3091 County Center Drive, Suite 240, Auburn, CA 95603 (530) 745-2330 Fax (530) 745-2373

www.placer.ca.gov/apcd Thomas J. Christofk, Air Pollution Control Officer

MEMORANDUM 

TO: Board of Directors, Placer County Air Pollution Control District

FROM: John Finnell, Senior Air Pollution Control Engineer

AGENDA DATE: December 10, 2009

SUBJECT: Adoption of Amendments to Rule 233, Biomass Boilers (Action/Public 

Hearing)

Action Requested:

1) Conduct a Public Hearing regarding the proposed adoption of amendments to 

Rule 233, Biomass Boilers.

2) Approve and adopt all Findings and Recommendations found in Attachment #2

and approve Resolution #09-12 (Attachment #1) thereby adopting amendments to 

Rule 233, Biomass Boilers.

Background:

The District Rules and Regulations include three boiler regulations. These regulations 

were intended to regulate nitrogen oxide (NOx) emissions. Since carbon monoxide (CO) 

emissions generally have an inverse relationship to NOx, CO is also regulated.

Natural gas and oil fired boilers rated at greater than 5 million Btu per hour are subject to 

the requirements of Rule 231, Industrial, Institutional, and Commercial Boilers Steam 

Generators and Process Heaters. There are a number of facilities in Placer County which 

must meet the requirements of this rule.

Suspension biomass boilers at medium density fiberboard (MDF) plants are required to 

meet Rule 232, Biomass Suspension Boilers. This regulation only applies to SierraPine in 

Rocklin.

Biomass boilers that are major sources of NOx and are not located at an MDF plant are 

required to meet the Rule 233, Biomass Boiler. This rule applies to the Rio Bravo Rocklin 

and Sierra Pacific Industries, Lincoln, facilities in Placer County.

There are technical issues making the NOx and CO standard difficult to achieve during 

some startups and shutdowns. As a result, an amendment was adopted on October 11, 

2007 which allowed alternate emission limits during startup and shutdown. 
Adoption of Amended Rule 233, Biomass Boilers

District Board of Directors

Agenda Date: December 10, 2009

Page 2

The October 11, 2007, rule amendment was forwarded to the California Air Resources 

Board (CARB) for approval into the California State Implementation Plan (SIP). This was 

approved by CARB and forwarded to the U.S. Environmental Agency (USEPA) for 

approval.

USEPA declined to approve the amendment as inconsistent with federal regulation and 

policy. Their objections were in two areas:

1. The 115 ppm limit for NOx does not apply during startup and shutdown. Instead 

mass emission limits in the Permit to Operate would apply. Although these limits 

were already in place in the both the District Permit to Operate and federal Title 

V, EPA has requested that the limitations be listed in the Rule itself.

2. The amendment must provide a demonstration that both the length of time of the 

startups and shutdown and the emissions were minimized as much as 

technologically feasible.

In acknowledgement of USEPA’s intention to disapprove the October 11, 2007, 

amendment, the District requested the withdrawal of the amendment from SIP 

consideration in a letter dated October 14, 2008.

Discussion:

As there are only two boilers, one a stoker boiler and one a circulating fluidized bed 

boiler, that this rule applies to Section 101 has been amended to address those specific 

types of boilers by changing the applicability section to read:

“This rule applies to stoker and circulating fluidized bed boilers and steam 

generators which have a heat input rating of less than 500 million Btu per 

hour and a potential to emit, as defined in Rule 502, NEW SOURCE 

REVIEW, 25 tons or more of NOx emissions and which have a primary 

energy source of biomass consisting of a minimum of 75 percent of the total 

annual heat input.”

Any new stoker or circulating fluidized boilers rated less than 500 million Btu per hour 

would have to meet the proposed rule requirements and also apply Best Available 

Control Technology (BACT) to be determined during the permitting process.

If other types of boilers were proposed for installation in Placer County, the equipment 

would fall under other existing boiler rules, or possibly a new regulation would be 

considered.

Exemptions:

There are no changes to the Exemptions.
Adoption of Amended Rule 233, Biomass Boilers

District Board of Directors

Agenda Date: December 10, 2009

Page 3

Definitions:

Definitions of a circulating fluidized bed boiler and stoker boiler were added. The 

definition of shutdown was changed.

Standards:

Carbon monoxide emission limitations were added to Section 301.1. These limitations 

were previously required but existed only in the Permits to Operate for the two affected 

facilities.

Section 302, Startup and Shutdown Provisions, was added to allow the limitations for 

NOx and CO to be established in terms of mass emissions during startup and shutdown 

instead of the concentration of 115 ppmv.

Mass emission limitations for NOx and CO during startup and shutdown were added to 

Section 302.1.b. For a circulating fluidized bed boiler, the proposed NOx limitations are 

35 pounds per hour on a 24 hour average (and for curing of refractory on a 72 hour 

average) and CO limitations of 56 pounds per hour on a 24 hour average (and for curing 

of refractory on a 72 hour average). For a stoker boiler, the proposed NOx limitations are 

37.6 pounds per hour on a 24 hour average and CO limitations of 56 pounds per hour on a 

24 hour average.

Mass emissions limits are usually expressed as pounds per hour or pounds per day and do 

not require a CO2 correction. This removes the issue of low CO2 causing the corrected 

NOx and CO values to be artificially high in some cases. 

The proposed amendment removes Section 302.1.c. which requires a limit on the number 

of startups and shutdowns in a calendar year as a permit condition. These limitations are 

currently in the District Permits to Operate and are not believed to be needed in the Rule.

Fiscal Impact:

California Health and Safety Code Section 40728.5 required all air quality districts to 

consider and make public any findings relating to the cost effectiveness of implementing 

an emission control measure. The proposed Rule 233 amendment does not implement an 

emission control measure but instead allows emission limits in mass emission rates 

instead of concentrations during startup and shutdown and will not have a fiscal impact 

on any facility, and is not subject to the cost effectiveness mandate.

Public Outreach:

The hearing notice was published in the Auburn Journal and Press Tribune newspapers on 

or before November 8, 2009, in advance of the scheduled public hearing. No other public 

meetings were held. In lieu of public meetings the District staff emailed notices and 

copies of the proposed amended rule to the affected permitted sources of the District 

advising them directly of the proposed rule and of their opportunity to comment either in 
Adoption of Amended Rule 233, Biomass Boilers

District Board of Directors

Agenda Date: December 10, 2009

Page 4

writing or before the District Board’s public hearing. Comments have been received and 

some of the comments have been entered in the final proposed rule.

Recommendation:

The purpose of the Board Hearing is to consider public testimony regarding the rule and 

to consider whether the proposed rule amendment is to be adopted.

Staff recommends and requests that the Board:

(1) Approve and adopt all Findings and Recommendations found in Attachment #2,

(2) Adopt Resolution #09-12, Attachment #1, thereby adopting the proposed 

amendment to Rule 233, Biomass Boilers, as shown in Exhibit I of the resolution.

Attachment(s) #1: Resolution #09-12, Adoption of Amendment to Rule 233, Biomass Boilers, 

and Exhibit I (Proposed Rule 233, strikeout version)

#2: Analysis and Findings Required for Rule Adoption

#3: Staff Report, Rule 233, Biomass Boilers
ATTACHMENT #1

SUBJECT:

Resolution #09-12
- 1 -

1 BEFORE THE BOARD OF DIRECTORS

2 PLACER COUNTY AIR POLLUTION CONTROL DISTRICT

3 STATE OF CALIFORNIA

4

5 RESOLUTION NO: _09-12_

6

7 In the matter of: Approve Resolution #09-12, thereby adopting the Placer County Air 

8 Pollution Control District’s proposed Amendments to Rule 233, Biomass 

9 Boilers, as Shown in Exhibit I

10

11

12 The following RESOLUTION was duly passed by the Board of Directors, Placer County Air 

13 Pollution Control District, at a regular meeting held December 10, 2009 by the following vote:

14

15 Ayes: Holmes, M._____ Ucovich _____ Weygandt_____ Holmes, J. _____ Barkle _____

16 Nakata_____ Hill_____ Uhler_____ Allard _____

17 Noes: Holmes, M._____ Ucovich _____ Weygandt_____ Holmes, J. _____ Barkle _____

18 Nakata_____ Hill_____ Uhler_____ Allard _____

19 Abstain: Holmes, M._____ Ucovich _____ Weygandt_____ Holmes, J. _____ Barkle _____

20 Nakata_____ Hill_____ Uhler_____ Allard _____

21

22 Signed and approved by me after its passage.

23

24 ______________________________Chairperson

25

26 Attest:

27

28 ______________________________Clerk of said Board

29

30
- 2 -

1 WHEREAS, Section 40001 of the Health and Safety Code of the State of California authorizes 

2 the Placer County Air Pollution Control District, to adopt and enforce Rules and Regulations to 

