SW6210303_Watson Ridge_Calculations_20210601

Slormwoler MGnogemenl Reporl
May 27, 2021
Watson Ridge Subdivision,
Phase 1 and Phase 2
Sheriff Watson Road
Harnett County, NC
Prepared for:
Double D Engineering, PLLC
150 S. Page Street
Southern Pines, NC 28387
910-684-8646
Prepared by:
Triangle Site Design, PLLC
4004 Barrett Drive, Suite 101
Raleigh, NC 27609
(9 19) 553— 6570
License#P-061 9
RIANGLE
S I T E D E S I G N
CARO
16,
SEA
24
ort , r,,,-, , � I " ,,,

TABLE OF CONTENTS
OVERVIEW
FIGURES
SOILS SURVEY & SOIL INFORMATION
USGS TOPOGRAPHIC MAP
FEMA FIRM MAP
WATER SURFACE CLASSIFICATIONS
HUC
NOAA POINT PRECIPITATION FREQUENCY ESTIMATES
SHWT REPORT
WATER QUANTITY- I NFI LTRATION BASIN #1
DRAINAGE AREA MAP
DESIGN SUPPLEMENT
CN VALUES
PRE -DEVELOPMENT HYDROGRAPHS
POST -DEVELOPMENT HYDROGRAPHS
TIME VS. VOLUME (STORAGE)
TIME VS. ELEVATION (STAGE)
ELEVATION -VOLU M E- FLOW SUMMARY
SCM SUMMARY
TIME OF CONCENTRATION
WATER QUANTITY- IN FILTRATION BASIN #2
DRAINAGE AREA MAP
DESIGN SUPPLEMENT
CN VALUES
PRE -DEVELOPMENT HYDROGRAPHS
POST -DEVELOPMENT HYDROGRAPHS
TIME VS. VOLUME (STORAGE)
TIME VS. ELEVATION (STAGE)
ELEVATION -VOLUME- FLOW SUMMARY
SCM SUMMARY
TIME OF CONCENTRATION
WATER QUANTITY -WET POND #3
DRAINAGE AREA MAP
DESIGN SUPPLEMENT
CN VALUES
PRE -DEVELOPMENT HYDROGRAPHS
POST -DEVELOPMENT HYDROGRAPHS
TIME VS. VOLUME (STORAGE)
TIME VS. ELEVATION (STAGE)
ELEVATION -VOLU M E- FLOW SUMMARY
SCM SUMMARY
TIME OF CONCENTRATION

OVERVIEW
This report contains the storm water management calculations for the proposed residential
development Watson Ridge Subdivision, Phase 1 and Phase 2 on Sheriff Watson Road in
Harnett County. The project site is currently un—cleveloped wooded area. The proposed
site consists of 39.625 ac and approximately 8.209 ac will be disturbed as part of this
project for the construction of the site improvements. There is approximately 18,683 sf (0.43
ac) of surface wafer area which results in approximately 39.196 cc of total project area.
The proposed site is located in Flood Zone 'X' as shown on FEMA FIRM Panel 9546L with an
effective date of 10/17/06. Flood zones are subject to change by FEMA.
There are existing stream or wefland features on the proposed property.
The proposed storm
water management facilities
(two infiltration basins and
a wet pond)
outlined in this report
have been designed for posf—developmenf
peak attenuation
to treat the
impervious areas of
the development in Harnett
County.
Infiltration Basin#1
is designed to
capture a drainage
area of 6.04 ac with an impervious
area of 1.68 ac. Infiltration Basin#2
is designed to capture a drainage area of 9.76
cc with
an impervious area
of 2.29 ac. Wet
pond is designed to
capture a drainage area of
7.39 ac
with an impervious
area of 1.34 ac.
The balance of the
site is open space and will
by—pass
the proposed SCMs.
The SCMs are
designed to treat a
1.0" storm event.
Soils
The County Soils Survey indicates that Candor Sand, Blaney Loamy Sand and Gilead Loamy
Sand soils are present on the site.

FIGURES

35- 20'27 N
35- 2(Y I' N
Hydrologic Soil Group—Hamett County, North Carolina, and Lee County, North Carolina
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k Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 17N WGS84
usDA Natural Resources Web Soil Survey 1/28/2021
Conservation Service National Cooperative Soil Survey Page 1 of 5
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Hydrologic Soil Group—Hamett County, North Carolina, and Lee County, North Carolina
Hydrologic Soil Group
�—M—apun It syrmbo I Map unit name Rating Acres In AOI Percent of AOI
BnB Blaney loamy sand, 2 to
C
2.8
9.5%
8 percent slopes
BnD Blaney loamy sand, 8 to
C
10.5
35.0%
15 percent slopes
CaB Candor sand, 0 to 8
A
13.1
43.8%
percent slopes
GaB Gilead loamy sand, 2 to
C
1.2
3.9%
8 percent slopes
Subtotals for Soil Survey Area
27.6
92.1%
Totals for Area of Interest
30.0
100.0%
Map unit symbol
Map unit name
Rating
Acres In AOI
Peftlwt Of A01
BaB Blaney loamy sand, 2 to
C
0.4
1.5%
8 percent slopes
BaD Blaney loamy sand, 8 to
C
1.6
5.3%
15 percent slopes
CaB Candor sand, 0 to 8
A
0.3
1.1%
percent slopes
Subtotals for Soil Survey Area
2.4
7.9%
Totals for Area of Interest
30.0
100.0%
USI)A Natural Resources Web Soil Survey 1/28/2021
Conservation Service National Cooperative Soil Survey Page 4 of 5

