NEW_Volume II FUTURE-YEAR-CONVEYANCE-Draft 2008-06-06.doc 

PHOTOCHEMICAL MODELING IN SUPPORT OF 

ATTAINING THE FEDERAL 8-HOUR OZONE 

AIR QUALITY STANDARD IN CENTRAL CALIFORNIA 

Volume 2: 

8-hour Ozone 

Future Year Design Value and 

Carrying Capacity Calculations 

for the 

Sacramento Non-Attainment Area 

California Air Resources Board 

Planning and Technical Support Division 

Sacramento, California 95814 

Preliminary Draft Date 9/25/06 

Revised Draft Date 6/6/08 

(Provided for District Review and Comment) 

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TABLE OF CONTENTS 

1 APPROACH............................................................................................................. 5

1.1 Description of Methodology............................................................................................. 5

2 FUTURE YEAR RESULTS.................................................................................... 13

2.1 Base-Year Design Values................................................................................................ 13

2.2 Future Year Design Value and Carrying Capacity Estimates.................................... 13

3 ANALYSIS OF MODEL-SIMULATED, UNMONITORED PEAKS......................... 18

4 REFERENCES....................................................................................................... 18

5 APPENDICES........................................................................................................ 19

5.1 Future Year 2018 ............................................................................................................ 19
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For District review purposes, this document summarizes modeling-based calculation 

procedures to estimate future year design values in support of determining future year 

carrying capacity. Chapter 1 of this document describes the approach utilized while 

Chapter 2 presents the associated results using the model simulations presented in the 

Volume 1 document, which describes model performance results for 8-hour ozone 

model simulations of the July 1999 and July-August, 2000, episodes. 

As indicated in the Volume 1 documentation and repeated here, sub-regional model 

performance was conducted for 5 days per episode (10 days total) for each of the 15 

sub-regions (Figure 1). Table 1 summarizes the number of modeled days that satisfied 

model performance criteria. With the exception of the North Coast (0 days), 2-9 days of 

the possible 10 days per sub-region are available for consideration in calculating future 

year design values. 

Table 1. Combined Number of Available Days Per Sub-region Under 8-hour Metrics 

Region Name 

July 

1999 

July-Aug 

2000 Total 

North Coast 1 0 1 

BAAQMD 1 2 3 

MBAQMD 1 2 3 

Sacramento Valley North 4 4 8 

Sacramento Region 5 3 8 

SJVAPCD Central 3 5 8 

SJVAPCD Kern 4 5 9 

SJVAPCD North 3 2 5 

Sierra Nevada Central 2 3 5 

SJVAPCD Above 3000 ft 3 4 7 

South Central Coast 3 1 4 

Sierra Nevada North 3 5 8 

Desert 1 5 6 

Nevada 3 0 3 

Total 37 41 78 
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Figure 1. Sub-regions used in the air quality model performance evaluation (3: 

Bay Area region, 6: Sacramento Metro region, 7: Central San Joaquin Valley 

region , 8 Southern San Joaquin Valley region, 9: Northern San Joaquin Valley 

region). 

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15
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1 Approach 

This Chapter describes ARB’s proposed procedures, based on USEPA guidance, for 

calculating and applying RRFs for California’s 8-hour ozone State Implementation 

Plans. The information in this section was previously provided to the Sacramento 

Metropolitan Air Quality Management District for review and comment. 

1.1 Description of Methodology 

While the emphasis of this discussion is on site-specific RRFs, it is noted that the 

USEPA (2005) also requires an analysis to demonstrate that high ozone concentrations 

occurring away from monitors (e.g., unpaired in space) will also be controlled in future 

years to meet air quality standards. This issue is addressed as well. 

The application of photochemical ozone models has a long history in California, for uses 

ranging from the preparation of State Implementation Plans to research activities to 

regulatory development. The modeling community has applied these tools in the State 

for over 30 years, and much has been learned about their proper uses and limitations. 

One of the fundamental understandings that has been learned about photochemical 

models is that they are best used to estimate the relative difference between scenarios, 

rather than for absolute concentration estimates. That is, their strength is in estimating 

the relative change in concentration levels from a baseline condition (e.g., a current 

year) to an alternative scenario (e.g., a future year), rather than predicting the exact 

concentration level that will result from the alternative scenario. 

The USEPA’s guidance on the use of models for attainment demonstrations in support 

of 8-hour ozone planning (USEPA, 2005) is consistent with the fundamental strength of 

models described above. USEPA’s recommended modeled attainment test is to utilize 

relative model response on a site-by-site basis, in the form of a relative response factor 

(RRF), to predict future-year 8-hour ozone design values. This methodology relies on 

the base year for the modeling for conducting model performance analyses, a reference 

year of 2002 for projecting forward site-specific design values, and a future year for the 

attainment test. 
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DVF = (RRF) (DVR) 

where DVR = a reference year (2002) concentration (design value) 

measured at a monitoring site 

 DVF = the estimated future year design value at the same site 

 RRF = the relative response factor at the same site 

The RRF is calculated as the ratio of future year to reference year modeled ozone 

concentrations at a site: 

8 hr

8 hr

RY

FY

RRF

−

−

=

where RRF = the relative response factor for a monitor 

 FY8-hr = the modeled future year 8-hour daily maximum 

concentration predicted near the same monitor 

 RY8-hr = the modeled reference year 8-hour daily maximum 

concentration predicted near the same monitor 

In principle, this concept is simple. Unfortunately, it can be confounded by a number of 

factors, including the limited number of modeled days available, the choice of year(s) to 

use for specification of the reference year design value, the uncertainties inherent in air 

quality modeling, and the presence of a non-zero background level of ozone. As a 

result of this, EPA technical staff have indicated that there is flexibility in the application 

of RRFs, as long as the methodology is technically sound and is properly documented. 

