COLORADO
DISCHARGE
PERMIT
SYSTEM
(
CDPS)

SUMMARY
OF
RATIONALE
DENVER
INTERNATIONAL
AIRPORT
CDPS
PERMIT
NUMBER
COS­
000008,
DENVER
COUNTY
TABLE
OF
CONTENTS
+­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­+
I.
TYPE
OF
PERMIT
................................................................................................
1
II.
FACILITY
INFORMATION................................................................................
1
III.
RECEIVING
STREAM.........................................................................................
2
IV.
FACILITY
DESCRIPTION..................................................................................
3
V.
PERFORMANCE
HISTORY...............................................................................
7
VI.
TERMS
AND
CONDITIONS
OF
PERMIT.....................................................
13
VII.
REFERENCES......................................................................................................
24
VII.
CHANGES
AFTER
PUBLIC
NOTICE.............................................................
25
+­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­+

I.
TYPE
OF
PERMIT
New
Industrial
­
Stormwater
II.
FACILITY
INFORMATION
A.
Facility
Type:
Individual
Industrial,
>
10
acres
Fee
Category:
Category
24,
Subcategory
2
Annual
Fee:
$
317
B.
Primary
SIC
Code:
4581
­
Airports
C.
Legal
Contact:
Bruce
Baumgartner
Manager
of
Aviation
Denver
International
Airport
Airport
Office
Building,
10th
Floor
8500
Pena
Boulevard
Denver,
Colorado
80249­
6340
(
303)
342­
2200
D.
Facility
Contact:
Janell
Barrilleaux
Environmental
Services
Denver
International
Airport
Airport
Office
Building,
7th
Floor
8500
Pena
Boulevard
Denver,
Colorado
80249­
6340
(
303)
342­
2730
E.
Facility
Location:
NW3
Sec.
21,
T2S,
R65
W,
6th
P.
M.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
2,
Permit
No.
COS­
000008
II.
FACILITY
INFORMATION
F.
Monitoring
Points/
Outfalls:
E
Outfall
­
Concrete
detention
structure
at
flood
control
pond
T­
239
on
Third
Creek
approximately
100
yards
upstream
of
DIA's
boundary
(
39.895900
lat/
104.745944
long)
­
Sub­
basin
C+
­
monitoring
station
on
Third
Creek,
west
of
runway
34R
(
39.515750
lat/
104.422252
long)
­
Second
Creek
­
Second
Creek
immediately
north
of
Pena
Boulevard,
near
the
west
end
of
runway
7/
25,
south
of
the
west
end
of
runway
7/
25
(
38.37264
lat/
104.733040
long)
­
Runway
35R
­
the
outfall
to
Box
Elder
Creek
immediately
downstream
of
the
runway
(
39.854736
lat/
104.640416
long)
­
Runway
26
­
the
outfall
to
Box
Elder
Creek
at
the
east
end
of
runway
8/
26,
just
inside
the
security
fence
(
39.877168
lat/
104.613424
long)
­
Hayesmount
­
the
outfall
to
the
Denver
Hudson
Canal,
east
of
the
Fire
Training
Facility,
on
the
north
side
of
runway
8/
26,
between
taxiways
R7
and
R8
(
39.879640
lat/
104.653216
long)
­
Barr
Lake
Drainage
­
outfall
to
Barr
Lake
Drainage
channel,
just
west
of
runway
34,
between
taxiways
F9
and
F10
(
39.892236
lat/
104.685328
long)
­
Runway
7/
25,
the
outfall
to
Second
Creek
at
the
southwest
corner
of
the
runway
(
39.840152
lat/
104.727008
long)

III.
RECEIVING
STREAM
A.
Identification,
Classification
and
Standards
1.
Identification:
Discharges
to
Second
Creek
and
Third
Creek
(
which
are
in
segment
16
of
the
Upper
South
Platte
River
Basin),
which
flow
to
the
South
Platte
River,
Segment
15
of
the
Upper
South
Platte
River
Sub­
basin
of
the
South
Platte
River
Basin.
(
Discharges
to
Second
and
Third
Creeks
can
also
be
diverted
to
Barr
Lake
and/
or
the
O'Brien
Canal,
which
are
part
of
the
Farmer's
Reservoir
and
Irrigation
Company
(
FRICO)
system.)

Discharges
to
Hayesmount
Tributary
(
which
is
in
segment
3
of
the
Middle
South
Platte
River
Basin),
which
flows
to
Segment
1
of
the
Middle
South
Platte
River
Sub­
basin
of
the
South
Platte
River
Basin.

Discharges
to
Box
Elder
Creek
(
which
is
in
segment
5
of
the
Middle
South
Platte
River
Basin),
which
flows
to
Segment
1
of
the
Middle
South
Platte
River
Sub­
basin
of
the
South
Platte
River
Basin.

2.
Classification:
Segment
16
of
the
Upper
South
Platte
River
Basin
and
Segment
3
of
the
Middle
South
Platte
River
Basin
are
designated
as
Use
Protected,
and
are
classified
for
the
following
uses:
Recreation,
Class
1­
a;
Aquatic
Life,
Class
2
(
Warm);
and
Agriculture.
Applicable
numeric
standards
for
the
segments
are
listed
below,
in
accordance
with
the
above
classification
as
found
in
Regulation
No.
38
,
Classifications
and
Numeric
Standards
for
the
South
Platte
River
Basin
(
5
CCR
1002­
38).

Physical
and
Biological
D.
O.
=
5.0
mg/

pH
=
6.5
­
9.0
s.
u.
Fecal
Coliform
=
200/
100
ml
E­
coli
=
126/
100
ml
Segment
5
of
the
Middle
South
Platte
River
Basin
is
designated
as
Use
Protected,
and
is
classified
for
the
following
uses:
Recreation,
Class
2;
Aquatic
Life,
Class
2
(
Warm);
and
Agriculture.
Applicable
numeric
standards
for
the
segments
are
listed
below,
in
accordance
with
the
above
classification
as
found
in
Regulation
No.
38
,
Classifications
and
Numeric
Standards
for
the
South
Platte
River
Basin
(
5
CCR
1002­
38).
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
3,
Permit
No.
COS­
000008
III.
RECEIVING
STREAM
Physical
and
Biological
D.
O.
=
5.0
mg/

pH
=
6.5
­
9.0
s.
u.
Fecal
Coliform
=
2000/
100
ml
E­
coli
=
630/
100
ml
In
addition,
interim
organic
pollutant
standards
from
the
Basic
Standards,
section
31.11(
3)
Awater
and
fish
@
classification
table
apply
to
Barr
Lake.
As
part
of
a
water
quality
study
(
see
Section
V.
B.
2
of
the
Rationale),
volatile
and
semi­
volatile
analyses
were
conducted
at
several
points.
All
were
nondetects
except
for
2,4­
dimethlyphenol,
which
is
a
typical
laboratory
blank
residue
contaminant.
Therefore,
it
was
determined
that
none
of
these
parameters
are
an
issue
with
this
facility,
and
so
they
are
not
dealt
with
in
the
permit.
However,
a
periodic
resampling
(
once
every
permit
term,
for
the
renewal
application)
will
be
required.

3.
Impacts
on
Downstream
Water
Supplies
or
Other
Receiving
Waters:

The
stream
segments
downstream
of
the
discharge
are
not
classified
as
drinking
water
supplies.
Of
all
the
receiving
waters,
the
discharge
into
Third
Creek
is
of
main
concern.
(
Most
of
the
runoff
from
the
industrialized
areas
at
Denver
International
Airport
(
DIA)
drains
to
Third
Creek.)
Third
Creek
flows
for
about
two
miles
northwest
of
the
airport,
until
it
reaches
the
O=
Brian
Canal.
From
there,
the
flow
can
be
diverted
to
either
Barr
Lake,
or
the
Denver
Hudson
Canal.
Both
canals
are
owned
by
FRICO.
(
See
Figure
1,
Part
I.
G
of
the
permit.)
Barr
Lake
is
classified
for
the
same
uses
as
listed
above.
However,
it
is
also
a
wildlife
sanctuary,
and
so
attention
must
be
given
to
any
potential
impacts
from
the
discharge
to
Third
Creek.

IV.
FACILITY
DESCRIPTION
A.
Industry
Description
1.
Type
of
Industry:
The
facility
is
Denver
International
Airport
(
DIA),
which
opened
in
February,
1995.
During
1997,
DIA
handled
490,000
aircraft
operations
and
over
34
million
passengers,
making
it
the
sixth
busiest
airport
in
the
country.
Airport
activity
is
projected
to
grow
to
45
million
passengers
and
650,000
aircraft
operations
annually
by
2010.

There
are
currently
50
tenants
leasing
facilities
from
DIA
which
have
industrial
activities
exposed
to
stormwater.
These
include
airlines,
air
cargo
lines,
aircraft
services,
and
car
rental
agencies.
The
following
activities
occur
at
one
or
more
of
these
leaseholds
at
DIA:

­
aircraft
deicing,
fueling,
maintenance,
washing,
painting/
stripping,
lavatory
services
­
building
and
ground
maintenance
­
cargo
handling
­
chemical
storage
and
handling
­
equipment
cleaning/
degreasing,
fueling,
maintenance,
storage
­
fuel
storage
­
material
storage
­
outdoor
apron
cleaning
­
vehicle
fueling,
maintenance,
storage,
washing
­
waste
storage
and
disposal
In
addition,
three
tenant
leaseholds
are
covered
by
separate
general
stormwater
permit
certifications,
and
will
not
be
covered
under
this
permit:
the
Aircraft
Services
International
Group
fuel
farm,
and
the
United
Airlines
and
Continental
Airlines
maintenance
hangars.
To
the
extent
that
other
tenant
leaseholds
and
facilities
obtain
coverage
under
separate
stormwater
permits
in
the
future,
they
also
will
not
be
addressed
in
this
permit.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
4,
Permit
No.
COS­
000008
IV.
FACILITY
DESCRIPTION
Stormwater
Permit
Coverage:
Stormwater
discharges
from
airports
that
have
vehicle
maintenance,
fueling,
equipment
cleaning
and/
or
airport
deicing
are
required
to
be
covered
by
a
Colorado
Discharge
Permit
System
(
CDPS)
permit
in
order
to
be
discharged
to
Waters
of
the
State.
This
coverage
may
be
obtained
under
either
a
general
or
individual
CDPS
Stormwater
Discharge
Permit.

DIA
was
previously
covered
under
the
general
permit
for
Stormwater
Discharges
Associated
with
Heavy
Industrial
Activity,
certification
number
COR­
020267.
However,
given
the
size
and
complexity
of
the
site,
past
violations,
and
special
requirements
in
terms
of
monitoring
and
management
practices,
the
Division
determined
that
coverage
under
an
individual
stormwater
permit
(
including
numeric
action
levels
and
mandatory
Best
Management
Practices)
would
provide
more
environmental
control,
and
was
more
appropriate
for
this
site.
The
general
permit
certification
will
be
inactivated
once
the
individual
permit
goes
into
effect.

Aircraft
Deicing
Fluids
(
ADF):
DIA,
like
most
larger
airports,
seasonally
utilizes
chemicals
for
aircraft
and
runway
deicing
to
enhance
the
safety
of
air
travel
and
airport
operations.
The
open­
air
application
of
these
chemicals
to
aircraft
and
pavement
surfaces
can
result
in
migration
of
deicing
fluids
to
the
storm
sewer
system
and
eventual
discharge
to
receiving
streams.
The
primary
aircraft
deicing
fluid
(
ADF)
used
at
DIA
is
propylene
glycol
(
PG).
Propylene
glycol
exerts
a
significant
oxygen
demand
that
can
deplete
dissolved
oxygen
(
DO)
in
receiving
waters,
threatening
aquatic
life.
DIA
also
currently
uses
potassium
acetate
for
runway,
taxiway
and
apron
area
deicing.
During
the
1997­
1998
deicing
season,
DIA
used
nearly
one
million
gallons
of
PG­
based
ADF
for
aircraft
deicing.
The
use
of
these
chemicals
at
DIA
is
expected
to
increase
with
the
growth
in
aircraft
operations.

Aircraft
Deicing:
Limited
deicing,
which
is
allowed
at
the
A
and
C
concourse
gates,
is
defined
as
the
minimum
level
of
deicing
required
to
ensure
that
it
is
safe
to
taxi
the
aircraft
to
the
full
deicing
site.
Full
deicing
typically
uses
a
higher
quantity
of
deicing
fluid,
based
on
the
airline=
s
and
pilot=
s
judgment,
such
that
the
aircraft
is
safe
for
takeoff.
Full
deicing
is
normally
restricted
to
the
designated
deicing
areas
shown
in
Figure
2,
Part
I.
G
of
the
permit.
See
discussion,
Section
VI.
B.
2.
c.
1
of
the
Rationale.
Figure
2
shows
only
those
areas
where
deicing
is
allowed
as
of
the
issuance
date
of
this
permit.
Future
modifications
to
deicing
areas
during
the
permit
term
will
not
result
in
a
change
to
Figure
2,
but
rather
will
be
reflected
in
DIA's
SWMP.

There
are
several
types
of
ADF
used
at
DIA.
Type
1
is
the
deicer
used
at
least
90%
of
the
time,
for
both
limited
and
full
deicing.
Types
2
are
4
are
anti­
icers,
which
are
thicker
than
deicers.
A
small
amount
of
an
anti­
icer
is
used
after
limited
and
full
deicing,
to
prevent
additional
ice
buildup.
Type
2
is
rarely
used
at
DIA,
as
Type
4
is
considered
to
provide
better
performance.
All
decisions
on
which
types
of
deicers
to
use
and
when
are
made
by
the
airlines.

Federal
Regulations:
There
are
currently
no
specific
federal
guidelines
or
effluent
limits
in
place
for
this
type
of
facility.
EPA
has
conducted
a
nationwide
study
to
determine
the
feasibility
and
necessity
of
such
guidelines,
and
has
determined
not
to
promulgate
industry­
specific
effluent
limits
or
guidelines
for
aircraft
deicing
at
this
time.
Any
changes
in
federal
guidelines
will
be
handled
by
an
amendment
to
the
permit,
as
necessary.
(
See
Section
VI.
E.
1
of
the
Rationale.)

2.
Facility
Systems
Description:
The
discharges
covered
by
this
permit
originate
from
the
storm
sewer
system.

a.
Clean
and
Dirty
Water
Systems:
DIA
operates
a
state­
of­
the­
art
ADF
collection,
retention
and
recycling
system.
The
system
known
as
the
Adirty
water
system@
separately
conveys
spent
ADF
with
stormwater
from
authorized
deicing
areas
(
e.
g.,
deicing
pads
and
concourse
gates)
to
retention
ponds
(
also
called
industrial
stormwater
ponds)
for
subsequent
recycling,
or
treatment
by
the
Metro
Wastewater
Reclamation
District
(
Metro).
Stormwater
from
other
portions
of
the
airport
property
are
conveyed
to
Second
Creek,
Third
Creek,
Box
Elder
Creek,
and
other
drainageways
via
the
Aclean
water
system.@

The
majority
of
the
deicing
fluids
are
applied
to
passenger
aircraft
at
dedicated
deicing
pads
located
just
west
of
each
of
the
three
concourses.
ADF­
contaminated
runoff
from
these
pads
is
collected
and,
if
in
sufficient
concentration,
is
conveyed
to
the
spent
glycol
storage
tanks
located
adjacent
to
the
recycling
plant,
for
subsequent
treatment
and
offsite
reuse.
Approximately
20
to
35
percent
of
the
ADF
used
at
DIA
is
recycled.
If
the
concentration
of
deicing
fluid
is
too
low
for
cost­
effective
recycling,
then
this
stormwater
is
directed
to
the
West
Pond
(
002)
for
pumping
to
Metro
for
treatment
and
disposal.
The
stormwater
from
deicing
at
the
gates
on
the
west
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
5,
Permit
No.
COS­
000008
IV.
FACILITY
DESCRIPTION
ramp
area
is
directed
to
the
Northwest
Pond
(
002)
and
the
runoff
from
the
east
ramp
is
directed
to
the
Northeast
Pond
(
001).

Full
deicing
is
allowed
at
B
Concourse.
Fluid
from
this
activity
may
be
collected
for
recycling
into
Pond
003A,
adjacent
to
the
recycling
facility.
This
pond,
however,
is
now
also
being
used
to
collect
runoff
from
the
West
Airfield
Diversion
System,
and
is
therefore
only
partially
available
for
full
recycling
of
runoff
from
Concourse
B.
A
new
high
capacity
pond
system
is
under
construction
to
serve
the
West
Airfield
Diversion
System,
which
will
allow
Pond
003A
to
more
effectively
contain
full
gate
deicing
at
B
Concourse
for
recycling
(
see
Compliance
Schedule,
Section
VI.
E.
4.
a
of
the
Rationale).
When
not
being
recycled,
B
Concourse
runoff
goes
to
pond
001
and/
or
pond
002.

Similarly,
the
South
Cargo
Apron,
General
Aviation
Ramp,
and
other
authorized
locations
are
served
by
industrial
stormwater
ponds
for
collection
of
deicer
contaminated
runoff,
for
pumping
to
Metro.
From
time
to
time,
when
the
concentration
in
ponds
001,
002
and
005
(
South
Cargo)
is
high
enough
to
permit
economical
recycling,
water
from
these
ponds
is
trucked
to
the
recycling
facility.
Pond
004,
serving
the
General
Aviation
area,
has
never
been
pumped
to
Metro,
as
the
deicing
taking
place
on
the
General
Aviation
ramp
has
been
very
limited,
and
so
evaporation
has
been
sufficient
to
regenerate
pond
capacity.
(
See
Figures
3
and
4,
Part
I.
G
of
the
permit,
for
a
stormwater
management
flow
schematic
and
a
contaminated
stormwater
system
process
schematic.)

