U.
S.
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
DC
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
MEMORANDUM
PC
Code
No.
120051
DP
Barcode
D285445
April
22,
2003
SUBJECT:
IR­
4
Tolerance
Petition
for
Dimethenamide­
P1
(
Outlook
and
Frontier
®
6.0)
Use
on:
Onion
(
Dry
Bulb),
Garlic,
Shallots
(
Dry
Bulb),
Tuberous
and
Corm
Vegetables,
Sugar
Beet,
Garden
Beet
and
Horseradish.

TO:
Robert
Forrest,
Product
Manager
05
Shaja
Brothers,
PM
Team
Reviewer
Registration
Division
FROM:
Lucy
Shanaman,
Chemist;
ERB
III,
EFED
(
7507C)
James
Wolf,
Soil
Scientist;
ERB
III,
EFED
(
7507C);
scenario
development
PEER
REVIEW:
Kevin
J.
Costello,
Geologist,
RAPL;
ERB
III,
EFED
(
7507C)

THROUGH:
Ben
Smith,
Chief;
ERB
III,
EFED
(
7507C)

1
The
Data
Package
Record
("
Bean
Sheet")
spells
the
product
name
as
it
appears
throughout
this
document.
However,
the
actual
petition
document
submitted
by
the
IR­
4,
the
EFED
Section
3
document
produced
for
the
initial
registration
of
the
resolved
isomer,
and
the
British
Compendium
of
Pesticide
Common
Names
web
site
all
lists
the
spelling
of
the
common
chemical
name
associated
with
the
stated
Chemical
Abstract
Registration
Number,
as
"
Dimethenamid­
P"
(
http://
www.
hclrss.
demon.
co.
uk/
index.
html).
REFS
lists
both
as
correct
spellings
for
the
common
name.
2
The
Environmental
Fate
and
Effects
Division
(
EFED)
has
reviewed
the
IR­
4
tolerance
petition
(
DP
Barcode
D285445)
for
use
of
the
herbicide,
Dimethenamide­
P1
(
Outlook
and
Frontier
®
6.0),
on
onion
(
dry
bulb),
garlic,
shallots
(
dry
bulb),
tuberous
and
corm
vegetables,
sugar
beet,
garden
beet
and
horseradish.
Dimethenamide­
P
(
PC120051)
is
the
94%
resolved
s­
isomer
of
the
racemic
r/
smixture
registered
under
product
code
129051.
The
maximum
proposed
seasonal
application
rate
is
1.5
lb
a.
i./
acre
(
maximum
of
1.5
lb
a.
i./
acre
for
individual
applications),
which
can
be
divided
into
2
applications
per
year,
made
at
14­
day
intervals.
Drinking
water
concentrations
have
been
predicted
using
a
standard
Georgia
onion
scenario
as
a
surrogate
for
use
on
all
proposed
crops
at
the
maximum
early
postemergence
application
rate
for
onions,
and
using
acceptable
environmental
fate
and
transport
data
submitted
to
the
Agency.
Tier
II
surface
water
concentrations
are
predicted
by
the
PRZM/
EXAMS
model
at
49
µ
g/
L
for
acute
exposure,
7.9
µ
g/
L
for
non­
cancer
chronic
exposure,
and
5.1
µ
g/
L
for
overall
chronic
exposure.
Ground
water
concentrations
of
0.42
µ
g/
L
were
predicted
by
the
Tier
I
model,
SCIGROW.
(
Table
2)
This
assessment
is
for
parent
compound
only.
After
HED
has
held
a
MARC
meeting,
EFED
can
revise
this
drinking
water
assessment
to
include
any
degradates
of
concern.

Environmental
Fate
Assessment
Dimethenamide­
P
[(
2­
chloro­
N­(
1­
methyl­
2­
methoxy)
ethyl)­
N­(
2,4­
dimethyl­
thien­
3­
yl)
acetamide;
see
structure
below]
is
mobile
(
Kd
=
1.4
to
3.0)
and
moderately
persistent
in
the
environment.
Dimethenamide­
P
is
moderately
susceptible
to
aerobic
biodegradation
(
mean
half­
life
=
37
days
at
the
90%
confidence
interval),
and
stable
to
hydrolysis.
Photodegradation
in
aqueous
media
is
expected
to
be
a
minor
route
of
dissipation.
Dimethenamide­
P
is
likely
to
leach
to
ground
water,
and
has
the
potential
to
contaminate
drinking
water.

Dimethenamide­
P
(
CASRN
163515­
14­
8)

Drinking
Water
Assessment
Models
Used
3
The
Tier
II
estimated
concentrations
for
drinking
water
derived
from
surface
water
sources
were
modeled
using:
(
1)
PRZM
version
3.12
(
documented;
Carsel
et
al.,
1997),
model
dated
May
7,
1998
to
simulate
the
transport
of
the
pesticide
off
the
field,
and
(
2)
EXAMS
2.97.5
(
documented;
Burns,
1997),
model
dated
June
13,
1997,
to
simulate
the
fate
of
the
chemicals
in
the
water
body.
Both
models
were
launched
from
a
shell
(
pe3)
recently
developed
within
EFED,
and
adopted
for
use
on
February
27,
2002.
Reported
values
were
adjusted
for
percent
cropped
area,
as
per
EFED
policy.

SCIGROW
(
version
2.2,
November
1,
2001)
provided
the
Tier
1,
groundwater
screening
exposure
value
to
be
used
in
determining
the
potential
risk
to
human
health
from
drinking
water
contaminated
with
the
pesticide.
In
most
cases,
a
large
majority
of
the
use
area
will
have
groundwater
that
is
less
vulnerable
to
contamination
than
the
areas
used
to
drive
the
SCIGROW
estimate.

Surface
Water
Scenarios
Two
standard
scenarios
were
chosen
to
model
estimated
environmental
concentrations
in
surface
water
resulting
from
the
proposed
new
uses
of
dimethenamide­
P,
based
on
particularly
vulnerable
crop
sites
and
the
higher
application
rates
proposed
for
use
on
onion
crops.
California
and
Georgia
onion
index
reservoir
scenarios
were
chosen
as
surrogates
for
estimating
environmental
concentrations
in
sites
more
vulnerable
to
the
offsite
movement
of
pesticide
than
most
sites
planted
with
the
respective
new
crops
proposed
for
this
registration.
Background
Information
for
the
PRZM/
EXAMS
Index
Reservoir
Standard
Scenarios
appear
in
Appendix
B.

Modeling
Inputs
and
Results
Table
1
summarizes
the
general
input
values
used
in
the
model
runs
for
PRZM/
EXAMS
and
SCIGROW,
respectively
for
dimethenamide­
P,
applied
annually
by
aerial
spray
to
onions
at
a
rate
of
1.5
pounds
per
acre.
Surface
water
and
ground
water
modeling
results
appear
in
Table
2.
PRZM/
EXAMS
and
SCIGROW
output
files
have
been
appended
to
this
document.
(
Appendix
A)

The
PRZM/
EXAMS
input
parameters
for
metabolism
half­
lives
were
selected
in
accordance
with
US
EPA
OPP
EFED
water
model
parameter
selection
guidelines,
Guidance
for
Selecting
Input
Parameters
in
Modeling
the
Environmental
Fate
and
Transport
of
Pesticides,
Version
II,
February
28,
20022.
Dimethenamide­
P
is
the
94%
resolved
s­
isomer
of
the
racemic
r/
s­
mixture
(
registered
under
product
code
129051).
In
most
cases
(
Table
1),
data
for
both
the
racemic
mixture
and
the
resolved
isomer
were
used
to
generate
input
values.
Submitted
aerobic
soil
metabolism
half­
lives
were
not
significantly
different,
and
therefore
not
distinguishable,
between
the
resolved
and
the
mixed
isomers.
Both
data
sets
were
used
to
generate
a
more
statistically
powerful
aerobic
soil
input
parameter
value.

