SW1200502_00000 GE-159 - WETLAND REPORT - ALL_5/14/2020

 
Garner Engineering Inc. [e-mail]
9 Davis Lane 828.337.5716
Fairview, North Carolina, 28730

STORMWATER WETLAND ANALYSES REPORT 
WILLOW POND WETLAND SYSTEM 

ASHEVILLE, NORTH CAROLINA 
PREPARED FOR: 

MR. DANA BOLDEN, PE 

PREPARED BY: 

8 May 2020 

Garner Engineering Inc.  john@garner‐eng.com 
9 Davis Lane    828.337.5716 
Fairview, North Carolina, 28730    
May 8, 2020 
Bell Engineering 
Asheville, North Carolina 

Attention: Mr. Dana Bolden, PE 

Subject:  STORMWATER WETLAND ANALYSES – WILLOW POND WETLAND SYSTEM 
  North Carolina Arboretum – Parking Lot Expansion 
Asheville, North Carolina  
  Project ID: GE‐159 
Dear Dana: 
Garner Engineering is pleased to provide this report of hydrologic and hydraulic analyses for the 
Willow Pond wetland system at the North Carolina Arboretum in Asheville, NC. This report with 
supporting materials is provided in general conformance with our agreement dated 12 November 
2019. The purpose of this report is to provide supporting documentation and verification of the 
effectiveness of the Willow Pond system to treat post‐construction stormwater runoff from the main 
parking area at the Arboretum.   
The evaluation of the pond system is made in accordance with regulatory guidance for the 
Stormwater Wetland Best Management Practice in the Stormwater BMP Manual by the NC 
Department of Environmental Quality.  Based upon our analyses and our understanding of the 
operations of the Willow Pond system, we believe that the ponds, as constructed will meet or exceed 
the Minimum Design Criteria for the Stormwater Wetland BMP. 
We appreciate the opportunity to work with Bell Engineering on this project.  Please contact us with 
questions or concerns regarding our report.  
Sincerely, 
Garner Engineering, Inc. 

John F. Garner, PE 
Principal 

05/08/2020

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JOB NO. GE‐159 SHEET 1 OF 8 
PROJECT WILLOW POND STORMWATER TREATMENT 
TASK STORMWATER WETLAND MDC DESIGN 
BY JFG DATE 5/8/2020 
REVIEW     

OBJECTIVE 
The objective of these calculations is to demonstrate that the existing Willow Pond system will provide adequate 
stormwater treatment as a “Stormwater Wetland” to treat runoff from the upland parking areas with proposed 
improvements developed by Bell Engineering.   
PURPOSE 
The Willow Pond system provides habitat enhancement and stormwater protection from runoff for the NC 
Arboretum main parking area with proposed improvements.  Prior to the current improvements, the pond was 
functioning as defunct sediment basin associated with the original construction of the parking lot. Over the last 
10 years, the pond has impounded water at varying levels sufficient to support natural habitat for the mole 
salamander. The new Willow Pond system was designed to preserve and enhance habitat for the threatened 
salamander and provide a teaching and learning venue for the Arboretum. These calculations will verify the extent 
of the post‐construction stormwater treatment capacity for the purpose of obtaining post‐construction 
stormwater permitting for the proposed improvements to the parking area from the NC Department of 
Environmental Quality (NCDEQ).   
METHODS 
The previous design of the Willow Pond system did not verify stormwater treatment by NC DEQ standards.  The 
standing assumption is that the pond system will function as a “Stormwater Wetland” Best Management Practice 
(BMP).  The following methodologies are applied to the evaluation of stormwater treatment: 
1. Watershed characterization by the NRCS Curve Number Method 
2. Rainfall characterization by Department of Water Quality and frequency‐based depth values derived from 
the Precipitation Frequency Data Server (PFDS) and temporal distribution from NOAA Rainfall Atlas 14.  
3. Design Volume calculation using the Curve Number Method and a rainfall depth of 1 inch. 
4. Runoff hydrograph development using the Soil Conservation Service (SCS) Unit Hydrograph method. 
5. Calculation and routing of runoff through the pond system and associated spillways using the HEC‐HMS 
computer model. 
6. Wetland and forebay volume calculations in accordance with NCDEQ Stormwater Design Manual. 
INPUTS 
Garner Engineering (GE) relied on the following project‐specific data from previous work by others and 
development information from Bell Engineering: 
TABLE 1 – INPUT DATA SUMMARY 
Parameter Pond 1 Pond 2 Ponds 3 
Basin Area 8.13 acres 1.10 acres (combined) 
Top of Dam Elevation 2140.0 feet 2136.0 feet 2135.0 feet 

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Normal Pool Elevation 2136.0 feet 2133.25 feet 2132.5 feet 
Principal Spillway Elevation 2136.0 – orifice 
2139.0 ‐ overflow 
2133.25 – orifice 
2134.5 ‐ overflow 
2132.5 – orifice 
2134.0 ‐ overflow 
Emergency Spillway – Crest 
Elevation 2139.0 feet (aux. spillway) 2134.75 feet 2134.25 feet 

ASSUMPTIONS 
The following assumptions facilitate the calculation of the hydraulic capacity of the existing spillway:  
 The treatment volume for the “Stormwater Wetland” configuration is the volume of runoff from the 1.00” 
storm event over the developed watershed. 
 Design storm for spillway hydraulic capacity is the 25‐year storm event with a 24‐hour duration. 
ANALYSES 
CALCULATION 1 – HYDROLOGIC MODEL 
1.1 – DESIGN RAINFALL 
Rainfall data was assembled for the 24‐hour storms shown in Table 2 below using PFDS Point Precipitation 
Frequency Estimates (see Figure A1).  
Input for Precipitation Depth Estimates are summarized as follows:  
TABLE 2: FREQUENCY STORM RAINFALL DEPTHS (INCHES) 
AVERAGE RECURRENCE INTERVAL (YEARS) DEPTH FOR 24‐HOUR DURATION STORM 
(INCHES)  
Treatment Volume (for drawdown routing) 1.00 
1‐year 2.72 
2‐year 3.26 
10‐year 4.63 
25‐year 5.46 
50‐year 6.14 

A single 24‐hour temporal distribution was developed and applied to all rainfall depths. We referenced temporal 
distributions provided in NOAA Atlas 14, and we selected the temporal distribution that produces the maximum 
peak rainfall intensity which corresponds to the distribution representing the storms where most of the rainfall 
fell in the first 10% of the storm duration.  Using this temporal distribution, the rainfall depths were distributed 
over 24 hours in incremental rainfall depths at 6‐minute intervals.   
1.2 – WATERSHED AREA  
The area draining to the Willow Pond system is taken from previous work performed by others for the NC 
Arboretum and used with their permission. Watershed areas were verified for accuracy.  The size of the 
watersheds for Pond 2 and Pond 3 are nearly equivalent and small relative to the Pond 1 watershed. For this 

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reason, the entire watershed for Pond 3 was routed through both Pond 2 and Pond 3. This combination is reflected 
in the parameters listed later. 
1.3 ‐ CURVE NUMBER 
Runoff from rainfall events is calculated by characterizing the watershed using techniques developed by the Natural 
Resources Conservation Service (NRCS) and described in their publication, Technical Release 55 (TR55).  TR55 
characterizes watersheds by assigning a Curve Number to regions of the watershed based on land use and soil 
properties.  The Curve Number Method is used to develop a weighted average Curve Number for the entire 
watershed. The Hydrologic Soil Group (HSG) and Curve Number calculation is given in the attached calculation sheet. 
1.4 – TREATMENT VOLUME 
The Treatment Volume is calculated using the NRCS Curve Number equation applied to the developed areas within 
each watershed.  In this case, the impervious areas in each watershed produced the runoff volume to be treated 
by the wetland pond system. The treatment volume calculations are included in the attached spreadsheets. 
1.5 – TRANSFORM METHOD 
The runoff generated from each watershed is distributed over the duration of the storm event by using a method 
of hydrograph transformation.  The Soil Conservation Service (SCS) Unit Hydrograph method provides this 
distribution based on the basin lag watershed parameter.  Calculations of basin lag for the area draining to Pond 
1 and the area draining to Ponds 2 and 3 are included in the attached calculation sheets. 
1.6 – STORMWATER BMP CALCULATIONS 
The stormwater wetland BMP has been developed through extensive research and development.  The 
regulations for Stormwater Wetlands include minimum design criteria (MDC) for the design of new stormwater 
wetland systems.  The Stormwater Wetland BMP regulations include 17 MDC’s for the design new wetland 
systems.  Each MDC is discussed in the Calculations below. 
CALCULATION 2 – HYDRAULIC MODELING OF PROPOSED SPILLWAYS 
2.1 – PRINCIPAL SPILLWAY HYDRAULICS CALCULATION 
The Willow Pond system is unique in that it was originally designed to function as a wetland habitat that would 
support the threatened Mole Salamander.  The system was originally developed by Equinox Environmental. 
Improvements have been principally completed and include three distinct pond areas. We developed a HEC – 
HMS computer model to incorporate the rainfall distribution, and watershed characterization previously 
described with hydraulic capacity calculations for the specific spillway systems for the three ponds in the Willow 
Pond system. The HEC‐HMS model allows us to evaluate the proposed spillway structures and incorporate 
additional spillway modifications and systems, where needed.  We calculated the hydraulic capacity of each 
primary spillway system using an internally developed spreadsheet. Hydraulic parameters for each spillway were 
estimated and used to calculate the stage‐discharge relationship shown on the attached calculations. Spillway 
structures are shown in the construction drawings. 
The principal spillway structures for each pond are a proprietary flashboard system developed by Agri‐drain.  The 
flashboards allow for stormwater control orifi to be drilled at precise elevations. The system also allows for 
overflow during larger storm events.  We modeled these systems using orifice, weir and pipe flow equations taking 
the most‐limiting flow device as the control for the system at various pool elevations.  Thereby, we create a rating 

