5103_JohnstonLF_SedEroCtrol_20200214

Attachment
Erosion and Sedimentation Control Plan
Permit to Construct Application
Johnston County MSW Landfill - Phase 6
Smithfield, North Carolina

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Erosion and Sedimentation Control Plan
Johnston County MSW Landfill- Phase 6
Smithfield, North Carolina
Prepared for:
Johnston County Department of Solid Waste Services
Smithfield, North Carolina
March 2019
NCLIC.NO.F-1370 (ENGINEERING)
SMITH GARDNER
14 N. Boylan Avenue, Raleigh NC 27603 1 919.828.0577
PRINTED ON 100% RECYCLED PAPER
© 2079 Smith Gardner, Inc.
This document is intended for the sole use of the client for which it was prepared and
for the purpose agreed upon by the client and Smith Gardner, Inc.

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Erosion and Sedimentation Control Plan
Johnston County MSW Landfill- Phase 6
Smithfield, North Carolina
Prepared For:
Johnston County Department of Solid Waste Services
Smithfield, North Carolina
S+6 Project No.JOHNSTON-16-4
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Spencer W. Hollomon, P.E.
Project Engineer
DocuSigned by:
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Pieter K. Scheer, P.E.
Vice President, Senior Engineer
March 2019
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NC LIC. NO.F-1370 (ENGINEERING)
SMITH GARDNER
14 N. Boylan Avenue, Raleigh NC 27603 1 919.828.0577

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Landfill- Phase 6
Smithfield, North Carolina
Erosion and Sedimentation Control Plan
Table of Contents
Paqe
1.0
NARRATIVE......................................................................................................................... 1
1.1 Project Description.................................................................................................... 1
1.2 Site Location.............................................................................................................. 1
1.3 Contact Information..................................................................................................2
1.3.1 Engineer........................................................................................................ 2
1.3.2 Owner............................................................................................................ 2
1.4 Existing Site Conditions.............................................................................................2
1.5 Adjacent Areas........................................................................................................... 3
1.6 Site Soils Information................................................................................................3
2.0
DESIGN GUIDELINES AND PROCEDURES......................................................................... 3
3.0
RUNOFF CALCULATIONS................................................................................................... 3
4.0
EROSION AND SEDIMENTATION CONTROL MEASURES - INITIAL ................................... 4
4.1 Sediment Basins........................................................................................................4
4.2 Drainage Channels....................................................................................................4
4.3 Culverts......................................................................................................................5
4.4 Drop Inlets.................................................................................................................5
4.5 Silt Fence................................................................................................................... 5
4.6 Vegetative Stabilization............................................................................................. 5
5.0
EROSION AND SEDIMENTATION CONTROL MEASURES - FINAL ..................................... 5
5.1 Rain Gutters...............................................................................................................5
5.2 Down Pipes................................................................................................................ 6
6.0
SCHEDULE FOR IMPLEMENTATION.................................................................................. 6
7.0
INSPECTION AND MAINTENANCE..................................................................................... 7
FIGURES
Figure 1 USGS Map (Powhatan Quadrangle)
Figure 2 USDA NRCS Map
APPENDICES
Appendix A Erosion and Sedimentation Control Calculations
Appendix B Erosion and Sedimentation Control Technical Specifications
(see Attachment C)
Appendix C Erosion and Sedimentation Control Plans and Details (see Attachment L)
Johnston County MSW Landfill - Phase 6 Erosion and Sedimentation Control Plan
March 2019 Table of Contents Page i

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
1.0 NARRATIVE
1.1 Project Description
Johnston County plans to construct a lined expansion (Phase 6) of their existing
municipal solid waste (MSW) landfill at the County's landfill facility located off of NC
Highway 210 on County Home Road near Smithfield. The construction and operation of
the landfill expansion will require the disturbance of approximately 30 acres, which have
not been previously approved for disturbance. Previously approved plans for this portior
of the site were as follows:
Johnston County Subtitle D Landfill - Phase 5 Sediment and Erosion Control Plan
(prepared by McKim & Creed Engineers, P.A., June 19951 (Approved ca. 1995);
and
Johnston County Landfill Borrow Area D (prepared by G.N. Richardson &
Associates, Inc. (now Smith Gardner, Inc.)) (Approved March 2, 2002).
This plan discusses both the initial and long term (final) erosion and sedimentation
control measures used on this project.
1.2 Site Location
The attached USGS map (Powhatan Quadrangle) shows the approximate location of the
site and the location of stormwater outfalls for this project. Additional information is as
follows:
Address:
680 County Home Road
Smithfield, NC 27577
Coordinates
(Site Entrance):
Latitude: 35.51 degrees
Longitude: -78.43 degrees
River Basin:
Neuse
Receiving Stream(s)
(Stream Classification):
Middle Creek (C; NSW1
Johnston County MSW Landfill - Phase 6
March 2019
Erasion and Sedimentation Control Plan
Page 1

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
1.3 Contact Information
1.3.1 Engineer
For questions regarding this erosion and sedimentation control plan, please
contact the following:
Smith Gardner, Inc.
Attn.: Pieter K. Scheer, P.E.
14 N. Boylan Ave.
Raleigh, NC 27603
Phone: [phone]
Fax: [phone]
Email: pieter(asmithgardnerinc.com.
1.3.2 Owner
The owner of the site and the person to contact should sediment control issues
arise during the land -disturbing activity is as follows:
Johnston County
P.O. Box 1049
Smithfield, NC 27577
Phone: [phone]
Fax: [phone]
Contact: Rick Hester, County Manager
rick.hester(ajohnstonnc.com
Johnston County Department of Solid Waste Services
680 County Home Road
P.O. Box 2263
Smithfield, NC 27577
Phone: [phone]
Fax: [phone]
Contact: Rick Proctor, Director
rick.proctor(ajohnstonnc.com
1.4 Existing Site Conditions
The proposed Phase 6 MSW landfill unit occupies a valley on County -owned property to
the west of the existing Phase 5 MSW landfill unit. Existing ground surface elevations
vary from approximately El. 230 (feet) at the southeast end of the project area to El. 170
at the outlet of proposed Sediment Basin 1 W at the north end of the project area.
Johnston County MSW Landfill - Phase 6 Erasion and Sedimentation Control Plan
March 2019 Page 2

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Currently, much of the site is wooded. A previously permitted borrow area (Borrow Area
D) lies to the west of the proposed Phase 6 landfill unit.
1.5 Adjacent Areas
The proposed project area lies within County -owned property on all sides. Middle Creek
lies to the north and west of the project area. An unnamed tributary of Middle Creek lies
to the north of the project area. The landfill facility is accessed from County Home Road
at the south end of the facility.
1.6 Site Soils Information
The native surficial soils at the site within the project area fall under the categories of
Bonneau sand (BOA), Gilead sandy loam (GeB), and Uchee loamy coarse sand (UcB and
UcC) according to the USDA Natural Resources Conservation Service (Johnston County)
soil survey (see attached soil survey map). These soils are classified as being in
hydrologic soil groups (HSG) "A" or "C". For purposes of runoff calculations, HSG "B"
was assumed in the calculations.
2.0 DESIGN GUIDELINES AND PROCEDURES
The erosion and sediment control design for the landfill was conducted based on guidelines and
procedures as set forth in the following references:
A. HydroCAD Software Solutions, LLC (2006), HydroCAD Stormwater Modeling System
Owner's Manual - Version 8, Chocorua, NH.
B. Malcom, H. Rooney (1989 & 2003 Supplement), Elements of Urban Stormwater Design,
NC State Univ., Raleigh, NC.
C. North Carolina Division of Land Resources (2013 Update), North Carolina Erosion &
Sediment Control Planning & Design Manual, Raleigh, NC.
3.0 RUNOFF CALCULATIONS
All stormwater flow volumes were calculated using the HydroCAD computer program (utilizing
USDA-NRCS (SCS) methods) and/or the Rational Method based on a 25 year 24-hour storm
event. This storm event, which is a requirement of current North Carolina solid waste
regulations, exceeds the 10-year event required by current North Carolina Sediment Control
regulations. Rainfall quantities and/or intensities used in the analyses were derived from an
analysis of design storms for the site. Drainage areas were determined using a planimeter
and/or AutoCAD on topographic sheets of the project area. For each drainage area, runoff
curve numbers (SCS methods) and/or runoff coefficients (Rational Method) were selected based
Johnston County MSW Landfill - Phase 6
March 2019
Erasion and Sedimentation Control Plan
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DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
on ground cover conditions. Times of concentration were calculated by HydroCAD using SCS
methods.
4.0 EROSION AND SEDIMENTATION CONTROL MEASURES - INITIAL
The following erosion and sedimentation control measures are to be constructed as part of the
proposed construction. Appendices A, B, and C to this plan include calculations, technical
specifications, and plans and details (project drawings) for each of these measures,
respectively.
4.1 Sediment Basins
There are two permanent sediment basins (Sediment Basins 1W and 3W) and one long-
term temporary sediment basin (Borrow Area D Sediment Basin) which will serve the
project area. Sediment Basin 1W will be located at the northwest end of the project
area. Sediment Basin 3W will be located to the south end of the project area. The
existing Borrow Area D Sediment Basin is located on the west side of the project area.
New basins were designed in accordance with E&SCP&DM Section 6.61.
Sediment basins are subject to several design requirements. Each sediment basin must
have a basin volume of 1,800 ft3/acre of disturbed area and should have a surface area
(measured at crest of principal spillway (riser)) of 0.01 acres/cfs (based on the peak flow
from at least the 10-year storm). Each basin must include a riser/barrel principal
spillway and must have an emergency spillway (preferably a weir type spillway). The
crest of the emergency spillway is set at least one foot above the invert of the riser and
the spillway must pass the peak run off from the design storm event with one foot (min.)
of freeboard to the crest of berm. Each riser/barrel assembly must be provided with an
anchor displacing a buoyant weight of at least 1.1 times the weight of water displaced by
the riser. Each riser must also be provided with a method of dewatering the basin. In
addition to E&SCP&DM requirements, each sediment basin was designed to have an
adequate surface area to achieve an 80% settling efficiency of a 40 micron (silt size)
particle at the peak discharge from the design storm. Each sediment basin was
modeled with the HydroCAD computer program and a spreadsheet was used to verify
the design requirements for new basins.
4.2 Drainage Channels
Drainage channel calculations were conducted using a reformulation of Manning's
Equation in a spreadsheet format. The calculations determine the normal depth of flow
based on the peak discharge from the design storm (from HydroCAD) and assumed
channel dimensions/slope(s). Both temporary and/or permanent channel linings were
chosen, as appropriate, based on the calculated velocity and/or shear stress.
Temporary channel linings (if specified) were designed based on the peak discharge
from a 2-year 24-hour design storm.
Johnston County MSW Landfill - Phase 6
March 2019
Erasion and Sedimentation Control Plan
Page 4

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
4.3 Culverts
There are several culverts which will be used at the site to convey flow beneath
roadways and embankments. Culverts will be directed to one of the site sediment
basins. Culverts were designed either using HydroCAD or a spreadsheet based on an
analysis of inlet and outlet control under the influence of the design storm to determine
the maximum headwater elevation. Where required, culvert outlets were designed for
outlet stabilization based on criteria set forth in E&SCP&DM, Section 6.41.
4.4 Drop Inlets
Weir -type drop inlets will be used in the perimeter drainage channel to route flows into
one of the sediment basins. These drop inlets were designed either using HydroCAD or
a spreadsheet based on an analysis of the flow capacity of the open sides (weirs) of the
drop inlet compared to the maximum flow from the design storm. Prior to vegetative
stabilization of the perimeter channel, each drop inlet will be protected from
sedimentation by a placing a wire mesh and coarse aggregate filter around all sides of
the drop inlet.
4.5 Silt Fence
Silt fencing design was based on criteria set forth in E&SCP&DM, Section 6.62 including
the limitation of 100 feet of fencing for each acre of drainage area.
4.6 Vegetative Stabilization
Vegetative stabilization will be in accordance with the seeding schedule on the project
drawings and/or in the project specifications.
5.0 EROSION AND SEDIMENTATION CONTROL MEASURES - FINAL
The following erosion and sedimentation control measures are to be constructed as part of final
cover construction. Appendices A, B, and C to this plan include calculations, technical
specifications, and plans and details (project drawings) for each of these measures,
respectively.
5.1 Rain Gutters
Rain gutters will be placed along final cover side slopes at a maximum spacing of
approximately 150 feet. Flow from the rain gutters will be directed to the down pipes.
Rain gutters were designed using a spreadsheet. The capacity of the rain gutters was
checked based on partial flow to determine flow depth and velocity then compared with
the full flow capacity of each pipe size with the calculated peak discharge to verify the
Johnston County MSW Landfill - Phase 6
March 2019
Erasion and Sedimentation Control Plan
Page 5

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
desired factor of safety. Rain gutter drop inlets (inlet to down pipes) were analyzed as
orifices.
5.2 Down Pipes
Down pipes will be used to carry flows from diversion berms and/or rain gutters to the
bottom of final cover slopes. Down pipes were designed based on the same procedures
as rain gutters. Down pipes will be adequately anchored to the landfill side slopes by
use of a soil cover and each will be outleted either directly to perimeter sediment basins
(with rip rap apron at outlet) or to energy dissipating structures (precast energy
dissipaters, drop inlets, stone structures, etc.) at the base of each slope.
6.0 SCHEDULE FOR IMPLEMENTATION
Erosion and sedimentation control measures will be established prior to, or as soon as practical
thereafter, any land disturbance or construction activities may begin in that portion of the site
which drains to the erosion control measures. The following general schedule will be followed
for this project:
A. Flag the clearing limits and identify any tree protection areas.
B. Install temporary gravel construction entrance/exit.
C. Clear the vegetated portion of the site and install silt and stone filter fencing prior to
stripping/grubbing.
D. Only strip/grub areas required for installation of structures, berms, and drainage
channels. Other areas will be stripped/grubbed once each sediment basin is completed.
E. Install each sediment basin outlet structure; outlet protection and/or channel, berm, and
emergency spillway.
F. Perform earthwork as required for construction.
G. Perform fine grading and establish permanent vegetation on completed areas.
H. After stabilization, remove silt and stone filter fencing and other temporary measures
and install permanent vegetation on the disturbed areas.
Soil stabilization will be achieved on any area of the site where land disturbing activities have
temporarily or permanently ceased according to the following schedule:
A. All perimeter dikes, swales, ditches, perimeter slopes, and all slopes steeper than 3
horizontal to 1 vertical (3H:1V) will be provided temporary or permanent stabilization
with ground cover as soon as practicable but in any event within 7 calendar days from
the last land disturbing activity.
B. All other disturbed areas will be provided temporary or permanent stabilization with
ground cover as soon as practicable but in any event within 14 calendar days from the
last land disturbing activity.
C. Basins, traps, channels, and diversions will be lined with anchored rolled erosion control
products or rip rap and/or vegetated upon construction.
Johnston County MSW Landfill - Phase 6 Erasion and Sedimentation Control Plan
March 2019 Page 6

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
D. Permanent ground cover for all disturbed areas will be established within 15 working
days or 90 calendar days (whichever is shorter) following completion of construction or
development.
7.0 INSPECTION AND MAINTENANCE
All erosion and sedimentation control measures will be inspected at least once every 7 calendar
days and within 24 hours after any storm event of greater than 0.5 inches of rain per 24 hour
period and appropriate maintenance conducted. A rain gauge will be maintained on the site and
a record of the rainfall amounts and dates will be kept.
During inspections, any stormwater discharges from the site will be observed for stormwater
discharge characteristics to evaluate the effectiveness of the erosion and sedimentation control
measures incorporating Best Management Practices (BMPs). If visible sedimentation is leaving
the disturbed limits of the site, corrective action will be taken immediately to control the
discharge of sediments.
Maintenance activities will include, but not be limited to the following:
A. The removal and satisfactory disposal of trapped or deposited sediments from basins,
traps, barriers, filters, and/or drainage features/devices;
B. Replacement of filter fabrics used for silt fences upon loss of efficiency; and
C. Replacement of any other components which are damage or cannot serve the intended
use.
Johnston County MSW Landfill - Phase 6
March 2019
Erasion and Sedimentation Control Plan
Page 7

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E — y
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DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Appendix A
Erosion and Sedimentation Control
Calculations
Erosion and Sedimentation Control Plan
Johnston County MSW Landfill - Phase 6
Smithfield, North Carolina

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Erosion and Sedimentation Control Plan
Appendix A: Erosion and Sedimentation Control Calculations
Table of Contents
1.0 Drainage and E&S Control Calculations - Overview
2.0 Analysis of Design Storms
3.0 Drainage Area Figure
4.0 Stormwater Routing (HydroCAD output)*
• 25-Year 24-Hour Storm
5.0 Drainage Channel Analysis
• Perimeter Road Drainage Channel
6.0 Drop Inlet Analysis
• DI with Maximum Area
7.0 Rain Gutter and Down Pipe Analysis
8.0 Sedimentation Basin Analysis
• Sediment Basin 1W
• Sediment Basin 3W
9.0 Outlet Protection Analysis
• C-11, C-12, C-35, C-Al, & C-A2
• Sediment Basins 1 W & 3W
*The design of culverts is included in the HydroCAD output.
Johnston County MSW Landfill - Phase 6 Erasion and Sedimentation Control Plan
March 2019 Appendix A: Table of Contents Page Al

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
RESS
TEL I WEB
SMITH GAR D N E R 1 14 N. Boylan Avenue, Raleigh, NC 27603 919.828.0577 1 www.smithgardnerinc.com
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 1 OF 2 DATE
COMPUTED BY
SUBJECT Drainage & E&SC Calcs. - Overview JOB # JOHNSTON-16-4 CHECKED BY
3/11/2019
PKS
SWH
OBJECTIVE: To design stormwater conveyance, detention, and erosion and sedimentation control measures to remove
and contain stormwater flow from the design storm. The design of these measures will be based on:
• Design storm information for the site;
• Peak discharge calculations using the Rational Method and/or USDA-NRCS (SCSI Methods; and
• Stormwater routinq using USDA-NRCS (SCS) or other methods.
REFERENCES: Debo, T.N., and Reese, A.J. 11995), Municipal Storm Water Management, Lewis Publishers, Boca Raton, FL.
Federal Highway Administration (2001), Urban Drainage Design Manual, Hydraulic Engineering Circular
No. 22, FHWA NHI-01-021, Second Ed., U.S. Dept. of Transportation, Washington, D.C.
Georgia Soil and Water Conservation Commission (20001, Manual for Erosion and Sediment Control in
Georgia, Fifth Edition, Athens, GA.
HydroCAD Software Solutions, LLC (2006), HydroCAD Stormwater Modeling System Owner's Manual -
Version 8, Chocorua, NH.
Malcom, H. Rooney 11989 & 2003 Supplement), Elements of Urban Stormwater Design, NC State Univ.,
Raleigh, NC.
North Carolina Division of Land Resources (2013 Updates), North Carolina Erosion & Sediment Control
Planning & Design Manual, Raleigh, NC.
North Carolina Division of Water Quality (July 2005) Updated Draft Manual of Stormwater Best
Management Practices, (Public Comment Version), Raleigh, NC.
Pennsylvania DEP Bureau of Watershed Protection (20001, Erosion and Sediment Pollution Control
Program Manual.
USDA-NRCS (19921, Computer Program for Project Formulation Hydrology (TR-20).
USDA-NRCS (1986 & 1999 Update), Urban Hydrology for Small Watersheds (TR-55).
Virginia Department of Conservation and Recreation (1992), Virginia Erosion & Sediment Control
Handbook, Third Edition, Richmond, VA.
ANALYSIS: The main design criteria will be to ensure that all stormwater conveyance and detention measures will be
able to accommodate the runoff from the design storm. Drainage channels, culverts, etc. were designed
based on the peak discharge to each measure. Detention measures were designed based on stormwater
routing methods and/or State/local criteria.
CALCULATIONS:
- Peak Discharge Calculations:
USDA-NRCS (SCS) Methods:
Use HydroCAD program to determine the peak discharge to each device or structure. HydroCAD is based
on the SCS unit hydrograph procedure, which is a principal component of NRCS TR-20. Alternatively
spreadsheets can be used to determine flow rates using the procedures detailed in NRCS TR-55.
SMITH GARNER, INC. JC D&E&SC OVERVIEW