1.1.1 Estimating Reference Year (2002) Design Values 

Specification of the reference year design value is a key consideration in the modeled 

attainment test, since this is the value that is projected forward and used to test for 

attainment at each site. Since the reference design value is presumably reflective of 

conditions in the reference year, it should be representative of the emissions used for 

that year. However, many areas experience fluctuations in their year-to-year 

meteorology, as well as emissions levels. In recognition of this year-to-year variability, 

the reference design value should in some fashion also reflect this variability. A 

standard methodology for minimizing the influence of year-to-year variations is to 

calculate an average value over multiple years. Therefore, the following methodology is 

recommended for specification of the reference design value at each monitoring site: 

The reference design value (DVR) will be calculated as the average of 

the three design values for the three years commencing with the 

reference year of the modeling. The reference year for modeling in 

support of the 8-hour ozone SIPs is 2002. Therefore, the reference 
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design value will be calculated at each monitoring site as the 

average of the design values for 2002, 2003, and 2004. 

California design values are calculated as the three-year average of the 4th highest 

8-hour ozone peak values, and are assigned to the last year. Thus, a design value for 

2002 would be based on data for 2000-2002. The recommendation above implies that 

the reference design value at each monitoring site will be calculated as the average of 

nine design values over five years: the three years which make up the 2002 design 

value (2000-2002), the 2003 design value (2001-2003), and the 2004 design value 

(2002-2004). This gives the greatest weight to 2002, since that year is included in the 

calculation of the design value for all three years. 

The following table summarizes the recommended process for calculating the reference 

design value at each monitoring site. 

Year Years Averaged for Design Value 

2002 2000 2001 2002 

2003 2001 2002 2003 

2004 2002 2003 2004 

Yearly Weighting for Average Design Value for Modeled Attainment Test

2002-2004 

Average 9

Year (2)(Year ) (3)(Year ) (2)(Year ) Year

DV 2000 2001 2002 2003 2004

R

+ + + +

=

1.1.2 Relative Response Factors

As discussed above, the relative response factor (RRF) is a monitor-specific value that 

is calculated based on daily peak 8-hour ozone concentrations simulated in a future 

year, divided by daily peak concentrations simulated in the reference year. To be 

consistent with the principle that the modeled attainment test and design values should 

be robust and stable over a number of different types of meteorology, the RRF should 

be based on multiple simulated days. The following methodology will be used to 

calculate site-specific RRFs: 

Site-specific RRFs will be calculated as the ratio of the average daily peak 8-hour 

modeled ozone concentration in the future year, divided by the average daily peak 8-

hour modeled ozone concentration in the reference year. Only those days satisfying the 

model performance and threshold criteria described below shall be included in the RRF 

calculation. 
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( )

( ) 8 hr AVG

8 hr AVG

AVG RY

FY

RRF

−

−

=

where RRFAVG = the average relative response factor for a monitor 

 (FY8-hr)AVG = the average future year 8-hour daily maximum 

concentration predicted near the same monitor, 

averaged over those days which satisfy model 

performance and threshold criteria 

 (RY8-hr)AVG = the modeled reference year 8-hour daily maximum 

concentration predicted near the same monitor, 

averaged over those days which satisfy model 

performance and threshold criteria 

1.1.3 Criteria for Use of Modeled Days in RRF Calculations 

Adequate model performance is a requirement for use of modeled results. The lack of 

acceptable performance greatly increases uncertainty in the use of the modeling results, 

and casts doubt on conclusions based on the modeling. Although it is desirable to 

include as many days as possible in the RRF calculations, our experience has 

demonstrated that not all modeled days meet the minimum performance standards, and 

are thus not suitable for use. Therefore only those days which satisfy the following 

model performance criteria will be utilized in subsequent RRF calculations. 

The USEPA (1991) and ARB (1990) outline a number of procedures for analysis of 

base year, air quality model performance. These include spatial and time-series plots, 

and statistical analyses, comparing simulated and observed pollutant concentrations, as 

well as sensitivity analysis of selected input fields. The purpose of the performance 

analysis is to provide some confidence that the air quality simulations – which are the 

basis of future-year ozone concentration estimates – are performing properly. 

The application of air quality modeling results to demonstrate attainment of the federal 

1-hour ozone standard emphasized the simulated unpaired peak ozone concentration. 

Three statistical measures were recommended to evaluate model performance: 

unpaired peak ratio (UPR), paired mean normalized bias (NB), and paired gross error 

(GE). These statistical measures were calculated for the modeling domain as a whole, 

and the NB and GE were calculated from all hourly concentrations in excess of 60 ppb 

(to avoid biasing the statistical measures with low concentrations). To meet 

performance guidelines, recommendations were that the UPR should be within ± 20%, 

NB should be within ± 15%, and the GE less than 35%. However, California’s 

geography is very complex and modeling domains have evolved to cover large 

geographic areas. Thus it is recommended that the domains be divided into subregions, and that the performance measures be calculated independently for each sub-
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region. The configuration of these sub-regions is somewhat arbitrary; however, they 

should be configured to isolate "common" regions of higher ozone. 