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1/28/2021 Precipitation Frequency Data Server
NOAA Atlas 14, Volume 2, Version 3
Location name: Sanford, North Carolina, USA*
09*
Latitude: 35.3362*, Longitude: -79.15
Elevation: 343.36 ft**
source: ESRI Maps
source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D Riley
NOAA. National Weather Service, Silver Spring, Maryland
PF tabular I PF gLapLi�cal I Maps & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)l
Average
recurrence interval (years)
2 IF-
5
F-1000
F-O-.4-35-�7-0.6-14--IF-O-.5-97-�7-0.6-.S8-7F-O-.7-29--IF-O-.7-78--II
0.824
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[(0.396-0.482)
1(0.467-0..570)11(0.542-0.662)
](0.597-0�728)
1(0.657-0.805)
1(0.700-0.858)
1(0.737-0.908)
1(0.770-0.954) 11(0�806-1.01)
[(0,832-1 05)
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0.957
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1 1.37
1(0.632-0.770)
j(0.747-0.911)
1 (0.868-1.06)
] (0.954-1.16)
(1.05-1.28)
1 (1.17-1.44) 11
(1.22-1.51)
j(1.27-1.59)
j(1.31-1.65)
[ 0.869
1 1.03 11
1.21
F-T-66-�
1 1.73
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1 (1,10-1.34)
1 (1.211-1,47)
(1.33-1.63)
1 (1.48-1.82) 11
(1.54-1.91)
j(1.60-2.00)
1(1.65-2.07)
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2.90
1 3.04
(1.08-1.32)
(1.30-1.58)
(1.56-1.90)
(1.75-2.13)
(1.97-2.41)
1 (2.13-2.61)
1 (2.27-2.79)
�0-1
L(j�4 2.97
(2.55 -3.19)11(2.66-3.35)
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1.79
2.20
2.51
2.90
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F-T.4-9-�
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1 4.15
1 (1.35-1.65)
(1.63-1.99)
(2.00-2.44)
(2.28-2.
(2.62-3.21)
1 (2.88-3.53)
1 (3.12-3.85) 11
(3.36-4.17)
1(3.66-4.58)
F-157-5�F-2-.1-2--JF-256-4�1
3.04
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1 (1.57-1.96)
1 (1.91-2.37)
1 (2.38-2.95)
1 (2.73-3.39)
1 (3.18-3.98)
1 (3.53-4.43)
1 (3.87-4.87)
1 (4.20-5.33)
1(4.63-5.93)
1(4.96-6.40)
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3587-7F-4.-36-�F-
4-85---JF--S.-37-�F-6-.08--�F-6.-65--�
(1.68-2�08)
1 (2.03-2.52)
j.(2.65-.3.10
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(4.28-5.41)
1 (4.70-5.98)
1(5.26-6.77)
1(5.69-7.40)
F-2.-68--�F-3.-36-�7-3.-90-�F-4.-65-7F
-6.25-71
6.87
F-655-1�F-7-.4-2�F-8-.1-4--j
(Z44-2,97) 11
(3.05-3.72)
(3.53-4.32)
(4.18-5.13)
(4.68-5.78)
(5.19-6.46)
(5.71-7.16) 1[
(6.42-8.15)
1(6.96-8.95)
2.61
1 3.17
F-3
7.99
(2,38-2-90)
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(3.62-4.43)
(4.21-5.16)
(5.00-6.16)
(5,64-6.9
(15.2G-7.85)
(6.96-8.77)
1(7.88-10.1)
1(8.59-11.1)
3.07
3.71
4.68
9.07
F-1-0.-3�F-1-1.-31
(2.85-3.32)
(3,44-4-01)
(4,34-5,M)
(5.98-7.01)
(6.73-7.91)
(7.50-8.83)
(8.30-9.79)
1(9.37-11.1)
1(10.2-12.2)
F-3.-58-�
4.32
5-.4-0 -71
6.26
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10.3
1 11.7
[ 12.8
�3.33-3.85)
(4.01-4.64)
02-5.82) 11
(5.80-6.74)
1 (6.86-8.00)
1 (7710-9.00)
1 (a.561U.0)
1 (9.43-11.1) 11
(10.6-12.6) 11(11.6-13.8)
3.80
F--4-.5-7---JF--S-.6-9
-7
1 7.78
F-18-.7 -5--]
F-T.7-4-�
1 10.8
1 12.2 11
13.3
(154A.07)
(4.26-4.90)
(5.30-6.10)
(7.21-8.34)
(8.07-9.37)
(8.96-10.4)
1 (9.87-11.6)
1(11.1-13.1)
1(12.1-14.3)
(3.75-4.20)
(4.51-5,18)
(5,57-6,35)
(GA1-7.34)
(7.55-8.69)
(8.45-9.75)
(9.37-10.8)
1 (10.3-12.0)
1(11.6-13.6)
1(12.6-14.B)
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6.77
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11.3
1 (5.17-5.02)
(6-31-7.24)
1 (&44-151.72) 1[
(0.41-10.9)__
1 (10.4-12.1)
1 (11.4-13.3)
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1 6.29
11.0
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13.2
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(4�97 5.62)
11 (5.91-6.6a)
(7�11-8,06)
(8.05-9,14)
1 (9.30-10.6)
(10.3-11.7)
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11 (12.2-14.1)
1(14.6-17.0)j
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(9.35-10.6)
1 28
12.0-13 . 6
1 (14.3-16.4)
1 (15.5-17.8)
1(17.1-19.7)
1(18.3-21.3)
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(8.35
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(9.83 11
(11.5 -12.9)
1 (12.7 -14.3)
1 3-16 . 2
(16.8-19.1)
1 (18.0-20.6)
] (19.6-22.5)
j(20.8-24.0)
11.2
13.2
F-2-4.-6IF-2-6-.07
45-day
(10.6-11.9)
(12.4-13.9)
1 (14.3-15.9)
1 (15.6-17-5)
1 (17.4-19.5)
(18.8-21.1)
(23.0-26.1)
1 (24.2-27.6)
195
7-23-.I-��F--2-6.-1-7F-128-1
11
29.5
4.2
L�j �.8-1�L
(14 9-16 6) j
L11L.9-18.8
----Ll
(18.4-' 5)
20
IF
1 (20.4-22.7) IL(21.8-24.4)
J
L24.6-27.6LL2L4-29.7
JJL2L____
.7-31.3�]
Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS)
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for
a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are
not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. I
Please refer to NOAA Ages 14 document for more information.
Back to Top
PF graphical
httpr,:Ilhclsc.nm.niDaa.govlhdsclpfdslpfds-printpage.html?lat=35.3362&lon�79.1 609&deta=depth&units=erigilsh&series=pds 1/4

Scott Cole, NCLSS
312 Copples Road Ext
Asheboro, NC 2 7205
[phone]
Double D Engineering, PLLC
Attn: Mr. Lee Humphrey
ISO S. Page Street
Southern Pines, NC 28387
January 21, 202 1
Re: Seasonal Iligh-Water Table Identification and Soil Infiltration Rates: Watson Ridge; Harnett County NC Parcel
9557-57-4906
Soil conditions and infiltration rates were evaluated and measured oil the above -referenced property within proposed
storm water BMP devices. Work was conducted in accordance with Parts A-2 and C- I of the North Carolina Department
of Environmental Quali1j, Slormwaler Design Manual. Soil samples were evaluated with a hand auger.
SEASONAL HIGH WATER TABLE IDENTIFICATION
Seasonal High Water Table depth is determined by field evaluation for soil wetness conditions which are indicated by tile
presence of redoximorphic (redox) features with a chroma of 2 or less (in Munsell color notation) in mottles or the
horizon matrix. Colors of chrorna 2 or less due to relic minerals from parent material (underlying rock), anaerobic activity
created by placernent of fill material, or soil textural class transitions (perched water) are not considered as indicators for
seasonal high water. Upon deten-nination of SHWT depth, an additional 6" will be deducted from the observed depth to
account for capillary fringe water movement above the SHWT. Stormwater infiltration trenches are designed to ensure
the lowest point is at least two feet above the Seasonal High Water Table (SHWT).
SATURATED HYDRAULIC CONDUCTIVITY (&.0
Soils evaluated oil this property are typical of those within the Candor Sand series (CaB), Blaney Loamy Sand series
(BnB) and the Gilead Loamy Sand series (GaA). These soil series consist of deep, well drained soils with varying rates of
permeability. Infiltration rates were measured to determine if soil conditions were suitable for the installation of
storrilwater infiltration trenches. Infiltration rates were measured using a Johnson Constant Head Permeameter.
Measurements were recorded at varying intervals until equilibrium was reached.
A summary of observations within each proposed Storinwater BMP Device is shown in the tables below.
BMP Device Site #1
SHWT
Munsell Color
Ksat
Ksat
(inches below
Notation
(0-48"; SULS)
(48"-72";
uound surface)
SCL/SQ
72" (elevation
2.5Y 8/1
18.15" / hour
.545" / hour
365.5')
2.5Y 7/1
BMP Device Site #2
SHWT
Munsell Color
Ksat
Ksat
(inches below
Notation
(0-45"; LS)
(45"-56";
eround surface)
SCL/SQ
56" (elevation
2.5Y 8/1
20" / hour
.545" / hour
— 332')

SHWT
(inches below
,2round �UIT.ICV)
Depths vary
between 32"-72"
Scott Cole, NCLSS
312 Copples Road Ext
Asheboro, NC 2 7205
[phone]
BMP I
Munsell Color
Notation
2.5Y 8/1
2.5Y 7/1
Site #3
Ksat
(0-32"; LS)
18.15" / hour
Ksat
(32"-72";
.545" / hour
Note: BMP site #3 has 18' of elevation change. Expansive clay layer present at depths ranging from 32-72" bgs.
BMP Device Site #3 (Ahernale Locaflun)
SHWT
Munsell Color
Ksat
(inches below
Notation
P-round surface)
Not Observed
Heavy Gleying
Not measured
within 15' of
within expansive
ground surface.
Clay layer due to
(Evaluation
perched water,
conducted to
elevation 317')
CONCLUSION
Field evaluation of hydraulic conductivity provides estimations of soil infiltration rates; however, methods used to
measure these rates can influence the results. Side walls of the bore hole are "smeared" by the soil auger as the hole is
prepared and loose soil in the bottom of the hole is placed in suspension when water is applied; both of these factors
negatively influence water infiltration rates. To help overcorne these issues, after excavation of each infiltration trench, it
is recommended the trench bottom and sidewalls be raked and dusted with pulverized limestone. These are practices that
have been in place within the on -site wastewater industry to help loosen the soil and aid in restoration of soil structure.
I am pleased to be of service in this matter and can be contacted at your convenience should you have any questions
concerning information within this report. —0000--M-�
Thank you.
Scoff Cole
North Carolina Licensed Soil Scientist
SOIL
C/X,
0
Q
co
M
263
QC

