hydrologic analysis - nc

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Hydrologic Analysis Buck Steam Station

Rowan County, North Carolina

Prepared for:

Duke Energy Corporation ECllJ / PO Box 1006

Charlotte, North Carolina 28201-1006

Prepared by:

ESP Associates, P .A. 5121 Kingdom Way, Suite 208, Raleigh, North Carolina 27607

April 20, 2012

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5121 Kingdom Way • Suite 208 • Raleigh, NC 27607

919.678.1070 • fax 919.677.1252

www.espassociates.com

April 20, 2012

Alex Papp Duke Energy EC11J / PO Box 1006 Charlotte, NC 28201-1006 RE: Buck Stream Station Hydrologic Analysis Dear Mr. Papp: Under Purchase Order 380209 with Duke Energy Corporation, ESP Associates, P.A. was contracted to conduct a hydrologic analysis to analyze the existing wet-ash pond system at the Buck steam station and their response during the specified spillway design flood (SDF). As high hazard dams, the SDF analyzed was the ¾ Probable Maximum Flood. The study area is located in Rowan County close to Salisbury, NC adjacent to the Yadkin River just downstream of Interstate 85 and upstream of the headwaters of High Rock Lake. The results of the hydrologic analysis show that the SDF can be passed through the pond system without overtopping any of the embankments. A summary of the approach used for the analysis and results along with supporting data can be found in the attached report. If you have any questions or need additional information, please do not hesitate to call me at 919-678-1070. Sincerely, ESP Associates, P.A.

Matthew Dudley, P.E., CFM Project Manager

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Table of Contents Introduction .................................................................................................................................................. 4

Review of Available Data .............................................................................................................................. 5

Field Reconnaissance .................................................................................................................................... 6

Topographic Data .......................................................................................................................................... 6

Hydrologic Parameter Calculation ................................................................................................................ 7

Drainage Area ....................................................................................................................................... 7

Curve Number ....................................................................................................................................... 8

Time of Concentration ........................................................................................................................ 10

Probable Maximum Precipitation Calculation ............................................................................................ 11

Stage/Storage/Discharge Curve Development ........................................................................................... 13

Hydrologic Model Development and Results ............................................................................................. 16

Additional Modeling Considerations .......................................................................................................... 19

Wave Heights ...................................................................................................................................... 19

Main Dam Spillway Usage ................................................................................................................... 20

Optional Outlet Pipe Modification for Main Dam .............................................................................. 20

Conclusions ................................................................................................................................................. 21

References .................................................................................................................................................. 21

List of Figures Figure 1: Project Area ................................................................................................................................... 5

Figure 2: Watershed Delineations ................................................................................................................ 8

Figure 3: Project Area Soils (HSG = Hydrologic Soil Group) .......................................................................... 9

Figure 4: Project Area Land-Cover .............................................................................................................. 10

Figure 5: Time of Concentration Flow Paths ............................................................................................... 11

Figure 6: HEC-HMS Existing Conditions Basin Model.................................................................................. 16

List of Tables Table 1: General Dam Information ............................................................................................................... 4

Table 2: Hydrologic Parameters .................................................................................................................... 7

Table 3: Land-Cover Categories .................................................................................................................... 9

Table 4: ¾ PMP Development ..................................................................................................................... 12

Table 5: Additional Primary Stage/Storage Curve ...................................................................................... 13

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Table 6: Primary Stage/Storage Curve ........................................................................................................ 14

Table 7: Secondary Stage/Storage Curve .................................................................................................... 15

Table 8: Cell 1 Stage/Storage/Discharge Curve .......................................................................................... 17

Table 9: Cell 2 Stage/Storage/Discharge Curve .......................................................................................... 17

Table 10: Cell 3 Stage/Storage/Discharge Curve ........................................................................................ 18

Table 11: HEC-HMS Results ......................................................................................................................... 19

List of Appendices

Appendix A: USDA Soil Report

Appendix B: WinTR-55 Output

Appendix C: Time of Concentration Calculations

Appendix D: HMR-52 Output

Appendix E: Stage/Discharge Calculations

Appendix F: HEC-HMS Output HEC-RAS Model Results

Appendix G: NOAA ATLAS 14 Data

Appendix H: Digital Data

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Buck Steam Station Hydrologic Analysis Submission: 4/20/12 Rowan County, NC Page 4

Buck Steam Station Hydrologic Analysis Summary

Introduction Under Purchase Order 380209 with Duke Energy Corporation, ESP Associates, P.A. (ESP) was contracted to conduct a hydrologic analysis at the Duke Energy (DEC) Buck steam station. The study area is located in Rowan County close to Salisbury, NC adjacent to the Yadkin River just downstream of Interstate 85 and upstream of the headwaters of High Rock Lake. The analysis was performed to determine if the existing wet-ash pond system could safely pass the spillway design flood (SDF) without overtopping any of the embankments. As shown in Figure 1 below, the pond system consists of three cells bounded and separated by five dams. Table 1 presents basic information for the five dams. The dam characteristics presented in Table 1 are based on findings as part of this analysis.

Table 1: General Dam Information

General Dam Information

Name Additional

Primary Basin 1 to

Basin 2 Basin 2 to

Basin 3 Divider Main

State ID ROWAN-

068 ROWAN-

069 ROWAN-

070 ROWAN-

071 ROWAN-

047

Hazard Classification High High High High High

Height (ft) 71 22 14 9 59

Normal Storage (ac-ft) 470 470 225 225 225*

100**

Minimum Crest Elevation (ft, NAVD-1988)

708.9 710.6 688.4 688.3 688.9*

679.6**

Notes

* Cell 2

** Cell 3

All five embankments are classified by North Carolina Department of Environment and Natural

Resources (NCDENR) as High hazard dams. This classification is driven by the potential environmental effects of a failure of the ash pond embankments. As high hazard dams, and due to the size of the Main and Additional Primary Dikes (per NCAC 15A2K.0205, Ref. 1), the SDF analyzed for the pond system is the ¾ Probable Maximum Flood (PMF). Results of the analysis indicate that the pond system can safely pass the SDF. This report will outline the procedures and methods used for the analysis and present the details of the results.

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Figure 1: Project Area

Review of Available Data DEC provided ESP with all pertinent available data for the Buck Steam Station basin system. Provided

data included a previous H&H study performed by DEC in 1985 (Ref. 3), original design drawings with

original dates from 1956 (with revisions noted, Ref. 4), bathymetric pond surveys performed by McKim

& Creed in 2004 (Ref. 5), and a topographic map developed with aerial survey by Aero-Dynamics from

1993 (Ref 6). Various other files and drawings were provided as well.

In addition to the data supplied by DEC, ESP obtained other datasets as needed to perform the

hydrologic analysis. ESP acquired processed bare earth LiDAR data collected in 2003 (Ref. 7) as part of

the North Carolina state-wide floodplain mapping program (NCFMP). New aerial photography from

2010 was also obtained from the NCFMP (Ref. 2). Soil survey data in the form of SSURGO Geographic

Information System (GIS) data (Ref. 8) was obtained from the United State Department of Agriculture

(USDA). ESP processed new one-foot contours for all dams from the embankment survey scan

previously performed by ESP (Ref. 9).

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Collected data were reviewed for use in this analysis. Factors impacting the use of the data were

documented for reference while performing subsequent tasks.

Field Reconnaissance On Thursday, March 8, 2012, ESP staff performed field reconnaissance of the project area. The purpose

of the field reconnaissance was to gain familiarity with the project area and an understanding of normal

conditions and operations. All embankments, ponds, and outlet works were observed and

photographed.

The field reconnaissance performed as part of this project was not intended to serve as a safety

inspection of the dams and should not be considered as such.

Topographic Data As introduced in the “Review of Available Data” section, multiple sources of topographic data were

obtained for the project area. Particular care was taken in consideration of the vertical datum of the

elevation datasets. The original design drawings and 1993 aerial survey based topographic map

provided by DEC was in NGVD 1929. The 2004 bathymetric survey, 2003 LiDAR data, and 2012 ESP

embankment scan data was in NAVD 1988. Using a database of known points across the state, a datum

conversion value of -0.73’ was identified to convert NGVD 1929 elevations to NAVD 1988 elevations

within the project area.

The various topographic datasets utilized were:

2004 Bathymetric Survey. Developed by McKim & Creed (Ref. 5), this dataset was in vertical

datum NAVD 1988. Sub-surface contours in two foot intervals were provided. The data was

used to help develop stage/storage curves for the ponds for use in the hydrologic model.

1993 Aerial Survey. Developed by Aero-Dynamics (Ref. 6), this dataset was in vertical datum

NGVD 1920. Two foot contours were provided covering the impounded areas of the ponds from

the water surface to the embankment crest, as well as the surrounding area on Duke property.

The data was used to help develop stage/storage curves for the ponds for use in the hydrologic

model.

2003 Statewide LiDAR. Developed by the North Carolina Floodplain Mapping program (Ref. 7),

this dataset was in vertical datum NAVD 1988. Bare earth mass points were provided. These

points were processed into a digital elevation model (DEM) and contours with two foot intervals

covering the entire project area including beyond Duke property. The processed DEM was used

for watershed delineation while the contours were used for time of concentration calculations

as well as to help develop stage/storage curves for the ponds for use in the hydrologic model.

2012 Embankment Scan. Developed by ESP Associates (Ref. 9) using a mobile LiDAR system,

this dataset was in vertical datum NAVD 1988. A processed bare earth point cloud was used to

develop one foot contours covering the dam embankments from the toe of the downstream

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face to the water surface on the upstream face. The contours and points were used to verify

the embankment crest elevations.

Hydrologic Parameter Calculation The available data collected was utilized to calculate hydrologic parameters for use in the hydrologic

model. TR-55 (Ref. 10) methodology was used for the hydrologic parameter calculation. Calculated

hydrologic parameters are summarized in Table 2. Further discussion for each parameter is included

below.

Table 2: Hydrologic Parameters

Hydrologic Parameters

Watershed Additional

Primary Primary Secondary

Drainage Area (ac) 179 154 45

Curve Number 78 69 74

Time of Concentration (min) 28.13 17.93 18.95

Lag Time (min) 16.88 10.76 11.37

Drainage Area

The DEM created from the 2003 NCFMP LiDAR was utilized in ESRI Arc Map using the ArcHydro tools

(Ref. 11) extension to delineate the contributing watershed to each of the three pond cells. Various GIS

processing was performed to fill low points in the DEM, calculate flow direction, and calculate flow

accumulation before delineating the watersheds. The two foot contours derived from the 2003 NCFMP

LiDAR were used to confirm the delineations. Figure 2 presents the watershed delineations.

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Figure 2: Watershed Delineations

Curve Number

Soil Conservation Service (SCS) curve numbers correlate to the volume of runoff produced for a given

watershed for a defined storm event. Higher curve numbers produce greater runoff volume. Curve

numbers are calculated by considering the combination of land-cover and hydrologic soil group for a

given area. For the three watersheds identified in the project area, curve numbers were calculated

using SSURGO soil data and land-cover delineated from the 2010 aerial imagery obtained from NCFMP.

Antecedent Moisture Condition Type II was assumed for the project area.

The USDA website (Ref. 12) was used to select a study area and identify the soils names within the study

area based on SSURGO. For each soil name, a hydrologic soil group was reported. The selected study

area soil report from the USDA website is available in Appendix A. Figure 3 presents the hydrologic soil

groups within the study area.

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Figure 3: Project Area Soils (HSG = Hydrologic Soil Group)

The 2010 aerial imagery from NCFMP was used to manually delineate land-cover for the study area. The

land-cover was categorized into seven categories. Table 3 presents the categories with a description for

each.