2
http://
www.
epa.
gov/
oppefed1/
models/
water/
index.
htm
4
While
no
anaerobic
metabolic
data
were
available
for
s­
dimethenamid,
anaerobic
data
for
the
r/
s­
racemic
mixture
suggests
the
need
for
a
more
conservative
input
value
than
that
produced
by
applying
the
standard
EFED
estimating
approach
for
generating
anaerobic
metabolism
half­
lives
by
multiplication
of
the
aerobic
soil
metabolism
data
for
the
resolved
s­
isomer.
The
soil
to
water
partitioning
coefficient
values,
Kd
and
Koc,
selected
as
input
parameter
values
under
EFED
guidance
policy
would
remain
unchanged
regardless
of
using
either
combined
s­
and
r/
s­
data,
or
data
only
for
the
resolved
s­
isomer.
Application
methods
and
rates
for
the
modeled
onion
crops
were
obtained
from
submitted
labels.

Table
1:
Drinking
Water
Model
Input
Parameters
for
Dimethenamide­
P
Input
Value
Study
Type
s­
Dimethenamid
MRID
#
r/
s­
Dimethenamid
MRID
#
SCIGROW
PRZM
/
EXAMS
Hydrolysis
stable
44332258
stable
41596531
­­­
stable
Aqueous
Photolysis
25.7
days
44332259
16.4
days
42266207
­­­
26
days
(
dark
corrected)

31
days
44332261
30
days
44332261
Aerobic
Soil
Metabolism
38
days
41596532
31
days
(
average)
37
days
(
mean
t1/
2
+
(
t90
x
s)/
n1/
2)

Anaerobic
Soil
Metabolism
54
days
41706801
162
days
(
one
value,
54
x
3)

Anaerobic
Aquatic
Metabolism
36
days
42367201
108
days
(
one
value,
36
x
3)

Kd
=
3.5,
0.7,
2.0
Koc
=
121,
233,
118
42034806
Mobility
(
lowest
non­
sand
value)
Kd
=
2.1,
2.5,
3.0,
1.4,
2.0
Koc
=
212,
105,
247,
396,
129
44332263
Koc
=
390,
188,
417
41596533
105
mL/
g
(
lowest
nonsand
Koc)
1.4
(
lowest
non­
sand
Kd)

Maximum
Application
Rate
for
use
on:
onion,
garlic,
shallot
1.5
lb.
a.
i./
acre
Application
Efficiency
Fraction
ariel
application
­­­
0.95
5
Spray
Drift
Fraction
ariel
application
­­­
0.16
CA
onions
Dec.
15th
Application
Date
for
early
postemergence
application
­­­

GA
onions
Sep.
20th
Incorporation
Depth
wetted
in
­­­
CAM
=
1
Aqueous
Solubility
(
25
°
C)
41596507
­­­
1174
mg/
L
As
previously
noted,
PRZM/
EXAMS
drinking
water
concentrations
have
been
predicted
for
dimethenamide­
P,
a
94%
resolved
s­
isomer,
used
at
the
maximum
proposed
early
postemergence
application
rate
of
1.5
lb
a.
i./
acre
for
dry
bulb
onions
grown
in
Georgia
and
California.
Predicted
concentrations
in
drinking
water
derived
from
surface
water
sources
resulting
from
the
use
of
dimethenamide­
P
on
California
onion
crops
were
predicted
to
be
40
µ
g/
L
for
acute
exposure,
10
 
g/
L
for
non­
cancer
chronic
exposure,
and
5.0
 
g/
L
for
overall
chronic
exposure.
Predicted
concentrations
in
drinking
water
derived
from
surface
water
sources
resulting
from
the
use
of
dimethenamide­
P
on
Georgia
onion
crops
were
predicted
to
be
49
µ
g/
L
for
acute
exposure,
7.9
 
g/
L
for
non­
cancer
chronic
exposure,
and
5.1
 
g/
L
for
overall
chronic
exposure.
Reported
values
have
been
adjusted
for
percent
crop
area
by
multiplying
by
the
default
factor
of
0.87,
as
dictated
by
EFED
policy.
(
Appendix
A)
Ground
water
concentrations
of
0.42
µ
g/
L
were
predicted
by
the
Tier
I
model,
SCIGROW.
(
Table
2)
This
assessment
is
for
parent
compound
only.
After
HED
has
held
a
MARC
meeting,
EFED
can
revise
this
drinking
water
assessment
to
include
any
degradates
of
concern.

Table
2.
Estimated
Drinking
Water
Concentrations
for
Dimethenamide­
P
Acute
Exposure
(
one
in
10
year
peak
value)
Non­
Cancer
Chronic
Exposure
(
one
in
10
year
annual
mean
value)
36
Year
Average
(
surface
water
is
overall
mean
annual
value
for
36
years)

Groundwater1
­­­
­­­
0.421502
µ
g/
L
Georgia
California
Georgia
California
Georgia
California
Surface
Water2
49
µ
g/
L
*
40
µ
g/
L
*
7.9
µ
g/
L
*
10
µ
g/
L
*
5.1
µ
g/
L
*
5.0
µ
g/
L
*

1
Appendix
A
contains
output
for
SCIGROW
model
used
to
estimate
groundwater
concentration
2
Appendix
A
contains
output
for
PRZM/
EXAMS
model
using
a
standard
Georgia
onion
and
a
California
onion
scenario
for
an
index
reservoir
scenario
used
to
estimate
upper
tenth
percentile
surface
(
drinking)
water
concentration.

*
Reported
values
adjusted
for
percent
crop
area
by
multiplying
by
a
factor
of
0.86,
as
dictated
by
EFED
policy.
6
Files
used
in
generating
and
capturing
the
modeling
values
above
can
be
located
at:
F:\
User\
LShanama\
110051dimethenamide\
ScigrowOnions.
txt
F:\
User\
LShanama\
110051dimethenamide\
w03822.
dvf
F:\
User\
LShanama\
110051dimethenamide\
w23155.
dvf
F:\
User\
LShanama\
110051dimethenamide\
CAonions.
pzr
F:\
User\
LShanama\
110051dimethenamide\
GAonions.
pzr
F:\
User\
LShanama\
110051dimethenamide\
dmaCAon.
out
F:\
User\
LShanama\
110051dimethenamide\
dmaGAon.
out
F:\
User\
LShanama\
110051dimethenamide\
reportdmaCAon.
xms
F:\
User\
LShanama\
110051dimethenamide\
reportdmaGAon.
xms
7
APPENDIX
A
PRZM/
EXAMS
(
Surface
Drinking
Water
Concentrations
using
Index
Reservoir
Scenario)

California
Onions
stored
as
dimethenamide­
P.
out
Chemical:
dimethenamide­
P
PRZM
environment:
CAonionC.
txt
modified
Monday,
23
December
2002
at
06:
48:
48
EXAMS
environment:
ir298.
exv
modified
Thuday,
29
August
2002
at
15:
34:
12
Metfile:
w23155.
dvf
modified
Wedday,
3
July
2002
at
09:
04:
20
Water
segment
concentrations
(
ppb)

