Attachment 1

State of Washington

Area Designations For the 

24-Hour Fine Particle National Ambient Air Quality Standard

The table below identifies the counties in Washington State that EPA has
designated as not attaining the 2006 24-hour fine particle (PM2.5)
standard.  A county (or part thereof) is designated as nonattainment if
it has an air quality monitor that is violating the standard or if the
county is determined to be contributing to the violation of the
standard. 

 

Area 	WA Recommended Nonattainment Counties	EPA’s Designated
Nonattainment Counties

Wapato Hills-Puyallup River Valley (Tacoma)	Pierce (partial) 	Pierce
(partial) 



EPA has designated the remaining counties in the state as
“attainment/unclassifiable.”  

EPA Technical Analysis for the Wapato Hills-Puyallup River Valley
nonattainment area in Washington State

Introduction  

Pursuant to section 107(d) of the Clean Air Act, EPA must designate as
nonattainment those areas that violate the NAAQS and those nearby areas
that contribute to violations.  This technical analysis for the Wapato
Hills-Puyallup River Valley nonattainment area identifies the single
county in Washington State with a monitor that violates the 24-hour
PM2.5 standard (Pierce County) and evaluates nearby counties in the
Seattle-Tacoma-Olympia area for contributions to fine particle
concentrations in the area.  EPA has evaluated these counties based on
the weight of evidence of the following nine factors recommended in EPA
guidance and any other relevant information:  

- pollutant emissions

- air quality data

- population density and degree of urbanization

- traffic and commuting patterns

- growth

- meteorology

- geography and topography

- jurisdictional boundaries

- level of control of emissions sources

We also used analytical tools and data such as pollution roses, fine
particle composition monitoring data, back trajectory analyses, and the
contributing emission score (CES) to evaluate these areas. (See
additional discussion of the CES under factor 1 below.)

 

Figure 1 is a map of the counties in the Seattle-Tacoma-Olympia area and
other relevant information such as the locations and design values of
air quality monitors, and the metropolitan area boundary.  

Figure 1. Wapato Hills-Puyallup River Valley (partial Pierce County)
nonattainment area and surrounding counties in Seattle Tacoma area

The violating monitor in the Pierce County area is located at 7802 South
L Street (South L Street monitor) in a suburban area of the City of
Tacoma.  The nonattainment area is referred to as the Wapato
Hills-Puyallup River Valley (WHPRV) area.  The City of Tacoma is a major
urban center in the Southern Puget Sound Region. Situated on
Commencement Bay, an inlet of Puget Sound, Tacoma lies at the foot of
Mt. Rainier in the Puyallup River valley, bordered by mountains. 
Commencement Bay serves the Port of Tacoma, a major center of
international trade. The Port handled more than $36.33 billion in annual
trade and nearly 2 million TEUs (Twenty-foot Equivalent container Units)
in 2007.  Tacoma is situated in the Seattle-Tacoma-Olympia Consolidated
Statistical Area, a highly urbanized area along the Interstate 5
corridor.  To the east of Interstate 5, along the eastern portion of
Pierce, King, Snohomish, and Thurston Counties the Cascade mountains
rise to over 14,000 feet in elevation at Mt Rainier in Pierce County. 
Tacoma is about 36 miles south from the city of Seattle, the largest
city in Washington State and 30 miles north of the City of Olympia, the
Capitol of Washington State.  See Figure 2.  The Puyallup Indian
Reservation is located in the Tacoma Area, about five miles northeast of
the violating monitor and is located within in the Wapato Hills-Puyallup
River Valley partial county nonattainment area boundary.  See Figure 3. 
The nonattainment area boundary is the pink line and the Puyallup Indian
Reservation is shown in cross hatch.

Figure 2. Southern Puget Sound area topography

 

Figure 3.  Wapato Hills-Puyallup River Valley Nonattainment Area

The boundary of the Wapato Hills-Puyallup River Valley nonattainment
area is described as follows:

Starting from where an extension of Kennedy Road Northeast would
intersect Commencement Bay, proceed north to the intersection of Marine
View Drive (State Route 509) and Kennedy Road Northeast.

Proceed south on Marine View Drive to Hylebos Creek.

Proceed south along Hylebos Creek to 12th Street East.

Proceed east on 12th Street East to 70th Avenue East.

Proceed south on 70th Avenue East to State Route 99 (S.R. 99).

Proceed north on S.R. 99 0.1 mile north of Birch Street to a driveway to
the east.

Proceed east along the driveway and continue east along the same
alignment to the Pierce County Line/Comprehensive Urban Growth Area
(CUGA) boundary.

Proceed east along the Pierce County Line/CUGA boundary to the eastern
boundary of Edgewood.

Proceed south along the eastern boundary of Edgewood to eastern boundary
of the Sumner Urban Service Area.

Proceed south along eastern boundary of the Sumner Urban Service Area to
the eastern boundary of the Puyallup Urban Service Area.

Proceed south along the eastern boundary of the Puyallup Urban Service
Area to the eastern boundary of Puyallup/CUGA boundary.

Proceed south and then west along the CUGA boundary to the eastern
boundary of McChord Air Force Base.

Proceed north along the eastern boundary of McChord Air Force Base to
the northernmost point on the eastern boundary.

Proceed from the northernmost point on the eastern boundary of McChord
Air Force Base to the south right-of-way of S.R. 512.

Proceed west along the south right-of-way of S.R. 512 to the south
right-of-way of I-5.

Proceed south along the south right-of-way to I-5 to the point opposite
the boundary between Lakewood and Camp Murray.

Proceed north across I-5 to the boundary between Lakewood and Camp
Murray.

Proceed north along the western boundary of Lakewood to the point where
the western boundary coincides with the CUGA boundary.

Proceed north along the CUGA boundary to the southern boundary of Point
Defiance Park.

Proceed east along the southern boundary of Point Defiance Park to
Commencement Bay/CUGA boundary.

Proceed southeast, then northeast, and finally northwest along the CUGA
boundary to the starting point. 

In December 2007, the State of Washington recommended that a portion of
Pierce County (the Wapato Hills-Puyallup River Valley area) be
designated as “nonattainment” for the 2006 24-hour PM2.5 standard
based on air quality data from 2004-2006.  These data are from Federal
Reference Method (FRM) monitors located in the State.  See December 18,
2007 letter from Jay Manning, Director of the Washington Department of
Ecology to Elin Miller, Regional Administrator EPA Region 10.  On March
13, 2008, the State submitted to EPA the partial county boundary shown
in Figure 27.  The State also submitted the following information to
supplement their recommendation in a letter to EPA on July 25, 2008:  

An analysis of speciation data for the South L Street monitor and
monitors in the Duwamish area and Lake Forest Park area

An analysis of meteorological data from meteorological instrumentation
co-located with the South L Street monitor

An analysis of continuous monitoring data including diurnal air quality
trends for monitors in King and Pierce Counties

Based on EPA's technical analysis and review of information provided by
the State as described below, EPA has designated the Wapato
Hills-Puyallup River Valley area (a portion of Pierce County) in State
of Washington as nonattainment for the 24-hour PM2.5 air-quality
standard, based upon currently available information (see table below).

Wapato Hills-Puyallup River Valley nonattainment area	WA Recommended
Nonattainment Counties	EPA’s-Final Designated Nonattainment Counties

Washington State	Pierce (partial) 	Pierce (partial) 



The following is a technical analysis for the Wapato Hills-Puyallup
River Valley nonattainment area (a portion of Pierce County) in State of
Washington. 