Table 3: Land-Cover Categories

Land-Cover Category

Description

Brush Brush, weed, grass mix - overgrown

Dirt Dirt, disturbed surface

Gravel Gravel, rock surface

Open Lawn, parks, maintained, grass cover > 75%

Residential 1/2 acre lots

Water Open water

Woods Woods

Figure 4 presents the land-cover as delineated for the study area.

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Figure 4: Project Area Land-Cover

The GIS datasets for soils and land-cover were intersected using ESRI Arc Map. The intersection of the

datasets allowed isolation of each combination of hydrologic soil group and land-cover. The total area

for each combination of hydrologic soil group and land-cover was summarized for each watershed and

entered into USDA’s WinTR-55 program (Ref. 13). Woods, brush, and open space were assumed to be in

“good” condition. Based on average lot size, all areas defined as “residential” were assumed to have ½

acre lots. Open water was categorized as “impervious area”. The WinTR-55 program calculated

weighted curve numbers for each watershed. The WinTR-55 output is available in Appendix B.

Time of Concentration

Time of concentration (tc) is defined as the time required for runoff from the most remote part of a

watershed to reach the outlet (or point of interest). Time of concentration is calculated by defining the

longest flow path and breaking it into segments based on the type of flow. Sheet flow is unconcentrated

overland flow that occurs at the upper reaches of a watershed. Shallow concentrated flow occurs where

runoff begins to accumulate into a defined flow path. Channel flow is concentrated runoff that occurs

within a defined channel.

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For each watershed, multiple flow paths were delineated using the two foot contours derived from the

2003 NCFMP LiDAR. The flow paths resulting in the greatest tc for each watershed were selected. All

sheet flow segments occurred in grassed areas. As such, sheet flow was limited to less than 150 feet.

Shallow concentrated flow was used to describe the flow path until a more defined channel was evident.

Channel flow was used to describe the flow path until it reached the normal pool of each pond. Once

the tc path reached the normal pool, it was assumed to instantaneously reach the watershed outlet.

Channel dimensions for the channel tc segments were estimated from the aerial photography, contour

data and typical channel geometry. Figure 5 presents the segmented tc flow paths. The tc calculations

can be found in Appendix C.

Figure 5: Time of Concentration Flow Paths

Probable Maximum Precipitation Calculation As discussed in the introduction, the SDF for the pond system is ¾ PMF. The PMF is the flood that

results from the probable maximum precipitation (PMP). The PMP is defined as statistically the greatest

amount of rainfall that can occur for a given geographic area. The ¾ PMF is calculated by entering the ¾

PMP into a hydrologic model. The rainfall amount and distribution for the PMP is calculated using

Hydrometeorological Reports 51 and 52 (HMR-51, Ref. 14 and HMR-52, Ref. 15).

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The HMR-52 computer program (Ref. 16) was used to calculate the PMP with a 15 minute time interval.

Required inputs for the program include watershed coordinates and storm/rainfall information found in

HMR-51 and HMR-52. The program will automatically vary storm size and orientation to produce the

greatest amount of rainfall on the watershed. The program results include the PMP distribution and

total rainfall. The maximum 6 hour period of rainfall is the PMP used for this analysis. The total PMP

rainfall was calculated to be 29.49 inches. The HMR-52 computer program output can be found in

Appendix D.

A factor of 0.75 was applied to the PMP distribution to obtain the ¾ PMP for use in the hydrologic

model. The total rainfall for the ¾ PMP was calculated to be 22.12 inches. Table 4 presents the rainfall

distributions for the full and ¾ PMP.

Table 4: ¾ PMP Development

Time (min)

Cumulative Precipitation (in)

Full PMP 3/4 PMP

0 0.00 0.00

15 0.34 0.26

30 0.76 0.57

45 1.25 0.94

60 1.79 1.34

75 2.37 1.78

90 2.99 2.24

105 3.69 2.77

120 4.57 3.43

135 5.45 4.09

150 6.50 4.88

165 8.95 6.71

180 13.72 10.29

195 18.87 14.15

210 22.38 16.79

225 23.73 17.80

240 24.62 18.47

255 25.53 19.15

270 26.34 19.76

285 26.97 20.23

300 27.57 20.68

315 28.13 21.10

330 28.65 21.49

345 29.11 21.83

360 29.49 22.12

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Stage/Storage/Discharge Curve Development In order to properly model a pond or reservoir’s ability to pass a flood event, stage/storage/discharge

curves must be developed to describe the available storage within the impoundment and discharge

capacity of the outlet structures.

The stage/storage curves for the three ponds were calculated by using the topographic data sources

discussed previously. The 2004 bathymetric data was used in its entirety. Above the water surface, a

combination of the 2003 NCFMP LiDAR-derived contours and the 1993 aerial survey contours (with

datum shift applied) was used up to the embankment crests. When both contour datasets were

available, preference was given to the 2003 LiDAR contours due to the more recent collection date.

To calculate the storage volume within the ponds, surface areas at various contours were measured

using Arc Map. Using the measured areas and depths between contours, storage volumes were

calculated. Tables 5, 6, and 7 present the stage/storage curves for the additional primary, primary, and

secondary ponds.

Table 5: Additional Primary Stage/Storage Curve

Additional Primary

Elevation (ft)

NAVD88

Area (ac)

Average Area (ac)

Depth (ft)

Interval Storage (ac-ft)

Cumulative Storage (ac-ft)

696 31.29 0.000

44.145 2.00 88.290

698 57.000 88.290

57.680 2.00 115.360

700 58.360 203.650

58.535 2.00 117.070

702 58.710 320.720

65.220 2.00 130.440

704 71.730 451.160

73.195 2.00 146.390

706 74.660 597.550

76.285 2.00 152.570

708 77.910 750.120

79.710 1.27 101.232

709.27 81.510 851.352

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Table 6: Primary Stage/Storage Curve

Primary

Elevation (ft)

NAVD88

Area (ac)

Average Area (ac)

Depth (ft)



662 0.62 0.000

1.350 2.00 2.700

664 2.080 2.700

2.850 2.00 5.700

666 3.620 8.400

4.255 2.00 8.510

668 4.890 16.910

5.535 2.00 11.070

670 6.180 27.980

6.920 2.00 13.840

672 7.660 41.820

8.605 2.00 17.210

674 9.550 59.030

10.595 2.00 21.190

676 11.640 80.220

12.750 2.00 25.500

678 13.8600 105.720

15.220 2.00 30.440

680 16.5800 136.160

17.900 2.00 35.800

682 19.2200 171.960

19.885 1.27 25.254

683.27 20.5500 197.214

28.335 2.00 56.670

685.27 36.1200 253.884

44.010 0.73 32.127

686 51.9000 286.011

56.055 2.00 112.110

688 60.2100 398.121

61.110 1.27 77.610

689.27 62.0100 475.731

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Table 7: Secondary Stage/Storage Curve

Secondary

Elevation (ft)

NAVD88

Area (ac)

Average Area (ac)

Depth (ft)



658 0.79 0.000

1.935 2.00 3.870

660 3.080 3.870

3.900 2.00 7.800

662 4.720 11.670

5.350 2.00 10.700

664 5.980 22.370

6.495 2.00 12.990

666 7.010 35.360

7.570 2.00 15.140

668 8.130 50.500

8.785 2.00 17.570

670 9.440 68.070

10.050 2.00 20.100

672 10.660 88.170

11.810 3.27 38.619

675.27 12.9600 126.789

15.530 2.00 31.060

677.27 18.1000 157.849

18.730 2.00 37.460

679.27 19.3600 195.309

The stage/discharge curves for the three ponds were calculated using standard weir and pipe flow equations for the riser structures. The original design drawings were consulted for the details of the riser outlet structures. The outlet structures were verified during the field reconnaissance. Two of the structures were found to have been constructed differently than the design drawings indicated. The Basin 1 to Basin 2 Dam outlet tower was designed to discharge through all four sides of the tower, however, only one side is actually discharging. The Basin 2 to Basin 3 Dam outlet tower was designed to discharge through all four sides of the tower, however, only two sides are actually discharging.

At each elevation, the weir and pipe flow were calculated and the lesser of the two was used in the discharge rating curve. The weir coefficients used for the discharge calculations over the stop logs of the outlet towers were obtained from the table of broad crested weir coefficients in Brater and King (1976) and varied with head over the weir. The weir equation was also used to calculate the discharge capacity of the emergency spillway for the main dam using a minimum weir coefficient of 2.6 given the breadth of the weir. For the pipe flow calculations, the “invert” of the outlet was entered as the maximum water surface elevation of the receiving body of water during the SDF. Using the actual pipe outlet invert would not have been appropriate based on the tailwater conditions. The stage/discharge spreadsheet calculations can be found in Appendix E. It should be noted that the discharge capacity of the outlet structures were initially calculated on the NGVD 1929 vertical datum based on the original design drawings. The elevations were then converted to the NAVD 1988 vertical datum.

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Hydrologic Model Development and Results Following calculation of the hydrologic parameters, ¾ PMP distribution, and stage/storage/discharge curves, the hydrologic model was created. The United States Corps of Engineers Hydraulic Engineering Center (HEC) Hydrologic Modeling System (HMS) version 3.4 (Ref. 17) was used to model the study area.

An existing conditions basin model was created with the three watersheds, ponds, and junctions as needed for appropriate reporting locations. Normal operating conditions base flow from the coal and natural gas plants, as well as from the coal yard’s sump was provided by DEC and entered as sources into the basin model. DEC reported normal base flow from each plant as 1.0 mgd and the coal yard sump as 0.5 mgd. Both plants discharge into the additional primary pond (Cell 1) while the coal yard sump discharges into the primary pond (Cell 2). The existing conditions basin model schematic is shown in Figure 6.

Figure 6: HEC-HMS Existing Conditions Basin Model

The HEC-HMS model accounts for the stage/storage/discharge curves by pairing the data points from both curves. The stage is paired with the storage and then the storage is paired with the discharge.

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Therefore, the curves had to be modified slightly to insert interpolated points as needed to obtain the appropriate pairings. The final data points as entered into the models are shown in Tables 8, 9, and 10 as follows.

Table 8: Cell 1 Stage/Storage/Discharge Curve

Basin 1 to Basin 2 Dam (Cell 1 Pond)

Elevation (ft, NAVD 1988)

Storage (ac-ft)

Flow (cfs)

696 0 0

698 88.29 0

700 203.65 0

702 320.72 0

704 451.16 0

704.27 470.92 0

704.77 507.52 4.71

705.77 580.00 27.63

706.77 656.29 58.88

707.77 731.79 93.48

708.77 811.5 129.94

709.27 851.35 148.47




Storage (ac-ft)

Flow (cfs)

662 0 0

664 2.7 0

666 8.4 0

668 16.91 0

670 27.98 0

672 41.82 0

674 59.03 0

676 80.22 0

678 105.72 0

680 136.16 0

682 171.96 0

683.27 197.21 0

684.27 225.55 28.61

684.77 239.72 55.26

685.27 253.88 85.87

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Storage (ac-ft)

Flow (cfs)

685.77 273.12 117.76

686.77 329.17 186.96

687.77 384.07 227.86

688.77 445.18 238.76

689.27 475.73 244.04


Main Dam (Cell 3 Pond)


Storage (ac-ft)

Flow (cfs)

658 0 0

660 3.87 0

662 11.67 0

664 22.37 0

666 35.36 0

668 50.5 0

670 68.07 0

672 88.17 0

673.27 103.17 0

673.77 109.07 7.98

674.77 120.88 46.44

675.27 126.79 71.87

675.77 134.55 98.13

676.77 150.08 154.35

677.27 157.85 321.15

677.77 167.21 602.34

678.77 185.94 1339.79

679.27 195.31 1779.71

The control specifications of the model were set to run for 3 days following the start of the 6-hr ¾ PMP. This helped ensure that the majority of the full outflow hydrograph was captured.

