2.
Response
to
Comments
2.9
Individual
Responses
to
Comments
from
Organizations
resultant
vibration
levels
expected
at
the
nearest
receptors
using
vibration
propagation
equations
also
contained
in
this
document.
Soil
and
subsurface
conditions
are
known
to
have
an
influence
on
the
levels
of
ground-borne
vibration.
Experience
with
ground-borne
vibration
is
that
vibration
propagation
is
more
efficient
in
stiff
clay
soils.
The
reference
vibration
levels
inventoried
by
U.S.
DOT
were
developed
to
include
a
reasonable
estimate
for
a
wide
range
of
soil
conditions
(FTA,
2006),
including
those
present
on
the
Baylands
Project
Site.
The
nearest
structures
referred
to
on
page
4.J-23
with
regard
to
on-site
receptors
would
be
the
proposed
residential
units
proposed
to
be
constructed
as
part
of
the
DSP
and
DSP-V
scenarios.
Specifically,
these
would
be
proposed
high-density
flats
indicated
in
dark
gold
at
the
eastern
terminus
of
the
proposed
O
Street
and
M
Street
in
Figures
and
of
Chapter
3,
Project
Description
.
The
Draft
EIR
presented
the
impact
data
for
residences
at
a
distance
of
400
feet
on
page
4.J-23
and
identified
a
less-
than-significant
impact.
Therefore
it
can
be
assumed
that
even
a
lesser
impact
would
be
experienced
at
a
distance
of
1,000
feet.
Data
used
for
assessment
of
vibration
impacts
from
pile
driving
were
derived
from
the
U.S.
Department
of
Transportation’s
document
Transit
Noise
and
Vibration
Impact
Assessment.
This
document
identifies
vibration
levels
from
a
variety
of
construction
equipment
at
a
reference
distance
of
25
feet.
For
pile
driving
this
reference
vibration
level
is
0.644
inches
per
second
at
25
feet.
Applying
a
vibration
propagation
equation
of
PPV
equip
=
PPVref
x
(25/D)1.5
results
in
a
vibration
level
of
0.0025
inches
per
second
at
1,000
feet.
At
this
distance,
pile-driving
vibration
would
be
less
than
0.01
in/sec
(barely
perceptible),
and
therefore
the
vibration
would
have
a
less-than-significant
impact
with
regard
to
human
annoyance.
The
Draft
EIR
identifies
a
significant
impact
with
regard
to
vibration
impacts
to
proposed
residences
within
200
feet
of
the
Caltrain
right-of-way
under
the
DSP
and
DSP-V
scenarios.
Mitigation
Measure
4.J-2a
establishes
a
vibration
performance
standard
for
residential
developments
within
200
feet
of
the
Caltrain
Station
and
mainline
track
and
requires
that
detailed
project-level
vibration
analyses
be
prepared
to
ensure
that
a
standard
of
72
VdB
will
be
met.
This
quantitative
standard
was
developed
by
the
Federal
Transit
Administration
as
acceptable
ground
borne
vibration
levels
specifically
for
assessing
impacts
related
to
vibration
from
rail
projects
on
residential
uses
and
other
uses
where
people
sleep.
This
criterion
was
developed
based
on
passenger
train
operations
such
as
Caltrain.
Brisbane
Baylands
Final
EIR
2.9.2-118
May
2015