From
time
to
time,
various
utility
vaults,
sumps
and
manholes
surrounding
the
concourses
and
on
other
locations
around
the
airfield,
become
filled
with
water.
For
maintenance
reasons,
this
water
must
be
removed
periodically.
The
estimated
annual
volume
is
about
100,000
gal.
This
water
frequently
contains
glycol,
and
may
also
contain
fuel
or
other
constituents.
The
pumped
water
is
handled
as
per
BMP
#
7
(
see
Section
VI.
B.
2.
c
of
the
Rationale).

Despite
the
recycling/
collection
system,
during
initial
operations
at
DIA
it
was
discovered
that
underdrains
along
the
runways
and
taxiways
were
providing
a
conduit
for
some
ADF
and
pavement
deicers
to
reach
the
clean
water
system.
This
was
due
to
ADF
dripping
off
the
aircraft
in
areas
outside
of
the
collection
system,
or
being
wind­
blown
to
such
areas
during
application.
ADF
that
escapes
the
dirty
water
system
has
been
termed
Afugitive
ADF.@

The
discharge
of
relatively
large
quantities
of
fugitive
ADF
to
Third
Creek
resulted
in
the
Division
and
DIA
entering
into
a
Compliance
Order
on
Consent.
It
also
resulted
in
many
changes
to
the
management
of
the
ADF­
contaminated
runoff,
including
an
expansion
of
the
collection
system.
(
This
is
discussed
further
in
Section
V.
B.
2
of
the
Rationale.)

The
capacity
of
the
current
dirty
water
system
to
handle
storm
events
has
two
primary
limitations.
First,
the
recycling
plant
can
process
up
to
25
gallons
per
minute
(
gpm)
for
stormwater
containing
at
least
a
10
percent
concentration
of
PG.
The
processing
rate
is
reduced
at
lower
ADF
concentrations
because
more
water
must
be
removed
to
achieve
the
target
finished
PG
concentration.
A
4.2
million
gallon
retention
pond
and
four
420,000
gallon
tanks
provide
storage.
However,
if
deicer­
contaminated
stormwater
flows
exceed
storage
and
recycling
plant
processing
capacity,
then
the
runoff
is
directed
to
the
West
Pond.

A
second
limitation
to
the
dirty
water
system
capacity
is
the
amount
of
deicer­
contaminated
stormwater
that
can
be
discharged
to
the
Metro
Wastewater
Reclamation
District
("
Metro").
Metro
limits
BOD5
contributions
from
DIA
to
a
daily
maximum
of
9
tons
and
a
30­
day
average
limit
of
7
tons
per
day,
based
on
Metro=
s
capacity
to
handle
high
BOD
loads
without
violating
their
own
discharge
permit.
(
DIA
monitors
COD
and
then
calculates
the
BOD
loading.
COD
monitoring
is
used
because
results
can
be
obtained
in
two
hours,
whereas
monitoring
for
BOD5
takes
five
days
to
process.)

Five
ponds,
ranging
in
size
from
3.6
to
13.7
million
gallons,
currently
provide
storage
of
ADF­
contaminated
stormwater
flows
such
that
they
can
be
pumped
to
Metro
at
a
controlled
rate,
consistent
with
BOD5
loading
limitations.
Flows
in
excess
of
pond
storage
and
pumping
capacity
would
overflow
to
Third
Creek
and
other
receiving
drainages.
This
has
occurred
several
times.
An
additional
22
million
gallons
of
new
industrial
stormwater
pond
capacity
is
being
constructed.
Also,
another
5.7
million
gallon
pond
cell
will
be
constructed
before
the
new
runway
is
operational.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
6,
Permit
No.
COS­
000008
IV.
FACILITY
DESCRIPTION
b.
Site
Drainage
System:
The
Third
Creek
basin
drains
most
of
the
western
and
most
of
the
southern
portions
of
the
airport
operations
area.
Third
Creek
sub­
basins
A
and
B
drain
the
south
cargo
area,
the
general
aviation
area
and
the
parking
structures.
Third
Creek
sub­
basins
C
and
D
drain
the
west
portion
of
all
three
concourses,
including
the
dedicated
deicing
pads,
and
the
glycol
recycling
facility.
Third
Creek
sub­
basin
E
drains
the
north
campus
area
(
flight
kitchens,
mail
facility,
etc.).
No
aircraft
de­
icing
occurs
in
this
sub­
basin.
(
Sub­
basin
E
is
not
the
same
as
the
monitoring
point
"
E
Outfall,"
which
is
the
outfall
from
pond
T­
239
to
Third
Creek
near
DIA's
boundary.
See
description,
Section
II.
F
of
the
Rationale.)
Another
drainage,
flowing
directly
to
Barr
Lake,
drains
the
far
northern
segment
of
the
west
airfield.
No
aircraft
deicing
occurs
at
DIA
in
this
basin.

DIA
had
constructed
temporary
retention
ponds
in
the
Third
Creek
drainage
within
airport
property
to
capture
ADF
that
escapes
the
dirty
water
system.
This
was
done
as
an
interim
measure
while
facility
improvements
were
being
designed
and
constructed
(
see
Compliance
Schedule,
Section
VI.
E.
4.
a
of
the
Rationale).
These
ponds
were
referred
to
as
the
C,

>
D
and
C+
ponds
(
see
Figure
5,
Part
I.
G
of
the
permit).
The
C
and
D
ponds
included
permanent
headwalls
and
sluice
gates
to
control
flow
rates.
The
ponds
were
used
to
hold
contaminated
stormwater
from
those
sub­
basins
until
it
could
be
pumped
to
one
of
the
industrial
ponds,
for
eventual
disposal
to
Metro.
DIA
also
constructed
an
aeration
system
in
the
C
pond
in
an
attempt
to
reduce
BOD
levels
and
raise
DO
in
the
ADF­
contaminated
stormwaters.
In
addition,
in
late
1997,
DIA
constructed
the
West
Airfield
Diversion
System
to
divert
contaminated
runoff
(
tributary
to
Ponds
C
and
D),
that
was
going
to
the
clean
water
system,
to
the
dirty
water
system
instead.

Ponds
C,
D
and
C+
had
to
be
drained,
and
the
dam
at
C+,
the
headwall
at
D,
and
the
aeration
system
at
C,
had
to
be
removed
to
allow
for
construction
of
a
new
runway
and
the
new
containment
ponds
(
see
Compliance
Schedule,
Section
VI.
E.
4.
a
of
the
Rationale).
The
headwall
at
D
will
be
replaced
once
the
construction
is
completed.
Once
the
runway
becomes
operational,
the
C
and
D
ponds
cannot
be
used
routinely
for
retention,
due
to
the
potential
hazard
to
aircraft
caused
by
a
wildlife
attractant.
The
ponds
will
only
be
used
in
emergency
situations.

DIA
has
completed
a
water
quality
study
of
the
facility,
which
outlines
several
more
improvements
to
be
made
in
the
system,
including
a
60%
increase
in
the
capacity
of
the
dirty
water
pond
system.
These
improvements
are
discussed
in
more
detail
in
the
Compliance
sections
of
the
Rationale.
It
is
not
known
at
this
time
whether
or
not
these
additional
measures
will
be
sufficient
to
prevent
future
impacts
to
water
quality
from
the
discharge.

A
monitoring
station,
referred
to
as
C+,
is
being
installed
downstream
of
the
confluence
of
flow
from
C
and
D
ponds.

c.
Future
Infrastructure:
A
sixth
runway
is
now
under
construction.
Some
of
the
earthwork
for
construction
was
completed
as
part
of
overall
airport
construction
in
the
early
1990s.
Completion
of
the
runway
was
then
deferred.
The
remainder
of
the
construction
was
begun
in
Spring
2001
and
will
continue
through
2003.

A
new
deicing
pad
(`
J')
is
under
construction
east
of
the
existing
C
pad.
This
is
to
augment
existing
pad
capacity,
and
is
expected
to
be
completed
in
late
2001.

3.
Chemicals
Used:
Table
IV­
1
lists
the
main
chemicals
used
at
the
facility
that
may
be
in
the
discharge.

Table
IV­
1
­­
Chemical
Additives
Chemical
Name
Purpose
Constituents
of
Concern
Propylene
Glycol­
based
deicing
fluid
Ice
removal
and
prevention
on
aircraft
BOD,
COD,
corrosion
inhibitors,
fire
retardants
Ethylene
Glycol
Antifreeze
for
vehicles
BOD,
COD,
corrosion
inhibitors,
fire
retardants
Potassium
acetate
Airfield
pavement
anti­
icer/
deicer
BOD,
COD
Magnesium
chloride
Roadway
anti­
icer/
deicer
Chloride
Sand
Pavement
traction
Sediment
Salt
Pavement
deicer
Sodium
chloride
E­
36
Liquid
Runway
Deicer
Runway/
taxiway
anti­
icer/
deicer
Potassium
acetate,
BOD,
COD
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
7,
Permit
No.
COS­
000008
Oil
and
Grease
Vehicle,
aircraft
lubrication,
maintenance
Oil
and
Grease
Jet
Fuel
Aircraft
fueling
Total
Petroleum
Hydrocarbons
(
TPH)

V.
PERFORMANCE
HISTORY
A.
Monitoring
Data
1.
Discharge
Monitoring
Results:
Table
V­
1
summarizes
the
effluent
data
reported
at
the
designated
sampling
points
as
required
by
the
stormwater
permit
for
DIA,
from
10/
27/
97
to
9/
20/
00,
based
the
Annual
Reports
for
that
period.
Where
only
one
or
two
sample
results
are
available,
the
average
was
not
calculated.

Table
V­
1
­­
Self­
Monitoring
Results
Sub­
basin
A
Sub­
basin
C
Parameter
No.
of
Samples
Reported
Concentrations
Avg/
Min/
Max
No.
of
Samples
Reported
Concentrations
Avg/
Min/
Max
Flow,
MGD
5
0.20/
0.07/
0.51
4
0.06/
0.01/
0.15
BOD5,
mg/

15
65/
4/
334
10
188/<
2/
784
TSS,
mg/

24
97/
10/
415
22
266/
6/
4520
Oil
&
Grease,
mg/

23
2.3/
6/
12a/
22
2.2/<
5/
25
pH,
s.
u.
(
range)
24
6.8­
10.0
22
6.7­
8.1
Propylene
Glycol,
mg/

24
27/<
1/
336
22
51/<
1/
540
Ethylene
Glycol,
mg/

22
0.5/<
1/
10
21
1/<
1/
8
Total
Petroleum
Hydrocarbons,
mg/

11
0.3/<
1/
3
11
<
1/<
1/<
1
Total
Phosphorus,
as
P,
mg/

12
0.20/
0.04/
0.67
11
0.64/<
0.02/
4.75
Total
Kjeldahl
Nitrogen,
as
N,
mg/

12
1.5/<
0.3/
3.6
11
7.5/
0.4/
28.4
Chloride,
mg/

11
49/
5/
132
7
1389/<
1/
4500
Fecal
Coliform,
#/
100
ml
2
­­/<
4/
340
2
­­/
9/
180
Nitrate/
Nitrite,
as
N,
mg/

12
1.18/
0.06/
4.12
11
0.5/
0.02/
1.13
Total
Organic
Carbon,
mg/

15
48/
7/
195
10
93/
8/
284
Acetate,
mg/

6
5/<
5/
28
5
34/<
5/
120
a/
All
results
were
below
15
mg/

,
except
for
one
result
at
457
mg/

;
see
explanation
below.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
8,
Permit
No.
COS­
000008
V.
PERFORMANCE
HISTORY
Sub­
basin
D
E
Outfall
Parameter
No.
of
Samples
Reported
Concentrations
Avg/
Min/
Max
No.
of
Samples
Reported
Concentrations
Avg/
Min/
Max
Flow,
MGD
3
0.25/
0.06/
0.47
5
1.38/
0.02/
6.42
BOD5,
mg/

12
432/
8/
1050
13
39/<
2/
434
TSS,
mg/

21
98/
5/
1060
24
98/
3/
812
Oil
&
Grease,
mg/

20
4.1/<
5/
44
24
1.8/<
5/
21
pH,
s.
u.
(
range)
21
6.0­
8.5
24
6.9­
8.0
Propylene
Glycol,
mg/

21
230/<
1/
850
24
10/<
1/
238
Ethylene
Glycol,
mg/

20
0.3/<
1/
3
23
0.1/<
1/
2
Total
Petroleum
Hydrocarbons,
mg/

11
<
1/<
1/<
1
12
<
1/<
1/<
1
Total
Phosphorus,
as
P,
mg/

11
0.17/<
0.02/
1.33
12
0.1/<
0.02/
0.27
Total
Kjeldahl
Nitrogen,
as
N,
mg/

11
3.0/
0.5/
12.1
12
0.9/<
0.03/
1.90
Chloride,
mg/

8
17/<
1/
73
9
215/
56/
576
Fecal
Coliform,
#/
100
ml
2
­­/
6/
200
2
­­/
11/
160
Nitrate/
Nitrite,
as
N,
mg/

11
0.44/<
0.02/
0.86
12
1.99/<
0.02/
15.8
Total
Organic
Carbon,
mg/

12
205/
6/
392
13
23/
5/
150
Acetate,
mg/

3
33/
9/
79
6
<
5/<
5/<
5
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
9,
Permit
No.
COS­
000008
Runway
35R
Second
Creek
Parameter
No.
of
Samples
Reported
Concentrations
Avg/
Min/
Max
No.
of
Samples
Reported
Concentrations
Avg/
Min/
Max
Flow,
MGD
0
­­­
0
­­­

BOD5,
mg/

9
65/
3/
401
11
101/
4/
434
TSS,
mg/

19
31/
3/
192
13
444/
21/
2840
Oil
&
Grease,
mg/

19
2.4/<
5/
12
13
0.9/<
5/
12
pH,
s.
u.
(
range)
19
6.5­
8.1
13
6.9­
8.1
Propylene
Glycol,
mg/

17
5/<
1/
52
13
<
1/<
1/<
1
Ethylene
Glycol,
mg/

19
<
1/<
1/<
1
13
0.2/<
1/
1
Total
Petroleum
Hydrocarbons,
mg/

9
<
1/<
1/<
1
8
<
1/<
1/<
1
Total
Phosphorus,
as
P,
mg/

9
0.21/
0.05/
0.49
8
0.7/
0.10/
2.64
Total
Kjeldahl
Nitrogen,
as
N,
mg/

9
1.2/<
0.01/
6.40
8
1.4/
0.8/
3.0
Chloride,
mg/

8
6.6/
5/
24
8
1339/
32/
730
Fecal
Coliform,
#/
100
ml
0
­­­
0
­­­

Nitrate/
Nitrite,
as
N,
mg/

9
0.66/
0.07/
1.73
8
0.42/
0.04/
0.80
Total
Organic
Carbon,
mg/

9
42/
6/
244
9
72/
6/
220
Acetate,
mg/

6
37/<
5/
220
4
63/<
5/
204
2.
Additional
Discharge
Monitoring
Results:
Table
V­
2
summarizes
the
additional
COD
monitoring
required
at
E
Outfall
for
DIA,
from
3/
97
to
12/
99.

Table
V­
2
­­
Self­
Monitoring
Results
­
E
Outfall
­
COD,
mg/

Month
#
of
Samples
Avg.
Min.
Max.
Std.
Dev.
#
over
100
mg/

b/

Mar
97
17
1359
212
3230
897
17
Apr
97
15
634
114
2848
766
15
May
97
33
81
0
198
41
12
Jun
97
28
73
16
260
63
4
Jul
97
31
64
4
156
32
3
Aug
97
31
42
0
190
34
2
Sep
97
30
35
8
112
24
1
Oct
97
28
77
15
301
75
8
Nov
97
30
256
31
1008
258
18
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
10,
Permit
No.
COS­
000008
Dec
97
29
61
0
159
34
2
All
97
272
196
0
3230
443
82
Jan
98
31
33
11
71
14
0
Feb
98
28
36
7
56
13
0
Mar
98
30
44
17
66
12
0
Apr
98
30
122
19
423
107
10
May
98
31
47
17
121
19
1
Jun
98
30
32
0
58
14
0
Jul
98
31
27
0
78
20
0
Aug
98
31
37
14
128
24
1
Sep
98
30
35
12
64
13
0
Oct
98
31
35
12
65
13
0
Nov
98
29
29
5
67
16
0
Dec
98
30
36
3
71
15
0
All
98
362
42
0
423
42
12
Jan
99
29
34
8
143
24
1
Feb
99
28
35
19
61
9
0
Mar
99
31
31
9
61
11
0
Apr
99
30
57
1
150
39
5
May
99
31
73
15
334
70
3
Jun
99
30
29
10
53
11
0
Jul
99
30
37
10
77
14
0
Aug
99
29
38
15
92
18
0
Sep
99
30
30
5
92
20
0
Oct
99
31
23
4
49
10
0
Nov
99
30
24
6
56
12
0
Dec
99
27
25
4
39
9
0
All
99
356
36
1
334
30
9
b/
See
Discussion
of
Limitations,
Section
VI.
B.
2.
b
of
the
Rationale.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
11,
Permit
No.
COS­
000008
V.
PERFORMANCE
HISTORY
B.
Compliance
With
Terms
and
Conditions
of
Previous
Permit
1.
Discussion
of
Monitoring
Data:
The
Oil
and
Grease
sample
for
6/
5/
98
showed
a
result
of
457
mg/

.
The
permittee
believes
this
result
is
inaccurate,
and
is
probably
a
lab
error,
since
no
sheen
or
odor
was
observed
during
the
sampling
event.

See
Section
VI.
B.
2.
b
of
the
Rationale
for
a
further
discussion
of
the
monitoring
data.

2.
Permit
Conditions:
On
May
27,
1994,
DIA
was
issued
permit
certification
number
COR­
020267
under
the
general
permit
for
Stormwater
Discharges
Associated
with
Heavy
Industrial
Activity.
The
permit
states,
in
part,
that
"
Stormwater
discharges
from
industrial
activities
shall
not
cause
or
threaten
to
cause
pollution,
contamination
or
degradation
of
State
waters."
It
also
states
that
"
Except
as
provided
.
.
.
all
discharges
authorized
by
this
permit
shall
be
composed
entirely
of
stormwater."