The ¾ PMP was entered into the model using a defined hyetograph with a precipitation gage reflecting the rainfall distribution calculated using HMR-52.

Starting water surface elevations for each pond were entered into the HEC-HMS model based on maximum operating levels provided by DEC.

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Table 11 presents the results of the hydrologic analysis for each dam within each cell.

Table 11: HEC-HMS Results

Additional HEC-HMS output including hydrographs and summary tables can be found in Appendix F.

Additional Modeling Considerations In order to adhere to certain requirements of NCAC 15A2K, some additional modeling considerations

were investigated. In addition, DEC requested an optional modeling run be performed to evaluate a

potential modification to the Main dam’s outlet structure. The implementation of this potential

modification is not required.

Wave Heights

Although this analysis shows that the ¾ PMF can be routed through the pond system without

overtopping any of the dam embankments, additional consideration was given to potential wave heights

within the ponds that could produce overtopping.

Wave heights are affected by depth of water, wind speed, and fetch length. The fetch length is the

distance over open water available for the wave to form. The United States Army Corps of Engineers

(USACE) Engineering Manual (EM) 110-2-1420 (Ref. 18) discusses dam freeboard requirements and

addresses wave height considerations in Chapter 15. The manual refers to USACE EM 110-2-1414 (Ref.

19) for additional references.

Section VI 2 of chapter 3 in the USACE Shore Protection Manual (Ref. 20) explains propagation and

decay of waves over flooded, vegetated land. Figure 3-37 specifically depicts the elevated bottom

friction factors of areas with dense vegetation. Based on the results of the hydrologic analysis, the dams

Dam

Additional

Primary

Basin 1 to

Basin 2

Basin 2 to

Basin 3 Divider Main Divider Main

State ID

ROWAN-

068

ROWAN-

069

ROWAN-

070

ROWAN-

071

ROWAN-

047

ROWAN-

071

ROWAN-

047

Minimum Crest

Elev. (ft, NAVD 1988) 708.9 710.6 688.4 688.3 688.9 688.3 679.6

Maximum Operating

WSEL (ft, NAVD 1988) 704.27 704.27 682.27 682.27 682.27 674.27 674.27

Peak WSEL

(ft, NAVD 1988) 707.8 707.8 687.5 687.5 687.5 677.3 677.3

Peak Storage

(ac-ft) 735.3 735.3 370.4 370.4 370.4 158.1 158.1

Peak Inflow

(cfs) 2407.7 2407.7 2124.1 2124.1 2124.1 747.8 747.8

Peak Outflow

(cfs) NA 95.1 217.6 NA NA NA 327.3

Minimum

Freeboard (ft) 1.1 2.8 0.9 0.8 1.4 11.0 2.3

Cell 2Cell 1 Cell 3

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with the least amount of freeboard are the Additional Primary in Cell 1 and the Basin 2 to Basin 3,

Divider, and Main in Cell 2. In each of these instances, the dams have adjacent dense vegetation that

was observed during the field reconnaissance and the 2010 aerial imagery from NCFMP. In the case of

Cell 2, where the Basin 2 to Basin 3 and Divider dams have less than one foot of freeboard, there is

substantial vegetation consisting of stands of large trees. The effective flow path of any wave within Cell

2 would travel a greater distance through this dense vegetation than the fetch length over open water

for the wave setup. As such, it is reasonable to assume any waves formed over the open water portion

of the ponds would be decayed before reaching the embankment.

Main Dam Spillway Usage

Per NCAC 15A2K.205b, a vegetated spillway for an existing Class C dam should not be activated more

often than once every 50 years (once every 100 years for a large new Class C dams). In order to evaluate

the recurrence of the emergency spillway activation for the main dam, an additional modeling run for

the 100-yr storm (also known as the 1% annual chance event or the storm which has a 1% chance in any

given year of being equaled or exceeded) was performed.

The 100-yr storm was evaluated in the HEC-HMS model by creating an additional meteorological model.

The National Ocean and Atmospheric Administration (NOAA) Atlas 14 (Ref. 21) was utilized to obtain the

24-hr 100-yr rainfall of 7.15 inches for the 24-hr 100-yr storm. The Atlas 14 information for the project

area can be found in Appendix G. The rainfall was distributed using the SCS Type II distribution. All

other modeling components remained the same as the base SDF run.

The 100-yr modeling run produced a peak water surface elevation within Cell 3 of 674.3 ft (NAVD 1988).

This is approximately 2.5 ft below the spillway crest. Since the emergency spillway does not activate

during the 100-yr flood, the spillway meets the requirements of NCAC 15A2K.205b.

Optional Outlet Pipe Modification for Main Dam

DEC requested that ESP evaluate a potential modification to the outlet pipe beneath the main dam. DEC

is considering the placement of a slip liner within the outlet pipe. ESP performed an additional modeling

run to determine the potential effects of a slip liner installation on the passage of the SDF.

The additional modeling run was performed to determine if a slip liner with a maximum wall thickness of

6 inches could be installed and still allow the main dam to pass the SDF with adequate freeboard. The

stage/discharge curve for the main dam was modified to account for the reduction in diameter of the

outlet pipe from 36 to 30 inches. Although slip liner manning’s “n” roughness coefficients are typically

lower than that of the concrete surface it is replacing (0.008-0.01 vs 0.012 for concrete), the manning’s

“n” roughness coefficient was conservatively kept constant at 0.012. The revised stage/discharge curve

can be found in Appendix A.

The results of the additional SDF modeling run with decreased main dam outlet pipe diameter indicate

that the peak WSEL within Cell 3 increased 0.2 feet from elevation 677.3 to elevation 677.5 (NAVD 1988

– feet). Although the peak WSEL increased slightly, the main dam can still pass the SDF with adequate

freeboard when a slip liner is installed such that the resulting inside diameter of the pipe is not less than

30 inches and the manning’s coefficient is not more than 0.012.

BC-Unit 5-6-0008


Conclusions The HEC-HMS model used in this analysis was developed using information obtained during the review

of available data. The developed model is deemed a reasonable estimation of the existing condition for

the project area. The analysis was performed using conservative assumptions where appropriate for

hydrologic parameter calculation and hydraulic capacity of the outlet structures. Based on the results of

this analysis, the additional primary, primary, and secondary pond system at the DEC Buck steam station

can safely pass the 6-hr ¾ PMF without any required remediation actions.

References 1. North Carolina Administrative Code – Title 15A Department of Environment and Natural

Resources of Subchapter 2K – Dam Safety. http://portal.ncdenr.org/web/lr/dams

2. North Carolina Statewide Orthoimagery 2010. North Carolina Center for Geographic

Information and Analysis. North Carolina 911 Board and City of Durham Emergency

Communications Center. September 2011.

http://data.nconemap.com/geoportal/catalog/main/home.page

3. Duke Energy Corporation Calculation # BC-0238. Buck Steam Station – Units 3-6. ¾ PMP Study

and supporting calculations. August 23, 1985. Provided by Duke Energy Corporation January 27,

2012.

4. Duke Energy Corporation Buck Steam Station Design Plans. 1956, 1977, 1979, and 1982.

Drawing numbers 3039-d, 3039-d-01, 3039-d-02, 3039-e, 3039-f, b-3066, b-3066-a, b-3066-b, b-

3066-c, b-3066-d. Provided by Duke Energy Corporation January 25, 2012.

5. Topographic Survey of Buck Station Ash Pond. Duke Energy Corporation. Developed by McKim

& Creed, June 18, 2004. Provided by Duke Energy Corporation January 25, 2012.

6. Topographic Map of Buck Steam Station. Duke Energy Corporation. Developed by Aero-

Dynamics, Corp. January 25, 1993. Provided by Duke Energy Corporation January 25, 2012.

7. North Carolina Floodplain Mapping: Yadkin River Basin; LIDAR Bare Earth Mass Points, Feb-Apr

and Dec 2003. Floodplain Mapping Program, North Carolina Division of Emergency

Management. Available at http://www.ncfloodmaps.com

8. United States Department of Agriculture. Natural Resources Conservation Service. Soil Survey

Geographic (SSURGO) Database. http://soils.usda.gov/survey/geography/ssurgo/

9. Mobile LIDAR Scan of Buck Steam Station Dam Embankments. Collected by ESP Associates, P.A.

March 8, 2012.

10. Urban Hydrology for Small Watersheds. TR-55. USDA. NRCS. Conservation Engineering

Division. June 1986.

http://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/technical/alphabetical/water/hy

drology/?&cid=stelprdb1042925

11. ESRI ArcHydro Hydro Data Model for ArcGIS. March 25, 2010.

http://support.esri.com/en/downloads/datamodel/detail/15

12. Web Soil Survey for Project Area. USDA. NRCS. May 28, 2009.

http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx

http://portal.ncdenr.org/web/lr/dams

http://data.nconemap.com/geoportal/catalog/main/home.page

http://www.ncfloodmaps.com/

http://soils.usda.gov/survey/geography/ssurgo/

http://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/technical/alphabetical/water/hydrology/?&cid=stelprdb1042925


http://support.esri.com/en/downloads/datamodel/detail/15

http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx

BC-Unit 5-6-0008


13. WinTR-55 User Guide. Small Watershed Hydrology. January 2009. USDA. NRCS.

http://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/technical/alphabetical/water/hy

drology/?&cid=stelprdb1042901

14. Probable Maximum Precipitation Estimates, United States East of the 105th Meridian.

Hydrometeorological Report No. 51. NOAA. June 1978.

http://www.nws.noaa.gov/oh/hdsc/studies/pmp.html#PMP_documents

15. Application of Probable Maximum Precipitation Estimates – United States East of the 105th

Meridian. Hydrometeorological Report No. 52. NOAA. August 1982.


16. HMR52 Probable Maximum Storm (Eastern United States) User’s Manual. USACE, Hydrologic

Engineering Center. March 1984.

17. USACE Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) User’s Manual.

Version 3.4, August 2009. http://www.hec.usace.army.mil/software/hec-hms/

18. USACE Engineer Manual 1110-2-1420. Hydrologic Engineering Requirements for Reservoirs.

October 31, 1997.

19. USACE Engineer Manual 1110-2-1414. Water Levels and Wave Heights for Coastal Engineering

Design. July 5, 1989.

