SW4210704_Plansheet - SCM Detail_20210803

�g NOTE: ROUTINE MAINTENANCE - To be provided by the Property Owner at the designated frequencies for each of the
12 TOP WIDTH following items that apply:
54" TRASH RACK C.A.P. CORRUGATED ALUMINUM PIPE TOP OF DAM EL = 732.5
FINAL GRADE A) MOWING - Quarterly - Grass vegetation is an effective way to prevent erosion of the embankment surfaces.
hti -- - - - - - (SEE DETAIL) (MAX. OF 10:1 SLOPE) While not necessary for embankment stabilization, mowing the area surrounding a and helps eliminate problems
- - - - FINAL GRADE (98% COMPACTION) SEEDING ON ALL y g g p p
APPROXIMATE - - _ POND SLOPES SHALL from animal pests and provides a more aesthetically appealing area. Grass shall be mowed when the uniform
EXISTING GRADE ' - - - - - - - - - - - - - - _ _ EMERGENCY 3 height exceends six (6) inches.
_ SPILLWAY 3�5- - - BE NON -CLUMPING
�1 TURF GRASS B) DEBRIS REMOVAL - Many permanent runoff control structures have pipe and riser spillways with low flow
100 YR. H.W.L. EL, 729.5 TOP OF RISER FILL-� - - - zs _ - - - orifices. Any of these that become plugged with trash or debris will reduce the spillway capacity. As a result, the
10 YR. H.W.L. EL. = 727.6 EL. = 729.0 1 MATERIAL p _ - - - _ emergency spillway will operate more frequently and there is a greater potential for overtopping the dam. Trash racks
2 YR. H.W.L. EL: = 726.9 3 (MIN. 98% COMPACTION) - - are normally installed to prevent clogging and debris must be removed from these devices periodically. For these
3 = C� reasons, it is recommended to inspect the trash racks monthly and/or after major storm events and to remove debris as
TEMP. 3" (W/3" HEAD) FAIRCLOTH SKIMMER _ necessary.
W/ 4" SCHD 40 PVC BARREL 4" SKIMMER - C) MINOR SLOPE FAILURES - Minor slope failures should be repaired by seeding or sodding as soon as they are
FLEXIBLE HOSE AND 4" STEEL NIPPLE HOSE discovered to prevent major damage or sediment build-up in the pond. Re -occurring slope failures may be an
} (TO BE REMOVED UPON CONVERSION TO indication of a more serious problem and should be brought to the attention of the governmental office having
_ PERM POND (SEE SEQUENCE) 36" jurisdiction for watershed protection.
C A.P.
rn 117 L.F. 24 C.A.P. W FLANGE
BIESECKER ROAD Z o RISER JOINTS AND GASKETS @ 1.20% D) PERIODIC INSPECTIONS - After storm inspections should be done after major storm events (more than 2 inches
rn 2'% GRADE'---+ of rainfall in 24 hours) or after extended periods of rainy weather (more than 2 or three days). Major items to look for
12" STUBBED OUT OF (MIN)
are damage to spillways or channels, excessive debris build-up on trash guards, and eroded or slumped embankments.
RISER 12" AT ELEV 720.0 WITH SMALL POOL ® FLANGED JOINT CUT-OFF COLLAR _ E) VALVES AND GATES - The reservoir drain should always be operable so that the permanent pool can be drawn
WITH GASKET SEE DETAIL NEW INV IN=718. O down in case of an emergency, p
4" THREADED HOLE TO PERM. ORIFICE ( ) � -+-� �- 4'(MIN) g y, for repairs, or for clean -out of sediment. Reservoir drain valves that have not been
RECEIVE THE 4" NIPPLE PREFABRICATED BARREL TO RISER operated for a long time are often a problem in that the valve may not open. Also it may not close after opening which
r� o�scn E BOTTOM POND=720f WATERTIGHT CONNECTION KEYWAY will drain the impoundment. All valves should be operated from the fully closed to the fully open position at least
TO BE REMOVED AT COMPLETION ( ) (SEE NOTE) twice a year.
