Document ID: EPA-HQ-OW-2002-0030-0009
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2002-06-24T04:00Z

Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
1
SECTION
5:
TECHNOLOGY
ASSESSMENT
This
technology
assessment
of
available
data
sources
is
intended
to
determine
the
depth
and
breadth
of
effectiveness
data
for
various
erosion
and
sediment
controls,
and
to
identify
the
amount
and
quality
of
data
available
to
describe
the
performance
of
all
currently
used
and
innovative
runoff
control
practices,
the
ability
of
each
practice
to
effectively
control
impacts
due
to
runoff,
and
the
design
criteria
or
standards
currently
used
to
size
each
practice
to
ensure
effective
control
of
runoff.

5.1
CONSTRUCTION
EROSION
AND
SEDIMENT
CONTROLS
5.1.1
INTRODUCTION
Part
1,
reported
in
this
sub­
section,
addresses
the
erosion
and
sediment
control
BMPs
for
the
construction
phase
of
development.
Prior
to
initiating
this
aspect
of
the
work,
EPA
reviewed
the
findings
of
information
sources
and
literature
assessments
to
identify
the
appropriate
definition
of
"performance"
or
the
various
definitions
or
"levels"
of
performance
that
are
considered
in
evaluating
and
defining
the
levels
of
performance
for
these
BMPs.
A
scientific­
based
approach
to
describe
the
performance
of
erosion
and
sediment
control
BMPs
was
devised
similar
to
the
approach
developed
by
Barfield
and
Clar
(1985)
in
the
evaluation
of
the
Maryland
Erosion
and
Sediment
Control
Standards,
as
well
as
the
one
recently
developed
in
the
American
Society
of
Civil
Engineers
BMP
Database
(ASCE,
1999).
The
approach
used
in
this
assessment
has
been
designed
to
provide
the
information
needed
to
address
several
important
issues,
including
whether
to
use
a
design­
based
approach,
or
an
effluent­
based
concentration,
or
a
loading
approach
in
reporting
on
the
current
status
of
the
technology.
This
sub­
section
identifies
the
following:

°
The
amount
and
quantity
of
data
available
to
describe
the
performance
of
all
currently
used
and
innovative
runoff
control
practices.

°
The
ability
of
each
practice
to
effectively
control
impacts
due
to
runoff.

°
The
design
criteria
or
standards
currently
used
to
size
each
practice
to
ensure
effective
control
of
runoff.

Before
a
detailed
evaluation
of
the
BMPs
can
be
provided,
some
background
information
is
necessary.
Sub­
section
5.2
describes
the
procedure
for
assessing
the
technology.
Sub­
section
5.3
provides
a
historical
background
on
the
subject.
Next,
sub­
section
5.4
presents
a
discussion
of
goals,
control
strategies,
criteria,
and
standards
in
general,
and
sub­
section
5.5
provides
a
detailed
description
and
discussion
of
each
BMP.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
2
In
the
discussion
of
BMPs
in
sub­
section
5.5,
the
major
focus
will
be
on
sediment.
This
does
not
imply
that
there
are
no
other
impacts;
however,
construction
BMPs
have
focused
on
erosion
and
sediment
control
rather
than
on
other
impacts.

In
the
assessment
of
BMPs,
considerable
attention
is
focused
on
whether
to
use
a
design­
based
approach,
an
effluent­
based
concentration,
or
a
loading
approach
in
reporting
on
the
current
status
of
the
technology.
Attention
is
also
given
to
the
recent
emphasis
in
the
literature
on
the
use
of
an
integrated
approach
to
evaluate
impacts
to
the
receiving
waters
and
downstream
areas.

5.1.2
PROCEDURE
FOR
TECHNOLOGY
ASSESSMENT
5.1.2.1
IDENTIFICATION
OF
PERFORMANCE
GOALS
In
assessing
the
literature,
particular
consideration
was
given
to
definitions
of
performance
of
BMPs
and
how
they
addressed
the
range
of
receiving
water
impacts
identified.
It
is
important
to
point
out
that
the
overarching
performance
goal
of
all
the
BMPs
is
to
minimize
the
impact
of
construction
site
runoff
on
receiving
waters
and
downstream
areas.

Control
strategies
that
have
been
identified
for
construction
BMPs
can
be
divided
into
three
categories.

Strategy
1.
Control
Based
on
Design
Standards—
Control
at
this
level
is
based
on
standard
designs
that
may
include
such
things
as
volume
requirements
for
reservoirs,
detention
time,
and
trapping
efficiency
that
do
not
directly
limit
an
allowable
discharge
to
receiving
waters
or
limit
a
downstream
impact.

Strategy
2.
Control
Based
on
Effluent
Standards—
Control
at
this
level
is
based
on
limiting
the
quantity
of
one
or
more
substances
such
as
peak
discharge,
runoff
volume,
TSS,
and
settleable
solids.
This
directly
addresses
effluent,
but
does
not
directly
address
downstream
impacts.

Strategy
3.
Control
Based
on
an
Integrated
Approach—
Control
at
this
level
uses
an
integrated
approach
(Snodgrass
et
al.,
1998),
including
biological,
chemical,
and
physical
criteria,
to
define
BMP
performance.
A
combination
of
water
quality,
biohabitat,
and
geomorphic
criteria
is
used
to
evaluate
whether
a
receiving
stream
is
at
the
targeted
goal
of
fishable
and
swimmable,
or
the
extent
of
departure
from
this
goal.

The
majority
of
BMPs
address
Strategies
1
or
2.
Although
Strategy
3
is
being
discussed
in
the
literature,
it
has
not
been
adopted
in
practice.
There
is
an
analog
in
the
surface
mining
industry,
where
a
cumulative
hydrologic
impact
analysis
on
a
watershed
basis
is
required
by
the
U.
S.
Surface
Mining
and
Reclamation
Act
of
1977
(PL95­
87).
When
moving
from
Strategy
2
to
Strategy
3,
a
number
of
other
parameters
are
added
to
the
performance
criteria
in
Strategy
2,
Development
Document
for
Construction
and
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Proposed
Effluent
Guidelines
June
2002
5­
3
including
(1)
stream
buffer
retention
and
thermal
impacts
considerations,
(2)
volume
control
considerations
such
as
are
presented
in
the
Low
Impact
Development
concept
approach,
which
are
added
to
the
peak
discharge
and
ground
water
recharge
criteria
to
achieve
maintenance
of
hydrologic
function
at
a
site­
specific
level,
and
(3)
geomorphic
criteria
as
described
by
Lane
(1955),
Leopold
et
al.
(1964),
Rosgen
(1996),
and
others.

An
important
point
must
be
made
about
controlling
sediment.
From
a
practical
standpoint,
a
reasonably
sized
structure
should
not
necessarily
be
expected
to
meet
an
effluent
TSS
standard
unless
the
TSS
specified
in
the
standard
is
set
at
a
very
high
value
or
unless
some
form
of
chemical
treatment
is
used
to
enhance
flocculation.
The
settling
velocity
for
primary
clay
particles
is
in
the
range
of
feet
per
month
for
all
but
the
largest
particles.
Since
these
size
particles
are
frequently
encountered
in
large
percentages
in
sediment
from
construction
sites,
the
expected
trapping
efficiencies
will
not
approach
100
percent,
nor
will
the
effluent
TSS
be
in
the
range
of
100
mg/
L
or
lower
(Haan
et
al.,
1994).

5.1.2.2
GOALS,
ENVIRONMENTAL
IMPACT
AREAS,
AND
ASSESSMENT
SCALES
For
the
purposes
of
this
report,
impact
areas
are
divided
into
three
categories,
local
area,
receiving
water,
and
downstream
areas.

Local
Area.
This
is
the
area
between
the
construction
site
and
the
receiving
stream.
Typically,
these
areas
have
ephemeral
streams
with
low
baseflows
and
highly
variable
flow
rates.
In
these
areas,
the
flows
fluctuate
widely,
with
geomorphology
and
habitat
being
very
susceptible
to
changes
in
hydrologic
regime
(Klaine,
2000).
In
some
developments,
there
would
essentially
be
no
local
area,
and
flows
would
exit
directly
into
receiving
waters.

Receiving
Waters.
This
is
the
point
at
which
flows
enter
a
well­
defined
stream.
Depending
on
the
local
geology,
flows
may
primarily
be
ephemeral,
there
may
be
a
well­
established
baseflow,
or
there
may
be
something
intermediate
between
the
two
extremes.
The
degree
to
which
flows,
sediment,
and
chemicals
impact
the
receiving
waters
depends
largely
on
the
type
of
receiving
water.
For
example,
if
the
receiving
waters
have
a
low
baseflow
and
highly
variable
flow
rates,
the
habitat
and
geomorphology
will
be
very
sensitive
to
significant
changes
in
the
hydrologic
regime.
However,
if
the
receiving
waters
have
a
high
baseflow,
the
sensitivity
to
changes
in
flow
rate
will
be
much
less
and
the
primary
problems
will
likely
be
chemical
in
nature.
Thus,
it
is
important
to
address
impacts
on
a
site­
specific
basis.

Downstream
Areas.
A
definition
of
the
downstream
area
can
be
somewhat
nebulous.
(A
definition
of
the
aerial
extent
of
"downstream
areas"
is
something
that
needs
to
be
developed
in
follow­
up
studies.)
However,
consideration
of
this
area
is
important.
For
example,
use
of
peak
discharge
criteria
may
directly
control
the
local
area
impacts
and
impacts
to
the
point
at
which
Development
Document
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Construction
and
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Proposed
Effluent
Guidelines
June
2002
5­
4
flow
enters
the
receiving
waters.
If
the
watershed
being
considered
is
combined
with
other
downstream
watersheds
and
all
use
peak
discharge
control
without
controlling
runoff
volume,
there
can
be
an
increase
in
flooding
due
to
superposition
of
long
duration
peak
flows
exiting
the
numerous
reservoirs
(Smiley
and
Haan,
1976).
This
increased
discharge
can
negatively
impact
channel
geomorphology,
habitat,
and
riparian
areas.

Another
important
issue
related
to
construction
is
the
fraction
of
the
watershed
under
construction
at
any
one
time.
One
argument
about
the
relative
importance
of
the
construction
phase
versus
the
post­
construction
phase
is
that
the
construction
phase
is
short­
lived
and
the
impact
may
be
reversible
after
the
site
has
stabilized.
While
this
argument
may
have
some
validity
on
the
local
area,
it
is
invalid
when
considering
the
downstream
areas.
On
a
larger
watershed
under
development,
major
construction
may
occur
in
the
watershed
for
a
long
time,
with
a
potential
long­
term
major
cumulative
impact.
When
considering
the
entire
watershed,
it
may
be
desirable
to
limit
the
area
under
construction
at
any
one
time
to
prevent
exceeding
some
threshold
that
would
result
in
an
irreversible
impact.
This
indicates
the
need
to
conduct
a
cumulative
impact
analysis
on
a
river
basin
scale
to
evaluate
the
potential
for
such
an
impact
to
occur.

When
considering
area
impacts,
the
following
comments
can
be
made
about
the
strategies
listed
above.

Strategy
1.
No
guarantees
can
be
made
that
impacts
would
be
controlled
at
any
level
unless
the
design
standards
are
highly
conservative.
This
would
result
in
overdesign
for
most
situations
so
that
the
standard
would
be
adequate
for
all
situations.

Strategy
2.
This
strategy
should
ensure
control
at
the
local
level.
Downstream,
the
impacts
may
be
positive
or
negative
as
a
result
of
the
control.
Examples
include
the
control
of
peak
discharge
only
in
storm
water
runoff.
Control
of
peak
discharge
on
all
construction
areas
at
the
local
level
can
result
in
increased
peak
discharge
downstream
(Smiley
and
Haan,
1976).
These
increases
result
from
detaining
increased
volumes
of
runoff
resulting
from
urbanization
and
releasing
them
at
the
predisturbed
peak
rate
over
a
long
period
of
time.

Strategy
3.
This
approach
should
ensure
control
in
both
the
local
area
and
downstream
areas.

Scale
is
very
important
to
BMP
effectiveness
analyses.
A
given
BMP
may
be
quite
effective
in
controlling
impacts
nearby
but
have
a
significant
negative
impact
when
applied
over
a
large
area.
In
the
final
analysis,
effectiveness
should
be
evaluated
at
multiple
scales
before
a
decision
is
made.
This
will
require
both
local
and
watershed
level
analyses.
Development
Document
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Effluent
Guidelines
June
2002
5­
5
5.1.2.3
QUALITATIVE
VERSUS
QUANTITATIVE
ASSESSMENT
In
the
assessments,
the
issue
may
be
addressed
on
a
qualitative
or
a
quantitative
basis.
The
difference
can
be
explained
in
the
following
manner,
using
water
temperature
as
an
example.
It
is
well
known
that
turbidity
impacts
the
depth
of
penetration
of
solar
energy
into
a
waterbody;
hence,
turbidity
impacts
temperature.
When
evaluating
the
impact
of
standards
on
water
temperature,
it
is
obvious
that
a
TSS
standard
directly
addresses
water
temperature
because
of
the
impact
of
TSS
on
turbidity.
Thus,
a
qualitative
analysis
would
simply
state
that
TSS
standards
may
impact
water
temperature,
but
give
no
degree
to
which
the
standard
does
impact
temperature.
A
quantitative
analysis,
however,
would
define
the
degree
to
which
a
given
TSS
standard
increased
or
decreased
the
impact
of
storm
water
TSS
on
temperature.

5.1.3
REVIEW
OF
HISTORICAL
APPROACHES
TO
EROSION
AND
SEDIMENT
CONTROL
Most
early
sediment
control
was
related
to
agriculture
and
was
installed
as
a
way
to
maintain
our
natural
resource
base.
On­
site
control
was
the
primary
emphasis,
attempting
to
prevent
erosion
rather
than
trap
sediment.
Strategies
were
developed
to
minimize
exposure
of
bare
soil
to
the
erosive
power
of
rainfall
and
runoff,
using
aboveground
cover
management,
residue
management,
strip
cropping,
and
terracing
to
limit
the
length
of
overland
flow.
Impacts
to
receiving
streams
and
downstream
areas
had
not
yet
been
identified
as
an
issue.
In
the
1960s,
concern
began
to
be
expressed
about
the
quantities
of
sediment
in
streams
and
reservoirs,
and
sediment
was
first
identified
as
a
pollutant.
Initially,
the
major
focus
of
sediment
control
was
on
the
surface
mining
industry,
with
the
passage
of
the
Clean
Water
Act
and
then
the
Surface
Mining,
Reclamation,
and
Control
Act
(SMRCA)
(PL
95­
87)
(U.
S.
Congress,
1977).
The
first
approach
taken
to
sediment
control
was
a
design
standard,
requiring
a
sediment
detention
basin
with
a
24­
hour
detention
time;
TSS
standards
of
35
mg/
L
average
and
70
mg/
L
peak
were
also
promulgated,
but
were
not
typically
enforced.
The
U.
S.
Environmental
Protection
Agency
(USEPA)
later
evaluated
the
TSS
standard
and
moved
to
a
settleable
solids
standard
of
0.5
ml/
L,
based
on
a
modeling
effort
that
showed
that
it
was
not
possible
to
trap
fine
sediments,
but
that
a
0.5
ml/
L
settleable
solids
standard
could
be
met
with
a
reasonably
sized
sediment
basin
(Ettinger
and
Lichty,
1979).

In
the
late
1960s
and
early
1970s,
sediment
in
streams
and
waterways
originating
from
urban
construction
sites
became
an
issue,
which
was
then
addressed
in
the
Clean
Water
Act.
EPA
developed
a
list
of
BMPs
and
standards
for
their
construction.
(USEPA,
1971).
In
general,
these
standards
were
adopted
from
those
of
other
agencies
and
were
not
based
on
studies
related
to
urban
runoff.

In
1987,
the
Clean
Water
Act
was
amended
to
include
storm
water
discharges
from
urban
areas.
The
Phase
I
NPDES
Stormwater
regulations
were
published
in
1990,
requiring
all
municipalities
Development
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June
2002
5­
6
with
Municipal
Separate
Storm
Sewer
System
(MS4)
serving
populations
over
100,000,
construction
sites
5
acres
and
larger,
and
certain
industrial
sites
to
obtain
a
permit.
The
permit
required
the
development
of
a
stormwater
pollution
prevention
plan
(SWPPP)
that
typically
included
a
storm
water
and
sediment
control
plan.
In
1999,
the
Phase
II
NPDES
stormwater
regulations
were
published,
extending
permit
coverage
to
construction
sites
of
1
acre
or
larger
and
municipalities
to
50,000
or
10,000
population
if
the
density
is
more
than
1,000
per
square
mile.
The
regulations
allow
use
of
general
permits
in
lieu
of
individual
site
or
facility
permits.
The
degree
of
oversight
of
construction
varies
widely
among
the
states.

In
the
last
two
decades,
increased
concern
at
the
local
level
has
been
focused
on
sediment
pollution
of
streams
and
waterways,
particularly
originating
from
construction,
while
less
concern
has
been
focused
on
the
impacts
of
increased
construction
on
storm
water
and
chemical
production.
Much
of
this
government
concern
originated
from
the
Phase
I
and
Phase
II
NPDES
stormwater
regulations.
A
number
of
states
and
their
local
agencies
have
developed
standards
and
BMPs
for
sediment
control,
most
of
which
do
not
have
a
scientific
basis,
but
were
adopted
from
other
agencies.
Some
states,
however,
did
conduct
studies
that
gave
their
standards
some
scientific
basis.
For
example,
Maryland
evaluated
its
BMP
standards
in
the
1980s
by
using
modeling
techniques
and
the
state
changed
its
sediment
basin
standards
to
account
for
the
impacts
of
surface
area
on
the
trapping
efficiency
in
sediment
ponds.
Based
on
typical
soils
in
the
region
and
modeling
studies,
the
state
adopted
a
surface
area
to
peak
discharge
ratio
of
0.01
cfs/
acre
as
a
criterion
(Barfield
and
Clar,
1985;
McBurnie,
1990).
Maryland
was
thus
the
first
state
to
use
a
design
criterion
that
was
related
to
the
overflow
rate.
Other
states
also
used
some
of
Maryland's
results
(Smolen
et
al.,
1988).

Recent
efforts
have
moved
closer
to
an
effluent
standard
approach.
South
Carolina
conducted
a
detailed
analysis
and
published
regulations
that
required
a
trapping
efficiency
or
settleable
solids
standard
(SCDHEC,
1995).
In
addition,
results
from
a
detailed
model
were
used
to
develop
simplified
design
aids
(Hayes
and
Barfield,
1995;
Holbrook
et
al.,
1998).
Some
municipalities
are
following
suit
to
develop
scientifically
based
standards
of
their
own.
For
example,
in
1998
Louisville,
Kentucky
(Hayes
et
al.,
2001)
developed
standards
and
design
aids
for
their
storm
water
and
sediment
control,
following
the
example
of
South
Carolina.

There
are
no
analogs
in
which
the
integrated
approach
to
storm
water
and
sediment
control
have
been
used
on
construction
sites.
The
closest
analog
is
the
Cumulative
Hydrologic
Impact
Analysis
(CHIA)
required
in
surface
mining
by
the
SMRCA.
SMRCA
requires
each
applicant
for
a
surface
mining
permit
to
conduct
a
hydrologic
impact
analysis.
Subsequently,
the
regulatory
authority
is
required
to
conduct
a
CHIA
for
the
entire
watershed.
It
should
be
pointed
out
that
although
a
CHIA
is
required,
it
is
seldom
undertaken
on
a
scale
that
is
useful.

Many
of
the
advances
in
sediment
control
have
been
based
on
the
capability
to
predict,
a
priori,
the
ability
of
a
given
design
to
meet
a
standard.
For
example,
when
the
settleable
solids
standard
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
7
was
developed
for
surface
mining,
most
regulatory
authorities
adopted
it,
with
the
requirement
that
permit
applicants
would
demonstrate
through
the
use
of
widely
accepted
computer
models,
that
the
proposed
design
would
meet
the
settleable
solids
standard.

Most
of
the
early
work
in
modeling
sediment
production
stemmed
from
efforts
in
the
1950s
to
develop
a
soil
loss
equation
that
would
apply
to
the
entire
nation
and
allow
evaluation
of
alternative
erosion
control
practices.
This
led
to
the
relationship
known
as
the
Universal
Soil
Loss
Equation
(USLE)
(Wischmeier
and
Smith,
1965)
and
its
subsequent
derivative,
the
Revised
USLE
(RUSLE)
(Renard
et
al.,
1994).
These
efforts
focus
on
erosion
control;
thus,
the
relationships
do
not
predict
sediment
yield.
A
flurry
of
efforts
were
addressed
in
the
late
1970s
and
early
1980s
leading
to
the
development
of
sediment
yield
relationships
such
as
yielding
the
Modified
USLE
(MUSLE)
by
Williams
(Williams,
No
Date),
the
CREAMS
model
(Knisel,
1980),
and
SEDIMOT
II
(Wilson
et
al.,
1982),
and
its
derivatives.
The
MUSLE
and
CREAMS
models
did
not
include
methods
to
evaluate
the
impact
of
sediment
trapping
structures,
but
SEDIMOT
II
contained
relationships
developed
at
the
University
of
Kentucky
to
predict
the
impact
of
reservoirs
(Ward
et
al.,
1977;
Wilson
et
al.,
1984),
check
dams
(Hirschi,
1981),
and
vegetative
filter
strips
(Hayes
et
al.,
1984).
The
MUSLE
and
SEDIMOT
II
models
were
based
on
single
storms
while
the
CREAMS
model
was
based
on
continuous
simulation
modeling.
Details
on
these
models
can
be
found
in
Haan
et
al.
(1994).

More
recently,
modeling
has
improved,
resulting
in
several
new
relationships.
The
WEPP
watershed
model
is
one
example
of
a
continuous
simulation
approach.
It
includes
computational
procedures
for
a
wide
variety
of
sediment
control
structures
(Lindley
et
al.,
1998).
Another
example
of
a
single
storm­
based
model
is
SEDIMOT
III
(Barfield
et
al.,
1996),
which
modifies
the
earlier
SEDIMOT
II
model
to
include
channel
erosion
routines
and
a
wide
variety
of
sediment
control
techniques.
A
significant
drawback
in
the
SEDIMOT
III
and
WEPP
models
is
that
they
do
not
have
a
good
technique
for
predicting
the
impact
of
filter
fence,
which
is
the
most
common
technique
used
today
for
sediment
control.

Concerns
for
changes
in
geomorphology
resulting
from
flow
changes
have
resulted
in
several
modeling
approaches.
Early
efforts
were
focused
on
what
is
known
as
the
regime
theory,
in
which
changes
in
channel
property
are
linked,
qualitatively,
to
changes
in
flow.
Examples
include
models
of
Lane
(1955)
and
Schumm
(1977).
In
addition,
some
statistically
based
models
were
developed,
but
they
are
not
universally
applicable
(Blench,
1970;
Simons
and
Albertson,
1960).
More
recently,
models
have
been
developed
using
physically
based
concepts
to
predict
changes
in
geomorphology
as
related
to
changes
in
flow.
The
models
of
Chang
(1988)
are
good
examples.
It
is
possible
to
predict,
to
a
limited
extent,
the
change
in
channel
properties
as
impacted
by
changes
in
flow.

The
impact
of
changes
in
flow
and
geomorphology
on
habitat
is
one
major
area
where
information
is
lacking.
Although
this
deficiency
can
be
addressed
in
a
qualitative
manner,
it
is
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
8
not
possible
to
predict
quantitatively
how
a
given
change
in
geomorphology
will
impact
habitat.
Additional
information
is
needed
to
develop
a
strategy
based
on
the
integrated
assessment
approach.

5.1.4
GOALS,
CONTROL
STRATEGIES,
CRITERIA,
AND
STANDARDS
5.1.4.1
GOALS,
CONTROL
STRATEGIES,
CRITERIA,
AND
STANDARDS:
HOW
THEY
RELATE
The
relationship
between
goals,
control
strategies,
criteria,
and
standards
can
sometimes
be
confusing.
For
the
purposes
of
the
discussion
on
construction
BMPs,
the
following
definitions
will
be
used.

Goal.
The
overarching
objective
of
having
a
storm
water,
sediment,
and
pollution
control
program
is
known
as
the
goal.
It
is
what
the
program
is
trying
to
achieve.
All
BMPs
should
relate
to
that
goal.
As
stated
earlier,
the
goal
of
this
program
is
to
minimize
the
impact
of
construction
on
receiving
water
and
downstream
areas.
The
impacts
of
concern
are
identified
in
the
Environmental
Assessment.

Control
Strategies.
The
methods
by
which
the
regulatory
agency
tries
to
achieve
the
goal
are
called
control
strategies.

Criteria.
The
particular
variables
that
are
targeted
by
a
given
strategy
are
known
as
the
criteria.
For
example,
if
the
strategy
is
to
control
impacts
by
limiting
the
discharge
of
sediment
generated
to
the
receiving
waters,
then
sediment
becomes
the
criterion.

Standard.
The
specific
variable
chosen
for
the
criteria
and
its
numeric
value
is
referred
to
as
the
standard.
For
example,
if
the
control
strategy
is
to
limit
sediment
discharge
to
the
receiving
waters,
the
criterion
is
sediment,
and
the
particular
limiting
variable
and
numeric
value
chosen
is
a
peak
settleable
solids
concentration
of
0.5
mg/
L,
then
the
standard
would
be
a
peak
settleable
solids
concentration
of
0.5
mg/
L.

The
relationship
among
goals,
control
strategies,
criteria,
and
standards
is
shown
graphically
in
Figure
5­
1.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
9
Figure
5­
1.
Flow
Diagram
Showing
Relationship
Among
Goals,
Strategies,
Criteria,
and
Standards
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
10
5.1.4.2
LEVELS
OF
PERFORMANCE
OR
"HOW
WELL
DO
THE
STRATEGIES
WORK?"

Table
5­
1
provides
a
description
on
the
level
of
performance
for
the
three
strategies
discussed
in
sub­
section
5.2.1.

Table
5­
1.
Description
of
Levels
of
Performance
of
Three
Control
Strategies
Level
Description
of
Performance
0
No
consideration
of
impact.

1
Performance
defined
by
a
design
standard.
No
guarantee
that
the
design
will
control
the
impact
to
a
desired
level
on
the
specific
watershed.
Example:
reservoir
volume
standard
for
runoff
control.

2
Effluent
standard
based
on
controlling
a
single
entity
entering
receiving
waters.
Control
of
the
single
parameter
will
not
guarantee
that
the
desired
protection
will
occur
for
receiving
waters
or
downstream
impact.
Example:
controlling
peak
storm
water
discharge
or
peak
TSS.

3
Effluent
standard
based
on
controlling
two
or
more
entities
entering
receiving
waters,
but
not
all
entities
causing
environmental
impact.
Example:
controlling
peak
discharge
and
sediment,
but
not
storage
volume
or
runoff
volume.

4
Effluent
standards
for
all
entities
entering
receiving
waters
and
causing
environmental
impact.
Even
controlling
all
quantities
entering
receiving
waters
will
not
guarantee
that
there
are
no
undesired
downstream
impacts.
Example:
Controlling
runoff
rate,
runoff
volume,
peak
discharge,
and
TSS
in
receiving
streams
does
not
guarantee
that
there
will
be
no
undesirable
biological
impacts.

5
Control
based
on
integrated
evaluation
of
impacts
on
receiving
stream
and
downstream.

5.1.4.3
STRATEGIES,
CRITERIA,
STANDARDS,
AND
ENFORCEMENT
The
effectiveness
of
a
given
strategy,
criterion,
or
standard
is
directly
related
to
the
ability
of
an
enforcement
agency
to
enforce
the
rules.
Thus,
a
given
standard
may
theoretically
provide
excellent
protection
to
the
environment,
but
be
so
difficult
to
enforce
that
it
is
less
effective
than
a
less
stringent
standard
that
is
enforceable.
In
general,
the
difficulty
in
enforcement
increases
as
the
level
of
desired
performance
increases.
An
estimate
of
relative
difficulty
in
enforcement
is
given
in
Table
5­
2
for
the
various
levels
of
performance
from
Table
5­
1.
For
example,
it
is
easiest
to
enforce
the
design
standard,
since
enforcement
is
based
entirely
on
reviewing
plans
and
inspection
of
the
site
to
ensure
that
the
plans
are
put
into
action
properly.

Important
issues
related
to
enforcement
include
the
following:

°
A
priori
demonstration
by
the
best
computational
technology
that
the
proposed
design
can
meet
the
standard.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
11
°
As­
built
inspections
to
verify
that
the
installed
practices
match
the
approved
plan.

°
Self­
monitoring
of
effluent
in
the
case
of
effluent
standards,
with
spot
checks
by
the
regulatory
authority
to
make
sure
that
evaluations
are
being
done
properly.

°
Evaluation
of
downstream
impacts.

°
Clearly
defined
rules
for
monitoring
the
effectiveness
of
a
practice.

Table
5­
2.
Descriptions
of
Levels
of
Difficulty
in
Enforcement
Level
of
Performance
from
Table
1­
1
Difficulty
in
Enforcing
(Relative)
Description
of
Difficulty
0
0
Nothing
to
enforce.
1
1
Enforcement
consists
of
reviewing
plans
and
ensuring
proper
installation
and
maintenance.
2
2
Enforcement
requires
some
monitoring
and
typically
requires
a
preconstruction
review
of
plans
and
submission
of
calculations
showing
that
the
standard
can
be
met.
3
2.5
Same
as
above
except
multiple
variables.
4
2.5
Same
as
above.
5
5
Enforcement
required
some
a
priori
demonstration
of
the
expected
flow
and
concentration
changes
and
their
impact
of
the
receiving
waters
and
downstream
variables.
In
addition,
routine
monitoring
of
downstream
variables
such
as
geomorphology,
aquatic
life,
aesthetics,
and
riparian
zones
would
be
required.

A
Priori
Demonstration
of
Performance.
A
priori
demonstration
that
a
given
design
can
meet
the
standard
is
very
important.
Experience
with
the
surface
mining
industry
indicates
that
a
sediment
control
plan
is
no
better
than
its
design.
If
the
best
computational
technology
indicates
that
the
design
will
not
meet
the
standard,
then
field
monitoring
of
the
BMP
is
not
likely
to
show
that
the
standards
are
being
achieved.
Thus,
it
will
be
important
to
have
scientifically
based
and
verified
computational
technologies
to
predict
the
performance
of
BMPs
relative
to
meeting
a
specified
standard.

In
recognition
of
this
need
the
USEPA
funded
the
development
of
the
National
Stormwater
BMP
Database
project
by
the
Urban
Water
Resources
Research
Council
of
the
American
Society
of
Civil
Engineers
(ASCE,
1999)
in
order
to
establish
the
state
of
the
art
of
BMP
performance
with
respect
to
pollutant
removal
and
peak
discharge
control
(level
3).
The
database
can
be
found
at:
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
12
http://
www.
bmpdatabase.
org/.
The
ASCE
project
team
prepared
a
report
that
contains
several
different
methods
of
evaluating
BMP
efficiency
data.
This
report
presents
statistically
based
approaches
that
involve
conducting
a
statistical
analysis
to
characterize
inflow
and
outflow
EMCs,
and
then
evaluates
whether
or
not
there
is
a
statistically
significant
difference
between
the
two.
The
application
of
this
approach
in
evaluating
the
data
contained
in
the
database
has
led
the
study
team
to
conclude
that
evaluating
effluent
quality
is
a
good
indicator
of
performance
of
BMPs
with
respect
to
pollutant
removal.
A
brief
summary
of
the
approach
is
provided
in
Appendix
A.

As­
built
Inspections
Another
important
issue
related
to
enforcement
is
as­
built
inspections
of
installed
practices.
Although
the
rules
may
call
for
certification
by
an
appropriately
licensed
professional,
it
is
important
that
the
regulatory
authority
conduct
routine
inspections
to
ensure
that
the
licensed
professionals
are
doing
their
job
properly.

Monitoring
Finally,
there
are
issues
related
to
self­
monitoring
versus
monitoring
conducted
by
the
regulatory
authority.
The
use
of
effluent
standards
would
require
some
type
of
monitoring
to
ensure
that
performance
meets
the
standards.
However,
storm
water
and
sediment
control
structures
that
control
flows
are
highly
variable
and
temporally
stochastic.
This
means
that
it
is
not
possible
to
plan
ahead
when
the
monitoring
will
occur.
It
will
be
necessary
to
have
trained
professionals
to
conduct
the
monitoring.

A
monitoring
methodology
for
BMPs
should
meet
three
criteria:
(1)
provide
scientifically
based
numbers
to
evaluate
effectiveness,
(2)
be
executable
and
sufficiently
simple
to
allow
the
use
of
trained
technicians
who
would
reasonably
be
available
to
do
the
monitoring,
and
(3)
be
adequate
to
ensure
that
the
desired
standards
are
met
without
excessive
sampling
or
analysis.
The
first
criterion
could
be
met
by
providing
clear
documentation
on
the
monitoring
methodology
that
specifies
times,
frequency,
and
location
of
sampling
relative
to
storms,
as
well
as
clearly
articulated
protocols
for
handling
samples.
The
second
criteria
can
be
met
by
being
sure
that
the
techniques
proposed
have
actually
been
field
applied
by
technicians
in
the
monitoring
business.
The
third
criterion
can
be
evaluated
by
an
error
analysis
that
determines
the
expected
accuracy
of
measurement
as
a
function
of
number
and
frequency
of
sampling.

Several
possible
criteria
or
standards
have
special
measurement
problems
that
should
be
mentioned.
These
include
criteria
or
standards
based
on
trapping
efficiency,
and/
or
effluent
TSS
and
settleable
solids
(average
or
peak).
The
issues
associated
with
these
criteria
are
discussed
below.
Development
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June
2002
5­
13
Trapping
Efficiency.
Literature
citations
frequently
include
studies
that
attempt
to
measure
trapping
efficiency
by
sampling
one
or
more
inflow
and
outflow
concentrations
(Barrett
et
al.,
1995).
While
this
simplicity
seems
attractive,
it
is
a
grossly
erroneous
measure
of
trapping
efficiency.
A
correct
definition
of
trapping
efficiency
is
given
in
Equation
1:

Equation
1:
TE
=
(Mi
­
Mo
)
/
Mi
where:
Mi
is
inflow
total
mass
Mo
is
outflow
total
mass
Mi
is
given
by
integrating
the
product
of
inflow
concentration
and
inflow
rate
over
the
duration
of
a
hydrograph
or
Equation
2:
Mi
=
Ci
qi
dt
0
t
D
 
where:
Ci
is
inflow
concentration
qi
is
inflow
flow
rate
t
is
time
tD
is
the
duration
of
the
storm
Outflow
total
mass
Mo
is
calculated
by
substituting
the
subscript
o
for
i
in
Equation
2.
Thus,
to
monitor
trapping
efficiency
correctly,
it
is
necessary
to
measure
both
flow
and
concentration
as
a
function
of
time
over
the
duration
of
both
inflow
and
outflow.
Such
measurement
is
quite
difficult
and
time­
consuming,
requiring
many
samples.

Statistical
Evaluation
of
Inflow/
Outflow
Data
(mean,
median,
standard
deviation,
coefficient
of
variance).
To
measure
average
or
peak
TSS,
it
is
necessary
to
measure
TSS
in
the
effluent
over
the
duration
of
the
outflow
hydrograph
as
well
as
the
flow
rate.
This
requires
that
multiple
samples
be
taken
and
that
the
samples
be
centered
around
the
peak
discharge.
The
ACSE
database
data
analysis
document
has
the
ability,
depending
upon
the
number
of
samples
collected,
to
show
a
difference
between
various
samples.
Again,
this
is
time­
consuming
and
difficult
since
the
timing
of
an
event
and
the
timing
of
the
peak
discharge
are
not
known
a
priori.
The
average
concentration
is
a
weighted
concentration,
using
flow
rate
as
a
weighting
function.
Development
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2002
5­
14
5.1.5
CONTROL
TECHNIQUES,
BMP
SYSTEMS
5.1.5.1
EROSION
CONTROL
AND
PREVENTION
5.1.5.1.1
PLANNING,
STAGING,
SCHEDULING
General
Description
A
construction
sequence
schedule
is
a
specified
work
schedule
that
coordinates
the
timing
of
land­
disturbing
activities
and
the
installation
of
erosion
and
sediment
control
measures.
The
goal
of
a
construction
sequence
schedule
is
to
reduce
on­
site
erosion
and
off­
site
sedimentation
by
performing
land­
disturbing
activities
and
installing
erosion
and
sediment
control
practices
in
accordance
with
a
planned
schedule
(Smolen
et
al.,
1988).

Construction
site
phasing
involves
disturbing
only
part
of
a
site
at
a
time
to
prevent
erosion
from
dormant
parts
(Claytor,
1997).
Grading
activities
and
construction
are
completed
and
soils
are
effectively
stabilized
on
one
part
of
the
site
before
grading
and
construction
commence
at
another
part.
This
differs
from
the
more
traditional
practice
of
construction
site
sequencing,
in
which
construction
occurs
at
only
one
part
of
the
site
at
the
time,
but
site
grading
and
other
site­
disturbing
activities
typically
occur
simultaneously,
leaving
portions
of
the
disturbed
site
vulnerable
to
erosion.
Construction
site
phasing
must
be
incorporated
into
the
overall
site
plan
early
on.
Elements
to
consider
when
phasing
construction
activities
include
the
following
(Claytor,
1997):

°
Managing
runoff
separately
in
each
phase.

°
Determining
whether
water
and
sewer
connections
and
extensions
can
be
accommodated.

°
Determining
the
fate
of
already
completed
downhill
phases.

°
Providing
separate
construction
and
residential
accesses
to
prevent
conflicts
between
residents
living
in
completed
stages
of
the
site
and
construction
equipment
working
on
later
stages
(USEPA,
2000).

Applicability
Construction
sequencing
can
be
used
to
plan
earthwork
and
erosion
and
sediment
control
activities
at
sites
where
land
disturbances
might
affect
water
quality
in
a
receiving
waterbody.
Development
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2002
5­
15
Design
and
Installation
Criteria
Construction
sequencing
schedules
should,
at
a
minimum,
include
the
following
(NCDNR,
1988;
MDE,
1994):

°
The
erosion
and
sediment
control
practices
that
are
to
be
installed
°
The
principal
development
activities
°
The
measures
that
should
be
installed
before
other
activities
are
started
°
The
compatibility
with
the
general
contract
construction
schedule
Development
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2002
5­
16
Table
5­
3
summarizes
other
important
scheduling
considerations
in
addition
to
those
listed
above.

Table
5­
3.
Scheduling
Considerations
for
Construction
Activities
Construction
Activity
Schedule
Consideration
Construction
survey
stakeout
Prior
to
initiating
any
construction
activity
a
construction
survey
stakeout
should
be
conducted.
The
stakeout
should
identify
the
limits
of
disturbance,
and
location
of
control
structures,
especially
perimeter
controls
Pre­
construction
meeting
between
owner,
contractor
and
regulatory
agency
This
meeting
should
take
place
before
any
construction
activity
begins
at
the
site.
The
survey
stakeout
is
reviewed,
especially
the
limits
of
disturbance
and
location
of
controls
Construction
access
—entrance
to
site,
construction
routes,
areas
designated
for
equipment
parking
This
is
the
first
land­
disturbing
activity.
As
soon
as
construction
takes
place,
stabilize
any
bare
areas
with
gravel
and
temporary
vegetation.

Clearing
and
grading
required
for
the
installation
of
controls
In
conjunction
with
the
construction
access,
the
clearing
and
grading
required
for
the
installation
of
E&
S
controls
should
take
place.
Sediment
traps
and
barriers—
basin
traps,
silt
fences,
outlet
protection
After
construction
site
has
been
accessed,
install
principal
basins,
with
the
addition
of
more
traps
and
barriers
as
needed
during
grading.
Runoff
control—
diversions,
perimeter
dikes,
water
bars,
outlet
protection
Install
key
practices
after
the
installation
of
principal
sediment
traps
and
before
land
grading.
Additional
runoff
control
measures
may
be
installed
during
grading.
Runoff
conveyance
system—
stabilize
streambanks,
storm
drains,
channels,
inlet
and
outlet
protection,
slope
drains
If
necessary,
stabilize
streambanks
as
soon
as
possible,
and
install
principal
runoff
conveyance
system
with
runoff
control
measures.
The
remainder
of
the
systems
may
be
installed
after
grading.
Land
clearing
and
grading—
site
preparation
(cutting,
filling,
and
grading;
sediment
traps;
barriers;
diversions;
drains;
surface
roughening)
Implement
major
clearing
and
grading
after
installation
of
principal
sediment
and
key
runoff
control
measures,
and
install
additional
control
measures
as
grading
continues.
Clear
borrow
and
disposal
areas
as
needed,
and
mark
trees
and
buffer
areas
for
preservation.
Surface
stabilization—
temporary
and
permanent
seeding,
mulching,
sodding,
riprap
Immediately
apply
temporary
or
permanent
stabilizing
measures
to
any
disturbed
areas
where
work
has
been
either
completed
or
delayed.

Building
construction—
buildings,
utilities,
paving
During
construction,
install
any
erosion
and
sedimentation
control
measures
that
are
needed.
Landscaping
and
final
stabilization—
adding
top
soil,
trees,
and
shrubs;
permanent
seeding;
mulching;
sodding;
riprap
This
is
the
last
construction
phase.
Stabilize
all
open
areas,
including
borrow
and
spoil
areas,
and
remove
and
stabilize
all
temporary
control
measures.

Effectiveness
Construction
sequencing
can
be
an
effective
tool
for
erosion
and
sediment
control
because
it
ensures
that
management
practices
are
installed
where
necessary
and
when
appropriate.
A
comparison
of
sediment
loss
from
a
typical
development
and
from
a
comparable
phased
project
showed
a
42
percent
reduction
in
sediment
export
in
the
phased
project
(Claytor,
1997).
Development
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2002
5­
17
Limitations
Weather
and
other
unpredictable
variables
may
affect
construction
sequence
schedules.
The
proposed
schedule
and
a
protocol
for
making
changes
resulting
from
unforseen
problems
should
be
plainly
stated
in
an
applicable
erosion
and
sediment
control
plan.

Maintenance
The
construction
sequence
should
be
followed
throughout
the
project,
and
the
written
erosion
and
sediment
control
plan
should
be
modified
before
any
changes
in
construction
activities
are
executed.
The
plan
can
be
updated
if
a
site
inspection
indicates
the
need
for
additional
erosion
and
sediment
control
as
determined
by
contractors,
engineers,
or
developers.

Cost
Construction
sequencing
is
a
low­
cost
BMP
because
it
requires
a
limited
amount
of
a
contractor's
time
to
provide
a
written
plan
for
the
coordination
of
construction
activities
and
management
practices.
Additional
time
might
be
needed
to
update
the
sequencing
plan
if
the
current
plan
is
not
providing
sufficient
erosion
and
sediment
control.

Although
little
research
has
been
done
to
assess
the
costs
of
phasing
versus
conventional
construction
costs,
it
is
known
that
it
will
be
to
implement
successful
phasing
for
a
larger
project
(Claytor,
1997).

5.1.5.1.2
VEGETATIVE
STABILIZATION
Vegetation
can
be
used
during
construction
to
stabilize
and
protect
soil
exposed
to
the
erosive
forces
of
water,
as
well
as
during
post­
construction
to
provide
a
filtration
mechanism
for
storm
water
runoff
pollutants.
The
following
discussion
refers
to
vegetative
stabilization
as
a
construction
BMP
that
stabilizes
and
protects
soil
from
erosion.

General
Description
Vegetative
stabilization
measures
employ
plant
material
to
protect
soil
exposed
to
the
erosive
forces
of
water
and
wind.
Selected
vegetation
can
reduce
erosion
by
more
than
90
percent
(Fifield,
1999).
Natural
plant
communities
that
are
adapted
to
the
site
provide
a
self­
maintaining
cover
that
is
less
expensive
than
structural
alternatives.
Plants
provide
erosion
protection
to
vulnerable
surfaces
by
the
following
(Heyer,
n.
d.):

°
Protecting
soil
surface
from
the
impact
of
raindrops.

°
Holding
soil
particles
in
place.
Development
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2002
5­
18
°
Maintaining
the
soil's
capacity
to
absorb
water.

°
Using
living
root
systems
to
hold
soil
in
place,
increasing
overall
bank
stability.

°
Directing
flow
velocity
away
from
the
streambank.

°
Acting
as
a
buffer
against
abrasive
transported
materials.

°
Causing
sediment
deposition,
which
reduces
sediment
load
and
reestablishes
the
streambank.

The
designer
should
be
aware
of
and
respond
to
local
conditions
that
may
influence
the
development
of
vegetative
stabilization
measures.
As
with
any
planting
design,
climate,
maintenance
practices,
the
availability
of
plant
material
(including
native
species),
and
many
other
factors
will
influence
such
considerations
as
plant
or
seed
mix
selection,
installation
methods,
and
project
scheduling.

Slope
Stabilization.
On
slopes,
the
goal
of
vegetative
stabilization
is
not
only
to
reduce
surface
erosion
but
also
to
prevent
slope
failure.
Vegetation
should
provide
dense
coverage
to
protect
soils
from
the
direct
impact
of
precipitation
and
help
intercept
runoff.
A
variety
of
plants
should
be
used
to
provide
root
systems
that
are
distributed
throughout
all
levels
of
the
soil,
increasing
slope
shear
strength
and
giving
plants
a
greater
ability
to
remove
soil
moisture.
Uniform
mats
of
shallow
rooting
plants
should
be
avoided
because,
while
such
plants
may
increase
runoff
infiltration,
they
cannot
remove
soil
moisture
beyond
the
surface
level,
leaving
slopes
potentially
saturated
and
prone
to
slippage.
Shallow,
interlocking
root
systems
may
also
increase
the
size
of
a
soil
slippage
by
holding
together
and
pulling
down
a
larger
area
of
slope
after
a
small
section
has
given
way.
Large
trees
that
have
become
unstable
may
also
pull
down
slopes
and
should
be
removed.
Using
plants
with
low
water
requirements
can
reduce
the
potential
for
soil
saturation
from
irrigation.

Swale
Stabilization.
On
swales,
the
goal
of
vegetative
stabilization
is
to
prevent
erosion
within
the
swale,
where
runoff
is
concentrated
and
flows
at
higher
velocities.
If
natural
stream
channels
are
involved,
vegetation
with
deep
root
systems
should
be
preserved,
or
if
absent,
planted
above
the
channel
to
help
maintain
the
channel
banks.
More
information
is
provided
in
the
subsequent
section
dealing
with
grass­
lined
swales.

Surface
Stabilization.
On
large,
flat
areas,
the
goal
of
vegetative
stabilization
is
to
reduce
the
loss
of
surface
soil
from
sheet
erosion.
Vegetation
should
provide
complete
coverage
to
reduce
the
force
of
precipitation,
which
can
shift
soil
particles
to
seal
openings
in
the
soil,
reducing
infiltration
and
increasing
runoff.
Vegetation
should
also
provide
many
stem
penetrations
to
slow
runoff
and
increase
infiltration.
Deep
rooting
plants
are
less
critical
for
erosion
control
in
flat
areas
than
on
slopes
because
soils
are
not
subject
to
the
same
forces
that
may
cause
slippage
on
a
slope.
However,
trees
and
shrubs
can
increase
infiltration,
lessening
the
buildup
of
runoff,
and
transpire
large
volumes
of
water,
reducing
soil
saturation.
Development
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2002
5­
19
In
areas
susceptible
to
wind
erosion,
the
goal
of
vegetative
stabilization
is
to
establish
direct
protection
of
the
soil.
Vegetation
should
provide
dense
and
continuous
surface
cover.
Binding
the
soil
deeply
is
generally
not
a
requirement.
The
ideal
vegetation
for
this
purpose
is
grass,
which
forms
a
mat
of
protection.
In
areas
where
the
vegetation
is
developed,
the
grass
generally
has
high
maintenance
requirements.
In
less
developed,
open
areas,
unmown
grass,
including
perennial
native
species,
can
be
used
to
provide
protection.
Trees
and
shrubs
also
can
provide
protection
from
the
wind.

Shoreline
Stabilization.
In
lakes
and
ponds,
the
goal
of
vegetative
stabilization
is
to
prevent
erosion
of
the
shoreline.
Wetland
plants
anchor
the
bottom
of
the
lake
or
pond
adjacent
to
the
shore
and
help
dissipate
the
erosive
energy
of
waves.
An
important
consideration
in
planting
along
shorelines
is
the
need
to
establish
favorable
conditions
for
plant
establishment
and
growth.
These
include
the
proper
grading
of
side
slopes
and
the
control
of
upland
erosion
to
prevent
the
buildup
of
silt
and
associated
pollutants
in
the
water.
Designers
should
maintain
awareness
of
regulatory
requirements
that
may
influence
vegetation
projects
in
a
wetland
environment
(USAF,
1998).

Vegetation
used
for
shoreline
stabilization
work
should
be
native
material
selected
on
the
basis
of
strength,
resiliency,
vigor,
and
ability
to
withstand
periodic
inundation.
Woody
vegetation
with
short,
dense,
flexible
tops
and
large
root
systems
works
well.
Other
important
factors
include
rapid
initial
growth,
ability
to
reproduce,
and
resistance
to
disease
and
insects.

