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Chapter 4 - Hest. .Management. Practices for Erosion. and.:Sediment.Gontrol.
Good timing is essential to fill construction. The filling operation should be completed as
quickly as possible and the permanent slope protection measures and slope stabilization
measures installed as soon after completion as possible: With quick and proper
construction, the developer or contractor will save both time and money in building,
repairing and stabilizing the fill area. The longer the time period for construction and
stabilization, the more prone the fill operation is to damages by erosion. Repairing the
damages adds additional time and expense to the project.
` Design Criteria
M No formal design is required. The following criteria shall be met:
Drainage Area
` The maximum allowable drainage area is 5 acres (2 ha).
r
Height
•
The minimum height of the supporting. ridge shall be 9 inches (23 cm). (See Plate 4.16a).
Grade
The channel shall have a positive grade to a stabilized outlet.
Outlet
The diverted runoff should be released through a stabilized outlet, slope drain or sediment
trapping measure.
Construction Specifications
1. The diversion shall be constructed at the top of the fill at the end of each work day
as needed.
2. The diversion shall be located at least 2 feet (60 cm) inside the top edge of the fill.
(See Plate 4.16a).
3. The supporting ridge of the lower side shall be constructed with a uniform height
` along its entire length.
Maintenance
Since the practice is temporary and under most situations will be covered the next work
day, the maintenance required should be low. If the practice is to remain in use for more
than one day, an inspection will be made at the end of each work day and repairs made to
the measure if needed. The contractor should avoid the placement of any material over
the structure white it is in use. Construction traffic should not be permitted to cross the
diversion.
Florida Erosion and -Sediment Control Inspector's Manual
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Chapter 4,: -,Best Man agement. Practices_for Erosion and Sediment. Control
•
4.17 TEMPORARY RIGHT-OF-WAY DIVERSION
• (ES BMP 1.17)
Definition
• A ridge of compacted soil or loose rock or gravel constructed across disturbed
rights-of-way and similar sloping areas.
Purpose
�. To shorten the flow length within a long sloping right-of-way, thereby reducing the erosion
potential by diverting storm runoff to a stabilized outlet or sediment trapping device.
r Conditions Where Practice Apniles: .
Generally, earthen diversions are- applicable where there will be little or no construction
• traffic within the right-of-way. Gravel structures are. more ap"piicable to roads and other
rights-of-way which accommodate vehicular traffic:
• Planning Considerations
Construction of utility lines and: roads often requires the clearing of long strips of
.. right-of-way over sloping terrain. The volume.and velocity of stormwater runoff tend to
increase in these. cleared strips and the potential for erosion is much greater since the
vegetative cover is diminished or removed. To compensate forthe loss of vegetation, itis
usually a good practice to break up the flow length within the cleared strip so that runoff
does not have a chance to concentrate and cause erosion. At proper spacing intervals,
Temporary Right -of -Way Diversions can significantly reduce the amount of erosion which
,. will occur until the area is permanently stabilized.
Design Criteria
• No formalAesign is required. The following criteria shall be met:
,. Drainage Area
Less than 5 acres (2 he). For larger drainage areas use a DIVERSION. -Section 5.18 (ES
• BMP 1.18).
Dimensions
The minimum allowable height measured from the upslope side of the diversion is 18
inches (45 cm). The minimum top width shall be 2 feet (60 cm) and the base width
• minimum is 6 feet (1.8 m). (See Plate 4.17a)
Side Slopes
3:1 or flatter to allow the passage of construction traffic.
Florida Erosion and Sediment Control Inspector's Manual
Width
The measure should be constructed completely across the disturbed portion of the
right-of-way.
Plate 4.17a Temporary Right-of-way Diversions
Source: Virginia OSWC
Chapter4- Best Management rraottces Tor erosion
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Spacing
The following table will be used to determine.the spacing of right-of-way diversions:
% Slope 'Spacing in feet(m).
Less than 5% 300 (90 m)
Between 5% and 10% 200 (60 m)
Greater than 10% 100 (30 m)
Grade
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Positive drainage, With less than 2% slope, should be provided to a stabilized outlet or
sediment trapping facility.
Outlet
Interceptor dikes must have an outletwhich is not subject to erosion. The on-site location
may need to be adjusted to meet field conditions in order to utilize the most suitable outlet.
Concentrated flows should spread over the widest possible area after release. Flows with
r high sediment concentrations should pass through a sediment trapping measure. (See
Plate 4.17b)
Construction Specifications
1. The diversion shall be installed as soon as the right-of-way has been cleared
and/or graded.
2. All earthen diversions shall be machine- or hand -compacted in 8 -inch (20 cm) lifts.
it
3. The outlet of the diversion shall be located on an undisturbed and stabilized area
when at all possible. The field location should be adjusted as needed to utilize a
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stabilized outlet. Sediment laden flows shall be conveyed.to a sediment trapping
device.
4. Earthen diversions which will not be subject to construction traffic should be
stabilized in accordance with TEMPORARY SEEDNG - Section 6.65 (ES BMP
.65).
•
Maintenance
The practice shall be inspected after every rainfall and repairs made if necessary.
Approximately once every week, whether a storm has occurred or not, the measure, shall
be inspected and repairs made if needed. Diversions which are subject to damage by
,,,, vehicular traffic should be reshaped at the end of each working day.
Florida Erosion and. Sediment Control Inspector's Manual
t,
�raly-
2:i SIDE 5LOMS -
3i I MAX
I— FFOOR Yee' illrRE G7smc,
SLOM
q '::�'_'_• law MIN.
.I
SECTION
Plate 4.17b Rolling Dip and Water Bar
Source: Erosion Draw
4-66
a
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- Rest M.anaaement Practices.for.Eroslon and
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4.25 TEMPORARY SEDIMENT TRAP
(ES BMP 1.25)
Definition
r A small temporary ponding area formed by excavation and/or an embankment across a
draihageway.
r
Purpose
.. To detain sediment -laden runoff from small disturbed areas long enough to allow most of
the sediment to settle out thereby protecting drainageways, properties, and rights-of-way
from sedimentation.
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Conditions WherePractice Apolies
r 1'. A sediment trap is usually installed in a drainageway, at a storm drain inlet or at
other points of discharge from a disturbed area.
., 2. Below drainage areas of 5 acres (2 ha) or less.
3. Where the sediment trap will be used less than 18 months.
r
4. The sediment trap may be constructed either independently or in conjunction with
a TEMPORARY DIVERSION DIKE - Section 4.15 (ES BMP 1.15).
Plannirrg Considerations
The sediment trap should be located to obtain the maximum storage benefit from the
terrain, for ease of clean out and disposal of the trapped sediment and to minimize
interference with construction activities.
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Sediment traps should be used only for small drainage areas. If the contributing drainage
area is greater than 5 acres (2 ha), refer to SEDIMENT BASINS - Section 4.26 (ES BMP
,. 1.26).
Sediment must be periodically removed from the trap. Plans should detail how this
., sediment is to be disposed of, such as by use in fill areas on site or removal to an
approved off-site dump.
r Sediment traps, along with other perimeter controls, shall be installed before any land
disturbance takes place in the drainage area.
L-1
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Florida Erosion and Sediment Control Inspector's Manual
Dike if Required to Divert Water to Trap �
:;::!: f::g
Section A A
Excavated Earth Outlet SedimentTrap
Excavate, if Necessary, for Storage
Flow
Embankment,X-4'0
21 or Flatter
Width (ft)
6 x Drainage Area (Ac.)
Outlet Section
Embankment Earth Outlet Sediment Trap
Construction o if ations
1. Area under embankment shall be cleared, grubbed and stripped of any vegetation and root mat The
pool area shall be cleared.
2. The fill material for the embankment shall be free of roots or other woody vegetation as well as over-
sized stones, rocks, organic material, or other objectionable matsdai.The embankment shall be
compacted by traversing with equipment while it is being constructed
a. Sediment shall be removed and trap restored to its original dimensions when the sediment has
accumulated to 112 the design depth of the trap. Removed sediment shall be deposited in a suitable
area and in such a manner that it will not erode.
4. The structure shall be inspected after each rain and repairs made as needed.
5. Construction operations shall be carried out in such a manner that erosion and water pollution are
minimized.
S. Tile structure shall be removed and area stabilized when the drainage area has been properly stabirized.
7. All out and fill slopes shall be 2:1 or flatter.
S. Outlet crest elevation shall be at least one foci below the top of the embankment
Plate 4.25a Earth Outlet Sediment Trap
Source: NRCS
Chapte
.r
Design Criteria
Trap Capacity
Erosion and
The sediment trap must have an initial storage volume of 134 cubic yards, or 3600 cubic
feet per acre ( 252 m3/ha) of drainage area, measured from the low point of the ground to
the crest of the gravel outlet. Sediment should be removed from the basin when the
volume is reduced by one-half.
r
For a natural basin, the volume may be approximated. as follows:
• V=0.4xAxD
where: V = the storage volume in ft.3
• A = the surface area of the flood area at the crest of the outlet, in ft.Z
D = the maximum depth, measured from low point in trap to crest of outlet,
in ft.
Excavation
If excavation is necessary to attain the required storage volume, side slopes should be no
steeper than 2:1.
• Embankment Cross -Section
The maximum height of the sediment trap embankment shall be 5 feet (1.5 m) as
• measured from the low point. Minimum top widths (W) and outlet heights (Ho) for various
embankment heights (H) are shown in Table 4.25a. Side slopes of the embankment shall
be 2:1 or flatter.
•
Table 4.25a7
MINIMUM TOP WIDTH (W) AND OUTLET HEIGHT (Ho) REQUIRED FOR
SEDIMENT TRAP EMBANKMENT ACCORDING TO HEIGHT OF EMBANKMENT (feet)
W H: Ho W
2.0
1.0
2.0
.. 2.5
1.5
2.5
3.0
2.0
2.5
3.5
2.5
3.0
4.0
3.0
3.0
4.5.
3.5
4.0'
5.0
4.0
4.5
Florida Erosion and Sediment Control Inspector's Manual
Earth Embankment .
Nutlet Protection
All Slopes 2:1 or Flatter
Excavate, if Necessary, for Storage
Flow
Lam•.
4'
�.�. ;1^-6' Min.
5' Max.
Welded All Around
Embankment SectionThru Fuser
Construction Specifications
Perforated Riser
1. Area under embankment shall be cleared, grubbed and stripped of any vegetation and root mat. The
pool area shall be cleared
2. The fill material for the embankment shall be free of roots.or other woody vegetation as well as over-
sized stones, rocks, organic material, or other objectionable material.The embankment shall be
compacted by traversing with equipment while it is being constructed.
3. Sediment shall be removed and trap restored to its original dimensions when the sediment has
accumulated to 1/2 the design depth of the trap. Removed sediment shall be.deposhed in a suitable
area and in such a manner that it will not erode.
4. The structure shall be Inspected after each rain and repairs made as needed.
5. Construction operations shall be carried out in such a manner that erosion and water polluflon are
minimized.
6. Tile structure shall be removed and area stabilized when the drainage area has been properly stabilized.
7. All cut and fill slopes shall be 2.1 or flatter.
B. All pipe connections shall be watertight
9. At least the top 213 of the riser shall be perforated with 112 -inch diameter holes spaced a inches
vertically and 10 -12 inches horizontally.