INV. EL = 720.0
F) TREES AND BRUSH - Trees and brush should not be permitted on embankment surfaces or in vegetated
117 L.F. OF 24" C.A.P. spillways. Brush and trees provide a haven for burrowing animals (like muskrats and groundhogs) and extensive root
NOTE: systems can weaken an earth fill dam or provide a pathway for excessive water flow through the dams. Tree growth
OWNER SHALL PROVIDE SOILS ENGINEER TO @ 1.20% adjacent to concrete walls and structures will eventually cause damage to footings creating cracks and possible
APPROVE SUBGRADE AND KEYWAY PRIOR TO IT SHALL BE THE RESPONSIBILITY OF THE DRY DETENTION POND TYPICAL SECTION 24" RCP structure failure.
ANY FILL MATERIAL BEING PLACED. ALL 6.Tx x W 6. ' W 2 ' H = 90 CF CONTRACTOR TO COORDINATE ALL CONSTRUCTION
FILL MATERIAL AND COMPACTION WILL ALSO ( ) ( ) ( ) NOT TO SCALE G) MISCELLANEOUS ITEMS - Excessive plant growth, algae blooms, odors, discoloration, perceived animal pests,
3000 PSI CONCRETE POURED IN ACTIVITIES WITH THE SOILS ENGINEER PROVIDED BY etc. should be addressed with the governmental office leaving jurisdiction for watershed protection on an as needed
8E MONITORED BY SOILS ENGINEER TO BE g g �
PROVIDED BY OWNER. AND AROUND BASE SECTION THE OWNER. NO CONSTRUCTION ACTIVITIES SHALL basis. Solutions to these types of problems should be non -chemical and deemed safe for drinking water supply
BE INITIATED UNTIL WHICH TIME A SITE MEETING reservoir application.
GENERAL NOTES HAS OCCURRED TO ESTABLISH/COORDINATE A
SCHEDULE AND BASIS OF COMMUNICATION. H) ANNUAL INSPECTIONS - Annual maintenance inspections will be performed by the owner. Documentation of
1. THE OWNER IS RESPONSIBLE FOR MAINTAINING THE COMPLETED inspections and maintenance must be submitted to the Stormwater Engineer annually upon the anniversary of the
PERMANENT DRY DETENTION POND AS DIRECTED BY THE GOVERNMENTAL as -built plan set approval by the City. The "Wet Detention Basin Operation and Maintenance Manual" is available
OFFICE HAVING JURISDICTION FOR WATERSHED PROTECTION, IN CONFORMANCE NO TREES OR SHRUBS SHOULD BE PLANTED WITHIN on the City of Greensboro website. This form shall be utilized for the annual inspection.
WITH THE APPROVED MAINTENANCE PLAN. 10 FEET OF INLET OR OUTLET PIPES, SPILLWAYS OR NON -ROUTINE MAINTENANCE - To be provided by the Property Owner at the designated frequencies for each of
2. THE PERMANENT DRY DETENTION POND SHALL HAVE FULL DESIGN VOLUME FLOW SPREADERS, OR, ON ANY DAM AREAS. the following items. These maintenance items will require a registered professional engineer to prepare a plan and/or
AVAILABLE PRIOR TO ANY ISSUANCE OF CERTIFICATES OF OCCUPANCY FOR THE detail(s) and to certify completion of the maintenance in accordance with the plan and/or detail(s). All revisions and
SITE AND/OR PRIOR TO ANY PLAT RECORDATION FOR THE SITE. THIS MAY repairs to permanent runoff control structures shall be done in accordance with City of Winston-Salem guidelines and
BEFORE YOU DIG! REQUIRE THE CLEANOUT AND DISPOSAL OF SEDIMENT FROM THE POND. MAINTENANCE REQUIREMENTS specifications.
CALL 811 3. FINAL APPROVAL OF INSTALLED RUNOFF CONTROL STRUCTURES WILL BE DESCRIPTION FREQUENCY MAINTENANCE REQUIRED
REQUIRED AT FINALIZATION OF THE GRADING PERMIT OR AT ISSUANCE OF THE Mow maintain buffer vegetation Quarterly As needed A) SEDIMENT CLEAN -OUT - Water quality measures like wet detention ponds and retention ponds trap sediment
N.C. ONE -CALL CENTER FINAL BUILDING CERTIFICATE OF OCCUPANCY (COMPLIANCE), WHICHEVER COMES Inspect bank embankment for erosion Quarterly Repair as needed as an inherent part of their function. With time, the volume allocated to sediment will become filled and they must be
LATER. ENGINEERING CERTIFICATION OF COMPLETION SHALL BE REQUIRED cleaned out to remain effective.
