1
COMMENTS
FROM
EPA
REGION
III
On
DRAFT
GUIDANCE
FOR
EVALUATION
THE
VAPOR
INTRUSION
TO
INDOOR
AIR
PATHWAY
FROM
GROUNDWATER
AND
SOILS
Prepared
by
Andrew
Fan,
Fan.
andrew@
epa.
gov,
215­
814­
3426
3WC23,
1650
Arch
Street,
Philadelphia,
Pa
19103­
2029
General
Comments
(
1)
Target
Concentration
Tables
The
guidance
provides
tables
of
media
target
concentrations
by
back
calculating
groundwater
and
soil
gas
concentrations
from
indoor
air
Risk
Based
Concentrations
(
RBCs).
The
Region
understands
that
HQ's
intent
was
to
simplify
the
risk
screening
process
by
standardizing
the
results,
reducing
irregularities,
and
avoiding
the
burden
to
collect
indoor
air
samples
until
it
was
proven
necessary.
Unfortunately,
the
proposed
tables
present
new
concerns
such
that
the
Region
recommends
their
removal
from
the
guidance.

One
concern
about
the
guidance
is
that
although
the
target
concentrations
are
provided
for
risk
screening
purpose
only,
the
tabulated
values
are
capped
at
Maximum
Contamination
Limits
(
MCLs).
While
the
Region
agrees
that
below
MCL
extrapolation
needs
to
be
addressed,
there
are
inherent
problems
using
the
proposed
approach.
For
example,
if
MCLs
are
back
calculated
to
soil
air
and
indoor
air
levels,
they
will
not
match
the
corresponding
levels
back
calculated
in
the
other
direction
from
indoor
air
RBCs.
Also
there
is
no
technical
basis
to
cap
the
target
concentrations
at
MCLs.
Therefore,
the
guidance's
disclaimer
that
the
target
concentrations
are
not
risk
management
goals
is
contradictory.
Further
evidence
of
this
confusion
is
that
a
section
of
the
guidance
is
devoted
to
discussing
the
applicability
of
target
concentrations
to
occupational
settings
and
non­
residential
settings
where
OSHA
standards
may
or
may
not
apply.
This
clearly
implies
that
the
target
concentrations
provide
risk
management
function
comparable
to
the
OSHA
standards.

Another
concern
is
that
the
target
concentrations,
once
published,
will
likely
be
perceived
and
misinterpreted
as
risk
management
goals
by
some
users
despite
disclaimers
to
the
contrary.
The
target
concentrations
were
derived
from
RBCs.
The
implementing
agencies
may
choose
to
use
background,
technological
limitation,
or
other
policy
considerations
besides
RBCs
to
establish
risk
management
goals.
In
fact,
several
states
have
already
established
indoor
air
standards
by
considering
background
levels,
which
can
deviate
from
RBCs
by
several
orders
of
magnitude.
Once
the
target
concentration
numbers
are
published,
comparison
and
dispute
of
the
numbers
will
likely
occur.
This
will
increase
the
burden
of
the
implementing
agencies
to
defend
the
risk
management
goals
that
deviate
from
the
target
concentrations.
2
In
addition,
it
has
been
the
Region's
experience
that
target
concentrations
can
change
rather
drastically
with
corresponding
changes
in
the
RBCs.
Most
likely,
by
the
time
this
guidance
is
finalized,
some
RBC
values
that
the
tables
are
based
on
may
have
already
been
changed.
Unlike
policy
standards,
revisions
of
RBC
values
do
not
require
a
promulgation
process
that
mandates
public
participation
and
comment
on
the
proposed
changes.
RBCs
were
established
by
consensus
values
based
on
the
best
available
scientific
data.
The
consensus
process
has
not
been
defined.
The
best
available
scientific
data
do
not
mean
that
the
data
are
necessarily
the
best
data
or
even
sound
scientific
data.
The
scientific
basis
of
the
RBCs
are
not
equal
as
some
values
are
more
or
less
certain
than
others.
The
guidance
has
acknowledged
such
uncertainty
by
stating
in
Appendix
D,
Toxicity
Values
paragraph,
that
"
for
most
compounds,
extrapolation
from
oral
data
introduces
considerable
uncertainty
into
the
resulting
inhalation
value.
Values
obtained
from
inhalation
studies
or
from
pharmacokinetic
modeling
applied
to
oral
doses
will
be
less
uncertain
than
those
calculated
using
the
equations
below."
Note
that
about
half
the
values
in
the
tables
were
extrapolated
from
provisional
oral
toxicity
values.
Since
the
RBCs
can
change
rather
drastically
(
as
evidenced
by
recent
proposed
revision
of
TCE
and
1,
1
DCE
toxicity
values),
the
implementing
agencies
will
have
to
bear
the
burden
to
explain
such
drastic
changes
to
the
public
after
an
action
has
been
implemented
based
on
an
outdated
RBC.

