22-Detail Sheets-502-ESC Details

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Definition Planting rapid -growing annual grasses, small grains, or legumes to provide
initial, temporary cover for erosion control on disturbed areas.
Purpose To temporarily stabilize denuded areas that will not be brought to final grade
for a period of more than 21 calendar days.
Temporary seeding controls runoff and erosion until permanent vegetation or
other erosion control measures can be established. In addition, it provides
residue for soil protection and seedbed preparation, and reduces problems of
mud and dust production from bare soil surfaces during construction.
Conditions Where On any cleared, unvegetated, or sparsely vegetated soil surface where
vegetative cover is needed for less than 1 year. Applications of this practice
Practice Applies include diversions, dams, temporary sediment basins, temporary road banks,
and topsoil stockpiles.
Planning Annual plants, which sprout and grow rapidly and survive for only one season,
Considerations are suitable for establishing initial or temporary vegetative cover. Temporary
seeding preserves the integrity of earthen sediment control structures such
as dikes, diversions, and the banks of dams and sediment basins. It can also
reduce the amount of maintenance associated with these devices. For example,
the frequency of sediment basin cleanouts will be reduced if watershed areas,
outside the active construction zone, are stabilized.
Proper seedbed preparation, selection of appropriate species, and use of quality
seed are as important in this Practice as in Practice 6.11, Permanent Seeding.
Failure to follow established guidelines and recommendations carefully may
result in an inadequate or short-lived stand of vegetation that will not control
erosion.
Temporary seeding provides protection for no more than 1 year, during which
time permanent stabilization should be initiated.
Specifications Complete grading before preparing seedbeds, and install all necessary erosion
control practices such as, dikes, waterways, and basins. Minimize steep slopes
because they make seedbed preparation difficult and increase the erosion
hazard. If soils become compacted during grading, loosen them to a depth of
6-8 inches using a ripper, harrow, or chisel plow.
SEEDBED PREPARATION
Good seedbed preparation is essential to successful plant establishment. A
good seedbed is well -pulverized, loose, and uniform. Where hydroseeding
methods are used, the surface may be left with a more irregular surface of
large clods and stones.
Liming -Apply lime according to soil testrecommendations. IfthepH (acidity)
of the soil is not known, an application of ground agricultural limestone at the
rate of 1 to 1 1/2 tons/acre on coarse -textured soils and 2-3 tons/acre on fine -
textured soils is usually sufficient. Apply limestone uniformly and incorporate
into the top 4-6 inches of soil. Soils with a pH of 6 or higher need not be
limed.
Fertilizer -Base application rates on soil tests. When these are not possible,
apply a 10-10-10 grade fertilizer at 700-1,000 lb/acre. Both fertilizer and lime
should be incorporated into the top 4-6 inches of soil. If a hydraulic seeder is
used, do not mix seed and fertilizer more than 30 minutes before application.
Surface roughening -If recent tillage operations have resulted in a loose
surface, additional roughening may not be required, except to break up large
clods. If rainfall causes the surface to become sealed or crusted, loosen it
just prior to seeding by disking, raking, harrowing, or other suitable methods.
Groove or furrow slopes steeper than 3:1 on the contour before seeding
(Practice 6.03, Surface Roughening).
PLANT SELECTION
Select an appropriate species or species mixture from Table 6.1 Oa for seeding
in late winter and early spring, Table 6.1Ob for summer, and Table 6.1Oc for
fall.
In the Mountains, December and January seedings have poor chances of
success. When it is necessary to plant at these times, use recommendations
for fall and a securely tacked mulch.
SEEDING
Evenly apply seed using a cyclone seeder (broadcast), drill, cultipacker seeder,
or hydroseeder. Use seeding rates given in Tables 6.1Oa-6.IOc. Broadcast
seeding and hydroseeding are appropriate for steep slopes where equipment
cannot be driven. Hand broadcasting is not recommended because of the
difficulty in achieving a uniform distribution.
Small grains should be planted no more than 1 inch deep, and grasses and
legumes no more than 1/2 inch. Broadcast seed must be covered by raking
or chain dragging, and then lightly firmed with a roller or cultipacker.
Hydroseeded mixtures should include a wood fiber (cellulose) mulch.
MULCHING
The use of an appropriate mulch will help ensure establishment under normal
conditions, and is essential to seeding success under harsh site conditions
(Practice 6.14, Mulching). Harsh site conditions include:
• seeding in fall for winter cover (wood fiber mulches are not considered
adequate for this use),
• slopes steeper than 3: 1,
• excessively hot or dry weather,
• adverse soils (shallow, rocky, or high in clay or sand), and
• areas receiving concentrated flow.
