Document ID: EPA-HQ-OAR-2003-0083-0651
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2003-08-28T04:00Z

TECHNICAL
ANALYSIS
USED
TO
DEVELOP
OPTIONAL
NONATTAINMENT
BOUNDARIES
FOR
8­
HOUR
OZONE
FOR
THE
GREATER
PHOENIX
AREA
July
2003
Prepared
For
Arizona
Department
of
Environmental
Quality
Prepared
By
Air
Pollution
Evaluations
and
Solutions
Gary
R.
Neuroth
Page
1
Introduction
Ozone
concentrations
in
the
Greater
Phoenix
Area
exceed
the
U.
S.
Environmental
Protection
Agency
(
EPA)
8­
hour
ozone
standard
of
0.08
parts
per
million
(
ppm),
or
an
equivalent
value
of
80
parts
per
billion
(
ppb).
Due
to
rounding
conventions,
a
concentration
of
85
ppb
or
higher
exceeds
the
standard.
Compliance
with
the
standard
is
based
on
three­
year
averages
of
the
fourth
highest
value
for
each
year,
at
each
monitor.
Ozone
concentrations
in
areas
influenced
by
emissions
in
the
Phoenix
area
have
exceeded
the
standard
for
each
three­
year
period
since
the
standard
was
proposed
by
EPA
in
1997.
Maximum
values
have
been
in
the
range
of
85
to
88
ppb.

The
methods
used
to
develop
the
optional
nonattainment
area
boundaries
for
8­
hour
ozone
described
in
this
report
use
information
covering
each
of
the
eleven
designation
criteria
in
EPA
Guidance
on
establishing
boundaries
for
the
8­
hour
standard,
dated
March
28,
2000.
The
actual
technical
approach
directly
follows
the
requirements
in
Section
107
(
d)
(
1)
of
the
Clean
Air
Act
Amendments
which,
"
requires
all
areas
to
be
designated
nonattainment
if
they
do
not
meet
the
standard
or
contribute
to
ambient
air
quality
in
a
nearby
area
that
does
not
meet
the
standard."

Per
the
requirement
quoted
above,
the
nonattainment
boundary
options
were
developed
by
separate
analyses
to
map
the
areas
of
ozone
impact
where
the
standard
is
exceeded,
and
a
separate
but
closely­
related
analysis,
to
determine
the
geographic
area
where
pollutant
emissions
contribute
to
the
ozone
concentrations
above
the
standard.
The
area
where
ozone
exceeds
the
ambient
standard
is
referred
to
in
this
report
as
the
"
Receptor
Area",
and
the
area
where
emissions
occur
which
contribute
to
ozone
violations
is
referred
to
as
the
"
Source
Area."

Two
alternative
design
criteria
were
used
to
produce
the
optional
boundaries.
One
design
criterion
is
an
85
ppb,
three­
year
average
of
the
fourth
high
value,
which
is
the
effective
level
of
the
standard.
Under
this
criterion,
the
boundary
was
constrained
to
enclose
the
geographic
area
where
there
is
high
confidence
that
the
standard
is
exceeded.
The
other
design
criterion
value
is
80
ppb.

The
boundary
developed
using
the
80­
ppb
criterion
is
a
larger
area
because
it
includes
the
entire
85­
ppb
area
as
well
as
additional
areas
where
concentrations
are
generally
in
the
80­
85
ppb
range,
but
without
any
measurements
indicating
ozone
levels
above
the
standard.
Page
2
Receptor
Area
Analysis
An
attempt
was
made
to
use
all
available
information
relevant
to
determine
the
geographic
extent
of
ozone
violations
in
the
vicinity
of
the
Phoenix
area
under
current
emissions.
The
three
basic
information
tools:
ozone
monitoring
data,
ozone
simulation
modeling,
and
wind
measurement
analysis,
were
used
in
this
evaluation.
These
tools
and
their
specific
roles
in
the
development
of
the
boundary
options
are
described
below.

Ozone
Monitoring
Maricopa
County,
Pinal
County,
and
ADEQ,
operate
an
extensive
network
of
ozone
monitors
in
and
around
the
Greater
Phoenix
Area.
Currently
there
are
26
monitors
in
operation,
mostly
in
the
urbanized
area,
but
a
significant
number
are
located
in
rural
and
even
remote
locations
as
far
as
80
miles
from
central
Phoenix.