The
Region
does
not
believe
there
is
an
easy
way
to
fix
the
tables
to
address
all
underling
problems
in
a
satisfactory
and
clear
manner.
As
long
as
the
target
concentrations
are
RBC
based,
the
uncertainty,
confusion
and
misinterpretation
of
the
RBC
linked
values
will
remain.
Therefore,
the
Region
recommends
the
elimination
of
the
target
concentration
tables
as
an
integral
component
of
the
guidance.
This
will
remove
potential
misinterpretation
of
the
target
concentrations
and
all
uncertainty
associated
with
RBC
linked
values.
In
lieu
of
the
target
concentration
tables,
the
guidance
should
recommend
and
tabulate
attenuation
factors
under
different
scenarios.
Deriving
risk
screening
or
risk
management
values
from
the
recommended
attenuation
factors
is
a
simple
task
and
the
guidance
can
provide
a
series
of
examples
on
how
to
perform
the
calculation.
This
approach
will
make
it
clear
that
implementation
agencies
have
multiple
options
to
choose
a
risk
management
policy
most
appropriate
for
the
region,
state
or
site
as
well
as
to
validate
alternate
approaches
already
established
out
there.

A
sample
of
the
tables
can
be
included
in
the
appendix
as
a
reference
for
one
of
the
examples.
The
entire
set
of
tables
can
also
be
moved
to
a
web
link
as
independent,
life­
update
tables.
The
tables
should
be
renamed
"
Risk
Screening
Tables"
so
that
there
is
no
ambiguity
of
their
intended
use.
An
appropriate
location
for
the
tables
is
in
the
EPA
J&
E
Model
spreadsheet
web
page
and
the
tables
can
be
described
as
pre
calculated
screening
values
based
on
default
EPA
parameters.
By
segregating
the
tables
and
clearly
defining
their
function,
there
is
no
need
to
cap
the
values
at
MCLs.
3
(
2)
Guidance
Format
The
guidance
follows
the
Q
&
A
format
of
the
EI
forms.
This
was
an
appropriate
choice
when
the
guidance
was
developed
for
EI
use
only.
However,
the
guidance
has
now
expanded
to
cover
multiple
objectives.
It
addresses
not
only
EI
determination,
but
also
remedy
selection
for
the
RCRA
and
Superfund
programs.
It
may
eventually
address
the
LUST
program
as
well.
Although
the
guidance
has
improved
greatly
in
content
by
considering
many
factors
neglected
in
the
original
EI
version,
it
has
become
very
prescriptive
and
cumbersome
to
read.
Reconciling
multiple
objectives
with
different
standards
in
one
guidance
can
be
challenging.
The
Region
recommends
that
the
guidance
to
be
reorganized
to
make
it
easier
to
follow.
One
solution
is
to
move
the
EI
component
to
an
appendix
by
retaining
the
Q&
A
format
in
simplified
form,
and
rewrite
the
guidance
in
narrative
format.

