SW6231002_Design Calculations_20231031

DocuSign Envelope ID: DAC187C9-00F1-4930-95CC-AD32FAFOC8C8
WithersRavenel
II/ Our People.Your Success.
Stormwater Management Plan
Serenity - Phases 8 & 9
Harnett Co., North Carolina
Greenfield Communities
Prepared For:
Greenfield Communities, LLC
8601 Six Forks Road, Suite 270
Raleigh, NC 27615
[phone]
ATTN: Matt Brubaker
Prepared By:
WithersRavenel
O°
115 MacKenan Drive NARO �
Cary, NC 27511 0`� � OFESS�p °29
[phone] < 47t7 SEAL r
License No.: F-1479 t DMA
GiNe
WithersRavenel Project No. 02190647.00 DocuSigned J
9cc7D0nn°c0 9/20/2023
1'r'a.t oln, k t V
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September 20, 2023
Brandon J. Miller, PE
Becca A. Rahn
A

Stormwater Management Plan Serenity - Phases 8 & 9
Table of Contents
Introduction/Project Data 1
Site History 1
Proposed Development 1
Quantifying Land Disturbance and Changes in Impervious Surface 2
Watershed Protection Overlay 2
Streams 2
Applicable Requirements 3
Methodology 4
Hydrology Calculations 4
Hydraulic Calculations 5
Conclusions 5
Water Quality 5
Peak Flows 5
SCM Design Summaries 6
List of Tables
Table 1 - Project Information Summary 1
Table 2 - Phase Lot Counts, Types, and Impervious Area 2
Table 3 - Peak Summary at POA 8A 5
Table 4 - Peak Summary at POA 8B 5
Table 5 - Peak Summary at POA 9A 6
Table 6 - Peak Summary at POA 9B 6
Table 7 - SCM Wet Pond Freeboard Summary 6
Table 8 - SCM Treatment Swale Freeboard Summary 6
Table 9 -SCM 6 - Routing Summary 7
Table 10 - SCM 7 - Routing Summary 8
Table 11 - SCM 8 - Routing Summary 9
Table 12 - SCM 9 - Routing Summary 10
Table 13 - SCM 10 - Routing Summary 11
Table 14 - SCM 11 - Routing Summary 12
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Stormwater Management Plan Serenity - Phases 8 & 9
List of Figures
Figure 1 - Site Map 3
Appendices
Appendix 1: Reference Materials
• USGS 7.5-Minute Quadrangle Map
• Web Soil Survey Map
• NOAA Atlas 14 Precipitation Frequency Estimates
• PONDPACK Precipitation Hydrograph Input Data
Appendix 2: Peak Flow Analysis
• Existing Drainage Area Map
• Existing CN Calculations
• Existing Tc Calculations
• Existing PONDPACK Schematic
• Existing PONDPACK Model Data & Results
• Proposed Drainage Area Map
• Proposed CN Calculations
• Proposed Tc Calculations
• Proposed PONDPACK Schematic
• Proposed PONDPACK Model Data & Results
Appendix 3: SCM Design Calculations
• SCM 6 - Wet Pond MDC Requirements
• SCM 7 - Wet Pond MDC Requirements
• SCM 8 - Wet Pond MDC Requirements
• SCM 9 - Wet Pond MDC Requirements
• SCM 10 - Wet Pond MDC Requirements
• SCM 11 - Wet Pond MDC Requirements
• SCM 12 - Treatment Swale MDC Requirements
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Stormwater Management Plan Serenity - Phases 8 & 9
• SCM 13 - Treatment Swale MDC Requirements
Appendix 4: SCM Design Summaries
• SCM 6 - Outlet Structure Design
• SCM 6 - Elevation-Volume Table
• SCM 7 - Outlet Structure Design
• SCM 7 - Elevation-Volume Table
• SCM 8 - Outlet Structure Design
• SCM 8 - Elevation-Volume Table
• SCM 9 - Outlet Structure Design
• SCM 9 - Elevation-Volume Table
• SCM 10 - Outlet Structure Design
• SCM 10 - Elevation-Volume Table
• SCM 11 - Outlet Structure Design
• SCM 11 - Elevation-Volume Table
• SCM 12 - Treatment Swale Design Velocity and Normal Depth
• SCM 13 - Treatment Swale Design Velocity and Normal Depth
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Stormwater Management Plan Serenity - Phases 8 & 9
Intrnrluctinn/Project nata
The Serenity and Smith Betts Tract PUD totals 573.34 acres east of Rollins Rd., Harnett Co., NC.
Phases 8 & 9 encompasses ±170 acres of the tract (Figure 1). The Phase 8 & 9 project area is
bordered by 2-acre residential lots and row crop lots to the north and west, other phases of the
subdivision to the south and east, and Hectors Creek along the eastern edge of the phase
boundaries. Detailed project information is listed in Table 1.
Table 1 - Project Information Summary
Project Name Serenity - Phases 8 & 9
Project Address Rollins Rd., Harnett Co., NC
0655-23-9685, 0655-13-8762, 0655-
PIN(s) 03-4488, 0645-95-9146, 0645-82-
8633, 0645-72-7454
Zoning RA-40, RA-30, CONSERVATION
River Basin Cape Fear River Basin
Receiving Stream Hector Creek
Hydrologic Unit(HUC12) 030300040502
Watershed Protection Overlay HQW; WS-IV
Total Site Area 573.34 AC
Total Project Area 170.33 AC
Existing Impervious % 0%
Proposed Impervious % 32%
Site Histon-
The property is in the Piedmont of North Carolina. The existing site consists primarily of wooded
area and row crops with Hydrologic Soil Groups (HSG) 'A', `B', and D' soils. There are four(4)
points analysis for Phases 8 & 9, which are at the confluence points between the unnamed
tributaries of Hector Creek and Hector Creek. There are several unnamed tributaries of Hector
Creek within the property boundary and two existing ponds.
Proposed Development
The Serenity - Ph. 8 & 9 property area is zoned RA-40, RA-30 and Conservation District. Phases
8 & 9 will consist of 358 single-family lots and their associated infrastructure
Table 2). The phased areas will also include pocket amenity spaces with associated infrastructure.