A
concern
with
using
historical
ozone
measurement
records
for
the
purpose
of
designating
a
nonattainment
area
occurs
when
there
is
any
evident
trend
in
the
data.
Over
time,
ozone
concentrations
have
decreased
in
the
Phoenix
area,
as
is
evident
by
the
attainment
of
the
1­
hour
standard
in
1997.
The
measurement
record
of
8­
hour
ozone
concentrations
from
1995
through
2002
was
evaluated
for
possible
use
in
this
project.
It
was
concluded
that
ozone
concentrations
decreased
through
1996
but
that
no
apparent
trend
has
occurred
since
then.

Table
1
shows
the
fourth
highest
ozone
concentrations
for
the
ozone
monitoring
network
for
the
period
1995
through
2002.
The
last
row
on
this
table
shows
the
average
concentration
for
the
network
by
year.
These
averages
reveal
a
drop
in
concentration
levels
after
1996,
with
stable
values
thereafter.
Average
values
for
a
subset
of
the
network
comprised
of
ten
monitors
that
were
in
operation
for
all
eight
years
reveals
the
same
pattern
of
stable
concentrations
from
1997
through
2002,
see
Table
2.
Therefore,
the
1997
through
2002
portion
of
the
historical
record
was
used
in
the
development
of
the
boundary
options
and
is
considered
representative
of
current
conditions.

All
ozone
ambient
measurements
available
for
the
1997through
2002
time
period
were
used
in
this
evaluation
including
data
from
discontinued
monitors,
those
with
fewer
than
three
years
of
data,
and
new
monitors.
The
monitoring
record
and
judgments
regarding
the
spatial
representation
of
each
monitor
were
the
principle
tools
used
in
developing
the
boundary
options.
Page
3
Table
1.
Annual
Fourth
Highest
8­
Hour
Ozone
Concentrations,
1995
 
2002
Annual
Fourth
Highest
8­
Hour
Ozone
Concentration
in
Parts
per
Billion
(
PPB)

Monitor
Site
Abbreviation
1995
1996
1997
1998
1999
2000
2001
2002
Gila
County
Rye
RY
56
65
80
Tonto
N.
M.
TONO
87
Maricopa
County
Blue
Point
BP
83
89
87
87
80
86
Cave
Creek
CC
83
86
Central
Phoenix
CP
85
76
77
79
78
76
75
76
Emergency
Management
EM
85
81
86
70
63
Falcon
Field
FF
81
83
82
75
81
84
Fountain
Hills
FH
88
86
86
85
83
86
Glendale
GL
80
72
76
70
81
81
78
83
Humboldt
Mountain
HM
81
90
86
82
85
90
Lake
Pleasant
LP
82
81
82
73
Maryvale
MA
78
86
77
80
73
84
Mesa
ME
92
90
84
80
83
75
74
72
Mt.
Ord
MO
84
88
87
90
77
North
Phoenix
NP
92
95
91
89
84
86
86
85
Palo
Verde
PAVE
71
77
80
80
80
74
78
Pinnacle
Peak
PP
91
91
82
86
83
86
85
84
Rio
Verde
RV
85
79
86
86
83
85
Roosevelt
RO
84
Salt
River
Pima
SRPI
92
92
82
87
82
South
Phoenix
SP
84
91
75
80
75
83
76
81
South
Scottsdale
SS
89
87
76
78
72
80
79
77
Super
Site
PXSS
87
79
79
76
79
76
Surprise
SU
71
79
Tempe
TE
78
79
80
Vehicle
Emissions
VE
92
80
West
Chandler
WC
77
74
69
74
78
83
West
Phoenix
WP
84
81
78
86
91
81
75
84
Pinal
County
Apache
Junction
AJ
91
85
82
82
80
82
78
80
Casa
Grande
CG
71
79
72
68
78
75
74
78
Queen
Valley
QUAZ
79
83
Yavapai
County
Hillside
HISD
85
76
83
84
83
76
89
Gila,
Maricopa,
Pinal,
and
Yavapai
Counties
Average
All
Monitors
87
84
80
81
82
81
78
82
Page
4
Table
2.
Annual
Fourth
Highest
8­
Hour
Ozone
Concentrations
for
Monitors
in
Operation,
1995
­
2002
Exceedances
of
the
8­
hour
ozone
standard
are
represented
in
blue.