If the area to be mulched is subject to concentrated waterflow, as in channels,
anchor mulch with netting (Practice 6.14, Mulching).
Maintenance Reseed and mulch areas where seedling emergence is poor, or where erosion
occurs, as soon as possible. Do not mow. Protect from traffic as much as
possible.
References Site Preparation
6.03, Surface Roughening
6.04, Topsoiling
Surface Stabilization
6.11, Permanent Seeding
6.14, Mulching
Appendix
8.02, Vegetation Tables
TEMPORARY SEEDING DETAIL
Table 6.10a
Temporary Seeding
Recommendations for Late
Winter and Early Spring
Table 6.1 Ob
Temporary Seeding
Recommendations for
Summer
Table 6.10c
Temporary Seeding
Recommendations for Fall
Seeding mixture
Species Rate (lb/acre)
Rye (grain) 120
Annual lespedeza (Kobe in
Piedmont and Coastal Plain,
Korean in Mountains) 50
Omit annual lespedeza when duration of temporary cover is nor to
extend beyond June.
Seeding dates
Mountains -Above 2500 feet: Feb. 15 - May 15
Below 2500 feet: Feb. 1- May 1
Piedmont -Jan. 1 - May 1
Coastal Plain -Dec. 1 - Apr. 15
Soil amendments
Follow recommendations of soil tests or apply 2,000 lb/acre ground
agricultural limestone and 750 lb/acre 10-10-10 fertilizer.
Mulch
Apply 4,000 Ib/acre straw. Anchor straw by tacking with asphalt, netting;
or a mulch anchoring tool. A disk with blades set nearly straight can be
used as a mulch anchoring tool.
Maintenance
Refertilize if growth is not fully adequate. Reseed, refertilize and mulch
immediately following erosion or other damage.
Seeding mixture
Species
German millet
Rate (lb/acre)
40
In the Piedmont and Mountains, a small -stemmed Sudangrass may be
substituted at a rate of 50 lb/acre.
Seeding dates
Mountains -May 15 -Aug. 15
Piedmont -May 1 -Aug. 15
Coastal Plain -Apr. 15 -Aug. 15
Soil amendments
Follow recommendations of soil tests or apply 2,000 lb/acre ground
agricultural limestone and 750 lb/acre 10-10-10 fertilizer.
Mulch
Apply 4,000 lb/acre straw. Anchor straw by tacking with asphalt, netting,
or a mulch anchoring tool. A disk with blades set nearly straight can be
used as a mulch anchoring tool.
Maintenance
Refertilize if growth is not fully adequate. Reseed, refertilize and mulch
immediately following erosion or other damage.
Seeding mixture
Species Rate (lb/acre)
Rye (grain) 120
Seeding dates
Mountains -Aug. 15 - Dec. 15
Coastal Plain and Piedmont -Aug. 15 - Dec. 30
Soil amendments
Follow soil tests or apply 2,000 lb/acre ground agricultural limestone
and 1,000 lb/acre 10-10-10 fertilizer.
Mulch
Apply 4,000 lb/acre straw. Anchor straw by tacking with asphalt, netting,
or a mulch anchoring tool. A disk with blades set nearly straight can be
used as a mulch anchoring tool.
Maintenance
Repair and refertilize damaged areas immediately. Topdress with 50
lb/acre of nitrogen in March. If it is necessary to extent temporary
cover beyond June 15, overseed with 50 lb/acre Kobe (Piedmont and
Coastal Plain) or Korean (Mountains) lespedeza in late February or
early March.
NOTES:
1. STRUCTURAL STONE SHALL BE
CLASS B STONE.
2. SEDIMENT CONTROL STONE
SHALL BE NO.5 OR NO.57
GTGIJE.
3. DIMENSIONS ARE MINIMUM
ACCEPTABLE UNLESS OTHERWISE
SPECIFIED BY THE ENGINEER.
/
PIPE
FLOW
A
STRUCTURALSTONE
FLOOD STORAGE ZONE MI .
1�
SEDIMENT STORAGE ZONE
CV
/ V O INVERT PIPE FLOW
NATURAL GROUND
36" PIPE MAX.
SEDIMENT CONTROL STONE SECTION A -A
5 STANDARD ROCK PIPE INLET PROTECTION
C502
7 MIN_ 10'
1. REMOVE AND PROPERLY DISPOSE OF ALL TREES, BRUSH, STUMPS AND OTHER OBJECTIONABLE
MATERIAL.