Year
Peak
96hr
21Day
60Day
90Day
Yearly
1961
9.794
9.761
7.805
2.732
1.821
0.4491
1962
12.73
12.69
10.72
9.915
9.669
6.79
1963
15.29
15.25
15.03
14.58
14.12
9.783
1964
40.63
40.53
40.03
38.77
37.66
23.83
1965
40.07
33.75
22.6
21.84
21.79
14.89
1966
40
39.91
39.43
38.62
37.75
24.32
1967
21.97
21.91
21.59
20.91
20.96
14.68
1968
27.01
26.95
26.62
25.75
24.98
16.23
1969
16.66
16.63
16.46
16.06
15.67
10.35
1970
14.42
14.38
13.68
13.55
13.38
9.096
1971
19.87
19.82
18.75
18.11
17.55
11.78
1972
24.61
24.56
24.22
23.4
22.69
15.07
1973
19.2
19.16
18.94
18.35
17.87
11.89
1974
15.62
15.58
15.37
14.81
14.66
10
1975
35.45
35.37
34.94
33.86
32.86
20.79
1976
38.08
38
37.54
36.33
35.22
22.36
1977
31.63
31.55
28.32
27.3
26.54
18.15
1978
31.41
31.35
30.99
30.26
29.56
19.11
1979
19.87
19.83
19.68
19.18
18.71
12.35
1980
17.47
17.44
17.26
16.81
16.36
10.86
1981
26.57
26.52
26.23
25.41
24.6
15.77
1982
16.58
16.55
16.37
15.94
15.55
10.28
1983
26.48
26.41
16.85
16.28
15.81
10.86
1984
32.2
32.13
31.73
30.69
29.8
19.79
1985
24.87
24.82
24.57
23.91
23.64
15.7
1986
20.84
20.79
16.23
15.8
15.42
10.41
1987
38.14
38.05
37.6
36.55
35.58
22.78
1988
24.53
24.48
24.14
23.33
22.58
15.06
1989
25.41
25.36
25.06
24.32
23.64
15.37
1990
16.18
16.15
15.97
15.55
15.39
10.35
Sorted
results
8
Prob.
Peak
96hr
21Day
60Day
90Day
Yearly
0.032258064516129
40.63
40.53
40.03
38.77
37.75
24.32
0.0645161290322581
40.07
39.91
39.43
38.62
37.66
23.83
0.0967741935483871
40
38.05
37.6
36.55
35.58
22.78
0.129032258064516
38.14
38
37.54
36.33
35.22
22.36
0.161290322580645
38.08
35.37
34.94
33.86
32.86
20.79
0.193548387096774
35.45
33.75
31.73
30.69
29.8
19.79
0.225806451612903
32.2
32.13
30.99
30.26
29.56
19.11
0.258064516129032
31.63
31.55
28.32
27.3
26.54
18.15
0.290322580645161
31.41
31.35
26.62
25.75
24.98
16.23
0.32258064516129
27.01
26.95
26.23
25.41
24.6
15.77
0.354838709677419
26.57
26.52
25.06
24.32
23.64
15.7
0.387096774193548
26.48
26.41
24.57
23.91
23.64
15.37
0.419354838709677
25.41
25.36
24.22
23.4
22.69
15.07
0.451612903225806
24.87
24.82
24.14
23.33
22.58
15.06
0.483870967741936
24.61
24.56
22.6
21.84
21.79
14.89
0.516129032258065
24.53
24.48
21.59
20.91
20.96
14.68
0.548387096774194
21.97
21.91
19.68
19.18
18.71
12.35
0.580645161290323
20.84
20.79
18.94
18.35
17.87
11.89
0.612903225806452
19.87
19.83
18.75
18.11
17.55
11.78
0.645161290322581
19.87
19.82
17.26
16.81
16.36
10.86
0.67741935483871
19.2
19.16
16.85
16.28
15.81
10.86
0.709677419354839
17.47
17.44
16.46
16.06
15.67
10.41
0.741935483870968
16.66
16.63
16.37
15.94
15.55
10.35
0.774193548387097
16.58
16.55
16.23
15.8
15.42
10.35
0.806451612903226
16.18
16.15
15.97
15.55
15.39
10.28
0.838709677419355
15.62
15.58
15.37
14.81
14.66
10
0.870967741935484
15.29
15.25
15.03
14.58
14.12
9.783
0.903225806451613
14.42
14.38
13.68
13.55
13.38
9.096
0.935483870967742
12.73
12.69
10.72
9.915
9.669
6.79
0.967741935483871
9.794
9.761
7.805
2.732
1.821
0.4491
0.1
39.814*
38.045
37.594
36.528
35.544*
22.738*
Average
of
yearly
averages:
14.3049366666667*

Inputs
generated
by
pe3.
pl
1.2
­
15­
October­
2002
*
Indicates
upper
tenth
percentile
drinking
water
assessment
endpoints
BEFORE
correction
for
percent
cropped
area,
as
pre
EFED
policy.
9
PRZM/
EXAMS
(
Surface
Drinking
Water
Concentrations
using
Index
Reservoir
Scenario)

Georgia
Onions
stored
as
dmaGAon.
out
Chemical:
dimethenamide­
P
PRZM
environment:
GAOnionsC.
txt
modified
Thuday,
30
January
2003
at
08:
26:
54
EXAMS
environment:
ir298.
exv
modified
Thuday,
29
August
2002
at
15:
34:
12
Metfile:
w03822.
dvf
modified
Wedday,
3
July
2002
at
09:
04:
32
Water
segment
concentrations
(
ppb)

Year
Peak
96
hr
21
Day
60
Day
90
Day
Yearly
1961
18.63
18.16
15.97
14.12
12.22
3.235
1962
29.09
28.28
24.49
19
15.99
5.22
1963
53.98
52.52
46.95
36.43
30.25
9.03
1964
32.51
31.73
27.78
21.25
17.87
7.105
1965
26.56
25.88
23.23
18.05
15.09
5.384
1966
12.51
12.2
10.62
9.067
8.066
3.253
1967
18.12
17.62
15.52
11.92
10.07
3.358
1968
28.28
27.56
24.38
18.52
15.5
4.831
1969
28.02
27.31
23.73
19.4
16.53
5.65
1970
40.4
39.28
34.08
25.75
21.3
7.05
1971
21.12
20.58
18.52
14.32
12.27
4.89
1972
16.65
16.23
14.18
12.03
10.63
3.811
1973
18.6
18.09
16.11
12.98
11.18
3.877
1974
16.5
16.09
14.08
11.2
9.855
3.507
1975
50.52
49.12
42.92
33.17
27.49
8.026
1976
13.87
13.49
11.95
9.855
8.306
4.128
1977
12.14
11.82
10.38
9.014
7.725
2.651
1978
9.765
9.493
8.552
7.299
6.349
2.284
1979
34.39
33.48
29.17
22.4
18.64
5.42
1980
17.7
17.24
15.36
12.36
10.61
4.179
1981
29.74
28.93
25.3
19.09
15.93
5.032
1982
26.9
26.15
22.5
16.84
13.89
4.855
1983
24.98
24.35
22.18
18.07
15.13
4.915
1984
57.53
56.04
49.62
37.77
31.25
9.17
1985
13.32
13.04
11.58
8.984
7.509
4.135
1986
24.41
23.8
20.9
15.85
13.43
4.061
1987
18.37
17.91
15.72
12.11
10.67
4.017
1988
15.81
15.41
13.82
11.56
9.904
3.54
1989
154
150
131
98.27
81.01
21.89
1990
111
110
96.16
72.85
60.41
20.8
10
Sorted
results
Prob.
Peak
96
hr
21
Day
60
Day
90
Day
Yearly
0.032258064516129
154
150
131
98.27
81.01
21.89
0.0645161290322581
111
110
96.16
72.85
60.41
20.8
0.0967741935483871
57.53
56.04
49.62
37.77
31.25
9.17
0.129032258064516
53.98
52.52
46.95
36.43
30.25
9.03
0.161290322580645
50.52
49.12
42.92
33.17
27.49
8.026
0.193548387096774
40.4
39.28
34.08
25.75
21.3
7.105
0.225806451612903
34.39
33.48
29.17
22.4
18.64
7.05
0.258064516129032
32.51
31.73
27.78
21.25
17.87
5.65
0.290322580645161
29.74
28.93
25.3
19.4
16.53
5.42
0.32258064516129
29.09
28.28
24.49
19.09
15.99
5.384
0.354838709677419
28.28
27.56
24.38
19
15.93
5.22
0.387096774193548
28.02
27.31
23.73
18.52
15.5
5.032
0.419354838709677
26.9
26.15
23.23
18.07
15.13
4.915
0.451612903225806
26.56
25.88
22.5
18.05
15.09
4.89
0.483870967741936
24.98
24.35
22.18
16.84
13.89
4.855
0.516129032258065
24.41
23.8
20.9
15.85
13.43
4.831
0.548387096774194
21.12
20.58
18.52
14.32
12.27
4.179
0.580645161290323
18.63
18.16
16.11
14.12
12.22
4.135
0.612903225806452
18.6
18.09
15.97
12.98
11.18
4.128
0.645161290322581
18.37
17.91
15.72
12.36
10.67
4.061
0.67741935483871
18.12
17.62
15.52
12.11
10.63
4.017
0.709677419354839
17.7
17.24
15.36
12.03
10.61
3.877
0.741935483870968
16.65
16.23
14.18
11.92
10.07
3.811
0.774193548387097
16.5
16.09
14.08
11.56
9.904
3.54
0.806451612903226
15.81
15.41
13.82
11.2
9.855
3.507
0.838709677419355
13.87
13.49
11.95
9.855
8.306
3.358
0.870967741935484
13.32
13.04
11.58
9.067
8.066
3.253
0.903225806451613
12.51
12.2
10.62
9.014
7.725
3.235
0.935483870967742
12.14
11.82
10.38
8.984
7.509
2.651
0.967741935483871
9.765
9.493
8.552
7.299
6.349
2.284
0.1
57.175*
55.688
49.353
37.636
31.15
9.156*
Average
of
yearly
averages:
5.9768*

