SW6210903_Stormwater Narrative_20210914

Slorm wafer Manc7gemenl Design Calculations
September 7, 2021
Carolina Crossing
N. Horace Walters Road
Raeford, Hoke 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
[phone]
License#P-0619
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STORM WATER MANAGEMENT CALCULATIONS
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OVERVIEW
This report contains the storm water management calculations for the proposed residential
development en N. Horace Walters Road in Hoke County. The project site is currently un—
developed wooded area with an existing residential property. The proposed site consists of
44.436 acres and approximately 5.305 acres will be disturbed as pant of this project for
the construction of the site improvements.
The proposed site is loomed in Flood Zone 'X' as shown on FEMA FSRM Panel 3710848400L
with an effec,ive date of 7/7/14. Fleod zones are subject to change by FEMA.
There are no existing stream or wetland feafures on the proposed property,
The drainage area consists of the existing residential structures, which includes
cpproximately 4,028sf of impervious area that will be removed. The proposed storm water
management facility (infiltration basin) outlined in this report has been designed for post ---
development peak attenuation to treat the impervious areas of the development in Hoke
County. The Infiltration Basin is designed to capture a drainage area of 34.53 ac with an
impervious area of 9.07 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.
Imnendo ,rem Sum -Mery — Irfi tlMan ft-21t #1
Road +_Kiosk
1194030
2.73
Sidewalk
20,006 —
0.46
Lots 4,000§fJIot2
256 000
5.88
Total IA to Pond
395 036
9.07
Soils
The County Soils Survey indicates that Autryville Loamy Sand, Blaney Loamy Sand, and
Candor Sand soils are present on the site.

w o urN
3P W40N
Hydrologic Soil Group ---Hoke County, North Carolina
"a
p MapScale: 1:5,6W f prlr M an AMn*Kape (1r X &5!) ft!BL
Mks
N c 50 100 2w 300
�.,�Feet
a � 500 „xo �
Mat Po]ectk n: W b tuna for OaaW vaxdhd es V+GSM Edge um UrM awe 17N VVG684
US(3a Natural Resources Web Soil Survey 712&2021
in Conservation Service National Cooperative Soil Survey Page 1 of 4
3.7 0' 10' N
34' 'R SB N

Hydrologic Soil Group —Hoke County, North Carolina
MAP LEGEND
Area of Irrterest (AOII
Area of interest (ACI)
Soils
Soil Rating
Polygons
X"
A
0
A'D
F-1
13
BID
C
0
CAD
0
D
Not rated ur not availatrte
Soli Rating Lines
.,
A
AID
�y
3
,ter
BID
. r
C
.y
CID
D
r •
Not rated or not avaflable
Soil Rating Points
®
A
13
A/D
S
B
■
BID
B C
1
13 D
0 Not ratee or not. available
Water Features
Streams and Canals
Transportation
i--" Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
a Aenal Photography
MAP INFORMATION
The soil surveys that comprise your AOI were mapped at
1:24.000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each reap sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System. Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A pmjection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Hoke County, North Carolina
Survey Area Data: Version 17, Jun 4, 2020
Soil map units are labeled (as space allows) for map scales
t :50,000 or larger.
Date(s) aerial images were photographed: Jul 28, 2019—Jul 30.
2019
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shirting of map unit boundaries may be evident.
USDA Natural Resources Web Soil Survey 7l28r2021
oliiiO Conservation Service National Cooperative Soil Survey Page 2 of 4

Hydrologic Soil Croup --Hoke County, North Carolina
Hydrologic Soil Group
tdrap:unit`syrtrboi ;: Map unik narne Rating Acres to A04 Peroent of A01
AuA
Autryville loamy sand, 0 I A
38.7
66.7°U
to 2 percent slopes
BaB
- .. ._ `Blaney loamy sand, .Zte I[;:. ,
29
5.0°%
8 percent slopes
BaD
Blaney loamy sand, 8 to I C
9.4 .
16.3%
i
15 percent slopes
I
CaB
i Candor sand, 1 to 8 A
7,0E
12 0%
percent slopes
Totals for
Area of Interest
58.01
100 0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long -duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (AID, BID, and CID). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow Infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink -swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Natural Resources _., ......:,.. web Soil Survey 71282021
Conservation Service National Cooperative Soil Survey Page 3 of 4

