# Northern Ada County

PM 10 

# S tate I mplementation P lan
Maintenance Plan

Ten

- Year Update

State of Idaho Department of Environmental Quality

February 201 3Printed on recycled paper, DEQ June 2012,

PID TVMB , CA code 41300 . Costs associated with this publication are available from the State of Idaho Department of Environmental Quality in accordance
with Section 60

- 202, Idaho Code.

# Northern Ada County

PM 10 

# S tate I mplementation P lan
Maintenance Plan

Ten

- Year Update

February 201 3

Prepared by Idaho Department of Environmental Quality

Boise Regional Office

1445 North Orchard Boise, Idaho 83706This page intentionally left blank for correct double

- sided printing.Northern Ada County PM 10 Maintenance Plan

iii 

### Table of Contents

1 Introduction and History

................................ ................................ ................................ .......... 1

2 Northern Ada County PM 10 Maintenance Area Description

................................ ................... 2

3 Requirements for Maintenance Plan Update

................................ ................................ ........... 3

3.1 NAAQS Attainment Verification

................................ ................................ ..................... 3

3.2 SIP Approval

................................ ................................ ................................ .................... 3

3.3 Permanent and Enforceable Improvements in Air Quality

................................ .............. 3

3.4 Full Approval of the PM 10 Maintenance Plan

................................ ................................ .. 3

3.5 Maintenance Plan Elements

................................ ................................ ............................. 4

4 Air Quality Monitoring

— Verification of Attainmen t

................................ ............................. 4

4.1 PM 10 Monitoring

................................ ................................ ................................ .............. 4

4.2 Quality Assurance Program

................................ ................................ .............................. 4

4.3 Continued Attainment of the PM 10 Standard

................................ ................................ .... 4

4.4 Continued Air Monitoring and Verification of Attainment

................................ ............. 4

5 Emissions Inventory

................................ ................................ ................................ ................ 6

5.1 Base Year (2008) Annual and Episode Emissions Inventory

................................ .......... 7

5.1.1 Area Sources

................................ ................................ ................................ ................ 9

5.1.2 On

- Road Mobile Sources

................................ ................................ .......................... 10

5.1.3 Non

- Road Mobile Sources

................................ ................................ ........................ 11

5.1.4 Point Sources

................................ ................................ ................................ ............. 11

5.2 Projected Inventories

................................ ................................ ................................ ...... 12

5.3 Motor Vehicle Emissions Budget

................................ ................................ ................... 13

5.3.1 MVEB for PM 10

................................ ................................ ................................ ......... 13

5.3.2 MVEB for NO

x and VOC

................................ ................................ .......................... 14

5.3.3 MVEB Conclusion

................................ ................................ ................................ ..... 14

6 Maintenance Demonstration

................................ ................................ ................................ .. 15

6.1 Air Quality Modeling Approach

................................ ................................ .................... 15

6.2 Attainment Demonstration

................................ ................................ ............................. 16

6.2.1 Annual Average

................................ ................................ ................................ ......... 16

6.2.2 No nwinter High Crustal Mass Scenario

................................ ................................ .... 17

6.2.3 Nonwinter High Carbon Scenario

................................ ................................ ............. 17

6.2.4 High Winter Scenario

................................ ................................ ................................ 18

6.2.5 Stagnant Winter Scenario

................................ ................................ .......................... 19

6.3 Modeling Summary

................................ ................................ ................................ ........ 20

7 Permanent and Enforceable Improvement in Air Quality

................................ ..................... 21

7.1 Control Measures

................................ ................................ ................................ ............ 21Northern Ada County PM 10 Maintenance Plan

iv 7.1.1 Air Quality Index Program

................................ ................................ ........................ 21

7.1.2 Residential Wood Burning Program

................................ ................................ .......... 21

7.1.3 Open Burning Ban Program

................................ ................................ ...................... 21

7.1.4 Stationary Source Control Measure

................................ ................................ ........... 22

8 Contingency Plan

................................ ................................ ................................ ................... 22

8.1 Tracki ng

................................ ................................ ................................ .......................... 23

8.2 Triggering

................................ ................................ ................................ ....................... 23

8.3 Potential Contingency Measures

................................ ................................ .................... 23

9 Summary

................................ ................................ ................................ ................................ 24

9.1 Attainment Verification

................................ ................................ ................................ .. 24

9.2 Full Approval of the State Implementation Plan under Section 110

.............................. 24

9.3 Permanent and Enforceable Improvement in Air Quality

................................ .............. 24

9.4 Maintenance Plan Elements

................................ ................................ ........................... 24

9.5 Subsequent Maintenance Plan Revisions

................................ ................................ ....... 24

References

................................ ................................ ................................ ................................ ..... 25
Appendices

................................ ................................ ................................ ................................ .... 27Northern Ada County PM 10 Maintenance Plan

v 

### List of Figures

Figure 1. Northern Ada County PM 10 Maintenance Area

................................ .............................. 2
Figure 2. PM 10 annual emissions in the four source categories (to the nearest ton).

...................... 9
Figure 3. PM 10 paved road dust compared to all other area sources.

................................ ............ 10
Figure 4. Predicted annual average PM 10 concentration (in micrograms per cubic meter).

......... 16
Figure 5. Predicted 24

- hour average PM 10 levels (in micrograms per cubic meter) for high

crustal mass scenario in nonwinter seasons.

................................ ................................ ... 17
Figure 6. Predicted 24

- hour averag e PM 10 levels (in micrograms per cubic meters) for high

carbon scenario in nonwinter seasons.

................................ ................................ ........... 18
Figure 7. Predicted 24

- hour aver age PM 10 levels (in micrograms per cubic meters) for high

winter scenario.

................................ ................................ ................................ ............... 19
Figure 8. Predicted 24

- hour average PM 10 levels (in micrograms per cubic meter) for stagnation scenario in winter season.

................................ ................................ ............. 20



### List of Tables

Table 1. Highest certified 24

- hour average PM 10 values measured at the Boise fire station.

........ 5
Table 2. Annual average PM 10 concentrations me asured at Boise Fire Station #5.

....................... 6
Table 3. Annual emissions by source category

— 2008.

................................ ................................ .. 7

Table 4. Emission for winter seasons

— 2008.

................................ ................................ ................ 8

Table 5. Emission for non

- winter seasons

— 2008.

................................ ................................ ......... 8
Table 6. Ada County paved road dust emissions.

................................ ................................ ......... 10
Table 7. Annual emissions by source category

— 2015.

................................ ................................ 12
Table 8. Annual emissions by source category

— 2023.

................................ ................................ 12

Table 9. PM 10 motor vehicle emissions budget.

................................ ................................ ........... 14

Table 10. NO

x and VOC motor vehicle emissions budget.

................................ .......................... 14
Table 11. Predicted annual average PM 10 levels.

................................ ................................ ......... 16

Table 12. Predicted 24

- hour average PM 10 levels for high crustal mass scenario in nonwinter

seasons.

................................ ................................ ................................ ........................... 17

Table 13. Predicted 24

- hour average PM 10 levels for high carbon scenario in nonwinter

seasons.

................................ ................................ ................................ ........................... 18

Table 14. Predicted 24

- hour average PM 10 l evels for high winter scenario.

................................ 18

Table 15. Predicted 24

- hour average PM 10 levels for stagnation scenario in winter season.

....... 19Northern Ada County PM 10 Maintenance Plan

vi This page intentionally left blank for correct double

- sided printing.

## 1 Introduction and History

The Northern Ada County Maintenance A rea was identified as a n area of concern for PM 10 with

the promulgation of the PM 10 N ational A mbient A ir Q uality S tandards ( NAAQS ) in 1987 and was formally designated as a mode rate PM 10 nonattainment area upon passage of the 1990 C lean

A ir A ct

. 1 Idaho developed a s tate i mplementation p lan (SIP) and submitted it to the United States

E nvironmental P rotection A gency (EPA) in November 1991, later submitting revisions in

December 1994 and July 1995. EPA gave final approval to the Northern Ada County PM 10 SIP in May 1996.