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 2 OF 2 DATE 3/11/2019
COMPUTED BY PKS
SUBJECT Drainage & E&SC Calcs. - Overview JOB # JOHNSTON-16-4 CHECKED BY SWH
Rational Method:
0 = CIA (Malcom Eq. 1 -1)
where: G = peak discharge (cfs)
C = rational runoff coefficient
I = applicable rainfall intensity (in/hr) of storm event (based on time of concentration)
A = drainage area (acres)
Time of Concentration:
The time of concentration for use in determining the peak discharge in the NRCS and/or Rational methods
can be determined by the methods detailed in NRCS TR-55 or other methods. HydroCAD uses the NRCS
methods.
- Stormwater Routing:
Stormwater routing was accomplished using the HydroCAD program, which is based on USDA-NRCS (SCSI methods.
Unless otherwise specified, the unit hydrograph method was used. The storm type (i.e. Type 124-hr., Type II 24-hr.,
etc.) was selected as appropriate for the project location.
SMITH-GARDNER
SMITH GARDNER, INC. JC D&E&SC OVERVIEW

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
ADDRESS TEL WEB
SMITH GAR D N E R 14 N. Boylan Avenue, Raleigh, NC 27603 919.828.0577 www.smithgardnerinc.com
PROJECT Johnston County Landfill Facility SHEET 1 OF 2 DATE 3/11/2019
COMPUTED BY PKS
SUBJECT Analysis of Design Storms JOB # JOHNSTON-16-4 CHECKED BY SWH
OBJECTIVE: To compile the expected design storm depths and intensities over various return periods. These design
storm values will be used in various calculations.
REFERENCES: Rainfall data was obtained from the following references:
Frederick, R.H., V.A. Myers, and E.P. Anciello (1977), "Five to 60-Minute Precipitation Frequency for the
Eastern and Central United States," NOAA Technical Memo. NWS HYDRO-35, National Weather Service,
NOAA, U.S. Dept. Of Commerce, Silver Spring, MD.
U.S. Weather Bureau (1961), "Rainfall Frequency Atlas of the United States for Durations from 30 Minutes
to 24 Hours and Return Periods from 1 to 100 Years," U.S. Weather Bureau Technical Paper 40.
SMITH GARNER, INC. JC DESIGN STORMS

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston County Landfill Facility
SHEET
2/2
JOB #
JOHNSTON-16-4
SUBJECT Analysis of Design Storms
DATE
3/11/2019
COMPUTED BY
PKS
CHECKED BY
SWH
LOCATION: Smithfield, North Carolina
RETURN PERIOD
2-YR P
100-YR P
SOURCE
DURATION
(in)
(in)
5 min
0.48
0.81
NOAA HYDRO-35
15 min
1.03
1.81
NOAA HYDRO-35
60 min
1.80
3.75
NOAA HYDRO-35
2 hr to 24 hr Rainfall Events =
USER INPUT
USWB TP-40
DEPTH -DURATION -FREQUENCY TABLE:
RETURN PERIOD
2-YR
5-YR
10-YR
25-YR
50-YR
100-YR
DURATION
(in)
(in)
(in)
(in)
(in)
(in)
5 min
0.48
0.55
0.60
0.68
0.75
0.81
10 min
0.80
0.93
1.03
1.17
1.29
1.40
15 min
1.03
1.20
1.32
1.51
1.66
1.81
30 min
1.41
1.72
1.94
2.26
2.51
2.76
60 min
1.80
2.26
2.58
3.04
3.39
3.75
2 hr
2.20
2.80
3.25
3.70
4.20
4.60
3 hr
2.40
3.10
3.60
4.10
4.55
5.10
6 hr
2.85
3.60
4.20
4.90
5.50
6.10
12 hr
3.35
4.20
5.00
5.80
6.40
7.20
24 hr
3.70
4.85
5.80
6.60
7.40
8.20
INTENSITY -DURATION -FREQUENCY TABLE:
RETURN PERIOD
2-YR
5-YR
10-YR
25-YR
50-YR
100-YR
DURATION
(in/hr)
(in/hr)
(in/hr)
(in/hr)
(in/hrl
(in/hr)
5 min
5.76
6.58
7.22
8.19
8.96
9.72
10 min
4.83
5.59
6.17
7.03
7.72
8.40
15 min
4.12
4.79
5.29
6.05
6.65
7.24
30 min
2.81
3.43
3.88
4.52
5.02
5.52
60 min
1.80
2.26
2.58
3.04
3.39
3.75
2 hr
1.10
1.40
1.63
1.85
2.10
2.30
3 hr
0.80
1.03
1.20
1.37
1.52
1.70
6 hr
0.48
0.60
0.70
0.82
0.92
1.02
12 hr
0.28
0.35
0.42
0.48
0.53
0.60
24 hr
0.15
0.20
0.24
0.28
0.31
0.34
SMITH GARDNER
SMITH GARONER, INC. Jc DESIGN STORMS

DocuSign Envelope ID: 6raaFnna-Alcg-dann-AR27-�dR'IRR1rgFQF
CD

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
32
see eaxn w. wv � �YIIIII 33 }���/
51 10 11 21 O I R 2P35�
� O O 31A
�� / xee� rvo. 121 � Pit DP21 P32 � � 32
052 P14 �o--O OP31
seeawnh .s➢v� ��� 13 O �� � DPdS O �ib ���_ 30 \ DPd6
P52
DP13 P12 PIµ 46 ��� ei�xo. aw
5 � P53 O 41 P43 8 44 �ti 45 ��u �'O
O ���0 DP42 D'O
Subcat Reach on Link

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10
Prepared by Pieter K. Scheer, P.E. Page 2
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Area Listing (all nodes)
Area (acres) CN Description (subcats)
156.900 61 >75% Grass cover, Good, HSG B (10,11,12,13,20,21,22,23,30,31,32,33,34,40,41,42,43,44,4E
7.700 85 Gravel roads, HSG B(10,11,12,13,21,22,23,30,31,32,33,34,40,41,42,43,44,45,46,50,51,52,5":
3.900 98 Paved parking & roofs (A)
1.400
98
Sed. Basin No. 1 W - Riser Elev.
(10)
1.100
98
Sed. Basin No. 2W - Riser Elev.
(20)
1.200
98
Sed. Basin No. 3W - Riser Elev.
(30)
1.800
98
Sed. Basin No. 4W - Riser Elev.
(40)
0.900
98
Sed. Basin No. 5W - Riser Elev.
(50)
174.900

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 3
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Time span=0.00-30.00 hrs, dt=0.01 hrs, 3001 points x 3
Runoff by SCS TR-20 method, UH=SCS
Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method
Subcatchment 10: Runoff Area=2.900 ac Runoff Depth=4.43"
Flow Length=60' Slope=0.3300 '/' Tc=2.0 min CN=81 Runoff=25.41 cfs 1.072 of
Subcatchment 11: Runoff Area=2.400 ac Runoff Depth=2.70"
Flow Length=550' Tc=6.4 min CN=64 Runoff=11.44 cfs 0.540 of
Subcatchment 12: Runoff Area=1.500 ac Runoff Depth=2.70"
Flow Length=350' Tc=5.5 min CN=64 Runoff=7.40 cfs 0.338 of
Subcatchment 13: Runoff Area=2.600 ac Runoff Depth=2.70"
Flow Length=300' Tc=5.3 min CN=64 Runoff=12.93 cfs 0.585 of
Subcatchment 20: Runoff Area=3.200 ac Runoff Depth=3.70"
Flow Length=100' Slope=0.3300 '/' Tc=3.0 min CN=74 Runoff=23.32 cfs 0.985 of
Subcatchment 21: Runoff Area=2.300 ac Runoff Depth=2.61"
Flow Length=200' Slope=0.2500 '/' Tc=5.8 min CN=63 Runoff=10.82 cfs 0.499 of
Subcatchment 22: Runoff Area=2.200 ac Runoff Depth=2.70"
Flow Length=100' Slope=0.2500 '/' Tc=3.3 min CN=64 Runoff=11.81 cfs 0.495 of
Subcatchment 23: Runoff Area=1.900 ac Runoff Depth=2.80"
Flow Length=100' Slope=0.2500 '/' Tc=3.3 min CN=65 Runoff=10.56 cfs 0.443 of
Subcatchment 30: Runoff Area=2.500 ac Runoff Depth=4.43"
Flow Length=100' Slope=0.3300 '/' Tc=3.0 min CN=81 Runoff=21.21 cfs 0.924 of
Subcatchment 31: Runoff Area=1.100 ac Runoff Depth=2.80"
Flow Length=340' Tc=4.2 min CN=65 Runoff=5.91 cfs 0.256 of
Subcatchment 32: Runoff Area=2.500 ac Runoff Depth=2.80"
Flow Length=400' Tc=4.7 min CN=65 Runoff=13.17 cfs 0.583 of
Subcatchment 33: Runoff Area=3.000 ac Runoff Depth=2.70"
Flow Length=650' Tc=6.9 min CN=64 Runoff=14.02 cfs 0.675 of
Subcatchment 34: Runoff Area=1.400 ac Runoff Depth=2.70"
Flow Length=300' Tc=5.3 min CN=64 Runoff=6.96 cfs 0.315 of
Subcatchment 40: Runoff Area=3.800 ac Runoff Depth=4.33"
Flow Length=100' Slope=0.3300 '/' Tc=3.0 min CN=80 Runoff=31.63 cfs 1.370 of
Subcatchment 41: Runoff Area=1.100 ac Runoff Depth=2.80"
Flow Length=300' Tc=4.2 min CN=65 Runoff=5.91 cfs 0.256 of

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 4
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Subcatchment 42: Runoff Area=1.600 ac Runoff Depth=2.89"
Flow Length=350' Tc=4.5 min CN=66 Runoff=8.79 cfs 0.386 of
Subcatchment 43: Runoff Area=1.700 ac Runoff Depth=2.80"
Flow Length=480' Tc=5.7 min CN=65 Runoff=8.62 cfs 0.396 of
Subcatchment 44: Runoff Area=1.000 ac Runoff Depth=2.89"
Flow Length=300' Tc=4.2 min CN=66 Runoff=5.55 cfs 0.241 of
Subcatchment 45: Runoff Area=1.800 ac Runoff Depth=2.80"
Flow Length=510' Tc=6.4 min CN=65 Runoff=8.89 cfs 0.419 of
Subcatchment 46: Runoff Area=2.100 ac Runoff Depth=2.70"
Flow Length=490' Tc=5.9 min CN=64 Runoff=10.21 cfs 0.473 of
Subcatchment 50: Runoff Area=4.700 ac Runoff Depth=3.59"
Flow Length=300' Slope=0.0300 '/' Tc=18.7 min CN=73 Runoff=19.54 cfs 1.407 of
Subcatchment 51: Runoff Area=3.900 ac Runoff Depth=2.80"
Flow Length=980' Tc=9.0 min CN=65 Runoff=17.45 cfs 0.909 of
Subcatchment 52: Runoff Area=2.200 ac Runoff Depth=2.70"
Flow Length=410' Tc=6.0 min CN=64 Runoff=10.65 cfs 0.495 of
Subcatchment 53: Runoff Area=3.600 ac Runoff Depth=2.80"
Flow Length=650' Tc=6.9 min CN=65 Runoff=17.44 cfs 0.839 of
Subcatchment A: Runoff Area=23.900 ac Runoff Depth=2.99"
Flow Length=800' Tc=27.5 min CN=67 Runoff=64.71 cfs 5.957 of
Subcatchment DP-41: Runoff Area=1.900 ac Runoff Depth=2.42"
Flow Length=380' Tc=3.7 min CN=61 Runoff=8.98 cfs 0.383 of
Subcatchment DP11: Runoff Area=7.900 ac Runoff Depth=2.42"
Flow Length=850' Tc=4.1 min CN=61 Runoff=36.77 cfs 1.591 of
Subcatchment DP12: Runoff Area=2.800 ac Runoff Depth=2.42"
Flow Length=690' Tc=4.0 min CN=61 Runoff=13.08 cfs 0.564 of
Subcatchment DP13: Runoff Area=1.000 ac Runoff Depth=2.42"
Flow Length=400' Tc=3.7 min CN=61 Runoff=4.73 cfs 0.201 of
Subcatchment DP14: Runoff Area=3.100 ac Runoff Depth=2.42"
Flow Length=510' Tc=5.2 min CN=61 Runoff=13.82 cfs 0.624 of
Subcatchment DP21: Runoff Area=7.500 ac Runoff Depth=2.42"
Flow Length=950' Tc=5.3 min CN=61 Runoff=33.31 cfs 1.511 of
Subcatchment DP22: Runoff Area=8.300 ac Runoff Depth=2.42"
Flow Length=1,020' Tc=4.6 min CN=61 Runoff=37.88 cfs 1.672 of

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 5
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Subcatchment DP31: Runoff Area=7.700 ac Runoff Depth=2.42"
Flow Length=1,000' Tc=5.3 min CN=61 Runoff=34.20 cfs 1.551 of
Subcatchment DP32: Runoff Area=4.800 ac Runoff Depth=2.42"
Flow Length=650' Tc=4.3 min CN=61 Runoff=22.17 cfs 0.967 of
Subcatchment DP33: Runoff Area=3.300 ac Runoff Depth=2.42"
Flow Length=750' Tc=4.1 min CN=61 Runoff=15.36 cfs 0.665 of
Subcatchment DP34: Runoff Area=2.900 ac Runoff Depth=2.42"
Flow Length=570' Tc=3.7 min CN=61 Runoff=13.71 cfs 0.584 of
Subcatchment DP35: Runoff Area=4.800 ac Runoff Depth=2.42"
Flow Length=800' Tc=5.0 min CN=61 Runoff=21.57 cfs 0.967 of
Subcatchment DP42: Runoff Area=3.700 ac Runoff Depth=2.42"
Flow Length=620' Tc=4.3 min CN=61 Runoff=17.09 cfs 0.745 of
Subcatchment DP43: Runoff Area=4.900 ac Runoff Depth=2.42"
Flow Length=600' Tc=4.0 min CN=61 Runoff=22.89 cfs 0.987 of
Subcatchment DP44: Runoff Area=6.700 ac Runoff Depth=2.42"
Flow Length=1,020' Tc=4.6 min CN=61 Runoff=30.58 cfs 1.350 of
Subcatchment DP45: Runoff Area=9.300 ac Runoff Depth=2.42"
Flow Length=1,090' Tc=5.3 min CN=61 Runoff=41.30 cfs 1.873 of
Subcatchment DP46: Runoff Area=5.300 ac Runoff Depth=2.42"
Flow Length=900' Tc=5.1 min CN=61 Runoff=23.72 cfs 1.068 of
Subcatchment DP51: Runoff Area=3.000 ac Runoff Depth=2.42"
Flow Length=600' Tc=4.0 min CN=61 Runoff=14.02 cfs 0.604 of
Subcatchment DP52: Runoff Area=2.700 ac Runoff Depth=2.42"
Flow Length=550' Tc=4.9 min CN=61 Runoff=12.18 cfs 0.544 of
Subcatchment DP53: Runoff Area=2.400 ac Runoff Depth=2.42"
Flow Length=540' Tc=4.8 min CN=61 Runoff=10.87 cfs 0.483 of
Reach 21A: Avg. Depth=2.19' Max Vet=4.55 fps Inflow=98.29 cfs 4.620 of
n=0.050 L=400.0' S=0.0175 '/' Capacity=196.70 cfs Outflow=95.53 cfs 4.620 of
Reach 21 B: Avg. Depth=1.69' Max Vet=4.00 fps Inflow=58.30 cfs 2.610 of
n=0.050 L=550.0' S=0.0182 '/' Capacity=131.36 cfs Outflow=54.56 cfs 2.610 of
Reach 21C: Avg. Depth=0.70' Max Vet=2.58 fps Inflow=10.56 cfs 0.443 of
n=0.050 L=550.0' S=0.0200 '/' Capacity=137.77 cfs Outflow=9.24 cfs 0.443 of
Reach 31A: Avg. Depth=1.96' Max Vet=3.82 fps Inflow=93.14 cfs 9.163 of
n=0.050 L=580.0' S=0.0121 T Capacity=217.56 cfs Outflow=88.72 cfs 9.163 of

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 6
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Reach 32A: Avg. Depth=1.01' Max Vet=2.96 fps Inflow=28.53 cfs 1.282 of
n=0.050 L=400.0' S=0.0150 '/' Capacity=103.36 cfs Outflow=26.92 cfs 1.282 of
Pond 34A: Peak Elev=233.48' Inflow=39.00 cfs 1.866 of
42.0" x 820.0' Culvert Outflow=39.00 cfs 1.866 of
Pond C11: Peak EIev=178.46' Inflow=47.65 cfs 2.131 of
36.0" x 88.0' Culvert Outflow=47.65 cfs 2.131 of
Pond C12: Peak EIev=177.00' Inflow=20.34 cfs 0.902 of
30.0" x 76.0' Culvert Outflow=20.34 cfs 0.902 of
Pond C13: Peak EIev=177.00' Inflow=31.30 cfs 1.411 of
30.0" x 66.0' Culvert Outflow=31.30 cfs 1.411 of
Pond C21A: Peak EIev=171.00' Inflow=95.53 cfs 4.620 of
42.0" x 48.0' Culvert Outflow=95.53 cfs 4.620 of
Pond C21 B: Peak EIev=202.00' Inflow=95.53 cfs 4.620 of
42.0" x 180.0' Culvert Outflow=95.53 cfs 4.620 of
Pond C31A: Peak EIev=206.47' Inflow=39.97 cfs 1.807 of
42.0" x 164.0' Culvert Outflow=39.97 cfs 1.807 of
Pond C31 B: Peak EIev=208.52' Inflow=39.97 cfs 1.807 of
42.0" x 40.0' Culvert Outflow=39.97 cfs 1.807 of
Pond C32: Peak EIev=206.48' Inflow=35.33 cfs 1.549 of
42.0" x 90.0' Culvert Outflow=35.33 cfs 1.549 of
Pond C33A: Peak EIev=226.88' Inflow=67.57 cfs 3.206 of
42.0" x 320.0' Culvert Outflow=67.57 cfs 3.206 of
Pond C33B: Peak EIev=227.58' Inflow=28.64 cfs 1.340 of
36.0" x 40.0' Culvert Outflow=28.64 cfs 1.340 of
Pond C34B: Peak EIev=235.29' Inflow=39.00 cfs 1.866 of
36.0" x 40.0' Culvert Outflow=39.00 cfs 1.866 of
Pond C35: Peak EIev=207.15' Inflow=88.72 cfs 9.163 of
48.0" x 88.0' Culvert Outflow=88.72 cfs 9.163 of
Pond C41A: Peak EIev=148.83' Inflow=40.71 cfs 1.770 of
42.0" x 140.0' Culvert Outflow=40.71 cfs 1.770 of
Pond C41 B: Peak EIev=157.36' Inflow=14.88 cfs 0.639 of
48.0" x 170.0' Culvert Outflow=14.88 cfs 0.639 of
Pond C41C: Peak EIev=163.36' Inflow=14.88 cfs 0.639 of
48.0" x 200.0' Culvert Outflow=14.88 cfs 0.639 of

