20070452 Ver 2_Worksheets_20070703

Project Name: Elkin WalMart
Project No. DWQ EXP 07-0452v2
Pond 1
SUBMITTED DESIGN.
elevations
Bottom of Basin (ft) 1083
Permanent Pool (ft) 1087
Temporary Pool (ft) 1093
areas
Permanent Pool SA (sq ft) 40336
Drainage Area (ac) 23.1
Impervious Area (ac) 23.1
volumes
Permanent Pool (cu ft) 122244
Temporary Pool (cu ft) 316683
Forebay (cu ft) 23953
other parameters
SA/DA 3.5
Orifice Diameter (in) 6
Design Rainfall (in) 1
Linearlnterpolation of Correct SA/DA***
Im ervious
Next Lowest 90
Project Impervious 100.0
Next Highest 105

REQUIRED DESIGN:
3.0 average depth status
4 ft. depth ok
6 ft. depth ok
35487 sq. ft. ok
34804 based on avg depth ok
100.0 % -
79660 cu. ft. ok
19.6 % ok
3.53 -
1.64 cfs drawdown -
2.2 day drawdown ok
4 ft. Permanent Pool Depth
SA/DA fron (Avg. Depth)
3.1` 3.038101944
3.53 3.46
3.74 3.669215589
aft
730
1.08
1.31
1.43
4

Project No. DWQ ~ ©.~ - b~Z. / L (to be provided by DWQJ
DNISION OF WATER QUALITY - 401 WET DETENTION BASIN WORKSHEET
DWQ Stormwater Management Plan Review:
A complete stormwater management plan submittal- includes a wet detention basin worksheet for each basin,
design calculations, plans and specifications showing all basin and outlet structure details, 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.
I. PROJECT INFO
Project Name
Contact Person: ~,~~ ~( ~~(~EN~It3~13T Phone Number: (86 YL6 7 L -' 3 7Z
For projects with multiple basins, specify which basin this worksheet applies to:
Basin Bottom Elevation ~83 ft. (average elevation of the floor of the basin)
Permanent Pool Elevation ft. (elevation of the orifice invert out)
Temporary Pool Elevation / D 9 ~ . Q ft. (elevation of the outlet structure invert in)
Permanent Pool Surface Area ~ 6 sq. ft. (watersurface area at permanent pool elevation-
Drainage Area 2 ~ _ I~ 0 as (on-site and off-site drainage to the basin) r~
Impervious Area ,Z 3 .~0 ac. (on-site and off-site drainage to the basin) :a
,,'~;- :~
,y:~' ~~-
Permanent Pool Volume Z cu. ft: (combined volume of main basin and forebay ~ ,~, 7~~:~'
Temporary Pool Volume / cu. ft. (volume detained on top of the permanent po ~ ,:,~;.. ~"
Forebay Volume ~~~~_ cu. ft. ~ c,°
e ~ ~
SA/DA used _3. S ~b (surface area to drainage area ratio) (,~
Diameter of Orifice in. (draw down orifice diameter}
II. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices manual
(N.C. Department. of Environment, Health and Natural Resources, November 1995) and Administrative Code
Section: 15 A NCAC 2H .1008. 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 met, attach an explanation of
why.
The temporary pool controls runoff from the 1 inch storm event. ~,
it ~._
~S The basin length to width ratio is greater than 3:1. ~~-- --._
~~~The basin side slopes are no steeper than 3:1. ~,t"~
A submerged and vegetated perimeter shelf at less than 6:1 is provided. ~-._,~ ? ' !~
~~
Vegetation to the permanent pool elevation is specified. t ~ ~,
An emergency drain is provided to drain the basin. ;~~ ~ ~' ~
The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet) ;~J i
~. ~ ~
~S The temporary pool draws down in 2 to 5 days.

The forebay volume is approximately equal to 20% of the total basin volume. !; -~ ~~f
Sediment storage is provided in the permanent pool. ------~---
_._ ._.:
_ __
Access is provided for maintenance.
- -- _
A minimum 30-foot vegetative filter is provided at the nutlet.
A site specific operation and maintenance (0&M) plan is provided.
___
A vegetation management/mowing schedule is provided in the O&M plan. -
Semi-annual inspections are specified in the O&M plan.
A debris check is specified in the 0&M plan to be performed after every storm event.
A specific sediment clean-out benchmark is listed (elevation or depth) in 0&M plan.
A responsible party is designated in the O&M plan.
FORM SWG100 09/97 Page 1 of 1
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Applicants Initials