The
first
documented
violation
of
the
permit
was
on
April
7,
1996,
when
small
quantities
of
PG
were
discovered
in
Third
Creek.
A
subsequent
investigation
by
airport
and
State
Health
Department
officials
determined
that
the
ADF
had
dripped
off
airplanes
as
they
taxied
from
de­
icing
pads
and
approached
taxiways
and
runways
for
takeoff.
The
fugitive
ADF
then
drained
into
the
airport=
s
underground
drainage
system
located
along
the
edges
of
the
runways
and
taxiways
and
during
subsequent
rain
storms
or
snowmelt
washed
into
Third
Creek.

A
second
incident
occurred
on
March
5,
1997,
when
102
gallons
of
ADF
were
spilled
after
a
valve
failed.
Some
of
the
ADF,
which
subsequently
mixed
with
approximately
3,000
gallons
of
storm
water,
made
its
way
to
Third
Creek.
Damage
to
Third
Creek,
in
terms
of
a
lack
of
insect
and
invertebrate
life,
and
a
black
tarry
substance
in
the
stream
bed,
was
observed
following
this
incident.
Subsequent
observations
by
staff
from
the
Water
Quality
Control
Division
(
the
"
Division")
indicated
that
the
damage
was
not
permanent.
According
to
a
report
commissioned
by
the
Farmers
Reservoir
and
Irrigation
Company,
prepared
by
Dr.
John
Stednick,
and
dated
May
28,
1997,
"[
w]
ater
quality
measurements
at
Third
Creek
at
O=
Brian
and
at
Barr
Lake
suggest
that
no
propylene
glycol
had
reached
these
points."

In
the
months
following
that
incident,
there
were
numerous
reports
of
glycol
or
glycol
by­
products
in
Third
Creek,
again
due
to
the
ADF
dripping
off
aircraft
during
taxiing
and
take­
off.
The
primary
indication
was
a
strong
odor
in
the
creek
associated
with
the
breakdown
of
glycol.

The
violations
resulted
in
the
Division
and
DIA
entering
into
a
Compliance
Order
on
Consent,
on
August
5,
1998.
The
order
provided
for
a
$
273,800
civil
penalty.
This
included
a
$
29,000
cash
fine
(
based
on
economic
benefit),
and
a
$
244,800
violations
penalty,
which
DIA
proposed
to
offset
with
three
Supplemental
Environmental
Projects
(
SEPs).
At
a
2:
1
ratio
($
2
spent
for
every
1$
of
the
penalty),
the
total
cost
of
the
SEPs
was
$
489,600.
Division
policy
requires
that
SEPs
not
be
used
for
immediate
permit
compliance.
The
agreed­
upon
SEPs
were
designed
to
address
future
compliance,
by
predicting
future
problems
and
proposing
solutions.
The
SEPs
included:

a.
A
detailed
study
and
evaluation
of
the
airport=
s
industrial
waste
management
system,
to
identify
all
sources
of
contamination
which
may
be
entering
state
waters
(
including
Box
Elder
and
Second
Creeks,
as
well
as
Third
Creek)
and
impacting
water
quality.
The
report
on
this
study
was
submitted
to
the
Division
on
September
30,
1998.

b.
A
two
year
monitoring
program
for
the
wells
which
have
the
potential
to
be
impacted
by
glycol
in
Third
Creek.
This
addressed
concerns
that
the
drinking
water
supplies
of
downstream
residents
might
be
adversely
affected
by
any
glycol
reaching
the
creek.
The
program
was
completed
at
the
end
of
1999,
with
no
observed
impacts
to
the
monitored
groundwater
wells.

c.
A
study
to
examine
water
quantity/
stormwater
drainage
issues
impacted
by
DIA,
and
how
these
impacts
can
be
mitigated.
The
report
on
this
study
was
submitted
to
the
Division
on
February
26,
1999.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
12,
Permit
No.
COS­
000008
V.
PERFORMANCE
HISTORY
While
negotiations
on
the
order
were
proceeding,
DIA
initiated
several
temporary
and
permanent
improvements
to
their
system.
The
main
permanent
change
was
a
$
2.6
million
project
which
modified
the
storm
drainage
system,
so
that
runoff
and
fugitive
ADF
from
the
underdrain
system
in
the
vicinity
of
the
de­
icing
pads
would
generally
be
diverted
to
DIA=
s
dirty
storm
water
system,
and
then
into
the
Metro
Waste
Water
Treatment
system.
The
project
was
completed
in
December,
1997.
It
has
eliminated
the
majority
of
the
problem,
as
the
1998
sampling
results
in
Table
V­
2
demonstrate;
however,
additional
measures
are
still
needed.

More
detailed
investigations
of
the
problem
revealed
another
concern
in
the
design
of
the
deicing
pads
west
of
the
concourses.
Numerous
utility
corridors
and
vaults
are
routed
directly
beneath
the
pads.
Elevated
concentrations
of
PG
and
COD
observed
in
the
utility
corridors
suggested
that
ADF
may
be
entering
the
corridors
through
utility
manholes
on
the
pads.
Seepage
through
joints
in
the
pads=
concrete
may
also
contribute
to
migration
of
ADF
to
the
clean
water
system,
either
via
the
utility
corridors
or
more
directly
via
seepage
from
under
the
concrete
at
the
edges
of
the
pads,
ramps,
and
aprons.

To
address
this
issue,
DIA
sealed
all
manholes
on
the
pads,
and
sealed
concrete
joints
at
the
pads
and
around
the
concourses.
Sealing
of
the
manholes
has
met
with
only
limited
success,
due
to
the
occasional
need
to
access
these
manholes.
These
actions
appear
to
have
helped
reduce
the
amount
of
seepage
into
the
subgrade
in
the
1997­
1998
deicing
season,
in
turn
reducing
the
amount
of
ADF
observed
in
the
underdrains.
The
vaults
are
also
pumped
out
on
a
periodic
basis,
with
the
captured
fluids
being
recycled
onsite
or
pumped
to
Metro.
In
the
first
quarter
of
1999,
DIA
connected
selected
utility
conduits
into
the
West
Airfield
Diversion
System,
which
drains
to
the
glycol
collection
system.

The
result
of
these
measures
has
been
a
substantial
decrease
in
the
amount
of
ADF
reaching
Third
Creek,
and
a
subsequent
decrease
in
the
levels
of
COD
reported
(
see
Table
V­
2).
The
Water
Quality
Study
(
SEP
#
1)
resulted
in
numerous
recommendations
for
further
system
improvements,
as
follows:

1.
diversion
system
capacity
improvements
2.
drain
selected
utility
manholes
and
underdrains
to
dirty
system
(
completed)
3.
contain
surface
runoff
at
east
end
of
Concourse
B
commuter
gates
4.
construction
of
additional
contaminated
snow
dumps
5.
paving
of
selected
landscaped
islands
west
of
the
west
deicing
pads
6.
contaminated
snow
management
7.
revise
city
plowing
procedures
8.
increase
tenants=
awareness
Recommendation
1,"
diversion
system
capacity
improvements"
will
be
implemented
by
constructing
a
new
industrial
stormwater
containment
pond
and
upgrading
the
capacity
of
the
West
Airfield
Diversion
System,
as
stated
in
the
Compliance
Schedule
(
see
Section
VI.
E.
4.
a
of
the
Rationale).

Recommendation
2,
"
drain
selected
utility
manholes
and
underdrains
to
the
dirty
system"
has
already
been
completed.

The
need
for
implementing
Recommendation
3,
"
containment
of
runoff
at
east
end
of
B
Concourse
commuter
gates",
will
be
further
analyzed.
Due
to
infrastructure
changes
east
of
this
ramp
area,
this
recommendation
may
no
longer
be
pertinent.

Recommendations
4,
6
and
7,
regarding
construction
of
a
contaminated
snow
dump,
contaminated
snow
management
and
revision
of
City
plowing
procedures,
will
not
be
needed.
This
is
because
the
landscaped
islands
surrounding
the
deicing
pads
are
used
by
DIA
Maintenance
for
storage
of
contaminated
snow
from
the
pads,
This
contaminated
snowmelt
will
flow,
through
the
ADF
Management
System,
to
the
new
industrial
stormwater
ponds.

A
training
program
is
being
developed
to
implement
recommendation
8,
"
increase
tenant
awareness."
(
Additionally,
a
meeting
was
held
in
April,
2001
to
improve
overall
tenant
awareness
of
their
environmental
responsibilities.)

The
Division
reserves
the
right
to
require
additional
measures
to
be
implemented,
if
the
currently
planned
improvements
are
not
sufficient
to
protect
water
quality.
However,
the
Division
recognizes
that
it
is
infeasible
to
completely
eliminate
fugitive
ADF
from
site
runoff.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
13,
Permit
No.
COS­
000008
V.
PERFORMANCE
HISTORY
Additionally,
SEP
#
3,
the
water
quantity/
stormwater
drainage
study
described
above,
recommended
construction
of
a
regional
detention
pond
near
the
DIA
property
boundary
for
flood
control
purposes.
Pond
T­
239
and
the
associated
concrete
detention
structure
were
completed
in
2000.
This
is
now
the
official
monitoring
point
for
the
"
E
Outfall".

VI.
TERMS
AND
CONDITIONS
A.
Stormwater
Management
Plan
The
purpose
of
a
Stormwater
Management
Plan
(
SWMP)
is
to
identify
possible
pollutant
sources
to
stormwater
and
to
set
out
best
management
practices
that,
when
implemented,
will
reduce
or
eliminate
any
possible
water
quality
impacts.
A
SWMP
shall
be
developed
for
the
overall
site,
and
for
each
tenant
covered
by
this
permit,
and
submitted
to
the
Division.
SWMPs
shall
be
prepared
in
accordance
with
good
engineering
practices.
(
The
plan
need
not
be
completed
by
a
registered
engineer.)

The
plan
shall
identify
potential
sources
of
pollution
which
may
reasonably
be
expected
to
affect
the
quality
of
stormwater
discharges
associated
with
industrial
activity
from
the
facility.
In
addition,
the
plan
shall
describe
practices
which
will
be
used
to
reduce
the
pollutants
in
stormwater
discharges
associated
with
industrial
activity
at
the
facility
and
to
assure
compliance
with
the
terms
and
conditions
of
this
permit.
DIA
must
implement
the
provisions
of
their
SWMP
as
a
condition
of
their
permit.

DIA
submitted
a
SWMP
to
the
Division
in
May,
1994.
This
submittal
also
included
SWMPs
prepared
for
each
tenant
with
industrial
activities
exposed
to
stormwater.
The
general
SWMP
has
since
been
updated,
and
was
re­
submitted
to
and
reviewed
by
the
Division
in
draft
form.
The
revised
SWMP
will
be
resubmitted
in
final
form
within
30
days
after
the
effective
date
of
this
permit,
to
take
into
account
any
new
requirements
imposed
by
the
permit.
The
Division
reserves
the
right
to
review
the
SWMP
and
require
additional
measures
to
prevent
and
control
pollution.

The
SWMP
shall
include
the
following
items,
at
a
minimum:

1.
Industrial
activity
description
2.
Site
map
3.
Stormwater
management
controls,
including:
­
Name
of
the
SWMP
administrator
­
Identification
of
potential
pollutant
sources
and
Best
Management
Practices
­
Sampling
information
­
Preventive
maintenance
­
Good
housekeeping
­
Spill
prevention
and
response
procedures
­
Employee
training
­
Identification
of
discharges
other
than
stormwater
4.
Comprehensive
inspections
5.
Consistency
with
other
plans
(
See
Part
I.
C
of
the
permit
for
a
more
detailed
description
of
SWMP
requirements.)
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
14,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
B.
Determination
of
Action
Levels
1.
Action
Levels
a.
The
following
action
levels
will
apply
at
Outfall
E,
and
are
discussed
in
Section
VI.
B.
2.

Table
VI­
1
­­
Action
Levels
Parameter
Limitation
Rationale
COD,
mg/

100
­
action
level
c/
Best
Management
Practices/
Best
Professional
Judgment
b.
The
following
action
levels
will
apply
at
monitoring
station
C+,
and
are
discussed
in
Section
VI.
B.
2.

Table
VI­
2
 
Action
Levels
Parameter
Limitation
Rationale
COD,
mg/

200
 
action
level
c/
Best
Management
Practices/
Best
Professional
Judgment
c/
Daily
Maximum
The
permit
also
contains
a
provision
that
exceedances
caused
by
severe
natural
conditions
(
such
as
tornadoes,
widespread
flooding,
etc.),
if
adequately
documented,
shall
not
be
subject
to
enforcement
action
by
the
Division.
However,
notification
and
follow­
up
reporting
to
the
Division
will
be
required.

2.
Discussion
of
Action
Levels,
Best
Management
Practices
(
BMPs)

a.
Applicable
Federal
Effluent
Guidelines
and
Standards:
No
federal
guidelines
have
been
promulgated
for
this
type
of
facility
at
this
time
(
see
Section
IV.
A.
1,
Federal
Regulations).

b.
Discussion
of
Limitations:
The
"
action
levels"
for
COD
as
listed
above
are
not
effluent
limitations.
They
indicate
that,
when
COD
exceeds
this
level,
DIA
must
implement
additional
Best
Management
Practices
(
BMPs)
to
supplement
the
routine
BMPs
already
in
use.
These
may
include
the
reasonably
available
measures
as
defined
in
Section
VI.
B.
2.
c.
d/,
and/
or
the
BMPs
9
and
10
described
in
Section
VI.
B.
2.
c
of
the
Rationale.

The
permit
contains
a
compliance
schedule
for
the
construction
and
implementation
of
system
improvements.

The
action
levels
for
COD
were
derived
from
several
sources,
and
are
consistent
with
the
information
presented
in
EPA's
recent
study
of
the
ADF
industry.
Daily
COD
monitoring
at
outfall
E
has
shown
a
dramatic
drop
in
COD
levels
from
before
the
West
Airfield
Diversion
System
was
constructed
to
after
the
diversion
was
operational
(
see
Table
V­
2).
This
is
ascribed
to
the
various
BMPs
undertaken
during
that
time,
as
well
as
the
diversion.
In
general,
field
experience
and
review
of
the
data
indicate
that
the
system
is
functioning
satisfactorily
when
the
COD
level
is
below
100
mg/

at
E
Outfall.
However,
there
have
been
situations
where
the
COD
level
is
greater
than
100
mg/

,
and
no
odor
or
other
impacts
associated
with
high
COD
have
been
observed.
Alternately,
there
have
been
situations
where
a
COD
level
of
slightly
more
than
100
mg/

has
been
reported,
concurrent
with
operational
difficulties.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
15,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
Another
consideration
is
what
the
COD
levels
might
be
in
a
natural
setting,
with
no
human­
induced
impacts
occurring.
A
review
was
done
of
COD
data
from
stream
reaches
in
Colorado
that
are
similar
to
Third
Creek.
(
The
data
are
from
the
STORET
system,
a
nation­
wide
data
system
which
includes
monitoring
data
collected
by
the
Division,
the
U.
S.
Geological
Survey,
and
other
entities.)
The
characteristics
used
for
sample
stations
were:
non­
urbanized
areas,
minimal
slope,
with
open
areas,
and
an
intermittent
or
low
instream
flow.
The
data
indicate
a
wide
variability
in
COD
levels.
The
majority
of
sample
results
were
under
100
mg/

;
however,
there
were
also
numerous
instances
of
levels
above
100
mg/

,
with
a
high
reading
of
280
mg/

.
(
The
data
are
available
in
the
permit
file.)
In
natural
settings,
COD
can
be
caused
by
a
number
of
sources,
such
as
animal
droppings,
decaying
vegetation,
and
other
organic
material.

Thus,
while
COD
has
proven
to
be
a
very
useful
indicator
in
general,
it
is
possible
for
abnormally
high
readings
to
exist
even
when
there
are
no
causes
directly
attributable
to
DIA
activities.
Therefore,
the
Division
has
decided
to
use
a
multiple
approach
to
numeric
limits.
The
data
demonstrate
that,
in
general,
the
COD
level
at
E
Outfall
under
normal
operating
circumstances
is
below
100
mg/

.
If
the
COD
level
exceeds
100
mg/

at
E
Outfall,
the
potential
for
noncompliance
exists,
and
additional
BMPs
must
be
implemented.
However,
since
there
is
the
possibility
that
slightly
elevated
COD
levels
are
due
to
factors
not
related
to
DIA
operations,
such
exceedances
would
not
be
considered
a
permit
violation.
However,
failure
to
implement
additional
BMPs
in
this
case
would
be
a
violation.
Although
the
naturally
occurring
COD
levels
may
be
much
less
than
100
mg/

,
this
action
level
is
based
upon
a
Best
Professional
Judgment
(
BPJ)
determination
by
the
Division
for
a
technology­
based
level.