3 achieve and maintain ambient air quality standards within the District; and

4

5 WHEREAS, Section 40702 of the Health and Safety Code of the State of California requires a 

6 district to adopt rules and regulations and do such acts as may be necessary or proper to execute 

7 the powers and duties granted; and

8

9 WHEREAS, these proceedings were held in a public hearing and were properly noticed 

10 pursuant to Section 40725 of the Health and Safety Code of the State of California; with any 

11 evidence having been received concerning the proposed adoption of this Resolution and this 

12 Board having duly considered such evidence; and

13

14 WHEREAS, the District has considered the relative cost effectiveness of the measure as well as 

15 other factors, as required by Health and Safety Code Section 40922, and made reasonable efforts 

16 to determine the direct costs expected to be incurred by regulated parties pursuant to Health and 

17 Safety Code Section 40703; and

18

19 WHEREAS, Portions of the Placer County Air Pollution Control District (PCAPCD) have been 

20 designated as “severe” non-attainment areas for the federal 8-hour ozone standard and non21 attainment for the 1-hour ozone standard pursuant to the Federal Clean Air Act Amendments of 

22 1990 (FCAA): and

23

24 WHEREAS, the proposed rule is a rule change to address a technical issue with startup and 

25 shutdowns of applicable biomass boilers and make it SIP approvable but not specifically an 

26 emission control measure; it was listed in the District’s annual “Regulatory Measures List “ 

27 pursuant to Health and Safety Code Section 40923.

28

29
- 3 -

1 NOW, THEREFORE, BE IT RESOLVED, that this Board approves and adopts this Rule 233, 

2 Biomass Boilers, as shown in Exhibit I. 

3

4 BE IT RESOLVED AND ORDERED that the Air Pollution Control Officer is hereby 

5 authorized and directed to submit this adopted rule, in the form as required by the California Air 

6 Resources Board, on behalf of the Placer County Air Pollution Control District, and to perform 

7 such acts as are necessary to carry out the purpose of this resolution.

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EXHIBIT I

RULE 233, BIOMASS BOILERS

(Strikeout Version)
Strikeout Version December 10, 2009

Placer County APCD 233 - 1 Rules and Regulations

 RULE 233 BIOMASS BOILERS

Adopted 10-6-94

(Amended 10-11-07, Amended 12-10-09)

CONTENTS

100 GENERAL

101 APPLICABILITY

102 FEDERAL REGULATIONS

103 EXEMPTION, BOILERS, STEAM GENERATORS, AND PROCESS HEATERS

104 EXEMPTION, BIOMASS SUSPENSION BOILERS

105 EXEMPTION, MUNICIPAL SOLID WASTE

106 EXEMPTION, WASTE HEAT RECOVERY BOILERS

200 DEFINITIONS

201 BIOMASS

202 BIOMASS BOILER OR STEAM GENERATOR

203 BRITISH THERMAL UNIT

204 CIRCULATING FLUIDIZED BED BOILER

205 CURING STARTUP

2064 HEAT INPUT

2075 HIGHER HEATING VALUE (HHV)

2086 MUNICIPAL SOLID WASTE

2097 NOX EMISSIONS 

21008 PARTS PER MILLION BY VOLUME (PPMV)

21109 RATED HEAT INPUT CAPACITY

21210 RESPONSIBLE OFFICIAL

21311 SHUTDOWN

21412 STARTUP

215 STOKER BOILER

2136 UNIT

2147 WOOD

300 STANDARDS

301 LIMITATIONS

302 STARTUP AND SHUTDOWN PROVISIONS

400 ADMINISTRATIVE REQUIREMENTS

401 OPERATION AND MAINTENANCE PLAN

402 COMPLIANCE COSTS

403 CERTIFICATION

500 MONITORING AND RECORDS

501 RECORDKEEPING

502 CONTINUOUS EMISSIONS MONITORING

503 INITIAL COMPLIANCE TEST

504 TEST METHODS

505 CORRECTION OF EMISSION CONCENTRATIONS
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Rules and Regulations 233 - 2 Placer County APCD

506 DURATION OF RECORDS
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Placer County APCD 233 - 3 Rules and Regulations

This Page Intentionally Left Blank
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Rules and Regulations 233 - 4 Placer County APCD

100 GENERAL

101 APPLICABILITY: This rule applies to stoker and circulating fluidized bed boilers and steam 

generators which have a heat input rating of less than 500 million Btu per hour and a 

potential to emit, as defined in Rule 502, NEW SOURCE REVIEW, 25 tons or more of NOx

emissions and which have a primary energy source of biomass consisting of a minimum of 75 

percent of the total annual heat input.

102 FEDERAL REGULATIONS: Compliance with this rule shall not exempt a person from 

complying with any federal regulation promulgated pursuant to the Clean Air Act (42 U.S.C. 

Section 7401 et seq.).

103 EXEMPTION, BOILERS, STEAM GENERATORS, AND PROCESS HEATERS: This rule 

shall not apply to boilers, steam generators, and process heaters subject to Rule 231, 

INDUSTRIAL, INSTITUTIONAL, AND COMMERCIAL BOILERS, STEAM GENERATORS, 

AND PROCESS HEATERS.

104 EXEMPTION, BIOMASS SUSPENSION BOILERS: This rule shall not apply to existing 

boilers and steam generators subject to Rule 232, BIOMASS SUSPENSION BOILERS.

105 EXEMPTION, MUNICIPAL SOLID WASTE: This rule shall not apply to combustion units 

whose primary purpose is to burn municipal solid waste, as defined in Section 2068.

106 EXEMPTION, WASTE HEAT RECOVERY BOILERS: The provisions of this rule do not 

apply to waste heat recovery boilers used to recover sensible heat from the exhaust of 

combustion turbines or unfired waste heat recovery boilers used to recover sensible heat 

from the exhaust of any combustion equipment.

200 DEFINITIONS

201 BIOMASS: Any organic material not derived from fossil fuels, such as agricultural crop 

residues, bark, lawn, yard and garden clippings, leaves, silvicultural residue, tree and brush 

pruning, wood and wood chips, and wood waste, including these materials when separated 

from other waste streams. Biomass does not include material containing sewage sludge, 

industrial sludge, medical waste, hazardous waste, or radioactive waste.

202 BIOMASS BOILER OR STEAM GENERATOR: Any combustion equipment used in any 

industrial, institutional, or commercial operation designed to burn biomass to produce steam, 

heat water or other fluids, and/or produce electricity.

203 BRITISH THERMAL UNIT (BTU): The amount of heat required to raise the temperature of 

one pound of water from 59 degrees F to 60 degrees F at one atmosphere.

204 CIRCULATING FLUIDIZED BED BOILER: A boiler that burns solid fuel in a moving 

suspension of inert materials, forced through upward blowing of air jets, and where the ash 

and inerts are captured and recirculated back into the moving fluidized bed.

205 CURING STARTUP: A startup which includes heating the boiler at predetermined rate and 

holding temperature at several points to allow for insulating materials to cure in the boiler 

refractory. A curing startup shall not exceed 96 hours.

2046 HEAT INPUT: The chemical heat released due to fuel combustion in a boiler, using the 

higher heating value of the fuel. This does not include the sensible heat of incoming 

combustion air.
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Placer County APCD 233 - 5 Rules and Regulations

2057 HIGHER HEATING VALUE (HHV): The total heat liberated per mass of fuel burned (BTU 

per pound), when fuel and dry air at standard conditions undergo complete combustion and 

all resultant products are brought to their standard states at standard conditions. HHV shall 

be determined by one of the following test methods:

2057.1 ASTM E711 for biomass; or

2057.2 ASTM D 240-87 or ASTM D 2382-82 for liquid hydrocarbon fuels; or

2057.3 ASTM D 1826-88 or ASTM D 1945-81 in conjunction with ASTM D 3588-89 for 

gaseous fuels.

2068 MUNICIPAL SOLID WASTE: Household, commercial/retail, and/or institutional waste. 

Household waste includes material discarded by single or multiple residential dwellings, 

hotels, motels, and other similar permanent or temporary housing establishments or facilities. 

Commercial/retail waste includes material discarded by stores, offices, restaurants, 

warehouses, non-manufacturing activities at industrial facilities, and other similar

establishments or facilities. Institutional waste includes material discarded by schools, 

hospitals, prisons, and government facilities and other similar establishments or facilities.

2079 NOX EMISSIONS: The sum of nitric oxides and nitrogen dioxide in the flue gas, collectively 

expressed as nitrogen dioxide (NO2).

20810 PARTS PER MILLION BY VOLUME (PPMV): The ratio of the number of gas molecules 

of a given species, or group, to the number of millions of total gas molecules.