2. ENSURE THAT THE MINIMUM CONSTRUCTED CROSS SECTION MEETS ALL DESIGN REQUIREMENTS
3. ENSURE THAT THE TOP OF THE DIKE IS NOT LOWER AT ANY POINT THAN THE DESIGN ELEVATION
PLUS THE SPECIFIED SETTLEMENT.
4. PROVIDE SUFFICIENT ROOM AROUND DIVERSIONS TO PERMIT MACHINE REGRADING AND
CLEANOUT.
5. VEGETATE THE RIDGE IMMEDIATELY AFTER CONSTRUCTION, UNLESS IT WILL REMAIN IN PLACE
LESS THEN 30 WORKING DAYS.
MAINTENANCE:
INSPECT TEMPORARY DIVERSIONS ONCE A WEEK AND AFTER EVERY RAINFALL. IMMEDIATELY
REMOVE SEDIMENT FROM THE FLOW AREA AND REPAIR THE DIVERSION RIDGE. CAREFULLY
CHECK OUTLETS AND MAKE TIMELY REPAIRS AS NEEDED. WHEN THE AREA PROTECTED IS
PERMANENTLY STABILIZED, REMOVE THE RIDGE AND THE CHANNEL TO BLEND WITH THE NATURAL
GROUND LEVEL AND APPROPRIATELY STABILIZE IT.
JEMPORARY DIVERSION DITCH
STEEL POST
CLASS 1 OR 2 V MIN WASHED STONE
RIP -RAP (NCDOT #5 OR #57)
'Jmr�OW
'�
4' MAX
STEEL POST
WIRE FENCING
(IF APPLICABLE)
WOVEN FILTER
FABRIC
GENERAL NOTES:
1. SEDIMENT FILTER OUTLET SHALL BE 16 INCHES HIGH BUT NO
TALLER THAN 18 INCHES
2. CLASS 1 OR 2 RIP -RAP SHALL BE USED AND COVERED WITH
6 INCHES OF NCDOT #5 OR #57 WASHED STONE ON THE
UPSLOPE SIDE.
3. POSTS SHALL BE NO MORE THAN 4 FEET APART.
4. SITE OUTLETS AT ANY POINT SMALL CONCENTRATED FLOWS
ARE ANTICIPATED AND AT THE DIRECTION OF THE
INSPECTOR.
5. ONE ACRE MAXIMUM DRAINAGE AREA PER OUTLET.
Q7 W A SIDES PM
OF HAIRI AI 'C ,OP
OF HARDWARE CLOTH
1M IRNYIIY
sraNE Iloart\
MAINTENANCE NOTES:
1. FILTER OUTLETS SHALL BE INSPECTED BY THE FINANCIALLY
RESPONSIBLE PARTY OR HIS AGENT IMMEDIATELY AFTER
EACH RAINFALL AND AT LEAST DAILY DURING PROLONGED STAKES MUST N
NO MORE THAN
RAINFALL. ANY REPAIRS NEEDED SHALL BE MADE APART
IMMEDIATELY.
2. THE STONE SHALL BE REPLACED PROMPTLY AFTER ANY
EVENT THAT HAS CLOGGED OR REMOVED IT.
3. SEDIMENT DEPOSITS SHOULD BE REMOVED WHEN
DEPOSITS REACH HALF THE HEIGHT OF THE BARRIER. ANY
SEDIMENT DEPOSITS REMAINING IN PLACE AFTER THE SILT
FENCE OUTLET IS REMOVED SHALL BE DRESSED TO
CONFORM TO THE EXISTING GRADE, PREPARED AND
SEEDED.
IIAR
SILT FENCE STONE OUTLET
UP
ON
SECTION
FILTER OF HARDWARE CLOTH AID F
UN7 WASHED
STONE IS WRAPPED AROUND THE I LET
FLAN
#57 WASHED STONE & WIRE INLET PROTECTION
12' MIN. WASHED TOP OF DAM
II
STONE FILTER 5' MIN. TOP OF WEIR
0.35x"L"
0.25x"L"
0.25x"L"
0.15x"L"
NCDOT STD. #57
WATER SURFACE LENGTH 1"3600
CU. FT. /ACRE
.5'
NOTE:
SEDIMENT TRAP o Q0
ti- 00 �o 00 ?.
5' MAX.