A
review
of
the
data
from
the
C+
pond
indicates
that
COD
levels
are
lower
than
the
action
level
of
200
mg/

most
of
the
time.
The
COD
action
level
at
C+
is
also
based
on
Best
Professional
Judgement,
and
represents
a
temporary
benchmark
level.
Benchmark
levels
are
the
pollutant
concentrations
which,
when
exceeded,
the
Division
has
determined
represent
a
level
of
concern.
The
benchmarks
also
provide
an
appropriate
level
to
determine
whether
a
facility's
stormwater
management
measures
are
being
successfully
implemented.
For
DIA,
the
200
mg/

action
level
is
appropriate
for
the
current
operating
conditions,
but
may
need
to
be
revised
when
the
stormwater
management
measures
are
fully
complete
(
April
1,
2002)
and
the
Receiving
Water
Study
results
are
known
(
see
Section
VI.
E.
2
of
the
Rationale).
As
is
the
case
for
the
action
levels
at
E
Outfall,
when
COD
concentrations
at
C+
exceed
200
mg/

,
DIA
must
implement
additional
BMPs
to
supplement
the
routine
BMPs
already
in
use.
These
may
include
the
reasonably
available
measures
as
defined
in
Part
I.
D.
2
of
the
permit
The
action
levels
are
based
on
a
combination
of:
an
analysis
of
the
potential
instream,
naturally
occurring
conditions,
the
aesthetic
impacts,
and
a
Division­
based
Best
Professional
Judgment
determination
for
a
technology­
based
level,
i.
e.,
the
achievable
levels
based
on
the
stormwater
management
technology
which
is
technically
and
economically
feasible
for
the
site.
The
Division
has
determined
that
DIA
is
utilizing
a
state­
of­
the­
art
facility
in
terms
of
glycol
management,
in
comparison
with
other
airport
sites
in
the
nation.
This
determination
is
supported
by
EPA's
recent
study
of
the
ADF
industry.
EPA
concluded,
in
part,
that
if
all
airports
across
the
country
achieved
as
high
a
percentage
of
ADF
collection
as
DIA,
the
result
would
be
a
significant
positive
impact
on
water
quality
across
the
nation.
Thus,
this
level
of
glycol
management
and
treatment
at
DIA
is
considered,
at
this
time,
to
satisfy
the
requirement
for
a
best
practical,
available,
and
economically
achievable
technology
for
establishing
the
COD
levels
in
this
permit.
Once
any
final
technology­
based
levels
have
been
determined
by
EPA,
the
Division
will
evaluate
these
levels
in
relation
to
the
limits
in
this
permit.

The
Division
considered
setting
an
effluent
limit
based
on
the
Dissolved
Oxygen
(
DO)
Water
Quality
Standard
(
WQS)
for
Third
Creek
(
5.0
mg/
minimum),
but
has
found
that
further
study
is
warranted
before
an
appropriate
limit
can
be
established.
(
See
discussion,
Section
VI.
E.
2
of
the
Rationale.)
Although
the
WQS
for
Segment
16
of
the
Upper
South
Platte
River
remain
in
effect,
they
were
originally
derived
from
a
1976
EPA
publication
and
were
not
based
on
historic
ambient
water
quality
data
from
the
DIA
watersheds.

Data
from
DIA
over
the
past
two
years
show
that
low
DO
concentrations
can
routinely
occur
even
when
no
impacts
from
DIA
are
present.
DO
levels,
especially
in
intermittent
streams,
can
vary
widely
based
on
a
number
of
factors,
including
flow
rate,
pooling,
temperature,
stream
bed
characteristics,
direct
rainfall,
and
degree
of
turbulence,
in
addition
to
organic
loading.
In
most
cases,
it
would
be
difficult
to
ascribe
DO
levels
solely
to
DIA
activities.
As
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
16,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
discussed
in
Regulation
No.
31.7(
1)(
b),
natural
conditions
can
cause
or
contribute
to
allowable
exceedances
of
numeric
WQS.
Since
there
is
no
clear
idea
of
what
causes
these
fluctuations,
or
if
they
are
naturally
occurring,
it
is
not
reasonable
to
impose
an
effluent
limit
and
hold
DIA
responsible
for
the
DO
levels
in
the
creek,
at
least
until
the
creek
is
better
understood.
Therefore,
DIA
will
conduct
an
in­
depth
study
of
Third
Creek
(
see
Section
VI­
E.
2
of
the
Rationale),
with
a
focus
on
DO.
The
Division
will
evaluate
the
completed
study,
and
consider
the
application
of
appropriate
effluent
limits
via
a
permit
amendment.

In
the
meantime,
the
Division
has
extensive
COD
data
available,
indicating
that
deicing/
anti­
icing
activities
typically
have
a
direct
bearing
upon
the
instream
COD
levels.
Thus,
COD
measures
the
potential
impact
that
DIA
activities
have
on
the
stream,
with
reasonable
accuracy
(
see
above
discussion).
Using
a
COD
limit
provides
a
far
greater
correlation
between
instream
levels
and
DIA
activities,
and
so
is
the
limiting
factor
at
this
time.

An
effluent
limitation
for
PG
is
not
included
in
the
permit.
Although
PG
is
the
main
source
of
oxygen
depletion
in
Third
Creek,
it
can
begin
to
break
down
relatively
quickly.
High
levels
of
oxygen
demand
can
remain
even
when
no
PG
is
present.
Monitoring
data
from
the
past
two
years
indicates
that
the
levels
of
PG
can
fluctuate
greatly,
without
a
corresponding
fluctuation
in
the
COD
levels.
Thus,
it
is
not
considered
a
reliable
indicator
of
water
quality
impacts.
Monitoring
is
still
required
on
a
monthly
basis,
however,
to
provide
information
on
when
elevated
levels
may
be
present
and
under
what
circumstances.

c.
Best
Management
Practices
(
BMPs):
A
wide
variety
of
BMPs
are
used
at
DIA
for
managing
ADF,
as
listed
in
their
SWMP.
Including
a
BMP
in
the
SWMP
means
that
it
becomes
a
permit
requirement,
and
must
be
carried
out
in
order
to
remain
in
compliance
with
the
permit.
Usually,
BMPs
as
listed
in
a
SWMP
can
be
amended
as
needed,
and
are
sent
to
the
Division
for
review.
The
following
BMPs,
among
others,
are
included
in
DIA=
s
SWMP.
These
BMPs
are
also
listed
in
the
permit
(
meaning
that
they
cannot
be
changed
without
a
permit
amendment
or
modification,
as
opposed
to
only
a
SWMP
modification).
(
Note
that
in
the
case
of
pond
004
(
General
Aviation),
these
will
apply
only
when
discharge
to
Metro
begins
from
that
pond.
This
has
not
yet
occurred.)

1)
Full
deicing
activities
are
normally
restricted
to
the
areas
at
the
site
identified
in
Figure
2.
Under
special
situations,
Airport
Operations
may
grant
permission
for
full
deicing
at
the
A
and
C
concourse
gates
where
it
is
not
normally
allowed.
This
would
be
necessitated
by
operational
considerations
of
mechanical
or
safety
issues.
For
example,
if
the
pads
are
at
capacity
so
that
some
planes
do
not
have
access,
at
a
time
when
there
is
heavy
traffic
flow,
overcrowding
can
create
a
hazard
at
the
ramp
and
gate
areas.
In
addition,
there
can
be
mechanical
malfunctions
whereby
planes
cannot
get
to
the
pad.
Full
deicing
at
A
and
C
concourse
gates
will
only
be
allowed
when
authorized
by
the
Airport
Manager
with
concurrence
by
Environmental
Services.
Such
concurrence
would
only
be
given
if
pond
capacity
were
available
to
handle
the
extra
loading.
Historically,
this
has
happened
on
less
than
0.5%
of
deicing
event
departures.
Full
deicing
at
any
other
areas
is
prohibited.

Figure
2
shows
only
those
areas
where
deicing
is
allowed
as
of
the
issuance
date
of
this
permit.
Future
modifications
to
deicing
areas
during
the
permit
term
will
not
necessarily
result
in
a
change
to
Figure
2,
but
rather
must
be
reflected
in
DIA's
SWMP.

2)
To
the
maximum
extent
practicable,
ADF
mixed
with
stormwater
runoff
collected
from
the
three
west
deicing
pads
is
recycled
at
the
on­
site
recycling
facilities.
However,
if
the
concentration
of
spent
deicing
fluid
received
by
the
facility
is
too
low
for
recycling
(
due
to
technical
or
economic
factors),
the
fluid
is
instead
pumped
to
Metro
for
disposal.

3)
Each
of
the
industrial
stormwater
ponds
has
the
capability
to
discharge
to
Metro.
All
the
ponds
but
one
are
constructed
with
two
cells,
such
that
efficient
pumping
to
Metro
from
one
cell
and
inflow
to
the
other
can
occur
concurrently.
Since
DIA=
s
Metro
contribution
permit
limits
the
amount
of
BOD
that
can
be
sent
to
Metro,
the
concentration
of
BOD
in
the
pumped
water
must
be
determined,
so
that
pumping
rates
can
be
established.
DIA
shall
maintain
analytical
equipment
on­
site
to
allow
efficient
coordination
of
pumping
rates
with
concentrations.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
17,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
4)
Level
monitoring
procedures
will
be
used
to
allow
accurate
and
timely
monitoring
of
industrial
stormwater
pond
levels.
DIA
environmental
staff
will
observe
the
level
of
each
pond
at
least
daily
during
periods
of
significant
precipitation
or
periods
of
significant
runoff.
Observations
of
pond
levels
will
be
conducted
at
least
weekly
during
periods
of
dry
weather.

5)
Since
the
capacity
of
the
industrial
stormwater
ponds
is
limited,
the
levels
in
the
ponds
shall
be
managed
to
maintain
the
maximum
practicable
capacity
available
at
all
times
by
pumping
to
Metro
up
to
the
BOD
permit
limit,
or
to
the
pumping
capacity
of
the
pumps,
whichever
is
less.

DIA
environmental
staff
will
determine
which
industrial
stormwater
pond
has
the
highest
priority
for
pumping
to
Metro.
Factors
to
be
considered
in
setting
the
pumping
priority
include
the
pond
levels
and
their
rates
of
change,
the
ponds=
COD
concentrations,
and
climactic
conditions.

6)
Daily
logs
of
observations
will
be
maintained
by
DIA
environmental
laboratory/
field
staff
and
periodically
reviewed
by
the
environmental
engineering/
scientist
staff.

7)
If
any
of
the
various
utility
vaults,
sumps
and
manholes
surrounding
the
concourses
and
on
other
locations
around
the
airfield
become
filled
with
water
which
must
be
pumped
out,
the
pumped
water
is
inspected,
tested
and
disposed
of
as
appropriate.
It
will
not
be
discharged
into
the
clean
water
system
without
prior
Division
approval.

8)
In
order
to
avoid
unnecessary
hydraulic
load
to
the
industrial
stormwater
ponds,
thus
reducing
the
possibility
of
overflow,
DIA
personnel
will
have
the
option
of
closing
the
inlet
valves
to
the
industrial
stormwater
ponds
and
diversion
system
valves
during
times
when
runoff
to
the
pond
is
clean
(
COD
at
30
minute
digestion
time
is
<
75
mg/

)
.
This
is
expected
to
occur
in
late
spring
and
summer.
Periodic
sampling
of
the
discharge
for
COD
shall
be
required,
at
a
frequency
which,
based
on
site
and
weather
conditions,
reflects
DIA's
best
judgment
in
ensuring
that
discharges
greater
than
75
mg/

do
not
occur.
Additional
sampling
will
be
required
at
each
instance
of
such
closures,
as
outlined
in
Part
I.
B.
1.
c
of
the
permit;
however,
Division
notification
is
not
required.

9)
In
general,
DIA
must
utilize
all
elements
of
the
glycol
management
system.
However,
in
the
event
that
an
industrial
stormwater
pond
is
nearing
capacity,
but
the
water
flowing
into
the
pond
is
not
clean,
and
all
other
reasonably
available
and
applicable
measures
d/
have
been
employed
to
prevent
environmental
impacts
from
this
situation,
DIA
personnel
will
have
the
option
of
closing
the
inlet
valve
to
avoid
overfilling
and
overflowing
the
pond.
Prior
to
making
this
decision,
DIA
personnel
will
determine
the
relative
COD
concentration
of
the
water
in
the
pond
versus
the
water
currently
flowing
to
the
pond
(
based
on
a
30
minute
digestion
period),
and
close
the
inlet
valve
if
the
pond
contents
are
determined
to
be
more
concentrated.
Division
notification
will
be
required
within
8
hours
of
valve
closure.
Additional
sampling
will
be
required
at
each
instance
of
such
closure,
as
outlined
in
Part
I.
B.
1.
c
of
the
permit.

10)
In
the
event
that
an
industrial
stormwater
pond
is
nearing
capacity,
and
the
water
in
the
pond
has
a
lower
COD
concentration
than
the
water
flowing
to
the
pond,
and
all
other
reasonably
available
and
applicable
measures
d/
have
been
employed
to
prevent
environmental
impacts
from
this
situation,
DIA
shall
have
the
option
to
release
water
from
the
pond
to
the
clean
system,
in
order
to
maintain
or
increase
capacity
for
the
higher
concentration
inflow.
The
COD
reading
from
the
pond
cell
contents
must
then
be
less
than
the
COD
reading
of
the
pond
inflow
(
based
on
30
minute
digestion
period)
for
release
to
begin.
Sampling
of
pond
contents
and
inflow
will
continue
at
least
every
4
hours
throughout
the
discharge
operation,
with
the
COD
of
pond
contents
remaining
less
than
that
of
the
inflow
for
discharge
to
continue.
Additional
sampling
will
be
required
at
each
instance
of
such
closures,
as
outlined
in
Part
I.
B.
1.
c
of
the
permit.
Division
notification
must
be
made
within
8
hours
of
starting
release.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
18,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
11)
Regardless
of
the
volume
of
water
in
the
industrial
stormwater
pond,
or
of
pond
inflow
conditions,
if
the
water
in
the
pond
cell
is
below
75
mg/

COD,
DIA
shall
have
the
option
to
release
it
to
the
clean
stormwater
system.
Sampling
must
continue
at
least
every
4
hours
while
release
continues,
with
the
same
sample
results
being
required.
Additional
sampling
will
be
required
at
each
instance
of
such
discharge,
as
outlined
in
Part
I.
B.
1.
c
of
the
permit.
Division
notification
will
be
required
within
8
hours
of
starting
release.

d/
Reasonably
available
measures
can
include,
but
are
not
limited
to,
additional
small
scale
aeration,
requesting
Metro
to
allow
increased
pumping
volume
on
a
temporary
basis,
or
other
forms
of
water
management.
These
particular
measures
are
not
required
in
every
case;
unique
situations
can
arise
at
DIA
that
require
unique
solutions.
It
is
the
permittee=
s
responsibility
to
choose
the
most
appropriate
measures,
and
then
to
provide
adequate
documentation
and
justification
as
to
the
reasoning
behind
and
efficacy
of
those
measures.

BMPs
#
8
through
11
allow
the
permittee
a
great
deal
of
freedom
in
operating
their
collection
system.
They
are
designed
to
reduce,
to
the
greatest
extent
practical,
the
COD
concentration
of
water
flowing
to
the
clean
stormwater
system,
and
to
minimize
the
amount
of
water
diverted
from
the
natural
waterway.
It
should
be
recognized
that
the
COD
samples
are
not
necessarily
representative
of
the
entire
pond
contents
nor
of
all
pond
inflow.
These
decisions
must
usually
be
made
very
quickly,
under
demanding
conditions.
BMP
#
8
will
probably
be
the
most
commonly
employed
of
these
options.
The
conditions
required
for
implementation
of
BMPs
#
10
and
11
are
very
unlikely,
but
they
are
included
for
completeness.
These
BMPs
are
considered
Atime
critical
decisions,@
therefore
the
30
minute
COD
digestion
period
is
used,
although
it
is
somewhat
less
accurate
than
the
2­
hour
digestion
period.
Full
documentation
and
justification
will
be
required
by
the
permittee
whenever
BMPs
#
9
through
11
are
used.
COD
readings
are
observed
in
Third
Creek
significantly
above
50
mg/
l
when
no
impacts
from
DIA
are
present.
The
action
level
is
100
mg/
l.
Therefore,
75
mg/
l
is
considered
a
reasonable
intermediate
COD
value
to
consider
"
clean"
for
the
purposes
of
BMPs
#
8,
9
and11
as
discussed
above.
Sampling
and
analytical
methods
can
also
result
in
considerable
statistical
variation
in
measured
COD
values
from
the
same
flow
stream.
For
this
reason
,
for
COD
results
of
less
than
100
mg/

,
if
subsequent
COD
measurements
from
a
particular
sample
point
vary
by
less
than
10%
from
the
initial
COD
measurement
at
that
point,
it
can
be
considered
for
the
purpose
of
valve
control
during
operation
of
these
BMPs
that
the
COD
has
not
changed.

d.
Antidegradation:
Since
the
receiving
water
is
Use
Protected,
an
antidegradation
review
is
not
required
pursuant
to
section
31.8(
2)(
b)
of
The
Basic
Standards
and
Methodologies
for
Surface
Water.