Factor 1:  Emissions data

For this factor, EPA evaluated county level emission data for the
following PM2.5 components and precursor pollutants:  “PM2.5 emissions
total,” “PM2.5 emissions carbon,” “PM2.5 emissions other,”
“SO2,” “NOx,” “VOCs,” and “NH3.”  “PM2.5 emissions
total” represents direct emissions of PM2.5 and includes:   “PM2.5
emissions carbon,” “PM2.5 emissions other”, primary sulfate (SO4),
and primary nitrate.  (Although primary sulfate and primary nitrate,
which are emitted directly from stacks rather than forming in
atmospheric reactions with SO2 and NOx, are part of “PM2.5 emissions
total,” they are not shown in Table 1 as separate items).  “PM2.5
emissions carbon” represents the sum of organic carbon (OC) and
elemental carbon (EC) emissions, and “PM2.5 emissions other”
represents other inorganic particles (crustal).  Emissions of SO2 and
NOx, which are precursors of the secondary PM2.5 components sulfate and
nitrate, are also considered.  VOCs (volatile organic compounds) and NH3
(ammonia) are also potential PM2.5 precursors and are included for
consideration. 

Emissions data were derived from the 2005 National Emissions Inventory
(NEI), version 1.  See
http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html.

EPA also considered the Contributing Emissions Score (CES) for each
county.  The CES is a metric that takes into consideration emissions
data, meteorological data, and air quality monitoring information to
provide a relative ranking of counties in and near an area.  Note that
this metric is not the exclusive manner for considering data for these
factors.  A summary of the CES is included in attachment 2, and a more
detailed description can be found at
http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html#C. 

Table 1 shows emissions of PM2.5 and precursor pollutants components
(given in tons per year) and the CES for violating and potentially
contributing counties in the Seattle-Tacoma-Olympia area.  Counties are
listed in descending order by CES.

Table 1.  PM2.5 Related Emissions and Contributing Emissions Score

County	State Recommended Nonattainment?	CES Score (Rank)	PM2.5 emissions
- total (tpy)	PM2.5 emissions - carbon (tpy)	PM2.5 emissions - other
(tpy)	SO2 emissions (tpy)	NOx emissions (tpy)	VOC emissions (tpy)	NH3
emissions (tpy)

King	No	100 (1)	6,362	4,168	2,194	7,361	75,825	89,446	2,564

Pierce	Yes (partial)	60 (2)	3,766	2,255	1,511	3,200	31,905	32,097	1,410

Thurston	No	17 (3)	2,221	1,348	873	478	8,389	14,985	1,620

Kitsap	No	14 (4)	2,204	1,201	1,004	442	6,199	9,588	274

Snohomish	No	13 (5)	3,714	2,223	1,492	2,256	22,687	28,861	1,932

Skagit	No	11	1,605	819	786	10,345	12,417	11,173	1,809

Island	No	4	841	453	388	485	4,463	4,128	358

Mason	No	3	767	439	328	100	1,623	3,846	90



Total PM2.5 emissions in King County as well as individual chemical
precursor components of PM2.5 are generally two times the emissions in
Pierce County, the county which contains the violating monitor.  In
addition, the CES score of 100 indicates potential contributing
emissions from King County.  The next highest CES score of 17 was for
Thurston County, which contains the City of Olympia located 36 miles to
the south of the violating monitor.  Given the low CES scores and
relatively low emissions in Thurston, Kitsap, Snohomish, Skagit, Island
and Mason Counties these Counties are less likely to contribute to the
exceedences at the South L Street monitor than King County and Pierce
County which have higher emissions and CES scores.  We note that in
counties with large land areas and complex terrain such as King and
Pierce Counties, the CES does not account for diurnal variation in
hourly PM2.5 and sharp spatial gradients in emissions.  Those factors
were separately considered and used in developing our designation
rationale.

	The State of Washington submitted seasonal emissions inventory data as
part of its nine factors analysis attachment to its letter to EPA dated
December 18, 2007.  Figure 4 and Table 2 display seasonal emissions in
Pierce County, Washington for 2005 from the State’s submittal.  As
discussed below in factor 2 (air quality data), PM2.5 exceedences at the
violating monitor in Pierce County have occurred in the months of
November, December, January and February during the years 2004-2007.  

Winter season (December through February) air emissions of PM2.5 in
Pierce County are balanced among:

	(1) outdoor open burning (202 tons per season, 24%),

	(2) mobile sources (230 tons per season, 27%),

	(3) fireplaces and woodstoves (326 tons per season, 39%), and

	(4) other sources (84 tons per season, 10%)

Washington noted that these are estimates for a countywide emission
inventory, and that outdoor open burning (with an estimated 24%
contribution) is likely not occurring in the urban portion of the county
near the violating monitor.  Open burning is prohibited in these areas. 


Figure 4. 



Table 2.  Pierce County Seasonal PM2.5 Emission Sources in 2005

Fireplaces and woodstoves are the largest source of emissions in Pierce
County (39%).  The State conducted additional analyses to determine the
spatial variation in wood burning activities.  Figure 5 displays the
number of people using wood as a primary source of heat in the immediate
area of the South L monitor, per square mile.  The information source is
the 2000 census, and is presented at a block group level.  This
information does not capture those who use wood as a secondary heat
source, or those who use fireplaces for ambiance.  The highest density
of woodstove/fireplace use occurs within the Tacoma urban growth
boundary and in census blocks north of SR 512 in the vicinity of the
monitor.  See Figures 5 and 6.

Based on annual emissions inventory data for Pierce, King and
surrounding counties, VOC and NOx emissions comprise the largest portion
of total PM2.5 emissions.  However, this data is annual data and
exceedences of the 24-hour PM2.5 standard at the South L Street monitor
occur exclusively in the late fall-winter seasons.  Seasonal emissions
inventory data submitted by the State indicates that emissions from
woodstoves and fireplaces account for over 40% of the total emissions in
Pierce County, while mobile sources account for 27% of total emissions
in Pierce County during the winter season when exceedences of the
24-hour PM2.5 standard occur.   

	Based on emission levels and CES values, EPA considered King and Pierce
Counties candidates for a 24-hour PM2.5 nonattainment designation for
violations at the South L Street monitor in Pierce County.  However, we
have further evaluated potential contributions from surrounding counties
in the Seattle-Tacoma-Olympia area in our analysis of the remaining
nine-factors.

Figure 5.

Figure 6.



Factor 2:  Air quality data 

This factor considers the 24-hour PM2.5 design values (in µg/m3) for
air quality monitors in counties in the Seattle-Tacoma-Olympia based on
data for the 2005-2007 period.  A monitor’s design value indicates
whether that monitor attains a specified air quality standard. The
24-hour PM2.5 standards are met when the 3-year average of a monitor’s
98th percentile values is 35 µg/m3 or less.  A design value is only
valid if minimum data completeness criteria are met.

. 

The 24-hour PM2.5 design values for counties in the
Seattle-Tacoma-Olympia area are shown in Table 3.

Table 3. Air Quality Data for Seattle-Tacoma-Olympia Area

County	State 

Recommended

 Nonattainment?	Design Values

2004-06

(µg/m3)

	Design Values

2005-07

(µg/m3)



Pierce, WA	Yes	42	43

King, WA	No	29	31

Snohomish, WA	No	33	35

Thurston, WA	No	N/A	N/A

Island, WA	No	N/A	N/A

Kitsap, WA	No	N/A	N/A

Mason, WA	No	N/A	N/A



In Washington State, the monitor at 7802 South L Street in Tacoma
(Pierce County) is the only monitor that violates the 24-hour PM2.5
standard based on 2005-2007 data.  King and Snohomish County do not
violate based on 2004-2006 or 2005-2007 data.  The remaining counties do
not have Federal Reference Method monitor, therefore Federal Reference
Method data is not available for these counties.  

	Although the surrounding counties of King and Snohomish do not violate
the standard, this alone was not sufficient information for EPA to
eliminate King County or Snohomish County as candidates for inclusion in
the nonattainment area.   Nearby counties could be contributing to the
violations at the South L Street monitor even though there are no
violating monitors in those counties.  

