Appendix C – Maintenance Receptors

1 Technical Support Document for EPA’s Proposed Actio n on the Montana’s 2010 Infrastructure State Implementation Plan (Transport Portion) for the 2006 24-hour Fine Particulate (PM2.5) National Ambi ent Air Quality Standard



### Appendix C – Maintenance Receptors

1. EPA Region 9 States – California and Arizona 1. California/Mexico Border – Imperial County
2. Northern California/San Francisco Bay Area – Alamed a, Santa Clara, and Solano Counties
3. Northern California – Sacramento County
4. Southern California – Orange, Los Angeles, Riversid e, and San Bernardino Counties 5. Arizona – Pinal County (Cowtown) 6. Arizona – Santa Cruz County (Nogales)

2. EPA Region 8 States – Utah 1. Utah – Utah County (Provo-Orem) 2. Utah – Salt Lake and Weber Counties (Greater Salt L ake Area)

Note: See Appendix E for further technical data for Greater S alt Lake Area, Utah.Appendix C – Maintenance Receptors

2 1. 1. California/Mexico Border – Imperial County

Levels of PM2.5 in Imperial County that exceed the 2006 24-hour PM2.5 NAAQS are recorded at the Calexico – Ethel Street monitoring site, which is l ocated near the Mexican Border (see Figure 1.1.A, below). The elevated levels of PM2.5 occur primaril y in the wintertime, and fifteen of the eighteen values above the level of 35 μg/m3 in the years 200 6-2010 occur in December or January (See Table 1.1.A, below).

The levels of PM2.5 measured at the Brawley and El Centro monitoring sites are always lower – usually
much lower – than those measured at the Calexico Et hel Street monitor on days when the PM2.5 levels at the Calexico Ethel Street monitor exceed 35 μg/m 3 (see Figure 1.1.B, below). Because these nearby
monitors do not show similar increases in monitored values, it appears that the cause of elevated PM2. 5 appears to be from a local source near the Californ ia/Mexico Border. This consideration, combined with the significant distance between Montana and this r eceptor, make it reasonable to conclude that
emissions from Montana will not interfere with the maintenance of the 24-hour PM2.5 standard at this
receptor.

Figure 1.1.A: PM2.5 Monitoring Sites in Imperial Co unty, CaliforniaAppendix C

Table 1.1.A: Calexico

for the Years 2006 through 2010

Year 2006 January 8, 14, 17, 29 and December 22, 25
2007 November 20, and December 5, 17
2008 January 4, and December 22, 25
2009 September 4, and December 12, 21, 24
2010 June 28, and December 4

Figure 1.1.B : PM2.5 levels

from 2006 to 2010 0 10 20 30 40 50 60 70 Appendix C – Maintenance Receptors

3 - Ethel Street: Dates of PM2.5 Values A bove 35μg/m for the Years 2006 through 2010

Date January 8, 14, 17, 29 and December 22, 25 November 20, and December 5, 17 January 4, and December 22, 25 September 4, and December 12, 21, 24 28, and December 4

: PM2.5 levels (μg/m3) at Imperial County PM2.5 Monitoring Sites from 2006 to 2010 , for Days of Elevated PM2.5 bove 35μg/m 3

PM2.5 Monitoring Sites

Calexico -Ethel

El Centro

BrawleyAppendix C – Maintenance Receptors

4 1.2. Northern California/San Francisco Bay Area – A lameda, Santa Clara, and Solano Counties

Table 1.2.A: San Francisco Bay Area Maintenance Rec eptor Design Values

County ID Design Value (μg/m 3 )

2006-2008 Design Value

(μg/m 3 )

2007-2009 Design

Value(μg/m 3 )

2008-2010 Alameda 060010007 36 34 30 Santa Clara 060850005 36 34 30 Solano 060950004 36 36 31

The maintenance receptors in the San Francisco Bay Area, shown in Table 1.2.A and Figure 1.2.A, were only slightly above the standard (1 μg/m 3 above) for the years 2006-2008 and 2007-2009. Ther e is a downward trend in the 24-hour PM2.5 design value at each of the receptors.