20911 RATED HEAT INPUT CAPACITY: The heat input capacity, in million BTU per hour, 

specified on the nameplate of the combustion unit. If the combustion unit has been altered or 

modified such that its maximum heat input is different than the input capacity specified on the 

nameplate, and this alteration or modification has been approved by the Air Pollution Control 

Officer and made a limiting condition of operation, then the new maximum heat input shall be 

considered as the rated heat input capacity.

21012 RESPONSIBLE OFFICIAL: An individual with the authority to certify that a source 

complies with all applicable requirements, including the conditions of permits issued to 

sources in accordance with Regulation 5, PERMITS. A "responsible official" means one of the 

following:

21012.1 For a corporation, a president, secretary, treasurer, or vice-president of the 

corporation in charge of a principal business function, or any other person who 

performs similar policy or decision-making functions for the corporation, or a duly 

authorized representative of such person if the representative is responsible for the 

overall operation of one or more manufacturing, production, or operating facilities 

applying for or subject to a permit and either:

21112.1.1 The facilities employ more than 250 persons or have gross annual sales 

or expenditures exceeding $25 million (in second quarter 1980 dollars); or

21112.1.2 The delegation of authority to such representative is approved in 

advance by the Air Pollution Control Officer;

21012.2 For a partnership or sole proprietorship, a general partner or the proprietor, 

respectively; or

21012.3 For a municipality, state, federal, or other public agency, either a principal 

executive officer or a ranking elected official; or
December 10, 2009 Strike out Version

Rules and Regulations 233 - 6 Placer County APCD

21012.4 For an acid rain unit subject to Title IV (Acid Deposition Control) of the Clean Air 

Act, the "responsible official" is the designated representative of that unit for any 

purposes under Title IV and Rule 507, FEDERAL OPERATING PERMITS 

PROGRAM.

2113 SHUTDOWN: A shutdown starts when fuel feed is curtailed and the unit begins cooling from 

the unit’s normal operating temperature, as specified by the manufacturer, and ends when 

the unit is 150 degrees F steam flow is zero or less for at least one hour,or 24 hours has 

elapsed since the start of the shutdown, or fuel feed resumes, whichever occurs first.

2124 STARTUP: The period of time a unit is heated to the normal operating temperature, as 

specified by the manufacturer, following a shutdown. A normal startup shall not exceed 24 

hours. A curing startup shall not exceed 96 hours.

2135 STOKER BOILER: A boiler that burns solid fuel on a stationary or moving grate located at 

the bottom of the furnace, and where the fuel is supplied and ash removed continuously.

2146 UNIT: Any biomass boiler or steam generator as defined in Sections 202.

2157 WOOD: Wood, wood residue, bark, or any derivative fuel or residue thereof, in any form, 

including but not limited to sawdust, sanderdust, wood chips, scraps, slabs, millings, 

shavings, and processed pellets made from wood or other forest residues.

300 STANDARDS

301 LIMITATIONS:

301.1 No person shall allow the discharge of NOx and CO emissions into the atmosphere 

from a biomass boiler or steam generator in excess of the following standards, 

whichever is less stringent,excluding startup and shutdown conditions:

a. An exhaust concentration of 115 parts per million (ppmv) corrected to 12 percent 

by volume stack gas carbon dioxide (CO2) on a three-hour average dry basis.

b. 50 percent of the uncontrolled NOx emission concentration in the exhaust gas 

stream. A corresponding controlled concentration limit, expressed in ppmv 

corrected to 12 percent by volume stack gas CO2 on a three-hour average dry 

basis, shall be established in a Permit to Operate for the purpose of 

demonstrating continuous compliance with the 50 percent emission reduction.

Type of Boiler NOx CO

Circulating Fluidized Bed

(<500 MMBtu/hour)

115 

ppmv corrected to 

12% CO2

(3 hour rolling 

average)

400 

ppmv corrected to 

12% CO2

(3 hour rolling 

average)

Stoker

(<500 MMBtu/hour)

115 

ppmv corrected to 

12% CO2

(3 hour rolling 

average)

1000

ppmv corrected to 

12% CO2

(3 hour rolling 

average)
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Placer County APCD 233 - 7 Rules and Regulations

302 STARTUP AND SHUTDOWN PROVISIONS

302.1 The emission limits of Section 301.1 shall not apply during startup or shutdown 

provided the following requirements are met:

a.302.1.1 CO2 emissions are 10 percent or less by volume stack gas on a one-hour 

average dry basis.

b. Emission units subject to this rule shall have mass emission limitations for 

NOx and CO applicable to startup and shutdown established in permit(s) to 

operate by January 1, 2008, for existing facilities or in the initial Authority to 

Construct for new facilities.

302.1.2 During startup and shutdown, the mass emissions of NOx and CO shall not 

exceed the levels shown below:. The block averaging time starts at the 

beginning of either the startup or the shutdown.

Type of Boiler

NOx CO

Circulating Fluidized Bed

(<500 MMBtu/hour)

35 

pounds per hour

(24 hour block 

average)

56 

pounds per hour

(24 hour block 

average)

35 

pounds per hour

(72 hour block 

average during 

curing of 

refractorystartup)

56 

pounds per hour

(72 hour block 

average during 

curing startupof 

refractory )

Stoker

(<500 MMBtu/hour)

37.6

pounds per hour 

(3 hour rolling 

average)

170

pounds per hour 

(3 hour rolling 

average)

302.1.3. A normal startup shall not exceed 24 hours. A startup which involves 

curing of refractory shall not exceed 96 hours.

c. Emission units subject to this rule shall have a limit on the number of startups and 

shutdowns in a calendar year as a permit condition.
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Rules and Regulations 233 - 8 Placer County APCD

400 ADMINISTRATIVE REQUIREMENTS

401 OPERATION AND MAINTENANCE PLAN: Any person installing an emission control device 

as a means of complying with the emission limitations of Section 301 shall submit an 

Operation and Maintenance Plan with the application for Authority to Construct for the 

emission control device.

401.1 The Operation and Maintenance Plan shall specify:

a401.1.1. Operation and maintenance procedures that will demonstrate continuous 

operation of the emission control device during emission-producing 

operations; and

401.1.2b. Records that must be kept to document the operation and maintenance 

procedures.

401.1.3. Each source must provide to the District a description of the actions that 

will be taken to minimize emissions during startup and shutdown events. 

401.2 The records must comply with Sections 501, 502, and 504.

401.3 The Operation and Maintenance Plan shall be implemented upon approval by the Air 

Pollution Control Officer.

401.4 Subsequent to the construction of any emission control device used for 

demonstrating compliance with the emission limitation of Section 301, an Operation 

and Maintenance Plan shall be submitted or resubmitted in conjunction with any

changes in the procedures addressed in the plan, or upon the request of the Air 

Pollution Control Officer.

402 COMPLIANCE COSTS: A person operating a unit subject to this rule shall bear all expenses 

associated with compliance with the monitoring and reporting provisions of this rule.

403 CERTIFICATION: All reports submitted in accordance with this rule shall be signed by a

responsible official who shall certify the truth, accuracy, and completeness of the report.

500 MONITORING AND RECORDS

501 RECORDKEEPING: A person operating a unit subject to this rule shall keep the following 

records for each unit:

501.1 Calendar date of record.

501.2 Number of hours the unit is operated during each day.

501.3 Boiler load.

501.4 Fuel types, including supplementary gaseous or liquid fuels.

501.5 Duration of startups and shutdowns.

501.6 Type and duration of maintenance and repairs.

501.7 Results of compliance tests.
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Placer County APCD 233 - 9 Rules and Regulations

501.8 Three-hour average NOx emission concentration (expressed as NO2 and 

corrected to 12 percent by volume stack gas CO2).

501.9 Three-hour average CO emission concentration (corrected to 12 percent by 

volume stack gas CO2).

501.10 Startup and shutdown emissions records using averaging periods as required in 

Section 302.1.

501.110 Identification of time periods during which NOx and CO emission limitations are 

exceeded, the reason for the exceedance, and a description of corrective action 

taken.

501.121 Identification of time periods during which operating condition and pollutant 

emission data were not obtained, the reason for not obtaining this information, and a 

description of corrective action taken.

502 CONTINUOUS EMISSIONS MONITORING

502.1 A person operating a unit subject to this rule shall install, calibrate, operate, and 

maintain a Continuous Emissions Monitoring System (CEMS) in accordance with 

applicable requirements of Appendices B and F of Title 40 Code of Federal 

Regulations Part 60 (40 CFR 60).

502.2 The CEMS shall include equipment that measures and records the following:

502.2.1a. Continuous exhaust gas NOx and CO concentrations corrected to 12 

percent by volume stack gas CO2 dry basis.

502.2.2b. Average NOx and CO concentrations calculated on a three-hour average 

basis.

