20080398 Ver 1_More Info Received_20081218

Peddler's Square 401 Wet Detension Basin Supplement Form
Subject: Peddler's Square 401 Wet Detension Basin Supplement Form
From: "Kevin Alford" <[e-mail]>
Date: Thu, 18 Dec 2008 01:00:27 -0500
To: <Annette. Lucas@ncmai Lnet>
Annette,
Here is the filled out Wet Detention Basin Supplement Form as per your request. This should be the last
required information you need to approve the wet detention pond design for the Peddler's Square project.
The original will be Fed-Ex to you tomorrow. Enjoy your vacation time for Christmas. If you have any
further questions, please feel free to call me at 828-506-3411(cell) or 828-926-8341 (office).
Kevin R Alford, PE
Alford Engineering, RLLP
Peddler's Square SW401-WetPond-Rev.2.xls Content-Type: application/vnd.ms-excel
Content-Encoding: base64
1 of 1 12/18/2008 1:18 PM
Permit No.
(to be provided by DWQ)
PW ,UF W A TFq
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NCDENR y
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part 01) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name Peddler's Square
Contact person Kevin R Alford, PE
Phone number 828-506-3411
Date 12/18/2008
Drainage area number
11. DESIGN INFORMATION
Site Characteristics
Drainage area 255,697 ft2
Impervious area 118,048 ft2
% impervious 46.16714314 %
Design rainfall depth 1.0 in
Storage Volume: Non-SR Waters
Minimum volume required ft3
Volume provided ft3
Storage Volume: SR Waters
1-yr, 24-hr runoff depth in
Pre-development 1-yr, 24-hr runoff ft3
Post-development 1-yr, 24-hr runoff ft3
Minimum volume required ft3
Volume provided ft3
Peak Flow Calculations
Is pre/post control of the 1-yr 24-hr peak flow required? N (Y or N)
1-yr, 24-hr rainfall depth in
Rational C, pre-development (unitless)
Rational C, post-development (unitless)
Rainfall intensity: 1-yr, 24-hr storm in/hr
Pre-development 1-yr, 24-hr peak flow ft3/sec
Post-development 1-yr, 24-hr peak flow ft3/sec
Pre/Post 1-yr, 24-hr peak flow control ft3/sec
Basin Elevations
Basin bottom elevation 2936.00 ft
Sediment cleanout elevation 2937.00 ft
Permanent pool elevation 2940.00 It
Temporary pool elevation 2941.00 ft
Volume and Surface Area Calculations
SA/DA ratio 2.30 (unitless)
Permanent pool, surface area required 5,881 ft2
Permanent pool, surface area provided 5,894 ft2
Permanent pool volume 9,801 ft3
Average depth for SAIDA tables 1.662877503 ft
Forebay volume 1,960 ft3
Forebay % of permanent pool volume 20 %
Temporary pool, surface area provided 1,229 ft2
OK
Minimum of 3 It required, Increase depth
OK
Form SW401-Wet Detention Basin-Rev.2 Parts I. & II. Design Summary, Page 1 of 2
Permit No
(to be provided by DWQ)
II. DESIGN INFORMATION -?
Drawdown Calculations
Treatment volume drawdown time 4.3 days OK
Treatment volume discharge rate 0.03 ft3/s
Pre-development 1-yr, 24-hr discharge 26.11 ft3/s OK
Post-development 1-yr, 24-hr discharge 23.92 ft3/s OK
Additional Information
Diameter of orifice 1.00 in
Design TSS removal 90 %
Basin side slopes 3 :1 OK
Vegetated shelf slope 10 :1 OK
Vegetated shelf width 10 ft OK
Length of flowpath to width ratio 3 :1 OK
Length to width ratio 3 :1 OK
Trash rack for overflow & orifice? Y (Y or N) OK
Freeboard provided 1 ft OK
Vegetated filter provided? N (Y or N) Design must be based on 90% TSS removal
Recorded drainage easement provided? Y (Y or N) OK
Capures all runoff at ultimate build-out? Y (Y or N) OK
Drain mechanism for maintenance or emergencies :mergency Spillway
Form SW401-Wet Detention Basin-Rev.2 Parts I. & II. Design Summary, Page 2 of 2