UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
REGION
IX
75
Hawthorne
Street
San
Francisco,
CA
94105
July
16,
2003
MEMORANDUM
SUBJECT:
Comments
on
Subsurface
Vapor
Intrusion
Pathway
Guidance
FROM:
Keith
Takata,
Director
Superfund
Division,
Region
9
Amy
Zimpfer,
Acting
Director
Waste
Management
Division,
Region
9
TO:
Marianne
Lamont
Horinko,
Assistant
Administrator
Office
of
Solid
Waste
and
Emergency
Response
Thank
you
for
the
opportunity
to
comment
on
the
OSWER
draft
guidance
on
subsurface
vapor
intrusion
["
Draft
Guidance
For
Evaluating
The
Vapor
Intrusion
to
Indoor
Air
Pathway
From
Groundwater
And
Soils"
(
Docket
ID
No.
RCRA­
2002­
0033)].
I
apologize
for
our
very
late
comments.

We
understand
that
the
draft
guidance
was
designed
to
be
a
tool
to
help
determine
if
the
vapor
intrusion
exposure
pathway
is
complete
and
if
it
poses
a
potential
significant
threat
to
human
health.
We
believe
that
the
draft
guidance
is
largely
successful
in
this
regard.
In
general,
the
document
is
well
organized
and
presents
a
tiered
screening
approach
that
is
both
objective
and
appropriate.

We
have,
however,
identified
three
significant
One
Cleanup
Program
issues
that
should
be
considered
in
the
final
document.
We
also
would
direct
your
attention
to
the
February
27,
2003
comment
letter
from
the
EPA
Regional
Risk
Assessors
group
which
incorporates
much
of
the
specific
input
from
our
Region
9
toxicologists.

1.
OSHA
Standards
in
RCRA
v.
Risk
Assessment
The
discussion
of
OSHA
workplace
standards
and
the
application
of
the
guidance
to
"
occupational"
settings
in
Section
D(
1)
of
the
draft
guidance
needs
to
be
clarified.
The
draft
suggests
that
OSHA
standards
should
apply
to
all
occupational
settings,
even
in
office
buildings
where
chemicals
are
not
routinely
handled.
In
the
RCRA
program,
the
OSHA
standards
are
used
in
making
interim
RCRA
Environmental
Indicator
(
EI)
determinations
that
current
human
exposures,
due
to
the
vapor
intrusion
pathway,
are
under
control.
It
is
our
understanding
that
the
OSHA
standards
are
intended
for
use
only
to
make
EI
determinations,
which
are
interim
determinations
and
may
not
reflect
the
final
cleanup
status
of
a
site.
We
are
concerned
that
applying
OSHA
standards
to
our
sites
as
cleanup
standards
is
inconsistent
with
accepted
program
guidance
as
adopted
in
the
Risk
Assessment
Guidance
for
Superfund
(
RAGS).
This
is
primarily
due
to
the
fact
that
although
both
OSHA
standards
and
the
Superfund
risk
assessment
approach
protect
the
health
of
workers
exposed
to
toxic
substances,
the
conditions
of
exposure
for
each
set
of
values
differ
significantly
[
see
the
discussion
of
this
issue
in
the
Supplemental
Guidance
for
Developing
Soil
Screening
Levels
for
Superfund
Sites,
Peer
Review
Draft,
OSWER
9355.4­
24,
March
2001,
p.
4­
31]
.
At
both
RCRA
corrective
action
and
Superfund
sites,
site
specific
conditions
will
be
evaluated
to
determine
a
final
cleanup
goal.

The
problem
with
applying
OSHA
standards
versus
a
risk­
based
approach
to
site
contamination
is
emphasized
when
RCRA
and
CERCLA
sites
are
located
in
the
same
community
such
as
the
MEW
(
Superfund)
and
GTE
(
RCRA)
sites
here
in
California.
As
written,
the
draft
guidance
would
suggest
that
EPA
use
different
approaches
and/
or
screening
levels
at
each
of
these
sites
which
are
directly
adjacent
to
each
other,
concern
the
same
contaminants,
and
share
the
same
concerned
community.
It
would
be
difficult
to
justify
different
approaches
to
community
members
and
local
government
officials.