20. Shore Protection Manual. Coastal Engineering Research Center. USACE. 1984.

21. NOAA Atlas 14 Precipitation-Frequency Atlas of the United States. Volume 2 Version 3.0. 2006.

http://hdsc.nws.noaa.gov/hdsc/pfds/index.html





http://www.hec.usace.army.mil/software/hec-hms/

http://hdsc.nws.noaa.gov/hdsc/pfds/index.html

BC-Unit 5-6-0008

Appendix A

USDA Soil Report

Water Features


Map symboland soil name

[Depths of layers are in feet. See text for definitions of terms used in this table. Estimates of the frequency of ponding and flooding apply to the whole year rather than to individual months. Absence of an entry indicates that the feature is not a concern or that data were not estimated. This report shows only the major soils in each map unit]

Surface water depth

Duration Frequency

FloodingPondingWater tableHydrologic

group Upperlimit

Lowerlimit

Ft

Months

Ft Ft

Duration FrequencySurface runoff

ArA:

Armenia, undrained D Negligible --- Rare Brief Frequent---January 0.5-1.5 >6.0--- Rare Brief Frequent---February 0.5-1.5 >6.0--- Rare Brief Frequent---March 0.5-1.5 >6.0--- Rare Brief Frequent---April 1.0-2.5 >6.0--- Rare Brief Frequent---May 1.5-4.0 >6.0--- Rare Brief Frequent---June 4.0-5.0 >6.0--- Rare --- None---July --- ------ Rare --- None---August --- ------ Rare --- None---September --- ------ Rare --- None---October 4.0-5.0 >6.0--- Rare Brief Frequent---November 0.5-1.5 >6.0--- Rare Brief Frequent---December 0.5-1.5 >6.0

CcB:

Cecil B Medium --- None --- None---Jan-Dec

CcC:

Cecil B Medium --- None --- None---Jan-Dec

CeB2:

Cecil, moderately eroded B Medium --- None --- None---Jan-Dec

CeC2:

Cecil, moderately eroded B Medium --- None --- None---Jan-Dec

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Water Features


Map symboland soil name Surface water

depthDuration Frequency


group Upperlimit

Lowerlimit

Ft

Months

Ft Ft


ChA:

Chewacla C Very high --- None Brief Frequent---January 0.5-2.0 >6.0--- None Brief Frequent---February 0.5-2.0 >6.0--- None Brief Frequent---March 0.5-2.0 >6.0--- None Brief Frequent---April 1.0-2.5 >6.0--- None Brief Frequent---May 1.5-4.0 >6.0--- None Brief Frequent---June 4.0-5.0 >6.0--- None --- None---October 4.0-5.0 >6.0--- None Brief Frequent---November 1.0-2.5 >6.0--- None Brief Frequent---December 0.5-2.0 >6.0

DAM:

Dam --- --- --- None --- None---Jan-Dec

EnB:

Enon C Medium --- None --- None---Jan-Dec

EnC:


LcD:

Lloyd B High --- None --- None---Jan-Dec

LdB2:

Lloyd, moderately eroded B Low --- None --- None---Jan-Dec

LdC2:

Lloyd, moderately eroded B Medium --- None --- None---Jan-Dec

MbC:

Mecklenburg C Medium --- None --- None---Jan-Dec

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Water Features





group Upperlimit

Lowerlimit

Ft

Months

Ft Ft


MeB2:

Mecklenburg, moderately eroded

C Medium --- None --- None---Jan-Dec

MeC2:

Mecklenburg, moderately eroded

C Medium --- None --- None---Jan-Dec

PaD:

Pacolet B High --- None --- None---Jan-Dec

PaE:

Pacolet B High --- None --- None---Jan-Dec

PcB2:

Pacolet, moderately eroded B Medium --- None --- None---Jan-Dec

PcC2:

Pacolet, moderately eroded B Medium --- None --- None---Jan-Dec

PxD:

Poindexter B High --- None --- None---Jan-Dec

Rowan B High --- None --- None---Jan-Dec

Ud:

Udorthents, loamy C Medium --- None --- None---Jan-Dec

VnB2:

Vance, moderately eroded C Medium --- None --- None---Jan-Dec

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Water Features





group Upperlimit

Lowerlimit

Ft

Months

Ft Ft


W:

Water --- --- --- None --- None---Jan-Dec

WaA:

Warne, drained D Very high --- None Brief Occasional---January 0.5-1.5 >6.0--- None Brief Occasional---February 0.5-1.5 >6.0--- None Brief Occasional---March 0.5-1.5 >6.0--- None Brief Occasional---April 1.0-2.0 >6.0--- None --- None---May 2.0-2.5 >6.0--- None --- None---June 4.0->6.0 >6.0--- None --- None---October 4.0->6.0 >6.0--- None --- None---November 2.0-2.5 >6.0--- None Brief Occasional---December 0.5-1.5 >6.0

Warne, undrained D Very high --- None Brief Occasional---January 0.5-1.5 >6.0--- None Brief Occasional---February 0.5-1.5 >6.0--- None Brief Occasional---March 0.5-1.5 >6.0--- None Brief Occasional---April 1.0-2.0 >6.0--- None --- None---May 2.0-2.5 >6.0--- None --- None---June 4.0->6.0 >6.0--- None --- None---October 4.0->6.0 >6.0--- None --- None---November 2.0-2.5 >6.0--- None Brief Occasional---December 0.5-1.5 >6.0

WtC:

Wynott C Medium --- None --- None---Jan-Dec


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Appendix B

WinTR-55 Output

ESP Buck Station Buck Rowan County, North Carolina

Sub-Area Land Use and Curve Number Details

Sub-Area Hydrologic Sub-Area CurveIdentifier Land Use Soil Area Number Group (ac)--------------------------------------------------------------------------------AP Open space; grass cover > 75% (good) B 17.028 61 Open space; grass cover > 75% (good) C 9.261 74 Open space; grass cover > 75% (good) D 1.949 80 Paved parking lots, roofs, driveways B 3.64 98 Paved parking lots, roofs, driveways C 12.033 98 Paved parking lots, roofs, driveways D 55.771 98 Gravel (w/ right-of-way) B .096 85 Gravel (w/ right-of-way) C 3.158 89 Residential districts (1/2 acre) B 16.5 70 Brush - brush, weed, grass mix (good) B 6.761 48 Brush - brush, weed, grass mix (good) C 12.987 65 Brush - brush, weed, grass mix (good) D .015 73 Woods (good) B 26.972 55 Woods (good) C 10.067 70 Woods (good) D 1.727 77

Total Area / Weighted Curve Number 177.97 78 ====== ==

SEC Open space; grass cover > 75% (good) B 10.921 61 Open space; grass cover > 75% (good) C 7.089 74 Open space; grass cover > 75% (good) D .506 80 Paved parking lots, roofs, driveways C 16.354 98 Gravel (w/ right-of-way) C .122 89 Dirt (w/ right-of-way) B 6.013 82 Dirt (w/ right-of-way) C .158 87 Residential districts (1/2 acre) B .847 70 Residential districts (1/2 acre) C 7.821 80 Brush - brush, weed, grass mix (good) B .497 48 Brush - brush, weed, grass mix (good) C 3.888 65 Brush - brush, weed, grass mix (good) D .162 73 Woods (good) B 48.177 55 Woods (good) C 42.835 70 Woods (good) D 5.194 77

Total Area / Weighted Curve Number 150.58 69 ====== ==

PRIM Open space; grass cover > 75% (good) B 12.599 61 Open space; grass cover > 75% (good) C 2.707 74 Open space; grass cover > 75% (good) D .5 80 Paved parking lots, roofs, driveways B .474 98 Paved parking lots, roofs, driveways C .635 98 Paved parking lots, roofs, driveways D 12.794 98 Residential districts (1/2 acre) B 2.291 70 Woods (good) B 8.652 55 Woods (good) C 3.261 70 Woods (good) D 2.332 77

Total Area / Weighted Curve Number 46.25 74 ===== ==

WinTR-55, Version 1.00.09 Page 1 4/4/2012 6:06:31 PM

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Appendix C

Time of Concentration Calculations

ID Type of Flow n U/S D/S Length Slope Velocity TcElev. Elev. (ft) (fps) (hours)

Sheet Flow (P= 3.5 in)0.15 742 740 124 0.016 0.202

Shallow Concentrated FlowPaved x Unpaved 740 732 886 0.009 1.5 0.161Paved x Unpaved 732 716 427 0.037 3.1 0.038Paved Unpaved Paved Unpaved Paved Unpaved

Channel Flowb d z80 5 4 0.1 716 714 455 0.004 2.5 0.0507 2 2 0.04 714 698 533 0.030 8.0 0.019

Storm Draindiameter (in)

*Based on the June 1986 version of SCS TR-55 Total = 0.469 Lg = 0.28 hours16.88 minutes

b - bottom width storm drain - use 6 to 7 fps and input a lengthd - depthz - side slope ex 2:1 so enter 2trapezoidal or square channels onlyP = 2yr storm

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Sheet Flow (P= 3.5 in)0.15 727 725 137 0.015 0.228

Shallow Concentrated FlowPaved x Unpaved 725 710 368 0.041 3.3 0.031Paved Unpaved Paved Unpaved Paved Unpaved Paved Unpaved

Channel Flowb d z4 2 2 0.05 710 682 878 0.032 6.1 0.040




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Sheet Flow (P= 3.5 in)0.15 709 707 133 0.015 0.220

Shallow Concentrated FlowPaved x Unpaved 707 702 341 0.015 2.0 0.048Paved Unpaved Paved Unpaved Paved Unpaved Paved Unpaved

Channel Flowb d z3 1 2 0.05 702 676 734 0.035 4.3 0.048




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Appendix D

HMR-52 Output

BC-Unit 5-6-00081***************************************** *************************************** * * * * * PROBABLE MAXIMUM STORM (HMR52) * * U.S. ARMY CORPS OF ENGINEERS * * NOVEMBER 1982 * * THE HYDROLOGIC ENGINEERING CENTER * * REVISED APRIL 91 * * 609 SECOND STREET * * * * DAVIS, CALIFORNIA 95616 * * RUN DATE 03/14/2012 TIME 21:10:30 * * (916) 551-1748 OR (FTS) 460-1748 * * * * * ***************************************** ***************************************

H H M M RRRRRR 5555555 22222 H H MM MM R R 5 2 2 H H M M M M R R 5 2 HHHHHHH M M M RRRRRR 555555 2 H H M M R R 5 2 H H M M R R 5 5 2 H H M M R R 55555 2222222 1 HEC PROBABLE MAXIMUM STORM (HMR52) INPUT DATA PAGE 1 LINE ID.......1.......2.......3.......4.......5.......6.......7.......8.......9......10 1 ID PMS FOR BUCK STATION DAMS 2 ID ESP ASSOCIATES 3 ID RALEIGH, NC 4 ID WATERSHED OBTAINED FROM Arc-HYDRO TOOLS AND GENERALIZED TO LIMIT VERTI 5 BN BUCK 6 BS 1 7 BX 301.93 301.96 302.23 302.24 302.22 302.24 302.25 302.33 302.25 302.22 8 BX 302.17 302.16 302.19 302.20 302.17 302.17 302.20 302.15 302.11 302.12 9 BX 302.08 301.96 301.93 301.91 301.87 301.87 301.84 301.86 301.85 301.86 10 BX 301.84 301.81 301.80 301.77 301.72 301.72 301.68 301.63 301.52 301.55 11 BX 301.56 301.50 301.50 301.48 301.50 301.53 301.51 301.51 301.53 301.66 12 BX 301.72 301.76 301.75 301.80 301.79 301.81 301.81 301.87 301.93 13 BY 135.80 135.78 135.66 135.60 135.59 135.57 135.49 135.34 135.22 135.21 14 BY 135.23 135.19 135.17 135.15 135.11 135.08 135.06 135.03 135.02 134.99 15 BY 134.94 134.97 135.01 134.90 134.87 134.81 134.77 134.72 134.71 134.69 16 BY 134.69 134.64 134.64 134.56 134.61 134.68 134.66 134.68 134.64 134.68 17 BY 134.71 134.78 134.94 134.99 135.14 135.17 135.21 135.37 135.40 135.47 18 BY 135.46 135.44 135.51 135.56 135.59 135.61 135.66 135.70 135.80 19 HO 208 20 HP 10 29.6 35.1 39.9 44.0 46.2 21 HP 200 21.4 25.6 30.0 34.0 35.9 22 HP 1000 15.6 20.4 25.5 28.3 29.8 23 HP 5000 9.2 13.1 17.0 21.0 22.1 24 HP 10000 7.1 10.4 14.0 17.8 19.5 25 HP 20000 5.1 8.3 11.3 14.8 16.6 26 SA 0 0 27 ST 15 0.283 28 PU ON 29 ZZ 1***************************************** *************************************** * * * * * PROBABLE MAXIMUM STORM (HMR52) * * U.S. ARMY CORPS OF ENGINEERS * * NOVEMBER 1982 * * THE HYDROLOGIC ENGINEERING CENTER * * REVISED APRIL 91 * * 609 SECOND STREET * * * * DAVIS, CALIFORNIA 95616 *