The monitored PM2.5 values above 35μg/m 3 likely reflect localized sources because they occu r during wintertime temperature inversions with low winds th at persist for several days, which allow directly emitted and secondary PM to build up over a few day s. 1 Figures 1.2.B and 1.2.C illustrate the wind speed and direction for various levels of PM2.5, an d show that elevated levels of PM2.5 occur during wintertime conditions with light wind speed. The Ba y Area Air Quality Management District analyses show that during the winter peak season wood burnin g can account for 33 to over 80 percent of the
PM2.5 concentrations. Ammonium nitrate and elementa l carbon from diesel sources can also contribute
to elevated PM2.5 concentrations.

During summer, the Pacific high pressure system (Pa cific High) typically strengthens and resides in th e northeastern Pacific Ocean, pushing the jet stream and its attendant storm systems well to the north o f California. In winter, the Pacific High weakens and shifts southward, which allows storm systems to come across central California. As a result, almost all of the Bay Area’s annual precipitation takes p lace in the November through April period. During the wi nter rainy periods, inversions are weak or nonexistent, winds are often moderate and air pollu tion potential is very low. However, during winter periods when high pressure systems become establish ed over the Bay Area, inversions become strong, winds are light and pollution potential is high. Th ese periods are characterized by winds that flow ou t of the Central Valley into the Bay Area and often incl ude tule fog.

The San Francisco Air Basin encompasses approximate ly 5,430 square miles and consists of all of Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo and Santa Clara counties, the southern half of Sonoma County and the southwestern portion of Solano County. The region is characterized by

1 BAAQMD Reports: Sources of Bay Area Fine Particula tes (2008); Fine Particulate Matter Data Analysis a nd Modeling in the Bay Area (2009); Evaluation of the Effectivenes s and Benefits of the Wood Burning Rule in the San Francisco Bay Area for winter 2009-2010 (2010); Trends in Bay Area Amb ient Particulates (2011).Appendix C – Maintenance Receptors

5 complex terrain, consisting of coastal mountain ran ges, rugged hillsides, and inland valleys and bays. Elevations range from sea level to 1,500 feet.

EPA believes that, based on the local nature of the PM2.5 problem and the distance of the area from Montana, it is reasonable to conclude that emission s from Montana will not interfere with the
maintenance of the 24-hour PM2.5 standard at these receptors.Appendix C – Maintenance Receptors

6 Figure 1.2.A: San Francisco Bay AreaAppendix C – Maintenance Receptors

7 Figure 1.2.B: Alameda County Pollution Rose for 200 5-2007 S W E

2 4 6 8 10 12+

Wind Speed (mph) Site 060011001 San Francisco Bay Area, CA [Alameda County, CA]

Pollution Rose, 2005-2007

Year

2004

2005

2006 98th %-ile

27.6

30.4

33.3 # days > 35

. 2

2

Design Value 30-A

2 exceedance(s) not plotted (due to missing or variable wind data) San Francisco Bay Area, CA Meteorological data from 11.8 miles away

SAN_JOSE_INTL_AP (ID=23293) 2005

2006

2007 Concentration :

 > 40 μg/m3

 35 - 40 μg/m 3

 30 - 35 μg/m 3

 < 30 μg/m 3

Season : cool (Oct-Apr) warm (May-Sep)Appendix C – Maintenance Receptors

8 Figure 1.2.C: Santa Clara County Pollution Rose for 2005-2007Appendix C – Maintenance Receptors

9 1.3 Northern California – Sacramento County

County Site Name Description

Sacramento Site ID:

060670010 This receptor is in the Sacramento Metro nonattainm ent area.

The monitored exceedances likely reflect localized sources occurring during wintertime temperature inversions with low w inds that persist for several days. The speciation data on days durin g cold seasons in 2004-2006 with the highest 5 percentile of PM2.5 co ncentrations show that the mass is 47-60% total carbon mass (TCM), wh ich indicates residential wood burning as a significantly contrib uting source of emissions. ( http://www.epa.gov/pmdesignations/2006standards/fin al/TSD/tsd_F_li mited_2004-06_speciation_data_report.pdf ).