	EPA analyzed data submitted by the State of Washington collected from
monitoring several sites in addition to the Pierce County Tacoma South L
Street Site to better characterize PM2.5 in Tacoma and in the
surrounding counties.  Since the high CES score for King County
indicates a potential contribution to the exceedences at the South L
Street monitor from King County, and since western King County is a
highly urbanized area, this analysis focused in particular on examining
additional air quality data for King County.  

	Figure 7 shows the location of several monitors in the Puget Sound
area. The following pages discuss air quality data from these sites
located along the Interstate 5 corridor in Pierce and King Counties. 
These areas include Marysville, Lynnwood, Lake Forest Park and Tacoma,
which are largely urban-suburban residential areas, and the Duwamish,
Puyallup South and Kent Valley areas, which are more industrialized
areas.  

	Table 4 displays the top 5% of concentrations at the South L Street
Monitor from 2004-2007 from EPA’s Air Quality System (AQS) repository
of ambient air quality data. All of these concentrations occurred during
the months of November, December, January or February with the exception
of one which occurred in late October, 2007.  The exceedences at the
South L Street monitor occur during the winter as the State suggests in
its nine factor analysis.

Table 4. Top 5% values at Tacoma L Street Monitor from 2004-2007

Figure 7. Puget Sound Area monitor locations

Lake ForestSpeciation Profiles

The State submitted chemical speciation monitoring data collected at the
Tacoma South L Street monitoring site in the year 2006.  Fifty nine (59)
samples were collected (one sample every six days).  Out of these 59
samples, four samples were for days above 30 µg/m3, and 55 samples were
for days that were below 20 µg/m3.  Figure 8 displays percentage of the
speciated components of total PM2.5 for the two highest days in 2006 for
which the speciation data was collected.  On December 19th, 21.57 µg/m3
(74%) of the total PM2.5 was organic and elemental carbon.  Sulfate and
nitrate were .87 µg/m3 (3%) and 1.86 (6%) respectively of the total PM
2.5.  On December 31, 37.67 µg/m3 of PM2.5 (69%) was organic carbon,
2.86 µg/m3 was elemental carbon (5%), 1.94 (4%) was sulfate and 1.54
µg/m3 (3%) was nitrate. 

Figure 8.  Speciated components of Total PM2.5 from the Tacoma South L
Street Monitor on high days in 2006 

Figure 9 is a plot of PM2.5 fraction components by season against PM2.5
concentration.  The highest concentrations of PM2.5 occur at the L
Street monitor in November and December.  During the first (Jan- March)
and fourth (Oct-Dec) quarters when the exceedences occur, the ratios of
sulfate and nitrate with total PM2.5 are generally less than 0.2.  The
highest ratios of sulfate and nitrate to total PM2.5 (above 0.2) occur
in the second (April-June) and third (June-August) quarters when PM2.5
concentrations are less than 15 µg/m3.  The organic carbon fraction to
total PM2.5 ratio is highest of any component at all times during the
year ranging from 0.2-0.5). In the fourth quarter, the OC/total PM
reaches its highest levels when PM2.5 concentrations are greater than 30
µg/m3. 

Figure 9.  Seasonal PM2.5 components collected at the South L Street
monitor in 2006.

 

Positive Matrix Factorization analysis of chemical components on Pierce
County filter

Since an analysis of chemical speciation data for high PM2.5 days at the
South L Street monitor in 2006 was an important part of the State’s
submittal, EPA evaluated the State's submittal of speciation data for
the South L Street site using the Positive Matrix Factorization (PMF)
tool.  PMF is one of the receptor models that EPA’s Office of Research
and Development has developed to provide scientific support for current
ambient air quality standards and for implementation of those standards
by identifying and quantifying contributions for source apportionment.
This model draws from ambient air quality data sets and receptor model
algorithms to compute profiles and relative contributions from different
source categories. See http://www.epa.gov/heasd/products/pmf/pmf.htm. 
This evaluation using the PMF tool also supplements the speciation data
and other information provided by the State on source contributions to
the violations at the South L Street monitor by providing information on
categories of sources and relative contributions from these sources to
the violations at the South L Street Federal Reference Monitor.  This
analysis was particularly informative in our evaluation of the unique
Tacoma area PM 2.5 pollution problem where the State's submittal
suggests localized sources cause and contribute to the violations at the
South L Street monitor and where, as explained above, and distinct from
most other areas in the country we have evaluated, the CES tool had
limitations for the area.  Additionally, and as explained above, our
final boundary determination for this area is based on a myriad of
factors and various analyses, only one of which is a PMF analysis. 
Taken together with other data and facts analyzed and explained in
detail elsewhere in this document, it helps us to better understand the
types of source categories which cause or contribute to the PM2.5
pollution in the Tacoma area.

The 2006-07 PMF data set included 111 data points (a sample every 6th
day), most of which was the same period that the State used in their
speciation monitoring study of the area. EPA's evaluation of this
dataset using PMF indicates relative source contributions that support
the State’s analysis of the chemical speciation and other air quality
data which indicates that smoke from woodstoves and fireplaces is the
major contributor to PM2.5 on high days at the South L Street monitor. 
PMF results indicate that wood smoke contributed 60-90% of the mass on 6
out of 7 days when total PM2.5 mass exceeded 30 µg/m3.  See Table 5. 
More detailed information on the PMF analysis for the South L Street
monitor is included in the docket for this action.

Table 5.  Positive Matrix Factorization Results for L Street monitor
for days over 30 in 2006 and 2007

Comparison with monitoring data from other sites in King County

Figure 10 contains seasonal PM2.5 components from two monitors, one in
an industrialized area the southern portion of King County (Duwamish)
and the other in northern King County in a residential area, Lake Forest
Park.  The Lake Forest Park monitor is a neighborhood scale site and is
representative of the Lake Forest Park general area.  Figure 11 shows
the location of these monitors in relation to the South L Street Monitor
in Tacoma.  The Duwamish monitor is about 30 miles north of the South L
Street Monitor and the Lake Forest Park Monitor is about 50 miles north
of the South L Street Monitor.

	The Lake Forest Park monitor generally shows the same pattern observed
at the South L Street monitor.  Organic carbon dominates all fractions
but the highest (>20 ug/m3 occur) fraction occurs in the first and
fourth quarters.  The highest fractions of sulfate and nitrate occur in
the second and third quarters of the year when PM2.5 concentrations are
lowest (generally below 10).  The Duwamish monitor shows a shift upward
of sulfate/ PM2.5 ratio for all quarters.  Ratios of sulfate to total
PM2.5 are more consistent throughout the year at the Duwamish monitor
and generally range between .1-.3.   The data points at this monitor are
more tightly clustered showing less seasonal variation then at the Lake
Forest Park and Tacoma monitor.

 Figure 10.  Seasonal PM2.5 components at Lake Forest Park and Duwamish
since 2005

Figure 11.  Location of monitors in the Southern Puget Sound Area 

Figure 9 Seasonal PM2.5 components at Duwamish since 2005

Diurnal Profiles

Figures 12-14 display diurnal PM2.5 concentrations at continuous
monitors throughout the Puget Sound Area.  Figure 12 shows diurnal PM2.5
concentrations at the South L Street monitor for the period 2001-2007. 
PM concentrations at the South L Street monitor rise sharply beginning
in the late afternoon and then peak around midnight then tail off around
mid day.  Survey data from Washington State indicate that this profile
is related to woodstove use. Surveys indicate that individuals ignite or
add fresh fuel in the late afternoon or early evening and often add fuel
before bedtime resulting in peak concentrations at night and lowest
concentrations during the day while individuals are away from home.  The
diurnal profile for the Lake Forest Park monitor (Figure 13) shows a
similar “V” shaped profile to the profile observed at the L Street
monitor while the profile while the profile for the Duwamish monitor
(Figure 14) is relatively flat.  Figure 15 is a map of the monitors
throughout the Puget Sound area with diurnal profiles.  The “V”
shaped profile is observed at monitors in the communities in Snohomish
County to the North (Lynnwood, Lake Forest Park and Marysville).  A
flatter profile is observed at the monitors in central and southern King
County; the Queen Anne monitor, the Seattle Duwamish Valley monitor and
the Kent Valley monitor.  

