SW5190701_Calcs_20201217

Chad Abbott
From: Sutton, Rahn <[e-mail]>
Sent: Wednesday, January 8, 2020 3:57 PM
To: Chad Abbott
Subject: Siler Square Project - Filterra Sizing
Attachments: Siler School Square Filterra Sizing 1-2-20.pdf
Chad,
I was asked to send this to you verifying the Filterra sizing is per the MDC ratios for media surface area to drainage
area. The charts in the MDC are based on 100% impervious drainage areas. All that the attached spreadsheet does is
weight the C factor accordingly to determine the correct sizing.
We used the info below per your 12/30/19 email:
• Proposed Drainage area to the FILTERRA = +/-17,526 (0.40 acres) (MAP ATTACHED)
0 12,302 sf (0.28 acres) impervious areas
0 4,954 sf (0.113 acres) pervious/landscaped areas
I'll give you a call shortly to confirm you got this and to see if you have any questions.
Thanks,
1"1T1
L. Rahn Sutton, P.E.
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Contech Engineered Solutions, LLC
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1

Design Engineer:
Date
Site Information
Project Name
Project State
Project Location
Drainage Area, Ad
Impervious Area, Ai
Impervious Runoff Coefficient, Ci
Pervious Area, Ap
Pervious Area Runoff Coefficient, Cp
% Impervious
Weighted Runoff Coefficient, Cw
Filterra Sizing Calculations
Filter Surface Area / Drainage Area Ratio
Required Filterra Media Surface Area,
Filterra System
Filterra Configuration
Filterra Model ID
Filterra Sizing in North Carolina
JMR
Blue Cells = Input
11212020
Black Cells = Calculation
Siler School Square
North Carolina
Siler City
0.40 ac
0.28 ac
0.90
0.12
0.30
70%
0.72
0.39%
Per NCDEQ Manual, Chapter D.3, Table 1
55 ft2
Offline
FT 6x10 1 10x6
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