SW6200303__2020-06-05 Boykin Stormwater Report_20200605

*Ballentine
Associates, P.A.
Stormwater Management Report
For
Boykin PV1 Farm Solar Power Plant
Wade, Cumberland County, North Carolina
(PIN# 0479-45-2358; 0479-53-7215; 0479-28-8759)
Prepared by:
Ballentine Associates, P.A.
Consulting Engineers
221 Providence Road
Chapel Hill, NC 27514
[phone]
BA Project #: 114003.19
Issue Dates Description
30 Mar 20 To NCDEQ
05 Jun 20 To NCDEQ

Boykin PV 1 Farm Solar Power Plant
05 Jun 20
Existing Conditions Description:
Ballentine
Associates, P.A.
The Boykin PV1 Solar Power Plant is located off James Dail Road in Wade, Cumberland County, North
Carolina. The properties contain 285.30 acres of forest. The entire property will be used for stormwater
permitting as can be seen in the Project Area Exhibit Located in Appendix A of this report. The existing
soils on site are: Candor sand, 1 to 8 percent slopes (CaB), Coxville loam (Co), Exum loam, 0 to 2
percent slopes (ExA), Goldsboro loamy sand 0 to 2 percent slopes (GoA), Johnston loam (IT),
Lynchburg sandy loam, 0 to 2 percent slopes (Ly), Nahunta loam (Na), Norfolk loamy sand, 0 to 2
percent slopes (NoA), Norfolk loamy sand, 2 to 6 percent slopes (NoB), Pantego loam (Pg), Rains sandy
loam, 0 to 2 percent slopes (Ra). A majority of the site (40.2%) is in hydrologic soils group "A"; with
the remaining being hydrologic soil groups "C" (32.5 %), "C/D" (13.2 %), "A/D" (9.6 %), "B" (3.7%)
and "B/D" (0.8%). Almost the entire site drains west towards Bakers Swamp. There are multiple
wetlands throughout the property. Wetlands are located mostly on south and west portion of the site.
FIRM Panel 3720046800J indicates the project limits do not lie within a special flood hazard area. The
surface water classification for the site is C. The site is located in the Cape Fear River basin. Project site
Latitude and Longitude is 35.1108440°and-78.7512888°.
Description of Proposed Proiect and Stormwater Design:
The proposed solar farm consists of tracker solar panels, dual inverter/transformer areas and a chain link
fence along the perimeter of the array. The project will also include temporary laydown and parking
areas, and a two permanent driveway aprons along Poverty Flats Road and James Dial Road. The
installation of the solar panels themselves will not generally create significant land disturbance. The
panels will be mounted to racks, which are supported by a series of posts. The posts will be driven
directly into the existing ground without excavation or land disturbance and the existing ground cover
will be allowed to remain to the extent possible. Overall, approximately 158.1 acres of land will be
disturbed by construction; this is our entire project limits for Erosion Control Permitting. The project
areas true disturbance is caused by the installation of the proposed sediment basins, the proposed
diversion ditches, rubber tire vehicles accessing the site to distribute and install above grade material and
several small trenches (2' wide, 36" deep) for wiring the array. The rack posts are mechanically driven
directly into the ground. The temporary sediment basins will be installed at the bottom of the sites major
drainage areas and will treat the majority of the disturbed area. The remainder of the disturbed area will
be protected by silt fence with silt fence outlets. No change in drainage patterns (site drainage remains as
sheet flow) or additional ponding of water will occur as a result of this project. At the completion of
construction, the entire site will be seeded to create a good stand of grass.
Stormwater sheet flows off the panels and infiltrates into the ground beneath the panels, as described in
Chapter E-6 of NCDEQ's Stormwater Design Manual, and therefore does not contribute to the post
development impervious cover on the site. The proposed gravel drive, inverter pads, and rack posts will
contribute a total of 148,607 s.f. of impervious surface. An Impervious allowance of 195,735 s.f. has
been added incase additional impervious is needed as construction of the site progresses. As shown in
the Boykin PV1 — Impervious Percentage Calculations included in Appendix B, the post development
impervious cover is 2.77% of the total project area. Therefore, this project is considered Low Density
and does not alter the pre -development stormwater runoff characteristics of the site.

