SW6221201_Design Calculations_20230404

CSD
ENGINEERING
PROJECT NARRATIVE
With Project Calculations & Supporting Documents
Ample Storage — Erwin, NC
INTRODUCTION
0
:v E r. f
032721
CA
4/4/2023
Turtle Run, LLC is proposing to build an Ample Storage facility at 404 E. Jackson Boulevard in the Town of
Erwin, Harnett County, NC. The development will consist of buildings for indoor storage, office, and on -
site apartment for facility manager. Submittals for approval and permitting include detailed construction
drawings for site plan, grading, paving, drainage, and stormwater management for the site and minor
improvements within the public right-of-way for driveway access. Approval of the construction drawings
are under the jurisdiction of the Town of Erwin for site plan approval and zoning permit; N.C. Department
of Environmental Quality (NCDEQ), Division of Water Resources (DWR) for stormwater management
permit; and NCDEQ, Division of Land Resources (DLR), Land Quality Section for approval of the erosion
and sediment control plan. The proposed driveway access will be reviewed and permitted by the N.C.
Department of Transportation (NCDOT) District Office for Harnett County.
CjOM
Soil data was obtained from the NRCS Web Soil Survey for the project area of interest in Harnett County,
NC. The soil map from the web application is included with the project calculations and supporting
documents. The site mostly consists of loamy sand to sandy loam soils. The soils on the site are associated
with uplands and are not a flood prone soil. The soils for the Goldsboro and Marlboro soil series are
moderately well -drained soils; therefore, ponding on the surface of bare soil is not expected during
construction. Unified classification (used in channel analysis) is SM at the surface. The site grading requires
import of soils for the building and driveway foundations. A geotechnical engineering study for the borrow
soils is recommended for structural purposes; however, for the purposes of stormwater runoff and
erosion and sediment control, the properties of the in -situ soils were used. Regarding drainage, the soils
have moderate permeability and fall into Hydrologic Soil Group B. The soil survey states that the water
table is from 2 to 3 feet below the surface in the winter and spring; therefore, water may be encountered
during installation of storm drainage pipes and the wet pond.
1

Project Narrative
Ample Storage — Erwin, NC
The soil composition was considered during design and analysis for hydrology, hydraulics, and erosion and
sediment control. The soil map for the area of interest and sections of the soil report that were used to
gather data used in the design and analysis have been included in the calculations and supporting
documents.
HYDROLOGY
The area of improvement consists of one (1) drainage area within the site boundary. The total site area is
6.18 acres; however, the hydrologic analysis was conducted for the drainage area to the proposed wet
pond (4.65 acres) which is all the new impervious area plus some pervious areas within the site
development. The remaining on -site may be disturbed during construction; however, this area will remain
pervious and not affect the pre- and post -development analysis. The hydrologic calculations for the
drainage area to the pond includes pre -development curve number (CN) for the existing conditions and
post -development CN for the proposed conditions. The drainage area analyzed was delineate using the
post -development grading which was designed to drain all on -site impervious areas to the proposed wet
pond. The existing area within the post -development drainage area drains to the lowest point on the site,
which is the outfall point for the proposed wet pond.
The pre- and post -development Drainage Area Maps show drainage area delineations, along with
unimproved areas that do not drain to the proposed wet pond. The impervious surfaces on the Ample
Storage site will be drained through a closed drainage system to the proposed wet pond.
NRCS Peak Runoff Method
The methods outlined in NRCS TR-55 were used to calculate peak runoff for land uses, time of
concentration, and peak runoff for the drainage area. The Curve Numbers used were calculated using a
composite curve number calculation. Precipitation data was obtained from NOAA's Precipitation
Frequency Data Server (web -based), Atlas 14 Point Precipitation Frequency Estimates. The latitude and
longitude were entered for the location and the 24-hour precipitation depths for the 1, 2, 10, 25, and 100-
year storm recurrence interval were recorded and used in subsequent hydrologic calculations. The
precipitation depth for the 1-year. 24-hour storm is 3.70 inches according to the NOAA estimates and this
was used in time of concentration calculations.
The computer software program Hydraflow Hydrographs was used to calculate peak runoff hydrographs
and used to determine the storage required for proposed detention ponds. A copy of the Hydraflow
Hydrograph reports for peak flow have been included in this submittal. The hydrologic calculations are
summarized as follows:
➢ Drainage Area:
➢ Pre -development CN
➢ Post -development CN
➢ Time of Concentration
➢ Pre -development runoff (cfs):
➢ Post -development runoff (cfs)
4.65 acres
68
94
12 minutes
Q1=3.88; Q2=6.47; Q10=15.30; Q25=21.54; Q100=32.65
Q1=15.39; Q2=19.19; Q10=30.06; Q25=36.81; Q100=48.08
STORMWATER CONTROL MEASURE
A stormwater wet pond is proposed to capture runoff from the site and release it slowly; and the size
needed has been calculated and represented in the plans. Hydraflow Hydrographs was used to calculate
2

Project Narrative
Ample Storage — Erwin, NC
the peak flow hydrographs for multiple storm recurrence intervals and subsequently used to route the
inflow hydrographs and generate an outflow hydrograph for the temporary pool and outlet structure.
Data used in site runoff calculations was used to estimate the size needed to meet water quality and water
quantity treatment requirements as to improve the post -development stormwater management of the
overall drainage area. Once the area needed for the pond was estimated, design for the actual pond
grading was entered to determine the actual storage.
Various outlet structure and spillway combinations were tried until an optimal solution was reached. A
concrete riser with sloped top and trash rack is proposed and adequately stores the 1-year, 24-hour. 2-
year, 24-hour storm , and 10-year 24-hour storm volumes. The secondary spillway will be a 15-feet weir
in the wet pond dam. A copy of the Hydraflow calculation reports for the 1, 2, 10, 25 and 100-year storms
are included in the calculations and supporting documentation. A schematic showing the estimated water
surface elevations for the pond and the orifice sizing calculation for release of the overall storage volume
have also been included. A summary of the routing calculations follows the next section of the narrative.
Minimum Design Criteria
The proposed wet pond was designed for water quality treatment and water quantity storage. The main
pool surface area and volume was computed using the SA/DA and average depth method. Through
iterations of main pool, forebay, and vegetated shelf configurations, the average depth of the pond was
calculated to meet MDC (3 to 8 feet below permanent pool elevation). The average depth of the pond
was used to determine the minimum surface area of the permanent pool to remove 85% TSS; from Table
1 in Chapter C-3 of the NCDEQ Stormwater Design Manual. The actual surface area at the permanent pool
elevation is nearly twice what is needed for 85% TSS removal. The "Simple Method" was used to
determine the minimum storage needed for the temporary water quality pool (volume of the 1"
precipitation or the "first flush"). The final pond design adequately provides storage above the permanent
pool for water quality treatment (see summary and supporting calculations).
For the main pool depth, Equation 3 in Chapter C-3 of the Stormwater BMP Manual was used because the
vegetated shelf was excluded from the average depth calculation. Through several iterations, the forebay
volume was designed to be within 15 to 20 percent of the main pool volume. The proposed grading
contours on the plans show the forebay entrance is deeper than the exit. The berm that separates the
forebay from the main pool will be submerged and flows will be non -erosive. The forebay and main pool
will be excavated to meet sediment storage requirements.
The wet pond inlet and outlets were configurated to maximize the flow path. The pond will outlet along
the length of the pond giving a wide area to facilitate settling. The pond has been routed for an outlet
structure that will adequately convey storm events and provide adequate detention to protect
downstream property. The drawdown of wet pond will be gradual within 2 to 3 days. The sloped top of
the riser shall be covered by a prefabricated metal grate and help prevent debris from blocking top of
riser.
The wet pond will include a 12-foot-wide vegetated shelf at a 6:1 slope; 1 foot elevation above the
permanent pool to one foot elevation below the permanent pool. A landscape plan is included in the
construction drawings for planting of the vegetated shelf and mesic area around the pond. The plant
schedule calls for Pickerelweed, Arrow Arum, and Bull Tongue within the submerged vegetated shelf; and,
a variety of sedges within the wet mesic part of the vegetated shelf. Juncus will be planted along the
water's edge to protect the more fragile submergent plants from potential rouge mowing by maintenance
3

