20190121 Ver 1_WakeCountyStormwaterDesignToolV2.2_2019.1.14_20190307

e�7K/KE
rh
Wl
COUNTY
—It, I1 C4❑(H.I-
SITE DATA
Wake County Stormwater Hybrid Tool Version 2.2
Project Information
Project Name:
Layhill Estates
Permit No (if known):
PLG -001113-2018
Applicant:
IC Engineering, Inc
Applicant Contact Name:
Joe Ogden, P.E.
Applicant Contact Number:
919-948-9590
Contact Email:
k.alzoubi(@icengineeringinc.com
Last Modified Date:
Monday, January 14, 2019
Site Data:
River Basin:
Neuse
Regulatory Watershed:
Swift
Physiographic/Geologic Region:
Piedmont
Type of Development (Select from Dropdown menu):
Residential
Zoning:
R -40W
Total Site Area (Ac):
5.28
Existing Lake/Pond Area (Ac):
0.00
Proposed Disturbed Area (Ac):
1.96
Proposed Impervious Surface Area from DA Sheets (acre):
1.56
Percent Built Upon Area (BUA):
30%
Is the proposed project a site expansion?
No
Number of Drainage Areas on Site (Points of Analysis):
1
Annual Rainfall (in):
45.41
One-year, 24-hour rainfall (in):
3.00
Two-year, 24-hour rainfall (in):
3.60
Proposed Residential Stormwater Details (if applicable):
Site Square Footage:
229,997
Total Acreage in Lots:
6.92
Lot Square Footage:
301,435
Number of Lots:
6
Average Lot Size (SF):
51,110
Proposed Impervious Surface Area from DA sheets (SF):
67,954
Proposed Impervious Surface Area Devoted to Lots (SF):
56,628
Total Impervious Surface Area Devoted to Roads (SF):
13,919
Other Impervious Surface Area (SF):
53,143
SITE DATA Page 1
PDF processed with CutePDF evaluation edition www.CutePDF.com

W akeCountyStormwaterDesignTooIV2.2
Project Name: Layhill Estates
DRAINAGE AREA 1
WAKE STORMWATER PRE -POST CALCULATIONS
COUNTY
LAND USE & SITE DATA
PRE -DEVELOPMENT
POST -DEVELOPMENT
Drainage Area (Acres)=
5.50
5.50
Site Acreage within Drainage=
5.28
5.28
One-year, 24-hour rainfall (in)=
3.00
Land Use (acres) by Soil Group:
A Soils
B Soils
C Soils
D Soils
A Soils
B Soils
C Soils
D Soils
Commercial
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Parking lot
Roof
Open/Landscaped
Industrial
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Parking lot
I
I
I
I
I
I
I
I
Roof
I
I
I
I
I
I
I
I
Open/Landscaped
Transportation
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
High Density (interstate, main)
High Density (Grassed Right-of-ways)
Low Density (secondary, feeder)
Low Density (Grassed Right-of-ways)
I
I
I
I
I
I
I
I
Rural
I
I
I
I
I
I
I
I
Rural (Grassed Right-of-ways)
Sidewalk
Misc. Pervious
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Managed pervious (Open Space)
Unmanaged (pasture)
I
I
I
I
I
I
I
I
Woods (not on lots)
I
I
I
I
I
I
I
I
Residential
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Site
j Offsite
Roadway
0.24
0.02
'
Grassed Right-of-ways
0.33
0.02
Driveway
0.65
Parking lot
0.02
Roof
I
0.02
I
I
I
I
0.65
I
I
Sidewalk (Includes Patios)
I
I
I
I
I
I
I
Lawn
j
1.94
j 0.22
I
I
I
1.57
0.22
I
I
Managed pervious (Open Space)
Woods (on lots)
2.71
0.59
;
1.10
0.35
Land Taken up by BMP
0.31
0.04
;
JURISDICTIONAL LANDS
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Site
Offsite
Natural wetland
I
I
I
I
I
I
I
I
Riparian buffer (Zone 1 only)
I
I
I
I
I
I
I
I
Open water
Totals (Ac)=1
0.00
1 0.00
4.69
0.22
0.00
0.00
0.59
1 0.00 1
0.00
t0.00
4.85
0.22
0.00
0.00
0.43
0.00 j
DA1 Page 1