Ballentine
Boykin PV 1 Farm Solar Power Plant
05 Jun 20
List of Appendices:
Appendix A - Maps
o DA 1 Proposed Site Area Map
o Soils Maps
■ Hardbound Soils Map
■ NRCS — Soil Survey Map
■ NRCS — Soil Survey Map — Hydrologic Soil Group
o USGS Topo Map
o FIRM Panel 3720046800J
o Aerial Photo
o Existing Slope Exhibit
o Project Area Exhibit
• Appendix B — Stormwater Design Calculations
o Boykin PV1 — Impervious Percentage Calculation
Associates, P.A.

Ballentine
Boykin PV 1 Farm Solar Power Plant
05 Jun 20
Appendix A - Maps
o DA 1 Proposed Site Area Map
o Soils Maps
■ Hardbound Soils Map
■ NRCS — Soil Survey Map
■ NRCS — Soil Survey Map — Hydrologic Soil Group
o USGS Topo Map
o FIRM Panel 3720046800J
o Aerial Photo
o Existing Slope Exhibit (Full Size Sheet for Clarity)
o Project Area Exhibit (Full Size Sheet for Clarity)
Associates, P.A.

OZ Nn SO
Z# IVllIW8f1S 030ON
W �
OZ 8vvi orl
l# 1V11IW8f1S MOON 11
OZ Nnr gol
S1N3WW00 030ON 83d
o
31VO
03f1SSI
31V0
I NOISIA38
jvqnN
VNI'10HVO HIHON `A1Nnoo ONV iu3snno `30VM
s
V
z�oaN
a o a Q
J Q
Q
dVW V3HV 30VNIVua 311S
Q C3
m m
0
1NVld U3MOd dVIOS
m ON
}
w Z w
Md NDIAOG
� a o 0 W
�o�oce
daal'Wd 8V:ZO:Z OZOZ/9/9'6mp'uijAoS-deyy eery e6eu-(]\iajemwiojS\sajij pVO u6isap lapopy VS\6ma L\uiMAog--Ido3361'£OMILLVeloS snxaldm3 xx'£OOtIWsP8foidVN

x .

In
35o 7' 10" N
r
r
35o 6'9"N
704400 704600 7048D0 705000 70520C
Map Scale: 1:9,220 if printed on A portrait (8.5" x 11") sheet.
` Meters
N 0 100 200 400 E00
Feet
0 400 8D0 1600 2400
Map projection: Web Mercator Conermordinates: WGS84 Edge tics: lfrM Zone 17N WGS84
USDA Natural Resources Web Soil Survey
Conservation Service National Cooperative Soil Survey
Soil Map —Cumberland County, North Carolina
7044W 704600 704800 705000 70552W
705400
705400
705600
35' 710" N
1
35o 6' 9" N
7055600
12/12/2018
Pagel of 3