Figure 12.

Figure 13.

Figure 14.

 

Figure 15.  Diurnal profiles at monitoring sites in Pierce, King and
Snohomish Counties

Figure 16 plots one hour averages from a co-located nephelometer at the
Tacoma L Street monitor during an episode.  On January 12, 2007 the
24-hour design value at the L Street monitor was 44.7 µg/m3 and on
January 15, 2007, the 24-hour design value at the L Street monitor was
58.6 µg/m3.  The red line indicates the 24-hour standard, 35 µg/m3. 
Peak PM2.5 during this episode occurred around midnight on January 13
and January 15.  During the day of the 12th and the 13th PM2.5 levels
dropped to less than 10 µg/m3.  The pattern repeats with nighttime
highs climbing well above the standard and daytime lows. 

	When this pattern is observed at Tacoma, an identical pattern is noted
at the other monitors throughout the Region with the V shaped profile.  
In between events, PM2.5 levels generally drop to very low levels (<10
µg/m3) indicating that there is not significant transport of PM
precursors from other areas (Figure 18).  Days that do not drop to very
low levels are days where inversions have not broken down completely.  

Figure 16.  PM2.5Tacoma L Street January 11-16 2007

	 

Figure 17.  Simultaneous PM2.5 peaks at Southern Puget Sound monitors

 

Air Quality Data Discussion/Conclusions

Concentrations of PM2.5 throughout the Southern Puget Sound area peak at
night and in the winter.  The diurnal patterns are observed at
neighborhood scale monitors in Pierce and King County and show peaks
consistent with use of woodstoves collected through woodstove surveys. 
Monitors in the more industrial areas in southern King County (Kent and
Duwamish) between the neighborhood scale monitors to the north and the
South L Street monitor to the south do not exhibit strong diurnal
patterns consistent with woodstove use surveys.  Seasonality of sulfate
and nitrate concentrations at these monitors is also less variable than
the seasonality of sulfate, nitrate and organic carbon observed at the
South L Street monitor and other neighborhood monitors (Lake Forest
Park). The diurnal profiles and seasonality of organic carbon
(components that are associated with burning of wood) indicate that
emissions from woodstoves and fireplaces contribute to elevated
wintertime concentrations in residential areas such as the South L
Street and Lake Forest Park areas.

	Based on EPA’s PMF analysis, organic carbon/woodstoves contribute
60-90% of PM2.5 to the exceedences at the South L Street Monitor.  
Contributions of regional PM2.5 precursors (SOx and NOx) that dominate
the King County emissions inventory contribute less than 20-30% of total
PM2.5  to the Tacoma monitor.  Based on speciation monitoring at the
South L Street monitoring site, organic carbon and elemental carbon
contribute over 70% of the PM2.5 concentration on the highest days in
2006 and sulfate and nitrate contribute less than 10% combined of the
total PM2.5 concentration on these days.  Based on speciation
monitoring, emissions from King County (over 75,000 tpy NOx and 7500 tpy
SOx) as well as emissions from the other counties in the CMSA
potentially contribute less than 10 % of total PM2.5 concentrations on
high days at the South L Street Monitor.

	Based on the foregoing analyses, EPA concludes that sources
contributing the violations of the PM2.5 exceedences at the South L
Street monitor are predominantly local sources dominated by woodstove
and fireplace emissions in the Tacoma area and not transport from King
County or other counties in the Seattle-Tacoma-Olympia area.  

	This information along with the information discussed in the other
factors, particularly factors 6 and 7 (meteorology and topography) was
used to determine that the partial Pierce County boundary submitted by
the State on March 13, 2008 is sufficiently large enough to contains
sources contributing to the 24-hour PM2.5 violations at the South L
Street monitor.

Factor 3: Population density and degree of urbanization (including
commercial development)

Table 6 shows the 2005 population for each county in the
Seattle-Tacoma-Olympia area being evaluated, as well as the population
density for each County in that area. Population data give an indication
of whether it is likely that population-based emissions might contribute
to violations of the 24-hour PM2.5 standards.  King County, Pierce
County and Snohomish County contain large cities with large populations.
 Most of the areas in between are urban or suburban.  The City of
Everett is the largest city in Snohomish County.  King County has the
highest population (1.79 million) and the highest population density
with 824 people/square mile.  Pierce County has the next highest
population at 753,209 with the third highest population density in the
Seattle-Tacoma-Olympia area.  Snohomish County has the third highest
population in the area.  King County and Pierce Counties have the
highest CES scores at 100 and 60 respectively.  The CES Score for
Snohomish County is much lower at 13.

Table 6.  Population in the Puget Sound area

County	State Recommended Nonattainment?	2005 Population	2005 Population
Density (people/sq mi)	Percent Population Change (2000-05)

King	No	      1,799,119 	824	3 

Pierce	Yes	       753,209 	445	7 

Thurston	No	        228,881 	305	10 

Kitsap	No	        241,525 	583	4 

Snohomish	No	       655,564 	312	8 

Skagit	No	          113,181 	65	9 

Island	No	         79,983 	377	11 

Mason	No	          54,169 	54	9 



The State addressed population density in its nine factor analysis. 
Figure 18 shows population density for the city of Tacoma and
surrounding Pierce County areas, at the 2000 census block group level. 
In Pierce County, the highest population density occurs inside of the
Comprehensive Urban Growth Area (CUGA) in the vicinity of the L Street
monitor, and along the eastern shore of the Puget Sound to the north of
the Port of Tacoma.  Population density generally decreases to the south
and the east of the Port of Tacoma and the CUGA.  Figure 19 shows the
population of the recommended nonattainment area and the surrounding
portions of Pierce County.  

Based on the air quality data we reviewed above and the additional
factors that we review below which indicate that local sources cause the
violations at the South L Street monitor, and based on population data
which indicate that the highest population density in the Pierce County
area is within the Tacoma CUGA, EPA concludes that a boundary that
includes populations/potential sources in the Tacoma CUGA is
appropriately large enough to include populations and sources
contributing to the violations at the South L Street monitor.

Figure 18.

Figure 19. Pierce County Population Density with recommended
nonattainment area boundary

Factor 4: Traffic and commuting patterns 

This factor considers the number of commuters in each county who drive
to another county within the Seattle-Tacoma-Olympia area, the percent of
total commuters in each county who commute to other counties within the
Seattle-Tacoma-Olympia area, as well as the total Vehicle Miles Traveled
(VMT) for each county in millions of miles (see Table 7). A county with
numerous commuters is generally an integral part of an urban area and
could be an appropriate county for implementing mobile-source emission
control strategies, thus warranting inclusion in the nonattainment area.


Table 7. Traffic and commuting patterns in the Puget Sound area

County	State recommended Nonattainment?	 Vehicle Miles Traveled in 2005
(millions annually) 	 Percent VMT Growth (1996-2005) 	Number commuting
into any violating counties	Percent commuting into any violating
counties	Number commuting into and w/in the statistical area	Percent
commuting into and w/in the statistical area

King	No	  16,806 	         10 	18,560 	2 	  903,520 	         99 

Pierce	Yes (P)	    6,247 	         13 	228,280 	70 	   319,830 	        
99 

Thurston	No	    2,146 	           7 	14,350 	14 	    96,030 	         95


Kitsap	No	    1,633 	(10)	5,120 	5 	   104,640 	         98 

Snohomish	No	    5,225 	           9 	1,240 	0 	  296,750 	         99 

Skagit	No	     1,185 	         35 	140 	0 	    42,950 	         95 

Island	No	       397 	         (5)	50 	0 	      31,510 	         97 

Mason	No	       438 	         13 	860 	5 	      18,310 	         97 



The listing of Counties on Table 7 reflects a ranking based on the
number of people commuting to other counties.  King County VMT in 2005
was the highest in the area with historic VMT growth of 10%.  Two
percent of commuters from King County commute into Pierce County, the
County with the violating monitor.  Seventy percent of commuters in
Pierce County remain within Pierce County.  VMT growth in Pierce County
between 1996-2005 was 13%.  Both King County and Pierce County contain
major ports (the Port of Tacoma and the Port of Seattle), so there are
increased levels of diesel traffic to move goods at the Ports. 
Interstate 5 is a major N-S corridor along the West Coast of the United
States with significant diesel truck traffic.