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curve for the principal spillway which is applied to the HEC‐HMS model.  The HEC‐HMS model also allows us to 
evaluate the drawdown time for the treatment volume storm event. 
2.2 – STORMWATER WETLAND MDC’S 
The Stormwater Wetland MDC’s encompass all aspects of the wetland design.  The Willow Pond system is 
comprised of 3, separate, but hydraulically connected, pond areas.  Each pond has a principal spillway and auxiliary 
spillway to control stormwater releases. The ponds each have a slightly different permanent pool elevation 
descending from Pond 1 to Pond 3. This complicates the application of the MDC regulations to the Willow Pond 
system.  Each MDC is discussed below: 
1. Temporary Ponding Depth – the temporary ponding depth is set at a maximum depth of 15 inches above 
the permanent pool. We calculated our treatment volume storage capacity based upon 15 inches of 
storage above the permanent pool elevation of Pond 2 and Pond 3. We designed Pond 1 to function with 
an emphasis on the forebay treatment functions. We therefore allow Pond 1 to fill up to 36 inches above 
the normal pool to create depth for energy dissipation and settling of solids. The forebay function and 
storage are critical to the successful operation of the wetland habitat in Pond 2 and Pond 3.  The calculated 
design volume was less than the available treatment volume. 
2. Peak Attenuation Depth – The wetland water surface elevation can rise above the 15‐inch temporary 
ponding limit for storage and attenuation of larger volume storms. The peak attenuation depth is different 
for each pond, with most of the peak attenuation storage volume being available in Pond 1, the forebay 
for the system. 
3. Surface Area – we calculated the surface area of each pond to verify that the design volume can be stored 
within the 15‐inch temporary ponding depth. Surface areas were obtained from our proposed grading for 
each pond. Grading was adjusted to meet the Surface Area and other MDC criteria. 
4. Soil Amendments – The pond system had been previously functioning as a construction stormwater 
sediment catchment for the original construction of the parking area. It was never removed from service 
and developed into a preferred habitat for the threatened mole salamander species. This habitat is 
desired in the finished wetland system.  Therefore, no soil amendments are anticipated.  
5. Location of Inlets and Outlets – Inlets and Outlets are to be located to promote flow mixing and to avoid 
short‐circuiting of the wetland. For this reason, the outlet location from Pond 2 into Pond 3 has been 
adjusted to promote mixing. 
6. Forebay – The forebay provides an essential function as the first treatment area for incoming flows.  The 
MDC specifies a forebay that is 10‐15% of the total wetland surface, 24‐40 inches deep with an inlet lower 
in elevation than the outlet. These design criteria allow the forebay to remove gross pollutants and 
sediments before entering the main body of the wetland.  In the Willow Pond installation, Pond 1 
functions as the forebay.  The surface area of Pond 1 is within the prescribed limits relative to the 
temporary storage area. The proposed configuration has a permanent pool depth of 12 inches.  The 
unique spillway system of Pond 1 allows the forebay to fill without passing significant flows to the 
downstream wetlands. Therefore, the forebay functions of Pond 1 are dramatically enhanced by a 
relatively rapid initial rise and the longer‐term detention of initial flows. Additionally, Arboretum Staff will 
be consistently monitoring sediment and debris levels in Pond 1. Staff will be proactive in removing 
sediment and debris at frequent intervals when needed. 
7. Non‐forebay Deep Pools – Deep pools are to be 5‐15% of the wetland surface area and are a minimum of 
18 inches deep.  Non‐forebay Deep pools are proposed in both Pond 2 and Pond 3 to meet this MDC. We 

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note that the area of the non‐forebay deep pools is taken as any area that would impound water that is 
18 inches below the permanent pool.  By this criterion, the non‐forebay deep pools make up 
approximately 20% of the total surface area.  Additionally, site soils were analyzed by a geotechnical 
consultant relative to the function of the earthen embankment dam.  Site soils were classified as fine to 
medium micaceous silty sands (SM). We note that the pond and embankment had been holding water for 
up to 10 years prior with these same soils. Construction of the new pond system incorporated the existing 
site soils into the grading of the embankment and pond bottoms. Additionally, the pond bottoms were 
cleared of existing sediments and organic material and replaced with clean compacted fill. 
8. Shallow Water Zone – shallow water zones are represented by the difference in surface area between the 
permanent pool and 9 inches below permanent pool.  This region should cover an area that is 35‐45% of 
the total wetland area at temporary ponding depth elevation. Through selective grading this MDC is met 
by the project.   
9. Temporary Inundation Zone – The additional area covered by the wetland at temporary ponding depth 
should make up 30‐45% of the total wetland area at temporary ponding depth. The Willow Pond system 
meets this criterion. 
10. Drawdown Time – The temporary ponding storage volume should be released over a 2‐5 day period.  HEC‐
HMS routings demonstrate that the principal spillway systems function in tandem to release the 
treatment volume runoff for the specified time. 
11. Protection of the Receiving Stream – the downstream channel receives flow from the Pond 3 principal 
and emergency spillways as well as the Pond 1 auxiliary spillway.  We used NRCS design criterial to design 
a rip rap plunge pool to protect the channel in storms up to the 25‐year event.   
12. Landscaping Plan – A landscaping plan was developed by Equinox Environmental and is provided with the 
construction drawings. 
13. Shallow Water Plantings – refer to the landscape plan by Equinox Environmental. 
14. Temporary Inundation Zone Plantings ‐ refer to the landscape plan by Equinox Environmental. 
15. Dam Structure and Perimeter Fill Slopes – Permanent turf establishment has been accomplished for the 
impoundment embankment and wetland perimeter. Refer to the landscape plan by Equinox 
Environmental.  
16. No Cattails – Cattails are expressly prohibited in the landscape plan. 
17. Trash Rack – the auxiliary spillway for Pond 1 is equipped with a trash rack. All other principal spillways 
include submerged intakes with debris guards. 
Pond areas and a calculation of required areas for the “Stormwater Wetland” minimum design criteria are 
included in the attached calculations.  
2.3 – HMS MODEL 
 A 5‐day simulation time with a 1‐minute computation interval was used for all storms. The treatment 
volume storm was evaluated for retention time over the 5‐day period. Due to the relative low flows 
produced during the treatment volume storm, the model does not register a  
 The basin model describes the basin curve number, SCS unit hydrograph, and area of the watershed 
 Watershed parameters summary: 

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TABLE 3: HEC‐HMS BASIN MODEL PARAMETER SUMMARY 
Parameter HEC‐HMS Model Values 
 POND 1 POND 2 and 3 
Area (mi2) 0.0127 0.00171 
Curve Number 76.8 65 
Standard Lag, tp (minutes) 4 12 