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 7
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Pond C41 D: Peak Elev=165.51' Inflow=14.88 cfs 0.639 of
36.0" x 48.0' Culvert Outflow=14.88 cfs 0.639 of
Pond C42: Peak EIev=164.09' Inflow=25.87 cfs 1.131 of
36.0" x 48.0' Culvert Outflow=25.87 cfs 1.131 of
Pond C43A: Peak EIev=156.21' Inflow=150.79 cfs 6.807 of
48.0" x 120.0' Culvert Outflow=150.79 cfs 6.807 of
Pond C43B: Peak EIev=166.36' Inflow=31.29 cfs 1.383 of
36.0" x 48.0' Culvert Outflow=31.29 cfs 1.383 of
Pond C43C: Peak EIev=173.92' Inflow=119.77 cfs 5.424 of
48.0" x 300.0' Culvert Outflow=119.77 cfs 5.424 of
Pond C43D: Peak EIev=178.42' Inflow=119.77 cfs 5.424 of
48.0" x 300.0' Culvert Outflow=119.77 cfs 5.424 of
Pond C43E: Peak EIev=180.34' Inflow=83.98 cfs 3.833 of
48.0" x 72.0' Culvert Outflow=83.98 cfs 3.833 of
Pond C43F: Peak EIev=183.07' Inflow=83.98 cfs 3.833 of
48.0" x 300.0' Culvert Outflow=83.98 cfs 3.833 of
Pond C43G: Peak EIev=186.27' Inflow=33.88 cfs 1.540 of
42.0" x 348.0' Culvert Outflow=33.88 cfs 1.540 of
Pond C43H: Peak EIev=188.37' Inflow=33.88 cfs 1.540 of
42.0" x 230.0' Culvert Outflow=33.88 cfs 1.540 of
Pond C44: Peak EIev=179.53' Inflow=36.11 cfs 1.591 of
36.0" x 40.0' Culvert Outflow=36.11 cfs 1.591 of
Pond C45: Peak EIev=185.67' Inflow=50.11 cfs 2.293 of
36.0" x 40.0' Culvert Outflow=50.11 cfs 2.293 of
Pond C46: Peak EIev=191.50' Inflow=33.88 cfs 1.540 of
36.0" x 40.0' Culvert Outflow=33.88 cfs 1.540 of
Pond C51: Peak EIev=163.26' Inflow=29.31 cfs 1.513 of
36.0" x 48.0' Culvert Outflow=29.31 cfs 1.513 of
Pond C52: Peak EIev=155.95' Inflow=50.66 cfs 2.361 of
42.0" x 48.0' Culvert Outflow=50.66 cfs 2.361 of
Pond SBAW: Sed Basin No. 1W Peak EIev=176.48' Storage=221,023 cf Inflow=120.26 cfs 5.516 of
Primary=0.47 cfs 0.670 of Secondary=0.00 cfs 0.000 of Outflow=0.47 cfs 0.670 of
Pond SB-2W: Sed Basin No. 2W Peak EIev=169.51' Storage=222,009 cf Inflow=111.94 cfs 5.605 of
Primary=0.53 cfs 0.751 of Secondary=0.00 cfs 0.000 of Outflow=0.53 cfs 0.751 of

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type/1 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 8
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Pond SB-3W: Sed Basin No. 3W Peak EIev=206.47' Storage=325,273 cf Inflow=171.62 cfs 13.444 of
Primary=18.14 cfs 6.796 of Secondary=0.00 cfs 0.000 of Outflow=18.14 cfs 6.796 of
Pond SB-4W: Sed Basin No. 4W Peak EIev=148.83' Storage=408,983 cf Inflow=220.07 cfs 9.947 of
Primary=0.60 cfs 0.846 of Secondary=0.00 cfs 0.000 of Outflow=0.60 cfs 0.846 of
Pond SB-5W: Sed Basin No. 5W Peak EIev=148.50' Storage=205,592 cf Inflow=92.03 cfs 5.282 of
Primary=0.58 cfs 0.837 of Secondary=0.00 cfs 0.000 of Outflow=0.58 cfs 0.837 of
Total Runoff Area = 174.900 ac Runoff Volume = 39.794 of Average Runoff Depth = 2.73"
94.11% Pervious Area = 164.600 ac 5.89% Impervious Area = 10.300 ac

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 9
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Subcatchment 10:
Runoff = 25.41 cfs @ 11.92 hrs, Volume= 1.072 af, Depth= 4.43"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
1.200
61
>75% Grass cover, Good, HSG B
1.400
98
Sed. Basin No. 1 W - Riser Elev.
0.300
85
Gravel roads, HSG B
2.900
81
Weighted Average
1.500
Pervious Area
1.400
Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
2.0 60 0.3300 0.51 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
Subcatchment 11:
Runoff = 11.44 cfs @ 11.98 hrs, Volume= 0.540 af, Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.100 61 >75% Grass cover, Good, HSG B
0.300 85 Gravel roads, HSG B
2.400 64 Weighted Average
2.400 Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
1.8
400
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
M.
Runoff =
550 Total
Subcatchment 12:
7.40 cfs @ 11.97 hrs, Volume= 0.338 af, Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 10
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Area (ac) CN Description
1.300 61 >75% Grass cover, Good, HSG B
0.200 85 Gravel roads, HSG B
1.500 64 Weighted Average
1.500 Pervious Area
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
4.6 150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.9 200
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
5.5
Runoff =
350 Total
Subcatchment 13:
12.93 cfs @ 11.97 hrs, Volume= 0.585 af, Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.300
61 >75% Grass cover, Good, HSG B
0.300
85 Gravel roads, HSG B
2.600
64 Weighted Average
2.600
Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.7
150
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
5.3
Runoff =
300 Total
Subcatchment 20:
23.32 cfs @ 11.94 hrs, Volume= 0.985 af, Depth= 3.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.100 61 >75% Grass cover, Good, HSG B
1.100 98 Sed. Basin No. 2W - Riser Elev.
3.200
74 Weighted Average
2.100
Pervious Area
1.100
Impervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 11
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.0 100 0.3300 0.56 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
Subcatchment 21:
Runoff = 10.82 cfs @ 11.97 hrs, Volume= 0.499 af, Depth= 2.61"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.100 61 >75% Grass cover, Good, HSG B
0.200 85 Gravel roads, HSG B
2.300 63 Weighted Average
2.300 Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.8 200 0.2500 0.58 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
Subcatchment 22:
Runoff = 11.81 cfs @ 11.94 hrs, Volume= 0.495 af, Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
1.900 61 >75% Grass cover, Good, HSG B
0.300 85 Gravel roads, HSG B
2.200 64 Weighted Average
2.200 Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.3 100 0.2500 0.50 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
Subcatchment 23:
Runoff = 10.56 cfs @ 11.94 hrs, Volume= 0.443 af, Depth= 2.80"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 12
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Area (ac) CN Description
1.600 61 >75% Grass cover, Good, HSG B
0.300 85 Gravel roads, HSG B
1.900 65 Weighted Average
1.900 Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.3 100 0.2500 0.50 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
Subcatchment 30:
Runoff = 21.21 cfs @ 11.94 hrs, Volume= 0.924 af, Depth= 4.43"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac)
CN
Description
1.100
61
>75% Grass cover, Good, HSG B
1.200
98
Sed. Basin No. 3W - Riser Elev.
0.200
85
Gravel roads, HSG B
2.500
81
Weighted Average
1.300
Pervious Area
1.200
Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.0 100 0.3300 0.56 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
Subcatchment 31:
Runoff = 5.91 cfs @ 11.95 hrs, Volume= 0.256 af, Depth= 2.80"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
0.900 61 >75% Grass cover, Good, HSG B
0.200 85 Gravel roads, HSG B
1.100 65 Weighted Average
1.100 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 13
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
3.0 90
0.2500
0.49
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
1.2 250
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
4.2
Runoff =
340 Total
Subcatchment 32:
13.17 cfs @ 11.96 hrs, Volume= 0.583 af, Depth= 2.80"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.100 61 >75% Grass cover, Good, HSG B
0.400 85 Gravel roads, HSG B
2.500 65 Weighted Average
2.500 Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
1.4
300
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
4.7
Runoff =
400 Total
Subcatchment 33:
14.02 cfs @ 11.99 hrs, Volume= 0.675 af, Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.600 61 >75% Grass cover, Good, HSG B
0.400 85 Gravel roads, HSG B
3.000 64 Weighted Average
3.000 Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
2.3
500
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
6.9 650 Total

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 14
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Subcatchment 34:
Runoff = 6.96 cfs @ 11.97 hrs, Volume= 0.315 af, Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
1.200 61 >75% Grass cover, Good, HSG B
0.200 85 Gravel roads, HSG B
1.400 64 Weighted Average
1.400 Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.7
150
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
5.3
Runoff =
300 Total
Subcatchment 40:
31.63 cfs @ 11.94 hrs, Volume= 1.370 af, Depth= 4.33"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
1.700
61
>75% Grass cover, Good, HSG B
1.800
98
Sed. Basin No. 4W - Riser Elev.
0.300
85
Gravel roads, HSG B
3.800
80
Weighted Average
2.000
Pervious Area
1.800
Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.0 100 0.3300 0.56 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
Subcatchment 41:
Runoff = 5.91 cfs @ 11.95 hrs, Volume= 0.256 af, Depth= 2.80"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 15
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Area (ac) CN Description
0.900 61 >75% Grass cover, Good, HSG B
0.200 85 Gravel roads, HSG B
1.100 65 Weighted Average
1.100 Pervious Area
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
3.3 100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.9 200
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
4.2
Runoff =
300 Total
Subcatchment 42:
8.79 cfs @ 11.96 hrs, Volume= 0.386 af, Depth= 2.89"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
1.300
61 >75% Grass cover, Good, HSG B
0.300
85 Gravel roads, HSG B
1.600
66 Weighted Average
1.600
Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
1.2
250
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
4.5
Runoff =
350 Total
Subcatchment 43:
8.62 cfs @ 11.97 hrs, Volume= 0.396 af, Depth= 2.80"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN D
1.400 61 >75% Grass cover, Good, HSG B
0.300 85 Gravel roads, HSG B
1.700 65 Weighted Average
1.700 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 16
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
4.1 130
0.2500
0.53
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
1.6 350
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
5.7
Runoff =
480 Total
Subcatchment 44:
5.55 cfs @ 11.95 hrs, Volume= 0.241 af, Depth= 2.89"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
0.800 61 >75% Grass cover, Good, HSG B
0.200 85 Gravel roads, HSG B
1.000 66 Weighted Average
1.000 Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.9
200
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
4.2
Runoff =
300 Total
Subcatchment 45:
8.89 cfs @ 11.98 hrs, Volume= 0.419 af, Depth= 2.80"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
1.500 61 >75% Grass cover, Good, HSG B
0.300 85 Gravel roads, HSG B
1.800 65 Weighted Average
1.800 Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.8
160
0.2500
0.55
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
1.6
350
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
6.4 510 Total

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 17
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Subcatchment 46:
Runoff = 10.21 cfs @ 11.98 hrs, Volume= 0.473 af, Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
1.800 61 >75% Grass cover, Good, HSG B
0.300 85 Gravel roads, HSG B
2.100 64 Weighted Average
2.100 Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.3
140
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
1.6
350
0.0200
3.62
28.98 Channel Flow,
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
5.9
Runoff =
490 Total
Subcatchment 50:
19.54 cfs @ 12.11 hrs, Volume= 1.407 af, Depth= 3.59"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.800
61
>75% Grass cover, Good, HSG B
0.900
98
Sed. Basin No. 5W - Riser Elev.
1.000
85
Gravel roads, HSG B
4.700
73
Weighted Average
3.800
Pervious Area
0.900
Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
18.7 300 0.0300 0.27 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
Subcatchment 51:
Runoff = 17.45 cfs @ 12.01 hrs, Volume= 0.909 af, Depth= 2.80"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 18
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Area (ac) CN Description
3.300 61 >75% Grass cover, Good, HSG B
0.600 85 Gravel roads, HSG B
3.900 65 Weighted Average
3.900 Pervious Area
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
5.3 180
0.2500
0.57
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
3.7 800
0.0200
3.62
28.98 Channel Flow, Perimeter Channel
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
Runoff =
980 Total
Subcatchment 52:
10.65 cfs @ 11.98 hrs, Volume= 0.495 af, Depth= 2.70"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
1.900
61 >75% Grass cover, Good, HSG B
0.300
85 Gravel roads, HSG B
2.200
64 Weighted Average
2.200
Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.8
160
0.2500
0.55
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
1.2
250
0.0200
3.62
28.98 Channel Flow, Perimeter Channel
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
6.0
Runoff =
410 Total
Subcatchment 53:
17.44 cfs @ 11.99 hrs, Volume= 0.839 af, Depth= 2.80"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN D
3.000 61 >75% Grass cover, Good, HSG B
0.600 85 Gravel roads, HSG B
3.600 65 Weighted Average
3.600 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 19
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc Length
Slope
Velocity
Capacity Description
(min) (feet)
(ft/ft)
(ft/sec)
(cfs)
4.6 150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
2.3 500
0.0200
3.62
28.98 Channel Flow, Perimeter Channel
Area= 8.0 sf Perim= 10.0' r= 0.80' n= 0.050
Runoff =
650 Total
Subcatchment A:
64.71 cfs @ 12.22 hrs, Volume= 5.957 af, Depth= 2.99"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
20.000 61 >75% Grass cover, Good, HSG B
3.900 98 Paved parking & roofs
23.900 67 Weighted Average
20.000 Pervious Area
3.900 Impervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
21.9
300
0.0200
0.23
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
5.6
500
0.0100
1.50
Shallow Concentrated Flow,
Grassed Waterwav Kv= 15.0 fDs
27.5 800 Total
Subcatchment DP-41:
Runoff = 8.98 cfs @ 11.95 hrs, Volume= 0.383 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN D
1.900 61 >75% Grass cover, Good, HSG B
1.900 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.4
200
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.0
80
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
3.7 380 Total

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 20
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Subcatchment DP11:
Runoff = 36.77 cfs @ 11.96 hrs, Volume= 1.591 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
7.900 61 >75% Grass cover, Good, HSG B
7.900 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.6
300
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.2
450
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
4.1
Runoff =
850 Total
Subcatchment DP12:
13.08 cfs @ 11.95 hrs, Volume= 0.564 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.800 61 >75% Grass cover, Good, HSG B
2.800 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.6
350
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.1
240
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
M
Runoff =
690 Total
Subcatchment DP13:
4.73 cfs @ 11.95 hrs, Volume= 0.201 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 21
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Area (ac) CN Description
1.000 61 >75% Grass cover, Good, HSG B
1.000 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.3
160
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.1
140
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
3.7
Runoff =
400 Total
Subcatchment DP14:
13.82 cfs @ 11.97 hrs, Volume= 0.624 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
3.100 61 >75% Grass cover, Good, HSG B
3.100 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.6
300
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.0
60
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
5.2
Runoff =
510 Total
Subcatchment DP21:
33.31 cfs @ 11.97 hrs, Volume= 1.511 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN D
7.500 61 >75% Grass cover, Good, HSG B
7.500 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 22
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.4
200
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.3
600
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
5.3
Runoff =
950 Total
Subcatchment DP22:
37.88 cfs @ 11.96 hrs, Volume= 1.672 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
8.300 61 >75% Grass cover, Good, HSG B
8.300 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.8
120
0.2500
0.52
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.5
250
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.3
650
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
4.6 1,020 Total
Subcatchment DP31:
Runoff = 34.20 cfs @ 11.97 hrs, Volume= 1.551 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
7.700 61 >75% Grass cover, Good, HSG B
7.700 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 23
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.4
200
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.3
650
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
5.3 1,000 Total
Subcatchment DP32:
Runoff = 22.17 cfs @ 11.96 hrs, Volume= 0.967 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
4.800 61 >75% Grass cover, Good, HSG B
4.800 Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
3.8 120 0.2500 0.52 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.3 150 0.0400 9.00 3.14 Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.2 380 0.2500 38.64 68.28 Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
4.3 650 Total
Subcatchment DP33:
Runoff = 15.36 cfs @ 11.96 hrs, Volume= 0.665 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
3.300 61 >75% Grass cover, Good, HSG B
3.300 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 24
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.6
300
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.2
350
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
4.1
Runoff =
750 Total
Subcatchment DP34:
13.71 cfs @ 11.95 hrs, Volume= 0.584 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.900 61 >75% Grass cover, Good, HSG B
2.900 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.2
120
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.2
350
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
3.7
Runoff =
570 Total
Subcatchment DP35:
21.57 cfs @ 11.97 hrs, Volume= 0.967 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
4.800 61 >75% Grass cover, Good, HSG B
4.800 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 25
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.1
50
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.3
600
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
5.0
Runoff =
800 Total
Subcatchment DP42:
17.09 cfs @ 11.96 hrs, Volume= 0.745 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
3.700 61 >75% Grass cover, Good, HSG B
3.700 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.8
120
0.2500
0.52
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.4
200
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.1
300
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
4.3
Runoff =
620 Total
Subcatchment DP43:
22.89 cfs @ 11.95 hrs, Volume= 0.987 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
4.900 61 >75% Grass cover, Good, HSG B
4.900 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 26
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.6
300
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.1
200
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
M
Runoff =
600 Total
Subcatchment DP44:
30.58 cfs @ 11.96 hrs, Volume= 1.350 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
6.700 61 >75% Grass cover, Good, HSG B
6.700 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.8
120
0.2500
0.52
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.5
250
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.3
650
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
4.6 1,020 Total
Subcatchment DP45:
Runoff = 41.30 cfs @ 11.97 hrs, Volume= 1.873 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
9.300 61 >75% Grass cover, Good, HSG B
9.300 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 27
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.4
200
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.3
740
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
5.3 1,090 Total
Subcatchment DP46:
Runoff = 23.72 cfs @ 11.97 hrs, Volume= 1.068 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
5.300 61 >75% Grass cover, Good, HSG B
5.300 Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
4.6 150 0.2500 0.54 Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.2 100 0.0400 9.00 3.14 Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.3 650 0.2500 38.64 68.28 Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
5.1 900 Total
Subcatchment DP51:
Runoff = 14.02 cfs @ 11.95 hrs, Volume= 0.604 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
3.000 61 >75% Grass cover, Good, HSG B
3.000 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 28
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
3.3
100
0.2500
0.50
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.6
300
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.1
200
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
M
Runoff =
600 Total
Subcatchment DP52:
12.18 cfs @ 11.96 hrs, Volume= 0.544 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.700 61 >75% Grass cover, Good, HSG B
2.700 Pervious Area
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.6
150
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.2
100
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.1
300
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
W.
Runoff =
550 Total
Subcatchment DP53:
10.87 cfs @ 11.96 hrs, Volume= 0.483 af, Depth= 2.42"
Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs
Type II 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Area (ac) CN Description
2.400 61 >75% Grass cover, Good, HSG B
2.400 Pervious Area