Inputs
generaged
by
pe3.
pl
1.2
­
15­
October­
2002
*
Indicates
upper
tenth
percentile
drinking
water
assessment
endpoints
BEFORE
correction
for
percent
cropped
area,
as
pre
EFED
policy.
11
SCIGROW
(
Groundwater
Concentrations)

SCIGROW
VERSION
2.2:
NOVEMBER
1,
2001
RUN
No.
1
FOR
dimethenamide­
P
**
INPUT
VALUES
**
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
APP
RATE
APPS/
TOTAL/
SOIL
AEROBIC
SOIL
METAB
(
LBS/
AC)
YEAR
SEASON
KOC
HALFLIFE
(
DAYS)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
1.500
1
1.500
105.0
31.00
GROUND­
WATER
SCREENING
CONCENTRATION
(
IN
UG/
L
­
PPB)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
.421502
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
12
APPENDIX
B
PRZM/
EXAMS
Index
Reservoir
Standard
Scenario
Background
Information
The
major
onion
growing
states
are
AZ,
CA,
GA,
and
TX.
California
is
first
in
production
all
types
of
onions
(
spring,
summer­
non­
storage,
summer­
storage)
(
NASS,
USDA
Vegetables
2001
Summary).
Fresh
market
bulb
onions
are
produced
throughout
California.
The
main
production
areas
are
low
desert
(
Imperial
and
Riverside
Counties),
the
San
Joaquin
Valley
(
Kern,
Fresno,
and
San
Joaquin
Counties),
the
southern
and
central
coast
(
San
Benito,
Ventura,
Santa
Clara,
and
Monterey
Counties),
the
high
desert
(
eastern
Los
Angeles
County),
and
the
northern
mountain
valleys
(
Shasta,
Lassen,
Siskiyou
and
Modoc
Counties).
(
R.
E.
Voss
and
K.
S.
Mayberry.
Fresh
Market
Bulb
Onion
Production
in
California.
Univ.
of
California,
Vegetable
Research
and
Information
Center,
Publication
No.
7242).

Bulb
onions
are
planted
from
September
through
May.
Harvest
begins
in
April
and
May
and
is
completed
in
September.
RUSLE
has
planting
on
1/
1
and
harvest
6/
15.
(
PIC
has
plant
=
12/
1,
emergence
12/
11,
maturity
5/
7,
and
harvest
6/
1).
PIC
values
were
adjusted
based
upon
RUSLE
plant
and
harvest
dates.
Onions
are
most
commonly
grown
in
multiple
rows
on
raised
beds
102
­
107
cm
wide
(
other
bed
widths
are
narrower
91
cm
or
wider
152­
203
cm).
Distribution
of
rows
depends
upon
irrigation
method
and
planter.
With
sprinkler
or
drip
irrigation
rows
are
spaced
equidistance
across
a
bend
at
about
10­
cm
intervals.
(
Voss
and
Mayberry).

RUSLE
file
is
C21ONONC.
txt.
This
is
a
Sacramento,
CA
onion,

The
amount
and
frequency
of
irrigation
depend
upon
method,
soil
type
and
conditions,
and
temperature.
For
optimal
plant
growth,
irrigate
when
25
percent
of
the
available
moisture
in
the
top
61
cm
of
soil
is
depleted.
An
onion
crop
typically
uses
61
to
76
cm
(
mid­
value
68.5cm)
of
water.
Parameters
for
irrigation
(
growing
season
only)
were
set
at
3,
0.10,
0.12,
and
0.2
(
card
no.
27).
The
time
series
PRZM
output
variable
INFL
for
layer
1
is
the
daily
infiltration
(
precipitation
and
irrigation
for
Jan
through
June)
into
the
soil
surface
ranged
from
48.4
to
79.9
cm
with
an
average
of
70.2
cm
(
comparable
to
68.5
cm).