EPA revised the PM 10 NAAQS in 1997

, and Idaho demonstrated to EPA’s satisfaction that it complied with the new standard. As a result, EPA rescinded the applicabil ity of the PM 10 NAAQS in Northern Ada County on March 12, 1999. Shortly thereafter, litigation at the national

level vacated the new PM 10 NAAQS. Subsequent litigation in Idaho to have EPA restore the

federal standards for n orthern Ada County resulted in a settlement agreement that required Idaho

to submit a PM 10 m aintenance SIP by September 30, 2002

, and for EPA to take final action within one year. The Northern Ada County PM 10 SIP Maintenance Plan and Redesignation Request (2002 maintenance p lan) was submitted to EPA in September 2002. EPA approved the

p lan in September 2003, restoring northern Ada County to attainment status for PM 10 (Environ 2002)

.

The control strategy in the 2002 m aintenance p lan includes the measures in the approved 1991

attainment SIP and additional contingency measures. The key 1991 SIP measures revised and enhanced in the 1994 and 1995 supplemental submissions and the 2002 m aintenance p lan are residential wood burning and open burning programs. Both consist of voluntary and manda tory
burn bans in the various communities and unincorporated areas of n orthern Ada County during periods of high PM 10 levels.

During the e nvironmental i mpact and subsequent modeling stage of the 2002 maintenance plan development process, the Idaho Departm ent of Environmental Quality ( DEQ ) identified

13 facilities with potentials to emit well in excess of their actual emissions. In accordance with

the “ Rules for the Control of Air Pollution in Idaho ” ( IDAPA 58.01.01.401.03 ) , DEQ issued permits reducing allo wable emissions from these facilities. In addition to the se 13 point sources,

t he Amalgamated Sugar Company (TASCO) in Canyon County was shown to potentially

contribute to PM 10 exceedances in both Ada and Canyon Counties. To address this problem, DEQ issued a Tier II o perating p ermit that require d the company to reduce emissions sufficiently to address these air quality concerns.

Contingency measures in the 2002 m aintenance p lan include additional controls in the wood

burni ng program and a reduction of fugitive road dust through a road sweeping program designed to reduce particulate emissions by prioritizing road sweeping for certain problem areas. Additional potential contingency measures include requiring material transpor t load covering,

eliminati ng mud track

- out onto paved roads, reduc ing uncontrolled outdoor burning, expanding the existing vehicle inspection and maintenance program in Ada County, prohibiting new

1 PM 10 is particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers.Northern Ada County PM 10 Maintenance Plan

2 unpaved roadways or parking lots through local ordinances

, and including clean burning woodstoves in mandatory burn

- ban situations.

During 1986

– 1991, seven recorded PM 10 values exceed ed the 24

- hour standard (150 micrograms per cubic meter [μg/m 3 ] ) in the Northern Ada County M aintenance A rea. With one exception,

th e exceedances were all measured in winter months (January). The highest measured 24

- hour

PM 10 value was 314 μg/m 3 measured at the downtown Boise fire station in January 1986. With the exception of an agricultural

- influenced exceedance in 1997, no exceedances were recorded from 1992 through 2002. From 2003 through 2008, the highest measured 24

- hour PM 10 value

was 97 μg/m 3 measured at the downtown Boise fire station. No exceedances were recorded during this time period.

Based on preliminary data, two exceedance s w ere recorded o n February 15 and 16, 201 1 with a

24

- hour average of 183 and 156 μg/m 3 respectively. DEQ is currently evaluating this

exceedance. Sustained winds and extremely dry winter conditions contributed significantly to the

event. Thu s, the 3

- year average number of 24

- hour exceedances was less than one per year. Based upon monitoring data, the area has attained the 24

- hour PM 10 NAAQS. The now revoked

annual PM 10 standard of 50 μg/m 3 wa s never violated in n orthern Ada County.

Monitoring data show that northern Ada County has moved away from the preponderance of high peak values occurring in the winter season ( i.e., PM season) to lower peaks, distributed through four distinct scenarios, which are discussed in section 6

.

This m ai ntenance p lan fulfill s the requirements for the n orthern Ada County maintenance plan update for the second 10

- year maintenance period. The existing control measures in effect will

remain u nchanged

. However, DEQ will request that the permit requirements for the facilities currently include d in the Idaho SIP be removed. This request will demonstrate that the permit program is an adequate existing control measure for industrial sources. See specifically, IDAPA

58.01.01.401.03 (Appendix A)

.



## 2 Northern Ada County PM 10 

## Maintenance Area Description

The Northern Ada County Maintenance Area includes the portion of Ada County north of the Boise baseline (43 degrees north latitude) as shown in Figure 1

.

Figure 1

. Northern Ada County PM 10 Maintenance Area ( indicated by gray s haded a rea)

.Northern Ada County PM 10 Maintenance Plan

3 South of the maintenance area

, the land is largely unpopulated and is primar ily managed by federal agencies such as the Bureau of Land Management and Department of Defense ( the Idaho

National Guard )

. To the east and north, the Boise front blocks movement of air and pollution between Ada County and neighboring Boise, Elmore, and Ge m Counties. Canyon County is

located on the weste rn edge of the maintenance area. The legal description for the maintenance

area can be found in Appendix B

.



## 3 Requirement s for Maintenance Plan Update

Clean Air Act § 175A and related provisions establish the criteria that must be satisfied for a maintenance plan update :
Attainment of the NAAQS for PM 10  Full approval of the SIP under § 110  Demonstration that air quality improvement is due to permanent and enforceable  emissio n reductions Full approval of the PM 10 m aintenance p lan  Fulfillment of all applicable § 110 (maintenance plan) requirements 



### 3.1 NAAQS Attainment Verification

A maintenance area must meet the applicable NAAQS. Attainment of the NAAQS for PM 10 in

n orthern Ada Cou nty is discussed in s ection 4, “ Air Quality Monitoring

— Verification of

Attainment .”



### 3.2 SIP Approval

EPA must have fully approved the applicable SIP for the area pursuant to § 110(k) of the C lean

A ir A ct

. DEQ submitted a PM 10 SIP in November 1991, with revisions in December 1994 and July 1995. EPA gave final approv al to the n orthern Ada County SIP in May 1996. A PM 10

m aintenance p lan and redesignation request was submitted to EPA in September 2002. EPA approved the p lan in Sep tember 2003, restoring northern Ada County to attainment status for

PM 10

.

Section 110 requirements were addressed by the n orthern Ada County PM 10 m aintenance p lan and requested redesignation to attainment status

— adop ted by DEQ on September 26, 2002

, and

ap proved by EPA effective September 2003

— and subsequent infrastructure SIP submittals

.



### 3.3 Permanent and Enforceable Improvements in Air Quality

Permanent and enforceable reductions in emissions and improved ambient PM 10 concentrations

in the n orthern Ada County area are discussed in s ection 7

.



### 3.4 Full A pproval of the PM 10 

### Maintenance Plan

DEQ is submitting this plan to EPA for approval, as required.Northern Ada County PM 10 Maintenance Plan

4 

### 3.5 Maintenance Plan Elements

Section 175A of the Clean Air Act requires DEQ to submit a revision to the original PM 10 maintenance plan eight years after redesignation that demonstrates maintenance of the air quality

standard for an additional 10

- year period. This revision modifies the original PM 10 maintenance plan and includes the following maintenance plan requirements:

Section 4: Continued Air Monitoring and Verification of Attainment 
Section 5 : Emissions Inventory 
Section 6 : Maintenance Demonstration 
Section 7: Permanent and Enforceable Controls 
Section 8 : Contingency Plan 



## 4 Air Quality Monitoring

— Verification of Attainm ent

4.1 PM 10 

### Monitoring

PM 10 ambient air monitoring in n orthern Ada County consists of one monitor located at the downtown Boise fire station (i.e., Fire Station #5 at 16th and Front Streets in downtown Boise )

. This site is operated by DEQ

. The monitor is a t apered e lement o scillating m icrobalance (TEOM) monitor

, which provides continuous, real

- time direct measurement of PM 10 concentrations. The TEOM monitor is part of the approved DEQ monitoring network and is operated in accordance with 40 CFR Part 58. DEQ w ill continue to operate an appropriate PM 10 air quality monitor in accordance with 40 CFR Part 58 to verify continued attainment of the

PM 10 NAAQS. Annual review of the m onitoring network will continue.



### 4.2 Quality Assurance Program

PM 10 monitoring data for the Northern Ada County M aintenance A rea have been collected and quality assured in accordance with 40 CFR Part 58, Appendix A ; EPA’s Quality Assurance Handbook for Air Pollution Measurement Systems (EPA 2008) ; DEQ’s s tandard o perating

p rocedures ; and DEQ’s Quality Assurance Project Plan for the State of Idaho Ambient Air Quality Monitoring Program (DEQ 2009 )

.