The USEPA (2005) recommends that the emphasis for 8-hour model performance be 

based on concentrations occurring at, or in the vicinity of, individual monitoring sites. 

Specifically, modeled concentrations occurring within 15 km of a site are considered to 

be in the vicinity of the site. The recommended statistical measures to assess 

simulated versus observed maximum 8-hour ozone concentrations include paired (in 

space, but not time) peak prediction accuracy (PPPA), paired mean normalized bias 

(NB), and paired gross error (GE). Although limited performance analysis has been 

completed for 8-hour ozone modeling in California, it seems prudent at this point to 

carry forward the 1-hour statistical goals and apply them for the 8-hour standard (UPR 

within ± 20%, NB within ± 15%, and the GE less than 35%). However, these limits may 

need to be revised as 8-hour SIP modeling progresses and rigorous model performance 

evaluations are completed. 

While statistical measures for 1-hour model performance were typically calculated 

independently for each modeled day available, the USEPA also recommends that 

PPPA, NB, and GE be calculated for each site over all modeled days. However, 

because the number of episode days available may be very limited, the statistical 

uncertainties in these latter calculations would be large and they are not recommended 

herein. 

In order to have confidence in future year estimates from air quality models, there must 

be confidence in the air quality modeling for the base year. That is, days not meeting 

model acceptance criteria provide high uncertainty, and should not be used for the 

modeled attainment test. 

In addition to the issue of model performance, analyses conducted by the USEPA 

(2005) suggest that air quality models respond more to emission reductions at higher 

predicted ozone values. Correspondingly, the model predicts less benefit at lower 

concentrations. This is consistent with preliminary modeling in support of the 8-hour 

ozone standard conducted by the ARB and the districts. These results imply that RRF 

calculations should be restricted to days with predicted high ozone concentrations. It is 

thus reasonable to establish a minimum threshold for predicted peak 8-hour ozone 

concentrations in the reference year. Days for which the predicted daily peak 8-hour 

ozone concentration at a site is less than the threshold, would not be used for 

calculating RRFs at that site. Consistent with USEPA’s recommendation, we propose 

to use a value of 85 ppb for the reference year threshold. 

Based on the above discussion, we propose the following methodology for determining 

sites and modeled days to be used in the RRF calculations: 
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Only those modeled days meeting the following criteria will be used 

to calculate site-specific RRFs: 

1) The modeled daily 8-hour peak ozone concentration within 15 km 

of the site for the base year of the modeling must be within ± 20% 

of the observed value at the site. 

2) The modeled daily 8-hour peak ozone concentration within 15 km 

of the site in the reference year must be 85 ppb or greater. 

3) The sub-regional 1-hour and 8-hour statistical measures of NB 

and GE must fall within the thresholds of ± 15% and 35%, 

respectively. 

1.1.4 Estimating Future-Year Design Values 

As discussed above, the USEPA’s 8-hour modeling guidance recommends utilizing 

relative model response on a site-by-site basis, in the form of an average relative 

response factor (RRFAVG), to predict future-year 8-hour design values for attainment 

planning. The average RRF is then multiplied by a site-specific design value to 

estimate the future-year design value. One of the confounding factors in this approach 

is consideration of the effects that background levels have on the effectiveness of 

emission control programs. 

There is a large body of information that suggests that ambient concentrations consist 

of some (perhaps nonlinear) background value and a contribution due to anthropogenic 

emissions. That is, if all man-made emissions could be zeroed out, ozone 

concentrations would not go to zero but rather some finite value. The literature 

suggests that 40 ppb is a reasonable global background ozone value, and it is quite 

likely that continental background is some other, somewhat higher, value. One 

possibility for estimating background ozone values in a given modeling domain would 

be to exercise the model without anthropogenic emissions, and to thus develop a 

gridded “background” ozone field. One concern with this approach is that at such low 

levels, the model’s boundary conditions exert a large influence, and appropriate 

temporally- and spatially-resolved data to specify boundary conditions rarely exist. 

Thus boundary conditions can be subjective and uncertain. Whether the background 

value is established at some finite value (e.g., 40 ppb) or is model-derived, it represents 

that portion of a site’s ozone problem that cannot be mitigated by anthropogenic 

emission controls. 

According to EPA’s 8-hour ozone modeling guidance, the modeled attainment test 

requires that a future year Design Value (DVF) be calculated at each site and compared 

to the standard to determine if the site is predicted to be in attainment. To calculate the 

future year Design Value, the Design Value for the reference year (DVR) is multiplied by 

RRFAVG. Although EPA’s guidance says nothing about background ozone, we propose 

to calculate the future year Design Value with consideration of background. The Table 

below illustrates calculation of the DVF with and without background. 
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Calculation of the Average Relative Reduction Factor with and 

without Consideration of Background Ozone 

Without consideration of background With consideration of background 

( )

( )AVG

AVG

AVG RY

FY

RRF =

DVF = (RRFAVG) x (DVR) 

( )

( )AVG

AVG

AVG RY -BG

FY -BG

RRF =

DVF = [(RRFAVG) x (DVR – BG)] + BG 

Definitions 

DVR = Design Value for the reference year 

RY = reference year model prediction 

FY = future year model prediction 

BG = background ozone 

Future year design values will be calculated with consideration of 

background ozone. Because the model’s boundary conditions exert 

a large influence on modeled background ozone levels, 40 ppb will 

be used to represent background ozone concentrations. 