Project Narrative
Ample Storage — Erwin, NC
crews. The embankments may be planted with love grass; however, a non -clumping turf grass will likely
be used.
For the final pond grading design, outlet details, and landscape plan, see the construction drawings. The
water quality and water quantity calculations, hydrograph reports, routing, drawdown, and anti -floatation
calculations are included in the project calculations and supporting documents. A summary of the final
wet pond design and calculations is provided below:
➢ Permanent Pool Water Elevation:
➢ Forebay Volume:
➢ Main Pool Volume:
➢ Vegetated Shelf Volume:
➢ Surface Area at Bottom of Shelf:
➢ % Forebay Volume:
➢ Average Depth:
➢ Drainage Area:
➢ Impervious Area:
➢ % Impervious:
➢ SA/DA (Table 1; interpolated)
➢ Surface Area Required (85% TSS):
➢ Actual Surface Area @ 192.0 feet:
➢ Water Quality Volume to be controlled:
➢ Depth of runoff added to permanent pool
➢ Temporary Water Quality Pool Elevation:
➢ Actual Storage at 193.36 feet:
Pond Routing Summary:
➢ Top of Dam:
➢ Emergency Spillway weir elevation and length
➢ Riser weir elevation and length:
➢ Culvert size/type and invert elevation:
➢ 1-Year Stage, Storage, and Outflow:
➢ 2-Year Stage, Storage, and Outflow:
➢ 10-Year Stage, Storage, and Outflow:
➢ 25-Year Stage, Storage, and Outflow:
➢ 100-Year Stage, Storage, and Outflow:
➢ Water Quality Volume to Drawdown:
➢ Drawdown Orifice Size:
➢ Drawdown Time:
HYDRAULIC DESIGN
192 feet
3,987 cubic feet (cf)
21,950 cf
1,680 cf (below Permanent Pool Elevation)
5,070 square feet (sf)
18.2
4.0 feet (Main Pool — Veg. shelf / SA at shelf)
4.65 Acres
3.92 Acres
84.3
2.51
5,084 sf
10,035 sf
13,651 cf
1.36 feet
193.36 feet
16,833 cf
197.00 feet
195.40 feet; 15.0 feet (Cipoletti)
193.70 feet; 5.0 feet (one side of box)
18 inches; R.C. Pipe; 191.60 feet
193.92 feet; 24,908 cf; 1.87 cfs
194.18 feet: 28,878 cf; 5.60 cfs
194.94 feet: 41,077 cf; 12.70 cfs
195.38 feet: 48,963 cf; 14.40 cfs
195.82 feet; 56,887 cf; 28.14 cfs
16,833 cf
1.0 inches (hole drilled in 4-inch PVC cap)
2.3 days
The closed storm drainage system were designed and analyzed using Hydraflow Storm Sewers software,
using the methods outlined by Dr. Rooney Malcolm in "Elements of Stormwater Design" for closed system
design (Rational Formula used for estimating runoff to inlets). The worst case scenario for water surface
elevation in the wet pond was used for the starting elevation in the hydraulic grade line calculations. Some
of the drainage system will be wet during normal conditions; therefore, the pipes were sized to
4

Project Narrative
Ample Storage — Erwin, NC
accommodate the storm runoff under "wet" conditions. The 100-year storm was analyzed for potential
site flooding and the 100-year hydraulic grade line does not exceed the finish floor elevations of the
building. The grading plan also shows areas where ponding water may runoff site prior to flooding
buildings.
The roadside channel along St. Matthews Road was analyzed for stability using a custom design
spreadsheet workbook that was developed using the normal depth method outlined by Dr. Rooney
Malcolm in "Elements of Stormwater Design" and methods outlined in FHWA HEC-15 "Design of Roadway
Channels with Flexible Linings" (3rd Ed.). The spreadsheet inputs require discharge, slope, channel
geometry, soil data, and permissible shear stress values. For the input given, the normal depth of flow is
determined through iteration of values until the solution is met. The shear stress is calculated, and
appropriate liners are determined for stability. Normal depth for the channel downstream of driveway
culvert was used in the sizing of the driveway pipe. The channel analysis calculations have been included
in this submittal.
EROSION AND SEDIMENT CONTROL
The erosion and sediment control plan includes measures to keep runoff from disturbed areas from
leaving the site, minimize initial erosion, and to capture sediment from disturbed areas. The plan is divided
into two phases: demolition/clear and grub (1) and intermediate/final (2). The plans show a constructed
berm at the low end of the site to be built to finished slope and grade. The berm will act as a temporary
diversion to drain disturbed areas to the sediment basin. The construction drawings show detailed
sections for the berm/diversion. The sediment basin will be constructed in the footprint of the proposed
wet pond. The contractor has the option of building the pond riser and grading the pond first. The site will
be graded through stages so that runoff will be intercepted by the diversion. A basin dimension worksheet
summarizes the basin design, and the sediment basin will be dewatered from surface with a skimmer. The
wet pond riser detail shows how a skimmer can be attached to the permanent riser. Temporary inlet
protection will be utilized to keep sediment out of the drainage system boxes and pipes. The site will be
stabilized throughout construction with erosion control matting, gravel subgrade, pavement, concrete,
and permanent vegetation as construction progresses.
UTILITIES
The site will be served by an existing water service. A septic permit has been obtained to repair/relocate
the existing septic system. Construction of a new septic system is included in the limits of disturbance;
however, there will be limited disturbance in this area beside Building A. Minimal disturbance is
anticipated for modifications of the water service from the meter to the buildings.
5

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ENGINEERING AMPLE STORAGE USGS QUAD MAP DATE: 1012512022
LAND PLANNING DRAWN BY. JFO
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r.a � 12M LAND OWNER. TURTLE RUN, LLC HARNETT COUNTY, NC
w 1rc 27591 225 PEEDIN ROAD 7.5—MINUTE SERIES
LICENSE # c-2ro SMITHFIELD, NC 27577 2016 UAD-1
19191 �ho27' PROD. NO: 21-0590 �

712680
35° 19'49"N
712770 712860 712950
Soil Map —Harnett County, North Carolina
(Ample Storage - Irwin)
713040 713130 713220
1 1 1
ExA
a ,
r
Soil MaN 11 iaot h �aliel at this scale.
712680 712770 712860 712950 713040 713130
Map Scale: 1:4,190 if printed on A landscape (11" x 8.5") sheet.
Meters
N 0 50 100 200 500
Feet
0 200 400 8D0 1200
Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 17N WGS84
USDA Natural Resources Web Soil Survey
IiI Conservation Service National Cooperative Soil Surve
713310 713400 713490
713220 713310 713400
35° 19' 49" N
0
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- 35° 19' 30" N
713490 713580
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5/9/2022
Page 1 of 3

MAP LEGEND
Area of Interest (AOI)
0
Area of Interest (AOI)
Soils
0
Soil Map Unit Polygons
,N
Soil Map Unit Lines
Soil Map Unit Points
Special
Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
�i
Gravelly Spot
0
Landfill
A.
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
o
Sodic Spot
Soil Map —Harnett County, North Carolina
(Ample Storage - Irwin)
MAP INFORMATION
Spoil Area
The soil surveys that comprise your AOI were mapped at
1:24,000.
Stony Spot
Very Stony Spot
Warning: Soil Map may not be valid at this scale.
Wet Spot
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
4�
Other
line placement. The maps do not show the small areas of
Special Line Features
contrasting soils that could have been shown at a more detailed
scale.
Water Features
Streams and Canals
Please rely on the bar scale on each map sheet for map
measurements.
Transportation
Rails
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
. 0
Interstate Highways
Coordinate System: Web Mercator (EPSG:3857)
US Routes
Maps from the Web Soil Survey are based on the Web Mercator
Major Roads
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Local Roads
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
Background
Aerial Photography
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Harnett County, North Carolina
Survey Area Data: Version 19, Jan 21, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Oct 22, 2018—Oct
25, 2018
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
usoA Natural Resources Web Soil Survey 5/9/2022
Conservation Service National Cooperative Soil Survey Page 2 of 3

Soil Map —Harnett County, North Carolina
Ample Storage - Irwin
Map Unit Legend
Map Unit Symbol
Map Unit Name
Acres in AOI
Percent of AOI
Co
Coxville loam
16.0
21.1 %
ExA
Exum very fine sandy loam, 0
to 2 percent slopes
1.5
1.9%
GoA
Goldsboro loamy sand, 0 to 2
percent slopes, Southern
Coastal Plain
13.3
17.5%
MaA
Marlboro sandy loam, 0 to 2
percent slopes
21.6
28.4%
MaB
Marlboro sandy loam, 2 to 6
percent slopes
1.3
1.7%
Na
Nahunta loam
0.5
0.7%
NoA
Norfolk loamy sand, 0 to 2
percent slopes
6.7
8.8%
NoB
Norfolk loamy sand, 2 to 6
percent slopes
6.4
8.4%
OrB
Orangeburg loamy sand, 2 to 6
percent slopes
8.8
11.5%
Totals for Area of Interest
76.9
100.0%
USDA Natural Resources Web Soil Survey 5/9/2022
Conservation Service National Cooperative Soil Survey Page 3 of 3

Plasticity Index ---Harnett County, North Carolina
Plasticity Index
Map unit symbol
Map unit name
Rating (percent)
Acres in AOI
Percent of AOI
Co
Coxville loam
24.0
16.0
21.1 %
ExA
Exum very fine sandy
19.0
1.5
1.9%
loam, 0 to 2 percent
slopes
GoA
Goldsboro loamy sand,
11.0
13.3
17.5%
0 to 2 percent slopes,
Southern Coastal
Plain
MaA
Marlboro sandy loam, 0
13.0
21.6
28.4%
to 2 percent slopes
MaB
Marlboro sandy loam, 2
13.0
1.3
1.7%
to 6 percent slopes
Na
Nahunta loam
19.0
0.5
0.7%
NoA
Norfolk loamy sand, 0 to
11.6
6.7
8.8%
2 percent slopes
NoB
Norfolk loamy sand, 2 to
9.7
6.4
8.4%
6 percent slopes
OrB
Orangeburg loamy
11.0
8.8
11.5%
sand, 2 to 6 percent
slopes
Totals for Area of Interest
76.9
100.0%
USDA Natural Resources Web Soil Survey 5/9/2022
Conservation Service National Cooperative Soil Survey Page 1 of 2