According
to
Heyer,
n.
d.,
most
streambank
stabilization
plantings
have
used
various
willows,
including
black
willow
(Salix
nigra),
sandbar
willow
(S.
interior),
meadow
willow
(S.
petiolaris),
heartleaf
willow
(S.
rigida),
and
Ward
willow
(S.
caroliniana).
The
size
used
depends
on
the
severity
of
the
erosion
and
the
type
of
bank
to
be
stabilized.
Whatever
the
size,
it
is
important
to
use
dormant
cuttings
and
to
remove
all
lateral
branches.
Most
tree
revetment
projects
used
either
eastern
red
cedar
(Juniperus
virginiana)
or
hardwoods
such
as
northern
pin
oak
(Quercus
ellipsoidalis).
Important
suggestions
include
the
following:

°
Choose
trees
with
many
limbs
and
branches
to
trap
as
much
sediment
as
possible.

°
Select
decay­
resistant
trees.

°
Use
recently
cut
trees—
dead
trees
are
more
brittle
and
likely
to
break
apart.

°
The
tree
size­
diameter
of
the
tree
crown
should
be
about
two­
thirds
of
the
height
of
the
eroding
bank.

°
Cut
off
any
trunk
without
limbs.
°
Place
the
tree
revetments
overlapping,
butt
end
pointing
upstream.

°
Begin
and
end
revetments
at
stable
points
along
the
bank.
Development
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5­
20
°
Choose
an
anchoring
system
according
to
the
bank
material
to
be
stabilized
and
the
weight
of
the
object
to
be
anchored.

Vegetative
measures
for
streambank
stabilization
offer
an
alternative
to
structural
measures
and
are
becoming
well
known
as
bioengineering
techniques
for
streambanks.
Utilizing
vegetative
material
for
streambank
stabilization
could
be
the
first
step
in
the
reestablishment
of
the
riparian
forest,
which
is
essential
for
long­
term
stability
of
the
streamside
and
floodplain
areas.
Each
site
must
be
evaluated
separately
as
to
the
feasibility
of
using
natural
material
(Heyer,
n.
d.).

Vegetative
streambank
stabilization,
with
the
goal
to
protect
streambanks
from
the
erosive
forces
of
flowing
water,
is
generally
applicable
where
bankfull
flow
velocity
does
not
exceed
6
ft/
sec
and
soils
are
erosion
resistant
(Smolen,
1988).
Table
5­
4
includes
general
guidelines
for
maximum
allowable
velocities
in
streams
to
be
protected
by
vegetation.

Table
5­
4.
Conditions
Where
Vegetative
Streambank
Stabilization
Is
Acceptable
Frequency
of
Bankfull
Flow
Maximum
Allowable
Velocity
for
Highly
Erodible
Soil
Maximum
Allowable
Velocity
for
Erosion­
Resistant
Soil
>
4
times/
yr
4
ft/
sec
5
ft/
sec
1
to
4
times/
yr
5
ft/
sec
6
ft/
sec
<
1
time/
yr
6
ft/
sec
6
ft/
sec
Source:
Smolen,
1988.

Temporary
Vegetative
Stabilization.
Temporary
vegetative
cover
such
as
rapidly
growing
annuals
and
legumes
can
be
used
to
establish
a
temporary
vegetative
cover.
Such
covers
are
recommended
for
areas
that
(Fifield,
1999):

°
Will
not
be
brought
to
final
grade
within
30
days
or
are
likely
to
be
redisturbed.

°
Require
seeding
of
cut
and
fill
slopes
under
construction.

°
Require
stabilization
of
soil
storage
areas
and
stockpiles.

°
Require
stabilization
of
temporary
dikes,
dams,
and
sediment
containment
systems.

°
Require
development
of
cover
or
nursery
crops
to
assist
with
establishing
perennial
grasses.

Examples
of
temporary
vegetation
include
wheat,
oats,
barley,
millet,
and
sudan.
Temporary
seeding
may
not
be
effective
in
arid
or
semi­
arid
regions
where
seasonal
conditions
(lack
of
moisture)
prevent
germination.
It
may
be
necessary
to
use
a
mixture
of
warm
and
cool
season
grasses
to
ensure
germination.
Mulching
and
geotextiles
can
be
used
to
help
provide
temporary
stabilization
with
vegetation,
particularly
in
situations
where
establishing
cover
may
be
difficult.
Development
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2002
5­
21
Permanent
Vegetative
Stabilization.
Permanent
vegetative
cover
such
as
a
perennial
grass
or
a
legume
cover
can
be
used
to
establish
a
permanent
vegetative
cover.
Permanent
vegetation
is
recommended
for
(Fifield,
1999)

°
Final
graded
or
cleared
areas
where
permanent
vegetative
cover
is
needed
to
stabilize
the
soil
°
Slopes
designated
to
be
treated
with
erosion
control
blankets
°
Grass­
lined
channels
or
waterways
designed
to
be
channel
liners
The
following
sub­
sections
discuss
the
various
types
or
means
of
providing
vegetative
stabilization.

5.1.5.1.2.1
GRASS­
LINED
CHANNELS
General
Description
Grass­
lined
channels,
or
swales,
convey
storm
water
runoff
through
a
stable
conduit.
Vegetation
lining
the
channel
reduces
the
flow
velocity
of
concentrated
runoff.
Grassed
channels
are
usually
not
designed
to
control
peak
runoff
loads
by
themselves
and
are
often
used
in
combination
with
other
BMPs
such
as
subsurface
drains
and
riprap
stabilization.

Applicability
Grassed
channels
should
be
used
in
areas
where
erosion­
resistant
conveyances
are
needed,
such
as
in
areas
with
highly
erodible
soils
and
slopes
of
less
than
5
percent.
They
should
be
installed
only
where
space
is
available
for
a
relatively
large
cross­
section.
Grassed
channels
have
a
limited
ability
to
control
runoff
from
large
storms
and
should
not
be
used
in
areas
where
velocity
exceeds
5
feet
per
second
unless
they
are
on
erosion­
resistant
soils
with
dense
groundcover
at
the
soil
surface.

Design
and
Installation
Criteria
Because
of
their
ease
of
construction
and
low
cost,
vegetated­
lined
waterways
are
frequently
used
on
diversion
and
collection
ditches.
USDA's
Soil
Conservation
Service's
(SCS)
Engineering
Field
Manual
(1979)
recommends
the
following
maximum
permissible
velocities
for
individual
site
conditions
shown
in
Table
5­
5.
Development
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2002
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22
Table
5­
5.
Maximum
Permissible
Velocities
for
Individual
Site
Conditions
for
Grass
Swales
Site
Location
Velocity
Areas
where
only
a
sparse
cover
can
be
established
or
maintained
because
of
shale,
soils,
or
climate
3.00
ft/
sec
(0.91
m/
sec)
If
the
vegetation
is
to
be
established
by
seeding
3.00
to
4.00
ft/
sec
(0.91
to
1.22
m/
sec)
Areas
where
a
dense,
vigorous
sod
is
obtained
quickly
or
where
the
runoff
can
diverted
out
of
the
waterway
while
the
vegetation
is
being
established
4.00
to
5.00
ft/
sec
(1.22
to
1.52
m/
sec)
Source:
USDA,
1979
Grassed
waterways
typically
begin
eroding
in
the
invert
of
the
channel
if
the
velocity
exceeds
the
sheer
strength
of
the
vegetation
soil
interface.
Once
the
erosion
process
has
started,
it
will
continue
until
an
erosion­
resistant
layer
is
encountered.
If
erosion
of
a
channel
bottom
is
occurring,
rock
or
stone
should
be
placed
in
the
eroded
area
or
the
design
should
be
changed
(UNEP,
1994).

Grassed
waterways
on
construction
land
must
be
able
to
carry
peak
runoff
events
from
snowmelt
and
rainstorms
(in
some
areas
limited
to
up
to
1
cubic
meter
of
water
per
second).
The
size
of
the
waterway
depends
on
the
size
of
the
area
to
be
drained.
A
typical
grassed
waterway
cross­
section
is
parabolic­
shaped
with
a
nearly
flat­
bottomed
channel,
a
bottom
width
of
3
m
and
channel
depth
of
at
least
30
cm.
Side
slopes
usually
rise
about
1
m
for
every
10
m
horizontal
distance
but
may
be
as
steep
as
a
1
m
rise
for
every
2
m
of
horizontal
distance.
The
waterway
should
follow
the
natural
drainage
path
if
possible
(Vanderwel,
1998).
The
design
should
be
site­
specific
and
use
available,
well­
established
procedures.

Lined
channels
are
a
means
of
dropping
water
to
lower
elevations
along
steep
parts
of
a
waterway.
Those
portions
of
the
waterway
are
precisely
shaped
and
carefully
lined
with
heavyduty
erosion
control
matting,
a
type
of
geotextile
product.
The
lining
is
covered
with
a
layer
of
soil
and
seeded
to
grass.
The
resulting
channel
is
highly
resistant
to
erosion.
Lined
channels
are
appropriate
for
waterways
that
only
carry
water
occasionally
and
have
slopes
of
up
to
10
percent.
Companies
that
sell
geotextile
products
provide
detailed
information
on
installation
of
their
products
(Vanderwel
and
Abday,
1998).
The
design
should
be
site­
specific,
using
wellestablished
procedures.
No
standard
procedure
is
available
for
evaluating
the
effectiveness
of
geotextile
liners
for
pollutant
removal.

Grass­
lined
channels
should
be
sited
in
accordance
with
the
natural
drainage
system
and
should
not
cross
ridges.
The
channel
design
should
not
have
sharp
curves
or
significant
changes
in
slope.
The
channel
should
not
receive
direct
sedimentation
from
disturbed
areas
and
should
be
sited
only
on
the
perimeter
of
a
construction
site
to
convey
relatively
clean
storm
water
runoff.
They
should
be
separated
from
disturbed
areas
by
a
vegetated
buffer
or
other
BMP
to
reduce
sediment
loads.
Development
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2002
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Although
exact
design
criteria
should
be
based
on
local
conditions,
basic
design
recommendations
for
grassed
channels
include
the
following:

°
Construction
and
vegetation
of
the
channel
should
occur
before
grading
and
paving
activities
begin.

°
Design
velocities
should
be
less
than
5
ft/
sec.

°
Geotextiles
can
be
used
to
stabilize
vegetation
until
it
is
fully
established.

°
Covering
the
bare
soil
with
sod
or
geotextiles
can
provide
reinforced
storm
water
conveyance
immediately.

°
Triangular­
shaped
channels
should
be
used
with
low
velocities
and
small
quantities
of
runoff;
parabolic
grass
channels
are
used
for
larger
flows
and
where
space
is
available;
trapezoidal
channels
are
used
with
large
flows
of
low
velocity
(low
gradient).

°
Outlet
stabilization
structures
might
be
needed
if
the
runoff
volume
or
velocity
has
the
potential
to
exceed
the
capacity
of
the
receiving
area.

°
Channels
should
be
designed
to
convey
runoff
from
a
10­
year
storm
without
erosion.

°
The
sides
of
the
channel
should
be
sloped
less
than
3:
1,
with
V­
shaped
channels
along
roads
sloped
6:
1
or
less
for
safety.

°
All
trees,
bushes,
stumps,
and
other
debris
should
be
removed
during
construction.

Effectiveness
Grass­
lined
channels
can
effectively
transport
storm
water
from
construction
areas
if
they
are
designed
for
expected
flow
volumes
and
velocities
and
if
they
do
not
receive
sediment
directly
from
disturbed
areas.
The
primary
function
is
to
carry
the
flow
at
a
higher
velocity
without
eroding
or
overtopping
the
channel.

Limitations
Grassed
channels,
if
improperly
installed,
can
alter
the
natural
flow
of
surface
water
and
have
adverse
impacts
on
downstream
waters.
Additionally,
if
the
design
capacity
is
exceeded
by
a
large
storm
event,
the
vegetation
might
not
be
sufficient
to
prevent
erosion
and
the
channel
might
be
destroyed.
Clogging
with
sediment
and
debris
reduces
the
effectiveness
of
grass­
lined
channels
for
storm
water
conveyance.
Development
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2002
5­
24
Maintenance
Maintenance
requirements
for
grass
channels
are
relatively
minimal.
During
the
vegetation
establishment
period,
the
channels
should
be
inspected
after
every
rainfall.
Other
maintenance
activities
that
should
be
carried
out
after
vegetation
is
established
are
mowing,
litter
removal,
and
spot
vegetation
replacement.
The
most
important
objective
in
the
maintenance
of
grassed
channels
is
the
maintaining
of
a
dense
and
vigorous
growth
of
turf.
Periodic
cleaning
of
vegetation
and
soil
buildup
in
curb
cuts
is
required
so
that
water
flow
into
the
channel
is
unobstructed.
During
the
growing
season,
channel
grass
should
be
cut
no
shorter
than
the
level
of
design
flow,
and
the
cuttings
should
be
removed
promptly.

Cost
Costs
of
grassed
channels
range
according
to
depth,
with
a
1.5­
foot­
deep,
10­
foot­
wide
grassed
channel
estimated
at
between
$6,395
and
$17,075
per
trench,
while
a
3.0­
foot­
deep,
21­
footwide
grassed
channel
is
estimated
at
$12,909
to
$33,404
per
trench
(SWRPC,
1991).

As
an
alternative
cost
approximation,
grassed
channel
construction
costs
can
be
developed
using
unit
cost
values.
Shallow
trenching
(1
to
4
feet
deep)
with
a
backhoe
in
areas
not
requiring
dewatering
can
be
performed
for
$4
to
$5
per
cubic
yard
of
removed
material
(R.
S.
Means,
2000).
Assuming
no
disposal
costs
(i.
e.,
excavated
material
is
placed
on
either
side
of
the
trench),
only
the
cost
of
fine
grading,
soil
treatment,
and
grassing
(approximately
$2
per
square
yard
of
earth
surface
area)
should
be
added
to
the
trenching
cost
to
approximate
the
total
construction
cost.
Site­
specific
hydrologic
analysis
of
the
construction
site
is
necessary
to
estimate
the
channel
conveyance
requirement,
however,
it
is
not
unusual
to
have
flows
on
the
order
of
2
to
4
cfs
per
acre
served.
For
channel
velocities
between
1
and
3
feet
per
second,
the
resulting
range
in
the
channel
cross­
section
area
can
be
as
low
as
0.67
square
foot
per
acre
drained
to
as
high
as
4
square
feet
per
acre.
If
the
average
channel
flow
depth
is
1
foot,
then
the
low
estimate
for
grassed
channel
installation
is
$0.27
per
square
foot
of
channel
bottom
per
acre
served
per
foot
of
channel
length.
The
high
estimate
is
$1.63
per
square
foot
of
channel
bottom
per
acre
served
per
foot
of
channel
length.

5.1.5.1.2.2
SEEDING
General
Description
Permanent
seeding,
is
used
to
control
runoff
and
erosion
on
disturbed
areas
by
establishing
perennial
vegetative
cover
from
seed.
It
is
used
to
reduce
erosion,
decrease
sediment
yields
from
disturbed
areas,
and
provide
permanent
stabilization.
This
practice
is
both
economical
and
adaptable
to
different
site
conditions,
and
it
allows
selection
of
the
most
appropriate
plant
materials.
Seeding
is
a
best
management
practice
that
is
particularly
susceptible
to
local
conditions
such
as
the
climatic
conditions,
physical
and
chemical
characteristics
of
the
soil,
topography,
and
time
of
year.
Development
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2002
5­
25
Applicability
Permanent
seeding
is
well­
suited
in
areas
where
permanent,
long­
lived
vegetative
cover
is
the
most
practical
or
most
effective
method
of
stabilizing
the
soil.
Permanent
seeding
can
be
used
on
roughly
graded
areas
that
will
not
be
regraded
for
at
least
a
year.
Vegetation
controls
erosion
by
protecting
bare
soil
surfaces
from
displacement
by
raindrop
impacts
and
by
reducing
the
velocity
and
quantity
of
overland
flow.
The
advantages
of
seeding
over
other
means
of
establishing
plants
include
lower
initial
costs
and
labor
inputs.

Design
and
Installation
Criteria
Areas
to
be
stabilized
with
permanent
vegetation
must
be
seeded
or
planted
1
to
4
months
after
the
final
grade
is
achieved
unless
temporary
stabilization
measures
are
in
place.
Successful
plant
establishment
can
be
maximized
with
proper
planning;
consideration
of
soil
characteristics;
selection
of
plant
materials
that
are
suitable
for
the
site;
adequate
seedbed
preparation,
liming,
and
fertilization;
timely
planting;
and
regular
maintenance.
Climate,
soils,
and
topography
are
major
factors
that
dictate
the
suitability
of
plants
for
a
particular
site.
The
soil
on
a
disturbed
site
might
require
amendments
to
provide
sufficient
nutrients
for
seed
germination
and
seedling
growth.
The
surface
soil
must
be
loose
enough
for
water
infiltration
and
root
penetration.
Soil
pH
should
be
between
6.0
and
6.5
and
can
be
increased
with
liming
if
soils
are
too
acidic.
Seeds
can
be
protected
with
mulch
to
retain
moisture,
regulate
soil
temperatures,
and
prevent
erosion
during
seedling
establishment.

Seedbed
preparation
is
critical
in
established
vegetation.
Spraying
seeds
on
a
scraped
slope
will
generally
not
provide
satisfactory
results.
Typical
seedbed
preparation
will
begin
with
a
soil
test
to
determine
the
amount
of
lime
or
fertilizer
that
should
be
added.
In
addition,
tillage
should
be
performed
that
will
break
up
clods
so
that
seed
contact
can
be
established.
When
the
seed
is
applied,
it
should
be
covered
and
lightly
compacted.
An
appropriate
natural
or
synthetic
mulch
is
recommended
to
provide
surface
stabilization
until
the
vegetation
is
established.
In
addition
to
providing
surface
stabilization,
the
mulch
will
also
retard
evaporation
and
encourage
rapid
growth.
A
suitable
tack
to
hold
the
mulch
may
be
necessary
if
the
mulch
is
not
otherwise
anchored.
Mulches
are
covered
in
a
subsequent
sub­
section.

Depending
on
the
amount
of
use
permanently
seeded
areas
receive,
they
can
be
considered
highor
low­
maintenance
areas.
High­
maintenance
areas
are
mowed
frequently,
limed
and
fertilized
regularly,
and
either
(1)
receive
intense
use
(for
example,
athletic
fields)
or
(2)
require
maintenance
to
an
aesthetic
standard
(for
example,
home
lawns).
Grasses
used
for
highmaintenance
areas
are
long­
lived
perennials
that
form
a
tight
sod
and
are
fine­
leaved.
High­
maintenance
vegetative
cover
is
used
for
homes,
industrial
parks,
schools,
churches,
and
recreational
areas.

Low­
maintenance
areas
are
mowed
infrequently
or
not
at
all
and
do
not
receive
lime
or
fertilizer
on
a
regular
basis.
Plants
must
be
able
to
persist
with
minimal
maintenance
over
long
periods
of
Development
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2002
5­
26
time.
Grass
and
legume
mixtures
are
favored
for
these
sites
because
legumes
fix
nitrogen
from
the
atmosphere.
Sites
suitable
for
low­
maintenance
vegetation
include
steep
slopes,
streambanks
or
channel
banks,
some
commercial
properties,
and
"utility"
turf
areas
such
as
road­
banks.

Effectiveness
Seeding
that
results
in
a
successful
stand
of
grass
has
been
shown
to
remove
between
50
and
100
percent
of
total
suspended
solids
from
storm
water
runoff,
with
an
average
removal
of
90
percent
(USEPA,
1993).

Limitations
The
effectiveness
of
permanent
seeding
can
be
limited
because
of
the
high
erosion
potential
during
establishment,
the
need
to
reseed
areas
that
fail
to
establish,
limited
seeding
times
depending
on
the
season,
and
the
need
for
stable
soil
temperature
and
soil
moisture
content
during
germination
and
early
growth.
Permanent
seeding
does
not
immediately
stabilize
soils—
temporary
erosion
and
sediment
control
measures
should
be
in
place
to
prevent
off­
site
transport
of
pollutants
from
disturbed
areas.
Use
of
mulches
and/
or
geotextiles
may
improve
the
likelihood
of
successfully
establishing
vegetation.

Maintenance
Grasses
should
emerge
within
4
to
28
days
and
legumes
5
to
28
days
after
seeding,
with
legumes
following
grasses.
A
successful
stand
should
exhibit
the
following:

°
Vigorous
dark
green
or
bluish
green
seedlings—
not
yellow
°
Uniform
density,
with
nurse
plants,
legumes,
and
grasses
well
intermixed
°
Green
leaves—
perennials
remaining
throughout
the
summer,
at
least
at
the
plant
bases
Seeded
areas
should
be
inspected
for
failure,
and
necessary
repairs
and
reseeding
should
be
made
as
soon
as
possible.
If
a
stand
has
inadequate
cover,
the
choice
of
plant
materials
and
quantities
of
lime
and
fertilizer
should
be
reevaluated.
Depending
on
the
condition
of
the
stand,
areas
can
be
repaired
by
overseeding
or
reseeding
after
complete
seedbed
preparation.
If
the
timing
is
bad,
an
annual
grass
seed
can
be
overseeded
to
temporarily
thicken
the
stand
until
a
suitable
time
for
seeding
perennials.
Consider
seeding
temporary,
annual
species
if
the
season
is
not
appropriate
for
permanent
seeding.
If
vegetation
fails
to
grow,
the
soil
should
be
tested
to
determine
whether
low
pH
or
nutrient
imbalances
are
responsible.
Local
NRCS
or
county
extension
agents
can
also
be
contacted
for
seeding
and
soil
testing
recommendations.

On
a
typical
disturbed
site,
full
plant
establishment
usually
requires
refertilization
in
the
second
growing
season.
Soil
tests
should
be
used
to
determine
whether
more
fertilizer
needs
to
be
Development
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June
2002
5­
27
added.
Do
not
fertilize
cool
season
grasses
in
late
May
through
July.
Grass
that
looks
yellow
may
be
nitrogen
deficient.
Nitrogen
fertilizer
should
not
be
used
if
the
stand
contains
more
than
20
percent
legumes.

Cost
Seeding
costs
range
from
$200
to
$1,000
per
acre
and
average
$400
per
acre.
Maintenance
costs
range
from
15
to
25
percent
of
initial
costs
and
average
20
percent
(USEPA,
1993).
R.
S.
Means
(2000)
indicates
the
cost
of
mechanical
seeding
to
be
approximately
$900
per
acre,
and
demonstrates
that
the
coverage
cost
varies
with
the
seed
type,
seeding
approach
and
scale
(total
acreage
to
be
seeded).
For
example,
hydro
or
water­
based
seeding
for
grass
is
estimated
to
be
$700
per
acre
but
seeding
of
"field"
grass
species
is
only
$540
per
acre
(Costs
include
materials,
labor,
and
equipment,
with
profit
and
overhead).
If
surface
preparation
is
required,
then
the
installation
costs
increase.
R.
S.
Means
suggests
the
cost
of
fine
grading,
soil
treatment,
and
grassing
is
approximately
$2
per
square
yard
of
earth
surface
area.

5.1.5.1.2.3
SODDING
General
Description
Sodding
is
a
permanent
erosion
control
practice
that
involves
laying
a
continuous
cover
of
grass
sod
on
exposed
soils.
In
addition
to
stabilizing
soils,
sodding
can
reduce
the
velocity
of
storm
water
runoff.
Sodding
can
provide
immediate
vegetative
cover
for
critical
areas
and
stabilize
areas
that
cannot
be
vegetated
by
seed.
It
can
also
stabilize
channels
or
swales
that
convey
concentrated
flows
and
reduce
flow
velocities.
While
sodding
is
not
as
dependent
as
seeding
on
local
conditions,
it
does
depend
on
soil
and
climatic
conditions
to
be
successful.
Capability
to
water
immediately
after
installation
and
occasionally
until
establishment
is
generally
beneficial.

Applicability
Sodding
is
appropriate
for
any
graded
or
cleared
area
that
might
erode,
requiring
immediate
vegetative
cover.
Locations
particularly
well­
suited
to
sod
stabilization
are:

°
Waterways
and
channels
carrying
intermittent
flow
°
Areas
around
drop
inlets
that
require
stabilization
°
Residential
or
commercial
lawns
and
golf
courses
where
prompt
use
and
aesthetics
are
important
°
Steeply
sloped
areas
Development
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Guidelines
June
2002
5­
28
Design
and
Installation
Criteria
Sodding
eliminates
the
need
for
seeding
and
mulching
and
produces
more
reliable
results
with
less
maintenance.
Sod
can
be
laid
during
times
of
the
year
when
seeded
grasses
can
fail.
The
sod
must
be
watered
frequently
within
the
first
few
weeks
of
installation.
Some
seedbed
preparation
is
recommended,
including
smoothing
to
provide
contact
between
the
sod
and
the
soil
surface
and
soil
testing
to
determine
liming
and
fertilizer
application
rates.
Since
sod
provides
instantaneous
cover,
mulches
are
not
typically
recommended,
but
anchoring
may
be
appropriate
on
steep
slopes.

The
type
of
sod
selected
should
be
composed
of
plants
adapted
to
site
conditions.
Sod
composition
should
reflect
environmental
conditions
as
well
as
the
function
of
the
area
where
the
sod
will
be
laid.
The
sod
should
be
of
known
genetic
origin
and
be
free
of
noxious
weeds,
diseases,
and
insects.
The
sod
should
be
machine
cut
at
a
uniform
soil
thickness
of
15
to
25
mm
at
the
time
of
establishment
(this
does
not
include
top
growth
or
thatch).
Soil
preparation
and
addition
of
lime
and
fertilizer
may
be
needed—
soils
should
be
tested
to
determine
whether
amendments
are
needed.
Sod
should
be
laid
in
strips
perpendicular
to
the
direction
of
water
flow
and
staggered
in
a
brick­
like
pattern.
The
corners
and
middle
of
each
strip
should
be
stapled
firmly.
Jute
or
plastic
netting
may
be
pegged
over
the
sod
for
further
protection
against
washout
during
establishment.

Areas
to
be
sodded
should
be
cleared
of
trash,
debris,
roots,
branches,
stones,
and
clods
larger
than
2
inches
in
diameter.
Sod
should
be
harvested,
delivered,
and
installed
within
a
period
of
36
hours.
Sod
not
transplanted
within
this
period
should
be
inspected
and
approved
prior
to
its
installation.

Limitations
Compared
to
seed,
sod
is
more
expensive
and
more
difficult
to
obtain,
transport,
and
store.
Care
must
be
taken
to
prepare
the
soil
and
provide
adequate
moisture
before,
during,
and
after
installation
to
ensure
successful
establishment.
If
sod
is
laid
on
poorly
prepared
soil
or
unsuitable
surface,
the
grass
will
die
quickly
because
it
is
unable
to
root.
Sod
that
is
not
adequately
irrigated
after
installation
may
cause
root
dieback
because
grass
does
not
root
rapidly
and
is
subject
to
drying
out.

Effectiveness
Sod
has
been
shown
to
remove
between
98
and
99
percent
of
total
suspended
solids
in
runoff
(USEPA,
1993).
It
is
therefore
a
highly
effective
management
practice
for
erosion
and
sediment
control.
Development
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June
2002
5­
29
Maintenance
Watering
is
very
important
to
maintain
adequate
moisture
in
the
root
zone
and
to
prevent
dormancy,
especially
within
the
first
few
weeks
of
installation,
until
it
is
fully
rooted.
Mowing
should
not
result
in
the
removal
of
more
than
one­
third
of
the
shoot.
Grass
height
should
be
maintained
at
between
2
and
3
inches.
After
the
first
growing
season,
sod
might
require
fertilization
or
liming.
Permanent,
fine
turf
areas
require
yearly
maintenance
fertilization.
Warm­
season
grass
should
be
fertilized
in
late
spring
to
early
summer,
and
cool­
season
grass
in
late
winter
and
again
in
early
fall.

Cost
Average
construction
costs
of
sod
average
$0.20
per
square
foot
and
range
from
$0.10
to
$1.10
per
square
foot;
maintenance
costs
are
approximately
5
percent
of
installation
costs
(USEPA,
1993).
R.
S.
Means
(2000)
indicates
the
sodding
ranges
between
$250
and
$750
per
1000
square
feet
for
1"
deep
bluegrass
sod
on
level
ground,
depending
on
the
size
of
the
area
treated
(unit
costs
value
are
for
orders
over
8,000
square
feet
and
less
than
1000
square
feet,
respectively).
Bent
grass
sod
values
range
between
$350
and
$500
per
1000
square
feet,
again
the
lower
value
is
more
likely
for
most
construction
sites
because
it
is
for
large
area
applications.
(Costs
include
materials,
labor,
and
equipment,
with
profit
and
overhead).

5.1.5.1.2.4
MULCHING
General
Description
Mulching
is
a
temporary
erosion
control
practice
in
which
materials
such
as
grass,
hay,
wood
chips,
wood
fibers,
straw,
or
gravel
are
placed
on
exposed
or
recently
planted
soil
surfaces.
Mulching
is
highly
recommended
as
a
stabilization
method
and
is
most
effective
when
anchored
in
place
until
vegetation
is
well
established.
In
addition
to
stabilizing
soils,
mulching
can
reduce
the
velocity
of
storm
water
runoff.
When
used
in
combination
with
seeding
or
planting,
mulching
can
aid
plant
growth
by
holding
seeds,
fertilizers,
and
topsoil
in
place;
by
preventing
birds
from
eating
seeds;
by
retaining
moisture;
and
by
insulating
plant
roots
against
extreme
temperatures.

Mulch
mattings
are
materials
such
as
jute
or
other
wood
fibers
that
are
formed
into
sheets
and
are
more
stable
than
loose
mulch.
They
can
also
be
easily
unrolled
during
the
installation
process
and
are
particularly
useful
in
steeper
areas
or
in
channels.
Netting
can
be
used
to
stabilize
soils
while
plants
are
growing,
although
netting
does
not
retain
moisture
or
insulate
against
extreme
temperatures.
Mulch
binders
consist
of
asphalt
or
synthetic
materials
that
are
sometimes
used
instead
of
netting
to
bind
loose
mulches
but
have
been
found
to
have
limited
usefulness.
Development
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June
2002
5­
30
Applicability
Mulching
is
often
used
in
areas
where
temporary
seeding
cannot
be
used
because
of
environmental
constraints.
Mulching
can
provide
immediate,
effective,
and
inexpensive
erosion
control.
On
steep
slopes
and
critical
areas
such
as
waterways,
mulch
matting
is
used
with
netting
or
anchoring
to
hold
it
in
place.
Mulches
can
be
used
on
seeded
and
planted
areas
where
slopes
are
steeper
than
2:
1
or
where
sensitive
seedlings
require
insulation
from
extreme
temperatures.

Design
and
Installation
Criteria
When
possible,
organic
mulches
should
be
used
for
erosion
control
and
plant
material
establishment.
Suggested
materials
include
loose
straw,
netting,
wood
cellulose,
or
agricultural
silage.
All
materials
should
be
free
of
seed,
and
loose
hay
or
straw
should
be
anchored
by
applying
tackifier,
stapling
netting
over
the
top,
or
crimping
with
a
mulch
crimping
tool.
Materials
that
are
heavy
enough
to
stay
in
place
do
not
need
anchoring
(for
example,
gravel).
Steepness
of
the
slope
will
also
affect
the
extent
of
anchoring
the
mulch.
Other
examples
include
hydraulic
mulch
products
with
100
percent
post­
consumer
paper
content,
yard
trimming
composts,
and
wood
mulch
from
recycled
stumps
and
tree
parts.
Inorganic
mulches
such
as
pea
gravel
or
crushed
granite
can
be
used
in
unvegetated
areas.

Mulches
may
or
may
not
require
a
binder,
netting,
or
tacking.
All
straw
and
loose
materials
must
have
a
binder
to
hold
them
in
place.
Mulch
materials
that
float
away
during
storms
can
clog
drainage
ways
and
lead
to
flooding.
The
extent
of
binding
depends
on
the
type
of
mulch
applied.
Effective
use
of
netting
and
matting
material
requires
firm,
continuous
contact
between
the
materials
and
the
soil.
If
there
is
no
contact,
the
material
will
not
hold
the
soil
and
erosion
will
occur
underneath
the
material.
Grading
is
not
necessary
before
mulching.

There
must
be
adequate
coverage,
or
erosion,
washout,
and
poor
plant
establishment
will
result.
If
an
appropriate
tacking
agent
is
not
applied,
or
if
it
is
applied
in
an
insufficient
amount,
mulch
will
not
withstand
wind
and
runoff.
The
channel
grade
and
liner
must
be
appropriate
for
the
amount
of
runoff,
or
the
channel
bottom
will
erode.
Also,
hydromulch
should
be
applied
in
spring,
summer,
or
fall
to
prevent
deterioration
of
the
mulch
before
plants
can
become
established.
Table
5­
6
presents
guidelines
for
installing
mulches,
but
local
conditions
may
warrant
additional
requirements.
Development
Document
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June
2002
5­
31
Table
5­
6.
Typical
Mulching
Materials
and
Application
Rates
Material
Rate
per
Acre
Requirements
Notes
Organic
Mulches
Straw
1­
2
tons
Dry,
unchopped,
unweathered;
avoid
weeds.
Spread
by
hand
or
machine;
must
be
tacked
or
tied
down.

Wood
fiber
or
wood
cellulose
0.5­
1
ton
Use
with
hydroseeder;
may
be
used
to
tack
straw.
Do
not
use
in
hot,
dry
weather.

Wood
chips
5­
6
tons
Air
dry.
Add
fertilizer
N,
12
lb/
ton.
Apply
with
blower,
chip
handler,
or
by
hand.
Not
for
fine
turf
areas.

Bark
35
yd
3
Air
dry,
shredded
or
hammermilled,
or
chips.
Apply
with
mulch
blower,
chip
handler,
or
by
hand.
Do
not
use
asphalt
tack.
Nets
and
Mats
Jute
net
Cover
area
Heavy,
uniform;
woven
of
single
jute
yarn.
Used
with
organic
mulch.
Withstands
water
flow.
Excelsior
(wood
fiber)
mat
Cover
area
Fiberglass
roving
0.5­
1
ton
Continuous
fibers
of
drawn
glass
bound
together
with
a
non­
toxic
agent.
Apply
with
compressed
air
ejector.
Tack
with
emulsified
asphalt
at
a
rate
of
25­
35
gal/
1,000
ft
2
.

Effectiveness
Mulching
effectiveness
varies
with
the
type
of
mulch
used
and
local
conditions
such
as
rainfall
and
runoff
amounts.
Percent
soil
loss
reduction
for
different
mulches
ranges
from
53
to
99.8
percent
used
and
associated
water
velocity
reductions
range
from
24
to
78
percent
(Harding,
1990).
Table
5­
7
shows
soil
loss
and
water
velocity
reductions
for
different
mulch
treatments.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
32
Table
5­
7.
Measured
Reductions
in
Soil
Loss
for
Different
Mulch
Treatments
Mulch
characteristics
Soil
loss
reduction
(%)
Water
velocity
reduction
(%)
relative
to
bare
soil
100%
wheat
straw/
top
net
97.5
73
100%
wheat
straw/
two
nets
98.6
56
70%
wheat
straw/
30%
coconut
fiber
98.7
71
70%
wheat
straw/
30%
coconut
fiber
99.5
78
100%
coconut
fiber
98.4
77
Nylon
monofilament/
two
nets
99.8
74
Nylon
monofilament/
rigid/
bonded
53.0
24
Vinyl
monofilament/
flexible/
bonded
89.6
32
Curled
wood
fibers/
top
net
90.4
47
Curled
wood
fibers/
two
nets
93.5
59
Antiwash
netting(
jute)
91.8
59
Interwoven
paper
and
thread
93.0
53
Uncrimped
wheat
straw–
2,242
kg/
ha
84.0
45
Uncrimped
wheat
straw–
4,484
kg/
ha
89.3
59
Source:
Harding,
1990,
as
cited
in
USEPA,
1993.

Limitations
Mulching,
matting,
and
netting
might
delay
seed
germination
because
the
cover
changes
soil
surface
temperatures.
The
mulches
themselves
are
subject
to
erosion
and
may
be
washed
away
in
a
large
storm
if
not
sufficiently
anchored
with
netting
or
tacking.
Maintenance
is
necessary
to
ensure
that
mulches
provide
effective
erosion
control.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
33
Maintenance
Mulches
must
be
anchored
to
resist
wind
displacement.
Netting
should
be
removed
when
protection
is
no
longer
needed
and
disposed
of
in
a
landfill
or
composted.
Mulched
areas
should
be
inspected
frequently
to
identify
areas
where
mulch
has
loosened
or
been
removed,
especially
after
rain
storms.
Such
areas
should
be
reseeded
(if
necessary)
and
the
mulch
cover
replaced
immediately.
Mulch
binders
should
be
applied
at
rates
recommended
by
the
manufacturer.
If
washout,
breakage,
or
erosion
occurs,
surfaces
should
be
repaired,
reseeded,
and
remulched,
and
new
netting
should
be
installed.
Inspections
should
be
continued
until
vegetation
is
firmly
established.

Cost
The
costs
of
seed
and
mulch
average
$1,500
per
acre
and
range
from
$800
to
$3,500
per
acre
(USEPA,
1993).
R.
S.
Means
(2000)
estimates
the
cost
of
power
mulching
to
be
$22.50
per
1000
square
feet,
for
large
volume
applications.
In
addition,
hydro­
and
mechanical
seeding
are
approximately
$700
to
$900
per
acre.
Coverage
cost
varies
with
the
seed
type,
seeding
approach,
and
scale
(total
acreage
to
be
seeded).
For
example,
hydro
or
water­
based
seeding
for
grass
is
estimated
to
be
$700
per
acre,
but
seeding
of
"field"
grass
species
is
only
$540
per
acre.
(Costs
include
materials,
labor,
and
equipment,
with
profit
and
overhead.)
If
surface
preparation
is
required,
then
the
installation
costs
increase.
R.
S.
Means
(2000)
suggests
the
cost
of
fine
grading,
soil
treatment,
and
grassing
is
approximately
$2
per
square
yard
of
earth
surface
area.

5.1.5.1.2.5
GEOTEXTILES
General
Description
Geotextiles
are
porous
fabrics
also
known
as
filter
fabrics,
road
rugs,
synthetic
fabrics,
construction
fabrics,
or
simply
fabrics.
Geotextiles
are
manufactured
by
weaving
or
bonding
fibers
made
from
synthetic
materials
such
as
polypropylene,
polyester,
polyethylene,
nylon,
polyvinyl
chloride,
glass,
and
various
mixtures
of
these
materials.
As
a
synthetic
construction
material,
geotextiles
are
used
for
a
variety
of
purposes
such
as
separators,
reinforcement,
filtration
and
drainage,
and
erosion
control
(USEPA,
1992).
Some
geotextiles
are
made
of
biodegradable
materials
such
as
mulch
matting
and
netting.
Mulch
mattings
are
jute
or
other
wood
fibers
that
have
been
formed
into
sheets
and
are
more
stable
than
normal
mulch.
Netting
is
typically
made
from
jute,
wood
fiber,
plastic,
paper,
or
cotton
and
can
be
used
to
hold
the
mulching
and
matting
to
the
ground.
Netting
can
also
be
used
alone
to
stabilize
soils
while
the
plants
are
growing;
however,
it
does
not
retain
moisture
or
temperature
well.

Geotextiles
can
aid
in
plant
growth
by
holding
seeds,
fertilizers,
and
topsoil
in
place.
Fabrics
are
relatively
inexpensive
for
certain
applications—
a
wide
variety
of
geotextiles
exist
to
match
the
specific
needs
of
the
site.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
34
Applicability
Geotextiles
can
be
used
for
erosion
control
by
using
it
alone.
Geotextiles
can
be
used
as
matting,
which
is
used
to
stabilize
the
flow
of
channels
or
swales
or
to
protect
seedlings
on
recently
planted
slopes
until
they
become
established.
Matting
may
be
used
on
tidal
or
streambanks
where
moving
water
is
likely
to
wash
out
new
plantings.
They
can
also
be
used
to
protect
exposed
soils
immediately
and
temporarily,
such
as
when
active
piles
of
soil
are
left
overnight.

Geotextiles
are
also
used
as
separators.
An
example
of
such
a
use
is
geotextile
as
a
separator
between
riprap
and
soil.
This
"sandwiching"
prevents
the
soil
from
being
eroded
from
beneath
the
riprap
and
maintaining
the
riprap's
base.

Design
and
Installation
Criteria
Many
types
of
geotextiles
are
available.
Therefore,
the
selected
fabric
should
match
its
purpose.
State
or
local
requirements,
design
procedures,
and
any
other
applicable
requirements
should
be
considered.
In
the
field,
important
concerns
include
regular
inspections
to
determine
whether
cracks,
tears,
or
breaches
are
present
in
the
fabric
and
appropriate
repairs
should
be
made.
Effective
netting
and
matting
require
firm,
continuous
contact
between
the
materials
and
the
soil.
If
there
is
no
contact,
the
material
will
not
hold
the
soil
and
erosion
will
occur
underneath
the
material.

Effectiveness
A
geotextile's
effectiveness
depends
upon
the
strength
of
the
fabric
and
proper
installation.
For
example,
when
protecting
a
cut
slope
with
a
geotextile,
it
is
important
to
properly
anchor
the
fabric
using
appropriate
length
and
spacing
of
wire
staples.
This
will
ensure
that
it
will
not
be
undermined
by
a
storm
event.

Limitations
Geotextiles
(primarily
synthetic
types)
have
the
potential
disadvantage
of
being
sensitive
to
light
and
must
be
protected
prior
to
installation.
Some
geotextiles
might
promote
increased
runoff
and
might
blow
away
if
not
firmly
anchored.
Depending
on
the
type
of
material
used,
geotextiles
might
need
to
be
disposed
of
in
a
landfill,
making
them
less
desirable
than
vegetative
stabilization.
If
the
fabric
is
not
properly
selected,
designed,
or
installed,
the
effectiveness
may
be
reduced
drastically.

Maintenance
Regular
inspections
should
be
made
to
determine
whether
cracks,
tears,
or
breaches
have
formed
in
the
fabric—
it
should
be
repaired
or
replaced
immediately.
It
is
necessary
to
maintain
contact
between
the
ground
and
the
geotextile
at
all
times.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
35
Cost
Costs
for
geotextiles
range
from
$0.50
to
$10.00
per
square
yard
depending
on
the
type
chosen
(SWRCP,
1991).
Geosynthetic
turf
reinforcement
mattings
(TRMs)
are
widely
used
for
immediate
erosion
protection
and
long­
term
vegetative
reinforcement,
usually
for
steeply
sloped
areas
or
areas
exposed
to
runoff
flows.
The
Erosion
Control
Technology
Council
(a
geotextile
industry
support
association)
estimates
TRMs
cost
approximately
$7.00
per
square
yard
(installed)
for
channel
protection
(ECTC,
2002a).
Channel
protection
is
one
of
the
most
demanding
of
installations
(much
more
demanding
than
general
coverage
of
denuded
area).
The
ECTC
estimates
the
cost
to
install
a
simple
soil
blanket
(or
rolled
erosion
control
product),
seed,
and
fertilizer
to
be
$1.00
per
square
yard
(ECTC,
2002b).

5.1.5.1.2.6
VEGETATED
BUFFER
STRIPS
General
Description
Vegetated
buffers
are
areas
of
either
natural
or
established
vegetation
that
are
maintained
to
protect
the
water
quality
of
neighboring
areas.
Buffer
zones
reduce
the
velocity
of
storm
water
runoff,
provide
an
area
for
the
runoff
to
permeate
the
soil,
allow
groundwater
recharge,
and
act
as
filters
to
catch
sediment.
The
reduction
in
velocity
also
helps
to
prevent
soil
erosion.

Applicability
Vegetated
buffers
can
be
used
in
any
area
that
is
able
to
support
vegetation,
but
they
are
most
effective
and
beneficial
on
floodplains,
near
wetlands,
along
streambanks,
and
on
steep,
unstable
slopes.
They
are
also
effective
in
separating
land
use
areas
that
are
not
compatible
and
in
protecting
wetlands
or
waterbodies
by
displacing
activities
that
might
be
potential
sources
of
nonpoint
source
pollution.

Design
and
Installation
Criteria
To
establish
an
effective
vegetative
buffer,
the
following
guidelines
should
be
followed:

°
Soils
should
not
be
compacted.

°
Slopes
should
be
less
than
5
percent.

°
Buffer
widths
should
be
determined
after
careful
consideration
of
slope,
vegetation,
soils,
depth
to
impermeable
layers,
runoff
sediment
characteristics,
type
and
quantity
of
storm
water
pollutants,
and
annual
rainfall.

°
Buffer
widths
should
increase
as
slope
increases.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
36
°
Zones
of
vegetation
(native
vegetation
in
particular),
including
grasses,
deciduous
and
evergreen
shrubs,
and
understory
and
overstory
trees,
should
be
intermixed.

°
In
areas
where
flows
are
concentrated
and
velocities
are
high,
buffer
zones
should
be
combined
with
other
structural
or
nonstructural
BMPs
as
a
pretreatment.

Vegetated
strips
have
been
studied
extensively,
with
emphasis
placed
on
their
effectiveness
in
removing
sediment
and
other
pollutants.
Vegetated
strips
are
most
appropriate
at
sites
where
sediment
loads
are
relatively
low,
as
high
sediment
loads
will
cause
large
quantities
of
deposition
along
the
leading
edge
of
the
vegetation.
This
deposition
will
cause
the
flow
to
divert
around
the
vegetation
in
a
concentrated
flow
pattern,
which
will
cause
short­
circuiting
and
greatly
reduce
removal
efficiency.
Variability
in
vegetation
density
and
uniformity
often
causes
similar
problems.
Removal
efficiency
depends
on
a
combination
of
slope,
length,
and
width
of
the
filter;
density
of
the
vegetation;
sediment
characteristics,
hydraulics
of
the
flow;
and
infiltration.
The
interaction
of
these
variables
is
complex
and
prevents
the
process
from
being
reduced
to
a
simple
relationship
except
on
a
local
basis.
For
site­
specific
local
conditions,
methods
have
been
developed
that
allow
trapping
to
be
related
to
strip
length
and
slope.

Effectiveness
Considerable
data
have
been
collected
on
the
effectiveness
of
buffer
strips
for
specific
conditions.
Numerous
factors
such
as
infiltration
rate,
flow
depth,
slope,
dimensions
of
the
buffer,
density
and
type
of
vegetation,
sediment
size,
and
sediment
density
impact
removal
rates.
Recent
studies
show
that
even
short
vegetative
buffers
can
trap
high
percentages
of
sediment
and
certain
chemicals.
A
significant
concern
is
whether
flow
is
allowed
to
concentrate,
which
will
greatly
reduce
the
travel
time
through
the
buffer
and
prevent
the
removal
of
pollutants.

Several
researchers
have
measured
greater
than
90
percent
reductions
in
sediment
and
nitrate
concentrations;
buffer/
filter
strips
do
a
reasonably
good
job
of
removing
phosphorus
attached
to
sediment,
but
are
relatively
ineffective
in
removing
dissolved
phosphorus
(Gillman,
1994).
However,
since
the
hydraulics
of
flow
through
buffers
strips
are
not
well
defined
and
can
vary
considerably
based
on
site
conditions,
it
is
difficult
to
consistently
estimate
the
effectiveness
of
buffers
strips.

Limitations
Vegetated
buffers
require
plant
growth
before
they
can
be
effective,
and
land
must
be
available
on
which
to
plant
the
vegetation.
If
the
cost
of
the
land
is
very
high,
buffer
zones
might
not
be
cost­
effective.
Although
vegetated
buffers
help
to
protect
water
quality,
they
usually
do
not
effectively
counteract
concentrated
storm
water
flows
to
neighboring
or
downstream
wetlands.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
37
Maintenance
Keeping
vegetation
in
vegetated
buffers
healthy
requires
routine
maintenance,
which
(depending
on
species,
soil
types,
and
climatic
conditions)
can
include
weed
and
pest
control,
mowing,
fertilizing,
liming,
irrigating,
and
pruning.
Inspection
and
maintenance
are
most
important
when
buffer
areas
are
first
installed.
Once
established,
vegetated
buffers
do
not
require
much
maintenance
beyond
the
routine
procedures
listed
earlier
and
periodic
inspections
of
the
areas,
especially
after
any
heavy
rainfall
and
at
least
once
a
year.
Inspections
should
focus
on
encroachment,
gully
erosion,
density
of
vegetation,
evidence
of
concentrated
flows
through
the
areas,
and
any
damage
from
foot
or
vehicular
traffic.
If
there
is
more
than
6
inches
of
sediment
in
one
place,
it
should
be
removed.