1.1.5 Unpaired Peak Concentrations 

The USEPA (2005) recommends that maximum simulated and observed 8-hour ozone 

concentrations be investigated and combined to demonstrate attainment for all areas in 

a region. This can be cause for concern because peak simulated ozone concentrations 

rarely occur at the exact location of a monitoring site. Conceptually, a design value for 

the location of the unpaired peak can be determined by extrapolation from existing 

monitoring sites. However, this could lead to design value ozone concentrations that 

are greater than those that have been measured and may be the limiting factor in an 

attainment demonstration. 

California’s modeling domains include extreme variations in terrain and meteorology. 

Even during the most intense of field studies, the monitoring network is not sufficient to 

capture all of the gradients in the ozone concentration field. The modeling is subject to 

inaccuracies in the input data, and terrain gradients are smoothed over the spatial 

resolution of the model. However, the modeling does provide information on 

concentration gradients throughout the domain. To take advantage of the strengths of 

the modeling and the monitoring network, we propose the following approach for 

addressing unmonitored peak areas. 
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An unmonitored design value for the reference year and for each 

sub-region will be estimated by averaging the sub-regional maximum 

8-hour ozone concentrations for all days which satisfy the model 

performance criteria described earlier. A sub-regional RRF will be 

calculated by averaging all site-specific RRFs in the sub-region. The 

estimated unmonitored design value and sub-regional RRF will then 

be used in the attainment test. 

This approach to the unpaired peak 8-hour ozone concentration differs from that 

described in the USEPA (2005) guideline document. However, we believe the 

approach described above is consistent with use of the modeled and monitoring data, 

and provides a reasonable alternative to EPA’s methodology. 

1.1.6 Other Potential Technical Issues

The process outlined above for calculating site-specific RRFs seems straightforward. 

However, in practice, the process may turn out to be tedious and cumbersome; 

especially if a large number of sites need to be evaluated, and for different years. The 

greatest difficulty may be that the number of days used for the calculation of the RRF for 

each site may vary. The days used for each site in the future year must match those 

used in the reference year. Because the selection of these days is based, in part, on 

model performance statistical measures, it may be necessary to do much of this work 

by hand. 

Another problem that is almost certain to arise is that for some sites either the model 

performance or the observed and simulated concentrations will fail to meet the 

recommended guidelines on all of the available episode days. This may result in 

situations wherein the day of the peak ozone concentration is not used in the calculation 

of the RRF and days with lesser concentrations are. The risk is that if the episode and 

simulation results do not adequately represent high ozone concentrations at a site, the 

simulation results may overstate the emissions reductions necessary to reach 

attainment for the ozone air quality standards due to the model’s relatively limited 

response to controls at lower concentrations. In addition, the process of estimating a 

future year design value at an unmonitored peak location will always be subject to great 

uncertainty. 

Some of the above difficulties may be avoided if a more simple and straightforward 

approach was used. For example, an RRF could be calculated from the reference- and 

future-year sub-regional maximum 8-hour daily maximum ozone concentrations. The 

RRF could then be multiplied by the maximum design value within the control district or 

attainment area. This would deviate from the USEPA (2005) guidelines in a number if 

respects. But, it would greatly simplify the required calculations. A lot more study of 

this approach would be necessary to understand the implications of such an 

approximation. This would also have to be vetted with the USEPA. 
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2 Future Year Results 

This chapter presents draft reference year design values and describes the future year 

design values and carrying capacity results contained in the Appendices. 

2.1 Base-Year Design Values 

Chapter 1 (Section 1.1.1) discusses a proposed approach for calculating future year 

design values. Based on this recommended approach, Table 2 presents the results of 

reference year design value calculations for the Sacramento Non-Attainment Area. 

Table 2. Sacramento Non-Attainment Area Design Values for 2002-2004 

(Non-Attainment Sites Only) 

8-Hour Ozone Design Values Site 2002 2003 2004 2002-04 Avg. 

El Dorado County

Coo l -Highway 193 106 107 102 105 

Placerville - Gold Nugget Way 94 95 94 94 

 

Placer County 

Auburn - Dewitt-C Avenue 101 99 95 98 

Roseville - N Sunrise Blvd 92 90 87 90 

 

Sacramento County

Folsom - Natoma Street 100 100 97 99 

North Highlands - Blackfoot Way 92 91 85 89 

Sacramento - Del Paso Manor 95 97 95 96 

Sloughhouse 95 95 94 95 

2.2 Future Year Design Value and Carrying Capacity Estimates 

Data processing programs are used to generate reports from modeling results to 

illustrate future year design values and carrying capacities. These reports are 

generated for each 8-hour ozone non-attainment monitoring station following the 

methodology described in Chapter 1, sections 1.1.3 and 1.1.4. For illustration 

purposes, this section discusses the information contained on a sample report page 

(Figure 2). The Appendices contain future-year-specific results for specific years in the 

same form as the sample format. 