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BC-Unit 5-6-0008 * RUN DATE 03/14/2012 TIME 21:10:30 * * (916) 551-1748 OR (FTS) 460-1748 * * * * * ***************************************** ***************************************

PMS FOR BUCK STATION DAMS ESP ASSOCIATES RALEIGH, NC WATERSHED OBTAINED FROM Arc-HYDRO TOOLS AND GENERALIZED TO LIMIT VERTI

PMP DEPTHS FROM HMR 51 AREA DURATION (SQ. MI.) 6-HR 12-HR 24-HR 48-HR 72-HR 10. 29.60 35.10 39.90 44.00 46.20 200. 21.40 25.60 30.00 34.00 35.90 1000. 15.60 20.40 25.50 28.30 29.80 5000. 9.20 13.10 17.00 21.00 22.10 10000. 7.10 10.40 14.00 17.80 19.50 20000. 5.10 8.30 11.30 14.80 16.60

STORM AREA PMP DEPTHS FOR 6-HOUR INCREMENTS 10. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 25. 27.58 5.38 2.68 1.80 1.35 1.09 .91 .78 .68 .61 .55 .50 50. 25.98 5.14 2.62 1.77 1.34 1.08 .90 .77 .68 .60 .54 .50 100. 23.64 4.79 2.52 1.72 1.31 1.06 .89 .76 .67 .60 .54 .49 175. 21.74 4.53 2.45 1.69 1.29 1.04 .88 .75 .66 .59 .53 .49 300. 19.81 4.72 2.42 1.64 1.24 1.00 .84 .72 .63 .56 .51 .46 450. 18.34 4.96 2.41 1.61 1.21 .97 .81 .69 .61 .54 .49 .44 700. 16.72 5.25 2.39 1.56 1.17 .93 .77 .66 .58 .51 .46 .42 1000. 15.43 5.45 2.37 1.53 1.14 .90 .75 .64 .56 .50 .45 .41 1500. 13.84 5.12 2.33 1.53 1.14 .91 .75 .65 .56 .50 .45 .41 2150. 12.42 4.84 2.30 1.52 1.14 .91 .76 .65 .57 .51 .46 .41 3000. 11.09 4.60 2.26 1.51 1.14 .91 .76 .65 .57 .51 .46 .42 4500. 9.50 4.27 2.21 1.51 1.14 .92 .77 .66 .58 .52 .47 .43 6500. 8.30 3.90 2.15 1.49 1.14 .93 .78 .67 .59 .53 .48 .44 10000. 7.02 3.44 2.06 1.47 1.15 .94 .80 .69 .61 .55 .49 .45 15000. 5.89 3.25 1.95 1.40 1.09 .89 .76 .66 .58 .52 .47 .43 20000. 5.08 3.10 1.88 1.35 1.05 .86 .73 .64 .56 .50 .46 .421

BOUNDARY COORDINATES FOR BUCK X 301.9 302.0 302.2 302.2 302.2 302.2 302.3 302.3 302.3 302.2 Y 135.8 135.8 135.7 135.6 135.6 135.6 135.5 135.3 135.2 135.2 X 302.2 302.2 302.2 302.2 302.2 302.2 302.2 302.1 302.1 302.1 Y 135.2 135.2 135.2 135.1 135.1 135.1 135.1 135.0 135.0 135.0 X 302.1 302.0 301.9 301.9 301.9 301.9 301.8 301.9 301.9 301.9 Y 134.9 135.0 135.0 134.9 134.9 134.8 134.8 134.7 134.7 134.7 X 301.8 301.8 301.8 301.8 301.7 301.7 301.7 301.6 301.5 301.5 Y 134.7 134.6 134.6 134.6 134.6 134.7 134.7 134.7 134.6 134.7

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BC-Unit 5-6-0008 X 301.6 301.5 301.5 301.5 301.5 301.5 301.5 301.5 301.5 301.7 Y 134.7 134.8 134.9 135.0 135.1 135.2 135.2 135.4 135.4 135.5 X 301.7 301.8 301.8 301.8 301.8 301.8 301.8 301.9 301.9 Y 135.5 135.4 135.5 135.6 135.6 135.6 135.7 135.7 135.8

SCALE = 1.0000 MILES PER COORDINATE UNIT BASIN AREA = .6 SQ. MI. BASIN CENTROID COORDINATES, X = 301.9, Y = 135.21

VARYING STORM AREA SIZE AND FIXED ORIENTATION SUM OF DEPTHS ORIEN- FOR 3 PEAK STORM AREA TATION BASIN-AVERAGED INCREMENTAL DEPTHS FOR 6-HR PERIODS 6-HR PERIODS 10. 210. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 25. 210. 28.13 5.54 2.70 1.80 1.35 1.09 .91 .78 .68 .61 .55 .50 36.38 50. 210. 27.54 5.43 2.66 1.77 1.34 1.08 .90 .77 .68 .60 .54 .50 35.63 100. 210. 26.48 5.18 2.58 1.72 1.31 1.06 .89 .76 .67 .60 .54 .49 34.24 175. 210. 25.87 4.98 2.51 1.69 1.29 1.04 .88 .75 .66 .59 .53 .49 33.37 300. 210. 24.96 5.26 2.51 1.64 1.24 1.00 .84 .72 .63 .56 .51 .46 32.72 450. 210. 24.21 5.60 2.50 1.61 1.21 .97 .81 .69 .61 .54 .49 .44 32.31 700. 210. 23.41 6.01 2.49 1.56 1.17 .93 .77 .66 .58 .51 .46 .42 31.91 1000. 210. 22.99 6.33 2.48 1.53 1.14 .90 .75 .64 .56 .50 .45 .41 31.80 1500. 210. 22.42 6.00 2.45 1.53 1.14 .91 .75 .65 .56 .50 .45 .41 30.86 2150. 210. 21.85 5.74 2.42 1.52 1.14 .91 .76 .65 .57 .51 .46 .41 30.01 3000. 210. 21.19 5.49 2.39 1.51 1.14 .91 .76 .65 .57 .51 .46 .42 29.07 4500. 210. 20.14 5.16 2.35 1.51 1.14 .92 .77 .66 .58 .52 .47 .43 27.65 6500. 210. 19.35 4.76 2.29 1.49 1.14 .93 .78 .67 .59 .53 .48 .44 26.39 10000. 210. 18.40 4.27 2.20 1.47 1.15 .94 .80 .69 .61 .55 .49 .45 24.86 15000. 210. 17.07 4.06 2.09 1.40 1.09 .89 .76 .66 .58 .52 .47 .43 23.22 20000. 210. 15.86 3.91 2.02 1.35 1.05 .86 .73 .64 .56 .50 .46 .42 21.79

FIXED STORM AREA SIZE AND VARYING ORIENTATION SUM OF DEPTHS ORIEN- FOR 3 PEAK STORM AREA TATION BASIN-AVERAGED INCREMENTAL DEPTHS FOR 6-HR PERIODS 6-HR PERIODS 10. 140. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 150. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 160. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 170. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 180. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 190. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 200. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 210. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 220. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 230. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 240. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 250. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 260. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 270. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 280. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 290. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92

Page 3

BC-Unit 5-6-0008 10. 300. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 310. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 155. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.92 10. 165. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 37.921

PROBABLE MAXIMUM STORM FOR BUCK STORM AREA = 10. SQ. MI., ORIENTATION = 160., PREFERRED ORIENTATION = 208. STORM CENTER COORDINATES, X = 301.9, Y = 135.2 AREA ISOHYET WITHIN AREA BASIN DEPTHS (INCHES) FOR 6-HOUR INCREMENTS OF PMS (SQ.MI.) (SQ.MI.) 1 2 3 4 5 6 7 8 9 10 11 12 A 10. 1. 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .50 B 25. 1. 18.87 3.64 1.79 1.19 .89 .72 .60 .51 .45 .40 .36 .33 C 50. 1. 14.15 2.73 1.32 .88 .66 .53 .44 .38 .33 .29 .27 .24 D 100. 1. 11.21 2.22 1.07 .71 .54 .43 .36 .31 .27 .24 .22 .20 E 175. 1. 8.85 1.71 .82 .55 .41 .33 .28 .24 .21 .18 .17 .15 F 300. 1. 7.08 1.36 .66 .44 .33 .26 .22 .19 .17 .15 .13 .12 G 450. 1. 5.60 1.14 .55 .37 .27 .22 .18 .16 .14 .12 .11 .10 H 700. 1. 4.13 .80 .38 .26 .19 .15 .13 .11 .10 .09 .08 .07 I 1000. 1. 2.95 .57 .27 .18 .14 .11 .09 .08 .07 .06 .06 .05 J 1500. 1. 1.77 .40 .18 .12 .09 .07 .06 .05 .04 .04 .04 .03 K 2150. 1. .59 .17 .08 .05 .04 .03 .03 .02 .02 .02 .02 .02 L 3000. 1. .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 M 4500. 1. .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 N 6500. 1. .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 O 10000. 1. .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 P 15000. 1. .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 Q 25000. 1. .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 R 40000. 1. .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 S 60000. 1. .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 AVERAGE DEPTH 29.49 5.69 2.75 1.83 1.37 1.10 .92 .79 .69 .61 .55 .501

TIME INTERVAL = 15. MINUTES 1-HR TO 6-HR RATIO FOR ISOHYET A AT 20000 SQ. MI. = .283

DEPTH VS. DURATION ISOHYET 5MIN 10MIN 15MIN 30MIN 1-HR 2-HR 3-HR 6-HR 12-HR 18-HR 24-HR 30-HR 36-HR 42-HR 48-HR 54-HR 60-HR 66-HR 72-HR A 1.72 3.45 5.15 9.93 15.88 20.04 23.34 29.49 35.17 37.92 39.75 41.13 42.23 43.15 43.93 44.62 45.24 45.79 46.29 B .34 .68 1.02 2.03 4.07 8.04 11.71 18.87 22.51 24.30 25.49 26.38 27.10 27.69 28.20 28.65 29.05 29.41 29.74 C .25 .51 .76 1.53 3.05 6.03 8.78 14.15 16.88 18.20 19.08 19.74 20.27 20.71 21.09 21.42 21.71 21.98 22.22 D .20 .40 .60 1.21 2.41 4.77 6.94 11.21 13.42 14.50 15.21 15.74 16.17 16.53 16.84 17.11 17.35 17.56 17.76 E .16 .32 .48 .95 1.91 3.77 5.49 8.85 10.55 11.38 11.93 12.34 12.67 12.94 13.18 13.39 13.57 13.74 13.89 F .13 .25 .38 .76 1.53 3.02 4.39 7.08 8.44 9.10 9.54 9.87 10.13 10.35 10.54 10.71 10.86 10.99 11.11 G .10 .20 .30 .60 1.20 2.38 3.47 5.60 6.74 7.29 7.66 7.93 8.15 8.33 8.49 8.63 8.75 8.86 8.96 H .07 .15 .22 .44 .89 1.76 2.56 4.13 4.92 5.31 5.57 5.76 5.91 6.04 6.15 6.25 6.33 6.41 6.48 I .05 .11 .16 .32 .64 1.26 1.83 2.95 3.52 3.79 3.98 4.11 4.22 4.31 4.39 4.46 4.52 4.58 4.63 J .03 .06 .09 .19 .38 .75 1.09 1.77 2.17 2.35 2.46 2.55 2.63 2.69 2.74 2.78 2.82 2.86 2.89 K .01 .02 .03 .06 .12 .24 .35 .59 .76 .84 .90 .94 .97 1.00 1.02 1.04 1.06 1.08 1.09 L .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 M .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 N .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

