SW5230901_Design Calculations_20230919

Design Calculations
Pre-Post Development Hydraulic Routing
Wet Pond Design
Supplement EZ
SNAP Tool (for Nutrient Accounting)
Riprap Calculations

STORM DRAINAGE / HYDRAULIC GRADE LINE DATE DESIGN PHASE
ANALYSIS 8/31/2023 PRELIM / /
PROJECT NAME PROJECT NO CONSTR /X /
NCNG Camp Butner BOM Yard 42324 REVISION / /
LOCATION BY RECORD / /
Stem, NC JL OTHER / /
CHECKED BY (SPECIFY)
n= 0.013 STORM DRAINAGE SCHEDULE CONTINUED
g= 195
h= 22
1= 7.22 INLET Tc I Cc
INLET INLET Cc INLET TOTAL INLET PIPE TIME RUNOFF
FROM TO AREA AREA IMPERVIOUS RUNOFF DISCHARGE AREAS TIME TIME OF CONC. INTENSITY COEFF.
(SF) (AC) (%) COEFF. (CFS) (AC) (MIN) (MIN) (MIN) (IN/HR)
B6 B5 70,348 1.61 100 0.50 5.83 1.61 5.00 0.00 5.00 7.22 0.50
B5 B4 29,099 0.67 91 0.48 2.32 0.67 5.00 0.77 5.77 7.02 0.48
B4 B3 90,806 2.08 91 0.48 7.25 2.08 5.00 1.71 6.71 6.79 0.48
B3 B2 30,051 0.69 75 0.45 2.25 2.77 5.00 2.11 7.11 6.70 0.47
B2 B1 0 0.00 0 0.30 0.00 2.77 5.00 2.51 7.51 6.61 0.47
Pipe Sizing BOM 18STORM Page 1 of 5

STORM DRAINAGE / HYDRAULIC GRADE LINE DATE DESIGN PHASE
ANALYSIS 8/31/2023 PRELIM / /
PROJECT NAME PROJECT NO CONSTR /x /
NCNG Camp Butner BOM Yard 42324 REVISION / /
LOCATION BY RECORD / /
Stem, NC JL OTHER / /
CHECKED BY (SPECIFY)
STORM DRAINAGE SCHEDULE -CONTINUED
Q Q UPSTREAM
SIDE- CAPACITY SEGMENT UPPER LOWER TOP PIPE
DISCHARGE STREAM SLOPE DIA. (FULL) V FULL LENGTH TIME INV. INV. ELEV. COVER
(CFS) (CFS) (IN) (CFS) (FPS) (FT) (MIN) (FT) (FT) (FT) (FT)
5.83 0.00 0.55% 15 4.8 3.9 181 0.77 465.02 464.03 468.40 2.02
2.26 0.00 0.55% 15 4.8 3.9 219 0.94 463.93 462.72 467.50 2.21
6.81 0.00 0.55% 15 4.8 3.9 94 0.40 462.62 462.10 465.56 1.58
8.80 0.00 0.55% 18 7.8 4.4 105 0.40 461.90 461.32 465.50 1.96
8.68 0.00 0.55% 24 16.8 5.3 22 0.07 461.12 461.00 467.00 3.70
Pipe Sizing BOM 18STORM Page 2 of 5

STORM DRAINAGE / HYDRAULIC GRADE LINE DATE DESIGN PHASE
ANALYSIS 8/31/2023 PRELIM / /
PROJECT NAME PROJECT NO CONSTR /X /
NCNG Camp Butner BOM Yard 42324 REVISION / /
LOCATION BY RECORD / /
Stem, NC JL OTHER / /
CHECKED BY (SPECIFY)
HYDRAULIC GRADE LINE CONTINUED -v
BEND LOSS K'S
90 DEG=0.7 30 DEG=0.28
60 DEG=0.55 15 DEG=0.10
PIPE HYDRAULIC SIDESTREAM HEAD LOSS BEND FRICTION FRICTION
AREA RADIUS SUMMATION Hf He He Hb Ht LOSS SLOPE VELOCITY
(FT) (FT) (CFS) K (FT/FT) (FPS)
1.2272 0.3125 0.00 1.47 0.09 0.00 0.00 1.55 0.00 0.0081 4.73
1.2272 0.3125 0.00 0.27 0.01 0.12 0.10 0.50 0.28 0.0012 1.83
1.2272 0.3125 0.00 1.04 0.12 0.02 0.01 1.20 0.28 0.0111 5.53
1.7671 0.3750 0.00 0.73 0.10 0.17 0.13 1.13 0.28 0.0070 4.96
3.1416 0.5000 0.00 0.03 0.03 0.13 0.11 0.30 0.28 0.0015 2.75
Pipe Sizing BOM 18STORM Page 3 of 5

STORM DRAINAGE / HYDRAULIC GRADE LINE DATE DESIGN PHASE
ANALYSIS 8/31/2023 a 0
PROJECT NAME PROJECT NO 0 0
NCNG Camp Butner BOM Yard 42324 0 0
LOCATION BY 0 0
Stem, NC JL 0 / /
CHECKED BY 0
DESIGN CRITERIA:
HYDRAULIC GRADE LINE -CONTINUED 1. DESIGN FOR THE 10YRSTORM
2.ASSUME TIME OF CONCENTRATION TO
AN INDIVIDUAL INLET=5 MIN.
INLET W.S. ELEV. 3. INTENSITY=g/(h+T),FOR 10 YR STORM
OUTLET OUTLET INLET USE FLOW FREE- UPSTREAM g=195,h=22,T=TIME OF CONCENTRATION
W.S. ELEV CONTOL CONTROL CONDITION BOARD INLET COMMENTS 4. MANNINGS"n"FACTOR=.013
(FT) (FT) (FT) I (FT) CONTROL ) TYPE 5. RATIONAL METHOD:C=.30 GRASS,C=.95 PAVEMENT
465.72 467.28 466.62 467.28 OUTLET 1.12 DI OK
465.23 465.72 464.70 465.72 OUTLET 1.78 DI OK
464.03 465.23 464.58 465.23 OUTLET 0.33 DI OK
462.90 464.03 463.72 464.03 OUTLET 1.47 DI OK
462.60 462.90 462.45 462.90 OUTLET 4.10 MH OK
Tailwater Elev= 462.60
Pipe Sizing BOM 18STORM Page 4 of 5