Annual
Fourth
Highest
8­
Hour
Ozone
Concentration
in
Parts
per
Billion
(
PPB)
 
for
monitors
in
operation
1995
through
2002
Monitor
Site
Abbreviation
1995
1996
1997
1998
1999
2000
2001
2002
Maricopa
County
Central
Phoenix
CP
85
76
77
79
78
76
75
76
Glendale
GL
80
72
76
70
81
81
78
83
Mesa
ME
92
90
84
80
83
75
74
72
North
Phoenix
NP
92
95
91
89
84
86
86
85
Pinnacle
Peak
PP
91
91
82
86
83
86
85
84
South
Phoenix
SP
84
91
75
80
75
83
76
81
South
Scottsdale
SS
89
87
76
78
72
80
79
77
West
Phoenix
WP
84
81
78
86
91
81
75
84
Pinal
County
Apache
Junction
AJ
91
85
82
82
80
82
78
80
Casa
Grande
CG
71
79
72
68
78
75
74
78
Maricopa
and
Pinal
Counties
Average
All
Monitors
86
85
79
80
81
81
78
80
Page
5
The
density
and
distribution
of
ozone
monitors
in
the
urbanized
area
is
adequate
to
define
the
portions
of
the
urbanized
area
that
exceed
either
the
80­
or
85­
ppb
design
criteria.
However,
in
rural
areas
there
are
relatively
large
distances
between
monitors.
The
extensive
areas
with
mountainous
and
complex
terrain
complicate
the
interpretation
of
the
measurement
data
and
require
the
consideration
of
such
phenomena
as
plume
impingement
on
high
terrain,
and
ozone
shadows
on
the
leeward
side
of
mountains.
Furthermore,
some
of
the
highest
concentrations
of
ozone
have
been
measured
at
the
periphery
of
the
monitoring
network,
which
begs
the
question
as
to
the
extent
of
ozone
at
levels
that
exceed
the
standard
beyond
these
monitor
locations.

The
first
step
in
attempting
to
fill
the
gaps
between
and
beyond
the
rural
monitors
is
to
determine
the
spatial
representation
of
each
monitor.
This
was
accomplished
by
a
careful
review
of
the
measurements
record
of
each
monitor
and
comparisons
between
measurements
at
different
sites.
This
evaluation
was
done
in
the
consideration
of
topographic
influences,
airflow
patterns,
and
ozone
formation
dynamics.

The
results
of
the
dispersion
modeling
and
an
analyses
of
wind
conditions
during
the
two
ozone
episode
periods
in
2002
were
used
in
this
exercise
to
interpret
the
ambient
ozone
data
record.

Modeling
ADEQ
contracted
with
the
Arizona
State
University's,
Environmental
Fluid
Dynamics
Program
to
perform
ozone
modeling
for
two
episode
periods
in
2002,
June
4
through
7
and
July
9
through
13.
Emissions
inventories
for
the
two
episodes
were
developed
by
Dr.
Susanne
Grossman­
Clark,
using
the
EPA
approved
SMOKE
model
for
anthropogenic
and
biogenic
emissions
of
nitrogen
oxides
(
NOx)
and
volatile
organic
compounds
(
VOC's).
Ozone
dispersion
modeling
was
performed
by
Dr.
Sang­
Mi
Lee
and
Dr.
S.
Fernando.
The
ozone
modeling
employed
EPA
approved
models.
The
MM5
model
was
used
for
the
meteorological
modeling
which
was
input
to
the
CMAQ
model
for
ozone
simulations.

Both
the
MM5
and
CMAQ
modeling
results
were
validated
by
comparison
with
measured
meteorological
and
ozone
data,
and
were
found
to
exceed
EPA
criteria
for
acceptable
model
performance.
Although
the
models
performed
well,
the
winds
predicted
by
MM5
tended
to
be
late
on
the
timing
of
the
daily
wind
shift
from
nighttime
drainage
winds,
generally
from
the
east,
to
upslope
flow,
generally
from
the
southwest.
Unfortunately,
this
shift
actually
occurs
within
a
few
hours
after
sunrise
at
the
beginning
of
the
daily
ozone
production
period.
The
effect
is
modeled
over­
predictions
of
the
geographic
extent
and
concentrations
of
ozone
to
the
west
of
the
urbanized
area
and
a
delay
in
transport
to
the
northeast
resulting
in
under­
predictions
of
ozone
to
the
northeast.