FILL
BASIN DESIGN
o
SEE PROJECT EROSION CONTROL PLAN FOR SPECIFIC BASIN DIMENSIONS AND ORIENTATION
Z
WATER LEVEL ELEV
? ¢
5'-0" o
TYPICAL BASIN PLAN
0
COARSE STONE FILL
CLASS B EROSION FILTER FABRIC
FLOATING SURFACE
SKIMMER. SEE DETAIL o
-
o 00
MIN. LL
TOP OF DAM
ELEVATION
CONTROL STONE
2
CROSS SECTION
OVERFILL 6" FOR
EMERGENCY BY-PASS 6"
DESIGN 21"
SETTLEMENT
BELOW SETTLED TOP
SETTLED MIN.
OF DAM
TOP
I=1
5. 1.5'
-1 L-I
5' M. 1 1 l_
O
a� _
NATURAL
L
O
OO
GROUND
3'
2:1 SIDE
FILTER
IN
SLOPE MAX.
FABRIC
1:1 SIDE
SLOPE MAX.
STONE SECTION
CONSTRUCTION SPECIFICATIONS
1. CLEAR, GRUB, AND STRIP THE AREA UNDER THE EMBANKMENT OF ALL VEGETATION
AND ROOT MAT. REMOVE ALL SURFACE SOIL CONTAINING HIGH AMOUNTS OF
ORGANIC MATTER AND STOCKPILE OR DISPOSE OF IT PROPERLY. HAUL ALL
OBJECTIONABLE MATERIAL TO THE DESIGNATED DISPOSAL AREA.
2. ENSURE THAT FILL MATERIAL FOR THE EMBANKMENT IS FREE OF ROOTS, WOODY
vCGC TAIVIV, VRGANIV IVIAI ICR, AND VTHER VD- IIVNABLC IVIAI C-L. PLAVC
THE FILL IN LIFTS NOT TO EXCEED 9-INCHES AND MACHINE COMPACT IT. OVER FILL
THE EMBANKMENT 6-INCHES TO ALLOW FOR SETTLEMENT.
3. CONSTRUCT THE OUTLET SECTION IN THE EMBANKMENT. PROTECT THE CONNECTION
BETWEEN THE RIPRAP AND THE SOIL FROM PIPING BY USING FILTER FABRIC OR A
KEYWAY CUTOFF TRENCH BETWEEN THE RIPRAP STRUCTURE AND THE SOIL.
a. PLACE THE FILTER FABRIC BETWEEN THE RIPRAP AND SOIL. EXTEND THE FABRIC
ACROSS THE SPILLWAY FOUNDATION AND SIDES TO THE TOP OF THE DAM;
OR
b. EXCAVATE A KEYWAY TRENCH ALONG THE CENTERLINE OF THE SPILLWAY
FOUNDATION EXTENDING UP THE SIDES TO THE HEIGHT OF THE DAM. THE TRENCH
SHOULD BE AT LEAST 2-FEET DEEP AND 2-FEET WIDE WITH 1:1 SIDE SLOPES.
4. CLEAR THE POND AREA BELOW THE ELEVATION OF THE CREST OF THE EMBANKMENT.
5. ALL CUT AND FILL SLOPES SHOULD BE 2:1 OR FLATTER.
6. ENSURE THAT THE STONE (DRAINAGE) SECTION OF THE EMBANKMENT HAS A MINIMUM
BOTTOM WIDTH OF 3-FEET AND MAXIMUM SIDE SLOPES OF 1:1 THAT EXTEND TO THE
BOTTOM OF THE SPILLWAY SECTION.
7. CONSTRUCT THE MINIMUM FINISHED STONE SPILLWAY BOTTOM WIDTH, AS SHOWN ON
THE PLANS, WITH 2:1 SIDE SLOPES EXTENDING TO THE TOP OF THE OVER FILLED
EMBANKMENT. KEEP THE THICKNESS OF THE SIDES OF THE SPILLWAY OUTLET STRUCTURE
AT A MINIMUM OF 21-INCHES. THE WEIR MUST BE LEVEL AND CONSTRUCTED TO GRADE
TO ASSURE DESIGN CAPACITY.
8. MATERIAL USED IN THE STONE SECTION SHOULD BE WELL -GRADED MIXTURE OF STONE
WITH A d50 SIZE OF 9-INCHES (CLASS B EROSION CONTROL STONE IS RECOMMENDED)
AND A MAXIMUM STONE SIZE OF 14-INCHES. THE STONE MAY BE MACHINE PLACED
AND THE SMALLER STONES WORKED INTO THE VOIDS OF THE LARGER STONES. THE
STONE SHOULD BE HARD, ANGULAR, AND HIGHLY WEATHER -RESISTANT.