L07
r 4,;-
20, 7 S, F
L
LOT,4.2
21,fl78 S P L T 36
7,946
0 T 7
PROPOSED 2" 2 0 '14 F 22 7. 6 S F
WATER MAIN
BMP Site #3 (Alternate location)
SHWr Not Observed within
15'of surface. (evaluated to elevation 31T) 1.0'f 4
20,010 SF
NOTE: Heavy Expansive Clay observed
from surface to 16'bgs.
1561,
1 inch
V;
0
h
1 40
5,841 SF/ L—WT39
46,6'8,
ZI
A� / /
0
04
CI)
79 , hea exp.
n
In10 15' heavy [By;
UNSUITALKE SOILS
STORM -WATER
TREATMEN�
�OPEN SPACE
101,291 SF
90
100 feet/.
SH)N TNO
N,
PRO!
LIGH
avo 1%. J S A C, W E T L.
LI N Ir
OPEN SIPACE
4,2719 SF
PROPOSED 20'
IRAINAGE AND ACCESS
.ASEMENT
ID SOIL S
do& tk, C)
0
M
1263 14
K'%SQ!A0m C

BMP Site #1
SHWP 72" (6') bgs
SHWT Elevation: 365.5'
'W ].0 r
-48" (04') LS/SL: 18" hour
Ksat 0
Ksat 48"-72" (4'-6') SCUSC: .6.:45" h
4
161� 5 S 1!
i we er
h,M BMP Site #2
L
SHVVT-. 56" (4.6') bgs
'7�6&4u.$2 S V�'ls 56sc *wt exp FW
SHWT Elevation: 332'
Is 56"
Ksat 0-45" (0-3.75'1 LS; 20" 1 hour
Lhour
Ksat 45"-56" (3.75'-4.7') SCLISC: .645" hour
fAms 56scl shwt water
V
4514Asri shwt free water
1.4.
n8 4811
112 241s 36scl �A S
1 inch = 250 feet
t
/
02 4Ens k*.72scl exp
if
MOW 70sh 301s 45scl exp shwt
6 32scl exp shwt
I
Are -s �
IN
BMP Site #3
SHWP Varies (see note below)
SHWT Elevation: Varies
NOTE: Approx. 18'elevation change
in BMP area. SHVVT depth varies
from 3'- G'bgs.
Expensive Clay layer encountered at
11 varying depths within BMP area
0-0
. W4% W, . T 1�1
301, '?18 63 C
304
29b 300 298
"A

WATER QUANTITY- IN FILTRATION BASIN#1

10 t, k
(,. /A4-,e a -,- 6, c)--f a,-
�fsw\
I rri -S

SUPPLEMENT-EZ COVER PAGE
F- FORMS LOADED
PROJECT INFORMATION
F1 Project Name
2 Proiect Area (ac)
3 Coastal Wetland Area (ac)
__i
4 Surface Water Area (ac)
5 Is this Droiect High nr I nw noncifu'?
6 Does this project use an off -site SCM?
Watson Ridge
39.625
0.429
No
COM LIANCE NTH 02H.IDQ3(4)
7
Width of vegetated setbacks provided (feet)
30
8
Will the vegetated setback remain vegetated?
Yes
9
If BUA is proposed in the setback. does it meet NCAC 02H.1003(4)(c-d)?
No
10
Is streambank stabilization proposed on this project?
No
NUMBER AND TYPE OF SCM9:
11
Infiltration System
2
12
Bioretention Cell
0
13
Wet Pond
I
14
Stormwater Wetland
0
15
Permeable Pavement
0
16
Sand Filter
0
17
Rainwater Harvesting (RWH)
0
18
Green Roof
0
ilter Strip (LS-FS)
0
20
IDisconnected Impervious Surface (DIS)
0
21
Treatment Swale
0
22
Dry Pond
0
23
StormFilter
0
24
Silva Cell
0
25
Bayfilter
0
26
, Filterra
0
I FORMS LOADED
DESIGNER CERTIFICATION
27
Name and Title:
Matt Lowder, PE
28
Organization:
Street address:
City� St te, Zip:
Phone number(s).*
1 Email:
Triangle Site Design, PLLC
29
4004 Barrett Drive, Suite 101
30
Raleigh, NC 27609
31
919-553-6570
32
mlowder(cbtrianglesitedesign.Gom
Certification Statement:
I certify, under penalty of law that this Supplement-EZ form and all supporting information were prepared under my direction or supervision; that the
information provided in the form is, to the best of my knowledge and belief, true, accurate, and complete; and that the engineering plans,
specifications, operation and maintenance agreements and other supporting information are consistent with the information provided here.
L"L�T?
SEAL,
2A 4 3,:
T�A
e �kc"'
Signature of Designer
3 �6'(
Date

DRAINAGE AREAS
1
Is this a high density project?
Yes
2
If so, number of drainage areas/SCMs
3
3
Does this project have low density areas?
No
4
q :umber q low density drainage areas
:Tf —so,::n f
0
5
Is all/part of this project subject to previous rule
versions?
No
I FORMS LOADED
D AGE AREA INFORMATION
Enfire Site
2
3
4
Type of SCM
-
Infiltration Basin
Infiltration Basin
Wet Pond
5
Total drainage area (sq ft)
1010204
262994
425090
322120
6
Onsite drainage area (sq ft)
987169
239959
425090
322120
7
Ofisite drainage area (sq ft)
23035
23035
8
Total BUA in project (sq ft)
230951
73116 sf
99538sf
58298 sf
9
New BUA on subdivided lots (subject to permitting)
(sq ft)
New BUA not on subdivided lots (subject to
permitting) (s�
_10
11
Offsite BUA (sq ft)
7686
7686sf
12
Breakdown of new BUA not on subdivided lots:
Parkinq (sq ft)
Sidewalk (sq ft)
Roof (sq ft)
16 8000
48000 sf
72000sf
48000sf
Roadway (sq ft)
'
55265
17429sf
27538sf
10298 sf
Future (sq ft)
Other, please specify in the comment box
below (sq ft)
13
New infiltrating permeable pavement on
subdivided lots (sq ft)
14
New infiltrating permeable pavement not on
subdivided lots (sq ft)
15
Existing BUA that will remain (not subject to
permitting) (sq ft)
16
Existing BIJA that is already permitted (sq ft)
17
ExistinQ BUA that will be removed (sq 4)
18
Percent BUA
28%
23%
18%
19
Desion storm (inches)
1.0 in
1.0 in
1.0 in
20
Desiqn volume of SCM (cu ft)
6579 cf
9237 cf
5715 cf
21
Calculation method for design volume
Simple Method
Simple Method
Simple Method
ADDITIONAL INFORMATION
-221Please
use this space to provide any additional information about the
drainage area(s):
Infiltration Basin #1 - there is o#s--ite drainage area from the Lee County
portion of the overall development.