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 29
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Tc
Length
Slope
Velocity
Capacity
Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
4.3
140
0.2500
0.54
Sheet Flow, Sheet Flow
Grass: Short n= 0.150 P2= 3.70"
0.4
200
0.0400
9.00
3.14
Circular Channel (pipe), Rain Gutter
Diam= 8.0" Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010
0.1
200
0.2500
38.64
68.28
Circular Channel (pipe), Down Pipe
Diam= 18.0" Area= 1.8 sf Perim= 4.7' r= 0.38' n= 0.010
4.8 540 Total
Reach 21 A:
[61 ] Hint: Submerged 22% of Reach 21 B bottom
Inflow Area = 22.200 ac, Inflow Depth = 2.50" for Johnston 25Yr 24Hr event
Inflow = 98.29 cfs @ 11.98 hrs, Volume= 4.620 of
Outflow = 95.53 cfs @ 11.99 hrs, Volume= 4.620 af, Atten= 3%, Lag= 1.0 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 4.55 fps, Min. Travel Time= 1.5 min
Avg. Velocity = 1.30 fps, Avg. Travel Time= 5.1 min
Peak Storage= 8,398 cf @ 11.99 hrs, Average Depth at Peak Storage= 2.19'
Bank -Full Depth= 3.00', Capacity at Bank -Full= 196.70 cfs
3.00' x 3.00' deep channel, n= 0.050
Side Slope Z-value= 3.0 '/' Top Width= 21.00'
Length= 400.0' Slope= 0.0175 '/'
Inlet Invert= 211.00', Outlet Invert= 204.00'
Reach 21 B:
[61 ] Hint: Submerged 15% of Reach 21 C bottom
Inflow Area = 12.400 ac, Inflow Depth = 2.53" for Johnston 25Yr 24Hr event
Inflow = 58.30 cfs @ 11.96 hrs, Volume= 2.610 of
Outflow = 54.56 cfs @ 11.98 hrs, Volume= 2.61Oaf, Atten= 6%, Lag= 1.5 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 4.00 fps, Min. Travel Time= 2.3 min
Avg. Velocity = 1.13 fps, Avg. Travel Time= 8.1 min
Peak Storage= 7,505 cf @ 11.98 hrs, Average Depth at Peak Storage= 1.69'
Bank -Full Depth= 2.50', Capacity at Bank -Full= 131.36 cfs

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 30
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
3.00' x 2.50' deep channel, n= 0.050
Side Slope Z-value= 3.0 7' Top Width= 18.00'
Length= 550.0' Slope= 0.0182 7'
Inlet Invert= 221.00', Outlet Invert= 211.00'
Inflow Area =
Inflow =
Outflow =
Reach 21 C:
1.900 ac, Inflow Depth = 2.80" for Johnston 25Yr 24Hr event
10.56 cfs @ 11.94 hrs, Volume= 0.443 of
9.24 cfs @ 11.97 hrs, Volume= 0.443 af, Atten= 12%, Lag= 1.9 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 2.58 fps, Min. Travel Time= 3.6 min
Avg. Velocity = 0.70 fps, Avg. Travel Time= 13.1 min
Peak Storage= 1,968 cf @ 11.97 hrs, Average Depth at Peak Storage= 0.70'
Bank -Full Depth= 2.50', Capacity at Bank -Full= 137.77 cfs
3.00' x 2.50' deep channel, n= 0.050
Side Slope Z-value= 3.0 7' Top Width= 18.00'
Length= 550.0' Slope= 0.0200 7'
Inlet Invert= 232.00', Outlet Invert= 221.00'
Reach 31 A:
Inflow Area = 39.300 ac, Inflow Depth = 2.80" for Johnston 25Yr 24Hr event
Inflow = 93.14 cfs @ 11.99 hrs, Volume= 9.163 of
Outflow = 88.72 cfs @ 12.02 hrs, Volume= 9.163 af, Atten= 5%, Lag= 1.9 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 3.82 fps, Min. Travel Time= 2.5 min
Avg. Velocity = 1.23 fps, Avg. Travel Time= 7.9 min
Peak Storage= 13,478 cf @ 12.02 hrs, Average Depth at Peak Storage= 1.96'
Bank -Full Depth= 3.00', Capacity at Bank -Full= 217.56 cfs

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 31
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
6.00' x 3.00' deep channel, n= 0.050
Side Slope Z-value= 3.0 7' Top Width= 24.00'
Length= 580.0' Slope= 0.0121 T
Inlet Invert= 219.00', Outlet Invert= 212.00'
f
Inflow Area =
Inflow =
Outflow =
Reach 32A:
6.200 ac, Inflow Depth = 2.48" for Johnston 25Yr 24Hr event
28.53 cfs @ 11.97 hrs, Volume= 1.282 of
26.92 cfs @ 11.99 hrs, Volume= 1.282 af, Atten= 6%, Lag= 1.4 min
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Max. Velocity= 2.96 fps, Min. Travel Time= 2.2 min
Avg. Velocity = 0.74 fps, Avg. Travel Time= 9.1 min
Peak Storage= 3,634 cf @ 11.99 hrs, Average Depth at Peak Storage= 1.01'
Bank -Full Depth= 2.00', Capacity at Bank -Full= 103.36 cfs
6.00' x 2.00' deep channel, n= 0.050
Side Slope Z-value= 3.0 7' Top Width= 18.00'
Length= 400.0' Slope= 0.0150 '/'
Inlet Invert= 240.00', Outlet Invert= 234.00'
f
Pond 34A:
Inflow Area =
9.100 ac,
Inflow Depth
= 2.46" for Johnston 25Yr 24Hr event
Inflow =
39.00 cfs @
11.97 hrs,
Volume= 1.866 of
Outflow =
39.00 cfs @
11.97 hrs,
Volume= 1.866 af, Atten= 0%, Lag= 0.0 min
Primary =
39.00 cfs @
11.97 hrs,
Volume= 1.866 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 233.48' @ 11.97 hrs
Flood Elev= 236.00'
Device Routing Invert Outlet Devices
#1 Primary 231.00' 42.0" x 820.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 223.50' S= 0.0091 T Cc= 0.900
n= 0.013 Corrugated PE, smooth interior

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 32
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Primary OutFlow Max=38.92 cfs @ 11.97 hrs HW=233.47' TW=226.87' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 38.92 cfs @ 5.35 fps)
Pond C11:
Inflow Area = 10.300 ac, Inflow Depth = 2.48" for Johnston 25Yr 24Hr event
Inflow = 47.65 cfs @ 11.96 hrs, Volume= 2.131 of
Outflow = 47.65 cfs @ 11.96 hrs, Volume= 2.131 af, Atten= 0%, Lag= 0.0 min
Primary = 47.65 cfs @ 11.96 hrs, Volume= 2.131 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 178.46' @ 11.96 hrs
Flood Elev= 196.00'
Device Routing Invert Outlet Devices
#1 Primary 175.00' 36.0" x 88.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 173.00' S= 0.0227 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=47.62 cfs @ 11.96 hrs HW=178.46' TW=173.65' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 47.62 cfs @ 6.74 fps)
Pond C12:
Inflow Area =
4.300 ac,
Inflow Depth
= 2.52" for Johnston 25Yr 24Hr event
Inflow =
20.34 cfs @
11.96 hrs,
Volume= 0.902 of
Outflow =
20.34 cfs @
11.96 hrs,
Volume= 0.902 af, Atten= 0%, Lag= 0.0 min
Primary =
20.34 cfs @
11.96 hrs,
Volume= 0.902 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 177.00' @ 11.96 hrs
Flood Elev= 190.50'
Device Routinq Invert Outlet Devices
#1 Primary 175.00' 30.0" x 76.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 173.00' S= 0.0263 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=20.31 cfs @ 11.96 hrs HW=177.00' TW=173.64' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 20.31 cfs @ 4.82 fps)
Pond C13:
Inflow Area = 6.700 ac, Inflow Depth = 2.53" for Johnston 25Yr 24Hr event
Inflow = 31.30 cfs @ 11.97 hrs, Volume= 1.411 of
Outflow = 31.30 cfs @ 11.97 hrs, Volume= 1.411 af, Atten= 0%, Lag= 0.0 min
Primary = 31.30 cfs @ 11.97 hrs, Volume= 1.411 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 33
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Peak Elev= 177.00' @ 11.97 hrs
Flood Elev= 184.00'
Device Routing Invert Outlet Devices
#1 Primary 174.00' 30.0" x 66.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 172.00' S= 0.0303 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=31.22 cfs @ 11.97 hrs HW=176.99' TW=173.70' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 31.22 cfs @ 6.36 fps)
Pond C21A:
Inflow Area = 22.200 ac, Inflow Depth = 2.50" for Johnston 25Yr 24Hr event
Inflow = 95.53 cfs @ 11.99 hrs, Volume= 4.620 of
Outflow = 95.53 cfs @ 11.99 hrs, Volume= 4.620 af, Atten= 0%, Lag= 0.0 min
Primary = 95.53 cfs @ 11.99 hrs, Volume= 4.620 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 171.00' @ 11.99 hrs
Flood Elev= 180.00'
Device Routing Invert Outlet Devices
#1 Primary 165.00' 42.0" x 48.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 164.00' S= 0.0208 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=95.31 cfs @ 11.99 hrs HW=170.98' TW=165.94' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 95.31 cfs @ 9.91 fps)
Pond C21 B:
Inflow Area = 22.200 ac, Inflow Depth = 2.50" for Johnston 25Yr 24Hr event
Inflow = 95.53 cfs @ 11.99 hrs, Volume= 4.620 of
Outflow = 95.53 cfs @ 11.99 hrs, Volume= 4.620 af, Atten= 0%, Lag= 0.0 min
Primary = 95.53 cfs @ 11.99 hrs, Volume= 4.620 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 202.00' @ 11.99 hrs
Flood Elev= 204.00'
Device Routing Invert Outlet Devices
#1 Primary 196.00' 42.0" x 180.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 174.00' S= 0.1222 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=95.31 cfs @ 11.99 hrs HW=201.98' TW=170.98' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 95.31 cfs @ 9.91 fps)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 34
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Pond C31A:
[80] Warning: Exceeded Pond C31 B by 0.08' @ 24.31 hrs (0.02 cfs 0.000 af)
Inflow Area =
8.800 ac,
Inflow Depth = 2.46"
for Johnston 25Yr 24Hr event
Inflow =
39.97 cfs @
11.97 hrs, Volume=
1.807 of
Outflow =
39.97 cfs @
11.97 hrs, Volume=
1.807 af, Atten= 0%, Lag= 0.0 min
Primary =
39.97 cfs @
11.97 hrs, Volume=
1.807 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 206.47' @ 13.17 hrs
Flood Elev= 214.00'
Device Routing Invert Outlet Devices
#1 Primary 202.00' 42.0" x 164.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 198.00' S= 0.0244 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=39.88 cfs @ 11.97 hrs HW=204.51' TW=202.33' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 39.88 cfs @ 5.40 fps)
Pond C31 B:
Inflow Area =
8.800 ac,
Inflow Depth
= 2.46" for Johnston 25Yr 24Hr event
Inflow =
39.97 cfs @
11.97 hrs,
Volume= 1.807 of
Outflow =
39.97 cfs @
11.97 hrs,
Volume= 1.807 af, Atten= 0%, Lag= 0.0 min
Primary =
39.97 cfs @
11.97 hrs,
Volume= 1.807 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 208.52' @ 11.97 hrs
Flood Elev= 214.00'
Device Routing Invert Outlet Devices
#1 Primary 206.00' 42.0" x 40.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 204.00' S= 0.0500 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=39.88 cfs @ 11.97 hrs HW=208.51' TW=204.51' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 39.88 cfs @ 5.40 fps)
Pond C32:
Inflow Area =
7.300 ac,
Inflow Depth
= 2.55" for Johnston 25Yr 24Hr event
Inflow =
35.33 cfs @
11.96 hrs,
Volume= 1.549 of
Outflow =
35.33 cfs @
11.96 hrs,
Volume= 1.549 af, Atten= 0%, Lag= 0.0 min
Primary =
35.33 cfs @
11.96 hrs,
Volume= 1.549 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 206.48' @ 13.17 hrs
Flood Elev= 222.00'

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 35
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Device Routing Invert Outlet Devices
#1 Primary 204.00' 42.0" x 90.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 198.00' S= 0.0667 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=35.29 cfs @ 11.96 hrs HW=206.33' TW=202.22' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 35.29 cfs @ 5.19 fps)
Pond C33A:
Inflow Area =
15.400 ac,
Inflow Depth
= 2.50" for Johnston 25Yr 24Hr event
Inflow =
67.57 cfs @
11.97 hrs,
Volume= 3.206 of
Outflow =
67.57 cfs @
11.97 hrs,
Volume= 3.206 af, Atten= 0%, Lag= 0.0 min
Primary =
67.57 cfs @
11.97 hrs,
Volume= 3.206 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 226.88' @ 11.97 hrs
Flood Elev= 234.00'
Device Routing Invert Outlet Devices
#1 Primary 223.00' 42.0" x 320.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 220.00' S= 0.0094 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=67.52 cfs @ 11.97 hrs HW=226.87' TW=220.85' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 67.52 cfs @ 7.02 fps)
Pond C33B:
Inflow Area =
6.300 ac,
Inflow Depth
= 2.55" for Johnston 25Yr 24Hr event
Inflow =
28.64 cfs @
11.97 hrs,
Volume= 1.340 of
Outflow =
28.64 cfs @
11.97 hrs,
Volume= 1.340 af, Atten= 0%, Lag= 0.0 min
Primary =
28.64 cfs @
11.97 hrs,
Volume= 1.340 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 227.58' @ 11.97 hrs
Flood Elev= 234.00'
Device Routing Invert Outlet Devices
#1 Primary 224.50' 36.0" x 40.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 223.50' S= 0.0250 '/' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=28.59 cfs @ 11.97 hrs HW=227.57' TW=226.86' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 28.59 cfs @ 4.04 fps)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 36
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Pond C34B:
[61] Hint: Submerged 21% of Reach 32A bottom
Inflow Area =
9.100 ac,
Inflow Depth = 2.46"
for Johnston 25Yr 24Hr event
Inflow =
39.00 cfs @
11.97 hrs, Volume=
1.866 of
Outflow =
39.00 cfs @
11.97 hrs, Volume=
1.866 af, Atten= 0%, Lag= 0.0 min
Primary =
39.00 cfs @
11.97 hrs, Volume=
1.866 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 235.29' @ 11.97 hrs
Flood Elev= 236.00'
Device Routing Invert Outlet Devices
#1 Primary 232.50' 36.0" x 40.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 231.50' S= 0.0250 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=38.92 cfs @ 11.97 hrs HW=235.29' TW=233.47' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 38.92 cfs @ 5.68 fps)
Pond C35:
Inflow Area = 39.300 ac, Inflow Depth = 2.80" for Johnston 25Yr 24Hr event
Inflow = 88.72 cfs @ 12.02 hrs, Volume= 9.163 of
Outflow = 88.72 cfs @ 12.02 hrs, Volume= 9.163 af, Atten= 0%, Lag= 0.0 min
Primary = 88.72 cfs @ 12.02 hrs, Volume= 9.163 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 207.15' @ 12.02 hrs
Flood Elev= 220.00'
Device Routing Invert Outlet Devices
#1 Primary 203.00' 48.0" x 88.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 201.00' S= 0.0227 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=88.66 cfs @ 12.02 hrs HW=207.15' TW=202.96' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 88.66 cfs @ 7.06 fps)
Pond C41 A:
[87] Warning: Oscillations may require Finer Routing or smaller dt
Inflow Area =
8.300 ac,
Inflow Depth
= 2.56"
for Johnston 25Yr 24Hr event
Inflow =
40.71 cfs @
11.96 hrs,
Volume=
1.770 of
Outflow =
40.71 cfs @
11.96 hrs,
Volume=
1.770 af, Atten= 0%, Lag= 0.0 min
Primary =
40.71 cfs @
11.96 hrs,
Volume=
1.770 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 37
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Peak Elev= 148.83' @ 24.09 hrs
Flood Elev= 160.00'
Device Routing Invert Outlet Devices
#1 Primary 146.00' 42.0" x 140.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 142.00' S= 0.0286 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=40.58 cfs @ 11.96 hrs HW=148.54' TW=144.39' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 40.58 cfs @ 5.43 fps)
Pond C41 B:
Inflow Area = 3.000 ac, Inflow Depth = 2.56" for Johnston 25Yr 24Hr event
Inflow = 14.88 cfs @ 11.95 hrs, Volume= 0.639 of
Outflow = 14.88 cfs @ 11.95 hrs, Volume= 0.639 af, Atten= 0%, Lag= 0.0 min
Primary = 14.88 cfs @ 11.95 hrs, Volume= 0.639 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 157.36' @ 11.95 hrs
Flood Elev= 170.00'
Device Routing Invert Outlet Devices
#1 Primary 156.00' 48.0" x 170.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 146.50' S= 0.0559 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=14.85 cfs @ 11.95 hrs HW=157.35' TW=148.54' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 14.85 cfs @ 3.96 fps)
Pond C41 C:
Inflow Area = 3.000 ac, Inflow Depth = 2.56" for Johnston 25Yr 24Hr event
Inflow = 14.88 cfs @ 11.95 hrs, Volume= 0.639 of
Outflow = 14.88 cfs @ 11.95 hrs, Volume= 0.639 af, Atten= 0%, Lag= 0.0 min
Primary = 14.88 cfs @ 11.95 hrs, Volume= 0.639 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 163.36' @ 11.95 hrs
Flood Elev= 170.00'
Device Routing Invert Outlet Devices
#1 Primary 162.00' 48.0" x 200.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 156.50' S= 0.0275 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=14.85 cfs @ 11.95 hrs HW=163.35' TW=157.35' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 14.85 cfs @ 3.96 fps)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 38
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Pond C41 D:
Inflow Area = 3.000 ac, Inflow Depth = 2.56" for Johnston 25Yr 24Hr event
Inflow = 14.88 cfs @ 11.95 hrs, Volume= 0.639 of
Outflow = 14.88 cfs @ 11.95 hrs, Volume= 0.639 af, Atten= 0%, Lag= 0.0 min
Primary = 14.88 cfs @ 11.95 hrs, Volume= 0.639 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 165.51' @ 11.95 hrs
Flood Elev= 170.00'
Device Routing Invert Outlet Devices
#1 Primary 164.00' 36.0" x 48.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 162.50' S= 0.0313 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=14.85 cfs @ 11.95 hrs HW=165.51' TW=163.35' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 14.85 cfs @ 4.18 fps)
Pond C42:
Inflow Area = 5.300 ac, Inflow Depth = 2.56" for Johnston 25Yr 24Hr event
Inflow = 25.87 cfs @ 11.96 hrs, Volume= 1.131 of
Outflow = 25.87 cfs @ 11.96 hrs, Volume= 1.131 af, Atten= 0%, Lag= 0.0 min
Primary = 25.87 cfs @ 11.96 hrs, Volume= 1.131 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 164.09' @ 11.96 hrs
Flood Elev= 173.00'
Device Routing Invert Outlet Devices
#1 Primary 162.00' 36.0" x 48.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 156.00' S= 0.1250 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=25.82 cfs @ 11.96 hrs HW=164.09' TW=148.54' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 25.82 cfs @ 4.92 fps)
Pond C43A:
Inflow Area = 32.800 ac, Inflow Depth = 2.49" for Johnston 25Yr 24Hr event
Inflow = 150.79 cfs @ 11.97 hrs, Volume= 6.807 of
Outflow = 150.79 cfs @ 11.97 hrs, Volume= 6.807 af, Atten= 0%, Lag= 0.0 min
Primary = 150.79 cfs @ 11.97 hrs, Volume= 6.807 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 156.21' @ 11.97 hrs
Flood Elev= 170.00'
Device Routing Invert Outlet Devices
#1 Primary 148.00' 48.0" x 120.0' long Culvert RCP, square edge headwall, Ke= 0.500

