2.
Response
to
Comments
2.9
Individual
Responses
to
Comments
from
Organizations
sub-slab
vapor
barriers
to
minimize
potential
vapor
intrusion
into
buildings.
In
addition,
all
structures
built
on
or
within
1,000
feet
of
the
landfill
footprint
are
required
to
be
equipped
with
automatic
combustible
gas
sensors
in
sub-floor
areas
and
in
the
first
floor
of
occupied
interior
spaces.
See
See
for
discussion
regarding
the
Title
27
landfill
closure
review
and
approval
process
and
15
for
discussion
regarding
the
adequacy
of
existing
studies
for
use
in
the
Draft
EIR.
The
first
paragraph
on
page
4.G-97
is
revised
to
read
as
follows:
The
methane
in
landfill
gases
presents
an
explosion
risk
at
certain
concentrations.
The
methane
and
the
carbon
dioxide
in
landfill
gases
can
also
accumulate
in
confined
spaces
or
low
points
such
as
utility
vaults
or
utilities
trenches
during
construction.
Because
landfill
gas
is
denser
than
air,
it
is
able
to
displace
oxygen,
posing
an
asphyxiation
hazard.
Non-
methane
organic
compounds
such
as
TCE,
benzene,
and
vinyl
chloride
are
typically
found
in
very
low
concentrations
in
landfill
gases,
and
of
these,
only
benzene
has
been
identified
at
the
former
Brisbane
landfill
which
can
present
a
toxic
or
carcinogenic
hazard,
or
both,
above
certain
concentrations.
Tests
for
benzene
would
have
indicated
the
presence
of
these
other
compounds
had
they
been
present.
The
fact
that
benzene,
but
not
TCEs
or
vinyl
chloride,
was
detected
in
the
landfill
gases
is
not
indicative
that
VOC
gases
were
somehow
“inadequately
analyzed,”
but
is
indicative
of
the
relative
“cleanliness”
of
refuse
materials
within
the
landfill.
Contaminants
such
as
dry
cleaning
fluids
and
other
solvents
containing
PCEs
break
down
over
time
into
TCEs
that
further
break
down
into
DCEs,
and
ultimately
into
vinyl
chloride.
The
presence
of
benzene
within
the
former
landfill
would
come
from
oils,
tires,
and
other
household
wastes
deposited
within
the
landfill
prior
to
1967.
This
comment
acknowledges
that
VOCs
and
hydrogen
sulfide
gas
were
identified
by
Golder
in
their
2008
report.
However,
the
Draft
EIR
statement
to
which
this
comment
refers
addresses
non-methane
carcinogenics
(e.g.,
TCE,
vinyl
chloride).
As
required
by
Title
27
CCR
21190,
long-term
maintenance
to
ensure
the
integrity
of
the
final
cover
system
to
be
placed
on
the
former
landfill
is
required.
Due
to
the
anticipated
bearing
strength
of
the
landfill
cover,
it
is
anticipated
than
buildings
within
the
landfill
footprint
may
require
construction
of
piers
through
the
landfill
and
bay
mud
down
to
bedrock.
Any
piers
would
be
required
to
be
constructed
within
non-permeable
Brisbane
Baylands
Final
EIR
2.9.1-85
May
2015