INFILTRATION SYSTEM
�Dra,i,na o �area n�e 2
um r—
M
rQ", ftj����65�79c 9237,7
F2_ d treatment wl..�e _A
3
Is the SCM sized to treat the SW from all surfaces at build -out?
Yes
Yes
located away from contaminated soils?
Yes
Yes
5
_SCM
What are the side slopes of the SCM (H:V or enter "Vertical" for
trenches)?
3:1
3:1
6
Does the SCM have retaining walls, gabion walls or other engineered
side slopes?
-No
No
7
Are the inlets, outlets, and receiving stream protected from erosion
(1 0-year storm)?
Yes
Yes
—
8
Is there an overflow or bypass for inflow volume in excess of the
design volume?
Yes
Yes
9
What is the method for dewatering the SCM for maintenance?
Pump (preferred)
Pump (preferred)
10
If applica le, will the SCM be cleaned out after construction?
Yes
Yes
11
Does the maintenance access comply with General MDC (8)?
Yes
Yes
12
Does the drainage easement comply with General MDC (9)?
Yes
Yes
13
If the SCM is on a single family lot, does (will?) the plat comply with
General MDC (10)?
N/A
N/A
14
Is there an O&M Agreement that complies with General MDC (11)?
Yes
Yes
15
Is there an O&M Plan that complies with General MDC �1 2)?
Yes
Yes
16
!Does he SCM follow the device specific MDC?
Yes
Yes —
7:]
17
lWas the SCM designed by an NC licensed professional?
Yes
Yes
18 jProposed slope of the subgrade surface 0 0%
19 1 Are terraces or baffles provided? No No
20 IType of pretreatment: Forebay Forebay
C_;#� n.�
21
Was the soil investigated in the footprint and at the elevation of the
infiltration system?
Yes
Yes
22
SHWT elevation (frn_sl)
365.50
332.00
23
Depth to SHWT per soils report (in)
72.00
56.00
24
Ground elevation at boring in soils report (fmsl)
371.50
336.60
25
Is a detailed hydrogeologic study attached if the separation is
between 1 and 2 feet?
Yes
Yes
26
Soil infiltration rate (in/hr)
9.00
10.00
.27
lFactor of safety (FS) (2 is recommendeft
2.00
2.00
29 Bottom elevation (fmsl)
371 ft
336 ft
30 Storage elevation (fmsl)
1
372. ft
337. ft
31 Bypass elevation (fmsl)
373.2 ft
338.8 ft
For BaSWS Only
32 Bottom surface area (ft2) 6870 ft 10585 ft
33 Storage elevation surface area (fe) 7835. ft 12595. ft
Fnr Tranr-hoe nniv
34
Length (ft)
35
Width (ft)
36
Perforated pipe diameter, if a22licable (inches)
37
Number of laterals
38
Total length of perforated piping
39
Stone type, if applicable
40
Stone porosity (%)
41
Is stone free of fines?
42
Is the stone wrapped in gleotextile fabric?
43
Has at least one inspection port been provided?
VbluaxWDrawdown
44 IDesign volume of SCM (cuft) 6579 cf 9237 cf
45 1 Time to draw down (hours) 72 hrS 72 hrS
46 Please use this space to provide any additional information about the
I infiltration system(s): I
Infiltration 1 2:35 PM 3/4/2021

Triangle Site Design, PLLC
Watson Ridge, Harnett County, NC
Curve Number Calculation (CN)
Pre -Developed Conditions #1
Drainage Area Lacres 6.04
Existing Soil
Soil GroUD Map Symbo Soil Description Acres Per -cent of DA
A CaB Candor Sand 5.00 83%
C BnD Blaney Loamy Sand 1.04 17%
Land Uses:
Land Use Descri tion Existing Soil Gro Acres Curve # Wei.Qhted CN
Wooded - Good Stand A 5.00 50 41,4
Wooded - Good Stand C 1.04 74 12.7
Cumulative Curve # 54.1 _j

Triangle Site Design, PLLC
Watson Ridge, Harnett County, NC
Curve Number Calculation (CN)
Post -Developed Conditions to Infiltration Basin #1
QgLnage Area Lacres 6.04
soil Gro
Soil Group Map Symbo Soil Descrintion Acres Percent of DA
A CaB CandorSand 5.00 83%
C BnD Blaney Loamy Sand 1.04 17%
BnWosed Land Uses.
Land Use Qgsgn�2� Existing Soil Group Acres Curve # Weighted CN
Impervious Area -Residential Lots A/C 1.10 98 17.8
Impervious Area-Sidewalk/Road A/C 0.58 98 9.4
Wooded - Good Stand A 4.16 50 34.4
Wooded - Good Stand C 0.20 74 Z5
Cumulative Curve # 64.1

Infiltration Basin Design
Site Information
Sub Area Location:
Drainage To Infiltration Basin #1
Drainage Area (DA) =
6.04 Acres 26295'4— sf
Impervious Area (IA) =
1.68 Acres 73115 sf
Percent Impervious (1) =
27.8 %
Required Water Quality Volume
Design Storm =
1 inch
Determine Rv Value =
0.05 +.009 (1) = 0.30 in/in
Water Quality Volume =
0.151 ac-ft
Water Quality Volume =
6,579 cf
Water Quality Volume =
0.300 inches of runoff
I NOAA 1 -year. 24-hour event = 3.07 inches
Minimum Surface Area
SA =
(12'FS-DV)/(K-T)
Factor of Safety (FS) =
2
Design Volume (DV) =
6579.4 Cf
Hydraulic Conductivity of Soil =
9.00 in/hr
Max Dewatering Time =
72 hours
SA =
243.7 sf

'STAGEZSTORAGE TABLE
INFILTRATION BASIN
STAGE
EL EVA TION
CONTOUR
INCREMENTAL
TOTAL
(FT)
_LFT)
AREA (ZFJ
STORAGE (CF)
STORAGE
0.0
371.0
6870
0
0
1.0
372.0
7835
7353
7353
2.0
373.0
8855
8345
15698
3.0
374.0
9930
9393
25090
3.5
374.5
10490
5105
30195
STORMWATER MANAGEMENT DESIGN
INFILTRATION BASIN #1
RIVER BASIN:
RECEIVING STREAM:
STREAM INDEX:
STREAM CLASS:
HUC:
CAPE FEAR
CYPRESS CREEK (MCDONALD SWAMP)
18-20-13-3-4
C
03030004
POND DESIGN SUMMARY
DRAINAGE AREA TO POND: 6.04 ACRES
SITE IMPERVIOUS AREA TO POND: 1.68 ACRES
OFF -SITE DESIGN IMPERVIOUS AREA TO POND: 0.0 ACRES
TOTAL DESIGN IMPERVIOUS AREA TO POND: 1.68 ACRES
PRE -DEVELOPED POST -DEVELOPED POST DEVELOPED
THROUGH POND
DRAINAGE AREA: 6.04 AC 6.04 AC
CURVE NUMBER: 54.1 64.1
INFILTRATION RATE: 9.0 IN/HR
1.0" STORM EVENT:
0.000
CFS
0.000
CFS
I -YEAR STORM EVENT:
0.389
CFS
3.439
CFS
0.000
CFS
2-YEAR STORM EVENT:
1.658
CFS
6.530
CFS
0.000
CFS
10-YEAR STORM EVENT-
7.528
CFS
16.03
CFS
0.000
CFS
100-YEAR STORM EVENT:
20.65
CFS
34.26
CFS
21.58
CFS

Le
tag
18.
lw�
E! k4
11
N
�� I'! I "— I E � lz
w
o
m
60
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m
Him
d�lo zz 0 imlis

CD
LLi
LLJ
LLJ
m
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LLJ >.
LLJ
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LLI
CL.
I--
C.D Lai
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mt
_j I.;- LAJ
LLJ
-INC
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r.:
m
a;
=
C) C)
_j .i
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LL. C), Lq
ne
LAJ
m
m
LLJ
LL-
CD
CL.
:ill
C�
LLJ
—j
LLI
31:
i
LLJ
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LLI
<
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m
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�2 cn
LLJ
Lo
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CD C)
LL-J
V)
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Q
C) LLJ
U)

