Drinking
Water
Exposure
Assessment
Associated
with
the
Use
of
Direx
4L
®
Herbicide
on
Citrus
July
12,
2002
Background
Diuron
(
3­[
3,4­
dichlorophenyl]­
1,1­
dimethylurea)
is
the
active
ingredient
in
Direx
4L
®
herbidide
(
Direx).
Griffin
L.
L.
C.,
the
registrant
for
diuron,
is
working
with
Landis
International
(
Landis)
for
product
registration
support
for
Direx.
Landis
has
asked
Waterborne
Environmental,
Inc.
(
Waterborne)
to
assist
in
characterizing
the
risk
to
drinking
water
sources
associated
with
the
use
of
Direx
4L
herbicide
on
citrus
in
Southern
Florida
Flatwoods
(
MLRA
155).

Activities
being
performed
by
Waterborne
include
the
spatial
integration
of
information
on
surface
water
sources
for
drinking
water
in
the
Southern
Florida
Flatwoods
relative
to
citrus
production
and
soil
runoff
potential.
This
information
can
be
used
to
characterize
the
relative
vulnerability
of
surface
water
supplies
to
diuron
exposure.

Citrus
Production
in
the
Southern
Florida
Flatwoods
Commercial
citrus
acreage
in
Florida
was
estimated
at
approximately
832,500
acres
in
2000
(
FL
DACS,
2002).
The
geographical
distribution
by
county
is
presented
in
Figure
1.

The
Southern
Florida
Flatwoods
(
MLRA
155)
encompasses
approximately
54,570
square
miles
in
central
Florida
(
Figure
2)
and
corresponds
roughly
to
the
geographical
boundary
of
commercial
citrus
production.
The
primary
exceptions
are
the
high
citrus
production
areas
along
the
South
Central
Florida
Ridge
(
MLRA
154)
and
the
Southern
Florida
Lowlands
(
MLRA
156B).

Counties
identified
as
having
citrus
production
in
the
Southern
Florida
Flatwoods
are
listed
in
Table
1.
The
table
includes
the
county
name,
county
FIPS
code,
total
county
area,
the
portion
of
the
county
in
MLRA
155,
and
a
comparison
of
citrus
acreage
using
three
sources
of
information.
The
sources
are
discussed
below:

 
Information
obtained
from
the
Florida
Department
of
Agriculture
and
Consumer
Services
(
FL
DACS)
reflects
county­
level
estimates
last
updated
October
2000
(
FL
DACS,
2002).
This
information
is
believed
to
be
the
most
accurate
account
of
citrus
acreage
in
the
State.

 
Land
use
imagery
was
also
obtained
from
the
Florida
Department
of
Environmental
Protection
(
FL
DEP,
2002)
as
three
separate
shape
files
representing
the
three
water
management
districts
in
the
Southern
Florida
Flatwoods.
The
Southern
Florida
Water
Management
District
(
SFWMD)
and
the
Saint
Johns
River
Water
Management
District
(
SJRWMD)
data
are
from
1995,
and
the
Southwest
Florida
Water
Management
District
land
use
data
are
from
1999.
The
scale
of
the
land
use
data
is
1:
40,000,
and
the
projection
is
Albers
Equal
Area
Conic.
Counties
having
area
within
the
Southern
Florida
Flatwoods
were
selected
and
exported
to
a
separate
data
layer.
Land
uses
identified
as
citrus
groves
(
SFWMD
and
SJRWMD)
or
tree
crops
(
SWFWMD)
were
exported
to
create
a
single
citrusonly
data
layer
(
Figure
3).
This
database
provides
a
relatively
detailed
spatial
resolution
of
citrus
production.
Acreage
estimates
compare
favorably
to
the
FL
DACS
estimates
with
the
exception
of
St.
Lucie
County.

 
The
National
Resources
Inventory
(
NRI)
was
included
in
this
analysis
to
characterize
soils
used
to
produce
citrus
including
their
relative
runoff
potential.
The
NRI
is
a
national
survey
of
land
use
updated
every
five
years.
Data
presented
herein
is
from
the
1992
survey
(
USDA,
1994a).
Results
from
the
1997
have
recently
been
made
available,
but
could
not
be
readily
processed
for
this
evaluation.
Citrus
is
not
a
unique
land
use
category
in
the
NRI,
but
is
represented
within
NRI
land
use
001
("
Fruit").
Each
NRI
point
is
identified
spatially
at
the
county,
MLRA,
and
zip
code
level
and
identified
by
soil
type.
Appendix
A
contains
the
acreage
and
soil
properties
for
NRI
survey
points
surveyed
as
fruit
production
in
MLRA
155.
This
acreage
compares
less
favorably
to
the
FL
DACS
estimates,
particularly
for
DeSoto,
Indian
River,
and
Lake
counties.