 Pond 1 has an auxiliary spillway consisting of a riser and discharge conduit which bypasses both Pond 2 
and Pond 3. It is modeled as an additional spillway structure with a rating curve we developed. Rating 
curve calculations are included in the appendix. 
 Both Pond 2 and Pond 3 have earthen overflow emergency spillways modeled as an overflow weir spillway 
within the HEC HMS model.  The crest length for both is set at 5 feet, and weir coefficient used within the 
model for flow calculation was set to 2.6.  Emergency spillway crest elevations are noted previously in 
Table 1.  
RESULTS  
Computation of HMS models lead to the following results for discharges at the Willow Pond system: 
3.1 TREATMENT VOLUME 
The treatment volume was calculated by the NRCS method as the total runoff volume from the two watersheds 
during the design storm (1.00 inch rainfall depth).  The runoff volume from the impervious and pervious areas are 
calculated separately and then added to get the total treatment volume. We calculated a volume of 10,358 cubic‐
feet.  This volume is required to be stored within the temporary ponding depth of 15 inches for Ponds 2 and 3 and 
36 inches for Pond 1. We calculated the available storage volume to be 10,641 cubic‐feet.   
Retention of the stored stormwater is achieved by an orifice at the permanent pool level in each principal spillway 
device.  The HEC‐HMS model demonstrated that stormwater flows from the treatment volume storm are stored 
for more than 2 days. The storage hydrograph is attached. 
3.2 MDC VALUES 
We calculated the following values for each of the MDC’s that have a numeric criterion: 
1. Temporary Ponding Depth – 15 inches. 
2. Peak Attenuation Depth – 25‐year Storm Event 
a. Pond 1 – 2139.28 
b. Pond 2 – 2135.01 
c. Pond 3 – 2134.01 
3. Surface Area – 4,534 square‐feet (all 3 ponds) 
4. Soil Amendments – N/A.  
5. Location of Inlets and Outlets – See Drawings. 
6. Forebay  
a. Depth = 12 inches at permanent pool 
b. Area = 945 square‐feet, 13% of Temp Pool SA 

9 DAVIS LN|FAIRVIEW, NC 28730 
828.337.5716|GARNER‐ENG.COM 
JOB NO. GE‐159 SHEET 7 OF 8 
PROJECT WILLOW POND STORMWATER TREATMENT 
TASK STORMWATER WETLAND MDC DESIGN 
BY JFG DATE 5/8/2020 
REVIEW     

7. Non‐forebay Deep Pools  
a. Area = 715 square‐feet, 10% of Temp. Pool SA 
8. Shallow Water Zone 
a. Area = 2,767 square‐feet, 38% of Temp. Pool SA 
9. Temporary Inundation Zone  
a. Area = 2,372 square‐feet, 32% of Temp. Pool SA 
10. Drawdown Time – 4 days (see drawdown hydrograph, attached) 
11. Protection of the Receiving Stream – See drawings.  
12. Landscaping Plan – See Landscape drawings. 
13. Shallow Water Plantings – See Landscape drawings. 
14. Temporary Inundation Zone Plantings ‐ See Landscape drawings. 
15. Dam Structure and Perimeter Fill Slopes – See Landscape drawings. 
16. No Cattails – See Landscape drawings. 
17. Trash Rack – See drawings. 
3.3 HYDRAULIC STABILITY 
We performed hydraulic routing using HEC‐HMS for the three ponds to evaluate risks of failure in high flow 
situations. The following table provides results for the discharge locations and storms indicated.  
  TABLE 4: HYDRAULIC ROUTING RESULTS SUMMARY 
Location Discharge Values 
 25‐year 50‐year 100‐year 
Rip Rap Plunge Pool 
Pond 1 Aux/Pond 3 Primary 10.7 cfs 12.6 cfs 14.6 cfs 
Pond 2 Emergency Spillway 2.1 cfs 2.3 cfs 2.5 cfs 
Pond 3 Emergency Spillway 0.0 cfs 0.0 cfs 0.0 cfs 
CONCLUSIONS 
Hydrologic analyses were performed to evaluate the Willow Pond system for stormwater treatment as a 
“Stormwater Wetland” device.  These calculations demonstrate that the Willow Pond system would generally 
meet the design requirements of a Stormwater Wetland treatment system. The areas that are out of compliance 
with the MDC are the forebay depth (MDC 6).  The forebay depth is augmented by the hydraulic function of the 
forebay principal spillway which creates a higher level of detention for initial flows coming into the wetland 
system. Additionally, the Arboretum will dedicate staff to consistently monitor and maintain the forebay on 
frequent basis. 

The non‐forebay deep pools and shallow zones perform important functions in establishing specific habitats and 
pollutant removal.  Concern for stagnant water in the deep pools is offset by the unique configuration of the 
principal spillways which draw water from the bottom of the deep pools in each of the three ponds.  Discharges 
into Pond 2 and Pond 3 are located away from the principal spillway intakes. This promotes flow through all areas 
of the system and reduces the temperature of water released downstream.  

9 DAVIS LN|FAIRVIEW, NC 28730 
828.337.5716|GARNER‐ENG.COM 
JOB NO. GE‐159 SHEET 8 OF 8 
PROJECT WILLOW POND STORMWATER TREATMENT 
TASK STORMWATER WETLAND MDC DESIGN 
BY JFG DATE 5/8/2020 
REVIEW     

Shallow zones will be constantly maintained by Arboretum staff to ensure a well‐established perimeter at the 
edges of the permanent pool. The relative size of the shallow zones and deep pools reflects the surrounding terrain 
as well as the plans for creating accessible teaching and demonstration areas in and around the wetlands. We 
note that storm frequency in the Western NC mountains is typically higher than other regions due to the 
orographic effects of the terrain. Shallow zone areas will naturally extend beyond the planned permanent pool 
elevation due to the potential for prolonged elevated water surface levels, more frequent inundation above the 
permanent pool, and the relatively shallow slopes proposed for the areas immediately above the permanent pool 
level.  We believe that through constant monitoring these factors will enhance the effectiveness of the shallow 
zones.  We further believe that the enhanced features of the deep pools working in concert with the well‐
maintained shallow zones will meet the objectives of the Arboretum to preserve and expand habitat for the 
threatened salamander species and address the pollutant treatment and removal objectives of the Stormwater 
Wetland MDC’s. 
REFERENCES 
1. PDFS ‐ https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=ga 
2. NOAA Rainfall Atlas Vol. 9 Southeastern US: 
http://www.nws.noaa.gov/oh/hdsc/PF_documents/Atlas14_Volume9.pdf 
3. Hydrologic Modeling System (HEC‐HMS) version 4.2.1, US Army Corps of Engineers institute for Water 
Resources Hydrologic Engineering Center, Davis California, March 2017. 
4. Design Hydrology and Sedimentology for Small Catchments, Haan, Barfield, Hayes, Academic Press, 1994  
5. Stormwater BMP Manual, NCDEQ 
ATTACHMENT 
1. Calculations 