2/22/2021 ECMDS 7.0
I NORTH
AMERICAN
I GREEN'
SPILLWAY ANALYSIS
> > > Grass p L11way #1
Name
Grass Spillway #1
Discharge
21.6
Peak Flow Period
2
Channel Slope
0.3333
Channel Bottom Width
10
Low Flow Liner
North American Green
5401 St. Wendel -Cynthiana Rd.
Poseyville, Indiana 47633
Tel. [phone]
>Fax [phone]
www.nagreen.com
ECMDS v7.0
Retardence Class
C 6-12 in
Vegetation Type
Mix (Sod and Bunch)
Vegetation Density
Very Good 80-95%
Soil Type
Sand (SP)
Shoremax - Class
C - Mix (Sod & Bunch) - Very
Good 80-95%
Normal
Permissible
Calculated
afety
Staple
Phase
I
I
Reach ar
Velocity
I
Mannings N
I I
Remarks
Depth
Shear Stress
Shear Stres s
Factor
Pattern
Shoremax w/
Straight 21.6 cfs
11.04 ft1s
0.2 ft
0.026
8.5 lbs/ft2
4.06 lbs/ft2
2.09
STABLE
F
P300
Unvegetated
Underlying
Straight 21.6 cfs
11.04 ft/s
0.2 ft
0.026
5.25 lbs/ft2
3.91 lbs/ft2
1.34
STABLE
F
Substrate
Shoremax wl
Straight 21.6 cfs
10.7 ft/s
0.2 ft
0.027
14 lbs/ft2
4.19 lbs/ft2
3.34
STABLE
F
P300 Reinforced
Vegetation
Underlying
Straight 21.6 cfs
10.7 ft/s
0.2 ft
0.027
8.5 lbs/ft2
4.03 lbs/ft2
2.11
STABLE
F
Substrate
https://ecmds.com/project/142852/spillway-analysis/199308/show# 1/1

WATER QUANTITY- IN FILTRATION BASIN#2

SUPPLEMENT-EZ COVER PAGE
KORMS LOADED
�ROJECT INFORMATION
1 Project Name
Watson Ridge
2 Proiect Area ac)
30,6245
3 Coastal Wetland Area (ac)
-
4
Su rtace We ter Area (ac)
0.429.
5
Is this project High or Low DensA�?'
Hlah
6
Does this prolect use an off -site SCIVI?
No
'Com I NCF-VVITH02H.1.003(4)
7 .
Width of vegetated setbacks provided (feet)
30
8
Will the vegetated setback remain vegetated?
Y89
9
If BUA is proposed in the setback, does it meet NCAC 02H.1003(4)(c-d)?
No
10
Is streambank stabilization proposed on this project?
No
NUMBER AND TYPE OF SCMG:
11—
Infiltration System
2
12
Bionetention Cell
13
Wet Pond
1
14
Stormwater Wetland
0
15
Permeable Pavement
0
Filter
0
_116Q9.nd
17
1 Rainwater Harvesting (RWH)
0
18
IGFeen Roof
0
19
Level Spreader -Filter Strip 'LS-FS)
0
20
Disconnected Impervious Surface (DIS)
0
21
Treatment Swale
0
22
2[y
0
23
StormFilter
0
24
Silva C 11
0
25
Bayfilter
0
26
Filterra
0
I FORMS LOADED
ER CERTIFICATION
27
Name and Title
�8
Organization:
29
Street address:
30
City, St te, Zip:
31
Phone number(
32
Email:
Vlaft Lowder, PE
Trianale Site Design, PLLC
4004 Barrett Drive, Suite 10'
Certification Statement:
I certIfy, under penalty of law that this Supplement-EZ form and all supporting information were prepared under my direction or supervision; that the
information provided in the form is, to the best of my knowledge and belief, true, accurate, and complete; and that the engineering plans,
specifications, operation and maintenance agreements and other supporting infbrmabon are consistent with the information provided here.
4 1 IF � f I,
t
IF I
see
2�
Signature of Designer
Date
3 /Y�v

DRAINAGE AREAS
1
Is this a high density project?
Yes
2
If so, number of drainage areas/SCMs
3
3
Does this project have low density areas?
No
4
�: f �so, number of low density drainage areas
0
5
Is all/part of this project subject to previous rule
versions?
No
I FORMS LOADED
DRAINAGE AREA INFORMATION
Entire Site i
-1 1
2
3
4
Type of SCIVI
-
Infiltration Basin
Infiltration Basin
Wet Pond
5
Total drainage area (sq ft)
1010204
262994
425090
322120
6
Onsite drainage area (sq ft)
987169
239959
425090
322120
7
Offsite drainage area (sq ft)
23035
23035
8
Total BUA in project (sq ft)
230951
73115 sf
99538sf
58298 sf
9
New BUA on subdivided lots (subject to permitting)
(sq ft)
10
New BUA not on subdivided lots (subject to
permifting)_(g
11
Offsite BUA f§q ft)
7686
7686sf
12
Breakdown of new BUA not on subdivided lots:
Parking (sq ft
Sidewalk (sq ft)
Roof (sq ft)
168000
48000 sf
72000 sf
48000 sf
Roadway (sq ft)
55265
17429sf
27538 sf
10298 sf
Future (sq ft)
Other, please specify in the comment box
below (sq ft)
13
New infiltrating permeable pavement on
subdivided lots (sq ft)
14
New infiltrating permeable pavement not on
subdivided lots (sq ft)
15
Existing BUA that will remain (not subject to
permitting) (sq ft)
16
Existing BUA that is already permitted (sq f�)__
17
Existinq BUA that will be removed (sq ft)
18
Percent BUA
28%
23%
18%
19
Design torm (inches)
1.0 in
1.0 in
1.0 in
20
Design volume of SCIVI (cu ft)
6579 cf
9237 cf
5715 cf
21
Calculation method for design volume
Simple Method
Simple Method
I Simple Method
ADDMONAL INFORMATION
Please use this space to provide any additional information about the
22
Infiltration Basin #1 - there is offsIte drainage area from the Lee County
portion of the overall development.

INFILTRATION SYSTEM
FT: �Dlainogo area number 2
M, i", required treatment volume (cu ft) 6579 cf 9237_q___]
3
Is the SCM sized to treat the SW from all surfaces at build -out?
Yes
Yes
4
Is the SCM located away from contaminated soils?
Yes
Yes
5
What are the side slopes of the SCM (H:V or enter "Vertical" for
trenches)?
3:1
3:1
6
Does the SCM have retaining walls, gabion walls or other engineered
side slopes?
No
No
Are the inlets, outlets, and receiving stream protected from erosion
7
(1 0-year storm)?
Yes
Yes
—
8
Is there an overflow or bypass for inflow volume in excess of the
design volume?
Yes
Yes
9
What is the method for dewatering the SCM for maintenance?
Pump (preferred)
Pump (preferred)
10
If applicable, will the SCM be cleaned out after construction?
Yes
Yes
-T-1
Does the maintenance access comply with General MDC (8)?
Yes
Yes
12
Does the drainage easement comply with General MDC (9)?
Yes
Yes
If the SCM is on a single family lot, does (will?) the plat comply with
13
General MDC (10)?
N/A
N/A
14
Is there an O&M Agreement that complies with General MDC (11)?
Yes
Yes
15
Is there an O&M Plan that complies with General MDC (12)?_
Yes
Yes
16
Does the SCM follow the device specific MDC?
�Was
Yes
Yes
17
the SCM clesioned bv an NC licensed Drofessional?
Yes
Yes
18 Proposed slope of the subgrade surface(%) 0% 0%
19 Are te races or baffles provided? No No
20 Type of pretreatment: Forebay Forebay
c-U� n-m
21
Was the soil investigated in the footprint and at the elevation of the
I infiltration system?
Yes
Yes
22
SHWT elevation (fmsl)
365.50
332.00
23
Depth to SHWT per soils report (in)
72.00
56.00
24
Ground elevation at boring in soils report (fmsl)
371.50
336.60
25
Is a detailed hydrogeologic study attached if the separation is
between 1 and 2 feet?
Yes
Yes
26
Soil infiltration rate (in/hr)
9.0017
10.00
I
27
Factor y (FS). (2 is recommended):
of safet
2.00
2.00
I gri—Atinna
29
Bottom elevation (frnsl)
371 ft
336 ft
30
storage elevation (fmsl)
372. ft
337. ft
31
Bypass elevation (fmsI)
373.2 ft
338.8 ft
I r— 7'-h.. n.h,
34
1 Length (ft)
35
Width (ft)
36
Perforated pipe diameter, if applicable (inches)
37
Number of laterals
38
Total length of perforate piping
39
Stone type, if applicable
40
Stone porosity (%)
41
Is stone free of fines?
42
11sthe tone wrapped in geotextile fabric?
43
� Has at least one inspeCtiDn port been provided?
VolumeslDrawdown
44 Design volume of SCM (cu ft) 6579 cf 9�37 cf
45 Time to draw down (hours) 72 hrs 72 hrs
46 Please use this space to provide any additional information about the
I infiltration system(s): I
Infiltration 2:35 PM 3/4/2021