(
3)
Future
Land
Use
While
it
is
prudent
to
consider
future
land
uses,
experience
has
shown
that
it
is
not
possible
to
reliably
predict
future
use.
An
alternative
approach
is
to
recommend
the
use
of
appropriate
institutional
controls,
and
monitoring
sites
where
contaminated
soil
or
groundwater
will
remain
in
place.
Institutional
controls
with
proper
verification
can
be
designed
to
ensure
that
the
land
use
will
not
change
in
the
future
that
would
pose
unacceptable
risk,
and
that
future
construction
must
be
modified
in
such
a
way
that
entry
of
subsurface
vapor
can
be
minimized.
When
the
contaminated
media
is
groundwater,
long­
term
monitoring
may
be
necessary
to
ensure
that
a
stable
plume
will
not
be
affected
by
external
influences.

(
4)
Risk
Goal
­
EI
versus
Final
Remedy
As
written,
the
guidance
is
ambiguous
as
to
whether
the
Agency
expects
re­
evaluation
of
the
conditions
based
on
a
10­
6
risk
level
at
final
remedy
phase.
If
the
Agency
has
chosen
to
go
forward
with
screening
at
a
10­
5
risk
level
for
the
EI,
then
from
an
implementation
standpoint,
it
is
unrealistic
to
expect
the
site
to
be
re­
evaluated
at
10­
6
risk
level
at
the
final
remedy
phase.
Re­
screening
at
the
final
remedy
phase
contradicts
the
concept
that
the
EI
serves
as
an
intermediate
step
toward
final
remedy.
Re­
screening
is
an
inefficient
use
of
resources
and
would
be
difficult
to
justify
in
light
that
10­
5
risk
level
is
already
within
the
EPA
acceptable
risk
range.
And,
if
the
re­
evaluation
of
a
residential
neighborhood
resulted
in
a
determination
of
an
unacceptable
risk,
it
would
significantly
undermine
the
credibility
of
"
Human
Exposures
Under
Control"
determinations
in
general.
If
the
agency
goes
forward
with
a
screening
at
a
10­
5
risk,
they
should
be
prepared
to
accept
that
level
as
a
final
remedy.
If
a
10­
5
risk
level
is
inconsistent
with
the
Agency
policy
for
final
clean
up
goals,
then
a
lesser
standard
should
not
be
employed
just
to
meet
the
Agency's
EI
goals.
4
(
5)
Incomplete
Pathway
terminology
In
several
places
the
guidance
uses
the
determination
of
an
"
incomplete
pathway"
interchangeably
with
a
"
complete
pathway
at
levels
such
that
the
risk
is
negligible."
This
is
confusing,
since
the
terminology
"
incomplete
pathway"
has
the
very
specific
meaning
of
"
no
exposure"
in
the
field
of
environmental
science.
The
guidance
should
distinguish
between
an
incomplete
pathway
and
a
complete
pathway
which
does
not
pose
an
unacceptable
risk.
This
change
is
necessary
to
avoid
confusion
and
misinterpretation
which
could
lead
to
unacceptable
exposures
in
the
future.
If
the
guidance
states
that
there
is
an
"
incomplete
exposure,"
then
that
should
mean
that
the
use
of
that
building
can
change
without
concern
for
potential
exposures
in
the
future.
However,
in
the
current
dual
meaning,
a
change
in
use
can
create
a
complete
pathway.
This
is
not
logical.
This
clarification
would
require
some
editing
of
text
throughout
the
document.
Suggestions
are
provided
in
the
editorial
comments
section.

Specific
Comments
(
6)
Page
2,
Section
C,
"
We
recommend
that
State
and
Regional
UST
Corrective
Action
Programs
continue
to
use
a
risk
based
decision
making
approach
as
described
in
OSWER
Directive
9610.17:
Use
of
Risk­
Based
Decision
Making
in
UST
Corrective
Action
Program
to
address
this
pathway."