CALCULATIONS
Date:By:Calculation Title: Rainfall Storm Total ‐ NOAA, HDSCProject Name: WILLOW POND DAMS5/5/2020Project Number: GE‐159JFG9 Davis LaneFairview, NC 287301 of 1
Project Name: NC ARBORETUM ‐ WILLOW PONDDate: 5/4/2020Project Number: GE‐159By: JFGCalculation Title: Temporal Rainfall Distribution by Percent of Total Rainfallprobability of occurrence0% 8% 17% 25% 33% 42% 50% 58% 67% 75% 83% 92% 100%10% 0% 55% 86% 96% 99% 100% 100% 100% 100% 100% 100% 100% 100%20% 0% 42% 71% 87% 94% 98% 99% 100% 100% 100% 100% 100% 100%30% 0% 33% 60% 77% 87% 93% 97% 99% 100% 100% 100% 100% 100%40% 0% 27% 51% 68% 79% 87% 92% 95% 98% 99% 100% 100% 100%50% 0% 22% 44% 61% 72% 79% 85% 90% 94% 97% 99% 100% 100%60% 0% 17% 37% 55% 66% 73% 78% 83% 89% 93% 97% 99% 100%70% 0% 14% 32% 49% 59% 65% 71% 77% 82% 88% 93% 97% 100%80% 0% 11% 27% 43% 53% 59% 64% 70% 75% 81% 88% 95% 100%90% 0% 7% 21% 37% 46% 52% 57% 62% 67% 73% 80% 90% 100%The first row of each table is the percent of duration (x-axis) which ranges from 0 to 100 percent. The percent of total precipitation (y-axis) which also ranges from 0 to 100 percent is contained in the labeled rows. The spillway capacity analysis relies upon the 10% probability of occurrence because it represents the most intense rainfall distribution.percent of durationThe first column of each table contains labels (10 to 90%) corresponding to each line on the graph which represents the cumulative probability of occurrence for the temporal distribution.These files correspond to the graphs presented in Appendix A.1 of the NOAA Atlas 14 documentation which can be found at: http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_docs.html. 9 Davis LaneFirview, NC 287301 of 1
Project Name: NC ARBORETUM ‐ WILLOW PONDDate: 5/4/2020Project Number: GE‐159By: JFGCalculation Title: Depth‐Duration Data ‐ NOAA RAINFALL  ATLAS 140204060801000 102030405060708090100Percent of Rainfall VolumePercent of Storm DurationCumulative Rainfall Temporal DistributionFirst Quartile 24‐hour Storm Distribution9 Davis LaneFairview, NC 287301 of 1
Project Name: NC ARBORETUM ‐ WILLOW PONDDate: 5/5/2020Project Number: GE‐159By: JFGCalculation Title: RAINFALL HYETOGRAPH0.000.020.040.060.080.100.120.140.160.180.200 5 10 15 20Incremental Rainfall Depth (inches)Storm Duration (hours)24‐hour Rainfall Hyetograph for the 50‐year StormNOAA Atlas 14 Temporal Distribution9 Davis LaneFairview, NC 287301 of 1
Date:By:409,091             sq‐ft9.39 acres0.0147 sq‐mi985 feet120 feet 295 feet2206 feet P2198 feet 2198 feet0.067 ft/ft 2182 feet0.095 GRASS 0.054 ft/ft3.00 inches 4.73 ft/secVelocity 0.40 ft/sec 62.31 second5.02 minutes 1.04 minutes0.08 hour 0.02 hour570 feet2182.0 feet2135.0 feet0.082 ft/ft Total Travel Time 0.11 hourManning's n 0.024 Average Velocity 2.52 ft/secChannel Bottom Width 1.0 FEETChannel Top Width 3 FEET Lag Time 0.07 hourChannel Depth 2 FEET 3.9 minZ 0.50Hydraulic Radius 0.7 FEETVelocity 14.5 FT/SECWave Celerity 21.0 FT/SECTravel Time 27.1 SECOND0.5 MINUTE0.01 HOURProject Name:Project Number:5/5/2020JFGCalculation Title: TIME OF CONCENTRATION ‐ POND 1WILLOW PONDGE‐159Total Flow LengthSheet FlowSlopeManning's nWatershed Area, ATime of Concentration, tcElev. 1Elev. 2Index Rainfall (2‐yr, 24‐hr)ShallowSurface ConditionElev. 1Elev. 2SlopeVelocityTravel TimeTravel TimeChannel FlowElev. 1Elev. 2Slope9 Davis LaneFairview, NC 287301 of 1
Date:By:49,706                sq‐ft1.14 acres0.0018 sq‐mi252 feet86 feet 166 feet2165 feet U2162 feet 2162 feet0.035 ft/ft 2132.5 feet0.5 WOODS 0.178 ft/ft3.00 inches 1.06 ft/secVelocity 0.08 ft/sec 156.51 second18.81 minutes 2.61 minutes0.31 hour 0.04 hour0 feet2132.5 feet2132.0 feet50.000 ft/ft Total Travel Time 0.36 hourManning's n 0.024 Average Velocity 0.20 ft/secChannel Bottom Width 1.0 FEETChannel Top Width 3 FEET Lag Time 0.21 hourChannel Depth 2 FEET 12.9 minZ 0.50Hydraulic Radius 0.7 FEETVelocity 356.2 FT/SECWave Celerity 362.8 FT/SECTravel Time 0.0 SECOND0.0 MINUTE0.00 HOURTravel TimeTravel TimeChannel FlowElev. 1Elev. 2SlopeIndex Rainfall (2‐yr, 24‐hr)ShallowSurface ConditionElev. 1Elev. 2SlopeVelocityTotal Flow LengthSheet FlowSlopeManning's nWatershed Area, ATime of Concentration, tcElev. 1Elev. 2Project Name:Project Number:5/5/2020JFGCalculation Title: TIME OF CONCENTRATION ‐ POND 2+3WILLOW PONDGE‐1599 Davis LaneFairview, NC 287301 of 1
Date:By:354,195       SQ‐FT8.13 ACRES0.01270 SQ‐MIHSG CN (II) S P Q (in) V (cu‐ft)4.66 ACRES B 61 6.393 1 0.000 0.003.45 ACRES B 98 0.204 1 0.791 9904.840.02 ACRES 100 0.000 1 1.000 78.758.13 ACRES76.89983.5947,794         SQ‐FT1.10 ACRES0.00171 SQ‐MIHSG CN (II) S P Q (in) V (cu‐ft)0.98 ACRES B 61 6.393 1 0.000 0.000.06 ACRES B 98 0.204 1 0.791 181.910.05 ACRES 100 0.000 1 1.000 192.501.10 ACRES65.0374.41TOTAL DRAINAGE AREA 401,989       SQ‐FT10358.000.0144 SQ‐MIIMPERVIOUS 153,041       SQ‐FT 38.1%Project Name: WILLOW POND ‐ WETLAND ANALYSES 5/8/2020Project Number: GE‐159JFGCalculation Title: DESIGN VOLUME CALCULATIONWATERSHED AREA ‐ POND 1POND 1 ‐ DESIGN VOLUME CALCULATION ‐ DEVELOPEDLAND USE AREALANDSCAPE/WOODSPARKING, ROOFS, ETCPOND 1WATERSHED TOTALPONDS 2&3 ‐ DESIGN VOLUME CALCULATION ‐ DEVELOPEDWATERSHED AREA ‐ PONDS 2&3LAND USE AREALANDSCAPE/WOODSPAVED PATHS, IMPERV.PONDS 2+3WATERSHED TOTALTOTAL REQUIRED VOLUME9 Davis LaneFairview, NC 287301 of 1
Date:
By:
ELEV AREA (SQ‐FT) AREA (ACRES) VOL (CU‐FT) VOL ‐ CUM. (CU‐FT)
S.Z.2135 339 0.0078 0 0
N.P.2136 945 0.0217 642 642
2137 1342 0.0308 1144 1786
2137.25 1492.8 0.0343 354 2140
2138 1945 0.0447 1289 3429
2139 2527 0.0580 2236 5665
2140 3264 0.0749 2896 8561
ELEV AREA (SQ‐FT) AREA (ACRES) VOL (CU‐FT) VOL ‐ CUM. (CU‐FT)
2131 43 0.0010 0 0
2131.75 259.75 0.0060 114 114
2132 332 0.0076 74 188
2132.5 497 0.0114 207 395
2133 827 0.0190 331 726
N.P.2133.25 1280 0.0294 263 989
2134 1712 0.0393 1122 2111
2134.5 2070 0.0475 946 3057
2135 2513 0.0577 1146 4202
2136 4064 0.0933 3289 7491
ELEV AREA (SQ‐FT) AREA (ACRES) VOL (CU‐FT) VOL ‐ CUM. (CU‐FT)
