20061649 Ver 1_More Info Received_20061122

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DWO Project No.
DIVISION OF WATER QUALITY -401 EXTENDED DETENTION (and POCKET'S WETLAND WORKSHEET
I. PROJECT INFORMATION (please complete the following information}:
Project Name: Townes of Southgate
Contact Person: Robert Wingate Phone Number. (919} 848-8506
For projects with multiple basins, specify which basin this worksheet applies to: NA
Permanent Pool Elevation ft 295'
Temporary Pool Elevation ft 296'
Pem~anent Pool Surface Area sq. ft. 3,440 SF
Drainage Area ac. 7.03 ac.
Impervious Area ac. 3.04 ac.
Forebay Surface Area sq. ft 1,057 SF
Marsh 0°-9" Surface Area sq. ft. 1,287 SF
Marsh 9"-18° Surface Area sq. ft. 1,331 SF
Micro Pool Surface Area sq. ft 523 SF
Temporary Pool Volume cu. ft 4,783 cu. ft.
SA(DA used
Diameter of Orifice in. 6.75 in.
(elevation of the orifice invert out)
(elevation of the outlet structure invert in)
(water surface area at permanent pod elevation)
(on-site and off-site drainage to the basin}
(on-site and off-site drainage to the basin)
(at permanent pool elevation approximately 15%)`
(at permanent pool elevation approximately 35%)"
(at permanent pool elevation approximately 35°~)~
(at permanent pool elevation approximately 15%)*
(volume detained on top of the permanent pod}
(surface area to drainage area ratio)'
(draw down orifice dameter)
II. REQUIRED ITEMS CHECKLIST
Initial in the space provided to indicate the following design requirements have been met and supporting
documentation is attached. if a requirement has not been mei; a#ach an expianafion of why. At a minimum, a complete
stormwater management plan submittal includes a worksheet for each BMP, design calculations, plans and
specifications showing all BMPs and outlet structure details, a detailed drainage plan and a fully executed operation
and maintenance agreement. An incomplete submittal package will result in a request for additional information and
will substantially delay final review and approval of the project
Applicants Initials:
~ 1i/ The temporary pool controls runoff from the 1 inch rain.
BQ l~/ The basin side slopes are no steeper than 3:1.
R ~,~/ A planting plan for the marsh areas with plant species and densities is provided.
~ y~ Vegetation above the permanent pool elevation is specified.
,Q c.~ An emergency drain is provided to drain the basin.
/p W The temporary pool draws down in 2 to 5 days.
iQ ~/ Sediment storage is provided in the permanent pool.
~W A sediment disposal area is provided.
v/ Access is provided for maintenance.
(^/ A site specific, signed and notarized operation and maintenance agreement is ;provided.
~C `~/ The drainage area (including any offsite area) is delineated on a site plan.
~~ Access is provided for maintenance.
~ ~/ Plan details for the wetland are provided.
~P®~--~ Plan details for the inlet and outlet are provided.
~C w~ A site specific operation and maintenance agreement, signed and notarized by the responsible party is
provided (seehttp://h2o.ehnr.state.nc.us/ncwetlands/oandm.doc}.
Pocket Wetlands have different design parameters and are only assumed to remove 35°~ TSS - See pp. 19 and 20
of the NC DENR
Stormwater BMP Manual, April 1999. 10% open water, 50°~ high marsh, 40% low marsh.
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WETLAND DETENTION BASIN OPERATION AND MAINTENANCE AGREEMENT
The wetland detention basin system is defined as the wetland detention basin, pretreatment including
forebays and the vegetated filter if one is provided.
Maintenance activities shall be performed as follows:
After every significant runoff producing rainfall event and at least monthly:
a. Inspect the wetland detention basin system for sediment accumulation, erosion, trash accumulation,
vegetated cover, and general condition.
b. Check and clear the orifice of any obstructions such that drawdown of the temporary pool occurs
within 2 to 5 days as designed.
2. Repair eroded areas immediately, re-seed as necessary to maintain good vegetative cover, mow