Plasticity Index ---Harnett County, North Carolina
Description
Plasticity index (PI) is one of the standard Atterberg limits used to indicate the
plasticity characteristics of a soil. It is defined as the numerical difference
between the liquid limit and plastic limit of the soil. It is the range of water content
in which a soil exhibits the characteristics of a plastic solid.
The plastic limit is the water content that corresponds to an arbitrary limit
between the plastic and semisolid states of a soil. The liquid limit is the water
content, on a percent by weight basis, of the soil (passing #40 sieve) at which the
soil changes from a plastic to a liquid state.
Soils that have a high plasticity index have a wide range of moisture content in
which the soil performs as a plastic material. Highly and moderately plastic clays
have large PI values. Plasticity index is used in classifying soils in the Unified and
AASHTO classification systems.
For each soil layer, this attribute is actually recorded as three separate values in
the database. A low value and a high value indicate the range of this attribute for
the soil component. A "representative" value indicates the expected value of this
attribute for the component. For this soil property, only the representative value is
used.
Rating Options
Units of Measure: percent
Aggregation Method: Dominant Component
Component Percent Cutoff.- None Specified
Tie -break Rule: Higher
Interpret Nulls as Zero: No
Layer Options (Horizon Aggregation Method): Depth Range (Weighted Average)
Top Depth: 12
Bottom Depth: 24
Units of Measure: Inches
USDA Natural Resources Web Soil Survey 5/9/2022
Conservation Service National Cooperative Soil Survey Page 2 of 2

Hydrologic Soil Group and Surface Runoff ---Harnett County, North Carolina
Ample Storage - Irwin
Hydrologic Soil Group and Surface Runoff
This table gives estimates of various soil water features. The estimates are used
in land use planning that involves engineering considerations.
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long -duration storms.
The four hydrologic soil groups are:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink -swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas.
Surface runoff refers to the loss of water from an area by flow over the land
surface. Surface runoff classes are based on slope, climate, and vegetative
cover. The concept indicates relative runoff for very specific conditions. It is
assumed that the surface of the soil is bare and that the retention of surface
water resulting from irregularities in the ground surface is minimal. The classes
are negligible, very low, low, medium, high, and very high.
Report —Hydrologic Soil Group and Surface Runoff
Absence of an entry indicates that the data were not estimated. The dash
indicates no documented presence.
Hydrologic Soil Group and Surface Runoff —Harnett County, North Carolina
Map symbol and soil name
Pct. of map unit
Surface Runoff
Hydrologic Soil Group
Co—Coxville loam
Coxville, drained
85
Low
C/D
Coxville, undrained
10
Low
C/D
USDA Natural Resources Web Soil Survey 5/9/2022
Conservation Service National Cooperative Soil Survey Page 1 of 2

Hydrologic Soil Group and Surface Runoff ---Harnett County, North Carolina
Ample Storage - Irwin
Hydrologic Soil Group and Surface Runoff —Harnett County, North Carolina
Map symbol and soil name
Pct. of map unit
Surface Runoff
Hydrologic Soil Group
ExA—Exum very fine sandy loam, 0 to 2 percent
slopes
Exum
90
Low
C
GoA—Goldsboro loamy sand, 0 to 2 percent slopes,
Southern Coastal Plain
Goldsboro
85
—
B
MaA—Marlboro sandy loam, 0 to 2 percent slopes
Marlboro
90
Low
B
MaB—Marlboro sandy loam, 2 to 6 percent slopes
Marlboro
90
Low
B
Na—Nahunta loam
Nahunta, drained
80
Low
C/D
Nahunta, undrained
10
Low
C/D
NoA—Norfolk loamy sand, 0 to 2 percent slopes
Norfolk
83
—
A
NoB—Norfolk loamy sand, 2 to 6 percent slopes
Norfolk
83
—
A
OrB—Orangeburg loamy sand, 2 to 6 percent slopes
Orangeburg
90
Low
A
Data Source Information
Soil Survey Area: Harnett County, North Carolina
Survey Area Data: Version 19, Jan 21, 2022
USDA Natural Resources Web Soil Survey 5/9/2022
am Conservation Service National Cooperative Soil Survey Page 2 of 2

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CSD Engineering
Subject: Stormwater Detention Design Date: 10/25/2022
Set Up By: JO
Work: Pre -development Conditions - Outfall 1 Computed By: JO
Checked By: HR
Project: Ample Storage - Erwin JOB NO. 21-0590 Page No. 3 OF 8
Site Offsite
DA= 4.65
AC
4.65 0.00
SUB AREAS
Total Area Description
CN
Open Space
2.54
Managed Open Space
69
Open Space -UM
1.84
Unmanaged Open Space
61
Pavement
0.22
Drive Aisles & Parking
98
Sidewalk
0.00
Concrete Sidewalk
98
Building (Roof)
0.05
With roof drains
98
SCM
0.00
Wet Pond
80
Total
4.65
SOIL TYPES
Hydrologic Soil Group Sub Area Area (AcresCN
B Open Space 2.54 69
Open Space -UM 1.84 61
CURVE NUMBER
CN = (Area 1 x CN 1) + (Area2 x CN2) + ....
Sum(Areal, Area2...)
CN = 67.5
SAY 68
TIME OF CONCENTRATION
From TR-55 Worksheet: 12.0 min.
REMARKS:

CSD Engineering
Subject: Stormwater Detention Design Date: 10/25/2022
Set Up By: JO
Work: Pre -development Conditions - Outfall 1 Computed By: JO
Checked By: HR
Project: Ample Storage - Erwin JOB NO. 21-0590 Page No. 3 OF 8
Site Offsite
DA= 4.65
AC
4.65 0.00
SUB AREAS
Total Area Description
CN
Open Space
0.34
Managed Open Space
69
Open Space -UM
0.00
Unmanaged Open Space
61
Pavement
1.49
Drive Aisles & Parking
98
Sidewalk
0.02
Concrete Sidewalk
98
Building (Roof)
2.41
With roof drains
98
SCM
0.39
Wet Pond
80
Total
4.65
SOIL TYPES
Hydrologic Soil Group Sub Area Area (AcresCN
B Open Space 0.34 69
Open Space -UM 0.00 61
CURVE NUMBER
CN = (Area 1 x CN 1) + (Area2 x CN2) + ....
Sum(Areal, Area2...)
CN = 94.4
SAY 94
TIME OF CONCENTRATION
From TR-55 Worksheet: 12.0 min.
REMARKS:

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023 Tuesday, 10 / 25 / 2022
Hyd. No. 3
Pre -Development (NRCS)
Hydrograph type
= SCS Runoff
Peak discharge
= 3.876 cfs
Storm frequency
= 1 yrs
Time to peak
= 722 min
Time interval
= 2 min
Hyd. volume
= 11,359 cuft
Drainage area
= 4.650 ac
Curve number
= 68
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 12.00 min
Total precip.
= 3.05 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Pre -Development (NRCS)
Q (Cfs) Hyd. No. 3 -- 1 Year Q (Cfs)
4.00 4.00
3.00 3.00
2.00 2.00
1.00 1.00
0.00 - 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
— Hyd No. 3 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Tuesday, 10 / 25 / 2022
Hyd. No. 4
Post -Development (NRCS)
Hydrograph type =
SCS Runoff
Peak discharge
= 15.39 cfs
Storm frequency =
1 yrs
Time to peak
= 720 min
Time interval =
2 min
Hyd. volume
= 41,750 cuft
Drainage area =
4.650 ac
Curve number
= 94
Basin Slope =
0.0 %
Hydraulic length
= 0 ft
Tc method =
User
Time of conc. (Tc)
= 10.00 min
Total precip. =
3.05 in
Distribution
= Type II
Storm duration =
24 hrs
Shape factor
= 484
Q (Cfs)
18.00
15.00
12.00
•M
.M
3.00
a�ais
Post -Development (NRCS)
Hyd. No. 4 -- 1 Year
Q (Cfs)
18.00
15.00
12.00
• wo]
3.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 4 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Hyd. No. 3
Pre -Development (NRCS)
Hydrograph type =
SCS Runoff
Storm frequency =
2 yrs
Time interval =
2 min
Drainage area =
4.650 ac
Basin Slope =
0.0 %
Tc method =
User
Total precip. =
3.70 in
Storm duration =
24 hrs
Q (cfs)
7.00
N. 11
5.00
i
3.00
2.00
1.00
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
Pre -Development (NRCS)
Hyd. No. 3 -- 2 Year
0.00 ' '
0 120 240 360 480 600
Hyd No. 3
Tuesday, 10 / 25 / 2022
= 6.471 cfs
= 722 min
= 17,748 cuft
= 68
= 0 ft
= 12.00 min
= Type II
= 484
Q (cfs)
7.00
. ee,
5.00
4.00
3.00
2.00
1.00
/ I I I I I 1 1% 1 0.00
720 840 960 1080 1200 1320 1440 1560
Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Hyd. No. 4
Post -Development (NRCS)
Hydrograph type =
SCS Runoff
Storm frequency =
2 yrs
Time interval =
2 min
Drainage area =
4.650 ac
Basin Slope =
0.0 %
Tc method =
User
Total precip. =
3.70 in
Storm duration =
24 hrs
Q (Cfs)
21.00
18.00
15.00
12.00
• ee
3.00
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
Post -Development (NRCS)
Hyd. No. 4 -- 2 Year
Tuesday, 10 / 25 / 2022
= 19.19 cfs
= 720 min
= 52,757 cuft
= 94
= 0 ft
= 10.00 min
= Type II
= 484
Q (Cfs)
21.00
18.00
15.00
12.00
3.00
0.00 ' ' ' ' ' 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
— Hyd No. 4 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Hyd. No. 3
Pre -Development (NRCS)
Hydrograph type =
SCS Runoff
Storm frequency =
10 yrs
Time interval =
2 min
Drainage area =
4.650 ac
Basin Slope =
0.0 %
Tc method =
User
Total precip. =
5.58 in
Storm duration =
24 hrs
Q (Cfs)
18.00
15.00
12.00
M
ME
3.00
M
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
Pre -Development (NRCS)
Hyd. No. 3 -- 10 Year
120 240 360 480 600
Hyd No. 3
Tuesday, 10 / 25 / 2022
= 15.30 cfs
= 722 min
= 40,084 cuft
= 68
= 0 ft
= 12.00 min
= Type II
= 484
Q (Cfs)
18.00
15.00
12.00
Me]
CM
0.00
720 840 960 1080 1200 1320 1440 1560
Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Hyd. No. 4
Post -Development (NRCS)
Hydrograph type =
SCS Runoff
Storm frequency =
10 yrs
Time interval =
2 min
Drainage area =
4.650 ac
Basin Slope =
0.0 %
Tc method =
User
Total precip. =
5.58 in
Storm duration =
24 hrs
Q (Cfs)
35.00
30.00
25.00
20.00
15.00
10.00
5.00
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
Tuesday, 10 / 25 / 2022
= 30.06 cfs
= 720 min
= 84,962 cuft
= 94
= 0 ft
= 10.00 min
= Type II
= 484
Q (Cfs)
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00 1 1 1 10.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440
— Hyd No. 4 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023 Tuesday, 10 / 25 / 2022
Hyd. No. 3
Pre -Development (NRCS)
Hydrograph type
= SCS Runoff
Peak discharge
= 21.54 cfs
Storm frequency
= 25 yrs
Time to peak
= 720 min
Time interval
= 2 min
Hyd. volume
= 55,999 cuft
Drainage area
= 4.650 ac
Curve number
= 68
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tc method
= User
Time of conc. (Tc)
= 12.00 min
Total precip.
= 6.76 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
Pre -Development (NRCS)
Q (Cfs) Hyd. No. 3 -- 25 Year Q (Cfs)
24.00 24.00
20.00 20.00
16.00 16.00
12.00 12.00
8.00 8.00
4.00 4.00
0.00 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
— Hyd No. 3 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Hyd. No. 4
Post -Development (NRCS)
Hydrograph type =
SCS Runoff
Storm frequency =
25 yrs
Time interval =
2 min
Drainage area =
4.650 ac
Basin Slope =
0.0 %
Tc method =
User
Total precip. =
6.76 in
Storm duration =
24 hrs
Q (Cfs)
40.00
30.00
20.00
10.00
0.00 1
0 120 240
— Hyd No. 4
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
Post -Development (NRCS)
Hyd. No. 4 -- 25 Year
360 480 600 720 840 960
Tuesday, 10 / 25 / 2022
= 36.81 cfs
= 720 min
= 105,314 cuft
= 94
= 0 ft
= 10.00 min
= Type II
= 484
Q (Cfs)
40.00
30.00
20.00
10.00
0.00
1080 1200 1320 1440
Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Hyd. No. 3
Pre -Development (NRCS)
Hydrograph type =
SCS Runoff
Storm frequency =
100 yrs
Time interval =
2 min
Drainage area =
4.650 ac
Basin Slope =
0.0 %
Tc method =
User
Total precip. =
8.74 in
Storm duration =
24 hrs
Q (Cfs)
35.00
30.00
25.00
20.00
15.00
10.00
5.00
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
Tuesday, 10 / 25 / 2022
= 32.65 cfs
= 720 min
= 84,666 cuft
= 68
= 0 ft
= 12.00 min
= Type II
= 484
Q (Cfs)
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
— Hyd No. 3 Time (min)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Hyd. No. 4
Post -Development (NRCS)
Hydrograph type =
SCS Runoff
Storm frequency =
100 yrs
Time interval =
2 min
Drainage area =
4.650 ac
Basin Slope =
0.0 %
Tc method =
User
Total precip. =
8.74 in
Storm duration =
24 hrs
Q (Cfs)
50.00
30.00
20.00
10.00
0.00 1
0 120 240
— Hyd No. 4
Peak discharge
Time to peak
Hyd. volume
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
Post -Development (NRCS)
Hyd. No. 4 -- 100 Year
360 480 600 720 840
Tuesday, 10 / 25 / 2022
= 48.08 cfs
= 720 min
= 139,571 cuft
= 94
= 0 ft
= 10.00 min
= Type II
= 484
Q (Cfs)
50.00
w1 1I
30.00
20.00
10.00
' 0.00
960 1080 1200 1320 1440
Time (min)

Pond Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Monday, 03 / 20 / 2023
Pond No. 2 - Forebay - Sediment Storage
Pond Data
Contours -User-defined contour areas. Conic method used for volume
calculation. Begining
Elevation = 187.50 ft
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sgft)
Incr. Storage (cult)
Total storage (cult)
0.00 187.50 190
0
0
0.50 188.00 300
121
121
1.50 189.00 580
432
554
2.50 190.00 910
739
1,293
3.50 191.00 1,290
1,094
2,387
4.50 192.00 1,720
1,500
3,887
Culvert / Orifice Structures
[A]
[B]
[C]
[PrfRsr]
Rise (in)
= 0.00
0.00
0.00
0.00
Span (in)
= 0.00
0.00
0.00
0.00
No. Barrels
= 0
0
0
0
Invert El. (ft)
= 0.00
0.00
0.00
0.00
Length (ft)
= 0.00
0.00
0.00
0.00
Slope (%)
= 0.00
0.00
0.00
n/a
N-Value
= .000
.000
.000
n/a
Orifice Coeff.
= 0.00
0.00
0.00
0.00
Multi -Stage
= n/a
No
No
No
Stage (ft)
5.00
4.00
3.00
2.00
IR111l
0.00
0 400
Storage
Weir Structures
[A]
[B]
[C]
[D]
Crest Len (ft)
= 0.00
0.00
0.00
0.00
Crest El. (ft)
= 0.00
0.00
0.00
0.00
Weir Coeff.
= 0.00
0.00
0.00
0.00
Weir Type
= ---
---
---
---
Multi-Stage
= No
No
No
No
Exfil.(in/hr)
= 0.000 (by Wet area)
TW Elev. (ft)
= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage / Storage
800 1,200 1,600 2,000 2,400 2,800
Elev (ft)
192.50
191.50
190.50
189.50
188.50
187.50
3,200 3,600 4,000
Storage (cuft)

Pond Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Monday, 03 / 20 / 2023
Pond No. 1 - Main Pool - Sediment Storage
Pond Data
Contours -User-defined contour areas. Conic method used for volume
calculation. Begining
Elevation = 185.00 ft
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sgft)
Incr. Storage (cult)
Total storage (cult)
0.00 185.00 750
0
0
1.00 186.00 1,270
999
999
2.00 187.00 1,815
1,534
2,533
3.00 188.00 2,395
2,098
4,631
4.00 189.00 3,135
2,756
7,387
5.00 190.00 4,090
3,602
10,989
6.00 191.00 5,070
4,571
15,560
7.00 192.00 7,810
6,390
21,950
Culvert / Orifice Structures
Weir Structures
[A]
[B]
[C]
[PrfRsr]
[A]
[B]
[C]
[D]
Rise (in)
= 0.00
0.00
0.00
0.00
Crest Len (ft)
= 0.00
0.00
0.00
0.00
Span (in)
= 0.00
0.00
0.00
0.00
Crest El. (ft)
= 0.00
0.00
0.00
0.00
No. Barrels
= 0
0
0
0
Weir Coeff.
= 0.00
0.00
0.00
0.00
Invert El. (ft)
= 0.00
0.00
0.00
0.00
Weir Type
= ---
---
---
---
Length (ft)
= 0.00
0.00
0.00
0.00
Multi -Stage
= No
No
No
No
Slope (%)
= 0.00
0.00
0.00
n/a
N-Value
= .000
.000
.000
n/a
Orifice Coeff.
= 0.00
0.00
0.00
0.00
Exfil.(in/hr)
= 0.000 (by Contour)
Multi -Stage
= n/a
No
No
No
TW Elev. (ft)
= 0.00
Stage (ft)
8.00
6.00
4.00
2.00
0.00 _j
0
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage / Storage
Elev (ft)
193.00
191.00
189.00
187.00
' 185.00
2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 22,000
Storage Storage (cuft)