The
modeling
results
were
not
used
to
explicitly
to
determine
the
non­
attainment
boundaries
but
rather
provided
a
theoretical
input,
not
otherwise
available,
as
to
the
potential
extent
of
high
8­
hour
ozone
downwind
of
the
Greater
Phoenix
Area.
The
Page
6
modeling
indicates
the
potential
for
8­
hour
ozone
concentrations
above
85
ppb
at
distances
greater
than
80
miles
from
central
Phoenix,
as
can
be
seen
on
Figure
1,
which
shows
the
modeling
results
for
June
6,
2002.
This
potential
is
considered
in
the
interpretation
of
monitored
ozone
concentrations
in
light
of
actual
wind
persistence
from
a
given
direction
in
estimating
the
downwind
extent
of
the
non­
attainment
area.

Figure
1.
Highest
8­
Hour
Ozone
Concentrations:
1200
LST
June
5
through
7,
2002
Source:
ASU
Mechanical
and
Aerospace
Engineering
Department
Wind
Analysis
ADEQ
provided
hourly
records
of
wind
direction
and
speed
from
instruments
operated
by
Maricopa
County,
Salt
River
Project,
University
of
Arizona,
and
ADEQ
for
the
nine
days
of
the
two
ozone
episode
periods
in
2002
which
had
ozone
concentrations
higher
than
85
ppb.
The
wind
data
were
used
to
characterize
general
airflow
patterns
and
their
variations
on
the
nine
days
with
8­
hour
ozone
values
exceeding
the
standard.
The
location
of
the
wind
sites
are
shown
on
Figure
2.
HI
PV
SU
GL
SJN
MA
WPSS
NP
SP
CP
SC
TE
MC
CG
SCT
ME
PP
FH
BP
RV
CMB
AJ
CC
HU
QV
TO
25
30
35
40
45
50
55
60
20
25
30
35
40
45
Page
7
Figure
2.
Wind
Monitoring
Sites
Sources:
University
of
Arizona,
Salt
River
Project
(
SRP),
Maricopa
County,
Arizona
Department
of
Environmental
Quality
(
ADEQ),
U.
S.
Geological
Survey
(
USGS),
ALRIS
Each
episode
day
exhibited
the
same
general
pattern
and
consequent
ozone
transport.
Downslope
or
drainage
winds,
generally
from
the
east,
usually
persisted
till
a
few
hours
after
sunrise
which
is
typical
during
the
summer
ozone
season.
The
transition
from
drainage
to
upslope
typically
lasts
for
two
to
three
hours,
but
during
the
nine
days
studied
the
transition
varied
from
one
to
eight
hours.
The
transitional
period
corresponds
with
the
beginning
of
the
daily
photochemical
ozone
formation
period.
During
the
transition,
winds
rotate
in
a
clockwise
fashion
through
south
before
completing
the
shift
to
blowing
from
the
southwest
quadrant
which
is
typical
upslope
flow
for
this
area.
Upslope
winds
generally
begin
about
noon
and
last
till
near
sunset.
During
the
nine
days
studied
upslope
flow
varied
from
six
to
twelve
hours
duration.

The
few
hours
of
drainage
flow
during
the
early
daylight
hours
added
to
the
early
portion
of
the
transitional
winds,
transported
the
urban
plume
toward
the
northwest
under
ozone
formation
conditions
for
three
to
ten
hours
on
the
episode
days.
The
later
part
of
the
Page
8
transition
period
coupled
with
the
upslope
period
pushed
the
plume
into
the
mountainous
northeast
quadrant
for
periods
of
time
ranging
from
eight
to
twelve
hours.
Wind
speeds
averaged
five
to
ten
MPH
during
the
upslope
period
and
were
somewhat
lighter
during
transition
and
drainage
periods.
These
wind
direction
patterns
were
useful
in
interpreting
the
ozone
measurements
on
these
ozone
episode
days,
and
the
persistence
of
wind
in
the
different
directions
provided
a
sound
basis
for
estimating
the
transport
distance
of
the
urban
plume
and
the
extent
of
geographic
extent
of
ozone
violations.