Z
O
G
O
LL
Z
Ca
G
0
Z
/W
V
W
J
CL
v
0 a)
m
m
U
O
N
Uy U)
O0
N
u!
U
7 0
O
m
.N E
C
(n
O
E
O
ECL
m
O)
'0 U
u�
.a)
°' a
U
E
N
y-0 O
C
Q
N C7
N m
Z
Z O
U)
o 6
m
Cc: ILau)
w
U) m
0
Q
o
O
a)
!
3
E
U
U
m m w
CL
N m
CL
m
O
O
N
O Q
m
O
i m
N
m0= C 0
O
a)
O N
U U)
m
O
O-'— (6 m
E
C
3 U
a)
>'0 i U
" O
O)
(n
O
E m
U)
2
a)
2 (6
0-0
��
wm
o-
US E N
Ua)
7 w U O N
U) a) .O CL
w 'O
'6 a)
a) O
N
m- m m
O O C
U)
N .y
30
J
(6
0 (D CL'E
U) (
Q C
Utl)
i
U
N
y
t C
N
Z E
Q U
Q m O
a)
wl a)
is
m
a)
a)
rn
0 0
-0 'E
>+
L N a) jp
O)(
a)
CL) j
U)
Q
O '_
Q
m
Q m
my
sO
(E
E_aE
(cu
)
m
CLO
LO(UD
a)
07O_
)O
'QE°v
a) a)
O a) O
m O tl)
L
—(u
O 7
—
O
O LPm
?o
E m 55
FL E
u U
U
2 CL-0Q m
H o
U) U)
U)—
H 0 .9 U)
y
�
y
Q
m
lL
U
a
L
L
CL
Q
>.
a)
2
y
a
-yo
O
L
d
Q
0 0
CL
J
m
N
E
m
0
O
O
a
O
U) (o
N
>
L_
O
(n
y
2 (n
�
O
a)CL
U
S
a Q
R
a
R
�
C
�
.
*
+
45
F
m
y
C
O
y
0
.�
O
Q
U)
w
a°
w
a°
w w
y
N
c
N
a
Q
a
w
0
>
Q
> >
Q Q
w
R
fl Q
Q
w
fl
Q
(�
>,
3
3 y
O `O
O
w
N
2
N
°
w
o
(�
0
(�
°
w
,
w
Q
_
`o
0
O-
a o
a
a a
w
—
C)
3
3
O T
-a
w
>
>
=
a
F
M a
o
w
U
O
o
=
w
o
Y
w
a
y
Q
o
(n
0 0
(n (n
o
o
m
o a
m U
O
U
c7
c7
J
J
y
w
a
O
m
m
U)
U)
w
U)
in
a
U)
o
U)
w
a
R
O
Q
U)
m
Z

Soil Map —Cumberland County, North Carolina
Map Unit Legend
Map Unit Symbol
Map Unit Name
Acres in AOI
Percent of AOI
CaB
Candor sand, 1 to 8 percent
slopes
8.9
3.9%
Co
Coxville loam
2.8
1.2%
ExA
Exum loam, 0 to 2 percent
slopes
73.9
32.5%
GoA
Goldsboro loamy sand, 0 to 2
percent slopes, Southern
Coastal Plain
8.5
3.7%
JT
Johnston loam
5.1
2.2%
Ly
Lynchburg sandy loam, 0 to 2
percent slopes
0.1
0.0%
Na
Nahunta loam
27.3
12.0%
NoA
Norfolk loamy sand, 0 to 2
percent slopes
57.1
25.1 %
NoB
Norfolk loamy sand, 2 to 6
percent slopes
25.4
11.2%
Pg
Pantego loam
1.8
0.8%
Ra
Rains sandy loam, 0 to 2
percent slopes
16.8
7.4%
Totals for Area of Interest
227.6
100.0%
USDA Natural Resources Web Soil Survey 12/12/2018
Conservation Service National Cooperative Soil Survey Page 3 of 3

In
35o 7' 10" N
35o 6'9"N
Hydrologic Soil Group —Cumberland County, North Carolina
704400 704600 704800 705000 70552M
704400 704600 7048D0 705000 70520C
Map Scale: 1:9,220 if printed on A portrait (8.5" x 11") sheet.
` Meters
N 0 100 200 400 E00
Feet
0 400 8D0 1600 2400
Map projection: Web Mercator Conermordinates: WGS84 Edge tics: lfrM Zone 17N WGS84
USDA Natural Resources Web Soil Survey
Conservation Service National Cooperative Soil Survey
705400
705400
705600
35' 710" N
1
35o 6' 9" N
7055600
12/12/2018
Pagel of 4