Washington looked at Pierce County VMT growth in its nine factors
analysis.  Washington obtained information from the Puget Sound Regional
Council’s recently released draft Vision 2040 transportation plan for
the region, incorporating known travel improvements and the preferred
growth options emphasizing core centers for development.  The output
from PSRC's transportation demand model provides some travel growth
estimates for the Pierce County area and is shown in Table 8.

Table 8.  Pierce County Daily Travel Measures by Category in 2000 and
2040

Daily Category of Travel	2000 Reference Data	2040 	Units

Work Person Trips	293,886	535,330	Trips

Non-work Person Trips	1,757,784	3,183,447	Trips

Freeways Vehicle Miles Traveled	6,288,090	8,870,622	VMT

Arterials/Local Streets VMT	10,650,108	16,299,840	VMT

Freeways Vehicle Hours Traveled	129,929	191,106	VHT

Arterials/Local Streets VHT	363,175	617,769	VHT



Even with planned road and transit improvements, work and non-work
person trips are estimated to increase by over 80%, while vehicle miles
traveled and vehicle hours traveled are estimated to increase by 40% and
60%, respectively, from 2000 to 2040.  Based on EPA’s PMF analysis of
air quality data, mobile emissions likely do not contribute more than
5-10% of total PM2.5  at the L Street monitor on high days.  The
State’s boundary includes potential mobile source related
contributions in the Tacoma area including the Port of Tacoma as well as
sections of Interstate 5 and State Highway 99 and EPA has concluded that
the inclusion of these areas is sufficient to capture potential
contributions from these sources.  

Note:  The 2005 VMT data used for table 5 and 6 of the 9-factor analysis
have been derived using methodology such as that described in
"Documentation for the  2005 Mobile National Emissions Inventory,
Version 2," December 2008, prepared for the Emission Inventory Group,
U.S. EPA.  This document may be found at:
ftp://ftp.epa.gov/EmisInventory/2005_nei/mobile_sector/documentation/200
5_mobile_nei_version_2_report.pdf

Factor 5:  Growth rates and patterns  

This factor looks at expected population and VMT for Counties in the
Seattle-Tacoma-Olympia area from 2000 to 2005, as well as patterns of
population and VMT growth.  A county with rapid population or VMT growth
is generally an integral part of an urban area and could be contributing
to fine particle concentrations in the area. 

	Table 9 below shows population, population growth, VMT and VMT growth
for counties that are included in the Seattle-Tacoma-Olympia area. 
Counties are listed in descending order based on VMT growth between 1996
and 2005.

Table 9. Population and VMT Growth and Percent Change

County	2005 Population	Percent Population Change (2000-05)	 Vehicle
Miles Traveled in 2005 (millions annually) 	 Percent VMT Growth
(1996-2005) 

King, WA	1,799,119	3 	  16,806 	         10 

Pierce, WA	753,209	7 	    6,247 	         13 

Thurston, WA	228,881	10 	    2,146 	           7 

Kitsap, WA	241,525	4 	    1,633 	        (10)

Snohomish, WA	655,564	8 	    5,225 	           9 

Skagit, WA	113,181	9 	     1,185 	         35 

Island, WA	79,983	11 	       397 	         (5)

Mason,WA	54,169	9 	       438 	         13 



King County has the highest population but had the lowest population
growth rate from 2000-2005 (3%).  Pierce County population growth was
double that of King County for the same time period.  Thurston County
and Island Counties experienced the highest growth in population from
2000-2005 at 10% and 11% respectively.  However, the population of both
of these areas is 1-2 orders of magnitude lower than that of King County
and 3-8 times lower than that of Pierce County.   As stated above, based
on air quality data, mobile emissions likely do not contribute more than
5-10% of total PM2.5 to L Street monitor PM2.5 concentrations on high
days.  EPA’s final boundary includes most of the Pierce County Growth
area including the Port of Tacoma.  

Factor 6:  Meteorology (weather/transport patterns)

For this factor, EPA considered data from National Weather Service
instruments in the area.  Wind direction and wind speed data for
2005-2007 were analyzed, with an emphasis on “high PM2.5 days” for
each of two seasons (an October-April “cold” season and a
May-September “warm” season).  These high days are defined as days
where any FRM or FEM air quality monitors had 24-hour PM2.5
concentrations above 95% on a frequency distribution curve of PM2.5
24-hour values. 

	For each air quality monitoring site, EPA developed a “pollution
rose” to understand the prevailing wind direction and wind speed on
the days with highest fine particle concentrations.  The figure
identifies 24-hour PM2.5 values by color; days exceeding 35 ug/m3 are
denoted with a red or black icon.  A dot indicates the day occurred in
the warm season; a triangle indicates the day occurred in the cool
season.  The center of the figure indicates the location of the air
quality monitoring site, and the location of the icon in relation to the
center indicates the direction from which the wind was blowing on that
day.  An icon that is close to the center indicates a low average wind
speed on that day.  Higher wind speeds are indicated when the icon is
further away from the center.

	Figure 20 is a pollution rose from instrumentation at Boeing Field, a
King County airport which is located about 24 miles north of the
violating monitor. Based on this pollution rose, the prevailing surface
wind directions for the highest PM2.5 days in King County are from the
southeast of the Lake Forest Park monitoring site in King County. 

	Given terrain influence and complex meteorology in King County and
Pierce County, it was important to look at data from a meteorological
station located closer to the violating monitor.  As mentioned above,
the Boeing Field monitor is located 24 miles away from the South L
Street monitor.  EPA, therefore, also created a pollution rose using
data from the McChord Air Force Base which is located about 3 miles
southwest of the violating monitor.   Figure 21 is the pollution rose
created with the McChord data.  Based on this pollution rose, during
high days at the Tacoma L Street monitor, wind speeds are less than 2
miles per hour.  Because of these low wind speeds we could not draw a
conclusion on an average prevailing surface wind direction for high
PM2.5 days (exceeding 30 ug/m3).  For days below 30 ug/m3 average
prevailing winds are from the southwest.  The low wind speeds as well as
the direction of the average prevailing winds at the McChord indicate
that emissions from King County are not likely contributing to the
violations at the South L Street monitor.

Figure 20.  Pollution Rose for King County WA (Source: Boeing Field)

  

  SHAPE  \* MERGEFORMAT   Figure 21.  Pollution rose for Pierce County
WA (Source: McChord AFB) 

        

We note that the meteorology factor is also considered in each
county’s Contributing Emissions Score because the method for deriving
this metric included an analysis of trajectories of air masses for high
PM2.5 days.  The data used to create the CES for the Tacoma monitor was
from the Seattle –Tacoma International Airport which is located 6
miles south of Boeing Field.  Given the complex meteorology and
topography of the area, and given that EPA’s pollution roses for the
McChord Air Force Base meteorological site and the King County Boeing
Field Airport show very different wind patterns, EPA considered the data
from the McChord Air Force Base meteorological site in lieu of the CES
for the meteorological factor analysis for the Wapato Hills-Puyallup
River Valley area.

The wind rose from the McChord Air Force base demonstrates
meteorological conditions in the Wapato Hills-Puyallup River Valley area
during the fall and winter seasons when the exceedences occur at the
South L Street monitor.  During this time, regional air stagnations
interrupt westerly wind flows and strong subsidence temperature
inversions trap pollution levels and colder mean temperatures stimulate
the use of residential heating devices.   