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Stormwater Management Plan Serenity - Phases 8 & 9
Table 2 - Phase Lot Counts, Types, and Impervious Area
Max Impervious Phase 8&9
Type Area per Lot(sf) Count
60' Lots 4,850 124
50' Lots 4,000 159
43' Lots 3,200 75
Quantifying Land Disturbance and Changes in Impervious Surface
The proposed development will increase the impervious area of the Phase 8 & 9 project area
(Figure 1) from 0% to 32%.
Watershed Protection Overlay
Portions of the project site are within High Quality Water (HQW) and Water Supply Watershed
IV (WS-IV) watershed protection areas.
Streams
The project area drains to FEMA studied stream, Hector Creek(HUC12 - 030300040502), which
borders the eastern edge of the phased area with unnamed tributaries throughout the Phase 8 &
9 areas.
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Stormwater Management Plan Serenity - Phases 8 & 9
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Blue shaded area is other phases of the Serenity development
Applicable Requirements
The proposed development is in Harnett County and within the Cape Fear watershed. The
development must meet state and local stormwater management requirements as outlined in the
Harnett County Unified Development Ordinance and state stormwater rules.The following
requirements apply to the subject site:
Harnett County:
Per the approved Stormwater Master Plan for the PUD, peak flow analysis will be
provided for the 1, 2, and 10-year 24-hour design storms. Post development peak
flows shall not increase from existing conditions
• SCM's shall meet the design requirements of Article X.2.7 and NCDENR's most
current Stormwater Design Manual
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Stormwater Management Plan Serenity - Phases 8 & 9
State Stormwater:
High density projects in Water Supply Watersheds and draining to High Quality
Waters must control runoff from all surfaces generated by 1-inch of rainfall
• Low density projects in High Quality Waters will be limited to 12% BUA
Methodology
The stormwater study was conducted using the natural drainage features as depicted by Light
Detection and Ranging (LIDAR) topography and existing field surveys. Proposed drainage areas
were based on field survey data and proposed development within the drainage areas.
The scope of work included the following analyses:
Hydrology
• Simulation of the 1-year, 2-year, 10-year, and 100-year rainfall events for the Harnett Co., NC
area.
• Formulation of the 1-year, 2-year, 10-year, and 100-year hydrographs for the existing
development and proposed development drainage areas.
Hydraulic
• Routing the 1-year, 2-year, 10-year, and 100-year hydrographs for existing development
runoff from the site.
• Routing the 1-year, 2-year, 10-year, and 100-year hydrographs for proposed development
runoff through the SCM.
• Analyzing results at the analysis points.
The results of the hydrology calculations were used for the hydraulic analyses. The hydraulic
design requires the development of stage-storage and stage-discharge functions for the SCMs.
The rainfall/runoff hydrographs,stage-storage,and stage-discharge functions have been compiled
to create a computer routing simulation model using Bentley Systems PondPack v8i software.This
PondPack model was then used to assess the peak water surface elevations in the SCM for the
design rainfall events.The routing results,along with the hydrologic and hydraulic calculations,are
provided as in Appendix 2.
Hydrology Calculations
The Soil Conservation Service (SCS) Method, in conjunction with National Oceanic and
Atmospheric Administration (NOAA) Atlas 14 precipitation data for Harnett Co., NC was used to
develop runoff hydrographs for the storm events. This method requires three basic parameters,
including a curve number(CN), time of concentration (Tc), and drainage area (DA).
Composite CNs were calculated according to soil type, land cover, and area. Soil types were
delineated using the National Research Conservation Service (NRCS) Web Soil Survey database.
Directly connected impervious areas within SCM drainage basins were given a CN of 98, and
remaining areas were calculated per land cover impervious assumptions to determine a composite
CN for each DA.
Tc's for existing and proposed drainage areas were developed using the Technical Release 55 (TR-
55) method. This method models the flow path in segments; each segment is considered as either
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Stormwater Management Plan Serenity - Phases 8 & 9
sheet flow, shallow concentrated flow, or channel flow. A minimum Tc of 5-minutes was used for
the proposed piped drainage systems within the SCM drainage basins.
Drainage area maps showing Tc flow paths and land cover maps are presented in Appendix 2.
Hydraulic Calculations
Computer simulated reservoir routing of the 1-year, 2-year, 10-year, and 100-year design storms
utilized stage-storage and stage-discharge functions. A stage-storage function was derived from
the proposed geometry of the SCM. A non-linear regression relation for surface area versus
elevation was derived for the SCM. This relation estimates the incremental volume of the basin to
the stage or elevation of the basin.Stage-discharge functions were developed to size the proposed
outlet structures for the SCM.
Conclusions
Water Quality
The routing analysis indicates that the proposed stormwater management plan has sufficient
mitigation measures to comply with nutrient export and watershed protection overlay standards
in accordance with local and state regulations.
The proposed wet pond SCMs have been designed per NCDEQ MDC's to meet 85% TSS
removal requirements (see Appendix 3).
Peak Flows
Proposed peak flows associated with the 1-year,2-year,and 10-year(24-hour)design storms have
been attenuated at the POAs so as not exceed existing conditions (Tables 3-6).
Table 3 - Peak Summary at POA 8A
Storm Even Existing Dev Proposed Dev Peak Net Change Net Change
Peak Flow(cfs) Flow(cfs) (cfs) (%)
1-yr, 24-hr 18.7 10.5 -8.2 -44%
2-yr,24-hr 34.3 16.5 -17.7 -52%
10-yr, 24-hr 89.8 82.9 -6.9 -8%
100-yr, 24-hr 196.2 267.8 71.6 37%
Table 4 - Peak Summary at POA 8B
Storm Even Existing Dev Proposed Dev Peak Net Change Net Change
Peak Flow(cfs) Flow(cfs) (cfs) (%)
1-yr, 24-hr 6.3 4.7 -1.6 -25%
2-yr,24-hr 13.3 10.5 -2.8 -21%
10-yr, 24-hr 39.4 32.6 -6.9 -17%
100-yr, 24-hr 93.5 79.1 -14.4 -15%
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Stormwater Management Plan Serenity - Phases 8 & 9
Table 5 - Peak Summary at POA 9A
Storm Even Existing De Proposed Dev Peak Net Change Net Change
Peak Flow(cfs) Flow(cfs) (cfs) (%)
1-yr,24-hr 29.6 18.0 -11.6 -39%
2-yr,24-hr 54.0 41.0 -13.1 -24%
10-yr, 24-hr 134.1 128.5 -5.6 -4%
100-yr,24-hr 285.2 337.22 52.0 18%
Table 6 - Peak Summary at POA 9B
Storm Event Existing Dev Proposed Dev Peak Net Change Net Change
Peak Flow(cfs) Flow(cfs) (cfs) (%)
1-yr,24-hr 43.2 21.4 -21.8 -50%
2-yr,24-hr 73.5 46.0 -27.5 -37%
10-yr, 24-hr 170.4 137.2 -33.2 -19%
100-yr,24-hr 352.4 325.6 -26.8 -8%
SCM Design Summaries
The proposed wet pond SCMs (SCM 6-11) have been designed to safely pass the 100-year design
storm event via the primary and emergency spillways. In addition,the wet pond SCMs (SCM 6-11)
maintain a freeboard during a 100-year design storm event of at least 1-ft (Table 7).