2128 62 0.0014 0 0
2129 207 0.0048 135 135
2130 455 0.0104 331 466
2131 1112 0.0255 784 1249
2131.75 1219 0.0280 874 2123
2132 1662 0.0382 360 2483
N.P.2132.5 2309 0.0530 993 3476
2133 2771 0.0636 1270 4746
2133.75 3309 0.0760 2280 7026
2134 3490 0.0801 850 7876
2135 4130 0.0948 3810 11686
2136 6689 0.1536 5410 17095
PERM. POOL SURFACE AREA 4534 SQ‐FT DESIGN VOL. (1‐INCH RAIN) 10358 CU‐FT
SURF. AREA ‐ TEMP POOL 7324 SQ‐FT AVAILABLE STORAGE 10641 CU‐FT
FOREBAY SURFACE AREA 945 SQ‐FT 13% 10% TO 15% MDC 6
NON‐FOREBAY DEEP POOLS 715 SQ‐FT 10% 5% TO 15% MDC 7
SHALLOW ZONE 2767 SQ‐FT 38% 35% TO 45% MDC 8*
INNUND. ZONE 2372 SQ‐FT 32% 30% TO 45% MDC 9
Calculation Title: STORAGE VOLUME ‐ PONDS 1, 2, & 3 (STORMWATER WETLAND)
ELEVATION ‐ AREA TABLE ‐ POND 3
I.Z.
I.Z.
D.P.
Project Name: WILLOW POND 5/8/2020
Project Number: GE‐159 JFG
ELEVATION ‐ AREA TABLE ‐ POND 1
ELEVATION ‐ AREA TABLE ‐ POND 2
S.Z.
S.Z.
I.Z.
D.P.
9 Davis Lane
Fairview, NC 28730 1 of 1
WILLOW POND 1Date:By:STARTING POOL ELEV. 2136.00W.S. ELEV. ORIFICE WEIR PIPE COMBINEDSTAGE 1 ELEV. 2137.25 2136.00 0.00 0.00 2.21 0.00STG. 2 ‐ TOP OF DAM ELEV. 2140.00 2136.11 0.02 0.00 2.26 0.02STG. 3 ‐ MAX RATING CURVE 2142.00 2136.23 0.04 0.00 2.31 0.042136.34 0.05 0.00 2.35 0.052136.45 0.06 0.00 2.39 0.062136.57 0.07 0.00 2.44 0.072136.68 0.08 0.00 2.48 0.082136.80 0.09 0.00 2.52 0.092136.91 0.10 0.00 2.56 0.102137.02 0.10 0.00 2.60 0.102137.14 0.11 0.00 2.64 0.112137.25 0.11 0.00 2.68 0.112137.59 0.13 0.00 2.80 0.132137.94 0.14 0.00 2.91 0.142138.28 0.16 0.00 3.01 0.162138.63 0.17 0.00 3.12 0.172138.97 0.18 0.00 3.22 0.182139.31 0.19 7.97 3.31 3.312139.66 0.20 24.24 3.41 3.412140.00 0.21 45.60 3.50 3.502141.00 0.23 128.98 3.75 3.752142.00 0.26 236.94 3.99 3.99Project Name:5/8/2020Project Number: GE‐159JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ POND 1 AGRI‐DRAIN9 Davis LaneFairview, NC 287301 of 4
Date:By:Diameter 2 inchesW.S. ELEV. HEAD AREA FLOWDiameter 0.17 feet 2136.00 0.00 0.000 0.00C 0.60 2136.11 0.06 0.016 0.02Elev. 2136.00 feet 2136.23 0.14 0.022 0.04Mid. Elev. 2136.083 feet 2136.34 0.26 0.022 0.05Area 0.022 sq‐ft 2136.45 0.37 0.022 0.062136.57 0.48 0.022 0.072136.68 0.60 0.022 0.082136.80 0.71 0.022 0.092136.91 0.83 0.022 0.102137.02 0.94 0.022 0.102137.14 1.05 0.022 0.112137.25 1.17 0.022 0.112137.59 1.51 0.022 0.132137.94 1.85 0.022 0.142138.28 2.20 0.022 0.162138.63 2.54 0.022 0.172138.97 2.89 0.022 0.182139.31 3.23 0.022 0.192139.66 3.57 0.022 0.202140.00 3.92 0.022 0.212141.00 4.92 0.022 0.232142.00 5.92 0.022 0.26ORIFICE FLOW ‐ VERTICAL FACE ORIENTATIONProject Name: WILLOW POND 15/8/2020Project Number: GE‐159JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ ORIFICE ‐ VERTICAL FACE ORIENTATION9 Davis LaneFairview, NC 287302 of 4
Date:By:length=12.0 incheslength=1.000feetW.S. ELEV. HEAD FLOWC=3.8 2136.00 0.00 0.00Weir 1 Elev.=2139.00feet2136.11 0.00 0.00Normal Pool Elev.=2136.00feet2136.23 0.00 0.002136.34 0.00 0.002136.45 0.00 0.002136.57 0.00 0.002136.68 0.00 0.002136.80 0.00 0.002136.91 0.00 0.002137.02 0.00 0.002137.14 0.00 0.002137.25 0.00 0.002137.59 0.00 0.002137.94 0.00 0.002138.28 0.00 0.002138.63 0.00 0.002138.97 0.00 0.002139.31 0.31 7.972139.66 0.66 24.242140.00 1.00 45.602141.00 2.00 128.982142.00 3.00 236.94Project Name:Project Number:5/8/2020JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ WEIRWILLOW POND 1GE‐159WEIR FLOW9 Davis LaneFairview, NC 287303 of 4
Date:By:Pipe Diam.8INCHES 2136.002133.002.21Pipe Diam. 0.666667 FEET 2136.11 2133.00 2.26Manning's n0.012136.23 2133.00 2.31Entrance Loss Coeff. Ke2.00*** 2136.34 2133.00 2.35Bend Loss Coeff. Kb0N/A 2136.45 2133.00 2.39Friction Loss Coeff. Kc 0.031794 2136.57 2133.00 2.44Length of Pipe (ft)402136.68 2133.00 2.48Number of Bends0N/A 2136.80 2133.00 2.52Leq/D**16N/A 2136.91 2133.00 2.562137.02 2133.00 2.602137.14 2133.00 2.642137.25 2133.00 2.682137.59 2133.00 2.802137.94 2133.00 2.912138.28 2133.00 3.012138.63 2133.00 3.122138.97 2133.00 3.222139.31 2133.00 3.312139.66 2133.00 3.412140.00 2133.00 3.502141.00 2133.00 3.752142.00 2133.00 3.99Water Surface Elev. (ft) Outlet Invert Elev. (ft)Project Name: WILLOW POND 15/8/2020Project Number: GE‐159JFGFull Pipe Flow (cfs)Calculation Title: Hydraulic Rating Curve Calculation ‐ PIPE FLOW** Leq/D is a function of the angle of the bendand gives an equivalent length for each bend.This equivalent length can then be multipliedby Kc to get loss through the bend.Note that this cannot be used with Kb, the bend loss coefficient. One or the other must be used.From: Fundamentals of Fluid Mechanics, Second Edition, Gerhart, Philip M., Gross, and Hochstein, 1992, Pg. 519*** Per Soil Conservation Service - Design Note 8, the entrance loss coefficient accounts for the bend from the riser to the horizontal pipe. Assumed condition described by square, open-top riser - K'e of 1.20 to 2.0.9 Davis LaneFairview, NC 287304 of 4
WILLOW POND 1 ‐ AUX. Date:By:STARTING POOL ELEV. 2136.00W.S. ELEV. ORIFICE WEIR PIPE COMBINEDSTAGE 1 ELEV. 2139.00 2136.00 0.00 0.00 45.43 0.00STG. 2 ‐ TOP OF DAM ELEV. 2140.00 2136.27 0.00 0.00 45.94 0.00STG. 3 ‐ MAX RATING CURVE 2142.00 2136.55 0.00 0.00 46.45 0.002136.82 0.00 0.00 46.95 0.002137.09 0.00 0.00 47.45 0.002137.36 0.00 0.00 47.94 0.002137.64 0.00 0.00 48.42 0.002137.91 0.00 0.00 48.91 0.002138.18 0.00 0.00 49.38 0.002138.45 0.00 0.00 49.86 0.002138.73 0.00 0.00 50.32 0.002139.00 0.00 0.00 50.79 0.002139.13 15.32 2.23 51.00 2.232139.25 21.67 6.30 51.21 6.302139.38 26.54 11.57 51.42 11.572139.50 30.64 17.82 51.63 17.822139.63 34.26 24.90 51.84 24.902139.75 37.53 32.74 52.04 32.742139.88 40.54 41.25 52.25 40.542140.00 43.33 50.40 52.45 43.332141.00 61.28 142.55 54.07 54.072142.00 75.06 261.89 55.64 55.64Project Name:5/5/2020Project Number: GE‐159JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ POND 1 ‐ AUXILIARY SPILLWAY9 Davis LaneFairview, NC 287301 of 4
