
C:\
dmautop\
temp\
DCTM_
ARP.
wpd
MEMORANDUM
TO:
File;
Carey
Johnston,
USEPA/
EAD
FROM:
Mary
Willett
and
Mark
Briggs,
ERG
DATE:
July
15,
2004
SUBJECT:
DRAFT:
Costing
Assumptions
Regarding
Downtime
at
Existing
O&
G
Extraction
Facilities
This
memorandum
documents
the
assumptions
used
regarding
downtime
at
existing
O&
G
extraction
facilities
to
allow
for
CWIS
control
maintenance.
This
issue
was
evaluated
for
both
Mobile
Offshore
Drilling
Units
(
MODUs)
and
for
fixed
platform
facilities.

Information
was
gathered
from
experts
in
the
O&
G
extraction
field
regarding
typical
maintenance
practices
for
MODUs
and
fixed
facilities
as
follows:

°
April
4,
2001
Meeting
with
Mr.
James
M.
Magill,
U.
S.
Coast
Guard,
Vessel
and
Facility
Operating
Standards
Division.

°
June
8,
2004
Email
Correspondence
with
Mr.
Elmer
Danenberger,
Mineral
Management
Service
(
MMS).

°
June
9,
2004
Email
Correspondence
with
Mr.
Kent
Satterlee,
Shell
Oil
Company.

Mobile
Offshore
Drilling
Units
Mr.
Magill
of
the
U.
S.
Coast
Guard
provided
information
related
to
cooling
water
intake
structures
(
CWISs)
for
MODUs.
MODUs
typically
draw
in
intake
water
through
a
sea
chest.
The
sea
chest
is
a
cavity
in
the
hull
or
pontoon
of
the
MODU
and
is
exposed
to
the
ocean
with
a
screen
often
set
along
the
flush
line
of
the
sea
chest.
There
are
generally
two
sea
chests
for
each
drill
ship
or
semi­
submersible
(
port
and
starboard)
for
redundancy
and
ship
stability.
In
general,
only
one
sea
chest
is
required
at
any
given
time
for
drilling
operations.
Mr.
Magill
indicated
that
there
are
generally
three
pipes
for
each
sea
chest
(
including
cooling
water
intakes
and
fire
pumps).
One
of
the
intake
pipes
is
always
set
aside
for
use
solely
for
emergency
fire
fighting
operations.
Regarding
maintenance
downtime,
Mr.
Magill
stated
that
current
Coast
Guard
requirements
are
that
operators
must
inspect
sea
chests
twice
in
five
years
with
at
least
one
cleaning.
These
requirements
are
particularly
important
to
ensure
that
the
separate
intake
for
the
fire
pump
is
Memorandum
9
June
2004
Page
2
C:\
dmautop\
temp\
DCTM_
ARP.
wpd
clear.
Mr.
Magill
estimated
that
the
regular
cleaning
and
inspection
schedule
should
be
enough
to
control
marine
biofouling
in
the
Gulf
of
Mexico.

Based
on
this
information,
EPA
assumed
that
the
existing
Coast
Guard
requirements
for
MODU
sea
chest
maintenance
are
sufficient
and
no
downtime
or
additional
maintenance
costs
were
developed
for
MODUs.

Fixed
Platforms
Fixed
Platforms
were
costed
for
CWIS
control
maintenance
(
i.
e.,
annual
screen
inspection
and
cleaning
using
divers).
EPA
requested
information
from
Mr.
Danenberger
and
Mr.
Satterlee
to
determine
whether
regular
downtime
is
typical
for
fixed
platforms
during
which
CWIS
control
maintenance
could
occur
or
whether
maintenance
costs
would
need
to
account
for
potential
downtime
lost
production.
Both
Mr.
Danenberger
and
Mr.
Satterlee
indicated
that
it
is
usual
for
fixed
platforms
to
experience
periodic
shut
ins
for
production
maintenance
purposes.
Mr.
Danenberger
indicated
that
the
frequency
and
duration
of
the
production
maintenance
shut
ins
is
dependent
on
platform
age,
complexity,
condition
of
the
facility,
and
company
practices
and
policy.
Newer
facilities
might
only
shut
in
once
per
year
for
two
to
three
days,
other
facilities
might
average
two
shut
ins
per
year,
each
for
up
to
a
week.
Mr.
Satterlee
indicated
that
for
Shell
facilities,
on
average
there
are
one
to
two
scheduled
shut
ins
per
year
of
varying
duration.
He
estimated
that
on
average
a
typical
shut
in
would
be
two
to
three
days
depending
on
the
scope
of
work
to
be
performed.
In
addition,
there
can
also
be
unplanned
shut
ins
to
address
critical
maintenance
items.

Based
on
this
information,
EPA
assumed
that
for
fixed
platform
facilities,
CWIS
control
maintenance
can
occur
during
a
regularly
scheduled
downtime
and
costs
beyond
the
maintenance
costs
for
screen
inspection
and
cleaning
were
not
required.