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 39
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Outlet Invert= 144.00' S= 0.0333 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=150.40 cfs @ 11.97 hrs HW=156.18' TW=144.53' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 150.40 cfs @ 11.97 fps)
Pond C43B:
Inflow Area =
6.600 ac,
Inflow Depth
= 2.51" for Johnston 25Yr 24Hr event
Inflow =
31.29 cfs @
11.96 hrs,
Volume= 1.383 of
Outflow =
31.29 cfs @
11.96 hrs,
Volume= 1.383 af, Atten= 0%, Lag= 0.0 min
Primary =
31.29 cfs @
11.96 hrs,
Volume= 1.383 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 166.36' @ 11.96 hrs
Flood Elev= 178.00'
Device Routing Invert Outlet Devices
#1 Primary 164.00' 36.0" x 48.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 162.00' S= 0.0417 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=31.22 cfs @ 11.96 hrs HW=166.36' TW=156.12' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 31.22 cfs @ 5.23 fps)
Pond C43C:
Inflow Area =
26.200 ac,
Inflow Depth
= 2.48" for Johnston 25Yr 24Hr event
Inflow =
119.77 cfs @
11.97 hrs,
Volume= 5.424 of
Outflow =
119.77 cfs @
11.97 hrs,
Volume= 5.424 af, Atten= 0%, Lag= 0.0 min
Primary =
119.77 cfs @
11.97 hrs,
Volume= 5.424 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 173.92' @ 11.97 hrs
Flood Elev= 180.00'
Device Routing Invert Outlet Devices
#1 Primary 168.00' 48.0" x 300.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 162.00' S= 0.0200 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=119.52 cfs @ 11.97 hrs HW=173.90' TW=156.18' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 119.52 cfs @ 9.51 fps)
Pond C43D:
Inflow Area = 26.200 ac, Inflow Depth = 2.48" for Johnston 25Yr 24Hr event
Inflow = 119.77 cfs @ 11.97 hrs, Volume= 5.424 of
Outflow = 119.77 cfs @ 11.97 hrs, Volume= 5.424 af, Atten= 0%, Lag= 0.0 min
Primary = 119.77 cfs @ 11.97 hrs, Volume= 5.424 of

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 40
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 178.42' @ 11.97 hrs
Flood Elev= 183.00'
Device Routing Invert Outlet Devices
#1 Primary 172.50' 48.0" x 300.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 168.50' S= 0.0133 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=119.52 cfs @ 11.97 hrs HW=178.40' TW=173.90' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 119.52 cfs @ 9.51 fps)
Pond C43E:
Inflow Area =
18.500 ac,
Inflow Depth
= 2.49" for Johnston 25Yr 24Hr event
Inflow =
83.98 cfs @
11.97 hrs,
Volume= 3.833 of
Outflow =
83.98 cfs @
11.97 hrs,
Volume= 3.833 af, Atten= 0%, Lag= 0.0 min
Primary =
83.98 cfs @
11.97 hrs,
Volume= 3.833 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 180.34' @ 11.97 hrs
Flood Elev= 183.50'
Device Routing Invert Outlet Devices
#1 Primary 174.00' 48.0" x 72.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 173.00' S= 0.0139 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=83.92 cfs @ 11.97 hrs HW=180.33' TW=178.40' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 83.92 cfs @ 6.68 fps)
Pond C43F:
Inflow Area =
18.500 ac,
Inflow Depth
= 2.49" for Johnston 25Yr 24Hr event
Inflow =
83.98 cfs @
11.97 hrs,
Volume= 3.833 of
Outflow =
83.98 cfs @
11.97 hrs,
Volume= 3.833 af, Atten= 0%, Lag= 0.0 min
Primary =
83.98 cfs @
11.97 hrs,
Volume= 3.833 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 183.07' @ 11.97 hrs
Flood Elev= 187.00'
Device Routinq Invert Outlet Devices
#1 Primary 179.00' 48.0" x 300.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 174.50' S= 0.0150 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=83.93 cfs @ 11.97 hrs HW=183.07' TW=180.33' (Dynamic Tailwater)
L1=Culvert (Outlet Controls 83.93 cfs @ 8.16 fps)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 41
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Pond C43G:
Inflow Area = 7.400 ac, Inflow Depth = 2.50" for Johnston 25Yr 24Hr event
Inflow = 33.88 cfs @ 11.97 hrs, Volume= 1.540 of
Outflow = 33.88 cfs @ 11.97 hrs, Volume= 1.540 af, Atten= 0%, Lag= 0.0 min
Primary = 33.88 cfs @ 11.97 hrs, Volume= 1.540 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 186.27' @ 11.97 hrs
Flood Elev= 190.00'
Device Routing Invert Outlet Devices
#1 Primary 184.00' 42.0" x 348.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 179.50' S= 0.0129 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=33.86 cfs @ 11.97 hrs HW=186.27' TW=183.07' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 33.86 cfs @ 5.13 fps)
Pond C43H:
Inflow Area = 7.400 ac, Inflow Depth = 2.50" for Johnston 25Yr 24Hr event
Inflow = 33.88 cfs @ 11.97 hrs, Volume= 1.540 of
Outflow = 33.88 cfs @ 11.97 hrs, Volume= 1.540 af, Atten= 0%, Lag= 0.0 min
Primary = 33.88 cfs @ 11.97 hrs, Volume= 1.540 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 188.37' @ 11.97 hrs
Flood Elev= 195.00'
Device Routing Invert Outlet Devices
#1 Primary 186.00' 42.0" x 230.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 180.00' S= 0.0261 T Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=33.86 cfs @ 11.97 hrs HW=188.37' TW=186.27' (Dynamic Tailwater)
L1=Culvert (Outlet Controls 33.86 cfs @ 6.90 fps)
Pond C44:
Inflow Area = 7.700 ac, Inflow Depth = 2.48" for Johnston 25Yr 24Hr event
Inflow = 36.11 cfs @ 11.96 hrs, Volume= 1.591 of
Outflow = 36.11 cfs @ 11.96 hrs, Volume= 1.591 af, Atten= 0%, Lag= 0.0 min
Primary = 36.11 cfs @ 11.96 hrs, Volume= 1.591 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 179.53' @ 11.97 hrs
Flood Elev= 183.00'
Device Routing Invert Outlet Devices
#1 Primary 176.00' 36.0" x 40.0' long Culvert RCP, square edge headwall, Ke= 0.500

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 42
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Outlet Invert= 174.00' S= 0.0500 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=36.10 cfs @ 11.96 hrs HW=179.50' TW=178.38' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 36.10 cfs @ 5.11 fps)
Pond C45:
Inflow Area =
11.100 ac,
Inflow Depth
= 2.48" for Johnston 25Yr 24Hr event
Inflow =
50.11 cfs @
11.97 hrs,
Volume= 2.293 of
Outflow =
50.11 cfs @
11.97 hrs,
Volume= 2.293 af, Atten= 0%, Lag= 0.0 min
Primary =
50.11 cfs @
11.97 hrs,
Volume= 2.293 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 185.67' @ 11.97 hrs
Flood Elev= 187.00'
Device Routing Invert Outlet Devices
#1 Primary 182.00' 36.0" x 40.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 180.00' S= 0.0500 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=50.05 cfs @ 11.97 hrs HW=185.66' TW=183.06' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 50.05 cfs @ 7.08 fps)
Pond C46:
Inflow Area =
7.400 ac,
Inflow Depth
= 2.50" for Johnston 25Yr 24Hr event
Inflow =
33.88 cfs @
11.97 hrs,
Volume= 1.540 of
Outflow =
33.88 cfs @
11.97 hrs,
Volume= 1.540 af, Atten= 0%, Lag= 0.0 min
Primary =
33.88 cfs @
11.97 hrs,
Volume= 1.540 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 191.50' @ 11.97 hrs
Flood Elev= 195.00'
Device Routing Invert Outlet Devices
#1 Primary 189.00' 36.0" x 40.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 187.00' S= 0.0500 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=33.86 cfs @ 11.97 hrs HW=191.50' TW=188.37' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 33.86 cfs @ 5.38 fps)
Pond C51:
Inflow Area = 6.900 ac, Inflow Depth = 2.63" for Johnston 25Yr 24Hr event
Inflow = 29.31 cfs @ 11.98 hrs, Volume= 1.513 of
Outflow = 29.31 cfs @ 11.98 hrs, Volume= 1.513 af, Atten= 0%, Lag= 0.0 min
Primary = 29.31 cfs @ 11.98 hrs, Volume= 1.513 of

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 43
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 163.26' @ 11.98 hrs
Flood Elev= 168.50'
Device Routing Invert Outlet Devices
#1 Primary 161.00' 36.0" x 48.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 160.00' S= 0.0208 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=29.27 cfs @ 11.98 hrs HW=163.26' TW=144.48' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 29.27 cfs @ 5.12 fps)
Pond C52:
Inflow Area =
10.900 ac,
Inflow Depth
= 2.60" for Johnston 25Yr 24Hr event
Inflow =
50.66 cfs @
11.97 hrs,
Volume= 2.361 of
Outflow =
50.66 cfs @
11.97 hrs,
Volume= 2.361 af, Atten= 0%, Lag= 0.0 min
Primary =
50.66 cfs @
11.97 hrs,
Volume= 2.361 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 155.95' @ 11.97 hrs
Flood Elev= 160.00'
Device Routing Invert Outlet Devices
#1 Primary 153.00' 42.0" x 48.0' long Culvert RCP, square edge headwall, Ke= 0.500
Outlet Invert= 152.00' S= 0.0208 7' Cc= 0.900
n= 0.013 Corrugated PE, smooth interior
Primary OutFlow Max=50.56 cfs @ 11.97 hrs HW=155.95' TW=144.45' (Dynamic Tailwater)
L1=Culvert (Inlet Controls 50.56 cfs @ 5.85 fps)
Pond SB-1 W: Sed Basin No. 1 W
[80] Warning: Exceeded Pond C11 by 1.47' @ 24.30 hrs (14.23 cfs 1.885 af)
[80] Warning: Exceeded Pond C12 by 1.47' @ 24.19 hrs (12.45 cfs 1.366 af)
[80] Warning: Exceeded Pond C13 by 2.47' @ 24.19 hrs (26.24 cfs 2.305 af)
Inflow Area =
24.200 ac,
Inflow Depth
= 2.73"
for Johnston 25Yr 24Hr event
Inflow =
120.26 cfs @
11.95 hrs,
Volume=
5.516 of
Outflow =
0.47 cfs @
24.07 hrs,
Volume=
0.670 af, Atten= 100%, Lag= 727.2 min
Primary =
0.47 cfs @
24.07 hrs,
Volume=
0.670 of
Secondary =
0.00 cfs @
0.00 hrs,
Volume=
0.000 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 176.48' @ 24.07 hrs Surf.Area= 56,225 sf Storage= 221,023 cf
Flood Elev= 182.00' Surf.Area= 74,500 sf Storage= 581,400 cf
Plug -Flow detention time= 593.0 min calculated for 0.670 of (12% of inflow)
Center -of -Mass det. time= 436.3 min ( 1,274.8 - 838.6 )

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 44
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Volume Invert Avail.Storage Storage Description
#1 172.00' 581,400 cf Custom Stage Data (Prismatic)Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
172.00 42,700 0 0
174.00 48,600 91,300 91,300
176.00 54,700 103,300 194,600
178.00 61,100 115,800 310,400
180.00 67,700 128,800 439,200
182.00 74,500 142,200 581,400
Device Routing Invert Outlet Devices
#1 Primary 170.00' 24.0" x 90.0' long Culvert CMP, square edge headwall, Ke= 0.500
Outlet Invert= 169.00' S= 0.0111 T Cc= 0.900
n= 0.025 Corrugated metal
#2 Device 1 172.33' 3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 176.50' 4.0' long x 1.00' rise Sharp -Crested Rectangular Weir X 4.00
2 End Contraction(s) 1.0' Crest Height
#4 Secondary 180.00' 143.0 deg x 20.0' long Sharp -Crested Vee/Trap Weir C= 2.47
Primary OutFlow Max=0.47 cfs @ 24.07 hrs HW=176.48' (Free Discharge)
L1=Culvert (Passes 0.47 cfs of 24.82 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.47 cfs @ 9.66 fps)
13=S harp-C rested
Rectangular Weir( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=172.00' (Free Discharge)
L4=Sharp-Crested Vee/Trap Weir( Controls 0.00 cfs)
Pond SB-2W: Sed Basin No. 2W
[80] Warning: Exceeded Pond C21A by 0.15' @ 28.38 hrs (17.90 cfs 5.715 af)
Inflow Area = 25.400 ac, Inflow Depth = 2.65" for Johnston 25Yr 24Hr event
Inflow =
111.94 cfs @
11.98 hrs,
Volume=
5.605 of
Outflow =
0.53 cfs @
24.19 hrs,
Volume=
0.751 af, Atten= 100%, Lag= 732.3 min
Primary =
0.53 cfs @
24.19 hrs,
Volume=
0.751 of
Secondary =
0.00 cfs @
0.00 hrs,
Volume=
0.000 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 169.51' @ 24.19 hrs Surf.Area= 47,821 sf Storage= 222,009 cf
Flood Elev= 174.00' Surf.Area= 61,000 sf Storage= 466,100 cf
Plug -Flow detention time= 578.1 min calculated for 0.751 of (13% of inflow)
Center -of -Mass det. time= 427.5 min ( 1,275.4 - 847.9 )
Volume Invert Avail.Storage Storage Description
#1 164.00' 466,100 cf Custom Stage Data (Prismatic)Listed below (Recalc)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 45
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
164.00 33,100 0 0
166.00 38,200 71,300 71,300
168.00 43,600 81,800 153,100
170.00 49,200 92,800 245,900
172.00 55,000 104,200 350,100
174.00 61,000 116,000 466,100
Device Routing Invert Outlet Devices
#1 Primary 163.00' 24.0" x 100.0' long Culvert
CMP, square edge headwall, Ke= 0.500
Outlet Invert= 162.00' S= 0.0100 T Cc= 0.900
n= 0.025 Corrugated metal
#2 Device 1 164.33' 3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 170.00' 4.0' long x 1.00' rise Sharp -Crested Rectangular Weir X 4.00
2 End Contraction(s) 1.0' Crest Height
#4 Secondary 172.00' 143.0 deg x 20.0' long Sharp -Crested Vee/Trap Weir C= 2.47
Primary OutFlow Max=0.53 cfs @ 24.19 hrs HW=169.51' (Free Discharge)
L1=Culvert (Passes 0.53 cfs of 23.94 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.53 cfs @ 10.82 fps)
t3=S harp-C rested
Rectangular Weir( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=164.00' (Free Discharge)
L4=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs)
Pond SB-3W: Sed Basin No. 3W
[80] Warning: Exceeded Pond C31A by 4.12' @ 24.30 hrs (71.33 cfs 5.753 af)
[80] Warning: Exceeded Pond C32 by 2.13' @ 24.18 hrs (30.47 cfs 3.224 af)
[80] Warning: Exceeded Pond C35 by 0.17' @ 29.53 hrs (16.63 cfs 4.525 af)
Inflow Area = 57.900 ac, Inflow Depth = 2.79" for Johnston 25Yr 24Hr event
Inflow =
171.62 cfs @
11.98 hrs,
Volume=
13.444 of
Outflow =
18.14 cfs @
13.17 hrs,
Volume=
6.796 af, Atten= 89%, Lag= 71.9 min
Primary =
18.14 cfs @
13.17 hrs,
Volume=
6.796 of
Secondary =
0.00 cfs @
0.00 hrs,
Volume=
0.000 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 206.47' @ 13.17 hrs Surf.Area= 60,654 sf Storage= 325,273 cf
Flood Elev= 210.00' Surf.Area= 75,000 sf Storage= 563,000 cf
Plug -Flow detention time= 313.7 min calculated for 6.794 of (51 % of inflow)
Center -of -Mass det. time= 184.0 min ( 1,036.4 - 852.4 )
Volume Invert Avail.Storage Storage Description
#1 200.00' 563,000 cf Custom Stage Data (Prismatic)Listed below (Recalc)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 46
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
200.00 40,000 0 0
202.00 46,000 86,000 86,000
204.00 53,000 99,000 185,000
206.00 59,000 112,000 297,000
208.00 66,000 125,000 422,000
210.00 75,000 141,000 563,000
Device Routing Invert Outlet Devices
#1 Primary 199.00' 24.0" x 160.0' long Culvert
CMP, square edge headwall, Ke= 0.500
Outlet Invert= 196.00' S= 0.0187 T Cc= 0.900
n= 0.025 Corrugated metal
#2 Device 1 200.33' 3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 206.00' 4.0' long x 1.00' rise Sharp -Crested Rectangular Weir X 4.00
2 End Contraction(s) 1.0' Crest Height
#4 Secondary 208.00' 143.0 deg x 20.0' long Sharp -Crested Vee/Trap Weir C= 2.47
Primary OutFlow Max=18.13 cfs @ 13.17 hrs HW=206.47' (Free Discharge)
L1=Culvert (Passes 18.13 cfs of 24.63 cfs potential flow)
t2=Orifice/Grate (Orifice Controls 0.58 cfs @ 11.81 fps)
3=S harp-C rested
Rectangular Weir (Weir Controls 17.55 cfs @ 2.38 fps)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=200.00' (Free Discharge)
L4=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs)
Pond SB-4W: Sed Basin No. 4W
[80] Warning: Exceeded Pond C41A by 2.83' @ 24.12 hrs (47.69 cfs 3.810 af)
[80] Warning: Exceeded Pond C43A by 0.82' @ 24.26 hrs (4.71 cfs 0.602 af)
Inflow Area =
44.900 ac,
Inflow Depth
= 2.66"
for Johnston 25Yr 24Hr event
Inflow =
220.07 cfs @
11.96 hrs,
Volume=
9.947 of
Outflow =
0.60 cfs @
24.09 hrs,
Volume=
0.846 af, Atten= 100%, Lag= 727.9 min
Primary =
0.60 cfs @
24.09 hrs,
Volume=
0.846 of
Secondary =
0.00 cfs @
0.00 hrs,
Volume=
0.000 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 148.83' @ 24.09 hrs Surf.Area= 73,254 sf Storage= 408,983 cf
Flood Elev= 154.00' Surf.Area= 94,800 sf Storage= 843,000 cf
Plug -Flow detention time= 595.1 min calculated for 0.846 of (9% of inflow)
Center -of -Mass det. time= 432.7 min ( 1,274.4 - 841.7 )
Volume Invert Avail.Storage Storage Description
#1 142.00' 843,000 cf Custom Stage Data (Prismatic)Listed below (Recalc)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 47
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Elevation
Surf.Area
Inc.Store
Cum.Store
(feet)
(sq-ft)
(cubic -feet)
(cubic -feet)
142.00
47,000
0
0
144.00
54,400
101,400
101,400
146.00
62,000
116,400
217,800
148.00
69,900
131,900
349,700
150.00
78,000
147,900
497,600
152.00
86,300
164,300
661,900
154.00
94,800
181,100
843,000
Device Routing Invert Outlet Devices
#1
Primary
141.00'
24.0" x 80.0' long Culvert CMP, square edge headwall, Ke= 0.500
Outlet Invert= 140.00' S= 0.0125 '/' Cc= 0.900
n= 0.025 Corrugated metal
#2
Device 1
142.33'
3.0" Vert. Orifice/Grate C= 0.600
#3
Device 1
149.50'
4.0' long x 1.00' rise Sharp -Crested Rectangular Weir X 4.00
2 End Contraction(s) 1.0' Crest Height
#4
Secondary
152.00'
143.0 deg x 20.0' long Sharp -Crested Vee/Trap Weir C= 2.47
Primary OutFlow Max=0.60 cfs @ 24.09 hrs HW=148.83' (Free Discharge)
L1=Culvert (Passes 0.60 cfs of 28.93 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.60 cfs @ 12.16 fps)
t3=S harp-C rested
Rectangular Weir( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=142.00' (Free Discharge)
L4=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs)
Pond SB-5W: Sed Basin No. 5W
Inflow Area = 22.500 ac, Inflow Depth = 2.82" for Johnston 25Yr 24Hr event
Inflow =
92.03 cfs @
11.98 hrs,
Volume=
5.282 of
Outflow =
0.58 cfs @
24.11 hrs,
Volume=
0.837 af, Atten= 99%, Lag= 727.8 min
Primary =
0.58 cfs @
24.11 hrs,
Volume=
0.837 of
Secondary =
0.00 cfs @
0.00 hrs,
Volume=
0.000 of
Routing by Dyn-Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.01 hrs / 3
Peak Elev= 148.50' @ 24.11 hrs Surf.Area= 49,098 sf Storage= 205,592 cf
Flood Elev= 152.00' Surf.Area= 70,000 sf Storage= 417,100 cf
Plug -Flow detention time= 570.8 min calculated for 0.836 of (16% of inflow)
Center -of -Mass det. time= 425.0 min ( 1,268.3 - 843.4 )
Volume Invert Avail.Storage Storage Description
#1 142.00' 417,100 cf Custom Stage Data (Prismatic)Listed below (Recalc)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
Johnston County MSW Phases 5-10 Type 11 24-hr Johnston 25Yr 24Hr Rainfall=6.60"
Prepared by Pieter K. Scheer, P.E. Page 48
HydroCADO 8.00 s/n 004004 © 2006 HydroCAD Software Solutions LLC 3/13/2019
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
142.00 17,100 0 0
144.00 25,200 42,300 42,300
146.00 34,500 59,700 102,000
148.00 45,600 80,100 182,100
150.00 59,700 105,300 287,400
152.00 70,000 129,700 417,100
Device Routing Invert Outlet Devices
#1 Primary 141.70' 24.0" x 80.0' long Culvert CMP, square edge headwall, Ke= 0.500
Outlet Invert= 141.00' S= 0.0088 '/' Cc= 0.900
n= 0.025 Corrugated metal
#2 Device 1 142.33' 3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 148.50' 4.0' long x 1.00' rise Sharp -Crested Rectangular Weir X 4.00
2 End Contraction(s) 1.0' Crest Height
#4 Secondary 150.00' 143.0 deg x 20.0' long Sharp -Crested Vee/Trap Weir C= 2.47
Primary OutFlow Max=0.58 cfs @ 24.11 hrs HW=148.50' (Free Discharge)
L1=Culvert (Passes 0.58 cfs of 25.95 cfs potential flow)
�2=Orifi ce/G rate
(Orifice Controls 0.58 cfs @ 11.83 fps)
3=Sharp-Crested Rectangular Weir( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=142.00' (Free Discharge)
4=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs)

