SW6080804_Detail_20100608

CONSTRUCTION SEQUENCE:
THE CONTRACTOR MUST FOLLOW THE FOLLOWING CONSTRUCTION SEQUENCE. IT IS ABSOLUTELY
REQUIRED THAT ONCE THE PLANTING SOIL IS INSTALLED NO SEDIMENTATION BE ALLOWED TO
CONTAMINATE THE DEVICE. IF CONTAMINATION OCCURS, THE CONTRACTOR WALL BE REQUIRED TO
REMOVE AND REPLACE THE PLANTING SOIL AT HIS EXPENSE
1. ROUGH GRADING
2. EXCAVATION OF RETENTION AREA
3. NO ADDITIONAL WORK WILL BE PERFORMED IN THE CONSTRUCTION OF THE RETENTION AREA UNTIL
CONTRIBUTING DRAINAGE AREA IS GRADED AND STABILIZED.
4. IF RETENTION AREAS ARE USED FOR SEDIMENT AND EROSION CONTROL DURING SITE CONSTRUCTION
ACTIVITIES, AND AFTER THE SITE IS STABILIZED, THE RETENTION AREA SHALL BE UNDER CUT TO
REMOVE ALL SEDIMENT.
5. FINAL GRADING AND EXCAVATION OR RETENTION AREA.
6. UNDER DRAIN PIPING AND RAVEL INSTALLATION.
7. GRADED SLOPES ADJACENT TO RETENTION AREAS SHALL BE TREATED WITH POLYECRILMIDES TO
STABILIZE SOIL, EROSION CONTROL MATTING INSTALLED AND SLOPES SEEDED.
B. INSTALLATION OF ENGINEERED SOIL IN RETENTION AREA.
9. INSTALLATION OF LANDSCAPING AND MULCH.
NOTES:
1. PLANTING SOIL BED TO BE MINIMUM OF 2 FT. IN DEPTH. SOIL MUST BE SANDY LOAM, LOAMY SAND
OR LOAM TEXTURE. THE SOIL MUST HAVE AN INFILTRATION RATE OF AT LEAST 1 INCH PER HOUR, A
PHOSPHOROUS INDEX BETWEEN 10-30 AND A PH BETWEEN 5.5 AND 6.6. IN ADDITION, THE PLANTING
SOIL SHOULD HAVE A 3 PERCENT ORGANIC CONTENT AND A MAXIMUM 500 PPM CONCENTRATION OF
SOLUBLE SALTS.
2. THE MAXIMUM PONDING DEPTH IN THE BIO—RETENTION AREA SHALL BE 12 INCHES.
3. A MULCH LAYER SHALL BE PROVIDED CONSISTING OF 2 TO 4 INCHES OF COMMERCIALLY AVAILABLE
FINE SHREDDED DOUBLE —HAMMERED HARDWOOD MULCH.
4. THE UNDER DRAIN COLLECTION SYSTEM SHALL BE EQUIPPED WITH A PERFORATED PVC PIPE WITHIN
RAVEL LAYER. THE PIPE SHALL BE SPACED AT MAXIMUM OF 10 FT. ON CENTER AND A MINIMUM OF
0.5% SLOPE SHALL BE MAINTAINED. A PERMEABLE FILTER FABRIC IS PLACED BETWEEN THE PLANTING
SOIL BED AND THE RAVEL LAYER.
5. THE FILL BERM OF THE RAIN GARDEN SHALL BE 5 FT. WIDE TYPICAL AND COMPACTED TO 95%
STANDARD PROTOR WITH SOIL THAT IS NOT HIGHLY PERMEABLE OR WHICH DOES NOT EXHIBIT
SIGNIFICANT SHRINK SWELL OR DISPERSION PROPERTIES.
6. MINIMUM 2' COVER ON ALL PIPES.
BIORETENION FACILITIESAND MAINTENANCE:
THE OWNER IS RESPONSIBLE TO PERIODICALLY CLEAN THE FACILITY, REMULCH AND REPLACE DEAD, DYING OR
DISEASED PLANT MATERIAL. UNDER NO CIRCUMSTANCES WILL THERE BE ALLOWED TO HAVE ANY EROSION OR
SEDIMENT TRANSPORTED TO THE BIORETENT10N FACILITIES OR ANY OTHER INFLUENT WHICH MAY CREATE AN
IMPERMEABLE LAYER ON THE FACILITIES.
THE BIORETENTION SYSTEM IS DEFINED AS THE RETENTION AREA, MULCH, AND LANDSCAPING WITHIN THE
RETENTION AREA, AMENDED SOIL OR PLANTING SOIL SUBGRADE AND SUBDRAIN WITH RAVEL BED AND FILTER
FABRIC.
FOR THE FIRST COUPLE OF YEARS, PLANTS AND TREES MAY NEED WATER UNTIL THEY BECOME ESTABLISHED.
ALNTENANCE ACTIVITIES SHALL BE PERFORMED AS FOLLO
1. AFTER EVERY SIGNIFICANT RUNOFF PRODUCING RAINFALL EVENT AND AT LEAST MONTHLY:
A. VISUALLY INSPECT AND REPAIR ANY ERODED AREAS. REMOVE TRASH AND DEBRIS.
B. RE —MULCH ANY VOID AREAS BY HAND AS NEEDED.
C. AFTER RAINSTORMS, INSPECT THE RETENTION CELL AND MAKE SURE DRAINAGE PATHS ARE CLEAR AND
THAT PONDING WATER DISSIPATES OVER A 4 TO 6 HOUR PERIOD. KEEP IN MIND, THE BIORETENTION CELL
IS NOT A POND. IT SHOULD NOT PROVIDE BREEDING ROUND FOR MOSQUITOES. MOSQUITOES NEED AT
LEAST 4 DAYS OF STANDING WATER TO DEVELOP A LARVA.