Table 7 - SCM Wet Pond Freeboard Summary
op o 'am 100-yr Max provided
CM Elevation (ft) Water Surface Freeboard (ft)
Elevation (ft)
6 335.0 333.7 1.3
7 335.0 333.8 1.2
8 358.0 356.8 1.2
9 368.0 366.9 1.1
10 376.0 374.8 1.2
11 382.0 380.6 1.4
The proposed treatment swale SCMs (SCM 12-13) have been designed to safely pass the 100-yr
design storm and maintain a freeboard during a 10-yr design storm event of at least 0.5-ft (Table
8).
Table 8 - SCM Treatment Swale Freeboard Summary
op of Swale 10-yr Max Provided
SCM levation (ft) Water Surface Freeboard (ft)
Elevation (ft)
12 378.75 378.17 0.58
13 314.0 314.47 1.03
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Stormwater Management Plan Serenity - Phases 8 & 9
SCM 6 - Wet Pond
Drainage Area = 12.20 ac
Impervious Area = 6.30 ac
Impervious = 51.6%
Top of Dam = 335.0
Emergency Spillway Crest = 334.0
Bottom Width = 15 ft
Side Slopes = 5:1 ft/ft
4'x 4' Riser Crest= 332.5
Water Quality Overflow Elev. = 330.0
Rectangular Orifice L x H = 1.5 ft x 1.5 ft
Storage Volume = 34,767 cf
Normal Pool Orifice Elev. = 327.5
Main Pool Surface Area = 8,515 sf
Drawdown Orifice Diameter= 2.5 in
Outlet Barrel Diameter= 24 in RGRCP
Table 9 -SCM 6-Routing Summary
Storm Event Peak Discharge Peak WSEL(ft) Freeboard (ft)
(cfs)
1-yr, 24-hr 0.8 330.1 4.9
2-yr, 24-hr 2.6 330.4 4.6
10-yr, 24-hr 12.0 331.9 3.1
100-yr, 24-hr 52.9 333.7 1.3
September 20, 2023 7
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Stormwater Management Plan Serenity - Phases 8 & 9
SCM 7- Wet Pond
Drainage Area = 25.95 ac
Impervious Area = 12.41 ac
Impervious = 47.8%
Top of Dam = 335.0
Emergency Spillway Crest= 334.0
Bottom Width = 15 ft
Side Slopes = 5:1 ft/ft
5'x 5' Riser Crest = 332.0
Water Quality Overflow Elev. = 331.25
Rectangular Weir= 5.0 ft
Storage Volume = 85,034 cf
Normal Pool Orifice Elev. = 328.5
Main Pool Surface Area. = 21,078 sf
Drawdown Orifice Diameter= 3.5 in
Outlet Barrel Diameter= 42 in RGRCP
Table 10 - SCM 7-Routing Summary
Storm Event Peak Discharge Peak WSEL(ft) Freeboard (ft)
(cfs)
1-yr, 24-hr 0.9 331.3 3.7
2-yr, 24-hr 3.3 331.6 3.4
10-yr, 24-hr 46.1 332.6 2.4
100-yr, 24-hr 149.0 333.8 1.2
September 20, 2023 8
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Stormwater Management Plan Serenity - Phases 8 & 9
SCM 8 - Wet Pond
Drainage Area = 9.39 ac
Impervious Area = 4.34 ac
Impervious = 46.2%
Top of Dam = 358.0
Emergency Spillway Crest= 357.0
Bottom Width = 15 ft
Side Slopes = 5:1 ft/ft
4'x 4' Riser Crest = 356.0
Water Quality Overflow Elev. = 355.0
Rectangular Weir= 2 ft
Storage Volume = 40,529 cf
Normal Pool Orifice Elev. = 352.5
Main Pool Surface Area = 10,655 sf
Drawdown Orifice Diameter= 2.25 in
Outlet Barrel Diameter= 24 in RGRCP
Table 11 - SCM 8-Routing Summary
Storm Event Peak Discharge peak WSEL(ft) Freeboard (ft)
(cfs)
1-yr, 24-hr 0.2 354.6 3.4
2-yr, 24-hr 0.5 355.1 2.9
10-yr, 24-hr 4.8 355.8 2.2
100-yr, 24-hr 50.2 356.9 1.1
September 20, 2023 9
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Stormwater Management Plan Serenity - Phases 8 & 9
SCM 9 - Wet Pond
Drainage Area = 16.32 ac
Impervious Area = 8.63 ac
Impervious = 52.8%
Top of Dam = 368.0
Emergency Spillway Crest= 367.0
Bottom Width = 15 ft
Side Slopes = 5:1 ft/ft
5'x 5' Riser Crest = 365.75
Water Quality Overflow Elev. = 364.25
Rectangular Weir= 5.0 ft
Storage Volume = 36,545 cf
Normal Pool Orifice Elev. = 362.5
Main Surface Area = 14,664 sf
Drawdown Orifice Diameter= 3.0 in
Outlet Barrel Diameter= 42 in RGRCP
Table 12 - SCM 9-Routing Summary
Storm Event Peak Discharge Peak WSEL(ft) Freeboard (ft)
(cfs)
1-yr, 24-hr 2.4 364.5 3.5
2-yr, 24-hr 8.4 364.9 3.1
10-yr, 24-hr 44.8 366.1 2.0
100-yr, 24-hr 118.9 366.9 1.1
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Stormwater Management Plan Serenity - Phases 8 & 9
SCM 10 - Wet Pond
Drainage Area = 18.33 ac
Impervious Area = 9.87 ac
Impervious = 53.9%
Top of Dam = 376.0
Emergency Spillway Crest= 375.0
Bottom Width = 15 ft
Side Slopes = 5:1 ft/ft
5'x 5' Riser Crest = 373.5
Water Quality Overflow Elev. = 372.25
Rectangular Weir= 5.0 ft
Storage Volume = 44,087 cf
Normal Pool Orifice Elev. = 370.5
Main Pool Surface Area = 18,135 sf
Drawdown Orifice Diameter= 3.25 in
Outlet Barrel Diameter= 36 in RGRCP
Table 13 - SCM 10-Routing Summary
Storm Event Peak Discharge Peak WSEL(ft) Freeboard (ft)
(cfs)