502.3 A person operating a CEMS shall submit an excess emissions and monitoring 

systems performance report to the Air Pollution Control Officer within 30 days after 

the end of each calendar quarter in accordance with 40 CFR 60, Section 60.7(c) and 

(d) and Section 60.13.

502.4 The enhanced monitoring requirements of Sections 113 and 114 of the Federal 

Clean Air Act shall take precedence over the requirements of this Section for facilities 

subject to Rule 507, FEDERAL OPERATING PERMIT PROGRAM.

503 INITIAL COMPLIANCE TEST

503.1 An initial compliance test shall be conducted within 60 days of achieving the 

maximum firing rate at which the unit will be operated, but not later than 180 days 

after initial startup.

503.1.1 Each emission test run shall be conducted while the unit is operated within 

10% of the maximum steady-state steam production rate. No emission 

test shall be conducted during startup, shutdown, or under breakdown 

conditions for the purpose of the initial compliance test.

503.1.2. The initial compliance test shall be conducted for NOx and CO using the 

test methods specified in Section 504.
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Rules and Regulations 233 - 10 Placer County APCD

503.2 At least sixty (60) days prior to the initial compliance test, a written test plan detailing 

the test methods and procedures to be used shall be submitted for approval by the 

Air Pollution Control Officer. The plan shall cite the test methods to be used for the 

determination of compliance with the emission limitations of this rule. The plan shall 

provide the proposed procedures for the characterization of the representative 

biomass materials to be burned during testing.

504 CORRECTION OF EMISSION CONCENTRATIONS: NOx and CO concentrations may be 

corrected to 8 percent by volume stack gas O2 instead of 12 percent by volume stack gas 

CO2 if approved by the Air Pollution Control Officer in a Permit to Operate.

5053 TEST METHODS: A person conducting source tests shall use the following test methods:

503.1 Nitrogen Oxides (NOX): ARB Test Method 100, Title 17, CCR, Section 94114, 

Procedures for Continuous Emission Stack Sampling, or EPA Test Method 7E, 

40 CFR 60, Appendix A. A violation determined by any of these test methods shall 

constitute a violation of this rule.

503.2 Carbon Monoxide (CO): ARB Test Method 10, Title 17, CCR, Section 94109, 

Determination of Carbon Monoxide Emissions from Stationary Sources, or ARB Test 

Method 100, or EPA Test Method 10, 40 CFR 60, Appendix A. A violation determined 

by any of these test methods shall constitute a violation of this rule.

503.3 Carbon Dioxide (CO2): ARB Test Method 100, Title 17, CCR, Section 94114, 

Procedures for Continuous Emission Stack Sampling, or EPA Test Method 3A, 

40 CFR 60, Appendix A.

5064 DURATION OF RECORDS: All records maintained pursuant to this rule shall be retained for 

at least two years from date of entry, with the exception that sources subject to the 

requirements of Rule 507, FEDERAL OPERATING PERMIT PROGRAM, shall retain records 

at least five years. Records shall be made available for inspection by the Air Pollution Control 

Officer upon request.
ATTACHMENT #2

SUBJECT: 

ANALYSIS AND FINDINGS REQUIRED FOR RULE ADOPTION
ANALYSIS AND FINDINGS REQUIRED FOR RULE ADOPTION

1

The following Analysis and the subsequent Findings are intended to address the requirements set 

forth in the Health and Safety Code relating to adoption of a new District Rule, as well as other 

State statutes referenced herein. 

1. Cost-Effectiveness of a Control Measure

California Health & Safety Code (H&S) Section 40703 requires a District to consider and make 

public “the cost-effectiveness of a control measure”. As the proposed rule does not impose new 

requirements but allows alternative emission limits during startup and shutdown, it is not a control 

measure and no analysis is needed. There will be are no direct impacts to any operations that may 

be proposed by an applicant/Permittee.

2. Socioeconomic Impact

H&S Section 40728, in relevant part, requires the Board to consider the socioeconomic impact of 

any new rule if air quality or emission limits are significantly affected. Since proposed Rule 233, 

Biomass Boilers allows the use of alternative emission limits in mass emission rates instead of 

concentration only during startup and shutdown. The new emission limitations will allow or will 

not cause emission increases on a daily, quarterly or annual basis. The proposed rule will not affect 

air quality or emission limitations in Placer County. The evaluation set forth in H&S Section 40728 

is not needed.

3. California Environmental Quality Act (CEQA)

The proposed Rule Amendment is not an activity that may cause a direct or reasonably foreseeable 

indirect physical effect in the environment therefore not considered a “project”, as defined by 

Section 21065 of the California Public Resource Code and Section 15378(b)(4)&(5) of the CEQA 

guidelines. A CEQA analysis is therefore not necessary. 

4. Findings

H&S Code Section 40727 requires the PCAPCD, before adopting, amending, or repealing a rule 

or regulation, to “make findings of necessity, authority, clarity, consistency, nonduplication, and 

reference. These proposed findings are as follows:
ANALYSIS AND FINDINGS REQUIRED FOR RULE ADOPTION

2

A. Necessity – The amendment to the rule is needed to fix a technical requirement which 

was not identified in the previous rule development to address issues which occur 

during startup and shutdown. 

B. Authority – The proposed rule is not prohibited by any provision of law or state or

federal regulation, and is therefore permissible.

C. Clarity – The regulation is in substantial accord with the original rule but the 

amendment allows alternate limits at certain specified times which are startup and 

shutdown most indemnification agreements and is therefore found to be easily 

understood by the persons directly affected by it.

D. Consistency – The regulation is in harmony with, and not in conflict with or 

contradictory to, existing statutes, court decisions, or state or federal regulations.

E. Nonduplication – The regulation does not impose the same requirements as an existing 

state or federal regulation.

F. Reference – All statutes, court decisions, and other provisions of law used by PCAPCD 

in interpreting this regulation is incorporated into this analysis and this finding by 

reference.
ATTACHMENT #3

SUBJECT: 

Staff Report RULE 233, BIOMASS BOILERS
PLACER COUNTY

AIR POLLUTION CONTROL DISTRICT

STAFF REPORT

RULE 233

BIOMASS BOILERS

PROPOSED AMENDMENTS

DECEMBER 10, 2009
Staff Report – Rule 233, Biomass Boilers

Page 1

BACKGROUND

The Federal Clean Air Act, as amended in 1990, required adoption of source specific regulations 

for major sources of nitrogen oxides (NOx) pursuant to Sections 182(b)(2)(C) and 182 (f). These 

sections required the adoption of Reasonable Available Control Technology (RACT) rules. In 

addition, the California Clean Air Act transport mitigation provisions required the adoption of 

Best Available Retrofit Control Technology (BARCT) for sources compromising 75% of the 

actual NOx emission inventory in the District.

Biomass boilers were affected by this requirement. There are currently three facilities with 

biomass boilers in Placer County: Rio Bravo-Rocklin, Sierra Pacific Industries, and SierraPine 

Ltd. Rule 232, Biomass Suspension Boilers, applies to SierraPine Ltd. Rule 233, Biomass 

Boilers, applies to Rio Bravo-Rocklin which operates a fluidized bed biomass boiler and to 

Sierra Pacific Industries which operates a stoker biomass boiler.

Rule 233, Biomass Boilers, was adopted on October 6, 1994 and subsequently approved in the 

California State Implementation Plan (SIP).

The rule limited NOx emission to the least stringent of 115 ppmv corrected to 12% CO2 or 50% 

of the uncontrolled emission concentration in the boiler exhaust. The 115 ppmv limitation 

corresponds to the limitation in Sierra Pacific Industries Prevention of Significant Deterioration 

(PSD) permit issued by the U.S. Environmental Protection Agency (EPA). This emission 

limitation reflected a determination by the U.S. EPA that the selective non-catalytic reduction 

system used to control NOx constituted Best Available Control Technology (BACT). Therefore 

this control technology and limitation would also represent RACT and BARCT which are less 

stringent requirements than BACT.

NOx emissions are measured by a continuous emission monitoring system (CEMS) installed in 

the stack. The concentration is corrected or normalized to 12% CO2 so that one boiler may be 

compared to another. It is also corrected so that an operation can not introduce additional outside 

air into the boiler solely to lower the concentration. The correction is a simple calculation as 

follows:

NOx corrected to 12% CO2 = NOx measured x 12% / CO2 % measured

However, an issue arises when CO2 levels are low. Since the value is in the denominator of the 

formula, the corrected value for NOx concentration will be increased. For example if CO2 drops 

from normal operating levels of 10 to 12 percent down to 6 percent, the NOx concentration 

corrected value will be 12/6 or 2 times the measured value. This may cause the corrected NOx 

concentration value to be an exceedence, if there is a concentration emission limit that is based 

on steady-state operations.