W akeCountyStormwaterDesignTooIV2.2
SITE FLOW
PRE -DEVELOPMENT T.
POST -DEVELOPMENT Tc
Sheet Flow
Length (ft)=
100.00
100.00
Slope (fUft)=
0.03
0.03
Surface Cover:
Woods
Grass
n -value=
0.40
0.240
T, (hrs)=
0.29
0.19
Shallow Flow
Length (ft)=
257.00
134.00
Slope (fUft)=
0.14
0.04
Surface Cover:
Unpaved
Unpaved
Average Velocity (ftlsec)=
6.04
3.23
T, (hrs)=
0.01
0.01
Channel Flow 1
Length (ft)=
106.70
425.00
Slope (fUft)=
0.02
0.07
Cross Sectional Flow Area (ft2)=
8.60
8.60
Wetted Perimeter (ft)=
14.28
14.26
Channel Lining:
Weeds
Grass
n -value=
0.04
0.035
Hydraulic Radius (ft)=
0.60
0.60
Average Velocity (ftlsec)=
3.76
8.04
T, (hrs)=
0.01
0.01
Tc (hrs)=
RESULTS
0.30
PRE -DEVELOPMENT
0.22
POST -DEVELOPMENT
Site Impervious Surface Area (Ac) =
0.04
1.56
Lot Impervious Surface Area (Ac) =
0.02
1.30
1 -year, 24-hour storm (Peak Flow)
Volume of runoff (ft) =
6,886
21,680
Volume change (ft) =
14,794
Runoff (inches) = Q'=
0.3447
1.0859
Peak Discharge (cfs)= Q=
1.2469
6.3817
Composite Curve Number (DA)=
60
73
Composite Curve Number (Site only)=
60
73
DISCONNECTED IMPERVIOUS - Credit given only to residential development with drainage area with less than 30% impervious
Percent Disconnected Impervious Credit (Residential Only) =
50
Disconnected impervious area (Ac) =
0.78
Drainage Area CN�j,�=
70
Site Only CN�ju_=
71
Post -development peak flow exceeds pre -development peak flow for this DA!
DA1 Page 2

WAKE
COUNTY
NORTH CAROLINA
DA SITE SUMMARY
STORMWATER PRE -POST CALCULATIONS
Wake County SW Hybrid Tool Version 2.2
Project Name: I Layhill Estates
SITE SUMMARY
DRAINAGE AREA SUMMARIES
DRAINAGE AREA:
DA1
DA2
DA3
DA4
DA5
DA6
Pre -Development (1 -year, 24-hour storm)
Runoff (in)=Q* =
0.345
Peak Flow (cfs)=Qpost=
1.247
Post -Development (1 -year, 24-hour storm)
Proposed Impervious Surface (acre) =
1.56
Runoff (in)=Q* =
1.086
Peak Flow (cfs)=Qpost=
6.382
TARGET CURVE NUMBER (TCN) - Residential Only
SITE \SOIL COMPOSITION
HYDROLOGIC SOIL GROUP
Site Area
%
Target CN
A
0.00
0%
41
B
4.85
92%
62
C
0.00
0%
75
D
0.43
8%
80
Total Site Area (acres) =
5.28
Zoning =
R -40W
Target Curve Number (TCN) =
63
% Impervious =
30%
Post Development CNadjusted =
71
Required Volume to be Managed (TCN)= ft3 =
5,551
SITE NITROGEN AND PHOSPHORUS LOADING
Nitrogen and Phosphorus Targets (Based on Regulatory Watershed)
Target Nitrogen Load (Ib/ac/yr)=
3.6
Target Phosphorus Load (Falls and Jordan Lakes Only) (Ib/ac/yr)=
N/A
• N Loading Reduction Option for Expansions (Falls and Jordan Lakes Only) =
N/A
• Loading Reduction Nitrogen Target (Falls and Jordan Lakes Only) (Ib/ac/yr)=
N/A
• P Loading Reduction Option for Expansions (Falls and Jordan Lakes Only) =
N/A
% Loading Reduction Phosphorus Target (Falls and Jordan Lakes Only) (Ib/ac/yr)=
N/A
Pre Development Nitrogen and Phosphorus Load
Total Nitrogen (Ib/ac/yr)=
1.00
Total Phosphorus (Ib/ac/yr)=
N/A
Post Development Nitrogen and Phosphorus Load
Total Nitrogen (Ib/ac/yr)=
5.06
Total Phosphorus (Ib/ac/yr)=
N/A
SITE SUMMARY Page 1