Cost
Conceptual
cost
estimates
for
grassed
buffer
strips
can
be
made
based
on
square
footage
using
unit
cost
values.
R.
S.
Means
(2000)
estimates
the
cost
of
fine
grading,
soil
treatment,
and
grassing
to
be
$2
per
square
yard
of
earth
surface
area.
This
cost
estimate
is
based
on
application
of
traditional
lawn
seed.
The
cost
for
field
seed
is
lower
than
lawn
seed,
reducing
the
coverage
price.
Where
gently
sloping
areas
just
need
to
be
grassed
with
acceptable
species,
the
cost
can
be
as
low
as
$0.38
per
square
yard.

5.1.5.1.2.7
EROSION
CONTROL
MATTING
General
Description
Erosion
control
mats
can
be
either
organic
or
made
from
a
synthetic
material.
A
wide
variety
of
products
exist
to
match
the
specific
needs
of
the
site.
Organic
mats
are
made
from
such
materials
as
wood
fiber,
jute
net,
and
coconut
coir
fiber.
Unlike
organic
matter,
synthetic
mats
are
constructed
from
non­
biodegradable
materials
and
remain
in
place
for
many
years.
These
organic
mats
are
classified
as
Turf
Reinforcement
Mats
(TRMs)
and
Erosion
Control
and
Revegetation
Mats
(ECRMs)
(USDOT,
1995).

Erosion
control
matting
aids
in
plant
growth
by
holding
seeds,
fertilizers,
and
topsoil
in
place.
Matting
can
be
used
to
stabilize
the
flow
of
channels
or
swales
or
to
protect
seedlings
on
recently
planted
slopes
until
they
become
established.
Matting
can
be
used
on
tidal
or
streambanks
where
moving
water
is
likely
to
wash
out
new
plantings.
It
can
also
be
used
to
protect
exposed
soils
immediately
and
temporarily,
such
as
when
active
piles
of
soil
are
left
overnight.

Applicability
Mulch
mattings,
netting,
and
filter
fabrics
are
particularly
useful
in
steep
areas
and
drainage
swales
where
loose
seed
is
vulnerable
to
being
washed
away
or
failing
to
survive
dry
soil
(UNEP,
1992).
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
38
Erosion
control
mats
can
also
be
used
to
separate
riprap
and
soil.
This
results
in
a
"sandwiching"
effect,
maintaining
the
riprap's
base
and
preventing
the
soil
beneath
from
being
eroded.

Design
and
Installation
Criteria
Matting
is
especially
recommended
for
steep
slopes
and
channels
(UNEP,
1992).

Many
types
of
erosion
control
mats
are
available.
Therefore,
the
selected
product
should
match
its
purpose.
Effective
netting
and
matting
require
firm,
continuous
contact
between
the
materials
and
the
soil.
If
there
is
no
contact,
the
material
will
not
hold
the
soil
and
erosion
will
occur
underneath
the
material.

Wood
fiber
or
curled
wood
mat
consists
of
curled
wood
with
fibers,
80
percent
of
which
are
150
mm
or
longer,
with
a
consistent
thickness
and
even
distribution
of
fiber
over
the
entire
mat.
The
top
side
of
the
mat
is
covered
with
a
biodegradable
plastic
mesh.
The
mat
is
placed
in
the
channel
or
on
the
slope
parallel
to
the
direction
of
flow
and
secured
with
staples
and
check
slots.
This
is
applied
immediately
after
seeding
operations
(USDOT,
1995).

Jute
net
consists
of
jute
yarn,
approximately
5
mm
in
diameter,
woven
into
a
net
with
openings
that
are
approximately
10
by
20
mm
(or
0.40
to
0.79
inches).
The
jute
net
is
loosely
laid
in
the
channel
parallel
to
the
direction
of
flow.
The
net
is
secured
with
staples
and
check
slots
at
intervals
along
the
channel.
Placement
of
the
jute
net
is
done
immediately
after
seeding
operations
(USDOT,
1995).

Coconut
blankets
are
constructed
of
biodegradable
coconut
fibers
that
resist
decay
for
5
to
10
years
to
provide
long,
temporary
erosion
control
protection.
The
materials
are
often
encased
in
ultraviolet
stabilized
nets
and
sometimes
have
a
composite,
polypropylene
structure
to
provide
permanent
turf
reinforcement.
These
materials
are
best
used
for
waterway
stabilization
and
slopes
that
require
longer
periods
to
stabilize
(USDOT,
1995).

Under
the
synthetic
mat
category
there
are
TRMs
and
ECRMs.
Turf
reinforcement
mats
are
three­
dimensional
polymer
nettings
or
monofilaments
formed
into
a
mat.
They
have
sufficient
thickness
(>
13
mm
or
0.5
inch)
and
void
space
(>
90
percent)
to
allow
for
soil
filling
and
retention.
The
mat
acts
as
a
traditional
mat
to
protect
the
seed
and
increase
germination.
As
the
turf
establishes,
the
mat
remains
in
place
as
part
of
the
root
structure.
This
gives
the
established
turf
a
higher
strength
and
resistance
to
erosion
(USDOT,
1995).

Erosion
control
and
revegetation
mats
are
composed
of
continuous
monofilaments
bound
by
heat
fusion
or
stitched
between
nettings.
They
are
thinner
than
TRMs
and
do
not
have
the
void
space
to
allow
for
filling
of
soil.
They
act
as
a
permanent
mulch
and
allow
vegetation
to
grow
through
the
mat
(USDOT,
1995).
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
39
Effectiveness
The
effectiveness
of
erosion
control
matting
depends
upon
the
strength
of
the
material
and
proper
installation.
For
example,
when
protecting
a
cut
slope
with
an
erosion
control
mat,
it
is
important
to
anchor
the
mat
properly.
This
will
ensure
that
it
will
not
be
undermined
by
a
storm
event.

While
erosion
control
blankets
can
be
effective,
their
performance
varies.
Some
general
trends
are
that
organic
materials
tend
to
be
the
most
effective
(Harding,
1990)
and
that
thicker
materials
are
typically
superior
(Fifield,
1992),
but
there
are
exceptions
to
both
of
these
trends.
Information
about
product
testing
of
blankets
is
generally
lacking.
One
notable
exception
is
the
Texas
Department
of
Transportation,
which
publishes
the
findings
of
their
testing
program
in
the
form
of
a
list
of
acceptable
and
unacceptable
materials
for
specific
uses.

Limitations
Erosion
control
mats
(primarily
synthetic
types)
are
sensitive
to
light
and
for
this
reason
must
be
protected
prior
to
installation.
Some
erosion
control
mats
might
cause
an
increase
in
runoff
or
blow
away
if
not
firmly
anchored.
Erosion
control
mats
might
need
to
be
properly
disposed
of
in
a
landfill,
depending
on
the
type
of
material.
Effectiveness
may
be
reduced
if
the
fabric
is
not
properly
selected,
designed,
or
installed.

Maintenance
Regular
inspections
are
necessary
to
determine
whether
cracks,
tears
or
breaches
have
formed
in
the
fabric.
Contact
between
the
ground
and
erosion
control
mat
should
be
maintained
at
all
times
and
trapped
sediment
removed
after
each
storm
event.

Cost
Costs
for
erosion
control
mats
range
from
$0.50
to
$10.00
per
square
yard
depending
on
the
type
chosen
(SWRCP,
1991).
Geosynthetic
turf
reinforcement
mattings
(TRMs)
are
widely
used
for
immediate
erosion
protection
and
long­
term
vegetative
reinforcement,
usually
for
steeply
sloped
areas
or
areas
exposed
to
runoff
flows.
The
Erosion
Control
Technology
Council
(a
geotextile
industry
support
association)
estimates
TRMs
cost
approximately
$7.00
per
square
yard
(installed)
for
channel
protection
(ECTC,
2002a).
Channel
protection
is
one
of
the
most
demanding
of
installations
(much
more
demanding
than
general
coverage
of
denuded
area).
The
ECTC
estimates
the
cost
to
install
a
simple
soil
blanket
(or
rolled
erosion
control
product),
seed,
and
fertilizer
to
be
$1.00
per
square
yard
(ECTC,
2002b).
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
40
5.1.5.1.2.8
TOPSOILING
General
Description
Topsoiling
is
the
placement
of
a
surface
layer
of
soil
enriched
in
organic
matter
over
a
prepared
subsoil
to
provide
a
suitable
soil
medium
for
vegetative
growth
on
areas
with
poor
moisture,
low
nutrient
levels,
undesirable
pH,
and/
or
the
presence
of
other
materials
that
would
inhibit
the
establishment
of
vegetation.
Advantages
of
topsoil
include
its
high
organic­
matter
content
and
friable
consistency
and
its
available
water­
holding
capacity
and
nutrient
content.
The
texture
and
friability
of
topsoil
are
usually
more
conducive
to
seedling
emergence
root
growth.
In
addition
to
being
a
better
growth
medium,
topsoil
is
often
less
erodible
than
subsoils,
and
the
coarser
texture
of
topsoil
increases
infiltration
capacity
and
reduces
runoff.
During
construction,
topsoil
is
often
removed
from
the
project
area
and
stockpiled.
It
is
replaced
over
areas
to
be
grassed
or
landscaped
during
the
final
stages
of
the
project.

Applicability
Conditions
where
topsoiling
apply
include
the
following:

°
Where
a
sufficient
supply
of
quality
topsoil
is
available.

°
Where
the
subsoil
or
areas
of
existing
surface
soil
present
the
following
problems:
­
The
structure,
pH,
or
nutrient
balance
of
the
available
soil
cannot
be
amended
by
reasonable
means
to
provide
an
adequate
growth
medium
for
the
desired
vegetation.
­
The
soil
is
too
shallow
to
provide
adequate
rooting
depth
or
will
not
supply
necessary
moisture
and
nutrients
for
growth
of
desired
vegetation.
­
The
soil
contains
substances
toxic
to
the
desired
vegetation.

°
Where
high
quality
turf
or
ornamental
plants
are
desired.

°
Where
slopes
are
2:
1
or
flatter.

Design
and
Installation
Criteria
The
topsoil
should
be
uniformly
distributed
over
the
subsoil
to
a
minimum
compacted
depth
of
50
mm
(2
inches)
on
slopes
steeper
than
3
horizontal
to
1
vertical
and
100
mm
(4
inches)
on
flatter
slopes.
Thicknesses
of
100
to
150
mm
is
preferred
for
vegetation
establishment
via
seeding.
The
topsoil
should
not
be
placed
while
in
a
frozen
or
muddy
condition
or
when
the
subsoil
is
excessively
wet,
frozen,
or
in
a
condition
that
is
detrimental
to
proper
grading
or
seedbed
preparation.
The
final
surface
should
be
prepared
so
that
any
irregularities
are
corrected
and
depressions
and
water
pockets
do
not
form.
If
the
topsoil
has
been
treated
with
soil
sterilants,
it
should
not
be
placed
until
the
toxic
substances
have
dissipated
(USDOT,
1995).
Table
5­
8
summarizes
the
cubic
yards
of
topsoil
required
for
application
to
various
depths.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
41
Table
5­
8.
Cubic
Yards
of
Topsoil
Required
for
Application
to
Various
Depths
Depth
(inches)
Per
1,000
Sq
Ft
Per
Acre
1
3.1
134
2
6.2
268
3
9.3
403
4
12.4
536
5
15.5
670
6
18.6
804
Source:
Smolen
et
al.,
1988.

On
slopes
and
areas
that
will
not
be
mowed,
the
surface
may
be
left
rough
after
spreading
topsoil.
A
disk
may
be
used
to
promote
bonding
at
the
interface
between
the
topsoil
and
subsoil
(Smolen
et
al.,
1988).

Effectiveness
No
information
is
available
describing
the
effectiveness
of
applying
topsoil
as
a
BMP.

Limitations
Limitations
of
applying
topsoil
can
include
to
following:

°
Topsoil
spread
when
conditions
were
too
wet,
resulting
in
severe
compaction.

°
Topsoil
mixed
with
too
much
unsuitable
subsoil
material,
resulting
in
poor
vegetation
establishment.

°
Topsoil
contaminated
with
soil
sterilants
or
chemicals,
resulting
in
poor
or
no
vegetation
establishment.

°
Topsoil
not
adequately
incorporated
or
bonded
with
the
subsoil,
resulting
in
poor
vegetation
establishment
and
soil
slippage
on
sloping
areas.

°
Topsoiled
areas
not
protected,
resulting
in
excessive
erosion.

Maintenance
Newly
topsoiled
areas
should
be
inspected
frequently
until
the
vegetation
is
established.
Eroded
or
damaged
areas
should
be
repaired
and
revegetated.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
42
Cost
Top
soiling
costs
are
a
function
of
the
price
of
topsoil,
the
hauling
distance,
and
the
method
of
application.
R.
S.
Means
(2000)
report
unit
cost
values
of
$3
and
$4
per
square
yard,
for
4
and
6
inches
of
top
soil
cover,
respectively.
This
price
is
for
furnishing
and
placing
of
top
soil,
and
includes
materials,
labor,
and
equipment,
with
profit
and
overhead.

5.1.5.2
WATER
HANDLING
PRACTICES
5.1.5.2.1
EARTH
DIKE
General
Description
An
earth
dike
is
a
temporary
or
permanent
ridge
of
soil
designed
to
channel
water
to
a
desired
location.
Dikes
are
used
to
divert
the
flow
of
runoff
by
constructing
a
ridge
of
soil
that
intercepts
and
directs
the
runoff
to
the
desired
outlet
or
alternative
management
practice,
such
as
a
pond.
This
practice
serves
to
reduce
the
length
of
a
slope
for
erosion
control
and
protect
downslope
areas.
An
earth
dike
can
be
used
to
prevent
runoff
from
going
over
the
top
of
a
cut
and
eroding
the
slope,
directing
runoff
away
from
a
construction
site
or
building;
to
divert
clean
water
from
a
disturbed
area;
or
to
reduce
a
large
drainage
area
into
a
more
manageable
size.
Dikes
should
be
stabilized
with
vegetation
after
construction
(NAHB,
n.
d.).

Applicability
Earth
dikes
are
applicable
to
all
areas;
the
size
of
the
dike
is
correlated
to
the
size
of
the
drainage
area
(NAHB,
n.
d.).

Design
and
Installation
Criteria
The
location
of
dikes
should
take
into
consideration
outlet
conditions,
existing
land
use,
topography,
length
of
slope,
soils,
and
development
plans.
The
capacity
of
earth
dikes
and
diversions
should
be
suitable
for
the
area
that
is
being
protected,
including
adequate
freeboard,
or
extra
depth
that
is
added
as
a
safety
margin.
For
homes,
schools,
and
industrial
buildings,
the
recommended
design
frequency
storm
is
50
years
and
the
freeboard
is
0.5
feet
(NAHB,
n.
d.).

Earth
dikes
can
be
employed
as
a
perimeter
control.
For
small
sites,
a
compacted
2­
foot­
tall
dike
is
usually
suitable,
if
hydroseeded.
Larger
dikes
will
actually
divert
runoff
to
another
portion
of
the
site,
usually
to
a
downstream
sediment
trap
or
basin.
Therefore,
the
designer
should
ensure
that
they
have
the
capacity
for
the
10­
year
storm
event,
and
that
the
channel
created
behind
the
dike
is
properly
stabilized
to
percent
erosion
(Brown
et
al.,
1997).
In
addition,
the
downstream
structure
must
be
sized
to
handle
the
flow
from
the
dike.
Dikes
should
be
designed
using
standard
hydrologic
and
hydraulic
calculations
and
certified
by
a
professional
hydrologist
or
engineer.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
43
Diversion
dikes
should
be
installed
prior
to
the
majority
of
the
soil­
disturbing
activity.
As
soon
as
the
dike
form
is
completed,
it
should
be
machine
compacted,
fertilized,
and
either
seeded
and
mulched
or
sodded.
Excavated
materials
should
be
properly
stockpiled
for
future
use
or
disposed
of
properly.
Dikes
should
have
an
outlet
that
functions
with
a
minimum
of
erosion.
Depending
on
site
conditions
and
outlet
structures,
the
runoff
directed
by
dikes
may
have
to
be
conveyed
to
a
sediment­
trapping
device,
such
as
a
sediment
basin
or
detention
pond.
As
grades
increase
over
4
percent,
geotextile
material
or
sod
may
be
required
to
control
erosion.
Slopes
greater
than
8
percent
may
require
riprap.
Dikes
may
be
removed
when
stabilization
of
the
drainage
area
and
outlet
are
complete
(NAHB,
n.
d.).
Dike
design
criteria
must
incorporate
sitespecific
conditions,
as
dimensions
depend
on
expected
flows,
soil
types,
and
climatic
conditions.
All
of
these
inputs
vary
tremendously
over
different
sections
of
the
country.

Effectiveness
No
information
has
been
found
on
the
effectiveness
of
earth
dikes
used
as
BMPs,
although
terraces
often
have
sediment
removal
rates
of
up
to
90
percent.

Limitations
An
erosion­
resistant
lining
in
the
channel
may
be
needed
to
prevent
erosion
in
the
channel
caused
by
excessive
grade.
In
addition,
the
channel
should
be
deepened
and
the
grade
realigned
if
there
is
overtopping
caused
by
sediment
in
the
channel
where
the
grade
decreases
or
reverses.
If
overtopping
occurs
at
low
points
in
the
ridge
where
the
diversion
crosses
the
shallow
draw,
the
ridge
should
be
reconstructed
with
a
positive
grade
toward
the
outlet
at
all
points.
Finally,
if
there
is
erosion
at
the
outlet,
an
outlet
stabilization
structure
should
be
installed
and
if
sedimentation
occurs
at
the
diversion
outlet,
a
temporary
sediment
trap
should
be
installed.

Maintenance
An
earth
dike
should
be
inspected
for
signs
of
erosion
after
every
major
rain
event.
Any
repairs
and/
or
revegetation
should
be
completed
promptly
(NAHB,
n.
d.).
The
following
actions
can
be
taken
to
properly
maintain
an
earth
dike:

°
Remove
debris
and
sediment
from
the
channel
immediately
after
the
storm
event.

°
Repair
the
dike
to
its
original
height.

°
Check
outlets
and
make
necessary
repairs
to
prevent
gully
formation.

°
Clean
out
sediment
traps
when
they
are
50
percent
full.
Development
Document
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and
Development
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Guidelines
June
2002
5­
44
°
Once
the
work
area
has
been
stabilized,
remove
the
diversion
ridge,
fill
and
compact
the
channel
to
blend
with
the
surrounding
area,
and
remove
sediment
traps,
disposing
of
unstable
sediment
in
a
designated
area.

Cost
The
cost
of
an
earth
dike
depends
on
the
design
and
materials
used.
Small
dikes
can
cost
approximately
$2.00
per
linear
foot,
while
larger
dikes
can
cost
approximately
$2.00
per
cubic
yard.
EPA
states
that
an
earth
dike
can
cost
approximately
$4.50
per
linear
foot
(NAHB,
n.
d.).

An
alternative
means
to
estimate
conceptual
costs
for
earthen
dikes
is
to
use
unit
cost
values
and
a
rough
estimate
of
the
quantities
needed.
Shallow
trenching
(1
to
4
feet
deep)
with
a
backhoe
in
areas
not
requiring
dewatering
can
be
performed
for
$4
to
$5
per
cubic
yard
of
removed
material
(R.
S.
Means,
2000).
Based
on
this
value,
$2
per
linear
foot
provides
for
11
square
feet
of
flow
area
and
$4.50
per
linear
foot
provides
for
24
square
feet
of
flow
area.
This
suggests
that
the
size
of
the
dike
is
required
prior
to
specifying
a
cost,
which
requires
a
site­
specific
hydrologic
evaluation.
Based
on
standards
for
Virginia
(1992),
most
small
drainage
areas
(made
up
of
5
acre
or
less),
diversion
dikes
are
approximately
18"
tall,
with
a
4.5'
base.
Assuming
the
excavation
volume
equals
the
volume
of
the
dike,
the
resulting
excavation
volume
is
approximately
7
cubic
feet
per
linear
foot,
which
(conservatively)
equates
to
$1.03
to
$1.30
per
linear
foot
for
construction
costs.

If
the
earthen
dikes
are
to
be
permanent,
then
additional
costs
are
incurred
to
vegetate
the
dike.
R.
S.
Means
(2000)
estimates
the
cost
of
fine
grading,
soil
treatment,
and
grassing
is
approximately
$2
per
square
yard
of
earth
surface
area.
This
adds
approximately
$6
per
linear
foot
of
dike.
Where
gently
sloping
areas
just
need
to
be
grassed
with
acceptable
species,
the
cost
can
be
as
low
as
$0.38
per
square
yard.

5.1.5.2.2
TEMPORARY
SWALE
General
Description
The
term
swale
(grassed
channel,
dry
swale,
wet
swale,
biofilter)
refers
to
a
series
of
vegetated,
open
channel
management
practices
designed
specifically
to
treat
and
attenuate
storm
water
runoff
for
a
specified
water
quality
volume.
As
storm
water
runoff
flows
through
these
channels,
it
is
treated
by
filtering
through
the
vegetation
in
the
channel,
filtering
through
a
subsoil
matrix,
and/
or
infiltration
into
the
underlying
soils.
Variations
of
the
grassed
swale
include
the
grassed
channel,
dry
swale,
and
wet
swale.
The
specific
design
features
and
methods
of
treatment
differ
in
each
of
these
designs,
but
all
are
improvements
on
the
traditional
drainage
ditch
and
incorporate
modified
geometry
and
other
features
for
use
of
the
swale
as
a
treatment
and
conveyance
practice.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
45
Applicability
Grassed
swales
can
be
applied
in
most
situations
with
some
restrictions
and
are
very
well
suited
for
treating
highway
or
residential
road
runoff
because
they
are
linear
practices.
Perimeter
dikes/
swales
should
be
limited
to
a
drainage
area
of
no
more
than
0.8
hectare
and
usually
work
best
on
gently
sloping
terrain.
Perimeter
dikes
may
not
work
well
on
moderate
slopes,
and
they
should
never
be
established
on
slopes
exceeding
20
percent
(UNEP,
1994).

Regional
Applicability.
Grassed
swales
can
be
applied
in
most
regions
of
the
country.
In
arid
and
semi­
arid
climates,
however,
the
value
of
these
practices
needs
to
be
weighed
against
the
water
needed
to
irrigate
them.

Ultra­
Urban
Areas.
Ultra­
urban
areas
are
densely
developed
urban
areas
in
which
little
pervious
surface
exists.
Grassed
swales
are
generally
not
well
suited
to
ultra­
urban
areas
because
they
require
a
relatively
large
area
of
pervious
surfaces.

Storm
Water
Hot
Spots.
Storm
water
hot
spots
are
areas
where
land
use
or
activities
generate
highly
contaminated
runoff,
with
concentrations
of
pollutants
in
excess
of
those
commonly
found
in
storm
water.
A
typical
example
is
a
gas
station
or
convenience
store.
With
the
exception
of
the
dry
swale
design,
hot
spot
runoff
should
not
be
directed
toward
grassed
channels.
These
practices
either
infiltrate
storm
water
or
intersect
the
groundwater,
making
use
of
the
practices
for
hot
spot
runoff
a
threat
to
groundwater
quality.

Storm
Water
Retrofit.
A
storm
water
retrofit
is
a
storm
water
management
practice
(usually
structural),
put
into
place
after
development
has
occurred,
to
improve
water
quality,
protect
downstream
channels,
reduce
flooding,
or
meet
other
specific
objectives.
One
retrofit
opportunity
using
grassed
swales
modifies
existing
drainage
ditches.
Ditches
have
traditionally
been
designed
only
to
convey
storm
water
away
from
roads
as
quickly
as
possible.
In
some
cases,
it
may
be
possible
to
incorporate
features
to
enhance
pollutant
removal
or
infiltration
such
as
check
dams
(for
example,
small
dams
along
the
ditch
that
trap
sediment,
slow
runoff,
and
reduce
the
longitudinal
slope).
Since
grassed
swales
cannot
treat
a
large
area,
using
this
practice
to
retrofit
an
entire
watershed
would
be
expensive
because
of
the
number
of
practices
needed
to
manage
runoff
from
a
significant
amount
of
the
watershed's
land
area.

Cold
Water
(Trout)
Streams.
Grassed
channels
are
a
good
treatment
option
within
watersheds
that
drain
to
cold
water
streams.
These
practices
do
not
retain
water
for
a
long
period
of
time
and
often
induce
infiltration.
As
a
result,
standing
water
will
not
typically
be
subjected
to
warming
by
the
sun
in
these
practices.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
46
Design
and
Installation
Criteria
Temporary
swales
should
be
designed
using
standard
hydrologic
and
hydraulic
calculations.
Designs
should
be
certified
by
a
professional
hydrologist,
engineer,
or
other
appropriate
professional.

Perimeter
dikes/
swales
should
be
established
before
any
major
soil­
disturbing
activity
takes
place.
Dikes
should
be
compacted
with
construction
equipment
to
the
design
height
plus
10
percent
to
allow
for
settlement.
If
they
are
to
remain
in
place
for
longer
than
10
days,
they
should
be
stabilized
using
vegetation,
filter
fabric,
or
other
material.
Diverted
water
should
be
directed
to
a
sediment
trap
or
other
sediment
treatment
area
(UNEP,
1994).

In
addition
to
the
broad
applicability
concerns
described
above,
designers
need
to
consider
conditions
at
the
site
level.
In
addition,
they
need
to
incorporate
design
features
to
improve
the
longevity
and
performance
of
the
practice,
while
minimizing
the
maintenance
burden.

Siting
Considerations
In
addition
to
considering
the
restrictions
and
adaptations
of
grassed
swales
to
different
regions
and
land
uses,
designers
must
ensure
that
this
management
practice
is
feasible
at
the
site
in
question.
Depending
on
the
design
option,
grassed
channels
can
be
highly
restricted
practices
based
on
site
characteristics.

Drainage
Area.
Grassed
swales
generally
should
treat
small
drainage
areas
of
less
than
5
acres.
If
the
practices
are
used
to
treat
larger
areas,
the
flows
and
volumes
through
the
swale
become
too
large
to
design
the
practice
to
treat
storm
water
runoff
through
infiltration
and
filtration.

Slope.
Grassed
swales
should
be
used
on
sites
with
relatively
flat
slopes
(less
than
4
percent).
Runoff
velocities
within
the
channel
become
too
high
on
steeper
slopes.
This
can
cause
erosion
and
does
not
allow
for
infiltration
or
filtering
in
the
swale.

Soils
/Topography.
Grassed
swales
can
be
used
on
most
soils,
with
some
restrictions
on
the
most
impermeable
soils.
In
the
dry
swale,
a
fabricated
soil
bed
replaces
on­
site
soils
to
ensure
that
runoff
is
filtered
as
it
travels
through
the
soils
of
the
swale.

Groundwater.
The
depth
to
groundwater
depends
on
the
type
of
swale
used.
In
the
dry
swale
and
grassed
channel
options,
designers
should
separate
the
bottom
of
the
swale
from
the
groundwater
by
at
least
2
feet
to
prevent
a
moist
swale
bottom
or
contamination
of
the
groundwater.
In
the
wet
swale
option,
treatment
is
enhanced
by
a
wet
pool,
which
is
maintained
by
intersecting
the
groundwater.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
47
Design
Considerations
Although
the
grass
swale
has
different
design
variations,
including
the
grassed
channel,
dry
swale,
and
wet
swale,
some
design
considerations
are
common
to
all
three.
One
overriding
similarity
is
the
cross­
sectional
geometry
of
all
three
options.
Swales
should
generally
have
a
trapezoidal
or
parabolic
cross­
section
with
relatively
flat
side
slopes
(flatter
than
3:
1).
Designing
the
channel
with
flat
side
slopes
maximizes
the
wetted
perimeter.
The
wetted
perimeter
is
the
length
along
the
edge
of
the
swale's
cross­
section
where
runoff
flowing
through
the
swale
is
in
contact
with
the
vegetated
sides
and
bottom
of
the
swale.
Increasing
the
wetted
perimeter
slows
runoff
velocities
and
provides
more
contact
with
vegetation
to
encourage
filtering
and
infiltration.
Another
advantage
to
flat
side
slopes
is
that
runoff
entering
the
grassed
swale
from
the
side
receives
some
pretreatment
along
the
side
slope.
The
flat
bottom
of
all
three
should
be
between
2
and
8
feet
wide.
The
minimum
width
ensures
an
adequate
filtering
surface
for
water
quality
treatment,
and
the
maximum
width
prevents
braiding,
that
is,
the
formation
of
small
channels
within
the
swale
bottom.

Another
similarity
among
all
three
designs
is
the
type
of
pretreatment
needed.
In
all
three
design
options,
a
small
forebay
should
be
used
at
the
beginning
of
the
front
of
the
swale
to
trap
incoming
sediments.
A
pea
gravel
diaphragm,
a
small
trench
filled
with
river
run
gravel,
should
be
used
to
pretreat
runoff
entering
the
sides
of
the
swale.

Two
other
features
designed
to
enhance
the
treatment
ability
of
grassed
swales
are
a
flat
longitudinal
slope
(generally
between
1
and
2
percent)
and
a
dense
vegetative
cover
in
the
channel.
The
flat
slope
helps
to
reduce
the
velocity
of
flow
in
the
channel.
The
dense
vegetation
also
helps
reduce
velocities,
protect
the
channel
from
erosion,
and
act
as
a
filter
to
treat
storm
water
runoff.
During
construction,
it
is
important
to
stabilize
the
channel
before
the
turf
has
been
established,
either
with
a
temporary
grass
cover
or
with
the
use
of
natural
or
synthetic
erosion
control
products.

In
addition
to
treating
runoff
for
water
quality,
grassed
swales
need
to
convey
larger
storms
safely.
Typical
designs
allow
the
runoff
from
the
2­
year
storm
(for
example,
the
storm
that
occurs,
on
average,
once
every
2
years)
to
flow
through
the
swale
without
causing
erosion.
Swales
should
also
have
the
capacity
to
pass
larger
storms
(typically
a
10­
year
storm)
safely.

The
length
of
the
swale
necessary
to
infiltrate
runoff
waters
can
be
calculated
by
using
a
mass
balance
of
runoff
waters
and
infiltration
waters
for
a
triangular­
shaped
cross­
sectional
area.

Design
Variations
The
following
discussion
identifies
three
different
variations
of
open
channel
practices,
including
the
grassed
channel,
the
dry
swale,
and
the
wet
swale.
Development
Document
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and
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Guidelines
June
2002
5­
48
Grassed
Channel.
(Discussed
in
more
length
in
sub­
section
5.5.1.2.1)
Of
the
three
grassed
swale
designs,
grassed
channels
are
the
most
similar
to
a
conventional
drainage
ditch,
with
the
major
differences
being
flatter
side
slopes
and
longitudinal
slopes
and
a
slower
design
velocity
for
water
quality
treatment
of
small
storm
events.
Of
all
of
the
grassed
swale
options,
grassed
channels
are
the
least
expensive,
but
they
also
provide
the
least
reliable
pollutant
removal.
The
best
application
of
a
grassed
channel
is
as
pretreatment
to
other
structural
storm
water
practices.

One
major
difference
between
the
grassed
channel
and
most
of
the
other
structural
practices
is
the
method
used
to
size
the
practice.
Most
water
quality
practices
for
storm
water
management
are
sized
by
volume.
This
method
sets
the
volume
available
in
the
practice
equal
to
the
water
quality
volume,
or
the
volume
of
water
to
be
treated
in
the
practice.
The
grassed
channel,
on
the
other
hand,
is
a
flow
rate­
based
design.
Based
on
the
peak
flow
from
the
water
quality
storm
(this
varies
from
region
to
region
but
a
typical
value
is
the
1­
inch
storm),
the
channel
should
be
designed
so
that
runoff
takes,
on
average,
10
minutes
to
flow
from
the
top
to
the
bottom
of
the
channel.
A
procedure
for
this
design
can
be
found
in
Design
of
Storm
Water
Filtering
Systems
(CWP,
1996).

Dry
Swales.
Dry
swales
are
similar
in
design
to
bioretention
areas.
These
designs
incorporate
a
fabricated
soil
bed
into
their
design.
The
existing
soil
is
replaced
with
a
sand/
soil
mix
that
meets
minimum
permeability
requirements.
An
underdrain
system
is
used
under
the
soil
bed.
This
system
is
a
gravel
layer
that
encases
a
perforated
pipe.
Storm
water
treated
in
the
soil
bed
flows
through
the
bottom
into
the
underdrain,
which
conveys
this
treated
storm
water
to
the
storm
drain
system.
Dry
swales
are
a
relatively
new
design,
but
studies
of
swales
with
a
native
soil
similar
to
the
man­
made
soil
bed
of
dry
swales
suggest
high
pollutant
removal.

Wet
Swales.
Wet
swales
intersect
the
groundwater
and
behave
similarly
to
a
linear
wetland
cell.
This
design
variation
incorporates
a
shallow
permanent
pool
and
wetland
vegetation
to
provide
storm
water
treatment.
This
design
also
has
potentially
high
pollutant
removal.
One
disadvantage
of
the
wet
swale
is
that
its
use
in
residential
or
commercial
settings
is
unpopular
because
the
shallow
standing
water
in
the
swale
is
often
viewed
as
a
potential
nuisance
by
homeowners.

Regional
Variations
Cold
Climates.
In
cold
or
snowy
climates,
swales
may
serve
a
dual
purpose
by
acting
as
both
a
snow
storage/
treatment
and
a
storm
water
management
practice.
This
dual
purpose
is
particularly
relevant
when
swales
are
used
to
treat
road
runoff.
If
used
for
this
purpose,
swales
should
incorporate
salt­
tolerant
vegetation,
such
as
creeping
bentgrass.

Arid
Climates.
In
arid
or
semi­
arid
climates,
swales
should
be
designed
with
drought­
tolerant
vegetation,
such
as
buffalo
grass.
As
pointed
out
in
the
Applicability
discussion,
the
value
of
vegetated
practices
for
water
quality
needs
to
be
weighed
against
the
cost
of
water
needed
to
maintain
them
in
arid
and
semi­
arid
regions.
Development
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for
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June
2002
5­
49
Effectiveness
Swales
act
to
control
peak
discharges
in
two
ways.
First,
the
grass
reduces
runoff
velocity,
depending
on
the
length
and
slope
of
the
swale.
Second,
a
portion
of
the
storm
water
runoff
volume
passes
through
the
swale
and
infiltrates
into
the
soil.
Table
5­
9
summarizes
grassed
swale
pollutant
removal
efficiencies.

Table
5­
9.
Grassed
Swale
Pollutant
Removal
Efficiency
Data
Grassed
Swale
Removal
Efficiencies
Study
TSS
TP
TN
NO3
Metals
Bacteria
Type
Goldberg,
1993
67.8
4.5
­
31.4
42–
62
­100
Grassed
channel
Seattle
Metro
and
Washington
Department
of
Ecology,
1992
60
45
­
­25
2–
16
­25
Grassed
channel
Seattle
Metro
and
Washington
Department
of
Ecology,
1992
83
29
­
­25
46–
73
­25
Grassed
channel
Wang
et
al.,
1981
80
­
­
­
70–
80
­
Dry
swale
Dorman
et
al.,
1989
98
18
­
45
37–
81
­
Dry
swale
Harper,
1988
87
83
84
80
88–
90
­
Dry
swale
Kercher,
Landon,
and
Massarelli,
1983
99
99
99
99
99
­
Dry
swale
Harper,
1988
81
17
40
52
37–
69
­
Wet
swale
Koon,
1995
67
39
­
9
­35
to
6
­
Wet
swale
Occoquan
Watershed
Monitoring
Lab,
1983
­100
­100
­100
­
­100
­
Drainage
channel
Yousef
et
al.,
1985
­
8
13
11
14–
29
­
Drainage
channel
Occoquan
Watershed
Monitoring
Lab,
1983
­50
­9.
1
­18.2
­
­100
­
Drainage
channel
Yousef
et
al.,
1985
­
­19.5
8
2
41–
90
­
Drainage
channel
Occoquan
Watershed
Monitoring
Lab,
1983
31
­23
36.5
­
­100
to
33
­
Drainage
channel
Welborn
and
Veenhuis,
1987
0
­25
­25
­25
0
­
Drainage
channel
Yu,
Barnes,
and
Gerde,
1993
68
60
­
­
74
­
Drainage
channel
Dorman
et
al.,
1989
65
41
­
11
14–
55
­
Drainage
channel
Pitt
and
McLean,
1986
0
­
0
­
0
0
Drainage
channel
Oakland,
1983
33
­25
­
­
20–
58
0
Drainage
channel
Dorman
et
al.,
1989
­85
12
­
­100
14–
88
­
Drainage
channel
Limitations
Common
problems
associated
with
swales
include
excessive
erosion
along
unlined
channels
(usually
because
of
excessive
grade),
erosion
or
sedimentation
at
the
outlet
point,
or
overtopping
of
the
dike
at
low
points
(UNEP,
1994).

Additional
limitations
of
the
grass
swale
include
the
following:

°
Grassed
swales
cannot
treat
a
very
large
drainage
area.

°
Swales
do
not
appear
to
be
effective
at
reducing
bacteria.
Development
Document
for
Construction
and
Development
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Guidelines
June
2002
5­
50
°
Wet
swales
may
become
a
nuisance
because
of
mosquito
breeding.

°
If
designed
improperly
(for
example,
proper
slope
is
not
achieved),
grassed
channels
will
have
very
little
pollutant
removal.

°
A
thick
vegetative
cover
is
needed
for
these
practices
to
function
properly.

Maintenance
As
with
any
BMP,
swales
must
be
maintained
to
continue
functioning
as
effective
pollutant
removal
methods.
Maintenance
may
include
occasional
mowing,
fertilizing,
and
liming.
In
addition,
any
areas
that
become
damaged
by
erosion
should
be
immediately
repaired
and
replanted.
The
swales
should
be
protected
from
concentrated
flows
and
checked
for
downstream
obstructions.

Cost
To
produce
a
conceptual
cost
approximation,
grassed
channel
construction
costs
can
be
developed
using
unit
cost
values.
Shallow
trenching
(1
to
4
feet
deep)
with
a
backhoe
in
areas
not
requiring
dewatering
can
be
performed
for
$4
to
$5
per
cubic
yard
of
removed
material
(R.
S.
Means,
2000).
Assuming
no
disposal
costs
(i.
e.,
excavated
material
is
placed
on
either
side
of
the
trench),
only
the
cost
of
fine
grading,
soil
treatment,
and
grassing
(approximately
$2
per
square
yard
of
earth
surface
area)
should
be
added
to
the
trenching
cost
to
approximate
the
total
construction
cost.
Site­
specific
hydrologic
analysis
of
the
construction
site
is
necessary
to
estimate
the
channel
conveyance
requirement
and
the
desired
retention
time
in
the
swale.
It
is
not
unusual
to
have
flows
on
the
order
of
2
to
4
cfs
per
acre
served.

For
a
design
channel
velocity
of
1
foot
per
second,
the
resulting
range
in
the
channel
crosssection
area
can
be
as
low
as
2
but
as
high
as
4
square
feet
per
acre
drained.
If
the
average
channel
flow
depth
is
1
foot,
then
the
low
estimate
for
grassed
channel
installation
is
$0.74
per
square
foot
of
channel
bottom
per
acre
served
per
foot
of
channel
length.
The
high
estimate
is
$1.48
per
square
foot
of
channel
bottom
per
acre
served
per
foot
of
channel
length.

Table
5­
10
summarizes
additional
costs
of
grass
swales.
Development
Document
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June
2002
5­
51
Table
5­
10.
Average
Annual
Operation
and
Maintenance
Costs
for
a
Grass
Swale
Component
Estimated
Unit
Cost
($)
$
for
Swale
Size:
0.5
m
Deep
0.3
m
Bottom
Width
3
m
Top
Width
$
for
Swale
Size:
1
m
Deep
1
m
Bottom
Width
7
m
Top
Width
Comments
Mowing
0.89/
100
m
2
145.0
241.0
Mow
2­
3
times
per
year
General
grass
care
8.8/
100
m
2
162.98
274.0
Grass
maintenance
area
is
(top
width
+
3
m)
x
length
Debris/
litter
removal
0.51/
m
2
93.0
93.0
Reseeding/
fertilization
0.35/
m
2
5.9
10.37
Area
revegetated
is
1%
of
maintenance
area
per
year
Inspection
and
general
administration
0.74/
m
2
231.0
231.0
Inspection
once
per
year
TOTAL
638.0
850.0
Source:
Ellis,
1998.

5.1.5.2.3
TEMPORARY
STORM
DRAIN
DIVERSION
General
Description
A
temporary
storm
drain
diversion
is
a
pipe
that
reroutes
an
existing
drainage
system
to
discharge
flow
into
a
sediment
trap
or
basin.
This
practice
reduces
the
amount
of
sedimentladen
runoff
from
construction
sites
that
enters
waterbodies
without
treatment.
Temporary
storm
drain
diversions
can
be
used
when
a
permanent
storm
water
drainage
system
has
not
yet
been
installed.
It
should
be
recognized
that
diversion
channels
can
also
be
installed
but
are
not
considered
in
the
following
discussion.

Applicability
A
temporary
storm
drain
diversion
should
be
used
to
temporarily
redirect
discharge
to
a
permanent
outfall
and
should
remain
in
place
until
the
area
draining
to
the
storm
sewer
is
no
longer
disturbed.
Temporary
storm
drain
diversions
can
also
be
combined
with
other
structures
and
used
as
a
sediment­
trapping
device
when
the
completion
of
a
permanent
outfall
has
been
delayed;
alternatively,
a
sediment
trap
can
be
placed
below
a
permanent
outfall
to
remove
sediment
before
the
final
flow
discharge.

Design
and
Installation
Criteria
Since
the
diversion
is
only
temporary,
the
layout
of
piping
and
the
overall
impact
of
the
diversion's
installation
on
post­
construction
drainage
patterns
must
be
considered.
Once
construction
is
completed,
the
temporary
diversion
should
be
moved
to
restore
the
original
system.
The
following
activities
should
be
done
at
this
time:
Development
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June
2002
5­
52
°
The
storm
drain
should
be
flushed
before
the
sediment
trap
is
removed.

°
The
outfall
should
be
stabilized.

°
Graded
areas
should
be
restored.

°
State
or
local
specifications
should
be
checked
for
more
detailed
requirements
and
an
appropriate
professional
should
certify
that
the
design
meets
local
hydrologic
and
hydraulic
requirements.

Effectiveness
If
installed
properly
to
capture
the
bulk
of
runoff
from
a
construction
site,
temporary
storm
drain
diversions
can
be
effective
in
reducing
the
discharge
of
sediment­
laden,
untreated
water
to
waterbodies.
When
used
in
combination
with
other
erosion
and
sediment
control
practices
such
as
minimized
clearing
or
vegetative
and
chemical
stabilization,
the
level
of
pollution
from
a
construction
site
can
be
substantially
reduced
or
eliminated.

Limitations
Installation
of
a
temporary
storm
drain
diversion
may
result
in
the
disturbance
of
existing
storm
drainage
patterns.
Care
must
be
taken
to
ensure
that
the
original
system
is
properly
restored
once
the
temporary
system
is
removed.
The
most
common
source
of
problems
is
excessive
velocity
at
the
outlet.
Installation
of
an
outlet
stabilization
structure
is
typically
required
and
may
be
constructed
of
riprap,
reinforced
concrete,
geotextile
linings,
or
a
combination.

Maintenance
Once
installed,
temporary
storm
drain
diversions
require
very
little
maintenance.
Frequent
inspection
and
maintenance
of
temporary
storm
drain
systems,
especially
after
large
storms,
should
ensure
that
pipe
clogging
does
not
occur
and
that
runoff
from
the
site
is
being
successfully
diverted.
After
removal
of
the
temporary
diversion,
the
permanent
storm
drain
system
should
be
carefully
inspected
to
ensure
that
drainage
patterns
have
not
been
altered
by
the
temporary
system.

Cost
Depending
on
the
size
of
the
construction
site,
a
temporary
storm
drain
diversion
can
be
costly.
Costs
include
those
associated
with
materials
needed
to
construct
the
diversion
and
sediment
trap
or
basin
(mainly
piping,
concrete,
and
gravel),
and
also
labor
costs
for
installation
and
removal
of
the
system,
all
of
which
may
involve
excavation,
regrading,
and
inspections.
Based
on
the
variety
of
conditions
that
can
affect
storm
drain
diversion
designs,
typical
costs
per
installation
are
not
presented
here.
However,
site­
specific
cost
estimates
can
be
produced
using
unit
cost
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
53
values
along
with
site­
specific
quantity
estimates.
R.
S.
Means
(2000)
indicates
a
range
of
pipe
costs
for
surface
placement,
between
$5.00
per
linear
foot
for
4"
diameter
PVC
piping,
and
$9.20
per
linear
foot
for
10"
diameter
PVC
piping.
On
construction
sites,
temporary
inlets
and
outlets
are
usually
formed
by
small
rock­
lined
depressions.
Assuming
4
cubic
yards
of
crushed
rock
(1.5"
mean
diameter)
per
opening,
an
inlet
and
outlet
combine
to
add
approximately
$200
per
pipe
installation,
based
on
$25
per
cubic
yard
of
stone
(R.
S.
Means,
2000).

5.1.5.2.4
PIPE
SLOPE
DRAIN
General
Description
Pipe
slope
drains
are
used
to
reduce
the
risk
of
erosion
on
slopes
by
discharging
runoff
to
stabilized
areas.
Consisting
of
a
metal
or
plastic
flexible
pipe
if
temporary,
or
pipes
or
paved
chutes
if
permanent,
these
drains
are
placed
from
the
top
to
the
bottom
of
a
slope
to
carry
surface
runoff
from
the
top
to
the
bottom
of
a
slope
that
has
already
been
damaged
by
erosion
or
is
at
high
risk
for
erosion.
These
drains
are
also
used
to
drain
saturated
slopes
that
have
the
potential
for
soil
slides.

Applicability
Temporary
slope
drains
can
be
used
on
most
disturbed
slopes
to
eliminate
gully
erosion
problems
resulting
from
concentrated
flows
discharged
at
a
diversion
outlet.
Slope
drains
should
be
used
as
a
temporary
measure
for
as
long
as
the
drainage
area
remains
disturbed.
They
will
need
to
be
moved
once
construction
is
complete
and
a
permanent
storm
drainage
system
is
established.
Appropriate
restoration
measures
will
then
need
to
be
taken,
such
as
adjusting
grades
and
flushing
sediment
from
the
pipe
before
it
is
removed
(UNEP,
1994).

Design
and
Installation
Criteria
Pipe
slope
drains
can
be
placed
directly
on
the
ground
or
buried
under
the
surface.
The
inlet
should
be
located
at
the
top
of
the
slope
and
should
be
fitted
with
an
apron,
attached
with
a
water
tight
connection.
Filter
cloth
should
be
placed
under
the
inlet
to
prevent
erosion.
Flexible
pipes,
which
are
positioned
on
top
of
the
ground,
should
be
securely
anchored
with
grommets
placed
10
feet
on
center.
The
outlet
at
the
bottom
of
the
slope
should
also
be
stabilized
with
riprap.
The
riprap
should
be
placed
along
the
bottom
of
a
swale
that
leads
to
a
sediment­
trapping
structure
or
another
stabilized
structure.

Slope
drain
pipe
sizes
are
based
on
drainage
area
and
the
size
of
the
design
storm.
Pipes
should
be
connected
to
a
diversion
ridge
at
the
top
of
the
slope
by
covering
with
compacted
fill
material
where
it
passes
through
the
ridge.
Discharge
from
a
slope
drain
should
be
to
a
sediment
trap,
sediment
basin,
or
other
stabilized
outlet
(UNEP,
1994).
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
54
Pipe
slope
drains
should
be
installed
perpendicular
to
the
contour
down
the
slope,
and
the
design
should
be
able
to
handle
the
peak
runoff
for
the
10­
year
storm.
Recommendations
of
slope
drain
diameter
are
summarized
in
Table
5­
11
(NAHB,
n.
d).

Table
5­
11.
Recommended
Pipe/
Tubing
Sizes
for
Slope
Drains
Maximum
Drainage
Area
(acres)
Pipe/
Tubing
Diameter
a
(inches)
Pipe/
Tubing
Diameter
b
(inches)
Pipe/
Tubing
Diameter
c
(inches)
0­
0.5
0.5
12
12
8
0.75
10
1.0
12
1.5
18
18
Individually
designed
2.5
21
3.5
24
24
5.0
30
a
UNEP,
1994.
b
USDOT,
1995.
c
IDNR,
1992.

Recently
graded
slopes
that
do
not
have
permanent
drainage
measures
installed
should
have
a
temporary
slope
drain
and
a
temporary
diversion
installed.
A
temporary
slope
drain
used
in
conjunction
with
a
diversion
conveys
storm
water
flows
and
reduces
erosion
until
permanent
drainage
structures
are
installed.

The
following
are
design
recommendations
for
temporary
slope
drains:

°
The
drain
should
consist
of
heavy­
duty
material
manufactured
for
the
purpose
and
have
grommets
for
anchoring
at
a
spacing
of
10
feet
or
less.

°
Minimum
slope
drain
diameters
should
be
observed
for
varying
drainage
areas.