9. ENSURE THAT THE STONE SPILLWAY OUTLET SECTION EXTENDS DOWNSTREAM PAST THE
TOE OF THE EMBANKMENT UNTIL STABLE CONDITIONS ARE REACHED AND OUTLET
VELOCITY IS ACCEPTABLE FOR THE RECEIVING STREAM. KEEP THE EDGES OF THE STONE
OUTLET SECTION FLUSH WITH THE SURROUNDING GROUND AND SHAPE THE CENTER TO
CONFINE THE OUTFLOW STREAM (REFERENCES: OUTLET PROTECTION).
10. DIRECT EMERGENCY BYPASS TO NATURAL, STABLE AREAS. LOCATE BYPASS OUTLETS
SO THAT FLOW WILL NOT DAMAGE THE EMBANKMENT.
11. STABILIZE THE EMBANKMENT AND ALL DISTURBED AREAS ABOVE THE SEDIMENT POOL
AND DOWNSTREAM FROM THE TRAP IMMEDIATELY AFTER CONSTRUCTION
(REFERENCES: SURFACE STABILIZATION).
12. SHOW THE DISTANCE FROM THE TOP OF THE SPILLWAY TO THE SEDIMENT CLEANOUT
LEVEL (ONE-HALF THE DESIGN DEPTH) ON THE PLANS AND MARK IT IN THE FIELD.
MAINTENANCE
1. INSPECT TEMPORARY SEDIMENT TRAPS AFTER EACH PERIOD OF SIGNIFICANT
RAINFALL. REMOVE SEDIMENT AND RESTORE THE TRAP TO ITS ORIGINAL DIMENSIONS
WHEN THE SEDIMENT HAS ACCUMULATED TO ONE-HALF THE DESIGN DEPTH OF THE
TRAP. PLACE THE SEDIMENT THAT IS REMOVED IN THE DESIGNATED DISPOSAL AREA
AND REPLACE THE CONTAMINATED PART OF THE GRAVEL FACING.
2. CHECK THE STRUCTURE FOR DAMAGE FROM EROSION OR PIPING. PERIODICALLY
CHECK THE DEPTH OF THE SPILLWAY TO ENSURE IT IS A MINIMUM OF 1.5 FT. BELOW
THE LOW POINT OF THE EMBANKMENT. IMMEDIATELY FILL ANY SETTLEMENT OF THE
EMBANKMENT TO SLIGHTLY ABOVE DESIGN GRADE. ANY RIPRAP DISPLACED FROM
THE SPILLWAY MUST BE REPLACED IMMEDIATELY.
3. AFTER ALL SEDIMENT -PRODUCING AREAS HAVE BEEN PERMANENTLY STABILIZED.
REMOVE THE STRUCTURE AND ALL UNSTABLE SEDIMENT. SMOOTH THE AREA TO
BLEND WITH THE ADJOINING AREAS AND STABILIZE PROPERLY (REFERENCES:
SURFACE STABILIZATION).
TEMPORARY SEDIMENT TRAP
1
EMERGENCY SUPPORT ROPE OR SUPPORT POST STAKE TO
BAFFLE
1 SPILLWAY WIRE TO PREVENT 24" INTO BOTTOM SUPPORT WIRE
ELEVATION SAGGING OR SIDE
BASIN BOTTOM ELEVATION
COMPACTED EARTH
EMBANKMENT STABILIZED OUTLET
PARTIAL BASIN SECTION PROTECTION
COIR MESH OR SIMILAR
CONSTRUCTION SPECIFICATIONS
BAFFLE ELEVATION STAPLED OR TRENCHED
1. CLEAR, GRUB, AND STRIP THE AREA UNDER THE EMBANKMENT OF ALL VEGETATION AND
INTO BOTTOM OR SIDE
ROOT MAT. REMOVE ALL SURFACE SOIL CONTAINING HIGH AMOUNTS OF ORGANIC
CONSTRUCTION SPECIFICATION
MATTER AND STOCKPILE OR DISPOSE OF IT PROPERLY. HAUL ALL OBJECTIONABLE MATERIAL
TO THE DESIGNATED DISPOSAL AREA. PLACE TEMPORARY SEDIMENT CONTROL MEASURES
1. GRADE THE BASIN SO THE BOTTOM IS LEVEL FRONT TO BACK AND SIDE TO SIDE.
BELOW BASIN AS NEEDED.