The
Region
does
not
recommend
referencing
OSWER
Directive
9610.17
which
cited
ASTM
RBCA
guidance
approach
and
state
guidance
as
examples.
(
The
OSWER
Directive
9610.17:
Use
of
Risk­
Based
Decision
Making
in
UST
Corrective
Action
Programs,
March
1995,
can
be
found
at:
www.
epa.
gov/
swerust1/
directiv/
od961017.
pdf
)
The
reason
is
that
the
ASTM
guidance
uses
a
simplified
form
of
J&
E
Model
to
generate
screening
values
that
are
substantially
different
from,
and
less
conservative
than
the
guidance
target
concentrations.
In
light
of
the
fact
that
EPA
is
still
investigating
the
best
approach
for
UST
sites,
it
is
recommended
that
this
guidance
not
endorse
the
ASTM
RBCA
numerical
criteria
that
is
implicit
in
the
OSWER
directive.

Strictly
speaking,
only
the
numerical
criteria
(
attenuation
coefficients
and
target
media
concentrations)
in
the
guidance
may
not
be
appropriate
for
petroleum
sites
because
the
numerical
criteria
were
derived
almost
exclusively
(
239
of
274
data
points)
from
chlorinated
solvents
data.
The
technical
information
and
tools
presented
in
the
guidance
are
largely
appropriate.
The
Region
recommends
that
the
exclusion
statement
be
limited
to
numerical
criteria
only.

(
7)
Exclusion
criteria
in
Questions
4(
f),
4(
i)
and
5(
b).
Also,
Page
3
under
non­
residential
settings,
"
The
recommendations
in
this
guidance
may
be
appropriate
for
such
situations,
although
we
recommend
adjustments
appropriate
for
non­
residential
exposure
durations,
the
building
specific
air
volumes
and
air
exchange
rates,
as
well
as
other
relevant
factors
be
considered.
The
model
used
in
this
guidance
accommodates
the
inclusion
of
these
kinds
of
variables
and
for
comparison
of
computed
values
with
the
recommended
numerical
criteria
in
Tables
2
and
3."
5
Notwithstanding
the
need
to
adjust
for
exposure
assumptions,
the
numerical
criteria
in
Tables
2
and
3
are
categorically
inapplicable
to
non­
residential
buildings
where
air
exchange
rates
and
pressure
differential
are
completely
different
from
residential
homes.
The
heating
and
ventilating
system
designs
in
commercially
buildings
are
fundamentally
different
from
systems
in
residential
homes.
It
is
not
uncommon
for
commercial
buildings
to
be
positively
pressured
partially
or
wholly
and
so
the
"
chimney
effect"
assumption
may
not
necessarily
be
valid
for
commercial
buildings.
Therefore,
the
exclusion
criteria
should
include
all
commercial
buildings.

(
8)
OSHA
The
paragraphs
on
page
3,
Section
D,
referring
to
occupational
settings
are
problematic
because
a)
this
section
allows
for
a
risk
management
decision
to
supercede
an
evaluation
of
actual
risk,
and
b)
OSHA
is
not
applicable
to
all
RCRA
sites.
As
stated
in
Subpart
S,
under
OSHA
Instruction
CPL
2­
2.37A
of
January
29,
1986,
OSHA
and
EPA
have
agreed
that
OSHA
has
the
lead
role
in
providing
for
the
safety
and
health
of
workers
at
hazardous
waste
sites.
Many
RCRA
sites
are
no
longer
operating
as
hazardous
waste
sites
due
to
changes
in
use.
Some
sites
currently
undergoing
corrective
action
are
being
leased
as
commercial
office
space.
It
is
EPA's
responsibility
to
ensure
that
the
individuals
in
these
buildings
are
provided
with
adequate
protection.
After
screening
a
site
to
determine
the
risk,
the
risk
manager
can
then
decide
whether
the
situation
is
appropriate
to
defer
to
OSHA.
This
approach
would
be
consistent
with
the
overall
objective
of
the
guidance
which
is
to
assess
whether
there
is
a
complete
pathway,
and
if
so
to
determine
whether
the
exposure
may
pose
an
unacceptable
risk.
As
specifically
stated
on
page
9,
this
guidance
does
not
address
setting
risk
management
goals.
To
remedy
this
situation,
The
Region
recommends
that
the
guidance
recognize
OSHA
as
an
appropriate
risk
management
option
to
consider
after
proper
risk
screening.