### 4.3 Continued Attainment of the PM 10 

### Standard

T he 24

- hour PM 10 NAAQS

, which is 150 μ g/m 3 PM 10 in ambient air (based on 24

- hour averaging)

, is not to be exceeded more than once per year on average over 3 years.

Table 1 demonstrates that n orthern Ada County continues to attain the 24

- hour NAA QS for

PM 10

.



### 4.4 Continued Air Monitoring and Verification of Attainment

Ambient PM 10 concentrations continue to be below regulatory standards. With monitoring data used as the triggering mechanism, DEQ will continue to closely track PM 10 concentrations andNorthern Ada County PM 10 Maintenance Plan

5 ve rify continued attainment via the approved monitoring network operated in accordance with

40 CFR Part 58

.

Table 1

. Highest certified 24

- hour average PM 10 values measured at the Boise fire station

.

Year Highest 24

- Hour Average PM 10 Values ( μg/m 3 )

2000 95

2001 95

2002 150

2003 88

2004 70

2005 89

2006 97

2007 88

2008 92

2009

2010

2011 118

95

18 3

Note : Data for which e xceptional event exclusion requests will be submitted is included.

These data include some extreme natural conditions causing concentrations above the PM 10 standard. T he higher levels on these days were caused by dust storms. B ecause of the small

number of these extreme events, these higher values do not affect compliance with the NAAQS

nor sign ificantly affect the overall trend

. The 183 μ g/m 3 value (and a 156 μ g/m 3 value the following day) in 2011 ha ve been flagged by DEQ as extreme or exceptional event s . DEQ is in the process of preparing the exceptional event exclusion concurrence request s to the EPA for

these two days in 2011. Once granted, the removal of this monitoring data from consideration would result in a considerably lower design concentration (71 μ g/m 3 for 2009

- 2011) . Even with the inclusion of these two days, DEQ remains in compliance with the PM 10 NAAQS. The modeling conducted for this plan was completed prior to the 2011 data becoming official. The data from 2011, if included, even with two days that exceeded the daily standard would result in an increase of the design con centration of 1 μ g/m 3 . Even if this data was included, maintenance

would still be demonstrated. If the EPA concurs on these two exceptional events, as expected,

the exclusion of that data would result in a 3

- year design concentration of 71 μ g/m 3

, w hich is 19

μ g/m 3 lower than the design concentration used in DEQ’s rollback modeling. Thus, by including this data, an extremely conservative approach is being used by DEQ.Northern Ada County PM 10 Maintenance Plan

6 Table 2 shows the annual average PM10 concentrations for 2005

- 2011. While the annual

stand ard has been revoked by EPA, the annual averages are shown for informational purposes and for consistency with previous plans. The data demonstrate that the PM10 annual average has been stable and that northern Ada County continues to be well below the rev oked annual PM10 NAAQS of 50 μg/m3

.

Table 2

. Annual a verage PM 10 c oncentrations measured at Boise Fire Station #5.

Year Annual Average PM 10 Concentrations ( μg/m 3 )

2005 22

2006 25

2007 25

2008 23

2009 22

2010

2011 18

20

Note : All exceptional event

- flagged days are included in these averages

.

Based on the effectiveness of the existing control measures, the instances of high PM 10 days have changed from predominantly wintertime peaks to more dispersed elevated values at different times of year based on four distinct s cenarios. Those four scenarios

— winter stagnation, high winter, non

- winter high carbon, and non

- winter high crustal mass are discussed in detail in Appendix C

, Speciated Linear PM 10 Roll

- F orward Modeling Repor t

.



## 5 Emissions Inventory

Environ International Corporation (Environ ) and ERG , under contract with DEQ

, completed the 2008, 2015, and 2023 Emissions Inventories for the Treasure Valley Airshed ( ERG/ Environ

i nventory)

. A modified ERG/ Environ i nventory is included as Appendix D

. The ERG/ Environ inventory was designed to support this 10

- year maintenance plan update, the previously submitted carbon monoxide limited maintenance plan, and Treasure Valley airshed planning and management needs for the future; as such, it is a multi

- pollutant inventory. Two sections of the original 2010 ERG/ Environ inventory have been superseded to account for the most currently available information. Section 4 has been replaced to account for the adoption of the MOVES

model fo r motor vehicle emissions. This is explained in more detail in the next paragraph. The

second change was to replace the Treasure Valley Road Dust Study which was used by

ERG/Environ in the 2010 EI for paved road dust . This study was replaced by the Januar y 2011

AP

- 42 Compilation of Air Pollutant Em i ssion Factors (EPA 2011b, sec tion 13.2.1). Additional

information explaining and supporting this change is provided in Appendix E, Section 3. For purposes of this plan, average winter season (PM season) means from November 1 through February 29 (2008 was a leap year)

, and summer season (ozone season) refers to April 1 through

October 31

. The month of March is not considered to be part of either the high PM season, or of the ozone season, and as such, is not u sed in seasonal analyses.

The ERG/ Environ i nventory used the Mobile6 model, the only EPA

- approved model available at

the time to calculate emissions due to on

- road mobile sources. However, as this document wasNorthern Ada County PM 10 Maintenance Plan

7 being drafted, the Community Planning Associat ion of Southwest Idaho ( COMPASS )

, which is the designated Treasure Valley metropolitan planning organization, was expected to be required to begin using the newly released MOVES 2010a (MOVES) model for transportation conformity

determinations beginning in M arch 2012 ( 40 CFR 93.111(b)(1) ). T his date was later changed by

EPA to 2013, well after the modeling had begun

. DEQ, with input from COMPASS, has completed additional modeling that supplants portions of the ERG/ Environ inventory. Input from

COMPASS included projected growth rates, land use planning, vehicle miles traveled (VMT) estimates, road classification, and travel demand modeling outputs

. Total c arbon was speciated by DEQ using speciation profiles from the Receptor Model Source Composition Libr ary (EPA 1984)

. The mobile emissions were re

- modeled using the MOVE S 2010a model (MOVES)

, and DEQ re

- estimated the road dust using the new AP

- 42 method (EPA 2011).

MOVES is known to result in significantly higher estimates for PM 10 and nitrogen oxides ( NO

x )

emissions

. For this reason, DEQ is using MOVES to develop the motor vehicle emissions budget ( MVEB ) and will ask for an adequacy determination to allow the MVEB in this plan be used to demonstrate conformity as soon as the adequacy determination is compl eted and the MVEB approved.



### 5.1 Base Year (2008) Annual and Episode Emissions Inventory

The ERG/ Environ inventory includes Ada County in its entirety as opposed to just the Northern Ada County Maintenance Area. Using the entire county is a more conservative approach that meets the maintenance plan requirements while supporting the “airshed management” approach

used by DEQ.

The inventory is divided into f ive categories of sources : point, area, on

- road mobile

, non

- road

mobile

, and bioge nic

. These categories will be discussed in more detail below. Table 3

summarizes the 2008 annual PM 10 emissions for the maintenance area ; Table 4 summarizes the winter season average daily emissions; and Table 5 summarizes the non

- winter season average daily emissions

.

Table 3 . Annu al e missions by s ource c ategory

— 2008.

Source Type NO
x SO 2 VOC PM 10 PM 2.5 TC

(tons per year)

Point 356 66 268 169 143 77

Area 921 27 12

, 963 19

, 555 3

, 552 6

, 522

On

- road 9

, 775 67 4

, 182 41 3 330 384

Non

- road 2

, 895 90 2

, 031 258 245 227

Biogenic 202 0 12

, 802 0 0 0

Total 14,149 250 32,247 20

, 395 4

, 270 7

, 210

Note : nitrogen oxides (NO x ); sulfur dioxide (SO 2 ); volatile organic compounds (VOC); an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM 10 ); particulate matter with a diameter 2.5 micrometers or less (PM 2.5 ); total carbon (TC)

Note : Source type categories may not sum exactly to the total emissions listed due to rounding.Northern Ada County PM 10 Maintenance Plan

8 Table 4 . Emission for w inter s easons

— 2008.