Onions
will
grow
on
a
wide
range
of
soil
types:
sand,
loam,
clay,
and
organic/
peat.
Series
in
the
scenario
is
the
Ciervo
clay
(
Fine,
smectitic,
thermic
Vertic
Haplocambids).
The
soil
(
http://
ortho.
ftw.
nrcs.
usda.
gov/
osd/
dat/
C/
CIERVO.
html)
is
used
mainly
for
irrigated
cropland
(
cotton,
alfalfa,
sugar
beets,
wheat,
onions,
and
tomatoes.
The
soils
are
of
a
large
extent
in
MLRA
17.
The
weather
station
is
located
at
Bakersfield,
California,
meteorological
file
W23155.
txt
(
1961
through
1990).
13
PRZM/
EXAMS
CALIFORNIA
ONION
Scenario
Background
Information
The
field
used
to
represent
onion
production
in
California
is
located
in
Kern
County
in
the
San
Joaquin
Valley,
although
onion
production
areas
are
quite
extensive
(
San
Joaquin,
Coastal­
Intermediate
Region,
Imperial
Valley,
southern
and
central
coastal
regions,
the
high
desert
areas
of
Los
Angeles
County
and
the
northern
mountain
valleys).
According
to
the
1997
Census
of
Agriculture,
California
is
the
major
producer
of
onions
for
the
market.
Bulb
onions
are
planted
from
September
through
May
and
harvesting
begins
in
April
or
May
and
completed
by
September.
Onions
are
cools
season,
biennial
plants
that
are
commercially
grown
as
an
annual.
Most
onions
are
direct
seeded,
but
transplants
are
used
in
some
fall
planted
fields
for
an
earlier
harvest
of
short­
day
and
intermediate­
day
varieties
and
to
achieve
uniform
,
jumbo­
sized
bulbs.
Seeds
are
planted
uniformly
at
2
to
3
inches
between
plants
in
a
row.
Onions
are
most
commonly
grown
in
multiple
rows
on
raised
beds
40
to
42
inches
wide,
but
some
production
areas
use
36­
inch
wide
beds
or
beds
of
60
to
80
inches.
Distribution
of
rows
across
beds
varies
depending
on
irrigation
method
and
planter.
With
drip
and
sprinkler
irrigation
(
most
common
types),
rows
are
spaced
equidistant
across
the
bed
at
approximately
4­
inch
intervals.
When
furrow
irrigation
is
used,
the
center
of
the
bed
is
left
vacant
for
salt
accumulation
with
2
or
3
rows
planted
on
either
side.
Plant
canopy
can
approach
100
percent
in
some
narrow
row
fields
grown
under
drip
irrigation.
Irrigation
is
required
to
avoid
seed
or
plant
dry
out.
Generally
24
to
36
inches
of
irrigated
water
per
year
is
sufficient.
Onions
can
grow
on
a
wide
range
of
soils.
The
soil
selected
to
represent
the
field
is
Ciervo
clay.
Ciervo
clay,
is
a
fine,
semetic,
thermic
Vertic
Haplocambids.
These
soils
are
often
used
for
onion
and
other
truck
crop
production
under
irrigation.
Ciervo
clay
is
a
very
deep,
moderately
well
drained,
medium
to
high
runoff
soil
on
fan
skirts
that
formed
in
alluvium
mainly
from
sedimentary
rocks
at
elevation
of
170
to
735
feet
above
mean
sea
level.
The
Ciervo
clay
has
very
slow
permeability.
Slopes
range
from
0
to
2
percent.
The
soil
is
of
large
extent
in
MLRA
17.
Ciervo
clay
is
a
Hydrologic
Group
D
soil.

Table
1.
PRZM
3.12
Climate
and
Time
Parameters
for
Kern
County,
California
­
Onions
Parameter
Value
Source
Starting
Date
January
1,
1961
Meteorological
File
­
Southern:
Bakersfield,
CA
(
W23155)

Ending
Date
December
31,
1990
Meteorological
File
­
Southern:
Bakersfield,
CA
(
W23155)

Pan
Evaporation
Factor
(
PFAC)
0.7
PRZM
Manual
Figure
5.1
(
EPA,
1998)

Snowmelt
Factor
(
SFAC)
0.55
cm
C­
1
PRZM
Manual
Table
5.1
(
EPA,
1998)

Minimum
Depth
of
Evaporation
(
ANETD)
17.0
cm
PRZM
Manual
Figure
5.2
(
EPA,
1998)
14
Table
2.
PRZM
3.12
Erosion
and
Landscape
Parameters
for
Kern
County,
California
­
Onions
Parameter
Value
Source
Method
to
Calculate
Erosion
(
ERFLAG)
4
(
MUSS)
PRZM
Manual
(
EPA,
1998)

USLE
K
Factor
(
USLEK)
0.21
tons
EI­
1*
PRZM
Input
Collator
(
Burns,
1992)
and
FARM
Manual
(
EPA,
1985)

USLE
LS
Factor
(
USLELS)
0.303
Haan
and
Barfield,
1979
USLE
P
Factor
(
USLEP)
0.5
PRZM
Manual
(
EPA,
1998)

Field
Area
(
AFIELD)
172
ha
Area
of
Shipman
Reservoir
watershed
(
EPA,
1999)

NRCS
Hyetograph
(
IREG)
1
PRZM
Manual
Figure
5.12
(
EPA,
1998)

Slope
(
SLP)
1%
Mid­
point
of
the
Soil
Series,
Ciervo
Hydraulic
Length
(
HL)
600
m
Shipman
Reservoir
(
EPA,
1999)

Irrigation
Flag
(
IRFLAG)
2
(
cropping
period
only)
Voss,
R.
E.
Fresh
Market
Bulb
Onion
Production
in
California.
U.
fo
CA
Publication
7242.
1999.

Irrigation
Type
(
IRTYP)
3
(
Over
Canopy)
Voss,
R.
E.
Fresh
Market
Bulb
Onion
Production
in
California.
U.
fo
CA
Publication
7242.
1999.

Leaching
Factor
(
FLEACH)
0.1
Estimated
Fraction
of
Water
Capacity
when
Irrigation
is
Applied
(
PCDEPL)
0.12
Adjusted
so
that
infiltration
met
Voss
61
to
76
cm
of
water
use.

Maximum
Rate
at
which
Irrigation
is
Applied
(
RATEAP)
0.2
cm
hr­
1
PRZM
Manual,
Table
5.33
(
EPA,
1998)

*
EI
=
100
ft­
tons
*
in/
acre*
hr
Table
3.
PRZM
3.12
Crop
Parameters
for
Kern
County,
California
­
Onions
Parameter
Value
Source
15
Initial
Crop
(
INICRP)
1
Set
to
one
for
all
crops
(
EPA,
2001)

Initial
Surface
Condition
(
ISCOND)
1
Default
Number
of
Different
Crops
(
NDC)
1
Set
to
crops
in
simulation
­
generally
one
Number
of
Cropping
Periods
(
NCPDS)
30
Set
to
weather
data.
Meteorological
File
­
Bakersfield,
CA
(
W23155)

Maximum
rainfall
interception
storage
of
crop
(
CINTCP)
0.05
PRZM
Input
Collator
(
Burns,
1992)

Maximum
Active
Root
Depth
(
AMXDR)
30
cm
Voss,
R.
E.
Fresh
Market
Bulb
Onion
Production
in
California.
U.
fo
CA
Publication
7242.
1999.

Maximum
Canopy
Coverage
(
COVMAX)
80
Estimated
based
on
aerial
photography
Soil
Surface
Condition
After
Harvest
(
ICNAH)
1
Voss,
R.
E.
1999.
Fresh
Market
Bulb
Onion
Production
in
California.
U.
fo
CA
Publication
7242.

Date
of
Crop
Emergence
(
EMD,
EMM,
IYREM)
11/
01
PIC
Recommended
dates
adjusted
according
to
RUSLE
Project
planting
dates.

Date
of
Crop
Maturity
(
MAD,
MAM,
IYRMAT)
01/
06
PIC
Recommended
dates
adjusted
according
to
RUSLE
Project
planting
dates.

Date
of
Crop
Harvest
(
HAD,
HAM,
IYRHAR)
15/
06
PIC
Recommended
dates
adjusted
according
to
RUSLE
Project
planting
dates.