Temperature inversions vary in intensity and can persist over a period
of days. These inversions change the mixing layer depth dramatically but
generally lower the layer to less than 800m.  During persistent winter
stagnations, mixing heights less than 300m are frequently observed
typically these conditions occur when the duration of stable conditions
extends beyond three days.  This occurs approximately 3-4 times during
the fall and winter seasons.  

Puget Sound Clean Air Agency, in coordination with the National Weather
Service office in Seattle operates a radar wind profiler at the Sand
Point Laboratory of the NOAA.  Figure 22 displays the mixing height
during the typical stagnation event in the Puget Sound area.  Mixing
heights at 600 meters or less are observed during the typical PM2.5
event.

Figure 22.  Typical inversion profile for the Southern Puget Sound
Region stagnation

Air movement in the area surrounding the South L Street monitoring
station is influenced by these meteorological conditions.  Figure 26
plots wind direction against hourly concentrations, wind direction
against wind speed, wind speed against hourly concentrations and
temperature against hourly concentration data gathered from a 2001-2008
Washington State temporary monitoring study.  This data indicates that
meteorological conditions that are present at the L Street Monitoring
site are typical of those observed in the area's fall and winter seasons
including periods influenced by moderate temperatures, strong Pacific
storms, and air stagnations.  Highest hourly concentrations occur at
temperatures below freezing, highest concentrations are associated with
winds below 5 mph and often times less than 1 mph, and the highest winds
from the south and the southwest quadrant correspond to lowest PM2.5
concentrations and the lowest winds from the east to southeast
correspond to highest PM2.5 concentrations.  

EPA determined from this meterological data that transport from King
County and other areas is not occurring during the periods of the
highest concentrations and that a partial county boundary surrounding
the South L Street monitor and capturing the sources in the Tacoma area
within the CUGA is sufficiently large enough to sources of emissions
that contribute to the violations at the South L Street monitor.

Figure 23.  Hourly concentrations and wind speed at Tacoma L Street
Monitor from 2001-2008

2004

Factor 7:  Geography/topography (mountain ranges or other air basin
boundaries)

The geography/topography analysis evaluates the physical features of the
land that might have an effect on the air shed and therefore on the
distribution of PM2.5 over the Wapato Hills-Puyallup River Valley/Tacoma
area.  Tacoma lies east of the Cascade Mountains, which act as a
topographical barrier to pollution flow from east to west. The Olympic
Mountains to the west result also influence pollution flow.  Air flow
from the west typically flows around the Olympics and converges in the
Seattle Tacoma area.  See Figure 24.  This flow is interrupted during
periods of stagnation during which low lying topographic features can
influence the flow of pollution.  

	Local topography in the Tacoma area has an influence on pollutant
transport.  Figure 25 displays topography in the Tacoma area.  The Port
area of Tacoma is surrounded by bowl like topography.  Beyond the Port
to the north, hills rise to 400 ft creating a topographical barrier
between the north and the south.  The northernmost boundary occurs at
the foot of this bluff along SR 509.  Based on our review of
topographical information, as well as air quality data which shows that
local sources contribute to the violations at the South L Street monitor
and meteorology data which indicates that wind speeds are less than 5
mph during exceedences, EPA’s boundary follows the topographical bluff
along SR 509 is sufficiently large enough to capture the sources in the
area contributing to the violations at the South L Street monitor.

Figure 24.  Seattle-Tacoma-Olympia area topography

 

Figure 25.  Tacoma area topography

  

Factor 8:  Jurisdictional boundaries (e.g., existing PM2.5 areas) 

In evaluating the jurisdictional boundary factor, EPA gave special
consideration to areas that were already designated nonattainment in
2005 for violating the 1997 fine particle standards.  Analysis of
chemical composition data in these areas indicates that the same
components that make up most of the PM2.5 mass in the area on an annual
average basis (such as sulfate and direct PM2.5 carbon in many eastern
areas) also are key contributors to the PM2.5 mass on days exceeding the
24-hour PM2.5 standard.  These data indicate that in many cities, the
same source categories that contribute to violations of the annual
standard also contribute to exceedances of the 24-hour standard.  

Most areas that were originally designated nonattainment for the PM2.5
standards still have not attained the standards.  Thus, EPA has
generally concluded that counties that were designated as having
emissions sources contributing to fine particle concentrations which
continue to exceed the 1997 standards (all areas violated the annual
standard, two also violated the previous 24-hour standard) also
contribute to fine particle concentrations on the highest days.  For
this reason, EPA believes that for most existing nonattainment areas,
the nonattainment area for the 2006 24-hour standard should be the same.
 Consideration also should be given to existing boundaries and
organizations as they may facilitate air quality planning and the
implementation of control measures to attain the standard.  Areas
already designated as nonattainment represent important boundaries for
state air quality planning.

Given that no areas in Washington State violated the 1997 PM2.5
standards, our analysis of jurisdictional boundaries considered the
planning and organizational structure of the Seattle-Tacoma-Olympia area
to determine if the implementation of controls in a potential
nonattainment area can be carried out in a cohesive manner.  The
boundary of King and Pierce County is less than 5 miles north of the
Port of Tacoma and runs east-west along the top of the bluff north of
the Port of Tacoma.  

Puyallup Tribal trust land parcels are located within 5-10 miles to the
north and northwest of the L Street monitor and are contained within the
boundary of the nonattainment area recommended by the State.  To the
south of the L Street monitor, Fort Lewis and the McChord Airforce base
form a jurisdictional boundary (federal/state) land. (Figure 26).  

Figure 26. Wapato Hills-Puyallup River Valley nonattainment area and
jurisdictional boundaries of surrounding areas

EPA examined emissions from the two military jurisdictions to determine
if sources in these areas are contributing to the violations at the
South L Street Monitor.  Emissions from the McChord Airforce base are
less than 1.5 tons per year in 2006. On-base housing units include only
11 wood burning fireplaces and no woodstoves. Additionally, emissions at
Fort Lewis are 5 tons per year or less than 0.2% of the total PM2.5 for
the PM2.5 inventory for Pierce County.  Accordingly, EPA is excluding
these military areas from the nonattainment area boundary.

	The Wapato Hills-Puyallup River Valley nonattainment area contains the
Puyallup Indian Reservation.  Congress explicitly authorized the State
of Washington and local agencies to administer environmental laws
regulating activities on non-trust lands within the Puyallup Indian
Reservation under the Puyallup Tribe of Indians Land Claims Settlement
Act of 1989, 25 U.S.C. 1773.  Activities on trust and restricted lands
within the boundary of the Puyallup Reservation are the responsibility
of EPA and the Tribe.   Given these separate jurisdictions, the Wapato
Hills- Puyallup River Valley nonattainment area will be managed as a
multi-jurisdictional nonattainment area with the EPA and the Puyallup
Tribe responsible for nonattainment area air quality planning activities
on trust and restricted lands within the Puyallup Reservation and the
State responsible for nonattainment area air quality planning activities
on all other portions of the nonattainment area including non-trust
lands within the boundary of the Puyallup Reservation.

	 

	Given low potential contributions of the McChord Air Force Base, the
Fort Lewis Military Base, and King County to the north (based on the air
quality, topography and meteorology data discussed above), as well as
low potential contributions from areas outside of the Tacoma CUGA,
EPA’s boundary follows the Pierce-King County line, excluding King
County to the north and along the boundaries of the military bases, to
the south, excluding those boundaries as well as excluding areas to the
east of the easternmost boundary of the Tacoma CUGA.  

Factor 9:  Level of control of emission sources 

Under this factor, the existing level of control of emission sources is
taken into consideration.  The emissions data used by EPA in this
technical analysis and provided in Table 1 (under Factor 1) represent
emissions levels taking into account  any control strategies implemented
in the Seattle-Tacoma-Olympia area  before 2005 on stationary, mobile,
and area sources.  Data are presented for PM 2.5 components that are
directly emitted (carbonaceous PM 2.5 and crustal PM 2.5) and for
pollutants which react in the atmosphere to form fine particles (e.g.
SO2, NOx, VOC, and ammonia).  

