2.
Response
to
Comments
2.9
Individual
Responses
to
Comments
from
Organizations
precipitation,
but
also
from
groundwater
movement
from
upgradient
sources
as
well
as
Bay
intrusion.
Proposed
improvements
would
also
be
required
to
include
LID
drainage
features
that
encourage
onsite
infiltration
to
the
extent
possible
(as
stated
in
Draft
EIR
Mitigation
Measure
4.H-1c:
“The
SMP
shall
provide
operations
and
maintenance
guidelines
for
all
of
the
BMPs
identified
in
the
SMP,
including
LID
measures
and
other
BMPs
designed
to
mitigate
potential
water
quality
degradation
of
runoff
from
all
portions
of
the
completed
development).
Therefore,
with
the
absence
of
any
groundwater
extraction
and
the
inclusion
of
LID
measures,
there
would
be
little
likelihood
for
subsidence
resulting
from
groundwater
extraction
or
from
a
reduction
in
the
amount
of
onsite
groundwater
recharge.
Thus,
the
environmental
effects
of
proposed
Baylands
development
in
relation
to
Impact
4.H-2
are
less
than
significant
with
implementation
of
required
Mitigation
Measure
4.H-1c.
Subsidence
associated
with
the
lowering
of
the
groundwater
is
generally
observed
in
areas
where
substantial
groundwater
or
petroleum
extraction
is
occurring.
This
has
occurred
in
the
past
from
excessive
groundwater
pumping
in
other
areas
such
as
the
Santa
Clara
Valley
and
the
Central
Valley.
No
such
groundwater
pumping
is
proposed
for
Baylands
development.
In
addition,
the
cover
materials
on
the
former
landfill
area,
by
design,
would
have
a
very
low
permeability
in
order
to
prevent
vertical
migration
of
contamination.
Completion
of
the
final
cap
would
be
required
to
adhere
to
Title
27
specifications,
which
would
ensure
that
the
entire
cap
across
the
former
landfill
be
sufficiently
thick
enough
and
designed
to
prevent
infiltration
of
precipitation.
As
stated
on
page
4.G-78
of
the
Draft
EIR,
the
hydrologic
connection
of
the
former
landfill
to
groundwater
will
also
be
addressed
by
the
required
remediation
activities
for
final
closure
approval.
See
also
See
and
Draft
EIR
Mitigation
Measures
4.H-
4a,
-4b,
and
-4c
require
that
drainage
improvements
be
able
to
accommodate
runoff
produced
from
a
100-year
storm
event
with
an
additional
one-foot
of
freeboard
“above
the
100-year
storm
event
hydraulic
grade
line
water
elevation
with
tidal
flow
and
100
years
of
estimated
sea
level
rise.”
This
design
standard
has
more
to
do
with
precipitation
averages
and
amount
of
new
impermeable
surfaces
than
sea
level
rise,
but
as
quoted
above
does
take
future
sea
level
rise
into
account
(“100
years
of
estimated
sea
level
rise”).
The
ground
surface
level
used
in
determining
compliance
with
these
measures
would
include
anticipated
subsidence
addressed
through
geotechnical
site
preparation
measures
such
as
surcharging
and
dynamic
compaction
such
that
once
construction
is
complete
on
the
Baylands
Project
site,
additional
subsidence
would
fall
within
specified
tolerances.
Brisbane
Baylands
Final
EIR
2.9.3-85
May
2015