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NC0004961_RBSS_SARP_Rev0_Appx E_20161219
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016 Duke Energy Coal Combustion Residuals Management Program Riverbend Steam Station Site Analysis and Removal Plan Revision 0 APPENDIX E: ENGINEERING EVALUATIONS AND ANALYSES OF RIVERBEND CLOSURE DESIGN GRADING PLANS Riverbend Ash Basin Closure Plan Amec Foster Wheeler Project No. 6226-14-0007 CALC-1. 01-STORMWA TER, Rev. 0 December 2015 CALCULATION COVER SHEET Project Ash Basin Closure Design Grading Plans for Riverbend Steam Station Calc/Analysis No. CALC-1.01 STORMWATER-00 AMEC Project No. 6226-14-0007 Title Stormwater Evaluation Client Contract NA Sheet No. 1 of 15 Discipline Civil Computer Program Microsoft Office Excel 2007, AutoCAD Civil 3D 2013, H droCAD 10.0 Version / Release No. Purpose and Objective These calculations establish the pre -development and post -development base stormwater runoff flows for the Riverbend Steam Station site at each of the watershed outfalls identified on the plans. This package also contains the calculations used to evaluate the erosion & sediment control measures required during the construction phase of the project. The objective is to evaluate stormwater management system requirements and to demonstrate that stormwater management may be achieved for the proposed closure design of the ash ponds and storage areas at the Riverbend Steam Station. Quality Assurance Conditions (e.g. safety classification) NA Summary of Conclusion Throughout the development process for closing the Riverbend Steam Station ash ponds and storage areas, Amec Foster Wheeler's design principles entail an appropriately conservative approach to managing the stormwater runoff during the construction and post -construction phases of the project. The approach focuses on conveying stormwater runoff from the upland areas to Mountain Island Lake in a stable manner while providing multiple features with capacity to improve surface water quality. Based on the defined assumptions and requirements of the scope of work, the proposed stonnwater management system has been shown to be feasible. Revision Log Rev. No. Revision Description 00 Initial issue. Sign Off Rev. No. CIO Origi a or (Print) 2j l 7S�MA Verification Method D Design Review Verifier (Print) Sign ,t Technical Lead (Print) Aign / Date Chad N. Brown Richard Hiner, PE Brian Chrisman, PE Additional Reviewer (Print) Signature Date Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 2 RECORD OF REVISION Revision No. Date Revisions Made 00 12/2015 Initial issue Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 3 TABLE OF CONTENTS CALCULATION COVER SHEET .............................................................................................................. 1 RECORD OF REVISION ............................................................................................................................. 2 1.0 OBJECTIVE ........................................................................................................................................... 5 2.0 ASSUMPTIONS ..................................................................................................................................... 5 3.0 COMPUTER PROGRAM IDENTIFICATION ..................................................................................... 5 4.0 CALCULATION APPROACH AND INPUT........................................................................................ 6 4.1 PRE-CONSTRUCTION PHASE ................................................................................................................ 6 4.1.1 Watershed Delineation ............................................................................................................. 6 4.1.2 Land Use and Soils (CN Values) .............................................................................................. 6 4.1.3 Time of Concentration .............................................................................................................. 6 4.1.4 Summary of Results ................................................................................................................... 7 4.2 CONSTRUCTION PHASE ....................................................................................................................... 7 4.2.1 Watershed Delineation ............................................................................................................. 8 4.2.2 Land Use and Soils (CN Values) .............................................................................................. 8 4.2.3 Time of Concentration .............................................................................................................. 8 4.2.4 Erosion and Sediment Control Measures ................................................................................ 8 4.2.5 Summary of Results ................................................................................................................... 9 4.3 POST-CONSTRUCTION PHASE ............................................................................................................ 13 4.3.1 Watershed Delineation ........................................................................................................... 13 4.3.2 Land Use and Soils (CN Values) ............................................................................................ 13 4.3.3 Time of Concentration ............................................................................................................ 13 4.3.4 Summary of Results ................................................................................................................. 13 5.0 CONCLUSIONS AND DISCUSSIONS .............................................................................................. 14 6.0 WORK CITED ...................................................................................................................................... 15 Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 4 LIST OF TABLES Table 1: Pre-Construction Conditions .......................................................................................................... 7 Table 2: Pre-Construction Peak Flows ......................................................................................................... 7 Table 3: Construction Phase Conditions ...................................................................................................... 9 Table 4: Construction Phase Peak In-Flows ............................................................................................... 10 Table 5: Sediment Basin Summary Table ................................................................................................. 10 Table 6: Sediment Basin Peak Discharges ................................................................................................. 11 Table 7: Clean Water Diversion Ditch Summary Table (Stability Check) ................................................ 11 Table 8: Clean Water Diversion Ditch Summary Table (Capacity Check) ............................................... 12 Table 9: Rip Rap Outlet Protection Design Table (Sediment Basins) ....................................................... 12 Table 10: Rip Rap Outlet Protection Design Table (Clean Water Diversions) ......................................... 12 Table 11: Post-Construction Conditions .................................................................................................... 14 Table 12: Post-Construction Peak Flows ................................................................................................... 14 LIST OF FIGURES F-01: Pre-Construction Drainage Map F-02: During-Construction Phase 1 Drainage Map F-03: During-Construction Phase 2 Drainage Map F-04: Post-Construction Drainage Map REFERENCES Reference 1: Rainfall Data Reference 2: Pre-Construction HydroCAD Output Reference 3: During-Construction HydroCAD Output Reference 4: Calculations for Erosion and Sediment Control Measures (Sediment Basins, Clean Water Diversion Ditches, Rip Rap Aprons) Reference 5: Post-Construction HydroCAD Output Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 5 1.0 OBJECTIVE The objective is to evaluate stormwater management system requirements and to demonstrate that stormwater management may be achieved for the proposed closure design grading plans for the ash ponds and storage areas at the Riverbend Steam Station. These calculations establish the pre-construction, construction, and post-construction stormwater runoff base flows for the Riverbend Steam Station site at each of the watershed outfalls identified in the plans. This package also provides the calculations used to evaluate the erosion & sediment control (E&SC) measures that are required during the construction phase of the project based on the assumptions below. 2.0 ASSUMPTIONS For this design, a number of assumptions have been established and are listed below. Existing outfall locations will remain reasonably unchanged during and after construction. For Curve Number (CN) calculatons, coal ash is considered by the industry to behave as a non- plastic silt and is assumed to have physical properties most comparable to Hydrologic Soil Group (HSG) B soil. HSG B soils have a moderate infiltration rate when thoroughly wet and have moderately fine to moderately coarse texture. The assumed excavation grades shown in the ash pond and ash stack footprints were developed by interpolating boring log information and combining it with digitized topography from historic Duke Energy construction documents. (V-0.5). Means and methods for dewatering the ash ponds have yet to be determined but should not directly influence this work scope. The site will meet the permanent water quality and quantity requirements set forth by the North Carolina Department of Environmental Quality (NCDEQ). Within the disturbed area of the site, no impervious area will be added, therefore the post-construction runoff volume is expected to be less than or equal to the pre-construction runoff volume. The entire disturbed area will be stabilized and vegetated in the post-construction phase of the project. NCDEQ requirements will be met as a result of the reduction of runoff quantity resulting from improvements to the land use (ash pond to vegetated cover). This calculation utilizes industry standard methodology and the computational software products Microsoft Excel, AutoCAD, FlowMaster, and HydroCAD. 3.0 COMPUTER PROGRAM IDENTIFICATION The table below indicates the computer hardware, operating system, and software used by AMEC for the data analysis and/or calculations presented herein. User (Computer Name) Computer Hardware (Service Tag No.) Operating System Computer Software Chad Brown Dell Optiplex 390 (DG713039) Microsoft Windows 7 Professional Microsoft Office Excel 2007, Civil 3D AutoCAD 2013, HydroCAD 10.0 Bentley FlowMaster V8i Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 6 4.0 CALCULATION APPROACH AND INPUT These stormwater calculations consider rainfall data and soil classifications for the Riverbend Steam Station located at 175 Steam Plant Rd, Mount Holly, North Carolina (Coordinates: 35.3577, -80.9792). The rainfall data was taken from the National Oceanic and Atmospheric Administration (NOAA) website Atlas 14 rainfall depths for the referenced latitude and longitude coordinates. The soil data was obtained from USDA Soil maps. The rainfall data and soils data is provided in Reference 1 and Figure 2, respectively. The Natural Resource Conservation Service (NRCS) method was used to calculate the peak stormwater runoff flow rates at each outfall. The pre-construction condition utilizes the existing topography to calculate flows, whereas the during-construction and post-construction flows are based on the excavation and final grading plan. 4.1 Pre-Construction Phase Peak flows for the 1-yr, 2-yr, and 10-yr storm events were determined using HydroCAD 10.0 for the pre- construction condition. Three steps were taken to determine the base flows at each outfall of the site identified within the plans: watershed delineation, land use and soil (CN) classification, and time of concentration calculations. 4.1.1 Watershed Delineation The three existing drainage basins were delineated using existing topography. The delineated watersheds for the pre-construction condition are provided in F-01. 4.1.2 Land Use and Soils (CN Values) Land uses for the project were determined by recent publically available aerial imagery, survey data, and soil classifications. The hydrologic soil group (HSG) classifications for the site were obtained from USGS Soils maps. Amec Foster Wheeler, in keeping with industry standard practices, has assumed coal ash to be comparable to a non-plastic silt with physical properties similar to HSG B soils. HSG B soils have a moderate infiltration rate when thoroughly wet and have moderately fine to moderately coarse texture. 4.1.3 Time of Concentration The time of concentration for each delineated watershed was calculated using TR-55 methodology and existing topography. The flow paths consist of sheet flow, shallow concentrated flow, and concentrated flow segments. Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 7 4.1.4 Summary of Results The pre-construction results are displayed in the following tables. The HydroCAD output is provided in Reference 2. 4.1.4.1 Pre-Construction Conditions Table 1 displays the drainage area, weighted curve number, and time of concentrations for the pre- construction delineated watersheds for the site. Table 1: Pre-Construction Conditions Watershed Drainage Area (acres) Weighted CN Time of Concentration (min) Pre DA-01 95.0 87 29.4 Pre DA-02 32.6 68 34.0 Pre DA-03 27.9 68 31.6 4.1.4.2 Pre-Construction Peak Flows Table 2 displays the pre-construction peak flows for each delineated watershed in cubic feet per second (cfs). Table 2: Pre-Construction Peak Flows Watershed 1-yr (cfs) 2-yr (cfs) 10-yr (cfs) Pre DA-01 126.7 168.3 282.0 Pre DA-02 9.7 17.5 43.6 Pre DA-03 8.8 15.8 39.3 4.2 Construction Phase The construction phase of the project requires the use of erosion and sediment control measures to treat sediment laden stormwater runoff before ultimately discharging the runoff from the site. Grades during construction will be variable; therefore the drainage areas are determined using proposed excavation grades. The proposed sediment basins (SB-03, SB-04, and SB-05) are the primary sediment control measures and were designed to meet NCDEQ regulations. The sediment basins include a riser and outlet pipe along with skimmers for dewatering. The existing ash pond and cinder pit dikes along Mountain Island Lake are temporarily incorporated within the plan to prevent sediment-laden runoff from directly draining off-site. Although the height of the dikes will be reduced during construction, leaving the vegetated dike in place provides an effective means of separation from the construction site and Mountain Island Lake. While coal combustion residual (CCR) is being excavated and removed from the site, SB-01 and SB-02 will act as pump-and-treat basins with no riser or discharge pipe. SB-01 has been designed to store the runoff volume for the 25-yr storm with no pumping. SB-02 has been sized for the 10-yr storm with no pumping and the existing dike along the cinder pit will help contain runoff volume and prevent runoff from exiting the cinder pit area. After all of the CCR material is removed from the site, basin SB-03 can be can be constructed by enlarging basin SB-02 and adding the riser and discharge pipe along with the skimmer. Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 8 Once the rail spur is demolished and basin SB-03 is functioning as a traditional sediment basin, SB-01 can be taken out of service and backfilled. Basin SB-03 will then serve the ash stack and cinder pit areas through the remainder of construction until final stabilization is established. 4.2.1 Watershed Delineation The construction phase drainage basins were delineated using existing topography and proposed excavation grades. The delineated watersheds for the during-construction condition are provided in F-02 and F-03. 4.2.2 Land Use and Soils (CN Values) Land uses for the project were determined by recent publically available aerial imagery, survey data, and soil classifications. The hydrologic soil group (HSG) classifications for the site were obtained from USGS Soils maps. 4.2.3 Time of Concentration The time of concentration for each delineated watershed was calculated using TR-55 methodology and existing topography, proposed excavation grades, and land uses. The flow paths include sheet flow, shallow concentrated flow, and concentrated flow segments. 4.2.4 Erosion and Sediment Control Measures The Sedimentation Control Commission (SCC) adopts rules, sets standards, and provides guidance for the implementation of the N.C. Sedimentation Pollution Control Act of 1973 (SPCA). The law requires installation and maintenance of sufficient erosion control practices to retain sediment within the boundaries of the site. The following measures will be utilized for stormwater management and the Erosion and Sediment Control Plan for the project. Sediment basins and channels were evaluated to provide perspective on the size and geometry of required stormwater management features and to support developing the proposed plans. Other E&SC practices (rip rap outlets, wattles, check dams, temporary and permanent vegetation, etc.) are also used during the construction phases of this project as appropriate. 4.2.4.1 Sediment Basins Temporary sediment basins will be used as the primary features for treatment of sediment laden stormwater runoff of the site while construction is taking place. The basins are sized with a minimum surface area (at riser crest elevation) equal to or greater than 435 square feet per cfs of the construction phase Q10 peak inflow. A minimum sediment storage volume of 1,800 cubic feet per acre of disturbed area is required for all temporary sediment basins. Sediment basins utilize a riser/barrel configuration, baffles, and dewater through a skimmer. The minimum dewatering time for each basin is 48 hours (NC Sedimentation Control Commission 2013). A sediment basin summary table (Table 5) is provided in Section 4.2.5.3 of this calculation package. Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 9 4.2.4.2 Diversion Ditches Diversion ditches are runoff control measures used to subdivide the site into specific drainage areas. The proposed clean water diversion ditches are designed to convey the Q25 flows and installed prior to grading operations. Clean water diversion ditches keep water from flowing over unprotected down slope areas as well as diverting clean water away from the sediment basins. Temporary diversion ditches are installed during grading operation and keep sediment laden water on the down-slope side of a disturbed area. Sediment laden runoff is guided to a sediment basin before being released from the site (NC Sedimentation Control Commission 2013). Clean Water Diversion Ditches 1 and 2 shown in F-02 and F-03 will convey non-sediment laden runoff. Clean Water Diversion Ditch 1 will divert clean water away from disturbed areas directly off-site and Clean Water Diversion Ditch 2 will divert clean water to SB-01 until all CCR material is excavated and hauled off site. Once the excavation of CCR material is complete the existing railroad tracks shall be removed, SB-03 constructed, and SB-01 taken out of service and backfilled. Clean Water Diversion Ditch 2 at this point shall be extended as shown in F-03 and allowed to discharge directly off-site. The industry design standard for land fill diversion ditches is based on the 25-yr storm. As a conservative approach Clean Water Diversion Ditches 1 and 2 were designed according to this standard instead of the NCDEQ required 10-yr storm. 4.2.5 Summary of Results The during-construction results are displayed in the following tables. The HydroCAD output is provided in Reference 3. 4.2.5.1 Construction Phase Conditions Table 3 displays the drainage area, weighted curve number, and time of concentrations for the during-construction delineated watersheds for the site. Undisturbed drainage areas are denoted in Table 3 with “U”. Table 3: Construction Phase Conditions Watershed Drainage Area (acres) Weighted CN Time of Concentration (min) DA-01 65.9 91 12.9 DA-02 20.9 91 6.9 DA-03A 22.4 86 5.6 DA-03B-U 20.4 69 24.7 DA-04 14.1 86 5.0 Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 10 4.2.5.2 Construction Phase Peak Flows Table 4 displays the during-construction peak flows for each delineated basin. Undisturbed drainage areas are denoted in Table 4 with “U”. Table 4: Construction Phase Peak In-Flows Basin 1-yr (cfs) 2-yr (cfs) 10-yr (cfs) 25-yr (cfs) DA-01 164.4 209.6 330.0 401.5 DA-02 63.2 80.4 125.9 152.9 DA-03A 56.7 75.3 125.8 156.2 DA-03B-U 8.5 14.9 35.5 49.4 DA-04 36.7 48.6 81.2 100.8 4.2.5.3 Sediment Basin Summary Table 5 displays the designed sediment basins. Undisturbed drainage areas are denoted in Table 5 with “U”. See Reference 4 for detailed Riser Sediment Basin Design Information Table. Table 5: Sediment Basin Summary Table Sed Basin Contributing Drainage Areas Contributing Disturbed Area (ac) Min. Volume Req. (ft3) Q10 Inflow (cfs) Q25 Inflow (cfs) Min Surface Area Req. (ft2) SB-01* DA-03A DA-03B-U 22.4 40,320 139.1 176.0 60,913 SB-02* DA-04 14.1 25,380 81.2 100.8 35,331 SB-03* DA-03A DA-04 36.5 65,700 206.9 256.8 89,984 SB-04 DA-01 DA-02 86.8 156,240 433.7 527.8 188,646 SB-05 DA-01 DA-02 86.8 156,240 433.7 527.8 188,646 *Sediment Basin SB-01 acts as a reservoir for storing sediment laden runoff as well as diverted clean water. The existing discharge pipe will be plugged and the storage volume within the basin will be pumped and treated during the excavation of CCR. SB-01 is designed to store the entire runoff volume from the 25yr-24hr storm. Sediment Basin SB-02 acts as a reservoir for storing sediment laden runoff in the cinder pit area during the excavation of CCR material. Once all CCR material is excavated and the existing rail road tracks are no longer in service, SB-03 shall be constructed to service the sediment laden runoff from the Dry Stack and Cinder Pit area. Upon the completed construction of SB-03 and the removal of the rail road tracks SB-01 can be backfilled and taken out of service. Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 11 Table 6 displays the peak discharges for each of the designed sediment basins. Table 6: Sediment Basin Peak Discharges Sediment Basin 1-yr (cfs) 2-yr (cfs) 10-yr (cfs) SB-01 (Pumped and Treated) NA NA NA SB-02 (Pumped and Treated) NA NA NA SB-03 1.1 1.1 5.5 SB-04 2.3 2.3 19.0 SB-05 2.3 3.0 22.6 4.2.5.4 Clean Water Diversion Ditch Summary Tables 7, and 8 display the designed clean water diversion ditches. Table 7: Clean Water Diversion Ditch Summary Table (Stability Check) Ditch No. Dimensions Bottom Width (ft) Side Slopes (H:V) Avg Gradient (%) Drainage Area (ac) Peak Flow Q25* (cfs) Manning’s “n” (bare soil) Calculated Velocity** (fps) Calculated Shear Stress (lb/ft2) Erosion Control Measure 1 2.5’ Deep Trapezoidal 2 3:1 2.9 8.3 27.2 0.02 7.75 1.43 1.0’ Check Dam and Photodegradable ERC Blanket 2 (Phase 1) 2.5’ Deep Trapezoidal 2 3:1 3.2 6.0 13.6 0.02 6.43 1.14 1.0’ Check Dam and Photodegradable ERC Blanket 2 (Phase 2) 3.0’ Deep Trapezoidal 2 3:1 1.5 26.4 62.9 0.02 8.37 1.20 1.0’ Check Dam and Photodegradable ERC Blanket *Results from HydroCAD Software **Reults from TENSAR North American Green Erosion Control Materials Design Software (ECMDS Version 5.0) Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 12 Table 8: Clean Water Diversion Ditch Summary Table (Capacity Check) Ditch No. Dimensions Bottom Width (ft) Side Slopes (H:V) Min Gradient (%) Drainage Area (ac) Peak Flow Q25* (cfs) Manning’s “n” Depth of Flow** (ft) 1 2.5’ Deep Trapezoidal 2 3:1 0.5 8.3 27.2 0.066 (Vegetated) 2.00 2 (Phase 1) 2.5’ Deep Trapezoidal 2 3:1 0.5 6.0 13.6 0.083 (Vegetated) 1.64 2 (Phase 2) 3.0’ Deep Trapezoidal 2 3:1 0.5 26.4 62.9 0.052 (Vegetated) 2.59 *Results from HydroCAD Software ** Reults from TENSAR North American Green Erosion Control Materials Design Software (ECMDS Version 5.0) 4.2.5.5 Rip Rap Outlet Protection Design Table Tables 9 and 10 display summary tables of the rip rap aprons designed for each of the sediment basin discharge pipes and clean water diversion outfalls. See Reference 4 for detailed calculations of the Rip Rap Outlets. Table 9: Rip Rap Outlet Protection Design Table (Sediment Basins) Description Pipe Diameter (in) 10-Yr Velocity (fps)* Zone Apron Length (ft)** Apron Width (ft)** Stone Class ** Rip Rap D50 (in)** Apron Thickness (in)** SB-03 Outlet 24 1.43 1 8 6 A 4 12 SB-04 Outlet 24 6.04 2 12 7 B 8 18 SB-05 Outlet 24 7.20 2 12 7 B 8 18 *Results from HydroCAD Software **Aprons sized using the New York DOT Dissipater Method as outlined by NCDEQ (Erosion Control Manual, Section 8.06) Table 10: Rip Rap Outlet Protection Design Table (Clean Water Diversions) Description Ditch Bottom Width (in) 25-Yr Velocity (fps)*** Zone Apron Length (ft)** Apron Width (ft)** Stone Class** Rip Rap D50 (in)** Apron Thickness (in)** Clean Water Diversion Ditch 1 24 7.89 2 12 7 B 8 18 Clean Water Diversion Ditch 2 (Phase 2) 24 10.26 2 12 7 B 8 18 ** Aprons sized using the New York DOT Dissipater Method as outlined by NCDEQ (Erosion Control Manual, Section 8.06) ***Results from FlowMaster Software Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 13 4.3 Post-Construction Phase The site will meet the permanent water quality and quantity requirements set forth by the NCDEQ. No impervious area will be added within the disturbed area of the site, therefore the post-construction runoff volume will be less than or equal to the pre-construction runoff volume. The disturbed area will be stabilized and vegetated in the post-construction phase of the project. The NCDEQ requirements will be met due to the reduction of runoff quantity and improvements of land use (ash pond to vegetated cover) which may ultimately improve stormwater quality. Peak flows for the 1-yr, 2-yr, and 10-yr storm events were determined in the detailed design using HydroCAD 10.0 for the post-construction condition. Three steps were taken to determine the base flows at each outfall of the site: watershed delineation, land use and curve number (CN) classification, and time of concentration calculations. 