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
RESS
TEL I WEB
SMITH G A R D N E R 14 N. Boylan Avenue, Raleigh, NC 27603
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 1 OF
SUBJECT Drainage Channel Analysis JOB # JOHNSTON-16-4
919.828.0577 1 www.smithgardnerinc.com
5 DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
OBJECTIVE: To design drainage channels, ditches, etc. to handle stormwater flow from the design storm(s). The main
design criteria will be to ensure that all drainage channels, ditches, etc. will be able to accommodate the
peak discharge from the design storm without overtopping and without exceeding the allowable shear
stress and/or velocity of the selected channel Lining.
REFERENCES: Federal Highway Administration (2001), Urban Drainage Design Manual, Hydraulic Engineering Circular
No. 22, FHWA NHI-01-021, Second Ed., U.S. Dept. of Transportation, Washington, D.C.
North Carolina Division of Land Resources (2013 Updates), North Carolina Erosion & Sediment Control
Planning & Design Manual, Raleigh, NC.
Malcom, H. Rooney 11989 & 2003 Supplement), Elements of Urban Stormwater Design, NC State Univ.,
Raleigh, NC.
Pennsylvania DEP Bureau of Watershed Protection (2000), Erosion and Sediment Pollution Control
Program Manual.
ANALYSIS: The following approach is used in the design of drainage channels:
1 • Determine the peak discharge from the design storm(s) (from HydroCAD or spreadsheet
methods). For permanent linings (Grass, TRM, rip rap, gabions, etc.) use the peak discharge
from the 25-Yr 24-Hr storm unless otherwise specified. For grass lined channels, a smaller
design storm (2-Yr 24-Hr - unless otherwise specified) is used to evaluate temporary linings.
2• Input other design parameters (bottom width; side slopes; minimum freeboard, min./max.
slopes; and channel lining).
3• Based on the design parameters calculate normal depth of flow, velocity, Froude number, and
maximum shear stress for both max./min. slopes. Also determine the critical slope and
corresponding normal depth.
4. Compare the velocity and/or shear stress to allowable values (the maximum slope values will
control). If values are exceeded, revise design parameters as required.
5• Based on normal depth values and required freeboard (generally use the greater of 6 inches or
25% of the flow depth), determine the minimum channel depth and top width for both max./min.
slopes (the minimum slope values will control).
6• If the channel has a significant curved reach, evaluate the shear stress and superelevation of
the water surface in the bend.
CALCULATIONS:
- Manning's Equation:
1.49AR2'3S"2 AV (HEC-22 Eq. 5-5)
Q= =
n
where: Q = discharge (cfs)
n = Manning's roughness coefficient (See Below)
A = cross sectional area of flow (ft2)
R = hydraulic radius (ft) = A/P
P = wetted perimeter
S = slope of channel (ft/ft)
V = average channel velocity (ft/sec)
SMITH GARNER, INC. JC DRAINAGE CHANNEL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 2 OF 5 DATE 3/13/2019
COMPUTED BY PKS
SUBJECT Drainage Channel Analysis JOB # JOHNSTON-16-4 CHECKED BY SWH
- Maximum Shear Stress (Tractive Force Method]:
zd = ),ds (HEC-22 Eq. 5-131
where: ra = maximum shear stress on channel lining (psf)
y = unit weight of water (62.4 pcf)
d = maximum depth of flow (ft)
S = channel slope (ft/ft)
- Froude Number:
v
Fr = T
gA
T
where: F, = Froude number (dimensionless)
v = flow velocity (ft/sec)
g = acceleration of gravity (32.2 ft/sec`)
A = cross -sectional area of flow (ft`)
T = top width of flow (ft)
Note that A/T = the hydraulic depth (D). For Fr > 1.0, flow is supercritical; Fr < 1.0, flow is subcritical; F, = 1.0, flow is
critical.
Critical Slope:
The critical slope (S j is the slope at which F, = 1.0. When the slope is between 0.7S, and 1.3S, , unstable
flow may occur as small flow disturbances can initiate a change in the flow state. If slopes are within this
range, consider additional freeboard.
- Manning's Roughness Coefficient (n):
Grass:
n = 1 (HEC-22 Eq. 5-6 - 5-10)
[K+ 19.971og(R1ASOA)]
where: R =
hydraulic radius Ift)
K =
vegetative coefficient (depending on retardance class)
= 15.8 (Class A)
= 23.0 (Class B)
= 30.2 (Class C)
= 34.6 (Class D)
= 37.7 (Class E)
S =
slope of channel (ft/ft)
Rip Ram
1/6
n = Y
(PA DEP Manual Fig. 3)
21.6log ( Y + 14
Aso
where: y =
depth of flow (ft)
050 =
median size of rip rap Ift)
SMITH GARDNER
SMITH GARDNER, INC. JC DRAINAGE CHANNEL

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
PROJECT
Johnston
Co. MSWLF - Phase 6
SHEET
SUBJECT
Drainage
Channel Analysis
JOB #
3 OF 5
JOHNSTON-16-4
- Curved Channels (Where Applicable):
Shear Stress in Bend:
rh = Khzd (HEC-22 Eq.5-151
DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
where: Ta = bend shear stress (psf)
Kb = function of Rc/B (use HEC-22 Chart 211
Ta = maximum shear stress on channel lining (psf)
R = radius to the centerline of the channel (ft)
B = bottom width of channel (ft)
Superelevation at Outside of Bend:
z
Ad = O.SV T (HEC-22 Eq.5-11 modified)
gR,.
where: A a = superelevation of water surface between the outer channel bank and the
centerline of the channel (avg. water surface before bend) (ft)
V = average channel velocity (ft/sec)
T = top width of flow Ift)
g = acceleration of gravity (32.2 ft/sec2)
R , = radius to the centerline of the channel (ft)
Allowable Shear Stress/Velocity
Grass -Lined Channels:
For grass -lined channels, an allowable velocity approach is applicable for slopes flatter than 10%. For
slopes of 10% and steeper appropriate permanent linings should be used. For use in the evaluation of
curved channels, the following allowable shear stress values (lb/ft) can be assumed based on retardance
class:
Class A: 3.7
Class B: 2.1
Class C: 1
Class D: 0.6
Class E: 0.35
Rip Rap -Lined Channels:
For rip rap -lined channels, an allowable velocity approach is applicable for slopes flatter than 10% (see table
below). For slopes of 10% or steeper, use the following equation:
T'll—, = 4 x dso (HEC-22 Eq. 5-171
where: T auow = allowable shear stress (psf)
050 = median size of rip rap (ft)
SMITH GARDNER
SMITH GARNER, INC. JC DRAINAGE CHANNEL

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF - Phase 6 SHEET
SUBJECT Drainage Channel Analysis JOB #
4 OF 5 DATE
COMPUTED BY
JOHNSTON-16-4 CHECKED BY
Riprap Gradation, Filter Blanket Requirements, Maximum Velocities
3/13/2019
SWH
NSA No.
Graded Rock Size in
Filter Blanket Re uirements**
V..
(fusee
Max.
dffn'
Min.
Size NSA No.
Placement
Thickness
R-1
1.5
.75
No.8
FS-1
NIA
2.5
R-2
3
1.5
1
FS-1
NIA
4.5
R-3
6
3
2
FS-1
3
6.5
R-4
12
6
3
1 FS-2
4
9.0
R-5
18
9
5
FS-2
6
11.5
R-6
24
12
7
FS-3
8
13.0
R-7
1 30
15
1 12
FS-3
10
14.5
* The d50 stone size is the size exceeded by 50% of the total weight of the tonnage shipped (Le. 50%
by weight shall consist of pieces larger than the d5o stone size")
** This is a general standard. Soil conditions at each site should be analyzed to determine actual filter
size. A suitable woven or non -woven geotextile underlayment, used according to manufacturer's
recommendations, may be substituted for the filter stone.
Ref.• PA DEP Manual Table 9
Reno Mattress or Gabion-Lined Channels:
For Reno mattress or gabion-lined channels, use allowable velocity for slopes flatter than 10% and
allowable shear stress for slopes of 10% or steeper (see table below).
Maximum Permissible Velocities for Reno Mattress & Gabions
Permissible —
Thickness
Rock Fill
Permissible*
Shear Stress
Type
n
Inches
Gradation in
Velocity (fps)
Iblftz
.025 - .030
6
3-6
6.0
8,35
Reno
.025 - .030
6 - 10
3-6
12.0
8.35
025 - ,030
10 - 12
3-0
8.35
Mattress
15.0
025 - _030
12 - 18
4-6
18.0
B-35
Gabion
.027
>18
5-9
22.0
8.35
* Permissible velocities may be increased by the introduction of sand mastic grout_ Refer to
manufacturer's recommendations/specifications for permissible velocities and for recommendations
regarding filters or geotextile fabric underlayment when using Reno mattresses or gabions for
channel linings.
**Based on vegetation completely grown.
Ref.• PA DEP Manual Table 13
SMITHAARDNER
SMITH GARNER, INC. JC DRAINAGE CHANNEL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston County MSW Landfill- Phase 6
SHEET
5/5
JOB #
JOHNSTON-16-4
SUBJECT Drainage Channel Analysis (TRM
Lined)
DATE
3/13/2019
COMPUTED BY
PKS
Channel No.
Perimeter Road Drainage Channel
CHECKED BY
SWH
Design
Parameters:
PEAK DISCHARGE, 025 =
41.0
ft,/s
Source:
Est. 10 Acre Max.
-- 25-Yr 5-Min. -- O=CIA = 0.5 x 8.19 x 10 Acres
Bottom Width, B =
6.0
ft
Turf Reinforcement
Matting (TRMI Lining_
Left Side Slope, z I=
2.0
horizontal:1 vertical
Grass Retardance=
D
Right Side Slope, z2=
2.0
horizontal:1 vertical
K=
34.6
TRM Product Name =
Propex - Landlok
TRM 435, or equal
Minimum Freeboard =
0.5
ft
r,«o„, =
5.0
lb/ft2
Maximum Channel Slope, S.-=
0.040
ft/ft
Minimum Channel Slope, Sm =
0.010
ft/ft
Normal Depth
Depth of Flow
Manning's
Area
Wetted
Hydraulic
Top
Hydraulic
Average
Flow
Froude
Maximum
Factor
(Norm. Depth)
Roughness
of Flow
Perimeter
Radius
Width
Depth
Velocity
Rate
Number
Shear Stress
of Safety
Comment
Y„
Coefficient
A
P
R=A/P
T
D=A/T
V„
0
F, Normal]
rd
ft
n
ft2
ft
ft
ft
ft
ft/5
ft'/s
#
Lb/ft'
Maximum Slope:
0.99
0.048 7.90
10.43
0.76
9.96
0.79
5.19
41.0
1.03
2.5
2.0
0.K.
Minimum Slope:
1.52
0.052 13.74
12.80
1.07
12.08
1.14
3.01
41.3
0.50
0.9
5.3
0.K.
Critical Depth
Depth of Flow
Manning's
Area
Wetted
Hydraulic
Top
Hydraulic
Section
Flow
Average
Froude
Uniform -Flow
)Grit. Depth)
Roughness
of Flow
Perimeter
Radius
Width
Depth
Factor
Rate
Velocity
Number
Critical Slope
Comment
Y,
Coefficient
A
P
R=A/P
T
D=A/T
Z=AD
0
V,
F, (Critical/
SC
ft
n
ft2
ft
ft
ft
ft
ft-
ft,/5
ft/s
#
ft/ft
1.01
0.048
8.10
10.52
0.77
10.04
0.81
7.28
41.3
5.10
1.00
0.038
Slopes Near Sc - Check Freeboard.
Determination of Minimum Channel Depth & Top Width
Maximum
Slope
Minimum
Slope
Minimum
Minimum
Minimum
Minimum
Channel
Top Width
Channel
Top Width
Depth
T
Depth
T
ft
ft
ft
ft
1.49
11.96
2.02
14.08
SMITH GARDNER, INC. TRM JC DRAINAGE CHANNEL

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
ADDRESS TEL WEB
SMITH GAR D N E R 14 N. Boylan Avenue, Raleigh, NC 27603 919.828.0577 www.smithgardnerinc.com
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 1 OF 2 DATE 3/13/2019
COMPUTED BY PKS
SUBJECT Drop Inlet Analysis JOB # JOHNSTON-16-4 CHECKED BY SWH
OBJECTIVE: To design drop inlets to handle stormwater flow from the design storm(s). The main design criteria will be
to ensure that all drop inlets will be able to accommodate the peak rate of run off from the design storm
without exceeding the allowable headwater depth.
REFERENCE: Malcom, H. Rooney 11989 & 2003 Supplement), Elements of Urban Stormwater Design, NC State Univ.,
Raleigh, NC.
ANALYSIS_ The following approach is used in the design of drop Inlets:
1. Determine the peak discharge from the design storm(s) (from HydroCAD or spreadsheet
methods). Use the peak discharge from the 25-Yr 24-Hr storm unless otherwise specified.
2. As appropriate, analyze the inlet structure as a weir -type inlet and/or grated inlet.
3. Analyze the outlet structure separately by evaluating its behavior as a culvert.
CALCULATIONS:
- Weir -Type Inlet => Use the Weir Equation:
Q = C111LH312 (Malcom Eq. 1-6)
where: Q = peak discharge (cfs)
Cw = weir coefficient (=3.0 for free overfall)
L = Length of weir (ft)
H = driving head (ft) (= allowable headwater above crest of weir)
- Grated Inlet => Use the Orifice Equation:
Q = Cd A 2gh (Malcom Eq. 1-7)
where: G = peak discharge (cfs)
Cd = coefficient of discharge (0.6 = typical value)
A = cross -sectional area of flow at orifice entrance (ftz)
9 = acceleration of qravity (32.2 ft/seC2)
h = driving head (ft) (= allowable headwater above grate)
SMITH GARNER, INC. JC DROP INLET

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF - Phase 6 SHEET
2/2
JOB #
JOHNSTON-16-4
SUBJECT Drop Inlet Analysis DATE
3/13/2019
COMPUTED BY
PKS
CHECKED BY
SWH
Drop Inlet No.: Max. Area - Perimeter Channel
Peak Discharge:
PEAK DISCHARGE, 025 (cfs) = 41.0 Source: Assume 10 Acre Max. Area --->
25-Yr 5-Min. --->
Q=CIA = 0.5 x 8.19 x 10 Ac.
Drop Inlet Parameters:
Weir Coefficient = 3.0
Coefficient of Discharge (Orifice) = 0.6
Allowable Driving Head Ift) = 1.5
Weir -Type Inlet:
L (ft) =
Q (cfs) =
Drop Inlet No.: DI-35
Peak Discharge:
16
88.2 Flow is Greater than Maximum Flow ---> OK
PEAK DISCHARGE, 025 (cfs) = 88.7
Drop Inlet Parameters:
Weir Coefficient = 3.0
Coefficient of Discharge (Orifice) = 0.6
Allowable Driving Head Ift) = 2.0
Weir -Type Inlet:
Grated Inlet:
Source: HydroCAD 25-Yr 24-Hr
L (ft) = 16
Q Icfs) = 135.8 Flow is Greater than Maximum Flow ---> OK
N/A
SMITH GARDNER
SMITH GARDNER, INC. Max. Area JC DROP INLET