Report Header. At the top of the report, three header lines provide a variety of 

information, including the subject future year (2012), the station (site) name, the 

associated sub-region (per Figure 1, Chapter 1), and the 8-hour ozone design value for 
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the USEPA-defined reference year of 2002 (98 ppb) from Table 2, shown previously in 

Section 2.1). 

Report Table. The mid-section of the report contains a table with 8 rows: a header row, 

plus 7 rows of information. For specific episode days (columns), this table contains a 

pass/fail summary of sub-regional model performance results for the site (row 2), a 

variety of concentration data (rows 3-7), and a yes/no assessment as to whether the 

station data are useable in the RRF analysis (row 8). A “-99” value in rows 3-7 indicates 

that acceptable data are not available. The purpose of each row is described below: 

• Row 1: Header. Columns represent episode days via two digit year followed by 

three digit day-of-year, or Julian day. 

• Row 2: Performance Status: This line lists the model performance status for

each of the episode days. The model performance status is a pass/fail 

designation as to whether the model performance for the sub-region within which 

the monitoring station is located meets both the 1-hour and the 8-hour statistical 

model performance criteria, per Section 1.1.3 and the Volume 1 report. Per the 

Figure 2 report header, Auburn is located in Region 6. 

• Row 3: Peak Observed 8-hour Ozone. These data represent the peak, 

measured 8-hour ozone concentrations at the Auburn station for each specific 

day. These 8-hour ozone concentrations need to be above 70 ppb to be used in 

the RRF calculation (U.S. EPA guidance recommends excluding days with 

concentrations less than 70 ppb from RRF calculations to avoid a strong RRF 

dependence on the predicted baseline maximum concentrations). 

• Row 4: Peak Simulated 8-hour Ozone. These are the model-simulated, peak 

8-hour ozone concentrations occurring in the modeling grid cell within which the 

station (Auburn in this case) is geographically located. Per Section 1.1.3, 

simulated concentrations must be 85ppb or greater to be used in the RRF 

calculation. 
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Figure 2. Sample Report Page for the Auburn monitoring site. 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: AUBD - Auburn-Dewitt-C Avenue Subregion: 6 Reference Year Design Value: 98 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 105 103 107 102 91 -99 80 82 95 107 

Peak Simulated 8-hour Ozone 87 80 86 77 73 71 78 74 93 104 

Peak Simulated 8-hour Ozone within 15 km 106 84 101 84 77 79 86 83 106 106 

Reference Year 15-km, 8-hour Average Ozone 105 

Future Year 15-km, 8-hour Average Ozone 89 73 83 71 67 70 75 74 91 90 

Use in RRF Analysis? Yes No Yes No No No No No Yes Yes 

 85 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

AUBD Average 15-km Concentration (ppb)

Without RRFs

82

83

85

86

87

82

83

85

86

88

82

84

85

86

88

82

84

85

87

88

82

84

85

87

88

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

AUBD FY Design Value(ppb)

With RRFs

Offset = 0 ppb

76

78

79

80

81

76

78

79

80

82

77

78

79

81

82

77

78

79

81

82

77

78

80

81

82

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

AUBD FY Design Value(ppb)

With RRFs

Offset = 40 ppb

77

78

80

81

82

77

79

80

81

82

77

79

80

81

82

78

79

80

81

83

78

79

80

82

83
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• Row 5: Peak Simulated 8-hour Ozone within 15km. These values represent the 

model-simulated, daily 8-hour peak ozone concentration within 15 km of the site 

for the base year of the modeling. Per Section 1.1.3, these concentrations must 

be 85 ppb or greater and within ± 20% of the observed value at the site. 

• Row 6: Reference Year, 15km, 8-hour Average Ozone. This represents the 

average of the Row 4 values for which the data are useable in RRF analyses 

(per row 8). For Auburn, since row 8 indicates that only days 99190, 99192, 

00214, and 00215 are usable, 105 ppb is calculated from the average of 106, 

101, 106, and 106 ppb. 

• Row 7: Future Year, 15km, 8-hour Average Ozone. This represents the 

average, future-year simulated concentrations within 15 km of the site. 

• Row 8: Use in RRF Analysis? This YES/NO field represents whether data for 

the days can be used in calculating the RRF. As indicated in Section 1.1.3 and 

in the row descriptions above, the criteria for selecting which days will be used in 

the RRF calculation include an assessment of sub-regional model performance 

as well as concentration thresholds for observed and simulated 8-hour ozone 

concentrations. That is, in addition to meeting model performance criteria, the 

observed base-year ozone concentration must be 70 ppb or greater and the 

maximum simulated ozone concentration for the year 2002 must be 85 ppb or 

greater. 