UPSTREAM INLET TYPES STORM DRAINAGE / HYDRAULIC GRADE LINE DATE DESIGN PHASE
CB 0.5 ANALYSIS 8/31/2023 PRELIM / /
CI 0.5 PROJECT NAME PROJECT NO CONSTR /x /
CO 0.0 NCNG Camp Butner BOM Yard 42324 REVISION / /
DI 0.0 LOCATION BY RECORD / /
FES Check Stem, NC JL OTHER / /
HW Check CHECKED BY (SPECIFY)
JB 0.0 -
M H 0.0
PE Check
PO Check
YI 0.0 DRAINAGE STRUCTURE SCHEDULE
OTHER
STRUCTURE NO. PIPE PIPE PIPE PIPE UPPER LOWER UPSTREAM STRUCTURE DATA
UP STRM DN STRM SLOPE DIA. LENGTH MATRL INV. INV. TOP ELEV. DEPTH TYPE
(IN) (FT) (FT) (FT) (FT)(1) (FT)
B6 B5 0.55% 15 180.67 RCP 465.02 464.03 468.40 3.38 DI
B5 B4 0.55% 15 219.24 RCP 463.93 462.72 467.50 3.57 DI
B4 B3 0.55% 15 94 RCP 462.62 462.10 465.56 2.94 DI
B3 B2 0.55% 18 105 RCP 461.90 461.32 465.50 3.60 DI
B2 B1 0.55% 24 22 RCP 461.12 461.00 467.00 5.88 MH
Pipe Sizing BOM 18STORM Page 5 of 5

WET POND SIZING DATE
8/29/2023 •• •.�
PROJECT NAME PROJECT NO TIMMONS GROUP
NCNG CB BOM Yard 42324 °°""°'°"""`°""°"'°""
LOCATION BY
Stem,NC Jake Lewis
POND A
Drainage Area,(DA)= 8.10 ac
Impervious Area c=0.95 4.47 ac
Pervious Area c= 0.30 3.63 ac
Cc= 0.66
CN=
Permanent Water Quality Pool
% Impervious= 55.1 %
Permanent Pool Design Depth= 3.00 ft
SA/DA Ratio= 1.94 (from Tbl. 1.1)
Required Surface Area= 6,858 sf
Permanent Pool Volume Req.= 20,574 cf
Temporary Water Quality Pool
Design Storm Rainfall 1.00 in (Typically 1-in)
Runoff Coeff.(Rv=0.05+0.009(%Imperv.))= 0.55 in/in
Required Volume(design rainfall)(Rv)(DA)= 16,056.94 cf
Surface Area Provided:
Permanent Pool Max.Depth= 4.00 ft
Area of Pond Bottom(Above PSS)= 6,884 sf (EL=452.0)
Area Bottom of Shelf= 9,361 sf (EL=457.0)
Area of Permanent Pool= 10,466 sf (EL=457.5)
Area Top of Shelf= 11,489 sf (EL=458.0)
Perm.Pool Volume Provided= 33,300 cf > 20,574 OK
Avg.Perm.Pool Depth Provided(Eq.3). 3.18 ft > 3.00 OK
Surface Area at 1"Storage Volume= 15,492 sf (EL=1203.1)
1"Storage Volume Provided= 16,057 cf > 16,057 OK
Temp.Storage Depth above Dewatering Hole= 1.11 ft
Diameter of Dewatering Hole= 2.00 in
Detention(Draw-Down)Time = 3.0 days (2-5 days Required)
T days=(Temp.Storage Vol Req/(0.6"A*(2*g*(h))^1/2)*86400
(where h=one third temp.storage depth measured to centroid of orifice)
Max Drawdow Rate= 0.11 cfs
Permanent Pool Volume= 33,300 cf > 20,574 OK
Forebay Volume Required= 4,995 cf
Forebay Volume Provided= 5,127 cf
15.4% OK
Table 1.1
SA/DA Ratios 85%TSS efficiency
Permanent Pool Depth(ft)
%Impervious 3.0 4.0 5.0 6.0
10 0.51 0.43 0.37 0.30
20 0.84 0.69 0.61 0.51
30 1.17 0.94 0.84 0.72
40 1.51 1.24 1.09 0.91
50 1.79 1.51 1.31 1.13
60 2.09 1.77 1.49 1.31
70 2.51 2.09 1.80 1.56
80 2.92 2.41 2.07 1.82
90 3.25 2.64 2.31 2.04
s:\1319\0001\calcs\PondSize-Wet Pond-piedmont-90 tss-BOM printed:8/29/2023 6:00 PM Page 1 of 2