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
ADDRESS TEL WEB
SMITH GAR D N E R 14 N. Boylan Avenue, Raleigh, NC 27603 919.828.0577 www.smithgardnerinc.com
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 1 OF 14 DATE 3/13/2019
COMPUTED BY PKS
SUBJECT Sediment Basin Analysis JOB # JOHNSTON-16-4 CHECKED BY SWH
OBJECTIVE: To design a sediment basin(s) to satisfy erosion and sediment control requirements and to handle the flow
from the design storm.
REFERENCES: American Concrete Pipe Association (1996), "Design Data 41 - Manhole Floatation", ACPA, Irving, TX.
Malcom, H. Rooney 11989 & 2003 Supplement), Elements of Urban Stormwater Design, NC State Univ.,
Raleigh, NC.
North Carolina Division of Land Resources (2013 Updates), North Carolina Erosion & Sediment Control
Planning & Design Manual, Raleigh, NC.
Virginia Department of Conservation and Recreation (1992), Virginia Erosion & Sediment Control
Handbook, Third Edition, Richmond, VA.
ANALYSIS: The following approach is used to properly size and evaluate each sediment basin:
1. Design for Wet (If Applicable) and Dry Storage.
2. Route Design Storm.
3• Design Outlet Structures (Design Riser/Barrel Structures and Perform Riser Base Calculations,
Anti -Seepage Collar Calculations, & Emergency Spillway Calculations).
CALCULATIONS:
- Design for Wet (If Applicable) and Dry Storage:
Determine required wet (if applicable) and dry storage volumes based on applicable erosion and sedimentation
control requirements.
If applicable, calculate the desired surface area at the principal spillway. For some locations:
A = O.O1Qp
where: A = desired surface area (acres)
6, = peak discharge from design storm (cfs)
INC - Use 10-yr 24-hr storm; GA - Use 2-yr 24-hr storm)
Set up a stage -storage relationship for the proposed basin as shown below. Based on this relationship and the
required volumes) and/or desired surface area, determine the required wet storage (if applicable) and dry storage
elevations. Alternatively the elevation(s) can be determined from a graphical stage -storage relationship.
S = KZ' (Malcom Eq. III-7)
where: 5 = storaqe volume (ft)
KS, b = Linear regression constants describing the stage -storage relationship
2 = stage referenced to the bottom elevation included in the analysis (ft)
Set sediment basin cleanout elevation.
SMITH GARNER, INC. JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 2 OF 14 DATE 3/13/2019
COMPUTED BY PKS
SUBJECT Sediment Basin Analysis JOB # JOHNSTON-16-4 CHECKED BY SWH
Size the outlet device to release the dry storage volume (WQV) over the desired drawdown period (typically this is a
minimum of 24 hours). Use the following equation:
AS 2h (from Original Edition of NCE&SCP&DM)
A TCd(2O,428)
where: Ac = surface area of dewaterinq holes) (ft')
A, = surface area of basin (at principal spillway) (ftz)
h = average head of water above hole (_ (elev. of principal spillway - elev. of wet storage
or (if not applicable) bottom of basin)/2) (ft)
G a = coefficient of contraction (=0.60)
T = detention time (hrs.) (vary over recommended limits)
Select a standard pipe size and number of holes. Verify that the projected drawdown period is within the
recommended limits.
Where desired, size a drain for the basin for maintenance. The drain should dewater the basin (to principal
spillway) within 24 hours. Use the above equation to determine Ao of the basin drain. The inlet of the drain should
be protected from the sediment storage zone.
Evaluate basin shape. Compare with the recommended length to width ratio. If this ratio is not achieved, the basin
should be modified or baffles should be added as required.
Route Design Storm:
Route the design storm through the basin and determine the maximum pool elevation and the peak discharge (via
HydroCAD, spreadsheet methods, or other). Depending on local requirements, multiple design storms may need
to be considered and the peak discharge may need to be compared with the pre -development value.
Based on the peak stage of the design storm, check settling efficiency of the design particle. The design particle is
typically 40 microns (0.04 mm) (within silt size criteria).
Settling Velocity of Design Particle
V g � (ss _ 1)�dz (Malcom Eq. IV-3)
18 v J
where: Va = settling velocity (ft/s1 - convert from (m/s)
9 = gravitational acceleration (m/s')
S' = specific gravity of design particle
v = kinematic viscosity of the fluid (mZ/s)
(= 1.14 x 10-6 m2/s fa 16 C - Ref. Streeter, 19751
a = diameter of design particle (m)
Surface Area
As = WsZ(b-1) (Malcom Eq. IV-7)
where: As = surface area at given stage (Z) (ft)
K„b = linear regression constants describing the stage -storage relationship
SMITH GARDNER
SMITH GARNER, INC. JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF - Phase 6
SUBJECT Sediment Basin Analvsis
Settling Efficiency.
SHEET 3 OF 14
JOB # JOHNSTON-16-4
1 n
E= 1— �1+ Vo AS (Malcom Eq. IV-1)
DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
where: E = settling efficiency (decimal fraction - convert to %)
AS = surface area at given stage W (ft)
N = number of effective cells (N = 2 with forebay)
G = discharge at given stage W (cfs)
- Design of Outlet Structures:
Design riser/barrel structures based on information used in routing the design storm.
Design base for riser structure to resist design uplift force. Base must have a buoyant weight of at least the design
uplift force. If a concrete riser structure is used, the buoyant weight of the riser can be accounted for in the
calculations.
Design Uplift Force [TF]
O Spec. 3.14)
F _ �FS�VRiser %�H20 — WRrser —WTop — �Soi] — Rsoil (from VAE&SCH
where: TF = design uplift force (lbs)
FS = factor of safety (use 1.25)
VRfser = interior volume of the riser (ft) (base elevation to principal spillway elevation)
YH20 = density of water (62.4 pcf)
WRmer buoyant weight of riser (not including base or top) (lbs)
WTop = buoyant weight of riser top (lbs)
Wsoil = buoyant weight of soil backfill around riser (above base projection) (lbs)
Rsoil = sliding resistance of soil backfill around riser (lbs)*
* See American Concrete Pipe Association Design Data 41 for more information.
Volume of Concrete for Base
Vc( _ F — T F (from VAE&SCH Spec. 3.14)
...n�.,a (150 — 62.4)
where: V Conc = volume of concrete (ft)
W conc,5 = buoyant weight of concrete 1150 - 62.4 = 87.6 lbs)
Anti -Seepage Collar(sl
Determine anti -seepage collar requirements based on the following equation. Alternatively, a filter
diaphragm may be designed.
LS = y(z + 4)1 1 + (0.25 — s) I (VA E&SC Handbook p. III-102)
where: L, = length of pipe in the saturated zone (ft)
y = distance from barrel invert to riser crest (ft)
2 = slope of upstream embankment (zH:lV)
s = pipe slope [ft/ft]
SMITH GARDNER
SMITH GARNER, INC. JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 4 OF 14 DATE 3/13/2019
COMPUTED BY PKS
SUBJECT Sediment Basin Analysis JOB # JOHNSTON-16-4 CHECKED BY SWH
Determine Ls and use design chart to determine anti -seepage collar requirements. If more than one collar is used,
the spacing between collars should be 14 times the projection (P) of the collar above the barrel. The first collar
should be set at 2P from the riser or a minimum length to bury collar in slope.
Emergency Spillway
Design crest length of emergency spillway to handle flow from the design storm using the following equation.
Determine peak flow from stormwater routing program. If applicable, design outlet channel as a drainage channel
or rock chute.
QP = C"LH312 (Malcom Eq. 1-6)
where: 6, = peak discharge from design storm (cfs)
G w = weir coefficient (=3.0 for free overfall)
L = length of weir (ft)
h = driving head (ft) (= allowable headwater above crest of weir or calculated
value from stormwater routing program)
SMITH GARDNER
SMITH GARNER, INC. JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co.MSWLF-Phase6 SHEET 5/14
JOB If JOHNSTON-16-4
SUBJECT Sediment Basin Analysis DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
Basin No.: Basin 1 W
DESIGN FOR WET [IF APPLICABLEI
AND DRY STORAGE:
Areas Draining Into Basin:
Are
Drainage Area
(acres)
Drainage Area
24.2
Total. =
24.2 Acres
Basin Requirements:
Wet Storage,
Required Storage Capacity (ft'/Ac) =
0 Enter "0" if Not Applicable.
Required Storage Capacity lft'1=
0
Required Depth of Wet Storage (ft) =
0.0 Enter "0" if Not Applicable.
Dry Storage,
Required Storage Capacity (ft'/Ac.) =
1,800 To Crest of Principal Spillway
Required Storage Capacity(ft')=
43,560
Multipier
(XI for Desired Surface Area (Op x XI =
0.01 At Crest of Principal Spillway
Peak Discharge into Basin (Op) (cfs) =
120.3 From HydroCAD - 25-Yr, 24-Hr. Storm (Conservative)
Desired Surface Area (Ac) =
1.20
Determine Stage Function:
Desired Surface Area (ft2) =
52,385
-Storage
Contour
Area Area
Incremental Cumulative Stage
In
In
Zest
(fill Iacresl
Volume (it') Volume (ft'I (R)
172
42,700 0.98
0 0.0
174
48,600 1.12
91,300 91,300 2.0
11.42
0.69
2.03
176
54,700 1.26
103,300 194,600 4.0
12.18
1.39
3.93
178
61,100 1.40
115,800 310.400 6.0
12.65
1.79
5.90
180
67,700 1.55
128,800 439,200 8.0
12.99
2.08
7.99
182
74,500 1.71
142,200 581,400 10.0
13.27
2.30
10.20
Linear Regression Constants:
Ks= 40,497
Storage =4O497 z'l.15
b= 1.15
'CAUTION: CHECK INPUT FOR REGRESSION ANALYSIS[
Stage -Surface Area Relationship
184
182
180
178
Is
176
N
174
172
170
0 20,000 40,000 60,000 80,000
Surface Area (sf)
Stage -Storage Relationship
184
182
180
178
Z
176
N
174
172
170
0 200,000 400,000 600,000 800,000
Storage (cf)
SMITH GARDNER
SMITH CAROM ER, INC. Basin 1W JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF- Phase 6
SUBJECT Sediment Basin Analysis
Basin Design Elevations:
Elev. of Bottom of Basin (ft) = 172.0
Wet Storage,
Required Storage Capacity(f€')= 0
Min. Elev. of Wet Storage (Permanent Pool) = 172.0
Selected Elev. of Wet Storage (Permanent Pool) = 172.0 O.K.
Actual Wet Storage Volume (ft') = 0 O.K.
Dry Storage,
Required Storage Capacity (f€') _
Min. Elev. of Principal Spillway (it) _
Selected Elev. of Principal Spillway (ft) _
Actual Total Storage Volume (ft') _
Desired Surface Area Ift') _
Actual Surface Area at Principal Spillway (ft2) _
Cteanout,
Cleanout Requirement 1%of Wet Storage) _
Cleanout Requirement 1% of Total. Storage) _
Basin Cleanout Volume (ft') _
Basin Cleanout Elevation (ft) _
Dewatering of Dry Storage:
Fa'rcloth Skimmer
Actual Total Storage Volume to Dewater Of') _
Required Orifice Diameter (in) =
Basin Drain Calculations: N/A
43,560 = Required Dry Storage + Actual Wet Storage
173.1
176.5 O.K.
227,362 O.K.
52,385
57,956 O.K.
0 Enter "0" if Not Applicable
50
113,681 Based on 50%of Total Storage Volume
174.5
227,362 = Volume at Principal Spillway
6.0 From www.fairclothskimmer.com Based on 2 to 5 Day Drawdown
Length of Basin lft) = 170 Measured at Principal Spillway Elevation
Width of Basin Off - 370 Measured at Principal Spillway Elevation
Desired Length to Width Ratio (X:11=. 3
Actual Length to Width Ratio (X:11= 0.5 No Good. Add Baffles.
SHEET 6/14
JOB If JOHNSTON-16-4
DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
SMITH GARDNER
SMITH CAROM TO, INC. Basin 1 W JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co.MSWLF-Phase6 SHEET 7/14
JOB# JOHNSTON-16-4
SUBJECT Sediment Basin Analysis DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
ROUTE DESIGN STORM: Use Hydro CAD or Other Method.
Design Parameters,
Results:
Check Settling Efficienim.
Particle Data:
Efficiency Data,
DESIGN OUTLET STRUCTURES:
Design Riser/Barrel Structures:
Riser Des
Design Storm: 25-Yr, 24-Hr
Design Storm Rainfall (in) = 6.6
Rainfall Distribution: Type II
Runoff Method: SCS TR-20
Maximum Pool Elevation = 176.5
Surface Area at Maximum Pool Ift'I = 57,918
Peak Discharge (cfs) = 0.5
Diem. (microns) _
Specific Gravity =
Settling Veloc. Ift/sl =
Reynolds No. k0.51=
Desired Efficiency (%) _
No. of Effective Cells =
Settling Efficiency (%) =
40
2.65
0.004140
0.044284 O.K.
80
2 Uafflas Used
100.0 O.K.
Type of Riser: Concrete - Rectangular
Top of Riser Base Elevation Ift1= 169.5
Elev. of Principal Spillway IN 176.5
Riser Top Elevation Ht1= 178.0
Riser Height (ft) = 8.5
Outlets:
Outlet No. 1 (for Dewatering Dry Storage): Size: 6" Diam. For Skimmer From Above - Dewatering of Dry Storage
Invert Elevation: 172.0 May Vary For Multiple Holes
Outlet No.2 (Principal SpRlwayl: Size: 4.0' Wide x 1.0' H Weir Ix4)
Invert Elevation: 176.5
Concrete Riser Wall Thickness (in) = 6.0
Riser Inside Length Ift) _
Riser Inside Width (ft)=
Approx. Rect. Concrete Riser Interior Volume Of =
Approx. Rect. Concrete Riser Vol. of Concrete (cf) _
Barrel Design
Type of Barrel:
Diameter (in) _
Inv. In Elevation (k) =
Inv. Out Elevation (ft) _
Length (ft) _
Slope (ft/ft) _
5.0
5.0
175 (Top of Base to Principal Spillway)
77
CMP
24
170.0
169.0
90.0
0.011
SMITH GARDNER
SMITH CAROM TO, INC. Basin 1 W JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co.MSWLF-Phase6 SHEET 8/14
JOB If JOHNSTON-16-4
SUBJECT Sediment Basin Analysis DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
Riser Base Calculations:
Design Uplift Force,
Factor of Safety =
1.25
F (unadjusted) (lbs) =
13,650
0
Approx. Rect. Concrete Riser Buoyant Wt. (lbs) =
5,396 Factors in 80% of the Buoyant Weight of the Concrete Riser to Account for Outlets.
0
0
Wt. of Riser Top fibs) =
2,700 6' x 6' x 0.5' x Wt. of Concrete It 50 pcf) (Note: Box will Fill w/ Water if Water Level Rises Above Riser Top)
Buoyant Wt. of Surrounding Soil Acting on Ext. Base fibs) =
1.920 4' Min. Depth x Outside Perimeter (24'1 x Base Protrusion (0.5'1 x Buoyant Wt. of Soil 140 pcf)
Sliding Resistance of Surrounding Soil fibs) =
1,920 4' Min. Depth x Outside Perimeter (249 x Assumed Soil Cohesion/Friction (20 psf)
F (adjusted) (lbs) =
1,714
Concrete Base:
Required Volume of Concrete (f€') =
19.6
Length (it) =
7.0
Width (ft) =
7.0
Thickness Ift) =
0.8 (includes Concrete lnfIU Inside of Box)
Actual VOLume of Concrete (ft') =
36.8 O.K.
Anti -Seepage Colter Calculations: (Alternatively- Design Filter Diaphragm)
Slope of Upstream Embankment (ZH:1V) =
3
Slope of Outlet Pipe Ift/ft) =
0.011
L,(it)=
62
Number of Collars:
2
Length of Each Collar (ft) =
6.7 From Design Chart Based on L, and No. of Collars
Width of Each Collar (it) =
6.7 From Design Chart Based on L. and No. of Collars
CoUar Projection, P (ft) =
2,35
Spacing of Subsequent Anti -Seep Collars (ft) =
33 = 14P
Emergency Spillway Calculations:
Crest Elev. (it) =
180.0
Required Freeboard (ft) =
1.0
Top of Berm Elev. (ft) =
181.0
Required Capacity (cfs) =
20.0 From HydroCAD - No Outflow from 100-Yr, 24-Hr. Storm; Assume 20 cfs Capacity
Driving Head Ift) =
0.5 Assumed
Weir Coefficient =
3.0
Length of Crest (ft)
18.9 Determine by Weir Equation -
Design Crest Length (it) =
20
• Length =2O ft minimum.
SUMMARY DATA:
Basin No.: Basin 1 W
Elev. of Bottom of Basin (ft) =
172.0
Cleanout Elev. Ift) =
174.5 Say 174,O
Elev. of Wet Storage (Permanent Pool) (ft) =
NA
Elev. of Principal Spillway (it)
176.5 See Above for Riser and Other Design Information.
Emergency Spillway Elev. (ft) =
180.0
Top of Berm Elev. (ft) =
181.0
Top of Berm Width (ft) =
15
Barrel Diameter (in) =
24
Barrel Slope(%)=
1.1
SMITH GARDNER
SMITH CAROM ER. INC. Basin 1 W JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co.MSWLF-Phase6 SHEET 9/14
JOB If JOHNSTON-16-4
SUBJECT Sediment Basin Analysis DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
Basin No.: Basin 3W
DESIGN FOR WET [IF APPLICABLEI
AND DRY STORAGE:
Areas Draining Into Basin:
Are
Drainage Area
(acres)
Drainage Area
57.9
Total. =
57.9 Acres
Basin Requirements:
Wet Storage,
Required Storage Capacity (ft'/Ac) =
0 Enter "0" if Not Applicable.
Required Storage Capacity lh'1=
0
Required Depth of Wet Storage (ft) =
0.0 Enter "0" if Not Applicable.
Dry Storage,
Required Storage Capacity (ft'/Ac.) =
1,800 To Crest of Principal Spillway
Required Storage Capacity(ft')=
104,220
Multipier
(XI for Desired Surface Area (Op x XI =
0.01 At Crest of Principal Spillway
Peak Discharge into Basin (Op) (cfs) =
131.9 From HydroCAD - 10-Yr, 24-Hr. Storm
i
Desired Surface Area (Ac) =
1.32
Determine Stage Function:
Desired Surface Area (ft') =
57,456
-Storage
Contour
Area Area
Incremental Cumulative Stage
In
In
Zest
(fill Iacresl
Volume (ff) Volume (ft3I (R)
200
40,000 0.92
0 0.0
202
46.000 1.06
86,000 86,000 2.0
11.36
0.69
2.03
204
53,000 1.22
99,000 185,000 4.0
12.13
1.39
3.93
206
59,000 1.35
112,000 297,000 6.0
12.60
1.79
5.90
208
66,000 1.52
125,000 422,000 8.0
12.95
2.08
7.98
210
75,000 1.72
141,000 563,000 10.0
13.24
2.30
10.22
Linear Regression Constants:
Ks= 37,676
Storage = 37676 z"1.16
b= 1.16
'CAUTION: CHECK INPUT FOR REGRESSION ANALYSIS[
Stage -Surface Area Relationship
212
210
208
206
a:
I 204
w
202
200
198
0 20,000 40,000 60,000 80,000
Surface Area (sf)
Stage -Storage Relationship
212
210
208
206
z
204
m
202
200
198
0 100,000 200,000 300,000 400,000 500,000 600,000
Storage (cf)
SMITH GARDNER
SMITH CAROM ER, INC. Basin 3W JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF- Phase 6
SUBJECT Sediment Basin Analysis
Basin Design Elevations:
Elev. of Bottom of Basin Ift) = 200.0
Wet Storage,
Required Storage Capacity(f€')= 0
Min. Elev. of Wet Storage (Permanent Pool) = 200.0
Selected Elev. of Wet Storage (Permanent Pool) = 200.0 O.K.
Actual Wet Storage Volume (ft') = 0 O.K.
Dry Storage,
Required Storage Capacity (f€') _
Min. Elev. of Principal Spillway (it) _
Selected Elev. of Principal Spillway (ft) _
Actual Total Storage Volume (ft') _
Desired Surface Area Ift') _
Actual Surface Area at Principal Spillway (ft2) _
Cteanout,
Cleanout Requirement 1%of Wet Storage) _
Cleanout Requirement 1% of Total. Storage) _
Basin Cleanout Volume (ft') _
Basin Cleanout Elevation (ft) _
Dewatering of Dry Storage:
Fa'rcloth Skimmer
Actual Total Storage Volume to Dewater Of') _
Required Orifice Diameter (in) =
Basin Drain Calculations: N/A
104,220 = Required Dry Storage + Actual Wet Storage
202.4
206.0 O.K.
302,933 O.K.
57,456
58,737 O.K.
0 Enter "0" if Not Applicable
50
151,467 Based on 50%of Total Storage Volume
203.3
302,933 = Volume at Principal Spillway
0.0 From www.fairclothskimmer.com Based on 2 to 5 Day Drawdown
Length of Basin Ift) = 470 Measured at Principal Spillway Elevation
Width of Basin Off - 160 Measured at Principal Spillway Elevation
Desired Length to Width Ratio (X:11=. 3
Actual Length to Width Ratio IX:11= 2.9 No Good. Add Baffles.
SHEET 10/14
JOB If JOHNSTON-16-4
DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
SMITH GARDNER
SMITH CAROM TO, INC. Basin 3W JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co. MSWLF- Phase 6 SHEET 11/14
JOB# JOHNSTON-16-4
SUBJECT Sediment Basin Analysis DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
ROUTE DESIGN STORM: Use Hydro CAD or Other Method.
Design Parameters,
Results:
Check Settling Efficienim.
Particle Data:
Efficiency Data,
DESIGN OUTLET STRUCTURES:
Design Riser/Barrel Structures:
Riser Des
Design Storm: 25-Yr, 24-Hr
Design Storm Rainfall (in) = 6.6
Rainfall Distribution: Type II
Runoff Method: SCS TR-20
Maximum Pool Elevation = 206.5
Surface Area at Maximum Pool Ift'I = 59,466
Peak Discharge (cfs) = 0.5
Diem. (microns) _
Specific Gravity =
Settling Veloc. Ift/sl =
Reynolds No. k0.51=
Desired Efficiency (%) _
No. of Effective Cells =
Settling Efficiency (%) =
40
2.65
0.004140
0.044284 O.K.
80
2 Baffles Used
100.0 O.K.
Type of Riser: Concrete - Rectangular
Top of Riser Base Elevation Ift1= 198.5
Elev. of Principal Spillway IN 206.0
Riser Top Elevation Ht1= 207.5
Riser Height (ft) = 9.0
Outlets:
Outlet No. 1 (for Dewatering Dry Storage): Size: 8" Diam. For Skimmer From Above - Dewatering of Dry Storage
Invert Elevation: 200.0 May Vary For Multiple Holes
Outlet No.2 (Principal SpRlwayl: Size: 4.0' Wide x 1.0' H Weir Ix4)
Invert Elevation: 206.0
Concrete Riser Wall Thickness (in) = 6.0
Riser Inside Length Ift) _
Riser Inside Width Ift1=
Approx. Rect. Concrete Riser Interior Volume Of =
Approx. Rect. Concrete Riser Vol. of Concrete (cf) _
Barrel Design
Type of Barrel:
Diameter (in) _
Inv. In Elevation I111=
Inv. Out Elevation (n) _
Length Ift1=
Slope (ft/ft) _
5.0
5.0
188 (Tap of Base to Principal Spillway)
83
CMP
24
199.0
196.0
160.0
0.019
SMITH GARDNER
SMITH CAROM TO, INC. Basin - JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
PROJECT Johnston Co.MSWLF-Phase6 SHEET 12/14
JOB If JOHNSTON-16-4
SUBJECT Sediment Basin Analysis DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
Riser Base Calculations:
Design Uplift Force,
Factor of Safety =
1.25
F(unadjusted)(lbs)=
14,625
0
Approx. Rect. Concrete Riser Buoyant Wt. (lbs) =
5,782 Factors in 80% of the Buoyant Weight of the Concrete Riser to Account for Outlets.
0
0
Buoyant Wt. of Riser Top fibs) =
2,700 6' x 6' x 0.5' x Wt. of Concrete It 50 pcf) (Note: Box will Fill w/ Water if Water Level Rises Above Riser Top)
Buoyant Wt. of Surrounding Soil Acting on Ext. Base fibs) =
1.920 4' Min. Depth x Outside Perimeter (24'1 x Base Protrusion (0.5'1 x Buoyant Wt. of Soil 140 pcf)
Sliding Resistance of Surrounding Soil fibs) =
1.920 4' Min. Depth x Outside Perimeter (241 x Assumed Soil Cohesion/Friction (20 psf)
F (adjusted) (lbs) =
2,303
Concrete Base:
Required Volume of Concrete (f€') =
26.3
Length (it) =
7.0
Width (ft) =
7.0
Thickness lRl=
0.8includes Concrete lnfill Inside of Box)
Actual VOLume of Concrete (ft') =
36.8 O.K.
Anti -Seepage Colter Calculations: (Alternatively- Design Filter Diaphragm)
Slope of Upstream Embankment (ZH:1V) =
3
Slope of Outlet Pipe Ift/ft) =
0.019
L, (ft) =
68
Number of Collars:
2
Length of Each Collar (ft) =
7.0 From Design Chart Based on L, and No. of Collars
Width of Each Collar (it) =
7.0 From Design Chart Based on L. and No. of Collars
CoUar Projection, P (ft) =
2.5
Spacing of Subsequent Anti -Seep Collars (ft) =
35 = 14P
Emergency Spillway Calculations:
Crest Elev. (it) =
208.0
Required Freeboard (ft) =
2.0
Top of Berm Elev. (ft) =
210.0
Required Capacity (cfs) =
20.0 From HydroCAD - Outflow from 100-Yr, 24-Hr. Storm = 6.5 cfs; Assume 20 cfs Capacity
Driving Head Ift) =
0.5 Assumed
Weir Coefficient =
3.0
Length of Crest (ft)
18.9 Determine by Weir Equation -
Design Crest Length (it) =
20
• Length =2O ft minimum.
SUMMARY DATA:
Basin No.: Basin 3W
Elev. of Bottom of Basin (ft) =
200.0
Cleanout Elev. Ift) =
203.3 9ay2O3O
Elev. of Wet Storage (Permanent Pool) (ft) =
NA
Elev. of Principal Spillway (it)
206.0 See Above for Riser and Other Design Information.
Emergency Spillway Elev. (ft) =
208.0
Top of Berm Elev. (ft) =
210.0
Top of Berm Width (ft) =
10
Barrel Diameter (in) =
24
Barrel Slope (%) =
1.9
SMITH GARDNER
SMITH CAROM ER, INC. Basin 3W JC SED BASIN -GENERAL