The largest single source of Sacramento's wintertim e PM2.5 emissions is wood and other solid fuel burning in fireplaces, wood inserts, wood stoves and pellet stoves.

There is a strong downward trend in this area in re cent years ( http://www.epa.gov/region9/air/trends/pm25.html ).

The Northern Sacramento Valley Air Basin is bounded on the north and west by the Coastal Mountain Range, and on the east by the southern portion of t he Cascade Mountain Range and the northern portion of the Sierra Nevada Mountains. These mountain rang es reach heights in excess of 6,000 feet with peaks rising much higher. This provides a substantial phy sical barrier to locally created pollution.

The maintenance receptor identified above likely re flects localized sources occurring during wintertim e temperature inversions with low winds that persist for several days in an area that trap emissions together with complex topography. The speciation da ta from high concentration days indicates that the PM2.5 has a high carbon mass, which also indicates that residential wood burning emissions are the dominant source. 2 Also, as noted above, the largest single source of Sacramento's wintertime PM2.5 emissions is wood and other solid fuel burning in f ireplaces, wood inserts, wood stoves and pellet

stoves.

For the area under consideration, high PM2.5 concen trations mostly occur during stagnant conditions during winter, with radiation inversions. The cooli ng of the ground, as heat is radiated away, creates an inversion, since air near the ground is cooler than that above. This inhibits mixing and confines pollutants to a relatively shallow layer near the g round. A typical value for maximum mixing height during high PM2.5 conditions is 300 meters (984 fee t) AGL (above ground level). EPA recognizes that an inversion height is not a rigid boundary extendi ng through a fixed elevation. In reality the invers ion would be partly terrain-following, and the degree o f stagnation would be subject to additional influen ces

2 ARB Almanac website (2006). http://www.arb.ca.gov/ei/maps/statemap/cntymap.htmAppendix C – Maintenance Receptors

10 at the foothill edges, such as strong diurnal slope flows. In any case, mixing heights vary by site a nd date, so any single height can provide only a scale for comparison, not a definitive value. Neverthele ss, the inversion height provides an indicator of the a rea over which inversions may be enhancing pollutio n concentrations, and of the extent of the area that may interfere with maintenance of the NAAQS. Because these areas in Northern California have top ographical features higher than the typical daytime height of the inversion layer, EPA considered the i nversion height to estimate the size of the area li kely to have similar pollution conditions and to interfe re with maintenance of the NAAQS.
In summary, topography is an important factor for t his area, given that the inversion layer, which can lead to winter PM2.5 exceedances in the Sacramento Valley, is blocked by the Sierra foothills.
The steep terrain and speciated PM2.5 data at this Northern California receptor supports the fact that the PM2.5 is largely of local origin. This consideratio n, combined with the distance between Montana and this receptor, make it reasonable to conclude that transport from Montana does not interfere with maintenance of the 2006 PM2.5 standard at this rece ptor.

1.4. Southern California – Orange, Los Angeles, Riv erside, and San Bernardino Counties

Table 1.4.A: South Coast Air Basin Maintenance Rece ptor Design Values

County Site Name Description

Orange Anaheim The 2008-2010 design value for this site is 30 μg/m 3 . The previous design values were 38 μg/m 3 in 2006-2008, and 37 μg/m 3 in 2007-2009.