Maximum
Dry
Weight
(
WFMAX)
0.0
Set
to
"
0"
Not
used
in
simulation
SCS
Curve
Number
(
CN)
92,
85,
86
Gleams
Manual
Table
A.
3,
Meadows,
no
fallow
conditions
(
USDA,
1990)

Manning's
N
Value
(
MNGN)
0.011
RUSLE
Project;
C23ONONC;
Onions,
Fresno
CA
Conventional
Tillage
(
USDA,
2000)

USLE
C
Factor
(
USLEC)
0.521
­
0.732
RUSLE
Project;
C23ONONC;
Onions,
Fresno
CA
Conventional
Tillage
(
USDA,
2000)

Table
4.
PRZM
3.12
Ciervo
Soil
Parameters
for
Kern
County,
California
­
Onions
Parameter
Value
Verification
Source
16
Total
Soil
Depth
(
CORED)
150
cm
Number
of
Horizons
(
NHORIZ)
3
(
Base
horizons)
NRCS,
National
Soils
Characterization
Database
(
NRCS,
2001)

First,
Second
and
Third
Soil
Horizons
(
HORIZN
=
1,2,3)

Horizon
Thickness
(
THKNS)
12
cm
(
HORIZN
=
1)
50
cm
(
HORIZN
=
2)
88
cm
(
HORIZN
=
3)

Bulk
Density
(
BD)
1.40
g
 
cm­
3
(
HORIZN
=
1)
1.36
g
 
cm­
3
(
HORIZN
=
2)
1.17
g
 
cm­
3
(
HORIZN
=
3)

Initial
Water
Content
(
THETO)
0.259
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
1)
0.266
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
2)
0.345
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
3)

Compartment
Thickness
(
DPN)
0.1
cm
(
HORIZN
=
1)
1.0
cm
(
HORIZN
=
2)
2.0
cm
(
HORIZN
=
3)

Field
Capacity
(
THEFC)
0.259
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
1)
0.266
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
2)
0.345
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
3)

Wilting
Point
(
THEWP)
0.15
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
1)
0.158
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
2)
0.202
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
3)

Organic
Carbon
Content
(
OC)
0.91%
(
HORIZN
=
1)
0.43%
(
HORIZN
=
2)
0.32%
(
HORIZN
=
3)
NRCS,
National
Soils
Characterization
Database
(
NRCS,
2001)
http://
www.
statlab.
iastate.
edu/
s
oils/
ssl/)
17
EPA.
1985.
Field
Agricultural
Runoff
Monitoring
(
FARM)
Manual,
(
EPA/
600/
3­
85/
043)
Environmental
Research
Laboratory,
U.
S.
Environmental
Protection
Agency,
Athens,
GA.

EPA.
1998.
Carsel,
R.
F.,
J.
C.
Imhoff,
P.
R.
Hummel,
J.
M.
Cheplick,
and
A.
S.
Donigian,
Jr.
PRZM­
3,
A
Model
for
Predicting
Pesticide
and
Nitrogen
Fate
in
the
Crop
Root
and
Unsaturated
Soil
Zones:
Users
Manual
for
Release
3.0.
National
Exposure
Research
Laboratory,
Office
of
Research
and
Development,
U.
S.
Environmental
Protection
Agency,
Athens,
GA.

EPA.
1999.
Jones,
R.
D.,
J.
Breithaupt,
J.
Carleton,
L.
Libelo,
J.
Lin,
R.
Matzner,
and
R.
Parker.
Guidance
for
Use
of
the
Index
Reservoir
in
Drinking
Water
Exposure
Assessments.
Environmental
Fate
and
Effects
Division,
Office
of
Pesticide
Programs,
U.
S.
Environmental
Protection
Agency,
Washington.
D.
C.

EPA.
2001.
Abel,
S.
A.
Procedure
for
Conducting
Quality
Assurance
and
Quality
Control
of
Existing
and
New
PRZM
Field
and
Orchard
Crop
Standard
Scenarios.
Environmental
Fate
and
Effects
Division,
Office
of
Pesticide
Programs,
U.
S.
Environmental
Protection
Agency,
Washington,
D.
C.

Haan,
C.
T.
and
B.
J.
Barfield.
1978.
Hydrology
and
Sedimentology
of
Surface
Mined
Lands.
Office
of
Continuing
Education
and
Extension,
College
of
Engineering,
University
of
Kentucky,
Lexington,
Kentucky
40506.
pp.
286.

USDA.
1990.
Davis,
F.
M.,
R.
A.
Leonard,
W.
G.
Knisel.
GLEAMS
User
Manual,
Version
1.8.55.
USDA­
ARS
Southeast
Watershed
Research
Laboratory,
Tifton
GA.
SEWRL­
030190FMD.

USDA.
2000.
Revised
Universal
Soil
Loss
Equation
(
RUSLE)
EPA
Pesticide
Project.
U.
S.
Department
of
Agriculture,
National
Resources
Conservation
Service
(
NRCS)
and
Agricultural
Research
Service
(
ARS).

Voss,
R.
E.
and
K.
S.
Mayberry1999.
Fresh­
Market
Bulb
Onion
Production
In
California.
Vegetable
Research
and
Information
Center,
Vegetable
Production
Series,
University
of
California,
Division
of
Agriculture
and
Natural
Resources.
Publication
7242.
18
PRZM/
EXAMS
GEORGIA
ONION
Scenario
Background
Information
The
field
used
to
represent
Vidalia
or
Sweet
Onion
production
in
Georgia
is
located
in
Toombs
County
in
Southeastern
Georgia.
Vidalia
Onion
can
only
be
legally
grown
in
Southeastern
Georgia,
in
the
counties
of:
Appling,
Bacon,
Jeff
Davis,
Montgomery,
Tattnall,
Telfair,
Toombs,
Truetlen
and
Wheeler,
and
in
parts
of
Dodge,
Jenkins,
Laurens,
Long,
Pierce,
Screven,
and
Wayne
Counties
(
Federal
Market
Order
955)
.

Toombs
County,
Georgia
is
representative
of
the
Vidalia
onion
growing
region
of
Southeastern
Georgia.
Toombs
County
is
located
in
the
Southern
Coastal
Plain
(
MLRA
133A)
as
are
many
of
the
Vidalia
Onion
growing
counties.
However
some
of
these
counties
(
i.
e.,
Bacon,
Wayne)
also
extend
into
Atlantic
Coastal
Flatwoods
(
MLRA
153A).

According
to
the
1999­
2001
(
NASS,
http://
www.
usda.
gov/
nass/
pubs/
agr02/
02_
ch4.
pdf)
Georgia
is
a
major
producer
of
onions.
Vidalia
onions
are
typically
planted
from
mid­
September
(
Sept.
20)
through
mid­
October
(
Oct.
20)
and
harvesting
begins
in
mid­
June
(
June
15).
Onions
are
cool
season,
biennial
plants
that
are
commercially
grown
as
an
annual.
Most
onions
are
direct
seeded,
but
transplants
are
used
in
some
fall
planted
fields
for
an
earlier
harvest
of
short­
day
and
intermediate­
day
varieties
and
to
achieve
uniform
,
jumbo­
sized
bulbs.
Seeds
are
planted
into
6
foot
wide
raised
beds,
with
a
4­
to
6­
inch
within
row
spacing
and
10­
to
18­
inch
spacing
between
rows
(
Granberry
and
Kelly,
2000).
Distribution
of
rows
across
beds
varies
depending
on
irrigation
method
and
planter.
All
commercial
grown
onions
in
Georgia
are
irrigated
(
Harrison,
2001).
Irrigation
should
be
light
and
frequent
until
the
onion
plants
are
established.
The
onion
has
a
shallow
root
system,
with
most
of
the
roots
in
the
top
12
inches
of
soil.
Onions
continue
to
grow
new
roots
(
3
to
4
per
week)
throughout
the
entire
growing
season.
Maintaining
proper
soil
moisture
in
the
upper
3
to
4
inches
of
the
soil
is
critical
for
continuous
root
growth
and
for
supplying
the
needs
of
the
foliage
and
bulb.
Depending
upon
soil
type,
temperature,
wind
velocity
and
rainfall,
0.10
to
0.25
inches
of
irrigation
may
be
required
daily.
Boyhan
et
al.
(
1999)
and
Granberry
and
Kelley
(
2000)
provide
more
specific
information
concerning
the
irrigation
of
onions
in
Georgia).
Between
10
and
12
inches
of
irrigation
water
were
reportedly
applied
vegetable
crops
in
Georgia,
during
the
year
2000
(
Harrison,
2001).
The
irrigation
routine
was
used
in
PRZM.
An
overhead
sprinkler
system
is
used.
The
PRZM
variables
FLEACH
and
PCDEPL
were
set
to
0.05.
These
values
were
estimated
by
trail
an
error,
to
obtain
an
"
irrigation
amount"
within
the
range
stated
above.
PRZM
includes
irrigation"
as
infiltration
into
first
soil
compartment.
Irrigation
was
estimated
as
the
difference
of
water
entering
the
surface
layer
for
the
irrigated
scenario
compared
to
the
no­
irrigated
(
PRZM
variable
INFL
compartment
1).
For
the
30
years
of
data
used
in
the
simulation
(
1961­
1990),
irrigation
ranged
from
3.2
to
14.5
inches,
with
an
average
of
8.3
inches
(
CV%
=
31.4).