DATE
POND A
Main Pool Permanent Pool Volume
Stage(ft) Elevation Area(sf) Storage(cf)
Top of Sed.Stor.in Main Pond
-4.00 452.50 6,884
-3.50 453.00 7,218 3,525
-2.50 454.00 7,907 11,088
-1.50 455.00 8,621 19,352
-0.50 456.00 9,361 28,343 Inside of Shelf Elev.
0.00 456.50 10,466 33,300 Normal Pool Elev.
0.50 457.00 11,489 38,788 Outside of Shelf Elev.
Forebay Volume
Stage(ft) Elevation Area(sf) Storage(cf)
-4.00 452.50 644 0 Top of Sed.Stor.in Forebay
-3.50 453.00 770 354
-2.50 454.00 1,058 1,268
-1.50 455.00 1,390 2,492
-0.50 456.00 1,765 4,069
0.00 456.50 2,467 5,127 Normal Pool Elev.
Total Pond Stage/Storage Detail
Stage(ft) Elevation Area(sf) Storage(cf)
0.00 456.5 12,926 0 Normal Pool Elev.
0.50 457 14,489 6853.8175
16056.99999 Water Quality Elevation
1.50 458 16,122 22159.3175
2.50 459 17,815 31066.8175
3.50 460 20,414 50181.3175
s:\1319\0001\calcs\PondSize-Wet Pond-piedmont-90 tss-BOM printed:8/29/2023 6:00 PM Page 2 of 2

SUPPLEMENT-EZ COVER PAGE
FORMS LOADED
PROJECT INFORMATION
Project Name NCNG Camp Butner BOM Yard
2 Project Area(ac) 24.01
3 Coastal Wetland Area(ac) 0
4 Surface Water Area(ac) 0
5 Is this project High or Low Density? High
6 Does this project use an off-site SCM? No
COMPLIANCE WITH 02H.1003(4)
7 Width of vegetated setbacks provided(feet) N/A
8 Will the vegetated setback remain vegetated? Yes
9 Is BUA other that as listed in.1003(4)(c-d)out of the setback? Yes
10 Is streambank stabilization proposed on this project? No
NUMBER AND TYPE OF SCMs:
11 Infiltration System 0
12 Bioretention Cell 0
13 Wet Pond 1
14 Stormwater Wetland 0
15 Permeable Pavement 0
16 Sand Filter 0
17 Rainwater Harvesting(RWH) 0
18 Green Roof 0
19 Level Spreader-Filter Strip(LS-FS) 0
20 Disconnected 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
FORMS LOADED
DESIGNER CERTIFICATION
27 Name and Title: Frank Slinsky,P.E.,Senior Project Manager
28 Organization: Timmons Group
29 Street address: 5410 Trinity Road,Suite 102
30 City,State,Zip: Raleigh,NC,27607
31 Phone number(s): [phone]
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,operation and maintenance agreements and other supporting information are consistent
with the information provided here.
Designer
Signature of Designer
Seal Date

DRAINAGE AREAS
1 Is this a high density project? _ Yes
2 If so,number of drainage areas/SCMs _ 1
Is all/part of this project subject to previous rule
3 versions? No
FORMS LOADED
DRAINAGE AREA INFORMATION Entire Site 1
4 Type of SCM Wet Pond
5 Total BUA in project(sq ft) 225400 sf 194512 sf
New BUA on subdivided lots(subject to
6 permitting)(sq ft) sf sf
New BUA outside of subdivided lots(subject to
7 permitting)(sf) 207892 sf 194512 sf
8 Offsite-total area(sq ft)
9 Offsite BUA(sq ft)
10 Breakdown of new BUA outside subdivided lots:
-Parking(sq ft) 207892 sf 194512 sf
-Sidewalk(sq ft) sf
-Roof(sq ft) sf
-Roadway(sq ft) sf
-Future(sq ft)
-Other,please specify in the comment box
below(sq ft)
New infiltrating permeable pavement on
11 subdivided lots(sq ft) sf
New infiltrating permeable pavement outside of
12 subdivided lots(sq ft) sf
Exisitng BUA that will remain(not subject to
13 permitting)(sq ft) 17508 sf sf
14 Existing BUA that is already permitted(sq ft) sf
15 Existing BUA that will be removed(sq ft) 38475 sf 38475 sf
16 Percent BUA 22% 19%
17 Design storm(inches) 1 in
18 Design volume of SCM(cu ft) 16057 cf
19 Calculation method for design volume Simple Method
ADDITIONAL INFORMATION
Please use this space to provide any additional information about the
20 drainage area(s):