C.
Monitoring
1.
Effluent
Monitoring:

a.
Effluent
monitoring
will
be
required
at
Sub­
basin
A
outfall,
Sub­
basin
C
outfall,
Sub­
basin
C+
monitoring
station,
Subbasin
D
outfall,
and
E
Outfall
to
Third
Creek,
as
shown
in
Table
VI­
4.
Refer
to
the
permit
for
locations
of
monitoring
points.
However,
sampling
at
Sub­
basin
C
outfall
and
Sub­
basin
D
outfall
will
only
be
required
once
the
new
sampling
equipment
has
been
installed,
or
by
December
31,
2001,
whichever
comes
first.
See
Discussion,
Section
VIII.
5
of
the
Rationale.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
19,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
Table
VI­
4
­­
Monitoring
Requirements
­
Sub­
basin
A
outfall,
Sub­
basin
C
outfall,
Sub­
basin
C+
monitoring
station,
Sub­
basin
D
outfall,
E
Outfall
to
Third
Creek
Parameter
Measurement
Frequency
Sample
Type
Flow,
MGD
Quarterly
Instantaneous
or
Continuous
Chemical
Oxygen
Demand,
mg/

Daily
e/
Grab
Oil
and
Grease,
mg/

Monthly
Grab
Oil
and
Grease,
mg/

Weekly
Visual
pH,
s.
u.
Monthly
Grab
Total
Suspended
Solids,
mg/

Monthly
Grab
Acetate,
mg/

Monthly
Grab
Propylene
Glycol,
mg/

Monthly
f/
Grab
Ethylene
Glycol,
mg/

Quarterly
Grab
BOD5,
mg/

Quarterly
Grab
Total
Petroleum
Hydrocarbons
(
Jet
Fuel),
mg/

Quarterly
Grab
Total
Phosphorus,
as
P,
mg/

Quarterly
Grab
Nitrate
plus
Nitrite,
as
N,
mg/

Quarterly
Grab
Total
Kjeldahl
Nitrogen
(
TKN),
as
N,
mg/

Quarterly
Grab
Chloride,
mg/

Quarterly
Grab
e/
The
daily
monitoring
for
COD
is
used
as
a
process
control,
and
is
only
required
when
flow
conditions
and
other
factors,
in
the
judgment
of
DIA
personnel,
will
allow
representative
sampling.
While
representative
monitoring
should
be
performed
if
reasonably
possible,
operational
difficulties,
such
as
weather
or
personnel
restraints,
will
also
be
considered
when
reviewing
compliance
with
the
requirements.
f/
The
samples
should
be
taken
during
or
following
a
deicing
event,
at
such
time
to
be
as
representative
of
the
discharge
from
the
deicing
event
as
possible.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
20,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
b.
Effluent
monitoring
will
be
required
at
Second
Creek
(
near
the
west
end
of
runway
7/
25,
north
of
Pena
Blvd),
and
Runway
35R
(
east
side,
north
end),
as
shown
in
Table
VI­
5.
Refer
to
the
permit
for
locations
of
monitoring
points.

Table
VI­
5
­­
Monitoring
Requirements
­
Second
Creek,
Runway
35R
Parameter
Measurement
Frequency
Sample
Type
Chemical
Oxygen
Demand,
mg/

Weekly
g/
Grab
Dissolved
Oxygen,
mg/

Weekly
g/
i/
Grab
pH,
s.
u.
Weekly
g/
Grab
BOD5,
mg/

2X/
Month
g/
Grab
Acetate,
mg/

2X/
Month
g/
Grab
Propylene
Glycol,
mg/

2X/
Month
g/
h/
Grab
Oil
and
Grease,
mg/

2X/
Month
Visual
Oil
and
Grease,
mg/

Monthly
Grab
Total
Suspended
Solids,
mg/

Monthly
Grab
Flow,
MGD
Quarterly
Instantaneous
or
Continuous
Ethylene
Glycol,
mg/

Quarterly
Grab
Total
Petroleum
Hydrocarbons
(
Jet
Fuel),
mg/

Quarterly
Grab
Total
Phosphorus,
as
P,
mg/

Quarterly
Grab
Nitrate
plus
Nitrite,
as
N,
mg/

Quarterly
Grab
Total
Kjeldahl
Nitrogen
(
TKN),
as
N,
mg/

Quarterly
Grab
Chloride,
mg/

Quarterly
Grab
g/
Samples
may
be
taken
on
a
monthly
basis
during
June,
July
and
August
of
each
year.
h/
The
samples
should
be
taken
during
or
following
a
deicing
event,
at
such
time
to
be
as
representative
of
the
discharge
from
the
deicing
event
as
possible.
i/
DO
sampling
will
not
be
required
in
stagnant
water;
if
no
observable
flow
exists,
no
sampling
is
necessary.
If
sampling
conditions
are
such
(
e.
g.,
very
low
flow)
that
non­
representative
results
are
expected,
such
conditions
shall
be
recorded
and
reported.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
21,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
c.
Effluent
monitoring
will
be
required
at
E
Outfall,
Sub­
basin
C+
monitoring
station
and
Third
Creek
at
112th
Ave.,
as
shown
in
Table
VI­
6.
Refer
to
the
permit
for
locations
of
monitoring
points.

Table
VI­
6
­­
Monitoring
Requirements
­
E
Outfall
to
Third
Creek,
Sub­
basin
C+
monitoring
station,
Third
Creek
at
112th
Ave.

Parameter
Sample
Location
Measurement
Frequency
Sample
Type
Dissolved
Oxygen,
mg/

E
Outfall
to
Third
Creek,
Third
Creek
at
112th
Ave.
Daily
j/
Grab
Dissolved
Oxygen,
mg/

Sub­
basin
C+
monitoring
station
3X/
Week
j/
Grab
j/
DO
sampling
will
not
be
required
in
stagnant
water;
if
no
observable
flow
exists,
no
sampling
is
necessary.
If
sampling
conditions
are
such
(
e.
g.,
very
low
flow)
that
non­
representative
results
are
expected,
such
conditions
shall
be
recorded
and
reported.

2.
Dry
Weather
Monitoring:
Monitoring
is
also
required
whenever,
during
the
inspection
of
outfalls,
the
DIA
staff
observes
or
suspects
an
illicit
discharge.
The
required
parameters,
which
are
based
on
the
industrial
activities
within
the
drainage
area,
are
listed
in
Part
I.
B.
1.
b
of
the
permit.
Additional
parameters
may
be
added
to
the
initial
screening,
depending
upon
the
nature
of
the
discharge
and
attendant
conditions.

3.
Changes
to
Monitoring
Requirements:
Several
of
the
parameters
for
which
monitoring
is
required
are
not
believed
to
be
significant
sources
of
pollution
at
this
facility.
For
the
sampling
points
listed
in
Table
VI­
4
and/
or
Table
VI­
5,
the
sampling
frequencies
for
Oil
and
Grease,
pH,
Acetate,
Chloride
and
Total
Suspended
Solids
could
be
reduced
in
the
event
that
DIA
can
provide
adequate
justification,
based
on
each
of
the
following
items:

a.
The
permittee
can
provide
at
least
two
years
of
sampling
data
for
the
facility
(
for
each
discharge
point
where
sampling
is
required),
for
each
of
the
parameters
listed
above.
(
The
samples
must
be
from
at
least
two
different
calendar
years,
and
taken
in
1998
or
after.)
A
summary
of
all
available
monitoring
data
should
be
included
in
the
amendment
request,
whether
or
not
it
was
previously
submitted
to
the
Division.

b.
The
industrial
activities
at
the
site
(
such
as
materials
handling
and
storage,
chemical
use,
waste
disposal
practices,
erosion
controls,
and
other
types
of
industrial
activities
as
defined
in
Part
I.
B.
5.
b
of
the
permit)
have
not
changed
since
the
samples
were
taken
(
and
are
not
expected
to
change),
in
any
way
that
could
have
an
adverse
impact
on
stormwater
quality.

c.
The
sample
results
for
the
parameters
listed
above
do
not
demonstrate
any
problems
with
stormwater
quality.
The
permittee
may
compare
their
data
with
other
water
quality
data,
such
as
EPA's
list
of
stormwater
permit
benchmarks
from
the
multi­
sector
permit,
or
the
federal
Nationwide
Urban
Runoff
Program
(
NURP)
data.

The
Division
will
make
a
determination
on
the
merits
of
the
amendment
request
within
45
days
of
receipt.
If
the
request
is
deemed
adequate,
the
permittee
will
be
notified
and
their
permit
amended
to
change
the
sampling
requirement
for
the
outfall(
s)
in
question,
for
the
remainder
of
the
permit
term.
If
the
request
is
not
considered
adequate,
the
permittee
shall
be
notified
of
the
reason
for
the
Division's
determination.
The
permittee
will
also
be
able
to
re­
petition
the
Division
after
another
year
of
sampling
data
has
been
obtained.

D.
Reporting
1.
Discharge
Monitoring
Report:
DIA
must
submit
a
Discharge
Monitoring
Report
(
DMR)
on
a
monthly
basis
to
the
Division.
This
report
should
contain
the
required
summarization
of
the
test
results
for
the
parameters
shown
in
Tables
VI­
4,
VI­
5,
VI­
6
of
the
Rationale
and
Part
I.
B.
1
of
the
permit.
See
the
permit,
Part
I.
B.
2.
for
details
on
such
submission.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
22,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
2.
Annual
Report:
The
permittee
will
be
required
to
submit
an
Annual
Report,
covering
October
1
through
September
30,
on
the
overall
compliance
with
the
SWMP.
The
Annual
Report
will
be
due
to
the
Division
on
or
before
November
28
of
each
year.
An
Annual
Report
form
will
be
provided
by
the
Division.
(
See
Part
I.
F.
1
of
the
permit
for
a
list
of
Annual
Report
requirements.)

3.
Additional
Reporting:
DIA
must
continue
to
submit
a
monthly
status
report
on
the
status
of
glycol
management
at
DIA,
at
least
until
the
construction
compliance
schedule
items
have
been
completed.
After
that
time,
the
monthly
status
report
shall
be
required
until
such
time
as
the
Division
determines
that
the
increased
reporting
frequency
is
not
necessary,
based
on
DIA=
s
compliance
history.
(
See
Part
I.
F.
2
of
the
permit.)

4.
Reporting
to
Municipality:
Any
permitted
facility
discharging
to
a
municipal
storm
sewer
shall
provide
the
municipality
with
a
copy
of
the
permit
application,
Annual
Reports,
and/
or
Discharge
Monitoring
Reports,
upon
request.
A
copy
of
the
SWMP
shall
also
be
provided
to
the
municipality
upon
request.

5.
Special
Reports:
Special
reports
are
required
in
the
event
of
a
spill,
bypass,
or
other
noncompliance.
See
Part
II.
A.
of
the
permit
for
reporting
requirements.

E.
Additional
Terms
and
Conditions
1.
Aircraft
Deicing
Fluids
(
ADF)
Toxicity:
ADF
formulations
contain
various
additives
to
enhance
the
desired
properties
of
the
deicing
medium.
These
include
AdPack
(
corrosion
inhibitors,
surfactants,
and
buffers)
and
4(
5)­
methylbenzotriazole
(
MEBT)
(
fire
retardant)
as
well
as
others.
It
is
suspected
that
MEBT
is
detrimental
to
soil­
borne
organisms
that
biodegrade
propylene
glycol
(
PG)
and
that
AdPack
contains
constituents
that
are
toxic
to
aquatic
organisms.
Due
to
the
potential
negative
effects
of
ADF
additives
(
AdPack
and
MEBT)
in
general,
it
is
desirable
to
ascertain
the
impact
of
such
additives
on
the
State
Waters
involved
with
the
discharge.

EPA
has
recently
conducted
an
effluent
limitation
guideline
study
on
aircraft
deicing.
The
study
includes
an
assessment
of
the
need
for
various
testing,
including
toxicity.
The
final
report
was
released
at
the
end
of
1999,
and
concluded
that
no
ADF
effluent
limits
or
guidelines
would
be
developed
at
this
time.
Additionally,
a
subcommittee
of
the
Society
of
Automotive
Engineers
(
SAE),
which
sets
all
specifications
required
of
ADF,
is
working
with
the
Air
Transport
Association
(
ATA)
on
approving
environmental
testing
requirements
and
procedures
(
for
deicing
anti­
icing
and
runway
deicers),
and
on
testing
with
the
intent
of
obtaining
baseline
data
and
subsequently
considering
toxicity
data.
The
deicer
manufacturers
often
change
the
formulations,
which
are
proprietary,
and
DIA
does
not
have
control
over
the
specific
formulations
that
the
different
airlines
use
(
beyond
a
general
provision
that
propylene
glycol
be
used
instead
of
ethylene
glycol).

Therefore,
the
Division
has
determined
that
it
would
not
be
productive
at
this
time
to
require
DIA
to
conduct
a
similar
study.
If
federal
effluent
limits
or
guidelines
are
adopted
during
the
term
of
this
permit,
they
would
be
incorporated
in
the
permit
by
amendment.
The
Division
retains
the
right
to
require
that
DIA
conduct
a
follow­
up
study
on
the
impacts
of
the
discharge
of
ADF
on
Third
Creek,
if
needed.
Such
a
study
could
include
accumulative
impacts,
probable
dilution
factors,
the
environmental
fate
of
the
additives,
and
an
aquatic
organism
assessment
of
affected
areas.

2.
Receiving
Water
Study:
DIA
has
developed
a
work
plan
to
conduct
a
receiving
water
study
to
support
development
of
permit
conditions
and
water
quality
standards
for
dissolved
oxygen.
This
work
plan
details
the
physical,
chemical
and
biological
data
to
be
collected
and
analyzed
to
derive
permit
conditions
and
limitations.
It
contains
a
description
of
data
needs,
proposed
sampling,
modeling
efforts,
project
schedule,
and
study
deliverables.
This
study
will
be
a
multi­
year
study
designed
to
address
system
constraints,
permit
limits,
water
quality
standards
(
dissolved
oxygen)
and
the
use
classification
of
receiving
waters
which
surround
DIA.

3.
Signatory
and
Certification
Requirements:
Signatory
and
certification
requirements
for
reports
and
submittals
are
discussed
in
Part
I.
F.
6.
of
the
permit.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
23,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
4.
Compliance
Schedules:
Except
as
provided
below,
compliance
with
the
terms
and
conditions
of
this
permit,
including
the
Stormwater
Management
Programs,
shall
be
required
by
the
effective
date
of
the
permit.

a.
As
per
the
Water
Quality
Study
(
see
discussion,
Section
V.
B.
2
of
the
Rationale),
and
as
modified
by
various
correspondence
and
the
final
construction
plans
(
submitted
to
the
Division
on
July
12,
2001),
DIA
will
complete
the
following
construction
projects
by
the
dates
indicated:

1)
Paving
of
selected
portions
of
certain
islands
adjacent
to
the
west
deicing
pads
for
use
as
contaminated
snow
dumps
and/
or
modification
of
collection
structures
to
collect
snowmelt
and
to
collect
additional
subsurface
flows,
to
be
completed
by
April
1,
2002
k/.

2)
Increased
capacity
of
the
dirty
water
conveyance
system,
and
construction
of
at
least
22
million
gallons
of
new
containment
capacity
for
the
collection
of
dirty
stormwater,
to
be
implemented
as
indicated
in
Table
VI­
7,
above.

3)
Repair
of
the
existing
B­
Concourse
glycol
collection
system
by
January
1,
2000
to
facilitate
additional
recycling
of
deicing
fluids
from
full
gate
deicing
activities
(
completed).

Table
VI­
7
­­
Compliance
Schedule
­
Construction
Activity
Deadline
Notice
to
Proceed
for
design
contract
July
21,
1999
(
completed)

Design
complete
September
15,
2000
(
completed)

Notice
to
Proceed
for
construction
contract
February
1,
2001
(
completed)

Construction
complete
and
system
start­
up
December
15,
2001
Facility
fully
operational
April
1,
2002
k/

k/
This
date
may
be
extended
by
the
Division
if
insufficient
precipitation
is
received
by
then
to
allow
for
a
full
operational
testing
of
the
new
facilities.

b.
The
permittee
shall
complete
the
specified
activities
by
April
1,
2003,
in
accordance
with
the
following
schedule
of
compliance,
as
approved
by
the
Division.

Table
VI­
8
­­
Compliance
Schedule
 
Receiving
water
study
Activity
Deadline
Draft
study
work
plan
completed
March
30,
2001
(
completed)

Final
study
work
plan
completed
July
1,
2001
(
completed)

Data
collection
completed
December
31,
2002
Report
submitted
to
Division
April
1,
2003
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
24,
Permit
No.
COS­
000008
VI.
TERMS
AND
CONDITIONS
The
permittee
has
submitted
a
study
work
plan
to
the
Division.
The
plan
includes
data
collection
and
analysis,
reviewing
the
findings
with
the
Division
and
EPA,
and
submitting
a
final
report.

The
results
of
the
initial
study
may
indicate
the
need
for
additional
phases
of
study;
in
that
case,
the
additional
phases
will
automatically
be
included
in
the
permit
as
compliance
schedule
items.

For
each
activity
outlined
in
Tables
VI­
7
and
VI­
8,
above,
the
permittee
shall
be
required
to
submit
a
report
of
progress
to
the
Division,
no
later
than
14
calendar
days
following
the
identified
date.

F.
Waste
Minimization/
Pollution
Prevention
Waste
minimization
and
pollution
prevention
are
two
terms
that
are
becoming
increasingly
more
common
in
industry
today.
Waste
minimization
includes
reducing
the
amount
of
waste
at
the
source
through
changes
in
industrial
processes,
and
reuse
and
recycling
of
wastes
for
the
original
or
some
other
purpose
(
such
as
materials
recovery
or
energy
production).
Pollution
prevention
goes
hand­
in­
hand
with
waste
minimization.
If
the
waste
is
eliminated
at
the
front
of
the
line,
it
will
not
have
to
be
treated
at
the
end
of
the
line.
The
direct
benefits
to
the
industry
are
often
significant,
both
in
terms
of
increased
profit
and
in
public
relations.
This
program
can
affect
all
areas
of
process
and
waste
control
with
which
an
industry
deals.
Elimination
or
reduction
of
a
wastewater
pollutant
can
also
result
in
a
reduction
in
an
air
pollutant
or
a
reduction
in
the
amount
of
hazardous
materials
which
must
be
handled
or
disposed.

This
discharge
permit
does
not
specifically
dictate
waste
minimization
conditions
at
this
time.
The
Division
does
strongly
encourage
the
permittee
to
continue
working
on
developing
and
implementing
a
waste
minimization
plan.
Several
industries
have
already
developed
plans
and
found
that
implementation
resulted
in
substantial
savings.
Both
the
Colorado
Department
of
Public
Health
and
Environment
and
the
Environmental
Protection
Agency
(
EPA)
have
information
and
resources
available.
For
more
in­
depth
information,
please
contact
these
agencies.

Kathryn
Dolan
January
31,
2001
VII.
REFERENCES
A.
Camp
Dresser
&
McKee
Inc.
Water
Quality
Study
Final
Report.
Denver:
as
commissioned
by
Denver
International
Airport,
9/
30/
98.