	The State addressed the level of control of emission sources in the
Seattle-Tacoma-Olympia area in their nine factors analysis noting a
number of regulatory and non-regulatory programs in the area.  

However, given that EPA’s analysis of the other eight factors has
shown that the State’s boundary is sufficient to capture sources
contributing to the violations at the South L Street monitor, this
information was not an important consideration in our decision on our
intended boundary.

 The following is a summary of the State’s submittal followed by a
summary of EPA’s nine factor analysis.

Summary of the State’s submittals 

The State submitted to EPA the partial county boundary shown in Figure
27 to EPA on March 13, 2008.  In its nine factors analysis included with
this and its December 18, 2007 submittal, the State focused on local
sources potentially contributing to the violating monitor at South L
Street.  The State explained that air quality data indicates that
exceedences occur during the winter months (November-February), when
meteorology is conducive to inversions that trap pollutants and people
use wood to heat their homes.  Continuous air quality monitors and
woodstove survey data indicate that concentrations are highest during
evening hours, and this corresponds to times when people burn in
woodstoves and fireplaces.   The State also reviewed PM2.5 speciation
data from the South L Street monitor for the highest day in 2006 that
indicates that carbonaceous PM2.5, which is an indicator of emissions
from burning of wood, accounts for 74% or more of the total PM2.5
observed at the South L Street monitor.  

The State’s conclusion from this air quality data as well as the other
data it analyzed in its nine factors analysis is that elevated
concentrations at the South L Street monitor are due to local emissions
(dominated by woodstove and fireplace emissions) occurring under
meteorological conditions conducive to trapping those emissions locally.
 Accordingly, the State used the comprehensive urban growth area (CUGA)
as a starting point for defining the nonattainment area because it
encompasses woodstoves and other sources in Tacoma, its suburbs and the
Urban Growth Area. They further excluded areas in the CUGA from
inclusion in the boundary based on lack of population or sources of
emissions.  These areas include Port Defiance Park, Fort Lewis Base and
McChord Air Force Base to the south and a topographic bluff to the
northernmost edge of the (CUGA).  See Figure 27.  The State’s basis
for excluding these areas is:

The Fort Lewis and McChord Air Force Bases have minimal PM2.5 emissions,
population density and forecasted growth.  The State also argued that
these areas are not upwind of the violating monitor when it experiences
elevated PM2.5 concentrations.

Throughout the area near the Pierce-King County line, sites are either
on highlands or in valleys with little in between.  The State’s
analysis found that the highlands along the northern county line are in
a different air shed from the land to the south and that the bluffs
bordering Commencement Bay and the river valley to the south help trap
fine particulates and increase pollutant concentrations during
inversions that occur in the winter months. The State drew the
northwestern boundary of the proposed nonattainment area to exclude
these bluffs.  They used surrogates of a road (S.R 509) and a stream to
draw the boundary.  This use of surrogates does not exclude any major
sources from the nonattainment area.

The State excluded Point Defiance Park from the proposed nonattainment
area because the area does not contribute to nonattainment.  Only 105 of
the Park’s 702 acres are maintained.

In focusing its initial analysis on the CUGA and local sources, the
State did not directly address whether or not contributions from areas
outside of the CUGA contribute to the violations at the L Street
monitor.  After EPA shared information with the states from contributing
emissions score (CES) modeling which indicated a potential contribution
from regional sources to the north, the State submitted additional
analyses and data that focused on assessing regional contributions to
the Tacoma L Street Monitor. This information included the following:

Hourly monitoring data over 24-hour periods for the South L Street site
and other sites in Puget Sound that show 24-hour patterns in PM2.5
levels at sites in the southern King County industrial areas (Duwamish
and Kent), differ from those observed at monitors in N. King County
(Lake Forest Park) and in Tacoma.  In N. King County and in Tacoma,
“v” shaped diurnal patterns are observed.  These patterns indicate
that peak PM2.5 concentrations occur at night and concentrations
decrease during the day. These patterns generally correspond with
periods of increased woodstove use in the evening hours noted on surveys
conducted by the Puget Sound Clean Air Agency.

Speciated PM2.5 data for the South L Street monitor compared with data
for other sites indicating that carbonaceous PM impacts the Tacoma
monitor predominantly in the winter when fractions of sulfate and
nitrate compared with total PM2.5 are low.   The Duwamish monitor shows
ratios of sulfate/total PM that are more consistent throughout the year.

Additional meteorological data for the L Street Monitor showing that
exceedences occur in the winter during very low wind speeds (less than 5
mph) indicating stagnant conditions.

The State concluded from this additional analysis that high Tacoma
concentrations are due to local emissions dominated by emissions of
carbonaceous PM2.5 occurring under conditions conducive to high
concentrations (meteorology) and not transport.  

Conclusion:  EPA’s review of the State’s submittal and summary of
final decision

Based on monitoring data for the years 2005-2007, EPA’s nine factors
analysis for the Seattle-Tacoma-Olympia area and other relevant factual
and technical information as discussed above, EPA is designating the
Wapato Hills-Puyallup River Valley (a portion of Pierce County) area in
the State of Washington as “nonattainment” for the 24-Hour PM2.5
standard. See Figure 27.

	EPA’s final designations for the State of Washington also included a
review of information submitted by the State of Washington in
determining the attainment status for the 24-Hour PM2.5 standard areas
in the State of Washington as well as the boundary for the Wapato
Hills-Puyallup River Valley Nonattainment area.   

We note that The Wapato Hills-Puyallup River Valley nonattainment area
is a multi-jurisdictional nonattainment area, with the EPA and the
Puyallup Tribe responsible for nonattainment area air quality planning
activities on Puyallup tribal trust and restricted lands and the State
responsible for nonattainment area air quality planning activities on
all other portions of the nonattainment area including non-trust lands
within the boundary of the Puyallup Reservation..    

EPA conducted a nine factors analysis of data for the Wapato
Hills-Puyallup River Valley area and surrounding areas (counties in the
Seattle-Tacoma-Olympia CMSA) and reviewed information that Washington
State submitted on March 13, 2008 focused on the Tacoma CUGA as well as
the information it later submitted on July 25, 2008.  EPA’s nine
factors analysis and review of the State’s submittals supports using
the partial county boundary that the State of Washington submitted to
EPA because:

Chemical speciation data indicates that there is a 74% or more
contribution from carbonaceous PM2.5 PM which is associated with burning
in woodstoves and fireplaces, and 10% or less contribution from PM2.5
components that are typically regional such as sulfate and nitrate.  

EPA’s analysis of positive matrix factorization data indicates that
60-90% of total PM2.5 on exceeding days at the South L Street monitor is
from wood smoke.  There are no other sources of smoke during the winter
season in the CUGA.  By law outdoor burning is prohibited in this area. 


Hourly PM2.5 levels at the South L Street monitor peak in the evenings
and decrease dramatically during the day.  These patterns are consistent
with woodstove surveys conducted in Tacoma which show that on high PM2.5
days, woodstove use PM2.5 peaks in the late evening and is lowest around
noon. 

Meteorological data shows very low mixing heights during stagnation
events when the exceedences are occurring, and low wind speeds
(typically less than 5 mph).  Local topographical features in the area
restrict pollution flow in the Tacoma area during stagnation events.  

Population density in Pierce County is concentrated within the CUGA. 
The Fort Lewis and McChord Air Force Base military installations to the
south are not included in the nonattainment area because emissions from
the bases contribute  less than 0.2% to the total inventory of PM2.5
emissions in the area.