Pond Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Tuesday, 10 / 25 / 2022
Pond No. 3 - Temporary Pool
Pond Data
Contours -User-defined contour areas. Conic method used for volume
calculation. Begining
Elevation = 192.00 ft
Stage / Storage Table
Stage (ft) Elevation (ft)
Contour area (sgft)
Incr. Storage (cult)
Total storage (cult)
0.00 192.00
10,035
0
0
1.00 193.00
13,420
11,685
11,685
2.00 194.00
15,200
14,299
25,985
3.00 195.00
17,035
16,107
42,092
4.00 196.00
18,925
17,970
60,062
5.00 197.00
20,875
19,890
79,952
Culvert / Orifice Structures
[A]
[B]
[C]
[PrfRsr]
Rise (in)
= 18.00
1.50
0.00
0.00
Span (in)
= 18.00
1.50
0.00
0.00
No. Barrels
= 1
1
0
0
Invert El. (ft)
= 191.60
192.00
0.00
0.00
Length (ft)
= 44.00
2.00
0.00
0.00
Slope (%)
= 0.43
0.30
0.00
n/a
N-Value
= .013
.010
.013
n/a
Orifice Coeff.
= 0.60
0.60
0.60
0.60
Multi -Stage
= n/a
Yes
No
No
Stage (ft)
5.00
4.00
3.00
2.00
IR111l
0.00
0 8,000
Storage
Weir Structures
[A]
[B]
[C]
[D]
Crest Len (ft)
= 5.00
15.00
0.00
0.00
Crest El. (ft)
= 193.70
195.40
0.00
0.00
Weir Coeff.
= 3.33
3.00
3.33
3.33
Weir Type
= 1
Ciplti
---
---
Multi-Stage
= Yes
No
No
No
Exfil.(in/hr) = 0.000 (by Wet area)
TW Elev. (ft) = 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage / Storage
Elev (ft)
197.00
196.00
195.00
194.00
193.00
192.00
16,000 24,000 32,000 40,000 48,000 56,000 64,000 72,000 80,000
Storage (cuft)

CSD Engineering
Subject: Stormwater Detention Design Date: 3/20/2023
Set Up By: JO
Work: Forebay Volumen Check Computed By: JO
Checked By: HR
Project: Ample Storage - Erwin JOB NO. 21-0590 Page No. 1 OF 1
FOREBAY VOLUME =
3,987
CF
MAIN BAY VOLUME =
21,950
CF
Preimeter Max. Depth
6.0' Vegetated Shelf Volume =
1,680
CF 560.1 1.0
Surface area at Bottom of Shelf =
5,070
SF @ 191.0
3,987
FB VOL. =
x 100 =
18.2%
21,950
20,270
AVG. DEPTH =
=
4.00
5,070

CSD Engineering
Subject: Stormwater Detention Design Date: 3/20/2023
Set Up By: JO
Work: POOL SIZING (TSS REMOVAL) Computed By: JO
Checked By: HR
Project: Ample Storage - Erwin JOB NO. 21-0590 Page No.
DRAINAGE AREA = 4.65 AC
IMP. AREA = 3.92 AC
IMP = 3.92 x 100 =
84.3%
4.65
Equation 3 (NCDEQ Stormwater Design Manual, Part C-3): Average Depth
Average Depth =
3.998
Volume of Main Pool =
21,950
Volume of Vegetated Shelf =
1,680
Area of Main Pool at Bottom of Vegetated Shelf =
5,070
FOR 85% TSS REMOVAL; SAY PERMANENT POOL AVERAGE DEPTH = 4.0'
SA/DA 2.51% (NCDEQ SA/DA
TABLE 1; Interpolated)
SA = (SA/DA from TABLE 1) (DA) (43,560 SF/AC)
= 5,084
ACTUAL SA @ 192.0 = 10,035
SF
(above main pool & forebay)
OKAY

CSD Engineering
Subject: Stormwater Detention Design Date: 3/20/2023
Set Up By: JO
Work: 1" RUNOFF STORAGE Computed By: JO
Checked By: HR
Project: Ample Storage - Erwin JOB NO. 21-0590 Page No. 1 OF 1
USING "SIMPLE METHOD"
DA = 4.65 ACRES
IMPERVIOUS = 3.92 ACRES
RV = 0.05 + 0.0091
3.92
1 = % IMP = x 100 = 84.3%
4.65
RV = 0.05 + (0.009) (1) _
VOLUME TO BE CONTROLLED
VOLUME= (1")(RV)(DA)(I ft/l2in)
VOLUME = 0.31 AC-ft
VOLUME = 13,651 CF
SA @ 192.0 ft =
DEPTH OF RUNOFF ADDED TO PERMANENT POOL
DEPTH = 13,651
10,035
ELEVATION PERM POOL + HR = 193.36
*ACTUAL POND STORAGE @ 193.36
* FROM STAGE/STORAGE TABLE
0.8087 in/in
(REQUIRED)
10,035 sf
1.360 ft
16,833 CF
OKAY

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Tuesday, 10 / 25 / 2022
Hyd. No. 6
NRCS Outflow
Hydrograph type
= Reservoir
Peak discharge
= 1.873 cfs
Storm frequency
= 1 yrs
Time to peak
= 12.43 hrs
Time interval
= 2 min
Hyd. volume
= 35,283 cuft
Inflow hyd. No.
= 4 - Post -Development (NRCS)Max. Elevation
= 193.92 ft
Reservoir name
= Temporary Pool
Max. Storage
= 24,908 cuft
Storage Indication method used.
Q (cfs)
18.00
15.00
12.00
M
ME
3.00
M
NRCS Outflow
Hyd. No. 6 -- 1 Year
10 20 30 40
Hyd No. 6 Hyd No. 4
Q (cfs)
18.00
15.00
12.00
3.00
0.00
50 60 70 80 90 100
Time (hrs)
Total storage used = 24,908 cuft

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Tuesday, 10 / 25 / 2022
Hyd. No. 6
NRCS Outflow
Hydrograph type
= Reservoir
Peak discharge
= 5.602 cfs
Storm frequency
= 2 yrs
Time to peak
= 12.20 hrs
Time interval
= 2 min
Hyd. volume
= 46,267 cuft
Inflow hyd. No.
= 4 - Post -Development (NRCS)Max. Elevation
= 194.18 ft
Reservoir name
= Temporary Pool
Max. Storage
= 28,878 cuft
Storage Indication method used.
Q (cfs)
21.00
18.00
15.00
12.00
• ee
3.00
0.00 '
0 8
— Hyd No. 6
NRCS Outflow
Hyd. No. 6 -- 2 Year
16 24 32 40 48 56 64
Hyd No. 4 Total storage used = 28,878 cuft
Q (cfs)
21.00
18.00
15.00
12.00
3.00
0.00
72
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Tuesday, 10 / 25 / 2022
Hyd. No. 6
NRCS Outflow
Hydrograph type
= Reservoir
Peak discharge
= 12.70 cfs
Storm frequency
= 10 yrs
Time to peak
= 12.17 hrs
Time interval
= 2 min
Hyd. volume
= 78,425 cuft
Inflow hyd. No.
= 4 - Post -Development (NRCS)Max. Elevation
= 194.94 ft
Reservoir name
= Temporary Pool
Max. Storage
= 41,077 cuft
Storage Indication method used.
NRCS Outflow
Q (cfs) Hyd. No. 6 -- 10 Year Q (cfs)
35.00 35.00
30.00 30.00
25.00 25.00
20.00 20.00
15.00 15.00
10.00 10.00
5.00 5.00
0.00 0.00
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Time (hrs)
Hyd No. 6 — Hyd No. 4 Total storage used = 41,077 cuft

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Tuesday, 10 / 25 / 2022
Hyd. No. 6
NRCS Outflow
Hydrograph type
= Reservoir
Peak discharge
= 14.40 cfs
Storm frequency
= 25 yrs
Time to peak
= 12.17 hrs
Time interval
= 2 min
Hyd. volume
= 98,754 cuft
Inflow hyd. No.
= 4 - Post -Development (NRCS)Max. Elevation
= 195.38 ft
Reservoir name
= Temporary Pool
Max. Storage
= 48,963 cuft
Storage Indication method used
Q (cfs)
40.00
30.00
20.00
10.00
0.00
0 2 4
— Hyd No. 6
NRCS Outflow
Hyd. No. 6 -- 25 Year
6 8 10 12 14 16 18 20 22 24
— Hyd No. 4 Total storage used = 48,963 cuft
Q (cfs)
40.00
30.00
20.00
10.00
0.00
26
Time (hrs)

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023
Tuesday, 10 / 25 / 2022
Hyd. No. 6
NRCS Outflow
Hydrograph type
= Reservoir
Peak discharge
= 28.14 cfs
Storm frequency
= 100 yrs
Time to peak
= 12.13 hrs
Time interval
= 2 min
Hyd. volume
= 132,982 cuft
Inflow hyd. No.
= 4 - Post -Development (NRCS)Max. Elevation
= 195.82 ft
Reservoir name
= Temporary Pool
Max. Storage
= 56,887 cuft
Storage Indication method used.
NRCS Outflow
Q (cfs) Hyd. No. 6 -- 100 Year Q (cfs)
50.00 50.00
40.00 40.00
30.00 30.00
20.00 20.00
10.00 10.00
0.00 - 0.00
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Time (hrs)
Hyd No. 6 — Hyd No. 4 Total storage used = 56,887 cuft