As
previously
mentioned,
ozone
concentration
levels
are
well
defined
in
the
urbanized
area
by
the
relatively
dense
array
of
monitors.
In
the
outlying
areas
there
are
large
gaps
between
monitors
which
begs
the
question
as
to
the
extent
of
high
ozone
concentrations
beyond
the
peripheral
monitors
which
have
recorded
violations
of
the
standard.

In
consultation
with
ADEQ,
a
geographic
area
was
identified
that
required
further
analysis
to
identify
the
portions
that
exceed
the
80
and
85
ppb
design
criteria.
The
map
in
Figure
3
shows
the
area
in
question
broken
into
four
study
sectors.
The
following
section
of
this
report
describes
how
the
boundary
options
for
each
sector
were
derived
using
the
informational
tools
described
above.

Figure
3.
Map
of
Receptor
Area
Study
Zones
Sector
by
Sector
Boundary
Selections
Sources:
ADEQ,
USGS,
ALRIS,
Neuroth
Page
9
Sector
1­
This
sector,
shown
in
Figure
4,
lies
to
the
east
of
the
Phoenix
area
mostly
in
Pinal
County
extends
towards
the
town
of
Superior.
There
are
three
ozone
monitors
located
in
this
sector:
Falcon
Field,
Apache
Junction,
and
Queen
Valley.
Ozone
concentrations
measured
at
Falcon
Field
and
Apache
Junction
have
been
close
to
the
standard.
The
Queen
Valley
monitor
has
only
operated
for
two
years
with
fourth
high
values
of
79
and
83
ppb
in
2001
and
2002,
respectively.
Ozone
concentrations
to
the
south
of
this
sector
in
west
Chandler
and
Pinal
County
have
been
below
80
ppb
while
measurements
to
the
north
have
exceeded
the
standard.

Figure
4.
Map
of
Receptor
Area
Study
Zones
 
Sector
1
Sources:
ADEQ,
USGS,
ALRIS,
Neuroth
Prevailing
upslope
winds
provides
insight
into
the
ozone
pattern
described
above.
Typical
airflow
during
the
critical
ozone
formation
hours
transports
the
urban
plume
mostly
to
the
area
north
of
this
sector,
the
higher
concentrations
of
ozone
at
Falcon
Field
and
Apache
Junction
compared
to
measurements
to
the
south
indicate
that
the
northerly
portion
of
this
sector
is
grazed
by
the
transported
urban
plume.

Modeling
and
monitoring
data
support
the
idea
that
the
highest
ozone
concentrations
in
this
sector
occur
in
the
elevated
terrain
in
the
north
portion
of
this
sector.
Remote
areas
of
the
Superstition
Mountains
including
elevations
over
5000
feet,
without
the
ozone
Page
10
scavenging
effect
of
fresh
NO
emissions
almost
certainly
experience
higher
ozone
than
the
Falcon
Field
and
Apache
Junction
monitors
which
have
recorded
levels
near
the
standard.

The
boundary
for
the
80­
ppb
area
is
largely
based
on
measurements
at
Tempe
and
Queen
Valley
and
also
on
the
expectation
of
higher
concentrations
in
the
remote
portions
of
the
sector.
The
85­
ppb
boundary
includes
the
Falcon
Field
monitor
location
and
the
northern
portion
of
the
Superstition
Mountains
nearest
to
Phoenix.

Sector
2­
Figure
5
shows
the
location
of
this
sector
to
the
east­
northeast
of
Phoenix,
roughly
centered
on
the
Salt
River
valley
to
Roosevelt
Lake
and
the
Sierra
Ancha
Mountains,
and
the
Mogollon
Rim
beyond.

Figure
5.
Map
of
Receptor
Area
Study
Zones
 
Sector
2
Sources:
ADEQ,
USGS,
ALRIS,
Neuroth
Two
monitors
are
currently
operated
in
this
sector:
Blue
Point
and
Tonto.
Both
of
these
monitors
are
located
at
relatively
low
elevations
in
the
Salt
River
valley.
The
Blue
Point
monitor,
which
is
located
about
28
miles
east­
northeast
of
Phoenix,
has
measured
violations
of
the
8­
hour
ozone
standard.
The
Tonto
monitor
located
at
Tonto
National
Monument
near
Roosevelt
Lake
is
about
50
miles
from
Phoenix.
The
Tonto
monitor
has
Page
11
only
operated
for
one
full
ozone
season
and
measured
a
fourth
high
concentration
of
87
ppb
in
2002.
In
1997,
an
ozone
monitor
identified
as
Roosevelt
operated
near
the
location
of
the
current
Tonto
monitor.
The
Roosevelt
monitor
measured
a
fourth
high
concentration
of
84
ppb.