2. INSTALL POST ACROSS THE WIDTH OF THE SEDIMENT TRAP (PRACTICE 6.62, SEDIMENT FENCE)
3. STEEL POST SHOULD BE DRIVEN TO A DEPTH OF 24 INCHES,SPACED A MAXIMUM OF 4 FEET
2. ENSURE THAT FILL MATERIAL FOR THE EMBANKMENT IS FREE OF ROOTS, WOODY VEGETATION,
APART, AND INSTALLED UP THE SIDES OF THE BASIN AS WELL. THE TOP OF THE FABRIC SHOULD
ORGANIC MATTER, AND OTHER OBJECTIONABLE MATERIAL. PLACE THE FILL IN LIFTS NOT TO
BE 6 INCHES HIGHER THAN THE INVERT OF THE SPILLWAY. TOPS OF BAFFLES SHOULD BE 2 INCHES
EXCEED 9 INCHES, AND MACHINE COMPACT IT. OVER FILL THE EMBANKMENT 6 INCHES TO
LOWER THAN THE TOP OF THE BERMS.
ALLOW FOR SETTLEMENT.
4. INSTALL AT LEAST THREE ROWS OF BAFFLES BETWEEN THE AND THE OUTLET POINT. BASINS
LESS THAN 20 FEET IN LENGTH MAY USE 2 BAFFLES.
3. SHAPE THE BASIN TO THE SPECIFIED DIMENSIONS. PREVENT THE SKIMMING DEVICE FROM
5. WHEN USING POST, ADD A SUPPORT WIRE OR ROPE ACROSS THE TOP OF THE MEASURE TO
SETTLING INTO THE MUD BY EXCAVATING A SHALLOW PIT UNDER THE SKIMMER OR
PREVENT SAGGING.
OR PROVIDING A LOW SUPPORT UNDER THE SKIMMER OF STONE OR BLOCK.
6. WRAP POROUS MATERIAL, LIKE JUTE BACKED BY COIR MATERIAL, OVER THE TOP WIRE. THE FABRIC
SHOULD HAVE FIVE TO TEN PERCENT OPENINGS IN THE WEAVE. ATTACH FABRIC TO A ROPE AND A
4. PLACE THE BARREL (TYPICALLY 4-INCH SCHEDULE 40 PVC PIPE) ON A FIRM, SMOOTH
SUPPORT STRUCTURE WITH ZIP TIES, WIRE, OR STAPLES.
FOUNDATION OF IMPERVIOUS SOIL. DO NOT USE PERVIOUS MATERIAL SUCH AS SAND,
7. THE BOTTOM AND SIDES OF THE FABRIC SHOULD BE ANCHORED IN A TRENCH OR PINNED WITH
GRAVEL, OR CRUSHED STONE AS BACKFILL AROUND THE PIPE. PLACE THE FILL MATERIAL
8-INCH EROSION CONTROL MATTING STAPLES.
AROUND THE PIPE SPILLWAY IN 4-INCH LAYERS AND COMPACT IT UNDER AND AROUND
8. DO NOT SPLICE THE FABRIC, BUT USE A CONTINUOUS PIECE ACROSS THE BASIN.
THE PIPE TO AT LEAST THE SAME DENSITY AS THE ADJACENT EMBANKMENT. CARE MUST BE
TAKEN NOT TO RAISE THE PIPE FROM THE FIRM CONTACT WITH ITS FOUNDATION WHEN
MAINTENANCE
COMPACTING UNDER THE PIPE HAUNCHES.
PLACE A MINIMUM DEPTH OF 2 FEET OF COMPACTED BACKFILL OVER THE PIPE SPILLWAY
INSPECT BAFFLES AT LEAST ONCE A WEEK AND AFTER EACH RAINFALL. MAKE ANY REQUIRED REPAIRS
BEFORE CROSSING IT WITH CONSTRUCTION EQUIPMENT. IN NO CASE SHOULD THE PIPE
IMMEDIATELY.
CONDUIT BE INSTALLED BY CUTTING A TRENCH THROUGH THE DAM AFTER THE EMBANKMENT
IS COMPLETE.
BE SURE TO MAINTAIN ACCESS TO THE BAFFLES. SHOULD THE FABRIC OF A BAFFLE COLLAPSE, TEAR,
DECOMPOSE, OR BECOME INEFFECTIVE, REPLACE IT PROMPTLY.