WET POND
1 Drainage area number 1 (Wet Pond)
2 Design volume of SCM(Cu ft) 16057 cf I
GENERAL MDC FROM 02H.1050
3 Is the SCM sized to treat the SW from all surfaces at build-out? Yes
4 Is the SCM located away from contaminated soils? Yes
5 What are the side slopes of the SCM(H:V)? 3:1
Does the SCM have retaining walls,gabion walls or other engineered
6 side slopes? No
Are the inlets,outlets,and receiving stream protected from erosion
7(10-year storm)? Yes
Is there an overflow or bypass for inflow volume in excess of the
8 design volume? Yes
9 What is the method for dewatering the SCM for maintenance? Drawdown Orifice
10 If applicable,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)? No
If the SCM is on a single family lot,does(will?)the plat comply with
13 General MDC(10)?
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 specific MDC? Yes
17 Was the SCM designed by an NC licensed professional? Yes
WET POND MDC FROM 02H.1053
18 Method used SA/DA
19 Has a stage/storage table been provided in the calculations? Yes
Elevation of the excavated main pool depth(bottom of sediment
20 removal)(fmsl) 451.50
21 Elevation of the main pool bottom-(top of sediment removal)(fmsl) 452.50
22 Elevation of the bottom of the vegetated shelf(fmsl) 456.00
23 Elevation of the permanent pool(fmsl) 456.50
24 Elevation of the top of the vegetated shelf(fmsl) 457.00
25 Elevation of the temporary pool(fmsl) 457.61
26 Surface area of the main permanent pool(square feet) 10466.00
27 Volume of the main permanent pool(cubic feet) 33300 cf
28 Average depth of the main pool(feet) 3.18 ft
29 Average depth equation used Equation 2
30 If using equation 3,main pool perimeter(feet) N/A
31 If using equation 3,width of submerged veg.shelf(feet) N/A
32 Volume of the forebay(cubic feet) 5127 cf
33 Is this 15-20%of the volume in the main pool? Yes
34 Clean-out depth for forebay(inches) 48 in
35 Design volume of SCM(cu ft) 16057 cf
36 Is the outlet an orifice or a weir? Orifice
37 If orifice,orifice diameter(inches) 2.00 in
38 If weir,weir height(inches) N/A
39 If weir,weir length(inches) N/A
40 Drawdown time for the temporary pool(days) 3
Are the inlet(s)and outlet located in a manner that avoids short-
41 circuiting? Yes
42 Are berms or baffles provided to improve the flow path? No
43 Depth of forebay at entrance(inches) 48 in
44 Depth of forebay at exit(inches) 36 in
45 Does water flow out of the forebay in a non-erosive manner? Yes
46 Width of the vegetated shelf(feet) 6 ft
47 Slope of vegetated shelf(H:V) 6:1
Does the orifice drawdown from below the top surface of the
48 permanent pool? Yes
Does the pond minimize impacts to the receiving channel from the 1-
49 yr,24-hr storm? Yes
Are fountains proposed?(If Y,please provide documentation that
50 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 Bermuda
54 Has a planting plan been provided for the vegetated shelf? Yes
ADDITIONAL INFORMATION
Please use this space to provide any additional information about the
55 wet pond(s):
The property is a 5,000 acre,state owned parcel. It is exempt from
recording drainage easements.
2

Project Information Complete this sheet if required by your reviewing authority.
Contact them for any questions. Grey boxes/text are optional.
SNAPv4.2.0 LOCATION
Project Name(optional): NCNG Camp Butner BOM Yard Parcel ID(optional): 86900128714
Submission Date(optional): 8/31/2023 date Nutrient Management Watershed: Falls Lake menu
Local Jurisdiction/Reviewing Agency: Stem menu Subwatershed: Upper_Falls menu
Project Latitude Coordinates(optional): 36°11'38.4"N N Phosphorus Delivery Zone: Neuse- Upper 03020201 menu
Project Longitude Coordinates(optional): 78°47'25.6"W W Nitrogen Delivery Zone: Falls- Upper menu
PROJECT DETAILS
Development Land Use Type: Industrial menu Disturbed Area: 466,435 ft2
Part of Common Development Plan? .no yin Project Activity: Redevelopment menu
Designated Downtown Area? no yin Project Drains to SA Waters? no y/n
Public Linear Road/Sidewalk Project? .no yin Pre-Project Land Use: forest menu
Project Owner Type: State non-NCDOT menu Project Description(optional):
STORMWATER DETAILS
(Falls ONLY)Onsite Reduction%Req. 30% % Project Uses LID/Runoff Volume Match? no yin
Existing BUA/Development Onsite? yes y/n Local Gov't nutrient req's same as State? yes y/n
Local Gov't cutoff date for Existing BUA: 12/01/2006 date Project Drains to Regional SCM? no y/n
Nitrogen Export Rate Target: .2.20 Ib/ac/yr Total Nitrogen Offset Credits Needed: 0.0 Ib/yr
Phosphorus Export Rate Target: 0.33 Ib/ac/yr Total Phosphorus Offset Credits Needed: 0.0 Ib/yr

SNAP v4.2.0
Project Area and Offsite Land Cover Characteristics Precipitation Oxford
Station:
Copy ' Paste VALUES ONLY for Best Results Click here to scroll down to error messages on this sheet.
—
PROJECT AREA LAND COVERS TN EMC (mg/L) TP EMC (mg/L) Pre-Project Area (ft2) Post-Project Area (ft2) Change pre-to-post(ft2)
1
Roof 1.18 0.11 0
Roadway 1.64 0.34 0
Parking/Driveway/Sidewalk 1.42 0.18 57,711 225,400 167,689
Protected Forest 0.97 0.03 587,650 587,650 0
Managed Pervious/Landscaping 2.48 1.07 400,785 220,170 -180,615
Offsite or Existing Roof 1.18 0.11 0
Offsite or Existing Roadway 1.64 0.34 0
Offsite or Existing Parking/Driveway/Sidevin 1.42 0.18 0
Offsite Protected Forest 0.97 0.03 0
Offsite Managed Pervious I 2.48 1.07 0
CUSTOM LAND COVER 1 0
CUSTOM LAND COVER 2 0
CUSTOM LAND COVER 3 0
LAND TAKEN UP BY SCM 1.18 0.11 12,926 12,926
Total (Regulated & UnReg)Area 1,046,146.00 1,046,146.00
Project (Regulated)Area 1,046,146.00 1,046,146.00

SCM Characteristics
Stormwater Control Measure (SCM) Characteristics Click here to go to
Copy & Paste VALUES ONLY SCM101's Land Cover Data
SNAP v4.2.0
for Best Results
Catchment ID 1 1 1
Drains to Drains to
SCM ID 101 102 103
7 Type of SCM Wet Pond
rHydrologic soil group at SCM location C
' SCM Description
ftDesign Storm Size(inches/24hrs) 1.00
■ Percent of Full Size 100%
Annual Effluent 72% 0% 0%
Annual Overflow 16% 0% 0%
I. %Annual ET/Infiltrated 13% 0% 0%
ElCustom%Annual Effluent A
r� Custom%Annual Overflow
rCustom%Annual ET/Infiltrated 1
l SCM Effluent TP EMC(mg/L) 0.13 0.00 0.00
III SCM Effluent TN EMC(mg/L) 0.86 0.00 0.00
■ Custom Effluent TP EMC
1.1 Custom Effluent TN EMC
r SCM Land Cover TP EMC(mg/L) 0.11 0.00 0.00
L SCM Land Cover TN EMC(mg/L) 1.18 0.00 0.00
rThis SCM Drains to Numbered SCM 0 0 0
Catchment Routing Catchments Draining to Catchments Draining to Catchments Draining to
SCM 101 SCM 102 SCM 103
Catchment 1
Catchment 2
Catchment 3
Catchment 4
Catchment 5
Catchment 6
Error Check-Missing SCM Area:

SCM Characteristics
Error Check-Min/Max Size:
II— Error Check-Hydrology:
Error Check-Missing SCM Info:
Error Check-Drainage Data w/o SCM:
Error Checks-SCM Type:
- SCM ID: 101 102 103
TArea Draining Directly to Area Draining Directly to Area Draining Directly to
SCM Drainage Area Land Covers SCM 101 (ft2) SCM 102 (ft2) SCM 103 (ft2)
Roof
Roadway
Parking/Driveway/Sidewalk 194,512
Protected Forest 17,650
Managed Pervious/Landscaping 128,673
Offsite or Existing Roof
Offsite or Existing Roadway
Offsite or Existing Parking/Driveway/Sidewalk
Offsite Protected Forest
Offsite Managed Pervious
CUSTOM LAND COVER 1
CUSTOM LAND COVER 2
CUSTOM LAND COVER 3
LAND TAKEN UP BY SCM 12,926
TOTAL AREA DRAINING TO SCM (ft2): 353,761 0 0
CATCHMENT AREA(ft2): 353,761

SCM Characteristics
Stormwater Control Meast. Click here to go to Click here to go back to the
Click here to review Errors
Summary Data top
SNAP v4.2.0
I . Catchment ID 2 2 2
Drains to Drains to
SCM ID 201 > 202 > 203
r
Type of SCM
' Hydrologic soil group at SCM location
' SCM Description
' Design Storm Size (inches/24hrs)
L_ Percent of Full Size I I I
%Annual Effluent 0% 0% 0%
M %Annual Overflow 0% 0% 0%
I. %Annual ET/Infiltrated - 0% 0% 0%
. Custom%Annual Effluent
F-- Custom%Annual Overflow
ICustom%Annual ET/Infiltrated
SCM Effluent TP EMC(mg/L) 0.00 0.00 0.00
SCM Effluent TN EMC (mg/L) _J 0.00 0.00 0.00
. Custom Effluent TP EMC
. Custom Effluent TN EMC
rSCM Land Cover TP EMC(mg/L) 1 0.00 0.00 0.00
' SCM Land Cover TN EMC(mg/L) I 0.00 0.00 0.00
' This SCM Drains to Numbered SCM 0 0 0
L Catchment Routing Catchments Draining to Catchments Draining to Catchments Draining to
SCM 201 SCM 202 SCM 203
Catchment 1
Catchment 2
Catchment 3
Catchment 4
Catchment 5
Catchment 6
Error Check-Missing SCM Area:

SCM Characteristics
Error Check-Min/Max Size:
Error Check-Hydrology:
Error Check-Missing SCM Info:
Error Check-Drainage Data w/o SCM:
IIIError Checks-SCM Type:
SCM ID: 201 202 203
Area Draining Directly to Area Draining Directly to Area Draining Directly to
SCM Drainage Area Land Covers SCM 201(ft2) SCM 202(ft2) SCM 203(ft2)
i
roof
Roadway
Parking/Driveway/Sidewalk
Protected Forest
Managed Pervious/Landscaping
Offsite or Existing Roof
Offsite or Existing Roadway
Offsite or Existing Parking/Driveway/Side
Offsite Protected Forest
Offsite Managed Pervious
CUSTOM LAND COVER 1
CUSTOM LAND COVER 2
CUSTOM LAND COVER 3
LAND TAKEN UP BY SCM
TOTAL AREA DRAINING TO SCM (ft2): 0 0 0
CATCHMENT AREA(ft2): 0

SCM Characteristics
Stormwater Control Measi
SNAP v4.2.0
I . Catchment ID 3 3 3
Drains to Drains to
SCM ID 301 > 302 > 303
r
Type of SCM
hydrologic soil group at SCM location
' SCM Description
' Design Storm Size(inches/24hrs)
Percent of Full Size
%Annual Effluent 0% 0% 0%
M %Annual Overflow ■ 0% 0% 0%
I. %Annual ET/Infiltrated I. 0% 0% 0%
Custom%Annual Effluent
ITCustom%Annual Overflow
Custom%Annual ET/Infiltrated
OP SCM Effluent TP EMC(mg/L) 0.00 0.00 0.00
SCM Effluent TN EMC(mg/L) J 0.00 0.00 0.00
Custom Effluent TP EMC
Custom Effluent TN EMC
r SCM Land Cover TP EMC(mg/L) 1 0.00 0.00 0.00
SCM Land Cover TN EMC(mg/L) 0.00 0.00 0.00
This SCM Drains to Numbered SCM ' 0 0 0
L Catchment Routing Catchments Draining to Catchments Draining to Catchments Draining to
SCM 301 SCM 302 SCM 303
Catchment 1
Catchment 2
Catchment 3
Catchment 4
Catchment 5
Catchment 6
,
Error Check-Missing SCM Area:

SCM Characteristics
Error Check-Min/Max Size:
Error Check-Hydrology:
Error Check-Missing SCM Info:
Error Check-Drainage Data w/o SCM:
IIIError Checks-SCM Type:
SCM ID: 301 302 303
Area Draining Directly to Area Draining Directly to Area Draining Directly to
SCM Drainage Area Land Covers SCM 301(ft2) SCM 302(ft2) SCM 303(ft2)
i
roof
Roadway
Parking/Driveway/Sidewalk
Protected Forest
Managed Pervious/Landscaping
Offsite or Existing Roof
Offsite or Existing Roadway
Offsite or Existing Parking/Driveway/Side
Offsite Protected Forest
Offsite Managed Pervious
CUSTOM LAND COVER 1
CUSTOM LAND COVER 2
CUSTOM LAND COVER 3
LAND TAKEN UP BY SCM
TOTAL AREA DRAINING TO SCM (ft2): 0 0 0
CATCHMENT AREA(ft2): 0

SCM Characteristics
Stormwater Control Measi
SNAP v4.2.0
I . Catchment ID 4 4 4
I Drains to > Drains to
SCM ID 401 402 403
Type of SCM
hydrologic soil group at SCM location
' SCM Description
' Design Storm Size(inches/24hrs)
Percent of Full Size
%Annual Effluent 0% 0% 0%
M %Annual Overflow ■ 0% 0% 0%
I. %Annual ET/Infiltrated I. 0% 0% 0%
Custom%Annual Effluent
ITCustom%Annual Overflow
Custom%Annual ET/Infiltrated
OP SCM Effluent TP EMC(mg/L) 0.00 0.00 0.00
SCM Effluent TN EMC(mg/L) J 0.00 0.00 0.00
Custom Effluent TP EMC
Custom Effluent TN EMC
r SCM Land Cover TP EMC(mg/L) 1 0.00 0.00 0.00
SCM Land Cover TN EMC(mg/L) 0.00 0.00 0.00
This SCM Drains to Numbered SCM ' 0 0 0
L Catchment Routing Catchments Draining to Catchments Draining to Catchments Draining to
SCM 401 SCM 402 SCM 403
Catchment 1
Catchment 2
Catchment 3
Catchment 4
Catchment 5
Catchment 6
,
Error Check-Missing SCM Area:

SCM Characteristics
Error Check-Min/Max Size:
Error Check-Hydrology:
Error Check-Missing SCM Info:
Error Check-Drainage Data w/o SCM:
IIIError Checks-SCM Type:
SCM ID: 401 402 403
Area Draining Directly to Area Draining Directly to Area Draining Directly to
SCM Drainage Area Land Covers SCM 401(ft2) SCM 402(ft2) SCM 403(ft2)
i
roof
Roadway
Parking/Driveway/Sidewalk
Protected Forest
Managed Pervious/Landscaping
Offsite or Existing Roof
Offsite or Existing Roadway
Offsite or Existing Parking/Driveway/Sidew
Offsite Protected Forest
Offsite Managed Pervious
CUSTOM LAND COVER 1
CUSTOM LAND COVER 2
CUSTOM LAND COVER 3
LAND TAKEN UP BY SCM
TOTAL AREA DRAINING TO SCM (ft2): 0 0 0
CATCHMENT AREA(ft2): 0

SCM Characteristics
Stormwater Control Measi
SNAP v4.2.0
I . Catchment ID 5 5 5
I Drains to Drains to
SCM ID 501 502 503
Type of SCM
hydrologic soil group at SCM location
' SCM Description
' Design Storm Size(inches/24hrs)
Percent of Full Size
%Annual Effluent 0% 0% 0%
M %Annual Overflow ■ 0% 0% 0%
I. %Annual ET/Infiltrated I. 0% 0% 0%
Custom%Annual Effluent
ITCustom%Annual Overflow
Custom%Annual ET/Infiltrated
OP SCM Effluent TP EMC(mg/L) 0.00 0.00 0.00
SCM Effluent TN EMC(mg/L) J 0.00 0.00 0.00
Custom Effluent TP EMC
Custom Effluent TN EMC
r SCM Land Cover TP EMC(mg/L) 1 0.00 0.00 0.00
SCM Land Cover TN EMC(mg/L) 0.00 0.00 0.00
This SCM Drains to Numbered SCM ' 0 0 0
L Catchment Routing Catchments Draining to Catchments Draining to Catchments Draining to
SCM 501 SCM 502 SCM 503
Catchment 1
Catchment 2
Catchment 3
Catchment 4
Catchment 5
Catchment 6
,
Error Check-Missing SCM Area:

SCM Characteristics
Error Check-Min/Max Size:
Error Check-Hydrology:
Error Check-Missing SCM Info:
Error Check-Drainage Data w/o SCM:
IIIError Checks-SCM Type:
SCM ID: 501 502 503
Area Draining Directly to Area Draining Directly to Area Draining Directly to
SCM Drainage Area Land Covers SCM 501(ft2) SCM 502(ft2) SCM 503(ft2)
i
roof
Roadway
Parking/Driveway/Sidewalk
Protected Forest
Managed Pervious/Landscaping
Offsite or Existing Roof
Offsite or Existing Roadway
Offsite or Existing Parking/Driveway/Sidew
Offsite Protected Forest
Offsite Managed Pervious
CUSTOM LAND COVER 1
CUSTOM LAND COVER 2
CUSTOM LAND COVER 3
LAND TAKEN UP BY SCM
TOTAL AREA DRAINING TO SCM (ft2): 0 0 0
CATCHMENT AREA(ft2): 0