1-yr, 24-hr 1.5 372.4 3.6
2-yr, 24-hr 5.1 372.7 3.3
10-yr, 24-hr 37.0 373.8 2.2
100-yr, 24-hr 104.1 374.8 1.2
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Stormwater Management Plan Serenity - Phases 8 & 9
SCM 11 - Wet Pond
Drainage Area = 10.71 ac
Impervious Area = 5.76 ac
Impervious = 53.8%
Top of Dam = 382.0
Emergency Spillway Crest= 381.0
Bottom Width = 15 ft
Side Slopes = 5:1 ft/ft
4'x 4' Riser Crest = 379.5
Water Quality Overflow Elev. = 378.5
Rectangular Weir= 4.0 ft
Storage Volume = 28,803 cf
Normal Pool Orifice Elev. = 376.5
Main Pool Surface Area = 9,180
Drawdown Orifice Diameter= 2.5 in
Outlet Barrel Diameter= 30 in RGRCP
Table 14 - SCM 11 -Routing Summary
Storm Event Peak Discharge Peak WSEL(ft) Freeboard (ft)
(cfs)
1-yr, 24-hr 0.9 378.6 3.4
2-yr, 24-hr 3.2 378.9 3.2
10-yr, 24-hr 26.8 379.8 2.2
100-yr, 24-hr 69.6 380.6 1.4
September 20, 2023 12
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Stormwater Management Plan Serenity - Phases 8&9
Appendix 1: Reference Materials
• USGS 7.5-Minute Quadrangle Map
• Web Soil Survey Map
• NOAA Atlas 14 Precipitation Frequency Estimates
• PONDPACK Precipitation Hydrograph Input Data
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-01-10 Conservation Service National Cooperative Soil Survey Page 1 of 4

Hydrologic Soil Group—Harnett County,North Carolina
(Serenity Phases 8&9)
MAP LEGEND MAP INFORMATION
Area of Interest(AOI) p c The soil surveys that comprise your AOI were mapped at
Area of Interest(AOI) 1:24,000.
0 C/D
Soils • D Warning:Soil Map may not be valid at this scale.
Soil Rating Polygons
0 A p Not rated or not available Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
n A/D Water Features line placement.The maps do not show the small areas of
Streams and Canals contrasting soils that could have been shown at a more detailed
n B scale.
Transportation
Q B/D
r4-1. Rails Please rely on the bar scale on each map sheet for map
n C measurements.
ti Interstate Highways
C/D US Routes Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
0 D Major Roads Coordinate System: Web Mercator(EPSG:3857)
n Not rated or not available Local Roads
Maps from the Web Soil Survey are based on the Web Mercator
Soil Rating Lines Background projection,which preserves direction and shape but distorts
• • A distance and area.A projection that preserves area,such as the
1111 Aerial Photography Albers equal-area conic projection,should be used if more
• • A/D accurate calculations of distance or area are required.
^r B This product is generated from the USDA-NRCS certified data as
.v B/D of the version date(s)listed below.
• r C Soil Survey Area: Harnett County, North Carolina
Survey Area Data: Version 20,Sep 8,2022
• • C/D
Soil map units are labeled(as space allows)for map scales
• • D 1:50,000 or larger.
• w Not rated or not available Date(s)aerial images were photographed: Apr 24,2022—May
Soil Rating Points 9,2022
p A The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
O A/D imagery displayed on these maps.As a result,some minor
• B shifting of map unit boundaries may be evident.
• B/D
USDA Natural Resources Web Soil Survey 9/19/2023
Conservation Service National Cooperative Soil Survey Page 2 of 4

Hydrologic Soil Group—Harnett County, North Carolina Serenity Phases 8&9
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
CeB Cecil fine sandy loam,2 A 17.5 45.7%
to 8 percent slopes
CeD Cecil fine sandy loam,8 A 14.6 38.2%
to 15 percent slopes
PaE Pacolet fine sandy loam, B 6.1 16.1%
15 to 25 percent
slopes
Totals for Area of Interest 38.2 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential)when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential)when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
USDA Natural Resources Web Soil Survey 9/19/2023
Conservation Service National Cooperative Soil Survey Page 3 of 4

Hydrologic Soil Group—Harnett County, North Carolina Serenity Phases 8&9
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff.None Specified
Tie-break Rule: Higher
USDA Natural Resources Web Soil Survey 9/19/2023
Conservation Service National Cooperative Soil Survey Page 4 of 4

NOAA Atlas 14,Volume 2,Version 3
.00.4u. Location name: Fuquay Varina, North Carolina, r•-°°,
ase V USA* ibknoee \
Latitude: 35.5506°, Longitude: -78.8317° e
Elevation: 370.59 ft** '