°
The
entrance
to
the
pipe
should
consist
of
a
standard
flare
end
section
of
corrugated
metal.
The
corrugated
metal
pipe
should
have
watertight
joints
at
the
ends.
The
rest
of
the
pipe
is
typically
corrugated
plastic
or
flexible
tubing,
although
for
flatter,
shorter
slopes,
a
polyethylene­
lined
channel
is
sometimes
used.

°
The
height
of
the
diversion
at
the
pipe
should
be
the
diameter
of
the
pipe
plus
0.5
foot.

°
The
outlet
should
be
located
at
a
reinforced
or
erosion­
resistant
location.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
55
°
Temporary
slope
drains
should
be
designed
to
adequately
convey
runoff
for
a
desired
frequency
storm,
typically
either
2
years
or
10
years
depending
on
local
regulations.
Both
the
size
and
the
spacing
can
be
determined
based
on
the
contributing
drainage
area.
Drains
are
spaced
at
intervals
corresponding
to
the
specified
drainage
areas.
For
larger
drainage
areas
and
critical
locations,
the
drains
should
be
sized
on
an
individual
basis
(USDOT,
1995).

°
Slope
drains
should
be
constructed
in
conjunction
with
diversion
berms
such
that
the
berms
are
not
overtopped.
At
the
pipe
inlet,
the
top
of
the
berm
should
be
a
minimum
of
300
millimeters
(11.81
inches)
higher
than
the
top
of
the
pipe.
The
entrance
should
be
constructed
of
a
standard
flared
end
section
or
a
Tee
section
if
designed
properly.
The
entrance
should
be
placed
in
a
150
millimeters
(5.90
inches)
minimum
depressed
sump
(USDOT,
1995).

°
The
outlet
of
the
slope
drain
must
be
protected
with
a
riprap
apron.
If
the
slope
drain
is
draining
a
disturbed
area
and
sufficient
right­
of­
way
is
available,
the
drain
may
empty
into
a
sediment
trap
(USDOT,
1995).
Table
5­
12
summarizes
slope
drain
characteristics.

Table
5­
12.
Slope
Drain
Characteristics
Capacity
2­
yr
frequency,
24­
hr­
duration
storm
event
Material
Strong,
flexible
pipe,
such
as
heavy
duty,
nonperforated,
corrugated
plastic
Inlet
section
Standard
"T"
or
"L"
flared­
end
section
with
metal
toe
plate
Connection
to
ridge
at
top
of
slope
Compacted
fill
over
pipe
with
minimum
dimensions,
1.5
ft
depth,
4
ft
top
width,
and
6
in
higher
than
ridge
Outlet
Pipe
extends
beyond
toe
of
slope
and
discharges
into
a
sediment
trap
or
basin
unless
contributing
drainage
area
is
stable
Source:
IDNR,
1992.

Effectiveness
There
is
currently
no
information
on
the
effectiveness
of
pipe
slope
drains.

Limitations
The
area
drained
by
a
temporary
slope
drain
should
not
exceed
5
acres.
Physical
obstructions
substantially
reduce
the
effectiveness
of
the
drain.
A
common
slope
drain
problem
is
overtopping
of
the
inlet
due
to
an
undersized
or
blocked
pipe,
or
erosion
at
the
outlet
point
due
to
insufficient
protection
(UNEP,
1994).
Other
concerns
are
failures
from
overtopping
because
of
inadequate
pipe
inlet
capacity
and
reduced
diversion
channel
capacity
and
ridge
height.
Development
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June
2002
5­
56
Solutions
to
common
problems
include
the
following
(IDNR,
1992):

°
Washout
­
A
washout
along
a
pipe
due
to
seepage
and
piping
may
be
caused
by
inadequate
compaction,
insufficient
fill,
or
installation
that
may
be
too
close
to
the
edge
of
the
slope.

°
Overtopping
caused
by
undersized
or
blocked
pipe
­
The
drainage
area
may
be
too
large.

°
Overtopping
caused
by
improper
grade
of
channel
and
ridge
­
A
positive
grade
should
be
maintained.

°
Overtopping
caused
by
poor
entrance
conditions
and
trash
buildup
at
the
pipe
inlet
­
Deepen
and
widen
the
channel
at
the
pipe
entrance
and
frequently
inspect
and
clear
the
inlet.

°
Erosion
at
outlet
­
The
pipe
should
be
extended
to
a
stable
grade
or
an
outlet
stabilization
structure
is
needed.

°
Displacement
or
separation
of
pipe
­
The
pipe
should
be
tied
down
and
the
joints
secured.

Maintenance
Pipe
slope
drains
must
be
inspected
after
each
significant
runoff
event
for
evidence
of
erosion
and
uncontrolled
runoff.
Any
repairs
to
the
drain
should
be
made
immediately.
Significant
amounts
of
sediment
trapped
at
the
outfall
should
also
be
removed
in
a
timely
manner
and
disposed
of
properly
(NAHB,
n.
d.).

The
following
actions
should
be
taken
to
properly
maintain
a
pipe
slope
drain
(IDNR,
1992):

°
Inspect
slope
drains
and
supporting
diversions
once
a
week
and
after
every
storm
event.

°
Check
the
inlet
for
sediment
or
trash
accumulation;
clear
and
restore
to
proper
entrance
condition.

°
Check
the
fill
over
the
pipe
for
settlement,
cracking,
or
piping
holes;
repair
immediately.

°
Check
for
holes
where
the
pipe
emerges
from
the
dike;
repair
immediately.

°
Check
the
conduit
for
evidence
of
leaks
or
inadequate
anchoring;
repair
immediately.

°
Check
the
outlet
for
erosion
or
sedimentation;
clean
and
repair,
or
extend
if
necessary.

°
Once
slopes
have
been
stabilized,
remove
the
temporary
diversions
and
slope
drains,
and
stabilize
all
disturbed
areas.
Development
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June
2002
5­
57
Cost
The
cost
of
pipe
slope
drains
and
their
installation
varies
with
the
design
and
materials
used.
Site­
specific
cost
estimates
can
be
produced
using
unit
cost
values
with
site­
specific
quantity
estimates.
R.
S.
Means
(2000)
indicates
a
range
of
pipe
costs
for
surface
placement
between
$5.00
per
linear
foot
for
4"
diameter
PVC
piping,
and
$9.20
per
linear
foot
for
10"
diameter
PVC
piping.
On
construction
sites,
temporary
inlets
and
outlets
are
usually
formed
by
small
rock­
lined
depressions.
Assuming
4
cubic
yards
of
crushed
rock
(1.5"
mean
diameter)
per
opening,
an
inlet
and
outlet
combine
to
add
approximately
$200
per
pipe
installation,
based
on
$25
per
cubic
yard
of
stone
(R.
S.
Means,
2000).

5.1.5.2.5
STONE
CHECK
DAM
General
Description
A
check
dam
is
a
small
temporary
barrier
or
dam
constructed
across
a
drainage
channel
or
swale
to
reduce
the
velocity
of
the
flow.
By
reducing
the
flow
velocity,
the
erosion
potential
is
reduced,
detention
times
are
lengthened,
and
more
sediments
are
able
to
drop
out
of
the
water
column.
Check
dams
can
be
constructed
of
stone,
gabions,
treated
lumber,
or
logs
(NAHB,
n.
d.).

Check
dams
are
inexpensive
and
easy
to
install.
They
may
be
used
permanently
if
designed
properly
to
allow
a
high
proportion
of
sediment
in
the
runoff
to
settle
out
and
reduce
velocity
and
may
provide
aeration
of
the
water
(NAHB,
n.
d.).
However,
the
use
of
check
dams
in
a
channel
should
not
be
a
substitute
for
the
use
of
other
sediment­
trapping
and
erosion
control
measures.
As
with
most
other
temporary
structures,
check
dams
are
most
effective
when
used
in
combination
with
other
storm
water
and
erosion
and
sediment
control
measures.

Applicability
Check
dams
are
commonly
used
(1)
in
channels
that
are
degrading
but
where
permanent
stabilization
is
impractical
because
of
their
short
period
of
usefulness
and
(2)
in
eroding
channels
where
construction
delays
or
weather
conditions
prevent
timely
installation
of
erosion­
resistant
linings
(IDNR,
1992).

Check
dams
are
also
useful
in
steeply
sloped
swales,
in
small
channels,
in
swales
where
adequate
vegetative
protection
cannot
be
established,
or
in
swales
or
channels
that
will
be
used
for
a
short
period
of
time
where
it
is
not
practical
to
line
the
channel
or
implement
other
flow
control
practices
(USEPA,
1993).
In
addition,
check
dams
are
appropriate
where
temporary
seeding
has
been
recently
implemented
but
has
not
had
time
to
fully
develop
and
take
root.
The
contributing
drainage
area
should
range
from
2
to
10
acres.
Check
dams
should
be
used
only
in
small
open
channels
that
will
not
be
overtopped
by
flow
once
the
dams
are
built
and
should
not
be
built
in
stream
channels,
either
intermittent
or
perennial
(UNEP,
1994).
Development
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for
Construction
and
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Guidelines
June
2002
5­
58
Design
and
Installation
Criteria
Check
dams
can
be
constructed
from
a
number
of
different
materials.
Most
commonly,
they
are
made
of
rock,
logs,
sandbags,
or
straw
bales.
Rock
or
stone
is
often
preferred
because
of
its
cost­
effectiveness
and
longevity.
Logs
and
straw
bales
will
decay
with
time
and
are
not
recommended
as
they
may
cause
waterway
blockage
if
they
fail.
When
using
rock
or
stone,
the
material
diameter
should
be
2
to
15
inches.
The
stones
should
be
extended
18
inches
beyond
the
banks,
and
the
side
slopes
should
be
2:
1
or
flatter.
Lining
the
upstream
side
of
the
dam
with
a
foot
of
1­
to
2­
inch
gravel
may
improve
the
efficiency
of
the
dam
(NAHB,
n.
d.).
Logs
should
have
a
diameter
of
6
to
8
inches.
Regardless
of
the
material
used,
careful
construction
of
a
check
dam
is
necessary
to
ensure
its
effectiveness.

The
distance
between
rock
check
dams
will
vary
depending
on
the
slope
of
the
ditch,
with
closer
spacing
when
the
slope
is
steeper.
The
size
of
stone
used
in
the
check
dam
should
also
vary
with
the
expected
design
velocity
and
discharge.
As
velocity
and
discharge
increase,
the
rock
size
should
also
increase.
For
most
rock
check
dams,
3
inches
to
12
inches
is
a
suitable
stone
size.
To
improve
the
sediment­
trapping
efficiency
of
check
dams,
a
filter
stone
can
be
applied
to
the
upstream
face.
A
well­
graded
coarse
aggregate
that
is
less
than
1
inch
in
size
can
be
used
as
a
filter
stone.

All
check
dams
should
have
a
maximum
height
of
3
feet.
The
center
of
the
dam
should
be
at
least
6
inches
lower
than
the
edges.
This
design
creates
a
weir
effect
that
helps
to
channel
flows
away
from
the
banks
and
prevent
further
erosion.
Additional
stability
can
be
achieved
by
implanting
the
dam
material
approximately
6
inches
into
the
sides
and
bottom
of
the
channel
(VDCR,
1995).

When
installing
more
than
one
check
dam
in
a
channel,
outlet
stabilization
measures
should
be
installed
below
the
final
dam
in
the
series.
Because
this
area
is
likely
to
be
vulnerable
to
further
erosion,
riprap
or
some
other
stabilization
measure
is
highly
recommended.

Effectiveness
Field
experience
has
shown
that
rock
check
dams
are
more
effective
than
silt
fences
or
straw
bales
to
stabilize
wet­
weather
ditches
(VDCR,
1995).
Straw
bales
have
been
shown
to
have
very
low
trapping
efficiencies
and
should
not
be
used
for
check
dams.
For
long
channels,
check
dams
are
most
effective
when
used
in
a
series,
creating
multiple
barriers
to
sediment­
laden
runoff.
Development
Document
for
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and
Development
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Effluent
Guidelines
June
2002
5­
59
Limitations
Check
dams
should
not
be
used
in
perennial
streams
unless
approved
by
an
appropriate
regulatory
agency
(USEPA,
1992;
VDCR,
1995).
Because
the
primary
function
of
check
dams
is
to
slow
runoff
in
a
channel,
they
should
not
be
used
as
a
stand­
alone
substitute
for
other
sediment­
trapping
devices.
Also,
leaves
have
been
shown
to
be
a
significant
problem
as
they
clog
check
dams;
therefore,
increased
inspection
and
maintenance
might
be
necessary
in
the
fall.

Common
problems
with
check
dams
include
channel
bypass
and
severe
erosion
when
overtopped
and
ineffectiveness
due
to
accumulated
sediment
and
debris.
When
designing
check
dams,
the
fact
that
they
will
reduce
the
capacity
of
a
channel
to
transmit
storm
water
runoff
and
thus
will
need
to
be
sized
appropriately
should
be
taken
into
account
(UNEP,
1994).
The
check
dam
may
also
kill
grass
linings
in
the
channel
if
the
water
level
remains
high
after
it
rains
or
if
there
is
significant
sedimentation.
In
addition,
a
check
dam
may
reduce
the
hydraulic
capacity
of
the
channel
and
create
turbulence,
which
erodes
the
channel
banks
(NAHB,
n.
d.).

Maintenance
Check
dams
should
be
inspected
periodically
to
ensure
that
they
have
not
been
repositioned
as
a
result
of
storm
water
flow.
In
addition,
the
center
of
a
check
dam
should
always
be
lower
than
its
edges.
Additional
stone
may
have
to
be
added
to
maintain
the
correct
height.
Sediment
should
not
be
allowed
to
accumulate
to
more
than
half
the
original
dam
height.
Any
required
maintenance
should
be
performed
immediately.
When
check
dams
are
removed,
care
must
be
taken
to
remove
all
dam
materials
to
ensure
proper
flow
within
the
channel.
The
channel
should
subsequently
be
seeded
for
stabilization
(NAHB,
n.
d.).

Cost
The
cost
of
check
dams
varies
based
on
the
material
used
for
construction
and
the
width
of
the
channel
to
be
dammed.
In
general,
it
is
estimated
that
check
dams
constructed
of
rock
cost
about
$100
per
dam
(USEPA,
1992).
Brown
(1997)
estimated
rock
check
dam
would
cost
approximately
$62
per
installation,
including
the
cost
for
filter
fabric
bedding.
Other
materials,
such
as
logs
and
sandbags,
may
be
a
less
expensive
alternative,
but
they
might
require
higher
maintenance
costs.

5.1.5.2.6
LINED
WATERWAYS
General
Description
Lined
channels
convey
storm
water
runoff
through
a
stable
conduit.
Vegetation
lining
the
channel
reduces
the
flow
velocity
of
concentrated
runoff.
Lined
channels
usually
are
not
designed
to
control
peak
runoff
loads
by
themselves
and
are
often
used
in
combination
with
other
BMPs
such
as
subsurface
drains
and
riprap
stabilization.
Where
moderately
steep
slopes
Development
Document
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Development
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June
2002
5­
60
require
drainage,
lined
channels
can
include
excavated
depressions
or
check
dams
to
enhance
runoff
storage,
decrease
flow
rates,
and
enhance
pollutant
removal.
Peak
discharges
can
be
reduced
through
temporary
detention
in
the
channel.
Pollutants
can
be
removed
from
storm
water
by
filtration
through
vegetation,
by
deposition,
or
in
some
cases
by
infiltration
of
soluble
nutrients
into
the
soil.
The
degree
of
pollutant
removal
in
a
channel
depends
on
the
residence
time
of
the
water
in
the
channel
and
the
amount
of
contact
with
vegetation
and
the
soil
surface,
but
pollutant
removal
is
not
generally
the
major
design
criterion.

Often
construction
increases
the
velocity
and
volume
of
runoff,
which
causes
erosion
in
newly
constructed
or
existing
urban
runoff
conveyance
channels.
If
the
runoff
during
or
after
construction
will
cause
erosion
in
a
channel,
the
channel
should
be
lined
or
flow
control
practices
instituted.
The
first
choice
of
lining
should
be
grass
or
sod
since
this
reduces
runoff
velocities
and
provides
water
quality
benefits
through
filtration
and
infiltration.
If
the
velocity
in
the
channel
would
erode
the
grass
or
sod,
riprap,
concrete,
or
gabions
can
be
used
(USEPA,
2000).
Geotextile
materials
can
be
used
in
conjunction
with
either
grass
or
riprap
linings
to
provide
additional
protection
at
the
soil­
lining
interface.

Applicability
Lined
channels
typically
are
used
in
residential
developments,
along
highway
medians,
or
as
an
alternative
to
curb
and
gutter
systems.
Grass­
lined
channels
should
be
used
to
convey
runoff
only
where
slopes
are
5
percent
or
less.
These
channels
require
periodic
mowing,
occasional
spot­
seeding,
and
weed
control
to
ensure
adequate
grass
cover
(UNEP,
1994).

Lined
channels
should
be
used
in
areas
where
erosion­
resistant
conveyances
are
needed,
such
as
in
areas
with
highly
erodible
soils
and
slopes
of
less
than
5
percent.
They
should
be
installed
only
where
space
is
available
for
a
relatively
large
cross­
section.
Grassed
channels
have
a
limited
ability
to
control
runoff
from
large
storms
and
should
be
used
with
the
recommended
allowable
velocities
for
the
specific
soil
types
and
vegetative
cover.

Design
and
Installation
Criteria
The
design
of
a
lined
waterway
requires
proper
determination
of
the
channel
dimensions.
It
must
ensure
that
(1)
the
velocity
of
the
flowing
water
will
not
wash
out
the
waterway
and
that
(2)
the
capacity
of
the
waterway
is
sufficient
to
carry
the
surface
flow
from
the
watershed
without
overtopping.

Vegetative­
Lined
Channels.
Grass­
lined
channels
have
been
previously
discussed
in
detail
and
are
only
summarized
in
this
section.
The
allowable
velocity
of
water
in
the
waterway
depends
upon
the
type,
condition,
and
density
of
the
vegetation,
as
well
as
the
erosive
characteristics
of
the
soil.
Uniformity
of
vegetative
cover
is
important
because
the
stability
of
the
most
sparsely
covered
area
determines
the
stability
of
the
channel.
Grasses
are
a
better
vegetative
cover
than
legumes
because
grasses
resist
water
velocity
more
effectively.
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2002
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Vegetative­
lined
channels
may
have
triangular,
parabolic,
or
trapezoidal
cross­
sections.
Side
slopes
should
not
exceed
3:
1
to
facilitate
the
establishment,
maintenance,
and
mowing
of
vegetation.
A
dense
cover
of
hardy,
erosion­
resistant
grass
should
be
established
as
soon
as
possible
following
grading.
This
may
necessitate
the
use
of
straw
mulch
and
the
installation
of
protective
netting
until
the
grass
becomes
established.
If
the
intent
is
to
create
opportunities
for
runoff
to
infiltrate
into
the
soil,
the
channel
gradient
should
be
kept
near
zero,
the
channel
bottom
must
be
well
above
the
seasonal
water
table,
and
the
underlying
soils
should
be
relatively
permeable
(generally,
with
an
infiltration
rate
greater
than
2
centimeters
[0.78
inches]
per
hour).

Rock­
Lined
Channels.
Riprap­
lined
channels
may
be
installed
on
somewhat
steeper
slopes
than
grass­
lined
channels.
They
require
a
foundation
of
filter
fabric
or
gravel
under
the
riprap.
Generally,
side
slopes
should
not
exceed
2:
1,
and
riprap
thickness
should
be
1.5
times
the
maximum
stone
diameter.
Riprap
should
form
a
dense,
uniform,
well­
graded
mass
(UNEP,
1994).

Lined
channels
should
be
sited
in
accordance
with
the
natural
drainage
system
and
should
not
cross
ridges.
The
channel
design
should
not
have
sharp
curves
or
significant
changes
in
slope.
Channels
should
not
receive
direct
sedimentation
from
disturbed
areas
and
should
be
established
only
on
the
perimeter
of
a
construction
site
to
convey
relatively
clean
storm
water
runoff
and
separated
from
disturbed
areas
by
a
vegetated
buffer
or
other
BMP
to
reduce
sediment
loads.

Basic
design
recommendations
for
lined
channels
include
the
following:

°
Construction
and
vegetation
of
the
channel
should
occur
before
grading
and
paving
activities
begin.

°
Design
velocities
should
be
below
5
feet
per
second.

°
Geotextiles
can
be
used
to
stabilize
vegetation
until
it
is
fully
established.

°
Covering
the
bare
soil
with
sod
or
geotextiles
can
provide
reinforced
storm
water
conveyance
immediately.

°
Triangular­
shaped
channels
should
be
used
with
low
velocities
and
small
quantities
of
runoff;
parabolic
grass
channels
are
used
for
larger
flows
and
where
space
is
available;
trapezoidal
channels
are
used
with
large
flows
of
low
velocity
(low
slope).

°
Outlet
stabilization
structures
might
be
needed
if
the
runoff
volume
or
velocity
has
the
potential
to
exceed
the
capacity
of
the
receiving
area.

°
Channels
should
be
designed
to
convey
runoff
from
a
10­
year
storm
without
erosion.
Development
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°
The
sides
of
the
channel
should
be
sloped
less
than
3:
1,
with
V­
shaped
channels
along
roads
sloped
6:
1
or
less
for
safety.

°
All
trees,
bushes,
stumps,
and
other
debris
should
be
removed
during
construction.

Effectiveness
Lined
channels
can
effectively
transport
storm
water
from
construction
areas
if
they
are
designed
for
expected
flow
volumes
and
velocities
and
if
they
do
not
receive
sediment
directly
from
disturbed
areas.

Limitations
Lined
channels,
if
improperly
installed,
can
alter
the
natural
flow
of
surface
water
and
have
adverse
impacts
on
downstream
waters.
Additionally,
if
the
design
capacity
is
exceeded
by
a
large
storm
event,
the
vegetation
might
not
be
sufficient
to
prevent
erosion
and
the
channel
might
be
destroyed.
Clogging
with
sediment
and
debris
reduces
the
effectiveness
of
grass­
lined
channels
for
storm
water
conveyance.

Common
problems
in
lined
channels
include
erosion
of
the
channel
before
vegetation
is
fully
established
and
gullying
or
head
cutting
in
the
channel
if
the
grade
is
too
steep.
In
addition,
trees
and
brush
tend
to
invade
lined
channels,
causing
maintenance
problems.

Riprap­
lined
channels
can
be
designed
to
safely
convey
greater
runoff
volumes
on
steeper
slopes.
However,
they
should
generally
be
avoided
on
slopes
exceeding
10
percent
because
stone
displacement,
erosion
of
the
foundation,
or
channel
overflow
and
erosion
resulting
from
a
channel
that
is
too
small
can
occur.
Thus,
channels
established
on
slopes
greater
than
10
percent
will
usually
require
protection
with
rock
gabions,
concrete,
or
other
highly
stable
and
protective
surfaces
(UNEP,
1994).

Maintenance
Maintenance
requirements
for
lined
channels
are
relatively
minimal.
During
the
vegetation
establishment
period,
the
channels
should
be
inspected
after
every
rainfall.
Other
maintenance
activities
that
should
be
carried
out
after
vegetation
is
established
are
mowing,
litter
removal,
and
spot
vegetation
repair.
The
most
important
objective
in
the
maintenance
of
lined
channels
is
maintaining
a
dense
and
vigorous
growth
of
turf.
Periodic
cleaning
of
vegetation
and
soil
buildup
in
curb
cuts
is
required
so
that
water
flow
into
the
channel
is
unobstructed.
During
the
growing
season,
channel
grass
should
be
cut
no
shorter
than
the
level
of
design
flow,
and
the
cuttings
should
be
removed
promptly.
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2002
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Cost
Costs
of
grassed
channels
range
according
to
depth,
with
a
1.5­
foot­
deep,
10­
foot­
wide
grassed
channel
estimated
at
$6,395
to
$17,075
per
trench,
while
a
3.0­
foot­
deep,
21­
foot­
wide
grassed
channel
is
estimated
at
$12,909
to
$33,404
per
trench
(SWRPC,
1991).

Readers
are
also
referred
to
the
discussion
of
costs
for
grass­
lined
channels,
which
contains
many
of
the
design
and
cost
elements
required
for
installing
lined
waterways.
Designers
have
a
range
of
options
for
lining
new
channels.
Geosynthetic
turf
reinforcement
mattings
(TRMs)
can
be
used
for
immediate
erosion
protection
in
channels
exposed
to
runoff
flows.
The
Erosion
Control
Technology
Council
(a
geotextile
industry
support
association)
suggests
TRMs
cost
approximately
$7.00
per
square
yard
(installed)
for
channel
protection
(ECTC,
2002a).
R.
S.
Means
indicates
machine­
placed
riprap
costs
of
approximately
$40
per
cubic
yard.
The
riprap
maximum
size
is
typically
between
6
and
12
inches,
depending
on
the
channel
design
velocity.
A
cubic
yard
of
riprap
will
cover
between
36
and
18
square
feet
of
channel
bed
for
these
riprap
sizes
(assuming
depth
of
riprap
is
1.5
times
the
maximum
size).
These
estimates
suggests
that
riprap
lining
will
be
between
$10
and
$20
per
square
foot
of
channel
(Costs
include
materials,
labor,
and
equipment,
with
overhead
and
profit).

5.1.5.3
SEDIMENT
TRAPPING
DEVICES
The
devices
listed
under
this
group
of
BMPs
trap
sediment
primarily
through
impounding
water
and
allowing
for
settling
to
occur
(Haan
et
al.,
1994).
Silt
fence,
super
silt
fence,
straw
bale
dikes,
sediment
traps,
and
sediment
basins
all
control
flow
through
a
porous
flow
control
system
such
as
filter
fabric
or
straw
bales
or
they
use
a
dam
to
impound
water
with
a
pipe,
open
channel,
or
rock
fill
outlet.
The
filtering
capacity
of
silt
fence
(filter
fabric)
contributes
only
a
small
amount
of
trapping,
but
serves
to
make
the
fence
less
porous
and
hence
increases
ponding
.
For
steady­
state
flows,
the
trapping
that
occurs
behind
the
flow
control
device
can
be
shown
to
be
directly
proportional
to
the
surface
area
and
indirectly
proportional
to
flow
through
the
system
(Haan
et
al.,
1994).
The
ratio
of
the
surface
area
to
flow
is
known
as
the
overflow
rate,
and
trapping
in
such
systems
is
predicted
by
the
ratio
of
overflow
rate
to
particle
settling
velocity.
Although
flows
in
nature
are
inherently
non­
steady
state
and
more
complex
than
steady­
state
systems,
studies
have
shown
that
the
best
predictor
of
trapping
in
such
systems
is
still
the
ratio
of
settling
velocity
to
overflow
rate
(Hayes
et
al.,
1984).
In
the
case
of
non­
steady
state,
the
overflow
rate
is
best
defined
by
the
ratio
of
peak
discharge
from
the
system
to
a
surface
area
(Hayes
et
al.,
1984;
McBurnie
et
al.,
1990).

The
amount
of
trapping
in
these
structures
depends
on
the
size
of
the
structure,
flow
rates
into
the
system,
hydraulics
of
the
flow
control
system,
the
size
distribution
of
the
sediment
flowing
into
the
structure,
and
the
chemistry
of
the
sediment­
water
system
(Haan
et
al.,
1994).
Trapping
can
be
enhanced
by
chemical
treatment
of
flows
into
the
structure,
but
the
impacts
have
not
been
widely
defined
for
varying
mineralogy
and
chemistry
of
the
sediment­
water
system
(Haan
et
al.,
1994;
Tapp
and
Barfield,
1986).
Recent
studies
have
been
conducted
on
the
application
of
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June
2002
5­
64
polyacrilamides
(PACs)
to
disturbed
areas
for
enhancing
settling
(Benik
et
al.,
1998;
Masters
et
al.,
2000;
Roa­
Espinosa
et
al.,
2000),
but
results
have
not
been
definitive.
No
known
studies
have
evaluated
the
impacts
of
PAC
application
to
disturbed
areas
on
settling
in
sediment
trapping
devices.

Sediment
flowing
into
sediment
trapping
devices
is
composed
of
primary
particles
and
aggregated
particles.
Aggregates
are
formed
when
clays,
silts,
and
sands
are
cemented
together
to
form
larger
particles
that
have
settling
velocities
far
greater
than
those
of
any
individual
particles
alone
although
the
degree
of
aggregation
depends
on
the
amount
of
cementing
material
present
(typically
clays
and
organic
matter).
Since
the
aggregates
have
higher
settling
velocities
than
primary
particles,
the
degree
of
aggregation
that
is
present
has
a
large
impact
on
the
trapping
that
occurs.
Procedures
are
available
to
measure
the
combined
size
distribution
of
aggregate
and
primary
particle
size
distribution
(Barfield
et
al.,
1979;
Haan
et
al.,
1994).
Procedures
are
also
available
to
predict
particle
size
distributions
of
aggregates
and
primary
particles
(Foster
et
al.,
1985)
but
have
not
been
found
to
be
very
accurate
for
subsoils
exposed
during
construction
in
at
least
one
study
(Barfield
et
al.,
1983).

In
the
absence
of
chemical
treatment,
the
sediment
that
can
be
captured
in
sediment
trapping
devices
is
typically
the
settleable
solids.
To
trap
the
smaller
size
clay
particles,
structures
with
surface
areas
larger
than
the
construction
site
itself
would
have
to
built
in
many
cases
(Barfield,
2000).
Chemical
treatment
can
be
used
to
reduce
the
size,
but
it
has
not
been
adopted
on
a
wide
scale
because
of
the
cost
and
complexity
of
the
operation
(Tapp
et
al.,
1981).

Sediment
trapping
devices
also
provide
some
storm
water
detention
by
virtue
of
detaining
flows
long
enough
to
allow
sediment
to
settle
out
and
be
deposited.
However,
to
operate
as
a
storm
water
detention
structure,
the
design
should
include
storm
water
detention
as
well.

Virtually
all
of
the
available
information
on
sediment
trapping
structures,
both
theoretical
and
experimental,
is
on
impacts
to
receiving
waters
and
not
downstream
effects.
In
a
very
limited
analysis,
Barfield
(2000)
combined
the
SEDIMOT
II
computer
model
together
with
the
FLUVIAL
model
to
theoretically
evaluate
the
impact
of
sediment
trapping
structures
on
downstream
geomorphology
in
a
Puerto
Rican
watershed.

5.1.5.3.1
SILT
FENCE
General
Description
Silt
fences
are
used
as
temporary
sediment
barriers
consisting
of
filter
fabric
anchored
across
and
supported
by
posts.
Their
purpose
is
to
retain
sediment
from
small
disturbed
areas
by
reducing
the
velocity
of
sediment­
laden
runoff
and
promoting
sediment
deposition
(Smolen
et
al.,
1998).
Silt
fences
capture
sediment
by
ponding
water
and
allowing
for
deposition,
not
by
filtration.
Silt
fence
fabric
first
screens
silt
and
sand
from
runoff,
resulting
in
clogging
of
the
lower
part
of
the
Development
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2002
5­
65
fence.
The
pooling
water
allows
sediments
to
settle
out
of
the
runoff.
Silt
fences
work
best
in
conjunction
with
temporary
basins,
traps,
or
diversions.

Applicability
Silt
fences
are
generally
placed
at
the
toe
of
fills,
along
the
edge
of
waterways,
and
along
the
site
perimeter.
The
fences
should
not
be
used
in
drainage
areas
with
concentrated
and
high
flows,
in
large
areas,
or
in
ditches
and
swales
where
concentrated
flow
is
present.

The
drainage
area
for
the
fence
should
be
selected
based
on
design
storms
and
local
hydrologic
conditions
so
that
the
silt
fence
is
not
expected
to
overtop.
A
typical
design
calls
for
no
greater
than
¼
acre
per
100
feet
of
fence,
but
this
is
highly
variable
depending
on
climate.
The
fence
should
be
stable
enough
to
withstand
runoff
from
a
10­
year
peak
storm.
Table
5­
13
lists
the
maximum
slope
length
specified
by
the
USDOT.
These
slope
lengths
should
be
based
on
sediment
load
and
flow
rates.
This
would
mean
that
the
values
given
below
should
be
adjusted
for
climatic
conditions
instead
of
"one
size
fits
all"
for
a
silt
fence
to
ensure
maximum
effectiveness.

Table
5­
13.
Maximum
Slope
Lengths
for
Silt
Fences
Slope
(%)
18­
inch
(460
mm)
Fence
30­
inch
(760
mm)
Fence

2
250
ft
(75
m)
500
ft
(150
m)
5
100
ft
(30m)
250
ft
(75
m)
10
50
ft
(15
m)
150
ft
(45
m)
20
25
ft
(8
m)
70
ft
(21
m)
25
6
m
(20
ft)
55
ft
(17
m)
30
15
ft
(5
m)
45
ft
(14
m)
35
15
ft
(5
m)
40
ft
(12
m)
40
15
ft
(5
m)
35
ft
(10
m)
45
10
ft
(3
m)
30
ft
(9
m)
50
10
ft
(3m)
25
ft
(8m)
Source:
USDOT,
1995.

Typical
standards
and
specifications
call
for
the
silt
fence
to
be
located
on
fairly
level
ground
and
follow
the
land
contour.
However,
field
evaluations
by
Barfield
and
Hayes
(1992,
1999)
in
South
Carolina
and
Kentucky
indicate
that
installations
on
the
contour
as
well
as
along
a
slope
have
problems
with
undercutting.
In
either
case,
the
installations
are
such
that
a
slight
slope
may
occur
along
the
fence
in
spite
of
the
best
installation
practices.
Runoff
can
move
down
the
contour
until
a
weak
spot
occurs
in
the
buried
toe
and
undercuts
the
fence.
Alternatively,
flow
may
move
to
a
low
spot
where
it
accumulates
and
causes
an
overtopping.
In
either
case,
trapping
by
the
silt
fence
is
essentially
zero,
and
flows
have
then
been
concentrated
at
a
point
causing
downslope
channel
erosion.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
1
d15
:15
percent
by
weight
of
suspended
solids
are
smaller
than
those
that
are
trapped
by
this
device;
Similarly
d50
indicates
that
50
percent
by
weight
of
suspended
solids
are
smaller
than
those
trapped.

June
2002
5­
66
Design
and
Installation
Criteria
Design
criteria
are
of
two
types:

Hydrologic
design
for
a
required
trapping
of
sediment
and
flow
rate
to
pass
the
design
storm.
Selection
of
appropriate
installation
criteria
such
that
the
silt
fence
will
perform
as
designed.

Hydrologic
Design
Hydrologic
design
should
result
in
a
design
that
passes
the
design
storm
without
causing
damage
while
trapping
the
required
amount
of
sediment.
It
is
necessary
to
use
either
a
database
or
some
type
of
model
to
develop
the
appropriate
hydrologic
design.
Efforts
to
model
the
sediment
trapping
that
occurs
through
the
use
of
a
silt
fence
have
resulted
in
models
that
predict
the
settling
in
the
ponded
area
upstream
from
the
fence
(Barfield
et
al.,
1996;
Lindley
et
al.,
1998).
The
results
from
model
simulations
show
that
trapping
depends
primarily
on
the
surface
area
of
the
impounded
water
and
the
flow
rate
through
the
filter.
The
models
utilize
a
clear
water
slurry
flow
rate,
typically
specified
by
the
manufacturer,
to
predict
discharge.
However,
numerous
studies
have
shown
that
sediment
laden
flows
cause
clogging
of
the
geotextiles
used
to
construct
the
fence,
dependent
on
the
opening
size
and
size
of
the
sediment
(Britton
et
al.,
2001;
Wyant,
1980;
Barrett
et
al.,
1995;
Fisher
and
Jarret,
1984).
Thus,
results
from
model
studies
to
date
are
suspect
and
need
to
be
modified
to
account
for
the
impacts
of
clogging
on
flow
rate.
Barfield
et
al.,
(2000)
developed
a
model
of
flow
rate
using
conditional
probability
concepts,
but
the
results
have
not
been
experimentally
verified.

Design
aids
have
been
developed
for
silt
fence,
using
simulations
from
the
SEDIMOT
III
model
(Hayes
and
Barfield,
1995).
In
the
model,
predictions
are
made
about
trapping
efficiency
using
the
ratio
of
settling
velocity
for
the
d151
of
the
eroded
sediment,
divided
by
the
ratio
of
discharge
to
ponded
surface
area.
The
design
aids
yield
conservative
estimates
as
compared
to
the
SEDIMOT
III
model,
but
the
database
used
for
generating
the
design
aid
is
based
on
the
assumption
that
clogging
does
not
impact
flow
rates.
The
discussion
above
shows
that
assumption
to
be
erroneous.

The
bottom
line
on
the
discussion
above
is
that
it
is
not
possible
to
predict
with
any
expected
accuracy
the
trapping
efficiency
of
silt
fence
under
a
given
set
of
conditions.

Installation
Criteria
General
installation
criteria
for
the
silt
fence
should
incorporate
the
following
factors:
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
67
°
The
fabric
must
have
sufficient
strength
to
counter
forces
created
by
contained
water
and
sediment
(Sprague,
1999).

°
The
posts
must
have
sufficient
strength
to
counter
the
forces
transferred
to
them
by
the
fabric
(Sprague,
1999).

°
The
fabric
must
be
installed
to
ensure
that
the
loads
are
all
adequately
transferred
through
the
fabric
to
the
posts
or
the
ground
without
overstressing
(Sprague,
1999).

°
The
fence
must
be
designed
based
on
site­
specific
hydrologic
and
soil
conditions
such
that
it
will
not
overtop
during
design
events.

°
The
fence
must
be
installed
(anchored)
with
a
buried
toe
of
sufficient
depth
so
that
it
does
not
become
detached
from
the
soil
surface.

°
In
general,
the
fence
requires
a
metal
wire
backing
to
provide
sufficient
strength
to
prevent
failure
from
the
weight
of
trapped
sediment
and
to
prevent
the
toe
of
the
fabric
from
being
removed
from
the
ground.

°
Maximum
drainage
area
behind
the
fence
should
be
determined
based
on
the
local
rainfall
and
the
infiltration
characteristics
of
the
soil
and
cover.

Silt
fence
material
is
typically
synthetic
filter
fabric
or
a
pervious
sheet
of
polypropylene,
nylon,
polyester,
or
polyethylene
yarn.
The
fabric
should
have
ultraviolet
ray
inhibitors
and
stabilizers
to
provide
for
a
minimum
useful
construction
life
of
6
months
or
the
duration
of
construction,
whichever
is
greater.
The
height
of
the
fence
fabric
should
not
exceed
3
feet.
If
standard
strength
filter
fabric
is
used,
it
should
be
reinforced
with
a
wire
fence,
extending
down
into
the
trench
that
buries
the
toe.
The
wire
should
be
of
sufficient
strength
to
support
the
weight
of
the
deposited
sediment
and
water.
In
general,
a
minimum
14
gauge
and
a
maximum
mesh
spacing
of
6
inches
is
called
for
(Smolen
et
al.,
1988).
Typical
requirements
for
the
silt
fence
physical
properties,
as
specified
in
selected
local
BMP
standards
and
specifications,
are
included
in
Table
5­
14.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
68
Table
5­
14.
Typical
Requirements
for
Silt
Fence
Fabric
Physical
Property
Requirements
Woven
Fabric
Non­
Woven
Fabric
Filtering
Efficiency
85%
85%

Tensile
Strength
at
20%
(maximum)
Elongation
Standard
Strength
—30
pound/
linear
inch
Extra
Strength
—50
pound/
linear
inch
Standard
Strength
—50
pound/
linear
inch
Extra
Strength
—70
pound/
linear
inch
Slurry
Flow
Rate
0.
3
gallon/
square
feet/
minute
4.
5
gallon/
square
feet/
minute
Water
Flow
Rate
15
gallon/
square
feet/
minute
220
gallon/
square
feet/
minute
UV
Resistance
70%
85%

Source:
NCDNR,
1988;
IDNR
1992.

It
should
be
pointed
out
that
these
numbers,
particularly
the
flow
rates,
could
vary
widely
depending
on
the
local
soil
condition
due
to
possible
clogging
of
the
filter
material.

Material
for
the
posts
used
to
anchor
the
filter
fabric
can
be
constructed
of
either
wood
or
steel.
Wooden
stakes
should
be
buried
at
a
depth
sufficient
to
keep
the
fence,
when
loaded
with
sediment
and
water,
from
falling
over.
The
depth
of
burial
should
depend
on
soil
strength
characteristics
when
saturated
and
post
diameter.
Many
standards
and
specifications
set
a
minimum
length
of
the
post
of
5
feet
long,
and
a
diameter
of
4
inches
for
posts
composed
of
softwood
(e.
g,
pine),
and
2
inches
for
posts
composed
of
hardwood
(e.
g.,
oak)(
Smolen
et
al.,
1988).
Steel
posts
should
also
be
designed
based
on
local
soil
strength
characteristics
when
wet.
Some
standards
and
specifications
for
these
posts
set
a
minimum
weight
of
1.33
pound/
linear
feet
with
a
minimum
length
of
4
feet.
Steel
posts
should
also
have
projections
to
adhere
filter
fabric
to
the
post
(Smolen
et
al.,
1988).

A
silt
fence
should
be
erected
in
a
continuous
fashion
from
a
single
roll
of
fabric
so
as
to
eliminate
unwanted
gaps
in
the
fence.
If
a
continuous
roll
of
fabric
is
not
available,
the
fabric
should
overlap
from
both
directions
only
at
posts
with
a
minimum
overlap
of
6
inches
and
be
rolled
together
with
a
special
flexible
rod
to
keep
the
ends
from
separating.
Fence
posts
should
be
spaced
at
a
distance
based
on
wet
soil
strength
characteristics
and
post
size
and
strength;
generally,
the
posts
are
spaced
approximately
4
to
6
feet
apart.
If
standard
strength
fabric
is
used
in
combination
with
wire
mesh,
the
spacing
can
be
larger.
Typically,
the
standards
and
specifications
call
for
the
posts
to
be
no
more
than
10
feet
apart.
If
extra­
strength
fabric
is
used
without
wire
mesh
reinforcement,
some
standards
call
for
the
support
posts
to
be
spaced
no
more
than
6
feet
apart
(VDCR,
1995).
Again,
this
spacing
should
depend
on
wet
soil
strength
characteristics
and
post
size.

A
silt
fence
must
provide
sufficient
storage
capacity
or
be
stabilized
over
flow
outlets
such
that
the
storage
volume
of
water
will
not
overtop
the
fence.
The
return
period
event
(size
of
the
rainfall
event
managed)
used
for
design
is
typically
a
prerogative
of
the
regulatory
agency.
For
temporary
fences,
a
2­
year
storm
event
is
typically
used
as
a
design
standard.
Fences
that
will
be
in
place
for
6
months
or
longer
are
commonly
designed
based
on
a
10­
year
storm
event
Development
Document
for
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and
Development
Proposed
Effluent
Guidelines
June
2002
5­
69
(Sprague,
1999).
The
space
behind
the
fence
used
for
impoundment
volume
must
be
sufficient
to
adequately
contain
the
sediment
that
will
be
deposited.
Each
storm
will
deposit
sediment
behind
the
fence,
and
after
a
period
of
time
the
amount
of
sediment
accumulated
will
render
the
fence
useless.
Frequency
of
fence
management
is
a
function
of
its
sizing
(i.
e.
whether
the
fence
was
installed
for
a
2­
year
or
a
10­
year
storm
event)
(Sprague,
1999)
and
the
amount
of
erosion
that
occurs
in
the
area
draining
to
the
fence.

Effectiveness
The
performance
of
silt
fences
has
not
been
well
defined.
Laboratory
studies
using
carefully
controlled
conditions
have
shown
trapping
efficiencies
in
the
range
of
40
to
100
percent,
depending
on
the
type
of
fabric,
overflow
rate,
and
detention
time
(Barrett
et
al.,
1995;
Wyant,
1980;
Wishowski
et
al.,
1998).
Field
studies
have
been
limited
and
quite
inadequate;
however,
the
results
show
that
field­
trapping
efficiencies
are
very
low.
In
fact,
Barrett
et
al.
(1995)
obtained
a
value
of
zero
percent
trapping
averaged
over
several
samples
with
a
standard
error
of
26
percent.
Barrett
et
al.
(1995)
cite
the
following
reasons
for
the
field
tests
not
showing
the
expected
results:

°
Inadequate
fabric
splices
°
Sustained
failure
to
correct
fence
damage
resulting
from
overtopping
°
Large
holes
in
the
fabric
°
Under­
runs
due
to
inadequate
"toe­
ins"

°
Silt
fence
damaged
and
partially
covered
by
the
temporary
placement
of
stockpiles
of
materials
Field
inspections
conducted
by
Barfield
and
Hayes
(1992)
were
made
in
which
more
than
50
construction
sites
in
South
Carolina
and
Kentucky
were
visited.
Inspections
found
that
silt
fence
was
seldom
installed
and,
when
installed,
was
rarely
set
up
according
to
specifications.
In
areas
where
installations
did
meet
standards,
it
was
obvious
that
flows
sought
the
weakest
spot
on
the
fence
and
either
flowed
through
cuts
in
the
fabric,
or
undercut
or
overtopped
the
fence.
This
flow
was
thus
changed
from
the
overland
flow
coming
into
the
site
to
concentrated
flow,
causing
significant
erosion.

Silt
fences
are
effective
at
removing
large
particle
sediment,
primarily
aggregates,
sands,
and
larger
silts.
Sediment
is
removed
through
impounding
of
water
to
slow
velocity.
It
is
argued
that
the
silt
fence
will
not
contribute
to
a
reduction
in
small
particle
sediment
and
is
not
effective
against
other
pollutants
(WYDEQ,
1999).
EPA
(1993)
reports
the
following
effectiveness
ranges
for
silt
fences
constructed
of
filter
fabric:
average
total
suspended
solids
removal
of
70
percent,
sand
removal
of
80
to
90
percent,
silt­
loam
removal
of
50
to
80
percent,
and
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
70
silt­
clay­
loam
removal
of
0
to
20
percent.
However,
the
EPA
numbers
from
the
Nationwide
Urban
Runoff
Program
should
not
be
considered
to
apply
to
every
location.
The
actual
trapping
will
vary
widely
for
a
given
design
because
of
differences
in
hydrologic
regimes
and
soil
types.

The
advantages
of
using
silt
fences
include:
minimal
labor
requirement
for
installation,
low
cost,
high
efficiency
in
removing
sediment,
durability,
and
sometimes
reuse
(Sprague,
1999).
Silt
fences
are
the
most
readily
available
and
cost­
effective
control
options
where
options
like
diversion
are
not
possible.
Silt
fences
are
also
a
popular
choice;
because
contractors
have
used
them
extensively,
the
familiarity
makes
silt
fence
use
more
likely
for
future
construction
activities.
The
visibility
of
a
silt
fence
is
also
an
advantage,
for
the
fence
is
"advertising"
the
use
of
erosion
and
sediment
control
structures.
In
addition,
the
silt
fence
visibility
makes
site
inspection
easier
for
contractors
and
government
inspectors
(CWP,
1996).

Limitations
Silt
fences
should
not
be
installed
along
areas
where
rocks
or
other
hard
surfaces
will
prevent
uniform
anchoring
of
fence
posts
and
entrenching
of
the
filter
fabric
because
an
insufficient
anchor
will
greatly
reduce
the
effectiveness
of
silt
fencing
and
may
create
runoff
channels
leading
off­
site.
In
addition,
open
areas
where
wind
velocity
is
high
may
present
a
maintenance
challenge,
as
high
winds
may
accelerate
deterioration
of
the
filter
fabric
(Smolen
et
al.,
1988).
When
the
pores
of
the
silt
fence
fabric
become
clogged
with
sediment,
pools
of
water
are
likely
to
form
on
the
uphill
side
of
fence.
Siting
and
design
of
the
silt
fence
should
account
for
this
problem
and
care
should
be
taken
to
avoid
unnecessary
diversion
of
storm
water
from
these
pools
which
might
cause
further
erosion
damage.
Silt
fences
can
act
as
a
diversion
if
placed
slightly
off­
contour
and
can
control
shallow,
uniform
flows
from
small,
disturbed
areas
and
deliver
sediment­
laden
water
to
deposition
areas.

Silt
fences
will
sag
or
collapse
if
a
site
is
too
large,
if
too
much
sediment
accumulates,
if
the
approach
slope
is
too
steep,
or
if
the
fence
was
not
adequately
supported.
If
the
fence
bottom
is
not
properly
installed
or
the
flow
velocity
is
too
fast,
fence
undercuts
or
blowouts
can
occur
because
of
excess
runoff.
Erosion
around
the
end
of
the
fence
can
occur
if
the
fence
ends
do
not
extend
upslope
to
prevent
flow
around
the
fence
(IDNR,
1992).