4.3.1 Watershed Delineation The post-construction drainage basins were delineated using existing topography and proposed final grades. The delineated watersheds for the post-construction condition are provided in F-04. 4.3.2 Land Use and Soils (CN Values) Land uses for the project were determined by aerial imagery, survey data, proposed land uses, and soil classifications. The hydrologic soil group (HSG) classifications for the site were obtained from USGS Soils maps. 4.3.3 Time of Concentration The time of concentration for each delineated watershed was calculated using TR-55 methodology, existing topography, proposed contours, and land uses. Flow paths include sheet flow, shallow concentrated flow, and concentrated flow segments. 4.3.4 Summary of Results The post-development results are displayed in the following tables. The HydroCAD output is provided in Reference 5. 4.3.4.1 Post-Construction Conditions Table 11 displays the drainage area, weighted curve number, and time of concentrations for the post-construction delineated watersheds for the site. Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 14 Table 11: Post-Construction Conditions Basin Drainage Area (acres) Weighted CN Time of Concentration (min) Post DA-01 82.0 79 34.2 Post DA-02 23.0 78 30.8 Post DA-03 60.7 68 36.7 4.3.4.2 Post-Construction Peak Flows Table 12 displays the post-construction peak flows for each delineated watershed in cubic feet per second (cfs). Table 12: Post-Construction Peak Flows Watershed 1-yr (cfs) 2-yr (cfs) 10-yr (cfs) Post DA-01 62.5 90.7 173.1 Post DA-02 17.6 25.9 50.3 Post DA-03 17.1 30.9 77.1 5.0 CONCLUSIONS AND DISCUSSIONS The proposed stormwater management system for the Riverbend Steam Station has been evaluated for the pre-construction, construction, and post-construction phases of the ash basin closure grading project. The construction phase will use temporary sediment basins as the primary feature for erosion and sediment control. These basins will be designed according to NCDEQ standards. The minimum surface area and volume requirements of each sediment basin are included in this calculation package. The site will meet the permanent water quality and quantity requirements set forth by the NCDEQ. No impervious area will be added within the disturbed area of the site, therefore the post-construction runoff volume will be less than or equal to the pre-construction runoff volume. The disturbed area will be stabilized and vegetated in the post-construction phase of the project. The NCDEQ requirements will be met as a result of the reduction of runoff quantity due to improvements in the land use (from ash pond to vegetated cover), which may ultimately improve stormwater quality. The proposed stormwater management system outlined in this calculation package has been shown to be feasible for the proposed ash basin closure design of the Riverbend Steam Station. Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December 2015 15 6.0 WORK CITED NC Sedimentation Control Commission, NCDEQ, NC Arigultrural Extension Service. Erosion and Sediment Control Planning and Design Manual. Raleigh, 2013. North Carolina Division of Water Quality. Stormwater Best Management Practices Manual. Raleigh: NCDEQ, 2007. Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 Figures F-01: PRE-CONSTRUCTION DRAINAGE MAP F-02: DURING-CONSTRUCTION DRAINAGE MAP (PHASE 1) F-03: DURING-CONSTRUCTION DRAINAGE MAP (PHASE 2) F-04: POST-CONSTRUCTION DRAINAGE MAP v I^lam\\ \ vq 63 I' 171 WETLANDAREA -off \VA V�A I�I IIII �I•(Z,X2 (TYP. > ./ �wvv__avvv=>Illf/I � — — >III�IIIIlo1\ 1� 2s7 MOUNTAIN ISLAND LAKE A�111' \11V�)11�A111�� 3 -450 v- I )ii�iiUr��lr' WORKAREA BOUNDARY, W�\VA\ - �ir�/i�i i �//y�' / �-�jAv�- v-_-.i/��v�1A\1AIv�� es �'�- ///�j�iii //l��/r/i r V� �w��e\ ,�11•�0$� o`Av t��, v%�vAA� I _,� \�v°"��A� // � �----� �=o�� ri / / �e 'I lyts� � -_�6 "•231 -�ii �� ��� � IIA\ � \lAVv�� � 1 �-- _--_ vv����� V� \El / / � � �— '�-' !1 \ o n `c -� l • / of - i 1 i r / _ A�� -X- \ �. 4'�•_, 235 / // / //ii �/ _ / l /"�1�._—' ✓ / vOVvv VAV AAAI � V > v v v� a_ —__ __ - s7 � _ v f\ ( I / � A` � ,,"`�, � � 2a]fi l / l/IIII !11 //� ��� '/ v-�.�� /� �i- -- - ',- ��/-✓�%=�� v vw�wvvy�w �vvVAAA\�A\ f 1II III�1/// V1f11.:! 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MOUNTAIN ISLAND LAKE \VA��vv°vv�O v=,����v��v ��// / � ,J --�- =�� v �__� I / AvVA�A v �vvV ( IIII II II I � A / �, ✓ /llllll I cvvywAyam -/i% AA _���p0%yam- _ v v A V �I/ � \VAper � f-�vvV v �v�v���vv vA c f A � � II IIIIII III �I "/ � //i �L� l \) (3 I• r J 6/v/ �/vAv 00 V J / / / _ ! �v\ v vvv wyAvvA� `�v v VA��_r 1 r r / / / 11 1 ( Vv�Vvv �vv�� v vvvvwvso.v v v VI��AVI 1oz / r _ - vvOv v �v�vyvvvA� v v II II 1 I 1 111 i/11. r// lAVI r�tee DRY ASH STACK 24 _ / ! \ l\ \ 1111I1111\\\I r LIMITS OF DISTURBANCE Io L � IIIIIIII\ STONEWATEROWNER \1 \ I \ I \ ` \ \ ASSOCIATION INC. C CORPORATION PID# 1977fi3 \ PIN#4519422113 tom. ��% t������i DUKE ENERGY LEGEND EXISTING GRADE INDEX CONTOUR (10-) - - - - - - - EXISTING GRADE INTERMEDIATE CONTOUR (7) — PRE -CONSTRUCTION DRAINAGE AREA LOD LIMITS OF DISTURBANCE WORK AREA BOUNDARY . OUTFALL LOCATION ---- PROPERTY BOUNDARY 0 WETLANDAREAS PRELIMINARY FOR PERMIT APPROVAL ONLY \ \ \ \`/ ;� -_�_ - \\ \ - \ •' f ) I ! I / l / l 11 I / / CORPORATION PID# 175022 t vp0 (I ( `S \ / \I PIN#4519542126 l V AAA=:�� - _= /// / %1/ls/ \ownIII HENDERSON CEMETERY \� J // /> //>/ /�/�j/ _ NKOPLN I BOUNUnHV JUDITH E. ROZZELLE / PID#202721 PIN#4519520433-�_�/ VA A `II�IVIIII/A /� / \J Il\\(\\ i\\li DUKE ENERGY -`— -�.�\ /' I� \\\l�)II /I I Il CORPORATION PID4217766 i f- _-_-�\ \ \ \ \ IIII%// STONEWATEROWNER �\ )\\\ IIII f.� \� /- � yPIN—IB110111NAT/ \\�\\_ \\ \ \ III II�I�///// OATIONION INC.PID# 07327 I�// �.I ( j / / . /• S I IIII���\\` /))IIf //�/%� �/ // //// / / \ �\ �; \ \ \ \ \ II PIN #151952804s CORPOR(\III\)II��iII/A CLIENT LOGO. CLIENT. DATUM: PROJECT: PROJECT NO.: DUKE ENERGY CAROLINAS, LLC. NAD83 RIVERBEND STEAM STATION 6226-14-0007 DUKE ENERGY COUNTY, AS i ASH POND CCR REMOVAL GRADING PLAN B GASTONDUKE TITLE: ENERGY amec CNB DEC2014 ® 13 11 2015 ESC REVISIONS RI1 Amec Foster Wheeler Environment & Infrastructure, Inc. DRAWING NO. Q 31 12 2014 FOR DUKE REVIEW BC 2801YORKMONTROAD ,SUITE 100 foster BC PRE -CONSTRUCTION DRAINAGE AREAS CHARLOTTE, NC 28208 F _ O 1 REV D M Y ISSUEIREVISION DESCRIPTION ENG. APPR. TEL (704)357-8600 FAX:(704)357� wheeler AS NOTED LICENSURE: NC ENG: F-1253 NC GEOLOGY: C-247 WETLAND AREA(TVP.) /.�i i�/ ✓/ // f p s lllr 1 1 1 MOUNTAIN ISLAND LAKE / r // it � /�� � � —_, � � � � _ � I e]° „ � _ � , � ..� •� � _ ODTFALL 03 ��-' ��_�`-..•. COAL YARD e DUKE ENEROV _ � i � J� \ m $B-02 CORP❑ ORATION PID# 1]5022 PIN#4519542126 �� ` \ / `fO \. \� �2� \\1 \\, • 7 -- • � 11 \ \ 1� Q � � ` r 6 sTo V ��``� � - �650\ 1• C�I•i / , \\ - ORSE- -REA = �v Avv\VAAI�u� vI1��/' /if/{II�I11VAv\ I I I r �1 I LEGEND EXISTING GRADE INDEX CONTOUR (10') - - - - EXISTING GRADE INTERMEDIATE CONTOUR (2) PROPOSED GRADE INDEX CONTOUR (10') PROPOSED GRADE INTERMEDIATE CONTOUR (2) DURING -CONSTRUCTION DRAINAGE AREA . . TEMPORARY DIVERSION DITCH DRAINAGE AREA LOD LIMITS OF DISTURBANCE - - - - - - - WORK AREA BOUNDARY . OUTFALL LOCATION -_-� PROPERTY BOUNDARY WETLAND AREAS PRELIMINARY FOR PERMIT APPROVAL ONLY ( l STONEWATER OWNER ASSOCIATION INC. CORPORATION PID# 197763 PIN#4519422113 ASH STACK URBED AREA = 20.9 AC. E OF CONCENTRATION = 6. -..—'HTED CN = 91 CLEAN WATER DIVERSION DI DRAINAGE AREA = 6. TIME OF CONCENTRATION = 22-6 WEIGHTED C 1NC STATE DAM / ,i Ir GASTO-098 DISTURBED AREA = fi5.9 AC. Q H/ // / 13 TIME OF CONCENTRATION = 12.9 JN HTED CN = 91 PRIMARY ASH POND �0 /I�II/�2� �zo OUTFALL-01 \1,7 8 MOUNTAIN ISLAND LAKE 111 I I � �Op� II I I �/ 111A�11VAVA\�1 102 4 I I A�� AAVA�1VA/L c224 2 G7 9 v—vvvv\vvvvovv�� /// vv, 01�11`w // // o`I °III IIII I�I/���, 1�• ss. /i /• Co, \ 72I /// / IMITS OF DIS RBANCEi�� •/.�• _//�/�/'\�\\\ CORPORATION PIRD# GY 175022 1 / AlIII/IIII �� y II/ / // ^ /III /<f l f PIN#4519542126 <cb d'\ �-T Tf•{-�\off �s°- Ir/Y°., 1 \ s I \1'1\ \\ _ \\ \\� � � / ///�////////�f�// .� �\II 77-7 RRAINAGEAREA =8.3AC. E OF CONCENTRATION = IGHTEDCN=77 )PER BOUNDARY - DUKE ENERGY i - PRTY \ )\\\\ 11\\ r/ / ��., J l ate•/•/ \\\ l\) II 111/1' CORPORATION PID# 217766 HENDERSON CEMETERY STONEWATER OWNER \ \\\111 (111 / // ( 1 I • '4 "/I/l/lll//ll lPIN#4519730111 // JUDITH E. ROZZELLE I 1 ) // L• I ( ' / / //(� _ %�� ��_ \ \ \ I I Ill/ / // PID# 202721 ASSOCIATION INC. GORPORATION PID#207327 PIN#4519520433 PIN44619528048 - /- '/// I I 1 '/' •) / ( 11 \ \ \ ///�i/��� / // / / /'� \ \ \ \ \ \ l i f'III IJ�%// CLIENT LOGO: DUKE CLIENT. RGY CAROLINAS, LLC. DUKE ENEGASTRGCOUNTY, AS ON Zo amec - -. foster- wheeler DATUM: PROJECT: RIVERBEND STEAM STATION ASH POND CCR REMOVAL GRADING PLAN PROJECT NO.: 6226-14-0007 a CNB TITLE:ENERGY DURING -CONSTRUCTION DRAINAGE AREAS A PHASE DEC 2014 ® 13 11 201s ESC REVISIONS RIB Amec Foster Wheeler Environment & Infrastructure, Inc. 2801 VORKMONT ROAD, SUITE 100 CHARLOTTE, NC 28208 TEL (704)357-8W0 FAX:(704)357-038 TEL NC ENG: F-1253 NC GEOLOGY: C-247 B� DRAWING NO. F - 02 Q 31 12 2014 FOR DUKE REVIEW BC REV D M Y ISSUEIREVISION DESCRIPTION ENG. APPR. AS NOTED WETLAND AREA (TYR) 63 \\It\1\\I\ IIIIII r ( — 171 \)I III 111(1 I (• '58X2• �FX-. I / // JIII IIII 1\�I 1111 z� 1AAA�lj)$ %l MOUNTAIN ISLAND LAKE �� x )hIIII II; / �� - A� I IIIIIIV�11 j �IP o\\ a V A 1�11\V�A1AIp1/h/// �A�Vl `� vvAAA q� \ - l 1 v A `111 - 111V1A1 A �wv�\x 5���v •A\\C 40 �i(/\II�11111 I / f �1VAVAAII �E �i� J 1 � VAS A�VA\v x i VAk \oy� //� t �l///� �I� Ts a 1 ����-�JJ11� \ vwvvv-�AA� _ =AA�� ,�AVA�AA v�O� Cam- 19��`• -IT2�_ /%�=%///��5�J/1,I 'woRK AREA RouNt]ARv�'1 OUTFACE-03./.olr,/�67o/ Iio/�i 00 /�V � �-A- OUTF u- / / A� 1r IQ1p�VACOAL YARD 11 /l�llI�I�IIIIII IIII�IJIV�� QI� )']DUKE N �f 117,Ir\00� cP jlllllll/1; / 1��� ` n r' _ ��/ ♦ U / NI li 1111�1 \ ERGv - A7//// / - SECONDARY ASH POND (( (I 1 A\ CORPORATIONn PID# 5022 PIN#4519N#a5195az1261 p /SIB 03 I 212 7 NO STATE DAM ID '1 i CINDER PIT G 11 ��i 6 = \ ^ a�`�.—��SB-04 1ari� 7 DIS 34 vter. t _ i _^ >\ ,. / TUBBED AREA = 65.9 AC. I 1a3 3s •/• _ \, - - - - `-- - TIME OF CONCENTRATION = 12.9 - _-0 r)c13i� V % / se IED EI i ' 123i PRIMARY ASH POND �� 1 (�I II � � � x /1Z9 1 ouTFUL-o1 _ W _ - D is - - - v � y ♦ _ �_�- - - � �_ ; � < _ � / , ]_� ,. j1 �1 �1 'p EN EA A�Q2� - - �� I`� ✓/ j 1v39 N7 �16 S , U O CH / v II 11� HCR SN B MOUNTAIN ISLAND LAKE TURBEDAREA =22.4AC. d"Ib #V� \v F C Vv I •� / vv - �C A I /; / v \1��� 111 j G� - 1101 %//w mz DRY ASH STACK URBED AREA =�� EOFCONCENTRATION =6.9 GHTEDCN 91 t 750—jrAI l / / 24 �l�//il / / 1 " �- I fll 11 l l // �% AAVA�111 / 1 / c2z -1 7 \1v�VAAIIII 11�A�i/�%fllll�lll\�v�� �1 V�v w�VA\VAA�AVAoA�° �'vs� )/ �; 111\1\1 /I�ly�l/� 1\IIIIV\ -ice �� / � o�ill11111/ � 4%. LIMITS OF 019 RBANCE��/ •f.�• / f���\\�\\\`� LEGEND EXISTING GRADE INDEX CONTOUR (10') EXISTING GRADE INTERMEDIATE CONTOUR (2') PROPOSED GRADE INDEX CONTOUR (10') PROPOSED GRADE INTERMEDIATE CONTOUR (2') — DURING -CONSTRUCTION DRAINAGE AREA . . TEMPORARY DIVERSION DITCH DRAINAGE AREA LOD LIMITS OF DISTURBANCE — — — — — — — WORK AREA BOUNDARY . OUTFALL LOCATION ------- PROPERTY BOUNDARY EEEI WETLAND AREAS V� STONEWATER OWNER SOCIATION NCI \ \ \A� / / /(/ /I/ / CORPORATION PID# 197763 I \�.'\ \// Iii�i/��j //' _ DUKE ENERGY \ PIN#4519422113 ' \ / \ \ fi ^\�\\\ `/ J \� \. (pi /T/� ) \ I (� 1///6 1////11 A�/// \/��C! /)f ( I CORPORATION / 1,, ch; <� �{ / / , ///o( ,,III{\� / _--- I ))I? \\\\ �•I Il �l zI1\I\{Il 1//I%/ j//�II \ �\ _ �%/i \/.0'Ox 'ajll"1111)MI\\) I\\\\\I\\ \ \\ \- CLEAN WATER DIVERSI ' !/, DRAINAGE AREA=8.3AC. \ l ..`�t�'U(�//j%� ��\ J DRAINAGE AREA - `�� -_ - -' / / / / TIME OF CONCENTRATION /// TIME OF CONCENTRATION =_ \��_ - J ` �/ /1 !�i EIGHTED CN = 77 WEIGHT �--' !� \\\IIII\\\mil. i �( \lDUKE �//.I.i ENERGY `_ PROPERTY BOUNDARY \{ I / �f CORPORATION PID# 217766'i ) HENDERSON CEMETERY STONEWATER OWNER �— \ \\\ III I ( I , ,I I / / // / ( )f l /—_ / \ I// //' I , I �� PIN#4519730111 200 0 100 200 400 JUDI ID#2022721E. ELLE CORPORATIASSOCIATION ONIP D# 07327 -�`� l 1iI/ 1 1\I\\\� �/%1 / /—�'SI IIII\ll PIN#4519520433 PIN44519528046 _ /�/l/ f I (i / I I\\�-� 4✓ / / ( ill\ \\ \ 1///l��/ � /� /� i / / \ \ \ \ \ \ (1,1\)1(rPJ%// -.. CLIENT LOGO: CLIENT: DATUM: PROJECT: PROJECT NO.. NAD83 RIVERBEND STEAM STATION 6226-14-0007 DUKE ENERGY CAROLINAS, LLC. ASH POND CCR REMOVAL GRADING PLAN VI ION N a PRELIMINARY DUKE GASTON COUNTY, NC ENERGY 4A, °NB TITLE.DEC20,4 ® 13 11 2015 ESC REVISIONS PH Amec Foster Wheeler Environment & Infrastructure, Inc. amec DURING -CONSTRUCTION DRAINAGE AREAS DRAWING NO. FORPERMIT APPROVAL ONLY AA 31 12 2014 FOR DUKE REVIEW BC 2801YORKLOTTRN 2820TE100 foster 3C F - 03 CHARLOTTEFAX (OM) w{ eeler SCALE, PHASE 2 REV D M V ISSUEREVISION DESCRIPTION ENG. APPR. TEL: (]04)35]5600 FAX (/04)35]-8638 R IL AS NOTED LICENSURE: NO ENG: F-1253 NO GEOLOGY: C-247 ETLAND AREA (TYP ) — s� BID / � � _ u��l ol� — vV�� OVA. •�. i 00. I l �/b/ ourFALL-o3- llll III Ill v A /• A COAL YARD e OUTFALL DUKE ENERGY — 0 1 \ \ 7 — — 1 I I t CORPORATION PID# 1]5022 •- PIN#4519542126 - i � \ \\ /2j23�`—J \ 1 \\, • / 4 Ill 1 < � - -_ \ I ) 14�, •,� Jr v 50 i REA=60.7AC. \\ !¢z IME OF CONICENT nW "A��,I�I�VAVI��_\� ]30 _ - I rJ�v�VI\X�_ / /0- �v v AvvIItiN i IlA_/ /r/illl II Iv �_ ��_ l l l \ 1\) II!!,// / I\I II \ /. \ I � J / � 40, ill l`v \ STONEWATEi ASSOCIATIONON INC, INC. CORPORATION PID# 197763 LEGEND — • PINK 4519422113 \ �\ o, EXISTING INDEX CONTOUR (10') EXISTING INTERMEDIATE CONTOUR (2') PROPOSED INDEX CONTOUR (10') PROPOSED INTERMEDIATE CONTOUR (Z) — POST -CONSTRUCTION DRAINAGE AREA LOD — LIMITS OF DISTURBANCE — — — — — — — WORK AREA BOUNDARY . OUTFALL LOCATION ------ PROPERTY BOUNDARY �\ WETLAND AREAS PRELIMINARY FOR PERMIT APPROVAL ONLY X A Vv5 A�w I � Jv���( �� , MOUNTAIN ISLAND LAKE W\\ 1h REA BOUNDARY 231 23V 1] z 1/1411I 1 � • / J I � EW1'1 i I�r DDi C�� >pp iy, o AREA = 82.0 AC. TIME OF CONCENTRATION A §/ 141PI �l/14 is14 % 11'5 R1 tT J1s 4 7 5v 39 ' 134)�y 133 Y3 \ 5 • /• w OUTFACE-01 �..-79 /)Il�� /lll/��l 1//I/'l/1/l IIIII ml /ll1�lllllll���ll�l1 S5X,120. 1 / I ) Illllllll Il///I//I/ II / � III IIII �I//IIIII// ll�j//l/ >�� h �1g• MOUNTAIN ISLAND LAKE _ 680 If 1) \11111�>gg�Igg 11�1 >7p 680 of 1101 102 1 1tdQ3 or a Gz�24 710 \ v v vv vvv \vvv`1 >sp 720 LIMITS OF DISTURBANCE 4�/ — c ���✓ 00001����� < ;�� /y� I�,l(II I'..DUKE ENERGY %\/ 1A�w�� )III IIII/ ) •. 1� / / � �\ \ \ � \ - = � ( I / / J Ill/ III / l i I / \ / ! / I J ( / /2® CORPORATION PID# 175022 / jji\%"�/ \\ IIIIII ///�/ Ll� // \\\��� J�/ �_��� ��` �-_--�__�////, //�� \ / � �/ �/ IIIII ll III � I / i /, / /i%/i%/���/�_\o��i4//�� �_;- / lill�✓�li�\\l(I _�/�i�i/�/�%�/i �-%lllll�/ ./iPROPERTY BOUNDARY�/\ DUKE ENERGY I — \ I 1) //I CORPORATION PID#217766 H JUDETH E. ROZZELLE CEMETERY STASEWATSOCIATION NCER `-\ �.\ 1)\\IIIII ( I \)\ ( \ ( I I / / j / / l ill J/� ll/lam r PI N# 4519730117 PID#202721 CORP PIN#4519520433 PIN#45119521804807327 CLIENT LOGO: CLIENT: DUKE ENERGY CAROLINAS, LLC. r DATUM: NAD83 PROJECT: RIVERBEND STEAM STATION ASH POND CCR REMOVAL GRADING PLAN PROJECT NO.. 6226-14-0007 FIVIII.NN DUKE ENERGY GASTON COUNTY, NC � amen foster wheeler B CNB TREE POST -CONSTRUCTION DRAINAGE AREAS DATE DEC 2014 ® 13 11 2015 ESC REVISIONS RH Amec Foster Wheeler Environment & Infrastructure, Inc. 2801YORKMONTROAD ,SUITE 100 CHARLOTTE, NO 28208 TEL (704)357-8600 FAX: (704)357-6638 LIKENSUBE: NO ENS : F-1253 NC GEOLOGY: C-247 BC DRAWING NO. F - 04 AQ 31 12 2014 FOR DUKE REVIEW BC REV D M V ISSUE'REVISION DESCRIPTION ENG. APPR. ASI NiOf�D Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 Reference 1 RAINFALL DATA NOAA Atlas 14, Volume 2, Version 3 Location name: Mount Holly, North Carolina, US* Latitude: 35.3674°, Longitude: -80.9637° Elevation: 719 ft* * source: Google Maps POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF_tabular | PF_graphical | Maps_&_aerials PF tabular PDS-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 0.391 (0.361-0.424) 0.462 (0.427-0.503) 0.539 (0.497-0.586) 0.595 (0.547-0.645) 0.659 (0.602-0.713) 0.704 (0.640-0.762) 0.745 (0.673-0.806) 0.781 (0.701-0.847) 0.822 (0.730-0.894) 0.851 (0.748-0.929) 10-min 0.625 (0.577-0.677) 0.739 (0.683-0.804) 0.864 (0.796-0.938) 0.952 (0.874-1.03) 1.05 (0.960-1.14) 1.12 (1.02-1.21) 1.18 (1.07-1.28) 1.24 (1.11-1.34) 1.30 (1.15-1.42) 1.34 (1.18-1.46) 15-min 0.782 (0.721-0.846) 0.930 (0.858-1.01) 1.09 (1.01-1.19) 1.20 (1.11-1.30) 1.33 (1.22-1.44) 1.42 (1.29-1.54) 1.50 (1.35-1.62) 1.56 (1.40-1.69) 1.64 (1.45-1.78) 1.68 (1.48-1.84) 30-min 1.07 (0.989-1.16) 1.28 (1.19-1.40) 1.55 (1.43-1.69) 1.75 (1.60-1.89) 1.97 (1.80-2.13) 2.14 (1.94-2.31) 2.29 (2.07-2.48) 2.43 (2.18-2.64) 2.61 (2.31-2.83) 2.72 (2.40-2.97) 60-min 1.34 (1.23-1.45) 1.61 (1.49-1.75) 1.99 (1.83-2.16) 2.27 (2.09-2.46) 2.63 (2.40-2.84) 2.90 (2.63-3.13) 3.16 (2.85-3.41) 3.41 (3.06-3.70) 3.74 (3.32-4.07) 3.98 (3.50-4.34) 2-hr 1.55 (1.42-1.69) 1.87 (1.71-2.05) 2.33 (2.13-2.54) 2.67 (2.44-2.92) 3.12 (2.83-3.41) 3.47 (3.13-3.78) 3.81 (3.42-4.16) 4.15 (3.69-4.54) 4.60 (4.05-5.04) 4.94 (4.30-5.43) 3-hr 1.66 (1.52-1.82) 2.00 (1.83-2.19) 2.50 (2.28-2.74) 2.88 (2.63-3.16) 3.40 (3.09-3.72) 3.82 (3.44-4.18) 4.23 (3.79-4.63) 4.66 (4.14-5.11) 5.25 (4.58-5.76) 5.71 (4.92-6.28) 6-hr 2.02 (1.86-2.21) 2.43 (2.24-2.66) 3.04 (2.80-3.33) 3.52 (3.22-3.84) 4.17 (3.79-4.54) 4.69 (4.24-5.10) 5.21 (4.67-5.68) 5.75 (5.11-6.27) 6.50 (5.68-7.10) 7.09 (6.12-7.76) 12-hr 2.40 (2.21-2.61) 2.89 (2.67-3.16) 3.63 (3.34-3.96) 4.21 (3.86-4.58) 5.01 (4.56-5.44) 5.66 (5.11-6.14) 6.33 (5.66-6.85) 7.02 (6.21-7.60) 7.99 (6.95-8.64) 8.76 (7.52-9.49) 24-hr 2.75 (2.56-2.95) 3.32 (3.10-3.57) 4.17 (3.88-4.48) 4.84 (4.50-5.19) 5.75 (5.32-6.16) 6.47 (5.98-6.93) 7.21 (6.65-7.72) 7.96 (7.32-8.54) 8.99 (8.23-9.65) 9.79 (8.94-10.5) 2-day 3.23 (3.01-3.46) 3.88 (3.63-4.17) 4.84 (4.52-5.19) 5.59 (5.21-6.00) 6.61 (6.14-7.08) 7.42 (6.88-7.94) 8.24 (7.62-8.82) 9.08 (8.38-9.72) 10.2 (9.40-11.0) 11.1 (10.2-11.9) 3-day 3.43 (3.20-3.67) 4.12 (3.85-4.41) 5.11 (4.77-5.46) 5.88 (5.48-6.29) 6.94 (6.45-7.42) 7.78 (7.21-8.32) 8.64 (7.99-9.23) 9.51 (8.78-10.2) 10.7 (9.84-11.5) 11.6 (10.7-12.4) 4-day 3.63 (3.39-3.88) 4.35 (4.07-4.66) 5.37 (5.01-5.74) 6.17 (5.75-6.59) 7.27 (6.76-7.77) 8.15 (7.55-8.69) 9.03 (8.36-9.64) 9.94 (9.17-10.6) 11.2 (10.3-12.0) 12.1 (11.1-13.0) 7-day 4.18 (3.93-4.44) 4.98 (4.69-5.29) 6.06 (5.70-6.44) 6.92 (6.49-7.34) 8.10 (7.57-8.59) 9.03 (8.43-9.59) 9.98 (9.29-10.6) 11.0 (10.2-11.7) 12.3 (11.4-13.1) 13.3 (12.3-14.2) 10-day 4.78 (4.51-5.09) 5.69 (5.36-6.05) 6.84 (6.43-7.27) 7.73 (7.27-8.22) 8.94 (8.38-9.50) 9.88 (9.25-10.5) 10.8 (10.1-11.5) 11.8 (11.0-12.5) 13.1 (12.2-13.9) 14.1 (13.1-15.0) 20-day 6.42 (6.09-6.78) 7.58 (7.18-8.00) 8.94 (8.47-9.44) 10.0 (9.48-10.6) 11.5 (10.8-12.1) 12.6 (11.9-13.3) 13.7 (12.9-14.5) 14.9 (13.9-15.7) 16.4 (15.3-17.4) 17.6 (16.4-18.7) 30-day 7.92 (7.54-8.33) 9.32 (8.86-9.79) 10.8 (10.3-11.4) 12.0 (11.4-12.6) 13.5 (12.8-14.2) 14.7 (13.9-15.5) 15.9 (15.0-16.7) 17.0 (16.0-17.9) 18.6 (17.4-19.6) 19.7 (18.4-20.8) 45-day 9.95 (9.53-10.4) 11.6 (11.1-12.2) 13.3 (12.7-13.9) 14.6 (13.9-15.2) 16.2 (15.4-16.9) 17.4 (16.6-18.2) 18.6 (17.7-19.5) 19.8 (18.8-20.8) 21.3 (20.2-22.4) 22.4 (21.2-23.6) 60-day 11.8 (11.4-12.4) 13.8 (13.2-14.4) 15.6 (14.9-16.2) 17.0 (16.2-17.7) 18.7 (17.9-19.5) 20.1 (19.2-20.9) 21.3 (20.4-22.3) 22.6 (21.5-23.6) 24.2 (23.0-25.3) 25.4 (24.1-26.6) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top PF graphical Page 1 of 4Precipitation Frequency Data Server 7/8/2014http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.3674&lon=-80.9637&data=... Back to Top Maps & aerials Small scale terrain Map data ©2014 GoogleReport a map error50 km Page 2 of 4Precipitation Frequency Data Server 7/8/2014http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.3674&lon=-80.9637&data=... Large scale terrain Large scale map Large scale aerial Back to Top US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service Office of Hydrologic Development 1325 East West Highway Silver Spring, MD 20910 Map data © 2014 GoogleReport a map error2 km Map data © 2014 GoogleReport a map error2 km Imagery ©2014 TerraM etricsReport a map error2 km Page 3 of 4Precipitation Frequency Data Server 7/8/2014http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.3674&lon=-80.9637&data=... Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 Reference 2 PRE-CONSTRUCTION HYDROCAD OUTPUT 1S PRE DA - 03 2S PRE DA - 02 3S PRE DA - 01 14L Total Off-Site Runoff Routing Diagram for Riverbend Ash Pond Closure Prepared by AMEC, Printed 11/5/2015 HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 34.000 92 Ash, HSG B (3S) 0.926 85 Gravel roads, HSG B (1S, 2S) 1.610 89 Gravel roads, HSG C (3S) 29.634 69 Pasture/grassland/range, Fair, HSG B (1S, 2S) 28.770 79 Pasture/grassland/range, Fair, HSG C (3S) 1.240 98 Paved roads w/curbs & sewers, HSG B (2S) 3.730 88 Railbed - Gravel (1S, 2S) 20.900 98 Water Surface, HSG C (3S) 16.010 60 Woods, Fair, HSG B (1S, 2S) 8.770 73 Woods, Fair, HSG C (3S) 8.950 65 Woods/grass comb., Fair, HSG B (1S, 2S) 0.950 76 Woods/grass comb., Fair, HSG C (3S) 155.490 80 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Soil Listing (selected nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 90.760 HSG B 1S, 2S, 3S 61.000 HSG C 3S 0.000 HSG D 3.730 Other 1S, 2S 155.490 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.000 34.000 0.000 0.000 0.000 34.000 Ash 3S 0.000 0.926 1.610 0.000 0.000 2.536 Gravel roads 1S, 2S, 3S 0.000 29.634 28.770 0.000 0.000 58.404 Pasture/grassland/range, Fair 1S, 2S, 3S 0.000 1.240 0.000 0.000 0.000 1.240 Paved roads w/curbs & sewers 2S 0.000 0.000 0.000 0.000 3.730 3.730 Railbed - Gravel 1S, 2S 0.000 0.000 20.900 0.000 0.000 20.900 Water Surface 3S 0.000 16.010 8.770 0.000 0.000 24.780 Woods, Fair 1S, 2S, 3S 0.000 8.950 0.950 0.000 0.000 9.900 Woods/grass comb., Fair 1S, 2S, 3S 0.000 90.760 61.000 0.000 3.730 155.490 TOTAL AREA Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: PRE DA - 03 Runoff = 8.77 cfs @ 12.32 hrs, Volume= 1.169 af, Depth= 0.50" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 4.660 65 Woods/grass comb., Fair, HSG B 7.000 60 Woods, Fair, HSG B * 2.190 88 Railbed - Gravel 0.830 85 Gravel roads, HSG B 13.240 69 Pasture/grassland/range, Fair, HSG B 27.920 68 Weighted Average 27.920 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.3 100 0.0100 0.15 Sheet Flow, Range n= 0.130 P2= 3.32" 2.7 870 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.3 135 0.0400 7.49 23.53 Pipe Channel, CMP_Round 24" 24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50' n= 0.025 Corrugated metal 17.3 835 0.0260 0.81 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 31.6 1,940 Total Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 1S: PRE DA - 03 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 9 8 7 6 5 4 3 2 1 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=27.920 ac Runoff Volume=1.169 af Runoff Depth=0.50" Flow Length=1,940' Tc=31.6 min CN=68 8.77 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: PRE DA - 02 Runoff = 9.72 cfs @ 12.36 hrs, Volume= 1.363 af, Depth= 0.50" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 4.290 65 Woods/grass comb., Fair, HSG B 9.010 60 Woods, Fair, HSG B * 1.540 88 Railbed - Gravel 0.096 85 Gravel roads, HSG B 1.240 98 Paved roads w/curbs & sewers, HSG B 16.394 69 Pasture/grassland/range, Fair, HSG B 32.570 68 Weighted Average 31.330 96.19% Pervious Area 1.240 3.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.9 100 0.0300 0.09 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 2.4 160 0.0500 1.12 Shallow Concentrated Flow, Woods Woodland Kv= 5.0 fps 2.3 246 0.0120 1.76 Shallow Concentrated Flow, Grass Unpaved Kv= 16.1 fps 2.2 555 0.0468 4.24 31.82 Channel Flow, Grass Swale Area= 7.5 sf Perim= 30.1' r= 0.25' n= 0.030 2.2 692 0.0810 5.23 39.25 Channel Flow, Rip Rap Swale Area= 7.5 sf Perim= 30.1' r= 0.25' n= 0.032 6.4 395 0.0150 1.03 15.48 Channel Flow, Area= 15.0 sf Perim= 60.0' r= 0.25' n= 0.070 0.6 200 0.0200 5.30 16.64 Pipe Channel, CMP_Round 24" 24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50' n= 0.025 Corrugated metal 34.0 2,348 Total Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 2S: PRE DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 10 9 8 7 6 5 4 3 2 1 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=32.570 ac Runoff Volume=1.363 af Runoff Depth=0.50" Flow Length=2,348' Tc=34.0 min CN=68 9.72 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: PRE DA - 01 Runoff = 126.66 cfs @ 12.24 hrs, Volume= 12.056 af, Depth= 1.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 1.610 89 Gravel roads, HSG C * 34.000 92 Ash, HSG B 20.900 98 Water Surface, HSG C 0.950 76 Woods/grass comb., Fair, HSG C 8.770 73 Woods, Fair, HSG C 28.770 79 Pasture/grassland/range, Fair, HSG C 95.000 87 Weighted Average 74.100 78.00% Pervious Area 20.900 22.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods Woods: Light underbrush n= 0.400 P2= 3.32" 2.3 225 0.1100 1.66 Shallow Concentrated Flow, Woods Woodland Kv= 5.0 fps 0.8 290 0.1300 5.80 Shallow Concentrated Flow, Grass Unpaved Kv= 16.1 fps 2.8 335 0.0150 1.97 Shallow Concentrated Flow, Ash Unpaved Kv= 16.1 fps 2.4 3,675 25.38 Lake or Reservoir, Ash Ponds Mean Depth= 20.00' 29.4 4,625 Total Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 3S: PRE DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 140 120 100 80 60 40 20 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=95.000 ac Runoff Volume=12.056 af Runoff Depth=1.52" Flow Length=4,625' Tc=29.4 min CN=87 126.66 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 14L: Total Off-Site Runoff Inflow Area = 155.490 ac, 14.24% Impervious, Inflow Depth = 1.13" for 1yr - 24 hrs event Inflow = 143.32 cfs @ 12.25 hrs, Volume= 14.587 af Primary = 143.32 cfs @ 12.25 hrs, Volume= 14.587 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 14L: Total Off-Site Runoff Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 160 140 120 100 80 60 40 20 0 Inflow Area=155.490 ac 143.32 cfs143.32 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: PRE DA - 03 Runoff = 15.80 cfs @ 12.30 hrs, Volume= 1.858 af, Depth= 0.80" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 4.660 65 Woods/grass comb., Fair, HSG B 7.000 60 Woods, Fair, HSG B * 2.190 88 Railbed - Gravel 0.830 85 Gravel roads, HSG B 13.240 69 Pasture/grassland/range, Fair, HSG B 27.920 68 Weighted Average 27.920 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.3 100 0.0100 0.15 Sheet Flow, Range n= 0.130 P2= 3.32" 2.7 870 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.3 135 0.0400 7.49 23.53 Pipe Channel, CMP_Round 24" 24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50' n= 0.025 Corrugated metal 17.3 835 0.0260 0.81 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 31.6 1,940 Total Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 1S: PRE DA - 03 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 16 14 12 10 8 6 4 2 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=27.920 ac Runoff Volume=1.858 af Runoff Depth=0.80" Flow Length=1,940' Tc=31.6 min CN=68 15.80 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: PRE DA - 02 Runoff = 17.50 cfs @ 12.34 hrs, Volume= 2.168 af, Depth= 0.80" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 4.290 65 Woods/grass comb., Fair, HSG B 9.010 60 Woods, Fair, HSG B * 1.540 88 Railbed - Gravel 0.096 85 Gravel roads, HSG B 1.240 98 Paved roads w/curbs & sewers, HSG B 16.394 69 Pasture/grassland/range, Fair, HSG B 32.570 68 Weighted Average 31.330 96.19% Pervious Area 1.240 3.