SCM Characteristics
Stormwater Control Measi
SNAP v4.2.0
I . Catchment ID 6 6 6
Drains to Drains to
SCM ID 601 602 603
r
Type of SCM
hydrologic soil group at SCM location
1 SCM Description
1 Design Storm Size(inches/24hrs)
Percent of Full Size r-- I
%Annual Effluent 0% 0% 0%
M %Annual Overflow 0% 0% 0%
I. %Annual ET/Infiltrated 0% 0% 0%
Custom%Annual Effluent
ITCustom%Annual Overflow
Custom%Annual ET/Infiltrated
OP SCM Effluent TP EMC(mg/L) 0.00 0.00 0.00
SCM Effluent TN EMC(mg/L) J 0.00 0.00 0.00
Custom Effluent TP EMC
Custom Effluent TN EMC
r SCM Land Cover TP EMC(mg/L) 1 0.00 0.00 0.00
SCM Land Cover TN EMC(mg/L) 0.00 0.00 0.00
This SCM Drains to Numbered SCM ' 0 0 0
L Catchment Routing Catchments Draining to Catchments Draining to Catchments Draining to
SCM 601 SCM 602 SCM 603
Catchment 1
Catchment 2
Catchment 3
Catchment 4
Catchment 5
Catchment 6
,
Error Check-Missing SCM Area:

SCM Characteristics
Error Check-Min/Max Size:
Error Check-Hydrology:
Error Check-Missing SCM Info:
Error Check-Drainage Data w/o SCM:
IIIError Checks-SCM Type:
SCM ID: 601 602 603
Area Draining Directly to Area Draining Directly to Area Draining Directly to
SCM Drainage Area Land Covers SCM 601(ft2) SCM 602(ft2) SCM 603(ft2)
i
roof
Roadway
Parking/Driveway/Sidewalk
Protected Forest
Managed Pervious/Landscaping
Offsite or Existing Roof
Offsite or Existing Roadway
Offsite or Existing Parking/Driveway/Sidew
Offsite Protected Forest
Offsite Managed Pervious
CUSTOM LAND COVER 1
CUSTOM LAND COVER 2
CUSTOM LAND COVER 3
LAND TAKEN UP BY SCM
TOTAL AREA DRAINING TO SCM (ft2): 0 0 0
CATCHMENT AREA(ft2): 0

SCM Characteristics
Stormwater Control Measi
SNAP v4.2.0
I . Catchment ID
SCM ID
Type of SCM
hydrologic soil group at SCM location
' SCM Description
' Design Storm Size(inches/24hrs)
Percent of Full Size
%Annual Effluent
M %Annual Overflow
I. %Annual ET/Infiltrated
Custom%Annual Effluent
ITCustom%Annual Overflow
Custom%Annual ET/Infiltrated
OP SCM Effluent TP EMC(mg/L)
SCM Effluent TN EMC(mg/L)
Custom Effluent TP EMC
Custom Effluent TN EMC
rSCM Land Cover TP EMC(mg/L)
SCM Land Cover TN EMC(mg/L)
This SCM Drains to Numbered SCM
LCatchment Routing
Catchment 1
Catchment 2
Catchment 3
Catchment 4
Catchment 5
Catchment 6
Error Check-Missing SCM Area:

SCM Characteristics
Error Check-Min/Max Size:
Error Check-Hydrology:
Error Check-Missing SCM Info:
Error Check-Drainage Data w/o SCM:
IIIError Checks-SCM Type:
SCM ID:
Allowable Total Land Use
Total Land Use Area Post-Project Untreated
SCM Drainage Area Land Covers z Area to be Treated Based z
Treated By All SCMs(ft ) z Land Area (ft2)
on Post-Project Areas(ft2)
..roof 0 0 0
Roadway 0 0 0
Parking/Driveway/Sidewalk 194,512 225,400 30,888
Protected Forest 17,650 587,650 570,000
Managed Pervious/Landscaping 128,673 220,170 91,497
Offsite or Existing Roof 0 0 0
Offsite or Existing Roadway 0 0 0
Offsite or Existing Parking/Driveway/Sidew 0 0 0
Offsite Protected Forest 0 0 0
Offsite Managed Pervious 0 0 0
CUSTOM LAND COVER 1 0 0 0
CUSTOM LAND COVER 2 0 0 0
CUSTOM LAND COVER 3 0 0 0
LAND TAKEN UP BY SCM 12,926 12,926 0
TOTAL AREA DRAINING TO SCM (ft2): 353,761 1,046,146 692,385
CATCHMENT AREA(ft2):

Nutrient Export Summary
Landcover Et SCM Data Review
Errors/Advisories
Avg Annual precip(in) = 44.46
Total (Regulated+
1,046,146
Unregulated)Area (ftZ)=
Project(Regulated)
1,046,146
Area (ftZ) =
Net BUA(Project Area
2 167,689 Net BUA indicates new development or expansion.
BUA only ft )_
Custom Landcovers are
present:
no
Total Nitrogen Export Target
Scaled to Project Area (Ib/yr): 52.84
Total Area Total Area Project Area
Project Area
(Onsite+ Post-Project Post-Project
Nutrient Export Summary (Onsite Only)
Offsite) before before
Pre-Project
Pre-Project Treatment Treatment
Area (All Landcover Types) (acres) 24.0162 24.0162 24.0162 24.0162
Percent Built-Upon Area (BUA)(%) 6% I 6% 22% 22%
Built-Upon Area(BUA) (sqft) 57,711 57,711 225,400 225,400
Annual Runoff Volume(ft3/yr) 347,612 347,612 891,802 891,802
Annual Runoff%Change A 157% _ 157%
Total Runoff Change(cuft/yr) 544,190 544,190
Total Nitrogen EMC(mg/L) 1.50 1.50 1.40 1.40
Total Nitrogen Load Leaving Site(Ib/yr) 32.49 32.49 _ 78.11 I 78.11
Total Nitrogen Loading Rate(Ib/ac/yr) 1.35 1.35 3.25 3.25
Total Nitrogen%Change Pre-to-Post 140% 140%
Total Nitrogen Change(Ib/yr) Pre-to-Post 45.61 45.61
Total Phosphorus EMC(mg/L) 0.31 0.31 0.20 0.20
Total Phosphorus Load Leaving Site(Ib/yr) 6.70 6.70 10.96 10.96
Total Phosphorus Loading Rate(Ib/ac/yr) 0.28 0.28 0.46 0.46
Total Phosphorus%Change Pre-to-Post 63% -E_ 63%
Total Phosphorus Change (Ib/yr)Pre-to-Post 4.25 4.25
SCM/Catchment Summary
1