Onions
can
be
grown
on
a
wide
range
of
soils.
The
soil
selected
to
represent
the
field
is
Clarendon.
Clarendon
loamy
sand
is
a
fine­
loamy,
siliceous,
semiactive,
thermic
Plinthaquic
Paleudults.
These
soils
are
often
used
for
growing
tobacco,
cotton,
corn,
soybeans,
small
grain,
and
pasture
grasses.
Forested
areas
are
mostly
pine
with
scattered
hardwoods.
The
Clarendon
series
consists
of
very
deep,
moderately
well
drained,
slow
runoff,
loamy
soils
that
formed
in
marine
sediments.
The
Clarendon
19
loamy
sand
has
moderately
slow
permeability.
Slopes
range
from
0
to
6
percent.
The
soil
extends
along
the
Coastal
Plain
of
Alabama,
Florida,
Georgia,
and
South
Carolina.
The
series
is
of
large
extent
in
MLRA
133A
and
153A.
Clarendon
loamy
sand
is
a
Hydrologic
Group
C
soil.
The
Clarendon
soil
was
selected,
because
it
is
geographically
associated
with
the
competing
soil
Tifton
loamy
sand
(
Hydrologic
Group
B)
which
is
also
a
suitable
onion
soil.
Granberry
and
Kelley,
(
2000)
indicated
that
Tifton
soils
are
found
in
the
Vidalia
onion
growing
area
and
is
well
suited
for
onion
production.
The
use
and
vegetation
between
the
two
series
are
similar.

Metfile:
W03822.
dvf
(
Savannah,
GA)

Table
1.
PRZM
3.12
Climate
and
Time
Parameters
for
Southeastern
Georgia
­
Onions
Parameter
Value
Source
Starting
Date
January
1,
1961
Meteorological
File
­
Savannah,
GA
(
W03822)

Ending
Date
December
31,
1990
Meteorological
File
­
Savannah,
GA
(
W03822)

Pan
Evaporation
Factor
(
PFAC)
0.75
PRZM
Manual
Figure
5.1
(
EPA,
1998)

Snowmelt
Factor
(
SFAC)
0.15
cm
C­
1
PRZM
Manual
Table
5.1
(
EPA,
1998)

Minimum
Depth
of
Evaporation
(
ANETD)
30
cm
PRZM
Manual
Figure
5.2
(
EPA,
1998)

Table
2.
PRZM
3.12
Erosion
and
Landscape
Parameters
for
Southeastern
Georgia
­
Onions
Parameter
Value
Source
Method
to
Calculate
Erosion
(
ERFLAG)
4
(
MUSS)
PRZM
Manual
(
EPA,
1998)

USLE
K
Factor
(
USLEK)
0.
1
tons
EI­
1*
PRZM
Input
Collator
(
Burns,
1992)
and
FARM
Manual
(
EPA,
1985)

USLE
LS
Factor
(
USLELS)
0.44
Haan
and
Barfield,
1979
USLE
P
Factor
(
USLEP)
0.5
PRZM
Manual
(
EPA,
1998)

Field
Area
172
ha
Surface
area
of
Shipman
Reservoir
watershed
(
EPA,
20
(
AFIELD)
1999)

NRCS
Hyetograph
(
IREG)
4
PRZM
Manual
Figure
5.12
(
EPA,
1998)

Slope
(
SLP)
3%
Mid­
point
of
the
Soil
Series,
Clarendon
Loamy
Sand
Hydraulic
Length
(
HL)
600
m
Shipman
Reservoir
(
EPA,
1999)

*
EI
=
100
ft­
tons
*
in/
acre*
hr
Table
3.
PRZM
3.12
Crop
Parameters
for
Southeastern
Georgia
­
Onions
Parameter
Value
Source
Initial
Crop
(
INICRP)
1
Set
to
one
for
all
crops
(
EPA,
2001)

Initial
Surface
Condition
(
ISCOND)
1
Boyhan,
Granberry,
and
Kelley,
University
of
Georgia
Circular
821
(
5/
99)

Number
of
Different
Crops
(
NDC)
1
Set
to
crops
in
simulation
­
generally
one
Number
of
Cropping
Periods
(
NCPDS)
30
Set
to
weather
data.
Meteorological
File
­
Savannah,
GA
(
W03822)

Maximum
rainfall
interception
storage
of
crop
(
CINTCP)
0.1
cm
Estimated
from
PRZM3
Manual
Table
5­
4,
assuming
light
density
Maximum
Active
Root
Depth
(
AMXDR)
35
cm
Estimated
based
on
Onion
Production
Guide,
University
of
Georgia
Bulletin
1198;
July,
2001
Maximum
Canopy
Coverage
(
COVMAX)
80
Estimated
Soil
Surface
Condition
After
Harvest
(
ICNAH)
1
University
of
Georgia
Bulletin
1198,
July,
2001;
"
Harrison,
2001.
Bulletin
1198
University
of
Georgia
July
2001
Irrigating
Sweet
Onions
in
GA",
Granberry
and
Kelley,
2000
Circular
801
University
of
Georgia;
and
RUSLE
information
Date
of
Crop
Emergence
(
EMD,
EMM,
IYREM)
15/
09
RUSLE
Project
planting
dates
and
Circulars
801
and
821
and
Bulletin
1198.

Date
of
Crop
Maturity
(
MAD,
MAM,
IYRMAT)
01/
06
RUSLE
Project
planting
dates
and
Circulars
801
and
821
and
Bulletin
1198..

Date
of
Crop
Harvest
(
HAD,
HAM,
IYRHAR)
15/
06
RUSLE
Project
planting
dates
and
Circulars
801
and
821
and
Bulletin
1198..
21
Table
3.
PRZM
3.12
Crop
Parameters
for
Southeastern
Georgia
­
Onions
Parameter
Value
Source
Maximum
Dry
Weight
(
WFMAX)
0.0
Set
to
"
0"
Not
used
in
simulation
SCS
Curve
Number
(
CN)
91,
86,
87
Gleams
Manual
Table
A.
3,
Meadows,
no
fallow
conditions
(
USDA,
1990)

91"
GLEAMS
Manual
Table
A­
3;
Fallow
=
SR
­
middle
or
average
value
86"
GLEAMS
Manual
Table
A­
3;
Row
Crop
=
SR
poor,
Cropping
and
Residue
=
Row
Crop
poor"
87"
GLEAMS
Manual
Table
A­
3;
Row
Crop
=
SR/
poor,
Cropping
and
Residue
=
Row
Crop
SR/
poor"

Manning's
N
Value
(
MNGN)
0.011
RUSLE
Project;
Pb9ONONC,
Onions,
Augusta,
GA
Conventional
Tillage
(
USDA,
2000)