10. Fig matertail around pipe spillway shall be hand compacted in 4 -Inch layers. A minimum of two feet of
hand -compacted backtlll shall be placed over the pipe spillway before crossing If with construction equip- ,
ment.
Plate 4.25b Pipe Outlet Sediment Trap
Source: NRCS
M
w
;.-,
L7
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u
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Chapter 4 - Best Management Practices for Erosion and. Sediment Control
ORIGINAL
GROUND
ELEV.
Ill VARIABLE
67 CU. YD./ACRE — T
(EXCAVATED) V QAX'
FILTER CLOTH ORIGINAL
GROUND
ELEV.
COARSE AGGREGATE CLASS I WRAP
Crass -Section of outlet
CLASS I RIRRAP
LENGTH (IN FEET)
H X DRAINAGE AREA
I lip (LN AC.)
�.- ONERSION
DIKE'
Z MM
COARSE AGGREGATE4 ME
f f
EXCAVATED FILTER CL F/par_!
AREA
CGARSE AGlic(CijAtC SF:`Ai.t SE rTOT y3, X357 OR. #5
Outlet (Perspective View)
Plate 4.25c Slone Outlet Sediment Trap
Source: NRCS
r
441
TOE OF
U
KEY BALE INTO
BANKAT BOTH:
ENDS OF, BARRIER
It �-EMBED STRAW.
BALE 4' MIN,
U INTO SOIL
SECTION A - A
STRAW BALES
TIGHTLY ABUTTING. .
3
it . • Y
0
WOODEN STAKE
OR REBAR DRIVEN
T1qROV6H. SALE. ..
TYP. :Z= PER BALE' ..
TA A,yviy.
VIEW LOOKING UPSTREAM
NOTES,
I. PLACE BALES PERPENDICULAR
.. -
TO PLOW.
2. £t*15EP THE BALE
4' INTO THE SOIL AND
'KEY' THE END SALES
INTO THE CHANNEL' -
BAHKS.
S. BALES PLACED
IN A ROW WITH ENDS
TI6HnLY ABUTTING.
USE STRAW, ROCKS OR
FILTER FABRIC TO
PILL ANY 6AP5 BBTreEm
BALES AND TAMP
SACKFILL MATERIALS TO
FFMTV Mr EROSION
OR FLOYV AROUND THE
SALES.
4. POINT 'A' SHAH
BE HIGHH¢ THAN POINT 'B'.
5. SPILLWAY SHALL
NOT EXCE= 241.
Plate 4.25d Semi -pervious Straw Bale Sediment Barrier
Source: Erosion Draw
4-72
Chapter 4---7 Best -Managements Practices for Erosion and. Sediment uontrot
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Outlet
The outlets shall be designed, constructed and maintained so that sediment does not leave
the trap and that erosion of the outlet does not occur. A trap may have several different
outlets: with each outlet conveying part of the flow based on the criteria below. The
combined outlet capacity shall be sufficient for the drainage area. Foe. example, a 12 foot
(3.6 m),earth outlet, adequate for 2 acres (0.8 ha), and a 12 inch (30 cm) pipe outlet,
adequate for 1 acre (0.4 ha), could be used for a three acre (1.2 ha) drainage area.
There are four types of outlets for sediment traps. Each sediment trap is named according
r to the type of outlet that it has. Each type has different design criteria and will be
discussed separately.
1. An Earth Outlet Sediment Trap consists of a basin formed by excavation andloran
embankment. The trap has a discharge point overor cut into natural ground. The
outlet width (feet) shall be equal to 6 times the drainage area (acres). If an
embankment is used the outlet crest shall be at least one foot (30 cm) below the top
of the embankment. The outlet shall be free of any restriction to flow. The earthen
embankment shall be seeded with temporary or permanent vegetation (see
Sections 6.65. and 6.66) within 15 days of construction: (See Plate 4.25a)
2. A Pipe Outlet Sediment Trap consists of a basin. formed by an embankment, or an
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excavation and 'an embankment. The outlet for the trap is though`a perforated riser
and a. pipe through the embankment. The outlet pipe and riser shall be made of
corrugated metal. The riser diameter shall- be of the same or larger diameter than
the pipe. The top of the embankment shall be at least 1.5 feet (45 cm) above the
crest of the riser. At least the top 2/3 of the riser shall be perforated with 1/2 inch
(13 mm) diameter holesspaced 8 inches (20 cm) vertically and 10-12 inches (25
30 cm) horizontally. All pipe connections shall be watertight (See Plate 4.25b).
us Select pipe diameter from the following table:
4W 12
(30
cm)
1(0.8
18
(45
cm)
ha)`
21
(53
cm)
3
(1.2
ha)
24
(60
cm)
4
(1.6
ha)
30
(75
cm)
5
(2.0
ha)
3. A Stone Outlet Sediment Trap consists of a basin formed by an embankment or
excavation and an embankment. The outlet for the sediment trap shall consist of a
crushed stone section of the embankment located at the low point in the basin. The
f t1L� s L..❑ 5... t' 4 '- h r 9 r
minimum length o. ti le outlet shaft be 6 feet thanes the acreage of a talnage area
(4.5 m times hectares). The crest of the outlet must be at least lfoot (30 cm) below
the top of the embankment, to insure that the flow wilt travel over the stone and not
the embankment. The outlet shall be constructed of FDOT No. 1 size crushed
stone. (See Plate 4.25c) Avery temporary alternate trap can be constructed from
straw bales with a stone outlet. (See Plate 4.25d) Straw bales shall be installed per
Section 4.05 STRAW BALE BARRIER (ES BMP 1.05).
A.71
and. Sediment Control Inspectors Manual.
4. A Storm Inlet Sediment Trap consists of a basin formed by excavation or natural
ground that discharges through an opening in a storm drain inlet structure. This
opening, can either be the inlet opening or a temporary opening made by omitting
bricks or blocks in the inlet. The trap shall be between 1' and 2'(30 - 60 cm) deep
measured from the low point of the inlet. A yard drain inlet or an inlet in the median
strip of a dual highway would use the inlet opening for an outlet. (See Plate 4.25e)
A curb inlet would require a temporary opening. (See Plate 4.25f) The trap should
be out of the roadway to.avoid interference with constriction. Placing the trap on
the opposite side of the opening and diverting water from the roadway to the trap is
one means of accomplishing this.
5. Other applications Attimes a small trap may be constructed in a drainage channel
using the culvert for a road crossing. Straw bales or gravel filled bags maybe used
provided that there are no gaps in the installation. (See Plate 4.25g) In larger
traps baffles may be required to insure adequate flow length and prevent short-
circuiting: (See Plate 4.25h)
Construction Specifications
The area under the embankment shall be cleared, grubbed; and stripped of any
vegetation and root mat. To facilitate cleanout, the pool area should be cleared.
2. Fill material for the embankment shall be free of roots or other woody vegetation,
organic material, large stones, and other objectionable material. The embankment
should be compacted in 8 inch. (20 cm) layers by traversing with construction
equipment. - - .
3. The earthen embankment shall be seeded with temporary or pe rmanent vegetation
(see Sections -6.65 and 6.66) within 15 days of construction.
4. Construction operations shall be carried out so that erosion and water pollution are
minimized.
5. The structure shall be removed and the area stabilized when the upslope drainage
area has been stabilized:
Maintenance
Sediment shall be removed and the trap restored to its original dimensions when
the sediment has accumulated to 112 the design volume of the trap: Sedimeni
removed from the basin shall be deposited in a suitable area and in such a
manner that it will not erode.
2. The structure should be checked regularly to insure that it is structurally sound and
has not been damaged by erosion or construction equipment. The height of the
outlet should be checked to ensure that its center is at least one foot (30 cm) below
the top of the embankment.
4-74
an
Chapter 4 - Best Mans
a
t Practices for Erosion and Sediment
MAX. SLOPE 2
STORM WATER WITH
LaROER PARTICLES".
REMOVED
DRAIN INLET
FLOW
7�' 1 r
FLOW
FLgR
DEPTH BELOW TOP OF INLET:
MIN. I'— MA%. Z ,
WEEP
HOLES
1111.�f 11 - s
FOR
DEWA7ERING
_ _....
I[-1f=tf—ll—/-11-1
'=if=►f�f=fl=lr=ao=u=n.
TH!S METHOD OF INLET PROTECTION IS APPLICABLE WHERE HE"YY FLOWS
ARE EXPECTED AND WHERE AN OVERFLCW CAPAStLITY AND EASE OF
MAINTENANCE ARE DESIRABLE,
Plate 4.25e Excavated Drop Inlet Sediment Trap
Source: Michigan Sol Erosion and Sedimentation Control Guidebook
i
Florida Erosion and Sediment Control Inspector's Manual
Row• is - ROW
' l•,,i �\� `\:�-`-'. + 1. t j•L•i .;
�'t,♦ .l jA`• !C' fop
� � ori'}-+•�•
/'�^ Row'
Flow . - S`�•<� -
As Required —7 21 or Flatter
Cross -Section
Yard Drain
Block Inlet with Plywood and Sandbags,
as Necessary, to Prevent Water from Entering?
Flow �
er
L., I K\1�49
y .. 11it
'
A
Remove Bricks or::-1�-�•:
Blocks for outlet I -
Trap may be Placed Behind
or at End of Inlet
ff 2.1 or ��Fla��ttt�er
. 7r/V_,IiYLiIYrtlY11111iielr
4v
1 Min f'
Section A -A
Curb Drain .
NOTE Where curb is in place, provide a 1 foot wide
opening in the curb or use a sandbag dam to
force water over the curb to the trap.
Construction Soecifications
1. Sediment shall be removed and trap restored to its original dimensions when the sediment has
accumulated to 1/2 the design depth of the trap. Removed sediment shall be deposited in a suitable
area and in.such a manner that it will not erode.
2.The structure shall be inspected after each rain and repairs made as needed.
3. Construction operations shall be carried out in such a manner that erosion and water pollution shall
be minimized.
4. The sediment trap shall be removed and area stabilized when the remaining drainage area has been
properly stabilized.
S. All cut and fill slopes shall be 2:1 or flatter.
Plate 4.25f Storm Inlet Sediment Trap
Source; NRCS
M
W-
a.
W
W
W
for Erosion and Sediment Control
RemoVai
removedSedime nt traps must be
shou d show how the site of the sedi{ment trap Iso be graded anstabilized,
d stabilized after removal.
c_. a 1 M. - -..m ._
ra a- a �vm
SIDE VIEV
MW Meko MR
EA
em PM4TS -A' MST BE Hla-e
l,,m aim LITE Fmw •B'
A B. A
N2 rteS AF E m BE ermexr
FRONT VIEV
(NO SCALE)
FRONT VIEV
(ALTERNATIVE)
TDP VIEV GRAVEL CiMAII�ED IN PERVIOUS4BURLAP BAGSEiLR
syorE i IC NET BAGS (1/6 -INCH MESH AND BE
APPK-7l XW1 iELY. 24 INO-ES LONG. 12 INCES VIDE
PND 6 INCFES Rich
to Plate 4.26g Small Sediment Trap Located within a Stormwater Conveyance Channel
Source: HydroDynamics, Inc.