SCM ID and Type Volume TN Reduction TP Reduction TN Out I TP Out
Reduction(%) (%) (%) (Ibs/ac/yr) (Ibs/ac/yr)
Catchment 1 12.66% I 41.59% g 38.58% 4.41 0.65
101:Wet Pond 12.66% 41.59% 38.58% 4.41 0.65
102:NA 0.00% 0.00% 0.00% 0.00 0.00
103:NA 0.00% 0.00% 0.00% 0.00 0.00
Catchment 2 0.00% 0.00% _ 0.00% 0.00 0.00
201:NA 0.00% 0.00% 0.00% 0.00 0.00
202:NA 0.00% 0.00% _ 0.00% 0.00 0.00
203:NA 0.00% 0.00% 0.00% 0.00 0.00
Catchment 3 0.00% 0.00% 0.00% 0.00 0.00
301:NA 0.00% 0.00% 0.00% 0.00 0.00
302:NA 0.00% 0.00% _ 0.00% 0.00 0.00
303:NA 0.00% 0.00% 0.00% 0.00 0.00
Catchment 4 0.00% 0.00% 0.00% 0.00 0.00
401:NA 0.00% 0.00% 0.00% 0.00 0.00
402:NA 0.00% 0.00% 0.00% 0.00 0.00
403:NA 0.00% 0.00% 0.00% 0.00 0.00
Catchment 5 0.00% 0.00% 0.00% 0.00 0.00
501:NA 0.00% 0.00% 0.00% 0.00 0.00
502:NA 0.00% 0.00% _ 0.00% 0.00 _ 0.00
503:NA 0.00% 0.00% 0.00% 0.00 0.00
Catchment 6 0.00% 0.00% 0.00% 0.00 0.00
601:NA 0.00% 0.00% 0.00% 0.00 0.00
602:NA 0.00% 0.00% _ 0.00% 0.00 0.00
603:NA 0.00% 0.00% 0.00% 0.00 0.00
1

SNAP v4.2.0
Errors/Advisories
SCM Area (ft2) = 12,926
SCM Treated Area (ft2) = 353,761
Catchment Routing: No errors
Treating Runoff from
Existing BUA or Offsite:
no
Disturbed Area (ft2) = 466,435
Total Phosphorus Export Target
7.93
Scaled to Project Area (Ib/yr):
Total Area Project Area Total Area Project Area
Total Area Project Area
Post-Project Post-Project Post-Project Post-Project
Post-Project Post-Project
SCM-Treated SCM-Treated Untreated Untreated
after Treatment after Treatment
Area Only Area Only Areas Areas
24.0162 24.0162 8.1212 8.1212 15.8950 15.8950
22% I 22% 55% 55% 4% I 4%
225,400 225,400 194,512 194,512 30,888 _ 30,888
805,229 805,229 597,095 597,095 208,134 208,134
132% _ 132%
457,617 457,617
1.05 1.05 0.96 0.96 1.29 1.29
52.61 1 52.61 35.81 35.81 16.79 -L 16.79
2.19 2.19 4.41 4.41 1.06 1.06
62% 62%
20.12 20.12
0.15 0.15 0.14 0.14 0.18 0.18
7.62 7.62 - 5.32 5.32 2.30 2.30
0.32 0.32 0.65 0.65 0.14 0.14
14% 14%
0.91 0.91
1

Falls Lake ONLY: Onsite Reduction Compliance Check
Nitrogen Phosphorus
Onsite%Reduction Requirement 30% 30%
Export Target Scaled to Area (Ib/yr) 52.84 7.93
Export Load Post-Project Before Treatment 78.11 10.96
Total Reduction Need (Ib/yr) _ 25.27 3.03
Onsite Reduction Need (Ib/yr) _ 7.58 0.91
Onsite Export Target(Ib/yr) _ 60.42 8.83
Project Area Post-Project After Treatment 52.61 7.62
1

OUTLET PROTECTION DATE
DESIGN 8/31/2023 .•••••••
• •
PROJECT NAME PROJECT NO
NCNG CB BOM Yard 42324 TIMMONS GROUP
YOUR VISION ACHIEVED THROUGH OURS.
LOCATION BY
Stem, NC JDL
RIPRAP A
Pipe Diameter: 18.00 in
Upper Invert: 452.50
Lower Invert: 451.75
Pipe Length: 92.00 ft *Discharge from Storm Sewers
Pipe Slope: 0.008 Discharge: 9.38 cfs
Pipe Material: RCP
Qio= 9.38 cfs Q1o/Qfull = 0.99
Qfull = 9.50 cfs VNfull = 1.14
Vfull = 5.38 fps V= 6.12 fps
Dissipator Dimensions* Zone= 2
Stone Filling Class= B
Entry Width(3 X Do)= 4.5 ft
Length(6 X Do)= 9.0 ft
Width(La+ Do)= 10.5 ft
Min.Thickness= 12 inches
Stone Diameter(D50)= 6 inches
1- 9.0
4.5 10.5
All units are in feet
"Dissipator pad designed for full flow of pipe
Rip Rap Calcs 8/31/2023 Page 1 of 1