B.
Colorado
Department
of
Public
Health
and
Environment,
Water
Quality
Control
Commission.
Regulation
No.
31
The
Basic
Standards
and
Methodologies
for
Surface
Water
(
5
CCR
1002­
31).
Denver:
CDPHE,
as
revised
1/
12/
1998
and
effective
3/
2/
98.

C.
Colorado
Department
of
Public
Health
and
Environment,
Water
Quality
Control
Commission.
Regulation
No.
38
Classification
and
Numeric
Standards
for
South
Platte/
Laramie/
Republican/
Smoky
Hill
River
Basins.
Denver:
CDPHE,
as
revised
11/
9/
1998
and
effective
12/
30/
98.

D.
Colorado
Department
of
Public
Health
and
Environment,
Water
Quality
Control
Commission.
Regulation
No.
61
Colorado
Discharge
Permit
System
Regulations.
(
5
CCR
1002­
61).
Denver:
CDPHE,
as
revised
3/
9/
99
and
effective
4/
30/
99.

E.
Stednick,
John
D.,
Ph.
D.,
Mountain
River
Associates,
Inc.
Water
Quality
Monitoring
for
Propylene
Glycol
in
Third
Creek.
Fort
Collins:
as
commissioned
by
the
Farmer=
s
Reservoir
and
Irrigation
Company,
5/
28/
97.

F.
U.
S.
Government,
Office
of
the
Federal
Register,
National
Archives
and
Records
Administration.
Code
of
Federal
Regulations
(
Parts
400
to
424).
Washington:
7/
1/
96.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
25,
Permit
No.
COS­
000008
VIII.
CHANGES
AFTER
PUBLIC
NOTICE
Comments
on
the
draft
permit
were
received
from
DIA
and
the
Farmer's
Reservoir
and
Irrigation
Company
(
FRICO).
The
comments
that
resulted
in
changes
to
the
permit
and/
or
rationale
are
discussed
below.
The
Division's
response
to
FRICO's
comment
letter
is
available
for
review
in
the
permit
file.
In
addition,
other
changes
were
made
by
the
Division,
as
discussed
below.

1.
FRICO
pointed
out
that
the
classifications
for
some
of
the
receiving
waters
had
changed.
The
revised
Water
Quality
Standards
(
WQS)
have
been
included
in
Sections
III.
A.
1
and
III.
A.
2
of
the
Rationale.

2.
FRICO
expressed
concern
that
full
deicing
could
take
place
at
areas
other
than
those
authorized.
A
statement
was
added
to
the
permit
clarifying
that
full
deicing
is
only
allowed
at
the
areas
identified
in
Part
I.
D.
2.
a
of
the
permit.
New
areas
may
be
added
if
included
in
the
SWMP
and
adequate
preventative
measures
taken
(
see
discussion
under
Item
3,
below).
In
addition,
the
`
special
conditions'
authorizing
full
deicing
at
Concourses
A
and
C
were
questioned.
A
fuller
explanation
of
the
circumstances
and
requirements
has
been
added
to
Section
VI.
B.
2.
c.
1
of
the
Rationale
and
Part
I.
D.
2.
a
of
the
permit.

3.
DIA
asked
that
the
BMPs
described
in
Parts
I.
D.
2.
d
and
I.
D.
2.
i.
2
of
the
permit
be
deleted.
The
first
one
concerned
the
use
of
an
aeration
system
at
sub­
basin
C.
Due
to
construction
of
the
sixth
runway,
this
basin
has
been
drained
and
the
aeration
system
removed,
so
compliance
with
this
item
was
no
longer
possible.
The
second
BMP
concerned
allowing
runoff
from
the
dirty
water
system
to
bypass
the
collection
ponds
if
the
runoff
was
relatively
clean
and
sufficient
dilution
was
provided
within
the
receiving
stream,
thereby
reducing
the
hydraulic
load
to
Metro.
However,
due
to
infrastructure
changes
and
constraints,
it
is
not
practical
for
DIA
to
implement
this
BMP
routinely
at
this
time,
as
required.
DIA
will
continue
to
explore
other
practical
means
to
further
reduce
unnecessary
hydraulic
loads
to
the
ponds
as
the
receiving
water
study
and
site
construction
progress.
These
two
BMPs
have
been
deleted
from
the
permit
and
Rationale,
and
the
facility
description
amended.

For
the
BMP
in
Part
I.
D.
2.
h.
(
formerly
numbered
I.
D.
2.
i.
1),
the
draft
permit
contained
requirements
that
conflicted
with
the
provisions
in
the
final
paragraph
of
that
section
concerning
Division
notification.
With
the
elimination
of
the
second
part
of
that
BMP,
I.
D.
2.
i.
2
(
see
above),
which
by
its
nature
required
close
oversight,
the
permit
now
makes
clear
that
this
BMP,
the
diversion
of
clean
stormwater
(<
75
mg/

)
from
the
dirty
water
system,
does
not
require
Division
notification.
However,
a
provision
has
been
added
requiring
periodic
monitoring
for
COD
during
the
release,
instead
of
just
a
one­
time
sample.

For
the
BMP
in
Part
I.
D.
2.
k
(
formerly
numbered
I.
D.
2.
l),
it
has
been
clarified
that
Division
notification
is
required.

A
condition
has
been
added
addressing
the
variations
in
COD
levels
during
the
exercise
of
the
BMPs
in
Part
I.
D.
2.
h­
k.
Sampling
and
analytical
methods
can
result
in
considerable
statistical
variation
in
measured
COD
values
from
the
same
flow
stream.
A
slight
variation
in
COD
level
is
usually
insufficient
justification
for
a
major
operational
change,
as
the
impact
to
the
environment
would
be
minimal.
Therefore,
if
subsequent
COD
measurements
from
a
particular
sample
point
vary
by
less
than
10%
from
the
initial
COD
measurement
at
that
point
(
e.
g.,
first
sample
result
 
70
mg/

,
second
sample
result
 
76
mg/

)
,
it
can
be
considered
for
the
purpose
of
valve
control
during
operation
of
these
BMPs
that
the
COD
has
not
changed.

As
per
the
BMP
in
Part
I.
D.
2.
a,
Figure
2
in
Part
I.
G
of
the
permit,
shows
the
areas
where
full
deicing
is
allowed
as
of
the
time
of
permit
issuance.
However,
these
areas
can
be
added
to
or
changed.
For
the
sake
of
administrative
efficiency,
the
permit
has
been
amended
to
indicate
that
such
changes
can
be
handled
via
modifications
to
the
SWMP,
rather
than
a
permit
amendment.
The
Division
will
still
require
such
SWMP
changes
to
be
submitted
before
implementation,
and
reserves
the
right
to
require
stricter
controls
as
necessary
(
see
Part
I.
D.
3.
c
of
the
permit)
.

4.
In
conjunction
with
the
investigation
into
the
relationship
between
COD
and
DO
in
DIA's
discharges,
the
sampling
frequency
for
DO
has
been
increased
to
daily
at
E
Outfall
and
at
112th
Avenue.
(
This
eliminates
the
need
for
using
75
mg/
l
of
COD
as
a
trigger
for
increasing
the
DO
sampling
to
twice
per
week.)
Sampling
for
DO
three
times
per
week
has
been
added
at
the
monitoring
station
at
C+.
It
is
anticipated
that
with
this
increased
sampling
frequency,
samples
will
often
be
taken
when
the
flow
rate
is
very
low,
which
can
affect
the
readings.
Field
notes
will
include
any
information
on
conditions
that
could
cause
the
samples
results
to
not
be
representative
of
the
discharge.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
26,
Permit
No.
COS­
000008
VIII.
CHANGES
AFTER
PUBLIC
NOTICE
5.
Based
on
updated
information
from
DIA,
changes
were
made
to
the
facility
description.
Sub­
basins
C
and
D
are
no
longer
in
use
as
detention
ponds.
A
sampling
station
is
being
installed
at
C+.
Sampling
has
been
temporarily
halted
at
C
and
D
due
to
access
problems
caused
by
the
new
construction.
The
original
sampling
points
for
C
and
D
are
upstream
of
the
current
locations.
The
newer
locations
were
based
on
the
construction
of
headwalls
at
C
and
D.
Since
these
will
no
longer
be
used
as
ponds
on
a
regular
basis,
the
sampling
points
will
be
moved
back
to
their
original
locations.
New
sampling
equipment
is
being
installed
at
these
points,
and
will
be
in
place
by
late
2001.
Requirements
for
monitoring
at
C
and
D
will
be
temporarily
suspended
until
that
time.
Monitoring
at
the
new
station
at
C+
will
provide
the
necessary
information
for
permit
compliance;
the
stations
at
C
and
D
are
used
primarily
for
process
control.
The
facility
description
has
been
amended
to
reflect
these
changes.
In
addition,
the
footnote
describing
"
reasonably
available
measures"
(
Part
I.
D.
1.2,
footnote
h/)
has
been
changed
to
delete
examples
of
actions
to
be
taken
at
C
and
D,
as
they
are
no
longer
available
for
the
described
uses.

Figures
3,
4
and
5
have
been
updated
to
reflect
changes
at
DIA
since
the
original
figures
were
prepared.

6.
A
provision
has
been
added
in
Part
I.
B.
2
of
the
permit,
specifying
that
the
requirements
for
monitoring
conditions
only
apply
to
required
monthly
and
quarterly
sampling.
The
intent
of
this
section
is
to
ensure
that
the
samples
are
representative
of
a
typical
discharge
from
a
storm
event.
However,
they
are
not
appropriate
or
useful
for
the
more
frequent
sampling
required
(
e.
g.,
daily
COD
or
DO),
as
such
sampling
is
performed
on
a
routine
basis,
regardless
of
precipitation
conditions,
etc.
Part
I.
B.
2
of
the
permit
has
been
amended.

7.
In
the
public
notice
draft,
Item
1
under
the
compliance
schedule
in
Section
VI.
E.
4.
a
of
the
Rationale
and
Part
I.
A.
2.
a.
1
of
the
permit
contained
an
incorrect
date.
Compliance
is
required
by
April
1,
2002,
not
April
1,
2001,
as
the
improvements
are
tied
to
the
increased
capacity
of
the
dirty
water
conveyance
system.
These
dates
have
been
corrected.

8.
References
to
"
sub­
basin
E
outfall"
have
been
changed
to
"
E
outfall"
so
as
to
avoid
confusing
the
outfall
of
the
T­
239
pond
to
Third
Creek
near
DIA's
border
(
a
compliance
point),
with
the
actual
drainage
area
referred
to
as
sub­
basin
E,
which
drains
the
north
campus
area
(
see
description,
Section
IV.
A.
2.
b
of
the
Rationale).

9.
The
compliance
schedule
for
construction
of
increased
capacity
in
the
dirty
water
conveyance
system
and
containment
facilities
has
been
changed.
The
interim
date
of
November
1,
2001
for
completion
of
construction
has
been
changed
to
December
15,
2001,
at
DIA's
request,
due
to
construction
delays
and
difficulty
in
obtaining
a
building
permit.
The
compliance
date
for
the
facility
to
be
fully
operational
has
not
changed.

The
dates
for
the
receiving
water
study
compliance
schedule
have
been
added,
and
the
discussion
changed
to
acknowledge
the
items
that
have
been
completed.
See
Part
I.
A.
2.
b
of
the
permit.

Kathryn
Dolan
July
12,
2001
PERMIT
AMENDMENT
#
1
COLORADO
DISCHARGE
PERMIT
SYSTEM
(
CDPS)

SUMMARY
OF
RATIONALE
CITY
AND
COUNTY
OF
DENVER
­
DENVER
INTERNATIONAL
AIRPORT
CDPS
PERMIT
NUMBER
COS­
000008
By
letters
dated
October
23,
2001,
February
6,
2002,
and
February
15,
2002,
the
permittee
has
requested
three
changes
to
their
permit
regarding
compliance
schedule
items
and
monitoring
requirements.

I.
PURPOSE
OF
AMENDMENT
`
A'

Denver
International
Airport
(
DIA)
has
proposed
a
reduction
in
their
monitoring
program
for
the
number
of
constituents
tested,
frequency
of
testing,
and
number
of
sites
tested.
DIA
has
amassed
a
very
substantial
database
for
discharges
from
Sub­
basin
A
outfall,
Sub­
basin
C
outfall,
Sub­
basin
C+
monitoring
station,
Sub­
basin
D
outfall,
E
outfall,
Second
Creek
outfall,
and
Runway
35R.
Data
from
1/
98
through
11/
01
are
summarized
in
Table
1.
(
The
past
four
years
of
data
were
used;
data
collected
before
the
West
Airfield
Diversion
System
was
operational
are
not
considered
to
be
representative
of
current
conditions.)
The
data
were
analyzed,
to
determine
which
parameters
are
clearly
not
of
concern
and
might
be
deleted,
and
of
those
to
be
retained,
what
the
sampling
frequency
should
be.

Monitoring
­
Required
Parameters
The
data
show
that
monitoring
for
several
parameters
may
be
deleted,
based
on
a
comparison
with
EPA's
benchmark
values.
The
benchmark
values
from
the
NPDES
Stormwater
Multi­
Sector
General
Permit
for
Industrial
Activities
are
also
included
in
Table
1.
The
benchmarks
are
the
pollutant
concentrations
which,
when
exceeded,
EPA
determined
represent
a
level
of
concern.
The
level
of
concern
is
a
concentration
at
which
a
stormwater
discharge
could
potentially
impair
or
contribute
to
impairing
water
quality,
or
affect
human
health
from
ingestion
of
water
or
fish.

The
grab
samples
for
Oil
and
Grease
have
generally
shown
very
low
levels.
Therefore,
the
requirement
will
be
for
a
visual
check
for
Oil
and
Grease;
if
a
sheen
is
detected,
then
a
grab
sample
is
required.
Acetate,
Ethylene
Glycol,
and
Total
Petroleum
Hydrocarbons
(
TPH)
have
been
found
to
be
at
low
levels
or
below
detection
in
almost
all
cases,
and
so
monitoring
for
these
parameters
has
been
deleted.
The
visual
check
for
Oil
and
Grease
can
also
be
used
to
detect
the
potential
presence
of
TPH.

The
levels
of
Nitrate
plus
Nitrite,
as
N,
were
found
to
be
low
at
Sub­
basin
C,
Sub­
basin
D,
Second
Creek
and
Runway
35R.
Monitoring
for
Nitrate
plus
Nitrite
at
these
points
has
been
deleted.

The
levels
of
Total
Phosphorus
have
generally
been
well
below
the
EPA
benchmark
of
2
mg/
l,
and
so
monitoring
for
it
has
been
deleted.
The
levels
for
Total
Kjeldahl
Nitrogen
(
TKN)
were
low
at
Sub­
basin
E,
Second
Creek
and
Runway
35R.
Monitoring
for
TKN
is
at
these
points
has
been
deleted.

The
levels
for
Chloride
were
low
at
all
outfalls
except
for
Sub­
basins
C
and
E,
and
Second
Creek.
(
Chloride
is
a
constituent
of
Magnesium
Chloride,
a
deicing
compound
used
on
the
roads
around
DIA.
While
runoff
from
the
roadways
is
not
regulated
under
this
permit,
Chloride
has
been
shown
to
cause
interference
in
Chemical
Oxygen
Demand
(
COD)
tests,
and
so
monitoring
is
still
required
where
it
has
been
found
at
elevated
levels.)
Chloride
data
from
Sub­
basin
C
is
not
considered
to
be
representative
of
the
current
drainage
area
(
see
discussion
under
Monitoring
Location,
below),
since
it
no
longer
includes
as
large
an
area
of
roadway
deicing.
Roadways
make
up
a
large
part
of
the
Second
Creek
drainage,
which
accounts
for
the
high
Chloride
levels
found
there.
Monitoring
for
Chloride
at
Sub­
basin
E
and
C+
will
continue,
at
an
increased
frequency,
as
a
check
on
the
potential
for
interference
in
the
COD
test
accuracy.
However,
any
requirements
for
new/
changed
Best
Management
Practices
(
BMPs)
for
roadway
deicing
will
be
handled
under
Denver's
municipal
stormwater
permit,
as
it
is
not
related
to
the
industrial
activities
and
areas
covered
under
this
permit.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Amendment
#
1
Rationale
­
Page
2,
Permit
No.
COS­
000008
Monitoring
Locations
The
Division
considered
DIA's
request
to
eliminate
some
monitoring
points.
The
request
was
based
on
the
idea
of
using
representative
discharges.
When
a
facility
has
two
or
more
outfalls
that,
based
on
a
consideration
of
industrial
activity,
significant
materials,
and
management
practices
and
activities
within
the
area
drained
by
the
outfall,
the
permittee
reasonably
believes
discharge
substantially
identical
effluents,
the
permittee
may
test
the
effluent
of
one
such
outfall
and
report
that
the
quantitative
data
also
apply
to
the
substantially
identical
outfalls.

Given
the
size
and
scope
of
the
facility,
the
variety
of
activities
that
take
place,
and
the
facility's
compliance
history,
the
Division
determined
that
it
was
still
important
at
this
time
to
have
periodic
checks
on
the
stormwater
quality
at
all
of
the
points
originally
included
in
the
permit.
However,
DIA
has
made
tremendous
improvements
to
their
system
in
the
past
few
years,
and
so
a
reduction
in
monitoring
frequencies
is
justified
(
see
below).

The
one
exception
to
maintaining
the
present
locations
is
the
requirement
to
monitor
for
Dissolved
Oxygen
(
DO)
in
Third
Creek
at
112th
Avenue
(
about
one
mile
northwest
of
DIA's
boundary).
Since
this
site
is
not
on
DIA's
property,
and
incorporates
flow
from
non­
DIA
property,
the
requirement
to
monitor
at
this
site
will
be
deleted.
However,
the
Division
still
recommends
that
this
site
be
sampled
periodically,
to
give
some
indication
of
the
potential
downstream
impacts
from
DIA
discharges.