ITS THE LAW! Inspect pipe inlet and outlet areas for undercuttin erosion. Quarterly Repair as needed
PRIOR TO FINAL APPROVAL BY THE ENFORCEMENT OFFICER. Inspect trash rack principal and emergency spillways for trash blockage After large storms Remove trash as necessar
4. THE GOVERNMENT OFFICE HAVING JURISDICTION FOR STORMWATER DEVICES Sediment removal from the pool, sediment forebay(s) or rip -rap baffles shall be detailed to indicate finish elevations
Inspect structural integrity of outflow device Annually Repair as needed )
relative to riser removal and disposal methods stabilization of disturbed AND THEIR ASSIGNS HAVE RIGHT OF ACCESS. TO THE PERMANENT .DRY DETENTION ( ), p ( d areas, erosion control, and stabilization of
POND(S) FOR INSPECTIONS AND MAINTENANCE ENFORCEMENT. Inspect sediment accumulation Annually Remove when 50% of forebay capacity lost spoil areas. Engineering detail and certifications for rip -rap baffle clean -out only, may be waived on a case -by -case
basis depending upon the extent of the work involved and whether the baffle is damaged.
N B) CHANNEL STABILIZATION - Grassed waterways will filter out sediment (when there is a sediment load) and
they will in time aggrade to the point that they no longer have the capacity to handle the required flow. This is a major
maintenance problem. Another problem is erosion of the channel bottom, particularly before the grass can become
established.
Both situations require repair, possibly regrading. Small rills can be repaired by sodding, the preferred approach.
SITE DATA 1 5 ?, ' , j / ° However, waterways, which have lost much of their capacity due to sedimentation, will require reshaping and
+.
EXISTING ZONING: MX- / \ - rev g tati g
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PROP. LAND USE: SINGLE FAMILY ,-` '-� Waterways need to be mowed a minimum of three times a year to prevent tree growth and excessively high
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vegetation.
TOTAL No. LOTS PROPOSED: 119 '� `: �, � '' �. �: Q � � � / y.OVADA�DR. 1 � g
TOTAL SITE AREA: 77.73 AC. c ` \` �� ,� Rip -rap channels need to be maintained to prohibit tree growth on the banks and bottom as necessary to maintain the
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L.F. STREETS: 4710 L.F. soqurip�rappwlltneedhto be replacedunethehdamagedlareasld be inspected after major storms to see if it is damaged. If
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SEWER: CITY OF LEXINGTON \ _....
„ .- ` 2 C PRINCIPAL SPILLWAY CONDUITS - Most water quality ponds have a
WATER: CITY OF LEXINGTON \ / / > q Y P pipe e conduit that serves if a principal
�; �k spillway. These carry normal stream flow and small flood flows safely past the dam throughout the life of the
6oll SOIL TYPE: CeD2, CCB, PaE, SfB, ChA, /� / structure. Pipes through embankments can be extremely dangerous to the embankment i problems develop after
\ �'/ -�\construction.
PaD, EnD1-1,
' e u h ank e'f pr o
AVERAGE SLOPE: 8% f \ 3 ` Frequent inspection is necessary to ensure the spillway conduit is functioning
/ q p y p y properly. All conduits should be
DISTANCE TO FLOODWAY: 50 LF V ,' /.... 1-1 \ inspected for improper alignment, elongation and displacement of joints, cracks, leaks, loss of protective coating,
� v corrosion, and blockage.
loc age.
DISTURBED AREA: 44.3 AC.
PHASE 1: 21.0 AC.f g RCP W 1 1 \ Problems with conduits occur most frequently at joints. Open joints can cause erosion of embankment materials or
g.,
PHASE 2: 23.3 Ac.f
�P , .- '' cause leakage of water. The outlet should be checked for signs of water seeping along the exterior of the pipe. A
`, R � � _. / / 00 depression in the soil surface may be a sign the joint is no longer watertight and that soil is being removed from
PARCEL ID: 67216-01-36-0231 around the pipe. Metal pipe spillways will have to be replaced when they become so corroded that they are no longer
/ \ watertight.
so" DEED REF: 1584-1466
i ; \ Principal spillway replacement shall be detailed, approved, constructed, and certified in accordance with Guilford
RIVER BASIN: YADKIN/PEE-DEE 0' RrPRAP APRON / County guidelines.