Z
O
G
O
LL
Z
Ca
G
0
Z
/W
V
W
J
a
Q
O O �
7
U O 0-0
U O O
O) E
O_ O (6
U O C E C
y E m y Zi
y O O O
O C U)
U m V) a)
= a) E y -0
> L O O a)
C >
Q O
a) -0
-O U) 6
> Q � m U
m to E
E a-o
m a)CL
m
m E��N
O C m a) y
� a) N E rn
C
O E
E N 7 Q N
wE UU)
v
0 a)
m
m
U
O
N
Uy y
N
(n
LD
O
m
E
.N E
a) -0 Nw�
C
—
(U)
O
N
E
=Y)m
Q
'0 U
uO
a) a
U
E
N
y-0 O
C
QU)
C7
N m
Z
Z o
o >
E
U w
m m p
o
mCL
U
N m
O
O
O- Q
m
O
i m
N
(6 O C O
O
a)
O N
U U)
m
O
Q .— uj m
E
C
U
>' C U
p
'O O)
U)
O
E m
'� ) (6
O
Q
E N
U
a)
7 au)) U O n
U) Q
O-
w '6
a) O
-0U)
a)
Inm
m m m
O
.O
N .
30
Li
(6
nNQ
Q
-00a)
a)
a)
Z E
Q UU)
a) Q t6 o
a)
a)
rn
OOC
>+
L N N jp
O) m
-O
m
m
O _O T 7
C y
Q a) j,
L
a) (6 (6 7
,tl)
C
N o
y (6lu
O '6 O Q
O
g
m m
U .0
Q m
m
s n E
�+ E
_ (n a)
O (UD
E m 7 p
O a) N O
7 N
O>
Q
7 0
N
m
0 O
L O
U) U)i
O
-2
u)" N m
Q a)
(n a)
m O
E o
y
a) L,
O 'Q 0_'
m m
a) a)
�5-0 O
p a) p
Q a) U
m 0 n�2
n:5
L
= L
0 7
= o
O LPm
°?
a) E m 55
a E
U U
p
2 Q-0 Q m
H o
u) u)
u)—
N
H 0 .E y
a)
N
y
N C N L
as °-
o U L
0 o
0 to
a N 0 N r
m o m a
y w m `o m
U U o Z in O Q
R R C
0 7
0 ■ ■ 0 LL }{
R 4 Rt R
In
F m
o
a
o
O w
y
0)
`o
y
a o
>
w
H'a)
a°
o
0
0
0
c
Q
v
rn Q
�
a
m m
U U
o Z
rn Q
�
'16
❑
❑
❑
❑ ❑
❑ ❑
}f
'p
R
y p
1
0 U)
U)
Q
V)
.j
0
0
a y
m -0
0 0 0 o a. o 0
a m m U U o z 0) Q a m m
S
❑ ❑ o 0
U)
00 v
m
Z

Hydrologic Soil Group —Cumberland County, North Carolina
Hydrologic Soil Group
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
CaB
Candor sand, 1 to 8
percent slopes
A
8.9
3.9%
Co
Coxville loam
C/D
2.8
1.2%
ExA
Exum loam, 0 to 2
percent slopes
C
73.9
32.5%
GoA
Goldsboro loamy sand,
0 to 2 percent slopes,
Southern Coastal
Plain
B
8.5
3.7%
JT
Johnston loam
A/D
5.1
2.2%
Ly
Lynchburg sandy loam,
0 to 2 percent slopes
B/D
0.1
0.0%
Na
Nahunta loam
C/D
27.3
12.0%
NoA
Norfolk loamy sand, 0 to
2 percent slopes
A
57.1
25.1 %
NoB
Norfolk loamy sand, 2 to
6 percent slopes
A
25.4
11.2%
Pg
Pantego loam
B/D
1.8
0.8%
Ra
Rains sandy loam, 0 to
2 percent slopes
A/D
16.8
7.4%
Totals for Area of Interest
227.6
100.0%
USDA Natural Resources Web Soil Survey 12/12/2018
Conservation Service National Cooperative Soil Survey Page 3 of 4

Hydrologic Soil Group —Cumberland County, North Carolina
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 (A/D, B/D, and C/D). 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 (A/D, B/D, or C/D), 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.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff.- None Specified
Tie -break Rule: Higher
USDA Natural Resources Web Soil Survey 12/12/2018
Conservation Service National Cooperative Soil Survey Page 4 of 4

MWYY O.S.OEPAI-11TOFTMEMTERiOR ti xoRtR VANOER WADRANaE Nn u N E �aEaG— �N.�E a: US TopoIj
.I.R
I
�.. ! —ECT SITE
1 _
4
a _ —
oo = £
� 41,
rAmweyy m•unmds••w•;imlert45nmv '
�.w o es a nae•n � �
•e�w nw w'rtn xm me �
r�ry
Mrv..xr uu
xm ea • i •^+ •"• R•
w neti
.• •• uu .mm..ean�uaren•xum � �' .m v
»°w.n nova eaea.x�m'u�e� F M,
rs... r o-..a m• �_ _ vnrnru wmcu nwww �m
wme.. .....uem uv.n w•ua ..wn w ...Td .e.,.,,.w...... x.a...... s.n,...wr.' VANVEk INC
M.