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.9 100 0.0300 0.09 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 2.4 160 0.0500 1.12 Shallow Concentrated Flow, Woods Woodland Kv= 5.0 fps 2.3 246 0.0120 1.76 Shallow Concentrated Flow, Grass Unpaved Kv= 16.1 fps 2.2 555 0.0468 4.24 31.82 Channel Flow, Grass Swale Area= 7.5 sf Perim= 30.1' r= 0.25' n= 0.030 2.2 692 0.0810 5.23 39.25 Channel Flow, Rip Rap Swale Area= 7.5 sf Perim= 30.1' r= 0.25' n= 0.032 6.4 395 0.0150 1.03 15.48 Channel Flow, Area= 15.0 sf Perim= 60.0' r= 0.25' n= 0.070 0.6 200 0.0200 5.30 16.64 Pipe Channel, CMP_Round 24" 24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50' n= 0.025 Corrugated metal 34.0 2,348 Total Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 2S: PRE DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 18 16 14 12 10 8 6 4 2 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=32.570 ac Runoff Volume=2.168 af Runoff Depth=0.80" Flow Length=2,348' Tc=34.0 min CN=68 17.50 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: PRE DA - 01 Runoff = 168.27 cfs @ 12.23 hrs, Volume= 16.003 af, Depth= 2.02" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 1.610 89 Gravel roads, HSG C * 34.000 92 Ash, HSG B 20.900 98 Water Surface, HSG C 0.950 76 Woods/grass comb., Fair, HSG C 8.770 73 Woods, Fair, HSG C 28.770 79 Pasture/grassland/range, Fair, HSG C 95.000 87 Weighted Average 74.100 78.00% Pervious Area 20.900 22.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods Woods: Light underbrush n= 0.400 P2= 3.32" 2.3 225 0.1100 1.66 Shallow Concentrated Flow, Woods Woodland Kv= 5.0 fps 0.8 290 0.1300 5.80 Shallow Concentrated Flow, Grass Unpaved Kv= 16.1 fps 2.8 335 0.0150 1.97 Shallow Concentrated Flow, Ash Unpaved Kv= 16.1 fps 2.4 3,675 25.38 Lake or Reservoir, Ash Ponds Mean Depth= 20.00' 29.4 4,625 Total Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 3S: PRE DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=95.000 ac Runoff Volume=16.003 af Runoff Depth=2.02" Flow Length=4,625' Tc=29.4 min CN=87 168.27 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 14L: Total Off-Site Runoff Inflow Area = 155.490 ac, 14.24% Impervious, Inflow Depth = 1.55" for 2yr - 24hrs event Inflow = 199.40 cfs @ 12.25 hrs, Volume= 20.029 af Primary = 199.40 cfs @ 12.25 hrs, Volume= 20.029 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 14L: Total Off-Site Runoff Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 220 200 180 160 140 120 100 80 60 40 20 0 Inflow Area=155.490 ac 199.40 cfs199.40 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: PRE DA - 03 Runoff = 39.28 cfs @ 12.28 hrs, Volume= 4.110 af, Depth= 1.77" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 4.660 65 Woods/grass comb., Fair, HSG B 7.000 60 Woods, Fair, HSG B * 2.190 88 Railbed - Gravel 0.830 85 Gravel roads, HSG B 13.240 69 Pasture/grassland/range, Fair, HSG B 27.920 68 Weighted Average 27.920 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.3 100 0.0100 0.15 Sheet Flow, Range n= 0.130 P2= 3.32" 2.7 870 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.3 135 0.0400 7.49 23.53 Pipe Channel, CMP_Round 24" 24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50' n= 0.025 Corrugated metal 17.3 835 0.0260 0.81 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 31.6 1,940 Total Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 20HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 1S: PRE DA - 03 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 40 35 30 25 20 15 10 5 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=27.920 ac Runoff Volume=4.110 af Runoff Depth=1.77" Flow Length=1,940' Tc=31.6 min CN=68 39.28 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 21HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: PRE DA - 02 Runoff = 43.61 cfs @ 12.31 hrs, Volume= 4.795 af, Depth= 1.77" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 4.290 65 Woods/grass comb., Fair, HSG B 9.010 60 Woods, Fair, HSG B * 1.540 88 Railbed - Gravel 0.096 85 Gravel roads, HSG B 1.240 98 Paved roads w/curbs & sewers, HSG B 16.394 69 Pasture/grassland/range, Fair, HSG B 32.570 68 Weighted Average 31.330 96.19% Pervious Area 1.240 3.81% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.9 100 0.0300 0.09 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 2.4 160 0.0500 1.12 Shallow Concentrated Flow, Woods Woodland Kv= 5.0 fps 2.3 246 0.0120 1.76 Shallow Concentrated Flow, Grass Unpaved Kv= 16.1 fps 2.2 555 0.0468 4.24 31.82 Channel Flow, Grass Swale Area= 7.5 sf Perim= 30.1' r= 0.25' n= 0.030 2.2 692 0.0810 5.23 39.25 Channel Flow, Rip Rap Swale Area= 7.5 sf Perim= 30.1' r= 0.25' n= 0.032 6.4 395 0.0150 1.03 15.48 Channel Flow, Area= 15.0 sf Perim= 60.0' r= 0.25' n= 0.070 0.6 200 0.0200 5.30 16.64 Pipe Channel, CMP_Round 24" 24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50' n= 0.025 Corrugated metal 34.0 2,348 Total Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 22HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 2S: PRE DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 45 40 35 30 25 20 15 10 5 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=32.570 ac Runoff Volume=4.795 af Runoff Depth=1.77" Flow Length=2,348' Tc=34.0 min CN=68 43.61 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 23HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: PRE DA - 01 Runoff = 281.98 cfs @ 12.23 hrs, Volume= 27.050 af, Depth= 3.42" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 1.610 89 Gravel roads, HSG C * 34.000 92 Ash, HSG B 20.900 98 Water Surface, HSG C 0.950 76 Woods/grass comb., Fair, HSG C 8.770 73 Woods, Fair, HSG C 28.770 79 Pasture/grassland/range, Fair, HSG C 95.000 87 Weighted Average 74.100 78.00% Pervious Area 20.900 22.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods Woods: Light underbrush n= 0.400 P2= 3.32" 2.3 225 0.1100 1.66 Shallow Concentrated Flow, Woods Woodland Kv= 5.0 fps 0.8 290 0.1300 5.80 Shallow Concentrated Flow, Grass Unpaved Kv= 16.1 fps 2.8 335 0.0150 1.97 Shallow Concentrated Flow, Ash Unpaved Kv= 16.1 fps 2.4 3,675 25.38 Lake or Reservoir, Ash Ponds Mean Depth= 20.00' 29.4 4,625 Total Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 24HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcatchment 3S: PRE DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 300 250 200 150 100 50 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=95.000 ac Runoff Volume=27.050 af Runoff Depth=3.42" Flow Length=4,625' Tc=29.4 min CN=87 281.98 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 25HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 14L: Total Off-Site Runoff Inflow Area = 155.490 ac, 14.24% Impervious, Inflow Depth = 2.77" for 10yr - 24hrs event Inflow = 361.79 cfs @ 12.24 hrs, Volume= 35.955 af Primary = 361.79 cfs @ 12.24 hrs, Volume= 35.955 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 14L: Total Off-Site Runoff Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 400 350 300 250 200 150 100 50 0 Inflow Area=155.490 ac 361.79 cfs361.79 cfs Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 Reference 3 DURING-CONSTRUCTION HYDROCAD OUTPUT 4S DURING CONSTRUCTION DA - 01 5S DURING CONSTRUCTION DA - 02 6S DURING CONSTRUCTION DA - 03A 7S DURING CONSTRUCTION DA - 04 9S DURING CONSTRUCTION DA - 03B 18S DURING CONSTRUCTION DA - 01 19S DURING CONSTRUCTION DA - 02 25S DURING CONSTRUCTION DA - 04 26S DURING CONSTRUCTION DA - 03A 16P SB-01 17P SB-02 18P SB-04 21P SB-05 24P SB-03 8L Total 10L Total 20L Total 26L Total Routing Diagram for Riverbend Ash Pond Closure Prepared by AMEC, Printed 11/5/2015 HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 1.130 85 Gravel roads, HSG B (9S) 73.000 86 Newly graded area, HSG B (6S, 7S, 25S, 26S) 173.600 91 Newly graded area, HSG C (4S, 5S, 18S, 19S) 4.740 69 Pasture/grassland/range, Fair, HSG B (9S) 1.230 98 Paved parking, HSG B (9S) 1.530 88 Railbed - Gravel (9S) 8.520 60 Woods, Fair, HSG B (9S) 3.220 65 Woods/grass comb., Fair, HSG B (9S) 266.970 88 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Soil Listing (selected nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 91.840 HSG B 6S, 7S, 9S, 25S, 26S 173.600 HSG C 4S, 5S, 18S, 19S 0.000 HSG D 1.530 Other 9S 266.970 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.000 1.130 0.000 0.000 0.000 1.130 Gravel roads 9S 0.000 73.000 173.600 0.000 0.000 246.600 Newly graded area 4S, 5S, 6S, 7S, 18S, 19S, 25S, 26S 0.000 4.740 0.000 0.000 0.000 4.740 Pasture/grassland/range, Fair 9S 0.000 1.230 0.000 0.000 0.000 1.230 Paved parking 9S 0.000 0.000 0.000 0.000 1.530 1.530 Railbed - Gravel 9S 0.000 8.520 0.000 0.000 0.000 8.520 Woods, Fair 9S 0.000 3.220 0.000 0.000 0.000 3.220 Woods/grass comb., Fair 9S 0.000 91.840 173.600 0.000 1.530 266.970 TOTAL AREA Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: DURING CONSTRUCTION DA - 01 Runoff = 164.35 cfs @ 12.05 hrs, Volume= 10.101 af, Depth= 1.84" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 65.900 91 Newly graded area, HSG C 65.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.0150 0.37 Sheet Flow, Fallow n= 0.050 P2= 3.32" 8.4 1,150 0.0200 2.28 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 12.9 1,250 Total Subcatchment 4S: DURING CONSTRUCTION DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=65.900 ac Runoff Volume=10.101 af Runoff Depth=1.84" Flow Length=1,250' Tc=12.9 min CN=91 164.35 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: DURING CONSTRUCTION DA - 02 Runoff = 63.21 cfs @ 11.98 hrs, Volume= 3.204 af, Depth= 1.84" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 20.900 91 Newly graded area, HSG C 20.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.1600 0.96 Sheet Flow, Fallow n= 0.050 P2= 3.32" 5.2 1,220 0.0600 3.94 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 6.9 1,320 Total Subcatchment 5S: DURING CONSTRUCTION DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 70 60 50 40 30 20 10 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=20.900 ac Runoff Volume=3.204 af Runoff Depth=1.84" Flow Length=1,320' Tc=6.9 min CN=91 63.21 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: DURING CONSTRUCTION DA - 03A [49] Hint: Tc<2dt may require smaller dt Runoff = 56.73 cfs @ 11.97 hrs, Volume= 2.708 af, Depth= 1.45" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 22.400 86 Newly graded area, HSG B 22.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 2.4 100 0.0700 0.69 Sheet Flow, Fallow n= 0.050 P2= 3.32" 1.4 450 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.8 750 0.0200 7.07 113.09 Channel Flow, Temporary Diversion Area= 16.0 sf Perim= 29.0' r= 0.55' n= 0.020 5.6 1,300 Total Subcatchment 6S: DURING CONSTRUCTION DA - 03A Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 60 55 50 45 40 35 30 25 20 15 10 5 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=22.400 ac Runoff Volume=2.708 af Runoff Depth=1.45" Flow Length=1,300' Tc=5.6 min CN=86 56.73 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 7S: DURING CONSTRUCTION DA - 04 [49] Hint: Tc<2dt may require smaller dt Runoff = 36.68 cfs @ 11.96 hrs, Volume= 1.704 af, Depth= 1.45" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 14.100 86 Newly graded area, HSG B 14.100 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 7S: DURING CONSTRUCTION DA - 04 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 40 35 30 25 20 15 10 5 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=14.100 ac Runoff Volume=1.704 af Runoff Depth=1.45" Tc=5.0 min CN=86 36.68 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 9S: DURING CONSTRUCTION DA - 03B Runoff = 8.52 cfs @ 12.22 hrs, Volume= 0.917 af, Depth= 0.54" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 8.520 60 Woods, Fair, HSG B 3.220 65 Woods/grass comb., Fair, HSG B 1.130 85 Gravel roads, HSG B 1.230 98 Paved parking, HSG B * 1.530 88 Railbed - Gravel 4.740 69 Pasture/grassland/range, Fair, HSG B 20.370 69 Weighted Average 19.140 93.96% Pervious Area 1.230 6.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 3.6 740 0.0460 3.45 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 24.7 840 Total Subcatchment 9S: DURING CONSTRUCTION DA - 03B Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 9 8 7 6 5 4 3 2 1 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=20.370 ac Runoff Volume=0.917 af Runoff Depth=0.54" Flow Length=840' Tc=24.7 min CN=69 8.52 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 18S: DURING CONSTRUCTION DA - 01 Runoff = 164.35 cfs @ 12.05 hrs, Volume= 10.101 af, Depth= 1.84" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 65.900 91 Newly graded area, HSG C 65.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.0150 0.37 Sheet Flow, Fallow n= 0.050 P2= 3.32" 8.4 1,150 0.0200 2.28 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 12.9 1,250 Total Subcatchment 18S: DURING CONSTRUCTION DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=65.900 ac Runoff Volume=10.101 af Runoff Depth=1.84" Flow Length=1,250' Tc=12.9 min CN=91 164.35 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 19S: DURING CONSTRUCTION DA - 02 Runoff = 63.21 cfs @ 11.98 hrs, Volume= 3.204 af, Depth= 1.84" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 20.900 91 Newly graded area, HSG C 20.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.1600 0.96 Sheet Flow, Fallow n= 0.050 P2= 3.32" 5.2 1,220 0.0600 3.94 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 6.9 1,320 Total Subcatchment 19S: DURING CONSTRUCTION DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 70 60 50 40 30 20 10 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=20.900 ac Runoff Volume=3.204 af Runoff Depth=1.84" Flow Length=1,320' Tc=6.9 min CN=91 63.21 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 25S: DURING CONSTRUCTION DA - 04 [49] Hint: Tc<2dt may require smaller dt Runoff = 36.68 cfs @ 11.96 hrs, Volume= 1.704 af, Depth= 1.45" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 14.100 86 Newly graded area, HSG B 14.100 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 25S: DURING CONSTRUCTION DA - 04 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 40 35 30 25 20 15 10 5 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=14.100 ac Runoff Volume=1.704 af Runoff Depth=1.45" Tc=5.0 min CN=86 36.68 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 26S: DURING CONSTRUCTION DA - 03A [49] Hint: Tc<2dt may require smaller dt Runoff = 56.73 cfs @ 11.97 hrs, Volume= 2.708 af, Depth= 1.45" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 22.400 86 Newly graded area, HSG B 22.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 2.4 100 0.0700 0.69 Sheet Flow, Fallow n= 0.050 P2= 3.32" 1.4 450 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.8 750 0.0200 7.07 113.09 Channel Flow, Temporary Diversion Area= 16.0 sf Perim= 29.0' r= 0.55' n= 0.020 5.6 1,300 Total Subcatchment 26S: DURING CONSTRUCTION DA - 03A Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 60 55 50 45 40 35 30 25 20 15 10 5 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=22.400 ac Runoff Volume=2.708 af Runoff Depth=1.45" Flow Length=1,300' Tc=5.6 min CN=86 56.73 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 16P: SB-01 Inflow Area = 42.770 ac, 2.88% Impervious, Inflow Depth = 1.02" for 1yr - 24 hrs event Inflow = 58.31 cfs @ 11.97 hrs, Volume= 3.625 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 674.23' @ 25.45 hrs Surf.Area= 43,380 sf Storage= 157,889 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 670.00' 871,295 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 670.00 31,595 0 0 672.00 36,915 68,510 68,510 674.00 42,640 79,555 148,065 676.00 49,120 91,760 239,825 678.00 58,856 107,976 347,801 680.00 74,771 133,627 481,428 682.00 95,853 170,624 652,052 684.00 123,390 219,243 871,295 Pond 16P: SB-01 Inflow Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Inflow Area=42.770 ac Peak Elev=674.23' Storage=157,889 cf 58.31 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 17P: SB-02 Inflow Area = 14.100 ac, 0.00% Impervious, Inflow Depth = 1.45" for 1yr - 24 hrs event Inflow = 36.68 cfs @ 11.96 hrs, Volume= 1.704 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 654.79' @ 24.35 hrs Surf.Area= 34,568 sf Storage= 74,239 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 652.00' 195,565 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 652.00 14,641 0 0 654.00 33,039 47,680 47,680 656.00 36,932 69,971 117,651 658.00 40,982 77,914 195,565 Pond 17P: SB-02 Inflow Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 40 35 30 25 20 15 10 5 0 Inflow Area=14.100 ac Peak Elev=654.79' Storage=74,239 cf 36.68 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 18P: SB-04 Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 1.84" for 1yr - 24 hrs event Inflow = 215.75 cfs @ 12.02 hrs, Volume= 13.305 af Outflow = 2.26 cfs @ 11.85 hrs, Volume= 13.021 af, Atten= 99%, Lag= 0.0 min Primary = 2.26 cfs @ 11.85 hrs, Volume= 13.021 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 675.09' @ 24.05 hrs Surf.Area= 185,155 sf Storage= 474,129 cf Plug-Flow detention time= 2,014.8 min calculated for 13.015 af (98% of inflow) Center-of-Mass det. time= 2,003.4 min ( 2,813.6 - 810.2 ) Volume Invert Avail.Storage Storage Description #1 672.00' 1,435,854 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 672.00 94,232 0 0 674.00 180,443 274,675 274,675 676.00 189,080 369,523 644,198 678.00 197,875 386,955 1,031,153 680.00 206,826 404,701 1,435,854 Device Routing Invert Outlet Devices #1 Primary 672.00'24.0" Round CMP_Round 24" L= 150.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 672.00' / 670.00' S= 0.0133 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 676.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 672.00'2.260 cfs Constant Flow/Skimmer #4 Primary 677.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 Width (feet) 20.00 25.00 30.00 Primary OutFlow Max=2.26 cfs @ 11.85 hrs HW=672.89' (Free Discharge) 1=CMP_Round 24" (Passes 2.26 cfs of 3.23 cfs potential flow) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 3=Constant Flow/Skimmer (Constant Controls 2.26 cfs) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 18P: SB-04 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 240 220 200 180 160 140 120 100 80 60 40 20 0 Inflow Area=86.800 ac Peak Elev=675.09' Storage=474,129 cf 215.75 cfs 2.26 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 21P: SB-05 Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 1.84" for 1yr - 24 hrs event Inflow = 215.75 cfs @ 12.02 hrs, Volume= 13.305 af Outflow = 2.26 cfs @ 11.80 hrs, Volume= 13.080 af, Atten= 99%, Lag= 0.0 min Primary = 2.26 cfs @ 11.80 hrs, Volume= 13.080 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 653.20' @ 24.05 hrs Surf.Area= 179,780 sf Storage= 472,920 cf Plug-Flow detention time= 2,004.0 min calculated for 13.075 af (98% of inflow) Center-of-Mass det. time= 1,995.2 min ( 2,805.4 - 810.2 ) Volume Invert Avail.Storage Storage Description #1 650.00' 2,092,446 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 650.00 100,077 0 0 652.00 165,087 265,164 265,164 654.00 189,476 354,563 619,727 656.00 214,653 404,129 1,023,856 658.00 261,346 475,999 1,499,855 660.00 331,245 592,591 2,092,446 Device Routing Invert Outlet Devices #1 Primary 650.00'24.0" Round CMP_Round 24" L= 150.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 650.00' / 646.00' S= 0.0267 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 654.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 650.00'2.260 cfs Constant Flow/Skimmer #4 Primary 655.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 Width (feet) 20.00 25.00 30.00 Primary OutFlow Max=2.26 cfs @ 11.80 hrs HW=650.76' (Free Discharge) 1=CMP_Round 24" (Passes 2.26 cfs of 3.27 cfs potential flow) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 3=Constant Flow/Skimmer (Constant Controls 2.26 cfs) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 21P: SB-05 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 240 220 200 180 160 140 120 100 80 60 40 20 0 Inflow Area=86.800 ac Peak Elev=653.20' Storage=472,920 cf 215.75 cfs 2.26 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 20HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 24P: SB-03 Inflow Area = 36.500 ac, 0.00% Impervious, Inflow Depth = 1.45" for 1yr - 24 hrs event Inflow = 93.32 cfs @ 11.96 hrs, Volume= 4.412 af Outflow = 1.13 cfs @ 11.70 hrs, Volume= 4.404 af, Atten= 99%, Lag= 0.0 min Primary = 1.13 cfs @ 11.70 hrs, Volume= 4.404 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 654.45' @ 19.88 hrs Surf.Area= 90,019 sf Storage= 141,880 cf Plug-Flow detention time= 1,295.6 min calculated for 4.404 af (100% of inflow) Center-of-Mass det. time= 1,294.6 min ( 2,120.2 - 825.6 ) Volume Invert Avail.Storage Storage Description #1 652.00' 688,748 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 652.00 20,697 0 0 653.00 47,259 33,978 33,978 654.00 88,689 67,974 101,952 655.00 91,666 90,178 192,130 656.00 94,682 93,174 285,304 657.00 97,737 96,210 381,513 658.00 100,832 99,285 480,798 659.00 103,965 102,399 583,196 660.00 107,139 105,552 688,748 Device Routing Invert Outlet Devices #1 Primary 652.00'24.0" Round CMP_Round 24" L= 200.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 652.00' / 650.00' S= 0.0100 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 656.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 652.00'1.130 cfs Constant Flow/Skimmer #4 Primary 657.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 Width (feet) 20.00 25.00 30.00 35.00 Primary OutFlow Max=1.13 cfs @ 11.70 hrs HW=652.58' (Free Discharge) 1=CMP_Round 24" (Passes 1.13 cfs of 1.21 cfs potential flow) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 3=Constant Flow/Skimmer (Constant Controls 1.13 cfs) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 21HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 24P: SB-03 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 100 90 80 70 60 50 40 30 20 10 0 Inflow Area=36.500 ac Peak Elev=654.45' Storage=141,880 cf 93.32 cfs 1.13 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 22HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 8L: Total Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 1.84" for 1yr - 24 hrs event Inflow = 215.75 cfs @ 12.02 hrs, Volume= 13.305 af Primary = 215.75 cfs @ 12.02 hrs, Volume= 13.305 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 8L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 240 220 200 180 160 140 120 100 80 60 40 20 0 Inflow Area=86.800 ac 215.75 cfs215.75 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 23HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 10L: Total Inflow Area = 42.770 ac, 2.88% Impervious, Inflow Depth = 1.02" for 1yr - 24 hrs event Inflow = 58.31 cfs @ 11.97 hrs, Volume= 3.625 af Primary = 58.31 cfs @ 11.97 hrs, Volume= 3.625 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 10L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 60 50 40 30 20 10 0 Inflow Area=42.770 ac 58.31 cfs58.31 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 24HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 20L: Total Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 1.84" for 1yr - 24 hrs event Inflow = 215.75 cfs @ 12.02 hrs, Volume= 13.305 af Primary = 215.75 cfs @ 12.02 hrs, Volume= 13.305 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 20L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 240 220 200 180 160 140 120 100 80 60 40 20 0 Inflow Area=86.800 ac 215.75 cfs215.75 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 25HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 26L: Total Inflow Area = 36.500 ac, 0.00% Impervious, Inflow Depth = 1.45" for 1yr - 24 hrs event Inflow = 93.32 cfs @ 11.96 hrs, Volume= 4.412 af Primary = 93.32 cfs @ 11.96 hrs, Volume= 4.412 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 26L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 100 90 80 70 60 50 40 30 20 10 0 Inflow Area=36.500 ac 93.32 cfs93.32 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 26HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: DURING CONSTRUCTION DA - 01 Runoff = 209.60 cfs @ 12.04 hrs, Volume= 13.021 af, Depth= 2.37" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 65.900 91 Newly graded area, HSG C 65.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.0150 0.37 Sheet Flow, Fallow n= 0.050 P2= 3.32" 8.4 1,150 0.0200 2.28 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 12.9 1,250 Total Subcatchment 4S: DURING CONSTRUCTION DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 220 200 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=65.900 ac Runoff Volume=13.021 af Runoff Depth=2.37" Flow Length=1,250' Tc=12.9 min CN=91 209.60 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 27HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: DURING CONSTRUCTION DA - 02 Runoff = 80.36 cfs @ 11.98 hrs, Volume= 4.130 af, Depth= 2.37" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 20.900 91 Newly graded area, HSG C 20.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.1600 0.96 Sheet Flow, Fallow n= 0.050 P2= 3.32" 5.2 1,220 0.0600 3.94 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 6.9 1,320 Total Subcatchment 5S: DURING CONSTRUCTION DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 90 80 70 60 50 40 30 20 10 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=20.900 ac Runoff Volume=4.130 af Runoff Depth=2.37" Flow Length=1,320' Tc=6.9 min CN=91 80.36 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 28HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: DURING CONSTRUCTION DA - 03A [49] Hint: Tc<2dt may require smaller dt Runoff = 75.27 cfs @ 11.96 hrs, Volume= 3.621 af, Depth= 1.94" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 22.400 86 Newly graded area, HSG B 22.