4-77
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Florida Erosion and Sediment Control Inspectors Manual.
SEDIMENT TRAP GUIDELINES
lot
H (FT] I 20 aS 3.0 35 5A 4.5 5.0
v rF n eo as as ao 3:0 4 0 4s
104SWC'QdT. SIM SLD'ES ARE NiT TO M
STEEPER TK" a
SP3LLVAY MS136ED To PASS
10 -YR. 24 -FR PEAK FLDVS
l
WER EMlNATF9 VD_L!E' .
ru n. aTW gY SE9II T DJTET PIPE mrn To
STMAC8 EIIZYTZ - CaJVe! anTL NS
i0RE
Dag ,
a/, U%cs
DETENTION PCIND_ SEDIMENT TRAP/BASIN
OVER
:'�. a,E
.. .
seam
- .'a._
a a-
-a
HISTERIC
FLOW LENGTH
DETAIL
= UP
Wpnx My ix
FL.W LiNGT}i .
r
BAFFLE DETAIL
ELEVAT104 Cr
RISER CRESTS
CZVATZ:N or
naawn an-mn
Plate 4.25h Sediment Trap and Basin Guide
Source: HydroDynamics, Inc.
70
3
M"
4-78
nt Practices for -Erosion and Sediment Control
Chapter 4 -Best Mana eme
4.26 TEMPORARY SEDIMENT BASIL
(ES BMP 1.26)
Definitlon
A temporary basin with a controlled stormwater release structure, formed by constructing
an embankment of compacted soil across a drainageway.
` Pur ose
To detain sediment-laden runoff from disturbed areas long enough for most of the
` sediment to settle out.
Conditions Where Practice Acolles
Below disturbed areas greater than 5 acres (2 ha). There"must be sufficient space and
appropriate topography for the construction of a temporary impoundment. Thesestructures
` are limited to a useful life of 18 months unless they are designed as permanent ponds by a
qualified professional engineer.
` Planning Considerations
Effectiveness
Sediment basins are at best only 70-80% effective in trapping sediment which flows into
them. Therefore, they should be used together with erosion control practices such as
temporary seeding, mulching, diversion dikes, etc. to reduce the amount of sediment
flowing into the basin.
` Location
To improve the effectiveness of the basin, it should be located so as to intercept the largest
possible amount of runoff from the disturbed area. The best locations are generally low
areas and natural drainageways below disturbed areas. Drainage into the basin can be
improved by the use of diversion dikes and ditches. The basin must not bnters the strea e located in live
stream but should be located to trap sediment=laden runoff before it eam.
The basin should not be located where its failure would result in the loss of life, damage to
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adjacent properties, or interruption of the use of public utilities or roads.
Multiple
Sediment basins may be designed as permanent structures to remain in place after
construction is completed. The Stormwater Rule (Ch. 62-25, F.A.C.) makes the use of
these structures desirable for stormwater detention purposes. Always leave the bottom of
r the sediment basin 6" -12" higher than the eventual bottom of a retention basin. This will
ensure removal of accumulated fine sediments which could prematurely clog the retention
basin. Wherever these structures are to become permanent, or if they exceed the size
limitations of the design criteria, they must be designed as permanent ponds by a qualified
professional engineer. Permanent ponds are beyond the scope of this BMP -
4 -79
Florida Erosion and Sediment Control Inspector's Manual
Design Criteria
Maximum Drainage Area
Unless the structure is, designed as a permanent pond by a qualified professional engineer,
the maximum allowable drainage area.into the basin shall be 150 acres (61 ha).
Basin Capacity
The design capacity of the basin must be at least -134 cubic yards or 3600 cubic feet per
acre (252 m3/ha) of drainage area measured from the bottom of the basin to the crest of
the principal spillway (riser pipe). Sediment should be removed from the basin when the
volume of the basin has been reduced to 55 cubic yards per acre (104 m3/ha) of drainage
area. The elevation of the sediment clean out level. should be calculated and clearly
marked on the riser. In no case shall the sediment clean out level be higher than one foot
(30 cm) below the top of the riser. (See Plate 4.26a).
Basin Shape
To improve sediment trapping efficiency of the basin, the effective flow length must be
twice the effective flow width. This basin shape may be attained by properly selecting the
site of the basin, by excavation, or by the use of baffles. See Appendix 1.26A for design
details.
Plate 4.26a Sediment Basin Storage Volumes
Source: Virginia DSWC
67
C.Y. AC."
DRY STORAGE
DEWATERING
DEVICE
67 C.Y./ AC.
-
.
" WEr
" STORAGE
_
SEDIMENT
CLEANOUT POINT
{"E 3
STORAGE DUCED
E-
TO4
C.Y.f ACRE)
Plate 4.26a Sediment Basin Storage Volumes
Source: Virginia DSWC
Practices for Erosion. and Sediment Control.
Embankment Cross -Section
The embankment must have aminimum top width of a feet (2.5 m). The side slopes must
be 2:1 or flatter. The embankment may have a maximum height of 10 feet (3 m) if the side
slopes are 2:1. If the side slopes are 2.5:1 or flatter, the embankment may have a
.. maximum height of 15 feet (4.5 m).
Sgil U Design
The outlets for the basin may consist .of a combination of principal and emergency
spillways or a principal' spillway alone. In either case, the outlet(s) must pass the peak
runoff expected from the drainage area for. a 1t0 year storm without damage to the
embankment of the basin. Runoff computations shall be based upon the soil cover
conditions which are expected to prevail during the life of the basin. Refer to Chapter 3 of
• this manual for calculation of the peak rate of -runoff,
The spillways designed by the procedures contained in this BMP will not necessarily result
+. in any reduction in the peak rate of runoff. If a reduction in peak runoff is needed; the
appropriate hydrographs should be generated to choose the basin and outlet sizes.
n. To increase the efficiency of the basin, the spillway(s) must be designed to maintain a
permanent pool of water between storm events.
.. Principal Spillway
The principal spillway shall consist of a solid (non -perforated), vertical pipe or box of
r corrugated metal or reinforced concrete joined by a watertight connection to a horizontal
pipe (barrel) extending through the embankment and outletting beyond the downstream toe
of the fill. If the principal spillway is used in conjunction with an emergency spillway, the
.. ve a minimum capacity of 0.2 cfs per acre (0.015 m3 /sec. per ha)
principal spillway shall ha
of drainage area when the water surface is at the crest of the emergency spillway. If no
emergency spillway is used, the principal spillway, must be designed to pass the entire
w peak flow expected from a 10 -year storm.. See Appendix 1.26A of The Florida
Development Manualfor design details.
w Design Elevations
If the principal spillway is used together with an emergencyy spillway, the crest of the
principal spillway shall be a minimum of one foot (30 cm) below the crest of the emergency
spillway. if no emergency spillway is used, the crest of the principal spillway shall be a
minimum of 3 feet (90 cm) below the top of the embankment. (See Plate 4.26b.) In either
r case, a minimum freeboard of one foot (30 cm) shall be provided between the design high
water and the top of the embankment.
77
up
Florida Erosion and. Sediment Control Inspector's Manua!
HIGH WATER
STORM ELEV.)
O.S
CREST OF EMERGENCY
i SPILLWAY
f RISER CREST
67 C.Y./ AC. :•; !: DEWATERING
DRY " STORAGE ..... .... .'r _ DEVICE
67 C.Y./ AC.
" WET " STORAGE
(CLFANOUT POINT
�� STORAGE REDUCED
TO 34 C.Y./ ACRE)
Design Elevations with Emergency Spillway
DESIGN HIGH WATER U2,O6
(25-YR. STORM E1EV:), MINMIN .jr 0.
MIN. 1.0' L_
67 C.Y./ AC. -
DRY ' STORAGE
67 C.Y./ AC. -
" WET " STORAGE
SEDIMENT CLEANOUT
• . RISER CREST
DEWATERING
DEVICE
Design Elevations without Emergency Spillway
(Riser Passes 26 -Year Event)
Plate 4.26b Sediment Basin Schematic Elevations
Source: Virginia DSWC
4-82
►_,z
Anti -vortex device and trash rack
for Erosion and Sediment Control
An anti -vortex device and trash rack shall be attached to the top of the principal spillway to
improve the flow of water into the spillway and prevent floating debris from being carried
out of the basin. The anti -vortex device shall be of the concentric type. (See Plate 4.26c).
See Appendix 1.26A of The Florida Development Manual for design procedures for the
anti -vortex device and trash rack.
Dewatering:
Shall be done in a way that removes the relatively clean waterwithout removing any of the
.. sediment that has settled out and without removing any appreciable quantities of floating
debris. As a minimum, provisions shall be made to dewater the basin down to the
sediment cleanout elevation. This can be accomplishedby providing a hole at the
r maximum sediment retention elevation (See. Plate 4.26b). The dewatering hole shall be
no larger than 4 inches (10 cm) in diameter. Other means of automatic dewatering are
detailed in Appendix 1.26A of The Florida Development Manual.
It is also advantageous (but not required). to provide for dewatering. of trapped sediment
before clean out. Basin underdrains are generally installed for this purpose. Appendix
.. 1.26A contains details for the design of an underdrain system.
Base
r The base of the principal spillway must be firmly, anchored to prevent: its floating. If the
riser of the spillway is greater than 10 feet (3 m) in height, computations must be made to
�., determine the anchoring requirements.' As a minimum, a factor of safety of 1.25 shall be
used (downward forces = 1.25 x upward forces).
,. For risers 10 feet (3 m) or less in height, the anchoring may be done in one of the two
following ways:
op 1. A concrete base I's inches (45 cm) thick and twice the width of riser diameter shall
be used and. the riser embedded. 6 inches (15 cm) into the concrete. (See Plate
4.26d and Appendix 1.264 ofi The. Florida Development Manual for design details).
2. A square steel piste, a minimum of 114 inch (6.5 mm) thick and having a width equal
to twice the diameter of.the. riser..shall be welded to the base of the riser. •The plate
�. shall then be covered with 2.5 feet (76: cm) of stone, gravel, or compacted soil to
prevent floatation. (See Plate 4.26d and Appendix 1.26A for design details).
r. Barrel
The barrel of the principal spillway, which extends through the embankment, shall be
designed to cavy the flow provided by the riser of the principal spillway with the water level
at the crest of the emergency spillway. The connection between the riser and the barrel
must be watertight. The outlet of the barrel must be protected to prevent erosion or scour
of downstream areas. See Appendix 1.26A for design details.
Florida Erosion and Sediment Control Inspector's Manual
Plate 4.26c Anti -vortex Device Design
Source: NRCS
4-84
Chapter 4 Best, Management Practices for. Erosion. and Sediment Control
Plate 4.26e Location of Anti -seep Coilars
Source: Virginia CSWC
• 4-85
Florida Erosion and Sediment Control Inspector's Manual
Plate 4.26f 'Emergency Spillway
Source: Virginia DSWC
4-86
Practices for. Erosion and Sediment Control
Anti -seep collars
Anti -seep collars shall be used. on the barrel of the principal spillway within the normal
saturation zone of the embankment to Increase the seepage length by at least 10%, if
either of the following two conditions is met:
1. The settled. height of the embankment exceeds 10 feet (3 m).
2. The embankment has a low silt -clay content (Unified Soil Classes SM or GM) and
the barrel is greater than 10 inches (25 cm) in diameter.