5. ASSEMBLE THE SKIMMER FOLLOWING THE MANUFACTURERS INSTRUCTIONS, OR AS DESIGNED.
REMOVE SEDIMENT DEPOSITS WHEN IT REACHES HALF FULL TO PROVIDE ADEQUATE STORAGE
6. LAY THE ASSEMBLED SKIMMER ON THE BOTTOM OF THE BASIN WITH THE FLEXIBLE JOINT AT THE
VOLUME FOR THE NEXT RAIN AND TO REDUCE PRESSURE ON THE BAFFLES.
INLET OF THE BARREL PIPE. ATTACH THE FLEXIBLE JOINT TO THE BARREL PIPE AND POSITION THE
SKIMMER OVER THE EXCAVATED PIT OR SUPPORT. BE SURE TO ATTACH A ROPE TO THE SKIMMER
AFTER THE CONTRIBUTING DRAINAGE AREA HAS BEEN PROPERLY STABILIZED, REMOVE ALL BAFFLE
AND ANCHOR IT TO THE SIDE OF THE BASIN. THIS WILL BE USED TO PULL THE SKIMMER TO THE
MATERIALS AND UNSTABLE SEDIMENT DEPOSITS, BRING THE AREA TO GRADE, AND STABILIZE IT.
SIDE FOR MAINTENANCE.
Sediment Basin Baffle
7. EARTHEN SPILLWAYS - INSTALL THE SPILLWAY IN UNDISTURBED SOIL TO THE GREATEST EXTENT
POSSIBLE. THE ACHIEVEMENT OF PLANNED ELEVATIONS, GRADE, DESIGN WIDTH, AND
ENTRANCE AND EXIT CHANNEL SLOPES ARE CRITICAL TO THE SUCCESSFUL OPERATION OF
6" I.D. SCH. 40 SKIMMER
THE SPILLWAY. THE PILLWAY SHOULD BE LINED WITH LAMINATED PLASTIC OR IMPERMEABLE
PVC PIPE FLOAT INFLUENT
GEOTEXTILE FABRIC. THE FABRIC MUST BE WIDE AND LONG ENOUGH TO COVER THE BOTTOM
6" PVC 90°
AND SIDES AND EXTEND ONTO THE TOP OF THE DAM FOR ANCHORING IN A TRENCH. THE
BEND TYP.
EDGES MAY BE SECURED WITH 8-INCH STAPLES OR PINS. THE FABRIC MUST BE LONG ENOUGH
TO EXTEND DOWN THE SLOPE AND EXIT ONTO STABLE GROUND. THE WIDTH OF THE FABRIC
MUST BE ONE PIECE, NOT JOINED OR SPLICED; OTHERWISE WATER CAN GET UNDER THE FABRIC.
IF THE LENGTH OF THE FABRIC IS INSUFFICIENT FOR THE ENTIRE LENGTH OF THE SPILLWAY,
MULTIPLE SECTIONS, SPANNING THE COMPLETE WIDTH, MAY BE USED. THE UPPER SECTION(S)
SHOULD OVERLAP THE LOWER SECTION(S) SO THAT WATER CANNOT FLOW UNDER THE FABRIC.
4" PVC VENT 4" x 4" TEE
SECURE THE UPPER EDGE AND SIDES OF THE FABRIC IN A TRENCH WITH STAPLES OR PINS.
8. INLETS - DISCHARGE WATER INTO THE BASIN IN A MANNER TO PREVENT EROSION. USE
TEMPORARY SLOPE DRAINS OR DIVERSIONS WITH OUTLET PROTECTION TO DIVERT SEDIMENT
o
LADEN WATER TO THE UPPER END OF THE POOL AREA TO IMPROVE BASIN TRAP EFFICIENCY.
9. EROSION CONTROL - CONSTRUCT THE STRUCTURE SO THAT THE DISTURBED AREA IS MINIMIZED.
DIVERT SURFACE WATER AWAY FROM BARE AREAS. COMPLETE THE EMBANKMENT BEFORE
GALVANIZED STL
FLOW CONTROL
THE AREA IS CLEARED. STABILIZE THE EMERGENCY SPILLWAY EMBANKMENT AND ALL OTHER
STRAP TYPICAL
ORIFICE
DISTURBED AREAS ABOVE THE CREST OF THE PRINCIPAL SPILLWAY IMMEDIATELY AFTER
CONSTRUCTION.
4" I.D. SCH. 40
10. INSTALL POROUS BAFFLES AS INDICATED IN SEDIMENT BASIN BAFFLE DETAIL.
11. AFTER ALL THE SEDIMENT -PRODUCING AREAS HAVE BEEN PERMANENTLY STABILIZED, REMOVE
THE STRUCTURE AND ALL THE UNSTABLE SEDIMENT. SMOOTH THE AREA TO BLEND WITH THE
ADJOINING AREAS AND STABILIZE PROPERLY.