Source Type NO
x SO 2 VOC PM 10 PM 2.5 TC

(tons per day)

Point 1.0 0.2 0.7 0.5 0.4 0.2

Area 4.4 0.1 39.1 67. 6 15.1 19.9

On

- road 24.0 0.2 12.3 1.2 1.0 1.1

Non

- road 5.6 0.2 4.4 0.4 0.4 0.7

Biogenic 0.3 0.0 5.8 0.0 0.0 0.0

Total 35.2 0.7 62. 3 69. 7 16.9 21.9

Note : nitrogen oxides (NO x ); sulfur dioxide (SO 2 ); volatile organic compounds (VOC); an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM 10 ); particulate matter with a diameter 2.5 micrometers or less (PM 2.5 ); total carbon (TC)

Note : Source type categories may not sum exactly to the total emissions listed due to rounding.

Table 5 . Emission for n on
- w inter s easons

— 2008.

Source Type NO
x SO 2 VOC PM 10 PM 2.5 TC

(tons per day)

Point 1.0 0.2 0.7 0.5 0.4 0.2

Area 1.4 0.0 33.7 43.5 6.6 12.3

On

- road 28.5 0.2 10.9 1.1 0.9 1.0

Non

- road 10.1 0.3 7.2 0.9 0.9 0.8

Biogenic 0.7 0.0 55.6 0.0 0.0 0.0

Total 41. 7 0.7 108. 1 46. 1 8. 7 14.3

Note : nitrogen oxides (NO x ); sulfur dioxide (SO 2 ); volatile organic compounds (VOC); an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM 10 ); particulate matter with a diameter 2.5 micrometers or less (PM 2.5 ); total carbon (TC)

Note : Source type categories may not sum exactly to the total emissions listed due to rounding.Northern Ada County PM 10 Maintenance Plan

9 Total annual PM 10 emissions are predominantly due to area sources, which account for 19,555

tons per year ( 9 6 % ) of the total annual PM 10 emissions ( Table 3 ; Figure 2 )

.

Figure 2

. PM 10 a nnual e missions in the f our s ource c ategories ( to the nearest ton )

.

F our source categories are summarized below , including changes due to use of the MOVES

model. Biogenic emissions are not discussed.

5.1.1 Area Sources

In the Handbook for Criteria Pollutant Inventory Development: A Beginner’s Guide for Point

and Area Sources , the EPA describes area sources as “facilities or activities whose individual emissions do not qualify them as point sources. Area sources represent numerous facilities or activities that individually release small amounts of a given pollutant, but collectively they can release significant amounts of a pollutant” (EPA 1999 ). For the purposes of this emission s inventory, area sources are defined as tho se sources emitting annual emissions less than the point

source thresholds (see section 5.1.4 )

.

Specific categories of area sources include, but are not limited to

, residential wood burning

, agricultural and open burning, industrial fuel combustion, paved and unpaved road dust, commercial cooking, auto body refinishing, and construction. Residential wood burning was found to be the primary contributor to the original violations of the PM10 NAAQS, accounting for 22 wintertime tons per day (tpd) . The 2008 E I, attributes 13.4 tpd to residential wood smoke,

a reduction of 39% even with the county population almost doubling. This indicat es that the

residential wood burn ing program has been very successful at reducing PM 10 emissions. 169

19555 413 258 

## 2008 PM10 Annual Emissions by Source Category (Tons Per Year)

Point

Area

On-Road

Non-RoadNorthern Ada County PM 10 Maintenance Plan

10 For base year 2008, the largest contributor of PM 10 emissions is paved road dust

, which accounts

for 36.8 % of the annual PM 10 emissions and 49.9 % of the winter da il y emissions ( Table 6 )

.

Table 6

. Ada County p aved r oad d ust e missions

.
Paved Road D ust Emission (% of Total PM 10 ) Total PM 10 Emission

Year 2008 2015 2023 2008 2015 2023

Annual (t ons/ y ear ) 7

, 501

(36.8%) 9

, 164

(42.1 % ) 13

, 243

(51.2 % ) 20

, 395 21

, 756 25875

Non

- winter daily (t ons/ d ay ) 10

(22.5 % ) 12

(26.1 % ) 18

(33.7 % ) 46 48 53

Winter daily (t ons/ d ay ) 35

(49.9 % ) 43

(56.3 % ) 62

(64.8 % ) 70 77 96

The 2008 PM10 contribution from road dust for Ada County was 7,501 tons per year (tpy)

. Unpaved road dust accounted for 966 tpy. In total, road dust in Ada County contributed 8,467 tpy, or 41.5% of the total PM10 emissions in 2008. ( Figure 3 )

.

Figure 3

. PM 10 r oad d ust c ompared to a ll o ther s ources

.

5.1.2 On

- Road Mobile Sources

On

- road mobile source emissions were calculated using the MOVES model , which is ex pected to result in significantly higher PM 10 and NO

x emissions than the previous Mobile6 model. The

MOVES model calculated annual PM 10 o n

- r oad direct mobile emissions of 41 3 t ons p er y ear with 1.2 t ons p er d ay during the winter season. In addition, secondary aerosol precursor emissions estimated by the MOVES model included 9

, 775 t ons p er y ear NO

x , 67 t ons p er y ear sulfur dioxide ( SO 2 )

, and 4

, 182 t ons p er y ear volatile organic compounds ( VOCs )

. 7,501

966 11,928 

## 2008 Total PM 10 

## Road Dust Vs. Other 

# Sources (Tons Per Year)

Paved Road Dust

Unpaved Road Dust

All Other SourcesNorthern Ada County PM 10 Maintenance Plan

11 5.1.3 Non

- Road Mobile Sources

Non

- r oad mobile sources include a wide variety of equipment that either move under their own power or are capable of being moved from site to site. Non

- road mobile equipment sources not
licensed o r certified as highway vehicles are defined as those that move or are moved within a

12

- month period and are covered under EPA's emissions regulations as non

- road mobile sources.

The three types of non

- road mobile sources are non

- road equipment

, such as construction and

recreational off

- road vehicles ; locomotives ; and a ircraft . Non

- road mobile sources accounted for

258 t ons p er y ear PM 10, 2

, 89 5 t ons p er y ear NO

x , 90 t ons p er y ear SO 2 , and 4

, 182 t ons p er y ear VOC in the 2008 ERG/ E nviron inventory

.

5.1.4 Point Sources

To capture all pollutants and all facilities located within the maintenance area for the

ERG/ Environ inventory , facilities were divided into point or area sources based on the emission levels of all criteria pollutants. If a facility exceed ed a defined point for any pollutant, it was included as a po int source. The ERG/ Environ i nventory defines point sources as any facility emitting greater than any of the following thresholds:

5 tons per year of PM 10 , PM 2.5 , SO 2 , or ammonia ( NH 3 )  10 tons per year of VOCs  25 tons per year of NO

x or CO 

F acilities were included in the point source category for PM 10 if they exceeded the limit for any pollutant. Sources with annual emissions below these levels for all criteria pollutants were included in the area source inventory. T he universe of permitted point sourc es in n orthern Ada County is larger than the point sources included in the ERG/ Environ i nventory.

The total 2008 annual point source emissions inventory results were 169 t ons p er y ear of PM 10 emissions with 0 .45 tons per day emitted in the P M season and 0 .46 t ons p er d ay emitted in Ada County in the ozone season. Point sources also contribute 35 6 t ons p er y ear NO

x , 66 t ons p er

y ear SO 2 , and 268 t ons p er y ear VOC.

P revious modeling indicated that emissions from the TASCO facility in Canyon County, outside

o f the maintenance area were “shown to potentially contribute to PM 10 exceedances in Canyon County”, however neither the photochemical model nor the CMB modeling indicated an y significant impact in Ada County. Nevertheless TASCO’s permit

- allowable emission levels were addressed in the Tier II operating permit issued as part of the control measures in the 2002 SIP “to insure that TASCO impacts in Ada County are at acceptable levels.” Pertinent permit requirements are included in Idaho’s SIP at 40 CFR 52.670.

In view of the 2002 concerns about potential Canyon County PM 10 exceedances due to TASCO,

it should be noted that T ASCO’s 2008 PM10 emissions (219 μ g/m 3 ) repre sent a 35% reduction over the 1999 base year emission in the 2002 SIP. In addition, the Nampa, Idaho average 2 nd
high PM10 value for 2009

- 2011 is 85 μ g/m 3 at the Nampa Fire Station, approximately 2 miles from TASCO. Therefore, TASCO emissions, as limited by the Tier II operating permit, appear to have effectively eliminated the threat to the PM10 NA AQS in Canyon County.Northern Ada County PM 10 Maintenance Plan

12 

### 5.2 Projected Inventories

The methodologies used in the future year (2015 and 2023) emissions projections are discussed

in s ection 7 of the ERG/ Environ i nventory (Appendix D )

. Future year projections for o n

- road

MOVES emissions modeling a nd paved road dust emissions are included in Appendix E

, Development of the Base

- and Future

- Year Mobile Source Emission Inventories for the Treasure Valley, Idaho

.