NrEg0 *source:ESRI Maps k'`"w�+,,,
**source:USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M.Bonnin,D.Martin,B.Lin,T.Parzybok,M.Yekta,and D.Riley
NOAA,National Weather Service,Silver Spring,Maryland
PF tabular I PF graphical I Maps & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Average recurrence interval(years)
Duration
1 2 5 10 25 50 100 200 500 1000
5-min 0.420 0.492 0.567 0.630 0.698 0.749 0.795 0.837 0.886 1 0.926
(0.384-0.460) (0.450-0.540) (0.518-0.622) (0.574-0.690) (0.634-0.764) (0.677-0.818) (0.715-0.869) (0.749-0.915) (0.785-0.968) (0.814-1.01)
10-min 0.670 0.786 0.908 1.01 1.11 1.19 1.26 1.33 1.40 1.46
(0.613-0.735) (0.719-0.863) (0.830-0.996) (0.918-1.10) (1.01-1.22) (1.08-1.30) (1.14-1.38) (1.19-1.45) (1.24-1.53) (1.28-1.60)
15-min 0.838 0.988 1.15 1.27 1.41 1.51 1.60 1.67 1.76 1.83
(0.766-0.919) (0.904-1.09) (1.05-1.26) (1.16-1.40) (1.28-1.54) (1.37-1.65) (1.44-1.75) (1.50-1.83) (1.56-1.93) (1.61-2.00)
30-min 1.15 1.37 1.63 1.85 2.09 2.27 2.45 1 2.61 2.81 2.96
(1.05-1.26) (1.25-1.50) (1.49-1.79) (1.68-2.02) (1.90-2.29) (2.06-2.49) (2.20-2.67) (2.33-2.85) (2.49-3.07) (2.61-3.24)
60-min 1.43 1.71 2.09 2.40 2.78 3.08 3.37 3.66 4.03 4.33
(1.31-1.57) (1.57-1.88) (1.91-2.30) (2.19-2.63) (2.53-3.04) (2.79-3.37) (3.03-3.68) (3.27-4.00) (3.57-4.40) (3.80-4.74)
2-hr 1.68 2.02 2.50 2.91 3.42 3.84 4.25 r 4.68 5.24 5.72
(1.53-1.87) (1.84-2.24) (2.27-2.77) (2.63-3.21) (3.07-3.78) (3.44-4.24) (3.78-4.69) (4.14-5.16) (4.59-5.78) (4.96-6.31)
3-hr 1.78 2.15 2.67 3.12 3.71 4.21 4.71 5.24 5.96 6.59
(1.62-1.98) (1.96-2.38) (2.42-2.95) (2.82-3.45) (3.33-4.09) (3.76-4.64) (4.18-5.19) (4.61-5.77) (5.19-6.57) (5.67-7.27)
6-hr 2.13 2.56 3.19 3.73 4.45 5.07 5.70 6.37 7.29 8.09
(1.95-2.35) (2.34-2.83) (2.90-3.51) (3.39-4.11) (4.02-4.89) (4.55-5.56) (5.07-6.25) (5.60-6.97) (6.33-7.98) (6.93-8.86)
12-hr 2.51 3.02 3.77 4.44 5.34 6.12 6.92 7.79 9.00 10.1
(2.29-2.77) (2.76-3.34) (3.43-4.17) (4.03-4.90) (4.80-5.87) (5.46-6.70) (6.12-7.58) I (6.80-8.52) (7.74-9.85) I (8.52-11.0)
I 24-hr 2.94 3.56 4.49 5.22 6.24 7.05 7.88 8.75 9.95 10.9
(2.73-3.18) (3.30-3.85) (4.15-4.85) (4.82-5.64) (5.74-6.74) (6.47-7.61) (7.21-8.51) I (7.98-9.45) (9.03-10.8) (9.85-11.8)
2-day 3.41 4.11 5.15 5.97 7.09 7.99 8.91 9.86 11.2 12.2
(3.16-3.68) (3.81-4.44) (4.77-5.56) (5.51-6.44) (6.53-7.65) (7.33-8.62) (8.15-9.62) (8.99-10.7) (10.1-12.1)_ (11.0-13.2)
3-day 3.61 4.34 5.41 6.26 7.41 8.34 9.28 10.3 11.6 12.7
(3.35-3.88) (4.04-4.68) (5.02-5.82) (5.79-6.73) (6.84-7.97) (7.67-8.97) (8.51-9.99) (9.38-11.1) (10.6-12.5) (11.5-13.7)
4-day 3.81 4.58 5.68 6.54 I 7.73 I 8.68 I 9.66 10.7 12.1 13.2
(3.55-4.09) (4.26-4.91)_ (5.28-6.09) (6.07-7.01) (7.15-8.30) (8.00-9.31) (8.87-10.4) (9.77-11.5) (11.0-13.0) (11.9-14.2)
7-day 4.40 5.26 1 6.43 7.37 8.65 9.67 10.7 11.8 13.3 14.4
(4.10-4.71) (4.90-5.64) (6.00-6.90) (6.85-7.89) 1 (8.02-9.27) 1 (8.94-10.4) 1 (9.88-11.5) (10.8-12.7) (12.1-14.3) (13.1-15.5)
10-day 5.03 6.00 7.23 8.20 9.51 10.5 11.6 12.6 14.1 15.2
(4.72-5.37) (5.62-6.40) (6.77-7.72) (7.66-8.75) (8.86-10.1) (9.80-11.2) (10.7-12.4) (11.7-13.5) (13.0-15.1) (13.9-16.3)
20-day 6.74 7.97 9.46 10.6 12.2 13.4 14.7 15.9 17.7 19.0
(6.31-7.20) (7.47-8.51) (8.85-10.1) (9.93-11.3) (11.4-13.0) (12.5-14.3) (13.6-15.7) (14.7-17.0) (16.3-18.9) (17.4-20.4)
30-day 8.39 9.88 11.5 12.8 14.5 15.8 17.1 18.3 20.0 21.4
(7.88-8.94) (9.28-10.5) (10.8-12.3) (12.0-13.6) (13.5-15.4) (14.7-16.8) (15.9-18.2) i (17.0-19.6) (18.6-21.4) (19.7-22.9)
45-day 10.7 12.5 14.4 15.8 17.7 19.1 20.5 21.8 23.6 24.9
(10.1-11.3) (11.9-13.3) (13.6-15.2) (15.0-16.8) (16.7-18.7) (18.0-20.2) (19.2-21.7) (20.4-23.1) (22.0-25.0) (23.2-26.5)
60-day 12.8 15.0 17.0 18.6 20.6 22.1 23.5 25.0 26.8 28.2
(12.1-13.5) (14.2-15.8) (16.1-17.9) (17.5-19.6) (19.4-21.7) (20.8-23.3) (22.1-24.9) (23.4-26.4) (25.1-28.4) (26.4-29.9)
1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates(for a
given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5%.Estimates at upper bounds are not
checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
Back to Top
PF graphical

PDS-based depth-duration-frequency (DDF) curves
Latitude: 35.5506°, Longitude: -78.8317°
30 , I I r
Average recurrence
25 interval
(years)
— 1
-, 20 •
2
a) - 5
V .
c 15 . . ._ — 10
— 25
a — 50
•v 10 y.'. .._ — 100
a — 200
5 /--. • - 500
0 _— . . .
c c c c c - - - 6- I- >, >,>. >. >, >, >, >,>.