(
9)
Page
7,
"
Primary
Screening
.
.
.
immediate
action
.
.
.
If
inhabited
buildings
are
located
(
or
will
be
constructed
under
future
development
scenarios­
except
for
Environmental
Indicator
determinations
.
.
.)
above
or
in
close
proximity
to
subsurface
contamination."

This
is
a
vague
criterion
because
immediate
action
has
no
bearing
with
future
development,
and
potential
future
development
cannot
be
determined
or
ruled
out
under
present
condition.
Even
if
future
development
is
contemplated,
there
are
ways
to
construct
buildings
to
prevent
subsurface
vapor
intrusion
and
so
potential
future
development
is
not
a
valid
screening
criterion.

(
10)
Detection
limits
in
Table
2a,
b,
c
and
Tables
3
a,
b
and
c
A
number
of
values
in
the
above
tables
are
below
Average
Practical
Detection
Limits
as
listed
in
Table
A­
2
of
Appendix
A.
Whereas
the
table
values
are
capped
at
MCL
and
pure
compound
vapor
concentrations,
no
consideration
is
given
to
below
detection
limits.
The
Region
understands
that
there
is
no
one
detection
limit
as
it
varies
with
the
methods
and
testing
condition
and
so
it
is
impossible
to
pre
determine
the
detection
limits.
However,
this
important
issue
must
be
addressed
somewhere
in
the
guidance.
6
Also,
it
is
unclear
why
some
compounds,
such
as
Benzo(
b)
fluranthene
in
Table
2c
is
capped
at
maximum
pure
compound
vapor
concentration
in
groundwater.
Is
it
a
reference
error
as
it
really
means
to
cap
at
maximum
solubility?

(
11)
Appendix
A,
Table
A­
2
Appendix
A
provides
valuable
summary
information
on
EPA
analytical
methods;
however,
Table
A­
2
is
incomplete
with
exclusion
of
several
important
EPA
methods
for
VOC
analysis,
such
as
TO­
14a,
8015b,
8021b
.
.
.
etc.
Also,
there
should
be
a
discussion
on
the
pros
and
cons
of
common
air
sampling
devices
such
as
Tedlar
bag,
vial,
vacuum
box,
canister,
sorbent
tube,
syringe
and
peristaltic
pump.

(
12)
Appendix
E,
Section
III,
"
This
(
the
presence
of
LNAPL)
can
be
indicated
by
analytical
results
from
water
samples
taken
at
the
water
table
having
values
higher
than
the
theoretical
solubility
of
the
specific
LNAPL
compound
present."

The
statement
is
incorrect.
Numerous
field
studies
in
petroleum
sites
have
found
that
ground
water
constituent
concentrations
do
not
typically
reach
solubility
limits
of
the
pure
compounds
in
contact
with
groundwater.
An
API
report
has
shown
that
concentrations
of
compounds
leached
from
a
blend
of
pure
compounds
in
gasoline
can
be
as
small
as
0.01
of
the
concentration
leached
from
the
pure
compound.
The
analogy
can
be
drawn
from
the
observation
that
constituent
vapor
concentrations
above
the
water
table
rarely
reach
Henry
Law
limits
due
to
dynamic
nature
of
the
subsurface
systems
and
the
presence
of
other
competing
compounds.