Total PM 10 emissions in Ada County are projected to increase through 2023. Most of the increase in emissions can be attributed to an increase in paved road dust

, which increases in proportion to the increase in VMT. Despite th is expected increase, modeling shows tha t the PM 10 standard will be protected. A s such, the modeled concentrations are expected to be high (i.e., conservative ) compared to actual expected concentrations , for reasons summarized in Section6.3, second paragraph

.

NO

x and VOCs from on

- road sources , i mportant in secondary aerosol formation, are expected to

continue decreas ing over the life of the maintenance plan as more efficient vehicles continue to replace older, higher emitting vehicles. Table 7 and Table 8 show the annual emissions by source category for 2015 and 2023

, respectively

.

Table 7 . Annual e missions by s ource c ategory

— 2015.

Source Type NO
x SO 2 VOC PM 10 PM 2.5 TC

(tons per year)

Point 355.6 65.7 268.1 169.1 142.6 68.5

Area 900.0 23.6 14

, 551.2 21

, 107.4 3

, 651. 0 7

, 806.1

On

- road 5

, 856.6 33.4 2

, 939.7 283.0 193.0 246.0

Non

- road 1

, 979.8 28.2 1

, 480.7 196.9 185.8 172.7

Biogenic 202.3 0.0 12

, 802.5 0.0 0.0 0.0

Total 9

, 294.3 150.9 32

, 042.2 21

, 756.4 4

, 172. 4 8

, 293.3

Note : nitrogen oxides (NO x ); sulfur dioxide (SO 2 ); volatile organic compounds (VOC); an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM 10 ); particulate matter with a diameter 2.5 micrometers or less (PM 2.5 ); total carbon (TC)

Note : Source type categories may not sum exactly to the total emissions listed due to rounding.

Table 8 . Annual e missions by s ource c ategory

— 2023.

Source Type NO
x SO 2 VOC PM 10 PM 2.5 TC

(tons per year)

Point 391.2 72.3 294.9 186.0 156.8 75.3

Area 951.9 23.8 18

, 062.8 25

, 267. 1 4

, 072. 7 9

, 775.5

On

- road 4

, 306.4 42.0 2

, 396.8 285.2 157.1 228.6

Non

- road 1

, 355.0 33.8 1

, 407.9 135.8 125.9 119.9

Biogenic 202.3 0.0 12

, 802.5 0.0 0.0 0.0

Total 7

, 206.7 171.9 34

, 964.8 25

, 874. 1 4

, 512.5 10

, 199.2

Note : nitrogen oxides (NO x ); sulfur dioxide (SO 2 ); volatile organic compounds (VOC); an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM 10 ); particulate matter with a diameter 2.5 micrometers or less (PM 2.5 ); total carbon (TC)

Note : Source type categories may not sum exactly to the total emissions listed due to rounding.Northern Ada County PM 10 Maintenance Plan

13 

### 5.3 Motor Vehicle Emissions Budget

Clean Air Act § 176 requires any activity that is federally supported or permitted to conform with approved air quality SIPs . To help guide the transportation process, C lean A ir A ct § 108(e) compelled the EPA a dministrator and s ecretary of t ransportation to develop a “cont inuous transportation

- air quality planning” process and guidance on develop ing and implement ing transportation and other measures necessary to demonstrate and maintain attainment of NAAQS.

This effort led to the “conformity” rules found at 40 CFR 93.100

– 93 .129.

The intent of the conformity rules is to synchronize the air quality planning process with transportation plans developed by m etropolitan p lanning o rganizations (MPOs) and other transportation organizations to ensure air quality standards are met. S imply put, transportation plans must “conform” to air quality plans and show that t ransportation projects using federal funds or deemed to be “regionally significant” in air quality nonattainment and maintenance

areas do not contribute to a degr adation of air quality

.

COMPASS serves as the MPO for Ada County. COMPASS develops a regional long

- range transportation plan ( Communities in Motion ) that identifies needed transportation projects that can be funded within the life of the plan (20 years and beyond )

. O nly funded projects can be evaluated for air quality conformity.

Near

- term transportation projects are included in the t ransportation i mprovement p rogram (TIP)

. The TIP is a short

- range (3

– 5 year) budget of transportation projects that lists all projects for which federal funds are anticipated, along with non

- federally funded projects that are regionally significant. Projects in the TIP must be consistent with the regional long

- range transportation plan.

To reconcile long

- range transportation plans and TI Ps with air quality implementation plans, the conformity rules at 40 CFR 93.118 require these plans be consistent with the MVEB

, which is part of the air quality SIP

. This PM 10 m aintenance p lan cover s the time period of 2013 through

2023. Since the regional long

- range transportation plan has a t least a 20

- year horizon and updated plans will be developed in 2014, 2018, and 2022, the MVEB needs to cover transportation projects through the 2040s . For this plan

, DEQ has chosen to establish MVEB s for

the base year of 2008, an intermediary year of 2015, and an ending year of 2023 , which will be applied to transportation plans with horizon years extending to 2050

.

5.3.1 MVEB for PM 10
The PM 10 MVEB covers fugitive dust from paved and unpaved roads and direct PM 10 vehicle emissions ( due to exhaust, tire wear
, and break wear). Construction emissions from transportation projects were determined not to be significant and are not included in the MVEB for conformity purposes. EPA’s MOVES model was used to develop vehicl e emissions estimates

for the MVEB . The road dust and vehicle emissions were estimated for the time periods 2008

– 2015 and 2015

– 2023. To ensure the 2023 MVEB is sufficient to cover the horizon year of future transportation plans, the motor vehicle emissions in the last period (2023

– 2050) are forecasted 2050 emissions based only on VMT increases from 2015 to 2050. PM 10 emissions for the MVEB years 2015 and 2023 were increased by a 10% safety margin as allowed by the conformity rule at 40 CFR 93.124(a). Since PM 10 emissions are primarily influenced by VMT and the VMT is trending upward, the emissions are also projected to increase over time. Therefore, the largestNorthern Ada County PM 10 Maintenance Plan

14 emissions for PM 10 are in the last year of each of the time periods listed above. The conformity

r ule states that “ e missions in years for which no motor vehicle emissions budget are specifically established must be equal to the motor vehicle emission budget(s) established for the most recent prior year” (40 CFR 93.118(b)(1)(ii)). Table 9 highlights the PM 10 MVEB for each planning period.

Table 9 . PM 10 m otor v ehicle e missions b udget

.

Time Period PM 10 MVEB

(tons per day)

2008 31.0

2015 42.9

2023 60.1

Note : The PM 10 emissions were taken from the “ Development of the Base

- and Future

- Year Mobile Source Emission

Inventor ies for the Treasure Valley, Idaho ” (Appendix E)

. They include the annual tail pipe emissions (Table 10 ), annual paved road dust emissions (Table 13)

, and the unpaved road dust emissions (Table 16) in Appendix E . The annual emissions were divided by 365 days to calculate tons per day and for the 2008

– 2015 and 2015

– 2023 periods, increased by a 10% safety margin.

5.3.2 MVEB for NO x and VOC

The conformity rule requires a n MVEB for VOCs and NO

x as precursors to PM 10 when they are significant contributors (40 CFR 93.109(b)(2)(iii))

. Sulfur dioxide ( SO 2 ) is an insignificant

contribut or to the secondary aerosol formation and is not included. Although NH 3 contributes to secondary aerosol formation

, the region is “ammonia rich

, ” so the very small mobile source NH 3 emissions are also not considered in MVEBs

. Accordingly , DEQ is establishing NO

x and VOC emissions budgets for the base year 2008 as well as 2015 and 2023. The forecasted NO

x and VOC emissions are expected to decline over time even though the MVEB increases (see Table

10 footnote) . Similar to the PM 10 MVEB, a safety margin of 10% was added to the 2008

– 2015

and 2015

– 2023 planning periods ( Table 10 )

.