'F .- •� 'F •- -c -c -c -c -c ro ro ro ro ro ro to r0 ro
N A lb N 4 -0 -0-D - -0 -0 -0 -0-0
IA O r-1 N N A I� rIin—I -I rn D 4 f cr IrI
Duration
30 r
25
I
20 _ Duration
— 5-rnin 15 — 10-m 15-rn— 30-m 10 — 60-m— 2-hr — 20-day
— 3fir — 30-day
5
--- — 6fir — 45-day
, — 12-hr — 60-day
0 — I - 1 — I 1 I I I — 24-hr
1 —2 5 10 25 50 100 200 500 1000
Average recurrence interval (years)
NOAA Atlas 14,Volume 2,Version 3 Created(GMT):Thu Jul 14 20:08:11 2022
Back to Top
Maps & aerials
Small scale terrain

A---��Fuquay-Varina
xi\--
....\ /
' s11
l I,V1 +
�
3km
2mi
Lar a scale terrain
N,
inston-Salem 0
• • �Durham
Rocky Mount
Greensboro •
Raleigh '
4
! •
R T H C A R O t I N AI 'Greenville
*Charlotte
Otte Fayetteville•
F, •1a Hie
100km
I1‘. 11 60mi - Wilmington On stow'
• Rav
Large scale map
inston-6 lem Greensboro 0.
o D rham Rocky Mount
c
Raleigh
' Greenville
v
North —•
Carolina '
arl otte
Fayetteville
f.
Jac Ile
100km
60mi Wilmington
Large scale aerial

Winston-Salem
Greensboro Durham . Rocky Mount
Raleigh
• Greenville
North • •
Carolina •
•
Charlotte
Fayetteville
.
Jacl le
100km
60mi
Back to Top
US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
National Water Center
1325 East West Highway
Silver Spring,MD 20910
Questions?:[e-mail]
Disclaimer

Table of Contents
Time-Depth- 1
Time-Depth Curve, 100 years 1
Time-Depth Curve, 10 years 3
Time-Depth Curve, 1 years 5
Time-Depth Curve, 2 years 7

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Subsection: Time-Depth Curve Return Event: 100 years
Label: Time-Depth - 1 Storm Event: 100-yr, 24-hr
Time-Depth Curve: 100-yr, 24-hr
Label 100-yr, 24-hr
Start Time 0.000 hours
Increment 0.100 hours
End Time 24.000 hours
Return Event 100 years
CUMULATIVE RAINFALL (in)
Output Time Increment = 0.100 hours
Time on left represents time for first value in each row.
Time Depth Depth Depth Depth Depth
(hours) (in) (in) (in) (in) (in)
0.000 0.0 0.0 0.0I 0.0I 0.0I
0.500 0.0 0.0 0.1 0.1 0.1
1.000 0.1 0.1 0.1 0.1 0.1
1.500 0.1 0.1 0.1 0.2 0.2
2.000 0.2 0.2 0.2 0.2 0.2
2.500 0.2 0.2 0.2 0.3 0.3
3.000 0.3 0.3 0.3 0.3 0.3
3.500 0.3 0.3 0.3 0.4 0.4
4.000 0.4 0.4 0.4 0.4 0.4
4.500 0.4 0.4 0.5 0.5 0.5
5.000 0.5 0.5 0.5 0.5 0.5
5.500 0.6 0.6 0.6 0.6 0.6
6.000 0.6 0.6 0.7 0.7 0.7
6.500 0.7 0.7 0.7 0.7 0.8
7.000 0.8 0.8 0.8 0.8 0.8
7.500 0.9 0.9 0.9 0.9 0.9
8.000 0.9 1.0 1.0 1.0 1.0
8.500 1.0 1.1 1.1 1.1 1.1
9.000 1.2 1.2 1.2 1.2 1.3
9.500 1.3 1.3 1.3 1.4 1.4
10.000 1.4 1.5 1.5 1.5 1.6
10.500 1.6 1.7 1.7 1.7 1.8
11.000 1.9 1.9 2.0 2.1 2.1
11.500 2.2 2.4 2.8 3.4 4.5
12.000 5.2 5.4 5.5 5.6 5.7
12.500 5.8 5.9 5.9 6.0 6.0
13.000 6.1 6.1 6.2 6.2 6.3
13.500 6.3 6.3 6.4 6.4 6.4
14.000 6.5 6.5 6.5 6.5 6.6
14.500 6.6 6.6 6.7 6.7 6.7
15.000 6.7 6.7 6.8 6.8 6.8
15.500 6.8 6.9 6.9 6.9 6.9
16.000 6.9 7.0 7.0 7.0 7.0
16.500 7.0 7.0 7.1 7.1 7.1
17.000 7.1 7.1 7.1 7.2 7.2
17.500 7.2 7.2 7.2 7.2 7.2
18.000 7.3 7.3 7.3 7.3 7.3
18.500 7.3 7.3 7.4 7.4 7.4
19.000 7.4 7.4 7.4 7.41 7.4
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Subsection: Time-Depth Curve Return Event: 100 years
Label: Time-Depth - 1 Storm Event: 100-yr, 24-hr
CUMULATIVE RAINFALL (in)
Output Time Increment = 0.100 hours
Time on left represents time for first value in each row.
Time Depth Depth Depth Depth Depth
(hours) (in) (in) (in) (in) (in)
19.500 7.4 7.5 7.5 7.5 7.5
20.000 7.5 7.5 7.5 7.5 7.5
20.500 7.6 7.6 7.6 7.6 7.6
21.000 7.6 7.6 7.6 7.6 7.6
21.500 7.7 7.7 7.7 7.7 7.7
22.000 7.7 7.7 7.7 7.7 7.7
22.500 7.7 7.8 7.8 7.8 7.8
23.000 7.8 7.8 7.8 7.8 7.8
23.500 7.8 7.8 7.9 7.9 7.9
24.000 7.9 (N/A) (N/A) (N/A) (N/A)
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Subsection: Time-Depth Curve Return Event: 10 years
Label: Time-Depth - 1 Storm Event: 10-yr, 24-hr
Time-Depth Curve: 10-yr, 24-hr
Label 10-yr, 24-hr
Start Time 0.000 hours
Increment 0.100 hours
End Time 24.000 hours
Return Event 10 years
CUMULATIVE RAINFALL (in)
Output Time Increment = 0.100 hours
Time on left represents time for first value in each row.