The anti -seep collars shall be installed within the saturated zone. The maximum spacing
4 times the projection of the collar above the barrel. Collars shall
between collars shall be 1 o cm) to a pipe joint. Collars ssufficiently not be closer than 2 feet 4 should be placed suciently far
apart to allow space for hauling and compacting equipment. Connections between the
collars and the barrel shall be watertight. See Plate 4.26e and Appendix 1.26A for design
procedure and details.
Emergency Spillway
The emergency spillway shall consist of an open channel constructed next to the
embankment over undisturbed material or properly compacted fill. The spillway shall have
a control section at least 20 feet (6 m) in length. The control section is a level portion of
the spillway channel at the highest elevation in the channel. (See Appendix 1.26A and
plate 4.26f). The primary spillway and the emergency spillway shall both discharge to
stabilized outlets. (See Plate 4.26g)..
Ca acif
The emergeneyspillway shall be designed to carry the. peak rate of runoff expected from a
10 -year storm, less any reduction due to the flow through the principal spillway. See
Appendix 1.26A for: design details.
r
Design elevations
" The design high water through the emergency spillway shall be at least one foot (30 cm)
below the top of the embankment. The crest of the emergency spillway channel shall be at
least one foot (30 cm) above the crest of the principal spillway.
s
Location
an The emergency spillway channel shall be located to avoid fill material. if consucted on fill,
the fiilwill be properly compacted in lifts. The channel shall be located so as to avoid sharp
turns or bends. The channel shall return the flow of water to a defined channel
an downstream from the embankment.
4-8
Florida Erosion and Sediment Control Inspector's Manual
SEDIMENT RISER KITH _
15A51 TRASH RACK
STABILIZED
OUTLET
PLAN
`-TRASH RACK STABILIZE T
C�R� cmaRGENGY SPILLFNAY KITH VEGETATION
% 1 FT .,,. FRE=BOARD
T i �ENGMESZED _ - SPILLMNY
FT 7 1 SELEGTID FILL BARREL
I Imo,` �`i`"AG STI
STABILIZED
DRAINAG`
ANi f - COLLAR
7YP. of 3
SECTION
NOTES.
1. THE T'M'ORARY IMENT 5ASIN, D5516NED
BY A WALIFiED PROF�551aNAL, IS REaUIRi=D
FDR DISTURBED AREAS GREATER T+JAN 5 A4,RE5
NITHIN A DRAINAGE AREA LESS THAN 100 ACAS.
• 2. THE �5EWIMENT BASIN SHILL BE REMOVE17 K17H-
IN 3 TEARS.
Plate 4.26g Sediment Basin
Source; Erosion Draw
488
Best
Erosio
Maximum velocities
The maximum allowable velocity in the emergency spillway channel will depend upon the
type of lining used. For vegetated linings, allowable velocities are listed in Table 5.35a
(STORMWATER CONVEYANCE CHANNEL - Section 5.35 - ES SMP 1.35), For
non -erodible linings, such as concrete or asphalt paving and riprap, design velocities may
be increased. However, the emergency spillway channel shall return the flow to the natural
channel at a non -eroding velocity. See Appendix 1.26A for design details.
Stabilization of the Embankment and Basin
r The embankment of the sediment basin shall be temporarily seeded within
completion as perTEMPORARY SEEDING -Section 6.65 (ES BMP 1.65)
r required in the basin, side slopes should not be steeper than 2:1.
15 days after ifs
if excavation is
Cleanout
r Sediment shall be removed from the basin when the capacity is reduced to 55 cubic yards
per acre (104 m'lha) of drainage area. This elevation should be clearly marked; preferably
r sin shalt state the methods for disposing of
on the riser. Plans for the sediment. ba
sediment removed from the basin. Possible alternatives are the use of the material in fill
areas on-site or removal to an approved off-site dump.
Finaremoval
r. Sediment basin plans shall show the final disposition of the sediment basin after the
upstream drainage area is stabilized. The plans shall specify methods for the removal of
excess water lying over the sediment, stabilization of the basin site, and the disposal of any
excess material. Sediment shall not be flushed into the stream or drainageway.
Safe
VE Sediment basins are attractive to children and can be very dangerous. Therefore, they
should be fenced or otherwise made inaccessible to persons or animals unless this is
,. deemed unnecessary due to the remoteness of the site or other circumstances.
Strategically placed signs around the impoundment reading "DANGER -QUICKSAND"
should also be installed. In any case, local ordinances and regulations regarding health
r and safety must be adhered to.
Construction Specifications
r
Site Pry an
Areas under the embankment and any structural works shall be cleared, grubbed, and
stripped of topsoil to remove trees, vegetation, roots, or other objectionable material. In
order to facilitate cleanout and restoration, the pool area (measured at the top of the
+� principal spillway) will be cleared of all brush and trees.
INFLOW
D
D 2
Florida Erosion and. Sediment Control
NO SCALE
w 7'
spector's Manual
L = TOTAL DISTANCE FROM
THE POINT OF INFLOW
AROUND THE BAFFLE TO
THE RISER.
SHEETS OF V x as X 1/T' EXTERIOR
PLYWOOD OR EOUIVALENT
RISER CREST ELEVATION
4�SQUAE MIN,
ORSo ROUND. SET
AT
LEAST 34 INTO THE CROUNO.
e' I
Plate 4.26h Example Plan Views of Baffle Locations in Sediment Basins
Source: NRCS
t Practices for! Sediment Contro
Chapter 4 -Best Managemenl .
r
cutoff Trench
For earth fill embankments, a cutoff trench shall be excavated along the centerline of the
dam. The minimum depth shall be 2 feet (60 cm): The cutoff trench shall extend up both
abutments to the riser crest elevation. The minimum bottom width shall be 4 feet (1.2 m),
" but wide enough to allow operation of compaction equipment. The side slopes shall be no
steeper. than 111. Compaction requirements shall be the same as those for the
embankment. The trench shall be drained during the backfilling -compacting operations.
Embankment
The fill material shall be taken from approved borrow areas. It shall -be clean mineral soil,
free of roots, woodymegetation, oversized stones, rocks, or other objectionable material:
Areas on which fill is to be placed shall be scarified prior to placement. of fill. The fill
material should contain sufficient moisture so that it can be formed by hand into a bail
without crumbling. if water can be squeezed out of the ball, it is too wet for proper
compaction. Fill material will be placed in 6 to 8 inch (15 to 20 cm) continuous layers over
the entire length of the fill. Compaction shall be obtained by routing the hauling equipment
over the fill so that the entire surface of the fill is traversed by at least one wheel or tread
track of the equipment, or by using a compactor. The embankment shall be constructed to
an elevation 10% higher than the design height to allow for settlement if compaction is
obtained'with hauling. equipment. If compactors are used for compaction, the overbuild
may be reduced to not les s 't an
Principal Spillway
The riser of the principal spillway shall be securely attached to the barrel by a watertight
connection. The barrel and riser shall be placed on a firm compacted soil foundation. The
base of the riser shall be firmly anchored according to design criteria to prevent its floating.
Pervious material such as sand, gravel or crushed stone shall not be used as backfill
around the barrel or anti -seep collars. Fill material shall be placed around the pipe in 4
inch (10 cm) layers and compacted by hand at least to the same density as the
" embankment. A minimum of two feet (60 cm) of fill shall be hand -compacted over the
barrel before crossing it with construction equipment.
Emergency Spillwa
The emergency spillway should not be constructed over fill material. Design elevations,
widths, entrance and exit channel slopes are critical to the successful operation of the
spillway and should be adhered to closely during construction.
to Vegetative Stabilization
in
The embank
ment on within nd 15cdaysllofay of the sediment ompletioIn of the bas nshall
perTEMPORARY
stabilized with
to temporary 9
SEEDING - Section 6.65 (ES BMP 1.65).
Florida Erosion and Sediment Control Inspector's Manual
EMERGENCY SPILLWAY
CREST
DESIGN HIGH WATER
h
r--1
ANTI—SEEP
ANTI—VORTEX COLLARS
DEVICE or y
RISER - BARREL:
x �D
CONCRETE BASE
L
H = HEAD ON PIPE THROUGH EMBANKMENT
h _ HEAD OVER RISER CREST
L = LENGTH OF PIPE THROUGH EMBANKMENT
DP= DIAMETER OF PIPE THROUGH EMBANKMENT
D,= DIAMETER OF RISER
Plate 4.261 Principal Spillway Design
Source: Virginia DSWC
4-92
O
.. _. .. _.
Chapter -Best lvlana ementPractioes' .ot rosion,an -
Erosion and Sediment Control
The construction of the sediment basin shall be carried out in a manner such that erosion
and water pollution are minimized downstream.
w Final Disposal
When tem ora structures have served their intehded purpose and the contributing
drainage area has been properly stabilized, the embankment and resulting sediment
deposits are to be leveled or otherwise disposed of according to the approved pollution
control plan.
Maintenance
` The embankment of the basin should be checked regularly to ensure that it is structurally
sound and has not been damaged by erosion or construction equipment. The emergency
spillway should be checked regularly to ensure that its lining is well established and
erosion -resistant. The basin should be checked after each runoff -producing rainfall for
sediment cleanout: When the sediment reaches the cleanout level mark, it shall be
r.
removed and properly disposed of.
Information to be Submitted for Approval
Sediment Basin designs and construction plans submitted for review.to the appropriate
regulatory agency shall include:
` 1. Specific location of the dam.
2. Plan view of dam, storage basin and emergency spillway.
3. Cross-sections and profiles of dam, principal spillway and emergency spillway.
4_ Details of pipe connections, riser to pipe connection, riser base, anti -seep collars,
trash rack;. and anti -vortex device.
M 5. Runoff calculations for 10 -year frequency storm.
g. Storage Computations
a. Total required
b. Total available
rr c, Level of sediment at which cleanout shall be required; to be stated as a
distance from the riser crest to the sediment surface.
7. Calculations showing design of pipe and emergency spillway.
Florida Erosion and Sediment Control Inspector's Manual
LEVEL PORTION
CREST AND CONTROL SECTION
— FLOW _�
0
Em
EMBANKMENT
T
Plan View
LEVEL
I LEVET. OR I
GREATER
APPROACH
C14ANNE L
Profile Along Centerline
EXIT SECTOR
NOTE NEITHER THE LOCATION
NOR AUONMENT OF THE
CONTROL SECTION HAS .
TO COINCIDE WITH THE
CENTERLINE OF THE DAM.
X— LENGTH OF
EXIT CHANNEL
WT SECTOR
Cross -Section at Control Section
Plate 4.26j Excavated Earth Spillway
Source: NRCS
494
4:- Best. Management Practices for Erosion: and -Sediment Control... .