0=
WAKE
COUNTY
NORTH CAROLINA
Project Name: Layhill Estates
DRAINAGE AREA 1
BMP CALCULATIONS
Wake County SW Hybrid Tool Version 2.2
DRAINAGE AREA 1 - BMP DEVICES AND ADJUSTMENTS
DA1 Site Acreage=
5.28
DA1 Off -Site Acreage=
0.22
Total Required Storage Volume for Site
TCN Requirement (ft)=
5,551
Will site use underground water harvesting?
Enter % volume reduction in
decimal form=
Note: Supporting information/details
should be submitted to demonstrate
water usage.
ENTER AREA TREATED BY BMP
Land Use (acres)
Sub-DA1(a)
(Ac)
Sub-DA1(b)
(Ac)
Sub-DA1(c)
(Ac)
Sub-DA1(d)
(Ac)
Sub-DA1(e)
(Ac)
Commercial
Site
Off-site
Site
Off-site
Site
Off-site
Site Off-site
Site Off-site
Parking lot
Roof
Open/Landscaped
Industrial
Site
Off-site
Site
Off-site
Site
Off-site
Site Off-site
Site Off-site
Parking lot
Roof
I
I
I
I
I
Open/Landscaped
I
I
I
I
I
Transportation
Site
Off-site
Site
Off-site
Site
Off-site
Site
Off-site
Site
Off-site
High Density (interstate, main)
High Density (Grassed Right-of-ways)
Low Density (secondary, feeder)
Low Density (Grassed Right-of-ways)
Rural
I
I
I
I
I
Rural (Grassed Right-of-ways)
I
I
I
I
I
Sidewalk
I
I
I
I
I
Misc. Pervious
Site
Off-site
Site
Off-site
Site
Off-site
Site Off-site
Site Off-site—
Managed pervious
Unmanaged (pasture)
Woods (not on lots)
Residential
Site
Off-site
Site
Off-site
Site
Off-site
Site
Off-site
Site
Off-site
Roadway
0.26
Grassed Right-of-ways
0.35
I
I
I
I
I
Driveway
0.65
I
I
I
I
I
Parking lot
I
I
I
I
I
Roof
0.65
Sidewalk
Lawn
1.57
0.22
Managed pervious
I
I
I
I
I
Woods (on lots)
1.45
1
1
1
I
1
Land Taken up by BMP
0.35
1
1
1
1
1
JURISDICTIONAL LANDS
Site
Off-site
Site
Offsite
Site
Offsite
Site Offsite
Site Offsite
Natural wetland
Riparian buffer (Zone 1 only)
Totals (Ac)=,
5.28
0.22
0.00
0.00
0.00
0.00
0.00 0.00
0.00 0.00
DA1_BMPs Page 1