Time Depth Depth Depth Depth Depth
(hours) (in) (in) (in) (in) (in)
0.000 0.0 0.0 0.0 0.0 0.0
0.500 0.0 0.0 0.0 0.0 0.0
1.000 0.1 0.1 0.1 0.1 0.1
1.500 0.1 0.1 0.1 0.1 0.1
2.000 0.1 0.1 0.1 0.1 0.1
2.500 0.1 0.2 0.2 0.2 0.2
3.000 0.2 0.2 0.2 0.2 0.2
3.500 0.2 0.2 0.2 0.2 0.2
4.000 0.3 0.3 0.3 0.3 0.3
4.500 0.3 0.3 0.3 0.3 0.3
5.000 0.3 0.3 0.3 0.4 0.4
5.500 0.4 0.4 0.4 0.4 0.4
6.000 0.4 0.4 0.4 0.4 0.5
6.500 0.5 0.5 0.5 0.5 0.5
7.000 0.5 0.5 0.5 0.5 0.6
7.500 0.6 0.6 0.6 0.6 0.6
8.000 0.6 0.6 0.7 0.7 0.7
8.500 0.7 0.7 0.7 0.7 0.8
9.000 0.8 0.8 0.8 0.8 0.8
9.500 0.9 0.9 0.9 0.9 0.9
10.000 0.9 1.0 1.0 1.0 1.0
10.500 1.1 1.1 1.1 1.2 1.2
11.000 1.2 1.3 1.3 1.4 1.4
11.500 1.5 1.6 1.8 2.2 3.0
12.000 3.5 3.6 3.6 3.7 3.8
12.500 3.8 3.9 3.9 4.0 4.0
13.000 4.0 4.1 4.1 4.1 4.1
13.500 4.2 4.2 4.2 4.2 4.3
14.000 4.3 4.3 4.3 4.3 4.4
14.500 4.4 4.4 4.4 4.4 4.4
15.000 4.5 4.5 4.5 4.5 4.5
15.500 4.5 4.5 4.6 4.6 4.6
16.000 4.6 4.6 4.6 4.6 4.6
16.500 4.7 4.7 4.7 4.7 4.7
17.000 4.7 4.7 4.7 4.7 4.7
17.500 4.8 4.8 4.8 4.8 4.8
18.000 4.8 4.8 4.8 4.8 4.8
18.500 4.9 4.9 4.9 4.9 4.9
19.000 4.9 4.9 4.9 4.9 4.9
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Subsection: Time-Depth Curve Return Event: 10 years
Label: Time-Depth - 1 Storm Event: 10-yr, 24-hr
CUMULATIVE RAINFALL (in)
Output Time Increment = 0.100 hours
Time on left represents time for first value in each row.
Time Depth Depth Depth Depth Depth
(hours) (in) (in) (in) (in) (in)
19.500 4.9 4.9 4.9 5.0 5.0
20.000 5.0 5.0 5.0 5.0 5.0
20.500 5.0 5.0 5.0 5.0 5.0
21.000 5.0 5.0 5.0 5.1 5.1
21.500 5.1 5.1 5.1 5.1 5.1
22.000 5.1 5.1 5.1 5.1 5.1
22.500 5.1 5.1 5.1 5.1 5.2
23.000 5.2 5.2 5.2 5.2 5.2
23.500 5.2 5.2 5.2 5.2 5.2
24.000 5.2 (N/A) (N/A) (N/A) (N/A)
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Subsection: Time-Depth Curve Return Event: 1 years
Label: Time-Depth - 1 Storm Event: 1-yr, 24-hr
Time-Depth Curve: 1-yr,24-hr
Label 1-yr, 24-hr
Start Time 0.000 hours
Increment 0.100 hours
End Time 24.000 hours
Return Event 1 years
CUMULATIVE RAINFALL (in)
Output Time Increment = 0.100 hours
Time on left represents time for first value in each row.
Time Depth Depth Depth Depth Depth
(hours) (in) (in) (in) (in) (in)
0.000 0.0 0.0 0.0 0.0 0.0
0.500 0.0 0.0 0.0 0.0 0.0
1.000 0.0 0.0 0.0 0.0 0.0
1.500 0.0 0.1 0.1 0.1 0.1
2.000 0.1 0.1 0.1 0.1 0.1
2.500 0.1 0.1 0.1 0.1 0.1
3.000 0.1 0.1 0.1 0.1 0.1
3.500 0.1 0.1 0.1 0.1 0.1
4.000 0.1 0.1 0.1 0.2 0.2
4.500 0.2 0.2 0.2 0.2 0.2
5.000 0.2 0.2 0.2 0.2 0.2
5.500 0.2 0.2 0.2 0.2 0.2
6.000 0.2 0.2 0.2 0.3 0.3
6.500 0.3 0.3 0.3 0.3 0.3
7.000 0.3 0.3 0.3 0.3 0.3
7.500 0.3 0.3 0.3 0.3 0.3
8.000 0.4 0.4 0.4 0.4 0.4
8.500 0.4 0.4 0.4 0.4 0.4
9.000 0.4 0.4 0.5 0.5 0.5
9.500 0.5 0.5 0.5 0.5 0.5
10.000 0.5 0.5 0.6 0.6 0.6
10.500 0.6 0.6 0.6 0.7 0.7
11.000 0.7 0.7 0.7 0.8 0.8
11.500 0.8 0.9 1.0 1.3 1.7
12.000 1.9 2.0 2.1 2.1 2.1
12.500 2.2 2.2 2.2 2.2 2.3
13.000 2.3 2.3 2.3 2.3 2.3
13.500 2.3 2.4 2.4 2.4 2.4
14.000 2.4 2.4 2.4 2.4 2.5
14.500 2.5 2.5 2.5 2.5 2.5
15.000 2.5 2.5 2.5 2.5 2.5
15.500 2.6 2.6 2.6 2.6 2.6
16.000 2.6 2.6 2.6 2.6 2.6
16.500 2.6 2.6 2.6 2.6 2.6
17.000 2.7 2.7 2.7 2.7 2.7
17.500 2.7 2.7 2.7 2.7 2.7
18.000 2.7 2.7 2.7 2.7 2.7
18.500 2.7 2.7 2.7 2.7 2.8
19.000 2.8 2.8 2.8 2.8 2.8
Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i
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Subsection: Time-Depth Curve Return Event: 1 years
Label: Time-Depth - 1 Storm Event: 1-yr, 24-hr
CUMULATIVE RAINFALL (in)
Output Time Increment = 0.100 hours
Time on left represents time for first value in each row.