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E Skimmer Sizing
13 of 14
Home (/home) I About Us (/about -us) I Contact Us (/contact -us)
Installation Instructions Skimmer Sizing
(/instructions)
Manuals (/manuals) DETERMINING SKIMMER SIZE
Cut Sheets (/cut -sheets)
• Eight sizes available, ranging from 1 %" for small sediment traps to 8" for very large basins.
CAD Drawings (/cad -
drawings) • Size refers to the maximum diameter of the inlet. For example, a 4" Faircloth Skimmer® has a 4"
maximum orifice size.
Skimmer Sizing
(/skimmer -sizing) • Each Faircloth Skimmer® includes a plug and adjustable cutter for making an orifice (hole) smaller than
Prices/Ordering Info. the inlet to customize the flow rate for the particular basin.
(/prices -ordering -info)
TECHNICAL SIZING INSTRUCTIONS
FAQs (/fags)
Gallery (/gallery) To read "Determining the Skimmer Size and the Required Orifice for the Faircloth Skimmer® Surface Drain"
click here (/library/library/documents/skimmerandorificesizingll-07tm-OOO.pdf) .
Vent Color Codes (/vent -
color -codes) ONLINE SIZING CALCULATOR
Detailed instructions can be found here (/library/library/documents/sizing-template-instructions-10-08.pdf) .
Instructions:
1. Download (/library/library/documents/sizingtemplateforweb-003.xis) the Sizing Calculator. Microsoft
Excel is required.
2. Enter Volume (in cubic feet) of basin to be drained and Number of Days in the green boxes
3. Hit ENTER to run the spread sheet. The skimmer size and the orifice radius and diameter will appear in
the blue box'.
'Caution : This calculator does not take into consideration COMMON SENSE. For example, if the
volume entered is even one cubic foot greater that the maximum calculated capacity of a skimmer the
next larger size will be given as the answer. In reality a reasonable judgment would be that the smaller
size is adequate given the room for error in the assumptions that go along with the design and sizing
process. Therefore it is recommended that the following chart be used together with the spread sheet.
BASIN VOLUME ESTIMATOR
If you do not know the basin's volume but know the dimensions and depth of a square or rectangular basin,
enter the dimensions in the Volume Estimator portion of the SIZING CALCULATOR.
FLOW CAPACITIES (IN CU. FT.) FOR THE FAIRCLOTH SKIMMER®
Skimmer size
1.5" 2"
2.5"
24 hours
1,728 3,283
6,234
2 day
3,456 6,566
12,468
3 day
5,184 9,849
18,702
4 day
6,912 13,132
24,936
5 day
8,640 16,415
31,170
6 day
10,368 19,698
37,404
7 day
12,096 22,981
43,638
3" 4" 5" 6" 8"
9,774 20,109 32,832 51,840 97,978
19,548 40,218 65,664 103,680 195,956
29,322 60,327 98,496 155,520 293,934
39,096 80,436 131,328 207,360 391,912
48,870 100,545 164,160 259,200 489,890
58,644 120,654 196,992 311,040 587,868
68,418 140,763 229,824 362,880 685,846
Important note: The orifice sizing chart in the Pennsylvania Erosion Control Manual DOES NOT APPLY to
Faircloth Skimmer® surface drains. It will give the wrong size skimmer. Please use these instructions to choose
the size skimmer required for the basin volume and the orifice size.

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
14 of 14
M
I50
2MMEaJ
J
Figure 5A.33 (2)
Anti -Seep Collar Design Charts
IN
w
COLLAR PROJECTION , V, FEET
1 2 3 4 5
rIow pain.
3
2
Octobcr 1991 -Third Printing Page 5AA5 Ncw York Guideline for Urban
Erosion and 5edim. it Control

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
ADDRESS TEL WEB
SMITH GAR D N E R 14 N. Boylan Avenue, Raleigh, NC 27603 919.828.0577 www.smithgardnerinc.com
PROJECT Johnston Co. MSWLF - Phase 6 SHEET 1 OF 4 DATE 3/13/2019
COMPUTED BY PKS
SUBJECT Outlet Protection Analysis JOB # JOHNSTON-16-4 CHECKED BY SWH
OBJECTIVE: To design outlet protection for culverts and/or drainage channels based on the maximum flow from the
design storm. Rip rap aprons are applicable when the Froude Number (Fr) is Less than or equal to 2.5
(Debo and Reese). For higher Froude Numbers, rip rap outlet basins, baffled outlets, and/or other
methods are more appropriate.
REFERENCES: Debo, T.N., and Reese, A.J. (1995), Municipal Storm Water Management, Lewis Publishers, Boca Raton, FL,
Section 8.11 - pp. 289-290; Section 12.6 - pp. 523-526.
Federal Highway Administration (2000), Hydraulic Design of Energy Dissipators for Culverts and Channels,
Hydraulic Engineering Circular No. 14, FHWA EPD-86-110, Metric Ed., U.S. Dept. of Transportation,
Washington, D.C.
North Carolina Division of Land Resources (2013 Updates), North Carolina Erosion & Sediment Control
Planning & Design Manual, Raleigh, NC.
ANALYSIS: For each outlet, determine the Froude Number IF,) based on the pipe Manning's number, diameter, slope,
and design discharge. Use the methods described in Section 8.11 of Debo and Reese. Select the method of
outlet protection, as appropriate, and perform design calculations.
Rip Rap Aprons:
If Fr < 2.5, a rip rap apron may be used. The following design approach is based on Section 12.6 of Debo
and Reese and Section 8.06 of the NC Erosion & Sediment Control Planning and Design Manual:
1. Determine the tailwater condition and select the appropriate design chart.
2• Using the appropriate design chart, determine the d5o rip -rap size and minimum apron length
(La) based on the maximum design flow (Q), flow depth (d), and/or velocity (v) (depending on
whether the pipe is flowing full or partially full).
3. Using the same chart, determine apron dimensions.
4. Determine the maximum stone diameter: dmax = 1.5 x d50
5. Determine the apron thickness:
Thickness = 1.5 x dmax (No Filter Geotextile)
Thickness = 1.5 x d50 (With Filter Geotextile)
Other Methods:
If Fr > 2.5, consider the use of a rip rap basin, baffled outlet, or other device. Design method according to
FHA guidelines using HY8-Energy program (or other documented source).
SMITH GARNER, INC. JC OUTLET PROTECTION

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
PROJECT Johnston County MSW Landfill - Phase 6 SHEET 2/4
JOB # JOHNSTON-16-4
SUBJECT Outlet Protection Analysis - Rip Rap Aprons (Circular Pipe) DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
Outlet
C-11
C-12
C-35
C-Al
C-A2
Pipe Type:
Concrete
Concrete
Concrete
Concrete
Concrete
Manning's Coefficient:
0.012
0.012
0.012
0.012
0.012
Diameter IDo) (in) =
36
30
48
30
24
Slope (%I =
2.3
2.6
2.3
1.3
2.7
Design Discharge (cfsl =
47.7
20.3
88.7
41.0
32.8
10 Ac. Max.; 25-Yr 5-Min.
8 Ac. Max.; 25-Yr 5-Min.
Source of Discharge Data:
HydroCAD 25-Yr 24-Hr
HydroCAD 25-Yr 24-Hr
HydroCAD 25-Yr 24-Hr
O=CIA
O=CIA
=0.5x8.19in/hrx10Ac.
=0.5x8.19in/hrx8Ac.
K=
0.136
0.088
0.117
0.252
0.254
0(degrees)=
173
151
165
221
222
Flow Depth (d) (in] =
16.9
11.2
20.8
20.2
16.3
Flow Area Ift21 =
3.3
1.7
5.2
3.5
2.3
FLow Velocity (v) Ift/sec) =
14.6
12.1
17.0
11.6
14.5
Froude Number=
2.17
2.21
2.27
1.58
2.19
Rip Rap Aprons Applicable?
Yes
Yes
Yes
Yes
Yes
Tailwater Condition (Low or High)*:
Low
Low
Low
Low
Low
d5o (ftl** =
0.75
0.75
1.00
0.75
0.75
d_ (ft) =
1.13
1.13
1.50
1.13
1.13
Apron Thickness (XI (ftl:
-----
-----
-----
-----
No Geotextile:
1.69
1.69
2.25
1.69
1.69
With Geotextile:
1.13
1.13
1.50
1.13
1.13
Apron Dimensions (ft):
-----
-----
-----
-----
LengthlLal**=
18
15
24
19
18
Width IWI=
21.0
17.5
28.0
21.5
20.0
*TailwaterConditions: Low: Tw<0.5Do; High: Tw>0.5Do
** Value from Chart.
SMITH GARDNER
SMITH GARDNER, INC. Rip Rap Aprons 1 JC OUTLET PROTECTION

DocuSign Envelope ID: 6C446OA9-4162-49OA-AB87-34B368159E9E
PROJECT Johnston County MSW Landfill - Phase 6 SHEET 3/4
JOB # JOHNSTON-16-4
SUBJECT Outlet Protection Analysis - Rip Rap Aprons (Circular Pipe) DATE 3/13/2019
COMPUTED BY PKS
CHECKED BY SWH
Outlet
BASINS 1 W & 3W
Pipe Type:
CMP
Manning's Coefficient:
0.022
Diameter (Do) (in) =
24
Slope (%I =
1.0
Design Discharge (cfsl =
20.0
Source of Discharge Data:
»> Than Predicted by
HydroCAD 25-Yr 24-Hr
K=
0.466
0 (degrees) =
265
Flow Depth (d) (in1=
20.1
Flow Area (ft21=
2.8
FLow Velocity (v) Ift/sect =
7.1
Froude Number=
0.97
Rip Rap Aprons Applicable?
Yes
Tailwater Condition (Low or High)*:
Low
d50fftl**=
0.50
d_ (ft) =
0.75
Apron Thickness (XI (ft):
-----
No Geotextile:
1.13
With Geotextile:
0.75
Apron Dimensions (ft):
-----
LengthlLal**=
12
Width lWI=
14.0
*TailwaterConditions: Low: Tw<0.5Do; High: Tw>0.5Do
** Value from Chart.
SMITH GARDNER
SMITH GARDNER, INC. Rip Rap Aprons 2 JC OUTLET PROTECTION

DocuSign Envelope ID: 6C4460A9-4162-490A-AB87-34B368159E9E
1
4 of 4
Appendices
• 1 i��.11l .,:
. ��� +� i` 1�11 I -}IIr�' f1►�I!!jj1iiII��II
4
3
h,
2 'v
U)
Cl-
CIS
a
tr
O
{{il ,' jil;' ��Il�lf�!', _ f { {l { ��.. •If 1 :II' II I
L_= II 11
v=s
3 5 A, 50 100 200 500 1`000
C- Dis harge (ft3/sec)
a
Curves may not be extrapofat
Figure 6.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (Tw < 0.5 diameter).
till f
5
Lquil lull
Rev. 12/93 8.06.3