The current design value for the Anaheim site is 30 μg/m 3 , well below the 2006 24-hour PM2.5
standard. The Anaheim site has shown a consistent downward trend over the last ten years. (see Figur e 1.4.A: 24-Hour Average PM2.5 Design Concentrations 1999-2010). The South Coast Air Quality DRAFT 2012 Air Quality Management Plan air quality projections show that the emission control strategy outlined in the plan will result in air qu ality improvement at this site. (see Figure 1.4.B: Maximum 24-Hour Average PM2.5 Design Concentrations : 2008 Baseline, 2014 and 2014 Controlled). These considerations, combined with the distance fr om Montana to this receptor, make it reasonable to
conclude that emissions from Montana will not inter fere with the maintenance of the 24-hour PM2.5 standard at this receptor.

A more complete discussion of air quality in the So uth Coast Air Basin is included in Appendix B - Non-attainment Receptors at B.1.3.Appendix C – Maintenance Receptors

11 Figure 1.4.A : 24-Hour Average PM2.5 Design Concent rations 1999-2010. 3

Figure 1.4.B: Maximum 24-Hour Average PM2.5 Design Concentrations: 2008 Baseline, 2014 and
2014 Controlled 4

3 Joe Cassmassi, Item #2, Scientific, Technical & Mo deling Peer Review (STMPR) Advisory Group Meeting # 1 for 2012 Air Quality Management Plan (AQMP), September 22, 2011. http://aqmd.gov/gb_comit/stmpradvgrp/2012AQMP/meeti ngs/2011/sept22/stmpr01.pdfAppendix C – Maintenance Receptors

12 1.5 Arizona – Pinal County (Cowtown)

This monitoring site is a middle scale site and is only comparable to the 24-hour NAAQS due to its close proximity to nearby sources.

Emission inventory data, combined with speciation a nd source apportionment data, point to agricultural activities and cattle feedlots, as well as other ne arby sources of PM2.5, as primary sources contribut ing to PM2.5 levels at the Cowtown monitor on days with exceedances of the 24-hour PM2.5 NAAQS. 5

The Cowtown monitor has a consistent PM2.5/PM10 rat io that is lower than other nearby sites, suggesting that the causes of Cowtown PM2.5 concent rations are different than for other locations. Th e correlation of the PM2.5/PM10 ratio with PM2.5 conc entrations at the Cowtown monitor also suggests that PM2.5 and PM10 concentrations at the Cowtown m onitoring site are generated by the same sources. Also, the Cowtown monitor is the only site in the a rea with a pronounced diurnal pattern, with high PM in the morning and evening hours, further suggestin g the influence of local sources.

EPA believes that, based on the local nature of the PM2.5 problem and the distance of the area from Montana, it is reasonable to conclude that emission s from Montana do not interfere with the maintenance of the 24-hour PM2.5 standard at this r eceptor.

4 http://www.aqmd.gov/aqmp/2012aqmp/draft/Chapters/Ch 5.pdf

5 Arizona Area Designations for the PM2.5 24-Hour Fi ne Particle National Ambient Air Quality Standards, 2011 (76 FR 6056).Appendix C – Maintenance Receptors

13 Figure 1.5.A: Emission Sources and Design Values wi thin Fifty Miles of the Cowtown MonitorAppendix C – Maintenance Receptors

14 Figure 1.5.B: Cowtown Wind Roses 6

(Note: The different colors in Figure 1.5.B corresp ond to various levels of PM2.5: Blue is less than or equal to 30 μ g/m3; Yellow is 30-35 μ g/m3; Red is 35-40 μ g/m3; and Black greater than or equal to 40 μ g/m3. Also, values measured between October-April a re shown as triangles, and values measured between May-September are shown as circles.)