Maintenance
Site
operators
should
inspect
silt
fences
after
each
rainfall
event
to
ensure
they
are
intact
and
that
there
are
no
gaps
at
the
fence­
ground
interface
or
tears
along
the
length
of
the
fence.
If
gaps
or
tears
are
found,
they
should
be
repaired
or
the
fabric
should
be
replaced
immediately.
Accumulated
sediments
should
be
removed
from
the
fence
base
when
the
sediment
reaches
one­
third
to
halfway
up
the
height
of
the
fence.
Sediment
removal
should
occur
more
frequently
if
accumulated
sediment
is
creating
a
noticeable
strain
on
the
fabric
and
there
is
the
possibility
that
the
fence
might
fail
from
a
sudden
storm
event.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
71
Cost
There
is
a
wide
range
of
data
on
installation
costs
for
silt
fences.
EPA
estimates
these
costs
at
approximately
$6.00
per
linear
foot
(USEPA,
1992)
while
SWRPC
estimates
unit
costs
between
$2.30
and
$4.50
per
linear
foot
(SWRPC,
1991).
Silt
fences
have
an
annual
maintenance
cost
that
is
100
percent
of
installation
cost
(Brown
et
al.,
1997).
These
values
are
significantly
greater
than
that
reported
by
R.
S.
Means
(2000),
which
indicates
a
3
foot
tall
silt
fence
installation
cost
between
$0.68
and
$0.92
per
linear
foot
(for
favorable
and
challenging
installations).
It
should
be
noted
that
the
R.
S.
Means
value
covers
just
a
single
installation,
without
the
expected
costs
of
maintenance
(e.
g.,
removal
of
collected
sediment).
In
addition,
the
type
of
silt
fence
fabric
employed
will
also
affect
the
total
installation
costs.

5.1.5.3.2
SUPER
SILT
FENCE
General
Description
Super
silt
fence
is
a
modification
of
a
standard
silt
fence.
The
two
central
differences
between
the
standard
silt
fence
and
the
super
silt
fence
is
that
the
super
silt
fence
has
toe
that
is
buried
more
deeply
and
the
backing
material
is
chain
link
fence
held
in
place
by
steel
posts–
a
concept
that
originated
in
Maryland.
The
Maryland
super
silt
fence
requires
a
Geotextile
Class
F
fabric
over
a
chain
link
fence
to
intercept
sediment­
laden
runoff
from
small
drainage
areas.
The
super
silt
fence
provides
a
barrier
that
can
collect
and
hold
debris
and
soil
more
effectively
than
a
standard
silt
fence,
preventing
material
from
entering
critical
areas.
It
is
best
used
where
the
installation
of
a
dike
would
destroy
sensitive
areas,
woods,
and
wetlands.

Applicability
Super
silt
fences
can
be
used
in
the
same
conditions
as
a
silt
fence.
Fences
should
follow
the
contour
of
the
land.
Table
5­
15
lists
the
distance
a
super
silt
fence
should
be
from
a
slope
to
ensure
maximum
effectiveness
(MDE,
1994).

Table
5­
15.
Slope
Lengths
for
Super
Silt
Fences
Slope
(%)
Slope
Length
Minimum
Maximum
0­
10
Unlimited
Unlimited
10­
20
200
feet
1,500
feet
20­
33
100
feet
1,000
feet
33­
50
100
feet
500
feet
50+
50
feet
250
feet
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Design
and
Installation
Criteria
As
with
the
standard
silt
fence,
design
criteria
are
of
two
types,
hydrologic
design
for
a
required
trapping
of
sediment
and
flow
rate
to
pass
the
design
storm
and
selection
of
appropriate
installation
criteria
such
that
the
silt
fence
will
perform
as
designed.

Hydrologic
Design
Hydrologic
design
criteria
are
the
same
as
the
criteria
for
the
standard
silt
fence.

Installation
Criteria
The
criteria
used
for
the
Maryland
super
silt
fence
indicate
the
following,
although
they
have
not
been
tested
with
field
data:

°
The
fence
should
be
placed
as
close
to
the
contour
as
possible,
with
no
section
of
the
silt
fence
exceeding
a
grade
of
5
percent
for
a
distance
of
more
than
50
feet.

°
Fabric
should
be
no
more
than
42
inches
in
height
and
should
be
held
in
place
with
a
6­
foot
chain
link
fence.

°
Fabric
should
be
attached
to
the
steel
pole
using
wire
ties
or
staples.
Fabric
should
be
securely
fastened
to
the
chain
link
fence
with
ties
spaced
every
24
inches
at
the
top
and
midsection.

°
Fabric
should
be
embedded
into
the
ground
at
a
minimum
of
8
inches.

°
Edges
of
fabric
should
overlap
by
6
inches.

Table
5­
16
describes
the
physical
properties
of
Geotextile
class
F
fabric
(MDE,
1994).

Table
5­
16.
Minimum
Requirements
for
Super
Silt
Fence
Geotextile
Class
F
Fabric
Physical
Properties
Requirements
Tension
Strength
50
pound/
inch
Tensile
Modulus
20
pound/
inch
Flow
Rate
0.3
gallon/
ft
2
/minute
Filtering
Efficiency
75%
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Effectiveness
Performance
data
have
not
been
collected
for
super
silt
fences.
The
fences
have
been
proposed
for
locations
within
a
sensitive
watershed,
or
where
site
conditions
prohibit
the
use
of
a
standard
silt
fence.
However,
until
performance
data
are
collected
under
field
conditions,
effectiveness
is
speculative.

Limitations
Super
silt
fences
are
not
as
likely
to
fail
structurally
as
are
standard
silt
fences,
but
they
are
more
expensive
than
standard
silt
fences.

Maintenance
Maintenance
requirements
for
super
silt
fences
are
generally
the
same
as
for
standard
silt
fences.

Cost
The
cost
of
the
super
silt
fence
is
more
than
the
standard
silt
fence
because
of
deeper
burial
at
the
toe
and
the
cost
of
chain
linked
fencing.
R.
S.
Means
(2000)
indicates
a
rental
price
of
$10
to
$11
per
linear
foot
of
chain
linked
fence
for
periods
up
to
1
year.
Overall,
rental
is
expected
for
most
construction
site
installation
because
rental
rates
are
approximately
half
the
price
of
permanent
chain
link
fencing.

5.1.5.3.3
STRAW
BALE
DIKE
General
Description
The
straw
bale
dike
is
a
temporary
measure
used
to
trap
sediment
from
small,
sloping
disturbed
areas.
It
is
constructed
of
straw
bales
(not
hay
bales)
wedged
tightly
together
and
placed
along
the
contour
downslope
of
disturbed
areas.
The
bales
are
placed
in
a
shallow
excavation,
and
the
upslope
side
is
sealed
with
soil.
Stakes
are
driven
through
the
bales
into
the
soil
to
help
hold
the
bales
in
place.
The
dike
works
by
impounding
water,
which
allows
sediment
to
settle
out
in
the
upslope
area
(Haan
et
al.,
1994).
Straw
bale
dikes
are
recommended
for
short
duration
application
and
are
usually
effective
for
less
than
3
months
because
of
rapid
decomposition
(USDOT,
1995).

Applicability
Straw
bale
dikes
are
generally
placed
at
the
toe
of
fills
to
provide
for
a
broad
shallow
sediment
pool.
The
dikes
should
not
be
used
in
drainage
areas
with
concentrated
and
high
flows,
in
large
areas,
or
in
ditches
and
swales.
The
location
of
the
straw
bale
dike
should
be
fairly
level,
at
least
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10
feet
from
the
toe,
and
should
follow
the
land
contour.
Table
5­
17
lists
the
distance
a
straw
bale
dike
should
be
placed
from
a
slope
to
ensure
maximum
effectiveness.

Table
5­
17.
Maximum
Land
Slope
and
Distances
Above
a
Straw
Bale
Dike
Land
Slope
(%)
Maximum
Distance
Above
Dam
(ft)
Less
than
2
100
2­
5
75
5­
10
50
10­
20
25
More
than
20
15
Source:
USDOT,
1995.

Design
and
Implementation
Criteria
Hydrologic
Design
Hydrologic
design
dictates
the
structure
necessary
to
withstand
a
storm
without
causing
damage
while
trapping
the
required
amount
of
sediment.
Either
a
database
or
some
type
of
model
are
needed
to
find
the
appropriate
design.
Efforts
to
model
the
sediment
trapping
that
occurs
in
straw
bale
dikes
have
resulted
in
models
that
predict
the
settling
in
the
ponded
area
upstream
from
the
fence
(Barfield
et
al.,
1996;
Lindley
et
al.,
1998).
The
results
from
model
simulations
show
that
trapping
depends
primarily
on
the
surface
area
of
the
impounded
water
and
flow
rate
through
the
filter.
The
models
utilize
a
clear
water
slurry
flow
rate
to
predict
discharge.
It
is
anticipated,
based
on
visual
observations,
that
sediment
will
clog
the
straw
bale
barrier,
reducing
the
slurry
flow
rate.
Thus,
results
from
model
studies
to
date
are
suspect
and
need
to
be
modified
to
account
for
the
impact
of
clogging
on
flow
rate.

Installation
Criteria
The
USDOT's
BMP
Manual
and
the
Indiana
BMP
Manual
(IN
Manual)
calls
for
bales
to
be:

°
Anchored
by
driving
two
36­
inch
long
(minimum)
steel
rebars
or
2
x
2­
inch
hardwood
stakes
through
each
bale;

°
Sized
according
to
the
standard
bale
size
of
14
inches
x
18
inches
x
35
inches;

°
Placed
in
an
excavated
trench
at
least
4
inches
deep,
a
bale's
width,
and
long
enough
that
the
end
bales
are
somewhat
upslope
of
the
sediment
pool;

°
Abutted
tightly
against
each
other;
and,

°
Sized
such
that
impounded
water
depth
should
not
exceed
1.5
feet.
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The
USDOT
BMP
Manual
does
not
require
that
straw
bale
dikes
be
designed;
however,
the
Indiana
Manual
limits
the
drainage
area
to
¼
acre
per
100
feet
of
dam
and
the
total
drainage
area
draining
to
a
straw
bale
dike
to
2
acres.

Effectiveness
The
information
on
performance
of
straw
bale
dikes
is
very
limited.
In
laboratory
studies
of
bales
at
varying
orientations,
Kouwen
(1990)
found
that
trapping
efficiencies
ranged
from
60
to
100
percent.
Field
data
on
trapping
have
not
been
collected;
however,
visual
inspection
of
sites
indicate
that
straw
bales
are
not
properly
installed
to
prevent
flows
from
undercutting
or
flowing
between
bales
(Barfield
and
Hayes,
1992,
1999).
In
addition,
bales
deteriorate
rapidly
and
need
to
be
replaced
frequently.
Because
of
these
problems,
the
use
of
straw
bale
dikes
as
a
perimeter
control
is
not
recommended,
except
in
special
circumstances.
Only
27
percent
of
Erosion
and
Sediment
Control
(ESC)
experts
rated
the
straw
bale
dike
as
an
effective
ESC
practice,
although
its
use
was
still
allowed
in
half
of
the
communities
surveyed
(Brown
and
Caraco,
1997).

Limitations
Straw
bale
dikes
should
not
be
used
as
a
diversion,
in
streams,
in
channels,
or
in
areas
with
concentrated
flow.
The
bales
are
not
recommended
for
paved
areas
because
of
the
inability
to
anchor
the
bales
(IDNR,
1992).

Care
must
be
taken
to
ensure
that
the
bales
are
not
installed
in
an
area
where
there
is
a
concentrated
flow
of
runoff,
in
a
drainage
area
that
is
too
large,
or
on
an
excessive
slope
(IDNR,
1992).
Under
these
conditions,
erosion
around
the
end
of
the
bales,
overtopping
and
undercutting
of
the
bales,
and
bale
collapsing
and
dislodging
are
likely
to
occur.
Overtopping
will
also
occur
if
the
storage
capacity
is
underestimated
and
where
provisions
are
not
made
for
safe
bypass
of
storm
flow
(IDNR,
1992).
Undercutting
will
occur
if
the
bales
are
not
entrenched
at
least
4
inches
and
backfilled
with
compacted
soil
or
were
not
abutted
or
chinked
properly.
Straw
bale
dikes
are
likely
to
collapse
or
dislodge
if
the
bales
are
not
adequately
staked,
or
if
too
much
sediment
is
allowed
to
accumulate
before
cleanout
(IDNR,
1992).

Maintenance
For
the
straw
bale
dike
to
be
most
effective,
it
is
important
to
replace
deteriorated
bales
when
appropriate.

Cost
The
cost
of
straw
bale
dikes
are
relatively
low,
making
their
use
relatively
attractive.
R.
S.
Means
(2000)
indicates
a
staked
straw
bale
unit
cost
of
$2.61
per
linear
foot
(Costs
include
materials,
labor,
and
equipment,
with
profit
and
overhead).
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5.1.5.3.4
SEDIMENT
TRAP
General
Description
A
sediment
trap
is
a
temporary
control
device
used
to
intercept
sediment­
laden
runoff
and
to
trap
sediment
to
prevent
or
reduce
off­
site
sedimentation.
It
is
normally
a
more
temporary
type
of
structure
than
a
sediment
pond
and
is
constructed
to
control
sediment
on
the
construction
area
during
a
selected
phase
of
the
construction
operation.
A
sediment
trap
can
be
formed
by
excavation
and/
or
embankments
constructed
at
designated
locations
accessible
for
cleanout.
The
outlet
for
a
sediment
trap
is
typically
a
porous
rock
fill
structure,
which
serves
to
detain
the
flow,
but
a
pipe
structure
can
also
be
used.
A
temporary
sediment
trap
may
be
located
in
a
drainageway,
at
a
storm
drain
inlet,
or
at
other
points
of
discharge
from
a
disturbed
area.
They
may
be
constructed
independently
or
in
conjunction
with
diversions
and
may
be
used
in
most
drainage
situations
to
prevent
excessive
siltation
of
pipe
structures
(USEPA,
1992).

Applicability
Sediment
traps
can
simplify
the
storm
water
control
plan
design
process
by
trapping
sediment
at
specific
spots
at
a
construction
site
(USEPA,
1992).
They
should
be
installed
as
early
in
the
construction
process
as
possible
and
are
primarily
effective
as
a
short­
term
solution
to
trapping
sediment
from
construction
sites
(WYDEQ
1999).
Natural
drainage
patterns
should
be
noted,
and
sites
where
runoff
from
potential
erosion
can
be
directed
into
the
traps
should
be
selected.
Traps
are
most
effective
when
capturing
runoff
from
areas
where
2
to
5
acres
drain
to
one
location.
Sediment
traps
should
not
be
located
in
areas
where
their
failure
resulting
from
excess
storm
water
runoff
can
lead
to
further
erosive
damage
of
the
landscape.
Alternative
diversion
pathways
should
be
designed
to
accommodate
these
potential
overflows.
Traps
should
be
accessible
for
clean­
out
and
located
so
that
they
do
not
interfere
with
construction
activity.
In
addition,
the
traps
are
easily
adaptable
to
most
conditions.

Design
and
Implementation
Criteria
Hydrologic
Design
A
sediment
trap
should
be
designed
to
maximize
surface
area
and
sediment
settling.
This
will
increase
the
effectiveness
of
the
trap
and
decrease
the
likeliness
of
backup
during
and
after
periods
of
high
runoff
intensity.
The
design
of
a
trap
includes
determining
the
storage
volume,
surface
area,
dimensions
of
spillway
or
outlet,
and
elevations
of
embankment
(USDOT,
1995).
Sediment
traps
should
be
designed
to
meet
a
2­
year,
24­
hour
duration
storm
event,
but
the
selection
of
a
return
period
varies
among
regulatory
agencies
(IDNR,
1992).

Storage
volume
is
created
by
a
combination
of
excavation
of
land
and
construction
of
an
embankment
to
detain
runoff
(USDOT,
1995).
Trap
storage
volume
and
length
of
spillway
are
determined
as
a
function
of
the
runoff
volume
and
rate
for
the
design
storm.
These
parameters
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will
vary
depending
on
return
period
rainfall
and
watershed
hydrologic
characteristics.
Some
standards
specify
a
storage
volume
per
acre
disturbed.
For
example,
Smolen
et
al.
(1998)
specified
that
approximate
storage
capacity
of
each
trap
should
be
at
least
67
cubic
yards
per
acre
disturbed
draining
into
the
trap,
but
more
recent
guidelines
suggest
134
cubic
yards
per
acre
of
drainage
area
(VDCR,
2001).
Any
national
standard,
however,
should
be
based
on
runoff
volume
and
peak
discharge
in
order
to
be
generally
applicable.
Local
regulations
can
translate
this
into
applicable
volume
and
area
standards.

A
more
important
criterion
than
storage
volume
relates
to
sediment
trapping.
If
a
trapping
efficiency
is
specified,
as
in
the
case
of
South
Carolina
(SCDHEC,
1995),
it
is
necessary
to
design
for
trapping
efficiency.
If
a
TSS
or
settleable
solids
effluent
criterion
is
adopted
(SCDHEC,
1995),
settleable
solids
must
be
estimated.
In
both
cases,
a
national
standard
should
address
how
to
estimate
trapping
efficiency
or
settleable
solids.
Efforts
to
model
the
sediment
trapping
that
occurs
in
sediment
traps
have
resulted
in
models
that
predict
the
settling
in
the
ponded
area
(Barfield
et
al.,
1996;
Lindley
et
al.,
1998).
The
results
from
model
simulations
show
that
trapping
depends
primarily
on
surface
area
of
the
impounded
water
and
flow
rate
through
the
rock
fill
outlet.
In
fact,
the
ratio
of
peak
outflow
rate
to
surface
area
is
the
best
simple
predictor
of
trapping.
The
models
utilize
a
modification
of
the
Herrera
and
Felton
(1991)
relationship
developed
by
Haan
et
al.
(1994)
to
predict
discharge
rates.
The
predicted
flow
rates
do
not
take
into
account
clogging
that
can
occur
in
rock
fill.
No
models
or
procedures
are
available
to
estimate
this
clogging
or
its
impact
on
flow
criteria.

Design
aids
have
also
been
developed
for
sediment
traps,
using
simulations
from
the
SEDIMOT
III
(Barfield
et
al.,
2001;
Hayes
et
al.,
2001).
In
the
model,
predictions
are
made
of
trapping
efficiency
using
the
ratio
of
settling
velocity
for
the
d15
of
the
eroded
sediment,
divided
by
the
ratio
of
discharge
to
ponded
surface
area.
The
design
aid
yields
conservative
estimates,
but
the
database
used
for
generating
the
design
aid
is
based
on
the
assumption
that
flow
rates
are
not
impacted
by
clogging.
This
latter
assumption
is
not
likely
to
be
a
critical
issue,
but
should
be
addressed
in
future
research.

Installation
Specifications
USDOT
standards
call
for
the
embankment
to
be
constructed
of
compacted
earth,
at
a
maximum
height
of
5
feet
(1.5
meters),
a
width
of
4
to
5
feet
(1.2
meters),
and
side
slopes
of
2:
1or
flatter.
These
values
may
change
as
a
result
of
local
criteria
and
with
changing
soil
characteristics.
Temporary
vegetation
should
be
applied
to
the
embankment
(USDOT).
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2002
5­
78
Two
types
of
outlet
structures
are
typically
used
for
sediment
traps,
a
rock
outlet
and
a
pipe
outlet.
Spillways
of
large
stones
or
aggregate
are
the
most
common
type
of
outlet
designed
for
sediment
traps.
The
crest
of
the
spillway
should
be
constructed
1
foot
below
the
top
of
the
embankment
and
the
spillway
depth
1.5
feet
below
the
top
of
the
embankment.
Weir
length
of
the
spillway
is
determined
based
on
the
contributing
drainage
area
(Table
5­
18)
(USDOT,
1995).
The
outlet
apron
should
be
a
minimum
of
5
feet
long,
and
situated
on
level
ground
with
a
filter
fabric
foundation
to
ensure
exit
velocity
of
drainage
to
receiving
stream
is
nonerosive
(IDNR,
1992).

The
length
of
the
rock
outlet
should
be
determined
based
on
peak
discharge
required
and
rock
characteristics,
typically
rock
diameter.
Flow
rate
calculations
can
be
made
with
the
relationship
of
Herrera
and
Felton
(1991)
as
modified
by
Haan
et
al.
(1994).
Alternatively,
the
USDOT
has
specified
the
weir
length
for
a
given
drainage
area
as
shown
in
Table
5­
18.
However,
the
values
should
be
adjusted
for
each
climatologic
area
to
account
for
local
hydrologic
and
return
period
rainfall.

Table
5­
18.
Weir
Length
for
Sediment
Traps
Contributing
Drainage
Area
Weir
Length
(ft)
1
4
2
5
3
6
4
10
5
12
Source:
USDOT,
1995.

The
pipe
outlet,
constructed
of
corrugated
metal
or
PVC
pipe
riser,
is
an
alternative
to
the
rock
outlet.
Pipe
diameter
is
based
on
the
peak
discharge
rate
required.
To
obtain
appropriate
freeboard,
the
top
of
pipe
should
be
placed
1.5
feet
below
embankment
elevation.
Perforated
pipe
is
sometimes
used.
USDOT
suggests
perforations
of
1­
inch
(25
mm)
diameter
holes
or
0.5
x
6
inch
(13
x
15
mm)
slits
in
the
upper
two­
thirds
of
the
pipe;
however,
the
discharge
should
be
calculated
for
this
pipe
specification
to
ensure
that
it
matches
the
required
peak
discharge.

The
pipe
should
be
placed
vertically
and
horizontally
above
wet
storage
elevation
(USDOT,
1995).
Riprap
should
be
used
as
an
outlet
protection
and
placed
at
the
outlet
of
the
barrel
to
prevent
scour
from
occurring
(USDOT,
1995).
A
stable
channel
should
be
provided
to
convey
discharge
to
the
receiving
channel
(USDOT,
1995).

Effectiveness
If
it
is
assumed
that
the
flow
can
be
accurately
controlled
by
the
rock
fill
outlet,
sediment
traps
should
operate
as
effectively
as
sediment
basins,
with
trapping
efficiencies
reduced
as
a
result
of
smaller
surface
areas.
The
NURP
study
(USEPA,
1993),
Stahre
and
Urbonas
(1990),
and
Development
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June
2002
5­
79
Haan,
et
al.,
(1994),
report
that
sediment
basins
effectively
trapped
sediment
and
chemical
as
shown
in
Table
5­
19.

Table
5­
19.
Range
of
Measured
Long­
Term
Pollutant
Removal
for
Sediment
Detention
Basins
Item
Removable
Percentage
Total
suspended
solids
(TSS)
50­
70
Total
phosphorus
(TP)
10­
20
Nitrogen
10­
20
Organic
matter
20­
40
Lead
75­
90
Zinc
30­
60
Hydrocarbons
50­
70
Bacteria
50­
90
Source:
Stahre
and
Urbonas,
1990.

Information
on
the
actual
effectiveness
of
sediment
trapsis
limited.
The
discussion
should
start
first
with
the
flow
hydraulics
of
the
rock
fill
outlet
typically
employed
as
a
principal
spillway
for
sediment
traps.
Procedures
for
estimating
flow
through
rock
fill
have
been
developed
by
Herra
and
Felton
(1991)
to
estimate
flow
as
a
function
of
average
rock
diameter,
standard
deviation
of
rock
size,
and
flow
length.
If
these
parameters
could
be
controlled
in
an
actual
situation,
the
flow
could
be
accurately
predicted.
However,
given
that
standard
construction
practices
consist
of
end­
dumping
the
rock
fill
in
place,
one
would
expect
little
correlation
between
design
and
construction
and
the
actual
discharge
and
trapping
efficiency
would
be
expected
to
be
dramatically
different
from
the
design.
This
analysis
does
not
mean
that
sediment
traps
are
ineffective,
but
that
a
given
design
could
not
be
guaranteed
to
meet
the
effluent
criteria,
even
though
the
predictions
indicate
compliance.
Sediment
trapping
efficiency
is
a
function
of
surface
area
and
inflow
rate
(Smolen,
1988).
Those
traps
that
provide
pools
with
large
length­
towidth
ratios
have
a
greater
chance
of
success.

Sediment
traps
remove
larger
size
sediment,
primarily
sized
from
silt
to
sands,
by
slowing
water
velocity
and
allowing
for
sediment
settling
in
ponded
water
(Haan
et
al.,
1994).
Although
sediment
traps
allow
for
settling
of
eroded
soils,
because
of
their
short
detention
periods
for
storm
water
they
typically
do
not
remove
fine
particles
such
as
silts
and
clays
without
chemical
treatment.
Sediment
settling
ability
is
related
to
the
square
of
the
particle
size;
halving
particle
sizes
quadruples
the
time
needed
to
achieve
settlement
(WYDEQ
1999).
To
increase
overall
effectiveness,
traps
should
be
constructed
in
smaller
areas
with
low
slopes.

Sediment
traps
are
typically
designed
to
remove
only
sediment
from
surface
water,
but
some
non­
sediment
pollutants
are
trapped
as
well
(Haan
et
al.,
1994).
Development
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June
2002
5­
80
Limitations
Common
concerns
associated
with
sediment
traps
are
included
in
Table
5­
20.

Table
5­
20.
Common
Concerns
Associated
with
Sediment
Traps
Common
Concern
Result
Inadequate
spillway
size
Results
in
overtopping
of
the
dam
and
possible
failure
of
the
structure
Omission
or
improper
installation
of
geotextile
fabric
Results
in
piping
under
the
sides
or
bottom
of
the
stone
and
outlet
section
Low
point
in
embankment
caused
by
inadequate
compaction
and
settling
Results
in
overtopping
and
possible
failure
Stone
outlet
apron
does
not
extend
to
stable
grade
Results
in
erosion
below
the
dam
Stone
size
too
small
or
backslope
too
steep
Results
in
stone
displacement
Inadequate
vegetative
protection
Results
in
erosion
of
embankment
Inadequate
storage
capacity
Caused
by
sediment
not
being
removed
from
the
basin
enough
Contact
slope
between
stone
spillway
and
earth
embankment
too
steep
Results
in
piping
failure
Outlet
pipe
installed
in
vertical
side
of
trench
Results
in
piping
failure
of
embankment
Corrugated
tubing
used
as
outlet
pipe
Results
in
crushed
pipe
and
inadequate
outlet
capacity
Source:
IDMR,
1992.

Maintenance
The
primary
maintenance
consideration
for
temporary
sediment
traps
is
the
removal
of
accumulated
sediment
from
the
basin,
which
must
be
done
periodically
to
ensure
the
continued
effectiveness
of
the
sediment
trap.
Sediments
should
be
removed
when
the
basin
reaches
approximately
50
percent
sediment
capacity.

A
sediment
trap
should
be
inspected
after
each
rainfall
event
to
ensure
the
trap
is
draining
properly.
Inspectors
should
also
check
the
structure
for
damage
from
erosion
or
piping.
The
depth
of
the
spillway
should
be
checked
and
maintained
at
a
minimum
of
1.5
feet
below
the
low
point
of
the
trap
embankment.

Cost
The
cost
of
installing
temporary
sediment
traps
ranges
from
$0.20
to
$2.00
per
cubic
foot
of
storage
(about
$1,100
per
acre
of
drainage).
For
a
recent
national
assessment,
USEPA
(1999)
estimated
the
following
costs
for
sediment
traps,
which
vary
as
a
function
of
the
volume
of
storage:
$513
for
1,800
cubic
yards,
$1,670
for
3,600
cubic
yards,
and
$2,660
for
5,400
cubic
yards.
In
addition,
it
has
been
reported
that
a
sediment
trap
has
an
annual
maintenance
cost
of
20
percent
of
installation
cost
(Brown
et
al.,
1997).
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2002
5­
81
5.1.5.3.5
SEDIMENT
BASINS
General
Description
A
sediment
basin
is
a
storm
water
detention
structure
formed
by
constructing
a
dam
across
a
drainageway
or
excavating
a
storage
volume
at
other
suitable
locations
and
using
it
to
intercept
sediment­
laden
runoff.
Sediment
basins
are
generally
larger
and
more
effective
in
retaining
sediment
than
temporary
sediment
traps
and
typically
remain
active
throughout
the
construction
period.
Jurisdictions
that
require
postdevelopment
flow
to
be
less
than
or
equal
to
predevelopment
flow
during
construction
may
employ
the
designed
detention
facilities
as
a
temporary
sediment
basin
during
construction.

When
sediment
basins
are
designed
properly,
they
can
control
sediment
pollution
through
the
following
functions
(Faircloth,
1999):

°
Sediment­
laden
runoff
is
caught
to
form
an
impoundment
of
water
and
create
conditions
where
sediment
will
settle
to
the
bottom
of
the
basin.

°
Treated
runoff
is
released
with
less
sediment
concentration
than
when
it
entered
the
basin.

°
Storage
is
provided
for
accumulated
sediment,
and
resuspension
by
subsequent
storms
is
limited.

Applicability
Sediment
basins
should
be
located
at
a
convenient
concentration
point
for
sediment­
laden
flows
(NCDNR,
1988).
Ideal
sites
are
areas
where
natural
topography
allows
a
pond
to
be
formed
by
constructing
a
dam
across
a
natural
swale;
such
sites
are
preferred
to
those
that
require
excavation
(Smolen
et
al.,
1998).

Sediment
basins
are
also
applicable
in
drainage
areas
where
it
is
anticipated
that
other
erosion
controls,
such
as
sediment
traps,
will
not
be
sufficient
to
prevent
off­
site
transport
of
sediment.
Choosing
to
construct
a
sediment
basin
with
either
an
earthen
embankment
or
a
stone/
rock
dam
will
depend
on
the
materials
available,
location
of
the
basin,
and
desired
capacity
for
storm
water
runoff
and
settling
of
sediments.

Rock
dams
are
suitable
where
earthen
embankments
would
be
difficult
to
construct
or
where
riprap
is
readily
available.
Rock
structures
are
also
desirable
where
the
top
of
the
dam
structure
is
to
be
used
as
an
emergency
overflow
outlet.
These
riprap
dams
are
best
for
drainage
areas
of
less
than
50
acres.
Earthen
damming
structures
are
appropriate
where
failure
of
the
dam
will
not
result
in
substantial
damage
or
loss
of
property
or
life.
If
properly
constructed,
sediment
basins
with
earthen
dams
can
handle
storm
water
runoff
from
drainage
basins
as
large
as
100
acres.
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2002
5­
82
Design
and
Implementation
Criteria
Hydrologic
Design
A
sediment
basin
can
be
constructed
by
excavation
or
by
erecting
an
earthen
embankment
across
a
low
area
or
drainage
swale.
Sediment
basins
can
be
designed
to
drain
completely
during
dry
periods,
or
they
can
be
constructed
so
that
a
shallow,
permanent
pool
of
water
remains
between
storm
events.
Depending
on
the
size
of
the
basin
constructed,
the
basin
may
be
subject
to
additional
regulation,
particularly
state
and
federal
regulations
related
to
dam
safety.

Sediment
basins
can
be
used
for
any
size
watershed,
but
the
U.
S.
Department
of
Transportation
recommends
a
drainage
area
range
of
5
to
100
acres
(USDOT,
1995).
Components
of
a
sediment
basin
that
must
be
considered
in
the
hydrologic
design
include
the
following
(Haan
et
al.,
1994):

°
A
sediment
storage
volume
sized
to
contain
the
sediment
trapped
during
the
life
of
the
structure
or
between
cleanouts.

°
A
permanent
pool
volume
(if
included)
above
the
sediment
storage
to
protect
trapped
sediment
and
prevent
resuspension
as
well
as
providing
a
first
flush
of
discharge
that
has
been
subjected
to
an
extended
detention
period.

°
A
detention
volume
that
contains
storm
runoff
for
a
period
sufficient
to
trap
the
necessary
quantity
of
suspended
solids.

°
A
principal
spillway
that
can
be
a
drop­
inlet
pipe
and
barrel,
a
trickle
tube,
or
other
type
of
controlled
release
structure.

°
An
emergency
spillway
that
is
designed
to
handle
excessive
runoff
from
the
rarer
events
and
prevent
overtopping.

The
following
recommended
procedures
for
conducting
the
hydrologic
design
are
summarized
from
Haan
et
al.
(1994).

Sediment
Storage
Volume.
This
volume
should
be
sufficient
to
store
the
sediment
trapped
during
the
life
of
the
structure
or
between
cleanouts.
Sediment
storage
volume
can
be
calculated
based
on
sediment
yield
using
relationships
such
as
the
Revised
Universal
Soil
Loss
Equation
with
an
appropriate
delivery
ratio
(Renard
et
al.,
1994)
or
a
computer
model
such
as
SEDIMOT
III
(Barfield
et
al.,
1996).
Many
design
specifications,
however,
base
the
sediment
storage
volume
on
a
volume
per
acre
disturbed.
This
volume
is
highly
site­
specific,
depending
on
rainfall
distributions,
soil
types,
and
construction
techniques.
It
is
recommended
that
care
be
exercised
in
developing
appropriate
values
to
be
sure
that
existing
variations
in
rainfall
throughout
a
state
or
region
are
incorporated
in
the
statutory
requirements.
Development
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2002
5­
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Permanent
Pool
Volume.
Providing
a
first
flush
of
discharge
that
has
been
subjected
to
an
extended
detention
period
can
help
to
minimize
degradation
of
water
quality
and
justify
some
permanent
pool.
The
recommended
capacity
of
the
permanent
pool
varies
with
the
regulatory
agency.
The
U.
S.
Department
of
Transportation,
for
example,
recommends
67
cubic
yards
per
acre
(126
m
3
/ha)
(USDOT,
1995).
If
an
effluent
criterion
such
as
allowable
peak
TSS
or
peak
settleable
solids
is
used,
the
final
design
of
both
permanent
pool
and
detention
volume
should
be
selected
only
after
using
a
computer
model
to
predict
the
expected
peak
effluent
concentrations.

Detention
Volume.
Storm
runoff
must
be
contained
for
a
period
of
time
sufficient
to
trap
the
necessary
quantity
of
suspended
solids.
Since
inflow
is
occurring
simultaneously
with
outflow,
the
detention
time
for
each
plug
of
flow
is
different
and
should
be
considered
individually.
The
size
of
the
detention
volume,
as
stated
above,
should
also
be
developed
in
concert
with
determining
the
size
of
the
permanent
pool
volume
as
well
as
the
size
of
the
principal
spillway.
When
effluent
TSS
and
settleable
solids
criteria
are
used,
the
size
of
the
detention
volume
and
permanent
pool
volume
should
be
determined
through
on
a
computer
model
calculation
of
expected
effluent
concentrations
for
a
given
design.
The
return
period
used
to
size
the
detention
volume
depends
on
the
regulatory
agency,
but
a
return
period
of
10
years
is
typical.

Principal
Spillway.
The
principal
spillway
is
a
hydraulic
outlet
structure
sized
to
provide
the
appropriate
outflow
rate
to
meet
the
effluent
or
trapping
efficiency
criteria.
The
principal
spillway
should
have
a
dewatering
device
that
slowly
releases
water
contained
in
the
detention
storage
over
an
extended
period
of
time
and
at
a
rate
determined
to
trap
the
required
amount
of
sediment
and/
or
provide
for
the
appropriate
effluent
concentration
in
the
design
storm.
The
more
common
outlet
structures
are
the
drop­
inlet
structure
and
the
trickle
tube.
Sizing
of
the
principal
spillway
should
follow
standard
hydrologic
and
sedimentology
design
procedures
but
sizing
the
structure
to
simply
pass
the
design
storm
is
inappropriate
and
will
not
result
in
meeting
an
effluent
or
trapping
efficiency
standard.
The
size
to
be
used
in
a
given
structure
should
be
determined
based
on
the
effluent
or
trapping
efficiency
standard
being
targeted
and
site­
specific
hydrologic
and
soil
conditions.
Appropriate
design
will
require
the
use
of
a
computer
model
such
as
SEDIMOT
III
(Barfield
et
al.,
1996)
or
design
aids
such
as
those
developed
for
South
Carolina
(Hayes
and
Barfield,
1995).
In
general,
the
design
is
developed
to
maximize
surface
area,
which
will
minimize
peak
discharge.
Since
failure
of
the
dam
could
result
in
downstream
damage,
the
design
should
be
done
and
certified
by
a
licensed
engineer
with
expertise
in
hydrologic
computation.

It
has
been
proposed
that
a
surface
skimmer
made
of
PVC,
aluminum,
or
stainless
steel
and
designed
to
prevent
trash
from
clogging
and
can
also
be
used
to
replace
conventional
principal
spillways.
The
skimmer
puts
the
basin
drain
just
below
the
water
surface,
allowing
for
a
constant
head
rather
than
variable
head
from
the
bottom.
It
is
proposed
that
the
skimmer
allows
water
to
be
released
from
the
top
of
the
basin,
which
would
be
the
cleanest
water,
and
that
the
skimmer
properly
regulates
the
fill
and
draining
of
the
basin
(Fairchild,
1999).
The
skimmer
floats
on
the
surface
of
the
basin
and
rises
as
water
in
the
basin
rises
during
the
storm.
After
the
storm
the
skimmer
slowly
releases
water
from
the
basin.
As
the
basin
drains,
the
skimmer
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settles
to
the
bottom,
draining
the
entire
pool
except
for
a
pool
directly
under
the
skimmer.
The
skimmer
can
be
attached
directly
to
an
outlet
pipe
that
drains
through
the
dam
or
can
be
attached
to
an
outlet
pipe
through
a
riser.
It
is
important
to
point
out
that
use
of
the
skimmer
is
controversial
and
not
universally
recognized
as
a
good
concept.
Conventional
hydraulic
flow
theory
would
not
concur
with
the
statement
that
the
flow
would
come
only
from
the
surface,
unless
the
pond
had
significant
thermal
gradients
preventing
flow
from
deeper
levels.
A
single
hole
placed
just
above
the
sediment
cleanout
level
can
also
dewater
the
basin
slowly.

Emergency
Spillway.
Since
overtopping
of
the
dam
can
cause
failure
and
downstream
damage,
an
emergency
spillway
is
necessary
to
handle
excessive
runoff
from
the
rarer
events
and
prevent
overtopping.
The
design
storm
for
the
emergency
spillway
will
depend
on
the
hazard
classification
of
the
sediment
basin.
Typical
return
periods
vary
between
25
and
100
years,
with
25
years
recommended
by
the
USDOT.
Sizing
of
the
emergency
spillway
is
typically
accomplished
to
simply
transmit
the
rare
event
without
eroding
the
base
of
the
spillway.
Procedures
for
making
the
hydrologic
and
hydraulic
computations
are
summarized
in
Haan
et
al.
(1994).
Again,
since
failure
of
the
dam
could
result
in
downstream
damage,
the
design
should
be
done
and
certified
by
a
licensed
engineer
with
expertise
in
hydrologic
computation.

Installation
Criteria
The
embankment
for
permanent
sediment
basins
should
use
standard
geotechnical
construction
techniques.
The
fill
is
typically
constructed
of
earthen
fill
material
placed
and
compacted
in
continuous
layers
over
the
entire
length
of
the
fill.
USDOT
recommends
6­
to
8­
inch
layers
(USDOT,
1995).
The
embankment
should
be
stabilized
with
vegetation
after
construction
of
the
basin.
A
cutoff
trench
should
be
excavated
along
the
centerline
of
the
dam
to
prevent
excessive
seepage
beneath
the
dam,
and
sized
using
standard
geotechnical
computations.
USDOT
recommends
that
a
minimum
depth
of
the
cutoff
trench
should
be
about
2
feet
(600
mm),
the
height
should
be
to
the
riser
crest
elevation,
the
minimum
bottom
width
should
be
4
feet
(1.2
m)
or
wide
enough
for
compaction
equipment,
and
slopes
should
be
no
steeper
than
1:
1.

Sediment
basins
can
also
be
constructed
with
rock
dams
in
a
design
that
is
similar
to
a
sediment
basin
with
an
earthen
embankment.
It
is
important
to
remember
that
rock
fill
is
highly
heterogeneous
and
that
flow
rates
calculated
with
any
available
procedure
are
not
likely
to
match
those
that
will
actually
occur.
Since
sediment
trapping
is
inversely
proportional
to
flow
rate,
the
trapping
efficiency
will
be
impacted
significantly.
No
data
are
available
to
determine
the
variability
of
rock
fill
in
actual
installations
so
that
confidence
intervals
can
be
placed
on
predicted
flow
rates.
Such
data
should
be
collected
and
the
confidence
intervals
calculated
prior
to
recommending
the
use
of
rock
dams
as
outlets
on
any
structures
other
than
sediment
traps.

Effectiveness
The
effectiveness
of
a
sediment
basin
depends
primarily
on
the
sediment
particle
size
and
the
ratio
of
basin
surface
area
to
inflow
rate
(Smolen
et
al.,
1998;
Haan
et
al.,
1994).
Basins
with
a
Development
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5­
85
large
surface
area­
to­
volume
ratio
will
be
most
effective.
Studies
by
Barfield
and
Clar
(1985)
showed
that
a
surface
area­
to­
peak
discharge
ratio
of
0.01
acres
per
cubic
square
foot
would
trap
more
than
75
percent
of
the
sediment
coming
from
the
Coastal
Plain
and
Piedmont
regions
in
Maryland.
This
efficiency
might
vary
for
other
regions
of
the
country
and
should
not
be
used
as
a
national
standard.
Studies
by
Hayes
et
al.
(1984)
and
Stevens
et
al.
(2001),
however,
show
that
similar
relationships
can
be
developed
for
other
locations.

Laboratory
data
collected
on
pilot­
scale
facilities
are
available
on
the
trapping
efficiency
of
sediment
basins,
on
effluent
concentrations,
on
dead
storage
and
flow
patterns,
and
on
the
impacts
of
chemical
flocculants
on
sediment
trapping
(Tapp
et
al.,
1981;
Wilson
et
al.,
1984;
Griffin
et
al.,
1985;
Jarrett
et
al.,
1999;
Ward
et
al.,
1977,
1979).
In
general,
the
laboratory
studies
show
that
pilot­
scale
ponds
can
be
expected
to
trap
from
70
to
90
percent
of
sediment,
depending
on
the
sediment
characteristics,
pond
volume,
and
flow
rate.
The
trapping
efficiency
and
effluent
concentration
are,
in
general,
related
to
the
overflow
rate
and
can
be
reasonably
well
predicted
using
a
plug
flow
model
(Ward
et
al.,
1977,
1979)
and
a
Continuously
Stirred
Tank
Reactor
(CSTR)
model
(Wilson
et
al.,
1982;
Wilson
et
al.,
1984).
Extensive
field­
scale
data
are
available
on
long
term
trapping
efficiency
in
storm
water
detention
basins
(Brune,
1953)
in
which
the
annual
trapping
efficiency
is
related
to
the
annual
capacity
inflow
ratio
of
the
basin.
These
structures
are
not
representative
of
those
used
for
sediment
ponds,
but
would
be
representative
of
those
used
for
regional
detention.
A
more
limited
database
is
available
on
single
storm
sediment
trapping
in
the
larger
structures
(Ward,
et
al.,
1979)
and
on
a
field
laboratory
structure
at
Pennsylvania
State
University
(Jarret
et
al.,
1999).

For
maximum
trap
efficiency,
Smolen
et
al.
(1988)
recommend
the
following:

°
Allow
the
largest
surface
area
possible,
maximize
the
length­
to­
width
ratio
of
the
basin
to
prevent
short
circuiting,
and
ensure
use
of
the
entire
design
settling
area;

°
Locate
inlets
for
the
basin
at
the
maximum
distance
from
the
principal
spillway
outlet;

°
Allow
the
maximum
reasonable
time
to
detain
water
before
dewatering
the
basin;
and,

°
Reduce
the
inflow
rate
into
the
basin
and
divert
all
sediment­
free
runoff.

Jarett
(1999)
has
shown
that
the
smaller
the
depth
of
the
basin,
the
more
sediment
is
discharged.
A
0.15
m
(0.49
ft)
deep
basin
lost
twice
as
much
sediment
as
a
0.46
m
(1.50
ft)
deep
basin.
Jarrett
also
found
that
the
performance
of
a
sediment
basin
will
increase
with
the
use
of
a
skimmer
in
the
principal
spillway.
The
sediment
discharged
was
1.8
times
greater
with
just
a
perforated
riser
than
with
a
skimmer
in
the
principal
spillway.
In
addition,
increasing
the
dewatering
time,
which
will
allow
for
more
sediment
deposition,
decreases
the
sediment
loss
from
the
basin
(Jarett,
1999).
Development
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86
Limitations
Neither
a
sediment
basin
with
an
earthen
embankment
nor
a
rock
dam
should
be
used
in
areas
of
continuously
running
water
(live
streams).
The
use
of
sediment
basins
is
not
intended
for
areas
where
failure
of
the
earthen
or
rock
dam
will
result
in
loss
of
life,
or
damage
to
homes
or
other
buildings.
In
addition,
sediment
basins
should
not
be
used
in
areas
where
failure
will
interfere
with
the
use
of
public
roads
or
utilities.

Because
sediment
basins
are
usually
temporary
structures,
they
are
often
designed
poorly
and
rarely
receive
the
adequate
attention
and
maintenance.
As
a
result,
these
basins
will
not
achieve
the
function
for
which
they
were
designed,
especially
when
conventional
outlets
cannot
properly
meter
outflow
to
create
an
impoundment,
thus
allowing
rapid
release
of
sediment
laden
water
from
the
bottom
of
the
basin
to
escape
(Faircloth,
1999).

Common
concerns
associated
with
sediment
basins
are
included
in
Table
5­
21.

Table
5­
21.
Common
Concerns
Associated
with
Sediment
Basins
Common
Concern
Result
Piping
failure
along
conduit
Caused
by
improper
compaction,
omission
of
anti­
seep
collar,
leaking
pipe
joints,
or
use
of
unsuitable
soil
Erosion
of
spillway
or
embankment
slopes
Caused
by
inadequate
vegetation
or
improper
grading
and
sloping
Slumping
or
settling
of
embankment
Caused
by
inadequate
compaction
or
use
of
unsuitable
soil
Bank
failure
due
to
slumping
Caused
by
steep
side
slopes
Erosion
and
caving
below
principal
spillway
Caused
by
inadequate
outlet
protection
Basin
not
located
properly
for
access
Results
in
difficult,
ineffective,
and
costly
maintenance
Sediment
not
properly
removed
Results
in
inadequate
storage
capacity
and
potential
resuspension
Lack
of
anti­
flotation
Results
in
the
riser
and
barrel
being
blocked
with
debris
Principal
and
emergency
spillway
on
design
plans
Results
in
improper
disposal
of
accumulated
sediment
Safety
or
health
hazard
from
pond
water
Caused
by
gravel
clogging
the
dewatering
system
Principal
spillway
too
small
Results
in
frequent
operation
of
emergency
spillway
and
increased
erosion
potential
Source:
IDNR,
1992.

Maintenance
Routine
inspection
and
maintenance
of
sediment
basins
is
essential
to
their
continued
effectiveness.
Basins
should
be
inspected
after
each
storm
event
to
ensure
proper
drainage
from
the
collection
pool
and
determine
the
need
for
structural
repairs.
Erosion
from
the
earthen
embankment
or
stones
moved
from
rock
dams
should
be
replaced
immediately.

Sediment
basins
must
be
located
in
an
area
that
is
easily
accessible
to
maintenance
crews
for
removal
of
accumulated
sediment.
Sediment
should
be
removed
from
the
basin
when
its
storage
Development
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2002
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capacity
has
reached
approximately
50
percent.
Trash
and
debris
from
around
dewatering
devices
should
be
removed
promptly
after
rainfall
events.

Cost
The
sediment
basin
has
a
25
percent
annual
maintenance
cost
as
a
percentage
of
installation
(Brown
et
al.,
1997).

If
constructing
a
sediment
basin
with
less
than
50,000
cubic
feet
of
storage
space,
the
cost
of
installing
the
basin
ranges
from
$0.20
to
$1.30
per
cubic
foot
of
storage
(about
$1,100
per
acre
of
drainage).
The
average
cost
for
basins
with
less
than
50,000
cubic
feet
of
storage
is
approximately
$0.60
per
cubic
foot
of
storage
(USEPA,
1993).

If
constructing
a
sediment
basin
with
more
than
50,000
cubic
feet
of
storage
space,
the
cost
of
installing
the
basin
ranges
from
$0.10
to
$0.40
per
cubic
foot
of
storage
(about
$550
per
acre
of
drainage).
The
average
cost
for
basins
with
greater
than
50,000
cubic
feet
of
storage
is
approximately
$0.30
per
cubic
foot
of
storage
(USEPA,
1993).