Triangle Site Design, PLLC
Watson Ridge, Harnett County, NC
Curve Number Calculation (CN)
Pre -Developed Conditions #2
ngo?gg Area 9.76
&istinq Soil Gro
Soil Grow Map Symbo Soil Description Acres Per -cent of DA
A CaB Candor Sand 3.50 36%
C BnD Blaney Loamy Sand 5.76 59%
C GaB Gilead Loamy Sand 0.50 5%
Existing tand Uses:
Land Use Existing Soil Gro Acres Curve # We4ghted
Wooded - Good Stand A 3.50 50 17.9
Wooded - Good Stand C 6.26 74 47.5
Cumulative Curve # 65.4

Triangle Site Design, PLLC
Watson Ridge, Harnett County, NC
Curve Number Calculation (CN)
Post -Developed Conditions
to Infiltration Basin #2
Drainage Area Lacrejs: 9.76
Existing Soil Gro
Soil Group Map Symbo
Soil Description
Acres
Percent of DA
A CaB
Candor Sand
4.50
46%
C BnD
Blaney Loamy Sand
4.76
49%
C GaB
Gilead Loamy Sand
0.50
5%
8�q �osed Land Uses.,
Land Use
Existing Soil Gro Acres
Curve #
Wefghted CN
Impervious Area -Residential Lots
A/C 1.65
98
16.6
Impervious Area-Sidewalk/Road
A/C 0.63
98
6.3
Wooded - Good Stand
A 3.80
50
1 M
Wooded - Good Stand
C 3.68
74
27.9
Cumulative Curve #
70.3

Infiltration Basin Design
Site Information
Sub Area Location:
Drainage To Infiltration Basin #2
Drainage Area (DA) =
9.76 Acres 425090 sf
Impervious Area (IA) =
2.29 Acres 99538 sf
Percent Impervious (1) =
— 23.4 %
Required Water Quality Volume
Design Storm = I inch
Determine Rv Value = 0.05 + .009 (1) = 0.26 in/in
Water Quality Volume = 0.212 ac-ft
Water Quality Volume = 9,237 cf
Water Quality Volume = 0.261 inches of runoff
I NOAA I -year, 24-hour event = 3.07 inches I
Minimum Surface Area
SA =
(12-FS'DV)/(K-T)
Factor of Safety (FS) =
2
Design Volume (DV) =
9236.6 cf
Hydraulic Conductivity of Soil =
10.00 in/hr
Max Dewatering Time =
72 hours
SA =
307.9 sf

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ell
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30 a 15

STAGE/STORAGE TABLE
INFILTRATION BASIN
STAGE
ELEVA TION
CONTOUR
INCREMENTAL
TOTAL
(FT)
LFT)
A REA (�F
STORAGE (�F)
STORAGE &F
0.0
336.0
10585
0
0
1.0
337.0
12595
11590
11590
2.0
338.0
14665
13630
25220
3.0
339.0
16785
15725
40945
4.0
340.0
18965
17875
58820
STORMWATER MANAGEMENT DESIGN
INFILTRATION BASIN #2
RIVER BASIN:
RECEIVING STREAM:
STREAM INDEX:
STREAM CLASS:
HUC:
POND DESIGN
DRAINAGE AREA TO POND:
CAPE FEAR
CYPRESS CREEK (MCDONALD SWAMP)
18-20-13-3-4
C
03030004
9.76 ACRES
SITE IMPERVIOUS AREA TO POND: 2.29 ACRES
OFF -SITE DESIGN IMPERVIOUS AREA TO POND: 0.0 ACRES
TOTAL DESIGN IMPERVIOUS AREA TO POND: 2.29 ACRES
PRE -DEVELOPED POST -DEVELOPED POST DEVELOPED
THROUGH POND
DRAINAGE AREA: 9.7 6 AC 9.76 AC
CURVE NUMBER: 65.4 70.3
INFILTRATION RATE: 10.0 IN/HR
1.0" STORM EVENT:
0.046 CFS
0.000 CFS
1-YEAR STORM EVENT:
4.883 CFS
10.01 CFS
0.000 CFS
2-YEAR STORM EVENT:
9.033 CFS
16.03 CFS
0.000 CFS
10-YEAR STORM EVENT:
21.75 CFS
33.49 CFS
0.000 CFS
100-YEAR STORM EVENT:
46.16 CFS
65.53 CFS
44.15 CFS

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3/4/2021
ECMDS 7.0
[ NORTH
AMERICAN
I GREEN'
SPILLWAY ANALYSIS
> > > Grass p'llw y #2
North American Green
5401 St. Wendel -Cynthia na Rd.
Poseyville, Indiana 47633
Tel. [phone]
>Fax [phone]
www.nagreen.com
ECMDS v7.0
Name
Grass Spillway #2
Discharge
44.2
Peak Flow Period
2
Channel Slope
0.3333
Channel Bottom Width 25
Low Flow Liner
Retardence Class
C 6-12 in
Vegetation Type
Mix (Sod and Bunch)
Vegetation Density
Very Good 80-95%
Soil Type
Sandy Loam (GM)
Shoremax - Class C - Mix (Sod & Bunch) - Very Good 80-95%
Normal
Permissible
Calculated
Safety
staple
Phase
Reach
Discharge
Velocity
Mannings N
Remarks
Depth
Shear Stress
Shear St ess
Factor
Pattern
Shoremax w/
Straight 44.2 cfs
10.24 ft/s
0.17 ft
0.026
8.5 lbs/ft2
3.59 lbs/ft2
2.37
STABLE
F
P300
Unvegetated
Underlying
Straight 44.2 cfs
10.24 ft/s
0.17 ft
0.026
5.68 lbs/ft2
3.54 lbs/ft2
1.6
STABLE
F
Substrate
Shoremax w/
Straight 44.2 cfs
9.78 ft/s
0.18 ft
0.028
14 lbs/ft2
3.75 lbs/ft2
3.73
STABLE
F
P300 Reinforced
Vegetation
Underlying
Straight 44.2 cfs
9.78 ft/s
0.18 ft
0.028
8.5 lbs/ft2
3.7 lbs/ft2
2.3
STABLE
F
Substrate
https://ecmds.com/project/142852/spillway-analysis/200057/show 1/1

WATER QUANTITY -WET POND#3

SUPPLEMENT-EZ COVER PAGE
I FORMS LOADED
PROJ9CT INFORMATION
1
Project Name
Watson Ridge
2
Pr jectArea (ac)
39.625
3
Coastal Wetland Area (ac)
-
4
Surface Water Area (ac)
0.429
5
Is this project High or Low Density?
High
6
Does this project use an off -site SCM?
No
COMPUANCE WITH 02H .1 OD3(4)
7
Width of vegetated setbacks provided (feet)
30
8 .
Will the vegetated setback remain vegetated?
Yes
9
If BLIA is proposed in the setback, does it meet NCAC 02H.1003(4)(c-d)?
No
10
Is streambank stabilization proposed on this project?
No
NUMBER AND. TYPE OF SCMs:
11
Infiltration System
BioretentiQn Cell
---2
0
12
13
Wet Pond
1
14
Stormwater Wetland
0
15
Permeable Pavement
0
16
Sand Filter
0
a nwa er Harvesting (RWH)
0
�17
18
18
Green Roof
0
119
9
Level Spreader -Filter Strip (LS-FS)
0
20
Disconnected Impervious Surface (DIS)
0
21
Treatment Swale
0
22
Dly Pond
0
23
StormFilter
0
24
Silva Cell
0
25
Bayfilter
Filterra
0
26 J
0
FORMS LOAMP
tMSJGNER CERTIFICATION
27
JNa eandTitle�
Matt Lowder, PE
28
Orcianization:
Triangle Site Design, PLLC
29
Street address.
zq
4004 Barrett Drive, Suite 101
30
City, State, Zip:
Raleigh, NC 27609
31
Phone number(s):
919-553-6570
32
Email:
[e-mail]
Certification Statement:
I certify, under penalty of law that this Supplement-EZ form and all supporting information were prepared under my direction or supervision; that the
information provided in the form is, to the best of my knowledge and belief, true, accurate, and complete; and that the engineering plans,
specifications, operaflon and maintenance agreements and other supporting information are consistent with the information provided here.
14F
AL
.434
A,
'g %
Seal
; V-"V� R--
Signature of Designer
Date