On
a
separate,
but
related
issue,
the
draft
Vapor
Intrusion
and
RCRA
Corrective
Action
(
CA)
Environmental
Indicators
(
EI)
Fact
Sheet
(
6/
17/
03)
indicates
that
OSHA
standards
should
be
used
in
making
EI
determinations
at
occupational
settings
and
if
a
site
passes
this
screen,
then
confirmatory
sampling
will
not
be
necessary
for
purposes
of
making
an
EI
determination.
This
fact
sheet
will
likely
confuse
Potentially
Responsible
Parties
at
Superfund
sites
and
communities
because
it
does
not
explain
the
difference
between
an
EI
determination
and
a
risk­
based
cleanup
decision.
There
needs
to
be
clarification
that
the
OSHA
standards
are
intended
for
use
in
making
interim
RCRA
EI
determinations
at
occupational
settings
and
not
always
as
the
final
cleanup
standard
for
a
site.

2.
10­
5
Goal
for
Carcinogens
v.
Full
Risk
Range
We
believe
that
the
full
cancer
risk
range
should
be
considered
even
during
the
screening
process.
The
draft
guidance
[
Section
IV.
C]
recommends
that
EPA
use
an
incremental
individual
lifetime
cancer
risk
of
10­
5
for
EI
determinations
with
respect
to
vapor
intrusion
under
RCRA
and
CERCLA.
We
would
ask
that
program
management
decisions
be
made
using
the
full
10­
4
to
10­
6
range
as
is
typical
in
our
programs.
Such
an
approach
provides
necessary
flexibility
in
our
decision
making
and
is
consistent
with
the
approach
we
commonly
use
at
our
sites.

3.
Positive
Pressure
in
Buildings
v.
Permanent
Remedies
The
draft
guidance
implies
that
if
a
building
(
particularly
a
commercial
space)
is
under
positive
pressure
[
Section
IV.
G],
no
further
action
needs
to
be
taken
to
determine
whether
the
vapor
intrusion
pathway
is
complete.
We
have
found
in
our
own
site
specific
evaluations
that
this
assumption
can
pose
problems.
Many
issues
complicate
the
evaluation
of
the
presence
of
positive
pressure,
including
the
fact
that
ventilation
systems
are
typically
shut
down
at
night
and
on
weekends.
Also,
we
understand
that
rooms
which
tend
to
be
primary
entry
points
for
utilities,
electrical
conduits
or
floor
drains
(
potential
vapor
intrusion
paths)
can
be
under
negative
pressure,
even
in
those
buildings
with
overall
average
positive
pressure.
Additionally,
the
proper
assessment
of
plans
and
specifications
of
ventilation
systems
in
potentially
impacted
buildings
would
require
a
heating,
ventilation,
and
air
conditioning
(
HVAC)
consultant.
Relying
only
on
the
presence
of
positive
pressure
to
determine
whether
there
is
a
complete
pathway
raises
concerns
about
our
preference
for
remedy
permanence
and
the
implementation
and
effectiveness
of
institutional
controls.

In
closing,
Region
9
has
evaluated
the
vapor
intrusion
pathway
at
a
number
of
Superfund
and
RCRA
sites
over
the
past
decade.
As
such,
we
have
developed
experience
in
scoping
and
implementing
indoor
air
sampling.
We
look
forward
to
working
with
you
ensure
that
the
final
guidance
provides
the
best
information
available
to
address
this
important
issue.

If
you
have
any
questions,
please
call
me
or
have
your
staff
contact
Elizabeth
Adams
at
415­
972­
3183.

cc:
Mike
Cook
Bob
Springer