RRF Calculation Example. Of the 10 available episode days reported in Figure 2 for 

Auburn, six of the days fail to meet the 1-hour and/or the 8-hour model performance 

criteria ('99191', '99193', '99194', '00211', ‘00212’, and '00213'). The simulation results 

from the remaining four days are used in the RRF calculation: days '99190', ‘99192’, 

‘00214’, and '0215' (per row 8). Per Section 1.1.4 the sample RRF for Auburn, without a 

background offset, is calculated as follows: 

( )

( )AVG

AVG

AVG RY

FY

RRF = = ((89+83+91+90)/4) / ((106+101+106+106)/4) = (88/105) = 0.84 

Also per Section 1.1.4, with a 40 ppb background offset, the RRF is calculated as: 

( )

( )AVG

AVG

AVG RY -BG

FY -BG

RRF = = (88-40)/(105-40) = 0.74 

Reported Design-Value-Based Carrying Capacity Diagrams. The lower half of the page 

for each report contains four design-value-based carrying capacity diagrams. These 

diagrams are intended to characterize the effect of domain-wide emission changes on a 

design value, based upon multiple model simulations. The diagrams are based on 

model response to 25 future year emission scenarios for which baseline, domain-wide 

NOx and ROG emissions for the 2018 future year are scaled by factors ranging from 

0.80 to 1.00 in increments of 0.05 (i.e. 5% NOx and/or ROG reductions at a time). 
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

17 6/6/2008 

The diagram on the left side of the report is based on the average of the “Future Year 

15-km, 8-hour Average Ozone” values reflected in row 6 of the report table, for those 

days that meet all the criteria for RRF application. However, no RRF is applied. Thus 

the future year design value indicated at the top right of each diagram is calculated as 

follows: 

DVF = (89+83+91+90) / 4 = 88 ppb 

The two diagrams on the right incorporate RRFs, without consideration of background 

ozone (top diagram) and with consideration of background (bottom diagram). The 

future year design value indicated at the top right of the top diagram on the right is 

calculated as follows, using the RRFs discussed above: 

DVF = (RRFAVG) x (DVR) = 0.84 x 98 ppb = 82 ppb 

Similarly, the future year design value indicated at the top right for the bottom right 

diagram is calculated as follows, using the background-adjusted RRFs discussed 

previously and equations in section 1.1.4: 

DVF = [(RRFAVG) x (DVR – BG)] + BG = [ 0.74 x ( 98 – 40 ) ] + 40 = 83 ppb 
18 6/6/2008 

3 Analysis of Model-Simulated, Unmonitored Peaks 

This work will be reported separately. 

4 References 

Air Resources Board, 1990. “TECHNICAL GUIDANCE DOCUMENT: 

Photochemical Modeling”. 

USEPA, 1991. "Guideline for Regulatory Application of the Urban Airshed 

Model". EPA-450/4-91-013. USEPA, OAQPS. Research Triangle Park, NC 

27711. July, 1991. 

USEPA, 2005. "Guidance on the Use of Models and Other Analysis in the 

Attainment Demonstration for the 8-Hour Ozone NAAQS". Final Draft. USEPA, 

OAR/OAQPS, Research Triangle Park, NC 2771. February, 2005. 
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

19 6/6/2008 

5 Appendices 

5.1 Future Year 2018 
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

20 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: AUBD - Auburn-Dewitt-C Avenue Subregion: 6 Reference Year Design Value: 98 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 105 103 107 102 91 -99 80 82 95 107 

Peak Simulated 8-hour Ozone 87 80 86 77 73 71 78 74 93 104 

Peak Simulated 8-hour Ozone within 15 km 106 84 101 84 77 79 86 83 106 106 

Reference Year 15-km, 8-hour Average 

Ozone 

105 

Future Year 15-km, 8-hour Average Ozone 89 73 83 71 67 70 75 74 91 90 

Use in RRF Analysis? Yes No Yes No No No No No Yes Yes 

 85 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

AUBD Average 15-km Concentration (ppb)

Without RRFs

82

83

85

86

87

82

83

85

86

88

82

84

85

86

88

82

84

85

87

88

82

84

85

87

88

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

AUBD FY Design Value(ppb)

With RRFs

Offset = 0 ppb

76

78

79

80

81

76

78

79

80

82

77

78

79

81

82

77

78

79

81

82

77

78

80

81

82

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

AUBD FY Design Value(ppb)

With RRFs

Offset = 40 ppb

77

78

80

81

82

77

79

80

81

82

77

79

80

81

82

78

79

80

81

83

78

79

80

82

83
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

21 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: 3002 - Colfax-City Hall Subregion: 6 Reference Year Design Value: 85 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 89 86 87 82 69 -99 -99 -99 -99 -99 

Peak Simulated 8-hour Ozone 81 75 83 75 69 75 78 74 85 100 

Peak Simulated 8-hour Ozone within 15 km 92 80 91 82 74 78 83 79 92 105 

Reference Year 15-km, 8-hour Average 

Ozone 

91 

Future Year 15-km, 8-hour Average Ozone 76 70 75 69 65 70 73 69 79 89 

Use in RRF Analysis? Yes No Yes No No No No No No No 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

3002 Average 15-km Concentration (ppb)

Without RRFs

70

71

72

74

75

70

71

72

74

75

70

71

73

74

75

70

71

73

74

75

70

71

73

74

75

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

3002 FY Design Value(ppb)

With RRFs

Offset = 0 ppb

64

65

67

68

69

64

66

67

68

69

64

66

67

68

69

64

66

67

68

69

65

66

67

68

69

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

3002 FY Design Value(ppb)

With RRFs

Offset = 40 ppb

65

67

68

69

70

66

67

68

69

70

66

67

68

69

70

66

67

68

69

70

66

67

68

69

70
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

22 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: CUS - Cool Stn (1400 American Subregion: 6 Reference Year Design Value: 105 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 116 114 118 100 94 94 87 90 99 104 

