San Luis Obispo County APCD 213-1 8/10/93

RULE 213. CALCULATIONS 

 (Adopted 11/5/91; Revised 8/10/93)

A. APPLICABILITY 

This Rule specifies the provisions by which emission increases, emission reductions, and 

profile checks for offsets shall be calculated. Emission increases and emission reductions 

shall be calculated separately. Both the emission increase and emission decrease sections 

shall apply for many cases where an emissions unit is being replaced, modified, or 

relocated. Only the emission increase section would apply for new emissions units. 

B. POTENTIAL TO EMIT 

The potential to emit is an emission limit which specifies the maximum quantity of each 

air pollutant which may be emitted by an emission unit during a 12 calendar month 

rolling period. This limit shall be based on any period of 12 consecutive calendar months 

and shall be expressed in the units of tons per year. The potential to emit shall be 

calculated based on the maximum design capacity or other operating conditions which 

reflect the maximum potential emissions, unless specific limiting conditions on the 

Authority to Construct and/or Permit to Operate restrict emissions to a lower level. 

C. ACTUAL EMISSIONS 

The actual emissions of air pollutants from an emission unit shall be calculated based on 

the actual operating history of the emission unit. The actual operating history of the 

emission unit shall be averaged over a period of three years immediately preceding the 

date of application to bank emission reduction credits, or a more representative period, as 

determined by the Air Pollution Control Officer (APCO), of three consecutive years 

during the five years immediately preceding the date of such application. Actual 

emissions shall be expressed in the units of tons per year. In no case shall the actual 

emissions exceed the permitted emissions. If at any time during the specified three year 

period that an emissions unit was operated in violation of any applicable federal, state or 

District law, rule, regulation, order, or permit condition, then the actual emissions shall be 

adjusted to reflect the level of emissions that would have occurred if such violation did 

not occur. Permit conditions and permitted emissions shall only be applicable to 

emission units for which a Permit to Operate is required. 

D. EMISSION INCREASES 

1. Emission increases from the addition of an emission unit shall be calculated by 

using the potential to emit for the new emission unit. 

2. Emission increases from a modified or replacement emission unit shall be 

calculated as, the emission unit's post-project potential to emit adjusted to reflect 

the application of the current control technology required under Rule 204.A minus 
San Luis Obispo County APCD 213-2 8/10/93

the emission unit's pre-project potential to emit adjusted to reflect the application 

of the current control technology required under Rule 204.A. 

3. Emission increases from a relocated emission unit shall be calculated as, the 

emission unit's potential to emit, at the new location, adjusted to reflect the 

application of the current control technology required under Rule 204.A minus the 

emission unit's potential to emit, at the old location, adjusted to reflect the 

application of the current control technology required under Rule 204.A. 

4. Emissions increases from a modified emission unit where the modification is 

made for the purpose of complying with regulatory requirements shall be 

calculated as, the emission unit's post-project potential to emit minus the emission 

unit's pre-project potential to emit adjusted to reflect the application of the best 

control method to comply with the regulation currently available, as determined 

by the APCO. 

5. For a modified emission unit where the modification consists of the voluntary 

application of control equipment or the voluntary modification of the emission 

unit for the purpose of reducing the emission of air pollutants and where there is 

no increase in throughput, the emission increase for any pollutants that are not 

controlled by the proposed controls shall be calculated as, the emission unit's 

post-project potential to emit minus the emission unit's pre-project potential to 

emit. 

E. EMISSION REDUCTIONS CREDITS 

1. Emission reductions which result from the application of control equipment, a 

modified emission unit or the replacement of an emission unit with a lower 

emitting emission unit shall be calculated as, the emission unit's pre-project actual 

emissions minus the emission unit's post-project emissions based on the same 

throughput level as the actual emissions. 

2. Emission reductions which result from a reduction in throughput for an emission 

unit shall be calculated as, the actual emissions minus the new potential to emit at 

the proposed throughput level. 

3. Emission reductions which result from the shutdown of an emission unit shall be 

calculated as the actual emissions. 

4. If emission reduction credits, or community bank credits were provided as offsets 

after November 5, 1991 for the purpose of obtaining a Permit to Operate, 

emission reductions shall be calculated as follows:

a. Emission reductions which result from the application of control 

equipment, a modified emission unit or the replacement of an emission 

unit with a lower emitting emission unit shall be calculated as the greater 

of the values calculated as follows: 
San Luis Obispo County APCD 213-3 8/10/93

1) The emission reduction calculated pursuant to subsection E.1. 

2) The lesser of the two following values: 

i. The total amount of all emission reduction credits and 

community bank credits provided as offsets since 

November 5, 1991. 

ii. The emission units's pre-project potential to emit minus the 

emission units's post-project potential to emit. 

b. Emission reductions which result from a reduction in throughput for an 

emission unit shall be calculated as the greater of the values calculated as 

follows: 

1) The emission reduction calculated pursuant to subsection E.2. 

2) The lesser of the two following values: 

i. The total amount of all emission reduction credits and 

community bank credits, provided as offsets since 

November 5, 1991. 

ii. The emission units's pre-project potential to emit minus the 

emission unit's post-project potential to emit at the 

proposed throughput level. 

c. Emission reductions which result from the shutdown of an emissions unit 

shall be calculated as the greater of the two following values: 

1) The emission reduction calculated pursuant to subsection E.3. 

2) The total amount of all emission reduction credits and community 

bank credits provided as offsets since November 5, 1991. 

d. For the purpose of determining the portion of any emission reduction 

calculated pursuant to subsections E.4.a, E.4.b, or E.4.c, which shall be 

returned to the community bank, or shall be eligible for banking pursuant 

to Rule 211, the following procedure shall be used. The emission 

reduction shall be applied: 

1) First, to return any community emission reduction credits, which 

were used to obtain the Permit to Operate, to the community bank. 

2) Second, to allow any remaining portion of the emission reduction 

to be banked pursuant to Rule 211. 
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F. PROFILE CHECK FOR OFFSETS 

1. The profile check for offsets applies to all applications that propose to use 

emission reduction credits or community bank credits as offsets for emission 

increases. 

2. The procedure for determining if the credits are acceptable for use as offsets is as 

follows: 

a. For both the emission increase and the proposed offset, the percentage of 

yearly emissions shall be determined for each of the four quarters which 

shall begin on January 1, April 1, July 1, and October 1. 

b. For each quarter, the lower percentage value between the emission 

increase and the proposed offset shall be summed. 

c. For the credits to be acceptable for offsets, this sum shall be equal to at 

least 80 percent.