Table 10 . NO
x and VOC m otor v ehicle e missions b udget

.
Time Period NO
x MVEB VOC MVEB

2008 29.5 12.6

2015 29.5 12.6

20 23 34.2 17.2

Note : From Table 23 in the “Speciated Linear PM 10 Roll

- Forward Modeling Report” (Appendix C). As discussed in that report, the model does not treat nonlinear chemical processes

, so NO x and VOC were held constant for modeling purposes even though they are general ly declining over time. However, since the out year of 2050 was calculated by multiplyin g the projected 2050 vehicle miles traveled by the projected 2015 vehicle fleet emission rates, t his causes
an increase in NO x and VOC because the fleet emission rates are held constant and emissions reductions expected
from a newer fleet are not included. The emissions from this conservative approach were included in the PM 10 roll

forward modeling run to demonstrate adequacy of the MVEB.

5.3.3 MVEB Conclusion
Before the MVEB can be used for conformity purposes it must demonstrate “adequacy.” F or EPA to determine the MVEB is adequate, the conformity rule requires th at MVEB emissions must be considered with all other emissions sources and be consistent with the applicable maintenance plan (40 CFR 93.118(e)(4)(iv))

. M odeling must demonstrate that all emission sNorthern Ada County PM 10 Maintenance Plan

15 sourc es combined (point sources, area sources, and mobile sources) will not cause or contribute

to a violation of the PM 10 NAAQS. As required by the conformity rule, the MVEBs were included with all other emissions in modeling

, which demonstrated that future co ncentrations

were below the PM 10 NAAQS. For a complete discussion on the modeling demonstration

, see Appendix C, Speciated Linear PM 10 Roll

- Forward Modeling Report

.



## 6 Mainten ance Demonstration

DEQ has completed the Speciated Linear PM 10 Roll

- F orward Modeling Report , which is included as Appendix C

.



### 6.1 Air Quality Modeling Approach

Linear roll

- forward modeling is a relatively simple technique for evaluating the effect of emission reductions on ambient concentrations of air pollutants. The model assumes that ambie nt concentrations above some regional background level are proportional to the estimated emissions

of the local sources. By reducing the size of one or more of the local sources, the resulting

reduction in ambient concentrations can be estimated. Since PM 10 is composed of several different components (i.e.

, geologic material, carbon mass, ammonium nitrate

, and ammonium sulfate), roll

- forward calculations must be performed on each of these species individually to more accurately evaluate different emissions reductions or control options.

Although the roll

- forward model does not analyze the chemical reactions and dispersion of the pollutants and it provides neither spatial nor temporal information for pollutant concentrations, it does provide a low

- cost and r elatively reliable approach to estimate the pollutant levels for

worst

- case meteorology, annual average

, and seasonal average conditions. The roll

- forward

model can be used to safely estimate whether the PM 10 concentrations can be maintained below the NAAQ S in future years.

Since the 3

- year average 24

- hour PM 10 values have been significantly lower than the PM 10 NAAQS (150 μg/m 3 ) over the last two decades in n orthern Ada County, DEQ has determined

, and EPA has agreed

, that the roll

- forward model is an appro priate method to demonstrat e compliance in future years.

Four speciation profiles and an annual profile were created for the following scenarios: wintertime “stagnation” (severe stagn ation events, wet conditions); wintertime “high

- winter” (drier winter stagnation conditions); high carbon mass events ; high crustal mass events in

nonwinter seasons ; and annual average.

The d ata required to conduct roll

- forward modeling include d monitored PM 10 data, base

- year and projected future

- years emissions data

, and b ackground PM 10 data. All data were speciated for major PM 10 components : g eological mass (crustal mass), carbon mass, sulfate mass (ammonium sulfate), and nitrate mass (ammonium nitrate)

. Additionally, the emission s inventory included the precursor emission s (NO

x , SO 2 , and NH 3 ) for the secondary aerosols.

D ata from 2007

– 2009 were used for the demonstration

, as they were the most complete data set (including ambient concentrations, background

, and speciation) available at the time of thisNorthern Ada County PM 10 Maintenance Plan

16 analysis. Some a dditional data that have since become available are also discussed. The newer data do not change the conclusions reached in the completed analysis.



### 6.2 A ttainment Demonstration

The model has demonstrated that the PM 10 levels in n orthern Ada County will remain well under the NAAQS i n future years

, despite the increase of predicted county

- level road dust emission

rates. Tables 11

– 15 and F igures 4

– 8 show the relative importance of the major species at present
and in future years. Three species

— crustal mass, total carbon mass

, and nitrate mass

— will continue to play important roles in future years. In all scenario types and all time periods, the

contribution of sulfate remains low . T he sulfate contribution is decreasing even though the total

amount remains the same s ince total PM 10 is increasing

. The annual average scenario and other

four scenarios are described below.

6.2.1 Annual Average

In the case of annual average PM 10 concentration s
, Table 11 and Figure 4 show that crustal mass, which is mainly due to road dust, is primarily responsible for the increase in total PM 10 concentration s , while the other species remain virtually unchanged.

Table 11 . Predicted annual average PM 10 levels.

Year Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM 10 Total a

( μ g/m 3 )

2008 1.1 1.2 3.8 16. 9 0 .4 23.3

2015 1.1 1.2 4.2 17. 9 0 .4 2 4

. 7

2023 1.1 1.2 5.0 20 .2 0 .4 2 7

. 9

a For comparison to the now

- revoked NAAQS annual PM 10 standard of 50 μg/m 3

.

Figure 4

. Predicted annual average PM 10 concentration ( in micrograms per cubic meter )

. 0 5 10 15 20 25 30

Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM10 

# Predicted Annual PM 10

2008

2015

2023Northern Ada County PM 10 Maintenance Plan

17 6.2.2 Non w inter High Crustal Mass Scenario

In the nonwinter high crustal mass scenario, road dust (i.e., crustal mass) is the primary

contributor ( Table 12 ; Figure 5 )

. Similar to the annual average scenario, crustal mass increases

with time while the other contributors change very little.

Table 12 . Predicted 24

- hour average PM 10 levels for h igh crustal mass scenario in nonwinter

seasons

.

Year Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM 10 Total a

(μg/m 3 )

2008 3.2 0. 0 8 .6 77.2 1.0 90.0

2015 3.2 0. 0 9.7 80.1 1.1 94.1

2023 3.2 0. 0 11.7 8 9

. 1 1.2 105.1

a For comparison to the NAAQS 24

- hour PM 10 standard of 150 μg/m 3

.

Figure 5

. Predicted 24

- hour average PM 10 levels (in micrograms per cubic meter) for h igh crustal
mass scenario in nonwinter seasons

.

6.2.3 Non w inter High Carbon Scenario

In this scenario

, c rustal mass ( i.e.

, road dust ) is still the predominant contributor, but high levels of carbon mass indicate the presence of wildfires in the area. High carbon scenario days have

low er PM 10 concentrations than PM 2.5 , also indicating the presence of fires. Table 13 and Figure

6 show both carbon and crustal mass make significant contributions to PM 10

. 0 20 40 60 80 100 120

Sulfate Mass Nitrate Mass Total Carbon Crustal Mass Unknown PM10



## Predicted PM 10 

### Nonwinter High Crustal Scenario

2008

2015

2023Northern Ada County PM 10 Maintenance Plan

18 Table 13 . Predicted 24

- hour average PM 10 levels for h igh carbon scenario in nonwinter seasons

.

Year Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM 10 Total a

( μ g/m 3 )

2008 2.8 1. 5 2 9.7 54.8 1.2 90.0

2015 2.8 1.5 34.1 56.8 1.3 96.5

2023 2.8 1.5 41.5 62.8 1.5 110.1

a For comparison to the NAAQS 24

- hour PM 10 standard of 150 μg/m 3

.

Figure 6

. Predicted 24

- hour average PM 10 levels (in micrograms per cubic meters) for h igh carbon
scenario in nonwinter seasons

.

6.2.4 High Winter Scenario

The high winter scenario, while also stagnant, differs from the stagnant winter scenario due to relatively warmer and drier conditions. Table 14 and Figure 7 show that carbon mass plays the most important role

, followed by crustal mass ; the import ance of nitrate decreases with time as a result of tightening federal motor vehicle standards.

Table 14 . Predicted 24

- hour average PM 10 levels for h igh w inter scenario

.