As
an
alternative
costing
method,
designers
can
use
cost
curves
developed
for
permanent
basins
used
to
manage
storm
water
from
urban
areas.
However,
since
permanent
storm
water
basins
typically
include
design
features
that
would
not
be
included
in
temporary
sediment
basins,
this
approach
is
expected
to
greatly
overestimate
the
actual
costs
to
construct
sediment
basins.
For
many
sites,
sedimentation
basins
installed
for
erosion
and
sediment
control
during
the
construction
phase
are
retained/
modified
to
meet
other
runoff
management
requirements.
For
example,
site
flood
prevention
requirements
for
the
10­
year
rainfall
event
can
be
met
with
a
pond
made
from
a
converted
sedimentation
basin.
As
a
result,
sedimentation
basins
installation
costs
are
partially
offset
by
a
later
cost
reduction
or
savings.
Work
by
the
Center
for
Watershed
Protection
(CWP,
1996),
provides
capital
cost
equations
for
different
types
of
sediment
basins
for
permanent
installations.
For
example,

dry
extended
duration
ponds
CC
=
8.16
(Vs)
^
0.78
and
for
all
ponds
regardless
of
type
(including
wet
ponds)

CC
=
20.18
(Vs)
^
0.70
Where:
CC
=
base
construction
cost,
not
including
design,
engineering,
and
contingencies
Vs
=
Storage
volume
below
the
crest
of
the
emergency
spillway,
in
cubic
feet
Development
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Design,
engineering,
and
contingency
costs
are
given
as
approximately
32
percent
of
the
base
construction
costs.
Base
construction
costs
for
permanent
ponds
are
composed
of
approximately
48
percent
excavation/
grading
cost,
36
percent
control
structure
cost,
and
16
percent
appurtenances
cost.
R.
S.
Means
(2000)
suggests
the
cost
to
remove
the
eroded
sediment
collected
in
a
small
basin
during
construction
is
approximately
$4
per
cubic
yard
(value
includes
a
100
percent
surcharge
for
wet
excavation).
Disposal
of
material
on­
site
will
be
an
additional
cost
that
can
only
be
computed
from
site­
specific
conditions.
The
cheapest
management
of
dredge
material
is
application
to
land
areas
adjacent
to
the
basin,
followed
with
application
of
a
vegetative
cover.

5.1.5.4
OTHER
CONTROL
PRACTICES
5.1.5.4.1
STONE
OUTLET
STRUCTURE
Description
A
stone
outlet
structure
is
a
temporary
stone
dike
installed
in
conjunction
with
and
as
a
part
of
an
earth
dike.
The
purpose
of
the
stone
outlet
structure
is
to
impound
sediment­
laden
runoff,
provide
a
protected
outlet
for
an
earth
dike,
provide
for
diffusion
of
concentrated
flow,
and
allow
the
area
behind
the
dike
to
dewater
slowly.
The
stone
outlet
structure
can
extend
across
the
end
of
the
channel
behind
the
dike
or
be
placed
in
the
dike
itself.
In
some
cases,
more
than
one
stone
outlet
structure
can
be
placed
in
a
dike.

Applicability
Stone
outlet
structures
apply
to
any
point
of
discharge
where
there
is
a
need
to
discharge
runoff
at
a
protected
outlet
or
to
diffuse
concentrated
flow
for
the
duration
of
the
period
of
construction.
The
drainage
area
to
this
practice
is
typically
limited
to
one­
half
acre
or
less
to
prevent
excessive
flow
rates.
The
stone
outlet
structure
should
be
located
so
as
to
discharge
onto
an
already
stabilized
area
or
into
a
stable
watercourse.
Stabilization
should
consist
of
complete
vegetative
cover
and
paving,
sufficiently
established
to
be
erosion
resistant.

Design
and
Installation
Criteria
Design
criteria
are
of
two
types,
hydrologic
design
for
a
required
trapping
of
sediment
and/
or
flow
rate
to
pass
the
design
storm;
and
selection
of
appropriate
installation
criteria
such
that
the
stone
outlet
will
perform
as
designed
Development
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Guidelines
June
2002
5­
89
Hydrologic
Design
The
hydrologic
design
should
be
based
on
the
design
storm
and
standard
hydraulic
calculations
and
should
include
the
following
considerations:

°
Design
Rainfall
and
Design
Storm.
The
design
storm
should
be
specified
by
the
regulatory
authority.
Typically
a
return
period
of
2
to
5
years
is
used.
Runoff
rates
should
be
calculated
with
standard
hydrologic
procedures,
as
allowed
by
the
regulatory
authority.

°
Drainage
Area.
The
drainage
area
to
this
structure
is
typically
limited
to
less
than
half
an
acre
to
ensure
that
the
flow
rates
are
not
excessive.

°
Length
of
Crest
and
Height
of
Stone
Fill.
The
crest
length
and
height
of
stone
fill
should
be
of
sufficient
size
to
transmit
the
design
storm
without
overtopping.
The
volume
of
water
stored
behind
the
dike
can
be
estimated,
but
would
require
a
routing
of
the
storm
flow
in
the
design
storm.
Flow
through
the
stone
outlet
can
be
calculated
using
the
relationships
of
Herrera
and
Felton
(1991)
as
modified
by
Haan
et
al.
(1994).
The
height
of
the
fill
should
be
small
enough
to
prevent
excessive
flow
velocities
through
the
stone
fill
and
prevent
undercutting.

°
Outlet
Stabilization.
The
discharge
from
the
stone
outlet
should
be
stabilized
with
vegetated
waterways
or
riprap
until
the
flow
reaches
a
stable
channel.
Design
of
the
stabilized
outlet
should
follow
procedures
presented
earlier.

Installation
Criteria
Specifications
A
stone
outlet
structure
should
conform
to
the
following
specifications:

°
The
outlet
should
be
composed
of
2­
to
3­
inch
stone
or
recycled
concrete
equivalent
is
preferred,
but
clean
gravel
may
be
used
if
stone
is
not
available.

°
The
crest
of
the
stone
dike
should
be
at
least
6
inches
lower
than
the
lowest
elevation
of
the
top
of
the
earth
dike
and
should
be
level.

°
The
stone
outlet
structure
should
be
embedded
into
the
soil
a
minimum
of
4
inches.

°
The
minimum
length
of
the
crest
of
the
stone
outlet
structure
should
be
6
feet.

°
The
baffle
board
should
extend
1
foot
into
the
dike
and
4
inches
into
the
ground
and
be
staked
in
place.

°
The
drainage
area
to
this
structure
should
be
less
than
half
an
acre.
Development
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for
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Guidelines
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2002
5­
90
5.1.5.4.2
ROCK
OUTLET
PROTECTION
Description
Rock
outlet
structures
are
rocks
that
are
placed
at
the
outfall
of
channels
or
culverts
to
reduce
the
velocity
of
flow
in
the
receiving
channel
to
nonerosive
rates.

Applicability
This
practice
applies
where
discharge
velocities
and
energies
at
the
outlets
of
culverts
are
sufficient
to
erode
the
next
downstream
reach
and
it
applicable
to
outlets
of
all
types
such
as
sediment
basins,
storm
water
management
ponds,
and
road
culverts.

Design
and
Installation
Criteria
Hydrologic
Design
Hydrologic
design
consists
primarily
of
selecting
the
design
runoff
rate
and
sizing
the
outlet
protection.
Standard
hydrologic
calculations
should
be
used
to
make
the
calculation,
using
an
appropriate
return
period
storm
for
the
outlet
being
protected.
Typical
return
periods
range
from
2
to
10
years.

Sizing
the
outlet
protection
consists
of:

°
Selecting
the
Type
of
Outlet
Protection.
The
outlet
protection
may
consist
of
a
plunge
pool
(scour
hole),
an
apron­
type
arrangement,
or
an
energy
dissipation
basin
(Haan
et
al.,
1994).
The
design
of
each
differs.
Plunge
pools
are
typically
used
for
outlet
pipes
that
are
elevated
above
the
water
surface.
Aprons
are
used
for
other
types
of
outlets.

°
Selecting
the
Geometry
of
the
Outlet.
Plunge
pool
geometry
is
based
on
the
flow
rate,
pipe
size
and
slope,
tailwater
depth,
and
size
of
the
riprap
lining
(Haan
et
al.,
1994).
Apron
dimensions
are
determined
by
the
ratio
of
the
tailwater
depth
to
pipe
diameter
(Haan
et
al.,
1994).
Energy
dissipation
basins
are
used
as
an
alternative
to
the
plunge
pool.
Dimensions
are
a
function
of
the
brink
depth
in
the
pipe
at
the
design
flow,
pipe
diameter,
and
size
of
riprap
(Haan
et
al.,
1994).

°
Size
of
Rock
Lining.
The
size
of
the
rock
lining
is
a
function
of
the
discharge,
pipe
size,
tailwater
depth,
and
geometry
selected.
Details
on
sizing
the
rock
are
given
in
Haan
et
al.
(1994).

The
design
method
presented
here
applies
to
the
sizing
of
rock
riprap
and
gabions
to
protect
a
downstream
area.
It
does
not
apply
to
rock
lining
of
channels
or
streams.
The
design
of
rock
outlet
protection
depends
entirely
on
the
location.
Pipe
outlets
at
the
top
of
cuts
or
on
slopes
Development
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Development
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Guidelines
June
2002
5­
91
steeper
than
10
percent
cannot
be
protected
by
rock
aprons
or
riprap
sections
due
to
reconcentration
of
flows
and
high
velocities
encountered
after
the
flow
leaves
the
apron.

Installation
Criteria
The
following
criteria
should
be
considered.

°
Bottom
Grade:
The
outlet
protection
apron
should
be
constructed
with
no
slope
along
its
length.
There
should
be
no
obstruction
at
the
end
of
the
apron.
The
elevation
of
the
downstream
end
of
the
apron
should
be
equal
to
the
elevation
of
the
receiving
channel
or
adjacent
ground.

°
Alignment:
The
outer
protection
apron
should
be
located
so
that
there
are
no
beds
in
the
horizontal
alignment.

°
Materials:
The
outlet
protection
may
be
done
using
rock
riprap,
or
gabions.
Riprap
should
be
composed
of
a
well­
graded
mixture
of
stone
sized
so
that
50
percent
of
the
pieces,
by
weight,
should
be
larger
than
the
size
determined
by
using
the
charts.
The
minimum
d50
size
to
be
used
should
be
9
inches.
A
well­
graded
mixture
is
defined
as
a
mixture
composed
primarily
of
larger
stone
sizes
but
with
a
sufficient
mixture
of
other
sizes
to
fill
the
smaller
voids
between
the
stones.
The
diameter
of
the
largest
stone
in
such
a
mixture
should
be
2.0
times
the
size
selected
in
Table
5­
22
(MDE,
1994).

°
Thickness:
The
SHA
riprap
specification
values
are
summarized
in
Table
5­
22.

Table
5­
22.
Riprap
Sizes
and
Thicknesses
(SHA
Specifications)
D50
(inches)
D100
(inches)
Thickness
(inches)
Class
I
9.5
15
19
Class
II
16
24
32
Class
III
23
34
46
°
Stone
Quality:
Stone
for
riprap
should
consist
of
field
stone
or
rough
and
hewn
quarry
stone.
The
stone
should
be
hard
and
angular
and
of
a
quality
that
will
not
disintegrate
on
exposure
to
water
or
weathering.
The
specific
gravity
of
the
individual
stones
should
be
at
least
2.5.
Recycled
concrete
equivalent
may
be
used
provided
it
has
a
density
of
at
least
150
pounds
per
cubic
foot
and
does
not
have
any
exposed
steel
or
reinforcing
bars.

°
Filters:
A
filter
is
a
layer
of
material
placed
between
the
riprap
and
the
underlying
soil
surface
to
prevent
soil
movement
into
and
through
the
riprap
to
prevent
piping,
reduce
uplift
pressure,
and
collect
water.
Riprap
should
have
a
filter
placed
under
it
in
all
cases.
A
filter
can
be
of
two
general
forms:
a
gravel
layer
or
a
geotextile.
Development
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June
2002
5­
92
°
Gabions:
Gabion
baskets
may
be
used
as
rock
outlet
protection,
provided
they
are
made
of
hexagonal
triple
twist
mesh
with
heavily
galvanized
steel
wire.
The
maximum
lined
dimension
of
the
mesh
opening
should
not
exceed
4.5
inches.
The
area
of
the
mesh
opening
should
not
exceed
10
square
inches.
Gabions
should
be
fabricated
in
such
a
manner
that
the
sides,
ends,
and
lid
can
be
assembled
at
the
construction
site
into
a
rectangular
basket
of
the
specified
sizes.
Gabions
should
be
of
a
single
unit
construction
and
should
be
installed
according
to
the
manufacturer's
specifications.
The
area
on
which
the
gabion
is
to
be
installed
should
be
graded
as
shown
on
the
drawings.
Foundation
conditions
should
be
the
same
as
for
placing
rock
riprap.
Geotextiles
should
be
placed
under
all
gabions.
Gabions
must
be
keyed
in
to
prevent
undermining
of
the
main
gabion
structure.

°
The
subgrade
for
the
filter,
riprap,
or
gabion
should
be
prepared
to
the
required
lines
and
grades.
Any
fill
required
in
the
subgrade
shall
be
compacted
to
a
density
of
approximately
that
of
the
surrounding
undisturbed
material.

°
The
rock
or
gravel
should
conform
to
the
specified
grading
limits
when
installed
in
the
riprap
or
filter,
respectively.

°
Geotextiles
should
be
protected
from
punching,
cutting,
or
tearing.
Any
damage
other
than
occasional
small
holes
should
be
repaired
by
placing
another
piece
of
geotextile
fabric
over
the
damaged
part
or
by
completely
replacing
the
geotextile
fabric.
All
overlaps,
whether
for
repairs
or
for
joining
two
pieces
of
geotextile
fabric,
should
be
a
minimum
of
1
foot
in
length.

°
Stone
for
the
riprap
or
gabion
outlets
may
be
placed
by
equipment.
They
should
be
constructed
to
the
full
course
thickness
in
one
operation
and
in
such
a
manner
as
to
avoid
displacement
of
underlying
materials.
Care
should
be
taken
to
ensure
that
the
stone
is
not
placed
so
that
rolling
will
cause
segregation
of
stone
by
size,
i.
e.,
the
stone
for
riprap
or
gabion
outlets
should
be
delivered
and
placed
in
a
manner
that
will
ensure
that
it
is
reasonably
homogeneous
with
the
smaller
stones
filling
the
voids
between
the
larger
stones.
Riprap
must
be
placed
in
a
manner
to
prevent
damage
to
the
filter
blanket
or
geotextile
fabric.
Hand
placement
will
be
required
to
the
extent
necessary
to
prevent
damage
to
the
permanent
works.

°
Stone
should
be
placed
so
that
it
blends
in
with
the
existing
ground
and
the
depth
to
the
stone
surface
is
sufficient
to
transmit
the
flow
without
spilling
over
onto
the
unprotected
surface.

Effectiveness
There
is
currently
no
information
on
the
effectiveness
of
rock
outlet
structures.
Development
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June
2002
5­
93
Limitations
Common
problems
with
rock
outlet
structures
include
the
following:

°
Foundation
not
excavated
deep
enough
or
wide
enough—
restricts
the
flow
cross­
section,
resulting
in
erosion
around
the
apron
and
sour
holes
at
the
outlet.

°
Riprap
apron
should
be
placed
on
a
suitable
foundation
to
prevent
downstream
erosion.

°
Riprap
installed
smaller
than
specified—
results
in
rock
displacement;
selectively
grouting
over
the
rock
materials
may
stabilize
the
situation.

°
Riprap
not
extended
enough
to
reach
a
stable
section
of
the
channel—
results
in
downstream
erosion.

°
No
filter
installed
under
the
riprap—
results
in
stone
displacement
and
erosion
of
the
foundation.

Maintenance
Once
a
riprap
outlet
has
been
installed,
the
maintenance
needs
are
very
low.
It
should
be
inspected
after
high
flows
to
see
if
scour
has
occurred
beneath
the
riprap,
if
flows
have
occurred
outside
the
boundaries
of
the
riprap
and
caused
scour,
or
if
any
stones
have
been
dislodged.
Repairs
should
be
made
immediately.

Cost
R.
S.
Means
indicates
machine­
placed
riprap
costs
of
approximately
$40
per
cubic
yard.
For
a
riprap
maximum
size
between
15
and
24
inches,
a
cubic
yard
of
riprap
will
cover
between
13.5
and
17
square
feet
for
channel
bed
(assuming
depth
of
riprap
as
given
in
Table
5­
22).
This
suggests
that
riprap
lining
will
be
between
$21
and
$27
per
square
foot
of
outlet
(includes
materials,
labor,
and
equipment,
with
overhead
and
profit).
R.
S.
Means
(2000)
provides
a
cost
range
for
gabions
($
2.80
to
$9
per
square
foot
of
coverage)
for
stone
fill
depths
of
6"
to
36",
respectively.
These
costs
include
all
costs
of
materials,
labor,
and
installation.

5.1.5.4.3
SUMP
PIT
Description
A
sump
pit
is
a
temporary
pit
from
which
pumping
is
conducted
to
remove
excess
water
while
minimizing
sedimentation.
The
purpose
of
the
sump
pit
is
to
filter
water
being
pumped
to
reduce
sedimentation
to
receiving
streams.
Development
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2002
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94
Applicability
Sump
pits
are
constructed
when
water
collects
and
must
be
pumped
away
during
excavating,
cofferdam
dewatering,
maintenance
or
removal
of
sediment
traps
and
basins,
or
other
uses
as
applicable,
such
as
for
concrete
wash
out.

Design
and
Installation
Criteria
Hydrologic
Design
The
only
hydrologic
calculation
is
determining
the
expected
flow
rate
and
volume
to
be
handled.
This
should
follow
standard
hydrologic
computational
procedures
based
on
design
rainfall,
surface
and
soil
conditions,
and
the
size
of
the
pump.

Installation
Criteria
and
Specifications
The
number
of
sump
pits
and
their
locations
should
be
determined
by
the
designer
and
included
on
the
plans.
Contractors
may
relocate
sump
pits
to
optimize
use,
but
discharge
location
changes
should
be
coordinated
with
inspectors.

A
perforated
vertical
sandpipe
is
wrapped
with
½
inch
hardware
cloth
and
geotextiles
and
then
placed
in
the
center
of
an
excavated
pit
which
is
then
backfilled
with
filter
material
consisting
of
anything
from
clean
gravel
to
stone.
Water
is
then
pumped
from
the
center
of
the
sandpipe
to
a
suitable
discharge
area
such
as
into
a
sediment
trap,
sediment
basin,
or
stabilized
area.

A
sump
pit
should
conform
to
the
following
specifications:

°
Pit
dimensions
are
variable,
with
the
minimum
diameter
being
twice
the
diameter
of
the
sandpipe.

°
The
sandpipe
should
be
constructed
by
perforating
a
12­
to
36­
inch
diameter
pipe,
then
wrapping
it
with
½­
inch
hardware
cloth
and
geotextiles.
The
perforations
should
be
½­
x
6­
inch
slits
or
1­
inch
diameter
holes
6
inches
on
center.

°
The
sandpipe
should
extend
12
to
18
inches
above
the
lip
of
the
pit
or
riser
crest
elevation
(basin
dewatering),
and
filter
material
should
extend
3
inches
minimum
above
the
anticipated
standing
water
level.

Effectiveness
There
is
currently
no
information
on
the
effectiveness
of
the
sump
pit.
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Limitations
The
sump
pit
must
be
properly
maintained
and
pumped
regularly
to
avoid
clogging.

Maintenance
To
maintain,
sump
pits
must
be
removed
and
reconstructed
when
water
can
no
longer
be
pumped
out
of
the
sandpipe.

Cost
R.
S.
Means
(2000)
provides
information
appropriate
for
assessment
of
a
wide
range
of
dewatering
scenarios
(i.
e.,
different
sump
sizes,
dewatering
durations,
and
discharge
conditions).
In
general,
installation
of
earthen
sump
pits
are
listed
as
costing
approximately
$1.50
per
cubic
foot
of
sump
volume.
Piping
to
and
away
from
the
sump
ranges
from
$30
to
$60
per
linear
foot.
Pump
rentals
and
operation
range
between
$150
and
$500
per
day
of
pumping,
depending
on
the
rate
of
dewatering.
All
costs
include
material,
labor,
and
equipment,
with
overhead
and
profit.

5.1.5.4.4
SEDIMENT
TANK
Description
A
sediment
tank
is
a
compartmented
tank
container
through
which
sediment­
laden
water
is
pumped
to
trap
and
retain
the
sediment.
The
purpose
of
a
sediment
tank
is
to
trap
and
retain
sediment
prior
to
pumping
the
water
to
drainageways,
adjoining
properties,
and
rights­
of­
way
below
the
sediment
tank
site.

Applicability
A
sediment
tank
should
be
used
on
sites
where
excavations
are
deep
and
space
is
limited,
such
as
urban
construction,
where
direct
discharge
of
sediment­
laden
water
to
streams
and
storm
drainage
systems
should
be
avoided.

Design
and
Installation
Criteria
The
location
of
sediment
tanks
should
facilitate
easy
cleanout
and
disposal
of
the
trapped
sediment
to
minimize
interference
with
construction
activities
and
pedestrian
traffic.
The
tank
size
should
be
determined
according
to
the
storage
volume
of
the
sediment
tank,
1
cubic
foot
of
storage
for
each
gallon
per
minute
of
pump
discharge
capacity.
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Effectiveness
There
is
currently
no
information
on
the
effectiveness
of
sediment
tanks.

Limitations
The
sediment
tank
does
not
provide
any
natural
infiltration;
thus,
the
trapped
sediment
and
storm
water
must
be
disposed
of
properly.

Maintenance
To
properly
maintain
the
sediment
tank,
it
needs
to
be
in
a
location
that
is
easy
to
access.

Cost
There
is
currently
no
information
on
the
cost
of
sediment
tanks.

5.1.5.4.5
STABILIZED
CONSTRUCTION
ENTRANCE
Description
The
purpose
of
stabilizing
entrances
to
a
construction
site
is
to
minimize
the
amount
of
sediment
leaving
the
area
as
mud
attached
to
motorized
vehicles.
Installing
a
pad
of
gravel
over
filter
cloth
where
construction
traffic
leaves
a
site
can
help
stabilize
a
construction
entrance.
As
a
vehicle
drives
over
the
gravel
pad,
mud
and
other
sediments
are
removed
from
the
vehicle's
wheels
(sometimes
by
washing)
and
offsite
transport
of
soil
is
reduced.
The
gravel
pad
also
reduces
erosion
and
rutting
on
the
soil
beneath
the
stabilization
structure.
The
fabric
reduces
the
amount
of
rutting
caused
by
vehicle
tires
by
spreading
the
vehicle's
weight
over
a
larger
soil
area
than
just
the
tire
width.
The
filter
fabric
also
separates
the
gravel
from
the
soil
below,
preventing
the
gravel
from
being
ground
into
the
soil.

Applicability
Typically,
stabilized
construction
entrances
are
installed
at
locations
where
construction
traffic
leaves
or
enters
an
existing
paved
road.
However,
the
applicability
of
site
entrance
stabilization
should
be
extended
to
any
roadway
or
entrance
where
vehicles
will
access
or
leave
the
site.

From
a
public
relations
point
of
view,
stabilizing
construction
site
entrances
can
be
a
worthwhile
exercise.
If
the
site
entrance
is
the
most
publicly
noticeable
part
of
a
construction
site,
stabilized
entrances
can
improve
the
appearance
to
passersby
and
improve
public
perception
of
the
construction
project
by
reducing
the
amount
of
mud
tracked
onto
adjacent
streets.
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2002
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Design
and
Installation
Considerations
Hydrologic
Design
Not
applicable.

Installation
Criteria
and
Specifications
All
entrances
to
a
site
should
be
stabilized
before
construction
begins
and
further
disturbance
of
the
site
area
occurs.
The
stabilized
site
entrances
should
be
long
enough
and
wide
enough
so
that
the
largest
construction
vehicle
that
will
enter
the
site
will
fit
in
the
entrance
with
room
to
spare.
If
many
vehicles
are
expected
to
use
an
entrance
in
any
one
day,
the
site
entrance
should
be
wide
enough
for
the
passage
of
two
vehicles
at
the
same
time
with
room
on
either
side
of
each
vehicle.
For
optimum
effectiveness,
a
rock
construction
entrance
should
be
at
least
50
feet
long
and
at
least
10
to
12
feet
wide
(USEPA,
1992).
If
a
site
entrance
leads
to
a
paved
road,
the
end
of
entrance
should
be
"flared"
(made
wider
as
in
the
shape
of
a
funnel)
so
that
long
vehicles
do
not
go
off
the
stabilized
area
when
turning
onto
or
off
of
the
paved
roadway.

If
a
construction
site
entrance
crosses
a
stream,
swale,
roadside
channel,
or
other
depression,
a
bridge
or
culvert
should
be
provided
to
prevent
erosion
from
unprotected
banks.

Stone
and
gravel
used
to
stabilize
the
construction
site
entrance
should
be
large
enough
so
that
they
are
not
carried
off­
site
with
vehicle
traffic.
In
addition,
sharp­
edged
stone
should
be
avoided
to
reduce
the
possibility
of
puncturing
vehicle
tires.
Stone
or
gravel
should
be
installed
at
a
depth
of
at
least
6
inches
for
the
entire
length
and
width
of
the
stabilized
construction
entrance.

Effectiveness
Stabilizing
construction
entrances
to
prevent
sediment
transport
off­
site
is
effective
only
if
all
entrances
to
the
site
are
stabilized
and
maintained.
Also,
stabilization
of
construction
site
entrances
may
not
be
very
effective
unless
a
wash
rack
is
installed
and
routinely
used
(Corish,
1995)
but
this
can
be
problematic
for
sites
with
multiple
entrances
with
high
vehicle
traffic.

Limitations
Although
stabilizing
a
construction
entrance
is
a
good
way
to
help
reduce
the
amount
of
sediment
leaving
a
site,
some
soil
may
still
be
deposited
from
vehicle
tires
onto
paved
surfaces.
To
further
reduce
the
chance
that
these
sediments
will
pollute
storm
water
runoff,
sweeping
of
the
paved
area
adjacent
to
the
stabilized
site
entrance
is
recommended.

For
sites
using
wash
stations,
a
reliable
water
source
to
wash
vehicles
before
leaving
the
site
might
not
be
initially
available.
In
this
case,
water
may
have
to
be
trucked
to
the
site
at
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2002
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98
additional
cost.
Discharge
from
the
wash
station
should
be
directed
into
an
appropriate
sediment
control
structure.

Maintenance
Stabilization
of
site
entrances
should
be
maintained
until
the
remainder
of
the
construction
site
has
been
fully
stabilized.
Stone
and
gravel
might
need
to
be
periodically
added
to
each
stabilized
construction
site
entrance
to
keep
the
entrance
effective.
Soil
that
is
tracked
offsite
should
be
swept
up
immediately
for
proper
disposal.

For
sites
with
wash
racks
at
each
site
entrance,
sediment
traps
will
have
to
be
constructed
and
maintained
for
the
life
of
the
project.
Maintenance
will
entail
the
periodic
removal
of
sediment
from
the
traps
to
ensure
their
continued
effectiveness.

Cost
Without
a
wash
rack,
construction
site
entrance
stabilization
costs
range
from
$1,000
to
$4,000.
On
average,
the
initial
construction
cost
is
around
$2,000
per
entrance.
When
maintenance
costs
are
included,
the
average
total
annual
cost
for
a
2­
year
period,
is
approximately
$1,500.

If
a
wash
rack
is
included
in
the
construction
site
entrance
stabilization,
the
initial
construction
costs
range
from
$1,000
to
$5,000,
with
an
average
initial
cost
of
$3,000
per
entrance.
Total
annual
cost,
including
maintenance
for
an
estimated
2­
year
life
span,
is
approximately
$2,200
per
year
(USEPA,
1993).

5.1.5.4.6
LAND
GRADING
Description
Land
grading
involves
reshaping
the
ground
surface
to
planned
grades
as
determined
by
an
engineering
survey,
evaluation,
and
layout.
Land
grading
provides
more
suitable
topography
for
buildings,
facilities,
and
other
land
uses
and
helps
to
control
surface
runoff,
soil
erosion,
and
sedimentation
both
during
and
after
construction.

Applicability
Land
grading
is
applicable
to
sites
with
steep
topography
or
easily
erodible
soils
because
it
stabilizes
slopes
and
decreases
runoff
velocity.
Grading
activities
should
maintain
existing
drainage
patterns
as
much
as
possible.
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2002
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Design
and
Installation
Criteria
Before
grading
activities
begin,
decisions
should
be
made
regarding
the
steepness
of
cut­
and­
fill
slopes
and
how
the
slopes
will
be
protected
from
runoff,
stabilized,
and
maintained.
A
grading
plan
that
establishes
which
areas
of
the
site
will
be
graded,
how
drainage
patterns
will
be
directed,
and
how
runoff
velocities
will
affect
receiving
waters
should
be
prepared.
The
grading
plan
also
includes
information
regarding
when
earthwork
will
start
and
stop,
establishes
the
degree
and
length
of
finished
slopes,
and
dictates
where
and
how
excess
material
will
be
disposed
of
(or
where
borrow
materials
will
be
obtained
if
needed).
Berms,
diversions,
and
other
storm
water
practices
that
require
excavation
and
filling
should
also
be
incorporated
into
the
grading
plan.

A
low­
impact
development
BMP
that
can
be
incorporated
into
a
grading
plan
is
site
fingerprinting,
which
involves
clearing
and
grading
only
those
areas
necessary
for
building
activities
and
equipment
traffic.
Adhering
to
strict
limits
of
clearing
and
grading
helps
to
maintain
undisturbed
temporary
or
permanent
buffer
zones
in
the
grading
operation
and
provides
a
low­
cost
sediment
control
measure
that
will
help
reduce
runoff
and
off­
site
sedimentation.
The
lowest
elevation
of
the
site
should
remain
undisturbed
to
provide
a
protected
storm
water
outlet
before
storm
drains
or
other
construction
outlets
are
installed.

Effectiveness
Land
grading
is
an
effective
means
of
reducing
steep
slopes
and
stabilizing
highly
erodible
soils
when
implemented
with
storm
water
management
and
erosion
and
sediment
control
practices
in
mind.
Land
grading
is
not
effective
when
drainage
patterns
are
altered
or
when
vegetated
areas
on
the
perimeter
of
the
site
are
destroyed.

Limitations
Construction
sites
are
routinely
graded
to
prepare
a
site
for
buildings
and
other
structures.
Improper
grading
practices
that
disrupt
natural
storm
water
patterns
might
lead
to
poor
drainage,
high
runoff
velocities,
and
increased
peak
flows
during
storm
events.
Clearing
and
grading
of
the
entire
site
without
vegetated
buffers
promotes
off­
site
transport
of
sediments
and
other
pollutants.
Grading
plans
should
be
designed
with
erosion
and
sediment
control
and
storm
water
management
goals
in
mind;
grading
crews
should
be
carefully
supervised
to
ensure
that
the
plan
is
implemented
as
intended.
Development
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2002
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100
Maintenance
All
graded
areas
and
supporting
erosion
and
sediment
control
practices
should
be
periodically
checked,
especially
after
heavy
rainfalls.
All
sediment
should
be
promptly
removed
from
diversions
or
other
storm
water
conveyances.
If
washouts
or
breaks
occur,
they
should
be
repaired
immediately.
Prompt
maintenance
of
small­
scale
eroded
areas
is
essential
to
prevent
these
areas
from
becoming
significant
gullies.

Cost
Land
grading
is
practiced
at
virtually
all
construction
sites—
additional
site
planning
to
incorporate
storm
water
and
erosion
and
sediment
controls
in
grading
plans
can
require
several
hours
of
planning
by
a
certified
engineer
or
landscape
architect.
Extra
time
might
be
required
to
excavate
diversions
and
construct
berms,
and
fill
materials
might
be
needed
to
build
up
lowlying
areas
or
fill
depressions.

Where
grading
is
performed
to
manage
on­
site
storm
water,
R.
S.
Means
(2000)
suggests
the
cost
of
fine
grading,
soil
treatment,
and
grassing
to
be
approximately
$2
per
square
yard
of
earth
surface
area.
Shallow
excavation/
trenching
(1
to
4
feet
deep)
with
a
backhoe
in
areas
not
requiring
dewatering
can
be
performed
for
$4
to
$5
per
cubic
yard
of
removed
material.
Larger
scale
grading
requires
a
site­
specific
assessment
of
an
alternative
grading
apparatus
and
a
detailed
fill/
excavation
material
balance
to
retain
as
much
soil
on
site
as
possible.

5.1.5.4.7
TEMPORARY
ACCESS
WATERWAY
CROSSING
Description
A
temporary
stream
crossing
is
a
structure
erected
to
provide
a
safe
and
stable
way
for
construction
vehicle
traffic
to
cross
a
running
watercourse.
The
primary
purpose
of
such
a
structure
is
to
provide
streambank
stabilization,
to
reduce
the
risk
of
damaging
the
streambed
or
channel,
and
to
reduce
the
risk
of
sediment
loading
from
construction
traffic.
A
temporary
stream
crossing
may
be
a
bridge,
culvert,
or
ford.

Applicability
Temporary
stream
crossings
are
applicable
wherever
heavy
construction
equipment
must
be
moved
from
one
side
of
a
stream
channel
to
the
other
or
where
lighter
construction
vehicles
will
cross
the
stream
a
number
of
times
during
the
construction
period.
In
either
case,
an
appropriate
method
for
ensuring
the
stability
of
the
streambanks
and
preventing
large­
scale
erosion
is
necessary.

A
bridge
or
culvert
is
the
best
choice
for
most
temporary
stream
crossings.
If
properly
designed,
each
can
support
heavy
loads,
and
materials
used
to
construct
most
bridges
and
culverts
can
be
Development
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June
2002
5­
101
salvaged
after
they
are
removed.
Fords
are
appropriate
in
steep
areas
subject
to
flash
flooding,
where
normal
flow
is
shallow
or
intermittent
across
a
wide
channel.
Fords
should
be
used
only
where
stream
crossings
are
expected
to
be
infrequent.

Design
and
Installation
Criteria
Because
of
the
potential
for
stream
degradation,
flooding,
and
safety
hazards,
stream
crossings
should
be
avoided
on
a
construction
site
whenever
possible.
Consideration
should
be
given
to
alternative
site
access
routes
before
arrangements
are
made
to
erect
a
temporary
stream
crossing.
If
it
is
determined
that
a
stream
crossing
is
necessary,
an
area
where
the
potential
for
erosion
is
low
should
be
selected.
The
stream
crossing
structure
should
be
selected
during
a
dry
period
if
possible
to
reduce
sediment
transport
into
the
stream.

If
needed,
over­
stream
bridges
are
generally
the
preferred
temporary
stream
crossing
structure.
The
expected
load
and
frequency
of
the
stream
crossing,
however,
will
govern
the
selection
of
a
bridge
as
the
correct
choice
for
a
temporary
stream
crossing.
These
types
of
temporary
bridges
usually
cause
minimal
disturbance
to
a
stream's
banks
and
cause
the
least
obstruction
to
stream
flow
and
fish
migration.
They
should
be
constructed
only
under
the
supervision
and
approval
of
a
qualified
engineer.

As
general
guidelines
for
constructing
temporary
bridges,
clearing
and
excavation
of
the
stream
shores
and
bed
should
be
kept
to
a
minimum.
Sufficient
clearance
should
be
provided
for
floating
objects
to
pass
under
the
bridge.
Abutments
should
be
parallel
to
the
stream
and
on
stable
banks.
If
the
stream
is
less
than
8
feet
wide
at
the
point
where
a
crossing
is
needed,
no
additional
in­
stream
supports
should
be
used.
If
the
crossing
is
to
extend
across
a
channel
wider
than
8
feet
(as
measured
from
top
of
bank
to
top
of
bank),
the
bridge
should
be
designed
with
one
in­
water
support
for
each
8
feet
of
stream
width.

A
temporary
bridge
should
be
anchored
by
steel
cable
or
chain
on
one
side
only
to
a
stable
structure
on
shore.
Examples
of
anchoring
structures
include
trees
with
a
large
diameter,
large
boulders,
and
steel
anchors.
By
anchoring
the
bridge
on
one
side
only,
there
is
a
decreased
risk
of
causing
a
downstream
blockage
or
flow
diversion
if
a
bridge
is
washed
out.

When
constructing
a
culvert,
filter
cloth
should
be
used
to
cover
the
streambed
and
streambanks
to
reduce
settlement
and
improve
the
stability
of
the
culvert
structure.
The
filter
cloth
should
extend
a
minimum
of
6
inches
and
a
maximum
of
1
foot
beyond
the
end
of
the
culvert
and
bedding
material.
The
culvert
piping
should
not
exceed
40
feet
in
length
and
should
be
of
sufficient
diameter
to
allow
for
complete
passage
of
flow
during
peak
flow
periods.
The
culvert
pipes
should
be
covered
with
a
minimum
of
1
foot
of
aggregate.
If
multiple
culverts
are
used,
at
least
1
foot
of
aggregate
should
separate
the
pipes.

Fords
should
be
constructed
of
stabilizing
material
such
as
large
rocks.
Development
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2002
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Effectiveness
Both
temporary
bridges
and
culverts
provide
an
adequate
path
for
construction
traffic
crossing
a
stream
or
watercourse.

Limitations
Bridges
can
be
considered
the
greatest
safety
hazard
of
all
temporary
stream
crossing
structures
if
not
properly
designed
and
constructed.
Bridges
might
also
prove
to
be
more
costly
in
terms
of
repair
costs
and
lost
construction
time
if
they
wash
out
or
collapse
(Smolen
et
al.,
1988).

The
construction
and
removal
of
culverts
are
usually
very
disturbing
to
the
surrounding
area,
and
erosion
and
downstream
movement
of
soils
are
often
great.
Culverts
can
also
create
obstructions
to
flow
in
a
stream
and
inhibit
fish
migration.
Depending
on
their
size,
culverts
can
be
blocked
by
large
debris
in
a
stream
and
are
therefore
vulnerable
to
frequent
blockage
and
washout.

If
given
a
choice
between
building
a
bridge
or
a
culvert
as
a
temporary
stream
crossing,
a
bridge
is
preferred
because
of
the
relative
minimal
disturbance
to
streambanks
and
the
opportunity
for
unimpeded
flow
through
the
channel.
The
approaches
to
fords
often
have
high
erosion
potential.
In
addition,
excavation
of
the
streambed
and
approach
to
lay
riprap
or
other
stabilization
material
causes
major
stream
disturbance.
Mud
and
other
debris
are
transported
directly
into
the
stream
unless
the
crossing
is
used
only
during
periods
of
low
flow.

Maintenance
Temporary
stream
crossings
should
be
inspected
at
least
once
a
week
and
after
all
significant
rainfall
events.
If
any
structural
damage
is
reported
to
a
bridge
or
culvert,
construction
traffic
should
stop
using
the
structure
until
appropriate
repairs
are
made.
Evidence
of
streambank
erosion
should
be
repaired
immediately.

Fords
should
be
inspected
closely
after
major
storm
events
to
ensure
that
stabilization
materials
remain
in
place.
If
the
material
has
moved
downstream
during
periods
of
peak
flow,
the
lost
material
should
be
replaced
immediately.

Cost
In
general,
temporary
bridges
are
more
expensive
to
design
and
construct
than
culverts.
Bridges
are
also
associated
with
higher
maintenance
and
repair
costs
should
they
fail.
Additional
costs
may
accrue
to
the
site
team
in
terms
of
lost
construction
time
if
a
temporary
structure
is
washed
out
or
otherwise
fails.

Temporary
bridging
costs
range
as
a
function
of
the
width
of
the
bridge
span
and
the
duration
of
application.
If
the
bridging
is
permanent,
a
mean
cost
of
$50
per
square
foot
for
an
8­
foot
wide
Development
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Construction
and
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Proposed
Effluent
Guidelines
June
2002
5­
103
steel
arch
bridge
(no
foundation
costs
included)
can
be
used
for
conceptual
cost
estimation
(R.
S.
Means,
2000).
If
rental
bridging
is
employed,
then
rates
are
probably
on
the
order
of
20
to
50
percent
of
the
bridge
(permanent)
cost,
but
will
range
based
on
the
rental
duration
and
mobilization
distance.

5.1.5.4.8
DUST
CONTROL
General
Description
Dust
control
measures
are
practices
that
help
reduce
ground
surface
and
air
movement
of
dust
from
disturbed
soil
surfaces.
Construction
sites
are
good
candidates
for
dust
control
measures
because
land
disturbance
from
clearing
and
excavation
generates
a
large
amount
of
soil
disturbance
and
open
space
for
wind
to
pick
up
dust
particles.
To
illustrate
this
point,
research
at
construction
sites
has
established
an
average
dust
emission
rate
of
1.2
tons/
acre/
month
for
active
construction
(WA
Dept.
of
Ecology,
1992).
These
airborne
particles
pose
a
dual
threat
to
the
environment
and
human
health.
First,
dust
can
be
carried
off­
site,
thereby
increasing
soil
loss
from
the
construction
area
and
increasing
the
likelihood
of
sedimentation
and
water
pollution.
Second,
blowing
dust
particles
can
contribute
to
respiratory
health
problems
and
create
an
inhospitable
working
environment.

Applicability
Dust
control
measures
are
applicable
to
any
construction
site
where
dust
is
created
and
there
is
the
potential
for
air
and
water
pollution
from
dust
traveling
across
the
landscape
or
through
the
air.
Dust
control
measures
are
particularly
important
in
arid
or
semiarid
regions
where
soil
can
become
extremely
dry
and
vulnerable
to
transport
by
high
winds.

Also,
dust
control
measures
should
be
implemented
on
all
construction
sites
where
there
will
be
major
soil
disturbances
or
heavy
construction
activity,
such
as
clearing,
excavation,
demolition,
or
excessive
vehicle
traffic.
Earthmoving
activities
are
the
major
source
of
dust
from
construction
sites,
but
traffic
and
general
disturbances
can
also
be
major
contributors
(WA
Dept.
of
Ecology,
1992).

The
specific
dust
control
measures
implemented
at
a
site
will
depend
on
the
topography,
land
cover,
soil
characteristics
and
amount
of
rainfall
at
the
site.

Design
and
Installation
Criteria
When
designing
a
dust
control
plan
for
a
site,
the
amount
of
soil
exposed
will
dictate
the
quantity
of
dust
generation
and
transport.
Therefore,
construction
sequencing
and
disturbing
small
areas
at
one
time
can
greatly
reduce
problematic
dust
from
a
site.
If
land
must
be
disturbed,
additional
temporary
stabilization
measures
should
be
considered
prior
to
disturbance.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
104
A
number
of
methods
can
be
used
to
control
dust
from
a
site.
The
following
is
a
brief
list
of
control
measures
and
their
design
criteria.
Not
all
control
measures
will
be
applicable
to
a
given
site.
The
owner,
operator,
and
contractors
responsible
for
dust
control
at
a
site
should
determine
which
practices
accommodate
their
needs
based
on
specific
site
and
weather
conditions.

Sprinkling/
Irrigation:
Sprinkling
the
ground
surface
with
water
until
it
is
moist
is
an
effective
dust
control
method
for
haul
roads
and
other
traffic
routes
(Smolen
et
al.,
1988).
This
practice
can
be
applied
to
almost
any
site.

Vegetative
Cover:
In
areas
not
expected
to
handle
vehicle
traffic,
vegetative
stabilization
of
disturbed
soil
is
often
desirable.
Vegetative
cover
provides
protection
to
surface
soils
and
slows
wind
velocity
at
the
ground
surface,
thus
reducing
the
potential
for
dust
to
become
airborne.

Mulch:
Mulching
can
be
a
quick
and
effective
means
of
dust
control
for
a
recently
disturbed
area
(Smolen
et
al.,
1988).

Wind
Breaks:
Wind
breaks
are
barriers
(either
natural
or
constructed)
that
reduce
wind
velocity
through
a
site
and
therefore
reduce
the
possibility
of
picking
up
suspended
particles.
Wind
breaks
can
be
trees
or
shrubs
left
in
place
during
site
clearing
or
constructed
barriers
such
as
a
wind
fence,
snow
fence,
tarp
curtain,
hay
bale,
crate
wall,
or
sediment
wall
(USEPA,
1992).

Tillage:
Deep
tillage
in
large
open
areas
brings
soil
clods
to
the
surface
where
they
rest
on
top
of
dust,
preventing
it
from
becoming
airborne.

Stone:
Stone
can
be
an
effective
dust
deterrent
for
construction
roads
and
entrances.

Spray­
on
Chemical
Soil
Treatments
(palliatives):
Examples
of
chemical
adhesives
include
anionic
asphalt
emulsion,
latex
emulsion,
resin­
water
emulsions,
and
calcium
chloride.
Chemical
palliatives
should
be
used
only
on
mineral
soils.
When
considering
chemical
application
to
suppress
dust,
consideration
should
be
taken
as
to
whether
the
chemical
is
biodegradable
or
water­
soluble
and
what
effect
its
application
could
have
on
the
surrounding
environment,
including
waterbodies
and
wildlife.
Development
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and
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Proposed
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Guidelines
June
2002
5­
105
Table
5­
23
shows
application
rates
for
some
common
spray­
on
adhesives
as
recommended
by
Smolen
et
al.
(1988).

Table
5­
23.
Application
Rates
for
Spray­
On
Adhesives
Spray
on
Adhesive
Water
Dilution
Type
of
Nozzle
Application
(gal/
acre)

Anionic
Asphalt
Emulsion
7:
1
Coarse
spray
1,200
Latex
Emulsion
12.5:
1
Fine
spray
235
Resin
in
Water
4:
1
Fine
spray
300
Source:
Smolen
et
al.,
1988.

Effectiveness
Sprinkling/
Irrigation:
Not
available.

Vegetative
Cover:
Not
available.

Mulch:
Can
reduce
wind
erosion
by
80
percent.

Wind
Breaks/
Barriers:
For
each
foot
of
vertical
height,
an
8­
to
10­
foot
deposition
zone
develops
on
the
leeward
side
of
the
barrier.
The
barrier
density
and
spacing
will
change
its
effectiveness
at
capturing
windborne
sediment.

Tillage:
Roughening
the
soil
can
reduce
soil
losses
by
approximately
80
percent.

Stone:
The
sizes
of
the
stone
can
affect
the
amount
of
erosion
that
will
take
place.
In
areas
of
high
wind,
small
stones
are
not
as
effective
as
a
20
cm
stone.

Spray­
on
Chemical
Soil
Treatments
(palliatives):
Effectiveness
of
polymer
stabilization
methods
ranges
from
70
percent
to
90
percent.

Limitations
In
areas
where
evaporation
rates
are
high,
water
application
to
exposed
soils
may
require
near
constant
attention.
If
water
is
applied
in
excess,
runoff
may
result
from
the
site
and
possibly
create
conditions
where
vehicles
could
track
mud
onto
public
roads.

Chemical
applications
should
be
used
sparingly
and
only
on
mineral
soils
(not
high
organic
content
soils)
because
their
misuse
can
create
additional
surface
water
pollution
from
runoff
or
contaminate
groundwater.
Chemical
applications
might
also
present
a
health
risk
if
excessive
amounts
are
used.
Development
Document
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Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
106
Maintenance
Because
dust
controls
are
dependent
on
specific
site
conditions,
including
the
weather,
inspection
and
maintenance
are
unique
for
each
site.
Generally,
however,
dust
control
measures
involving
application
of
either
water
or
chemicals
require
more
monitoring
than
structural
or
vegetative
controls
to
remain
effective.
If
structural
controls
are
used,
they
should
be
inspected
for
deterioration
on
a
regular
basis
to
ensure
they
are
still
achieving
their
intended
purpose.

Cost
Chemical
dust
control
measures
can
vary
widely
in
cost
depending
on
specific
needs
of
the
site
and
level
of
dust
control
desired.
One
manufacturer
of
a
chloride
product
estimated
a
cost
of
$1,089
per
acre
for
application
to
road
surfaces,
but
cautioned
that
cost
estimates
without
a
specific
site
evaluation
are
rather
inaccurate.

5.1.5.4.9
STORM
DRAIN
INLET
PROTECTION
Description
Storm
drain
inlet
protection
measures
are
controls
that
help
prevent
soil
and
debris
from
on­
site
erosion
from
entering
storm
drain
drop
inlets.
Typically,
these
measures
are
temporary
controls
that
are
implemented
prior
to
large­
scale
disturbance
of
the
surrounding
site.
These
controls
are
advantageous
because
their
implementation
allows
storm
drains
to
be
used
during
even
the
early
stages
of
construction
activities.
The
early
use
of
storm
drains
during
project
development
significantly
reduces
the
occurrence
of
future
erosion
problems
(Smolen
et
al.,
1988).

Three
temporary
control
measures
to
protect
storm
drain
drop
inlets
are
°
Excavation
around
the
perimeter
of
the
drop
inlet
°
Fabric
barriers
around
inlet
entrances
°
Block
and
gravel
protection
Excavation
around
a
storm
drain
inlet
creates
a
settling
pool
to
remove
sediments.
Weep
holes
protected
by
gravel
are
used
to
drain
the
shallow
pool
of
water
that
accumulates
around
the
inlet.
A
fabric
barrier
made
of
porous
material
erected
around
an
inlet
can
create
an
effective
shield
to
sediment
while
allowing
water
to
flow
into
the
storm
drain.
This
type
of
barrier
can
slow
runoff
velocity
while
catching
soil
and
other
debris
at
the
drain
inlet.
Block
and
gravel
inlet
protection
uses
standard
concrete
blocks
and
gravel
to
form
a
barrier
to
sediments
while
permitting
water
runoff
through
select
blocks
that
are
laid
sideways.
Development
Document
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Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
107
In
addition
to
the
materials
listed
above,
limited
temporary
storm
water
drop
inlet
protection
can
also
be
achieved
with
the
use
of
straw
bales
or
sandbags
to
create
barriers
to
sediment.