National Flood Hazard Layer FIRMette
FEMA
] 250 500 1,000 1,5Oo 2,000
Legend
FLS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANT LAYOUT
Without Bete Flood Elevation (BFEj
zo- a r 1,
ECIAL FLOOD With BFE or DepthzoneAi. AD, AN. VE.AR
ZARD AREAS Regulatory Floodway
0 2% Annual Chance Flood Hazard, Are,
of 1% annual chance flood with averagt
depth less than one foot or with dralnaf
areas of iess than one square mRe zone
Future Conditions 196 Annual
` Chance Flood Hazard zone x
Area with Reduced Food Risk due to
ER AREAS OF Levee. See Notes. zone x
DOD HAZARD Area with Flood Risk due to Levee zone I
`NoscFmEN Area of Minimal Flood Hazard tones
Effective LOMRs
)THEIR AREAS Area of Undetermined Flood Hazard ron
GENERAL ---- Channel, Culvert, or Storm Sewer
STRUCTURES .r I I I I I I Levee, Dike, or Floodwatl
P
°.= Cross Sections with 196 Annual Chance
c 17-L Water SurfaceElevatlon
r r' - - - Coastal Transact
�+---rs— Base Flood Elevation Line (BFE)
Limit of Study
Jurlsdletlon Boundary
C035WITransect Baseline
OTHER profile Baseline
FEATURES Hydrographic Feature
Digital Data Available V
No Digital Data Available
MAP PANELS Unmapped
The pin displayed on the map is an approximat
point seiected by the user and dose not repres,
an authoritative property location.
This map compiles with FEMA's standards for the use of
digital flood (naps If It Is not void as described below.
The bosamap shown complies with FEMA's basemap
accuracy standards
The flood hazard Ittformatlon Is derived directly from the
authoritative NFHL websorAcesprovided by FEMA. This map
was exported on 7!2E 2021 at B 59 AM and does not
reflect changes or amendfnants subsequent to this date and
time. The NFHL and effective information may change or
become supersaded by new data over time.
This map image is void If the one or more of the following map
elements do not appear basemap imegsry, flood zone labs[&.
legend, scale bar, map creation date, Comm unity identifiers,
FIRM panel number, and FIRM effective date. Map Images for
unmapped and unmodemized areas cannot be used for
regulatory purposes,

Sarface WaterCleasifka6cros:
Stream Ind
14-2-17
I 5trearn Nar-
Little Creek
Descrpran:
From source to
Drowning Creek
Classification:
C
Date oaf Gass.:
November 301963
What does this Class_
More_i
= mean?
River Bas-n:
Lumber
LWrTI Yt
c
c
...
379 f
372 N
r
kt
All
36"
state of

z
12-Digit HUC 1 Su bv.rafers hed I
u-DigitName:
-: - - Drowning Greek
12-DigitCode--
030402030206
10-0P& -
rawer Draming Greek
10-Uigit --r
0304020302
Z)
03040203
RIVer 7 i"
Lumber
Area (2c):
34,143JW
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0
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y
Ahernrberlv