In addition to the intentional dilution of the exhaust gases which the CO2 correction adjusts for 

by increasing the corrected NOx concentration value, low CO2 levels and subsequent high NOx 

concentration values can occur if too much diluant air is added, such as occurs when the 

combustion process is interrupted or combustion is just beginning. The problem occurs primarily 

during startup and shutdown.
Staff Report – Rule 233, Biomass Boilers

Page 2

As will be discussed in detail later in this document, U.S. Environmental Agency (U.S. EPA)

policies on Startups, Shutdowns, and Malfunctions provides for excess emissions during startup 

or shutdown needs to be addressed. An amendment was adopted on October 11, 2007 which 

allowed alternate emission limits during startup and shutdown to be conditions of the Permit to 

Operate for the boilers.

The October 11, 2007, rule amendment was forwarded to the California Air Resources Board 

(CARB) for approval into the California State Implementation Plan (SIP). This was approved by 

CARB and forwarded to the U.S. EPA for approval.

U.S. EPA declined to approve that amendment into the SIP as inconsistent with federal 

regulation and policy. Their response was contained in an email in Attachment #1. The main 

objections were in two areas:

1. The 115 ppm limit for NOx does not apply during startup and shutdown. Instead mass 

emission limits in the Permit to Operate would apply. Although these limits were already 

in place in the both the District Permit to Operate and federal Title V, EPA has requested 

that the limitations be listed in the Rule itself.

2. The amendment must provide a demonstration that both the length of time of the startups 

and shutdown and the emissions were minimized as much as technologically feasible.

In acknowledgement of U.S. EPA intention to disapprove the October 11, 2007, amendment, the 

District requested the withdrawal of the amendment from SIP consideration in a letter dated 

October 14, 2008.

DISCUSSION OF PROPOSED RULE AMENDMENT

As there are only two boilers, one a stoker boiler and one a circulating fluidized bed boiler that 

this rule applies to, Section 101 has been amended to address those specific types of boilers by 

changing the applicability section to read

This rule applies to stoker and circulating fluidized bed boilers and steam generators 

which have a heat input rating of less than 500 million Btu per hour and a potential 

to emit, as defined in Rule 502, NEW SOURCE REVIEW, 25 tons or more of NOx

emissions and which have a primary energy source of biomass consisting of a 

minimum of 75 percent of the total annual heat input.

Any new stoker or circulating fluidized boilers rated less than 500 million Btu per hour would 

have to meet the proposed rule requirements and also apply Best Available Control Technology 

(BACT) to be determined during the permitting process.

If other types of boilers were proposed for installation in Placer County, the equipment would fall 

under other existing boiler rules, or possibly a new regulation would be considered.

Section 200, Definitions, has been amended to add definitions of circulating fluidized bed 

boilers, stoker boilers and a curing startup.
Staff Report – Rule 233, Biomass Boilers

Page 3

Changes were also made to the startup and shutdown definitions. A shutdown starts when fuel 

feed is curtailed and the unit begins cooling from the unit‟s normal operating temperature, as 

specified by the manufacturer, and ends when steam flow is zero or 24 hours has elapsed since 

the start of the shutdown, whichever occurs first.

A boiler only has one purpose, and that is to generate steam. The steam can be used for various 

reasons, including electric generation. When boiler conditions that do not allow for steam 

generation are reached, the boiler's operation is terminated. This point represents a useful 

indicator for the end of a "shutdown". Boiler steam flow is easily measured and is continuously 

monitored and recorded in the control room by the plant operator.

The steam flow was chosen instead of temperature because steam flow is more indicative of the 

operational condition of the boilers with regard to the end of a shutdown versus a temperature 

measurement. In addition, because steam flow is likely to cease before any likely temperature 

threshold that might be used to indicate a shutdown condition such as 150 degrees Fahrenheit or 

a “cold” shutdown at ambient temperature, the period of time defined as a shutdown using a zero 

steam flow threshold versus a temperature threshold is shortened. For example, Rio Bravo 

indicates that steam flow goes to zero at a boiler temperature of approximately 750 degrees F. At 

that time the biomass fuel is completely consumed and emissions are negligible. (See Attachment 

#4: Memo from Rio Bravo.) Therefore using zero steam flow to denote the end of a shutdown 

effectively reduces the possible period of time during which alternative emission limits for 

shutdown may be used. In addition, the alternative emission limits proposed for shutdowns are 

only effective when the CO2 level is reduced to below 10% due to the shutdown conditions of 

reduced combustion.

Historically, a shutdown under which the alternative emission limits would be used occurs in 

about approximately one-third of the shutdowns. Both facilities affected by this rule are limited by 

permit conditions to sixty (60) per year. One facility, Rio Bravo, reported two (2) qualifying 

shutdowns where alternative limits would have been used for a combined fourteen (14) hours and 

the other affected facility reported thirteen (13) shutdowns where alternative limits would have 

been used for a total of sixty-three (63) hours.

A startup is defined as the period of time a unit is heated to the normal operating temperature, as 

specified by the manufacturer. A normal startup shall not exceed 24 hours. A curing startup shall 

not exceed 96 hours.

Section 301, Limitations, which addresses limitations during normal operation, has been changed 

to add a carbon monoxide (CO) for each type of boiler. These limitations currently exist in the 

Permits to Operate for each facility.
Staff Report – Rule 233, Biomass Boilers

Page 4

TABLE 1 - NOx and CO Emission Limitations

Type of Boiler NOx CO

Circulating Fluidized Bed 115

ppmv corrected to 12% 

CO2

(3 hour rolling average)

400

ppmv corrected to 12%

CO2

(3 hour rolling 

average)

Stoker 115

ppmv corrected to 12% 

CO2

(3 hour rolling average)

1000

ppmv corrected to 12%

CO2

(3 hour rolling 

average)

To address EPA's concerns in effort to make the amendment SIP approvable, this rule amendment 

includes the mass emission limitations in pounds per hour as follows in Section 302, Startup and 

Shutdown Provisions.

Table 2 Startup and Shutdown Emission Limitations

Type of Boiler NOx CO

Circulating Fluidized Bed 35

pounds per hour

(24 hour block average)

56

pounds per hour

(24 hour block average)

35

pounds per hour

(72 hour block average during 

curing of refractory)

56

pounds per hour

(72 hour block average 

during curing of refractory )

Stoker 37.6

pounds per hour

(3 hour rolling average)

170

pounds per hour

(3 hour rolling average)

A normal startup will be limited to 24 hours. A startup which involves curing of refractory may 

not exceed 96 hours. A shutdown will also be limited to 24 hours.

Section 302.1 required emissions units subject to this rule to have a limit on the maximum number 

of startup and shutdowns allowed in a calendar year as a permit condition. Currently both facilities 

affected by this rule have these limits in their permits and this section should be removed as it is 

no longer needed.

MINIMIZING EMISSIONS AND DURATION OF STARTUP AND SHUTDOWN

U.S. EPA policy requires a demonstration that both the length of time of the startups and 

shutdown and the emissions are minimized as much as technologically feasible. (See Attachment 

#2)

As discussed earlier, high NOx concentrations may occur when the combustion process is 

interrupted or combustion is just beginning during startup and shutdown because of the correction 
Staff Report – Rule 233, Biomass Boilers

Page 5

to 12% CO2 and the ammonia injection NOx control are not effective. The proposed rule

amendment minimizes emissions at these times by:

1. Prohibiting the exceedences of the same pounds per hour limitations that were in the 

facility permits for normal operations. These pound per hour limitations for both facilities 

are more restrictive than the concentration limitation of 115 ppmv @12% CO2.

2. Emissions may go to zero if the shutdown requires maintenance inside the boiler. This is 

the case when the affected facilities need to repair tube leaks or conduct semi-annual 

maintenance. Typically the repair times last one to two days. Semi-annual maintenance 

lasts approximately seven days. For example, if the boiler is normally averaging 30 

pounds per hour of NOx, but is down for 7 days, there would 5, 040 pounds less NOx 

emissions.

For Rio Bravo's circulating fluidized bed boiler, the normal operating limitation of 115 ppm NOx 

corrected to 12% CO2 equates to 83.6 pounds per hour. The proposed NOx limit during startup 

and shutdown is 35 pounds per hour. The normal operating limit of 400 ppm CO corrected to 12% 

CO2 equates to 176.9 pounds per hour. The proposed CO limit during startup and shutdown is 56 

pounds per hour.

For Sierra Pacific Industries‟ stoker boiler, the normal operating limitation of 115 ppm NOx 

corrected to 12% CO2 equates to 60.6 pounds per hour. The proposed NOx limit during startup 

and shutdown is 37.6 pounds per hour. The normal operating limit of 1000 ppm CO corrected to 

12% CO2 equates to 227.5 pounds per hour. The proposed CO limit during startup and shutdown 

is 170 pounds per hour. 