Concrete Base for Embankment 10' or Less in Height
%s
Ss
Steel Basefor Embankment 1o' or Less in r+eig"L
Plate 4.26k Riser Pipe Base Conditions for. Embankments Less than 10 Feet High
Source: Virginia DSWC
Florida Erosion and Sediment
Control Inspector's Manual
kR 10
al Or.
1 e. GAGE
AS
THE
WK
N w
R IS WEO
PAIRS,
9.OREO HOLM
AT r GG SECTION 8=3
ELEVATION OF UNASSEMBLED COLLAR
Y MIN
DETAIL
Corrugated Metal
SIZE AND SPACING OF SLOTTED
OPENINGS SHALL BE THE SAME
AS SHOWN FOR CM COLLAR.
USE RODS AND LUGS TO CLAMP
BANDS SECURELY TO PIPE.
1Y tRNA
I MAO OF 2
NaICV. PWS
I1 Thor .E l 9101 " ORAWIIr+• 0 C=M OR B7N A 80
j 1 1/e NOTE FOR BAWDS AND COLLARS:
1� MODIFICATIONS OF THE DETAILS
SHOWN MAY BE USED PROVIDING
1 ,1le EQUAL WATERTIGHTNESS IS
MAWAINED AND DETAILED
DRAWINGS ARE SUBMITTED AND
POvED By
THE ENGINEER PRIOR
TODE
ISOMETRIC VIEW
war
�L— ,lL wsca�""HtEr n IC =u -m MRO AM 11S VEIOFD IRfl1 A COIIIROIOO" YSIO.
NOTE: SLOOTTR DE A OIRSDETAIL F FABRICATION AND NGTM SEW
DENSIONS•AROVE M GAGES.
vOOWJ 10 -eE
•evrka ro GFGiIE1t OF NOTE TWO OTHER TYPES OF ANTI—SEEP COLLARS ARE:
1!]1G1. PPE HYO .. _
1 EPT SHOP
WELDED TO SHORT AI� TS=nON OF O UPPM THE PIPE AND
CONNECTED WITN- CONNECTING BANDS TO. THE. PIPE..
PARTIAL ELEVATION z
MUM
WITH R¢3 FEBAARNCDT
SPCDT HKHORIIZOOHTA6LLLYUND THE PIPE
AND VERTICALLY.
DETAIL
Helical Pipe
Plate 4.26L Anti -seep Collar Details
Source: NRCS
3. UNASsEYBLED COLLARS
SHALL BE MARKED BY
PANTING OR TAGGING TO IDENTIFY MATCHING
ROTES FOR COl1AR5i
PAIRS,
1. ALL MATERIALS TO BE IN ACCORDANCE WITH
4. THE LAP RE7WEEN THE
TWO HALF SECTIONS
AND CONNECTING SAND
CONSTRUCTION AND
CONSTRUCTION MATERIAL
ANO BETWEEN THE PIPE
SHALL BE CAULKED WITH
ASPHALT MASTIC AT
SPECIFICATIONS.
2 WHEN SPECIRED ON
THE PLANS, COATING OF
TtME'or INSTALLATION.
BE
FURNISHEDWITH O
NR ON(C
ACCORDANCE WITH
MATERIAL
5. 1
/Y IAME>ER R
�i STANDARD TA
CONSTRUCTION
CONSTRUCTION
LUGS FOR CONNECTING
COLLARS TO PIPE.
SPECIFICATIONS.
DETAIL
Corrugated Metal
SIZE AND SPACING OF SLOTTED
OPENINGS SHALL BE THE SAME
AS SHOWN FOR CM COLLAR.
USE RODS AND LUGS TO CLAMP
BANDS SECURELY TO PIPE.
1Y tRNA
I MAO OF 2
NaICV. PWS
I1 Thor .E l 9101 " ORAWIIr+• 0 C=M OR B7N A 80
j 1 1/e NOTE FOR BAWDS AND COLLARS:
1� MODIFICATIONS OF THE DETAILS
SHOWN MAY BE USED PROVIDING
1 ,1le EQUAL WATERTIGHTNESS IS
MAWAINED AND DETAILED
DRAWINGS ARE SUBMITTED AND
POvED By
THE ENGINEER PRIOR
TODE
ISOMETRIC VIEW
war
�L— ,lL wsca�""HtEr n IC =u -m MRO AM 11S VEIOFD IRfl1 A COIIIROIOO" YSIO.
NOTE: SLOOTTR DE A OIRSDETAIL F FABRICATION AND NGTM SEW
DENSIONS•AROVE M GAGES.
vOOWJ 10 -eE
•evrka ro GFGiIE1t OF NOTE TWO OTHER TYPES OF ANTI—SEEP COLLARS ARE:
1!]1G1. PPE HYO .. _
1 EPT SHOP
WELDED TO SHORT AI� TS=nON OF O UPPM THE PIPE AND
CONNECTED WITN- CONNECTING BANDS TO. THE. PIPE..
PARTIAL ELEVATION z
MUM
WITH R¢3 FEBAARNCDT
SPCDT HKHORIIZOOHTA6LLLYUND THE PIPE
AND VERTICALLY.
DETAIL
Helical Pipe
Plate 4.26L Anti -seep Collar Details
Source: NRCS
No
7
IM
4 Best
for
POLYETHYLENE CAP
. PROVIDE ADEQUATE .
' ST{tAPPING
DEPTH
_ VARIES AS
REQUIRED
TACK WELD PERFORATED POLYETHYLENEFOR ORY
VtESG(SETEBG4LCULATIOENS IN STORAGE
APPENDIX 3.14—A)
1
WET
. • FERNCO-STYLE ' COUPLING STORAGE
DEWATERING GRIFICE,
�HEDUUE 40 STEEL STUS —FOOT WII
CORRUGAT@ MaAL RISER SC
DNMETER VARIES (SEE CALCULATIONSNltU)A
APPENDIX 3.14-0
See
Plate 4.26m Perforated Pipe Sediment Basin Dewatering Device
Source: Virginia DSWC
Qean Masonry sand Rrear
Welded or
2 4' Pedaaled Pleads placed Mortared Jaud pullet
Y
Minimarn with Pedarallons Dawn
Bed;inrg ,� Place F
over
ripe •: ,d'
P
Y Ris
er
1n 4ltrdmm un car en
Orasa-s n Oraue
piinTr
pe inTmeh ErreratalanaM
Edge at Pod
r n n (] RES"
NOTE Se 15 b 2S
y Met= lad plre L^. Trerslt ..
Plan Yew
SQ=M W Be*, _ pnaiile
— �—
E%Mmirrum Grade --
Plate 4.26n Dewatering a Sediment Basin with Subsurface Drain
Source: NRCS
rr
Florida Erosion and Sediment Control Inspectors Manual
This page left intentionally blank
4>98
)ter 4 - Best Management_. Practices for -Erosion: an(
4,30 TEMPORARY SLOPE DRAIN
.. (ES BMP 1,30)
Definition
A flexible tubing or conduit extending from the top to the bottom of a cut or fill slope.
" Purpose
To temporarily convey concentrated stormwater runoff safely down the face of a cut or fill
slope without causing erosion problems on or below the slope.
Conditions Where Practice Applies
On cut or fill slopes before permanent stormwater drainage structures are installed.
Planning Considerations
There is often a significant lag between the time a cut or fill slope is completed and the
time a permanent drainage system can be installed. During this period, the slope is usually
not stabilized and is particularly vulnerable to erosion. This situation also occurs on slope
construction which is temporarily delayed before final grade is reached. Temporary slope
drains can provide valuable protection of exposed slopes until permanent drainage
structures can be installed.
Earthen Dike
Corrugated'Metal (ComPacted)
Extension Collar �—A
Waterproof Seal
➢+6"
24:1
Protection / �iIII .IljP' Standard Flar
/ �llre — End Section
Section
M
Plate 4.30a Temporary Slope Drain
Source: Virginia SWCC
r
Florida Erosion and Sediment Control Inspectors Manual
�uu� � DIVERSION DIKE
0 Y
J Q
IL IL
Q STANDARD
0 - ICTAL END
F SECTION
STRAP o� •° °
00 o�A�Pj�.
9STA51LIZED
--
�,,
OUTLET
FLEXIBLE VCk*01RAIN
OR PLASTIC PIPE OR `:OP��O•P4AcP
SOCK' SElNN FILTER 666660 po'o; lI��JJSS22�
FAO, �'•Oa
ERI.p'
ISLAND
OVER KO� -
INLET J .
PLAN VIEW
DI Pl E
VSTRAP
OVERERINLET
COLLAR
5TASIL17E
OUTLET
Plate 4.30b Slope Drain
Source: Erosion Draw
4-100
Chapter4- Best Mane ament Practices:'. or rosion
When used in conjunction with diversion dikes., temporary slope drains can be used to
convey stcrmwater from the entire drainage area above a slope to the base of the slope
without erosion. it is very important that these temporary structures be installed properly
since their failure will often result in severe gully erosion.. The entrance section must be
securely entrenched, all connections must be watertight, and the conduit must be staked
securely.
Desia_ n criteria
Drainage--- Area
The maximum allowable drainage area per drain is 5 acres (2 ha).
Flexibles uit`
1, The slope drain sha{I consist of heavy duty.flexible material designed for this
purpose. The diameter of the slope drain shall be equal over its entire length.
Reinforced hold-down grommets shall be spaced at 10 foot (3 m), maximum
intervals.
2.. Slope drains shall be sized according to the folipwing table:
Table 4.30a
SIZE.OF SLOPE DRAIN
Maximum Drainage Area (Acresl
0.5
1.5
2.5
3.5
5.0
Piae Diameter in.
12
18
21
24
3p
Overside drain
ort slopes, an open top chute may be used in place of a pipe.
For small flows and/or sh
(See Plate 4.30c).
Entrance -Sections
The entrance to the slope drain shall consist of a Standard FDOT "Flared End -Section for
Metal Pipe Culverts." Extension collars shall consist of 12 inch (30 cm) long corrugated
metal pipe. Watertight fittings shall be provided. (See Plates 4.30d & 4.309).
Florida Erosion and Sediment Control
Manual.
MAX
n1
Y_
!J
IL
0
0.
OPEN TOP CHUTE
o •9
a.
TAPERED INLET
0
ANCH
o'CA o;
D15GHARGE 70
5TABILIZED WATER.
LU COURSE
Y
n
0
v
0
PLAN. VIEW
DIKE
b° MIN.
OPEN TOP CHUTE
i
ANCHORS AT 10' 04 WITH
MIN. OF 36° EMIMVMa T
SECTION o
Plate 4.30c Overside Drain
Source: Erosion Draw
4-102
r
Chapter 4. Best Management. Practices for Erosion and. Sediment. Control �®
Dike Design
1. An earthen dike shall be used to direct-stormwater runoff into the temporary slope
drain and shall be constructed according to the practice entitled DIVERSION -
r Section 5.18 (ES BMP 1.18). (See Plate 4.30a)
2. The height of the dike at the centerline of the inlet shall be equal to the diameter of
the pipe (D) plus 6 inches (15 cm). Where the dike height is greater than 18 inches
(45 cm) at the inlet, it shall be sloped at the rate of 3:1 or flatter to connect with the
remainder of the dike. (See Plate 4.30a)
Outlet Protection
.. The outlet of the slope drain shall be protected from erosion according to the practice
entitled OUTLET PROTECTION.- Section 5.36 (ES BMP 1.36). (See Plate 4.30b).