Peak Simulated 8-hour Ozone 95 82 93 83 76 75 83 78 92 100 

Peak Simulated 8-hour Ozone within 15 km 111 86 106 85 79 81 88 85 98 105 

Reference Year 15-km, 8-hour Average 

Ozone 

98 

Future Year 15-km, 8-hour Average Ozone 93 75 87 72 69 72 76 72 85 89 

Use in RRF Analysis? Yes Yes Yes Yes No No No No Yes Yes 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

CUS Average 15-km Concentration (ppb)

Without RRFs

78

79

80

82

83

78

79

81

82

83

78

79

81

82

83

78

80

81

82

83

78

80

81

82

84

85

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

CUS FY Design Value(ppb)

With RRFs

Offset = 0 ppb

83

84

85

87

88

83

84

86

87

88

83

84

86

87

88

83

84

86

87

88

83

85

86

87

89

 85 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

CUS FY Design Value(ppb)

With RRFs

Offset = 40 ppb

82

83

85

86

87

82

83

85

86

87

82

83

85

86

88

82

84

85

86

88

82

84

85

87

88
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

23 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: ELK - Elk Grove Stn (Brucevil Subregion: 6 Reference Year Design Value: 77 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 75 93 97 95 78 64 50 64 66 63 

Peak Simulated 8-hour Ozone 76 89 83 91 86 81 85 99 96 86 

Peak Simulated 8-hour Ozone within 15 km 80 99 95 102 88 91 91 110 100 87 

Reference Year 15-km, 8-hour Average 

Ozone 

96 

Future Year 15-km, 8-hour Average Ozone 76 84 80 84 79 83 83 97 88 80 

Use in RRF Analysis? No Yes Yes Yes Yes No No No No No 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

ELK Average 15-km Concentration (ppb)

Without RRFs

76

77

79

80

81

76

77

79

80

81

76

78

79

80

81

76

78

79

80

82

76

78

79

81

82

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

ELK FY Design Value(ppb)

With RRFs

Offset = 0 ppb

60

61

63

64

64

60

62

63

64

65

61

62

63

64

65

61

62

63

64

65

61

62

63

64

65

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

ELK FY Design Value(ppb)

With RRFs

Offset = 40 ppb

63

64

65

66

67

63

64

65

66

67

63

64

65

66

67

63

64

65

66

67

64

65

65

66

67
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

24 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: FLN - Folsom Stn (Natoma St.) Subregion: 6 Reference Year Design Value: 99 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 109 129 124 102 86 70 66 43 -99 95 

Peak Simulated 8-hour Ozone 109 96 121 87 87 88 97 84 105 88 

Peak Simulated 8-hour Ozone within 15 km 115 114 125 98 98 101 107 92 116 104 

Reference Year 15-km, 8-hour Average 

Ozone 

108 

Future Year 15-km, 8-hour Average Ozone 102 96 101 80 87 88 96 82 98 90 

Use in RRF Analysis? Yes Yes Yes Yes Yes Yes No No No Yes 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

FLN Average 15-km Concentration (ppb)

Without RRFs

86

87

88

90

91

86

87

89

90

91

86

88

89

90

91

86

88

89

91

92

87

88

90

91

92

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

FLN FY Design Value(ppb)

With RRFs

Offset = 0 ppb

78

79

81

82

83

78

80

81

82

83

79

80

81

82

83

79

80

81

83

84

79

80

82

83

84

85

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

FLN FY Design Value(ppb)

With RRFs

Offset = 40 ppb

79

80

82

83

84

79

81

82

83

84

80

81

82

83

84

80

81

82

83

85

80

81

83

84

85
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

25 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: PGN - Placerville Stn (Gold N Subregion: 6 Reference Year Design Value: 94 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 110 119 111 98 92 97 93 82 89 88 

Peak Simulated 8-hour Ozone 107 88 94 89 74 80 85 83 85 79 

Peak Simulated 8-hour Ozone within 15 km 115 106 106 95 92 97 94 86 93 91 

Reference Year 15-km, 8-hour Average 

Ozone 

99 

Future Year 15-km, 8-hour Average Ozone 98 89 87 78 78 83 82 75 81 78 

Use in RRF Analysis? Yes Yes Yes Yes Yes Yes No No Yes Yes 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

PGN Average 15-km Concentration (ppb)

Without RRFs

78

80

81

82

83

78

80

81

82

83

79

80

81

82

84

79

80

81

83

84

79

80

82

83

84

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

PGN FY Design Value(ppb)

With RRFs

Offset = 0 ppb

74

75

76

77

78

74

75

76

77

78

74

75

76

77

79

74

75

76

78

79

74

75

77

78

79

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

PGN FY Design Value(ppb)

With RRFs

Offset = 40 ppb

74

76

77

78

79

74

76

77

78

79

75

76

77

78

79

75

76

77

78

79

75

76

77

78

79
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

26 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: ROS - Roseville Stn (151 N Su Subregion: 6 Reference Year Design Value: 89 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 86 107 113 88 86 90 85 70 93 97 