(
13)
Page
10,
"
E.
What
Has
Changed
From
Previous
Guidance
Related
To
Vapor
Intrusion
That
I
Should
Be
Aware
Of?"

The
title
of
this
section,
"
Previous
Guidance",
is
confusing
to
majority
of
the
audience
who
are
not
aware
of
a
previous
version
written
for
EI
determination.
Since
the
EI
version
is
still
in
its
draft
form
and
has
never
been
finalized,
it
is
unnecessary
and
incorrect
to
reference
it
as
"
Previous
Guidance."
The
soil
screening
guidance
was
written
for
a
different
objective
and
scenario
and
has
little
if
anything
to
do
with
the
present
guidance.
The
changes
to
the
EPA
J
&
E
Model
spreadsheet
is
best
explained
in
the
spreadsheet
web
page
itself.
If
it
is
necessary
to
address
the
relationship
of
the
present
guidance
to
the
above
listed
documents,
it
is
best
be
placed
in
the
cover
letter
to
address
a
narrow
audience.

A
previous
Superfund
Guidance,
entitled
"
Assessing
Potential
Indoor
Air
Impacts
for
Superfund
Sites
(
EPA­
451/
R­
92­
002,
September
1992),"
does
exist
and
is
relevant,
but
it
is
not
mentioned
at
all.
If
it
is
necessary
to
explain
the
changes
of
this
guidance
from
the
previous
one,
the
1992
Superfund
Guidance
is
the
rightful
reference
and
should
be
addressed.

(
14)
Page
5,
Paragraph
B,
"
For
example,
where
groundwater
used
as
drinking
water
is
found
to
be
highly
contaminated,
the
groundwater
plume
may
be
cleaned
up
or
its
volume/
concentration
reduced,
or
people
may
drink
bottled
water,
or
they
can
be
connected
to
other
potable
sources.
In
the
case
of
significant
vapor
intrusion,
ventilation
is
likely
the
most
appropriate
approach."
7
Actually,
the
options
for
immediate
groundwater
protection
are
as
limited
as
for
indoor
air.
Cleaning
up
groundwater
will
likely
take
decades
to
achieve
the
risk
protection
level,
and
providing
bottled
drinking
water
will
not
eliminate
the
risk
associated
with
vapor
release
from
nonpotable
use.
Therefore,
neither
option
can
provide
immediate
groundwater
protection.
The
only
viable
option
for
immediate
groundwater
protection
is
to
provide
quick
connection
to
an
alternate
source
of
clean
water
but
it
can
still
take
weeks
or
months
to
complete
the
connection.
In
comparison,
it
is
relatively
easy
to
vent
or
pressurize
a
house
to
control
subsurface
vapor
intrusion.

(
15)
Appendix
I,
Consideration
of
Background
The
Region
is
in
the
opinion
that
it
is
best
to
tabulate
literature
background
concentrations
in
the
Appendix
for
quick
reference.
The
Region
understands
that
background
concentrations
are
highly
dynamic
because
they
vary
with
study,
location
and
time
and
no
published
concentrations
can
be
fully
representative.
However,
by
clearly
citing
the
reference
sources,
mis
representation
of
the
information
can
be
minimized.
The
Region
does
not
see
the
difference
between
publishing
literature
background
concentrations
versus
publishing
attenuation
factors
or
any
other
numerical
criteria
in
the
guidance.

(
16)
Appendix
I,
Tap
Water
Sampling
This
Appendix
addresses
background
sources
and
should
include
a
recommendation
to
sample
tap
water
even
if
the
source
is
public
water.
All
public
water
must
meet
MCLs
which
are
not
solely
risk
based
standards.
Volatilization
from
below
MCL
contaminated
water
can
still
impact
indoor
air
and
should
not
be
overlooked..