W Construction Specifications
W
M
177
W
1. The measure shall be placed on undisturbed soil or well -compacted fill.
2'. The entrance section shall slope toward. the slope drain at the minimum rate of
Yzinch per foot (4 cm/m).
3. The soil around and under the entrance section shall be hand -tamped in 8 inch (20
cm) lifts to the top of the dike to prevent piping failure around the inlet.
4. The slope drain shall. be securely staked to the slope at the grommets provided.
5. The slope drain sections shall be securely fastened together and have watertight
fittings.
Maintenance
The slope drain structure shall be inspected weekly and after every storm, and shall have
repairs made if necessary. The contractor should avoid the placement of any material on
and prevent construction traffic across the slope.drain..
Plate 4.30d Flared End Section Schematic
Source: VDH&T Road Desions and Standards
A 4r)3
C
' Plan
Eiees[Sw
Plate 4.30d Flared End Section Schematic
Source: VDH&T Road Desions and Standards
A 4r)3
Florida Erosion and Sediment Control inspector's Manual
Alternate Connection
Thr o
Toe plate, ,here needed, to be Punched to match holes in skirt lip. 3/8" gaty. bolls
to be lurnisrAd Length of toe plate is W* 10'for 12'1030'dka.Pipe and W�22"
for 36' to 60' dio, pipe.
skirt secilw for 12' to 30' ala. pipe to be made in one piece.
Skirt Sem len for 36" to 540 dIM PIPs may be mode tram two sheets joined by rlYM
inq ar bottinq an center I&M,60"may be constructed in 3 pmceL
Connector Section, carrier Ptme ano Toe Plate to be sant. sleet 1hicFn as skirt.
Ern -sections and fittings ore 10 be golvanixed vied or aiunenurn al{oy for use with
like pipe. }
I L �
I �Agprvx 2 Sg , l sly l
'.I f
1
7.
i"
Typical Cross -Section -r
8" Toe
—Plot* Thl 3 6A izoso
FLARED END -SECTION
(Continued.)
PIPE
DIA
,
SHEET
THICK-
NESS
DIMENSIONS
A 8 H L W
IMT07 Mal i` "T
C
I "
4"
"
I t
a"
I a"
15"
I .064"
7"
I
e"
i fi"
26' !
30'
I 24"
le"
064"
B"
t
t B'
f I' !
a"
24"
.D64'
10"
13�'
fi'
1� a IN !
ae"
I 24"
30"
.079"
12"
164
B.'.
i 5 f"
00""
24"
3647-579K
14"
1
19"
9"
6" 1
7
1 3"
42
JOS
16"
22"
1 12V
6 9' I
E4
36"
54
109"
I 60�e
l E1 IBI
3=
! I Z
t B
! 36'
Plate 4.30e Flared End Section Specifications
Source: VDH&T Road Designs and Standards
4-104
liter 4 Best Management Practices. fat Erosiort,and-pediment Control
4.38 TEMPORARY CHECK DAMS
Definition
Small temporary dams constructed across a swale or stormwater conveyance channel.
Pur ose
To reduce the velocity of concentrated stormwater flows, thereby reducing erosion of the
Swale or ditch. This practice also traps small amounts of sediment generated in the ditch
itself. These sediments will require periodic removal. However, this is not a sediment
trapping practice and should not be used as such.
Conditions JVhere Practice Apples
This practice is limited;to use in small open channels which drain 10 acres (4 ha) or less. It
should not be used in a live stream. This practice is especially applicable to sloping sites
where the gradient of waterways is close to the maximum for a grass lining. Some specific
applications include:
1. Temporary ditches orswales which, because of their short length of service, cannot
receive a non -erodible lining but still need some protection to reduce erosion.
2. Permanent ditches or swales which for some reason cannot receive a permanent
non -erodible lining for an extended period of time.
Either temporary or permanent. ditches or swales which need protection during the
establishment of grass linings..
Ptannino Considerations
.. Temporary check dams can be constructed of filter fence or straw bales forveryshortterm
applications; or either stone or logs for longer or permanent applications. Filterfence and
straw bale check dams are economical to purchase and simple to install. Log.check dams
,. are economical as for material costs, since logs can usually be salvaged.from clearing
operations. However; log :check dams require more time and hand -labor to install. Stone
for check darns, on the other hand, must generally be purchased. However, this cost is
offset somewhat by the ease of installation..
Specifications
No formal design is required for a check dam; however, the following criteria should be
adhered to when specifying check dams.
r
Erosion and Sediment Control
Manual
m m m
L
PLAN VIEW
4" TO. b' L065
4' MAX
18° TO 24'
VIEW LOOKING UPSTREAM
L' = THE PMTANCE SUCH THAT POINTS 'A' AND 'B'
ARE OF EQUAL ELEVATION
ILI
POINT 'A' POINT '8'
SPACING BETWEEN CHECK DAMS
NOT:
KEY THE EH05 OF THE CHECK
DAM INTO THE CHANNEL BANK.
LO&5 SiiALL BE PRESSUI;M
TREATED IF 6R4IDE 5TA$ILIZATION
5TK4TUR2 15 INTENDED TO BE
PERMAI%N .
Plate 4.38a Log Check Dam
Source: Erosion Draw
4-106
,ter4--Best- Management- Practices for
The drainage area of the ditch or swale being protected should not exceed 10 acres (4 ha).
The maximum height of the check dam should be 2 feet (60 cm). The center of the check
• dam must be at least 6 inches (15 cm) lower than the outer edges. (See Plate 4.38a) The
cross-sections of the dams should be as shown in Plates 4.38a through 4.38d,
respectively, for logs, stone, straw bales, and filter fence. The maximum spacing between
the dams should be such that the toe of the upstream dam is at the same eievation as the
top of the downstream dam. (See Plate 4.38c).
LooLoa ch� eck dams should be constructed of 4 to 6 inch (10 to 15 cm) logs salvaged from
clearing operation site, if possible. The logs should be embedded into the soil at least 18
inches (45 cm). The 6 inch (15 cm) lower height required at the center can be achieved
` either by careful placement of the logs or by. cutting.the logs after they are in place. (See
Plate 4:38a). Logs and/or brush should be placed on the downstream side of the dam to
prevent scour during high flows.
` Stone check dams should be constructed of FDOT' No. 1 Coarse Aggregate (1.5 to 3.5
inch stone) (4 to 9 cm). The stone should be placed according to the configuration in Plate
4.38b. Hand or mechanical placementwiil be necessary to achieve complete coverage of
the ditch or swale and to insure that the center of the dam is lower than the ends. (See
Plates 4.38b & 4.38e)
r Straw bale and filter fence check dams shall be installed as per STRAW BALE BARRIER
Section 4.05 (Channel Flow Applications) (See Plates 4.38c & 4.38f) and SILT FENCE -
Section 4.06 (Channel Flow Applications) (See Plate 4.38d).
Sediment Removal
While this practice is not intended to be used primarily for sediment trapping, some
sediment will accumulate behind the check dams. Sediment should be removed from
behind the check dams when it has accumulated to half of the original height of the dam.
_ Removai
Check dams must be removed when their'useful life has been completed. In temporary
ditches and swales, check dams should be removed and the ditch filled in when it is no
longer needed. In permanent structures, check dams should be removed when a
permanent lining can be installed. In grass -lined ditches, check dams should be removed
when the grass has matured sufficiently to protect the ditch or swale. The area beneath
` the check dams should be seeded and mulched. or sodded (depending upon velocity)
immedlately after they are removed.
` If.stone check dams are used in grass -lined channels which willbe mowed, care should be
taken to remove ail the stone from the dam when the dam is removed. This should include
r, any stone which has washed downstream. Since log check dams are embedded in the
soil, their removal wilt result in more disturbance of the soil than will removal of stone check
dams. Consequently, extra care should be taken to restabilize the areawhenlog dams are
,w used in permanent ditches or swales.
4-
Erosion and Sediment Control Inspector's Manual
VIEW LOOK1Nd UPSTREAM
NOTE:
K y 5TONE wT0 TFE DITGi-! 5AW5
AND EXTEND IT BEYOND THE ANTS
A MINIMUM OF IS" TO FREVENT OVA
FL.ON AROLMD DAM.
SECTION A - A
L' -He 015TANG= SUCH THAT FOINT5 'A' AND
'S' ARF OF EGUAL MLENATION.
SPACING BETWEEN CHECK DAMS
Plate 4.38b Rock Check Dam
Source: Erosion Draw
4-108
4' - Best
EN6 POIMS'A' N I BE HIVR
THAN
L&
VIDE
LINE POINT a
OVERLAP SME &qZS [N FLOV
1Ljj�;E BAUcSiO
PREVENT G*S
�. �,,
a a
wit a
` 18 3Z". EEY ¢ Z - � 7 5°!ES
1a LR. <
1 w -3s z•'
35 SO 3"
END POINTS MAM KIS BE HI
I Z � P1Sl£S Lz°Z1i ff VPiFit
THAN FILEN LkE POINT 7G -ER
jr
A A��
li I.
I'1�1� U ILL16f'
,5 10
it
�S➢, 0
1
IUWiLY
I
IlAi
PIAV'i PMNT air is �Y
LEVEL V1Tr: n -C L= 50 F .
aEVATIDT DF ThE l
i
i
4 �
NARROW CHANNELS
1
WIDE CHANNELS
Plate 4.38c .Straw Sale Check Dam.
Source: HydroDynamics, Inc.
A Ann
Erosion and Sediment Control Inspector's Manual
Maintenance
Check dams should be checked for sediment accumulation after each significant rainfall.
Sediment should be removed when it reaches one-half of the original height or before.
Regular inspections should be made to insure that the center of the dam is lowerthan the
edges. Erosion caused by high flows around the edges of the dam should be corrected
immediately.
Silt Flow
Note: Spacing for Type IIL Fence to be in
accordance with Chart I, Sheet 1 of 3
and ditch installations at drainage'
structures Sheet 2 of 3.
Type DI Silt Fence
Points A Should be Higher than Point 8
Drainageway installation
(Front Elevation)
Plate 4.38d Silt Fence Check Dam
Source: installation of Straw and Fabric Filter Barriers for Sediment Control Sherwood and Wyant
4-110
rhantar4- Best.
0=50 EONS FILM FLOVLSE S1tFc DF STRI CTUrE Fr/FT)
r CF ROD( nay =i 020 Ms aic
�7 M^.T1 VA a7TR OVER ROCK (M7 -E9
3 as CO 03 LO L3 t.9
6
14 Is 20 26 3.4
RECOMMENDED ROCK SIZE & FLIN DEPTHS
0.35 FT/FT OR FLATTER
r DrH KEL.q FLOW LINE SI
CaARSEA
and
END PMTS v LAl� MIST BE
2D M7
116 11
ft
MINIM, DEpTH cF caiRSE7
•
15 FEET
R•■ 0 1 ■ iDIFFERENCE
V•• i i • t
FRONTVINDII-13 17MCH FLM LM IS
.5 FEET
SIDE VIEW
Plate 4,38e Rock Check Dam Details
Source: HydroDynamics, Inc.