Peak Simulated 8-hour Ozone 92 83 86 71 73 75 83 80 107 102 

Peak Simulated 8-hour Ozone within 15 km 111 101 125 89 90 92 107 85 113 106 

Reference Year 15-km, 8-hour Average 

Ozone 

103 

Future Year 15-km, 8-hour Average Ozone 102 86 101 74 80 81 94 76 97 92 

Use in RRF Analysis? Yes Yes Yes Yes Yes Yes No No Yes Yes 

 85 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

ROS Average 15-km Concentration (ppb)

Without RRFs

83

85

86

87

88

83

85

86

87

88

84

85

86

88

89

84

85

87

88

89

84

85

87

88

89

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

ROS FY Design Value(ppb)

With RRFs

Offset = 0 ppb

71

72

73

74

75

71

73

74

75

76

72

73

74

75

76

72

73

74

75

76

72

73

74

75

76

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

ROS FY Design Value(ppb)

With RRFs

Offset = 40 ppb

73

74

75

76

77

73

74

75

76

77

73

74

75

76

77

73

75

76

76

77

74

75

76

77

78
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

27 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: SDP - Sacramento Stn (Del Pas Subregion: 6 Reference Year Design Value: 95 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 78 111 107 95 77 92 93 74 101 80 

Peak Simulated 8-hour Ozone 81 100 100 78 85 84 107 84 105 90 

Peak Simulated 8-hour Ozone within 15 km 103 113 124 102 95 99 110 99 115 102 

Reference Year 15-km, 8-hour Average 

Ozone 

107 

Future Year 15-km, 8-hour Average Ozone 100 97 101 84 88 89 100 92 98 92 

Use in RRF Analysis? Yes Yes Yes Yes Yes Yes No No Yes Yes 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SDP Average 15-km Concentration (ppb)

Without RRFs

87

89

90

91

92

88

89

90

92

93

88

89

91

92

93

88

90

91

92

93

88

90

91

93

94

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SDP FY Design Value(ppb)

With RRFs

Offset = 0 ppb

77

79

80

81

82

78

79

80

81

82

78

79

80

81

83

78

79

81

82

83

78

80

81

82

83

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SDP FY Design Value(ppb)

With RRFs

Offset = 40 ppb

79

80

81

82

83

79

80

81

82

83

79

80

81

82

83

79

81

82

83

84

80

81

82

83

84
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

28 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: SLU - Sloughouse Rd. Stn Subregion: 6 Reference Year Design Value: 94 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone -99 -99 -99 -99 -99 96 91 83 109 91 

Peak Simulated 8-hour Ozone 85 111 106 102 94 98 87 99 110 87 

Peak Simulated 8-hour Ozone within 15 km 99 116 125 107 99 102 110 110 116 91 

Reference Year 15-km, 8-hour Average 

Ozone 

103 

Future Year 15-km, 8-hour Average Ozone 94 98 101 87 88 90 100 97 98 85 

Use in RRF Analysis? No No No No No Yes No No Yes Yes 

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SLU Average 15-km Concentration (ppb)

Without RRFs

85

87

88

89

90

86

87

88

89

90

86

87

88

90

91

86

87

89

90

91

86

88

89

90

91

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SLU FY Design Value(ppb)

With RRFs

Offset = 0 ppb

77

78

79

80

81

77

79

80

81

82

78

79

80

81

82

78

79

80

81

82

78

79

80

82

82

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SLU FY Design Value(ppb)

With RRFs

Offset = 40 ppb

78

79

80

81

82

78

80

81

81

82

79

80

81

82

83

79

80

81

82

83

79

80

81

82

83
DRAFT FUTURE YEAR RESULTS – FOR DISTRICT REVIEW ONLY 

Please do not cite, quote, or distribute 

29 6/6/2008 

Year: 2018 Model: CAMX/MM5/SAPRC99 

Site: SNH - Sacramento-North Highla Subregion: 6 Reference Year Design Value: 89 ppb 

Episode Days 99190 99191 99192 99193 99194 00211 00212 00213 00214 00215 

Performance Status Pass Pass Pass Pass Pass Pass Fail Fail Pass Pass 

Peak Observed 8-hour Ozone 53 79 69 64 80 89 81 77 100 87 

Peak Simulated 8-hour Ozone 90 88 79 72 78 78 85 79 103 102 

Peak Simulated 8-hour Ozone within 15 km 103 105 124 85 90 94 110 87 113 105 

Reference Year 15-km, 8-hour Average 

Ozone 

101 

Future Year 15-km, 8-hour Average Ozone 100 91 101 72 84 84 99 78 98 92 

Use in RRF Analysis? No Yes No No Yes Yes No No Yes Yes 

85

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SNH Average 15-km Concentration (ppb)

Without RRFs

84

85

87

88

89

84

86

87

88

89

85

86

87

88

89

85

86

87

88

90

85

86

88

89

90

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SNH FY Design Value(ppb)

With RRFs

Offset = 0 ppb

73

74

75

76

77

74

75

76

77

78

74

75

76

77

78

74

75

76

77

78

74

75

76

77

78

0.80 0.85 0.90 0.95 1.00

0.80 0.85 0.90 0.95 1.00

ROG

NOx

SNH FY Design Value(ppb)

With RRFs

Offset = 40 ppb

75

76

77

77

78

75

76

77

78

79

75

76

77

78

79

75

76

77

78

79

75

76

77

78

79