Date:By:Length 3.00 feetW.S. ELEV. HEAD AREA FLOWWidth 3.00 feet 2136.00 0.00 9.000 0.00C 0.60 2136.27 0.00 9.000 0.00Elev. 2139.00 feet 2136.55 0.00 9.000 0.002136.82 0.00 9.000 0.00Area 9.000 sq‐ft 2137.09 0.00 9.000 0.002137.36 0.00 9.000 0.002137.64 0.00 9.000 0.002137.91 0.00 9.000 0.002138.18 0.00 9.000 0.002138.45 0.00 9.000 0.002138.73 0.00 9.000 0.002139.00 0.00 9.000 0.002139.13 0.13 9.000 15.322139.25 0.25 9.000 21.672139.38 0.38 9.000 26.542139.50 0.50 9.000 30.642139.63 0.63 9.000 34.262139.75 0.75 9.000 37.532139.88 0.88 9.000 40.542140.00 1.00 9.000 43.332141.00 2.00 9.000 61.282142.00 3.00 9.000 75.06Calculation Title: Hydraulic Rating Curve Calculation ‐ ORIFICE FLOW CONTROL AT RISERORIFICE FLOW ‐ HORIZONTAL ORIENTATIONProject Name: WILLOW POND 1 ‐ AUX.5/5/2020Project Number: GE‐159JFG9 Davis LaneFairview, NC 287302 of 4
Date:By:Length of side= 3.0 feet# of sides=2W.S. ELEV. HEAD FLOWlength=6.000feet2136.00 0.00 0.00C=2.8 2136.27 0.00 0.00Weir 1 Elev.=2139.00feet2136.55 0.00 0.00Normal Pool Elev.=2136.00feet2136.82 0.00 0.002137.09 0.00 0.002137.36 0.00 0.002137.64 0.00 0.002137.91 0.00 0.002138.18 0.00 0.002138.45 0.00 0.002138.73 0.00 0.002139.00 0.00 0.002139.13 0.13 2.232139.25 0.25 6.302139.38 0.38 11.572139.50 0.50 17.822139.63 0.63 24.902139.75 0.75 32.742139.88 0.88 41.252140.00 1.00 50.402141.00 2.00 142.552142.00 3.00 261.89Project Name:Project Number:5/5/2020JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ WEIRWILLOW POND 1 ‐ AUX.GE‐159WEIR FLOW9 Davis LaneFairview, NC 287303 of 4
Date:By:Pipe Diam.24INCHES 2136.002123.0045.43Pipe Diam. 2 FEET 2136.27 2123.00 45.94Manning's n0.012136.55 2123.00 46.45Entrance Loss Coeff. Ke1.30*** 2136.82 2123.00 46.95Bend Loss Coeff. Kb0N/A 2137.09 2123.00 47.45Friction Loss Coeff. Kc 0.007348 2137.36 2123.00 47.94Length of Pipe (ft)1902137.64 2123.00 48.42Number of Bends0N/A 2137.91 2123.00 48.91Leq/D**16N/A 2138.18 2123.00 49.382138.45 2123.00 49.862138.73 2123.00 50.322139.00 2123.00 50.792139.13 2123.00 51.002139.25 2123.00 51.212139.38 2123.00 51.422139.50 2123.00 51.632139.63 2123.00 51.842139.75 2123.00 52.042139.88 2123.00 52.252140.00 2123.00 52.452141.00 2123.00 54.072142.00 2123.00 55.64Water Surface Elev. (ft) Outlet Invert Elev. (ft)Project Name: WILLOW POND 1 ‐ AUX.5/5/2020Project Number: GE‐159JFGFull Pipe Flow (cfs)Calculation Title: Hydraulic Rating Curve Calculation ‐ PIPE FLOW** Leq/D is a function of the angle of the bendand gives an equivalent length for each bend.This equivalent length can then be multipliedby Kc to get loss through the bend.Note that this cannot be used with Kb, the bend loss coefficient. One or the other must be used.From: Fundamentals of Fluid Mechanics, Second Edition, Gerhart, Philip M., Gross, and Hochstein, 1992, Pg. 519*** Per Soil Conservation Service - Design Note 8, the entrance loss coefficient accounts for the bend from the riser to the horizontal pipe. Assumed condition described by square, open-top riser - K'e of 1.20 to 2.0.9 Davis LaneFairview, NC 287304 of 4
WILLOW POND 2Date:By:STARTING POOL ELEV. 2133.25W.S. ELEV. ORIFICE WEIR PIPE COMBINEDSTAGE 1 ELEV. 2134.50 2133.25 0.00 0.00 0.94 0.00STAGE 2 ELEV. 2136.00 2133.36 0.02 0.00 1.06 0.02STG. 3 ‐ MAX RATING CURVE 2137.00 2133.48 0.04 0.00 1.17 0.042133.59 0.05 0.00 1.27 0.052133.70 0.06 0.00 1.36 0.062133.82 0.07 0.00 1.45 0.072133.93 0.08 0.00 1.53 0.082134.05 0.09 0.00 1.60 0.092134.16 0.10 0.00 1.68 0.102134.27 0.10 0.00 1.75 0.102134.39 0.11 0.00 1.81 0.112134.50 0.11 0.00 1.88 0.112134.69 0.12 3.02 1.98 1.982134.88 0.13 8.54 2.08 2.082135.06 0.14 15.69 2.17 2.172135.25 0.15 24.16 2.26 2.262135.44 0.15 33.77 2.35 2.352135.63 0.16 44.39 2.43 2.432135.81 0.17 55.94 2.51 2.512136.00 0.17 68.34 2.59 2.592136.50 0.19 105.22 2.79 2.792137.00 0.20 147.05 2.97 2.97Project Name:5/5/2020Project Number: GE‐159JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ POND 2 AGRI‐DRAIN9 Davis LaneFairview, NC 287301 of 4
Date:By:Diameter 2 inchesW.S. ELEV. HEAD AREA FLOWDiameter 0.17 feet 2133.25 0.00 0.000 0.00C 0.60 2133.36 0.06 0.016 0.02Elev. 2133.25 2133.48 0.14 0.022 0.04Mid. Elev. 2133.333 feet 2133.59 0.26 0.022 0.05Area 0.022 sq‐ft 2133.70 0.37 0.022 0.062133.82 0.48 0.022 0.072133.93 0.60 0.022 0.082134.05 0.71 0.022 0.092134.16 0.83 0.022 0.102134.27 0.94 0.022 0.102134.39 1.05 0.022 0.112134.50 1.17 0.022 0.112134.69 1.35 0.022 0.122134.88 1.54 0.022 0.132135.06 1.73 0.022 0.142135.25 1.92 0.022 0.152135.44 2.10 0.022 0.152135.63 2.29 0.022 0.162135.81 2.48 0.022 0.172136.00 2.67 0.022 0.172136.50 3.17 0.022 0.192137.00 3.67 0.022 0.20ORIFICE FLOW ‐ VERTICAL FACE ORIENTATIONProject Name: WILLOW POND 25/5/2020Project Number: GE‐159JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ ORIFICE ‐ VERTICAL FACE ORIENTATION9 Davis LaneFairview, NC 287302 of 4
Date:By:length=12.0 inches1.000feetW.S. ELEV. HEAD FLOWC=3.1 2133.25 0.00 0.00Weir 1 Elev.=2134.50feet2133.36 0.00 0.00Normal Pool Elev.= 2 feet2133.48 0.00 0.002133.59 0.00 0.002133.70 0.00 0.002133.82 0.00 0.002133.93 0.00 0.002134.05 0.00 0.002134.16 0.00 0.002134.27 0.00 0.002134.39 0.00 0.002134.50 0.00 0.002134.69 0.19 3.022134.88 0.38 8.542135.06 0.56 15.692135.25 0.75 24.162135.44 0.94 33.772135.63 1.13 44.392135.81 1.31 55.942136.00 1.50 68.342136.50 2.00 105.222137.00 2.50 147.05Project Name:Project Number:5/5/2020JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ WEIRWILLOW POND 2GE‐159WEIR FLOW9 Davis LaneFairview, NC 287303 of 4