Soils
Used
for
Citrus
Production
in
the
Southern
Florida
Flatwoods
The
National
Resource
Inventory
(
NRI)
was
used
to
identify
candidate
soils
that
best
represent
citrus
production
in
the
Southern
Florida
Flatwoods
(
MLRA
155).
"
Fruit"
(
land
use
code
001)
was
used
as
a
land
use
category
to
identify
candidate
corn
soils
because
citrus
is
not
a
unique
land
use
category
in
the
NRI.
Candidate
soils
were
then
ranked
by
runoff
potential
(
Appendix
A).
Soil
properties
used
to
assess
runoff
potential
were
obtained
from
the
U.
S.
Department
of
Agriculture's
soil
property
database,
SOILS5
(
USDA,
1994b).
Hydrologic
Soil
Group
(
USDA,
1972)
was
used
as
the
primary
ranking
criteria,
in
which
"
D"
soils
were
ranked
above
"
C"
soils,
etc.
Sand
content
(
low
to
high)
was
used
as
a
secondary
ranking.
Average
organic
matter
(
high
to
low),
average
slope
(
high
to
low),
and
soil
series
name
(
ascending)
were
used
for
subsequent
ranking.
Soil
series
name
was
included
as
a
final
tiebreaker
so
that
multiple
NRI
entry
points
of
the
same
series
would
be
clustered
together.

Soils
classified
as
high
runoff
potential
(
Hydrologic
Soil
Group
D)
represent
approximately
3.5
percent
of
the
fruit
production
in
the
Southern
Florida
Flatwoods.
Hydrologic
Soil
Groups
C/
D,
C,
B/
D,
and
B
represent
approximately
3.0,
9.4,
71.9,
and
0.2
percent
of
fruit
production
in
the
MLRA.
Soils
classified
as
having
low
runoff
potential
(
Hydrologic
Soil
Group
A)
represent
11.8
percent
of
fruit
acreage
in
the
MLRA
Surface
Water
Supplies
in
Florida
Very
few
public
water
supplies
rely
on
surface
water
in
the
state
of
Florida.
Ground
water
accounts
for
90
percent
of
public­
supply
water
in
Florida
(
USGS,
1990).
The
locations
of
individual
drinking
water
supplies
relying
on
surface
water
in
the
Southern
Florida
Flatwoods
(
Figure
3)
were
identified
from
a
variety
of
sources,
including
the
Florida
Department
of
Environmental
Protection
(
FL
DEP,
2002);
the
U.
S.
Environmental
Protection
Agency
(
USEPA,
1990;
1999;
2002),
and
the
U.
S.
Geological
Survey
(
1990).
Sources
were
cross­
referenced
in
an
attempt
to
obtain
a
comprehensive
list.

Intakes
are
identified
by
facility
name
in
Table
2
and
Figure
4.
Although
efforts
were
made
to
screen
for
surface
water
supplies,
some
facilities
are
identified
by
name
as
well
fields,
indicating
that
these
facilities
may
rely
on
combination
ground
water
and
surface
water
resources.
Based
on
a
preliminary
analysis
of
Figures
3
and
4,
surface
water
sources
with
the
highest
density
of
citrus
appear
to
be
the
Peace
River,
Shell
Creek,
and
Fordham
Waterways
in
De
Soto
and
Charlotte
Counties.
Citrus
areas
outside
of
the
Southern
Florida
Flatwoods
(
e.
g.,
in
the
South
Central
Florida
Ridge,
MLRA
154)
may
also
be
in
the
contributing
watersheds
of
these
drinking
water
supplies.

Conclusions
and
Recommendations
 
The
Southern
Florida
Flatwoods
(
MLRA
155)
comprise
much
of
the
citrus
production
in
the
State
of
Florida.
Significant
production
also
occurs
along
the
South
Central
Florida
Ridge
(
MLRA
154)
and
the
Southern
Florida
Lowlands
(
MLRA
156B).
 