USLE
C
Factor
(
USLEC)
0.592
­
0.902
RUSLE
EPA
Pesticide
Project:
Pb9ONONC;
Onions,
Augusta,
GA
Conventional
Tillage"

Table
4.
PRZM
3.12
Clarendon
Loamy
Sand
Soil
Parameters
for
Southeastern
Georgia
­
Onions
Parameter
Value
Verification
Source
Total
Soil
Depth
(
CORED)
100
cm
Number
of
Horizons
(
NHORIZ)
3
(
Base
horizons)
NRCS,
National
Soils
Characterization
Database
(
NRCS,
2001)

First,
Second
and
Third
Soil
Horizons
(
HORIZN
=
1,2,3)

Horizon
Thickness
(
THKNS)
10
cm
(
HORIZN
=
1)
30
cm
(
HORIZN
=
2)
60
cm
(
HORIZN
=
3)

Bulk
Density
(
BD)
1.6
g
 
cm­
3
(
HORIZN
=
1)
1.6
g
 
cm­
3
(
HORIZN
=
2)
1.7
g
 
cm­
3
(
HORIZN
=
3)

Initial
Water
Content
0.115
cm3­
H2O
 
cm3­
soil
PIRANHA
Version
3.0
PRZM
Input
Collator
PIC
Version
2.0
22
(
THETO)
(
HORIZN
=
1)
0.115
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
2)
0.173
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
3)

Compartment
Thickness
(
DPN)
0.1
cm
(
HORIZN
=
1)
1.0
cm
(
HORIZN
=
2)
5.0
cm
(
HORIZN
=
3)

Field
Capacity
(
THEFC)
0.115
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
1)
0.115
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
2)
0.173
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
3)

Wilting
Point
(
THEWP)
0.035
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
1)
0.035
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
2)
0.093
cm3­
H2O
 
cm3­
soil
(
HORIZN
=
3)

Organic
Carbon
Content
(
OC)
1.74%
(
HORIZN
=
1)
1.74%
(
HORIZN
=
2)
0.174%
(
HORIZN
=
3)

Table
5.
PRZM
3.12
Irrigation
Parameters
for
Southeastern
Georgia
­
Onions
Parameter
Value
Source
Irrigation
Flag
(
IRFLAG)
2
Irrigate
during
cropping
period
(
Harrison
2001)
Harrison,
2001.
Irrigating
Sweet
Onions
in
Georgia.
In:
(
ed.)
G.
Boyhan
et
al.
Onion
Production
Guide
Bulletin
1198
University
of
Georgia.
Granberry
and
Kelley,
2000.
Dry
Bulb
Onions,
Circular
801
Coop.
Exten.
Service,
University
of
23
Georgia
Irrigation
Type
(
IRTYP)
3
Over
canopy
Harrison,
2001.
Irrigating
Sweet
Onions
in
Georgia.
In:
(
ED.)
G.
Boyhan
et
al.
Onion
Production
Guide.
Bulletin
1198
University
of
Georgia.
Granberry
and
Kelley,
2000.
Dry
Bulb
Onions,
Circular
801
Coop.
Exten.
Service,
University
of
Georgia
Leaching
Factor
(
FLEACH)
0.05
Estimated
Fraction
of
water
capacity
to
apply
irrigation
(
PCDEPL)
0.05
Adjusted
to
meet
irrigation
objective.
Harrison,
2001.
Irrigating
Sweet
Onions
in
Georgia.
In:
(
ED.)
G.
Boyhan
et
al.
Onion
Production
Guide.
Bulletin
1198
University
of
Georgia.
Granberry
and
Kelley,
2000.
Dry
Bulb
Onions,
Circular
801
Coop.
Exten.
Service,
University
of
Georgia
Maximum
rate
at
which
irrigation
is
applied
(
RATEAP))
5
cm
hr­
1
PRZM3
­
Manual
Table
5.33
(
EPA,
1998)

Boyhan,
G.
E.
and
D.
M.
Granberry,
and
W.
T.
Kelley.
1999.
Green
Onions.
Circular
821.
Cooperative
Extension
Service,
University
of
Georgia.

Bird,
S.,
M.
Cheplick,
R.
F.
Carsel
and
M.
Fendley.
1992.
PIRANHA
Version
3.0,
PRZM
Input
Collator,
PIC
Version
2.0,
Environmental
Research
Laboratory
U.
S.
Environmental
Protection
Agency.
Athens,
Georgia
Burns,
L.
A.
et
al.
1992.
Pesticide
and
Industrial
Chemical
Risk
ANalysis
and
Hazard
Assessment
Environmental
Research
Laboratory
U.
S.
Environmental
Protection
Agency.
Athens,
Georgia
EPA.
1985.
Field
Agricultural
Runoff
Monitoring
(
FARM)
Manual,
(
EPA/
600/
3­
85/
043)
Environmental
Research
Laboratory,
U.
S.
Environmental
Protection
Agency,
Athens,
GA.

EPA.
1998.
Carsel,
R.
F.,
J.
C.
Imhoff,
P.
R.
Hummel,
J.
M.
Cheplick,
and
A.
S.
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Jr.
PRZM­
3,
A
Model
for
Predicting
Pesticide
and
Nitrogen
Fate
in
the
Crop
Root
and
Unsaturated
Soil
Zones:
Users
Manual
for
Release
3.0.
National
Exposure
Research
Laboratory,
Office
of
Research
and
Development,
U.
S.
Environmental
Protection
Agency,
Athens,
GA.
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EPA.
1999.
Jones,
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D.,
J.
Breithaupt,
J.
Carleton,
L.
Libelo,
J.
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R.
Matzner,
and
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Parker.
Guidance
for
Use
of
the
Index
Reservoir
in
Drinking
Water
Exposure
Assessments.
Environmental
Fate
and
Effects
Division,
Office
of
Pesticide
Programs,
U.
S.
Environmental
Protection
Agency,
Washington.
D.
C.

EPA.
2001.
Abel,
S.
A.
Procedure
for
Conducting
Quality
Assurance
and
Quality
Control
of
Existing
and
New
PRZM
Field
and
Orchard
Crop
Standard
Scenarios.
Environmental
Fate
and
Effects
Division,
Office
of
Pesticide
Programs,
U.
S.
Environmental
Protection
Agency,
Washington,
D.
C.

Granberry,
D.
M.
and
W.
T.
Kelley.
2000.
Dry
Bulb
Onions.
Circular
801
(
January
2000).
Cooperative
Extention
Service.
University
of
Georgia.

Haan,
C.
T.
and
B.
J.
Barfield.
1978.
Hydrology
and
Sedimentology
of
Surface
Mined
Lands.
Office
of
Continuing
Education
and
Extension,
College
of
Engineering,
University
of
Kentucky,
Lexington,
Kentucky
40506.
pp.
286.

Harrison,
K.
2001.
Irrigation
Sweet
Onions
in
Georgia.
In
(
eds).
G.
Boyhan
et
al.
Onion
Production
Guide.
Bulletin
1198,
Cooperative
Extension
Service,
University
of
Georgia.

Harrison,
K.
A.
and
A.
W.
Tyson.
2001.
Georgia
Irrigation
Amount
by
Crop.
Irrigation
Survey
for
Georgia.
p.
421­
424.
In
K.
J.
Hatcher
(
ed.)
Proceedings
of
the
2001
Georgia
Resources
Conference.
Univ.
of
Georgia
Institute
of
Ecology,
Athens,
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(
http://
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org/
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survey/
amtbycrop.
asp)
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USDA.
1990.
Davis,
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M.,
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GLEAMS
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Version
1.8.55.
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ARS
Southeast
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Tifton
GA.
SEWRL­
030190FMD.

USDA.
2000.
Revised
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(
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