Date:By:1.258INCHES 2133.252132.500.94Pipe Diam. 0.666667 FEET 2133.36 2132.50 1.06Manning's n0.012133.48 2132.50 1.17Entrance Loss Coeff. Ke 2 *** 2133.59 2132.50 1.27Bend Loss Coeff. Kb0N/A 2133.70 2132.50 1.36Friction Loss Coeff. Kc 0.031794 2133.82 2132.50 1.45Length of Pipe (ft)222133.93 2132.50 1.53Number of Bends0N/A 2134.05 2132.50 1.60Leq/D**16N/A 2134.16 2132.50 1.682134.27 2132.50 1.752134.39 2132.50 1.812134.50 2132.50 1.882134.69 2132.50 1.982134.88 2132.50 2.082135.06 2132.50 2.172135.25 2132.50 2.262135.44 2132.50 2.352135.63 2132.50 2.432135.81 2132.50 2.512136.00 2132.50 2.592136.50 2132.50 2.792137.00 2132.50 2.97Water Surface Elev. (ft) Outlet Invert Elev. (ft)Project Name: WILLOW POND 25/5/2020Project Number: GE‐159JFGFull Pipe Flow (cfs)Calculation Title: Hydraulic Rating Curve Calculation ‐ PIPE FLOW** Leq/D is a function of the angle of the bendand gives an equivalent length for each bend.This equivalent length can then be multipliedby Kc to get loss through the bend.Note that this cannot be used with Kb, the bend loss coefficient. One or the other must be used.From: Fundamentals of Fluid Mechanics, Second Edition, Gerhart, Philip M., Gross, and Hochstein, 1992, Pg. 519*** Per Soil Conservation Service - Design Note 8, the entrance loss coefficient accounts for the bend from the riser to the horizontal pipe. Assumed condition described by square, open-top riser - K'e of 1.20 to 2.0.9 Davis LaneFairview, NC 287304 of 4
WILLOW POND ‐ POND 3 Date:By:STARTING POOL ELEV. 2132.50W.S. ELEV. ORIFICE WEIR PIPE COMBINEDSTAGE 1 ELEV. 2133.75 2132.50 0.00 0.00 4.45 0.00STAGE 2 ELEV. 2135.00 2132.61 0.01 0.00 4.48 0.01STG. 3 ‐ MAX RATING CURVE 2140.00 2132.73 0.01 0.00 4.50 0.012132.84 0.01 0.00 4.53 0.012132.95 0.02 0.00 4.56 0.022133.07 0.02 0.00 4.58 0.022133.18 0.02 0.00 4.61 0.022133.30 0.02 0.00 4.64 0.022133.41 0.02 0.00 4.66 0.022133.52 0.03 0.00 4.69 0.032133.64 0.03 0.00 4.72 0.032133.75 0.03 0.00 4.74 0.032133.91 0.03 2.30 4.78 2.332134.06 0.03 6.50 4.81 4.812134.22 0.03 11.94 4.85 4.852134.38 0.04 18.38 4.88 4.882134.53 0.04 25.69 4.92 4.922134.69 0.04 33.77 4.95 4.952134.84 0.04 42.55 4.98 4.982135.00 0.04 51.99 5.02 5.022137.50 0.06 270.14 5.53 5.532140.00 0.07 581.25 6.00 6.00Calculation Title: Hydraulic Rating Curve Calculation ‐ POND 3 AGRI‐DRAINProject Name:5/5/2020Project Number: GE‐159JFG9 Davis LaneFairview, NC 287301 of 4
Date:By:Diameter 1 inchesW.S. ELEV. HEAD AREA FLOWDiameter 0.08 2140 2132.50 0.00 0.000 0.00C 0.60 2132.61 0.07 0.005 0.01Elev. 2132.50 feet 2132.73 0.19 0.005 0.01Mid. Elev. 2132.542 feet 2132.84 0.30 0.005 0.01Area 0.005 sq‐ft 2132.95 0.41 0.005 0.022133.07 0.53 0.005 0.022133.18 0.64 0.005 0.022133.30 0.75 0.005 0.022133.41 0.87 0.005 0.022133.52 0.98 0.005 0.032133.64 1.09 0.005 0.032133.75 1.21 0.005 0.032133.91 1.36 0.005 0.032134.06 1.52 0.005 0.032134.22 1.68 0.005 0.032134.38 1.83 0.005 0.042134.53 1.99 0.005 0.042134.69 2.15 0.005 0.042134.84 2.30 0.005 0.042135.00 2.46 0.005 0.042137.50 4.96 0.005 0.062140.00 7.46 0.005 0.07ORIFICE FLOW ‐ VERTICAL FACE ORIENTATIONProject Name: WILLOW POND ‐ POND 35/5/2020Project Number: GE‐159JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ ORIFICE ‐ VERTICAL FACE ORIENTATION9 Davis LaneFairview, NC 287302 of 4
Date:By:length=12.0 inches1.000feetW.S. ELEV. HEAD FLOWC=3.1 2132.50 0.00 0.00Weir 1 Elev.=2133.75feet2132.61 0.00 0.00Normal Pool Elev.=2132.50feet2132.73 0.00 0.002132.84 0.00 0.002132.95 0.00 0.002133.07 0.00 0.002133.18 0.00 0.002133.30 0.00 0.002133.41 0.00 0.002133.52 0.00 0.002133.64 0.00 0.002133.75 0.00 0.002133.91 0.16 2.302134.06 0.31 6.502134.22 0.47 11.942134.38 0.63 18.382134.53 0.78 25.692134.69 0.94 33.772134.84 1.09 42.552135.00 1.25 51.992137.50 3.75 270.142140.00 6.25 581.25Project Name:Project Number:5/5/2020JFGCalculation Title: Hydraulic Rating Curve Calculation ‐ WEIRWILLOW POND ‐ POND 3GE‐159WEIR FLOW9 Davis LaneFairview, NC 287303 of 4
Date:By:28INCHES 2132.502123.004.45Pipe Diam. 0.666667 FEET 2132.61 2123.00 4.48Manning's n0.012132.73 2123.00 4.50Entrance Loss Coeff. Ke2.00*** 2132.84 2123.00 4.53Bend Loss Coeff. Kb0N/A 2132.95 2123.00 4.56Friction Loss Coeff. Kc 0.031794 2133.07 2123.00 4.58Length of Pipe (ft)202133.18 2123.00 4.61Number of Bends0N/A 2133.30 2123.00 4.64Leq/D**16N/A 2133.41 2123.00 4.662133.52 2123.00 4.692133.64 2123.00 4.722133.75 2123.00 4.742133.91 2123.00 4.782134.06 2123.00 4.812134.22 2123.00 4.852134.38 2123.00 4.882134.53 2123.00 4.922134.69 2123.00 4.952134.84 2123.00 4.982135.00 2123.00 5.022137.50 2123.00 5.532140.00 2123.00 6.00Water Surface Elev. (ft) Outlet Invert Elev. (ft)Project Name: WILLOW POND ‐ POND 35/5/2020Project Number: GE‐159JFGFull Pipe Flow (cfs)Calculation Title: Hydraulic Rating Curve Calculation ‐ PIPE FLOW** Leq/D is a function of the angle of the bendand gives an equivalent length for each bend.This equivalent length can then be multipliedby Kc to get loss through the bend.Note that this cannot be used with Kb, the bend loss coefficient. One or the other must be used.From: Fundamentals of Fluid Mechanics, Second Edition, Gerhart, Philip M., Gross, and Hochstein, 1992, Pg. 519*** Per Soil Conservation Service - Design Note 8, the entrance loss coefficient accounts for the bend from the riser to the horizontal pipe. Assumed condition described by square, open-top riser - K'e of 1.20 to 2.0.9 Davis LaneFairview, NC 287304 of 4
00.020.040.060.080.10.120 1440 2880 4320 5760 7200STORAGE (Ac‐Ft)TIME (minutes)STORAGE HYDROGRAPH ‐TREATMENT VOLUME STORMWillow Pond SystemCOMBINED STORAGE(POND 2+3)Storage ‐ Pond 3
RIPRAP LINED PLUNGE POOL FOR CANTILEVER OUTLET (Version 8/2015)
(Reference Design Note No. 6 (Second Edition), Jan. 23, 1986
JOB: WILLOW POND - POND 3 OUTLET PROTECTION
DESIGNER:JFG Date: 5/4/2020
CHECKER: Date:
INPUT DATA:
Conduit Diameter D =1.25 ft
Conduit Discharge: Q =11.00 cfs
Conduit Slope at Outlet: S =0.01 ft/ft
Conduit Outlet Invert Elevation: El, CO =2123.00 ft
Tailwater Elevation: El, TW =2121.75 ft
Outlet Channel Invert Elevation: El, CH =2121.50 ft
Water Density: RHO = 1.00
Bed/Riprap Particle Density: (Default 2.64) RHOS = 2.64
D50 Riprap Size (inches):12*RS =9.00 inches
D50 Riprap Size (feet):RS = 0.75 ft
Riprap Thickness: (2.5*D, 50 recommended) RT =1.88 ft
Bedding Thickness: (6 inch min. rec.) (Enter 0 for geotextile)BT =0.50 ft
Side Slope Ratio: Zw =2.00 ft/ft
Upstream End Slope Ratio: Zlu =3.40 ft/ft
Downstream End Slope Ratio: Zld =2.00 ft/ft
Combined End Slope Ratio: Z1 = 2.70 ft/ft