The
location
for
monitoring
at
Sub­
basin
C
has
changed.
When
the
airport
originally
opened,
monitoring
was
performed
at
the
outfall
from
Sub­
basin
C.
This
drainage
area
was
relatively
small,
consisting
of
the
west
half
of
Concourse
A
and
deicing
pad
A.
A
headwall
was
constructed
downstream
of
C
(
creating
Pond
C),
to
capture
all
drainage
in
Third
Creek
upstream
of
that
point
(
including
Sub­
basins
C
and
A,
and
roadways
and
open
space
as
well
as
industrialized
areas).
Due
to
the
new
pond,
the
outfall
from
Sub­
basin
C
was
frequently
underwater.
Therefore,
sampling
was
performed
at
the
headwall
instead.
The
data
in
Table
A
represent
drainage
from
this
larger
area.
The
headwall
was
removed
due
to
construction
on
the
new
Sixth
Runway.
Thus,
the
outfall
from
Sub­
basin
C
is
again
being
used
as
the
monitoring
point.

Monitoring
Frequency
The
most
onerous
requirement
in
the
permit,
in
terms
of
resources
required,
has
been
for
daily
COD
monitoring
at
five
of
the
seven
outfalls,
and
daily
DO
monitoring
at
two
outfalls.
COD
monitoring
was
originally
used
as
a
key
measure
of
permit
compliance,
in
that
a
correlation
was
found
between
the
amount
of
aircraft
deicing
fluids
and
the
amount
of
COD
present.
At
that
time,
the
trigger
levels
were
developed
based
on
existing
data
and
Best
Professional
Judgment,
and
additional
BMPs
were
being
implemented
on
an
as­
needed
basis.
Today,
many
improvements
have
been
made
to
the
ADF
management
system,
and
DIA
operates
the
system
to
the
fullest
extent
possible
on
a
routine
basis.
Therefore,
the
ambient
data
that
are
collected
are
not
being
directly
used
to
make
decisions
about
additional
BMPs.
(
The
primary
additional
BMP
in
use
at
this
time
is
construction
of
the
new
pond
capacity,
which
is
on­
going.
See
Amendment
B.)

The
permit
is
based
on
using
COD
levels
as
a
trigger
for
increased
Best
Management
Practices
(
BMPs).
While
there
is
some
initial
evidence
from
the
current
receiving
water
study
to
indicate
that
this
may
no
longer
be
the
most
appropriate
permit
structure
for
DIA,
the
Division
has
decided
not
to
change
that
section
until
the
results
of
the
study
are
final.
The
study
results
are
expected
to
lead
to
numerous
changes
in
the
permit,
and
in
the
assessment
of
the
potential
for
water
quality
impacts
from
DIA's
discharges.
This
permit
amendment
will
deal
with
the
reductions
in
monitoring
that
are
clearly
justifiable
at
this
time;
further
reductions
may
be
appropriate
in
the
future
based
on
the
study
results.

The
Division
believes
that
monitoring
for
COD
twice
a
week
at
Sub­
basin
C+
and
E
outfall
will
be
adequate
to
evaluate
COD
levels
in
the
receiving
waters
to
the
extent
necessary.
In
addition,
a
provision
has
been
added
requiring
that
at
the
time
of
sampling
for
COD
at
outfall
E
and
C+,
an
additional
sample
sufficient
to
test
for
BOD5
must
also
be
collected.
If
the
COD
result
is
greater
than
200
mg/
l,
then
the
BOD5
sample
must
also
be
analyzed.
This
is
required
in
order
to
determine
the
amount
of
oxygen
demand
present
when
there
is
the
potential
for
Chloride
interference.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Amendment
#
1
Rationale
­
Page
3,
Permit
No.
COS­
000008
Monitoring
for
all
parameters
at
Sub­
basin
A,
C
and
D
outfalls
has
been
standardized
to
require
that
all
remaining
parameters
be
monitored
once
every
two
months.
This
is
a
decrease
from
the
daily
COD
monitoring,
as
that
data
is
no
longer
used
as
a
process
control,
and
so
is
not
critical
to
airport
operations.
For
other
parameters,
the
frequency
has
been
increased
from
quarterly,
to
simplify
the
sampling
schedule.

Monitoring
at
Second
Creek
and
Runway
35R
has
been
decreased
in
frequency.
Monitoring
at
Runway
35
R
is
now
required
once
every
six
months;
for
Second
Creek,
monitoring
is
required
once
per
year.
Past
data
have
shown
low
pollution
potential
from
these
points,
which
is
due
to
the
low
level
of
industrial
activity
in
the
drainage
areas.

II.
PURPOSE
OF
AMENDMENT
`
B'

DIA
has
requested
a
change
in
the
final
two
dates
in
the
permit's
construction
compliance
schedule.

The
permit
was
originally
issued
in
July,
2001.
At
that
time,
the
compliance
schedule
for
construction
of
the
new
industrial
stormwater
ponds
was
based
on
the
best
estimates
and
contract
information
from
DIA
staff.
Since
that
time,
there
have
been
numerous
and
substantial
delays
in
the
construction:

­
There
were
delays
in
obtaining
the
Building
Permit
for
construction
of
the
laboratory
and
pumping
facilities
associated
with
the
project,
while
the
process
for
resolving
the
fees
to
be
paid
to
Denver
Wastewater
and
the
Metro
Wastewater
Reclamation
District
(
MWRD)
was
being
completed.

­
The
terrorist
attacks
of
September
11,
2001
had
impacts
on
all
areas
of
the
airport.
DIA
has
implemented
more
stringent
security
requirements
(
e.
g.,
badging,
fingerprinting
and
background
checks
for
construction
workers)
that
have
resulted
in
delays
to
the
construction
project.

­
A
portion
of
the
construction
requires
a
48­
inch
diameter
boring
under
the
runway
to
install
larger
pipes
to
enhance
collection
capabilities.
During
the
boring,
rock
was
encountered,
which
led
to
over
two
months
of
delay.

­
The
majority
of
the
delay
is
attributed
to
problems
with
the
construction
contractor
regarding
its
choice
of
means
and
methods,
sequencing
of
work
and
staffing
problems.
DIA
has
had
to
terminate
the
contractor
and
to
work
with
the
bonding
company
to
select
a
new
contractor.
In
addition,
some
of
the
installation
work
performed
by
the
original
contractor
was
determined
to
be
defective,
and
so
that
work
has
to
be
removed
and
replaced.

The
Colorado
Discharge
Permit
Regulations
(
No.
61.8(
3))
allow
the
permittee
a
reasonable
opportunity
to
attain
compliance
with
permit
requirements.
The
Division
has
determined
that
DIA
has
acted
in
good
faith
to
complete
the
project
as
quickly
as
possible,
and
that
the
proposed
new
schedule
is
reasonable.
It
is
important
to
amend
the
permit
as
expeditiously
as
possible,
so
that
DIA
is
not
put
in
a
situation
of
permit
non­
compliance
due
to
processing
delays.
However,
since
the
new
contractor
has
not
yet
been
chosen,
the
new
deadlines
proposed
by
DIA
are
based
on
an
estimated
project
schedule.
It
is
possible
that
these
dates
could
change,
based
on
new
information
presented
after
this
permit
is
at
Public
Notice.
In
that
case,
the
final
compliance
schedule
dates
could
change
by
up
to
three
months
either
way,
without
a
formal
Public
Notice
process.
If
either
of
the
dates
must
be
changed
by
more
than
three
months,
a
new
Public
Notice
will
be
published.

II.
PURPOSE
OF
AMENDMENT
`
C'

The
construction
compliance
schedule
originally
addressed
construction
of
two
new
ponds
(
10
million
gallons
total
capacity),
and
paving
of
certain
grass
`
islands'
adjacent
to
the
deicing
pads
and
connection
of
drainage
from
these
islands
directly
into
the
glycol
collection
ponds.
DIA
has
paved
some
areas
west
of
the
deicing
pads
for
use
in
stockpiling
contaminated
snow.
However,
experience
with
the
West
Airfield
Diversion
System
since
the
time
of
the
original
project
plan
indicated
a
need
for
increased
capacity
to
collect
flows
from
the
grass
islands
and
other
areas
as
well.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Amendment
#
1
Rationale
­
Page
4,
Permit
No.
COS­
000008
The
project
has
been
significantly
expanded
and
now
includes:

­
five
new
re­
engineered
diversion
structures
­
to
increase
conveyance
capacity,
48
inch
pipe
on
the
north
branch,
bored
under
a
runway
and
taxiways,
and
24
inch
pipe
on
the
south
branch
(
to
replace
existing
12
inch
line)
­
three
pond
cells
with
22.5
million
gallons
total
capacity
to
accommodate
the
increased
conveyance
capacity
(
replaces
two
originally
planned
ponds)

The
compliance
schedule
task
described
in
Part
A.
2.
a.
1
of
the
permit
(
paving
grass
areas)
has
been
amended
to
read:

1)
Modification
of
collection
system
to
collect
snowmelt
and
additional
surface
and
subsurface
flows,
to
be
completed
by
December
31,
2002.

The
new
compliance
schedule
is
as
follows:

The
permittee
shall
complete
the
specified
construction
activities
by
April
1,
2002
December
31,
2002,
in
accordance
with
the
following
schedule
of
compliance,
as
approved
by
the
Division.

Table
1
­­
Compliance
Schedule
­
Construction
Activity
Deadline
Notice
to
Proceed
for
design
contract
July
21,
1999
(
completed)

Design
complete
September
15,
2000
(
completed)

Notice
to
Proceed
for
construction
contract
February
1,
2001
(
completed)

Pond
construction
complete
and
system
start­
up
November
30,
2002
Facility
fully
operational
December
31,
2002
a/

a/
This
date
may
be
extended
by
the
Division
if
insufficient
precipitation
is
received
by
then
to
allow
for
a
full
operational
testing
of
the
new
facilities.

Pages
5,
6,
7,
8
and
9
of
the
permit
have
been
changed.
Page
7a
has
been
added.

Kathryn
Dolan
March
7,
2002
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
5,
Permit
No.
COS­
000008
Table
1
­
Summary
of
Historical
DMR
Data,
1/
98
 
11/
01
OUTFALL
A
COD
DO
Oil
and
Grease
pH
TSS
Acetate
Propylene
Glycol
Ethylene
Glycol
BOD5
TPH
Total
P
NO3
+
NO2
as
N
TKN
Chloride
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
s.
u.)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)

minimum
10.00
3.10
1.00
5.80
10.00
2.50
0.50
0.50
4.00
0.50
0.04
0.06
0.02
5.00
maximum
604.00
9.70
457.00
10.00
762.00
480.00
336.00
10.00
584.00
3.50
0.67
4.12
18.10
289.00
mean
119.66
5.39
16.62
7.53
125.21
46.94
21.59
1.03
99.40
1.22
0.21
1.27
2.79
78.88
standard
deviation
108.76
1.07
77.88
0.75
161.75
118.15
60.33
1.78
150.60
1.29
0.14
1.39
4.23
81.78
coefficient
of
variation
91%
20%
469%
10%
129%
252%
279%
173%
152%
106%
69%
109%
152%
104%

no.
of
samples
76
40
34
34
34
17
34
32
20
16
16
16
16
17
%
non­
detects
0%
0%
74%
0%
0%
76%
59%
91%
0%
94%
6%
6%
12%
0%

EPA
permit
benchmark
120
none
15
6.0­
9.0
100
none
none
none
30
none
2
0.68
1.5
860
OUTFALL
C
COD
DO
Oil
and
Grease
pH
TSS
Acetate
Propylene
Glycol
Ethylene
Glycol
BOD5
TPH
Total
P
NO3
+
NO2
as
N
TKN
Chloride
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
s.
u.)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)

minimum
2.00
­­
1.00
6.70
6.00
2.50
0.50
0.50
1.00
0.50
0.01
0.01
0.40
0.50
maximum
3805.00
­­
25.00
8.10
4520.00
990.00
540.00
8.00
784.00
3.50
4.75
1.13
28.40
4910.00
mean
242.66
­­
3.59
7.39
222.48
144.15
70.34
1.27
210.07
1.63
0.51
0.45
6.03
2049.45
standard
deviation
312.97
­­
4.76
0.37
831.56
300.08
162.49
1.88
248.81
1.50
1.15
0.34
8.20
1958.70
coefficient
of
variation
129%
­­
133%
5%
374%
208%
231%
148%
118%
92%
227%
76%
136%
96%

no.
of
samples
957
none
28
29
29
10
28
26
15
16
16
16
16
10
%
non­
detects
0%
­­
81%
0%
0%
30%
46%
78%
15%
100%
8%
8%
0%
18%

EPA
permit
benchmark
120
none
15
6.0­
9.0
100
none
none
none
30
none
2
0.68
1.5
860
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
6,
Permit
No.
COS­
000008
Table
1
­
Summary
of
Historical
DMR
Data,
1/
98
 
11/
01
(
cont.)

OUTFALL
D
COD
DO
Oil
and
Grease
pH
TSS
Acetate
Propylene
Glycol
Ethylene
Glycol
BOD5
TPH
Total
P
NO3
+
NO2
as
N
TKN
Chloride
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
s.
u.)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)

minimum
5.00
­­
1.00
6.00
5.00
9.00
0.50
0.50
8.00
0.50
0.01
0.01
0.50
0.50
maximum
29560.00
­­
44.00
8.50
1060.00
140.00
1160.00
3.00
768.00
3.50
1.33
0.86
6.60
73.00
mean
741.66
­­
5.75
7.23
94.38
59.75
257.31
0.70
375.55
1.40
0.19
0.40
2.08
17.19
standard
deviation
1468.99
­­
9.65
0.57
235.85
62.62
346.41
0.64
303.06
1.45
0.40
0.27
1.74
23.84
coefficient
of
variation
198%
­­
168%
8%
250%
105%
135%
91%
81%
104%
219%
68%
84%
139%

no.
of
samples
690
none
20
21
21
4
21
20
11
10
10
10
10
8
%
non­
detects
0%
­­
70%
0%
0%
0%
24%
90%
9%
100%
30%
20%
0%
13%

EPA
permit
benchmark
120
none
15
6.0­
9.0
100
none
none
none
30
none
2
0.68
1.5
860
OUTFALL
C+
COD
DO
Oil
and
Grease
pH
TSS
Acetate
Propylene
Glycol
Ethylene
Glycol
BOD5
TPH
Total
P
NO3
+
NO2
as
N
TKN
Chloride
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
s.
u.)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)

minimum
1.00
3.40
1.00
7.20
198.00
2.50
0.50
0.50
4.00
3.50
0.21
0.09
2.80
183.00
maximum
2880.00
17.80
10.00
8.00
8540.00
2.50
16.00
0.50
70.00
3.50
0.87
1.47
3.00
210.00
mean
165.64
6.84
2.80
7.54
2126.20
2.50
6.30
0.50
37.00
3.50
0.54
0.78
2.90
196.50
standard
deviation
218.30
2.30
4.02
0.31
3600.58
0.00
7.97
0.00
46.67
0.00
0.47
0.98
0.14
19.09
coefficient
of
variation
132%
34%
144%
4%
169%
0%
127%
0%
126%
0%
86%
125%
5%
10%

no.
of
samples
1455
168
5
5
5
5
5
5
2
3
2
2
2
2
%
non­
detects
0%
0%
80%
0%
0%
100%
60%
100%
0%
100%
0%
0%
0%
0%

EPA
permit
benchmark
120
none
15
6.0­
9.0
100
none
none
none
30
none
2
0.68
1.5
860
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
7,
Permit
No.
COS­
000008
Table
1
­
Summary
of
Historical
DMR
Data,
1/
98
 
11/
01
(
cont.)

OUTFALL
E
COD
DO
Oil
and
Grease
pH
TSS
Acetate
Propylene
Glycol
Ethylene
Glycol
BOD5
TPH
Total
P
NO3
+
NO2
as
N
TKN
Chloride
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
s.
u.)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)

minimum
1.00
0.50
1.00
6.90
3.00
2.50
0.50
0.50
1.00
0.50
0.01
0.01
0.02
3.00
maximum
2570.00
12.00
59.00
8.00
1010.00
92.00
164.00
2.00
318.00
3.50
1.05
15.80
5.10
3040.00
mean
71.29
5.96
4.63
7.61
173.58
11.65
8.79
0.55
31.72
2.19
0.16
2.57
1.26
499.00
standard
deviation
130.18
2.02
10.32
0.31
274.83
24.04
31.05
0.27
78.15
1.54
0.25
4.20
1.18
812.71
coefficient
of
variation
183%
34%
223%
4%
158%
206%
353%
48%
246%
70%
152%
164%
94%
163%

no.
of
samples
1433
342
34
34
33
17
34
32
18
16
16
16
16
15
%
non­
detects
0%
0%
74%
0%
0%
82%
82%
97%
28%
100%
6%
6%
19%
0%

EPA
permit
benchmark
120
none
15
6.0­
9.0
100
none
none
none
30
none
2
0.68
1.5
860
OUTFALL
112TH
COD
DO
Oil
and
Grease
pH
TSS
Acetate
Propylene
Glycol
Ethylene
Glycol
BOD5
TPH
Total
P
NO3
+
NO2
as
N
TKN
Chloride
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
s.
u.)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)

minimum
2.00
0.30
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­

maximum
1430.00
17.80
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­

mean
72.91
5.45
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­

standard
deviation
107.29
2.26
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­

coefficient
of
variation
147%
41%
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­

no.
of
samples
1203
277
none
none
none
none
none
none
none
none
none
none
none
none
%
non­
detects
0
0
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
­­
none
EPA
permit
benchmark
120
none
15
6.0­
9.0
100
none
none
none
30
none
2
0.68
1.5
860
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Rationale
­
Page
8,
Permit
No.
COS­
000008
Table
1
­
Summary
of
Historical
DMR
Data,
1/
98
 
11/
01
(
cont.)