Hydraflow Hydrographs Extension for Autodesk@ Civil 3D0 by Autodesk, Inc. v2023
we]
5.00 ft Riser
Meff
im
Top of pond _\
Elev. 197.00
15.00 ft Cipoletti weir
W-i,B Ber 1198.40
44.0 LF of 18.0 in @ 0.43%
Front View _25-yr
NTS - Looking Downstream
, 2-yr
1 00-yr 1 -yr
Inflow hydrograph = 4. SCS Runoff - Post -Development {MRCS}
I Project: Ample-Erwin.gpw I Tuesday, 10 / 25 / 2022 1

CSD Engineering
Subject: Stormwater Detention Design
Work: Storage Pool Drawdown & Anti -Flotation
Project: Ample Storage - Erwin JOB NO. 21-0590
Date: 4/4/2023
Set Up By: JO
Computed By:
Checked By:
Page No.
JO
HR
1 OF 1
Pond must detain the first 1" of runoff and release it in 2 to 5 days
INPUT
Number of Drains =
1.0
Starting Water Elevation =
193.36 ft
Diameter of Drains =
2.50
in Ending Water Elevation =
192.00 ft
Orifice Coefficient =
0.60
ft Average Head =
0.45 ft
Elevation of Drains =
192.00 ft
OUTPUT
Drawdown By the Orifice Equation:
Average Flow =
0.11 cfs
Volume of Storage =
21695 cfs
Length of Drawdown =
196294 sec or 2.27
days OK
Antiflotation:
Unit weight of water:
62.40
pcf
Volume of Riser:
Max. Height of Water:
4.00
ft Length (ft) Width (ft)
Thickness (ft)
Riser Height:
25.00
sf 5.00 5.00
Volume of Riser:
100.00
cf
Total Weight:
6240
pcf
Factor of Safety:
1.5
Therefore, needed total weight =
9360 Ibs
Weight of Riser Base:
2.1
ft height 788 Ibs
5.0
ft wide
0.5
ft thick
For concrete grout:
5.0
ft long Use 150 pcf for weight of concrete
5.0
ft wide
2.30
ft high
Total base weight:
9413
Ibs OKAY

Date: 10/25/2022
Project Name: Ample Storage - Erw
Station: Drive
Skew:
Size/Type Pipe:
Type Entrance:
Direction of Flow:
Hydrological Method:*
H.W. Control Elevation:
Shoulder
at St. Matthews Rd Elev.
0
Groove End
North to South
Rational
Inlet
196 Invert Elev
PIPE DATA SHEET
Sheet 1 of 1
I.D. No. 21-0590 County: Harnett Designed By: JFO Checked By: HSR
CL Elev.:
H.W.
LSo
JU- U.Yo /U
194.05 ft L= 144 ft
197 ft
H
T. W
Outlet Inv. Elev. 193.4 ft
Plan Summary Data
Drainage Area:
2.07
Design Freq.:
25 YR
Design Disch.:
7.7
Design H.W. Elev.:
196.00
Q10 Disch.:
6.8
Q10 HW Elev.:
195.72
Overtopping Freq.:
>100YR
Overtopping Disch.:
10.6
Overtopping Elev.:
197.05
PIPE CULVERT ANALYSIS (English) rcp=.012, cmp=.024 Channel Specs Slope: 0.0034 Lt. Side Slope 4
n= 0.012 11 Base= 0 n= 0.065 Rt_ Side Slone 4
Size & Type
TW
ft
Q*
ft^3/s
Nat.
H.W.
Allow.**
H.W.
Inlet Control
Outlet Control
HW
ELEV.
Vo
Q/A
Remarks
SIZE
#
FREQ
HW/D HW (ft)
Ke d� (d,+D)/2 ho H L*So I HW
Pipes*
18
1
2 YR
1.2
5.2
0.85
1.28
0.2
0.87
1.18
1.21
0.459
0.62
1.05
195.33
2.94
INLET CONTROL
18
1
10 YR
1.5
6.8
1.01
1.52
0.2
1.02
1.26
1.50
0.786
0.62
1.67
195.72
3.85
OUTLET CONTROL
18
1
25 YR
1.6
7.7
1.11
1.66
0.2
1.09
1.30
1.56
1.007
0.62
1.95
196.00
4.36
OUTLET CONTROL
18
1
100 YR
1.6
8.9
1.23
1.84
0.2
1.19
1.35
1.60
1.346
0.62
2.33
196.38
5.04
OUTLET CONTROL
18
1
OVERTOP
1.8
10.6
2.00
3.00
1.38
1.44
1.80
1.797
0.62
2.98
197.05
6.00
INLET CONTROL
Notes: *Hydrological Method: C=0.6 (R/W and Future Development)
Tc=15 min. (TR-55); IDF from NOAA Atlas 14 Point Precipitation Frequency
Recommendation: Install 1 @ 18" R.C. Pipe Class III
**Overtopping H.W: 2.98'
Elevation = 197.05' at shoulder point

2 1
12 Outfall
3
4
5
13
6
7
10
9 8
11
Project File: Ample-Erwin.stm Number of lines: 13 Date: 10/28/2022
Storm Sewers v2023.00

Page 1
Station
Len
Drng Area
Rnoff
Area x C
Tc
Rain
Total
Cap
Vel
Pipe
Invert Elev
HGL Elev
Grnd / Rim Elev
Line ID
coeff
(1)
flow
full
Line
To
Incr
Total
Incr
Total
Inlet
Syst
Size
Slope
Dn
Up
Dn
Up
Dn
Up
Line
(ft)
(ac)
(ac)
(C)
(min)
(min)
(in/hr)
(cfs)
(cfs)
(ft1s)
(in)
00
(ft)
00
(ft)
(ft)
00
I
End
36.000
0.37
4.11
0.95
0.35
3.90
5.0
9.8
6.5
25.37
5185
3.59
36
0.56
190.80
191.00
195.40
195.44
193.80
197.50
D11 TO OUTFALL
2
1
113.931
0.38
3.74
0.95
0.36
3.55
5.0
9.2
6.6
23.55
42.81
3.33
36
0.35
191.00
191.40
195.74
195.87
197.50
197.50
D12 TO D11
3
2
67.460
0.18
3.36
0.95
0.17
3.19
5.0
8.9
6.7
21.43
39.34
3.03
36
0.30
191.40
191.60
195.95
196.01
197.50
197.70
D13 TO D12
4
3
65.006
0.33
2.96
0.95
0.31
2.81
5.0
8.5
6.8
1916
40.08
2.71
36
0.31
191.60
191.80
196.23
196.27
197.70
197.50
D14 TO D13
5
4
100.000
0.33
2.63
0.95
0.31
2A9
5.0
7.9
7.0
17A5
45.70
2.47
36
0.40
191.80
192.20
196.33
196.39
197.50
197.50
D15 TO D14
6
5
74.462
0.18
2.30
0.95
0.17
2.18
5.0
6.8
7.3
15.95
91.72
1.13
36(2b)
0.40
192.20
192.50
196.43
196.44
197.50
197.60
D16 TO D15
7
6
59.517
0.32
1.71
0.93
0.30
1.62
5.0
6.4
7.4
12.05
31.54
2.45
30
0.50
192.50
192.80
196.47
196.52
197.60
197.00
D17 TO D16
8
7
43.507
0.32
1.39
0.95
0.30
1.32
5.0
6.1
7.5
9.93
15.34
3.16
24
0.46
192.80
193.00
196.60
196.68
197.00
197.40
D18 TO D17
9
8
95351
0.00
0.59
0.00
0.00
0.56
0.0
5.5
77
4.34
6.80
2A5
18
0.42
193.00
193.40
196.91
197.07
197.40
198.40
MI-19 TO D18
10
9
74.990
0.59
0.59
0.95
0.56
0.56
5.0
5.0
7.9
4.44
6.64
2.51
18
0.40
193.40
193.70
197.11
197.25
198.40
197.40
D110 TO MI-19
11
8
99.918
0.48
0.48
0.95
0.46
0.46
5.0
5.0
7.9
3.61
7.43
2.04
18
0.50
193.20
193.70
196.91
197.03
197.40
198.30
D11 I TO D18
12
3
80.002
0.22
0.22
0.95
0.21
0.21
5.0
5.0
7.9
1.65
7.43
0.94
18
0.50
193.00
193.40
196.23
196.25
197.70
197.50
D112 TO D13
13
6
95.990
0.41
0.41
0.95
0.39
0.39
5.0
5.0
7.9
3.08
10.17
1.74
18
0.94
193.00
193.90
196.47
196.56
197.60
197.40
D113 TO D16
Project File: Ample-Erwin.stm
Number of lines: 13
Run Date: 10/28/2022
NOTES:Intensity = 77.50 / (Inlet time + 12.30) 1 0.80; Return period =Yrs. 10 c = cir e = ellip b = box
Storm Sewers v2023.00

Proj. file: Ample-Erwin.stm
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Proj. file: Ample-Erwin.strn
IMUL2 �11
#
Storm Sewers