4.111
Florida Erosion and Sediment Control Inspector's Manual
loom
PONDING
VIEW LOOKING UPSTREAM
HEIGHT
4I
'L.''= Tt{E DISTANCE SUCH THAT POINT5'C!:.
ANO POINTS 'D" ARE Of EQUAL ELEVATION.
POINT 'C' POINT 'D'
EMBED STRAH
BALE 4" MIN.
INTO SOIL.
SECTION .A - A
SPACING BETWEEN CHECK DAMS
NOTFS=
1. Et E2 BALES 4" INTO -TM SOIL ANG "KZ'r'
BALES INTO THE CHANNEL. BANKS.
2. POINT 'A' MUST 5E HIGHER- THAN POINT B'.
(eFILLti4Y HEIGHT)
Plate 4.38f Straw Bale Check Dam Details
Source: Erosion Draw
U
OPTIONAL
ENERDY
D1551PATOR
3. PLACE BALES.PERPENDICUL.AR TO TriE
FLON KTH ENDS TIGHTLY ABUTTING. USE
57RAN,,ROCK5 OR FILTER FABRIC TO FILL
ANY GAPS AND TAMP BACKFILL MA'TRIAL
TO PREN/ENT ER0510N OR FLON AROUND
THE BALES.
4. SPILLNIAY HEIGHT SHALL NOT =XC 24".'
5. INSPECT AFTER EACH 51GNIFICANT STORM,
MAINTAIN AND REPAIR PROMPTLY.
4-112
Chapter 4 - Best. Management Practices for -Erosion -.a
4.40 DEWATERING
Definition
Lowering the water table by means of pumping.
Pur ose
To allow the construction of structural and stormwater improvements by removing water
from excavation areas and allowing construction by conventional "dry" methods.
Plannirio Considerations..
40 The major planning consideration in dewatering is disposal of removed water. Volume;
quality, and topography are the factors governing the method and destination of removed
water. Discharge from well -point dewatering is relatively clear except for the initial
discharge after installation or inactivity. Water pumped from a sump hole is thoroughly
sediment laden and must always be treated. Turbid water must either be filtered before
it is
leaving the site or must be impounded onsite and allowed to settle. In fiat terra
sometimes
long., sometimes more economical to impound relatively dean water rather than pip
distances to a receiving water body.
.. Specify ns
The two most common meth ods .of dewatering used in Florida are well'point systems and
,,. sump pumps. Awell-point system consists of. one or more rows of small 2" (5 cm) collector
pipes which are jetted vertically into theground near the proposed excavation. The small
pipes are connected by a larger 6" (15 cm) manifold.pipe which is connected to thdempW ng
and discharge line. The sump method is simply a hole in the ground with a pump
all of the water flowing into the hole. Excess water is conveyed to the sump by open
ditches or perforated pipes embedded in sand or gravel.
r
Sumps and Ditches
,. The water table is lowered by ditching and conveying water to a lowered sump hole. Water
pumped from a sump hole is usually heavily laden with sediments. Water flowing over
disturbed and saturated ground detaches and transports all sizes of soil particles into the
., sump pit to be sucked up by the pump. Saturated liquid soil (mud) is also drawn into the
pump. The discharged water must be treated.before release into a receiving water body or
stormwater system. Placing haybales around the pump intake or outlet is not sufficient
effective settling
.. filtration. by itself. Turbid water must either be impounded long enough for
of fines, or filtered through a temporary filter or sediment tank. Initially the water may
percolate freely into the ground, however this will diminish as the fine particles settle and
•. clog the surface layer of soil. In situations which preclude the use of filtration or settlement
facilities, and turbid water is discharged directly into a water body, a suitably designed
floating turbidity barrier must be used. Note that this method does not remove any
• sediments, it merely allows for dilution to lower the turbidity level.
rosion and Sediment Control Inspector's Manual
Horizontal Wells
This system also consists of a series of ditches leading to a sump hole or pump. The
ditches are filled with sand or gravel surrounding a perforated pipe. A geotextile may also
be used to prevent excessive migration of fines into the system. The discharged water
must be treated before release as described above.
Well -point Systems
The well -point system is the preferred system for dewatering and should be used whenever
possible. The initial discharge yields the sediments displaced by the installation of the
small collector pipes. This can be directed into the excavation, a small settling or filtration
facility, or larger temporary impoundment. Thereafter the water is generally clear ground
water and may be discharged into a receiving water body prodided that there is suitable
conveyance.
Maintenance
1. Any water impoundment must be inspected daily to preventfailur e of dikes, berms,
or control structures. Minor problems should be repaired at once. Major problems
will require a redesign and plan modification.
2. Any filtration device must be inspected and cleaned frequently. The discharge
should be monitored daily and whenever the pumps are started. Inspection and
maintenance of the system are best performed when the facility is dry. The first
signs of diminished performance should be an alarm that maintenance is required.
If the facilitywill no longer drain itself, the untreated water must be pumped back to
its source, rather than by-passing the facility and discharging to the water body or
stormwater system.
3. Floating turbidity barriers shall be maintained as per FLOATING TURBIDITY
BARRIER - Section 4.45
4-114
4,45 FLOATING TUREMOITY BARRIER
Definition
•
bed area
A floating, geotextils material which minimizes sediment transport from a distur
adjacent toor within a. body o#water.
land Pur ose.. .
w provide sedimentation os on and sediment controls cannot be usedon for a watercourse from , or from dredging or
where convention
filling within the watercourse...
Conditlons Where Practice Ap 1►es
!on: into: the Watercourse where in rus b
Apphcable o actio t esl'and has tbeen atercourses permuted a d subsequ nt sediment movemen s
construction
unavoidable.: . .
'� Planning Considerations
n of MeRt- in time, the
-term suspensio
Soil lossaatsedimentrmay t avel large distances and aff ctwidesp ead. areas.
turbidity
suspend .. .
curtain enough'Sesidenceaime so that soli pa'rtcd con '!es wdiit all out�tof suspension.and nod arena t travel to
r other areas...
I the
ons.
Turbidlty curtain types thmust be selected based onond,flor�a condittid 1i waterco�ursee waterThe
+� body, whether it be a flowing channel; lake, p
specifications, contained within this, practice pertain to minimal and moderate flow
conditions where the velocity of flgw.may reach,5 feet (1.5 m) per second (ora 'current of
approximately 3.knots)..Forsituations whee.there are greaterflowweloc�ties`or currents; a
qualified engineer and product manufacturer should be consulted:
ter
vement in channel
ow
M Consideration must ourtains are not.designed to act asv I en to the direction . of awater inipoundnie t dams and
situations. Turbidity
cannot be expected to stop the flow of a significant volume of water. They. st designed
and installed to trap sediment, not to half the movement of water itself; Inmost situations,
andjtjuLr�i i curtains should not be installed across channel flaws:
he
olume of water
be made to
ow
In tidal or
contained (thin thetcurtain er o ato ctaange provisionsmust
the tbottom of thecurtain{ain vs weighted and
con
external anchors a.re firequentlyadded, the voiume ofwater contained within; the curtain will
" . be much greater at high tide addition to allowing s low ti e ng s ackid in he curtain toures must arise and wateken to r
bnt e
curtain from submerging, g.
must be ailowedto flow through the curtain if.the curtain is to remain hldved by s roughly the same
" placpart of the
e and maintain thwoven filterame fabric.
abric. he. e. fabriythisc allows the water to. assgthro through the
curtain -from a_ heavy
Florida Erosion and Sediment Control Inspector's Manual
curtain, but retains the sediment particles. Consideration should be given to the volume of
water that must pass through the fabric and sediment particle size when specifying fabric
permeability.
Sediment which has been deflected and settled out by the curtain may be removed if so
directed by the on-site inspector or the permitting agency. However, consideration .must
be given to the probable outcome of the procedure - will it create more of a sediment
problem by resuspension of particles and by accidental dumping of the material by the
equipment involved? It is, therefore, recommended that the soil particles trapped by a
turbidity curtain only be removed if there has been a significant change in the original
contours of the effected area in the. watercourse. Regardless of the decision made, soil
particles should always be allowed to settle for a minimum of 6-12 hours before their
removal by equipment or before removal of a turbidity curtain.
It is imperative that the intended function of the other controls in this chapter, to keep
sediment out of the watercourse, be the strategy used in every erosion control plan.
However, when proximity to.the watercourse makes successfully mitigating sediment loss
impossible, the use of the turbidity curtain during land disturbance is essential. Underno
circumstances shall permitted land disturbing activities create violations of water
quality standards!
Desiqn Criteria
1. Type I configuration (see Plate 4.45a) should be' used in protected areas where
there is no current and the area is sheltered from wind and waves..
2. Type II configuration (see Plate 4.45a) should be used in areas where there may
be small to moderate current running (up to 2 knots or 3.5 feet (1 m) per second)
and/or wind and wave action can affect the curtain.
3. Type Ill'configuration (see Plate 4.45b) should be used in areas where considerable .
current (up..ta 3 knots, or 5 fe..et,.(1.5.m). per second) may be present;_ where tidal
action may be present; and/or where the curtain is potentially subject to wind and
wave action.
4. Turbidity curtains should extend the entire depth of the watercourse whenever the
watercourse in question is not subject to tidal action and/or significant wind and
Wave forces. This prevents silt laden water from escaping under the barrier,
scouring and resuspending additional sediments.
5. In tidal and/or wind and wave action situations, the curtain should never be so long
as to touch the bottom. 'A minimum 1 foot (30 cm) "gap" should exist
between the weighted lower end of the skirt and the bottom at "mean". low water.
Movement of the lower skirt overthe bottom due to tidal reverses orwind and
wave action on the flotation system may fan and stir sediments already settled out.
6. In tidal andlor wind and wave action situations, it seldom practical to extend, a
turbidity curtain depth lower than10 to 12 feet (3 to 4 m) .below the surface, even
in deep water. Curtains which are installed deeper than this will be subject to very
large loads with consequent strain on curtain materials and the mooring system.
A.1 IA
Chapter 4 ='Besf;Nana - ement Pzactices:fof:.Erosion and Sediment Control ...
In addition, a curtain installed in such a manner can "billow up" toward the surface
under the pressure of the moving water, which will result in an effective depth which
is significantly less than the skirt depth.
7, Turbidity curtains should be located parallel to the direction of flow of a moving body
of water. Turbiditycurtains should not be laced across. the main flow of a
significant body of moving water.
g, When sizing the length of the floating cuitain, allow an additional 10 - 20%variance
in the straight-line measurements. This will allow for measuring errors, make
_ installing easier and reduce stress from potential wave action during high winds.
g, An attempt should.be made to avoid an excessive number of joints in the curtain; a
minimum continuous span of 50 feet (15 m) between joints is a good "rule of
thumb."
tta
..
lo. orn'axe to follow. s.of 100 feet (30 m) between anchor or at
locations s also a goad
11.. The ends of the curtain, both floating upper and weighted lower, should extend well
up into the shoreline, especially if high water conditions are expected. The ends
should be secured firmly to the shoreline to fully enclose the area where sediment
may enter the water.