Very
little
acreage
of
this
acreage
resides
on
high
runoff
potential
soils.
Hydrologic
Soil
Group
D,
C/
D,
and
C
represent
3.0,
3.0,
and
9.3
percent
of
fruit
production
in
the
MLRA.
The
majority
of
citrus
acreage
resides
on
Hydrologic
Soil
Group
B/
D.
This
soils
classification
behaves
as
a
D
soil
unless
a
suitable
drainage
exists
on
site.
Anthropogenic
alteration
of
this
land
to
facilitate
agriculture
(
ditches,
canales,
etc.)
renders
the
behavior
as
a
B
soil.

 
Ground
water
accounts
for
90
percent
of
public­
supply
water
in
Florida
(
USGS,
1990).
Fifty­
five
surface
water
supplies
were
identified
as
potentially
impacted
by
land
use
activities
in
the
Southern
Florida
Flatwoods
(
MLRA
155)
and
adjacent
areas
in
the
South
Central
Florida
Ridge
(
MLRA
154)
and
the
Southern
Florida
Lowlands
(
MLRA
156B).
Many
of
these
intake
locations
are
identified
as
having
the
same
facility/
source
name,
identification
number,
and/
or
similar
latitude/
longitude
indicating
either
potential
duplicate
entries
or
multiple
withdrawals
from
the
same
location.

 
Surface
water
sources
with
the
highest
density
of
citrus
in
their
upstream
watersheds
appear
to
be
the
Peace
River,
Shell
Creek,
and
Fordham
Waterways
in
De
Soto
and
Charlotte
Counties.
Citrus
areas
outside
of
the
Southern
Florida
Flatwoods
(
e.
g.,
in
the
South
Central
Florida
Ridge,
MLRA
154)
may
also
be
in
the
contributing
watersheds
of
these
drinking
water
supplies.

 
Conclusions
cannot
be
drawn
about
the
likelihood
of
diruon
residues
in
these
drinking
water
supplies
without
verifying
intake
locations
and
better
characterization
of
watershed
composition
and
diuron
use.

References
1.
Florida
Department
of
Environmental
Protection
(
FL
DEP),
2002a.
GIS
GeoData.
Land
Use
Data
by
Water
Management
District.
http://
www.
dep.
state.
fl.
us/
gis/
datadir.
asp
(
updated
May
2
2002).

2.
Florida
Department
of
Environmental
Protection
(
FLDEP),
2002b.
Drinking
Water
Basic
Facility
Reports.
http://
www.
dep.
state.
fl.
us/
water/
drinkingwater/
bfr.
htm
(
updated
May
2
2002).

3.
Florida
Department
of
Agriculture
and
Consumer
Services
(
FL
DACS),
2002.
Florida
Agricultural
Statistics:
Citrus
Summary
2000­
01.
Published
January
2002.

4.
U.
S.
Department
of
Agriculture
(
USDA),
2002.
Southeast
Major
Land
Resource
Areas.
National
Resource
Conservation
Service.
http://
www.
nrcs.
usda.
gov/
technical/
land/
mlra/
mlrase.
html
(
verified
July
12,
2002).

5.
U.
S.
Department
of
Agriculture
(
USDA),
1994a.
1992
National
Resources
Inventory:
Soil
Conservation
Service.

6.
U.
S.
Department
of
Agriculture
(
USDA),
1994b.
Soil
Property
Database,
SOILS5:
Soil
Conservation
Service.

7.
U.
S.
Department
of
Agriculture
(
USDA),
1972.
National
Engineering
Handbook,
Section
4,
Hydrology:
Soil
Conservation
Service,
pp
71­
72.

8.
U.
S.
Environmental
Protection
Agency
(
USDA),
2002.
Safe
Drinking
Water
Information
System
(
SDWIS),
Local
Drinking
Water
Information.
http://
www.
epa.
gov/
safewater/
dwinfo/
fl.
htm
(
updated
June
11,
2002)
9.
U.
S.
Environmental
Protection
Agency
(
USEPA),
1999.
BASINS,
Version
2.0,
January
1999.
Region
4.
U.
S.
EPA
Office
of
Water,
Office
of
Science
and
Technology.
EPA­
823­
C­
98­
006.

10.
U.
S.
Environmental
Protection
Agency
(
USEPA),
1990.
Drinking
Water
Supply
(
DWS)
File.
Automated
database
developed
by
USEPA
Office
of
Water.