Page 4

BC-Unit 5-6-0008 O .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 P .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 Q .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 R .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 S .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 AVERAGE 1.72 3.45 5.15 9.93 15.88 20.04 23.34 29.49 35.17 37.92 39.75 41.13 42.23 43.15 43.93 44.62 45.24 45.79 46.291

PROBABLE MAXIMUM STORM FOR BUCK

DAY 1 TIME PRECIPITATION TIME PRECIPITATION TIME PRECIPITATION TIME PRECIPITATION INCR TOTAL INCR TOTAL INCR TOTAL INCR TOTAL 0015 .02 .02 0615 .03 .53 1215 .03 1.15 1815 .05 1.95 0030 .02 .04 0630 .03 .55 1230 .03 1.18 1830 .05 1.99 0045 .02 .06 0645 .03 .58 1245 .03 1.21 1845 .05 2.04 0100 .02 .08 0700 .03 .60 1300 .03 1.25 1900 .05 2.09 0115 .02 .10 0715 .03 .63 1315 .03 1.28 1915 .05 2.13 0130 .02 .13 0730 .03 .66 1330 .03 1.31 1930 .05 2.18 0145 .02 .15 0745 .03 .68 1345 .03 1.34 1945 .05 2.22 0200 .02 .17 0800 .03 .71 1400 .03 1.38 2000 .05 2.27 0215 .02 .19 0815 .03 .73 1415 .03 1.41 2015 .05 2.32 0230 .02 .21 0830 .03 .76 1430 .03 1.44 2030 .05 2.36 0245 .02 .23 0845 .03 .78 1445 .03 1.48 2045 .05 2.41 0300 .02 .25 0900 .03 .81 1500 .03 1.51 2100 .05 2.45 0315 .02 .27 0915 .03 .83 1515 .03 1.54 2115 .05 2.50 0330 .02 .29 0930 .03 .86 1530 .03 1.57 2130 .05 2.54 0345 .02 .31 0945 .03 .89 1545 .03 1.61 2145 .05 2.59 0400 .02 .33 1000 .03 .91 1600 .03 1.64 2200 .05 2.64 0415 .02 .36 1015 .03 .94 1615 .03 1.67 2215 .05 2.68 0430 .02 .38 1030 .03 .96 1630 .03 1.71 2230 .05 2.73 0445 .02 .40 1045 .03 .99 1645 .03 1.74 2245 .05 2.77 0500 .02 .42 1100 .03 1.01 1700 .03 1.77 2300 .05 2.82 0515 .02 .44 1115 .03 1.04 1715 .03 1.80 2315 .05 2.87 0530 .02 .46 1130 .03 1.06 1730 .03 1.84 2330 .05 2.91 0545 .02 .48 1145 .03 1.09 1745 .03 1.87 2345 .05 2.96 0600 .02 .50 1200 .03 1.12 1800 .03 1.90 2400 .05 3.00 6-HR TOTAL .50 .61 .79 1.101

DAY 2 TIME PRECIPITATION TIME PRECIPITATION TIME PRECIPITATION TIME PRECIPITATION INCR TOTAL INCR TOTAL INCR TOTAL INCR TOTAL 0015 .07 3.07 0615 .16 4.99 1215 .34 10.86 1815 .15 40.16 0030 .07 3.13 0630 .16 5.15 1230 .42 11.29 1830 .15 40.31 0045 .07 3.20 0645 .17 5.33 1245 .49 11.77 1845 .14 40.45 0100 .07 3.27 0700 .18 5.50 1300 .54 12.32 1900 .14 40.59 0115 .07 3.34 0715 .18 5.69 1315 .58 12.90 1915 .13 40.72 0130 .07 3.41 0730 .19 5.88 1330 .62 13.52 1930 .13 40.86 0145 .07 3.48 0745 .20 6.08 1345 .70 14.21 1945 .13 40.98 0200 .07 3.55 0800 .20 6.28 1400 .88 15.09 2000 .12 41.11 0215 .07 3.62 0815 .21 6.49 1415 .88 15.97 2015 .12 41.23 0230 .07 3.69 0830 .22 6.71 1430 1.05 17.02 2030 .12 41.34 0245 .07 3.77 0845 .23 6.94 1445 2.45 19.46 2045 .11 41.46

Page 5

BC-Unit 5-6-0008 0300 .07 3.84 0900 .23 7.17 1500 4.77 24.24 2100 .11 41.57 0315 .08 3.92 0915 .24 7.41 1515 5.15 29.39 2115 .11 41.68 0330 .08 3.99 0930 .25 7.65 1530 3.51 32.90 2130 .11 41.79 0345 .08 4.07 0945 .25 7.91 1545 1.35 34.24 2145 .10 41.89 0400 .08 4.15 1000 .26 8.17 1600 .89 35.14 2200 .10 41.99 0415 .08 4.23 1015 .27 8.44 1615 .91 36.05 2215 .10 42.09 0430 .08 4.31 1030 .28 8.71 1630 .81 36.86 2230 .10 42.19 0445 .08 4.39 1045 .28 8.99 1645 .63 37.48 2245 .10 42.29 0500 .08 4.48 1100 .29 9.28 1700 .60 38.09 2300 .10 42.38 0515 .09 4.57 1115 .30 9.58 1715 .56 38.65 2315 .09 42.48 0530 .09 4.65 1130 .31 9.89 1730 .52 39.17 2330 .09 42.57 0545 .09 4.74 1145 .31 10.20 1745 .46 39.62 2345 .09 42.66 0600 .09 4.83 1200 .32 10.52 1800 .38 40.01 2400 .09 42.76 6-HR TOTAL 1.83 5.69 29.49 2.751

DAY 3 TIME PRECIPITATION TIME PRECIPITATION TIME PRECIPITATION TIME PRECIPITATION INCR TOTAL INCR TOTAL INCR TOTAL INCR TOTAL 0015 .06 42.81 0615 .04 44.17 1215 .03 45.08 1815 .02 45.76 0030 .06 42.87 0630 .04 44.21 1230 .03 45.11 1830 .02 45.78 0045 .06 42.93 0645 .04 44.24 1245 .03 45.13 1845 .02 45.81 0100 .06 42.99 0700 .04 44.28 1300 .03 45.16 1900 .02 45.83 0115 .06 43.04 0715 .04 44.32 1315 .03 45.19 1915 .02 45.85 0130 .06 43.10 0730 .04 44.36 1330 .03 45.22 1930 .02 45.88 0145 .06 43.16 0745 .04 44.40 1345 .03 45.25 1945 .02 45.90 0200 .06 43.21 0800 .04 44.44 1400 .03 45.28 2000 .02 45.92 0215 .06 43.27 0815 .04 44.47 1415 .03 45.31 2015 .02 45.94 0230 .06 43.33 0830 .04 44.51 1430 .03 45.34 2030 .02 45.97 0245 .06 43.39 0845 .04 44.55 1445 .03 45.36 2045 .02 45.99 0300 .06 43.44 0900 .04 44.59 1500 .03 45.39 2100 .02 46.01 0315 .06 43.50 0915 .04 44.63 1515 .03 45.42 2115 .02 46.04 0330 .06 43.56 0930 .04 44.67 1530 .03 45.45 2130 .02 46.06 0345 .06 43.62 0945 .04 44.70 1545 .03 45.48 2145 .02 46.08 0400 .06 43.67 1000 .04 44.74 1600 .03 45.51 2200 .02 46.11 0415 .06 43.73 1015 .04 44.78 1615 .03 45.54 2215 .02 46.13 0430 .06 43.79 1030 .04 44.82 1630 .03 45.57 2230 .02 46.15 0445 .06 43.84 1045 .04 44.86 1645 .03 45.59 2245 .02 46.17 0500 .06 43.90 1100 .04 44.90 1700 .03 45.62 2300 .02 46.20 0515 .06 43.96 1115 .04 44.93 1715 .03 45.65 2315 .02 46.22 0530 .06 44.02 1130 .04 44.97 1730 .03 45.68 2330 .02 46.24 0545 .06 44.07 1145 .04 45.01 1745 .03 45.71 2345 .02 46.27 0600 .06 44.13 1200 .04 45.05 1800 .03 45.74 2400 .02 46.29 6-HR TOTAL 1.37 .92 .69 .551

Page 6

BC-Unit 5-6-0008

Appendix E

Stage/Discharge Calculations

CrestElevation= 705 NGVD 1929

ManningsRoughness= 0.012

Weir Length= 5

Pipe Diameter 3

Weir end Contractions= 2

Downstream Invert Elevation= 689 NGVD 1929

Elevation HeadWeir

Coefficient Flow Elevation Slope Flow Elevation Flow Elevation Flow705 0 0 0.0 705 0.095522 223.2 705 0.0 704.27 0.0

705.5 0.5 2.72 4.7 705.5 0.098507 226.7 705.5 4.7 704.77 4.7706 1 2.98 14.3 706 0.101493 230.1 706 14.3 705.27 14.3

706.5 1.5 3.2 27.6 706.5 0.104478 233.5 706.5 27.6 705.77 27.6707 2 3.3 42.9 707 0.107463 236.8 707 42.9 706.27 42.9

707.5 2.5 3.31 58.9 707.5 0.110448 240.0 707.5 58.9 706.77 58.9708 3 3.32 75.9 708 0.113433 243.3 708 75.9 707.27 75.9

708.5 3.5 3.32 93.5 708.5 0.116418 246.5 708.5 93.5 707.77 93.5709 4 3.32 111.6 709 0.119403 249.6 709 111.6 708.27 111.6

709.5 4.5 3.32 129.9 709.5 0.122388 252.7 709.5 129.9 708.77 129.9710 5 3.32 148.5 710 0.125373 255.8 710 148.5 709.27 148.5

Weir Flow Pipe Flow

Total Discharge NGVD 1929

Total Discharge NAVD 1988


mdudley

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BC-Unit 5-6-0008

mdudley

Typewritten Text

mdudley

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Weir Length= 10

Pipe Diameter 3


Downstream Invert Elevation= 678.3 NGVD 1929

Elevation HeadWeir

Coefficient Flow Elevation Slope Flow Elevation Flow Elevation Flow684 0 0 0 684 0.05561 170.3 684 0 683.27 0

684.5 0.5 2.72 9.4 684.5 0.060488 177.6 684.5 9.4 683.77 9.4685 1 2.98 28.6 685 0.065366 184.7 685 28.6 684.27 28.6

685.5 1.5 3.2 55.3 685.5 0.070244 191.4 685.5 55.3 684.77 55.3686 2 3.3 85.9 686 0.075122 198.0 686 85.9 685.27 85.9

686.5 2.5 3.31 117.8 686.5 0.08 204.3 686.5 117.8 685.77 117.8687 3 3.32 151.8 687 0.084878 210.4 687 151.8 686.27 151.8

687.5 3.5 3.32 187.0 687.5 0.089756 216.4 687.5 187.0 686.77 187.0688 4 3.32 223.1 688 0.094634 222.2 688 222.2 687.27 222.2

688.5 4.5 3.32 259.9 688.5 0.099512 227.9 688.5 227.9 687.77 227.9689 5 3.32 296.9 689 0.10439 233.4 689 233.4 688.27 233.4