D. WEED REGULARLY AS NEEDED.
2. EVERY 6 MONTHS:
A. ADD A FRESH LAYER OF MULCH AS NEEDED. THE PREVIOUS MULCH MAY BE REMOVED AND DISCARED
TO AN APPROPRIATE DISPOSAL AREA OR RETAINED IF IT IS DECAYED. THE MULCH SHOULD BE PLACED TO
DEPTHS NOT EXCEEDING 3 INCHES. SEEDED ROUND COVER OR GRASS AREAS SHOULD NOT RECEIVE
MULCHING.
B. VISUALLY INSPECT VEGETATION FOR DECEASE OR PEST PROBLEMS. IF TREATMENT IS WARRANTED,
USED LEAST TOXIC APPROACH. REMOVE AND REPLACE ALL DEAD AND DECEASED VEGETATION CONSIDERED
BEYOND TREATMENT.
3. ANNUALLY
A. CHECK THE PH OF THE PLANTING SOIL APPLY AN ALKALINE PRODUCT, SUCH AS LIMESTONE, AS
NEEDED.
B. PRUNE EXCESS GROWTH. TRIMMED MATERIALS MAY BE RECYCLED BACK IN THE REPLENISHED MULCH
OR LAND FILLED IF THERE IS A CONCERN OF HEAVY METALS ACCUMULATION.
C. CORE AERATION OR CULTIVATING OF UNVEGETATED AREAS MAY BE REQUIRED TO ENSURE ADEQUATE
FILTRATION.
D. THE OVERFLOW STRUCTURE SHOULD BE INSPECTED TO ENSURE THAT IT IS FUNCTIONING. ACCUMULATED
TRASH AND DEBRIS SHOULD BE REMOVED AS NECESSARY.
PRO OSED EDGE
OTTOM OF P D OF P VEMENT
PARKING LO SHEET FLOW PARKING OT SHEET FLO
IMF
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':i� '•,'•••'•,•,' '•♦♦ •••r','•,•,'''r•r•♦ • •, ♦ ♦', •, •' • 'r1—• ' •ry'' ', .r •may y—a•=,'.i_�=♦� ' •: ♦ �--
'• ✓j'.i•—� ��,rr �PROPOSEO
PROPOSED1 ` • , .' , , •' ' ' r i• r r r+ • • , • • ' . ♦' , SWALE 2
SWALE 1 i ' i' ' tii 'i' � h i '� 'mot' �'
4�'� I..� j PONDING DEPTH
6" UNDERDRAIN
6" UNDERDRAIN / / PIPE"
PIPE"
OVERFLOW "CATCH
BASIN" GRASS EIN R BERMUDA
BIORETENTION CELL
-do_t—
_
Ito] arelA o.0
TREATED WA
OUTFLOW
PARALLEL ST(
RAIN GARDEN PLAN VIEW
OVERFLOW DROP/CURB 6" PVC UNDER
1NLET 0F RATE SEE PLAN) TOP /—DRAIN CLEANOUT W/
/ SEALED END CAP
OF POND
ELEVATION BOTTOM
OF BIORETENTION
CELL= 496.75
SAND (4")
WASHED STONE
IEL LAYER (8")
APPROXIMATE SHWT
PONDING DEPTH/TOP
FABRIC
#57 WASHED STONE
GRAVEL LAYER (8")
STABILIZE SIDE
SLOPES AND BERM
WITH EXCELSIOR
MATTING AND
ESTABLISH GRASS
PER SEEDING
SPECIFICATIONS
OF POND ELEV.-499.75'
RAIN GARDEN SECTIONAL VIEW
SAND (4")
6" DIA. PERFORATED
PVC UNDER DRAIN
COLLECTION PIPE
PROP. RAIN GARDEN CALCULATIONS
DRAINAGE AREA = 13,863 S.F. OR 0.318 A.C.
IMPERVIOUS AREA TREATED — 9,862 S.F.=0.2264 A.C.
PERCENT IMPERVIOUS = 71.2%
WATER QUALITY VOLUME:
_ (P*Rv*DA)/12 Rv = 0.05+0.009(% IMPERVIOUS)
Rv = 0.05+0.009*71.2 = 0.6908
WQV — (1*0.6899*0.318)/12
=0.0183 AC—FT
-797.37 C.F.
ADDITIONAL 18% WQV - 797 C.F. * 1.18 = 940.89
SURFACE AREA REQ. - 940.89 C.F./0.75 FEET DEEP
= 1254.52 S.F.
SURFACE AREA PROVIDED = 1,332 S.F.
TOP OF BERM = 501.11'
TEMP. POOL ELEVATION = 500.61'
TOP OF RATE = 500.61'
BOTTOM OF POND = 499.75'
T.
411
p'ovecl Soo: env;.ater Farmit Documents
Construction m accordance with these documents is
required by the ,tnrmwater permit. North Carolina
rules require that the stormwater system designer
Inspect during construction- certify conformity with the
plans and specs, and certi!v compliancwith wth the
Stormwater rules. (15A NCAC 2H anc (j)t
Pennif#_j{�( �prf
by �tpP ._____ Date a ,c C-g-
NC Division of Water q ality
Sheet#_ G1, Z_—Revision. Date 9 0
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