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 2.4 100 0.0700 0.69 Sheet Flow, Fallow n= 0.050 P2= 3.32" 1.4 450 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.8 750 0.0200 7.07 113.09 Channel Flow, Temporary Diversion Area= 16.0 sf Perim= 29.0' r= 0.55' n= 0.020 5.6 1,300 Total Subcatchment 6S: DURING CONSTRUCTION DA - 03A Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 80 70 60 50 40 30 20 10 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=22.400 ac Runoff Volume=3.621 af Runoff Depth=1.94" Flow Length=1,300' Tc=5.6 min CN=86 75.27 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 29HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 7S: DURING CONSTRUCTION DA - 04 [49] Hint: Tc<2dt may require smaller dt Runoff = 48.64 cfs @ 11.96 hrs, Volume= 2.279 af, Depth= 1.94" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 14.100 86 Newly graded area, HSG B 14.100 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 7S: DURING CONSTRUCTION DA - 04 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 50 45 40 35 30 25 20 15 10 5 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=14.100 ac Runoff Volume=2.279 af Runoff Depth=1.94" Tc=5.0 min CN=86 48.64 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 30HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 9S: DURING CONSTRUCTION DA - 03B Runoff = 14.86 cfs @ 12.21 hrs, Volume= 1.440 af, Depth= 0.85" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 8.520 60 Woods, Fair, HSG B 3.220 65 Woods/grass comb., Fair, HSG B 1.130 85 Gravel roads, HSG B 1.230 98 Paved parking, HSG B * 1.530 88 Railbed - Gravel 4.740 69 Pasture/grassland/range, Fair, HSG B 20.370 69 Weighted Average 19.140 93.96% Pervious Area 1.230 6.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 3.6 740 0.0460 3.45 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 24.7 840 Total Subcatchment 9S: DURING CONSTRUCTION DA - 03B Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 16 14 12 10 8 6 4 2 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=20.370 ac Runoff Volume=1.440 af Runoff Depth=0.85" Flow Length=840' Tc=24.7 min CN=69 14.86 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 31HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 18S: DURING CONSTRUCTION DA - 01 Runoff = 209.60 cfs @ 12.04 hrs, Volume= 13.021 af, Depth= 2.37" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 65.900 91 Newly graded area, HSG C 65.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.0150 0.37 Sheet Flow, Fallow n= 0.050 P2= 3.32" 8.4 1,150 0.0200 2.28 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 12.9 1,250 Total Subcatchment 18S: DURING CONSTRUCTION DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 220 200 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=65.900 ac Runoff Volume=13.021 af Runoff Depth=2.37" Flow Length=1,250' Tc=12.9 min CN=91 209.60 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 32HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 19S: DURING CONSTRUCTION DA - 02 Runoff = 80.36 cfs @ 11.98 hrs, Volume= 4.130 af, Depth= 2.37" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 20.900 91 Newly graded area, HSG C 20.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.1600 0.96 Sheet Flow, Fallow n= 0.050 P2= 3.32" 5.2 1,220 0.0600 3.94 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 6.9 1,320 Total Subcatchment 19S: DURING CONSTRUCTION DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 90 80 70 60 50 40 30 20 10 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=20.900 ac Runoff Volume=4.130 af Runoff Depth=2.37" Flow Length=1,320' Tc=6.9 min CN=91 80.36 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 33HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 25S: DURING CONSTRUCTION DA - 04 [49] Hint: Tc<2dt may require smaller dt Runoff = 48.64 cfs @ 11.96 hrs, Volume= 2.279 af, Depth= 1.94" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 14.100 86 Newly graded area, HSG B 14.100 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 25S: DURING CONSTRUCTION DA - 04 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 50 45 40 35 30 25 20 15 10 5 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=14.100 ac Runoff Volume=2.279 af Runoff Depth=1.94" Tc=5.0 min CN=86 48.64 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 34HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 26S: DURING CONSTRUCTION DA - 03A [49] Hint: Tc<2dt may require smaller dt Runoff = 75.27 cfs @ 11.96 hrs, Volume= 3.621 af, Depth= 1.94" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 22.400 86 Newly graded area, HSG B 22.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 2.4 100 0.0700 0.69 Sheet Flow, Fallow n= 0.050 P2= 3.32" 1.4 450 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.8 750 0.0200 7.07 113.09 Channel Flow, Temporary Diversion Area= 16.0 sf Perim= 29.0' r= 0.55' n= 0.020 5.6 1,300 Total Subcatchment 26S: DURING CONSTRUCTION DA - 03A Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 80 70 60 50 40 30 20 10 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=22.400 ac Runoff Volume=3.621 af Runoff Depth=1.94" Flow Length=1,300' Tc=5.6 min CN=86 75.27 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 35HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 16P: SB-01 Inflow Area = 42.770 ac, 2.88% Impervious, Inflow Depth = 1.42" for 2yr - 24hrs event Inflow = 79.31 cfs @ 11.97 hrs, Volume= 5.061 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 675.60' @ 25.45 hrs Surf.Area= 47,824 sf Storage= 220,437 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 670.00' 871,295 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 670.00 31,595 0 0 672.00 36,915 68,510 68,510 674.00 42,640 79,555 148,065 676.00 49,120 91,760 239,825 678.00 58,856 107,976 347,801 680.00 74,771 133,627 481,428 682.00 95,853 170,624 652,052 684.00 123,390 219,243 871,295 Pond 16P: SB-01 Inflow Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 80 70 60 50 40 30 20 10 0 Inflow Area=42.770 ac Peak Elev=675.60' Storage=220,437 cf 79.31 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 36HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 17P: SB-02 Inflow Area = 14.100 ac, 0.00% Impervious, Inflow Depth = 1.94" for 2yr - 24hrs event Inflow = 48.64 cfs @ 11.96 hrs, Volume= 2.279 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 655.50' @ 24.35 hrs Surf.Area= 35,951 sf Storage= 99,286 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 652.00' 195,565 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 652.00 14,641 0 0 654.00 33,039 47,680 47,680 656.00 36,932 69,971 117,651 658.00 40,982 77,914 195,565 Pond 17P: SB-02 Inflow Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 50 45 40 35 30 25 20 15 10 5 0 Inflow Area=14.100 ac Peak Elev=655.50' Storage=99,286 cf 48.64 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 37HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 18P: SB-04 Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 2.37" for 2yr - 24hrs event Inflow = 275.29 cfs @ 12.02 hrs, Volume= 17.151 af Outflow = 2.26 cfs @ 11.65 hrs, Volume= 16.702 af, Atten= 99%, Lag= 0.0 min Primary = 2.26 cfs @ 11.65 hrs, Volume= 16.702 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 675.96' @ 24.11 hrs Surf.Area= 188,912 sf Storage= 636,856 cf Plug-Flow detention time= 2,556.4 min calculated for 16.702 af (97% of inflow) Center-of-Mass det. time= 2,540.5 min ( 3,343.5 - 803.0 ) Volume Invert Avail.Storage Storage Description #1 672.00' 1,435,854 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 672.00 94,232 0 0 674.00 180,443 274,675 274,675 676.00 189,080 369,523 644,198 678.00 197,875 386,955 1,031,153 680.00 206,826 404,701 1,435,854 Device Routing Invert Outlet Devices #1 Primary 672.00'24.0" Round CMP_Round 24" L= 150.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 672.00' / 670.00' S= 0.0133 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 676.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 672.00'2.260 cfs Constant Flow/Skimmer #4 Primary 677.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 Width (feet) 20.00 25.00 30.00 Primary OutFlow Max=2.26 cfs @ 11.65 hrs HW=672.82' (Free Discharge) 1=CMP_Round 24" (Passes 2.26 cfs of 2.75 cfs potential flow) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 3=Constant Flow/Skimmer (Constant Controls 2.26 cfs) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 38HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 18P: SB-04 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 300 250 200 150 100 50 0 Inflow Area=86.800 ac Peak Elev=675.96' Storage=636,856 cf 275.29 cfs 2.26 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 39HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 21P: SB-05 Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 2.37" for 2yr - 24hrs event Inflow = 275.29 cfs @ 12.02 hrs, Volume= 17.151 af Outflow = 2.97 cfs @ 24.03 hrs, Volume= 16.802 af, Atten= 99%, Lag= 720.5 min Primary = 2.97 cfs @ 24.03 hrs, Volume= 16.802 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 654.04' @ 24.03 hrs Surf.Area= 190,017 sf Storage= 627,883 cf Plug-Flow detention time= 2,498.1 min calculated for 16.795 af (98% of inflow) Center-of-Mass det. time= 2,486.9 min ( 3,289.9 - 803.0 ) Volume Invert Avail.Storage Storage Description #1 650.00' 2,092,446 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 650.00 100,077 0 0 652.00 165,087 265,164 265,164 654.00 189,476 354,563 619,727 656.00 214,653 404,129 1,023,856 658.00 261,346 475,999 1,499,855 660.00 331,245 592,591 2,092,446 Device Routing Invert Outlet Devices #1 Primary 650.00'24.0" Round CMP_Round 24" L= 150.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 650.00' / 646.00' S= 0.0267 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 654.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 650.00'2.260 cfs Constant Flow/Skimmer #4 Primary 655.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 Width (feet) 20.00 25.00 30.00 Primary OutFlow Max=2.73 cfs @ 24.03 hrs HW=654.04' (Free Discharge) 1=CMP_Round 24" (Passes 2.73 cfs of 21.37 cfs potential flow) 2=Sharp-Crested Rectangular Weir (Weir Controls 0.47 cfs @ 0.68 fps) 3=Constant Flow/Skimmer (Constant Controls 2.26 cfs) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 40HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 21P: SB-05 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 300 250 200 150 100 50 0 Inflow Area=86.800 ac Peak Elev=654.04' Storage=627,883 cf 275.29 cfs 2.97 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 41HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 24P: SB-03 Inflow Area = 36.500 ac, 0.00% Impervious, Inflow Depth = 1.94" for 2yr - 24hrs event Inflow = 123.80 cfs @ 11.96 hrs, Volume= 5.900 af Outflow = 1.13 cfs @ 11.45 hrs, Volume= 5.887 af, Atten= 99%, Lag= 0.0 min Primary = 1.13 cfs @ 11.45 hrs, Volume= 5.887 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 655.12' @ 24.00 hrs Surf.Area= 92,016 sf Storage= 202,791 cf Plug-Flow detention time= 1,736.2 min calculated for 5.884 af (100% of inflow) Center-of-Mass det. time= 1,736.4 min ( 2,553.6 - 817.3 ) Volume Invert Avail.Storage Storage Description #1 652.00' 688,748 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 652.00 20,697 0 0 653.00 47,259 33,978 33,978 654.00 88,689 67,974 101,952 655.00 91,666 90,178 192,130 656.00 94,682 93,174 285,304 657.00 97,737 96,210 381,513 658.00 100,832 99,285 480,798 659.00 103,965 102,399 583,196 660.00 107,139 105,552 688,748 Device Routing Invert Outlet Devices #1 Primary 652.00'24.0" Round CMP_Round 24" L= 200.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 652.00' / 650.00' S= 0.0100 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 656.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 652.00'1.130 cfs Constant Flow/Skimmer #4 Primary 657.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 Width (feet) 20.00 25.00 30.00 35.00 Primary OutFlow Max=1.13 cfs @ 11.45 hrs HW=652.58' (Free Discharge) 1=CMP_Round 24" (Passes 1.13 cfs of 1.21 cfs potential flow) 2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) 3=Constant Flow/Skimmer (Constant Controls 1.13 cfs) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 42HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 24P: SB-03 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 120 100 80 60 40 20 0 Inflow Area=36.500 ac Peak Elev=655.12' Storage=202,791 cf 123.80 cfs 1.13 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 43HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 8L: Total Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 2.37" for 2yr - 24hrs event Inflow = 275.29 cfs @ 12.02 hrs, Volume= 17.151 af Primary = 275.29 cfs @ 12.02 hrs, Volume= 17.151 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 8L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 300 250 200 150 100 50 0 Inflow Area=86.800 ac 275.29 cfs275.29 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 44HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 10L: Total Inflow Area = 42.770 ac, 2.88% Impervious, Inflow Depth = 1.42" for 2yr - 24hrs event Inflow = 79.31 cfs @ 11.97 hrs, Volume= 5.061 af Primary = 79.31 cfs @ 11.97 hrs, Volume= 5.061 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 10L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 80 70 60 50 40 30 20 10 0 Inflow Area=42.770 ac 79.31 cfs79.31 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 45HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 20L: Total Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 2.37" for 2yr - 24hrs event Inflow = 275.29 cfs @ 12.02 hrs, Volume= 17.151 af Primary = 275.29 cfs @ 12.02 hrs, Volume= 17.151 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 20L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 300 250 200 150 100 50 0 Inflow Area=86.800 ac 275.29 cfs275.29 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 46HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 26L: Total Inflow Area = 36.500 ac, 0.00% Impervious, Inflow Depth = 1.94" for 2yr - 24hrs event Inflow = 123.80 cfs @ 11.96 hrs, Volume= 5.900 af Primary = 123.80 cfs @ 11.96 hrs, Volume= 5.900 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 26L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 120 100 80 60 40 20 0 Inflow Area=36.500 ac 123.80 cfs123.80 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 47HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: DURING CONSTRUCTION DA - 01 Runoff = 329.95 cfs @ 12.04 hrs, Volume= 21.016 af, Depth= 3.83" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 65.900 91 Newly graded area, HSG C 65.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.0150 0.37 Sheet Flow, Fallow n= 0.050 P2= 3.32" 8.4 1,150 0.0200 2.28 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 12.9 1,250 Total Subcatchment 4S: DURING CONSTRUCTION DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 350 300 250 200 150 100 50 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=65.900 ac Runoff Volume=21.016 af Runoff Depth=3.83" Flow Length=1,250' Tc=12.9 min CN=91 329.95 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 48HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: DURING CONSTRUCTION DA - 02 Runoff = 125.90 cfs @ 11.98 hrs, Volume= 6.665 af, Depth= 3.83" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 20.900 91 Newly graded area, HSG C 20.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.1600 0.96 Sheet Flow, Fallow n= 0.050 P2= 3.32" 5.2 1,220 0.0600 3.94 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 6.9 1,320 Total Subcatchment 5S: DURING CONSTRUCTION DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 140 120 100 80 60 40 20 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=20.900 ac Runoff Volume=6.665 af Runoff Depth=3.83" Flow Length=1,320' Tc=6.9 min CN=91 125.90 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 49HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: DURING CONSTRUCTION DA - 03A [49] Hint: Tc<2dt may require smaller dt Runoff = 125.81 cfs @ 11.96 hrs, Volume= 6.194 af, Depth= 3.32" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 22.400 86 Newly graded area, HSG B 22.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 2.4 100 0.0700 0.69 Sheet Flow, Fallow n= 0.050 P2= 3.32" 1.4 450 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.8 750 0.0200 7.07 113.09 Channel Flow, Temporary Diversion Area= 16.0 sf Perim= 29.0' r= 0.55' n= 0.020 5.6 1,300 Total Subcatchment 6S: DURING CONSTRUCTION DA - 03A Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 140 120 100 80 60 40 20 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=22.400 ac Runoff Volume=6.194 af Runoff Depth=3.32" Flow Length=1,300' Tc=5.6 min CN=86 125.81 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 50HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 7S: DURING CONSTRUCTION DA - 04 [49] Hint: Tc<2dt may require smaller dt Runoff = 81.22 cfs @ 11.95 hrs, Volume= 3.899 af, Depth= 3.32" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 14.100 86 Newly graded area, HSG B 14.100 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 7S: DURING CONSTRUCTION DA - 04 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 90 80 70 60 50 40 30 20 10 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=14.100 ac Runoff Volume=3.899 af Runoff Depth=3.32" Tc=5.0 min CN=86 81.22 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 51HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 9S: DURING CONSTRUCTION DA - 03B Runoff = 35.47 cfs @ 12.19 hrs, Volume= 3.127 af, Depth= 1.84" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 8.520 60 Woods, Fair, HSG B 3.220 65 Woods/grass comb., Fair, HSG B 1.130 85 Gravel roads, HSG B 1.230 98 Paved parking, HSG B * 1.530 88 Railbed - Gravel 4.740 69 Pasture/grassland/range, Fair, HSG B 20.370 69 Weighted Average 19.140 93.96% Pervious Area 1.230 6.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 3.6 740 0.0460 3.45 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 24.7 840 Total Subcatchment 9S: DURING CONSTRUCTION DA - 03B Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 35 30 25 20 15 10 5 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=20.370 ac Runoff Volume=3.127 af Runoff Depth=1.84" Flow Length=840' Tc=24.7 min CN=69 35.47 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 52HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 18S: DURING CONSTRUCTION DA - 01 Runoff = 329.95 cfs @ 12.04 hrs, Volume= 21.016 af, Depth= 3.83" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 65.900 91 Newly graded area, HSG C 65.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.0150 0.37 Sheet Flow, Fallow n= 0.050 P2= 3.32" 8.4 1,150 0.0200 2.28 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 12.9 1,250 Total Subcatchment 18S: DURING CONSTRUCTION DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 350 300 250 200 150 100 50 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=65.900 ac Runoff Volume=21.016 af Runoff Depth=3.83" Flow Length=1,250' Tc=12.9 min CN=91 329.95 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 53HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 19S: DURING CONSTRUCTION DA - 02 Runoff = 125.90 cfs @ 11.98 hrs, Volume= 6.665 af, Depth= 3.83" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 20.900 91 Newly graded area, HSG C 20.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.1600 0.96 Sheet Flow, Fallow n= 0.050 P2= 3.32" 5.2 1,220 0.0600 3.94 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 6.9 1,320 Total Subcatchment 19S: DURING CONSTRUCTION DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 140 120 100 80 60 40 20 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=20.900 ac Runoff Volume=6.665 af Runoff Depth=3.83" Flow Length=1,320' Tc=6.9 min CN=91 125.90 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 54HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 25S: DURING CONSTRUCTION DA - 04 [49] Hint: Tc<2dt may require smaller dt Runoff = 81.22 cfs @ 11.95 hrs, Volume= 3.899 af, Depth= 3.32" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 14.100 86 Newly graded area, HSG B 14.100 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 25S: DURING CONSTRUCTION DA - 04 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 90 80 70 60 50 40 30 20 10 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=14.100 ac Runoff Volume=3.899 af Runoff Depth=3.32" Tc=5.0 min CN=86 81.22 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 55HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 26S: DURING CONSTRUCTION DA - 03A [49] Hint: Tc<2dt may require smaller dt Runoff = 125.81 cfs @ 11.96 hrs, Volume= 6.194 af, Depth= 3.32" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 22.400 86 Newly graded area, HSG B 22.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 2.4 100 0.0700 0.69 Sheet Flow, Fallow n= 0.050 P2= 3.32" 1.4 450 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.8 750 0.0200 7.07 113.09 Channel Flow, Temporary Diversion Area= 16.0 sf Perim= 29.0' r= 0.55' n= 0.020 5.6 1,300 Total Subcatchment 26S: DURING CONSTRUCTION DA - 03A Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 140 120 100 80 60 40 20 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=22.400 ac Runoff Volume=6.194 af Runoff Depth=3.32" Flow Length=1,300' Tc=5.6 min CN=86 125.81 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 56HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 16P: SB-01 Inflow Area = 42.770 ac, 2.88% Impervious, Inflow Depth = 2.61" for 10yr - 24hrs event Inflow = 139.06 cfs @ 11.97 hrs, Volume= 9.320 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 678.93' @ 25.45 hrs Surf.Area= 66,256 sf Storage= 405,973 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 670.00' 871,295 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 670.00 31,595 0 0 672.00 36,915 68,510 68,510 674.00 42,640 79,555 148,065 676.00 49,120 91,760 239,825 678.00 58,856 107,976 347,801 680.00 74,771 133,627 481,428 682.00 95,853 170,624 652,052 684.00 123,390 219,243 871,295 Pond 16P: SB-01 Inflow Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 140 120 100 80 60 40 20 0 Inflow Area=42.770 ac Peak Elev=678.93' Storage=405,973 cf 139.06 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 57HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 17P: SB-02 Inflow Area = 14.100 ac, 0.00% Impervious, Inflow Depth = 3.32" for 10yr - 24hrs event Inflow = 81.22 cfs @ 11.95 hrs, Volume= 3.899 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 657.36' @ 24.35 hrs Surf.Area= 39,690 sf Storage= 169,822 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 652.00' 195,565 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 652.00 14,641 0 0 654.00 33,039 47,680 47,680 656.00 36,932 69,971 117,651 658.00 40,982 77,914 195,565 Pond 17P: SB-02 Inflow Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 90 80 70 60 50 40 30 20 10 0 Inflow Area=14.100 ac Peak Elev=657.36' Storage=169,822 cf 81.22 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 58HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 18P: SB-04 Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 3.83" for 10yr - 24hrs event Inflow = 433.67 cfs @ 12.02 hrs, Volume= 27.681 af Outflow = 18.97 cfs @ 13.70 hrs, Volume= 27.188 af, Atten= 96%, Lag= 100.8 min Primary = 18.97 cfs @ 13.70 hrs, Volume= 27.188 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 676.76' @ 13.70 hrs Surf.Area= 192,437 sf Storage= 789,804 cf Plug-Flow detention time= 1,748.9 min calculated for 27.176 af (98% of inflow) Center-of-Mass det. time= 1,739.3 min ( 2,529.0 - 789.7 ) Volume Invert Avail.Storage Storage Description #1 672.00' 1,435,854 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 672.00 94,232 0 0 674.00 180,443 274,675 274,675 676.00 189,080 369,523 644,198 678.00 197,875 386,955 1,031,153 680.00 206,826 404,701 1,435,854 Device Routing Invert Outlet Devices #1 Primary 672.00'24.0" Round CMP_Round 24" L= 150.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 672.00' / 670.00' S= 0.0133 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 676.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 672.00'2.260 cfs Constant Flow/Skimmer #4 Primary 677.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 Width (feet) 20.00 25.00 30.00 Primary OutFlow Max=18.97 cfs @ 13.70 hrs HW=676.76' (Free Discharge) 1=CMP_Round 24" (Barrel Controls 18.97 cfs @ 6.04 fps) 2=Sharp-Crested Rectangular Weir (Passes < 34.56 cfs potential flow) 3=Constant Flow/Skimmer (Passes < 2.26 cfs potential flow) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 59HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 18P: SB-04 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 450 400 350 300 250 200 150 100 50 0 Inflow Area=86.800 ac Peak Elev=676.76' Storage=789,804 cf 433.67 cfs 18.97 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 60HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 21P: SB-05 Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 3.83" for 10yr - 24hrs event Inflow = 433.67 cfs @ 12.02 hrs, Volume= 27.681 af Outflow = 22.61 cfs @ 13.36 hrs, Volume= 27.318 af, Atten= 95%, Lag= 80.7 min Primary = 22.61 cfs @ 13.36 hrs, Volume= 27.318 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 654.77' @ 13.36 hrs Surf.Area= 199,130 sf Storage= 768,740 cf Plug-Flow detention time= 1,648.2 min calculated for 27.306 af (99% of inflow) Center-of-Mass det. time= 1,641.6 min ( 2,431.3 - 789.7 ) Volume Invert Avail.Storage Storage Description #1 650.00' 2,092,446 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 650.00 100,077 0 0 652.00 165,087 265,164 265,164 654.00 189,476 354,563 619,727 656.00 214,653 404,129 1,023,856 658.00 261,346 475,999 1,499,855 660.00 331,245 592,591 2,092,446 Device Routing Invert Outlet Devices #1 Primary 650.00'24.0" Round CMP_Round 24" L= 150.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 650.00' / 646.00' S= 0.0267 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 654.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 650.00'2.260 cfs Constant Flow/Skimmer #4 Primary 655.