Much
of
the
land
in
this
sector
is
mountainous,
with
peaks
above
7,000
feet.
An
ozone
monitor
was
operated
near
the
top
of7,300­
foot
Mount
Ord,
located
in
the
nearby
portion
of
sector
3,
from
1997
through
2001.
Concentrations
of
ozone
at
Mount
Ord
exceeded
the
standard
and
this
record
was
used
to
estimate
high
terrain
impacts
in
sector
2.
The
use
of
Mount
Ord
monitor
data
for
this
sector
is
supported
by
the
similarity
in
ozone
measurements
seen
when
comparing
the
Blue
Point
monitor
measurements
in
sector
2
with
corresponding
measurements
at
the
Fountain
Hills
monitor
in
sector
3.
The
Fountain
Hills
monitor
is
about
the
same
distance
from
Phoenix
and
at
a
comparable
elevation
to
Blue
Point.
It
is
also
on
the
same
trajectory
for
receipt
of
the
Phoenix
area
plume
as
Mount
Ord.
The
remarkably
similar
ozone
concentrations
at
Blue
Point
and
Fountain
Hills
can
be
seen
on
Table
1.
The
wind
analysis
for
the
nine
ozone
episode
days
also
supports
the
conclusion
that
airflow
from
the
urbanized
area
into
sectors
2
and
3
are
very
similar.

The
80­
and
85­
ppb
boundaries
shown
on
Figure
5,
are
virtually
the
same.
Although
concentrations
above
80­
ppb
probably
occur
beyond
the
most
distant
portion
of
the
boundary,
there
is
no
ambient
record
to
guide
a
boundary
line
beyond
that
shown.
It
is
concluded
that
the
concentrations
measured
at
Blue
Point
and
Tonto
indicate
that
concentrations
of
ozone,
at
or
above
the
standard,
occur
throughout
the
Salt
River
valley
at
relatively
low
elevations.
The
high
elevation
areas
around
Four
Peaks
and
in
the
Sierra
Ancha
Mountains
are
also
considered
to
experience
ozone
violations
based
on
the
Mount
Ord
record
as
well
as
modeling
predictions
and
the
occurrence
of
transport
winds
from
the
Phoenix
area
into
this
area
for
up
to
twelve
hours
at
velocities
in
the
five
to
ten
MPH
range
during
hours
of
high
ozone
formation
potential.

Sector
3­
This
sector,
shown
in
Figure
6,
is
to
the
north­
northeast
of
Phoenix,
and
is
predominantly
mountainous
National
Forest
land.
Three
of
the
four
ozone
monitors
that
have
operated
in
this
sector
have
recorded
concentrations
above
the
standard.
The
Fountain
Hills
monitor
referenced
in
the
sector
2
discussion,
is
located
in
a
residential
area
about
20
miles
from
Phoenix.
The
Mount
Ord
monitor,
installed
at
about
7,300
feet,
50
miles
northeast
of
Phoenix,
was
operated
from
1997
until
2001,
when
it
was
discontinued
due
to
difficulties
with
instrument
access
at
the
mountain­
top
location.
The
Humboldt
Mountain
monitor
is
located
about
40
miles
north­
northeast
of
Phoenix
at
4,900
feet.
Both
of
these
mountain
monitors
have
measured
8­
hour
violations,
and
the
Humboldt
Mountain
monitor
recorded
a
network
high
90
ppb
in
2002.
ADEQ
operated
an
ozone
monitor
at
the
small
town
of
Rye,
located
about
67
miles
northeast
of
Phoenix
at
an
elevation
of
3,000
feet
between
1997
and
1999.
Ozone
concentrations
at
this
site
were
below
80
ppb.

The
ozone
violation
level
concentrations
measured
at
Mount
Ord
and
Humbolt
Mountain,
at
distances
of
50
and
40
miles
from
central
Phoenix,
and
to
a
lesser
extent,
the
80­
85
ppb
Page
12
concentrations
at
the
Hillside
monitor
located
80
miles
northwest
of
Phoenix
in
sector
4,
demonstrate
the
influence
of
the
urban
plume
at
high
elevation
locations,
long
distances
from
ozone
producing
emissions.
The
low
ozone
concentrations
at
Rye
are
thought
to
indicate
that
an
ozone
shadow
occurs
at
low
elevations
leeward
(
downwind)
of
high
terrain.