Proj. file: Ample-Erwin.stm
Elev. (ft)
205.00
CO
CD
a
205.00
202.00
202.00
199.00
199.00
196.00
196.00
193.00
190.00
193.00
190.00
0 25 50 75 100 125 150 175
HGL EGL Reach (ft)
200 225
Storm Sewers

Storm Sewer Profile
Proj. file: Ample-Erwin.strn
Elev. (ft)
209.00
Qc
0 -c
J 0
209.00
205.00
205.00
MI
M
201.00
201.00
M
I
1
197.00
197.00
MI
M—M
193.00
189.00
193.00
189.00
=��Mm
MI
1
0 25 50 75 100 125 150 175
— HGL EGL Reach (ft)
Storm Sewers
11

Storm Sewer Profile
Proj. file: Ample-Erwin.stm
Elev. (ft)
204.00
204.00
189.00
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
— HGL EGL Reach (ft)
Storm Sewers

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Page 1 of 2
CHANNEL ANALYSIS WORKBOOK
10/25/2022 Computed: JO Checked: HR
Ample Storage - Erwin
Q...............
Design Year Discharge (cfs)
A............
Flow Area (sf)
Zreq...........
(Q x n)/(1.49 x Slope^0.5)
P............
Wetted Perimeter (ft)
B...............
Base Width (ft)
R............
Hydraulic Radius (ft)
d...............
Normal Depth (ft)
V............
Velocity (fps)
Z1..............
Left Side Slope
Zay.........
A"R^2/3
Z2..............
Right Side Slope
n.............
Manning's Roughness Coefficient (Reference 1)
PI ............... Plasticity Index of Soil (<10: Non -cohesive soil)
e............... Soil Void Ratio
Class ......... ,ASTM Soil Classification (Reference 1: Table 4.6)
Ret. Class... Retardance Classification of Vegetal Covers (Reference 1: Table 4.1)
Height........ Stem Height (feet)
Cn............. Roughness Coefficient of Grass
To .............. Mean Boundary Shear Stress (Reference 1; Eqn. 2.3); Applied Shear Stress on Grass
Cf.............. Cover Factor (Reference 1: Table 4.5)
T............... Shear Stress in Channel at maximum depth, pounds per square foot (psf) (Reference 1; Eqn. 2.4)
Tp.............. Permissable Shear Stress (Reference 1: Table 2.3; Eqn. 4.5, 4.6, 4.7)
Reference 1: FHWA Hydraulic Engineering Circular No. 15, Publication No. FHWA-NHI-05-114, 2005
Reference 2: Harnett County Soil Survey
Station: St. Matthews
Description: Roadside Channel US Driveway
Q =
5.2
cfs
Slope =
0.0210
ft/ft
n =
0.042
Zreq =
1.00 ft
RIPRAP,COBBLE, GRAVEL
Type
D50 (ft)
Top W
da
n1
Vs
0.69
Re
minD50 (ft)
2-year
Soil (Sandy Loam)
Vegetation
Tp,soil Coefficients, c
PI
12.0
Ret. Classl
D
Cn =
0.142
1
1.070
e
0.14
Height ft
0.25
To =
0.45
2
7.150
Class
SM
Condition
Good
Cf =
1 0.750
3
11.900
D75 in
0.020
Type
Mixed
Tp,veg
1 1.21
4
1.420
n (soil)
0.016
5
-0.610
_Tp,soil
0.04
1 6
0.000
GRAVEL/SOIL
Type
D75 (in)
Tp,soil
n (liner)
Tp,liner
ROLLED MAT/SOIL
Type
To
Ti
n (liner)
Tp,liner
TURF REINFORCE
Type
Tp,TRM
Tp,VEG
Cf,TRM
Tp,VEG
B d Z1 Z2 A P R V Zav T Tp Remarks
0.0 0.71 4.0 4.0 2.0 5.9 0.34 2.5 0.99 0.93 1.21 1 Stable
Station: St. Matthews
Description: Roadside Channel US Driveway
Q = 6.8 cfs
Slope = 0.0210 ft/ft
n = 0.040
Zreq = 1.27 ft
RIPRAP,COBBLE, GRAVEL
Type
D50 ft
Top W
da
n1
Vs
0.72
Re
minD50 ft
10-year
Soil (Sandy Loam)
Vegetation
Tp,soil Coefficients, c
PI
12.0
Ret. Class
D
Cn =
0.142
1
1.070
e
0.14
Height (ft)
0.25
To =
0.49
2
7.150
Class
SM
Condition
Good
Cf =
0.750
3
11.900
D75 (in)
0.020
Type
Mixed
Tp,veg
1.14
4
1.420
n soil
0.016
5
-0.610
Tp,soil
0.04
6
0.000
GRAVEL/SOIL
Type
D75 (in)
Tp,soil
n (liner)
Tp,liner
ROLLED MAT/SOIL
Type
To
Ti
n (liner)
Tp,liner
TURF REINFORCE
Type
Tp,TRM
Tp,VEG
Cf,TRM
Tp,VEG
B d Z1 Z2 A P R V Zav T Tp Remarks
0.0 0.77 4.0 4.0 2.4 6.3 0.37 2.8 1.23 1.01 1.14 1 Stable

Page 2 of 2
CHANNEL ANALYSIS WORKBOOK
10/25/2022 Computed: JO Checked: HR
Ample Storage - Erwin
Q...............
Design Year Discharge (cfs)
A............
Flow Area (sf)
Zreq...........
(Q x n)/(1.49 x Slope^0.5)
P............
Wetted Perimeter (ft)
B...............
Base Width (ft)
R............
Hydraulic Radius (ft)
d...............
Normal Depth (ft)
V............
Velocity (fps)
Z1..............
Left Side Slope
Zay.........
A"R^2/3
Z2..............
Right Side Slope
n.............
Manning's Roughness Coefficient (Reference 1)
PI ............... Plasticity Index of Soil (<10: Non -cohesive soil)
e............... Soil Void Ratio
Class ......... ,ASTM Soil Classification (Reference 1: Table 4.6)
Ret. Class... Retardance Classification of Vegetal Covers (Reference 1: Table 4.1)
Height........ Stem Height (feet)
Cn............. Roughness Coefficient of Grass
To .............. Mean Boundary Shear Stress (Reference 1; Eqn. 2.3); Applied Shear Stress on Grass
Cf.............. Cover Factor (Reference 1: Table 4.5)
T............... Shear Stress in Channel at maximum depth, pounds per square foot (psf) (Reference 1; Eqn. 2.4)
Tp.............. Permissable Shear Stress (Reference 1: Table 2.3; Eqn. 4.5, 4.6, 4.7)
Reference 1: FHWA Hydraulic Engineering Circular No. 15, Publication No. FHWA-NHI-05-114, 2005
Reference 2: Harnett County Soil Survey
Station: St. Matthews
Description: Roadside Channel DS Driveway
Q =
5.2
cfs
Slope =
0.0034
ft/ft
n =
0.070
Zreq =
4.17 ft
RIPRAP,COBBLE, GRAVEL
Type
D50 (ft)
Top W
da
n1
Vs
0.36
Re
minD50 (ft)
2-year
Soil Sandy Loam
Ve etation
Tp,soil Coefficients, c
PI
12.0
Ret. Classl
D
Cn =
0.142
1
1.070
e
0.14
Height ft
0.25
To =
0.12
2
7.150
Class
SM
Condition
Good
Cf =
1 0.750
3
11.900
D75 in
0.020
Type
Mixed
Tp,veg
1 3.39
4
1.420
n (soil)
0.016
5
-0.610
Tp,soil
0.04
1 6
0.000
GRAVEL/SOIL
Type
D75 (in)
Tp,soil
n (liner)
Tp,liner
ROLLED MAT/SOIL
Type
To
Ti
n (liner)
Tp,liner
TURF REINFORCE
Type
Tp,TRM
Tp,VEG
Cf,TRM
Tp,VEG
B d Z1 Z2 A P R V Zav T Tp Remarks
0.0 1.21 4.0 4.0 5.9 10.0 0.59 0.9 4.11 0.26 3.39 1 Stable
Station: St. Matthews
Description: Roadside Channel DS Driveway
Q = 6.8 cfs
Slope = 0.0034 ft/ft
n = 0.065
Zreq = 5.08 ft
RIPRAP,COBBLE, GRAVEL
Type
D50 ft
Top W
da
n1
Vs
0.40
Re
minD50 ft
10-year
Soil (Sandy Loam)
Vegetation
Tp,soil Coefficients, c
PI
12.0
Ret. Classl
D
Cn =
0.142
1
1.070
e
0.14
Height (ft)
0.25
To =
1 0.15
2
7.150
Class
SM
Condition
Good
Cf =
1 0.750
3
11.900
D75 (in)
0.020
Type
Mixed
Tp,veg
1 2.96
4
1.420
n soil
0.016
5
-0.610
Tp,soil
0.04
6
0.000
GRAVEL/SOIL
Type
D75 (in)
Tp,soil
n (liner)
Tp,liner
ROLLED MAT/SOIL
Type
To
Ti
n (liner)
Tp,liner
TURF REINFORCE
Type
Tp,TRM
Tp,VEG
Cf,TRM
Tp,VEG
B d Z1 Z2 A P R V Zav T Tp Remarks
0.0 1.47 3.0 3.0 6.5 9.3 0.70 1.0 5.10 0.31 2.96 1 Stable