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 Width (feet) 20.00 25.00 30.00 Primary OutFlow Max=22.61 cfs @ 13.36 hrs HW=654.77' (Free Discharge) 1=CMP_Round 24" (Barrel Controls 22.61 cfs @ 7.20 fps) 2=Sharp-Crested Rectangular Weir (Passes < 34.80 cfs potential flow) 3=Constant Flow/Skimmer (Passes < 2.26 cfs potential flow) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 61HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 21P: SB-05 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 450 400 350 300 250 200 150 100 50 0 Inflow Area=86.800 ac Peak Elev=654.77' Storage=768,740 cf 433.67 cfs 22.61 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 62HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 24P: SB-03 Inflow Area = 36.500 ac, 0.00% Impervious, Inflow Depth = 3.32" for 10yr - 24hrs event Inflow = 206.86 cfs @ 11.96 hrs, Volume= 10.092 af Outflow = 5.54 cfs @ 14.47 hrs, Volume= 10.061 af, Atten= 97%, Lag= 150.8 min Primary = 5.54 cfs @ 14.47 hrs, Volume= 10.061 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 656.19' @ 14.47 hrs Surf.Area= 95,264 sf Storage= 303,406 cf Plug-Flow detention time= 1,899.5 min calculated for 10.057 af (100% of inflow) Center-of-Mass det. time= 1,899.1 min ( 2,701.1 - 802.0 ) Volume Invert Avail.Storage Storage Description #1 652.00' 688,748 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 652.00 20,697 0 0 653.00 47,259 33,978 33,978 654.00 88,689 67,974 101,952 655.00 91,666 90,178 192,130 656.00 94,682 93,174 285,304 657.00 97,737 96,210 381,513 658.00 100,832 99,285 480,798 659.00 103,965 102,399 583,196 660.00 107,139 105,552 688,748 Device Routing Invert Outlet Devices #1 Primary 652.00'24.0" Round CMP_Round 24" L= 200.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 652.00' / 650.00' S= 0.0100 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 656.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 652.00'1.130 cfs Constant Flow/Skimmer #4 Primary 657.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 Width (feet) 20.00 25.00 30.00 35.00 Primary OutFlow Max=5.47 cfs @ 14.47 hrs HW=656.19' (Free Discharge) 1=CMP_Round 24" (Passes 5.47 cfs of 15.76 cfs potential flow) 2=Sharp-Crested Rectangular Weir (Weir Controls 4.34 cfs @ 1.43 fps) 3=Constant Flow/Skimmer (Constant Controls 1.13 cfs) 4=Custom Weir/Orifice ( Controls 0.00 cfs) Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 63HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 24P: SB-03 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 220 200 180 160 140 120 100 80 60 40 20 0 Inflow Area=36.500 ac Peak Elev=656.19' Storage=303,406 cf 206.86 cfs 5.54 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 64HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 8L: Total Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 3.83" for 10yr - 24hrs event Inflow = 433.67 cfs @ 12.02 hrs, Volume= 27.681 af Primary = 433.67 cfs @ 12.02 hrs, Volume= 27.681 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 8L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 450 400 350 300 250 200 150 100 50 0 Inflow Area=86.800 ac 433.67 cfs433.67 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 65HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 10L: Total Inflow Area = 42.770 ac, 2.88% Impervious, Inflow Depth = 2.61" for 10yr - 24hrs event Inflow = 139.06 cfs @ 11.97 hrs, Volume= 9.320 af Primary = 139.06 cfs @ 11.97 hrs, Volume= 9.320 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 10L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 140 120 100 80 60 40 20 0 Inflow Area=42.770 ac 139.06 cfs139.06 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 66HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 20L: Total Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 3.83" for 10yr - 24hrs event Inflow = 433.67 cfs @ 12.02 hrs, Volume= 27.681 af Primary = 433.67 cfs @ 12.02 hrs, Volume= 27.681 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 20L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 450 400 350 300 250 200 150 100 50 0 Inflow Area=86.800 ac 433.67 cfs433.67 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 67HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 26L: Total Inflow Area = 36.500 ac, 0.00% Impervious, Inflow Depth = 3.32" for 10yr - 24hrs event Inflow = 206.86 cfs @ 11.96 hrs, Volume= 10.092 af Primary = 206.86 cfs @ 11.96 hrs, Volume= 10.092 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 26L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 220 200 180 160 140 120 100 80 60 40 20 0 Inflow Area=36.500 ac 206.86 cfs206.86 cfs 6S DURING CONSTRUCTION DA - 03A 9S DURING CONSTRUCTION DA - 03B 16P SB-01 10L Total Routing Diagram for Riverbend Ash Pond Closure Prepared by AMEC, Printed 11/5/2015 HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 1.130 85 Gravel roads, HSG B (9S) 22.400 86 Newly graded area, HSG B (6S) 4.740 69 Pasture/grassland/range, Fair, HSG B (9S) 1.230 98 Paved parking, HSG B (9S) 1.530 88 Railbed - Gravel (9S) 8.520 60 Woods, Fair, HSG B (9S) 3.220 65 Woods/grass comb., Fair, HSG B (9S) 42.770 78 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Soil Listing (selected nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 41.240 HSG B 6S, 9S 0.000 HSG C 0.000 HSG D 1.530 Other 9S 42.770 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.000 1.130 0.000 0.000 0.000 1.130 Gravel roads 9S 0.000 22.400 0.000 0.000 0.000 22.400 Newly graded area 6S 0.000 4.740 0.000 0.000 0.000 4.740 Pasture/grassland/range, Fair 9S 0.000 1.230 0.000 0.000 0.000 1.230 Paved parking 9S 0.000 0.000 0.000 0.000 1.530 1.530 Railbed - Gravel 9S 0.000 8.520 0.000 0.000 0.000 8.520 Woods, Fair 9S 0.000 3.220 0.000 0.000 0.000 3.220 Woods/grass comb., Fair 9S 0.000 41.240 0.000 0.000 1.530 42.770 TOTAL AREA Type II 24-hr 25yr - 24hrs Rainfall=5.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 6S: DURING CONSTRUCTION DA - 03A [49] Hint: Tc<2dt may require smaller dt Runoff = 156.22 cfs @ 11.96 hrs, Volume= 7.788 af, Depth= 4.17" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 25yr - 24hrs Rainfall=5.75" Area (ac) CN Description 22.400 86 Newly graded area, HSG B 22.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 2.4 100 0.0700 0.69 Sheet Flow, Fallow n= 0.050 P2= 3.32" 1.4 450 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.8 750 0.0200 7.07 113.09 Channel Flow, Temporary Diversion Area= 16.0 sf Perim= 29.0' r= 0.55' n= 0.020 5.6 1,300 Total Subcatchment 6S: DURING CONSTRUCTION DA - 03A Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 160 140 120 100 80 60 40 20 0 Type II 24-hr 25yr - 24hrs Rainfall=5.75" Runoff Area=22.400 ac Runoff Volume=7.788 af Runoff Depth=4.17" Flow Length=1,300' Tc=5.6 min CN=86 156.22 cfs Type II 24-hr 25yr - 24hrs Rainfall=5.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 9S: DURING CONSTRUCTION DA - 03B Runoff = 49.40 cfs @ 12.19 hrs, Volume= 4.276 af, Depth= 2.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 25yr - 24hrs Rainfall=5.75" Area (ac) CN Description 8.520 60 Woods, Fair, HSG B 3.220 65 Woods/grass comb., Fair, HSG B 1.130 85 Gravel roads, HSG B 1.230 98 Paved parking, HSG B * 1.530 88 Railbed - Gravel 4.740 69 Pasture/grassland/range, Fair, HSG B 20.370 69 Weighted Average 19.140 93.96% Pervious Area 1.230 6.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 3.6 740 0.0460 3.45 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 24.7 840 Total Subcatchment 9S: DURING CONSTRUCTION DA - 03B Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 55 50 45 40 35 30 25 20 15 10 5 0 Type II 24-hr 25yr - 24hrs Rainfall=5.75" Runoff Area=20.370 ac Runoff Volume=4.276 af Runoff Depth=2.52" Flow Length=840' Tc=24.7 min CN=69 49.40 cfs Type II 24-hr 25yr - 24hrs Rainfall=5.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 16P: SB-01 Inflow Area = 42.770 ac, 2.88% Impervious, Inflow Depth = 3.38" for 25yr - 24hrs event Inflow = 176.02 cfs @ 11.97 hrs, Volume= 12.064 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 680.57' @ 25.45 hrs Surf.Area= 80,743 sf Storage= 525,482 cf Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 670.00' 871,295 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 670.00 31,595 0 0 672.00 36,915 68,510 68,510 674.00 42,640 79,555 148,065 676.00 49,120 91,760 239,825 678.00 58,856 107,976 347,801 680.00 74,771 133,627 481,428 682.00 95,853 170,624 652,052 684.00 123,390 219,243 871,295 Pond 16P: SB-01 Inflow Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 180 160 140 120 100 80 60 40 20 0 Inflow Area=42.770 ac Peak Elev=680.57' Storage=525,482 cf 176.02 cfs Type II 24-hr 25yr - 24hrs Rainfall=5.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 10L: Total Inflow Area = 42.770 ac, 2.88% Impervious, Inflow Depth = 3.38" for 25yr - 24hrs event Inflow = 176.02 cfs @ 11.97 hrs, Volume= 12.064 af Primary = 176.02 cfs @ 11.97 hrs, Volume= 12.064 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 10L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 180 160 140 120 100 80 60 40 20 0 Inflow Area=42.770 ac 176.02 cfs176.02 cfs 4S DURING CONSTRUCTION DA - 01 5S DURING CONSTRUCTION DA - 02 18S DURING CONSTRUCTION DA - 01 19S DURING CONSTRUCTION DA - 02 25S DURING CONSTRUCTION DA - 04 26S DURING CONSTRUCTION DA - 03A 18P SB-04 21P SB-05 24P SB-03 8L Total 20L Total 26L Total Routing Diagram for Riverbend Ash Pond Closure Prepared by AMEC, Printed 11/5/2015 HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 36.500 86 Newly graded area, HSG B (25S, 26S) 173.600 91 Newly graded area, HSG C (4S, 5S, 18S, 19S) 210.100 90 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Soil Listing (selected nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 36.500 HSG B 25S, 26S 173.600 HSG C 4S, 5S, 18S, 19S 0.000 HSG D 0.000 Other 210.100 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.000 36.500 173.600 0.000 0.000 210.100 Newly graded area 4S, 5S, 18S, 19S, 25S, 26S 0.000 36.500 173.600 0.000 0.000 210.100 TOTAL AREA Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: DURING CONSTRUCTION DA - 01 Runoff = 515.36 cfs @ 12.04 hrs, Volume= 33.749 af, Depth= 6.15" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr - 24hrs Rainfall=7.21" Area (ac) CN Description 65.900 91 Newly graded area, HSG C 65.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.0150 0.37 Sheet Flow, Fallow n= 0.050 P2= 3.32" 8.4 1,150 0.0200 2.28 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 12.9 1,250 Total Subcatchment 4S: DURING CONSTRUCTION DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 550 500 450 400 350 300 250 200 150 100 50 0 Type II 24-hr 100yr - 24hrs Rainfall=7.21" Runoff Area=65.900 ac Runoff Volume=33.749 af Runoff Depth=6.15" Flow Length=1,250' Tc=12.9 min CN=91 515.36 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: DURING CONSTRUCTION DA - 02 Runoff = 195.99 cfs @ 11.98 hrs, Volume= 10.703 af, Depth= 6.15" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr - 24hrs Rainfall=7.21" Area (ac) CN Description 20.900 91 Newly graded area, HSG C 20.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.1600 0.96 Sheet Flow, Fallow n= 0.050 P2= 3.32" 5.2 1,220 0.0600 3.94 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 6.9 1,320 Total Subcatchment 5S: DURING CONSTRUCTION DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 200 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 100yr - 24hrs Rainfall=7.21" Runoff Area=20.900 ac Runoff Volume=10.703 af Runoff Depth=6.15" Flow Length=1,320' Tc=6.9 min CN=91 195.99 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 18S: DURING CONSTRUCTION DA - 01 Runoff = 515.36 cfs @ 12.04 hrs, Volume= 33.749 af, Depth= 6.15" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr - 24hrs Rainfall=7.21" Area (ac) CN Description 65.900 91 Newly graded area, HSG C 65.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.0150 0.37 Sheet Flow, Fallow n= 0.050 P2= 3.32" 8.4 1,150 0.0200 2.28 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 12.9 1,250 Total Subcatchment 18S: DURING CONSTRUCTION DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 550 500 450 400 350 300 250 200 150 100 50 0 Type II 24-hr 100yr - 24hrs Rainfall=7.21" Runoff Area=65.900 ac Runoff Volume=33.749 af Runoff Depth=6.15" Flow Length=1,250' Tc=12.9 min CN=91 515.36 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 19S: DURING CONSTRUCTION DA - 02 Runoff = 195.99 cfs @ 11.98 hrs, Volume= 10.703 af, Depth= 6.15" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr - 24hrs Rainfall=7.21" Area (ac) CN Description 20.900 91 Newly graded area, HSG C 20.900 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.7 100 0.1600 0.96 Sheet Flow, Fallow n= 0.050 P2= 3.32" 5.2 1,220 0.0600 3.94 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 6.9 1,320 Total Subcatchment 19S: DURING CONSTRUCTION DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 200 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 100yr - 24hrs Rainfall=7.21" Runoff Area=20.900 ac Runoff Volume=10.703 af Runoff Depth=6.15" Flow Length=1,320' Tc=6.9 min CN=91 195.99 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 25S: DURING CONSTRUCTION DA - 04 [49] Hint: Tc<2dt may require smaller dt Runoff = 132.14 cfs @ 11.95 hrs, Volume= 6.542 af, Depth= 5.57" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr - 24hrs Rainfall=7.21" Area (ac) CN Description 14.100 86 Newly graded area, HSG B 14.100 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 25S: DURING CONSTRUCTION DA - 04 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 140 120 100 80 60 40 20 0 Type II 24-hr 100yr - 24hrs Rainfall=7.21" Runoff Area=14.100 ac Runoff Volume=6.542 af Runoff Depth=5.57" Tc=5.0 min CN=86 132.14 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 26S: DURING CONSTRUCTION DA - 03A [49] Hint: Tc<2dt may require smaller dt Runoff = 204.85 cfs @ 11.96 hrs, Volume= 10.393 af, Depth= 5.57" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr - 24hrs Rainfall=7.21" Area (ac) CN Description 22.400 86 Newly graded area, HSG B 22.400 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 2.4 100 0.0700 0.69 Sheet Flow, Fallow n= 0.050 P2= 3.32" 1.4 450 0.1100 5.34 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.8 750 0.0200 7.07 113.09 Channel Flow, Temporary Diversion Area= 16.0 sf Perim= 29.0' r= 0.55' n= 0.020 5.6 1,300 Total Subcatchment 26S: DURING CONSTRUCTION DA - 03A Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 220 200 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 100yr - 24hrs Rainfall=7.21" Runoff Area=22.400 ac Runoff Volume=10.393 af Runoff Depth=5.57" Flow Length=1,300' Tc=5.6 min CN=86 204.85 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 18P: SB-04 Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 6.15" for 100yr - 24hrs event Inflow = 677.69 cfs @ 12.01 hrs, Volume= 44.452 af Outflow = 133.41 cfs @ 12.33 hrs, Volume= 43.947 af, Atten= 80%, Lag= 19.2 min Primary = 133.41 cfs @ 12.33 hrs, Volume= 43.947 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 678.31' @ 12.33 hrs Surf.Area= 199,278 sf Storage= 1,093,411 cf Plug-Flow detention time= 1,146.7 min calculated for 43.929 af (99% of inflow) Center-of-Mass det. time= 1,141.3 min ( 1,918.4 - 777.1 ) Volume Invert Avail.Storage Storage Description #1 672.00' 1,435,854 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 672.00 94,232 0 0 674.00 180,443 274,675 274,675 676.00 189,080 369,523 644,198 678.00 197,875 386,955 1,031,153 680.00 206,826 404,701 1,435,854 Device Routing Invert Outlet Devices #1 Primary 672.00'24.0" Round CMP_Round 24" L= 150.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 672.00' / 670.00' S= 0.0133 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 676.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 672.00'2.260 cfs Constant Flow/Skimmer #4 Primary 677.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 Width (feet) 20.00 25.00 30.00 Primary OutFlow Max=133.11 cfs @ 12.33 hrs HW=678.31' (Free Discharge) 1=CMP_Round 24" (Barrel Controls 21.84 cfs @ 6.95 fps) 2=Sharp-Crested Rectangular Weir (Passes < 178.55 cfs potential flow) 3=Constant Flow/Skimmer (Passes < 2.26 cfs potential flow) 4=Custom Weir/Orifice (Weir Controls 111.27 cfs @ 3.64 fps) Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 18P: SB-04 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 700 600 500 400 300 200 100 0 Inflow Area=86.800 ac Peak Elev=678.31' Storage=1,093,411 cf 677.69 cfs 133.41 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 21P: SB-05 Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 6.15" for 100yr - 24hrs event Inflow = 677.69 cfs @ 12.01 hrs, Volume= 44.452 af Outflow = 133.12 cfs @ 12.33 hrs, Volume= 44.080 af, Atten= 80%, Lag= 19.2 min Primary = 133.12 cfs @ 12.33 hrs, Volume= 44.080 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 656.29' @ 12.33 hrs Surf.Area= 221,374 sf Storage= 1,086,617 cf Plug-Flow detention time= 1,082.7 min calculated for 44.062 af (99% of inflow) Center-of-Mass det. time= 1,079.1 min ( 1,856.2 - 777.1 ) Volume Invert Avail.Storage Storage Description #1 650.00' 2,092,446 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 650.00 100,077 0 0 652.00 165,087 265,164 265,164 654.00 189,476 354,563 619,727 656.00 214,653 404,129 1,023,856 658.00 261,346 475,999 1,499,855 660.00 331,245 592,591 2,092,446 Device Routing Invert Outlet Devices #1 Primary 650.00'24.0" Round CMP_Round 24" L= 150.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 650.00' / 646.00' S= 0.0267 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 654.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 650.00'2.260 cfs Constant Flow/Skimmer #4 Primary 655.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 Width (feet) 20.00 25.00 30.00 Primary OutFlow Max=132.83 cfs @ 12.33 hrs HW=656.29' (Free Discharge) 1=CMP_Round 24" (Barrel Controls 25.02 cfs @ 7.96 fps) 2=Sharp-Crested Rectangular Weir (Passes < 175.67 cfs potential flow) 3=Constant Flow/Skimmer (Passes < 2.26 cfs potential flow) 4=Custom Weir/Orifice (Weir Controls 107.81 cfs @ 3.61 fps) Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 21P: SB-05 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 700 600 500 400 300 200 100 0 Inflow Area=86.800 ac Peak Elev=656.29' Storage=1,086,617 cf 677.69 cfs 133.12 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Pond 24P: SB-03 Inflow Area = 36.500 ac, 0.00% Impervious, Inflow Depth = 5.57" for 100yr - 24hrs event Inflow = 336.74 cfs @ 11.96 hrs, Volume= 16.935 af Outflow = 33.01 cfs @ 12.38 hrs, Volume= 16.904 af, Atten= 90%, Lag= 25.6 min Primary = 33.01 cfs @ 12.38 hrs, Volume= 16.904 af Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Peak Elev= 657.37' @ 12.38 hrs Surf.Area= 98,875 sf Storage= 417,663 cf Plug-Flow detention time= 1,183.4 min calculated for 16.897 af (100% of inflow) Center-of-Mass det. time= 1,184.0 min ( 1,971.5 - 787.5 ) Volume Invert Avail.Storage Storage Description #1 652.00' 688,748 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 652.00 20,697 0 0 653.00 47,259 33,978 33,978 654.00 88,689 67,974 101,952 655.00 91,666 90,178 192,130 656.00 94,682 93,174 285,304 657.00 97,737 96,210 381,513 658.00 100,832 99,285 480,798 659.00 103,965 102,399 583,196 660.00 107,139 105,552 688,748 Device Routing Invert Outlet Devices #1 Primary 652.00'24.0" Round CMP_Round 24" L= 200.0' CMP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 652.00' / 650.00' S= 0.0100 '/' Cc= 0.900 n= 0.025 Corrugated metal, Flow Area= 3.14 sf #2 Device 1 656.00'16.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #3 Device 1 652.00'1.130 cfs Constant Flow/Skimmer #4 Primary 657.00'Custom Weir/Orifice, Cv= 2.62 (C= 3.28) Head (feet) 0.00 1.00 2.00 3.00 Width (feet) 20.00 25.00 30.00 35.00 Primary OutFlow Max=32.95 cfs @ 12.38 hrs HW=657.37' (Free Discharge) 1=CMP_Round 24" (Barrel Controls 17.84 cfs @ 5.68 fps) 2=Sharp-Crested Rectangular Weir (Passes < 82.21 cfs potential flow) 3=Constant Flow/Skimmer (Passes < 1.13 cfs potential flow) 4=Custom Weir/Orifice (Weir Controls 15.11 cfs @ 1.97 fps) Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Pond 24P: SB-03 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 350 300 250 200 150 100 50 0 Inflow Area=36.500 ac Peak Elev=657.37' Storage=417,663 cf 336.74 cfs 33.01 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 17HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 8L: Total Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 6.15" for 100yr - 24hrs event Inflow = 677.69 cfs @ 12.01 hrs, Volume= 44.452 af Primary = 677.69 cfs @ 12.01 hrs, Volume= 44.452 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 8L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 700 600 500 400 300 200 100 0 Inflow Area=86.800 ac 677.69 cfs677.69 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 18HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 20L: Total Inflow Area = 86.800 ac, 0.00% Impervious, Inflow Depth = 6.15" for 100yr - 24hrs event Inflow = 677.69 cfs @ 12.01 hrs, Volume= 44.452 af Primary = 677.69 cfs @ 12.01 hrs, Volume= 44.452 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 20L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 700 600 500 400 300 200 100 0 Inflow Area=86.800 ac 677.69 cfs677.69 cfs Type II 24-hr 100yr - 24hrs Rainfall=7.21"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 19HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 26L: Total Inflow Area = 36.500 ac, 0.00% Impervious, Inflow Depth = 5.57" for 100yr - 24hrs event Inflow = 336.74 cfs @ 11.96 hrs, Volume= 16.935 af Primary = 336.74 cfs @ 11.96 hrs, Volume= 16.935 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 26L: Total Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 350 300 250 200 150 100 50 0 Inflow Area=36.500 ac 336.74 cfs336.74 cfs Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 Reference 4 CALCULATIONS FOR EROSION AND SEDIMENT CONTROL MEASURES - SEDIMENT BASINS - CLEAN WATER DIVERSION DITCHES - RIP RAP APRONS Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 SEDIMENT BASIN CALCULATIONS Pr o j e c t I n f o r m a t i o n Pr o j e c t N a m e : Ri v e r b e n d A s h P o n d C l o s u r e Am e c F o s t e r W h e e l e r P r o j e c t # : De s i g n e d b y : CN B Da t e : 11 / 1 8 / 2 0 1 4 Re v i s e d b y : CN B Da t e : 11 / 2 / 2 0 1 5 Re v i s e d b y : Da t e : SE D I M E N T D R A I N A G E DI S T U R B E D DI S T U R B E D A R E A FL O W V OL U M E V OL U M E S U R F A C E A R E A SU R F A C E A R E A SI D E B O T T O M S P I L L W A Y SP I L L W A Y TO P O F B E R M R I S E R R I S E R C R E S T B A R R E L BARRE L BARRE L FAIRCLOTH SKIMMER A NTI BA S I N A R E A A R E A W E I G H T E D Q 10 RE Q U I R E D P R O V I D E D R E Q U I R E D P R O V I D E D S L O P E S E L E V A T I O N W I D T H M I N . E L E V A T I O N M I N . E L E V A T I O N D I M E N S I O N E L E V A T I O N D I A M E T E R I N V E R T I N I N V E R T O U T S K I M M E R S I Z E O R I F I C E D I A M E T E R F L O A T A T I O N (W A T E R S H E D ) ( A C R E S ) (A C R E S ) CN V A L U E ( C F S ) ( C F ) ( C F ) (S F ) (S F ) (H : V ) ( F T ) (F T ) (F T ) (F T ) (F T x F T ) (FT)(IN) ( F T ) (FT)(IN)(IN)DEVICE *S B - 0 1 42 . 8 0 22 . 4 0 86 . 0 0 13 9 . 1 4 0 , 3 2 0 8 7 1 , 2 9 5 6 0 , 4 9 1 12 3 , 3 9 0 2 . 5 : 1 6 7 0 . 0 0 N A NA 68 4 . 0 0 NA NA NA NA NA NA NA NA *S B - 0 2 14 . 1 0 14 . 1 0 86 . 0 0 81 . 2 2 5 , 3 8 0 1 9 5 , 5 6 5 3 5 , 3 3 1 40 , 9 8 1 2. 5 : 1 6 5 2 . 0 0 N A NA 65 9 . 0 0 NA NA NA NA NA NA NA NA SB - 0 3 36 . 5 0 36 . 5 0 86 . 0 0 20 6 . 9 6 5 , 7 0 0 2 8 5 , 3 0 4 8 9 , 9 8 4 94 , 6 8 2 2. 5 : 1 6 5 2 . 0 0 20 65 7 . 0 0 65 9 . 0 0 4 x 4 656.00 24 6 5 2 . 0 0 6 5 0 . 0 0 8 7.80 4.0' x 4.0 'x 2.0' CO N C R E T E B O X CMP CONCRETE ** S B - 0 4 8 6 . 8 0 86 . 8 0 91 . 0 0 43 3 . 7 1 5 6 , 2 4 0 6 4 4 , 1 9 8 1 8 8 , 6 4 6 18 9 , 0 8 0 2 . 5 : 1 6 7 2 . 0 0 20 67 7 . 0 0 67 9 . 0 0 4 x 4 676.00 24 6 7 2 . 0 0 6 7 0 . 0 0 2 @ 8"7.20 4.0' x 4.0 'x 2.0' CO N C R E T E B O X CMP CONCRETE ** S B - 0 5 8 6 . 8 0 86 . 8 0 91 . 0 0 43 3 . 7 1 5 6 , 2 4 0 6 1 9 , 7 2 7 1 8 8 , 6 4 6 18 9 , 4 7 6 2 . 5 : 1 6 5 0 . 0 0 20 65 5 . 0 0 65 7 . 0 0 4 x 4 654.00 24 6 5 0 . 0 0 6 4 6 . 0 0 2 @ 8"7.20 4.0' x 4.0 'x 2.0' CO N C R E T E B O X CMP CONCRETE *S E D I M E N T B A S I N S B - 0 1 W I L N O T D I S C H A R G E T H R O U G H A C O N V E N T I O N A L R I S E R / B A R R E L C O N F I G U R A T I O N . S B - 0 1 I S D E S I G N E D T O S T O R E T H E E N T I R E R U N O F F V O L U M E O F T H E 2 5 - Y R - 2 4 - H R S T O R M . T H E S T O R A G E V O L U M E O F S B - 0 1 W I L L B E P U M P E D A N D T R E A T E D U N T I L T H E E X I S T I N G R A I L R O A D T R A C K S A R E O U T O F S E R V I C E A N D S B - 0 3 I S C O N S T R U C T E D . S E D I M E N T B A S I N S B - 02 W I L L N O T D I S C H A R G E T H R O U G H A C O N V E N T I O N A L R I S E R / B A R R E L C O N F I G U R A T I O N U N T I L A L L C C R M A T E R I A L I S E X C A V A T E D A N D R E M O V E D F R O M S I T E . T H E S T O R A G E V O L U M E O F S B - 0 2 W I L L B E P U M P E D A N D T R E A T E D U N T I L A L L C C R M A T E R I A L I S E X C A V A T E D A N D R E M O V E D . A F T E R W A R D S , T H E R I S E R / B A R R E L C O N F I G U R A T I O N W I L L B E I N S T A L L E D A N D S B - 0 2 W I L L B E CO N V E R T E D T O S B - 0 3 A N D W I L L F U N C T I O N A S A C O N V E N T I O N A L S E D I M E N T B A S I N . RI S E R S E D I M E N T B A S I N D E S I G N I N F O R M A T I O N T A B L E DE S I G N O F S E D I M E N T B A S I N S 62 2 6 1 4 0 0 0 7 ** S B - 0 4 A N D S B - 0 5 A R E S I Z E D T O T R E A T T H E T O T A L D I S T U R B E D A R E A O F D U R I N G C O N S T R U C T I O N D A - 0 1 A N D 0 2 . D U E T O A S S U M E D B O T T O M O F A S H E L E V A T I O N W I T H I N T H E A S H P O N D S T H I S A P P R O A C H F L E X I B I L I T Y I N C O N S T R U C T I N G T H E B A S I N S S H O U L D T H E E X C A V A T I O N G R A D E S D I F F E R F R O M W H A T I S S H O W N I N T H E P L A N S H E E T S P R O V I D E D . Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 CLEAN WATER DIVERSION DITCH CALCULATIONS 16S CLEAN WATER DIVERSION DITCH 1- PHASE 1 17S CLEAN WATER DIVERSION DITCH 2 23S DURING CONSTRUCTION DA - 03B 24L Phase 2 Clean Water Diversion 2 Routing Diagram for Riverbend Ash Pond Closure Prepared by AMEC, Printed 11/6/2015 HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link Riverbend Ash Pond Closure Printed 11/6/2015Prepared by AMEC Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 1.490 85 Gravel roads, HSG B (17S, 23S) 0.280 89 Gravel roads, HSG C (16S) 5.715 69 Pasture/grassland/range, Fair, HSG B (17S, 23S) 4.460 79 Pasture/grassland/range, Fair, HSG C (16S) 1.640 98 Paved parking, HSG B (17S, 23S) 1.530 88 Railbed - Gravel (23S) 12.600 60 Woods, Fair, HSG B (17S, 23S) 3.600 73 Woods, Fair, HSG C (16S) 3.400 65 Woods/grass comb., Fair, HSG B (17S, 23S) 34.715 70 TOTAL AREA Riverbend Ash Pond Closure Printed 11/6/2015Prepared by AMEC Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Soil Listing (selected nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 24.845 HSG B 17S, 23S 8.340 HSG C 16S 0.000 HSG D 1.530 Other 23S 34.715 TOTAL AREA Riverbend Ash Pond Closure Printed 11/6/2015Prepared by AMEC Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.000 1.490 0.280 0.000 0.000 1.770 Gravel roads 16S, 17S, 23S 0.000 5.715 4.460 0.000 0.000 10.175 Pasture/grassland/range, Fair 16S, 17S, 23S 0.000 1.640 0.000 0.000 0.000 1.640 Paved parking 17S, 23S 0.000 0.000 0.000 0.000 1.530 1.530 Railbed - Gravel 23S 0.000 12.600 3.600 0.000 0.000 16.200 Woods, Fair 16S, 17S, 23S 0.000 3.400 0.000 0.000 0.000 3.400 Woods/grass comb., Fair 17S, 23S 0.000 24.845 8.340 0.000 1.530 34.715 TOTAL AREA Type II 24-hr 25yr - 24hrs Rainfall=5.75"Riverbend Ash Pond Closure Printed 11/6/2015Prepared by AMEC Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 16S: CLEAN WATER DIVERSION DITCH 1- PHASE 1 Runoff = 27.16 cfs @ 12.17 hrs, Volume= 2.267 af, Depth= 3.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 25yr - 24hrs Rainfall=5.75" Area (ac) CN Description 3.600 73 Woods, Fair, HSG C 0.280 89 Gravel roads, HSG C 4.460 79 Pasture/grassland/range, Fair, HSG C 8.340 77 Weighted Average 8.340 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 2.3 225 0.1100 1.66 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 0.5 175 0.1600 6.44 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 23.9 500 Total Subcatchment 16S: CLEAN WATER DIVERSION DITCH 1- PHASE 1 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 30 25 20 15 10 5 0 Type II 24-hr 25yr - 24hrs Rainfall=5.75" Runoff Area=8.340 ac Runoff Volume=2.267 af Runoff Depth=3.26" Flow Length=500' Tc=23.9 min CN=77 27.16 cfs Type II 24-hr 25yr - 24hrs Rainfall=5.75"Riverbend Ash Pond Closure Printed 11/6/2015Prepared by AMEC Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 17S: CLEAN WATER DIVERSION DITCH 2 Runoff = 13.63 cfs @ 12.17 hrs, Volume= 1.129 af, Depth= 2.26" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 25yr - 24hrs Rainfall=5.75" Area (ac) CN Description 0.180 65 Woods/grass comb., Fair, HSG B 4.080 60 Woods, Fair, HSG B 0.360 85 Gravel roads, HSG B 0.410 98 Paved parking, HSG B 0.975 69 Pasture/grassland/range, Fair, HSG B 6.005 66 Weighted Average 5.595 93.17% Pervious Area 0.410 6.83% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 17.9 100 0.0300 0.09 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 2.4 160 0.0500 1.12 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 2.3 246 0.0120 1.76 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 22.6 506 Total Subcatchment 17S: CLEAN WATER DIVERSION DITCH 2 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 14 12 10 8 6 4 2 0 Type II 24-hr 25yr - 24hrs Rainfall=5.75" Runoff Area=6.005 ac Runoff Volume=1.129 af Runoff Depth=2.26" Flow Length=506' Tc=22.6 min CN=66 13.63 cfs Type II 24-hr 25yr - 24hrs Rainfall=5.75"Riverbend Ash Pond Closure Printed 11/6/2015Prepared by AMEC Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 23S: DURING CONSTRUCTION DA - 03B Runoff = 49.40 cfs @ 12.19 hrs, Volume= 4.276 af, Depth= 2.52" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 25yr - 24hrs Rainfall=5.75" Area (ac) CN Description 8.520 60 Woods, Fair, HSG B 3.220 65 Woods/grass comb., Fair, HSG B 1.130 85 Gravel roads, HSG B 1.230 98 Paved parking, HSG B * 1.530 88 Railbed - Gravel 4.740 69 Pasture/grassland/range, Fair, HSG B 20.370 69 Weighted Average 19.140 93.96% Pervious Area 1.230 6.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 3.6 740 0.0460 3.45 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 24.7 840 Total Subcatchment 23S: DURING CONSTRUCTION DA - 03B Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 55 50 45 40 35 30 25 20 15 10 5 0 Type II 24-hr 25yr - 24hrs Rainfall=5.75" Runoff Area=20.370 ac Runoff Volume=4.276 af Runoff Depth=2.52" Flow Length=840' Tc=24.7 min CN=69 49.40 cfs Type II 24-hr 25yr - 24hrs Rainfall=5.75"Riverbend Ash Pond Closure Printed 11/6/2015Prepared by AMEC Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 24L: Phase 2 Clean Water Diversion 2 Inflow Area = 26.375 ac, 6.22% Impervious, Inflow Depth = 2.46" for 25yr - 24hrs event Inflow = 62.88 cfs @ 12.18 hrs, Volume= 5.405 af Primary = 62.88 cfs @ 12.18 hrs, Volume= 5.405 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 24L: Phase 2 Clean Water Diversion 2 Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 70 60 50 40 30 20 10 0 Inflow Area=26.375 ac 62.88 cfs62.88 cfs Tensar International Corporation 5401 St. Wendel-Cynthiana Road Poseyville, Indiana 47633 Tel. 800.772.2040 Fax 812.867.0247 www.nagreen.com Erosion Control Materials Design Software Version 5.0 Project Name: Riverbend Project Number: 52592 Project Location: Charlotte, NC Channel Name: Clean Water Diversion 1 - (Stability) Discharge 27.16 Peak Flow Period 12.5 Channel Slope 0.0288 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardance Class C Vegtation Type Bunch Type Vegetation Density Fair 50-75% Soil Type Loam C125 Phase Reach Discharge Velocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern C125 Unvegetated Straight 27.16 cfs 7.75 ft/s 0.8 ft 0.02 2.25 lbs/ft2 1.43 lbs/ft2 1.57 STABLE D Unreinforced Vegetation - Class C - Bunch Type - Fair 50-75% Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern Unreinforced Vegetation Straight 27.16 cfs 3.67 ft/s 1.27 ft 0.056 4.2 lbs/ft2 2.29 lbs/ft2 1.84 STABLE -- Underlying Substrate Straight 27.16 cfs 3.67 ft/s 1.27 ft -- 0.04 lbs/ft2 0.106 lbs/ft2 0.33 UNSTABLE -- Page 1 of 2 11/9/2015http://www.ecmds.com/print/analysis/52592/57089 Tensar International Corporation 5401 St. Wendel-Cynthiana Road Poseyville, Indiana 47633 Tel. 800.772.2040 Fax 812.867.0247 www.nagreen.com Erosion Control Materials Design Software Version 5.0 Project Name: Riverbend Project Number: 52592 Project Location: Charlotte, NC Channel Name: Clean Water Diversion 1 - (Capacity) Discharge 27.16 Peak Flow Period 12.5 Channel Slope 0.005 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardance Class C Vegtation Type Bunch Type Vegetation Density Fair 50-75% Soil Type Loam C125 Phase Reach Discharge Velocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern C125 Unvegetated Straight 27.16 cfs 4.35 ft/s 1.15 ft 0.019 2.25 lbs/ft2 0.36 lbs/ft2 6.29 STABLE D Unreinforced Vegetation - Class C - Bunch Type - Fair 50-75% Phase Reach Discharge Velocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern Unreinforced Vegetation Straight 27.16 cfs 1.69 ft/s 2 ft 0.066 4.2 lbs/ft2 0.63 lbs/ft2 6.71 STABLE -- Underlying Substrate Straight 27.16 cfs 1.69 ft/s 2 ft -- 0.04 lbs/ft2 0.021 lbs/ft2 1.67 STABLE -- Page 1 of 2 11/9/2015http://www.ecmds.com/print/analysis/52592/80147 Tensar International Corporation 5401 St. Wendel-Cynthiana Road Poseyville, Indiana 47633 Tel. 800.772.2040 Fax 812.867.0247 www.nagreen.com Erosion Control Materials Design Software Version 5.0 Project Name: Riverbend Project Number: 52592 Project Location: Charlotte, NC Channel Name: Clean Water Diversion 2 - Phase 1 (Stability) Discharge 13.63 Peak Flow Period 12.5 Channel Slope 0.032 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardance Class C Vegtation Type Bunch Type Vegetation Density Fair 50-75% Soil Type Loam C125 Phase Reach Discharge Velocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern C125 Unvegetated Straight 13.63 cfs 6.43 ft/s 0.57 ft 0.022 2.25 lbs/ft2 1.14 lbs/ft2 1.97 STABLE D Unreinforced Vegetation - Class C - Bunch Type - Fair 50-75% Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern Unreinforced Vegetation Straight 13.63 cfs 2.77 ft/s 0.99 ft 0.068 4.2 lbs/ft2 1.98 lbs/ft2 2.12 STABLE -- Underlying Substrate Straight 13.63 cfs 2.77 ft/s 0.99 ft -- 0.04 lbs/ft2 0.063 lbs/ft2 0.56 UNSTABLE -- Page 1 of 2 11/9/2015http://www.ecmds.com/print/analysis/52592/57092 Tensar International Corporation 5401 St. Wendel-Cynthiana Road Poseyville, Indiana 47633 Tel. 800.772.2040 Fax 812.867.0247 www.nagreen.com Erosion Control Materials Design Software Version 5.0 Project Name: Riverbend Project Number: 52592 Project Location: Charlotte, NC Channel Name: Clean Water Diversion 2 - Phase 1 (Capacity) Discharge 13.63 Peak Flow Period 12.5 Channel Slope 0.005 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardance Class C Vegtation Type Bunch Type Vegetation Density Fair 50-75% Soil Type Loam C125 Phase Reach Discharge Velocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern C125 Unvegetated Straight 13.63 cfs 3.44 ft/s 0.86 ft 0.02 2.25 lbs/ft2 0.27 lbs/ft2 8.35 STABLE D Unreinforced Vegetation - Class C - Bunch Type - Fair 50-75% Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern Unreinforced Vegetation Straight 13.63 cfs 1.2 ft/s 1.64 ft 0.083 4.2 lbs/ft2 0.51 lbs/ft2 8.21 STABLE -- Underlying Substrate Straight 13.63 cfs 1.2 ft/s 1.64 ft -- 0.04 lbs/ft2 0.011 lbs/ft2 3.2 STABLE -- Page 1 of 2 11/9/2015http://www.ecmds.com/print/analysis/52592/80165 Tensar International Corporation 5401 St. Wendel-Cynthiana Road Poseyville, Indiana 47633 Tel. 800.772.2040 Fax 812.867.0247 www.nagreen.com Erosion Control Materials Design Software Version 5.0 Project Name: Riverbend Project Number: 52592 Project Location: Charlotte, NC Channel Name: Clean Water Diversion 2 - Phase 2 (Stability) Discharge 62.9 Peak Flow Period 12.5 Channel Slope 0.015 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardance Class C Vegtation Type Bunch Type Vegetation Density Fair 50-75% Soil Type Loam C125 Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern C125 Unvegetated Straight62.9 cfs 8.37 ft/s 1.28 ft 0.018 2.25 lbs/ft2 1.2 lbs/ft2 1.87 STABLE D Unreinforced Vegetation - Class C - Bunch Type - Fair 50-75% Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern Unreinforced Vegetation Straight62.9 cfs 4.01 ft/s 1.98 ft 0.048 4.2 lbs/ft2 1.85 lbs/ft2 2.27 STABLE -- Underlying Substrate Straight62.9 cfs 4.01 ft/s 1.98 ft -- 0.04 lbs/ft2 0.118 lbs/ft2 0.3 UNSTABLE -- Page 1 of 2 11/9/2015http://www.ecmds.com/print/analysis/52592/57095 Tensar International Corporation 5401 St. Wendel-Cynthiana Road Poseyville, Indiana 47633 Tel. 800.772.2040 Fax 812.867.0247 www.nagreen.com Erosion Control Materials Design Software Version 5.0 Project Name: Riverbend Project Number: 52592 Project Location: Charlotte, NC Channel Name: Clean Water Diversion 2 - Phase 2 (Capacity) Discharge 62.9 Peak Flow Period 12.5 Channel Slope .005 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardance Class C Vegtation Type Bunch Type Vegetation Density Fair 50-75% Soil Type Loam C125 Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern C125 Unvegetated Straight62.9 cfs 5.95 ft/s 1.57 ft 0.016 2.25 lbs/ft2 0.49 lbs/ft2 4.58 STABLE D Unreinforced Vegetation - Class C - Bunch Type - Fair 50-75% Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern Unreinforced Vegetation Straight62.9 cfs 2.48 ft/s 2.59 ft 0.052 4.2 lbs/ft2 0.81 lbs/ft2 5.19 STABLE -- Underlying Substrate Straight62.9 cfs 2.48 ft/s 2.59 ft -- 0.04 lbs/ft2 0.043 lbs/ft2 0.81 UNSTABLE -- Page 1 of 2 11/9/2015http://www.ecmds.com/print/analysis/52592/80291 Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 RIP RAP APRON CALCULATIONS Pr o j e c t I n f o r m a t i o n Pr o j e c t N a m e : Ri v e r b e n d A s h P o n d C l o s u r e Am e c F o s t e r W h e e l e r P r o j e c t # : De s i g n e d b y : CN B Da t e : 11 / 1 0 / 2 0 1 4 Re v i s e d b y : CN B Da t e : 11 / 6 / 2 0 1 5 Re v i s e d b y : D a t e : TO P R E V E N T S C O U R H O L E RIPRAP ZO N E A PR O N M A T E R I A L DEPTH (in) C L A S S 1 1 2 I 2 18 I 3 24 I I 4 36 I I 5 36 I I 6 36 I I 7 S p e c i a l S t u d y R e q u i r e d ( E n e r g y D i s s i p a t e r s , S t i l l i n g B a s i n s , o r L a r g e r S i z e S t o n e Ap r o n w i d t h = p i p e d i a m e t e r + 0 . 4 * ( a p r o n l e n g t h ) Vel= [ 0 . 5 9 0 * ( d i a m ) ^ 2 / 3 * ( s l o p e ) ^ 1 / 2 ] / n CL A S S M I N I M U M M I D R A N G E M A X I M U M A2 " 4 " 6 " B 5 " 8 " 1 2 " 1 5 " 1 0 " 1 7 " Al l a p r o n s s i z e d u s i n g t h e N e w Y o r k D O T D i s s i p a t e r M e t h o d a s o u t l i n e d b y N C D E N R ( E r o s i o n C o n t r o l M a n u a l , S e c t i o n 8 . 0 6 ) 2 9 " 1 4 " 2 3 " P i p e 1 0 - y r A p r o n A p r o n S t o n e A p r o n De s c r i p t i o n D i a m e t e r V e l o c i t y Z o n e L e n g t h W i d t h C l a s s T h i c k n e s s ( D ) ( i n ) ( f p s ) ( - - ) ( L ) ( f t ) ( W ) ( f t ) ( - - ) ( T ) ( i n ) Zo n e D e p t h SB - 0 3 O U T L E T 24 1 . 4 3 1 86 A 1 2 11 2 SB - 0 4 O U T L E T 24 6 . 0 4 2 12 7 B 1 8 21 8 SB - 0 5 O U T L E T 24 7 . 2 0 2 12 7 B 1 8 32 4 43 6 53 6 63 6 7 D i t c h 2 5 - y r Ap r o n A p r o n S t o n e A p r o n De s c r i p t i o n Bo t t o m W i d t h V e l o c i t y Z o n e L e n g t h W i d t h C l a s s T h i c k n e s s (D ) ( i n ) ( f p s ) ( - - ) ( L ) ( f t ) ( W ) ( f t ) ( - - ) ( T ) ( i n ) CL E A N W A T E R D I V E R S I O N DI T C H 1 24 7 . 8 9 2 12 7 B 1 8 CL E A N WA T E R DI V E R S I O N DI T C H 2 ( P H A S E 2 ) 24 1 0 . 2 6 2 12 7 B 1 8 8 x (pipe diameter) St o n e F i l l i n g ( L i g h t ) St o n e F i l l i n g ( H e a v y ) St o n e F i l l i n g ( H e a v y ) 23"12 x (pipe diameter)23" 8 x ( p i p e d i a m e t e r ) 23" 1 0 x ( p i p e d i a m e t e r ) St o n e F i l l i n g ( H e a v y ) OU T L E T P R O T E C T I O N DE S I G N O F R I P R A P A P R O N S 62 2 6 1 4 0 0 0 7 13" St o n e F i l l i n g ( M e d i u m ) RI P R A P C L A S S E S RE Q U I R E D S T O N E S I Z E S - I N C H E S STONE DIAMETE R LENGTH OF APRO N St o n e F i l l i n g ( F i n e ) 6"4 x (pipe diameter)6"6 x (pipe diameter) Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.020 Channel Slope 0.02900 ft/ft Left Side Slope 3.00 ft/ft (H:V) Right Side Slope 3.00 ft/ft (H:V) Bottom Width 2.00 ft Discharge 27.20 ft³/s Results Normal Depth 0.79 ft Flow Area 3.45 ft² Wetted Perimeter 6.99 ft Hydraulic Radius 0.49 ft Top Width 6.73 ft Critical Depth 1.10 ft Critical Slope 0.00701 ft/ft Velocity 7.89 ft/s Velocity Head 0.97 ft Specific Energy 1.76 ft Froude Number 1.95 Flow Type Supercritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 0.79 ft Critical Depth 1.10 ft Channel Slope 0.02900 ft/ft Worksheet for Clean Water Diversion Ditch - 1 (Apron Design) 11/9/2015 8:56:50 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page Worksheet for Clean Water Diversion Ditch - 1 (Apron Design) GVF Output Data Critical Slope 0.00701 ft/ft 11/9/2015 8:56:50 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page Project Description Friction Method Manning Formula Solve For Normal Depth Input Data Roughness Coefficient 0.020 Channel Slope 0.03200 ft/ft Left Side Slope 3.00 ft/ft (H:V) Right Side Slope 3.00 ft/ft (H:V) Discharge 62.88 ft³/s Results Normal Depth 1.43 ft Flow Area 6.13 ft² Wetted Perimeter 9.04 ft Hydraulic Radius 0.68 ft Top Width 8.58 ft Critical Depth 1.94 ft Critical Slope 0.00632 ft/ft Velocity 10.26 ft/s Velocity Head 1.64 ft Specific Energy 3.06 ft Froude Number 2.14 Flow Type Supercritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 1.43 ft Critical Depth 1.94 ft Channel Slope 0.03200 ft/ft Critical Slope 0.00632 ft/ft Worksheet for Clean Water Diversion Ditch - 2 (Apron Design) 11/9/2015 8:58:51 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 1of1Page Riverbend Ash Basin Closure Plan CALC-1.01-STORMWATER, Rev. 0 Amec Foster Wheeler Project No. 6226-14-0007 December, 2015 Reference 5 POST-CONSTRUCTION HYDROCAD OUTPUT 11S POST DA - 01 12S POST DA - 02 13S POST DA - 03 15L Total Off-Site Runoff Routing Diagram for Riverbend Ash Pond Closure Prepared by AMEC, Printed 11/5/2015 HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 0.700 85 Gravel roads, HSG B (13S) 47.220 69 Pasture/grassland/range, Fair, HSG B (13S) 99.200 79 Pasture/grassland/range, Fair, HSG C (11S, 12S) 1.240 98 Paved parking, HSG B (13S) 8.510 60 Woods, Fair, HSG B (13S) 5.800 73 Woods, Fair, HSG C (11S, 12S) 3.030 65 Woods/grass comb., Fair, HSG B (13S) 165.700 75 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Soil Listing (selected nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 60.700 HSG B 13S 105.000 HSG C 11S, 12S 0.000 HSG D 0.000 Other 165.700 TOTAL AREA Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.000 0.700 0.000 0.000 0.000 0.700 Gravel roads 13S 0.000 47.220 99.200 0.000 0.000 146.420 Pasture/grassland/range, Fair 11S, 12S, 13S 0.000 1.240 0.000 0.000 0.000 1.240 Paved parking 13S 0.000 8.510 5.800 0.000 0.000 14.310 Woods, Fair 11S, 12S, 13S 0.000 3.030 0.000 0.000 0.000 3.030 Woods/grass comb., Fair 13S 0.000 60.700 105.000 0.000 0.000 165.700 TOTAL AREA Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 11S: POST DA - 01 Runoff = 62.52 cfs @ 12.31 hrs, Volume= 6.896 af, Depth= 1.01" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 78.940 79 Pasture/grassland/range, Fair, HSG C 3.060 73 Woods, Fair, HSG C 82.000 79 Weighted Average 82.000 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 2.3 225 0.1100 1.66 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 10.8 2,300 0.0490 3.56 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 34.2 2,625 Total Subcatchment 11S: POST DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 70 60 50 40 30 20 10 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=82.000 ac Runoff Volume=6.896 af Runoff Depth=1.01" Flow Length=2,625' Tc=34.2 min CN=79 62.52 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 12S: POST DA - 02 Runoff = 17.64 cfs @ 12.27 hrs, Volume= 1.829 af, Depth= 0.95" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 2.740 73 Woods, Fair, HSG C 20.260 79 Pasture/grassland/range, Fair, HSG C 23.000 78 Weighted Average 23.000 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 3.2 260 0.0730 1.35 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 6.5 1,530 0.0590 3.91 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 30.8 1,890 Total Subcatchment 12S: POST DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 18 16 14 12 10 8 6 4 2 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=23.000 ac Runoff Volume=1.829 af Runoff Depth=0.95" Flow Length=1,890' Tc=30.8 min CN=78 17.64 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 13S: POST DA - 03 Runoff = 17.10 cfs @ 12.40 hrs, Volume= 2.540 af, Depth= 0.50" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Area (ac) CN Description 8.510 60 Woods, Fair, HSG B 3.030 65 Woods/grass comb., Fair, HSG B 1.240 98 Paved parking, HSG B 0.700 85 Gravel roads, HSG B 47.220 69 Pasture/grassland/range, Fair, HSG B 60.700 68 Weighted Average 59.460 97.96% Pervious Area 1.240 2.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 27.8 100 0.0100 0.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 8.9 2,220 0.0660 4.14 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 36.7 2,320 Total Subcatchment 13S: POST DA - 03 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 18 16 14 12 10 8 6 4 2 0 Type II 24-hr 1yr - 24 hrs Rainfall=2.75" Runoff Area=60.700 ac Runoff Volume=2.540 af Runoff Depth=0.50" Flow Length=2,320' Tc=36.7 min CN=68 17.10 cfs Type II 24-hr 1yr - 24 hrs Rainfall=2.75"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 15L: Total Off-Site Runoff Inflow Area = 165.700 ac, 0.75% Impervious, Inflow Depth = 0.82" for 1yr - 24 hrs event Inflow = 96.08 cfs @ 12.32 hrs, Volume= 11.265 af Primary = 96.08 cfs @ 12.32 hrs, Volume= 11.265 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 15L: Total Off-Site Runoff Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 100 90 80 70 60 50 40 30 20 10 0 Inflow Area=165.700 ac 96.08 cfs96.08 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 9HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 11S: POST DA - 01 Runoff = 90.72 cfs @ 12.31 hrs, Volume= 9.754 af, Depth= 1.43" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 78.940 79 Pasture/grassland/range, Fair, HSG C 3.060 73 Woods, Fair, HSG C 82.000 79 Weighted Average 82.000 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 2.3 225 0.1100 1.66 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 10.8 2,300 0.0490 3.56 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 34.2 2,625 Total Subcatchment 11S: POST DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 100 90 80 70 60 50 40 30 20 10 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=82.000 ac Runoff Volume=9.754 af Runoff Depth=1.43" Flow Length=2,625' Tc=34.2 min CN=79 90.72 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 10HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 12S: POST DA - 02 Runoff = 25.92 cfs @ 12.27 hrs, Volume= 2.610 af, Depth= 1.36" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 2.740 73 Woods, Fair, HSG C 20.260 79 Pasture/grassland/range, Fair, HSG C 23.000 78 Weighted Average 23.000 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 3.2 260 0.0730 1.35 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 6.5 1,530 0.0590 3.91 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 30.8 1,890 Total Subcatchment 12S: POST DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 25 20 15 10 5 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=23.000 ac Runoff Volume=2.610 af Runoff Depth=1.36" Flow Length=1,890' Tc=30.8 min CN=78 25.92 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 11HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 13S: POST DA - 03 Runoff = 30.89 cfs @ 12.37 hrs, Volume= 4.040 af, Depth= 0.80" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr - 24hrs Rainfall=3.32" Area (ac) CN Description 8.510 60 Woods, Fair, HSG B 3.030 65 Woods/grass comb., Fair, HSG B 1.240 98 Paved parking, HSG B 0.700 85 Gravel roads, HSG B 47.220 69 Pasture/grassland/range, Fair, HSG B 60.700 68 Weighted Average 59.460 97.96% Pervious Area 1.240 2.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 27.8 100 0.0100 0.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 8.9 2,220 0.0660 4.14 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 36.7 2,320 Total Subcatchment 13S: POST DA - 03 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 30 25 20 15 10 5 0 Type II 24-hr 2yr - 24hrs Rainfall=3.32" Runoff Area=60.700 ac Runoff Volume=4.040 af Runoff Depth=0.80" Flow Length=2,320' Tc=36.7 min CN=68 30.89 cfs Type II 24-hr 2yr - 24hrs Rainfall=3.32"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 12HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 15L: Total Off-Site Runoff Inflow Area = 165.700 ac, 0.75% Impervious, Inflow Depth = 1.19" for 2yr - 24hrs event Inflow = 146.02 cfs @ 12.31 hrs, Volume= 16.405 af Primary = 146.02 cfs @ 12.31 hrs, Volume= 16.405 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 15L: Total Off-Site Runoff Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 160 140 120 100 80 60 40 20 0 Inflow Area=165.700 ac 146.02 cfs146.02 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 13HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 11S: POST DA - 01 Runoff = 173.08 cfs @ 12.30 hrs, Volume= 18.207 af, Depth= 2.66" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 78.940 79 Pasture/grassland/range, Fair, HSG C 3.060 73 Woods, Fair, HSG C 82.000 79 Weighted Average 82.000 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 2.3 225 0.1100 1.66 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 10.8 2,300 0.0490 3.56 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 34.2 2,625 Total Subcatchment 11S: POST DA - 01 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 180 160 140 120 100 80 60 40 20 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=82.000 ac Runoff Volume=18.207 af Runoff Depth=2.66" Flow Length=2,625' Tc=34.2 min CN=79 173.08 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 14HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 12S: POST DA - 02 Runoff = 50.29 cfs @ 12.26 hrs, Volume= 4.938 af, Depth= 2.58" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 2.740 73 Woods, Fair, HSG C 20.260 79 Pasture/grassland/range, Fair, HSG C 23.000 78 Weighted Average 23.000 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.1 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 3.2 260 0.0730 1.35 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 6.5 1,530 0.0590 3.91 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 30.8 1,890 Total Subcatchment 12S: POST DA - 02 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 55 50 45 40 35 30 25 20 15 10 5 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=23.000 ac Runoff Volume=4.938 af Runoff Depth=2.58" Flow Length=1,890' Tc=30.8 min CN=78 50.29 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 15HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 13S: POST DA - 03 Runoff = 77.12 cfs @ 12.35 hrs, Volume= 8.936 af, Depth= 1.77" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr - 24hrs Rainfall=4.84" Area (ac) CN Description 8.510 60 Woods, Fair, HSG B 3.030 65 Woods/grass comb., Fair, HSG B 1.240 98 Paved parking, HSG B 0.700 85 Gravel roads, HSG B 47.220 69 Pasture/grassland/range, Fair, HSG B 60.700 68 Weighted Average 59.460 97.96% Pervious Area 1.240 2.04% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 27.8 100 0.0100 0.