For
permanent
storm
drain
drop
inlet
protection
after
the
surrounding
area
has
been
stabilized,
sod
can
be
installed
as
a
barrier
to
slow
storm
water
entry
to
storm
drain
inlets
and
capture
sediments
from
erosion.
This
final
inlet
protection
measure
can
be
used
as
an
aesthetically
pleasing
way
to
slow
storm
water
velocity
near
drop
inlet
entrances
and
remove
sediments
and
other
pollutants
from
runoff.

A
new
technology
that
uses
an
insert
trap
into
the
inlet
itself
has
been
developed
(Adams
et
al.,
2000).
This
technique
showed
good
results
on
initial
tests,
trapping
more
than
50
percent
of
the
incoming
sediment
in
flows
typical
of
those
into
urban
storm
drains.
This
technique
is
being
further
developed
with
a
pending
patent
application.

Applicability
All
temporary
controls
should
have
a
drainage
area
no
greater
than
1
acre
per
inlet.
It
is
also
important
for
temporary
controls
to
be
constructed
prior
to
disturbance
of
the
surrounding
landscape.
Excavated
drop
inlet
protection
and
block
and
gravel
inlet
protection
are
applicable
to
areas
of
high
flow
where
overflow
is
anticipated
into
the
storm
drain.
Fabric
barriers
are
recommended
for
smaller,
relatively
flat
drainage
areas
(slopes
less
than
5
percent
leading
to
the
storm
drain).

Temporary
drop
inlet
control
measures
are
often
used
in
combination
with
each
other
and
with
other
storm
water
control
techniques.

Design
and
Installation
Considerations
Hydrologic
Design
Hydrologic
computations
are
not
necessary
with
present
technologies.
A
specified
limitation
of
1
acre
per
inlet
limits
flow
rates,
dependent
on
local
rainfall
and
runoff
considerations.

Installation
Criteria
and
Specifications
The
following
criteria
should
be
followed
until
future
research
establishes
better
techniques:

°
With
the
exception
of
sod
drop
inlet
protection,
these
controls
should
be
installed
before
any
soil
disturbance
in
the
drainage
area.

°
Excavation
around
drop
inlets
should
be
dug
a
minimum
of
1
foot
deep
(2
feet
maximum)
with
a
minimum
excavated
volume
of
35
cubic
yards
per
acre
disturbed.
Side
slopes
leading
to
the
inlet
should
be
no
steeper
than
2:
1.
The
shape
of
the
excavated
area
should
be
Development
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June
2002
5­
108
designed
such
that
the
dimensions
fit
the
area
from
which
storm
water
is
anticipated
to
drain.
For
example,
the
longest
side
of
an
excavated
area
should
be
along
the
side
of
the
inlet
expected
to
drain
the
largest
area.

°
Fabric
inlet
protection
is
essentially
a
filter
fence
placed
around
the
inlet.
The
fabric
asures
should
not
be
used
as
stand­
alone
sediment
control
measures.
To
increase
inlet
protection
effectiveness,
these
practices
should
be
used
in
combination
with
other
measures,
such
as
small
impoundments
or
sediment
traps
(USEPA,
1992).
Temporary
storm
drain
inlet
protection
is
not
intended
for
use
in
drainage
areas
larger
than
1
acre.
Generally,
storm
water
inlet
protection
measures
are
practical
for
relatively
low
sediment
and
low
volume
flows.

Frequent
maintenance
of
storm
drain
controls
is
necessary
to
prevent
clogging.
If
sediment
and
other
debris
clog
the
water
intake,
drop
intake
control
measures
can
actually
cause
erosion
in
unprotected
areas.

Maintenance
All
temporary
control
measures
must
be
checked
after
each
storm
event.
To
maintain
the
sediment
capacity
of
the
shallow
settling
pools
created
from
these
techniques,
accumulated
sediment
should
be
removed
from
the
area
around
the
drop
inlet
(excavated
area,
around
fabric
barrier,
or
around
block
structure)
when
the
sediment
storage
is
reduced
by
approximately
50
percent.
Additional
debris
should
be
removed
from
the
shallow
pools
on
a
periodic
basis.

Weep
holes
in
excavated
areas
around
inlets
can
become
clogged
and
prevent
water
from
draining
from
the
shallow
pools
that
form.
Should
this
happen,
unclogging
the
water
intake
may
be
difficult
and
costly.

Cost
The
cost
of
implementing
storm
drain
drop
inlet
protection
measures
will
vary
depending
on
the
control
measure
chosen.
Generally,
initial
installation
costs
range
from
$50
to
$150
per
inlet,
with
an
average
cost
of
$100
(USEPA,
1993).
Maintenance
costs
can
be
high
(annually,
up
to
100
percent
of
the
initial
construction
cost)
because
of
frequent
inspection
and
repair
needs.
The
Southeastern
Wisconsin
Regional
Planning
Commission
has
estimated
that
the
cost
of
installation
of
inlet
protection
devices
ranges
from
$106
to
$154
per
inlet
(SEWRPC,
1991).

5.1.5.4.10
POLYACRYLAMIDE
(PAM)

General
Description
The
term
polyacrylamide
(PAM)
is
a
generic
term
that
refers
to
a
broad
class
of
compounds.
There
are
hundreds
of
specific
PAM
formulations,
and
all
have
unique
properties
that
depend
on
polymer
chain
length
and
number
and
kinds
of
functional
group
substitutions
along
the
chain.
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2002
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PAMs
are
classified
according
to
their
molecular
weight
and
ionic
charge
and
are
available
in
solid,
granular,
liquid,
or
emulsion
forms.

PAM's
effectiveness
to
prevent
or
reduce
erosion
is
due
to
its
affinity
for
soil
particles,
largely
via
coulombic
and
Van
der
Waals
attraction.
These
surface
attractions
enhance
particle
cohesion,
stabilizing
soil
structure
against
shear­
induced
detachment
and
transport
in
runoff.
In
a
soil
application,
PAM
aggregates
soil
particles,
increasing
pore
space
and
infiltration
capacity,
resulting
in
reduced
runoff.
These
larger
particle
aggregates
are
less
susceptible
to
raindrop
and
scour
erosion,
thus
reducing
the
potential
to
mobilize
sediments.

Applicability
Because
of
ease
in
application,
PAM
is
well
suited
as
a
short­
term
erosion
prevention
BMP,
especially
for
areas
with
limited
access
or
steep
slopes
that
hinder
personnel
from
applying
other
cover
materials.
PAM
can
be
used
to
augment
other
cover
practice
BMPs,
though
it
can
be
effective
when
applied
alone.
Thus,
the
ease
of
application,
low
maintenance,
and
relatively
low
cost
associated
with
PAM
make
it
a
practical
solution
to
soil
stabilization
during
construction.

Application
Criteria
PAM
can
be
applied
to
soil
through
either
a
dry
granular
powder
or
a
liquid
spray
form.
Optimal
application
rates
to
prevent
erosion
on
construction
sites
are
generally
less
than
1
kg/
ha
(about
1
lb/
ac)
(Tobiason
et
al.,
2000).
However,
the
concentration
required
can
vary
for
specific
soil
properties
and
construction
phases.
WDOT
(2002)
suggests
a
dosage
of
60
mg/
L
for
roadway
erosion
and
sediment
control.
This
is
higher
than
the
rate
recommended
by
the
University
of
Nebraska
for
an
agricultural
application
(10
parts
per
million).
To
put
this
into
context,
one
half
pound
of
PAM
in1000
gallons
of
water
results
in
a
PAM
concentration
of
60
mg/
L,
which
treats
1
acre
of
exposed
soil
to
WDOT
recommendations.

Effectiveness
A
study
performed
in
Dane
County,
Wisconsin,
analyzed
15
small
plots
(1
meter
x
1
meter)
for
runoff
and
sediment
yield
on
a
construction
site.
The
study
concluded
that
when
a
solution
of
PAM­
mix
with
mulch/
seeding
was
applied
to
dry
soil
and
compared
with
the
control
(no
PAMmix
application
to
dry
soil),
an
average
reduction
of
93
percent
in
sediment
yield
was
found.
An
average
reduction
of
77
percent
in
sediment
yield
was
the
worst
performing
PAM
treatment
and
occurred
when
PAM­
mix
in
solution
was
applied
to
moist
soil.
The
application
of
dry
PAM­
mix
to
dry
soil
reduced
sediment
by
83
percent
and
decreased
runoff
by
16
percent
when
compared
to
the
control.
The
results
show
that
regardless
of
the
application
method,
PAM­
mix
was
effective
in
reducing
sediment
yield
in
the
test
plots
(Roa­
Espinosa
et
al.,
2000).
Development
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2002
5­
110
A
second
study
performed
in
Washington
analyzed
the
runoff
from
three
different
construction
sites:
an
erosion
control
test
facility,
a
highway
construction
site,
and
an
airport
runway.
Table
5­
24
summarizes
the
225
samples
analyzed
in
Tobiason
et
al.
(2000).

Table
5­
24.
Turbidity
Reduction
Values
from
PAM
Volume,
m
3
Turbidity
Reduction
(%)
Maximum
350
99.97
Median
285
97.6
Minimum
133
46
Limitations
Currently
PAMs
are
most
commonly
produced
as
dry
granules.
They
completely
dissolve
and
remain
dissolved
if
mixed
properly.
If
added
too
quickly
or
if
not
stirred
vigorously
the
granules
rapidly
form
nondissolvable
gels
on
contact
with
water
or
collect
in
low
turbulence
areas
as
syrupy
concentrations
that
dissolve
slowly
in
an
uncontrolled
pattern
over
a
period
of
hours
or
days
(USDA,
1994).

In
addition,
when
spilled
on
hard
surfaces,
PAM
solutions
are
extremely
slippery
and
hazardous
to
foot
and
vehicle
traffic.
PAM
dust
is
highly
hygroscopic
and,
if
inhaled,
could
impair
breathing.
Certain
neutral
and
cationic
PAMs
at
very
high
exposure
levels
produce
irritation
in
humans
and
are
somewhat
toxic
to
certain
aquatic
organisms;
therefore,
PAM
should
be
used
in
strict
compliance
with
state
and
federal
label
requirements.

Finally,
although
PAM
is
rather
inexpensive,
there
are
considerable
infrastructure
needs
and
operating
costs;
thus,
sophisticated
onsite
polymer
treatment
systems
may
not
be
appropriate
for
certain
projects.

Cost
The
cost
of
PAM
ranges
from
$1.25
per
pound
to
$5.00
per
pound
(Entry
et
al.,
1999).
The
cost
of
PAM
application
depends
on
the
system
employed.
PAM
can
be
used
in
a
centralized
treatment
system
(e.
g.,
at
a
sedimentation
basin)
to
treat
larger
areas,
or
dispersed
in
granular
or
liquid
form.
In
Tobiason
et
al.
(2000),
the
startup
costs
for
the
batch
treatment
system
amounted
to
$90,000.
Monthly
expenses
averaged
$18,000
for
operations
and
maintenance
and
$13,000
for
materials
and
equipment.
The
total
costs
for
this
phase
totaled
about
$245,000,
less
than
1
percent
of
total
construction
costs.
If
dispersed
through
irrigation
systems
(for
agriculture),
the
seasonal
cost
of
PAM
treatment
is
$9
to
$15
per
acre
(Kay­
Shoemake,
et.
al.,
2000),
where
a
season
probably
requires
between
5
and
10
applications.

For
construction
sites,
it
is
more
likely
that
PAM
would
be
applied
as
an
additive
to
the
hydroseed
mix
and
applied
when
final
grade
is
established
and
cover
vegetation
is
installed.
Development
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for
Construction
and
Development
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Effluent
Guidelines
June
2002
5­
111
Based
on
a
recent
scan
of
the
Internet,
there
are
numerous
suppliers
who
provide
PAM
as
a
low
cost
additive
for
hydroseeding,
suggesting
PAM
application
costs
can
be
incorporated
into
that
of
hydroseeding
($
540
to
$700
per
acre
depending
on
which
seed
is
applied).
An
additional
cost
would
be
incurred
to
sample
site
soils
to
customize
the
dosage
and
delivery
mechanisms
for
individual
sites.
In
addition,
re­
application
of
PAM
in
granular
or
liquid
form
to
areas
with
rill
development
(poor
vegetation
cover)
would
require
additional
funds.
Where
re­
application
of
granular
PAM
is
used,
R.
S.
Means
(2000)
suggests
a
cost
of
approximately
$5
per
1000
square
feet
for
spreading
soil
admixtures
by
hand.
Development
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June
2002
5­
112
5.1.6
SUMMARY
The
BMP
information
presented
in
sub­
section
5.1
is
summarized
in
Tables
5­
25
through
5­
28.

Table
5­
25.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.1)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
Planning/
Staging/
Scheduling
Could
be
low
cost.
One
data
set
shows
42%
reduction
in
sediment
yield
due
to
planning/
staging/
scheduling.
Requires
additional
advance
planning
and
management.
Impact
could
be
evaluated
with
models
as
well
as
experimentally
since
several
computer
models
are
available.
Could
be
low
cost.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.

Vegetative
Stabilization
Could
be
low
cost
Can
be
very
effective
in
some
cases
with
advance
planning.
Can
be
important
on
streambanks.
Limited
applicability
in
the
active
construction
area.
Complements
other
practices.
Practice
is
seasonably
dependent
in
most
of
nation.
Impact
could
be
evaluated
with
models
as
well
as
experimentally
since
several
computer
models
are
available.
Could
be
low
cost.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.

Grass
Lined
Channels
Long
history
of
use
in
channels
draining
disturbed
areas.
Well
established
procedures
for
design
and
extensive
database
on
stable
designs
under
widely
varied
conditions.
Some
procedures
are
available,
with
limited
validation,
to
obtain
a
first
estimate
of
sediment
trapping
by
grasslined
channels.
Limited
database
on
trapping
of
sediment.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
good
cause­
effect
relationships
available.
Database
shows
wide
variations
in
effectiveness
in
trapping
chemicals.
Other
impacts
not
evaluated.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
Table
5­
25.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.1)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
June
2002
5­
113
Seeding
Low­
cost
method
for
establishing
vegetation.
Occurs
near
the
end
of
active
construction.
Requires
significant
time
for
establishment.
Need
a
prepared
seedbed.
Good
database
on
impact
on
soil
erosion.
Should
be
supported
by
other
BMPs.
Should
not
be
evaluated
as
standalone
practice,
but
as
part
of
a
system.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.

Sodding
High­
cost
method
of
establishing
vegetation.
Immediate
stabilization.
Requires
significant
management
attention
during
establishment.
Good
database
on
impact
on
soil
erosion.
Very
effective
way
of
controlling
erosion.
Works
well
for
grass
waterways
and
other
significant
problems
area.
Should
be
supported
by
other
BMPs.
Should
not
be
evaluated
as
standalone
practice,
but
as
part
of
a
system.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.

Mulching
Relatively
low­
cost
method
of
providing
cover.
Can
be
highly
effective
in
reducing
soil
loss
when
properly
anchored.
Good
database
on
impact
on
soil
erosion.
Variety
of
materials
can
be
used.
Installation
is
rapid.
Not
a
stand­
alone
practice.
Due
to
interference
with
construction
operations,
the
times
that
it
can
be
used
during
active
construction
are
limited.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
Table
5­
25.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.1)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
June
2002
5­
114
Erosion
Control
Matting
/Geotextiles
Cost
is
highly
variable.
Effectiveness
in
controlling
sediment
is
variable
depending
on
type
material.
Can
provide
immediate
protection
to
exposed
soils.
Not
a
stand­
alone
practice.
Due
to
interference
with
construction
operations,
the
times
that
it
can
be
used
during
active
construction
are
limited.
Disposal
is
a
significant
problem
and
may
require
landfilling.
Can
be
used
for
channel
linings
as
stand
alone
or
under
riprap.
Fair
database
on
effectiveness
in
preventing
erosion.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.

Vegetative
Buffer
Strips
Can
be
highly
effective
in
trapping
sediment.
Effectiveness
is
well
established
and
considerable
data
collected.
Well­
validated
models
are
available
to
predict
the
impacts
of
constructed
filter
strips
on
sediment
trapping.
Models
are
included
in
watershed
stormwater
and
sediment
models.
Modifications
needed
for
natural
riparian
zones.
Require
routine
maintenance.
May
be
most
appropriate
where
sediment
loads
are
relatively
low.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
Table
5­
25.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.1)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
June
2002
5­
115
Topsoiling
Important
in
vegetative
establishment.
No
protection
until
cover
is
established.
Not
a
stand­
alone
practice,
but
must
be
supported
by
other
BMPs.
No
known
information
to
describe
effectiveness
and
cost
not
currently
available.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
116
Table
5­
26.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.2)

BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
Earth
Dike
°
Used
to
protect
down
slope
areas.
°
Should
be
stabilized
prior
to
use.
°
Requires
maintenance
after
every
major
storm.
°
Can
be
significant
source
of
sediment
if
not
properly
constructed.
°
Little
data
available
on
its
effectiveness
as
a
BMP.
°
Can
be
relatively
inexpensive,
depending
on
design.
°
Not
a
stand­
alone
procedure.
No
known
information
available.
No
known
information
available.

Temporary
Swale
°
Effectively
a
grass­
lined
drainage
ditch
with
shallow
side
slopes.
°
Can
be
applied
in
many
areas,
but
use
limited
in
arid
areas.
°
Contaminants
that
will
harm
vegetation,
such
as
oils
and
greases,
cannot
be
discharged
to
the
system.
°
Continuous
water
flow
cannot
be
tolerated
by
the
grass
lining.
°
Effectiveness
depends
on
infiltration.
Can
be
a
problem
of
groundwater
pollution
with
high
water
tables.
°
Some
studies
show
that
they
export
bacteria.
°
Some
studies
show
high
removal
efficiency
for
TSS,
fair
for
nutrients,
are
variable
for
metals.
°
No
general
relationships
available
to
predict
the
impact
under
widely
varied
climates
and
conditions,
hence
the
effectiveness
cannot
be
predicted
for
a
given
situation
beyond
the
limited
database.
No
known
information
available.
No
known
information
available.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
Table
5­
26.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.2)

BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
June
2002
5­
117
Temporary
Storm
Drain
Diversion
(Pipe)
°
Reroutes
existing
drainage
systems.
Primary
benefit
is
to
separate
drainage
water
originating
from
undisturbed
and
construction
and
reduce
the
volume
of
water
to
be
treated.
°
Can
be
combined
with
other
structures,
such
as
sediment
traps,
and
used
for
sediment
trapping.
°
Require
little
maintenance.
°
Requires
outlet
stabilization.
Can
be
a
significant
source
of
sediment
without
outlet
stabilization.
°
Can
be
costly,
depending
on
size,
installation,
and
removal.
No
known
information
available.
No
known
information
available.

Pipe
Slope
Drain
°
Routes
runoff
from
concentrated
flow
to
stabilized
areas.
°
Can
be
very
effective
in
eliminating
gully
erosion
problems,
if
properly
installed
and
maintained.
°
Can
be
constructed
from
low­
cost
corrugated
PVC,
but
must
be
anchored
or
buried
along
slope.
°
Needs
to
be
checked
frequently
for
sedimentation
and
other
maintenance
problems.
No
known
information
available.
No
known
information
available.

Stone
Check
Dams
°
Reduces
velocity
of
flow
and
prevents
erosion.
°
Stabilizes
channel
slope
on
steep
sections
by
stairstepping.
°
Can
trap
small
percentages
of
sediment
behind
dam.
°
Used
for
short
periods
of
time
where
channel
lining
is
impractical.
°
Limited
lab
studies
show
high
effectiveness,
but
very
limited
field
studies
show
low
trapping
efficiency.
°
Must
be
installed
such
that
overtopping
occurs
over
the
rock
fill
and
not
around
the
perimeter.
°
Should
not
be
used
in
continuously
flowing
streams.
°
Relatively
expensive,
if
properly
installed.
°
Procedures
for
predicting
impact
of
properly
installed
stone
check
dams
are
available
and
incorporated
into
watershed
computer
models.
No
known
information
available.
No
known
information
available.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
Table
5­
26.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.2)

BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
June
2002
5­
118
Lined
Waterways
°
Designed
for
stability
and
capacity.
°
Local
rainfall­
runoff
conditions
and
linings
will
influence
channel
dimensions.
°
Require
some
maintenance
during
vegetative
establishment.
°
Not
designed
as
sediment
removal
device,
but
to
prevent
channel
erosion.
No
known
information
available.
No
known
information
available.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
119
Table
5­
27.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.3)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
Silt
Fence
Most
widely
recognized
sediment
control
BMP.
Frequently
poorly
installed
with
little
design
consideration.
Maintenance
is
frequently
poor,
resulting
in
frequent
failure.
Frequent
maintenance
is
required
for
proper
operation.
Laboratory
studies
show
fair
to
good
sediment
trapping
by
filter
fence,
but
limited
field
studies
do
not
show
the
same
results.
Evaluations
of
installations
show
that
failure
is
frequent,
coming
from
undercutting
of
the
fabric
and
subsequent
gully
erosion.
Should
not
be
installed
where
rocks
and
other
hard
surfaces
prevent
anchoring.
No
validated
procedures
are
available
to
predict
the
effectiveness
of
the
filter
fence
in
trapping
sediment,
primarily
because
of
the
lack
of
validated
relationships
for
predicting
flow
through
the
filter
fence.
Procedures
for
evaluating
the
anchoring
requirements
and
support
post
requirements
have
not
adequately
accounted
for
variable
soil
strength
conditions,
resulting
in
frequent
failure
of
the
fence
under
loading.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.

Super
Silt
fence
Modification
of
standard
silt­
fence
to
improve
it
structurally.
No
validation
information
is
available.
Recommended
to
be
used
where
destruction
of
the
silt
fence
will
destroy
critical
areas.
More
expensive
than
standard
silt
fence.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
Table
5­
27.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.3)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
June
2002
5­
120
Straw
Bale
Dike
Works
by
impounding
water.
Primary
trapping
mechanism
is
by
settling
behind
straw
bale
dike.
Information
on
performance
is
very
limited
with
much
variation
in
the
limited
data.
Should
not
be
used
in
waterways
or
as
a
perimeter
control
due
to
biodegradation.
Idealized
models
of
performance
are
available
for
systems
that
are
properly
installed.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology
No
good
cause­
effect
relationships
available.
Other
impacts
not
evaluated.

Sediment
Traps
Formed
by
excavation
and/
or
embankment.
Can
simplify
stormwater
control
by
trapping
sediment
at
specific
spots.
Can
be
installed
quickly
and
serve
as
short­
term
solution
to
sediment
trapping
in
small
areas.
May
require
cleanout.
Detailed
models
as
well
as
simplified
design
aids
are
available
to
predict
performance
in
trapping
sediment.
Data
on
performance
are
available
from
both
laboratory
studies
and
field
studies.
Will
likely
control
only
the
settleable
solids
unless
enhanced
settling
is
developed
with
chemical
flocculation.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
Data
for
trapping
nutrients
are
available,
but
show
wide
variation.
General
models
of
nutrient
trapping
are
not
available.
Other
impacts
not
evaluated.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
Table
5­
27.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.3)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
June
2002
5­
121
Sediment
Basins
Normally
formed
by
construction
of
a
dam.
Stormwater
detention
basin
may
serve
as
sediment
basin
during
construction.
Can
be
used
for
any
size
watershed.
May
require
cleanout.
Data
on
performance
are
available
both
from
laboratory
studies
and
field
studies.
Will
likely
control
only
the
settleable
solids
unless
enhanced
settling
is
developed
with
chemical
flocculation.
Most
reliable
and
stable
structure
for
obtaining
high
sediment
trapping
efficiency
under
widely
varying
conditions.
Must
consider
dam
safety
issues
since
dam
failure
is
a
reasonable
possibility.
Structures
are
relatively
large
and
can
be
expensive.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
Data
for
trapping
nutrients
are
available,
but
show
wide
variation.
General
models
of
nutrient
trapping
are
not
available.
Other
impacts
not
evaluated.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
5­
122
Table
5­
28.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.4)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
Stone
Outlet
Structures
Porous
outlet
structure
constructed
of
dumped
rock,
used
as
the
outlet
for
earth
dikes.
Requires
a
stabilized
outlet
channel
until
the
flow
reaches
a
stable
channel.
Data
on
the
effectiveness
are
limited
to
visual
observations
of
field
installations
where
failure
was
frequent
due
to
poor
installation.
Models
are
available
to
predict
the
performance
of
stone
outlets,
but
field
data
have
not
been
collected
to
evaluate
the
accuracy
of
the
model.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
General
models
of
nutrient
trapping
are
not
available.
Other
impacts
not
evaluated.

Rock
Outlet
Protection
Used
to
reduce
velocity
of
flow
in
receiving
channel
and
prevent
scouring.
Very
effective
when
properly
installed.
Design
procedures
are
well
established.
Maintenance
is
low,
if
properly
installed.
Should
be
inspected
after
high
flows.
No
data
on
impact.
No
data
available.
No
data
available.

Sump
Pit
Used
to
dewater
during
excavation.
Effectiveness
not
evaluated.
Potential
exists
to
theoretically
evaluate
the
BMP's
effectiveness
in
trapping
sediment.
Could
be
used
at
times
other
than
storm
flow,
such
as
removal
of
groundwater
flow.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
data
available.

Storm
Drain
Inlet
Protection
Used
to
trap
sediment
that
would
otherwise
flow
into
storm
drain
inlet.
Should
be
installed
prior
to
land
disturbance.
Effectiveness
in
removing
sediment
has
not
been
evaluated,
but
is
thought
to
be
low
during
construction.
Potential
exists
to
use
computer
models
to
evaluate
effectiveness.
Cost
can
be
high
for
maintenance
requirements.
Should
not
be
used
as
stand­
alone
sediment
control.
Database
is
poor.
No
validated
urban
runoff
models
available
for
theoretical
analysis
of
downstream
impacts.
Some
potential
exists
to
modify
existing
models
to
make
the
analysis
of
downstream
impacts
on
geomorphology.
No
data
available.

Sediment
Tank
Portable
sediment
trap.
Flows
are
pumped
in
and
out
of
the
tank.
Used
where
spaced
is
limited
No
effectiveness
data
are
available.
Expected
to
be
relatively
expensive.
No
data
available.
No
data
available.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
Table
5­
28.
Summary
of
Information
on
Erosion
Control
and
Prevention
BMPs
(Sub­
section
5.1.5.4)
BMP
Type
Physical
Impact
Mitigation
Other
Impacts
Receiving
Water
Quality
Downstream
Impacts
June
2002
5­
123
Stabilized
Construction
Entrance
Used
to
minimize
mud
and
sediment
attached
to
motorized
vehicles.
Consists
of
an
area
that
is
covered
with
rocks
over
which
all
vehicles
must
drive.
Can
be
combined
with
a
wash
station.
Effective
only
if
all
entrances
are
maintained.
Relatively
expensive.
Will
not
remove
highly
cohesive
clays.
No
data
available.
No
data
available.

Stabilizes
slopes
and
decreases
runoff
velocity.
Can
be
incorporated
into
low­
impact
development
plans.
Not
effective
when
drainage
patterns
are
altered.
Not
effective
when
vegetative
areas
on
perimeter
are
destroyed.
Practiced
at
virtually
all
construction
sites.
No
data
available
on
BMP
effectiveness.
No
data
available.
No
data
available.

Temp
Access
Waterways
Crossing
Reduces
risk
to
damaging
streambed
from
construction
equipment
tracking.
Can
be
a
bridge,
culvert,
or
ford.
Bridges
and
culverts
preferred,
but
more
expensive.
Data
on
effectiveness
in
reducing
sediment
are
not
available.
No
data
available.
No
data
available.

Dust
Control
Important
in
arid
and
semi­
arid
regions.
Applicable
to
any
construction
site.
Construction
and
sequencing
and
limiting
exposure
area
can
reduce
problems.
Spray­
on
adhesives
are
recommended.
Water
application
may
require
near
constant
attention.
Excess
water
may
cause
runoff
or
tracking
of
mud.
Very
limited
effectiveness
information
available.
Costs
can
vary
widely,
depending
on
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No
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Development
Document
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http://
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stormwatercenter.
net
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
1
SECTION
6:
REGULATORY
DEVELOPMENT
AND
RATIONALE
In
this
section,
the
methodology
used
by
EPA
to
develop
regulatory
options
for
the
construction
and
land
development
industry
is
described.
EPA
methodology
first
evaluated
the
pollutants
discharged
from
the
industry
and
evaluated
existing
Federal,
State
and
local
control
strategies
designed
to
manage
impacts.
Based
on
this
analysis,
EPA
was
able
to
identify
several
key
components
of
existing
regulatory
strategies
that
would
be
applicable
for
national
effluent
guidelines
regulations
and
develop
regulatory
options
around
these
existing
strategies.
Following
development
of
regulatory
options,
EPA
evaluated
the
costs
and
environmental
benefits
of
several
options
and
determined
the
appropriate
option
for
proposal
based
on
factors
such
as
total
costs,
monetized
and
non­
monetized
environmental
benefits,
ease
of
implementation,
industry
financial
impacts,
and
industry
acceptance.
The
following
sections
describe
the
components
of
this
process
involving
identification
of
impacts,
evaluation
of
available
control
strategies,
and
formulation
of
regulatory
options.
Costs
of
regulatory
options
are
discussed
in
Section
7
of
this
document
while
a
description
of
the
environmental
benefits
estimation
and
industry
financial
analyses
can
be
found
in
the
other
supporting
documents
of
this
regulation
(USEPA,
2002
and
2002a).

6.1
IDENTIFICATION
OF
INDUSTRY
IMPACTS
In
developing
effluent
guidelines
for
controlling
storm
water
discharges
associated
with
construction
and
land
development
activities,
EPA
identified
pollutants
that
are
attributable
to
the
industry.
In
addition
to
pollutants
discharged
from
construction
sites
and
from
long­
term
storm
water
discharges,
EPA
also
looked
at
the
broader
range
of
environmental
impacts
that
the
land
development
process
influences
and
that
could
potentially
be
addressed
under
effluent
guidelines
regulations.
These
categories
include
physical
impacts
to
receiving
streams
due
to
the
increased
frequency
of
high
flow
rates
and
associated
discharge
of
sediment,
as
well
as
thermal
impacts
to
receiving
waters
due
to
the
increased
temperature
of
storm
water
discharges.

These
analyses
helped
EPA
to
develop
regulatory
options
and
associated
estimates
of
costs
and
benefits
for
temporary
erosion
and
sediment
controls.
This
approach
allowed
for
the
evaluation
of
different
combinations
of
regulatory
options
when
developing
an
overall
regulatory
strategy
for
this
industry,
with
different
combinations
addressing
various
impact
areas.

6.1.1
Pollutant
Indicators
When
determining
which
pollutants
to
assess,
EPA
applied
the
following
priorities
for
construction
storm
water
discharges:

°
Focus
on
pollutants
directly
attributable
to
the
industry,
using
indicator
pollutants
where
necessary;
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
2
°
Focus
on
pollutants
most
commonly
encountered
under
most
settings,
(i.
e.,
not
to
preconstruction
site
contamination
issues
or
accidental
discharges);
°
Focus
on
pollutants
that
are
most
manageable
given
the
current
suite
of
available
technologies;
and
°
Focus
on
pollutants
that
can
be
addressed
under
the
authority
of
effluent
guidelines.

EPA
conducted
an
extensive
evaluation
of
the
literature
to
identify
pollutants
present
in
storm
water
discharges
from
construction
and
land
development
sites.
While
the
literature
contains
extensive
information
on
pollutants
present
in
storm
water
discharges
from
urban
areas,
there
were
little
data
available
on
pollutants
present
in
storm
water
discharges
from
construction
sites
during
the
active
construction
phase
other
than
for
sediment,
TSS
and
turbidity.
This
is
not
surprising,
since
construction
site
storm
water
management
is
primarily
concerned
with
the
control
of
solids
from
exposed
soil
areas.
There
is
the
potential
for
other
pollutants
to
be
discharged
from
construction
sites
depending
on
factors
such
as
prior
land
uses.
For
example,
if
the
prior
land
use
was
agriculture,
there
is
the
potential
for
discharge
of
pollutants
such
as
nutrients
and
pesticides.
Likewise,
areas
of
redevelopment
that
occur
on
sites
where
previous
land
uses
included
industry
could
discharge
pollutants
such
as
organics
and
metals.
In
addition,
pollutants
such
as
metals
and
nutrients
can
be
present
in
native
site
soils,
and
could
be
discharged
from
construction
sites.
However,
EPA
was
not
able
to
identify
sufficient
data
in
the
literature
to
warrant
development
of
controls
specific
to
pollutants
other
than
sediment,
TSS
and
turbidity
in
storm
water
discharges
from
construction
sites.
Some
literature
suggests
that
pollutants
adhere
to
sediment
so
regulating
TSS
should
also
act
as
a
control
for
other
pollutants.

There
are
extensive
data
in
the
literature
describing
pollutants
present
in
storm
water
discharges
from
urban
areas.
The
most
comprehensive
evaluation
of
urban
storm
water
was
the
Nationwide
Urban
Runoff
Program
(NURP)
(USEPA,
1983).
While
somewhat
dated,
the
NURP
results
are
still
valid,
and
serve
as
a
primary
means
of
characterizing
urban
runoff
pollutants.
In
addition
to
NURP,
a
variety
of
other
analyses
conducted
over
the
past
20
years
have
contributed
greatly
to
the
understanding
of
pollutants
present
in
urban
storm
water
runoff.
Literally
thousands
of
references
can
be
found
in
the
literature
summarizing
hundreds
of
studies
evaluating
urban
runoff
pollutant
levels.
As
a
result,
there
are
sufficient
data
available
to
identify
the
major
pollutants
expected
to
be
discharged
from
new
land
development
activities.
Based
on
these
data
sources,
EPA
identified
sediments
(measured
as
TSS),
nutrients
and
metals
as
pollutants
of
concern
for
this
industry.
EPA
also
evaluated
the
inclusion
of
organics,
pesticides,
and
bacteria
as
potential
pollutants
of
concern,
but
the
literature
indicates
that
control
of
these
pollutants
through
conventional
storm
water
management
strategies
is
potentially
much
more
difficult,
and
that
there
are
little
data
linking
their
presence
in
storm
water
discharges
directly
with
new
land
development
activities.
Source
control
may
factor
greatly
into
controlling
these
pollutant
sources.

Although
EPA
identified
a
number
of
pollutants
of
concern
for
this
industry,
EPA
did
not
develop
regulatory
options
specifically
targeted
at
controlling
each
of
these
individual
pollutants.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
1
Not
all
pollutant
indicators
listed
above
are
directly
used
by
EPA
in
its
benefits
assessment,
or
in
developing
the
C&
D
effluent
guidelines.
Nevertheless,
EPA
has
collected
data
to
estimate
all
of
the
measures
for
potential
future
consideration
of
this
and
other
industries/
activities.

June
2002
6­
3
Instead,
EPA
chose
to
develop
regulatory
options
using
an
indicator
pollutant,
TSS.
While
TSS
levels
may
not
be
directly
correlated
with
all
pollutants
of
concern,
it
is
certainly
the
most
widely
reported
parameter
in
the
literature
due
to
its
relative
ease
of
collection
and
low
cost.
In
addition,
design
of
management
systems
for
the
control
of
TSS
will
likely
result
in
control
of
pollutants
such
as
sediment,
nutrients
and
metals
that
are
present
in
the
solid­
phase
(attached
to
sediments).
The
one
pollutant
of
concern
that
may
not
have
a
strong
correlation
with
TSS
is
turbidity,
since
particles
that
contribute
to
turbidity
may
not
be
removed
through
conventional
storm
water
management
practices
that
control
TSS.
Particles
that
contribute
to
turbidity
may
be
of
such
a
fine
grain
that
they
will
not
be
removed
by
the
mechanisms
whereby
most
BMPs
operate,
mainly
settling
and
filtration.

EPA's
assessment
of
pollutant
loadings
for
the
industry
was
based
on
mathematical
models.
These
models
were
developed
using
analyses
prepared
by
EPA
for
the
NPDES
Phase
II
rulemaking
(USEPA,
1999),
established
hydrologic
principles
and
storm
water
monitoring
data
from
the
literature.
EPA
estimated
annual
loadings
with
and
without
effluent
guidelines
from
construction
site
storm
water
discharges
using
225
site
models
which
varied
based
on
location,
site
size
and
site
slope.
In
its
assessment
of
the
industry,
EPA
elected
to
use
the
estimated
land
area
constructed
annually
in
the
nation
for
the
contiguous
states,
based
on
the
National
Resources
Inventory
(NRI)(
USDA,
2000).
EPA
did
not
develop
estimates
of
pollutant
loadings
for
Alaska,
Hawaii,
and
the
U.
S.
territories,
due
to
a
several
factors,
such
as
a
lack
of
rainfall
data
and
lack
of
data
on
annual
land
development.
However,
due
to
the
small
amount
of
development
that
occurs
in
these
areas,
the
omission
of
these
areas
from
the
analysis
is
not
expected
to
contribute
a
significant
error
to
EPA's
national
estimates.

In
developing
pollutant
loadings
of
the
land
development
industries,
a
distinction
was
made
between
primary
pollutant
loadings
(e.
g.,
discharge
of
sediments
from
disturbed
ground
surfaces)
and
secondary
pollutant
loadings
(e.
g.,
loadings
resulting
from
accelerated
erosion
of
streams
caused
by
increased
high
flows
from
urbanized
land
uses).
This
distinction
was
made
because
studies
focusing
on
the
impacts
of
land
development
have
sometimes
neglected
the
secondary
pollutant
loadings
that
result
when
changes
to
hydrology
cause
downstream
channels
to
become
unstable.
The
secondary
pollutant
loadings
that
occur
year
after
year
from
increased
stream
flows
have
not
been
well
inventoried.
1
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
2
Not
all
physical/
habitat
measures
listed
above
are
directly
used
by
EPA
in
its
benefits
assessment,
or
in
developing
the
C&
D
effluent
guidelines.
Nevertheless,
EPA
has
collected
data
to
estimate
all
of
the
measures
for
potential
future
consideration
of
this
and
other
industries/
activities.

June
2002
6­
4
6.1.2
Physical/
Habitat
Indicators
In
addition
to
assessing
impacts
of
the
construction
and
land
development
industry
due
to
discharge
of
pollutants
in
storm
water,
EPA
also
developed
a
methodology
for
assessing
the
physical
and
habitat
impacts
caused
by
changes
in
hydrology
and
stream
flow.
Land
development
activities
cause
significant
alterations
in
the
natural
hydrologic
regime
of
developing
watersheds.
The
removal
of
vegetation,
the
compaction
of
soils
by
construction
equipment
and
the
construction
of
impervious
surfaces
such
as
roads,
driveways
and
buildings
causes
a
marked
increase
in
the
total
volume
and
peak
flow
rate
of
storm
water
discharges
as
compared
to
forested,
open
and
agricultural
land
uses.
As
a
result,
streams
receiving
storm
water
discharges
will
frequently
undergo
significant
channel
alterations
in
order
to
adjust
to
the
altered
hydrologic
regime.
This
alteration
results
in
mobilization
of
high
quantities
of
sediment
and
associated
water
quality
problems.

EPA's
assessment
attempted
to
develop
an
impacts
time
line,
predicting
when
certain
impacts
will
occur.
Due
to
its
relatively
short
duration,
construction
impacts
(or
benefits)
were
assumed
to
occur
within
a
single
year.
The
assessment
of
long­
term
impacts
was
based
on
the
30
year
period
immediately
following
conversion
into
urban
land
use.
This
includes
characterization
of
physical/
habitat
impacts
related
to
hydrologic
changes
(e.
g.,
increased
flooding
and
stream
erosion)
and
changes
in
runoff
characteristics
(e.
g.,
runoff
thermal
signature).
In
its
modeling
effort,
EPA
made
assumptions
that
simplify
(spatial
and
temporally)
land
development,
compressing
the
period
required
for
land
to
reach
"build­
out."
EPA
performed
sensitivity
evaluations
to
verify
that
these
simplifications
do
not
distort
or
abrogate
its
assessment
of
potential
environmental
impacts.

Physical/
Habitat
Measures
Estimated
by
EPA
2
include:

°
Miles
of
stream
urbanized
(located
within
the
area
urbanized
nationally
in
a
single
year)
°
Number
of
new
stream
crossings
expected
to
become
fish
migration
barriers
°
Acres
of
stream
habitat
lost
to
new
stream
crossings
°
Acres
of
stream­
side
area
flooded
by
the
100­
year
rainfall
event
°
Tons
of
stream
bank/
bed
sediment
removed
as
a
result
of
increased
high
flow
rate
frequency
A
detailed
discussion
of
EPA's
environmental
assessment
methodology
and
results
is
presented
in
other
supporting
documents
of
this
rule
(USEPA,
2002
and
2002a).
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
5
6.2
DEVELOPMENT
OF
REGULATORY
OPTIONS
In
developing
effluent
guidelines
for
the
construction
and
development
industries,
EPA
evaluated
a
variety
of
state
and
local
programs
to
identify
various
management
strategies
and
regulatory
components
that
would
be
applicable
on
a
national
basis.
For
erosion
and
sediment
control
and
other
temporary
BMPs,
EPA
considered
a
series
of
regulatory
options.
These
options
are
designed
to
control
the
discharge
of
sediment,
storm
water
and
other
pollutants
from
sites
when
construction
is
taking
place.
EPA
considered
a
range
of
options
that
incorporate
varying
levels
of
management
and
various
control
strategies.
Because
long­
term
storm
water
management
is
beyond
the
scope
of
the
controls
proposed
by
EPA,
the
following
discussion
only
presents
information
related
to
options
for
controlling
storm
water
during
the
active
phase
of
construction.

The
following
discussion
presents
various
options
that
EPA
considered.

Codify
the
EPA
Construction
General
Permit
EPA
considered
an
option
that
would
essentially
codify
the
provisions
contained
in
EPA's
construction
general
permit
(CGP)
(USEPA,
1998)
as
minimum
national
standards
for
erosion
and
sediment
control
(i.
e.,
for
all
states,
not
only
those
with
EPA
as
permitting
authority)
for
sites
of
5
acres
or
more
of
disturbed
land.
Requirements
include
preparing
a
Storm
Water
Pollution
Prevention
Plan
(SWPPP)
or
equivalent,
provisions
for
installing
and
sizing
sediment
basins
on
sites
with
more
than
10
acres
of
disturbed
land,
requirements
for
providing
cover
on
exposed
soil
areas
within
14
days
after
construction
activity
has
ceased,
and
installation
and
maintenance
of
other
erosion
and
sediment
control
practices
and
other
temporary
BMPs
on
all
construction
sites,
such
as
silt
fencing,
seeding
and
mulching,
diversion
dikes
and
berms,
sediment
traps,
storm
drain
inlet
protection,
channel
liners,
erosion
control
blankets
and
mats,
stabilized
construction
entrances,
litter,
trash
and
debris
control,
discarded
building
material
control,
and
concrete
truck
wash
water
control.

Numerical
Design
Requirements
EPA
considered
an
option
that
would
establish
numerical
requirements
for
the
design
of
sediment
basins
and
traps
based
on
local
or
regional
rainfall
patterns
and
site­
specific
soil
types.
This
options
could
be
similar
to
existing
requirements
designed
for
managing
storm
water
discharges,
where
sediment
controls
are
sized
based
on
a
specified
rainfall
return
frequency
(such
as
the
2­
year,
24­
hour
storm),
or
a
specified
runoff
frequency
(such
as
the
90th
percentile
runoff
event).

Numerical
Pollutant
Removal
Requirements
EPA
considered
options
that
would
contain
numerical
requirements
for
the
removal
of
specific
pollutants
from
construction
site
runoff.
EPA
initially
considered
targeting
a
variety
of
pollutants
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
6
including
sediment,
TSS,
turbidity,
nutrients,
metals
and
other
priority
pollutants,
however
there
are
little
data
available
supporting
the
feasibility
of
controlling
pollutants
other
than
sediment
(or
associated
indicator
parameters
such
as
TSS,
turbidity,
total
suspended
sediment,
or
settleable
solids).
This
option
could
be
expressed
as
either
a
percent
removal
through
sediment
controls
(such
as
sediment
basins
or
traps),
or
as
a
total
site
reduction
(incorporating
consideration
of
sheet
flow
and
diffuse
runoff
in
addition
to
discrete
conveyances).
In
addition
to
establishing
numerical
requirements
for
the
control
of
sediment,
EPA
preliminarily
considered
establishing
requirements
for
removing
fine­
grained
and
slowly­
or
non­
settleable
particles
contained
in
construction­
site
runoff
(such
as
turbidity).
This
option
would
likely
have
relied
primarily
on
chemical
treatment
of
soils
or
construction
site
runoff
using
polymers
or
coagulants
such
as
alum
in
order
to
prevent
the
non­
settleable
fractions
of
solids
from
being
transported
off­
site.

Discharge
Monitoring
EPA
considered
the
inclusion
of
monitoring
requirements
for
evaluating
the
effectiveness
of
erosion
and
sediment
controls.
Monitoring
of
storm
water
discharges
from
construction
sites
could
be
used
to
evaluate
the
effectiveness
of
individual
sediment
controls
(such
as
sediment
basins),
or
monitoring
the
receiving
water
above
and
below
construction
sites.
Monitoring
requirements
could
be
incorporated
with
any
of
the
previously
discussed
regulatory
options
considered.

Inspection
and
Certification
EPA
considered
an
option
that
includes
mandatory
site
inspection,
maintenance
and
reporting
provisions
by
site
owners
and
operators
in
order
to
improve
confidence
in
the
implementation
and
performance
of
construction
site
erosion
and
sediment
controls.
These
certification
provisions
may
be
accomplished
either
through
self­
inspection
by
a
qualified
employee
of
the
owner
and
operator
(such
as
a
professional
engineer
or
person
trained
in
erosion
and
sediment
control
techniques)
or
inspection
by
a
third­
party
(such
as
a
consulting
firm).
The
certification
provisions
would
consist
of
a
checklist­
type
certification
form
that
the
permittee
would
be
required
to
complete
at
various
stages
of
the
project
to
certify
that
the
provisions
contained
in
the
permittee's
SWPPP
are
being
implemented.
In
addition,
the
permittees
would
be
required
to
conduct
periodic
inspections
in
order
to
confirm
that
the
permittee
is
conducting
the
maintenance
necessary
to
maintain
the
functionality
of
BMPs.
The
specific
activities
requiring
certification
include:
SWPPP
preparation;
installation
of
perimeter
controls
and
sediment
controls;
site
inspections
every
14
days;
final
stabilization
of
exposed
soils
and
removal
of
temporary
erosion
&
sediment
controls.
The
certification
and
inspection
forms
would
be
retained
on
the
site,
and
made
available
to
the
permitting
authority
and
the
public
upon
request.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
7
6.3
REGULATORY
OPTIONS
DEVELOPED
FOR
THE
PROPOSED
RULE
6.3.1
Option
1
­
Inspection
and
Certification
Option
1
proposed
by
EPA
would
establish
the
site
inspection
and
certification
provisions
discussed
above
as
minimum
requirements
for
all
construction
sites
subject
to
the
NPDES
storm
water
regulations.
This
includes
sites
from
1
up
to
5
acres
that
will
be
required
to
obtain
a
permit
once
the
Phase
II
regulations
are
implemented
and
sites
5
acres
or
greater
that
are
required
to
obtain
a
permit
under
the
Phase
I
regulations.
The
permittee
would
be
required
to
conduct
periodic
inspections
and
provide
certifications
as
to
certain
activities
(such
as
SWPPP
preparation,
BMP
installation,
periodic
maintenance,
etc.).
Under
this
option,
these
inspections
and
certifications
would
be
performed
by
a
qualified
professional,
such
as
a
registered
professional
engineer
or
person
trained
in
erosion
and
sediment
control.
The
permittee
may
provide
self­
certifications
if
qualified.