These calculations are shown in Attachment #3.

U.S. EPA prepared a Policy Clarification guidance memorandum1(1982-1983 timeframe) that 

presented a policy for SIPs regarding excess emissions during malfunctions, startup, shutdown, 

and maintenance. Interpretation of this policy allowed for enforcement discretion at national levels 

for emission exceedances during startup and shutdown (SU/SD) events. During a review of SIPs, 

U.S. EPA observed several provisions that appeared to be inconsistent with the original policy. 

The 1999 U.S. EPA Memorandum by Steven Herman and Robert Perciasepe “State 

Implementation Plans (SIPs): Policy Regarding Excess Emissions During Malfunctions, Startup, 

and Shutdown” was prepared and distributed to the control authorities. It was intended to take the 

opportunity to clarify several issues of interpretation and reaffirm and supplement the original 

policy. Various issues were discussed, including specific emission limits for startup and shutdown 

events, the “affirmative defense” concept, and how modifications to SIPs could occur and meet 

the requirements described in the 1999 U.S. EPA memorandum.

The main question of interpretation that has arisen regarding the original policy is whether a State 

may go beyond an “enforcement discretion” approach and include in its SIP a provision that 

would, in the context of an enforcement action for excess emissions, excuse a source from 

penalties if the source can demonstrate that it meets certain objective criteria (an “affirmative 

 

1 Kathleen Bennett, Assistant Administrator for Air, Noise and Radiation dated September 28, 1982 and 

February 15, 1983.
Staff Report – Rule 233, Biomass Boilers

Page 6

defense”). The 1999 memorandum clarifies that States have the discretion to provide such a 

defense to actions for penalties brought for excess emissions that occur during certain 

malfunction, startup, and shutdown episodes.

In general, because excess emissions that occur during these periods are reasonably foreseeable, 

they should not be excused. However, EPA recognizes that, for some source categories, even the 

best available emissions control systems might not be consistently effective during startup or 

shutdown periods. In areas where no single source or small group of sources has the potential to 

cause an exceedance of the NAAQS or PSD increments, these startup and shutdown periods may 

be addressed in the standards. This can be done through narrowly-tailored SIP revisions that take 

into account the potential impacts on ambient air quality caused by the inclusion of these excess 

emissions. In these instances, as part of its justification of the SIP revision, the State should 

analyze the impact of the potential worst-case emissions that could occur during startup and 

shutdown periods.

U.S. EPA recognizes that there are several approaches that may be used to incorporate excess 

emission provisions into SIPs so that they can in turn provide greater certainty to the regulated 

community. The main approaches are:

Enforcement Discretion, and/or

General Affirmative Defense Provision

In order to provide the most certainty to the regulated community, a SIP revision using a general 

affirmative defense provision meeting the requirements of the EPA Policy on Excess Emissions 

During Malfunctions, Startup, and Shutdown can be pursued. This is a more definitive approach, 

and thus does not rely on “agency enforcement discretion” for each event.

This amendment to Rule 233 is an opportunity to amend this Rule to include specific emission 

limits and conditions for startup and shutdown events in accordance with the United States 

Environmental Protection Agency (U.S. EPA) 1999 Memorandum, in regard to setting standards

satisfying affirmative defense provisions. Accordingly, a justification discussion of how each of 

the seven points described in the memorandum is met is provided in the following paragraphs.

The normal operating emission limits for NOx and CO expressed as a concentration will not apply 

during narrowly defined startup and shutdown periods. Instead, alternative emission limits in 

pounds per hour for startup and shutdown will apply and will be defined in the SIP amendment. 

To align with the EPA Policy, it must be demonstrated that the revision meets the following 

requirements:

U.S. EPA Policy Requirements:

1. Requirement: The revision must be limited to specific, narrowly-defined source 

categories using specific control strategies (e.g., cogeneration facilities burning 

natural gas and using selective catalytic reduction).

Justification Discussion: The Rule 233 SIP revision applies only to the following source category: 

Stoker and fluidized bed boilers and steam generators which have a potential to emit, as defined in 

Rule 502, New Source Review, 25 tons or more of NOx emissions and which have a primary 
Staff Report – Rule 233, Biomass Boilers

Page 7

energy source of biomass consisting of a minimum of 75 percent of the total annual heat input. 

This rule applies to two facilities which utilize selective non-catalytic reduction (SNCR) to control 

NOx emissions. These systems inject ammonia into the boilers.

2. Requirement: Use of the control strategy for this source category must be technically 

infeasible during start-up or shut-down periods.

Justification Discussion: The NOx control technology (either SCR or SNCR) requires a specific 

operating temperature range in order to function. Therefore, the NOx emission control system is 

technically limited during periods of start-up and shut-down periods when the boiler is not within 

the temperature range.

The SNCR process does not operate at low system temperatures (less than 1,400°F) and functions 

best at temperatures between 1,600°F and 1,800°F. During a startup, the combustion system is 

fired on natural gas (NG) or other similar startup fuel until the primary fuel can begin to be 

introduced into the system. Once the temperature of the combustion system reaches the normal 

operating temperature (and thermal equilibrium), ammonia injection begins, which allows for the 

non-catalytic NOx reduction reactions to occur.

If ammonia is injected before the system reaches the normal operating temperature, significant 

emissions of ammonia (ammonia slip) occur as the ammonia is not reduced by conversion to 

nitrogen and water prior to exiting the stack.

In addition, due to the combustion process characteristics, the CO emissions undergo significant 

variation until the flame stability improves. Generally, the flame stability improves as fuel flow 

increases and the system temperature rises. Once the system reaches thermal equilibrium, CO 

emissions are controlled by stable flame characteristics, which promote CO emissions that are in 

compliance with normal operations permit limits.

During a shutdown, the ammonia injection continues until the temperature of the system drops 

below the normal operating range for the SCR or SNCR control process to occur. The ammonia 

flow is then shut-off to eliminate ammonia slip. Thus, during a shutdown, the NOx control system 

can not be used to control NOx emissions throughout the complete shutdown cycle.

Furthermore, during a shutdown the combustion process characteristics vary and thus the flame 

stability can degrade sufficiently to cause high CO emissions before the fuel (either primary fuel 

or NG/propane/or other similar stabilization fuel) is completely shut off.

3. Requirement: The frequency and duration of operation in startup or shutdown mode 

must be minimized to the maximum extent practicable.

Justification Discussion: This requires implementation of narrowly defined periods for startup and 

shutdown which are unique to each boiler type. A startup commences when fuel is first introduced 

into the combustion unit. A startup ends when the combustion unit reaches normal operating 

temperatures as defined for each specific combustion unit. Typically for a woodfired boiler startup 

internal temperatures must not be raised more than 100 degrees F per hour or damage may occur 

to the boiler tubes. Initial preparation and firing takes several hours plus raising temperature from 
Staff Report – Rule 233, Biomass Boilers

Page 8

70 degrees to 1250 degrees F takes another 12 hours. A startup will not last longer than 24 hours 

(96 hours for a concrete curing startup).

The reason for a curing startup length of 96 hours is that this represents the length of time required 

to cure the refractory when it is poured in the combustor area.

The startup temperatures are controlled by the amount of fuel introduced into the boiler.

By definition, a shutdown commences when fuel load is reduced in preparation for shutting fuel 

flow off and the boiler begins cooling from normal operating temperature. It ends when one of the 

following occurs: (1) there is no steam flow, (2) more than 24 hours has elapsed since the start of 

shutdown. The duration is 24 hours to allow for sufficient time for most systems to cool down 

sufficiently so that the boiler system can be safely entered for maintenance purposes.

The number of startup and shutdown events must be limited for each facility to ensure that the 

emissions from these narrowly defined startup and shutdown events are minimized and accounted 

for in the ambient air modeling scenarios.

The number of startup and shutdown events for each facility over the course of a year is dependent 

on many factors including:

Type of facility (peaker facility, base load facility, utility boiler, independent power 

producer, etc.)

Type of fuel used (biomass from urban sources, biomass from agricultural sources, 

biomass from forests, biomass from industrial sources, etc.)

Boiler and facility design (Stoker boiler, circulating fluidized bed, bubbling bed, 

etc.)

If the facility has a power purchase agreement (PPA)

Age of facility 

Is original fuel still available?

Does available fuel meet all original design criteria? Or are there additional 

constituents that may cause problems in system?

Does available fuel meet all pollution control equipment design criteria? Or are 

there additional constituents that may cause problems in system?

The affected facilities are businesses, and thus it is in their best interest to be in “normal 

operations” as much as possible, and not in the process of shutting-down, starting-up, or in an 

outage. Going through a shutdown and startup cycle frequently is not in the interests of the facility 

and will be avoided to the greatest extent possible. Accordingly, market forces and finances will 

limit the viability of each facility if shutdowns and startups occur too frequently.