Year Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM 10 Total a

( μ g/m 3 )

2008 4.8 20.5 34.5 28.3 1.9 90.0

2015 4.8 20.5 37.8 32.4 2.0 97.6

2023 4.8 20.5 45.9 42.0 2.4 115.7

a For comparison to the NAAQS 24

- hour PM 10 standard of 150 μg/m 3

. 0 20 40 60 80 100 120

Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM10 

## Predicted PM 10 

### Nonwinter High Carbon Scenario

2008

2015

2023Northern Ada County PM 10 Maintenance Plan

19 Figure 7 . Predicted 24

- hour average PM 10 levels (in micrograms per cubic meters) for h igh w inter
scenario

.

6.2.5 Stagnant Winter Scenario

A s tagnant event is a high PM scenario with a severely stagnant atmosphere and very cold

, wet
conditions

, such as snow cover on the ground

. These episodes usually last for a week or longer.

Table 15 and Figure 8 show nitrate, carbon, and crustal mass hav ing approximately similar contributions near term, but with declining nitrate and increasing crustal mass contributions in future years.

Table 15

. Predicted 24

- hour average PM 10 levels for s tagn ation scenario in winter season

.

Year Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM 10 Total a

( μ g/m 3 )

2008 7.1 37.7 19.4 2 4.5 1.2 90.0

2015 7.1 37.7 21.3 27.8 1.3 95. 2

2023 7.1 37.7 25.8 35.6 1.5 10 7.7

a For comparison to the NAAQS 24

- hour PM 10 standard of 150 μg/m 3

. 0 20 40 60 80 100 120 140

Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM10 

## Predicted PM 10 

### High

- winter Scenario

2008

2015

2023Northern Ada County PM 10 Maintenance Plan

20 Figure 8 . Predicted 24

- hour average PM 10 levels (in micrograms per cubic meter) for s tagnation
scenario in winter season.



### 6.3 Modeling Summary

The roll

- forward modeling has demonstrated that northern Ada County will meet the PM 10 24

- hour NAAQS in future years up to 2023 with at least a 23% margin of safety. The model results

for mobile source emission s conformity also show that the ambient PM 10 concentrations will be below the NAAQS up to year 2023. Presently

, nitrate mass contributes much less to the total

ambient PM 10 compared to the early 1990s. Based on the future year inventories, particularly

NOx reductions due to federal vehicle emission standards, this trend in declining nitrate aerosol

will likely continue into the future or at least remain level

. Carbon mass will remain an important contributor in future years. Sulfate mass makes minimal contributions currently and

even less in the fut ure.

Crustal mass will be the important contributor to ambient PM 10 in all occasions

. The relative importance of crustal mass will increase over time due to an increase in vehicle miles travelled. The relative importance of nitrate mass is likely to drop with decreases in vehicle NOx

emissions , or at least remain level

. Nitrate mass was conservatively assumed to remain constant, rather than decrease as expected due to lower new car NO

x emissions in the future. This

conservative nitrate emissions treatment is intended to allow for potential uncertainty in the nitrate formation process (see Appendix C, Section 6.5).

In addition , the model results are conservative since the design value was determined based on

the relatively high monitored values on days that were often influenced by windblown dust or wildfire smoke. It is also important to note that projected future VMT increase s with associated

crustal mass increase will be spread throughout the valley rather than concentrated at the

downtown Boise area where exceedances have occurred in the past. As a result, future concentrations are not expected to increase with the same rate of VMT growth as assumed in this simplified roll

- forward model based on the downtown monitor

. This conclus ion is reinforce d by the steady decline in PM 10 levels witnessed over the past decade. 0 20 40 60 80 100 120

Sulfate

Mass Nitrate

Mass Total

Carbon Crustal

Mass Unknown PM10 

## Predicted PM 10 

### Winter Stagnation Scenario

2008

2015

2023Northern Ada County PM 10 Maintenance Plan

21 

## 7 Permanent and Enforceable Improvement in Air Quality

The Clean Air Act requires each maintenance plan to demonstrate that measures credited with bringing an area into attainment are fe derally enforceable and will continue into the future. The residential wood burning and open burning ban program meet this requirement as they are enacted and currently being implemented at the respective government level s throughout

n orthern Ada County. T hese programs were approved by EPA as meeting the RACM/RACT (reasonably available control measures/reasonably available control technology) requirements (see 59 FR 48583) and were found to meet the enforceability requirements of the C lean A ir A ct

. The m ain tenance d emonstration in s ection 6 provides documentation that the area will maintain

PM 10 attainment for the foreseeable future as a result of implementing these measures. Therefore, the n orthern Ada County plan meets the C lean A ir A ct requirement for permanent and

enforceable control measures.



### 7.1 Control Measures

The following control measures resulted in the area ’ s continued attainment of the PM 10 NAAQS

. C ontinued implementation of these measures should ensure future maintenance of the P M 10 NAAQS through the year 2023, which is the duration of the maintenance period.

7.1.1 Air Quality Index Program

DEQ operates an Air Quality Index (AQI) Program to support the public information and regulatory components of the PM 10 SIP. Through this program

, D EQ provides information on the measured and predicted ambient air pollution levels for the highest measured and highest predicted criteria pollutant. Information on voluntary or mandatory open burning bans and indoor wood burning bans is provided via sever al formats. AQI information a nd information on burn conditions is posted daily on DEQ’s website, is made available via recorded message 24

- hours per day, and is e

- mailed to people who wish to be on a daily or an “alert” list. The alert list is only sent on days when the AQI is forecast to be at a level where local no

- burn ordinances go

into effect.

7.1.2 Residential Wood Burning Program

Key elements in the current residential wood

- burning program include issuing a voluntary burn

ban when PM 10 is at, or is expected to reach approximately 6 4 μg/m 3 and a mandatory burn ban when levels reach approximately 100 μg/m 3 of PM 10

. Each city in Ada County and unincorporated Ada County has an existing ordinance prohibiting the use of woodstoves or fireplace s when an air quality alert is issued, as noted above

.

A woodstove change

- out program is in place, and the cities and counties have ordinances that prohibit installation of non

- EPA

- certified woodstoves. Additionally, Idaho provides tax

incentives for repla cing older, more polluting woodstoves for cleaner

- burning EPA

- certified

woodstoves.

7.1.3 Open Burning Ban Program

The open burn ban program includes voluntary bans when PM 10 reaches app roximately 64 μg/m 3
and mandatory bans when the forecast AQI is 60 or great er for any pollutant (i.e., approximately

74 μg/m 3 for PM 10 )

.Northern Ada County PM 10 Maintenance Plan

22 Additional mandatory burn bans can be implemented by DEQ beginning at the Stage 1

-- Air

Pollution Forecast and Caution l evel. The s tage one level is the 24

- h our NAAQS of 150 μg/m 3 as set in the “Rules for the Control of Air Pollution in Idaho” (IDAPA 58.01.01.550 )

.

7.1.4 Stationary Source Control Measure

In 2002, s tationary sources made up a relatively small fraction of the total annual PM 10 emissions inventory at 3. 2 %

. However, the modeling conducted for the 2002 analysis for future year compliance indicated that a subset of existing stationary sources had the potential to interfere

with maintenanc e of the NAAQS. Therefore, the 2002 maintenance p lan addressed 13 facilities

located within the maintenance area that had the potential to interfere with maintenance of the NAAQS based on their potential or allowable emissions ( Environ 2002)

. DEQ use d the authority provided in IDAPA 58.01.01.401.03 to require that Tier II permits be issued to these f acilities. These permits established federally enforceable permit conditions that limited the ambient impacts due to facility emissions to acceptable levels. Although actual emissions from these

facilities did not cause or contribute to a violation of the NAAQS, limits on the potential to emit were necessary to demonstrate ongoing maintenance of the NAAQS. Currently, 8 of th e se facilities continue to operate in the maintenance area.

In addition to the facilities discussed above, p ermit conditions for the TASCO facility in Nampa, Idaho, which is outside of the maintenance area but within the modeling domain, were included

in the 2002 m aintenance p lan

. A Tier II operating permit was issued to TASCO that required

reductions in actual , as opposed to potential, PM 10 emissio ns. TASCO emissions are 39% lower in the 2008 EI than they were in the 1999 inventory.

Based on the emissions inventory used for this plan, point sources within the maintenance area, accounted for 0.8% of the 2008, 0.8% of the 2015, and 0.7 % of the 2023 annual PM 10 emissions.