1.6 Arizona – Santa Cruz County (Nogales)

The PM2.5 monitoring site in Santa Cruz County is l ocated near the United States border with Mexico. (See Figure 1.6.A: Nogales PM2.5 Nonattainment Area ). High PM2.5 values in Nogales generally occur under stagnant, light wind conditions during winter and are associated with southerly flow (i.e., from the direction of Mexico). Nighttime drainage flow is ty pically from south to north along the Nogales Wash and the narrow valley topography can trap air pollu tants, especially during the evening hours when the diurnal flow is from the south, out of Nogales, Son ora. 7 Measurements of PM2.5 composition show that the main emission sources are wood burning, food co oking, open burning, dust emissions, and tailpipe emissions from on-road and off-road vehicles.

EPA believes that, based on the local nature of the PM2.5 problem, the direction of flow during period s of elevated PM2.5, and the distance of the area fro m Montana, it is reasonable to conclude that emissions from Montana do not interfere with the ma intenance of the 24-hour PM2.5 standard at this receptor.

6 Technical Support Document for Determination that the Cowtown Monitor is Ineligible for Comparison wi th the Annual PM2.5 NAAQS, U.S. EPA, Region 9, April 2 6, 2010.

7 Arizona Area Designations for the PM2.5 24-Hour Fi ne Particle National Ambient Air Quality Standards, 2009 (74 FR 58688).Appendix C – Maintenance Receptors

15 Figure 1.6.A: Nogales PM2.5 Nonattainment AreaAppendix C – Maintenance Receptors

16 2.1 Utah – Utah County

(Site ID: 490495008)

A large portion of Utah County is designated as the Provo 2006 PM2.5 nonattainment area (NAA).

The Provo NAA is situated in the Utah Valley. Like the other low-lying valleys just west of the Wasatc h Front, the topography of the Utah Valley makes it p rone to temperature inversions. During inversions, the Provo NAA features stagnant air masses and calm to light winds. As the airshed is essentially capped, PM2.5 is formed in-situ (and trapped) via f resh locally derived emission sources and secondary chemistry. Transport of air masses between the Salt Lake City and Provo NAAs can occur during inversions, as there is a 4.75-mile gap in the moun tains separating these airsheds which is below the approximate average inversion height for these area s.

Speciation data from exceedance days from 2004-2006 showed the average composition of PM2.5 in Provo is 71% ammonium nitrate, with 21% carbon and organic compounds, 8% ammonium sulfate, and 2% crustal.

Several factors, including significant mobile, poin t and area sources contribute to primary and secondarily formed PM2.5 that violate the standard during stable weather events associated with strong inversions. Because of the local nature of these ev ents, it is reasonable to conclude that emissions f rom Montana do not interfere with the maintenance of th e 24-hour PM2.5 standard at this receptor.

2.2 Utah – Salt Lake and W eber Counties (Greater Salt Lake Area)

(Site IDs: 490353007 (Salt Lake County) and 4905700 07 (Weber County))

All of Salt Lake County and a portion of Weber Coun ty are designated as part of the Salt Lake City (SLC) 2006 PM2.5 nonattainment area (NAA).

The SLC NAA is situated in a valley bordered on the west by the Stansbury Mountains, Promontory Mountains and the Great Salt Lake, and on the east by the Wasatch Front. During inversions, the NAA becomes a closed airshed (save for potential transp ort between the Salt Lake City and Provo NAAs) featuring stagnant air masses and light winds which typically oscillate back and forth within the airs hed. As the airshed is essentially capped during inversi ons, PM2.5 is formed in-situ (and trapped) via fres h locally derived emission sources and secondary chem istry.

Speciation data from exceedance days from 2004-2006 showed the average composition of PM2.5 in Salt Lake City is 58% ammonium nitrate, 31% carbon and organic compounds, 8% ammonium sulfate, and 2% crustal.

Several factors, including significant mobile, poin t and area sources contribute to primary and secondarily formed PM2.5 that violate the standard during stable weather events associated with strong inversions. Because of the local nature of these ev ents, it is reasonable to conclude that emissions f rom Montana do not interfere with the maintenance of th e 24-hour PM2.5 standard at these receptors.