A permitted number of startup and shutdown events may be derived from the anticipated number 

of startups and shutdowns required for the individual facility due to equipment variations and 

operating characteristics which are inherent to the individual design of each facility. Operations 

includes: scheduled maintenance, forced outages, utility dispatch, breakdowns and malfunctions. 

After reviewing all of the above factors and other performance related concerns, the number of 

startups and shutdowns are limited by permit conditions to provide a “not to exceed limit” 
Staff Report – Rule 233, Biomass Boilers

Page 9

although the actual number of startups and shutdowns will likely be much less and dictated by the 

desire of each facility to minimize the loss of revenue that outages represent. For cap purposes, 

Rio Bravo is limited to twenty (20) in a quarter and no more than sixty (60) in a year that exceed 

the normal operating emission limits. Sierra Pacific Industries is limited to fifty (50) per year.

4. Requirement: As part of its justification of the SIP revision, the state should analyze 

the potential worst-case emissions that could occur during startup and shutdown 

periods.

Justification Discussion: The worst case emissions were reviewed. The concentrations in the 

exhaust gas increase but the pounds per hour averaged over the periods shown in Table 2 are not 

expected to be exceeded. This indicates there are no impacts.

The emissions from each facility during a startup and shutdown period ramps-up to and rampsdown from the normal operating conditions and permit limits. For example, during startup, the 

emission control system (NOx) is not functioning and the combustion characteristics are poor 

(CO), thus, the NOx emissions and CO emissions are high in terms of concentration at the onset of 

a startup event. The NOx emissions are high because there is no control of emissions and the 

combustion process results in localized temperatures high enough to cause the N2 to NOx reaction 

to occur. The CO emissions are high because the poor combustion conditions do not facilitate 

complete combustion. This is a result of many factors including poor mixing, high localized 

temperatures, and low temperatures on average in the combustor region.

As the startup process continues, the startup fuel flow rate is increased with the result allowing 

steadily climbing average temperatures in the combustor, improving mixing characteristics, and 

overall better combustion characteristics to occur. This causes lower CO emissions due to the 

more complete burnout of the startup fuel. When the system heats up sufficiently, the NOx control 

system will begin operating, this usually occurs near the end of a startup event for facilities that 

use selective non-catalytic reduction (SNCR), because the optimum operating temperature range 

for the NOx control system is 1,500°F to 1,850°F.

Due to the nature of the combustion process, the startup emission limits are less likely to be 

exceeded the longer that the startup lasts and the longer the averaging period. However during the 

initial phases of a startup, any emission limits are likely to be exceeded for a short period of time 

because of the lack of effective pollution control techniques. For example, CO emissions will 

spike during initial phases of startup. As the startup progresses, the concentration of CO in the 

exhaust gases will drop to the normal operating levels.

Likewise the NOx emissions will spike during the startup event, but due to the nature of 

combustion process, and prior to initiating ammonia injection to begin the SNCR reaction. 

5. Requirement: All possible steps must be taken to minimize the impact of emissions 

during start-up and shut-down on ambient air quality.

Justification Discussion: Each source must provide to the District a description of the actions that 

will be taken to minimize emissions during startup and shutdown events. These will be 

incorporated into their Permit.
Staff Report – Rule 233, Biomass Boilers

Page 10

The startup and shutdown emission limits that were chosen for CO and NOx are the same limits 

that each facility complies with during normal operations but with a longer averaging period for 

the circulating fluidized bed boilers. The startup and shutdown limits (lbs/hour) are derived from 

the currently existing daily limits (lbs/day) that are in the PTO. The intent is to limit a facility to 

the same hourly emission rate, however allow for the emission spikes that occur during all startup 

and shutdown combustion events. The averaging period for circulating fluidized bed boilers for 

normal startup and shutdown events is a block 24 hour period, with the total startup and shutdown 

event not to exceed 24 hours.

The startup emission limit that was chosen for CO and NOx for a curing startup event is also the 

same limits that the facility complies with during normal operations but with a longer averaging 

period for circulating fluidized bed boilers. The intent is to limit the facility to the same hourly 

emission rate, however, allow for emission spikes that occur during the curing event. Since a 

curing event can last for a period longer than 24 hours depending on how much, which refractory 

areas, and what type of concrete are re-poured a longer averaging period is required. Quantity, 

location, and type of concrete can all affect the total curing time. The reason for this is that the 

curing process normally consists of heating the boiler system at a pre-determined rate and holding 

the system temperature constant at several points to allow for the concrete to dry and „set‟. 

Different quantities of concrete, areas repaired, and type of concrete all can affect the temperature 

curve and the temperature duration levels used during the curing process. The averaging period for 

a curing startup is thus minimized to a block 72 hour period, with the total curing startup not to 

exceed 96 hours.

U.S. EPA has issued startup and shutdown emission limits with block averages in other permits. 

The twenty-four or seventy-two block averaging periods represent normally expected startup or 

shutdown events. The block averaging period hours will be flagged in the CEMS data and will 

facilitate identifying and counting of each event. The CEMS averaging calculations will include 

valid data hours.

A facility is minimizing emissions by following the manufacturer‟s startup and shutdown 

procedures, which minimizes the “wear and tear” on the system. Deviating from these operational 

practices will increase maintenance costs, increase downtime for a facility, increase the number of 

startups and shutdowns, and increase the annual emissions from startup and shutdown events. The 

emission limits presented represent good engineering practice when the system is not at 

equilibrium (and therefore emitting higher CO levels than during normal operations) and the NOx 

air pollution control is not functioning due to technical constraints (and therefore emitting higher 

NOx levels than normal operations).

6. Requirement: At all times, the facility must be operated in a manner consistent with 

good practice for minimizing emissions and the source must have used best efforts 

regarding planning, design, and operating procedures to meet the otherwise 

applicable emission limitation.

Justification Discussion: Sources will be required in their Permit to be operated in a manner 

consistent with good practice for minimizing emissions, and the source must have used best 

efforts regarding planning, design, and operating procedures to meet the otherwise applicable 

emission limitations.
Staff Report – Rule 233, Biomass Boilers

Page 11

It should be understood that the facilities are businesses, and thus it is in their best interest to attain 

“normal operations” as soon as possible. Generating electricity at design conditions is the most 

efficient and cost effective scenario.

7. Requirement: The owner or operator’s actions during startup and shutdown periods 

must be documented by properly signed, contemporaneous operating logs, or other 

relevant evidence.

Justification Discussion: Sources must demonstrate that actions are being taken during startup and 

shutdown events to minimize emissions. This will be a requirement in their permit, and can be 

achieved in several ways: by maintaining operating logs, identifying periods of startup and 

shutdown in the CEMs, reported in quarterly and annual reports, and implementing site specific 

Plant Operating Procedures (POP), following manufacturer recommendations/guidelines during 

these periods.

The manufacturer‟s recommended operating practices and POPs can be discussed with agency 

personnel to describe how the plant operations minimized emissions during startup and shutdown 

events. 

On a case by case basis, the source can also offer other relevant evidence that describes these 

actions for District consideration.

RACT Evaluation

The RACT/BACT/LAER database contains case-specific information on the "Best Available" air 

pollution technologies that have been required to reduce the emission of air pollutants from 

stationary sources (e.g., power plants, steel mills, chemical plants, etc.). This information has been 

provided by State and local permitting agencies. The Clearinghouse also contains a regulation data 

base that summarizes EPA emission limits required in New Source Performance Standards 

(NSPS), National Emission Standards for Hazardous Air Pollutants (NESHAP), and Maximum 

Achievable Control Technology (MACT) standards. The database information pertains to normal 

operations of the facilities as can be seen because the facilities have pollution control equipment 

that does not operate at ambient and low temperatures (startup temperatures). Please note that the 

list reviewed has not been confirmed to be “demonstrated”.

The RACT/BACT/LAER database was reviewed for comparison purposes and the following 

information was identified:

The lbs/hr CO emission limit for Rio Bravo's circulating fluidized bed boilers (CFBs) equates to 

0.16 lbs/MMBtu. The lbs/hr CO emission limit for Sierra Pacific Industries stoker boilers equates 

to 0.59 lbs/MMBtu. The CO emission limit for facilities permitted since 1990 ranged from 0.1 

lbs/MMBtu to 0.63 lbs/MMBtu, with most of the units (10 of 14) in the range 0.3 ≤ x ≤ 0.5 

lbs/MMBtu. Two units had CO emission limits slightly lower than the 0.16 lbs/MMBtu presented 

in this revision. However, in one case, the system was required to have a CO oxidation catalyst 

(RBLC ID OH-0307) and in the other case (RBLC IDNH-0013), the averaging period was 24 

hours above 50% load. Interestingly, one other facility was required to install a CO oxidation 

catalyst, though the emission limit was 0.3 lbs/MMBtu. In the vast majority of the data reviewed, 
Staff Report – Rule 233, Biomass Boilers

Page 12

the control technology for CO emissions was described as “good combustion practices” and/or 

“combustor design.”