DRAINAGE AREAS
1
Is this a high density project?
Yes
If so, number of draina0e areas/SCMs
3
_2
3
Does this project have low density areas?
No
4
:7If =,o number of low density drainage areas
0
5
Is all/part of this project subject to previous rule
versions?
No
I FORMS LOADED
DRAINAGE AREA INFORMATION
Entire Site
1
2
3
Type of SCM
-
Infiltration Basin
Infiltration Basin
Wet Pond
--! ---
5,
Total drainage area (sq ft)
1010204
262994
425090
322120
Onsite drainage area (sq fl)
987169
239959
425090
322120
k4
7
:�6
Offsite drainage area (sq ft)
23035
23035
8
Total BLIA in project (sq fl)
230951
73115 sf
99538 sf
58298 sf
9
New BUA on subdivided lots (subject to permitting)
(sq ft)
10
New BUA not on subdivided lots (subject to
permitting) (sf)
11
Offsite BUA (sq ft)
7686
7686sf
12
Breakdown of new BUA not on subdivided lots:
Parkinq (sq ft)
Sidewalk (sq ft)
-
Roof (sq ft)
168000
48000sf
72000sf
48000sf
Roadway (sq ft)
55265
17429 sf
27538sf
10298sf
Future (sq fl)
Other, please specify in the comment box
below (sq ft)
13
New infiltrating permeable pavement on
subdivided lots (sq ft)
14
New infiltrating permeable pavement not on
subdivided lots (sq ft)
15
Existing BUA that will remain (not subject to
permitting) (sq ft)
16
permitted (sq ft)
17
Existing BUA that will be removed
18
Percent BLIA
28%
23%
18%
19
De i n storm (inches)
1.0 in
1 1.0 in
1.0 in
--f
20
D sign olume of SCM (cu ft)
. M
6579 cf
9237 cf
5715 cf
21
]CalculaTion method for design_volume_
Simple Method
Simple Method
Simple Method _J
ADDITIONAL INFORMATIO14
� Please use this space to provide any additional information about the
22 drainage area(s):
Infiltration Basin #1 - there is offsite drainage area from the Lee County
portion of the overall development.

WETPOND
area number
3
____�Drainage
.21
Minimum required treatment volume �cu ft)
5715 cf
GENERAL MQC FROM 02H.1050
311s
the SCM sized to treat the SW from all surfaces at build -out?
Yes
41
Is the SCM located away from contaminated soils?
Yes
5
What are the side slopes of the SCM (H:V)?
3:1
6
Does the SCM have retaining walls, gabion walls or other engineered
side slopes?
No
—
7
Are the inlets, outlets, and receiving stream protected from erosion
(1 0-year storm)?
Yes
8
Is there an overflow or bypass for inflow volume in excess of the
I design volume?
Yes
9
What is the method for dewatering the SCM for maintenance?
Pump (preferred)
10
If a2plicable. will the SCM be cleaned out after construction?
Yes
11
Does the maintenance access comply with General MDC (8)?
Yes
12
Does the drainage easement comply with General MDC (9)?
Yes
13
If the SCM is on a single family lot, does (will?) the plat comply with
General MDC (10)?_
NIA
14
Is there an O&M Agreement that complies with General MDC (11)?
Yes
15
Is there an O&M Plan that complies with General MDC (12)?
Yes
16
Does the SCM follow the device s2ecific MDC?
Yes
17
Was the SCM desiRned U an NC licensed ProfessionaT?
Yes
MOW
fib MDC FROM WN -100
18
Sizing met od used
SA/DA
19
Has a stage/storage table been provided in the calculations?
Yes
20
Elevation of the excavated main pool depth (bottom of sediment
removal) (fmsl)
324.00
21
Elevation of the main pool bottom (top of sediment removal) (fmsl)
325.00
2j2EIevation
va' of the bottom of the vegetated shelf (fmsl)
328.50
23
Elevation of the permanent pool (fmsl)
329.00
24
Elevation of the top of the vegetated shelf.(fmsl)_
329.50
25
Elevation of the temporary pool (fmsQ
330.10
26
Surface area of the main permanent -pool (square feet)
3155
27
Volume of the main permanent pool (cubic feet)
8003 cf
28
Average depth of the main pool (feet)
3.11 ft
L9
Average depth equation used
Equation 3
...
301
If using equation 3, main pool perimeter (feet)
220.0 ft
31
If using quation 3, width of submerged veg. shelf (feet)
3.0 ft
32
Volume of the forebay (cubic feet)
1496 cf —
33
Is this 15-20% of the volume in the main pool?
Yes
34
Clean -out depth for forebay (inches)
24 in
35
Design volume of SCM (cu ft)
5715 ef
36
Is the outlet an orifice or a weir?
Orifice
371
If orifice, orifice diameter (inches)
1.25 in
381
If weir, weir height (inches)
39
If weir, eir length (inches)
40
Drawdown time for the temporary pool (days)
2.06
41
Are the inlet(s) and outlet located in a manner that avoids short-
circuiting?
Yes
42
Are berms or baffies provided to improve the flow path?
Yes
43
Depth of forebay at entrance (inches)
36 in
44
Depth of forebay. at exit (inches)
30 in
45
Does water flow out of the forebay in a non -erosive manner?
Yes
46
Width of the v
me�e etated shelf (feeq
6 ft
47
Slope of vegetated shelf (H:V)
6:1
48
Does the orifice drawdown from below the top surface of the
permanent pool?
Yes
__
49
Does the pond minimize impacts to the receiving channel from the 1-
Xr, 24-hr storm?
Yes
50
Are fountains proposed? (if Y, please provide documentation that
MDC(9) is met.)
No
51
Is a trash rack or other device provided to protect the outlet system?
Yes
52
Are the dam and embankment planted in non -clumping turf grass?
Yes
53
Species of turf that will be used on the dam and embankment
Hybrid Berm
Has a planting 21an been provided for the vegetated shelf?
Yes
__.�4
ADDITIONAL
INFORMATION
55
Please use this space to provide any additional information about the
wet pond(s):
_j
Wet Pond 2:3S PM 3/4/2021

Triangle Site Design, PLLC
Watson Ridge, Harnett County, NC
Curve Number Calculation (CN)
Pre -Developed Conditions #3
Dwinage Area (ag2Ls 7.39
ExIsting Soil
50il G�Ou Mw SY Soil Description Acres Percent of DA
P -mb
A CaB Candor Sand 5.00 68%
C BnB Blaney Loamy Sand 2.39 32%
ExIstIng Land Uses
Land Use QgsQg�2� Existing Soil Gro Acres Curve # We�ghtqd CN
Wooded - Good Stand A 5.00 50 33.8
Wooded - Good Stand C 2.39 74 23.9
Cumulative Curve # 57.8

Triangle Site Design, PLLC
Watson Ridge, Harnett County, NC
Curve Number Calculation (CN)
Post -Developed Conditions to Wet Pond #3
Drainage Area Lacrejs: 7.39
Existing Soil
Soil GMU Soil Description
May Symbo
Acres
Percent of DA
A CaB Candor Sand
5.00
68%
C BnB Blaney Loamy Sand
2.39
32%
ftQosed Land Uses:
Land Use Descriotion Existing Soil Acres
Curve #
WeOlited CN
Impervious Area -Residential Lots A/C 1.10
98
14.6
Impervious Area-Sidewalk/Road A/C 0.24
98
3.2
Wooded - Good Stand A 3.50
50
217
Wooded - Good Stand C 2.55
74
25.5
Cumulative Curve #
67.0