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.32" 8.9 2,220 0.0660 4.14 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 36.7 2,320 Total Subcatchment 13S: POST DA - 03 Runoff Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 80 70 60 50 40 30 20 10 0 Type II 24-hr 10yr - 24hrs Rainfall=4.84" Runoff Area=60.700 ac Runoff Volume=8.936 af Runoff Depth=1.77" Flow Length=2,320' Tc=36.7 min CN=68 77.12 cfs Type II 24-hr 10yr - 24hrs Rainfall=4.84"Riverbend Ash Pond Closure Printed 11/5/2015Prepared by AMEC Page 16HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Link 15L: Total Off-Site Runoff Inflow Area = 165.700 ac, 0.75% Impervious, Inflow Depth = 2.32" for 10yr - 24hrs event Inflow = 298.11 cfs @ 12.30 hrs, Volume= 32.081 af Primary = 298.11 cfs @ 12.30 hrs, Volume= 32.081 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs Link 15L: Total Off-Site Runoff Inflow Primary Hydrograph Time (hours) 1201101009080706050403020100 Fl o w ( c f s ) 300 250 200 150 100 50 0 Inflow Area=165.700 ac 298.11 cfs298.11 cfs Dam Breach Stormwater Calculation Primary and Secondary Dam Decommissioning Plan ❑uke Energy— Riverbend Steam Station Calculation Title: Stormwater Analysis of Final Grades with Dam Breach Openings Summary: Dam breach openings were designed to convey stormwater for the 50-year, 24-hour design storm event considering final conditions after breaching of the primary and secondary ash basin dams. The primary ash basin dam (GASTO-097) breach utilizes 2 channels to convey the stormwater runoff. Both channels were designed for capacity and stabilization for the 50-year, 24-hour storm event. The secondary ash basin dam (GASTO-98) breach utilizes 2 low flow channels to convey smaller storm events while larger events will discharge through the approximately 350 feet wide breach opening. Notes: Revision Log:. No. Description Originator Verifier Technical Reviewer 0 Initial Submittal Chad Brown Josh Bell Richard, Hiner Ll i�t11IIFI �r s ►o ar� LP-f . Il ���lfllllrl�10 Amec Foster Wheeler Project No. 7810-16-0625 1 of 6 10/18/2016 (Initial Submittal) amec foster wheeler Dam Breach Stormwater Calculation Primary and Secondary Dam Decommissioning Plan Duke Energy – Riverbend Steam Station Amec Foster Wheeler Project No. 7810-16-0625 2 of 6 10/18/2016 (Initial Submittal) OBJECTIVE: The objective of these calculations is to support the design of stormwater conveyance measures based on final conditions following the decommissioning of the primary and secondary ash basin dams (GASTO-097 and GASTO-098). METHOD: Stormwater flow rates were calculated using the SCS method. The hydraulic capacity of proposed stormwater conveyances was evaluated using Manning’s equation within HydroCAD and HEC-RAS modeling software. DEFINITION OF VARIABLES: W = shear; A = area; b = bottom width; CN = curve number; d = flow depth; D = channel depth; i = rainfall intensity; L = length; n = Manning’s n; P = wetted perimeter; Q = flow rate; R = hydraulic radius; S = longitudinal slope; t = time T = top width; Tc = time of concentration; V = velocity; and Z = channel side slope. CALCULATIONS: 1.0 Design Dam Breach Conveyances The final grades of the ash stack and the ash basin areas will convey stormwater runoff to the proposed dam breach locations and ultimately discharge to Mountain Island Lake along the northeastern edge of the property. The design criteria used for the breach openings was determined by first estimating the peak flow to the conveyances using the SCS method, then evaluating the capacity using Manning’s equation. The conveyances were designed for capacity and stability for the 50-year, 24 hour design storm [Ref 1]. The precipitation frequency table is presented in Appendix 1. Dam Breach Stormwater Calculation Primary and Secondary Dam Decommissioning Plan Duke Energy – Riverbend Steam Station Amec Foster Wheeler Project No. 7810-16-0625 3 of 6 10/18/2016 (Initial Submittal) 1.1 Estimate drainage areas Drainage area delineation was based on the proposed final conditions after closure by removal of the existing ash basins and ash stack. The drainage areas are defined in Drawing RVB_C901.004.053 and are summarized in the following table: Drainage Area ID Drainage Area {A} (ac) Soil Class Curve Number (CN) DA-097-1 14.83 B69 DA-097-2 7.08 B69 DA-098-1 71.00 B69 Table 1: Summary of Drainage Areas 1.2 Calculate Time-of-Concentration The time-of-concentration (Tc) is the amount of time needed for water to travel from the hydrologically most distant point in a drainage area to the drainage area outlet. The estimated flow paths for the drainage areas are shown in Drawing RVB_C901.004.053. The total time-of-concentration for a catchment generally consists of the following three components: sheet flow, shallow concentrated flow and channel flow [Ref 2]. Details of the calculation method are presented in Appendix 2. In general, sheet flow was assumed for the first 100 feet of the flow path then shallow concentrated flow to the proposed conveyance channels. The remaining flow path within the contributing drainage areas was analyzed as channel flow. HydroCAD software was used to estimate time of concentration based on the SCS method [Ref. 2] and the input parameters summarized in the following tables: Drainage Area ID Flow Length {L} (ft.) Surface Description Manning No. {n} Land Slope (ft/ft) Time of Concentration {Tc,sheet} (min) DA-097-1 100 Range 0.130 0.090 4.7 DA-097-2 100 Range 0.130 0.100 4.5 DA-098-1 100 Range 0.130 0.020 8.6 Table 2: Time of Concentration from Sheet Flow Drainage Area ID Flow Length {L} (ft.) Surface Description Land Slope (ft/ft) Time of Concentration {Tc,scf} (min) DA-097-1 890 Unpaved 0.080 3.3 DA-097-2 435 Unpaved 0.080 1.6 DA-098-1 480 Unpaved 0.100 1.6 Table 3: Time of Concentration from Shallow Concentrated Flow Dam Breach Stormwater Calculation Primary and Secondary Dam Decommissioning Plan Duke Energy – Riverbend Steam Station Amec Foster Wheeler Project No. 7810-16-0625 4 of 6 10/18/2016 (Initial Submittal) Drainage Area ID Flow Length {L} (ft.) Channel Velocity {V} (ft/s) Time of Concentration {Tc,channel} (min) DA-097-1 750 9.37 1.3 DA-097-2 410 11.35 0.6 DA-098-1 1,475 5.83 4.2 Table 4: Time of Concentration from Channel Flow Drainage Area ID Time of Concentration {Tc,sheet} (min) Time of Concentration {Tc,scf} (min) Time of Concentration {Tc,channel} (min) Total Time of Concentration {Tc,total} (min) DA-097-1 4.7 3.3 1.3 9.3 DA-097-2 4.5 1.6 0.6 6.7 DA-098-1 8.6 1.6 4.2 14.4 Table 5: Total Time of Concentration 1.3 Describe land use conditions Land use conditions were estimated based on anticipated long-term conditions as shown in Drawing RVB_C901.004.053. Site soils information for calculations were assigned based on soils maps showing the site primarily consists of hydrologic soil group B soils [Ref 3]. The soils map is presented in Appendix 3. Given the site’s soils and the final conditions the land use was assumed to consist of fair condition grass with a CN value of 69. HydroCAD software [Ref. 4] was used to estimate final condition stormwater flows for drainage areas for the 50-year, 24-hour storm event based on the SCS method. Table 6 summarizes the peak flows into each of the proposed breach conveyance channels based on the delineated drainage areas. HydroCAD output is presented in Appendix 4. Drainage Area ID Peak Flow {Q50} (cfs) DA-097-1 71.26 DA-097-2 37.30 DA-098-1 286.47 Table 6: Peak Flow 1.4 Stormwater channel capacity and stability 1.4.1 GASTO-097 Breach Opening The GASTO-097 breach opening utilizes two channels that were designed to convey stormwater runoff. The GASTO-097 Breach Channel 1 is a 2-foot deep trapezoidal ditch with a 4-foot bottom width and 3H:1V side slopes. GASTO-097 Breach Channel 2 is a 2-foot deep trapezoidal ditch with a 2-foot bottom width and 3H:1V side slopes. The breach channels were modeled using HEC-RAS with stations starting at the downstream confluence with an existing swale located at the toe of the existing dam that discharges to existing wetlands before ultimately discharging to Mountain Island Dam Breach Stormwater Calculation Primary and Secondary Dam Decommissioning Plan Duke Energy – Riverbend Steam Station Amec Foster Wheeler Project No. 7810-16-0625 5 of 6 10/18/2016 (Initial Submittal) Lake. Sections were spaced at 50 feet along the channel lengths. The capacity of the proposed GASTO-097 breach channels were evaluated using HEC-RAS [Ref. 5] along with the stability for lining based on the computed shear forces. Flow depth, velocity, and shear forces for the breach opening channels during the 50-year peak discharge can be found in the included HEC-RAS output (Appendix 5). The permissible velocity for a channel with grass lining (tall fescue), slope of 0% to 5%, and easily erodible soils is 4.5 feet per second [Ref. 7]. Originally, the GASTO-097 breach channels were analyzed as grass lined channels using North America Green’s web application [Ref 6]. The web application was used to determine the type of erosion control matting needed within the channel prior to establishment of vegetation and to determine the Manning’s n values for the channels in the vegetated condition. Manning’s n values of 0.047 and 0.053 for Breach Channels 1 and 2 were calculated (Appendix 6) and input into the HEC-RAS model for each channel. The HEC-RAS models showed the four most down-gradient sections (Sections 0+00 – 1+50) for both channels proved to have velocities more than the permissible velocity for grass lining of 4.5 feet per second, thus the channel required armoring in these sections. In these steeper sloped sections of the channels 6-inch riprap with a Manning’s n value of 0.069 was then analyzed. The calculated shear forces exceeded the permissible shear force of 2.00 lb/ft2 reported in the North Carolina Erosion and Sedimentation Control Planning and Design Manual [Ref 7] and therefore, channel lining of Class B grouted riprap was chosen for these sections [Ref 8]. Tables of allowable velocities and shear forces for the design of stable channels and diversion are presented in Appendix 7. The North Carolina Department of Transportation (NCDOT) acceptance criteria table for riprap and stone for erosion control is presented in Appendix 8. 1.4.2 GASTO-098 Breach Opening The GASTO-098 breach opening is approximately 350-foot wide with two small 1-foot deep base flows channels located along both edges of the breach opening. The GASTO-098 breach opening was modeled using HEC-RAS [Ref. 5] with stations starting at the confluence with existing wetlands before discharging to Mountain Island Lake. Sections were spaced at 50 feet along the breach opening. The capacity and stability of the proposed GASTO-098 breach opening was evaluated using HEC-RAS. Flow depth, velocity and shear forces for the breach opening channel during the 50-year peak discharge can be found in the included HEC-RAS output (Appendix 5). The permissible velocity for a channel with grass lining (tall fescue), slope of 0% to 5%, and easily erodible soils is 4.5 feet per second. The breach opening was analyzed as a grass lined channel with a Manning’s n of 0.035. Every section proved to have velocities less than the permissible velocity for grass lining of 4.5 feet per second thus the channel does not require armoring [Ref 7]. DISCUSSION: The results from the analysis show that the proposed GASTO-097 Breach Channels 1 and 2, and the GASTO-098 breach opening have flow capacity and lining stability to convey the stormwater runoff from the 50-yr, 24-hr storm event. Dam Breach Stormwater Calculation Primary and Secondary Dam Decommissioning Plan Duke Energy – Riverbend Steam Station Amec Foster Wheeler Project No. 7810-16-0625 6 of 6 10/18/2016 (Initial Submittal) In comments regarding previous submittals, North Carolina Department of Environmental Quality Dam Safety personnel suggested consideration of armoring vegetated channels to the 25-year water surface elevation. Given the accessibility and size of the proposed vegetated sections of the breach channels, vegetation appears to be maintainable and is an acceptable long-term lining. DRAWINGS: 1. Drawing RVB_C901.004.053 Dam Breach Cross-Section Locations REFERENCES: 1. Bonnin, G.M. et. al., “NOAA Atlas 14, Volume 2, Version 3, Point Precipitation Frequency Estimates”, NOAA National Weather Service, obtained September 15, 2014. 2. United States Department of Agriculture, “Urban Hydrology for Small Watersheds”, Technical Release 55, June 1986. 3. USDA-FSA-APFO NAIP MrSID Mosaic for Gaston County, North Carolina, dated 2010; NRCS Soil Survey for Gaston County, dated 2013. 4. HydroCAD 10.00 (build 9), HydroCAD Software Solutions LLC, 2013. 5. HEC-RAS 4.1.0, U.S. Army Corps of Engineers – Hydrologic Engineering Center, January 2010. 6. North American Green Tensar, Erosion Control Materials Design Software – ECMDS Version 5.0, 2011. 7. North Carolina Department of Environment and Natural Resources, “Erosion and Sediment Control Planning and Design Manual”, Revised May 2013. 8. “Standard Specification for Roads and Structures”, North Carolina Department of Transportation, Raleigh, January 2012. APPENDICES: 1. Precipitation Frequency [Ref. 1] 2. Time of Concentration Calculation Method [Ref. 2] 3. Soil Survey [Ref. 3] 4. HydroCAD Output 5. HEC-RAS Output 6. ECMDS Output 7. Design of Stable Channels and Diversions [Ref. 7] 8. Riprap and Stone for Erosion Control [Ref. 8] DRAWING RVB_C901.004.053 Dam Breach Cross-Section Locations 10 20 30TENTHSINCHES123 DWG SIZE REVISION FOR DRAWING NO. TITLE FILENAME: DWG TYPE: JOB NO: DATE: SCALE: DES: DFTR: CHKD: ENGR: APPD: A F E D C B 2345 786 45 789106 A F C B 22"x34" ANSI D Environment & Infrastructure SEAL REV DATE JOB NO. PROJECT TYPE DES DFTR CHKD ENGR APPD DESCRIPTION N NC GEOLOGY: C-247 NC ENG: F-1253 LICENSURE: FAX: (704) 357-8638 TEL: (704) 357-8600 CHARLOTTE, NC 28208 SUITE 100 2801 YORKMONT ROAD 10/18/2016 6226-14-0007 DWG AS SHOWN KRD KRD TBM CNB CNB .053 DAM BREACH CROSS-SECTION ALIGNMENTS.dwg 0 0 . 0 5 3 RVB_C901.004.053 PERMIT ISSUE - NOT FOR CONSTRUCTION DAM BREACH CROSS-SECTION LOCATIONS RIVERBEND STEAM STATION ASH POND CCR REMOVAL GRADING PLAN 0 10/18/2016 7810160625 CLOSURE PLAN CNB TBM KRD KRD PERMIT ISSUE 0.053 EXISTING GRADE INDEX CONTOUR (10') EXISTING GRADE INTERMEDIATE CONTOUR (2') FINAL GRADE INDEX CONTOUR (10') FINAL GRADE INTERMEDIATE CONTOUR (2') DRAINAGE AREA BOUNDARY DIVERSION CHANNEL TIME OF CONCENTRATION FLOW PATH WETLAND AREAS WETLAND STREAM LEGEND 01:44:35 PM 10-18-2016 (-04'00' GMT) APPENDIX 1 Precipitation Frequency [Ref. 1] NOAA Atlas 14, Volume 2, Version 3 Location name: Mount Holly, North Carolina, US* Latitude: 35.3674°, Longitude: -80.9637° Elevation: 719 ft* * source: Google Maps POINT PRECIPITATION FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley NOAA, National Weather Service, Silver Spring, Maryland PF_tabular | PF_graphical | Maps_&_aerials PF tabular PDS-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 0.391 (0.361-0.424) 0.462 (0.427-0.503) 0.539 (0.497-0.586) 0.595 (0.547-0.645) 0.659 (0.602-0.713) 0.704 (0.640-0.762) 0.745 (0.673-0.806) 0.781 (0.701-0.847) 0.822 (0.730-0.894) 0.851 (0.748-0.929) 10-min 0.625 (0.577-0.677) 0.739 (0.683-0.804) 0.864 (0.796-0.938) 0.952 (0.874-1.03) 1.05 (0.960-1.14) 1.12 (1.02-1.21) 1.18 (1.07-1.28) 1.24 (1.11-1.34) 1.30 (1.15-1.42) 1.34 (1.18-1.46) 15-min 0.782 (0.721-0.846) 0.930 (0.858-1.01) 1.09 (1.01-1.19) 1.20 (1.11-1.30) 1.33 (1.22-1.44) 1.42 (1.29-1.54) 1.50 (1.35-1.62) 1.56 (1.40-1.69) 1.64 (1.45-1.78) 1.68 (1.48-1.84) 30-min 1.07 (0.989-1.16) 1.28 (1.19-1.40) 1.55 (1.43-1.69) 1.75 (1.60-1.89) 1.97 (1.80-2.13) 2.14 (1.94-2.31) 2.29 (2.07-2.48) 2.43 (2.18-2.64) 2.61 (2.31-2.83) 2.72 (2.40-2.97) 60-min 1.34 (1.23-1.45) 1.61 (1.49-1.75) 1.99 (1.83-2.16) 2.27 (2.09-2.46) 2.63 (2.40-2.84) 2.90 (2.63-3.13) 3.16 (2.85-3.41) 3.41 (3.06-3.70) 3.74 (3.32-4.07) 3.98 (3.50-4.34) 2-hr 1.55 (1.42-1.69) 1.87 (1.71-2.05) 2.33 (2.13-2.54) 2.67 (2.44-2.92) 3.12 (2.83-3.41) 3.47 (3.13-3.78) 3.81 (3.42-4.16) 4.15 (3.69-4.54) 4.60 (4.05-5.04) 4.94 (4.30-5.43) 3-hr 1.66 (1.52-1.82) 2.00 (1.83-2.19) 2.50 (2.28-2.74) 2.88 (2.63-3.16) 3.40 (3.09-3.72) 3.82 (3.44-4.18) 4.23 (3.79-4.63) 4.66 (4.14-5.11) 5.25 (4.58-5.76) 5.71 (4.92-6.28) 6-hr 2.02 (1.86-2.21) 2.43 (2.24-2.66) 3.04 (2.80-3.33) 3.52 (3.22-3.84) 4.17 (3.79-4.54) 4.69 (4.24-5.10) 5.21 (4.67-5.68) 5.75 (5.11-6.27) 6.50 (5.68-7.10) 7.09 (6.12-7.76) 12-hr 2.40 (2.21-2.61) 2.89 (2.67-3.16) 3.63 (3.34-3.96) 4.21 (3.86-4.58) 5.01 (4.56-5.44) 5.66 (5.11-6.14) 6.33 (5.66-6.85) 7.02 (6.21-7.60) 7.99 (6.95-8.64) 8.76 (7.52-9.49) 24-hr 2.75 (2.56-2.95) 3.32 (3.10-3.57) 4.17 (3.88-4.48) 4.84 (4.50-5.19) 5.75 (5.32-6.16) 6.47 (5.98-6.93) 7.21 (6.65-7.72) 7.96 (7.32-8.54) 8.99 (8.23-9.65) 9.79 (8.94-10.5) 2-day 3.23 (3.01-3.46) 3.88 (3.63-4.17) 4.84 (4.52-5.19) 5.59 (5.21-6.00) 6.61 (6.14-7.08) 7.42 (6.88-7.94) 8.24 (7.62-8.82) 9.08 (8.38-9.72) 10.2 (9.40-11.0) 11.1 (10.2-11.9) 3-day 3.43 (3.20-3.67) 4.12 (3.85-4.41) 5.11 (4.77-5.46) 5.88 (5.48-6.29) 6.94 (6.45-7.42) 7.78 (7.21-8.32) 8.64 (7.99-9.23) 9.51 (8.78-10.2) 10.7 (9.84-11.5) 11.6 (10.7-12.4) 4-day 3.63 (3.39-3.88) 4.35 (4.07-4.66) 5.37 (5.01-5.74) 6.17 (5.75-6.59) 7.27 (6.76-7.77) 8.15 (7.55-8.69) 9.03 (8.36-9.64) 9.94 (9.17-10.6) 11.2 (10.3-12.0) 12.1 (11.1-13.0) 7-day 4.18 (3.93-4.44) 4.98 (4.69-5.29) 6.06 (5.70-6.44) 6.92 (6.49-7.34) 8.10 (7.57-8.59) 9.03 (8.43-9.59) 9.98 (9.29-10.6) 11.0 (10.2-11.7) 12.3 (11.4-13.1) 13.3 (12.3-14.2) 10-day 4.78 (4.51-5.09) 5.69 (5.36-6.05) 6.84 (6.43-7.27) 7.73 (7.27-8.22) 8.94 (8.38-9.50) 9.88 (9.25-10.5) 10.8 (10.1-11.5) 11.8 (11.0-12.5) 13.1 (12.2-13.9) 14.1 (13.1-15.0) 20-day 6.42 (6.09-6.78) 7.58 (7.18-8.00) 8.94 (8.47-9.44) 10.0 (9.48-10.6) 11.5 (10.8-12.1) 12.6 (11.9-13.3) 13.7 (12.9-14.5) 14.9 (13.9-15.7) 16.4 (15.3-17.4) 17.6 (16.4-18.7) 30-day 7.92 (7.54-8.33) 9.32 (8.86-9.79) 10.8 (10.3-11.4) 12.0 (11.4-12.6) 13.5 (12.8-14.2) 14.7 (13.9-15.5) 15.9 (15.0-16.7) 17.0 (16.0-17.9) 18.6 (17.4-19.6) 19.7 (18.4-20.8) 45-day 9.95 (9.53-10.4) 11.6 (11.1-12.2) 13.3 (12.7-13.9) 14.6 (13.9-15.2) 16.2 (15.4-16.9) 17.4 (16.6-18.2) 18.6 (17.7-19.5) 19.8 (18.8-20.8) 21.3 (20.2-22.4) 22.4 (21.2-23.6) 60-day 11.8 (11.4-12.4) 13.8 (13.2-14.4) 15.6 (14.9-16.2) 17.0 (16.2-17.7) 18.7 (17.9-19.5) 20.1 (19.2-20.9) 21.3 (20.4-22.3) 22.6 (21.5-23.6) 24.2 (23.0-25.3) 25.4 (24.1-26.6) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top PF graphical Page 1 of 4Precipitation Frequency Data Server 7/8/2014http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.3674&lon=-80.9637&data=... Back to Top Maps & aerials Small scale terrain Map data ©2014 GoogleReport a map error50 km Page 2 of 4Precipitation Frequency Data Server 7/8/2014http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.3674&lon=-80.9637&data=... Large scale terrain Large scale map Large scale aerial Back to Top US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service Office of Hydrologic Development 1325 East West Highway Silver Spring, MD 20910 Map data © 2014 GoogleReport a map error2 km Map data © 2014 GoogleReport a map error2 km Imagery ©2014 TerraM etricsReport a map error2 km Page 3 of 4Precipitation Frequency Data Server 7/8/2014http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.3674&lon=-80.9637&data=... APPENDIX 2 Time of Concentration Calculation Method [Ref. 2] Chapter 3 3–1(210-VI-TR-55, Second Ed., June 1986) Technical Release 55 Urban Hydrology for Small Watersheds Time of Concentration and Travel TimeChapter 3 Time of Concentration and Travel Time Travel time ( Tt ) is the time it takes water to travel from one location to another in a watershed. Tt is a component of time of concentration ( T c ), which is the time for runoff to travel from the hydraulically most distant point of the watershed to a point of interest within the watershed. Tc is computed by summing all the travel times for consecutive compo- nents of the drainage conveyance system. Tc influences the shape and peak of the runoff hydrograph. Urbanization usually decreases Tc, thereby increasing the peak discharge. But Tc can be increased as a result of (a) ponding behind small or inadequate drainage systems, including storm drain inlets and road culverts, or (b) reduction of land slope through grading. Factors affecting time of concen- tration and travel time Surface roughness One of the most significant effects of urban develop- ment on flow velocity is less retardance to flow. That is, undeveloped areas with very slow and shallow overland flow through vegetation become modified by urban development: the flow is then delivered to streets, gutters, and storm sewers that transport runoff downstream more rapidly. Travel time through the watershed is generally decreased. Channel shape and flow patterns In small non-urban watersheds, much of the travel time results from overland flow in upstream areas. Typically, urbanization reduces overland flow lengths by conveying storm runoff into a channel as soon as possible. Since channel designs have efficient hydrau- lic characteristics, runoff flow velocity increases and travel time decreases. Slope Slopes may be increased or decreased by urbanization, depending on the extent of site grading or the extent to which storm sewers and street ditches are used in the design of the water management system. Slope will tend to increase when channels are straightened and decrease when overland flow is directed through storm sewers, street gutters, and diversions. Computation of travel time and time of concentration Water moves through a watershed as sheet flow, shallow concentrated flow, open channel flow, or some combination of these. The type that occurs is a function of the conveyance system and is best deter- mined by field inspection. Travel time ( Tt ) is the ratio of flow length to flow velocity: T L Vt= 3600 [eq. 3-1] where: Tt = travel time (hr) L = flow length (ft) V = average velocity (ft/s) 3600 = conversion factor from seconds to hours. Time of concentration ( Tc ) is the sum of Tt values for the various consecutive flow segments: TT T Tct t tm=++12K [eq. 3-2] where: Tc = time of concentration (hr) m = number of flow segments Technical Release 55 Urban Hydrology for Small Watersheds Time of Concentration and Travel TimeChapter 3 3–2 (210-VI-TR-55, Second Ed., June 1986) Figure 3-1 Average velocities for estimating travel time for shallow concentrated flow 10 20 Average velocity (ft/sec) Wa t e r c o u r s e s l o p e ( f t / f t ) .20 .50 Un p a v e d Pa v e d .06 .04 .02 .10 .01 .005 1 2 4 6 Chapter 3 3–3(210-VI-TR-55, Second Ed., June 1986) Technical Release 55 Urban Hydrology for Small Watersheds Time of Concentration and Travel Time Sheet flow Sheet flow is flow over plane surfaces. It usually occurs in the headwater of streams. With sheet flow, the friction value (Manning’s n) is an effective rough- ness coefficient that includes the effect of raindrop impact; drag over the plane surface; obstacles such as litter, crop ridges, and rocks; and erosion and trans- portation of sediment. These n values are for very shallow flow depths of about 0.1 foot or so. Table 3-1 gives Manning’s n values for sheet flow for various surface conditions. For sheet flow of less than 300 feet, use Manning’s kinematic solution (Overtop and Meadows 1976) to compute Tt: T nL Ps t =() () 0 007 08 2 05 04 .. ..[eq. 3-3] where: Tt = travel time (hr), n = Manning’s roughness coefficient (table 3-1) L = flow length (ft) P2 = 2-year, 24-hour rainfall (in) s = slope of hydraulic grade line (land slope, ft/ft) This simplified form of the Manning’s kinematic solu- tion is based on the following: (1) shallow steady uniform flow, (2) constant intensity of rainfall excess (that part of a rain available for runoff), (3) rainfall duration of 24 hours, and (4) minor effect of infiltra- tion on travel time. Rainfall depth can be obtained from appendix B. Shallow concentrated flow After a maximum of 300 feet, sheet flow usually be- comes shallow concentrated flow. The average veloc- ity for this flow can be determined from figure 3-1, in which average velocity is a function of watercourse slope and type of channel. For slopes less than 0.005 ft/ft, use equations given in appendix F for figure 3-1. Tillage can affect the direction of shallow concen- trated flow. Flow may not always be directly down the watershed slope if tillage runs across the slope. After determining average velocity in figure 3-1, use equation 3-1 to estimate travel time for the shallow concentrated flow segment. Open channels Open channels are assumed to begin where surveyed cross section information has been obtained, where channels are visible on aerial photographs, or where blue lines (indicating streams) appear on United States Geological Survey (USGS) quadrangle sheets. Manning’s equation or water surface profile informa- tion can be used to estimate average flow velocity. Average flow velocity is usually determined for bank- full elevation. Table 3-1 Roughness coefficients (Manning’s n) for sheet flow Surface description n 1/ Smooth surfaces (concrete, asphalt, gravel, or bare soil) .......................................... 0.011 Fallow (no residue).................................................. 0.05 Cultivated soils: Residue cover ≤20% ......................................... 0.06 Residue cover >20% ......................................... 0.17 Grass: Short grass prairie............................................ 0.15 Dense grasses 2/................................................ 0.24 Bermudagrass . ................................................. 0.41 Range (natural)......................................................... 0.13 Woods:3/ Light underbrush .............................................. 0.40 Dense underbrush ............................................ 0.80 1 The n values are a composite of information compiled by Engman (1986). 2 Includes species such as weeping lovegrass, bluegrass, buffalo grass, blue grama grass, and native grass mixtures. 3 When selecting n , consider cover to a height of about 0.1 ft. This is the only part of the plant cover that will obstruct sheet flow. Technical Release 55 Urban Hydrology for Small Watersheds Time of Concentration and Travel TimeChapter 3 3–4 (210-VI-TR-55, Second Ed., June 1986) Manning’s equation is: V rs n =149 2 3 1 2.