The lbs/hr NOx emission limit for the Rio Bravo's CFB equates to 0.098 lbs/MMBtu. The lbs/hr 

NOx emission limit for the Sierra Pacific Industries stoker boiler equates to 0.13 lbs/MMBtu. The 

NOx emission limit for facilities permitted since 1990 ranged from 0.075 lbs/MMBtu to 0.6 

lbs/MMBtu, with most of the units (13 of 17) in the range 0.1 ≤ x ≤ 0.3 lbs/MMBtu. One unit had 

a NOx emission limit slightly lower than the 0.098 lbs/MMBtu presented in this revision. 

However, in this case (RBLC ID NH-0013), the averaging period was 24-hours. 

The existing emission limits for the normal operations meet RACT/BARCT. Additionally the 

proposed startup and shutdown limits presented in this Rule 233 amendment also meet the 

RACT/BARCT requirements and do not represent a relaxation of current emission limits because 

the same pound/hour limitations apply.

DISCUSSION OF PROPOSED RULE AMENDMENT

Applicability:

The amendment changes the applicability to stoker and circulating fluidized bed boilers and steam 

generators with a heat input of less than 500 million Btu per hour. These are the two types of 

boilers operated in Placer County to which this rule currently applies.

Exemptions:

There are no changes to the Exemptions.

Definitions:

Definitions of a circulating fluidized bed boiler, stoker boiler and curing startup were added. The 

definitions of startup and shutdown were amended.

Standards:

Carbon monoxide emission limitations were added to Section 301.1.

Mass emission limitations for NOx and CO during startup and shutdown were added to Section 

302.1. For a circulating fluidized bed boiler, the proposed NOx limitations are 35 pounds per hour 

on a 24 hour average (and for curing of refractory on a 72 hour average) and CO limitations of 56 

pounds per hour on a 24 hour average (and for curing of refractory on a 72 hour average). For a 

stoker boiler, the proposed NOx limitations are 37.6 pounds per hour on a 24 hour average and CO 

limitations of 170 pounds per hour on a 24 hour average.

The proposed amendment removes Section 302.1.c. which required a limit on the number of 

startups and shutdowns in a calendar year as a permit condition.
Staff Report – Rule 233, Biomass Boilers

Page 13

Administrative:

There are no changes to the Administrative Requirements.

Monitoring and Records:

Section 501.5 was changed to require records of the duration of each startup and shutdown.

Section 501.10 was added to require records of the startup and shutdown emissions.

FINDINGS

FINDING DEFINITION REFERENCE

Authority The District is permitted or required 

to adopt, amend, or repeal the rule by 

a provision of law or a state or

federal regulation.

California Health and Safety Code, 

Section 40702 and Section 41010; 

1990 Federal Clean Air Act, Section 

110(a)(2)(H) and Section 182(d).

Necessity The District has demonstrated that a 

need exists for the rule, or for its 

amendment or repeal.

It is necessary for the District to 

adopt this rule in order to fulfill the 

requirements of the Federal Clean 

Air Act Amendments of 1990 and 

seek SIP approval.

Clarity The rule is written or displayed so 

that its meaning can be easily 

understood by the persons directly 

affected by it.

There is no indication at this time 

that the rule is not written in such a 

manner that the person affected by 

the rule can easily understand it.

Consistency The rule is in harmony with, and not 

in conflict with or contradictory to, 

existing statutes, court decisions, or 

state or federal regulations.

The District has found that the rule is 

consistent with existing state and 

federal guidelines.

Non-duplication The rule does not impose the same 

requirements as an existing state or 

federal regulation, unless the District 

finds that the requirements are 

necessary or proper to execute the 

powers and duties granted to, and 

imposed upon the District.

NSPS, Subpart Da and Db apply to 

these boilers but the requirements are 

less stringent than Rule 233.

Reference Any statute, court decision, or other 

provision of law that the District 

implements, interprets, or makes 

specific by adopting, amending, or 

repealing the rule. An example of 

this would be the 1988 EPA State 

Implementation Plan call to revise 

District rules.

This rule is being proposed because 

of the requirements of the Federal 

Clean Air Act Amendments of 1990.
Staff Report – Rule 233, Biomass Boilers

Page 14

SUMMARY

This amendment has been proposed to address comments from U.S. EPA and to make Rule 233, 

Biomass Boilers, SIP approvable. The amendment places requirements that are currently in the 

Permits to Operate for two facilities in Placer County into this rule.

Attachments(s) #1: EPA Comments on 2007 Amendment to Rule 233

#2: 1999 U.S. EPA Policy 

#3: Calculations

#4: Rio Bravo Memorandum
ATTACHMENT #1

SUBJECT:

EPA Comments on 2007 Amendment to Rule 233


ATTACHMENT #2

SUBJECT:

1999 U.S. EPA Policy










ATTACHMENT #3

SUBJECT:

Calculations
Rio Bravo Rocklin - Circulating Fluidized Bed Boiler

NOx Calculations (Enter number in cell with blue text)

ppm corrected to 12% CO2 115

typical %CO2 during normal operation 12.23

ppm actual = 117.20

dscfm =dry standard cubic feet per minute= 98,023

SV = specific molar volume = 379.5 @ 60 degrees F

Qsd = flowrate dscfm

MW = NOx = 46

lbs/hr = 

ppm x 10^-06[MW]/SV x Qsd x 

60 lbs/day

83.6 NOx lbs/hr 2005.3 lbs/day

Input 356.8 MMBtu/hr

lbs/MMBtu= 0.23

CO Calculations (Enter number in cell with blue text)

ppm corrected to 12% CO2 400

typical %CO2 during normal operation 12.23

ppm = 407.67

dscfm=dry standard cubic feet per minute= 98,023

SV = specific molar volume = 379.5 @ 60 degrees F

Qsd = flowrate dscfm

MW = CO 28

lbs/hr = 

ppm x 10^-06[MW]/SV x Qsd x 

60 lbs/day

176.9 CO lbs/hr

Input 356.8 MMBtu/hr

lbs/MMBtu= 0.50
Sierra Pacific Industries - Stoker Boiler

NOx Calculations (Enter number in cell with blue text)

ppm corrected to 12% CO2 115

typical %CO2 during normal operation 17.23

ppm actual = 165.12

dscfm=dry standard cubic feet per minute= 50,427

SV = specific molar volume = 379.5 @ 60 degrees F

Qsd = flowrate dscfm

MW = NOx = 46

lbs/hr = 

ppm x 10^-06[MW]/SV x Qsd x 

60 lbs/day

60.6 NOx lbs/hr 1453.4 lbs/day

Input 356.8 MMBtu/hr

lbs/MMBtu= 0.17

CO Calculations (Enter number in cell with blue text)

ppm corrected to 12% CO2 1000

typical %CO2 during normal operation 12.23

ppm = 1019.17

dscfm=dry standard cubic feet per minute= 50,427

SV = specific molar volume = 379.5 @ 60 degrees F

Qsd = flowrate dscfm

MW = CO 28

lbs/hr = 

ppm x 10^-06[MW]/SV x Qsd x 

60 lbs/day

227.5 CO lbs/hr

Input 356.8 MMBtu/hr

lbs/MMBtu= 0.64
ATTACHMENT #4

SUBJECT:

Rio Bravo Memorandum
MEMORANDUM

DATE: November 24, 2009

TO: John Finnell

FROM: Dr. Ted Guth, Maggie Estrada, Jack Snider

SUBJECT: Rio Bravo Rocklin

CC: Response to EPA Questions re: Rule 233

John: Please convey these thoughts to the person at EPA asking questions. 

1. Steam flow goes to zero during every shutdown. 

2. Steam flow goes to zero at a boiler temperature of approximately 750°F.

3. When the boiler temperature falls to approximately 750°F, the fuel is 

completely consumed and stack emissions cease.

4. When the boiler is at approximately 750°F, a “warm startup” can occur. It 

is estimated that the “warm startup” scenario occurs after about one-third of 

Rocklin‟s controlled shutdowns. Conversely, a “cold startup” occurs after 

approximately two-thirds of Rocklin‟s controlled shutdowns. 

5. During a maintenance outage, the boiler temperature will drop to between 

140°F and ambient to allow maintenance crews to safely enter and perform 

work within the boiler. Following a maintenance outage, a boiler “cold 

startup” would occur. 
6. The type and length of maintenance performed (inside or outside of the 

boiler) will determine whether a boiler “warm startup” or “cold startup” is 

necessary. A “warm startup” is always preferred, since it is the most 

efficient due to the least amount of heat lost and minimizes the stack 

emissions and the startup time.