689.5 5.5 3.32 334.0 689.5 0.109268 238.8 689.5 238.8 688.77 238.8690 6 3.32 370.8 690 0.114146 244.0 690 244.0 689.27 244.0

Basin 2 to Basin 3 Dam (Cell 2 Pond)Weir Flow Pipe Flow



mdudley

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BC-Unit 5-6-0008



CrestElevation= 677.5 NGVD 1929

Weir Length= 8.5

Pipe Diameter 3

Weir Length= 150



Weir Coefficient= 2.6

Elevation HeadWeir

Coefficient Flow Elevation Slope Flow Elevation Head Flow Elevation Flow Elevation Flow674 0 0 0.0 674 0.093468 220.8 674 0 0.0 674 0.0 673.27 0.0

674.5 0.5 2.72 8.0 674.5 0.094734 222.3 674.5 0 0.0 674.5 8.0 673.77 8.0675 1 2.98 24.1 675 0.096 223.8 675 0 0.0 675 24.1 674.27 24.1

675.5 1.5 3.2 46.4 675.5 0.097266 225.3 675.5 0 0.0 675.5 46.4 674.77 46.4676 2 3.3 71.9 676 0.098532 226.7 676 0 0.0 676 71.9 675.27 71.9

676.5 2.5 3.31 98.1 676.5 0.099797 228.2 676.5 0 0.0 676.5 98.1 675.77 98.1677 3 3.32 125.9 677 0.101063 229.6 677 0 0.0 677 125.9 676.27 125.9

677.5 3.5 3.32 154.3 677.5 0.102329 231.1 677.5 0 0.0 677.5 154.3 676.77 154.3678 4 3.32 183.3 678 0.103595 232.5 678 0.5 137.9 678 321.1 677.27 321.1

678.5 4.5 3.32 212.3 678.5 0.104861 233.9 678.5 1 390.0 678.5 602.3 677.77 602.3679 5 3.32 241.3 679 0.106127 235.3 679 1.5 716.5 679 951.8 678.27 951.8

679.5 5.5 3.32 269.8 679.5 0.107392 236.7 679.5 2 1103.1 679.5 1339.8 678.77 1339.8680 6 3.32 297.6 680 0.108658 238.1 680 2.5 1541.6 680 1779.7 679.27 1779.7

Main Dam (Cell 3 Pond)



Emergency Spillway Weir FlowWeir Flow Pipe Flow

mdudley

Typewritten Text

BC-Unit 5-6-0008



CrestElevation= 677.5 NGVD 1929

Weir Length= 8.5

Pipe Diameter 2.5

Weir Length= 150



Weir Coefficient= 2.6

Elevation HeadWeir

Coefficient Flow Elevation Slope Flow Elevation Head Flow Elevation Flow Elevation Flow674 0 0 0.0 674 0.093468 135.8 674 0 0.0 674 0.0 673.27 0.0

674.5 0.5 2.72 8.0 674.5 0.094734 136.7 674.5 0 0.0 674.5 8.0 673.77 8.0675 1 2.98 24.1 675 0.096 137.6 675 0 0.0 675 24.1 674.27 24.1

675.5 1.5 3.2 46.4 675.5 0.097266 138.5 675.5 0 0.0 675.5 46.4 674.77 46.4676 2 3.3 71.9 676 0.098532 139.4 676 0 0.0 676 71.9 675.27 71.9

676.5 2.5 3.31 98.1 676.5 0.099797 140.3 676.5 0 0.0 676.5 98.1 675.77 98.1677 3 3.32 125.9 677 0.101063 141.2 677 0 0.0 677 125.9 676.27 125.9

677.5 3.5 3.32 154.3 677.5 0.102329 142.1 677.5 0 0.0 677.5 142.1 676.77 142.1678 4 3.32 183.3 678 0.103595 143.0 678 0.5 137.9 678 280.9 677.27 280.9

678.5 4.5 3.32 212.3 678.5 0.104861 143.8 678.5 1 390.0 678.5 533.8 677.77 533.8679 5 3.32 241.3 679 0.106127 144.7 679 1.5 716.5 679 861.2 678.27 861.2

679.5 5.5 3.32 269.8 679.5 0.107392 145.6 679.5 2 1103.1 679.5 1248.7 678.77 1248.7680 6 3.32 297.6 680 0.108658 146.4 680 2.5 1541.6 680 1688.0 679.27 1688.0

Pipe FlowMain Dam (Cell 3 Pond) Optional

Emergency Spillway Weir Flow



Weir Flow

mdudley

Typewritten Text

BC-Unit 5-6-0008

BC-Unit 5-6-0008

Appendix F

HEC-HMS Output HEC-RAS Model Results

BC-Unit 5-6-0008

“Additional Primary” (Cell 1) Basin Results

,,;

w

w

m

w

,500

,000

,500

,000

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I

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01J an2012

Subbasin "Additional_Prim ary" Results for Run "3/4 PMF'

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I

12:00

02J an2012

,

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I

12:00

03J an2012

l~ (C~teT"" : O'lApr20 11, 15:'IO :ln

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-- Rl.n 3?4 fV EIome<t : AOOTONALJ~ARY Re, L.t:Ottfuw --- Rcn 3?4 fV EIome<t : AOOTONALJ~ARY Re, L.t:&O, efuw

Summary R~u lts for Subbasin "Additional_Primaryft =

Project: Buck Simulation Run : 3/4 PMF SUbbasin: Additional_Prmary

Start of Run: o lJan20 12, 00:00 Basin Model: Existilg Conditions End of Run : 04Jan20 12, 00 :00 Meteorologic Model: 6-hr 3/4PMP Compute lime: 09Apr20 12, 15:40: 27 Control Spedfications: Three-oay

Volume Units : @ IN IE> AC-FT

Computed Results

Peak Discharge: 2404.6 (CFS) Date/Tme of Peak Discharge : 0 lJan2012, 03:24 Total Predpitation : 22.12 (IN) Total Direct Runoff : 19.06 (IN) Total Loss: 3.06 (IN) Total Baseflow : 0.00 (IN) Total Excess: 19 .06 (IN) Discharge: 19.06 (IN)

,

00:01

I

BC-Unit 5-6-0008

“Pond_Add_Prim” (Cell 1) Pond Results

E 0 <

" ,

eo 8 ! "

" c

" c

0; c

oc c

" c

;c c / ! ,

" C

2,50 C

\

" " " " 2,000 n--

1,50

1,00

;c

C

C

" " " " " " " " " " , ,

" , , , , , , , , , ,

C ---"--,

,

, , , , , \ , , , , c ' , 00:00

I

12: 00

01Jan2012

Reservoir "Pond_Add_Prim ' Results for Run "3/4 PMF'

00:00

I

12:00

02J an2012

00:00

I

12:00

03J an2012

l~ (C~teT"" : O9Apr2011, 15 :'IO :2n

------ Rcn3?4 fV EIome<t : f'OI',V_AOO_~ Re, ut stc" "}e

-- Rl.n 3?4 f'Mf EIeme<t : f'OI',V_AOO_~ Re, ut Ottfuw

Rcn3?4 f'Mf EIome<t:f'Oi',V _ADD _~ Re" .t:Poo Elevotoo

--- Rl.n 3?4 f'Mf EIeme<t : f'OI',V_AOO_~ Re" .t:COOJbined .,fIow

= 0

Project: Buck. SWnulatioo Run: 3/4 PMF Reservoir : Pond_Add Prim

Start of Run : OlJan2012, OO :OO End of Run: 04Jan20 12,OO:OO Compute Tme: 09Apr20 12, 15:40:27

Basin Model: Existing Conditions Meteorologic Model: 6-hr 3/4PMP Conb"oI Specifications: TlYee-Day

Volume Units: @ IN IE) AC-FT

Computed Results

Peak Inflow : 2.qQ7.7 (CFS) Peak Outflow ; 95 . 1 (CFS) Totallnflow : 20 .29 (IN) Total Outflow : 15 .69 (IN)

Date/lime of Peak Inflow : OlJan20 1.2, 03:24 Date/r1tT1e of Peak Outflow ; 0 lJan20 12, 06: 21 Peak Storage: 735.3 (AC-fT) Peak Elevation: 707.8 (FT)

~ 8

708.00

707.33

706.67

706.00 E , w

-- 705.33 --70(67

70(00

00:00

I

BC-Unit 5-6-0008

“Primary” (Cell 2) Basin Results

Groph for Sub~io "",;mo'Y"

,000

,500

eo 8 ~ 1,000

"

12:00

01Jan2012

l~ (C~teT"" : O9Apr2011, 11 :'IO :2n

- Rl.n3?4 fV EIerne<t:f'RM'..RY Re, L.t:Prociphtoo

--- Rl.n 3?4 fV EIeme<t:f'RM'..RY Re, L.t:BMefuw

Subbasin "Primary" Results for Run "3/4 PMF"

00:00

I

12:00

02Jan2012

00:00

I

12:00

03Jan2012

Summary Resutts for Subbasin "Primary" = 8

Project: Buck Simulation Run: 3/4 PMF Subbasin: Primary

Start of Run: OUan2012, OO:00 Basin Model: Existing Conditions End of Run: 04Jan2012, OO:00 Meteorologic Model: 6-hr 3/4PMP Compute Tlrne : 09Apr2012, 15:40:27 Control Spedfications: Three-oay

Volume Units: @ IN IE) AC.fl

Computed Results

Peak Discharge: 2096.6 (CfS) Date/fme of Peak Discharge: OUan2012, 03: 19 Total Predpitation : 22. 12 (IN) Total DirectRlr1off: 17.51 (IN) Total loss : 4.61 (IN) Total Baseflow : 0.00 (IN) TotalExcess: 17.51 (IN) Discharge : 17. 5 1 (IN)

00:01

I

J

BC-Unit 5-6-0008

“Pond_Primary” (Cell 2) Pond Results

,;c

E ,CC 0 < , ,;c ,

,CC

J

2,000

_ rima

/

\--" "

"

" "

" 1,500 ---+j , ,

eo 8 ~ 1,000

"

, , , , , ,

: ' ,-,---, ' , ' , ' , ' , ' , ' , \---, , , ,

Reservoir "Pond_Primary" Results for Run "3/4 PMF"

"+ .... -. -"--.-.- ----.-.. - r=== L ····C ···, ±

, \ ,

c LL!r\==~, ~~~~,==~~~, ---7' ---"---~'

687.18

685.82

68((5

68309

00:00 12:00 00:00 12:00 00:00 12:00 00:00

I 01Jan2012 I 02Jan2012 I 03Jan2012 I l~(C~teT"" 1OApr2011, 10 :38 :36)

- - - - - - Rcn 3?4 f'Mf EIeme<t:f'Oi',V _f'RM'.RY Re" ':: ste<_ Rl.n 3?4 f'Mf EIeme<t:f'Oi',V _f'RM'.RY Re" .t:Poo Elevotoo

-- Rl.n3?4 fV EIerne<t:f'OI',V_f'RM'.RY Re" .t:W fuw - - - Rcn 3?4 f'Mf EIeme<t:f'Oi',V _f'RM'.RY Re" .t:COOJbined .,fIow

Summary Results for Res~rvo i r "Pond_Primary" = Project: Buck.