User Input Data
Calculated Value
Reference Data
Designed By: CFO Date: 10/28/2022
Checked By: HSR Date: 10/28/2022
Company:
Project Name:
Project No.:
Site Location (City/Town) Ervin, NC
Culvert Id. Driveway
Total Drainage Area (acres) 2.07
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter, it is classified rninirnurn tailwater condition_
If it is greater than half the pipe diameter, it is classified maximum condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to bane a nairtimuma tailwater condition unless reliable food stage elevations
show otherwise.
Outlet pipe diameter, Do (in.) 18
Tailwater depth (in.) 18
Minimum/Maximum tailwater? Max TW (Fig. 8.06b)
Discharge (cfs) 6.8
Velocity (ft./s) 3.85
Step 2. Based on the tarlwater conditions deterinurM rn step 1, enter Figure
8 06a or Figure 8 06b, and determine dsa riprap sin and minimum apron length
(L J The d� size is the median stone size in a well -graded riprap apron.
Step 3. Determine apron width at the pipe outlet, the apron shape, and the
apron width at the outlet end from the same figure used in Step 2.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d5g, (ft.)
0.5
Minimum apron length, La (ft.)
9
Apron width at pipe outlet (ft.)
4.5 4.5
Apron shape
Rectangle
Apron width at outlet end (ft.)
1.5 5.1
Step 4. Determine the --in n stone diameter:
d,,,,, = 1.5 x d.
Minimum TW Maximum TW
Max Stone Diameter, dmax (ft.) 0 0.75
Step 5, Determine the apron tluclaiess:
Apron thickness = 1.5 x d
Minimum TW Maximum TW
Apron Thickness(ft.) 0 1.125
Step 6. Fit the riprap apron to the site by making it level for the minimum
length, 1r, from Figure 8 06a or Figure 8 06b_ Extend the apron farther
downstream and along channel banks until stability is assured_ Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
Some locations may require lining of the entire charnel cross section to assure
stability
It may be necessary to increase the sire of riprap where protection of the
channel side slopes is necessary (Appendix 8.05). Where overfills exist at
pipe outlets at flows are excessive, a plunge pool should be considered, see
page 9.06.8.

User Input Data
Calculated Value
Reference Data
Designed By: CFO Date: 10/28/2022
Checked By: HSR Date: 10/28/2022
Company:
Project Name: Ample Storage
Project No.:
Site Location (City/Town) Ervin, NC
Culvert Id. 36" Pipe In
Total Drainage Area (acres) 4.11
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter, it is classified mimmurn tailwater condition_
If it is greater than half the pipe diameter, it is classified maximum condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to bave a nairtimuma tailwater condition unless reliable food stage elevations
show otherwise.
Outlet pipe diameter, Do (in.) 36
Tailwater depth (in.) 36
Minimum/Maximum tailwater? Max TW (Fig. 8.06b)
Discharge (cfs) 25.4
Velocity (ft./s) 3.6
Step 2. Based on the tarlwater conditions deterinurM rn step 1, enter Figure
8 06a or Figure 8 06b, and determine dsa riprap sin and minimum apron length
(L J The d� size is the median stone size in a well -graded riprap apron.
Step 3. Determine apron width at the pipe outlet, the apron shape, and the
apron width at the outlet end from the same figure used in Step 2.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d5g, (ft.)
0.75
Minimum apron length, La (ft.)
12
Apron width at pipe outlet (ft.)
9 9
Apron shape
Rectangle
Apron width at outlet end (ft.)
3 7.8
Step 4. Determine the —xiamm stone diameter:
d,,,,, = 1.5 x d.
Minimum TW Maximum TW
Max Stone Diameter, dmax (ft.) 0 1.125
Step 5, Determine the apron tluclaiess:
Apron thickness = 1.5 x d
Minimum TW Maximum TW
Apron Thickness(ft.) 0 1.6875
Step 6. Fit the riprap apron to the site by making it lerel for the minimum
length, 1r, from Figure 8 06a or Figure 8 06b_ Extend the apron farther
downstream and along channel banks until stability is assured_ Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
Some locations may require lining of the entire charnel cross section to assure
stability
It may be necessary to increase the sire of riprap where protection of the
channel side slopes is necessary (Appotidir 8.05). Where overfills exist at
pipe outlets at flows are excessive, a plunge pool should be considered, see
page 9.06.8.

User Input Data
Calculated Value
Reference Data
Designed By: CFO Date: 10/28/2022
Checked By: HSR Date: 10/28/2022
Company:
Project Name: Ample Storage
Project No.:
Site Location (City/Town) Ervin, NC
Culvert Id. Pond Outlet
Total Drainage Area (acres) 6.17
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter, it is classified minirnuru tailwater condition_
If it is greater than half the pipe diameter, it is classified maximum condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to have a mr-inum tailwater condition unless reliable flood stage elevations
show otherwise.
Outlet pipe diameter, Do (in.) 18
Tailwater depth (in.) 12
Minimum/Maximum tailwater? Max TW (Fig. 8.06b)
Discharge (cfs) 10
Velocity (ft./s) 4.6
Step 2. Based on the tailwater conditions determined in step 1, enter Figure
8 06a or Figure 8 06b_ and determine dsa riprap sin and minimum apron length
(L J The d� size is the median stone size in a well -graded riprap apron.
Step 3. Determine apron width at the pipe outlet, the apron shape, and the
apron width at the outlet end from the same figure used in Step 2.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d5g, (ft.)
0.5
Minimum apron length, La (ft.)
8
Apron width at pipe outlet (ft.)
4.5 4.5
Apron shape
Rectangle
Apron width at outlet end (ft.)
1.5 4.7
Step 4. Determine the --in n stone diameter:
d,,,,, = 1.5 x d.
Minimum TW Maximum TW
Max Stone Diameter, dmax (ft.) 0 0.75
Step 5. Determine the apron tluclaiess:
Apron thickness = 1.5 x d
Minimum TW Maximum TW
Apron Thickness(ft.) 0 1.125
Step 6. Fit the riprap apron to the site by making it lexel for the minimum
length, 1r, from Figure 8 06a or Figure 8 06b_ Extend the apron farther
downstream and along channel banks until stability is assured_ Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
Some locations may require lining of the entire channel cross section to assure
stability
It may be necessary to increase the sire of riprap where protection of the
channel side slopes is necessary (Appendix 8.05). Where ovcrfalls exist at
pipe outlets at flows are excessive, a plunge pool should be considered, see
page 9.06.8.

Figure 8.06b: Design of outlet protection from a round pipe flowing full, maximum
tailwater condition (Tw>=0.5 diameter)
Discharge (Olsec)
Curves may not be extrapolated_
Figure 8.O0b Design of outlot protection from a round pipe flowing full. maximum wilwater condition (T. >_ 0.5 diameter).
8.06.4 Rev.1"3

Project: Ample Storage Basin Dimension Worksheet ESC
Date: 10/25/2022
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Pond Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023 Wednesday, 10 / 26 / 2022
Pond No. 5 - Sediment Basin
Pond Data
Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 192.00 ft
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sgft) Incr. Storage (cult) Total storage (cult)
0.00 192.00 10,035 0 0
1.00 193.00 12,220 11,108 11,108
2.00 194.00 14,180 13,187 24,295
Culvert / Orifice Structures
Weir Structures
[A]
[B]
[C]
[PrfRsr]
[A]
[B]
[C]
[D]
Rise (in)
= 0.00
0.00
0.00
0.00
Crest Len (ft)
= 0.00
0.00
0.00
0.00
Span (in)
= 0.00
0.00
0.00
0.00
Crest El. (ft)
= 0.00
0.00
0.00
0.00
No. Barrels
= 0
0
0
0
Weir Coeff.
= 0.00
0.00
0.00
0.00
Invert El. (ft)
= 0.00
0.00
0.00
0.00
Weir Type
= ---
---
---
---
Length (ft)
= 0.00
0.00
0.00
0.00
Multi -Stage
= No
No
No
No
Slope (%)
= 0.00
0.00
0.00
n/a
N-Value
= .000
.000
.000
n/a
Orifice Coeff.
= 0.00
0.00
0.00
0.00
Exfil.(in/hr)
= 0.000 (by Wet area)
Multi -Stage
= n/a
No
No
No
TW Elev. (ft)
= 0.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage (ft) Stage / Storage Elev (ft)
2.00
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0 00
194.00
193.80
193.60
193.40
193.20
193.00
192.80
192.60
192.40
192.20
19200
0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 20,000 22,000 24,000 26,000
Storage Storage (cuft)

Ample Storage Skimmer Sizing 10/25/2022
Calculate Skimmer Size
Basin Volume in Cubic Feet
jDays to Drain*
I*1n NC assume 3 days to drain
24,295 Cu.Ft
3 Days
Skimmer Size
Orifice Radius
Orifice Diameter
3.0 Inch
1.4 Inch[es]
2.7 Inch[es]
Estimate Volume of Basin Length Width
Top of water surface in feet Feet VOLUME 0 Cu. Ft.
Bottom dimensions in feet Feet
Depth in feet Feet