The previously approved stationary source control measures included in the 2002 maintenance plan submittal and codified in 40 C.F.R. § 52.670 will remain in effect. In addition, Idaho’s permit program will continue to be the control measure for new and modified sources as well as any sources determined to pose a threat to continued maintenance of the PM 10 NAAQS.



## 8 Contingency Plan

Based on the emissions inventory used for this plan, point sources w ithin the maintenance area,

accounted for 0 .8% of the 2008, 0 .8% of the 2015, and 0 .7% of the 2023 annual PM 10 emissions.

T he previously approved stationary source control measures included in the 2002 maintenance plan submittal and codified in 40 C.F.R. § 52.670 will remain in effect. In addition, Idaho’s permit program will continue to be the control measure for and new and modified sources as well as any sources determined to pose a threat to continu ed maintenance of the PM10 NAAQS.

Section 175A of the Clean Air Act requires that a maintenance plan include contingency provisions as necessary to promptly correct any violation of the NAAQS that may occur after redesignation to attainment. Areas in att ainment are not required to have enacted contingency

measures
, just a list of measures that could be considered for future implementation.Northern Ada County PM 10 Maintenance Plan

23 The contingency plan must ensure that the contingency measures are adopted expeditiously once the need is triggered. The elements required of a contingency plan are the tracking plan and triggering mechanism to determine if and when contingency measures are needed, the list of potential contingency measures, and a description of the process for recommending and implement ing the contingency measures.



### 8.1 Tracking

The t racking plan for the Northern Ada County Maintenance Area will consist of monitoring and analyzing the PM 10 concentrations. DEQ will continue to operate and maintain the PM 10 monitor

in accordance with 40 CFR Part 58.



### 8.2 Triggering

The triggering mechanism for contingency measure implementation will be a violation of the

PM 10 NAAQS. Specifically, the 3

- year average number of expected exceedances at a monitoring

site would need to be greater than 1.0 for a violation to occur.

Contingency plan triggering does not necessarily mandate a SIP revision, nor is the area necessarily redesignated to nonattainment. The s tate will normally have an adequate and appropriate period of time to correct the violation by implementing one or more contingency measures, as appropriate. In the event that violations continue to occur after measures have been implemented, additional contingency measures will be implemented until the violations are

correc ted.



### 8.3 Potential Contingency Measures

If monitoring data indicate a violation of the PM 10 NAAQS, Idaho will examine the data to assess the spatial extent, severity, cause, and time period of the episode as well as trends over

time. Based on this analysis, Id aho will determine which measures to implement. The following list of potential contingency measures has been or can be implemented if a violation of the PM 10 standard occurs in the future.

Adopt local ordinances that require covering all loads of materia l that may have the  potential to contribute to particulate matter pollution. Adopt local ordinances that require no track

- out onto paved roads.  Adopt local ordinances that prohibit burning of household garbage.  Eliminate local permits that allow any kind of uncontrolled outdoor burning not  specifically allowed under state rule. Expand the mandatory burning restrictions to include clean

- burning woodstoves during  air quality alerts. Adopt local ordinances that prohibit constructi ng any unpaved private roads, driveways

,  or parking lots. Revise street sweeping plan with local highway districts and the Idaho Transportation  Department based on latest traffic data to prioritize street sweeping efforts to reduce fugitive road dust. Analyze the impacts from all indu strial sources

. Develop potential emission reductions, if 

necessary to maintain attainment, in accordance with the rules

.Northern Ada County PM 10 Maintenance Plan

24 Contingency measures that address emissions from stationary sources include the DEQ d irector’s compliance order and enforcement authorities and the authority provided by IDAPA 58.01.01.401.03 to require or revise a permit of any stationary source, at any time, whenever it is

determined that emission rate reductions are necessary to attain or maintain any ambient air quality standard.

In addition to the potential contingency measures discussed above

, DEQ may evaluate other strategies to address any future violations in the most appropriate and cost

- effective manner possible. Due to continual changes in the mixture of PM 10 sources and evolving technologies to

understand and control PM 10 emissions and precursors, other contingency measures may become viable in the future. DEQ will evaluate the need and viability of additional contingency measur es and will consider future additions to the listed measures

, if necessary.



## 9 Summary

This plan for continued attainment of the PM 10 NAAQS meets all requirements of a 10

- y ear

m aintenance p lan update

.



### 9.1 Attainment Verification

Attainment of the NAAQS for PM 10 in northern Ada County was demonstrated in s ection 4

, “ Air Quality Monitoring

— Verification of Attainment. ”



### 9.2 F ull A pproval of the State Implementation Plan under Section 110

The SIP has been fully approved per section 110, with approval dates included in s e ction 3 of this plan. Following a public comment period, DEQ will submit this maintenance plan update to EPA for approval. A summary of public participation will be provided in Appendix F.



### 9.3 Permanent and Enforceable Improvement in Air Quality

DEQ demonstra ted in s ection 7 that improvements in air quality are based on permanent and

enforceable emission s reductions.



### 9.4 Maintenance Plan Elements

The following sections have met the required maintenance plan requirements of section 110.

Section 5 : Emissions Invento ry 
Section 6 : Maintenance Demonstration 
Section 8 : Continue d Air Monitoring and Verification of Attainment 
Section 9 : Contingency Plan 



### 9.5 Subsequent Maintenance Plan Revisions

This revised maintenance plan provides for continued maintenance of the PM 10 NAAQS for an

additional 10 years beyond the original 10

- year period. Consequently, no further maintenance plan updates are anticipated.Northern Ada County PM 10 Maintenance Plan

25 

## References

CFR (Code of Federal Regulations). “Ambient Air Quality Surveillance.” 40 CFR Part 58.

CFR (Code of Federal Regulations). “ Approval and Promulgation of Implementation Plans .”

40 CFR Part 52.

CFR (Code of Federal Regulations). “ Determining Conformity of Federal Actions to State or Federal Implementation Plans .” 40 CFR Part 93.

CFR (Code of Federal Regulations). “ Requirements for Preparation, Adoption, and Submittal of Implementation Plans .” 40 CFR Part 51.

DEQ (Idaho Department of Environmental Quality). 2009. Quality Assurance Project Plan for the State of Idaho Ambient Air Quality Monitoring Program

. Boise, ID: DEQ.

Environ. 2002. Northern Ada County PM 10 SIP Maintenance Plan and Redesignation Request

. Novato, CA: Environ. Prepared for the Idaho Department of Environmental Quality.

EPA (United States Environmental Protection Agency). 1994. Receptor Model Sourc e Composition Library. Research Triangle Park, NC: EPA, Office of Air Quality Planning

and Standards.

EPA (United States Environmental Protection Agency). 1999. Handbook for Criteria Pollutant Inventory Development: A Beginner’s Guide for Point and Area S ources

. Research Triangle Park, NC: EPA, Office of Air Quality Planning and Standards.

EPA (United States Envir onmental Protection Agency). 2011

. AP 42 Compilation of Air Pollutant Emission Factors, Section 13.2. 1 Paved Roads.

EPA (United States Environmental Protection Agency). 2008. Quality Assurance Handbook for Air Pollution Measurement Systems . Volume II: Ambient Air Quality Monitoring Program. Research Triangle Park, NC: EPA, Office of Air Quality Planning and

Standards.

Idaho Code. 2011. “ Idaho Environmental Protection and Health Act.” Idaho Code 39

- 101 through 39

- 130.

IDAPA. 2012. “Rules for the Control of Air Pollution in Idaho.” Idaho Administrative Code.

IDAPA 58.01.01.

US Congress. 1970. Clean Air Act. 42 USC §7401 et seq.Northern Ada County PM 10 Maintenance Plan

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- sided printing.Northern Ada County PM 10 Maintenance Plan

27 

## Appendices

Appendix A. Rules Establishing State Authority

App endix B. Legal Description for N orthern Ada County PM 10 Maintenance Area

Appendix C. Speciated Linear PM 10 Roll

- F orward Modeling Report : I n Support of the Northern Ada County PM 10 Maintenance Plan Renewal

Ap pendix D. 2008, 2015, and 2023 Emissions Inventories for the Treasure Valley Airshed

Appendix E. Development of the Base

- and Future

- Year Mobile Source Emission s Inventor y for the Treasure Valley , Idaho

Appendix F. Legal Notification of Public Comment Period

, Public Comments Received, Public

Hearing Documents

, and Response to Public CommentsNorthern Ada County PM 10 Maintenance Plan

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- sided printing.