vegetative cover to maintain a maximum height of six inches, and remove trash as needed.
3. Inspect and repair the collection system (i.e. catch basins, piping, swales, riprap, etc.) quarterly to
maintain proper functioning.
4. Remove accumulated sediment from the wetland detention basin system semi-annually or when depth is
reduced to 75% of the original design depth {see diagram below). Removed sediment shall be disposed
of in an appropriate manner and shall be handled in a manner that will not adversely impact water quality
(i.e. stockpiling near a wetland detention basin or stream, etc.).
The measuring device used to determine the sediment elevation shall be such that it will give an
accurate depth reading and not readily penetrate into accumulated sediments.
When the permanent pool depth reads 292' feet in the main pond, the sediment shall be removed.
For stormwater wetlands: If the elevation of the marsh areas exceed the permanent pool elevation, the
sediment should be removed to design levels. This shall be performed by removing the upper 6 inches of
soil and stockpiling it. Then the marsh area shall be excavated six inches below design elevations.
Afterwards the stockpiled soil should be spread over the marsh surface. The soil should not be
stockpiled for more than two weeks.
When the permanent pool depth reads 292.75' feet in the forebay and micro-pool, the sediment shall
be removed.
BASIN DIAGRAM
(fill in the blanks)
Permanent Pool Elevation 295
Sediment moval EI. 292.5 75%
----- -- ______Sediment Removal Elevation _2.9.2_ 75°_/0_
----------------------
Bottom E vation 292 25% ~ ,
FOREBAY
MAIN POND
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6. If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment
through the emergency drain shall be minimized to the maximum extent practical.
7. All components of the wetland detention basin system shall be maintained in good working order.
8. Level spreaders or other structures that provide diffuse flow shall be maintained every six months. All
accumulated sediment and debris shall be removed from the structure, and a level elevation shall be
maintained across the entire flow spreading structure. Any down gradient erosion must be repaired and/or
replanted as necessary.
I acknowledge and agree by my signature below that I am responsible for the performance of the seven
maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any
changes to the system or responsible party.
Print name: ,~i5'f~,t~ pj~~Lt~S
Title: /~A~//4 ~~~(/~ PiCi /~Tii/~`"l~
Address: %..~ O,
Phon
Sign
Date:
mac.
Note: The legally responsible party should not be a homeowners association unless more than 50% of the
lots have been sold and a resident of the subdivision has been named the president.
I, ~:, ~ ~G?'Sq~ 4 ~ ~ , a Notary Public for the State of ~C ,
County of (~.~! ~'~ , do hereby certify that (~G~(/ !~~ N- i 1 ~ ~ I~(~-~
personally appeared before me this ~ I S~ day of ~(~(/~/(~~'~-i ~ , 2(~X ~ ,and acknowledge the due
execution of the forgoing wet [wetland] dte~ntio~ basin maintenance requirements. Witness my hand and
official seal, p 1~"`-'r- ..`t'"~~-~
Cr
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A ,.•
COUNT'
SEAL
My commission expires
2-~2_ ~~~U °~
Page 2 of 2

Page 1 of 1
David Phillips
From: "Robin Walsh" <[e-mail]>
To: <[e-mail]>
Sent: Tuesday, November 21, 2006 10:17 AM
Subject: Southgate
David,
We have reviewed DWQ's comment #3 which pertains to our drawing. Our written response to their comments is:
" The size of the plant material is indicated on the plans in the plant schedule".
Please forward this information to the lead person that will be re-submitting the plans.
Thanks,
Robin
11 /21 /2006

a PLANT SCHEDULE _N
BOTANICAL NAME COMMON NAME ~ NOTES
SHRUBS
31 ACOROUS OA LA MUS SWAT FLAG ~ GAL.
110 OARDC SPP. SEDGE 1 GAL.
9 C~FIALANTHUS OCCIDBJTAl15 BUTTON BUSH 3 GAL.
9 MYRIG~ CERIFEIiA WAX MYRTLE 3 GAI.
85 ELEOCHARISaIAADRANGULATA S~RUSH 1 GAL.
14 HIB5CU5 MOSq-BITOS MARSH FBISCUS t GAL.
21 JUNCOS EFFESUS SOFT RUSH 1 GAL.
26 R4NICUM VERGATUM S1MTGiGRASS 1 GAL.