The nonattainment area includes the Port of Tacoma because it has
substantial PM2.5 emissions (estimated at 90 tons per year).  This does
not include off-terminal emissions, which contribute additional PM2.5. 
The Port projects a dramatic increase of its cargo handling capacity in
the next two decades, with an estimated cargo growth factor of 4.8 from
1999 to 2015. 

 

Analyses of speciated PM 2.5 data, diurnal patterns of PM 2.5
concentrations, and meteorological information from the Puget Sound
region indicate that sources contributing the violations of the 24-hour
PM2.5 standard at the South L Street monitor are predominantly local
sources dominated by woodstove and fireplace emissions in the Tacoma
area and not transport from King County or other counties in the
Seattle-Tacoma-Olympia area.  

EPA has determined the boundary submitted by the State of Washington in
March 2008 is appropriately sized to contain the sources that contribute
to the violations at the South L Street monitor including populated
areas in the Tacoma area where households operate woodstoves and
fireplaces in the winter, and mobile sources and diesel traffic
associated with good movements at the Port of Tacoma and sections of
Interstate 5 and State Highway 99.  The final boundary includes all land
within the boundary of the Puyallup Indian Reservation.   

Additional information regarding responses to specific State comments
can be found in EPA's Response to Comments document at   HYPERLINK
"http://www.epa.gov/pmdesignations/2006standards/tech.htm" 
http://www.epa.gov/pmdesignations/2006standards/tech.htm .

Figure 27. Wapato Hills-Puyallup River Valley nonattainment area

Attachment 2

Description of the Contributing Emissions Score

The CES is a metric that takes into consideration emissions data,
meteorological data, and air quality monitoring information to provide a
relative ranking of counties in and near an area.  Using this
methodology, scores were developed for each county in and around the
relevant metro area.  The county with the highest contribution potential
was assigned a score of 100, and other county scores were adjusted in
relation to the highest county.  The CES represents the relative maximum
influence that emissions in that county have on a violating county.  The
CES, which reflects consideration of multiple factors, should be
considered in evaluating the weight of evidence supporting designation
decisions for each area.

The CES for each
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	Major PM2.5 components:  total carbon (organic carbon (OC) and
elemental carbon (EC)), SO2, NOx, and inorganic particles (crustal).

	PM2.5 emissions for the highest (generally top 5%) PM2.5 emission
days (herein called “high days”) for each of two seasons, cold
(Oct-Apr) and warm (May-Sept)

	Meteorology on high days using the NOAA HYSPLIT model for
determining trajectories of air masses for specified days

	The “urban increment” of a violating monitor, which is the urban
PM2.5 concentration that is in addition to a regional background PM2.5
concentration, determined for each PM2.5 component

	Distance from each potentially contributing county to a violating
county or counties

[A more detailed description of the CES can be found at
http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html#C.]

 EPA designated nonattainment areas for the 1997 fine particle standards
in 2005.  In 2006, the 24-hour PM2.5 standard was revised from 65
micrograms per cubic meter (average of 98th percentile values for 3
consecutive years) to 35 micrograms per cubic meter; the level of the
annual standard for PM2.5 remained unchanged at 15 micrograms per cubic
meter (average of annual averages for 3 consecutive years).  

 See the following docket materials:

July 25 WA State letter attachment PS Diurnals_2005-2007 data.png

July 25 WA State letter attachment Presentation to OAQPS_as
of25-Jul-08.pdf

July 25 WA State letter attachment Tacoma L Street characteristics.pdf

July 25 WA State letter attachment Tacoma L Street Speciation.pdf

July 25 WA State letter attachment Tacoma_PM2.5 episode_12-16-Jan-07.png

July 25 WA State letter attachment
Duwamish_SO4_NO3_OC_ECvs_PM2.5_with_FRM.png

July 25 WA State letter attachment Lake
Forest_Park_SO4_NO3_OC_ECvs_PM2.5_with_FRM.png

 See supporting documentation section on limitations of the CES. 
Because of differences in county size, and topography across the
country, the score may require careful interpretation for some areas,
particularly in the western United States.  

 US Census Bureau.   HYPERLINK
"http://factfinder.census.gov/home/saff/main.html" 
http://factfinder.census.gov/home/saff/main.html 

 Design values are based on data collected at FRM or FEM monitors.  The
State operates other monitors in these counties but they are not FRM or
FEM monitors.

  Positive matrix factorization (PMF) (Footnoted: A. Reff et al,
“Receptor Modeling of Ambient Particulate Matter Data Using Positive
Matrix Factorization: Review of Existing Methods,” Journal of the Air
and Waste Management Association, 57:146-154, February 2007.) is a
recent development in the class of data analysis techniques called
factor analysis, in which the fundamental problem is to resolve the
identities and contributions of components in an unknown mixture. PMF
has been used extensively for source apportionment of ambient
particulate matter (PM), to resolve the mixture of sources that
contributes to PM samples. PMF is especially applicable to working with
environmental data because it incorporates the variable uncertainties
often associated with measurements of environmental samples, and forces
all of the values in the solution profiles and contributions to be
nonnegative, which is more realistic than solutions from previously used
methods like principal components analysis.

 Washington State Department of Ecology 2008 Ambient Air Monitoring
Network Report

 Puget Sound Clean Air Agency 2007 woodstove use survey

 See Chapter 36.70A RCW for more on the Washington State Growth
Management Act which defines an urban growth area or areas within which
urban growth shall be encouraged and outside of which growth can occur
only if it is not urban in nature. 

 Note:  The 2005 VMT data used for table 5 and 6 of the 9-factor
analysis has been derived using methodology similar to that described in
“Documentation for the final 2002 Mobile National Emissions Inventory,
Version 3, September 2007, prepared for the Emission Inventory Group,
U.S. EPA.  This document may be found at: at
ftp://ftp.epa.gov/EmisInventory/2002finalnei/documentation/mobile/2002_m
obile_nei_version_3_report_092807.pdf

The 2005 VMT data were taken from documentation which is still draft,
but which should be released in 2008.

 Puget Sound Regional Council.  Draft Vision 2040 Supplemental Draft
Environmental Impact Statement (SDEIS).  July 2007.    HYPERLINK
"http://www.psrc.org/projects/vision/pubs/sdeis/index.htm" 
http://www.psrc.org/projects/vision/pubs/sdeis/index.htm  and  
HYPERLINK "http://www.psrc.org/tpbgrowthandtrans2.pdf" 
http://www.psrc.org/tpbgrowthandtrans2.pdf .

Puget Sound Regional Council.  Vision 2020 Update DEIS.  Transportation
Demand Model Output Data.  Appendix D-5, pages D-18 to D-29.   
HYPERLINK "http://www.psrc.org/projects/vision/deis/appd.pdf" 
http://www.psrc.org/projects/vision/deis/appd.pdf .

 A Presentation to Northwest AirQuest on Analysis of Sand Point Wind
Profiler and RASS system, included in the docket for this action.

 Study results are included in the State of Washington’s Nine Factors
Analysis

 On March 13, 2008, the State submitted a supplement to their initial
designation recommendation letter and nine factors analysis dated
December 18th letter and included a boundary recommendation for the area
surrounding the monitor at 7802 South L Street (South L Street monitor).
 In addition to the March 13th letter, the State submitted a letter
dated July 28, 2008 containing addition technical information for
EPA’s consideration.  

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ttlement Act of 1989, 25 U.S.C. 1773.  Activities on trust land
restricted ands within the boundary of the Puyallup Reservation are the
responsibility of EPA and the PuyallupTribe. 

 PAGE   

 PAGE   3 

Puyallup South

South L Street Monitor

Duwamish

Mountlake Terrace

Maryswville

Kent

Queen Anne Hill

Lake Forest Park

Tacoma S L.

Kent Valley

Duwamish

Queen Anne Hill

Mountlake Terrace

Lake Forest Park

Marysville

 

Marysville

Lake Forest Park

Duwamish Valley

Tacoma L Street

Lynnwood

Queen Anne

Kent Valley

Puyallup South Hill

Puyallup South