M WYY U.S. DEPARTMENT OFTHE IME0.40R STEOIUN QOA'Dt—E
u E �aE G— —S a US Topo ..R
11' PRWEET SITE
Y
_
III � r
C
o,.amv, IN t n
ua.. o..w.. STEOflAN, eK BEE
—.z
m,.

111 •1 1• 1
1 �
N
1 1•
�EMER
EMMEMN
®®®�®MEMO
2
ME
ME
�®®MOMSMOON
®®®�
�ME
NDRiH CAROLINA ROOOPLAIN MAPPING PRO6RAM
I_ NATIONAL FLOOD INSURANCE PROGRAM
LOGO INSURANCE RATE MAP
nA NORTH CAROLINA
raxe, 0468 04.
rrTT
C)
C
1111I
renlunrvur 3clDsANIL 3SU-
C
O
O
LL
C6
C
O
Z
372004fi8001
RE\1sEN

sa m S
snxald©:)a
SONIAVHa NoaonH1SNOD
vxnoxv0 xauox 'Alwlon axructewlo '3mrm
1Ntlld !l3MOd !lVIOS
LAd NIMAOS
a
o
g
'
a
u 11SINX3 3dalS
O
€ O
s
! r
03
02z
„„
NGIMI x3a
3—
as
a
e uj <u
x Z�_
= Z L.0
a
EB QdN 8 uj �' x
Qltl� JN
W
a
W o CJ a
J 8 5 gn
Z
� I
� I
I
I gg I
bey
I ion{
�P5
RRRR gm
7E� a�3
y/
hr
8
%
7-
�r>
a

snxald©:)a
SONIMVHO NOaonH1SNOO
vunouvo xaum'AiNwo axnu o amrM
1NVId H3MOd HVIOS
LAd NIVAOS
a
o
" s
p
a
`
1181HX3
V3HV 1O3PONd
40
1 r
°'
°
„0„ I-3°
3—
e uj <u
Z Wa
Q
EB QdN 8 uj �+ i
WQltl� JN / u
u,cn
�a P ;
7E� a�3
y/
/
L
L-7
/ v
a

Boykin PV 1 Farm Solar Power Plant
05 Jun 20
Appendix B — Stormwater Design Calculations
o Boykin PVI — Impervious Percentage Calculation
Ballentine
Associates, P.A.

Boykin PV1 Solar Power Plant - Impervious Calculation
Existing Conditions
Area (sf)
Area (ac)
% of Total
Pervious
Wooded Areas
12,427,736
285.302
100.00%
Agricultural Fields/Lawns
0
0.000
0.00%
Impervious
Drives (Gravel/Cone./Asphalt)
0
0.000
0.00%
Structures
0
0.000
0.00%
Existing Impervious=
0
0.000
0.00%
Total Site Area =
12,427,736
1 285.302
100.00%
Proposed Conditions
Area (sf)
Area (ac)
% of Total
Pervious
Wooded Areas
0
0.000
0.00%
Agricultural Fields/Lawns
12,083,394
277.397
97.23%
Impervious
Existing Drives to Remain
0
0.000
0.00%
Existing Structures to Remain
0
0.000
0.00%
Proposed Drives (Gravel/Cone./Asphalt)
143,649
3.298
1.16%
Switchgear Pads
# of Pads
Area/Pad (sf)
Inverter Total
6
400
2,400 7F
0.055
0.019%
Inverter Areas
(Assumes entire graded area)
# of Inverters
Area/Inverter
s
Inverter Total
6
400
2,400
0.055
0.02%
Rack Posts
Posts/Rack
# of Racks
Area/Post (in 2)
Rack Posts Total
13
761
2.3
158
0.004
0.00%
Impervious Allowance
195,735
4.493
1.57%
Proposed Impervious=
344,342
7.905
2.77%
Total Site Area =
12,427,736
285.302
100.00%
Boykin Farm Site Impervious Calcs
Impervious Calcs 6/5/2020