Wake County SW Hybrid Tool Version 2.2
Sub-DA1(a) BMP(s)
Device Name (As Shown on Plan)
Device Type
Water
Quality
Volume
(c.f.)
Inflow N
EMC
(mg/L)
Total
Inflow N
(Ib/ac/yr)
Inflow P
EMC
(mg/L)
Total
Inflow P
(Ib/ac/yr)
Outflow
N EMC
(mg/L)
Total
Outflow,
N
(Ib/ac/yr)
Outflow
p EMC
(mg/L)
Total
Outflow
P
(Ib/ac/yr)
Provided
Volume
Managed
(c.f.)
POND
Dry Detention Pond
6,095
1.31
5.10
0.29
1.13
1.21
4.71
0.21
0.81
10,613
Outflow Total Nitrogen (Ib/ac/yr)=
4.71
Outflow Total Phosphorus (Ib/ac/yr)=
0.81
Sub-DA7(b) BMP(s)
If Sub-DA1(b) is connected to upstream sub-basin(s), select all contributing sub-basin(s from
dropdown menus):
Device Name (As Shown on Plan)
Device Type
Water
Quality
Volume
(c.f.)
Inflow N
EMC
(mg/L)
Total
Inflow N
(Ib/ac/yr)
Inflow P
EMC
(mg/L)
Total
Inflow P
(Ib/ac/yr)
Outflow
N EMC
(mg/L)
Total
Outflow
N
(Ib/ac/yr)
Outflow
p EMC
(mg/L)
Total
Outflow
P
(Ib/ac/yr)
Provided
Volume
Managed
(c.f.)
4—
Outflow Total Nitrogen (Ib/ac/yr)=
Outflow Total Phosphorus (Ib/ac/yr)=
Sub-DA1 (c) BMP(s)
If Sub-DA1(c) is connected to upstream sub-basin(s), select all contributing sub-basin(s):
Device Name (As Shown on Plan)
Device Type
Water
Quality
Volume
(c.f.)
Inflow N
EMC
(mg/L)
Total
Inflow N
(Ib/ac/yr)
Inflow P
EMC
(mg/L)
Total
Inflow P
(Ib/ac/yr)
Outflow
N EMC
(mg/L)
Total
Outflow,
N
(Ib/ac/yr)
Outflow
p EMC
(mg/L)
Total
Outflow
P
(Ib/ac/yr)
Provided
Volume
Managed
(c.f.)
Outflow Total Nitrogen (Ib/ac/yr)=
Outflow Total Phosphorus (Ib/ac/yr)=
Sub-DA1 (d) BMP(s)
If Sub-DA1(d) is connected to upstream sub-basin(s), select all contributing sub-basin(s):
Device Name (As Shown on Plan)
Device Type
Water
Quality
Volume
(c.f.)
Inflow N
EMC
(mg/L)
Total
Inflow N
(Ib/ac/yr)
Inflow P
EMC
(mg/L)
Total
Inflow P
(Ib/ac/yr)
Outflow
N EMC
(mg/L)
Total
Outflow
N
(Ib/ac/yr)
Outflow
p EMC
(mg/L)
Total
Outflow
P
(Ib/ac/yr)
Provided
Volume
Managed
(c.f.)
Outflow Total Nitrogen (Ib/ac/yr)=
Outflow Total Phosphorus (Ib/ac/yr)=
Sub-DA1 (e) BMP(s)
If Sub-DA1(e) is connected to upstream sub-basin(s), select all contributing sub-basin(s):
DA1_BMPs Page 2

Wake County SW Hybrid Tool Version 2.2
Device Name (As Shown on Plan)
Device Type
Water
Quality
Volume
(c.f.)
Inflow N
EMC
(mg/L)
Total
Inflow N
(Ib/ac/yr)
Inflow P
EMC
(mg/L)
Total
Inflow P
(Ib/ac/yr)
Outflow
N EMC
(mg/L)
Total
Outflow
N
(Ib/ac/yr)
Outflow
p EMC
(mg/L)
Total
Outflow
P
(Ib/ac/yr)
Provided
Volume
Managed
(c.f.)
Outflow Total Nitrogen (Ib/ac/yr)=
Outflow Total Phosphorus (Ib/ac/yr)=
DA1 BMP SUMMARY
Total Volume Treated (c.f.)=
10613
DA1 Outflow Total Nitrogen (Ib/ac/yr)=
4.71
DA1 Outflow Total Phosphorus (Ib/ac/yr)=
0.81
1 -year, 24-hour storm
Pre Development Peak Discharge (cfs)= Ql_year
1.25
Post BMP Peak Discharge (cfs)= Ql_year
0.47
DA1_BMPs Page 3

Wake County SW Hybrid Tool Version 2.2
Project Name: Layhill Estates
�V� DA SITE SUMMARY
AKI BMP CALCULATIONS
COUNTY
NORTH CAROLINA
BMP SUMMARY
DRAINAGE AREA SUMMARIES
DRAINAGE AREA:
DA1
DA2
I DA3
DA4
DA5
DA6
Post -Development (1 -year, 24-hour storm)
Peak Flow (CfS)=Qt_year=
6.38
Post -Development with BMPs (1 -year, 24-hour storm)
% Impervious=
30%
Volume Managed (CF)=
10,613
Post BMP Peak Discharge (cfs)= Qt -year=
0.47
Have Target Curve Number Requirements been met?
YES
Pre Development Nitrogen and Phosphorus Load
Total Nitrogen (Ib/ac/yr)=
1.00
Total Phosphorus (Ib/ac/yr)=
N/A
Post Development Nitrogen and Phosphorus Load
Total Nitrogen (Ib/ac/yr)=
5.06
Total Phosphorus (Ib/ac/yr)=
N/A
Post -BMP Nitrogen Loading
Outflow Total Nitrogen (Ib/ac/yr)=
4.71
Outflow Total Phosphorus (Ib/ac/yr)=
0.81
Has site met the Target?
NO
Has site met requirements for offsetting?
YES
BMP SUMMARY Page 1