The
specific
inspection
and
certification
provisions
can
be
found
in
the
proposed
rule
language
and
are
summarized
below:

Site
log
book.
The
permittee
would
be
required
to
maintain
a
record
of
site
activities
in
a
site
log
book.
The
specific
requirements
and
information
contained
in
the
log
book
consists
of
the
following:

(1)
A
copy
of
the
site
log
book
would
be
required
to
be
maintained
on
site
and
be
made
available
to
the
permitting
authority
upon
request.
EPA
recommends
that
the
permittee
also
make
a
copy
of
the
site
log
book
available
to
the
public
upon
request
within
a
reasonable
period;

(2)
In
the
site
log
book,
the
permittee
shall
certify,
prior
to
the
commencement
of
construction
activities,
that
any
plans
required
by
the
permit
meet
all
Federal,
State,
Tribal
and
local
erosion
and
sediment
control
requirements
and
are
available
to
the
permitting
authority;

(3)
The
permittee
would
be
required
to
have
a
qualified
professional
conduct
an
assessment
of
the
site
prior
to
groundbreaking
and
certify
that
the
appropriate
BMPs
described
in
plans
required
by
the
permit
have
been
adequately
designed,
sized
and
installed
to
ensure
overall
preparedness
of
the
site
for
initiation
of
groundbreaking
activities.
The
permittee
would
be
required
to
record
the
date
of
initial
groundbreaking
in
the
site
log
book.
The
permittee
would
also
be
required
to
identify
and
conduct
any
soil
stabilization
and
BMP
maintenance
requirements
identified
in
the
permit
within
48
hours
of
their
identification;

(4)
The
permittee
would
be
required
to
post
at
the
site,
in
a
publicly­
accessible
location,
a
summary
of
the
site
inspection
activities
on
a
monthly
basis.
EPA
recommends
that
the
permittee
provide
contact
information
for
obtaining
a
copy
of
the
site
inspection
log
book;
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
8
Site
Inspections.
The
permittee
or
designated
agent
of
the
permittee
(such
as
a
consultant,
subcontractor,
or
third­
party
inspection
firm)
would
be
required
to
conduct
regular
inspections
of
the
site
and
record
the
results
of
such
inspection
in
the
site
log
book.
Specific
inspection
provisions
include:

(1)
After
initial
groundbreaking,
permittees
would
be
required
to
conduct
site
inspections
at
least
every
14
calendar
days
and
within
24
hours
of
the
end
of
a
storm
event
of
0.5
inches
or
greater.
These
inspections
would
be
required
to
be
conducted
by
a
qualified
professional.
During
each
inspection,
the
permittee
or
designated
agent
would
be
required
to
conduct
the
following
activities
and
record
the
following
information:

(i)
Indicate
the
extent
of
all
disturbed
site
areas
and
drainage
pathways.
Indicate
site
areas
that
are
expected
to
undergo
initial
disturbance
or
significant
site
work
within
the
next
14­
day
period;
(ii)
Indicate
all
areas
of
the
site
that
have
undergone
temporary
or
permanent
stabilization;
(iii)
Indicate
all
disturbed
site
areas
that
have
not
undergone
active
site
work
during
the
previous
14­
day
period;
(iv)
Inspect
all
sediment
control
practices
and
note
the
approximate
degree
of
sediment
accumulation
as
a
percentage
of
the
sediment
storage
volume
(for
example
10
percent,
20
percent,
50
percent,
etc.).
Note
all
sediment
control
practices
in
the
site
log
book
that
have
sediment
accumulation
of
50
percent
or
more;
and
(v)
Inspect
all
erosion
and
sediment
control
BMPs
and
note
compliance
with
any
maintenance
requirements
such
as
verifying
the
integrity
of
barrier
or
diversion
systems
(e.
g.,
earthen
berms
or
silt
fencing)
and
containment
systems
(e.
g.,
sediment
basins
and
sediment
traps).
Identify
any
evidence
of
rill
or
gully
erosion
occurring
on
slopes
and
any
loss
of
stabilizing
vegetation
or
seeding/
mulching.
Document
in
the
site
log
book
any
excessive
deposition
of
sediment
or
ponding
water
along
barrier
or
diversion
systems.
Note
the
depth
of
sediment
within
containment
structures,
any
erosion
near
outlet
and
overflow
structures,
and
verify
the
ability
of
rock
filters
around
perforated
riser
pipes
to
pass
water.

(2)
Prior
to
filing
of
the
Notice
of
Termination
or
the
end
of
permit
term,
the
permittee
or
designated
agent
would
be
required
to
conduct
a
final
site
erosion
and
sediment
control
inspection.
The
inspector
would
be
required
to
certify
that
the
site
has
undergone
final
stabilization
as
required
by
the
permit
and
that
all
temporary
erosion
and
sediment
controls
(such
as
silt
fencing)
not
needed
for
long­
term
erosion
control
have
been
removed.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
9
6.3.2
Option
2
­
Codify
EPA
CGP
Requirements
with
Site
Inspection
and
Certification
Provisions
Option
2
proposed
by
EPA
would
require
the
permittee
to
prepare
a
storm
water
pollution
prevention
plan
(SWPPP)
and
implement
the
erosion
and
sediment
controls
contained
in
the
EPA
CGP.
In
addition,
the
permittee
would
be
required
to
conduct
periodic
site
inspections
and
provide
certifications
in
a
site
log
book.
This
option
would
only
apply
to
sites
with
5
or
more
acres
of
disturbed
land.
The
details
of
this
option
can
be
found
in
the
proposed
rule
language
and
are
summarized
below:

General
Erosion
and
Sediment
Controls
Each
SWPPP
would
be
required
to
include
a
description
of
appropriate
controls
designed
to
retain
sediment
on
site
to
the
extent
practicable.
These
general
erosion
and
sediment
controls
would
be
required
to
be
included
in
the
SWPPP
described
below.
The
SWPPP
would
be
required
to
include
a
description
of
interim
and
permanent
stabilization
practices
for
the
site,
including
a
schedule
of
when
the
practices
will
be
implemented.
Stabilization
practices
may
include:

(1)
Establishment
of
temporary
or
permanent
vegetation;

(2)
Mulching,
geotextiles,
or
sod
stabilization;

(3)
Vegetative
buffer
strips;

(4)
Protection
of
trees
and
preservation
of
mature
vegetation.

EPA
recommends
that
all
controls
be
properly
selected
and
installed
in
accordance
with
sound
engineering
practices
and,
when
feasible,
manufacturer's
specifications.

Sediment
Controls
Operators
would
be
required
to
design
and
install
structural
controls
to
divert
flows
from
exposed
soils,
store
flows
or
otherwise
limit
runoff
and
the
discharge
of
pollutants
from
exposed
areas
and
to
describe
controls
in
the
SWPPP.
These
controls
are
as
follows:

(1)
For
common
drainage
locations
that
serve
an
area
with
10
or
more
acres
disturbed
at
one
time,
the
operator
would
be
required
to
provide
a
temporary
(or
permanent)
sediment
basin
that
provides
storage
for
a
calculated
volume
of
runoff
from
a
2
year,
24­
hour
storm
from
each
disturbed
acre
drained,
or
equivalent
control
measures,
where
attainable
until
final
stabilization
of
the
site.
Where
no
such
calculation
has
been
performed,
the
operator
would
be
required
to
provide
a
temporary
(or
permanent)
sediment
basin
providing
3,600
cubic
feet
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
10
feet
of
storage
per
acre
drained,
or
equivalent
control
measures,
where
attainable
until
final
stabilization
of
the
site.
When
computing
the
number
of
acres
draining
into
a
common
location
it
is
not
necessary
to
include
flows
from
off­
site
areas
and
flows
from
on­
site
areas
that
are
either
undisturbed
or
have
undergone
final
stabilization
where
such
flows
are
diverted
around
both
the
disturbed
area
and
the
sediment
basin.

(2)
In
determining
whether
a
sediment
basin
is
attainable,
the
operator
may
consider
factors
such
as
site
soils,
slope,
available
area
on
site,
etc.
In
any
event,
the
operator
would
be
required
to
consider
public
safety,
especially
as
it
relates
to
children,
as
a
design
factor
for
the
sediment
basin.
Use
of
alternative
sediment
controls
would
be
required
where
site
limitations
preclude
a
safe
basin
design.

(3)
For
portions
of
the
site
that
drain
to
a
common
location
and
have
a
total
contributing
drainage
area
of
less
than
10
acres,
the
operator
would
be
required
to
consider
installation
of
sediment
traps
or
other
sediment
control
devices.

(4)
Where
neither
a
sediment
basin
nor
equivalent
controls
are
attainable
due
to
site
limitations,
the
operator
would
be
required
to
install
silt
fences,
vegetative
buffer
strips
or
equivalent
sediment
controls
for
all
down
slope
boundaries
of
the
construction
area
and
for
those
side
slope
boundaries
deemed
appropriate
for
individual
site
conditions.

Pollution
Prevention
Measures
The
operator
would
be
required
to
implement
the
following
pollution
prevention
measures:

(1)
The
operator
would
be
required
to
prevent
litter,
construction
chemicals,
and
construction
debris
from
becoming
a
pollutant
source
in
storm
water
discharges;
and
(2)
The
operator
would
be
required
to
contain
construction
and
building
materials
in
appropriate
storage
areas
and
manage
the
materials
to
prevent
contamination
of
storm
water
runoff.

Storm
Water
Pollution
Prevention
Plan
Permittees
would
be
required
to
compile
Storm
Water
Pollution
Prevention
Plans
(SWPPPs)
prior
to
groundbreaking
at
any
construction
site.
In
areas
where
EPA
is
not
the
permit
authority,
operators
may
be
required
to
prepare
documents
that
may
serve
as
the
functional
equivalent
of
a
SWPPP.
Such
alternate
documents
would
satisfy
the
requirements
for
a
SWPPP
so
long
as
they
contain
the
necessary
elements
of
a
SWPPP.
A
SWPPP
would
be
required
to
incorporate
the
following
information:
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
11
(1)
A
narrative
description
of
the
construction
activity,
including
a
description
of
the
intended
sequence
of
major
activities
that
disturb
soils
on
the
site
(Major
activities
include
any
clearing,
grubbing,
excavating,
grading,
soil
stockpiling,
and
utilities
and
infrastructure
installation,
or
any
other
activity
that
results
in
significant
disturbance
of
soils.);

(2)
A
general
location
map
(e.
g.,
portion
of
a
city
or
county
map)
and
a
site
map.
The
site
map
shall
include
descriptions
of
the
following:

(i)
Drainage
patterns
and
approximate
slopes
anticipated
after
major
grading
activities;
(ii)
The
total
area
of
the
site
and
the
area
of
the
site
that
is
expected
to
be
disturbed
by
excavation,
clearing,
grading
and
other
construction
activities
during
the
life
of
the
permit;
(iii)
Areas
that
will
not
be
disturbed;
(iv)
Locations
of
erosion
and
sediment
controls
identified
in
the
SWPPP;
(v)
Locations
where
stabilization
practices
are
expected
to
occur;
(vi)
Locations
of
off­
site
material,
waste,
borrow
or
equipment
storage
areas;
(vii)
Surface
waters
(including
wetlands);
and
(viii)
Locations
where
storm
water
discharges
to
a
surface
water;

(3)
A
description
of
available
data
on
soils
present
at
the
site;

(4)
A
description
of
BMPs
to
be
used
to
control
pollutants
in
storm
water
discharges
during
construction
(5)
A
description
of
the
general
timing
(or
sequence)
in
relation
to
the
construction
schedule
when
each
BMP
is
to
be
implemented;

(6)
An
estimate
of
the
pre­
development
and
post­
construction
runoff
coefficients
of
the
site;

(7)
The
name(
s)
of
the
receiving
water(
s);

(8)
Delineation
of
SWPPP
implementation
responsibilities
for
each
site
owner
or
operator;

(9)
Any
existing
data
that
describe
the
storm
water
runoff
characteristics
at
the
site
(such
as
data
that
may
be
collected
during
a
site
assessment),
and
Updating
the
SWPPP
The
operator
would
be
required
to
amend
the
SWPPP
and
corresponding
erosion
and
sediment
control
BMPs
whenever:
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
12
(1)
There
is
a
change
in
design,
construction,
or
maintenance
that
is
expected
to
have
a
significant
effect
on
the
discharge
of
pollutants;
or
(2)
Inspections
or
investigations
by
site
operators,
local,
State,
Tribal
or
Federal
officials
indicate
that
any
BMPs
described
in
the
SWPPP
are
ineffective
in
eliminating
or
significantly
minimizing
pollutant
discharges.

Site
Log
Book/
Certification
The
operator
would
be
required
to
maintain
a
record
of
site
activities
in
a
site
log
book,
as
part
of
the
SWPPP.
The
site
log
book
shall
be
maintained
as
follows:

(1)
A
copy
of
the
site
log
book
would
be
required
to
be
maintained
on
site
and
be
made
available
to
the
permitting
authority
upon
request.
EPA
recommends
that
the
operator
make
a
copy
of
the
site
log
book
available
to
the
public
upon
request
within
a
reasonable
period;

(2)
In
the
site
log
book,
the
operator
would
be
required
to
certify,
prior
to
the
commencement
of
construction
activities,
that
the
SWPPP
meets
all
Federal,
State
and
local
erosion
and
sediment
control
requirements
and
is
available
to
the
permitting
authority;

(3)
The
operator
would
be
required
to
have
a
qualified
professional
conduct
an
assessment
of
the
site
prior
to
groundbreaking
and
certify
that
the
appropriate
BMPs
and
erosion
and
sediment
controls
described
in
the
SWPPP
have
been
adequately
designed,
sized
and
installed
to
ensure
overall
preparedness
of
the
site
for
initiation
of
groundbreaking
activities.
The
operator
would
be
required
to
record
the
date
of
initial
groundbreaking
in
the
site
log
book.
The
operator
would
be
required
to
certify
that
the
site
inspections,
soil
stabilization
activities,
and
maintenance
activities
required
by
the
proposed
rule
have
been
satisfied
within
48
hours
of
actually
meeting
such
requirements;

(4)
The
operator
would
be
required
to
post
at
the
site,
in
a
publicly­
accessible
location,
a
summary
of
the
site
inspection
activities
on
a
monthly
basis.
EPA
recommends
that
the
operator
provide
contact
information
for
obtaining
a
copy
of
the
SWPPP
and
a
copy
of
the
site
inspection
log
book;

Site
Inspections
The
operator
or
designated
agent
of
the
operator
(such
as
a
consultant,
subcontractor,
or
thirdparty
inspection
firm)
would
be
required
to
conduct
regular
inspections
of
the
site
and
record
the
results
of
such
inspection
in
the
site
log
book.
The
specific
activities
that
would
require
inspection
and
certification
are:
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
13
(1)
After
initial
groundbreaking,
operators
would
be
required
to
conduct
site
inspections
at
least
every
14
calendar
days
and
within
24
hours
of
the
end
of
a
storm
event
of
0.5
inches
or
greater.
These
inspections
would
be
required
to
be
conducted
by
a
qualified
professional.
During
each
inspection,
the
operator
or
designated
agent
would
be
required
to
record
the
following
information:

(i)
On
a
site
map,
indicate
the
extent
of
all
disturbed
site
areas
and
drainage
pathways.
Indicate
site
areas
that
are
expected
to
undergo
initial
disturbance
or
significant
site
work
within
the
next
14­
day
period;
(ii)
Indicate
on
a
site
map
all
areas
of
the
site
that
have
undergone
temporary
or
permanent
stabilization;
(iii)
Indicate
all
disturbed
site
areas
that
have
not
undergone
active
site
work
during
the
previous
14­
day
period;
(iv)
Inspect
all
sediment
control
practices
and
note
the
approximate
degree
of
sediment
accumulation
as
a
percentage
of
the
sediment
storage
volume
(for
example
10
percent,
20
percent,
50
percent,
etc.).
Record
all
sediment
control
practices
in
the
site
log
book
that
have
sediment
accumulation
of
50
percent
or
more;
and
(v)
Inspect
all
erosion
and
sediment
control
BMPs
and
record
all
maintenance
requirements
such
as
verifying
the
integrity
of
barrier
or
diversion
systems
(earthen
berms
or
silt
fencing)
and
containment
systems
(sediment
basins
and
sediment
traps).
Identify
any
evidence
of
rill
or
gully
erosion
occurring
on
slopes
and
any
loss
of
stabilizing
vegetation
or
seeding/
mulching.
Document
in
the
site
log
book
any
excessive
deposition
of
sediment
or
ponding
water
along
barrier
or
diversion
systems.
Record
the
depth
of
sediment
within
containment
structures,
any
erosion
near
outlet
and
overflow
structures,
and
verify
the
ability
of
rock
filters
around
perforated
riser
pipes
to
pass
water.

(2)
Prior
to
filing
of
the
Notice
of
Termination
or
the
end
of
permit
term,
a
final
site
erosion
and
sediment
control
inspection
would
be
required
to
be
conducted
by
the
operator
or
designated
agent.
The
inspector
would
be
required
to
certify
that
the
site
has
undergone
final
stabilization
using
either
vegetative
or
structural
stabilization
methods
and
that
all
temporary
erosion
and
sediment
controls
(such
as
silt
fencing)
not
needed
for
long­
term
erosion
control
have
been
removed.

Stabilization
The
operator
would
be
required
to
initiate
stabilization
measures
as
soon
as
practicable
in
portions
of
the
site
where
construction
activities
have
temporarily
or
permanently
ceased,
but
in
no
case
more
than
14
days
after
the
construction
activity
in
that
portion
of
the
site
has
temporarily
or
permanently
ceased.
This
provision
would
not
apply
in
the
following
instances:
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
14
(1)
Where
the
initiation
of
stabilization
measures
by
the
14th
day
after
construction
activity
temporarily
or
permanently
ceased
is
precluded
by
snow
cover
or
frozen
ground
conditions,
the
operator
shall
initiate
stabilization
measures
as
soon
as
practicable;
(2)
Where
construction
activity
on
a
portion
of
the
site
is
temporarily
ceased,
and
earthdisturbing
activities
will
be
resumed
within
21
days,
temporary
stabilization
measures
need
not
be
initiated
on
that
portion
of
the
site.
(3)
In
arid
areas
(areas
with
an
average
annual
rainfall
of
0
to
10
inches),
semi­
arid
areas
(areas
with
an
average
annual
rainfall
of
10
to
20
inches),
and
areas
experiencing
droughts
where
the
initiation
of
stabilization
measures
by
the
14th
day
after
construction
activity
has
temporarily
or
permanently
ceased
is
precluded
by
seasonably
arid
conditions,
the
operator
shall
initiate
stabilization
measures
as
soon
as
practicable.

Maintenance
The
operator
would
be
required
to
remove
accumulated
sediment
from
sediment
traps
and
ponds
identified
as
having
sediment
accumulation
greater
than
50
percent
to
restore
the
original
design
capacity,

6.3.3
Option
3
­
No
Regulation
EPA
also
considered
an
option
that
would
not
establish
effluent
guidelines
requirements
for
this
industry.

6.4
REFERENCES
USDA.
2000.
1997
National
Resources
Inventory.
U.
S.
Department
of
Agriculture,
Natural
Resources
Conservation
Service.
Washington,
DC.
http://
www.
nrcs.
usda.
gov/
technical/
NRI/

USEPA.
1983.
Final
Report
of
the
Nationwide
Urban
Runoff
Program.
U.
S.
Environmental
Protection
Agency.
Washington
DC.

USEPA.
1998.
Reissuance
of
NPDES
General
Permits
for
Storm
Water
Discharges
from
Construction
Activities.
("
Construction
General
Permit.")
Federal
Register,
Vo.
63,
No.
31,
p.
7858.
February
17,
1998.
Washington,
DC.
http://
cfpub.
epa.
gov/
npdes/
stormwater/
cpermit.
cfm?
program_
id=
6
USEPA.
1999.
Economic
Analysis
of
the
Final
Phase
II
Storm
Water
Rule.
U.
S.
Environmental
Protection
Agency.
Washington,
DC.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
6­
15
USEPA.
2002.
Economic
Analysis
of
Proposed
Effluent
Limitation
Guidelines
and
New
Source
Performance
Standards
for
the
Construction
and
Development
Category;
May
2002.
EPA
821­
R­
02­
008.
http://
www.
epa.
gov/
waterscience/
guide/
construction/

USEPA.
2002a.
Environmental
Assessment
for
Proposed
Effluent
Limitation
Guidelines
and
New
Source
Performance
Standards
for
the
Construction
and
Development
Category;
May
2002.
EPA
821­
R­
02­
009.
http://
www.
epa.
gov/
waterscience/
guide/
construction/
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
1
SECTION
7:
APPROACH
TO
ESTIMATING
COSTS
7.1
OVERVIEW
This
section
describes
EPA's
methodology
for
estimating
compliance
costs
associated
with
implementing
the
regulatory
options
proposed
for
the
construction
and
land
development
effluent
limitation
guidelines
(ELG).
EPA
estimated
three
distinct
cost
categories:
(1)
erosion
and
sediment
control
(ESC)
costs,
including
design,
installation,
operation,
and
maintenance;
(2)
administrative
costs
to
permittees
for
activities
such
as
site
inspections
and
certification
activities;
and
(3)
administrative
costs
to
permit
authorities
to
incorporate
the
effluent
guidelines
requirements
into
general
permits.
Costs
contained
in
categories
(1)
and
(2)
are
expected
to
be
borne
directly
by
the
construction
and
development
industry.

Costs
were
evaluated
individually
for
24
site
size
class
and
land
use
types.
EPA
developed
a
series
of
model
sites
for
each
land
use/
site
size
class
and
estimated
costs
of
proposed
options
for
each
of
these
model
sites.
Using
estimates
of
the
population
of
new
construction
acreage
developed
using
data
from
the
USDA's
National
Resources
Inventory
(NRI),
the
U.
S.
Census
Bureau,
EPA's
NPDES
Storm
Water
Phase
II
rulemaking,
and
other
national
data
sources
(described
in
Section
3
of
this
document),
EPA
summed
the
model
site
costs
to
the
national
level.
A
description
of
this
methodology
is
presented
in
the
Economic
Analysis
document
(USEPA,
2002).

The
total
costs
of
the
proposed
rule
options
are
presented
in
Table
7­
1.

Table
7­
1.
Total
Costs
of
Proposed
Rule
Options
Option
Annual
Cost
(millions
2000
dollars)

1
­
Inspection
and
Certification
sites

1
acre
126
2
­
Codify
EPA
Construction
General
Permit
(CGP)
with
Inspection
and
Certification
sites

5
acres
502
3
­
No
Regulation
0
7.2
METHODS
FOR
ESTIMATING
EROSION
AND
SEDIMENT
CONTROL
COSTS
7.2.1
OVERVIEW
EPA
used
four
land
use
types
to
account
for
variations
in
construction
operations
and
associated
ESCs
employed
for
various
development
types.
For
each
land
use
type,
EPA
evaluated
six
site
size
classes
to
account
for
economies
of
scale
that
might
occur
with
certain
best
management
practice
(BMP)
design
and
installation
costs
(some
BMPs
are
employed
only
if
the
site
size
is
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
2
greater
than
a
threshold
value).
EPA
also
considered
regional
cost
adjustments
due
to
variations
in
labor,
supply,
and
material
costs
(see
Table
7­
2).
EPA
used
an
industry
standard
reference
to
establish
appropriate
adjustment
factors
for
regional
compliance
costs
(R.
S.
Means,
2000).

The
costing
analysis
started
by
allocating
the
estimated
annual
construction
acreage
and
number
of
model
sites
developed
in
Section
4
(see
Table
4­
21)
for
one
of
19
EPA­
developed
ecoregions
shown
in
Figure
7­
1
(see
the
Environmental
Assessment
supporting
document
(EPA,
2002a)
for
a
complete
description
of
the
EPA
ecoregions).
Matrices
of
standard
BMP
quantities
for
the
technology­
based
option
(Option
2)
were
developed
for
the
various
model
site
sizes
using
the
NPDES
Phase
II
economic
analysis
(USEPA,
1999)
and
the
Agency's
engineering
judgement.
By
multiplying
the
two
matrices,
the
total
quantity
of
BMPs
for
all
of
the
model
sites
was
determined.
EPA
estimated
the
unit
costs
of
each
BMP
element
using
R.
S.
Means
(2000),
and
data
from
"The
Economics
of
Stormwater
Treatment:
An
Update"
from
the
Center
for
Watershed
Protection's
(CWP's)
book
entitled
The
Practice
of
Watershed
Protection
(Schueler,
2000).
Regional
costs
were
adjusted
using
cost
adjustment
factors
from
R.
S.
Means
(2000),
and
data
were
summed
across
the
different
site
size
categories
to
determine
engineering
costs
at
the
national
level.
Additional
costs
for
factors
such
as
design
and
contingencies
(described
in
the
Economic
Analysis)
were
added
to
these
national
costs
to
arrive
at
the
national
cost
figures
presented
in
Table
7­
1.
All
costs
presented
are
incremental
over
current
costs
to
the
industry
from
existing
Federal
and
State
requirements.

EPA
used
a
similar
approach
to
estimate
administrative
costs
to
permittees
for
conducting
the
site
inspection
and
certification
provisions
contained
in
Options
1
and
2.
EPA
estimated
the
number
of
site
inspections
needed
and
the
hours
required
for
conducting
site
inspections
and
certifications
for
each
of
the
model
site
sizes.
By
multiplying
these
hour
estimates
by
a
professional
labor
rate,
EPA
was
able
to
estimate
the
total
administrative
costs
to
permittees.
Similarly,
EPA
estimated
the
administrative
costs
to
permitting
authorities
to
revise
general
permits
to
incorporate
the
effluent
guideline
requirements
by
multiplying
the
estimated
hours
per
entity
by
the
number
of
entities
to
arrive
at
the
national
costs.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
3















	







Figure
7­
1.
EPA
Ecoregions
Source:
Composited
from
Omernik,
1987.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
4
Table
7­
2.
Regional
Compliance
Cost
Adjustment
Factors
EPA
Hydrologic
Region
Regional
Compliance
Cost
Adjustment
Factor
1
0.855
2
0.984
3
0.900
4
0.782
5
0.857
6
0.858
7
0.870
8
1.032
9
0.877
10
0.996
11
0.810
12
0.854
13
0.936
14
0.908
15
1.094
16
1.129
17
1.052
18
1.046
19
1.052
Source:
EPA
hydrologic
regions
are
composited
from
Omernik,
1987.
Regional
compliance
cost
adjustment
factors
are
computed
based
on
city
data
from
R.
S.
Means,
2000.

7.2.2
EROSION
AND
SEDIMENT
CONTROL
COSTS
In
this
analysis,
EPA
has
built
upon
a
number
of
previous
assessments
of
ESC
practices,
including
the
Economic
Analysis
of
the
Final
Phase
II
Storm
Water
Rule
(USEPA,
1999).
EPA
estimated
types
and
quantities
of
ESC
BMPs
that
are
commonly
employed
under
baseline
conditions
during
construction
activities
to
mitigate
impacts
from
construction
site
runoff
for
24
land
use/
site
size
class
models.
In
addition,
in
its
analysis
EPA
estimated
that
requirements
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
5
contained
in
existing
State
construction
general
permit
requirements
(or,
in
the
non
authorized
states,
the
region­
specific
EPA
construction
general
permits
(CGPs)
would
be
fully
implemented.
Although
Phase
II
is
not
fully
implemented
at
this
time,
the
requirements
will
be
implemented
by
the
time
final
action
is
taken
on
these
proposed
effluent
guidelines.
Furthermore,
as
proposed
Option
2
(the
only
option
for
which
EPA
is
establishing
technology­
based
requirements)
addressed
only
sites
with
5
or
more
acres
of
disturbed
land,
the
timing
of
Phase
II
implementation
is
not
an
issue.

EPA
took
a
model
site
approach
to
estimating
the
baseline
ESC
usage
and
quantities
of
materials,
as
well
as
design
costs
and
operation
and
maintenance
(O&
M)
costs
that
are
expected
to
be
applicable
given
a
range
of
physical
conditions
(1
to
7
percent
land
slopes
and
different
soil
types).
Table
7­
3
lists
the
construction
site
BMPs
included
in
the
baseline
analysis
for
various
site
sizes.
To
establish
baseline
BMP
usage,
EPA
started
with
the
model
site
estimates
generated
during
the
Phase
II
rulemaking,
scaling
up
the
BMP
quantities
to
sites
larger
than
5
acres,
and
adding
sediment
basins
for
larger
sites.
In
the
final
costing
analysis
of
this
option,
costs
for
BMPs
for
sites
less
than
5
acres
were
eliminated,
consistent
with
the
proposed
regulatory
requirements
for
Option
2.

Table
7­
3.
Construction
Site
ESC
BMP
Descriptions
and
Site
Thresholds
ESC
BMP
Description
Applicable
Site
Sizes
for
ESC
BMP
Quantity
Estimates
Silt
Fence,
Diversion
Dike,
Construction
Entrances,
Stone
Check
Dams
>
1
acre
Mulch
>
1
acre
Sediment
Traps
>
1
acre
and
<
10
acres
Polyacrylamide
(PAM)
>
1
acres
Sediment
Basins

10
acres
BMP
Installation
and
SWPPP
Certifications

1
acre
Site
Inspections

1
acres
To
determine
costs
of
the
regulatory
options,
EPA
first
evaluated
a
variety
of
State
construction
general
permits
and
erosion
and
sediment
control
regulations
and
found
that
many
States
have
requirements
similar
to
those
contained
in
the
EPA
construction
general
permit,
which
is
the
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
1
Although
EPA
attempted
to
obtain
comprehensive
information,
the
Agency
was
not
able
to
verify
the
presence
of
the
specific
components
in
Table
7­
4
for
all
States.
As
a
result,
the
absence
of
an
entry
does
not
necessarily
mean
that
the
State
does
not
currently
have
an
equivalent
requirement.

June
2002
7­
6
basis
for
the
requirements
contained
in
Option
2
(see
Table
7­
4)
1
.
In
evaluating
existing
State
programs,
EPA
specifically
examined
the
major
provisions
contained
in
Option
2,
namely
sediment
basins
designed
to
provide
3,600
cubic
feet
per
acre
of
storage;
requirements
for
stabilization
of
exposed
soil
areas
within
14
days
of
reaching
final
grade;
and
site
inspections
at
least
every
14
days.
In
addition,
EPA
evaluated
whether
the
annual
precipitation
in
each
State
is
less
than
20
inches,
since
the
soil
stabilization
requirements
are
linked
to
this
condition.
In
the
final
analysis
of
national
costs,
EPA
adjusted
the
estimates
of
the
national
costs
for
the
effluent
guidelines
to
account
for
States
with
programs
equivalent
to
EPA's
proposed
options.
Table
7­
5
summarizes
the
percentage
of
national
costs
eliminated
due
to
equivalent
State
programs.
This
is
only
applicable
to
Option
2,
as
EPA
has
not
determined
that
a
significant
number
of
States
have
requirements
equivalent
to
Option
1.

It
is
expected
that
on
some
construction
sites
there
will
be
some
portion
of
land
with
steeper
slopes
and
more
erosive
soils,
which
will
require
more
intensive
management
if
built
upon
than
is
assumed
by
EPA's
model.
Also,
a
State
with
less
than
20
inches
of
annual
rainfall
was
considered
to
be
equivalent
to
a
State
that
has
the
14­
day
cover
requirement
when
assessing
overall
equivalence.
Local
regulations
may
require
use
of
ESCs
that
are
more
stringent
than
the
Phase
I
and
II
requirements.
However,
EPA
expects
that
the
BMPs
selected
to
develop
its
model
sites
are
representative
of
baseline
conditions
for
the
majority
of
construction
activity
across
the
nation.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
7
Table
7­
4.
Components
of
Existing
State
Erosion
and
Sediment
Control
Requirements
a
State
Minimum
of
3,600
Cubic
Feet
per
Acre
Sediment
Basin
Requirement
Inspections
Required
at
Least
Every
14
Days
14­
Day
or
Less
Stabilization
Requirement
States
with
Less
than
20
Inches
of
Precipitation
Per
Year
Alabama
Alaska
Yes
Yes
Yes
Arizona
Yes
Yes
Yes
Yes
Arkansas
California
Yes
Yes
Yes
Colorado
Yes
Connecticut
Yes
Yes
Yes
Delaware
District
of
Columbia
Florida
Georgia
Hawaii
Idaho
Yes
Illinois
Yes
Indiana
Iowa
Yes
Yes
Yes
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Yes
Yes
Yes
Michigan
Minnesota
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
State
Minimum
of
3,600
Cubic
Feet
per
Acre
Sediment
Basin
Requirement
Inspections
Required
at
Least
Every
14
Days
14­
Day
or
Less
Stabilization
Requirement
States
with
Less
than
20
Inches
of
Precipitation
Per
Year
June
2002
7­
8
Mississippi
Missouri
Montana
Yes
Yes
Nebraska
Nevada
Yes
New
Hampshire
Yes
Yes
Yes
New
Jersey
New
Mexico
Yes
Yes
Yes
Yes
New
York
North
Carolina
North
Dakota
Yes
Ohio
Yes
Yes
Oklahoma
Yes
Oregon
Pennsylvania
Yes
Yes
Yes
Rhode
Island
South
Carolina
Yes
Yes
Yes
South
Dakota
Yes
Yes
Yes
Yes
Tennessee
Yes
Yes
Yes
Texas
Yes
Yes
Yes
Utah
Yes
Yes
Yes
Yes
Vermont
Virginia
Yes
Yes
Yes
Washington
West
Virginia
Yes
Yes
Wisconsin
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
State
Minimum
of
3,600
Cubic
Feet
per
Acre
Sediment
Basin
Requirement
Inspections
Required
at
Least
Every
14
Days
14­
Day
or
Less
Stabilization
Requirement
States
with
Less
than
20
Inches
of
Precipitation
Per
Year
June
2002
7­
9
Wyoming
Yes
Yes
a.
Information
is
accurate
as
of
May
2002
Table
7­
5.
State
Acreage
Equivalent
to
Proposed
Option
2
Equivalent
State
Acreage
for
Sites
>5
acres
Percent
of
Annual
(>
5
acre)
Developed
Acreage
Equivalent
Option
2
755,500
41
Once
EPA
estimated
the
quantities
of
ESC
BMPs
for
the
model
sites,
the
total
baseline
cost
of
BMP
installation
was
calculated
from
unit
costs
provided
by
R.
S.
Means
(2000)
and
cost
curves
from
"The
Economics
of
Stormwater
Treatment:
An
Update"
(Schueler,
2000).
R.
S.
Means
provides
national
average
unit
costs
that
include
materials,
installation,
and
labor.
Typically,
users
of
R.
S.
Means
adjust
the
national
unit
costs
up
or
down
to
obtain
their
local
estimates
based
on
city­
specific
adjustment
factors
provided
by
R.
S.
Means.
As
described
previously,
EPA
developed
and
used
the
regional
adjustment
factors
in
Table
7­
2
to
customize
unit
costs
on
an
ecoregion
basis,
not
on
a
city
basis.
To
compute
region­
specific
unit
costs
from
the
national
average
value,
city­
specific
adjustment
factors
provided
by
R.
S.
Means
were
converted
into
ecoregion
values.
First,
State­
average
adjustment
factors
were
estimated
based
on
the
values
for
cities
they
contained.
Then
ecoregion
values
were
computed
based
on
area­
weighting
for
those
states
that
fell
within
each
ecoregion.

Although
R.
S.
Means
is
expected
to
accurately
estimate
the
as­
built
cost
for
a
particular
element,
in
certain
cases
it
might
underestimate
the
cost
that
a
developer
or
ultimate
property
owner
might
need
to
pay
a
contractor
to
construct
a
particular
element.
This
is
due
to
additional
site­
specific
cost
factors
that
a
contractor
may
build
into
a
bid
package,
such
as
contingencies,
allowances
for
change
orders,
additional
time
and
labor
for
unseen
delays
due
to
weather,
unanticipated
problems
with
soils,
etc.
However,
for
the
majority
of
projects,
R.
S.
Means
is
expected
to
provide
accurate
cost
information.
In
addition,
EPA
adjusted
for
contingency
costs
in
its
analysis
of
economic
impacts
to
the
industry
(see
the
Economic
Analysis
document
for
a
description
of
this
methodology).

In
calculating
the
total
costs
for
erosion
and
sediment
control
activities,
EPA
added
estimated
design,
operation,
and
maintenance
costs.
Table
7­
6
shows
design
and
O&
M
costs
as
a
fraction
of
the
capital
cost
of
ESC
BMPs.
These
cost
ratios
were
obtained
from
published
sources
such
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
10
as
the
CWP
report
and
from
the
Agency's
engineering
judgement.

In
evaluating
the
proposed
rule
options,
EPA
used
the
model
site
approach
to
first
determine
the
baseline
compliance
costs,
then
to
modify
BMP
sizing
and
BMP
quantities
to
assess
the
incremental
costs
of
regulatory
options
of
the
proposed
rule.
The
resulting
suite
of
BMPs
evaluated
by
EPA
in
establishing
costs
of
the
proposed
rule
are
listed
in
Table
7­
7,
along
with
their
unit
costs.
Appendix
B
contains
additional
tables
indicating
EPA's
estimates
of
the
standard
quantity
needed
for
each
BMP
listed
in
Table
7­
7,
for
each
land
use
type
and
site
size.
In
addition,
Appendix
B
indicates,
for
key
BMPs,
the
number
of
equal
size
BMPs
of
a
single
type
that
EPA
estimates
will
be
needed
to
serve
a
single
site
(i.
e.,
a
single
200­
acre
site
will
be
served
by
four
equal­
size
sediment
basins,
each
of
which
manages
50
acres).

Table
7­
6.
Construction
ESC
BMP
Design
and
Operation
and
Maintenance
Costs
as
a
Percentage
of
Capital
Costs
Costed
Items
Effective
Life
in
Years
Design
Costs
as
Percent
of
Construction
Cost
Estimated
O&
M
as
Percent
of
Original
Installation
Costs
Silt
Fence
1
6%
100%

Diversion
Dike
1
6%
10%

Mulch
1
6%
2%

Construction
Entrance
1
6%
5%

Stone
Check
Dam
1
6%
5%

Sediment
Trap
1
6%
20%

Sediment
Basin
1
6%
25%

Polyacrylamide
(PAM)
1
6%
0
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
11
Table
7­
7.
Evaluated
Construction
Site
BMPs
that
Augment
the
Suite
of
Baseline
BMPs
BMP
Description
Costing
Rationale
Erosion
and
Sediment
Controls
Sediment
Basins
for
Sites

10
acres
Standardization
to
3,600
cubic
feet
of
storage
per
watershed
acre.
Cost
based
on
equation
for
installing
permanent
dry
detention
pond,
computed
from
the
equation:
[8.16
x
(volume
required,
cu.
ft./
number
of
ponds
per
site
size)
0.78
]
(Schueler,
2000).

Mulch
Mulching
of
any
denuded
surface
would
be
required
within
14
days
of
reaching
final
grade,
resulting
in
more
frequent
mulching
of
a
portion
of
the
site
acreage.
Cost
of
mulching
is
estimated
to
be
$0.23
per
square
yard
for
materials/
installation
(R.
S.
Means).
For
sites
larger
than
1
acre,
mulching
is
based
on
the
total
site
acreage
less
the
area
where
structures
are
being
built
(estimated
as
the
site
impervious
coverage).
The
maximum
coverage
for
single­
family
and
multifamily
residential
development
is
50%
of
the
total
site
area,
assuming
the
remaining
acreage
is
maintained
as
open
space
and/
or
permanent
vegetation/
cover
is
installed.

Polyacrylamide
(PAM)
EPA
estimates
that
a
single
application
of
PAM
would
be
used
as
a
temporary
stabilization
method
until
final
cover
can
be
installed.
PAM
was
estimated
to
be
appropriate
for
only
20%
of
construction
sites
due
to
physical
constraints.
PAM
is
costed
at
$200
per
acre
treated
based
on
a
survey
of
commercial
vendors
and
the
assumption
that
its
application
is
similar
to
that
of
herbicide
for
soil
treatment
($
0.04
per
square
yard
based
on
spraying
from
truck)
(R.
S.
Means).
The
acreage
treated
is
equal
to
the
site
size
times
the
ultimate
impervious
area,
to
a
maximum
of
50%
of
the
site
size.

Site
Administration
BMPs
Site
Certifications
For
each
site,
certification
activities
include
certification
of
storm
water
pollution
prevention
plan
(SWPPP)
completion,
certification
of
BMP
installations,
and
certification
of
final
stabilization
prior
to
filing
of
the
notice
of
termination
(NOT).
Certification
adds
an
estimated
cost
of
approximately
$11
per
acre
for
Options
1
and
2.

Site
Inspections
For
each
10­
acre
unit
in
the
total
site,
incremental
inspection
activities
over
baseline
are:
(a)
post­
BMP
installation;
(b)
once
during
building;
and
(c)
at
end
of
construction
(prior
to
filing
of
the
NOT).
Inspection
adds
an
estimated
cost
of
approximately
$45
per
acre
for
Options
1
and
2.

Table
7­
8
indicates
the
relative
change
in
quantities
of
BMPs
associated
with
Options
1
and
2.
Standard
quantities
of
BMPs
outlined
in
Table
7­
3
were
increased
or
decreased
according
to
multiplication
factors
in
Table
7­
8
to
reflect
changes
expected
due
to
each
option.
For
example,
in
the
case
of
mulch,
EPA
estimates
that
under
Option
2,
there
will
be
a
net
increase
in
the
use
of
mulch
by
20
percent
over
baseline
levels,
in
part
to
help
meet
the
requirements
for
14­
day
coverage
of
denuded
areas.
In
the
case
of
PAM,
EPA
anticipates
that
PAM
will
be
applied
to
20
percent
of
the
denuded
acreage,
as
it
is
an
inexpensive
and
effective
means
to
improve
erosion
control.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
12
Table
7­
8.
BMP
Quantity
Adjustment
Factors
for
Baseline
and
Proposed
Options
BMP
Type
Baseline
Construction
Option1
Inspection/
Certification
Option
2
Inspection/
Certification
with
Codification
of
CGP
Silt
Fence
1.0
1.0
1.0
Runoff
Diversion
1.0
1.0
1.0
Mulch
1.0
1.0
1.2
Construction
1.0
1.0
1.0
Stone
Check
Dam
1.0
1.0
1.0
Sediment
Trap
1.0
1.0
1.0
Sediment
Pond
1.0
1.0
1.1
E&
S
Certification
0.0
1.0
1.1
E&
S
Inspection
0.0
1.0
1.0
PAM
0.0
0.0
0.2
Using
the
information
in
Table
7­
8,
EPA
estimated
baseline
costs
as
well
as
the
costs
for
Options
1
and
2.
By
subtracting
the
baseline
costs
from
the
cost
of
each
option,
EPA
was
able
to
estimate
the
incremental
costs
of
the
proposed
options.
Table
7­
9
indicates
the
estimated
national
costs
over
baseline
of
the
proposed
rule
options.
Values
include
design,
maintenance,
and
opportunity/
interest
costs.
States
that
are
considered
to
be
equivalent
to
EPA's
proposed
options
are
removed
from
the
total
national
cost
estimate
increases.
The
proposed
rule
is
expected
to
increase
compliance
costs
for
ESCs
under
Option
1
by
$126
million,
and
by
$502
million
for
Option
2
(year
2000
dollars).
Option
3
is
not
expected
to
have
any
incremental
costs.
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
13
Table
7­
9.
National
Cost
Estimates
for
Proposed
Rule
Options
Sector
Option
1
Total
Cost
(millions,
1997
dollars)
Option
2
Total
Cost
(millions,
1997
dollars)

Single­
family
Residential
25.7
129.7
Multifamily
Residential
12.7
63.4
Commercial
83.8
296.2
Industrial
4.0
11.8
Total
126.2
501.1
7.3
METHODS
FOR
ESTIMATING
ADMINISTRATIVE
COSTS
7.3.1
OVERVIEW
The
analysis
of
administrative
costs
focused
on
the
costs
to
permit
authorities
to
incorporate
the
effluent
guidelines
requirements
into
general
permits.
Administrative
costs
are
expected
to
be
borne
by
both
EPA
and
States
(or
surrogate
agencies
such
as
conservation
districts).
EPA's
assessment
is
conservative
in
that
it
assumes
that
all
States
will
have
to
incorporate
the
effluent
guideline
requirements
into
their
permits.
However,
EPA
estimates
that
approximately
41
percent
of
developed
acreage
is
under
state
programs
that
are
equivalent
to
the
proposed
requirements
contained
in
Option
2
and,
therefore,
will
not
have
to
modify
their
permits
to
incorporate
these
requirements.

7.3.2
ADMINISTRATIVE
COSTS
TO
PERMITTEES
When
considering
the
administrative
costs
to
permittees
for
implementation
of
the
proposed
options,
EPA
estimated
the
number
of
CGPs
it
expects
to
be
issued
each
year.
Table
7­
10
indicates
the
number
of
construction
sites
under
permit
EPA
estimates
are
associated
with
current
development
rates,
categorized
by
Option.
In
its
analysis,
EPA
estimated
that
construction
sites
not
affected
by
effluent
guidelines
(those
smaller
than
5
acres
in
Option
2,
and
those
smaller
than
1
acre
in
Option
1)
would
not
incur
administrative
costs.

Annual
administrative
costs
are
expected
to
be
borne
by
construction
firms
as
a
result
of
site
certification
and
inspection
requirements
(See
Table
7­
7).
Under
Options
1
and
2,
site
operators
will
be
required
to
certify
that
the
Storm
Water
Pollution
Prevention
Plan
(SWPPP)
has
been
completed,
that
BMPs
are
installed
according
to
the
SWPPP,
that
periodic
inspections
have
been
completed,
and
that
the
site
has
been
stabilized
prior
to
filing
of
the
notice
of
termination
(NOT).
EPA
estimated
that
it
will
take
16
hours
per
10
acres
developed
to
meet
the
inspection
requirement.
(For
construction
sites
smaller
than
10
acres
only
16
hours
of
inspection
is
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
14
required.)
EPA
used
the
estimates
of
construction
projects
by
size
presented
in
Table
4­
21
to
estimate
the
total
hours
required
to
perform
administrative
activities.

EPA
estimated
the
total
national
costs
associated
with
site
certifications
to
be
$27,712,000
per
year
under
Option
1
and
$16,727,000
per
year
under
Option
2
(1997
dollars).
Based
on
a
review
of
States
with
greater
than
50,000
acres
per
year
development,
EPA
estimates
that
34
percent
of
acres
developed
are
within
States
with
14­
day
inspection
requirements
that
are
similar
to
those
proposed
under
Options
1
and
2.
As
a
result,
EPA
adjusted
downward
its
estimate
of
national
site
inspection
costs
to
reflect
equivalent
inspection
programs.
The
total
resulting
estimates
for
site
inspection
under
Options
1
and
2
are
$73,161,000
and
$44,160,000
per
year,
respectively.
EPA's
estimate
of
the
total
annual
administrative
cost
for
certification
and
inspection
for
Option
1
and
2
are
$100,873,000
and
$60,887,000,
respectively.
The
total
annual
administrative
costs
are
lower
for
Option
2
because
sites
of
less
than
5
acres
are
not
regulated.
EPA
adjusted
these
cost
estimates
upward
to
reflect
opportunity
costs,
resulting
in
overall
administrative
costs
to
permittees
of
$118,141,000
for
Option
1
and
$71,290,000
for
Option
2.
An
explanation
of
this
methodology
is
presented
in
the
Economic
Analysis
supporting
documentation.

7.3.3
ADMINISTRATIVE
COSTS
FOR
GENERAL
PERMIT
REVISIONS
EPA
estimated
the
total
one­
time
costs
for
permit
authorities
to
incorporate
the
erosion
and
sediment
control
effluent
guidelines
requirements
into
their
general
permits.
EPA's
estimates
of
full
time
equivalents
(FTEs)
and
costs
for
each
agency
to
incorporate
effluent
guidelines
requirements
are
indicated
in
Table
7­
10.
To
determine
costs
of
incorporating
the
effluent
guidelines
requirements
into
existing
State
CGPs,
EPA
estimated
that
each
State
will
require
200
hours
to
evaluate
and
then
modify
general
permits
to
incorporate
new
requirements.
All
50
States
were
estimated
to
encounter
administrative
costs,
even
though
many
States
already
have
general
permits
that
meet
some
of
the
proposed
requirements.
When
dividing
costs
between
Federal
and
State
entities,
EPA's
estimated
costs
will
be
allocated
based
on
the
percentage
of
States
currently
authorized
to
manage
the
NPDES
program
(i.
e.,
44
of
50,
or
88
percent).

Table
7­
10.
One­
Time
Hours
and
Costs
to
Incorporate
Erosion
and
Sediment
Control
Effluent
Guidelines
Requirements
into
General
Permits
(1997
Dollars)

Program
Element
Federal
State
Revise
General
Permits
(hours)
1,200
8,800
Revise
General
Permits
(dollars)
$31,000
$229,000
Development
Document
for
Construction
and
Development
Proposed
Effluent
Guidelines
June
2002
7­
15
7.4
REFERENCES
Schueler,
Thomas
R..
2000.
"The
Economics
of
Stormwater
Treatment:
an
Update".
Article
No..
68
in
the
Practice
of
Watershed
Protection.
Center
for
Watershed
Protection,
Ellicott
City,
MD.
http://
www.
stormwatercenter.
net
Omernik,
James
M.
1987.
Ecoregions
of
the
Conterminous
United
States.
Annal
of
the
Association
of
American
Georgraphers.
77(
1):
118­
125.

R.
S.
Means.
2000.
Site
Work
&
Landscape
Cost
Data,
19
th
Edition.
R.
S.
Means
Co.,
Kingston,
MA.

USEPA.
1999.
Economic
Analysis
of
the
Final
Phase
Ii
Storm
Water
Rule.
U.
S.
Environmental
Protection
Agency.
Washington,
DC.

USEPA.
2002.
Economic
Analysis
of
Proposed
Effluent
Limitation
Guidelines
and
New
Source
Performance
Standards
for
the
Construction
and
Development
Category;
May
2002.
EPA
821­
R­
02­
008.
http://
www.
epa.
gov/
waterscience/
guide/
construction/

USEPA.
2002a.
Environmental
Assessment
for
Proposed
Effluent
Limitation
Guidelines
and
New
Source
Performance
Standards
for
the
Construction
and
Development
Category;
May
2002.
EPA
821­
R­
02­
009.
http://
www.
epa.
gov/
waterscience/
guide/
construction/