OUTPUT---POOL LOCATION AND DIMENSIONS:
Vert. Dist. from Tailwater to Conduit Invert: Zp = 1.25 ft
Submergence Check: (If Zp < 0 , Use Zp = 0) Use Zp = 1.25 ft
Beaching Check: [Q/(gD^5)^0.5 <= (1.0+25*D,50/D)]O.K.
**Beaching Controlled**
Distance from Conduit Exit to C/L Pool: Xm = 4.00 ft
Pool depth at C/L Below Conduit Invert: Zp+0.8Zm = 2.31 ft
Pool Bottom Elev: El,PB = 2120.69 ft
Pool Bottom Length: 2Lr2 = 0.99 ft
Pool Bottom Width: 2Wr2 = 0.88 ft
Upstream Pool Length at Tailwater Elev.: Lru = 4.09 ft
Downstream Pool Length at Tailwater Elev.: Lrd = 2.61 ft
Pool Width at Tailwater Elev.: 2Wr = 5.11 ft
Check Side Slope Ratio: (Wr>=We) O.K.
**Side Slope Ratio Zw O.K.**
Check Min. End Slope Ratio: (Lru & Lrd >= Le) O.K.
**End Slope Ratios O.K.**
Check Upstream Length: (Lru >= Xm) O.K.
**End Slope Ratio Zlu O.K.**
Pool Bottom Elev. at Bottom of Riprap: El, BR = 2118.82 ft
Pool Bottom Elev. at Bottom of Bedding: El, BB = 2118.32 ft
OUTPUT---VOLUMES BELOW WATER SURFACE ELEVATION:
Volume of Excavation (measured from bottom
surface of bedding): V,pbs = 15.1 cu yd
Volume of Rock Riprap: V,rs = 9.1 cu yd
Volume of Bedding: V,bs = 5.5 cu yd
Spreadsheet developed by D. Hurtz, Midwest NTC, 1/90
Spreadsheet modified by M. Dreischmeier, Eau Claire TC, Wis., 3/98 and 5/2005
Design Note No. 6 (Second Edition), Jan. 23, 1986
"Riprap Lined Plunge Pool for Cantilever Outlet"
Natural Resources Conservation Service
Engineering Division
RIPRAP LINED PLUNGE POOL FOR CANTILEVER OUTLET
Reference Design Note No. 6 (Second Edition), Jan. 23, 1986
Elev.
Elev. 2123.0 C 2121.8 Elev.
2121.5
Elev.
2.3 2120.7
1.0
11
3.4 2.0
1.7
4.0
4.1 6.2
SECTION A-A
Elev.
13.5 2121.8
5.1
Elev.
2120.7
0.9 1
1.9 2.0
1.8 SECTION B-B
B
A A
ROCK GRADATION
% Passing Size (in) B
100 18 WILLOW POND - POND 3 OUTLET PROTECTION
60-85 13.5 LANDOWNER
25-50 9
5-20 4.5 DESIGNER: JFG
0-5 1.8 SHEET ___ OF ___
OUTLET PIPE
REFERENCES
Loose and firm, moist, reddish brown, slightly micaeous, fine to medium
SAND (SM) - (fill)
Dense, dry, dark brown and red, micaceous, silty fine to medium SAND
(SM) - (residuum)
Boring terminated at 15 feet. No groundwater encountered at time of
boring or backfilling.
SOIL DESCRIPTION SOIL
TYPE
SAMPLESLOCATION:
DRILLER:
DRILLING METHOD:
CAVING>
SOIL BORING NO. B-1
Sheet 1 of 1
08/03/17
DEPTH TO - WATER> INITIAL:
CLIENT:
PROJECT NO.:
END:NC Arboretum Society
Asheville, NC
METRO DRILL, INC., Chris & Roger
ELEVATION/
DEPTH (FT)
5
10
15
20
PROJECT:
Soil Sentry, 2 1/4" Hollow Stem Auger
11537-01
AFTER 24 HOURS:
SOIL BORING NO. B-1
START: 08/03/17
2134ELEVATION:
S. InterlicchiaLOGGED BY:
Willow Pond
2130
2125
2120
2115
2110
GEOT_NOWELL 11537-01.GPJ 8/31/172 5 20 30 40 50 70 90
STANDARD PENETRATION RESULTS
BLOWS/FOOT
10
4
4
5
4
5
8
14
22
27
17
26
32
15
17
18
Firm and loose, dry to moist, reddish brown, slightly micaceous, silty fine
to medium SAND (SM) - (fill)
Dense, tannish red, micaceous, silty fine to medium SAND (SM) -
(residuum)
Boring terminated at 20 feet. No groundwater encountered at time of
boring or backfilling.
SOIL DESCRIPTION SOIL
TYPE
SAMPLESLOCATION:
DRILLER:
DRILLING METHOD:
CAVING>
SOIL BORING NO. B-2
Sheet 1 of 1
08/03/17
DEPTH TO - WATER> INITIAL:
CLIENT:
PROJECT NO.:
END:NC Arboretum Society
Asheville, NC
METRO DRILL, INC., Chris & Roger
ELEVATION/
DEPTH (FT)
5
10
15
20
PROJECT:
Soil Sentry, 2 1/4" Hollow Stem Auger
11537-01
AFTER 24 HOURS:
SOIL BORING NO. B-2
START: 08/03/17
2134ELEVATION:
S. InterlicchiaLOGGED BY:
Willow Pond
2130
2125
2120
2115
2110
GEOT_NOWELL 11537-01.GPJ 8/31/172 5 20 30 40 50 70 90
STANDARD PENETRATION RESULTS
BLOWS/FOOT
10
5
6
7
7
7
9
4
4
4
3
4
5
9
10
10
11
13
17
Loose and firm, damp, reddish brown, micaceous, silty fine to medium
SAND (SM) - (fill)
Firm to dense, dry, dark brown, micaceous, silty fine to medium SAND
(SM) - (residuum)
Boring terminated at 20 feet. No groundwater encountered at time of
boring or backfilling.
SOIL DESCRIPTION SOIL
TYPE
SAMPLESLOCATION:
DRILLER:
DRILLING METHOD:
CAVING>
SOIL BORING NO. B-3
Sheet 1 of 1
08/03/17
DEPTH TO - WATER> INITIAL:
CLIENT:
PROJECT NO.:
END:NC Arboretum Society
Asheville, NC
METRO DRILL, INC., Chris & Roger
ELEVATION/
DEPTH (FT)
5
10
15
20
PROJECT:
Soil Sentry, 2 1/4" Hollow Stem Auger
11537-01
AFTER 24 HOURS:
SOIL BORING NO. B-3
START: 08/03/17
2135ELEVATION:
S. InterlicchiaLOGGED BY:
Willow Pond
2130
2125
2120
2115
GEOT_NOWELL 11537-01.GPJ 8/31/172 5 20 30 40 50 70 90
STANDARD PENETRATION RESULTS
BLOWS/FOOT
10
5
4
4
5
7
8
19
10
17
7
8
9
13
15
21
Hydrologic Soil Group—Buncombe County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
5/6/2020
Page 1 of 43929390392944039294903929540392959039296403929690392939039294403929490392954039295903929640353860353910353960354010354060354110354160354210354260354310
353860 353910 353960 354010 354060 354110 354160 354210 354260 354310
35° 30' 0'' N 82° 36' 41'' W35° 30' 0'' N82° 36' 22'' W35° 29' 50'' N
82° 36' 41'' W35° 29' 50'' N
82° 36' 22'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 17N WGS84
0 100 200 400 600
Feet
0 30 60 120 180
Meters
Map Scale: 1:2,150 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:12,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Buncombe County, North Carolina
Survey Area Data: Version 16, Sep 16, 2019
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Nov 23, 2011—Nov
28, 2017
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.
Hydrologic Soil Group—Buncombe County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
5/6/2020
Page 2 of 4
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
CsB Clifton sandy loam, 2 to
8 percent slopes
B 0.0 0.2%
CsC Clifton sandy loam, 8 to
15 percent slopes
B 0.5 5.2%
EwC Evard-Cowee complex,
basin, 8 to 15 percent
slopes, stony
B 0.4 3.8%
EwD Evard-Cowee complex,
basin, 15 to 30
percent slopes, stony
B 2.0 21.4%
UhE Udorthents-Urban land
complex, 2 to 50
percent slopes
A 0.2 2.6%
Ux Urban land 6.4 66.9%
Totals for Area of Interest 9.6 100.0%
Hydrologic Soil Group—Buncombe County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
5/6/2020
Page 3 of 4
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Buncombe County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
5/6/2020
Page 4 of 4