OUTFALL
35R
COD
DO
Oil
and
Grease
pH
TSS
Acetate
Propylene
Glycol
Ethylene
Glycol
BOD5
TPH
Total
P
NO3
+
NO2
as
N
TKN
Chloride
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
s.
u.)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)

minimum
­­
­­
1.00
6.50
3.00
2.50
0.50
0.50
3.00
0.50
0.05
0.01
0.01
2.00
maximum
­­
­­
59.00
8.50
192.00
220.00
78.00
0.50
401.00
3.50
0.49
1.73
6.40
3040.00
mean
­­
­­
4.97
7.46
35.62
37.74
6.45
0.50
78.29
2.43
0.22
0.69
1.26
241.77
standard
deviation
­­
­­
10.71
0.39
47.96
70.61
17.18
0.00
126.04
1.49
0.14
0.56
1.62
840.79
coefficient
of
variation
­­
­­
216%
5%
135%
187%
266%
0%
161%
61%
65%
82%
129%
348%

no.
of
samples
none
none
29
30
29
17
30
29
14
14
14
14
14
13
%
non­
detects
­­
­­
67%
0%
0%
65%
77%
100%
7%
100%
0%
7%
29%
7%

EPA
permit
benchmark
120
none
15
6.0­
9.0
100
none
none
none
30
none
2
0.68
1.5
860
OUTFALL
SECOND
CREEK
COD
DO
Oil
and
Grease
pH
TSS
Acetate
Propylene
Glycol
Ethylene
Glycol
BOD5
TPH
Total
P
NO3
+
NO2
as
N
TKN
Chloride
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
s.
u.)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)
(
mg/
L)

minimum
­­
­­
1.00
6.90
10.00
2.50
0.50
0.50
4.00
0.50
0.10
0.04
0.70
1.00
maximum
­­
­­
12.00
8.20
2840.00
204.00
3.00
1.00
434.00
3.50
2.64
1.04
3.00
7030.00
mean
­­
­­
2.09
7.61
349.55
21.50
0.61
0.57
87.31
2.25
0.56
0.51
1.52
1174.92
standard
deviation
­­
­­
2.30
0.31
591.88
53.80
0.52
0.18
135.28
1.54
0.69
0.27
0.71
2061.46
coefficient
of
variation
­­
­­
110%
4%
169%
250%
86%
31%
155%
69%
123%
54%
47%
175%

no.
of
samples
none
none
23
23
22
14
23
22
13
12
12
12
12
12
%
non­
detects
­­
­­
83%
0%
0%
71%
96%
95%
7%
100%
8%
8%
8%
0%

EPA
permit
benchmark
120
none
15
6.0­
9.0
100
none
none
none
30
none
2
0.68
1.5
860
PERMIT
AMENDMENT
#
2
COLORADO
DISCHARGE
PERMIT
SYSTEM
(
CDPS)

SUMMARY
OF
RATIONALE
CITY
AND
COUNTY
OF
DENVER
­
DENVER
INTERNATIONAL
AIRPORT
CDPS
PERMIT
NUMBER
COS­
000008
Amendment
Fee
(
55%
of
Annual
Fee)
$
7060
By
letter
dated
July
14,
2003,
the
permittee
has
requested
several
changes
to
their
permit
regarding
action
levels,
monitoring
requirements,
best
management
practices
(
BMPs),
system
capabilities,
and
Stormwater
Management
Plan
(
SWMP)
revision.

I.
ACTION
LEVELS
Denver
International
Airport
(
DIA)
has
requested
that
the
action
levels
contained
in
Part
I.
A.
1
of
the
permit
be
removed.
The
action
levels
require
the
implementation
of
reasonably
available
measures
and/
or
additional
BMPs
when
concentrations
of
Chemical
Oxygen
Demand
(
COD)
in
Third
Creek
meet
or
exceed
the
action
levels
This
was
based
on
the
premise
that
the
system
was
not
operating
optimally
when
the
COD
action
levels
were
reached.
These
action
levels
were
used
at
a
time
when
additional
improvements
to
the
spent
aircraft
deicing
fluid
(
ADF)
management
system
were
planned
but
not
yet
implemented.
Some
temporary
BMPs
were
being
used
while
design
and
construction
were
underway.
These
BMPs
are
no
longer
used,
given
the
facility
upgrades.
DIA
operates
the
system
to
optimize
collection
of
spent
ADF
at
all
times,
regardless
of
COD
concentrations
in
Third
Creek.
Therefore,
the
implementation
of
additional
BMPs
based
on
action
level,
is
no
longer
appropriate.

In
April
2003,
DIA
completed
a
Receiving
Water
Study
that
concluded
that
it
was
not
currently
possible
to
establish
a
reliable
correlation
of
Dissolved
Oxygen
(
DO)
to
COD
levels
in
Third
Creek.
Therefore,
COD
monitoring
on
Third
Creek
will
not
be
used
in
this
permit
as
a
measure
of
compliance
with
the
DO
standard.

There
has
also
been
some
intent
to
use
in­
stream
COD
concentrations
as
an
indicator
of
the
effectiveness
of
the
spent
ADF
management
system.
In­
stream
COD
concentrations
have
not
been
shown
to
be
a
reliable
indicator
of
the
effectiveness
of
the
system,
due
to
factors
such
as
the
dynamic
nature
of
the
stream
and
the
commingling
with
stormwater
runoff
from
other
sources,
such
as
municipal
activities
(
roadway
deicing
and
maintenance,
construction,
etc.).
Therefore,
the
Division
has
replaced
the
action
levels
with
a
requirement
that
DIA
provide
estimates
of
the
effectiveness
of
the
system
in
terms
of
the
level
of
ADF
capture
being
achieved.
This
information
will
be
used
by
the
Division,
together
with
other
information
(
annual
reports,
sampling
data,
etc.)
to
determine
the
effectiveness
of
the
current
system
and
the
need
for
any
new
or
revised
BMPs.

II
MONITORING
REQUIREMENTS
DIA
requested
reduction
and
clarification
of
the
wet
weather
monitoring
requirements
contained
in
Part
I.
B.
1.
a
of
the
permit.

DIA
requested
that
Second
Creek
and
Runway
35R
be
eliminated
as
discharge
points
for
wet
weather
monitoring
on
the
basis
that
residual
ADF
is
present
very
infrequently
in
these
streams,
at
levels
much
lower
than
observed
in
Third
Creek.
Therefore,
DIA
asserts
that
wet
weather
monitoring
of
Third
Creek
is
representative
of
potential
worst­
case
conditions
for
the
discharge
of
stormwater
associated
with
industrial
activity
at
the
site.
The
permittee
further
stated
that
the
Receiving
Water
study
adequately
characterizes
the
nature
of
discharge
from
these
locations.
The
Division
agreed
to
eliminate
Second
Creek
as
a
discharge
point
for
wet
weather
monitoring,
due
to
the
low
levels
of
residual
ADF
historically
observed,
and
the
fact
that
the
majority
of
activities
that
occur
upstream
of
the
outfall
are
commercial
and
municipal
rather
than
industrial
in
nature.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Amendment
#
2
Rationale
­
Page
2,
Permit
No.
COS­
000008
Given
the
size
and
scope
of
the
facility,
the
variety
of
industrial
activities
that
take
place
upstream
of
the
Runway
35R
outfall,
and
the
aquatic
life
known
to
exist
downstream
of
the
discharge,
the
Division
determined
that
it
was
still
important
to
have
periodic
checks
on
the
stormwater
quality
at
this
discharge
point.

DIA
requested
that
C+
and
E
on
Third
Creek
be
eliminated
as
discharge
points
from
the
permit
and
that
all
monitoring
requirements
for
these
locations
be
removed.
The
Division
agrees
that
these
locations
are
in­
stream
sample
sites,
not
industrial
outfalls,
and
recognizes
that
drainage
into
Third
Creek
also
occurs
from
other
activities
on
DIA
property
that
are
not
regulated
under
this
permit
(
e.
g.,
public
street
maintenance,
new
development,
commercial
facility
management).
However,
given
the
size
and
scope
of
industrial
activities
that
do
occur
on
DIA
property,
the
resulting
industrial
stormwater
drainage,
and
the
compliance
history,
the
Division
determined
that
it
is
reasonable
for
DIA
to
perform
biological
monitoring
on
Third
Creek
to
demonstrate
the
continued
viability
of
the
aquatic
life
community.
DIA
is
in
the
process
of
proposing
site
specific
standards
for
dissolved
oxygen
(
DO)
to
the
Water
Quality
Control
Commission
(
WQCC)
for
their
consideration.
The
Division
felt
that
the
biological
monitoring
should
be
performed
following
the
rulemaking
on
these
new
standards.
Therefore,
the
wet
weather
monitoring
requirements
at
these
locations(
C+
and
E)
have
been
eliminated,
while
wet
weather
monitoring
requirements
at
the
industrial
outfalls
have
been
retained.
A
requirement
to
perform
biological
monitoring
in
Third
Creek
at
E
on
DIA
property
has
been
added.

Monitoring
point
E
was
selected
as
a
future
biological
monitoring
site
because
the
completed
Receiving
Water
Study
identified
the
existence
of
a
persistent
fathead
minnow
population
in
this
area.
The
Division
determined
that
a
one­
time
fish
survey
should
be
performed
to
demonstrate
fish
community
persistence
as
a
means
of
measuring
attainment
of
the
aquatic
life
beneficial
use
in
this
waterbody.
The
survey
shall
be
conducted
according
to
the
following
parameters:
 
Sampling
will
occur
in
September
to
avoid
impacting
early
life
stages
that
would
likely
be
present
between
April
and
July,
and
avoid
presence
of
ice;
 
Sampling
will
occur
in
the
reach
at
monitoring
point
E
using
a
seine
of
an
appropriate
mesh
size
to
capture
adult
fathead
minnow;
 
Appropriate
sampling
protocols/
measurements
will
be
performed
to
allow
the
calculation
of
fish
density
(
number
of
fish/
square
meter);
 
Captured
fish
will
be
weighed
and
measured
before
being
returned
to
the
stream;
and
 
Fish
density
and
fish
measurements
will
be
collected
for
informational
purposes
only;
the
goal
of
the
survey
is
to
determine
the
presence
of
fish,
which
would
demonstrate
fish
community
persistence.

DIA
requested
that
the
A
discharge
monitoring
point
be
relocated
for
safety
reasons.
The
Division
concurred
with
this
request.
The
new
location
is
shown
in
Figure
5.

DIA
requested
that
the
measurement
frequency
for
Third
Creek
outfalls
be
reduced
from
once
every
two
months
to
quarterly.
DIA
has
amassed
a
substantial
amount
of
data
for
the
Third
Creek
industrial
outfalls
and
the
receiving
water.
As
described
in
Section
VIII
of
the
Rationale,
below,
the
Division
has
determined
that
sampling
once
every
two
months
is
appropriate
at
this
time
for
the
characterization
of
seasonal
differences
in
storm
events
that
result
in
the
discharge
of
stormwater
associated
with
industrial
activity,
in
particular
aircraft
deicing.

DIA
requested
that
the
permit
state
that
repeat
visits
to
discharge
outfalls
are
unnecessary
if
there
is
no
discharge
from
the
outfall
to
surface
waters
resulting
from
a
qualifying
event.
DIA's
basis
for
the
request
was
that
the
lack
of
discharge
from
an
event
was
itself
a
characterization
of
the
event.
DIA
noted
that
many
factors
could
cause
a
lack
of
discharge
from
a
qualifying
storm
event,
including
infiltration,
evaporation,
sublimation,
and
diversion
into
the
spent
ADF
management
system.
The
Division
determined
that
additional
attempts
to
meet
the
wet
weather
monitoring
requirements
should
be
made,
following
a
qualifying
event
that
does
not
result
in
discharge,
as
the
lack
of
discharge
could
simply
be
due
to
irregular
precipitation
patterns.
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Amendment
#
2
Rationale
­
Page
3,
Permit
No.
COS­
000008
DIA
requested
that
the
requirement
that
wet
weather
monitoring
samples
be
taken
during
the
first
hour
of
the
discharge
be
modified
to
require
that
the
sample
be
representative
of
the
first
flush
of
storm
water
runoff.
This
request
was
made
on
the
basis
that
stormwater
runoff
in
the
winter
months
often
does
not
occur
until
hours
or
days
following
the
storm
event.
The
language
in
the
permit
has
been
revised
in
response
to
this
request.

III
BEST
MANAGEMENT
PRACTICES
(
BMPs)

DIA
requested
that
the
BMPs
contained
in
Part
I.
D.
2
of
the
permit
be
removed,
and
that
such
BMPs
regarding
operation
of
the
spent
ADF
management
system
be
included
in
the
SWMP.
In
recent
years,
DIA
has
made
several
requests
to
the
Division
for
operational
flexibility
by
requesting
a
variance
from
the
BMPs
contained
in
the
permit.
Often
these
requests
have
been
made
during
or
immediately
following
unique
storm
events,
in
response
to
which
DIA
has
stated
that
different
operating
scenarios
for
the
spent
ADF
management
system
are
appropriate.
The
Division
determined
that,
while
some
changes
are
warranted,
it
is
important
that
the
permit
dictate
some
guiding
principals
regarding
operation
of
the
spent
ADF
management
system.
Therefore,
several
BMPs
that
apply
to
the
system
as
a
whole
have
been
retained.
The
Division
has
agreed
to
remove
other
BMPs
from
the
permit
that
specifically
describe
operational
procedures.
Such
BMPs
or
their
equivalent
will
be
included
in
the
SWMP.
As
per
Part
I.
C
of
the
permit,
implementation
of
the
BMPs
in
the
SWMP
is
a
permit
requirement.
The
Division
will
review
the
revised
SWMP,
and
may
require
additional
measures
as
needed
to
prevent
and
control
pollution,
based
on
the
SWMP
review
and/
or
additional
information
received.

IV
SYSTEM
CAPABILITIES
DIA
requested
that
it
be
explicitly
stated
in
the
permit
that
stormwater
associated
with
industrial
activity
may
contain
residual
levels
of
spent
ADF
that
migrate
beyond
the
capture
system.
DIA
also
requested
that
it
be
stated
that
the
spent
ADF
management
system
has
a
finite
capacity,
and
that
stormwater
associated
with
industrial
activity,
resulting
from
precipitation
events
that
exceed
the
capacity
of
the
system,
has
the
potential
to
be
discharged
from
areas
within
the
capture
system.
The
Division
determined
that
these
statements
would
be
more
appropriate
for
inclusion
in
DIA's
SWMP
than
in
the
permit.

V
SWMP
REVISION
DIA
requested
a
period
of
90
days
after
the
effective
date
of
the
revised
permit
for
updating
the
SWMP
in
final
form.
The
requirement
has
been
changed
from
the
original
30
day
deadline
in
the
permit
in
response
to
this
request.

VI.
CHANGES
TO
PERMIT
A
change
was
made
on
Page
1
of
the
permit,
to
clarify
that
discharges
are
also
authorized
to
Barr
Lake
Tributary
and
Hayesmount
Tributary.
On
Page
4
of
the
permit,
a
change
was
made
to
clarify
that
discharges
from
Runway
35R
flow
to
Hayesmount
Tributary,
and
not
directly
to
Box
Elder
Creek.

Pages
1,
4,
5,
7,
7a,
9,
10,
13,
14,
15,
17,
18
and
25
of
the
permit
have
been
changed.
Page
10a
has
been
added
(
but
does
not
contain
new
information).

Kathryn
Dolan
December
4,
2003
COLORADO
DEPARTMENT
OF
PUBLIC
HEALTH
AND
ENVIRONMENT,
Water
Quality
Control
Division
Amendment
#
2
Rationale
­
Page
4,
Permit
No.
COS­
000008
VII.
RESPONSE
TO
PUBLIC
NOTICE
COMMENTS
The
Division
received
comments
on
the
proposed
amendment
from
the
Farmers
Reservoir
and
Irrigation
Company
(
FRICO).
Based
on
these
comments,
three
changes/
clarifications
were
made
to
the
amendment:

1.
A
concern
was
expressed
about
the
potential
impacts
on
Third
Creek
from
the
new
Sixth
Runway,
since
it
was
not
fully
operational
at
the
time
that
the
Receiving
Water
Study
was
conducted.
A
wet
weather
monitoring
location
has
been
added
to
evaluate
the
quality
of
stormwater
runoff
from
the
Sixth
Runway.
The
sample
location,
within
the
southern
portion
of
the
runway,
will
be
representative
of
runoff
generated
from
areas
beyond
the
limits
of
the
edge
drain
collection
system
(
i.
e.,
beyond
the
pavement
area,
in
runway/
taxiway
infield
areas)
and
will
also
be
representative
of
any
runoff
generated
from
within
the
collection
area,
which
exceeds
the
collection
capacity
of
the
edge
drain
system.
Figure
5
has
been
amended
to
show
the
new
monitoring
location.
The
parameters
and
monitoring
frequency
will
be
the
same
as
for
outfalls
A,
C
and
D.

2.
The
items
to
be
included
in
the
ADF
capture
efficiency
annual
report
were
questioned.
The
reporting
elements
have
been
further
specified
as
the
total
amounts
of
ADF
that
are
applied,
recovered,
treated
(
via
Metro),
recycled,
and
not
collected
(
i.
e.,
fugitive
ADF).

3.
A
concern
was
expressed
about
the
reduction
in
monitoring
frequency
at
outfalls
A,
C
and
D,
from
once
every
two
months
to
quarterly,
and
a
requirement
for
Whole
Effluent
Toxicity
(
WET)
testing
was
suggested.
The
Division
has
determined
that
the
proposal
to
decrease
the
wet
weather
monitoring
may
not
be
sufficient
to
provide
a
reasonable
characterization
of
seasonal
differences
in
storm
events.
The
monitoring
frequency
will
remain
at
every
two
months
for
now;
this
issue
may
be
re­
examined
when
the
permit
is
renewed.
The
merits
of
WET
testing
will
also
be
considered
at
that
time.

Kathryn
Dolan
April
8,
2004