Time Depth Depth Depth Depth Depth
(hours) (in) (in) (in) (in) (in)
19.500 2.8 2.8 2.8 2.8 2.8
20.000 2.8 2.8 2.8 2.8 2.8
20.500 2.8 2.8 2.8 2.8 2.8
21.000 2.8 2.8 2.8 2.8 2.9
21.500 2.9 2.9 2.9 2.9 2.9
22.000 2.9 2.9 2.9 2.9 2.9
22.500 2.9 2.9 2.9 2.9 2.9
23.000 2.9 2.9 2.9 2.9 2.9
23.500 2.9 2.9 2.9 2.9 2.9
24.000 2.9 (N/A) (N/A) (N/A) (N/A)
Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i
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Subsection: Time-Depth Curve Return Event: 2 years
Label: Time-Depth - 1 Storm Event: 2-yr, 24-hr
Time-Depth Curve: 2-yr,24-hr
Label 2-yr, 24-hr
Start Time 0.000 hours
Increment 0.100 hours
End Time 24.000 hours
Return Event 2 years
CUMULATIVE RAINFALL (in)
Output Time Increment = 0.100 hours
Time on left represents time for first value in each row.
Time Depth Depth Depth Depth Depth
(hours) (in) (in) (in) (in) (in)
0.000 0.0 0.0 0.0 0.0 0.0
0.500 0.0 0.0 0.0 0.0 0.0
1.000 0.0 0.0 0.0 0.0 0.1
1.500 0.1 0.1 0.1 0.1 0.1
2.000 0.1 0.1 0.1 0.1 0.1
2.500 0.1 0.1 0.1 0.1 0.1
3.000 0.1 0.1 0.1 0.1 0.1
3.500 0.1 0.2 0.2 0.2 0.2
4.000 0.2 0.2 0.2 0.2 0.2
4.500 0.2 0.2 0.2 0.2 0.2
5.000 0.2 0.2 0.2 0.2 0.2
5.500 0.3 0.3 0.3 0.3 0.3
6.000 0.3 0.3 0.3 0.3 0.3
6.500 0.3 0.3 0.3 0.3 0.3
7.000 0.4 0.4 0.4 0.4 0.4
7.500 0.4 0.4 0.4 0.4 0.4
8.000 0.4 0.4 0.4 0.5 0.5
8.500 0.5 0.5 0.5 0.5 0.5
9.000 0.5 0.5 0.5 0.6 0.6
9.500 0.6 0.6 0.6 0.6 0.6
10.000 0.6 0.7 0.7 0.7 0.7
10.500 0.7 0.7 0.8 0.8 0.8
11.000 0.8 0.9 0.9 0.9 1.0
11.500 1.0 1.1 1.3 1.5 2.0
12.000 2.4 2.4 2.5 2.5 2.6
12.500 2.6 2.6 2.7 2.7 2.7
13.000 2.7 2.8 2.8 2.8 2.8
13.500 2.8 2.9 2.9 2.9 2.9
14.000 2.9 2.9 2.9 3.0 3.0
14.500 3.0 3.0 3.0 3.0 3.0
15.000 3.0 3.0 3.1 3.1 3.1
15.500 3.1 3.1 3.1 3.1 3.1
16.000 3.1 3.1 3.1 3.2 3.2
16.500 3.2 3.2 3.2 3.2 3.2
17.000 3.2 3.2 3.2 3.2 3.2
17.500 3.2 3.3 3.3 3.3 3.3
18.000 3.3 3.3 3.3 3.3 3.3
18.500 3.3 3.3 3.3 3.3 3.3
19.000 3.3 3.3 3.3 3.4 3.4
Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i
Serenity-Ph 8&9.ppc Center [08.11.01.56]
9/15/2023 27 Siemon Company Drive Suite 200 W Page 7 of 9
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Subsection: Time-Depth Curve Return Event: 2 years
Label: Time-Depth - 1 Storm Event: 2-yr, 24-hr
CUMULATIVE RAINFALL (in)
Output Time Increment = 0.100 hours
Time on left represents time for first value in each row.
Time Depth Depth Depth Depth Depth
(hours) (in) (in) (in) (in) (in)
19.500 3.4 3.4 3.4 3.4 3.4
20.000 3.4 3.4 3.4 3.4 3.4
20.500 3.4 3.4 3.4 3.4 3.4
21.000 3.4 3.4 3.4 3.4 3.5
21.500 3.5 3.5 3.5 3.5 3.5
22.000 3.5 3.5 3.5 3.5 3.5
22.500 3.5 3.5 3.5 3.5 3.5
23.000 3.5 3.5 3.5 3.5 3.5
23.500 3.5 3.5 3.5 3.6 3.6
24.000 3.6 (N/A) (N/A) (N/A) (N/A)
Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i
Serenity-Ph 8&9.ppc Center [08.11.01.56]
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Index
T
Time-Depth- 1 (Time-Depth Curve, 1 years)...5, 6
Time-Depth- 1 (Time-Depth Curve, 10 years)...3,4
Time-Depth- 1 (Time-Depth Curve, 100 years)...1, 2
Time-Depth- 1 (Time-Depth Curve, 2 years)...7, 8
Bentley Systems,Inc. Haestad Methods Solution Bentley PondPack V8i
Serenity-Ph 8&9.ppc Center [08.11.01.56]
9/15/2023 27 Siemon Company Drive Suite 200 W Page 9 of 9
Watertown,CT 06795 USA [phone]

Stormwater Management Plan Serenity - Phases 8&9
Appendix 2: Peak Flow Analysis
• Existing Drainage Area Map
• Existing CN Calculations
• Existing Tc Calculations
• Existing PONDPACK Schematic
• Existing PONDPACK Model Data & Results
• Proposed Drainage Area Map
• Proposed CN Calculations
• Proposed Tc Calculations
• Proposed PONDPACK Schematic
• Proposed PONDPACK Model Data & Results
September 20, 2023 �
WithersRavenel Project No.02190647.00 1� WithersRavenel
Our People.Your Success.