7/2812021
Precipitation Frequency Data Server
NOAA Atlas 14, Volume 2, Version 3
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Location name: Raeford, North Carolina, USA' s'.-r-"
Latitude: 34.9985°, Longitude:-79.3686' r
,'�,•
l
Elevation: 344.E it'" r
-
'source:ESRIMaps ,''
•. source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G M Bonnin, 0 Martin, B Lin, 7. Perzybok, M Yekta, ana O Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF tabular I PF gaph_I Waps & aerials
PF tabular
PD5-based point precipitation frequency estimates with 90% confidence intervals (in inches)l
Average recurrence interval (years)
iDuralion
i 6 10 26 64 100 - 200 500
F 1060
_2
6min t039B-0481)I 04770-0569y1[il 48-i76fi_3)_�[06050 f�.$o2.4�'f i074DOg' U76_00932 0804-0Ei 1(0 586205)
10�nin Q Of6I." , 0 7� 9( )`•'1 t0 879G13061 (0 96 O� 17) 1 07 1$ [t > :: (1 21-1 48} {1.27--11 561 0 35-612671
16 min (1179&0961' G 114ti0.872 0414 1 11-212'.ai (1 22--148 0 36-1 - ` It 45-11i6 f1 53-11671 (1 61- 971 (1 7 -210)
06
$0-Rlln {1 0920321 (1 31 1358} {1 5873911 f1 77$2 B} f." 01 22 (2 9-2 661 (2 35-2 87} (2 50-3-0 {2 70.i 341
6.1 1 a6+3j 2.22`.-' 1 ; ( 2.64 ,+ 2 96 -- 3.28 3.51 3.-4 4.37
[$�I]nF (1 316A9
31.279 66-3." 296 360) (324'395} f35i-4311 f387-4791
Z-hr 1 591 041 1 9112 ��t 2 55 r4 : 77 364ny (3 25 4201i I 3 634650] 4 M-4a991 (4 �.9fi191 [! 7-6 1Ci
3-h4.
r •TJI [1 678 OGI-i� 223,;:, 2.8214) [; 9� G5) 52�2 (396 931 (441-5S2y ,d 5.06615) (5 B-7631
J 2-19 2,6B 3.38 5.92 4.70 b.3d 6.01 6.72 7.79
-r i'!o-� 7_ 3 .. : �..) 4 22-5 1 �! . A � ` r'.t1 15, 32-6 G1 (r i!: 1) 6 r38.19 4,
i r 2 J Sr _ �'i �. �......�
2.li9 3.14 �I - 3.96 4.6Tr 6.64 6.48 7.30 8.22 79.53
12-hr j.:.i'.•-.> t38 [7 B4 3 =-+; yn-4 4?} 4 21 518) 'al (r 42 8 05) JL,
3.05 3.70 4.68 5.46 fi.62 7.38 8.27 9.19 10.6
24-hr I Z 5Z ti J I 1,5 4,1 A NJ is ;3.F Ufi {5 t]3 5 t10Y IF 00-7 (6 77-7 98 f f7 56-8 94) lr 37-9 19 46-11 31
3 5-56.38 6.25 7 A4 8.38 9.98 10.4 11.8
Z�ay i3303362) 1 {3 9462y I500-579) (5736i�1 %87r,;rq (7i3-803) (861-101 &_rli11'.; (107-1275
3 y (3 52.44 4 4- , I t�6 �07} 6 0.7 021 I7 7.79'"11 [e 0 �7391 f9 0 . 0 5 (9 94181.E 111 2-13 2)
4�sy 13 i33.�?64 t4 49 5g12y (5 b535 (416.g77 ,2 [7 57i8 rEl [g B 9675 J 410 49) 1014 12 0} (11.7?13 6)
4.62 5.62 6.7T 7,7fi 8.12 10.2 11.3 12.5 14.1
Tway (4 3__4 (G 33 7 23) { 24-8 2,,) 8 4E 9 Tn: (9 48.10 9} (10 5-121) (11 5-13 3) (12 9-15 1 )
�10dap� 6 2-9 6.31 7.62 0.64 10.0 11.1 12.2 13.3 14.5
L� [4 9t).5 62 5 94.6,74 f 7 17-B ne Lit' i 9 40-10 u) (10 4.11 8 {11 4.13 0)f 12 4-14 2}_ 03 8-15 81 i
20a18y (r, 27533 i7 6 iq1 !944.106) 11.2 (1o6-1 i1272 37) ;1313. 51 11415 65) I1576197It} {174-199)
8.83 10.4 12.2 13-5 15.8 16.7 18.0 19.4 21.2
3O�ay [B:M,-9344 (aB6.11 u) i 11 `• 128i , ('28.14-s) 1144-1621 i157-17G [26Si191i 182-205) (198-2251
i1.2 13.1 16.1 16.6 18.6 20.0 21.4 22.1 24.7
_!!-day 106-118) i (124-136] (1a3.1ti:f, 57-175) _I175-195} i189-211} (20^-::6) {215-241) (231.261)
21. 23.2
60�ey (1213.4 7--411 (14 9 6 5) (1619-18 7) (18 5-20 51 - (20 5-22 7) (21 9- 4 41 2a24 6 u} f24?�27 , } -6 5-29 91
i0887-111j
fl.40-11 741 .
0 75-219}
f2 64 3 54j
4.72 .
(415_S 171
(5 25-6 71)
6 1-7 5}
8.54
(731-9 37
F 10.6
F 11.6
10 4-12 41 j
12.9
f117-139)
3.4
0212- 4 4)
(12 7-14 91
15.3
{1 A r)_ 16 4}
16.0
(14 8-17 11
(186-214)
22.6
(210.240)
M1
(''br1-' 7}
2728. 1 41
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (P❑S)
rk i .,.e..1 jtetjnn lrani,anr•v
nc7imafPa Hnr
Numbers In parenthesis are PF esnmates at lower and upper bounds or me ae-m GonriucnGc --arWo+ +! = r = A� ^r •^u• r--r•• ••-•• ••-�--• •-r -- - --
3 given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5°f Estimates at upper bounds are
,not checked against probable maximum precipitation (PMP) estimates and may be higher than vxreNly valid PMP values
iPlease refer io NOAA Atlas 14 document for more mformation _
PF graphical
https:llhdsc.nws.nQaa.goy/hdsc/pfds/pfds_prin"ge him l?tat=34.9985&Ion=-79.3586&data=depth&units =eng(ish8series=pds 1/4

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