Figure
6.
Map
of
Receptor
Area
Study
Zones
 
Sector
3
Sources:
ADEQ,
USGS,
ALRIS,
Neuroth
The
80­
and
85­
ppb
boundary
lines
are
virtually
the
same
in
this
sector.
Pine
Mountain
at
6,300
feet
was
chosen
as
the
northernmost
boundary
limit.
Pine
Mountain
is
about
20
miles
beyond
Humboldt
Mountain,
along
the
same
trajectory
from
Phoenix,
and
is
about
1,800
feet
higher.
Modeling,
wind
persistence
during
ozone
formation
hours,
and
mountaintop
ozone
data,
support
the
boundaries
selected
for
this
sector.

Sector
4­
This
sector,
shown
in
Figure
7,
is
a
large
area
to
the
north
through
northwest
of
Phoenix.
Winds
from
the
Phoenix
area,
during
ozone
formation
hours,
blow
toward
this
direction
during
the
final
hours
of
drainage
flow
and
continue
during
the
transition
to
upslope.
Three
ozone
monitors
have
operated
in
this
sector,
however
only
one
has
a
lengthy
record.
The
Hillside
monitor,
located
about
80
miles
northwest
of
Phoenix
at
an
elevation
of
5,000
feet,
has
operated
since
1996.
Fourth
high
ozone
concentrations
have
been
in
the
80­
83
ppb
range,
except
in
2002
when
a
89­
ppb
concentration
was
recorded.
The
Cave
Creek
monitor
began
operation
in
2001,
and
has
recorded
fourth
high
values
of
Page
13
83
and
86
ppb
in
2001
and
2002.
An
ozone
monitor
was
operated
at
Lake
Pleasant
from
1998
to
2001
with
concentrations
averaging
about
80
ppb.

Figure
7.
Map
of
Receptor
Area
Study
Zones
 
Sector
4
Sources:
ADEQ,
USGS,
ALRIS,
Neuroth
The
higher
ozone
concentrations
at
Cave
Creek
compared
to
Lake
Pleasant
are
expected
because
of
the
higher
frequency
and
duration
of
winds
from
the
south
than
from
the
southeast
during
ozone
formation
hours.
The
still
higher
ozone
at
the
Humboldt
Mountain
monitor
located
just
4
miles
east
of
this
sector
also
reflect
greater
transport
influence
plus
the
lack
of
local
emissions
scavenging
ozone.
The
ozone
concentrations
at
Hillside
at
5,000
feet
and
80
miles
from
Phoenix
suggest
that
concentrations
on
higher
terrain
along
this
trajectory
and
closer
to
Phoenix
experience
higher
ozone
concentrations.
The
high
ozone
history
at
Humboldt
Mountain
also
lends
credence
to
this
idea.

Thus,
it
is
concluded
that
emissions
transported
into
this
sector
cause
concentrations
greater
than
85
ppb
in
the
Bradshaw
and
New
River
Mountains,
to
the
north
and
northnorthwest
of
the
urbanized
area,
and
the
lower
lying
areas
represented
by
the
Cave
Creek
monitor.
The
larger
80­
ppb
boundary
is
drawn
to
include
the
Lake
Pleasant
and
Hillside
monitors
locations.
The
western
boundary
line
simply
connects
the
northwest
corner
Page
14
anchored
by
the
Hillside
values
with
the
Palo
Verde
monitor
which
is
located
south
of
sector
4,
with
measured
ozone
concentrations
about
80
ppb.

The
80­
and
85­
ppb
boundaries
for
the
Receptor
Study
Area
described
above
were
extended
into
the
urbanized
area
to
complete
the
Receptor
Area
mapping.
The
80­
and
85­
ppb
boundaries
in
the
urbanized
area
were
drawn
strictly
to
fit
the
actual
measurements
in
this
area.
The
completed
maps
with
the
combined
rural
and
urban
areas
are
shown
in
Figure
8.

Figure
8.
Map
of
80
and
85
ppb
Receptor
Area
Boundaries
Sources:
ADEQ,
USGS,
ALRIS,
Neuroth