12. When there is a specific need to extend the curtain to thebottomvious
offiltt e watercourse
bric may be
in tidal or moving water conditions, a heavy
wo�fen"p substituted for the normally reco1.mmended impervious geotextile. This creates a
"flow-ituted fo the norr which significantly reduces.th1.e pressure,on the curtain and
will help to keep it in the same relative location and shape during the rise and fall
Ow of tidal waters.
13. Typical -alignments -of turbidity curtains can be -seen in Plate 4.45c:The number
and spacing of external anchors may vary depending on current velocities and
potential wind and wave. action; manufacturer's recommendations should' be
followed.
14. Be certain -that -the type, location; and. installation of the barrier is as shown on the
approved plan and permit Additional permits may be required in navigable
waterways, especially when the barrier creates an obstruction.
to
n
Florida. Erosion and Sediment Control Inspector's Manual
5/5 IN. POLYPROPYLENE ROPE
1/4 IN. TIE ROPE FLOATATION
FOLDS FOR COMPACT STORAGE
ACCORDING TO NEED%/
AVAJLA13LE
STANDARD
NYLON REINFORCED VINYL ALL SEMIS HEAT SFALED I/4 IN. CHAIN -
(BLOW-UP OF SHACKLE CONNECTION)
O
Typel
18 (OR 2Z) OZ. VINYL COVERED NYLON GALVAN2ED #24 SAFETY. HOOK
TOP LOAD LINE
\Fr4C, SLOT-
CONNECS� 5/16 VINYL COATED CABLE
L
;PLATE (TO REMOVE FLOAT7TION7i.SSURE FROM .QATS)
IDA FT. STANDARD LENGTH . FOLDS EVERY 6 FFFi
DEPTH ACCORDING TO NEED
STRESS BANG
STRESS
PLATE
S/16 IN.
CHAIN
BALLAST & LOAD
LINE
Type II
Plate 4.45a Type I and 11 Floating Turbidity Barriers
Source: American Boom and Barrier Corporation
4.118'
Chapter4`- Rest Mana ement Practices for Erosion and. Sediment.Contro
Construction Sgecificatlons
Materials
1. Barriers should be a bright color (yellow or"international" orange are recommended)
that will attract the attention of nearby boaters.
2. The curtain fabric must meet the minimum requirements noted in Table 3.27-A.
3. Seams in the fabric shall be either vulcanized welded or sewn;. and shall develop
the full strength of the fabric.
r ividual
4. Floatation devices shall be flexibie, buoyant units contained in an inaby the
r floatation sleeve or collar attached; to the curtain. Buoyancy p.
floatation units shall be sufficient to support:the weight of the curtain and maintain
a freeboard of at least 3 inches (8 cm) above the.water surface level. (See Plate
4.45c)
5• Load_line .a must be fabricated into the bottom of all floating turbidity curtains. Type
II and Type III must have load lines also fabricated into the top o€`the fabric. The top
` load line shall consist of woven webbing or vinyl -sheathed steel cable and shall
have a break strength in excess of 1o,000 pounds (4.5 t). The supplemental
` (bottom) load -line shall consist of a chain incorporated into the bottom hem of the
curtain of sufficient weight to serve ` as ballast to hold the curtain in a vertical
position. Additional anchorage shall be• proVided`as necessary.. The load lines shall
have suitable connecting devices which develop the full breaking strength for
connecting to load lines in adjacent sections (See Plates 4.45a and. 4.45b which
portray this orientation). .
6, Externatanchors may consist of 2 x 4 inch (5x 16 cm) or 2-1/2 inch (6 dm)minimum
diameter wooden stakes, or 1.33 pound sllinearfoot (2 kd1m) steel posts when Type
CinstMidtfon is. used when Type It orrType 11F.Installations are used, bottom anchors.
should be used.
7_ Bolton► anchors must be sufficient to hold the curtain.in the same position relative
to the bottom of the watercourse without interfering with the action oethoe may be
The anchor may dia into the bottom (grappling hook, plow or fluke-typ )
weighted (mushroom type) and should be attached to a floating anchor buoy via an
anchor line. The anchor line would then run from the buoy to the top load line of
the curtain. When used with Type Ill installations, these lines must contain enough
slack to allow the buoy and curtain to float freely.with tidal changes without pulling
VW the buoy or curtain down and must be checked regularly to make sure they do not
become entangied with debris. As previously noted, anchor spacing will vary with
current velocity and expected wind and wave action; manufacturer's
recommendations should be followed. See orientation of external anchors and
anchor buoys for tidal installation in Plate 4.45b.
a Erosion and Sediment Control Inspeciors lwanual
Type III
22 02. NYLON REINFORCED VINYL STRESS BARD FLOATATION
PVC SLOT - CONNECTOR
r]
ACCORDING TO NEED
VI
16 NYL COATING CABLE #24 SAFETY HOOK STRESS PLATE 'LIN% 6/CHAIN '
N 130TH SINOF
TO REDUCEDES STRIN)CURLAIN
Orientation When Installed
(Tidal Situation -Type 111).
NOTE: ANCHORING WITH BUOYS, ATTACH LINES AUTOMATIC FLASHING
AS SHOWN, REMOVES ALL -BUOY TO SHAC%LE LIGHT (ON AT DUSK -
VERTICAL FORCES FROM THE ��JJ _OFF AT DAWN) IGO
CURTAIN. HENCE; THE CURTAIN 1 „/ J `_n 1 / VCENTER
+ NAVIGABLE
SHALL BE
WILL NOT ORDS, FROM WINO OR \ — - - _ 3
CURRENT' LOADS, --��-77 i / � N ONLY
MIN 2 .. _............. STANDARD CONrATNA1ENr
SYSTEMS LIGHT BUOY
ANCHOR (AS,
WATER SURFACE .. _ ... RECOMMENDED BY
THE MANUFACTURER)
^v7 MIN,. 12CURTAIN RIVERBED
e 0 o a o o vv o v
v v o v vv. v o v' o v v vo o c o v,o a v v v a
0
0 0 0 0 0 0 .v v v v o 0 0 o v v v v voo 0 0
a v o v o v e v a o
v 9 v
Plate 4.45b Type III Floating Turbidity Barrier
Source: American Boom and Barrier Corporation and VDOT Standard Sheets
4-120
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it
Installation
1, In the calm water of lakes or ponds (Type 1 installation) it is usually sufficient to
merely set the curtain end stakes or anchor points (using anchor buoys if bottom
anchors are employed), then tow the curtain In the furled condition out and attach it
oyed
to these stakes or anchor points. Following this, any additional stakes or
bu
be set and
anchors required to maintain the desired location. of the curtain may.
rtain. Only then, the furling lines should be
these anchor points made fast to the cu
cut to let the curtain skirt drop.
2.. In rivers or in other moving water (Type 11 and Type Ili installations) it is important to
set all the curtain holding
power to retain fe ust be taken to the curtain under theure texpected chorcurrent
at an
are of sufficient holding p
rled curtain into thewater: Anchor buoys should be
conditions, before putting the fu
employed on all anchors to prevent the current from submerging the flotation at the
anchor points. If the moving water into which the curtain is being installed is tidal
and will subject the curtain to currents in both directions as de changes, it is
the ti
important to provide anchors on both sides of the curtain for two reasons:
a) Curtain movement will be minimized during tidal current reversals.
b) The curtain will -not overrun the anchors pull there out when the tide
reverses.
When the anchors are secure, the furled curtain should be secured to the upstream
anchorpoint and then sequentially -attached to each next downstream anchor point
until the entire curtain is in position. At this point, and before unfurling, the "lay of
the curtain should. be assessed ande any. necessary adjustments made to the
anchors. Finally; when the location is ascertained to be as desired, the furling lines
should be cut to allow the skirt to drop.
3. Alwa s attach'anchorlinesto-the flotattondevice-not to -the r%; the curtain_.
r The anchoring line attached to the floatation device on the downstream side. will
provide support for the curtain. Attaching the anchors to the bottom of the curtain
could cause premature failure of the -.curtain due to the stresses imparted on the
.• middle section of the curtain.
4, There is an exception to the rule that turbidity curtains should not be installed across
r channel flows -, it occurs when there is a danger of creating a silt buildup in the
middle of a watercourse, thereby blocking access or, creating a sand bar. Curtains
have been used effectively in large areas of moving water by forming a very
+� long -sided, sharp "V" to deflectclean water around a work site, confine a large part
of the silt -laden water to the work area inside the "V" and direct much of the silt
toward the shoreline. Care must be taken, however, not to install the curtain
perpendicular to the water current.
5. See Plate 4.45c for typical installation layouts.
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Florida:Erosion. and Sediment Control Inspectors Manual
Typical Layouts
Streams, Ponds, and Lakes (Protected and Non.Tidal)
STREAH4LOw
ANCHOR PT. ..
�- STAKE OR ANCHOR,
EVERY 100' (TYPICAL)
SHORELINE ® FILL AREA
CONSCONSTR. �.•
OF .. .
�
SHORELINE
ANCHOR PT. TURBIOfry
CURMN r. THIS DISTANCE IS VARIABLE
Tidal Waters andfor Heavy Wind and Wave Action
SHORELINE
ANCHOR PT:.
• THIS DISTANCE IS VARIABLE
EXISTING
CAUSEWAY
ANCHOR k
ANCHOR BUOY
BARRIER MOVEMENT
DUE TO TIDAL CHANGE
® FILL AREA
PROPOSED TOE
OF SLOPE
SHORELINE
ANCHOR PT
Plate 4.45c Typical Installation Layouts`
Source: FDOT Roadway and Trac Design Standards
4-122
-Best Wanagement Practices for Erosicn: and.Sedtment ont+.w::.
g, The effectiveness of the barrier can' be increased by installing two parallel curtains,
separated at regular intervals by 101 (3 m) long wooden boards or lengths of pipe.
Removal
1, Care should be taken to protect the skirt from damage as the turbidity curtain is
dragged from the water.
2. The site -selected to bring the curtain ashore should be free of sharp rocks, broken
cement, debris, etc. so as to minimize damage when hauling the curtain over the
area.
3. If the curtain has a deep skirt, it can be further protected by running a small boat
along its length with a crew installing furling lines before attempting to remove
the curtain from the water.
Maintenance
I= 3.
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The developerlowner shall be responsible for maintenance of the filter curtain for
the duration of the project to ensure the continuous protection of the watercourse.
Should repairs to the geotextile fabric become necessary, there are normally repair
kits available from the manufacturers; manufacturer's instructions must be followed
to ensure the adequacy of the repair.
When the curtain is no longer required as determined by the inspector, the curtain
and related components shall be removed in such a manner as to minimize turbidity.
Sediment shall be removed and the original depth ,(or plan elevation) restored
before removing the curtain. Remaining sediment shall be sufficiently settled before
removing the curtain. Any spoils must be taken to an upland area and stabilized.
Florida Erosion and Sediment Control Inspector's Manual
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Chapter 4 - Best Management Practices for Erosion and Sediment Control
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REFERENCES
Florida Department of Environmental Regulation, 1988, The Florida Development Manuai:
A Guide to Sound Land and Water Management (Chapter 6), Tallahassee, FL
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