(
17)
Appendix
I,
Individual
risk
versus
cumulative
risk
A
paragraph
should
be
devoted
to
discussing
individual
constituent
risk
versus
cumulative
risk.
Such
discussion
should
not
be
limited
to
only
subsurface
related
constituents,
but
also
background
constituents
unrelated
to
the
subsurface
source.
The
implementing
agencies
must
be
cognizant
of
the
total
cumulative
risk
from
all
sources
in
making
decision
on
how
to
manage
the
risk
from
the
subsurface
component.

Editorial
Comments
(
new
words
shown
in
bold)

Page
4,
Section
II,
second
sentence
­
Include
the
word
"
soil"
in
the
following
sentence.
"
Volatile
chemical
in
buried
wastes
and/
or
contaminated
soils
or
groundwater
can
emit
vapors..."

Page
6,
Section
III
­
This
paragraph
is
internally
redundant
and
could
be
significantly
streamlined,
by
removing
the
middle
portion
and
modifying
the
end.
The
following
revision
is
recommended.
"
This
draft
guidance
employs
a
tiered
approach
to
assist
the
user
in
determining
assessing
whether
the
exposure
pathway
is
complete
(
subsurface
vapors
intrude
into
indoor
air
spaces);
and
if
so,
whether
the
vapor
are
present
at
levels
that
may
pose
an
unacceptable
exposure
risk.
By
8
following
the
tiered
approach,
individuals
can
evaluate
whether
the
indoor
pathway
is
incomplete;
complete,
but
present
at
such
low
levels
that
the
risk
is
negligible;
or
complete
at
levels
which
may
pose
an
unacceptable
risk
to
human
health."

Page
8,
Tier
2­
Secondary
Screening,
last
sentence
­
Please
revise
this
sentence
as
follows
to
eliminate
the
inappropriate
use
of
the
term
"
incomplete
pathway."
"
When
results
from
secondary
screening
do
not
support
a
determination
that
the
pathway
is
incomplete
suggest
an
unacceptable
risk
may
be
present,
we
recommend
the
user
proceed
to
the
Site­
Specific
Pathway.

Page
16,
Q2
­
This
question
is
confusing
as
written
since
the
parallel
structure
should
belong
to
"
current
buildings"
and
"
areas
under
future
development."
The
question
should
be
revised
as
follows.
"
Are
currently
(
or
potentially)
inhabited
buildings
or
areas
of
concern
under
future
development
scenarios
(
alternative
choice
­
areas
expected
to
be
developed)
located
near
(
see
discussion
below)
subsurface
contaminants
found
in
Table
1?"
The
answers
to
this
question
would
also
need
some
modification.

Page
22,
top
paragraph
­
For
ease
of
reading,
the
second
sentence
should
be
revised
as
follows.
"
However
we
recommend
that
groundwater
data
be
evaluated
in
conjunction
with
soil
gas
data,
particularly
when
a
plume
extends
beyond
a
contaminated
source
located
in
the
unsaturated
zone."

Page
38­
39,
Site
Specific
Assessment
­
To
address
the
situation
where
no
buildings
currently
exist,
but
there
may
be
a
problem
if
built,
the
Region
recommends
that
this
section
be
revised
to
specifically
recommend
the
use
of
institutional
controls
or
administrative
actions
that
will
ensure
that
the
sites
will
be
evaluated
when
they
are
ready
for
development.

Page
42,
first
full
paragraph
­
To
address
incorrect
use
of
"
incomplete
pathway"
terminology,
please
revise
as
follows.
"
The
site­
specific
pathway
assessment
is
designed....
further
consideration
prior
to
concluding
either
that
the
pathway
is
incomplete
exposure
does
not
pose
an
unacceptable
risk,
or
that..."

Page
45,
question
8
­
To
address
incorrect
use
of
"
incomplete
pathway"
terminology,
please
revise
as
follows.
"
What
do
you
do
if
the
pathway
is
found
to
be
incomplete
to
pose
an
unacceptable
risk?"
And,
revise
the
answer
as
follows.
"
If
the
pathway
is
judged
to
pose
an
unacceptable
risk
during
the..."