LAT/LONG: 35.8466/-80.2766 l ,., ; /24" DEPTH '
i CLASS 1/STON / -� \ ' D) EMERGENCY SPILLWAYS - Channel and structure repair or replacement shall be detailed, approved,
IMPERVIOUS SURFACE AREA: i i constructed, and certified in accordance with these guidelines.
.� \ I4r THICKNESS
ROADS: 2.40 AC.t � l
�'�� `' / INV=72 , � \ E) DAM FAILURE - Which endangers the structural integrity or watertightness of the dam shall have a plan and
LOTS: 8.20 AC.f detail(s) red to repair said damage.
TOTAL: 10.60 AC.t (13.77) y v� E o$ v �.. - t remedial
ills) pre
�� gip'-� \ F) SEEPAGE - A most dams, some water will seep from the reservoir through the foundation. The need for reme is
OPEN SPACE: 39.2 AC.f (50%) ap. \ r seepage control will depend on the quantity and location of the seepage. As a general rule, seepage control measures
EX. INLET B \ (after construction is complete) will not be necessary unless seepage is threatening the safety of the dam. Remedial
CUT-OFF COLLARmust
EST. START DATE: JUNE, 2020 TOP=728.70 , \a O p� / measures to control seepage will be required if the safety of the dam is threatened. All methods to control seepage
EST. END DATE: DECEMBER, 2022 INV IN=720.55 \ 00000 00oOti \ /-'� dams.be designed and constructed under the supervision of and certified by a professional engineer experienced with
NOT TO SCALE INV OUT=720.45 i f
ALUMINUM BAPQ
f 4' 0.
ANTI -VORTEX PLATES
54' DIA. CORR.
ALUM. TRASH RACK
STAINLESS STEE
I Y SLOTS IN ANTI -VORTEX PLATES
j/ 36" C.A.P. RISER ARE USED TO POSITION THE TRASH
RACK ON THE RISER PIPE
TRASH RACK DETAIL
BOUYANCY CALCULATIONS NOT TO SCALE
RISER 0 136 212" IZIT = 63.6 FT.'FORCE OF H2O = (110.7 F) (62.4 lb./FT') 6907 lb.
BARREL CONCRETE = 7 907 = 79 FT 3 � USE 90 CF
(15.0')124212' 7T =47.1 FT•3 8 /F 3.4 C.Y.
F, = 110.7 F1
3
I1
20'
3 TOP DAM = 732.5
K
V, = 730,5
SYNTHETIC EROSION MATRIX
SECTION - EMERGENCY SPILLWAY
NOT TO SCALE
THIS IS NOT A SURVEY. NOT FOR RECORD, SALES, OR CONVEYANCE.
EX. 42"
INV OUT=716 5t
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30' 20' 10' 0 30' 60'
SCALE: 1 30'
DAM DESIGN DATA
SUMMARY
BOTTOM ELEV. =
720f
TOP OF RISER ELEVATION =
729.0
EMER. SPILLWAY ELEVATION =
730.5
TOP OF DAM =
732.5
2 YEAR H.W.L. =
726.9
10 YEAR H.W.L. =
727.6
25 YEAR H.W.L. =
728.4
50 YEAR H.W.L. =
729.0
100 YEAR H.W.L. =
729.5
WQV REQUIRED =
14,810 C.F.
WQV PROVIDED =
28,381 C.F.
DURING CONSTRUCTION, THE POND WILL FUNCTION AS A
TEMPORARY SEDIMENT BASIN FOR EROSION CONTROL. THE
FAIRCLOTH SKIMMER (OR APPROVED EQUAL) SHALL BE USED
TO DECANT/DRAIN THE BASIN TO THE ELEVATION OF THE
BARREL INVERT. UPON STABILIZATION OF THE SITE, ALL
SEDIMENT SHALL BE REMOVED FROM THE BASIN AND
THE SKIMMER SHALL BE REMOVED. THE CONTRACTOR
SHALL COMPLETE CONSTRUCTION OF THE POND
(SEE POND CONSTRUCTION SEQUENCE).
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