Proposed Wet Pond
Project Information
Project Name: Watson Ridge
Project #:
Designed by: CEP Date: 3/4/2021
Revised by: Date:
Checked by: Date:
Site Information
Sub Area Location: Drainage To Proposed Wet Pond
Drainage Area (DA) = 7.39 Acres 322,120 sf
Impervious Area (IA) = 1.34 Acres 58,298 sf
Percent Impervious (1) ---- % 18.10 %
Required Surface Area
Permament Pool Depth: 3.11 ft Non -Coastal County
SA/DA = 0.77
Min Req'd Surface Area = 2,480 sf (at Permanent Pool)
Required WQv Storage Volume
Design Storm = 1 inch Non -Coastal County
Determine Rv Value = 0.05 +.009 (1) = 0.213 in/in
Storage Volume Required = 5,715 cf (above Permanent Pool)
Elevations
Top of Pond Elevation =
334.00 ft
Temporary Pool Elevation =
330 10 ft
Permanent Pool Elevation =
329.00 ft
Shelf Begining Elevation =
32950 ft
Forebay Weir =
32800 ft
Shelf Ending Elevation =
328.50 ft
Bottom Elevation =
325.00 ft
Permanent Pool Area
Area @ Top of Permanent Pool = 3,155 sf
Volume of Temporary Storage = 5,988 cf
Is Permenant Pool Surface Area Sufficient (yes/no)? 3155 > 2480 ) sf
Volume of Storage for Design Storm 5988 > 5715 ) cf

Incremental Drawdown Time
Project Information
Project Nar Watson Ridge
Project #:
asigned by: CEP
iecked by:
STORMWATER POND
INCREMENTAL DRAWDOWN METHOD -Water Quality Volume
Date: 3/4/2021
Date:
Water Quality Orifice
* Incremental Determination of Water Quality Volume Drawdown Time
Zone 2
Q, = 0.0437 C, * D 2 (Z-D/24-Ei)'("23
Q2 = 0.372 CD * D*(Z-E!)^(312)
Q, = 0
Orifice Diameter (D) =
1.25 in
Cd =
0.6
Ei =
329
Orifice Inv.
Zonel Range=
0.00
to 329
Zone 2 Range =
329
to 329.1
Zone 3 Range =
329.1
to 329
Incremental Drawdown Method
Countour
Contour
Area
Incremental
Volume
Stage, Z
Zone
Q
Drawdown
Time
sq ft
cu ft
ft
cfs
min
329.00
4,460
0
0.00
2.00
0.000
--
329.50
5460
2,480
0.50
3.00
0.027
1 �507
330.00
6105
2,891
0.50
3.00
0.040
1.208
330.10
6235
617
0.10
3.00
0.042
245
Total
--
5.988
—
—
--
2,961
Drawdown Time = Incremental Volume I Q / 60sec/min
Summary
Total Volume = 5,988 cf
Total Time = 2,961 min
Total Time = 2.06 days
3/4/2021 Prop Wet Pond- new design-WR 1 of 1

Project: Pond #1 Date: 3/4/2021
Main -Pond Contours -Volumes
Elevation
Main -Pond
Incremental Vol.
Accumulated Vol.
Description
329
3,155
1,419
8,003
A2 (Perm —Pool)
328.5
2,520
1,211
6,584
Al (Bottom —Shelf)
328
2,325
2,138
5,373
327
1,950
1,780
3,235
326
1,610
1,455
1,455
325
1,300
0
0
A3 (Bottom —Pond)
Forebay Contours -Volumes
Elevation
FBI
FB2 FB3 Total -Areas
Incremental Vol.
Accumulated Vol.
329
1,155
1,155
533
1,496
328.5
975
975
444
964
328
800
800
520
520
327
240
240
0
0
Forebay Volume
Average Depth (Option 1)
Average Depth Calculation (Option 2)
Vpp
permeter of shelf
width of shelf
Al (Bottom —Shelf):
18.7% *Between 15% & 20%
2.61 *At least 3' average depth
8,003
220
3
2,520
Average Depth = 3.11

Proposed Wet Pond #1
Project Information
Project Name: Watson Ridge
Project #:
Designed by: CEP
Revised by:
Checked by:
Site Information
Date:
Date:
Date:
3/4/2021
Sub Area Location:
Drainage
to Proposed Pond
Drainage Area (DA) =
7 39
Acres
Impervious Area (IA) =
1.34
Acres
Percent Impervious (1) =
18.10
% (Drainage Area)
Orifice Sizing
Orifice Size in
Drawdown Time days
less than 5 days (yes/no) ? Yes
greater than 2 day (yes/no) ? yes
Anti -Flotation Device
4'x 4' Outlet Structure
(Diameter)
(incremental Draw Down Method)
Area:
16.0
sf
Volume:
144.0
cf
(Water Displaced - Top of Pond to Bottom of Pond)
Weight:
8986
lbs
Factor of Safety
1 �20
WT Req'd of Anti -Flotation Device.
10,783
lbs
Volume of Concrete Req'd:
71.9
cf
(Unit WT of Concrete = 150 pcf)
Volume Provided:
117.5
cf
(4'x4' riser x 5' = 80sf, 5'x5' footing x 1.5' =37.5cf)

-STAGE/STORAGE TABLE
STAGE ELEVA TION CONTOUR INCREMENTAL TOTAL
(FT) (FT) AREA (SF) STORAGE (CF) STORAGE (CF)
0.0
329.0
4460
0
0
0.5
329.5
5460
2480
2480
1.0
330.0
6105
2891
5371
1.1
330.1
6235
617
5988 (WQv)
2.0
331.0
7425
6147
12135
3.0
332.0
8735
8080
20215
4.0
333.0
9845
9290
29505
5.0
334.0
11015
10430
39935
STORMWATER MANAGEMENT DESIGN
WET DETENTION POND
RIVER BASIN:
RECEIVING STREAM:
STREAM INDEX:
STREAM CLASS:
HUC:
CAPE FEAR
CYPRESS CREEK (MCDONALD SWAMP)
18-20-13-3-4
C
03030004
POND DESIGN SUMMARY
DRAINAGE AREA TO POND:
SITE IMPERVIOUS AREA TO POND:
OFF -SITE DESIGN IMPERVIOUS AREA TO POND:
TOTAL DESIGN IMPERVIOUS AREA TO POND:
PRE -DEVELOPED
DRAINAGE AREA: 7.39 AC
CURVE NUMBER: 57.8
1.0" STORM EVENT:
I -YEAR STORM EVENT: 1.174 CFS
2-YEAR STORM EVENT: 3.068 CFS
10-YEAR STORM EVENT: 10.87 CFS
100-YEAR STORM EVENT: 26.94 CFS
7.39 ACRES
1.34 ACRES
0.0 ACRES
1.34 ACRES
POST -DEVELOPED POST DEVELOPED
7.39 AC
67.0
0.001 CFS
5.731 CFS
9.683 CFS
22.27 CFS
45.57 CFS
0.000 CFS
0.062 CFS
0.435 CFS
6.137 CFS
40.22 CFS

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TAB Ar aTn"fl" lBr UAT CUAWU rAD 1%1 AMW
TRASH RACK)
424
,V
OUTLET CONTROL STRUCTURE - INCREMENTAL WEIR
SCALE: N.T.S.
KlJLK alKU%,lURL
4" PVC SCREW CAP
FOR CLEANING ACCESS
12" MIN.
4"x4m PVC
PERM. POND ELEV.=329.0
129 MIN.
14"DIA. HOLE DRILLED
INTO BOTTOM CAP
PVC DRAIN OUTLET
5CALL: N. I.S.
EXTEND 4" PVC
THROUGH RISER
STRUCTURE