gaseous fuels, the District is revising the definition of 

gaseous fuels to include only commercial natural gas and liquefied petroleum 

gas. Any future unit operating on an alternative gaseous fuel will be subject to 

BACT and evaluated on a case-by-case basis.

Comment 5. Mr. Pocengal also commented that ISO correction is unnecessary for turbines 

equipped with dry low-NOx burners.

Response 5. Both the current and the proposed rule include frequent references to ISO 

conditions, and this terminology is an integral part of the emission standards. 

References to ISO conditions will not be deleted.

The District incorporated the above comments, as determined appropriate. A copy of the updated 

documents (final staff report and final rule language) were provided to the Governing Board prior 

to the hearing and posted on the District’s web page.

VIII. REFERENCES

- AP 42 Compilation of Air Pollution Emission Factors, Fifth Edition, Section 3.1, Stationary 

Gas Turbines, Published April, 2000

Page 16
ATTACHMENT A

PROPOSED RULE 2.34, STATIONARY GAS TURBINES

STRIKE-OUT UNDERLINE VERSION
ATTACHMENT B

NOTICE OF EXEMPTION FROM CEQA GUIDELINES
Notice of Exemption

To: ■ County Clerk

County of Yolo

625 Court Street, Room 105

Woodland, CA 95695

□ County Clerk

Solano County

600 Texas Street

Fairfield, CA 94533

From: Yolo Solano Air Quality Management District

1947 Galileo Court, Suite 103

Davis, CA 95616

Project Title: Revision of Rule 2.34 - Stationary Gas Turbines

Project Location: Yolo Solano Air Quality Management District

Project Description The revision of Rule 2.34 will lower the NOx emission limits of various 

categories of stationary gas turbines. The revision will also introduce 

separate start-up period exemptions from the emission limits for simple 

cycle and combined cycle turbine power plants.

Name of Public Agency Approving Project: Yolo Solano Air Quality Management District

Name of Person or Agency Carrying Out Project: Yolo Solano Air Quality Management District

Exempt Status:

□ Ministerial

□ Emergency Project

■ Categorical Exemption (CEQA Guidelines Section 15308, Action by Regulatory 

Agency for Protection of the Environment)

□ Statutory Exemption

Reason why project is exempt: The revision of Rule 2.34 is an action taken to protect the 

environment and is therefore exempt from CEQA because it 

constitutes a Class 8 categorical exemption pursuant to CEQA 

Guidelines 15308.

Lead Agency Contact Person Mat Ehrhardt, Air Pollution Control Officer

Telephone Number (530) 757-3650

Signature: Date: Title:
Notice of Exemption

To: ■ County Clerk

County of Yolo

625 Court Street, Room 105

Woodland, CA 95695

□ County Clerk

Solano County

600 Texas Street

Fairfield, CA 94533

From: Yolo Solano Air Quality Management District

1947 Galileo Court, Suite 103

Davis, CA 95616

Project Title: Revision of Rule 2.34 - Stationary Gas Turbines

Project Location: Yolo Solano Air Quality Management District

Project Description: The revision of Rule 2.34 will lower the NOx emission limits of 

various categories of stationary gas turbines. The revision will also 

introduce separate start-up period exemptions from the emission limits 

for simple cycle and combined cycle turbine power plants.

Name of Public Agency Approving Project: Yolo Solano Air Quality Management District

Name of Person or Agency Carrying Out Project: Yolo Solano Air Quality Management District

Exempt Status:

□ Ministerial

□ Emergency Project

■ Categorical Exemption (CEQA Guidelines Section 15308, Action by Regulatory 

Agency for Protection of the Environment)

□ Statutory Exemption

Reason why project is exempt: The revision of Rule 2.34 is an action taken to protect the 

environment and is therefore exempt from CEQA because it 

constitutes a Class 8 categorical exemption pursuant to CEQA 

Guidelines 15308.

Lead Agency Contact Person: Mat Ehrhardt, Air Pollution Control Officer

Telephone Number: (530) 757-3650

Signature: Date: Title:
ATTACHMENT C

RESOLUTION NO. 14-08
RESOLUTION NO. 14-08

RESOLUTION AMENDING YOLO-SOLANO AIR QUALITY MANAGEMENT 

DISTRICT RULE 2.34

WHEREAS, California Health and Safety Code section 40702 provides that an air 

quality management district shall adopt rules and regulations as may be necessary or proper to 

execute the powers and duties granted to, and imposed upon, the district by Division 26 of the 

Health and Safety Code; and

WHEREAS, Health and Safety Code section 40727 provides that before adopting, 

amending, or repealing a rule or regulation, a district board shall make findings of necessity, 

authority, clarity, consistency, nonduplication, and reference, based upon information developed 

pursuant to section 40727.2, information in the rulemaking record maintained pursuant to section 

40728, and relevant information presented at the public hearing required by section 40725; and

WHEREAS, section 15308 of the CEQA Guidelines provides that actions taken by 

regulatory agencies as authorized by state law to assure the maintenance, restoration, or 

enhancement of the environment where the regulatory process involves procedures for protection 

of the environment, are categorically exempt from CEQA review (Class 8 Categorical 

Exemption); and

WHEREAS, the purpose of amending Rule 2.34, Stationary Gas Turbines is to reduce 

gas turbine emission limits, require emissions control during turbine start-up, and establish a 

practical start-up period for combined cycle power plants.

NOW, THEREFORE, BE IT RESOLVED that the Board of Directors of the YoloSolano Air Quality Management District hereby finds, authorizes, directs and declares as 

follows:

1. The Board of Directors has considered and hereby adopts by reference the staff report 

prepared in this matter.

2. The Board of Directors makes the following findings pursuant to Health and Safety Code 

section 40727:

a. Necessity: Information in the District=s rulemaking record maintained pursuant to 

Health and Safety Code section 40728 demonstrates a need for amending District 

Rule 2.34;

b. Authority: Health and Safety Code section 40702 permits the District to amend 

District Rule 2.34;

c. Clarity: District Rule 2.34 as amended is written so that its meaning can be easily 

understood by the persons directly affected by it;

d. Consistency: District Rule 2.34 as amended is in harmony with, and not in 

conflict with or contradictory to, existing statutes, court decisions, or state or 

federal regulations;

e. Nonduplication: District Rule 2.34 as amended does not impose the same 
requirements as an existing state or federal regulation;

f. Reference: By adopting District Rule 2.34, the District meets the requirements of 

Health & Safety Code Sections 40702.

3. The Board of Directors finds that the District has complied with the procedural 

requirements set forth in Chapters 6 and 6.5 of Part 3 of Division 26 of the Health and 

Safety Code.

4. The Board of Directors finds that amending District Rule 2.34 is an action taken by a 

regulatory agency as authorized by state law to assure the maintenance, restoration, or 

enhancement of the environment where the regulatory process involves procedures for 

protection of the environment, and is therefore categorically exempt from CEQA review 

as a Class 8 Categorical Exemption.

5. The Board of Directors hereby amends District Rule 2.34, Stationary Gas Turbines, as set 

forth in Exhibit 1 (Attachment A of the Staff Report), which is attached and incorporated 

by reference. The amendment is effective November 12, 2014.

PASSED AND ADOPTED by the Board of Directors of the Yolo-Solano Air Quality 

Management District this 12th day of November, 2014, by the following vote:

Ayes:

Noes:

Absent:

Abstain:

Dilenna Harris, Chair

Board of Directors

Yolo-Solano Air Quality Management District

Attest: Approved as to Form:

Denise Almaguer, 

Board Clerk

Hope Welton, District Counsel
ATTACHMENT D

COMMENTS RECEIVED