Document ID: EPA-HQ-OW-2004-0002-0501
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2004-11-30T05:00Z

Cooling
Water
Intake
Structure
(
CWIS)
Information
Data
Required
Rig
Information
Rig
Name
ENSCO
7500
Rig
Type
Semi
submersible
(
Dynamically
Positioned)
Total
Installed
Power
Generation
Capacity
31,400
HP
Number
of
Cooling
Water
Intake
Structures
(
CWISs)
6
Brief
description
of
each
CWIS
(
e.
g.,
sea
chest,
simple
pipe)
Sea
Chests:
2­
ballast
2­
ballast/
thruster
cooling
2­
thruster
cooling/
engine
cooling/
seawater
service
Rough
dimensions
of
each
CWIS
and
indicate
whether
onboard
CWIS
has
an
existing
flange
Aft
Main
Seachests:
28"
W
x
24"
H,
w/
6.5"
radiused
corners
­
Flanged
(
Doubler
plate
with
tapped
blind
holes)
port
&
starboard,
open
area
462
sq
in
Aft
Ballast
Seachests:
28"
W
x
16"
H,
w/
6.5"
radiused
corners
­
Flanged
(
Doubler
plate
with
tapped
blind
holes)
port
&
starboard,
open
area
289
sq
in
Forward
Seachests:
28"
W
x
16"
H,
w/
6.5"
radiused
corners
­
Flanged
(
Doubler
plate
with
tapped
blind
holes)
port
&
starboard,
open
area
289
sq
in
Screen
type
(
e.
g.,
strainer,
wedge
wire)
with
mesh
size
1­
1/
4"
x
¼
"
Serrated
Bar
Grating
(
All
sea
chests
similar)

Total
Design
Specifications
for
Daily
Maximum
Water
Intake
Volume
of
each
CWIS
Aft
Main
Seachests:
10,224,000
gal
each
Aft
Ballast
Seachests:
2,592,000
gal
each
Fwd
Seachests:
3,312,000
gal
each
Total
Daily
Water
Intake
Volume
of
each
CWIS
(
Set­
up/
Drilling)
Total
Daily
Water
Intake
at
Set­
up
Stbd.
Aft
Main
Seachest:
10,224,000
gal
Stbd.
Aft
Ballast
Seachest:
324,000
gal
Stbd
Fwd
Seachest:
1,044,000
gal
Port
Aft
Main
Seachest:
720,000
gal
Port
Aft
Ballast
Seachest:
324,000
gal
Port
Fwd
Seachest:
1,044,000
gal
Total
Daily
Water
Intake
during
Drilling
Stbd.
Aft
Main
Seachest:
10,224,000
gal
Stbd.
Aft
Ballast
Seachest:
16,000
gal
Stbd
Fwd
Seachest:
16,000
gal
Port
Aft
Main
Seachest:
720,000
gal
Port
Aft
Ballast
Seachest:
16,000
gal
Port
Fwd
Seachest:
16,000
gal
Total
Daily
Cooling
Water
Intake
during
Setup
and
Drilling
Stbd.
Aft
Main
Seachest:
8,512,000
gal
Stbd.
Aft
Ballast
Seachest:
none
Stbd
Fwd
Seachest:
720,000
gal
Port
Aft
Main
Seachest:
720,000
gal
Port
Aft
Ballast
Seachest:
none
Port
Fwd
Seachest:
720,000
gal
Design
Specs
for
Through
Screen
Velocity
of
each
CWIS
(
i.
e.,
Q=
V*
A)
(
Set­
up/
Drilling)
Stbd.
Aft
Main
Seachest:
4.93
fps
Stbd.
Aft
Ballast
Seachest:
2.0
fps
Stbd
Fwd
Seachest:
2.55
fps
Port
Aft
Main
Seachest:
4.93
fps
Port
Aft
Ballast
Seachest:
2.0
fps
Port
Fwd
Seachest:
2.55
fps
List
of
Purposes
of
Cooling
Water
Intakes
(
e.
g.,
cool
crude
oil,
produced
water,
power
generators,
drill
pipe
brakes)
Aft
Main
Seachests:
cooling
to
power
rectifier
and
3
A/
C
units.
Aft
Ballast
Seachests:
None
Fwd
Seachest:
cooling
to
2
thrusters
List
of
Purposes
of
Non­
cooling
Water
Intakes
(
e.
g.,
fire
water,
hotel
loads)
Aft
Main
Seachests:
Distillation
units,
oil/
water
separators
(
4),
cuttings
washer,
flush
water
for
cuttings
dump
chute
Aft
Ballast
Seachests:
Ballast
Fwd
Seachest:
cooling
to
2
thrusters
Total
Volume
of
Water
Intake
for
Ballasting,
Duration
of
the
Ballast
intake,
and
the
Through
Screen
Velocity
of
the
Ballast
intake
Total
Daily
Water
Intake
for
Ballasting:
Duration
Velocity
Stbd.
Aft
Main
Seachest:
none
Stbd.
Aft
Ballast
Seachest:
3
hrs
2.0
fps
Stbd
Fwd
Seachest:
3
hrs
2.0
fps
Port
Aft
Main
Seachest:
none
Port
Aft
Ballast
Seachest:
3
hrs
2.0
fps
Port
Fwd
Seachest:
3
hrs
2.0
fps
Mitigation
Measures
for
reducing
Exotic
Species
Migration
through
Ballast
water
Aluminum
and
copper
impressed
current
anodes
at
all
seachests.
Deepwater
ballast
exchange
when
ballast
water
carried..
Mitigation
Measures
for
reducing
Impingement
and
Entrainment
of
Aquatic
Organisms,
as
well
as
Bio­
fouling
Prevention
Measures
Biocide
injection
and
corrosion
inhibitor
injection
into
engine
cooling
suctions
and
thruster
cooling
suctions.
No
injection
into
ballast
suctions.
Aluminum
and
copper
impressed
current
anodes
at
all
seachests.
Is
the
Rig
equipped
with
a
Radiator
Cooling
System
for
the
Main
Engines?
No