CALIFORNIA AIR RESOURCES BOARD 

APCD/AQMD RULE EVALUATION FORM -- Page 1

(Electronic Format) 

I. GENERAL INFORMATION

District: Placer County Air Pollution Control District

Rule No(s): 233 Date adopted/Amended/Rescinded: December 10, 2009

Rule Title(s): Biomass Boilers

Date Submitted to ARB: December 30, 2009

If an Amended Rule, Date Last Amended (or Adopted): October 11, 2007

Is the Rule Intended to be Sent to the U.S. EPA as a SIP Revision? Yes No (If No, do not complete remainder of form)

District Contact: John Finnell Phone Number: (530) 745-2324 E-mail Address: jfinnell@placer.ca.gov

Narrative Summary of New Rule or Rule Changes: New Rule Amended Rule 

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. 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.

The District requested the withdrawal of the amendment from SIP consideration and has worked with both the 

sources involved and EPA to prepare an approvable amendment.

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.

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.
CALIFORNIA AIR RESOURCES BOARD 

APCD/AQMD RULE EVALUATION FORM -- Page 2

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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, within 2 to 5 hours, and 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.

Section 301, Limitations, which addresses limitations during normal operation, has been changed to add a carbon 

monoxide (CO) limitation for each type of boiler. These limitations currently exist in the Permits to Operate for 

each facility.

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 in Section 302, Startup and Shutdown Provisions.

Pollutant(s) Regulated by the Rule (Check): ROG (NOx) SO2 

 (CO) PM TAC (name): 

II. EFFECT ON EMISSIONS

Complete this section ONLY for rules that, when implemented, will result in quantifiable changes in emissions. Attach reference(s) for emission factor(s) 

and other information. Attach calculation sheet showing how the emission information provided below was determined. 

Net Effect on Emissions: Increase Decrease N/A 

Emission Reduction Commitment in SIP for this Source Category: NA

Inventory Year Used to Calculate Changes in Emissions: NA Area Affected: NA

Future Year Control Profile Estimate (Provide information on as many years as possible): 

NA
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5/1/2002 

3

Baseline Inventory in the SIP for the Control Measure: NA

Emissions Reduction Commitment in the SIP for the Control Measure: NA

Revised Baseline Inventory (if any): NA

Revised Emission Reduction Estimate (if developed): NA

Note that the district’s input to the Rule Evaluation Form will not be used as input to the ARB’s emission forecasting and 

planning. 

III. SOURCES/ATTAINMENT STATUS

District is: Attainment Nonattainment Split 

Approximate Total Number of Small (<100 TPY) Sources Affected by this Amendment: 0

Percent in Nonattainment Area: NA% 

Number of Large (> 100 TPY) Sources Controlled: 2 Percent in Nonattainment Area: 100% 

Name(s) and Location(s) (city and county) of Large (> 100 TPY) Sources Controlled by Rule (Attach additional sheets as 

necessary): Rio Bravo, Lincoln and Sierra Pacific Industries, Lincoln.

IV. EMISSION REDUCTION TECHNOLOGY

Does the Rule Include Emission Limits that are Continuous? Yes No 

If Yes, Those Limits are in Section(s) Section 301, Limitations and Section 302, Startup and Shutdown Provisions of the 

Rule. 

Other Methods in the Rule for Achieving Emission Reductions are: NA

V. OTHER REQUIREMENTS

The Rule Contains: 

Emission Limits in Section(s): Section 301, Limitations and Section 302, Startup and Shutdown Provisions Work 

Practice Standards in Section(s): Section 401, Operation and Maintenance Plan

Recordkeeping Requirements in Section(s): Section 501, Recordkeeping Reporting Requirements in Section(s): Section 

502.3.
CALIFORNIA AIR RESOURCES BOARD 

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(Electronic Format) 

VI. IMPACT ON AIR QUALITY PLAN

 No Impact Impacts RFP Impacts attainment 

Discussion: The amendment adds CO limitations to the Limitations and also NOx and CO pounds per hour limitations to 

the Startup and Shutdown Provisions. These limitations are currenlty in existing permits to operate.