SKIMMER
6" PVC CAP INFLUENT
MAINTENANCE
1 6
5'-0"
INSPECT SKIMMER SEDIMENT BASINS AT LEAST WEEKLY AND AFTER EACH SIGNIFICANT (ONE-HALF
INCH OR GREATER) RAINFALL EVENT AND REPAIR IMMEDIATELY. REMOVE SEDIMENT AND RESTORE
SKIMMER PLAN
THE BASIN TO ITS ORIGINAL DIMENSIONS WHEN SEDIMENT ACCUMMULATES TO ONE-HALF THE
HEIGHT OF THE FIRST BAFFLE. PULL THE SKIMMER TO ONE SIDE SO THAT THE SEDIMENT UNDERNEATH
6" I.D. SCH. 40
IT CAN BE EXCAVATED. EXCAVATE THE SEDIMENT FROM THE ENTIRE BASIN, NOT JUST AROUND THE
4" PVC VENT PVC PIPE FLOAT
SKIMMER OR THE FIRST CELL. MAKE SURE VEGETATION GROWING IN THE BOTTOM OF THE BASIN
3'-6'' 1-6"
DOES NOT HOLD DOWN THE SKIMMER.
REPAIR THE BAFFLES IF THEY ARE DAMAGED. RE -ANCHOR THE BAFFLES IF WATER IS FLOWING
11
UNDERNEATH OR AROUND THEM.
4" 22.5° BEND
IF THE SKIMMER IS CLOGGED WITH TRASH AND THERE IS WATER IN THE BASIN, USUALLY JERKING
SP x HUB
ON THE ROPE WILL MAKE THE SKIMMER BOB UP AND DOWN AND DISLODGE THE DEBRIS AND
RESTORE FLOW. IF THIS DOES NOT WORK PULL THE SKIMMER OVER TO THE SIDE OF THE BASIN
4" PVC TEE
AND REMOVE THE DEBRIS. ALSO CHECK THE ORIFICE INSIDE THE SKIMMER TO SEE IF IT IS
STN.STL. HOSE 4" x 4" PVC TEE
CLOGGED; IF SO REMOVE THE DEBRIS.
CLAMPS TYP.
4" PVC FLANGE
IF THE SKIMMER ARM OR BARREL PIPE IS CLOGGED, THE ORIFICE CAN BE REMOVED AND THE
4" FLEXIBLE
OBSTRUCTION CLEARED WITH A PLUMBER'S SNAKE OR BY FLUSHING WITH WATER. BE SURE AND
HOSE
REPLACE THE ORIFICE BEFORE REPOSITIONING THE SKIMMER.
3" I.D. SCH. 40 FLOW CONTROL ORIFICE
PVC PIPE CUT SMOOTH CIRCULAR
CHECK THE FABRIC LINED SPILLWAY FOR DAMAGE AND MAKE ANY REQUIRED REPAIRS WITH
OPENING TO DIMENSION
FABRIC THAT SPANS THE FULL WIDTH OF THE SPILLWAY. CHECK THE EMBANKMENT, SPILLWAYS,
INDICATED ON BASIN SITE
AND OUTLET FOR EROSION DAMAGE, AND INSPECT THE EMBANKMENT FOR PIPING AND
BASIN BOTTOM PLAN
SETTLEMENT. MAKE ALL NECESSARY REPAIRS IMMEDIATELY. REMOVE ALL TRASH AND OTHER
DEBRIS FROM THE SKIMMER AND POOL AREAS.
SKIMMER ELEVATION
FREEZING WEATHER CAN RESULT IN ICE FORMING IN THE BASIN. SOME SPECIAL PRECAUTIONS
Floating Surface Skimmer
SHOULD BE TAKEN IN THE WINTER TO PREVENT THE SKIMMER FROM PLUGGING WITH ICE.
SEDIMENT BASIN AND SKIMMER
0=1 LaBeLLa
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F T
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© 2019 LaBella Associates
ALAMANCE
AGGREGATES, LLC
Mr. Chad Threatt, VP
Alamance County Mine
N0: DATE: DESCRIPTION:
REVISIONS
PROJECT NUMBER:
2180544
DRAWN BY: KCG/ATC
REVIEWED BY: PAS
ISSUED FOR:
REVIEW
DATE:
5/8/19
DRAWING NAME:
EROSION AND
SEDIMENT CONTROL
DETAILS
DRAWING NUMBER:
C502