SWnulation Run: 3/4 PMF Reservoir : Pond_Primary

Start of Run : o Uan20 12, 00:00 Basin Model: Existing Conditions End of Run: 04Jan2012, 00:00 Meteorologic Model: 6-hr 3/ 'WMP Compute Tm e : lOApr2012, 10:38:36 Control Spedfications: Three-Day

Volume Units : @ IN tEl ACfl

Computed Results

Peak Inflow : 2124. 1 (CFS) Peak Outflow : 217.6 (CFS) Total Inflow : 16 .70 (IN) Total Outflow ; 15 .26 (IN)

Date/Tme of Peak Inflow: o lJan20 12, 03: 19 Date{rme of Peak Outflow : o 1Jan20 12, 06: 10 Peak Storage: 370 .4 {AC-FT} Peak 8evation : 687.5 (FT)

; , W

BC-Unit 5-6-0008

“Secondary” (Cell 3) Basin Results

Groph for ~b~io "*o,,cJ.ry

0'"

W

~ ~ W

0

m

w

'"

occ

;"

." eo 8 ! " '"

,"

." -

\ ) 00.00 12.00

I 01J an2012

l <9<'ld (C~teT"" : O'lApr2011, 15 :'IO :2n

Subbasin ' Secondary" Results for Run ' 3/4 PMF'

00.00

I

12.00

02J an201 2

00.00

I

- Rcn 3?4 f'Mf EIeme<t:SEC()I',VAAY Re, L.t:Procipti>too - Rl.n 3?4 f'Mf EIeme<t:SECOKlAAY Re, L.t:Procipti>too lo"

- - - Rcn 3?4 f'Mf EIeme<t: SEC()I',VAAY Re, L.t:BM efuw

Summary R6 ultS for Subbasin "St:condary"

Project: Buc:k. Simulation Run: 3/4 PMF Subbasin: Secondary

12.00

03J an2012

Start of Roo : OlJan2012, 00:00 End of Roo: 04Jan2012, 00:00 Compute Time: 09Apr2012, 15:40:27

Basin Model: Existilg Conditions MeteOfoiogic Model: 6« 3/"1PMP Conuol Specifications: Three-Day

Volume Units: @ IN ~ AC -FT

Computed Results

Peak Discharge: 626.8 (CFS) Date(rllTle of Peak Discharge : a lJan2012, 03: 19 Total Precipitation: 22. 12 (IN) Total DifectRunoff: 18.40 (IN) Total Loss : 3,72 (IN) Total Baseflow : 0.00 (IN) Total Excess: 18.40 (IN) Discharge: 18.40 (IN)

00.01

I

BC-Unit 5-6-0008

“Pond_Second” (Cell 3) Pond Results

~ '" Reservoir "Pond_Second" Results for Run "3/4 PMF"

"C,---------------------------------------------------------------------------------T 677.50

:::'---~".rL'---~"·:'·C<:-.~--,-"--.. -"-j;.".-"---:cc__ i 1 ""-c .. c~"-

"" - --11---~ 1( 0 ---+ o i 135

~ 1301---j---w "'1---1----nc,-,~----

! " "

"

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, , , , " , , , , , ,

W __ L , 8 400

I I

, ' , , ,- 1_-

200 r

~ 300 --i-,\.~

,co J -~'-c-c----------_l----- -

00,00

I

12.00

01Jan2012

l~(C~teT"" 1OApr2012, 10 :38 :36)

- - - - - - Rl.n 3?4 f'Mf EIeme<t:f'Oi',V _SECOI'.v Re" ' ::ste<_

00,00

I

- - - Rcn3?4 f'Mf EIeme<t:f'Oi',V _SECOI'.v Re" .t:COOJbined .,fIow

12.00

02Jan2012

00,00

I

12.00

03Jan2012

Summary Results for Rese:rvoir "Pond_S&ond" = Project: Buck

Simulation Run: 3/4 PMF Reservoir : Pond_Second

Start of Run: OUan2012, 00:00 End of Run: 04Jan2012, OO:00 Compute lime: lOApr2012, 10:38:36

Basin Model : Existing Conditions Meteorologic Model: 641r 3/4PMP Control Specifications: Three-Day

Volume Units: @ IN eJ AC-FT

Computed Results

Peak Inflow : 747.8 (CFS) Peak Outflow: 327. 3 (CfS) Total Inflow : 15 .63 (IN) Total Outflow : 15 .68 (IN)

Date/rmeofPeakInflow : OlJan2012,03: 21 Date/rme of Peak Outflow : OlJan20 12,04:09 Peak Storage: 158 . 1 (AC-FT) Peak Bevation : 6n.3 (FT)

677.15

676.80

676 ( 5

676.10

675.75

675 ( 0

67505

67 0 0

67 U 5

67(. 00

00,00

I

; , W

BC-Unit 5-6-0008

Appendix G

NOAA ATLAS 14 Data

NOAA Atlas 14, Volume 2, Version 3Location name: Salisbury, North Carolina, US*

Coordinates: 35.7127, -80.3677Elevation: 703ft** source: Google Maps

POINT PRECIPITATION FREQUENCY ESTIMATESG.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley

NOAA, National Weather Service, Silver Spring, Maryland

PF_tabular | PF_graphical | Maps_&_aerials

PF tabularPDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1

Duration Average recurrence interval (years)1 2 5 10 25 50 100 200 500 1000

5-min 0.385(0.355-0.419)

0.456(0.421-0.497)

0.532(0.489-0.578)

0.583(0.535-0.632)

0.639(0.584-0.693)

0.676(0.615-0.733)

0.708(0.640-0.767)

0.734(0.660-0.797)

0.760(0.678-0.826)

0.776(0.686-0.845)

10-min 0.615(0.567-0.669)

0.730(0.673-0.795)

0.852(0.783-0.926)

0.933(0.856-1.01)

1.02(0.931-1.10)

1.08(0.979-1.17)

1.13(1.02-1.22)

1.16(1.05-1.26)

1.20(1.07-1.31)

1.22(1.08-1.33)

15-min 0.769(0.708-0.836)

0.917(0.846-0.999)

1.08(0.991-1.17)

1.18(1.08-1.28)

1.29(1.18-1.40)

1.36(1.24-1.48)

1.42(1.29-1.54)

1.47(1.32-1.59)

1.51(1.35-1.65)

1.53(1.36-1.67)

30-min 1.06(0.971-1.15)

1.27(1.17-1.38)

1.53(1.41-1.67)

1.71(1.57-1.85)

1.91(1.75-2.07)

2.05(1.87-2.23)

2.18(1.97-2.36)

2.28(2.06-2.48)

2.41(2.15-2.62)

2.48(2.20-2.71)

60-min 1.32(1.21-1.43)

1.59(1.47-1.73)

1.96(1.81-2.13)

2.23(2.04-2.41)

2.55(2.33-2.76)

2.78(2.53-3.02)

3.00(2.71-3.25)

3.20(2.88-3.48)

3.45(3.08-3.76)

3.63(3.21-3.95)

2-hr 1.52(1.40-1.65)

1.84(1.69-2.00)

2.28(2.10-2.49)

2.61(2.39-2.84)

3.03(2.76-3.29)

3.34(3.03-3.62)

3.64(3.28-3.95)

3.93(3.52-4.27)

4.30(3.80-4.67)

4.56(3.99-4.97)

3-hr 1.62(1.49-1.76)

1.95(1.80-2.13)

2.44(2.24-2.65)

2.80(2.57-3.04)

3.27(2.98-3.54)

3.63(3.28-3.93)

3.97(3.58-4.30)

4.31(3.85-4.67)

4.76(4.20-5.17)

5.09(4.43-5.53)

6-hr 1.96(1.80-2.14)

2.36(2.18-2.57)

2.94(2.70-3.21)

3.39(3.10-3.68)

3.98(3.62-4.32)

4.44(4.01-4.81)

4.90(4.39-5.30)

5.36(4.76-5.80)

5.97(5.22-6.46)

6.43(5.56-6.96)

12-hr 2.30(2.12-2.52)

2.78(2.56-3.04)

3.48(3.20-3.80)

4.03(3.69-4.39)

4.77(4.33-5.18)

5.36(4.83-5.81)

5.97(5.33-6.45)

6.59(5.82-7.11)

7.43(6.45-8.01)

8.07(6.91-8.71)

24-hr 2.76(2.57-2.97)

3.33(3.11-3.58)

4.17(3.89-4.49)

4.83(4.50-5.19)

5.72(5.31-6.15)

6.43(5.95-6.91)

7.15(6.60-7.68)

7.89(7.26-8.48)

8.89(8.14-9.57)

9.67(8.83-10.4)

2-day 3.20(2.99-3.43)

3.86(3.60-4.13)

4.79(4.47-5.13)

5.52(5.14-5.90)

6.49(6.04-6.94)

7.26(6.74-7.77)

8.04(7.44-8.61)

8.84(8.15-9.47)

9.91(9.10-10.6)

10.7(9.84-11.5)

3-day 3.41(3.19-3.64)

4.09(3.83-4.38)

5.06(4.73-5.41)

5.82(5.43-6.21)

6.84(6.37-7.31)

7.64(7.10-8.18)

8.46(7.84-9.06)

9.30(8.59-9.96)

10.4(9.59-11.2)

11.3(10.4-12.2)

4-day 3.61(3.39-3.85)

4.33(4.07-4.62)

5.33(4.99-5.69)

6.12(5.72-6.52)

7.18(6.70-7.67)

8.03(7.46-8.58)

8.89(8.24-9.51)

9.76(9.02-10.5)

11.0(10.1-11.8)

11.9(10.9-12.8)

7-day 4.16(3.92-4.43)

4.97(4.68-5.29)

6.03(5.67-6.42)

6.88(6.46-7.32)

8.03(7.52-8.54)

8.95(8.36-9.52)

9.88(9.19-10.5)

10.8(10.0-11.5)

12.1(11.2-13.0)

13.1(12.1-14.1)

10-day 4.74(4.49-5.02)

5.64(5.34-5.97)

6.77(6.40-7.16)

7.65(7.23-8.10)

8.84(8.33-9.36)

9.78(9.19-10.4)

10.7(10.0-11.4)

11.7(10.9-12.4)

13.0(12.1-13.8)

13.9(12.9-14.9)

20-day 6.38(6.07-6.70)

7.52(7.15-7.91)

8.88(8.43-9.34)

9.96(9.44-10.5)

11.4(10.8-12.0)

12.5(11.8-13.2)

13.7(12.9-14.4)

14.9(13.9-15.7)

16.4(15.3-17.4)

17.6(16.4-18.7)

30-day 7.89(7.54-8.27)

9.28(8.86-9.70)

10.8(10.3-11.3)

11.9(11.4-12.5)

13.5(12.8-14.1)

14.6(13.9-15.3)

15.8(14.9-16.5)

16.9(16.0-17.8)

18.5(17.4-19.4)

19.6(18.4-20.7)

45-day 9.92(9.52-10.4)

11.6(11.1-12.1)

13.3(12.7-13.8)

14.6(13.9-15.2)

16.2(15.5-16.9)

17.5(16.7-18.2)

18.7(17.8-19.5)

19.9(18.9-20.8)

21.5(20.3-22.5)

22.7(21.4-23.8)

60-day 11.8(11.4-12.3)

13.8(13.3-14.3)

15.5(15.0-16.1)

16.9(16.2-17.6)

18.6(17.9-19.4)

20.0(19.1-20.8)

21.2(20.3-22.1)

22.5(21.4-23.4)

24.0(22.9-25.1)

25.2(23.9-26.4)

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.

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PF graphical

Page 1 of 4Precipitation Frequency Data Server

3/27/2012http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.7127&lon=-80.3677&data...

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BC-Unit 5-6-0008

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BC-Unit 5-6-0008

Appendix H

Digital Data

(Attached CD containing HEC-HMS model and pertinent GIS spatial files)

hydrologic analysis - nc

Documents