[eq. 3-4] where: V = average velocity (ft/s) r = hydraulic radius (ft) and is equal to a/pw a = cross sectional flow area (ft 2) pw = wetted perimeter (ft) s = slope of the hydraulic grade line (channel slope, ft/ft) n = Manning’s roughness coefficient for open channel flow. Manning’s n values for open channel flow can be obtained from standard textbooks such as Chow (1959) or Linsley et al. (1982). After average velocity is computed using equation 3-4, Tt for the channel seg- ment can be estimated using equation 3-1. Reservoirs or lakes Sometimes it is necessary to estimate the velocity of flow through a reservoir or lake at the outlet of a watershed. This travel time is normally very small and can be assumed as zero. Limitations • Manning’s kinematic solution should not be used for sheet flow longer than 300 feet. Equation 3-3 was developed for use with the four standard rainfall intensity-duration relationships. • In watersheds with storm sewers, carefully identify the appropriate hydraulic flow path to estimate Tc. Storm sewers generally handle only a small portion of a large event. The rest of the peak flow travels by streets, lawns, and so on, to the outlet. Consult a standard hydraulics textbook to determine average velocity in pipes for either pressure or nonpressure flow. • The minimum Tc used in TR-55 is 0.1 hour. • A culvert or bridge can act as a reservoir outlet if there is significant storage behind it. The proce- dures in TR-55 can be used to determine the peak flow upstream of the culvert. Detailed storage routing procedures should be used to determine the outflow through the culvert. Example 3-1 The sketch below shows a watershed in Dyer County, northwestern Tennessee. The problem is to compute Tc at the outlet of the watershed (point D). The 2-year 24-hour rainfall depth is 3.6 inches. All three types of flow occur from the hydraulically most distant point (A) to the point of interest (D). To compute Tc, first determine Tt for each segment from the following information: Segment AB: Sheet flow; dense grass; slope (s) = 0.01 ft/ft; and length (L) = 100 ft. Segment BC: Shallow concentrated flow; unpaved; s = 0.01 ft/ft; and L = 1,400 ft. Segment CD: Channel flow; Manning’s n = .05; flow area (a) = 27 ft2; wetted perimeter (pw) = 28.2 ft; s = 0.005 ft/ft; and L = 7,300 ft. See figure 3-2 for the computations made on worksheet 3. A B C D 7,300 ft1,400 ft100 ft (Not to scale) APPENDIX 3 Soil Survey [Ref. 3] PREPARED BY DATE CHECKED BY DATE JOB NUMBER FIGURE 0 1,000 2,000 3,000 4,000500 Feet 2 Source: USDA-FSA-APFO NAIP MrSID Mosaic for Gaston County, North Carolina, dated 2010; NRCS Soil Survey for Gaston County, dated 2013. PaD2 Ud WeD WkF VaB PaD2 W CfB Ur PaE ApB WnB PaD2 LdB2 ChA ChA CfB CeD2 PaD2 PaE CoA PaE PaD2 CeB2 CeD2 ChA WnD ApB LdB2 WeD CeB2 PaD2 ChA ChA W PaD2 CeB2 W PaD2 CeB2 WeD CfD W PaE PaD2 ChA PaE NC OneMap, NC Center for Geographic Information and Analysis, NC 911 Board NRCS SOIL SURVEY RIVERBEND STEAM STATION GASTON COUNTY, NORTH CAROLINA r Soil Symbol Description Hydrologic Soil Group CeB2 Cecil sandy clay loam, 2 to 8 percent slopes, moderately eroded B CeD2 Cecil sandy clay loam, 8 to 15 percent slopes, moderately eroded B CfB Cecil-Urban land complex, 2 to 8 percent slopes B ChA Chewacla loam, 0 to 2 percent slopes, frequently flooded B/D CoA Congaree loam, 0 to 2 percent slopes, occasionally flooded C LdB2 Lloyd sandy clay loam, 2 to 8 percent slopes, moderately eroded B PaD2 Pacolet sandy clay loam, 8 to 15 percent slopes, moderately eroded B PaE Pacolet sandy loam, 15 to 25 percent slopes B Ud Udorthents, loamy C Ur Urban land NA W Water NA WeD Wedowee sandy loam, 6 to 15 percent slopes B WkF Wilkes loam, 15 to 30 percent slopes D WnB Winnsboro loam, 2 to 8 percent slopes C 7810-15-0348JMS 12/4/15 12/4/15CB Project Boundary Soil Type Boundary Do c u m e n t P a t h : F : \ A M E C _ P r o j e c t s \ 2 0 1 5 \ 7 8 1 0 - 1 5 - 0 3 8 4 R i v e r b e n d \ G I S \ M X D s \ F i g - 2 _ S o i l s . m x d APPENDIX 4 HydroCAD Output 2S DA-098-1 3S DA-097-1 4S DA-097-2 Routing Diagram for GASTO-097 and 098 Dam Breach Prepared by AMEC, Printed 10/17/2016 HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link GASTO-097 and 098 Dam Breach Printed 10/17/2016Prepared by AMEC Page 2HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CN Description (subcatchment-numbers) 92.910 69 50-75% Grass cover, Fair, HSG B (2S, 3S, 4S) 92.910 69 TOTAL AREA GASTO-097 and 098 Dam Breach Printed 10/17/2016Prepared by AMEC Page 3HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Soil Listing (selected nodes) Area (acres) Soil Group Subcatchment Numbers 0.000 HSG A 92.910 HSG B 2S, 3S, 4S 0.000 HSG C 0.000 HSG D 0.000 Other 92.910 TOTAL AREA GASTO-097 and 098 Dam Breach Printed 10/17/2016Prepared by AMEC Page 4HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Ground Covers (selected nodes) HSG-A (acres) HSG-B (acres) HSG-C (acres) HSG-D (acres) Other (acres) Total (acres) Ground Cover Subcatchment Numbers 0.000 92.910 0.000 0.000 0.000 92.910 50-75% Grass cover, Fair 2S, 3S, 4S 0.000 92.910 0.000 0.000 0.000 92.910 TOTAL AREA Type II 24-hr 50yr - 24hrs Rainfall=6.47"GASTO-097 and 098 Dam Breach Printed 10/17/2016Prepared by AMEC Page 5HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Time span=0.00-72.00 hrs, dt=0.05 hrs, 1441 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Runoff Area=71.000 ac 0.00% Impervious Runoff Depth=3.08"Subcatchment 2S: DA-098-1 Flow Length=2,055' Tc=14.4 min CN=69 Runoff=286.47 cfs 18.249 af Runoff Area=14.830 ac 0.00% Impervious Runoff Depth=3.08"Subcatchment 3S: DA-097-1 Flow Length=1,740' Tc=9.3 min CN=69 Runoff=71.26 cfs 3.812 af Runoff Area=7.080 ac 0.00% Impervious Runoff Depth=3.08"Subcatchment 4S: DA-097-2 Flow Length=945' Tc=6.7 min CN=69 Runoff=37.30 cfs 1.820 af Total Runoff Area = 92.910 ac Runoff Volume = 23.880 af Average Runoff Depth = 3.08" 100.00% Pervious = 92.910 ac 0.00% Impervious = 0.000 ac Type II 24-hr 50yr - 24hrs Rainfall=6.47"GASTO-097 and 098 Dam Breach Printed 10/17/2016Prepared by AMEC Page 6HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 2S: DA-098-1 Runoff = 286.47 cfs @ 12.07 hrs, Volume= 18.249 af, Depth= 3.08" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Type II 24-hr 50yr - 24hrs Rainfall=6.47" Area (ac) CN Description 71.000 69 50-75% Grass cover, Fair, HSG B 71.000 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.6 100 0.0200 0.19 Sheet Flow, Range n= 0.130 P2= 3.32" 1.6 480 0.1000 5.09 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 4.2 1,475 0.0200 5.83 17.48 Channel Flow, Area= 3.0 sf Perim= 6.3' r= 0.48' n= 0.022 Earth, clean & straight 14.4 2,055 Total Subcatchment 2S: DA-098-1 Runoff Hydrograph Time (hours) 7065605550454035302520151050 Fl o w ( c f s ) 300 250 200 150 100 50 0 Type II 24-hr 50yr - 24hrs Rainfall=6.47" Runoff Area=71.000 ac Runoff Volume=18.249 af Runoff Depth=3.08" Flow Length=2,055' Tc=14.4 min CN=69 286.47 cfs Type II 24-hr 50yr - 24hrs Rainfall=6.47"GASTO-097 and 098 Dam Breach Printed 10/17/2016Prepared by AMEC Page 7HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: DA-097-1 Runoff = 71.26 cfs @ 12.01 hrs, Volume= 3.812 af, Depth= 3.08" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Type II 24-hr 50yr - 24hrs Rainfall=6.47" Area (ac) CN Description 14.830 69 50-75% Grass cover, Fair, HSG B 14.830 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.7 100 0.0900 0.35 Sheet Flow, Range n= 0.130 P2= 3.32" 3.3 890 0.0800 4.55 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 1.3 750 0.0150 9.37 187.34 Channel Flow, Area= 20.0 sf Perim= 16.6' r= 1.20' n= 0.022 Earth, clean & straight 9.3 1,740 Total Subcatchment 3S: DA-097-1 Runoff Hydrograph Time (hours) 7065605550454035302520151050 Fl o w ( c f s ) 70 60 50 40 30 20 10 0 Type II 24-hr 50yr - 24hrs Rainfall=6.47" Runoff Area=14.830 ac Runoff Volume=3.812 af Runoff Depth=3.08" Flow Length=1,740' Tc=9.3 min CN=69 71.26 cfs Type II 24-hr 50yr - 24hrs Rainfall=6.47"GASTO-097 and 098 Dam Breach Printed 10/17/2016Prepared by AMEC Page 8HydroCAD® 10.00 s/n 08086 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: DA-097-2 Runoff = 37.30 cfs @ 11.98 hrs, Volume= 1.820 af, Depth= 3.08" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs Type II 24-hr 50yr - 24hrs Rainfall=6.47" Area (ac) CN Description 7.080 69 50-75% Grass cover, Fair, HSG B 7.080 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.5 100 0.1000 0.37 Sheet Flow, Range n= 0.130 P2= 3.32" 1.6 435 0.0800 4.55 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.6 410 0.0250 11.35 181.63 Channel Flow, Area= 16.0 sf Perim= 14.6' r= 1.10' n= 0.022 Earth, clean & straight 6.7 945 Total Subcatchment 4S: DA-097-2 Runoff Hydrograph Time (hours) 7065605550454035302520151050 Fl o w ( c f s ) 40 35 30 25 20 15 10 5 0 Type II 24-hr 50yr - 24hrs Rainfall=6.47" Runoff Area=7.080 ac Runoff Volume=1.820 af Runoff Depth=3.08" Flow Length=945' Tc=6.7 min CN=69 37.30 cfs APPENDIX 5 HEC-RAS Output HEC-RAS Plan: Plan 03 River: GASTO-097 BC 1 Reach: GASTO-097 BC 1 Profile: PF 1 Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Mann Wtd Chnl Froude # Chl Shear Chan Shear Total Max Chl Dpth (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) (lb/sq ft) (lb/sq ft) (ft) GASTO-097 BC 1 750 PF 1 71.26 683.23 685.13 684.72 685.36 0.012485 3.87 18.42 15.47 0.047 0.62 0.89 0.89 1.90 GASTO-097 BC 1 700 PF 1 71.26 682.60 684.48 684.72 0.013035 3.94 18.10 15.28 0.047 0.64 0.93 0.93 1.88 GASTO-097 BC 1 650 PF 1 71.26 681.95 683.88 684.10 0.011549 3.76 18.93 15.61 0.047 0.60 0.84 0.84 1.93 GASTO-097 BC 1 600 PF 1 71.26 681.37 683.25 683.49 0.013110 3.92 18.16 15.49 0.047 0.64 0.92 0.92 1.88 GASTO-097 BC 1 550 PF 1 71.26 680.71 682.58 682.82 0.013413 3.98 17.91 15.20 0.047 0.65 0.95 0.95 1.87 GASTO-097 BC 1 500 PF 1 71.26 680.04 681.93 682.16 0.012811 3.91 18.22 15.33 0.047 0.63 0.91 0.91 1.89 GASTO-097 BC 1 450 PF 1 71.26 679.40 681.29 681.53 0.012538 3.88 18.36 15.38 0.047 0.63 0.90 0.90 1.89 GASTO-097 BC 1 400 PF 1 71.26 678.77 680.66 680.89 0.012748 3.90 18.25 15.35 0.047 0.63 0.91 0.91 1.89 GASTO-097 BC 1 350 PF 1 71.26 678.13 680.05 680.27 0.011938 3.81 18.69 15.50 0.047 0.61 0.86 0.86 1.92 GASTO-097 BC 1 300 PF 1 71.26 677.53 679.41 679.65 0.013037 3.94 18.10 15.28 0.047 0.64 0.93 0.93 1.88 GASTO-097 BC 1 250 PF 1 71.26 676.88 678.77 679.01 0.012561 3.88 18.38 15.44 0.047 0.63 0.90 0.90 1.89 GASTO-097 BC 1 200 PF 1 71.26 676.25 678.12 678.36 0.013221 3.95 18.03 15.30 0.047 0.64 0.94 0.94 1.87 GASTO-097 BC 1 150 PF 1 71.26 675.67 677.16 677.16 677.65 0.014158 5.65 12.61 12.94 0.030 1.01 0.83 0.83 1.49 GASTO-097 BC 1 100 PF 1 71.26 674.70 676.01 676.19 676.74 0.023646 6.82 10.45 11.91 0.030 1.28 1.25 1.25 1.31 GASTO-097 BC 1 50 PF 1 71.26 673.01 674.17 674.49 675.21 0.038885 8.18 8.71 10.99 0.030 1.62 1.86 1.86 1.16 GASTO-097 BC 1 0 PF 1 71.26 668.00 668.82 669.49 671.61 0.151671 13.39 5.32 8.94 0.030 3.06 5.48 5.48 0.82 HEC-RAS Plan: Plan 01 River: GASTO-097 BC 2 Reach: GASTO-097 BC 2 Profile: PF 1 Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Mann Wtd Chnl Froude # Chl Shear Chan Shear Total Max Chl Dpth (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) (lb/sq ft) (lb/sq ft) (ft) GASTO-097 BC 2 550 PF 1 37.30 682.83 684.38 684.11 684.59 0.020077 3.63 10.28 11.27 0.053 0.67 1.09 1.09 1.55 GASTO-097 BC 2 500 PF 1 37.30 681.84 683.39 683.59 0.019951 3.62 10.31 11.31 0.053 0.67 1.09 1.09 1.55 GASTO-097 BC 2 450 PF 1 37.30 680.85 682.41 682.61 0.019292 3.57 10.44 11.37 0.053 0.66 1.06 1.06 1.56 GASTO-097 BC 2 400 PF 1 37.30 679.88 681.44 681.64 0.019094 3.56 10.48 11.40 0.053 0.65 1.05 1.05 1.56 GASTO-097 BC 2 350 PF 1 37.30 678.92 680.49 680.68 0.018863 3.54 10.52 11.41 0.053 0.65 1.04 1.04 1.57 GASTO-097 BC 2 300 PF 1 37.30 677.98 679.54 679.74 0.019325 3.58 10.43 11.37 0.053 0.66 1.06 1.06 1.56 GASTO-097 BC 2 250 PF 1 37.30 677.05 678.66 678.84 0.016579 3.37 11.05 11.70 0.053 0.61 0.94 0.94 1.61 GASTO-097 BC 2 200 PF 1 37.30 676.13 677.63 677.41 677.86 0.023353 3.84 9.72 10.97 0.053 0.72 1.24 1.24 1.50 GASTO-097 BC 2 150 PF 1 37.30 675.24 676.51 676.51 676.91 0.015476 5.03 7.42 9.66 0.030 1.01 0.71 0.71 1.27 GASTO-097 BC 2 100 PF 1 37.30 674.02 675.09 675.29 675.78 0.033107 6.67 5.59 8.44 0.030 1.44 1.32 1.32 1.07 GASTO-097 BC 2 50 PF 1 37.30 666.34 666.93 667.61 671.38 0.416223 16.94 2.20 5.52 0.030 4.72 10.03 10.03 0.59 GASTO-097 BC 2 0 PF 1 37.30 650.00 650.64 651.27 654.01 0.284471 14.73 2.53 5.87 0.030 3.95 7.40 7.40 0.64 HEC-RAS Plan: Plan 01 River: GASTO-098 BREACH Reach: GASTO-098 BREACH Profile: PF 1 Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Mann Wtd Chnl Froude # Chl Shear Chan Shear Total Max Chl Dpth (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) (lb/sq ft) (lb/sq ft) (ft) GASTO-098 BREACH 400 PF 1 286.47 656.96 658.23 658.23 658.36 0.040580 2.95 97.24 480.36 0.035 1.15 0.51 0.51 1.27 GASTO-098 BREACH 350 PF 1 286.47 655.77 657.08 657.05 657.17 0.020403 2.41 118.66 471.74 0.035 0.85 0.32 0.32 1.31 GASTO-098 BREACH 300 PF 1 286.47 654.58 655.87 655.86 655.98 0.028358 2.69 106.53 461.17 0.035 0.99 0.41 0.41 1.29 GASTO-098 BREACH 250 PF 1 286.47 653.39 654.71 654.66 654.80 0.019824 2.44 117.60 451.40 0.035 0.84 0.32 0.32 1.32 GASTO-098 BREACH 200 PF 1 286.47 652.21 653.50 653.49 653.62 0.028659 2.78 102.99 427.14 0.035 1.00 0.43 0.43 1.29 GASTO-098 BREACH 150 PF 1 286.47 651.04 652.34 652.30 652.44 0.019540 2.54 112.98 403.97 0.035 0.84 0.34 0.34 1.30 GASTO-098 BREACH 100 PF 1 286.47 649.88 651.14 651.13 651.27 0.028526 2.91 98.39 379.96 0.035 1.01 0.46 0.46 1.26 GASTO-098 BREACH 50 PF 1 286.47 648.79 649.73 649.73 649.88 0.027171 3.09 92.82 316.65 0.035 1.00 0.50 0.50 0.94 GASTO-098 BREACH 0 PF 1 286.47 646.59 647.31 647.46 647.81 0.067520 5.64 50.77 138.74 0.035 1.64 1.54 1.54 0.72 APPENDIX 6 ECMDS Output 10/17/2016 www.ecmds.com/print/analysis/103585/103590 http://www.ecmds.com/print/analysis/103585/103590 1/1 Tensar International Corporation 5401 St. Wendel-Cynthiana Road Poseyville, Indiana 47633 Tel. 800.772.2040 Fax 812.867.0247 www.nagreen.com Erosion Control Materials Design Software Version 5.0 Project Name: Riverbend Dam Decommissioning Project Number: 103585 Channel Name: GASTO-097 Breach Channel 1 Discharge 71.26 Peak Flow Period 12 Channel Slope 0.013 Channel Bottom Width 4 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardance Class C Vegtation Type Mix (Sod & Bunch) Vegetation Density Fair 50-75% Soil Type Loam C125 Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern C125 Unvegetated Straight 71.26 cfs 7.87 ft/s 1.19 ft 0.018 2.25 lbs/ft2 0.97 lbs/ft2 2.32 STABLE D Unreinforced Vegetation - Class C - Mix (Sod & Bunch) - Fair 50-75% Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern Unreinforced Vegetation Straight 71.26 cfs 3.9 ft/s 1.89 ft 0.047 4.2 lbs/ft2 1.53 lbs/ft2 2.74 STABLE -- Underlying Substrate Straight 71.26 cfs 3.9 ft/s 1.89 ft -- 0.04 lbs/ft2 0.066 lbs/ft2 0.53 UNSTABLE -- 10/17/2016 www.ecmds.com/print/analysis/103585/103595 http://www.ecmds.com/print/analysis/103585/103595 1/1 Tensar International Corporation 5401 St. Wendel-Cynthiana Road Poseyville, Indiana 47633 Tel. 800.772.2040 Fax 812.867.0247 www.nagreen.com Erosion Control Materials Design Software Version 5.0 Project Name: Riverbend Dam Decommissioning Project Number: 103585 Channel Name: GASTO-097 Breach Channel 2 Discharge 37.30 Peak Flow Period 12 Channel Slope 0.022 Channel Bottom Width 2 Left Side Slope 3 Right Side Slope 3 Low Flow Liner Retardance Class C Vegtation Type Mix (Sod & Bunch) Vegetation Density Fair 50-75% Soil Type Loam C125 Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern C125 Unvegetated Straight37.3 cfs 7.89 ft/s 0.97 ft 0.02 2.25 lbs/ft2 1.33 lbs/ft2 1.7 STABLE D Unreinforced Vegetation - Class C - Mix (Sod & Bunch) - Fair 50-75% Phase Reach DischargeVelocity Normal Depth Mannings N Permissible Shear Stress Calculated Shear Stress Safety Factor Remarks Staple Pattern Unreinforced Vegetation Straight37.3 cfs 3.77 ft/s 1.51 ft 0.053 4.2 lbs/ft2 2.08 lbs/ft2 2.02 STABLE -- Underlying Substrate Straight37.3 cfs 3.77 ft/s 1.51 ft -- 0.04 lbs/ft2 0.073 lbs/ft2 0.48 UNSTABLE -- APPENDIX 7 Design of Stable Channels and Diversions [Ref. 7] Appendices This section addresses the design of stable conveyance channels and diversions using flexible linings. A stable channel is defined as a channel which is nonsilting and nonscouring. To minimize silting in the channel, flow velocities should remain constant or increase slightly throughout the channel length. This is especially important in designing diversion channels and can be accomplished by adjusting channel grade. Procedures presented in this section address the problems of erosion and scour. More advanced procedures for permanent, unlined channels may be found elsewhere. (References: Garde and Ranga Raju, 1980) Diversions are channels usually with a supporting ridge on the lower side. They are generally located to divert flows across a slope and are designed following the same procedures as other channels. Design tables for vegetated diversions and waterways are included at the end of this section. Flexible channel linings are generally preferred to rigid linings from an erosion control standpoint because they conform to changes in channel shape without failure and are less susceptible to damage from frost heaving, soil swelling and shrinking, and excessive soil pore water pressure from lack of drainage. Flexible linings also are generally less expensive to construct, and when vegetated, are more natural in appearance. On the other hand, flexible linings generally have higher roughness and require a larger cross section for the same discharge. EROSION CONTROL CRITERIA The minimum design criteria for conveyance channels require that two primary conditions be satisfied: the channel system must have capacity for the peak flow expected from the 10-year storm and the channel lining must be resistant to erosion for the design velocity. In some cases, out-of-bank flow may be considered a functional part of the channel system. In these cases, flow capacities and design velocities should be considered separately for out- of-bank flows and channel flows. Both the capacity of the channel and the velocity of flow are functions of the channel lining, cross-sectional area and slope. The channel system must carry the design flow, fit site conditions, and be stable. STABLE CHANNEL DESIGN METHODS Two accepted procedures for designing stable channels with flexible linings are: (1) the permissible velocity approach; and (2) the tractive force approach. Under the permissible velocity approach, the channel is considered stable if the design, mean velocity is lower than the maximum permissible velocity. Under the tractive force approach, erosive stress evaluated at the boundary between flowing water and lining materials must be less than the minimum unit tractive force that will cause serious erosion of material from a level channel bed. 8.05 DESIGN OF STABLE CHANNELS AND DIVERSIONS 8.05.1 8 8.05.2 The permissible velocity procedure is recommended for the design of vegetative channels because of common usage and the availability of reliable design tables. The tractive force approach is recommended for design of channels with temporary synthetic liners or riprap liners. The tractive force procedure is described in full in the U.S. Department of Transportation, Federal Highway Administration Bulletin, Design of Roadside Channels with Flexible Linings. Permissible Velocity Procedure The permissible velocity procedure uses two equations to calculate flow: Manning’s equation, 9 R S n where: V = average velocity in the channel in ft/sec. n = Manning’s roughness coefficient, based upon the lining of the channel R = hydraulic radius, wetted cross-sectional area/wetted perimeter in ft S = slope of the channel in ft/ft and the continuity equation, 4 $9 where: Q = flow in the channel in cfs A = cross-sectional area of flow within the channel in ft2 V = average velocity in the channel in ft/sec. Manning’s equation and the continuity equation are used together to determine channel capacity and flow velocity. A nomograph for solving Manning’s equation is given in Figure 8.05a. 6HOHFWLQJ3HUPDQHQW Channel Lining Channel lining materials include such flexible materials as grass, riprap and gabions, as well as rigid materials such as paving blocks, flag stone, gunite, asphalt, and concrete. The design of concrete and similar rigid linings is generally not restricted by flow velocities. However, flexible channel linings do have maximum permissible flow velocities beyond which they are susceptible to erosion. The designer should select the type of liner that best fits site conditions. Table 8.05a lists maximum permissible velocities for established grass linings and soil conditions. Before grass is established, permissible velocity is determined by the choice of temporary liner. Permissible velocities for riprap linings are higher than for grass and depend on the stone size selected. Appendices 8.05.3 8 8.05.4 Table 8.05a Maximum Allowable Design Velocities1 for Vegetated Channels Typical Channel Slope Application Soil Characteristics2 Grass Lining Permissible Velocity 3 for Established Grass Lining (ft/sec) 0-5% Easily Erodible Non-plastic (Sands & Silts) Bermudagrass Tall fescue Bahiagrass Kentucky bluegrass Grass-legume mixture 5.0 4.5 4.5 4.5 3.5 Erosion Resistant Plastic (Clay mixes) Bermudagrass Tall fescue Bahiagrass Kentucky bluegrass Grass-legume mixture 6.0 5.5 5.5 5.5 4.5 5-10% Easily Erodible Non-plastic (Sands & Silts) Bermudagrass Tall fescue Bahiagrass Kentucky bluegrass Grass-legume mixture 4.5 4.0 4.0 4.0 3.0 Erosion Resistant Plastic (Clay mixes) Bermudagrass Tall fescue Bahiagrass Kentucky bluegrass Grass-legume mixture 5.5 5.0 5.0 5.0 3.5 >10% Easily Erodible Non-plastic (Sands & Silts) Bermudagrass Tall fescue Bahiagrass Kentucky bluegrass 3.5 2.5 2.5 2.5 Erosion Resistant Plastic (Clay mixes) Bermudagrass Tall fescue Bahiagrass Kentucky bluegrass 4.5 3.5 3.5 3.5 6RXUFH 86'$6&60RGL¿HG NOTE:1Permissible Velocity based on 10-year storm peak runoff 26RLOHURGLELOLW\EDVHGRQUHVLVWDQFHWRVRLOPRYHPHQWIURPFRQFHQWUDWHGÀRZLQJZDWHU 3Before grass is established, permissible velocity is determined by the type of temporary liner used. Selecting Channel Cross-Section Geometry To calculate the required size of an open channel, assume the design flow is uniform and does not vary with time. Since actual flow conditions change throughout the length of a channel, subdivide the channel into design reaches, and design each reach to carry the appropriate capacity. The three most commonly used channel cross-sections are “V”-shaped, parabolic, and trapezoidal. Figure 8.05b gives mathematical formulas for the area, hydraulic radius and top width of each of these shapes. Appendices 8.05.5 8 8.05.6 Rev. 12/93 Design Procedure- Permissible Velocity The following is a step-by-step procedure for designing a runoff conveyance channel using Manning’s equation and the continuity equation: Step 1. Determine the required flow capacity, Q, by estimating peak runoff rate for the design storm (Appendix 8.03). Step 2. Determine the slope and select channel geometry and lining. Step 3. Determine the permissible velocity for the lining selected, or the desired velocity, if paved. (see Table 8.05a, page 8.05.4) Step 4. Make an initial estimate of channel size—divide the required Q by the permissible velocity to reach a “first try” estimate of channel flow area. Then select a geometry, depth, and top width to fit site conditions. Step 5. Calculate the hydraulic radius, R, from channel geometry (Figure 8.05b, page 8.05.5). Step 6. Determine roughness coefficient n. Structural Linings—see Table 8.05b, page 8.05.6. Grass Lining: a. Determine retardance class for vegetation from Table 8.05c, page 8.05.8. To meet stability requirement, use retardance for newly mowed condition (generally C or D). To determine channel capacity, use at least one retardance class higher. b. Determine n from Figure 8.05c, page 8.05.7. Step 7. Calculate the actual channel velocity, V, using Manning’s equation (Figure 8.05a, pg. 8.05.3), and calculate channel capacity, Q, using the continuity equation. Step 8. Check results against permissible velocity and required design capacity to determine if design is acceptable. Step 9. If design is not acceptable, alter channel dimensions as appropriate. For trapezoidal channels, this adjustment is usually made by changing the bottom width. Table 8.05b Manning’s n for Structural Channel Linings Channel Lining Recommended n values Asphaltic concrete, machine placed Asphalt, exposed prefabricated Concrete Metal, corrugated Plastic Shotcrete Gabion Earth 0.014 0.015 0.015 0.024 0.013 0.017 0.030 0.020 6RXUFH $PHULFDQ6RFLHW\RI&LYLO(QJLQHHUV PRGL¿HG Appendices Rev. 12/93 8.05.7 Step 10. For grass-lined channels once the appropriate channel dimensions have been selected for low retardance conditions, repeat steps 6 through 8 using a higher retardance class, corresponding to tall grass. Adjust capacity of the channel by varying depth where site conditions permit. NOTE 1: If design velocity is greater than 2.0 ft/sec., a temporary lining may be required to stabilize the channel until vegetation is established. The temporary liner may be designed for peak flow from the 2-year storm. If a channel requires a temporary lining, the designer should analyze shear stresses in the channel to select the liner that provides protection and promotes establishment of vegetation. For the design of temporary liners, use tractive force procedure. NOTE 2: Design Tables—Vegetated Channels and Diversions at the end of this section may be used to design grass-lined channels with parabolic cross-sections. Step 11. Check outlet for carrying capacity and stability. If discharge velocities exceed allowable velocities for the receiving stream, an outlet protection structure will be required (Table 8.05d, page 8.05.9). Sample Problem 8.05a illustrates the design of a grass-lined channel. 8 8.05.8 Table 8.05c Retardance Classification for Vegetal Covers Retardance Cover Condition A Reed canarygrass Weeping lovegrass Excellent stand, tall (average 36”) Excellent stand, tall (average 30”) B Tall fescue Bermudagrass Grass-legume mixture (tall fescue,red fescue, sericea lespedeza) Grass mixture (timothy, smooth bromegrass or orchardgrass) Sericea lespedeza Reed canarygrass Alfalfa Good stand, uncut, (average 18”) Good stand, tall (average 12”) Good stand, uncut Good stand, uncut (average 20”) *RRGVWDQGQRWZRRG\WDOO DYHUDJH ´ Good stand, cut, (average 12-15”) Good stand, uncut (average 11”) C Tall fescue Bermudagrass Bahiagrass Grass-legume mixture-- summer (orchardgrass, redtop and annual lespedeza) Centipedegrass Kentucky bluegrass Redtop Good stand (8-12”) Good stand, cut (average 6”) Good stand, uncut (6-8”) Good stand, uncut (6-8”) Very dense cover (average 6”) Good stand, headed (6-12”) Good stand, uncut (15-20”) D Tall fescue Bermudagrass Bahiagrass Grass-legume mixture-- fall-spring (orchardgrass, redtop, and annual lespedeza) Red fescue Centipedegrass Kentucky bluegrass Good stand, cut (3-4”) Good stand, cut (2.5”) Good stand, cut (3-4”) Good stand, uncut (4-5”) Good stand, uncut (12-18”) Good stand, cut (3-4”) Good stand, cut (3-4”) E Bermudagrass Bermudagrass Good stand, cut (1.5”) Burned stubble 0RGL¿HGIURP 86'$6&6 (QJLQHHULQJ)LHOG0DQXDO Appendices 8.05.9 Table 8.05d Maximum Permissible Velocities for Unprotected Soils in Existing Channels. Materials Maximum Permissible Velocities (fps) )LQH6DQG QRQFROORLGDO Sand Loam (noncolloidal) Silt Loam (noncolloidal) 2UGLQDU\)LUP/RDP )LQH*UDYHO Stiff Clay (very colloidal) Graded, Loam to Cobbles (noncolloidal) Graded, Silt to Cobbles (colloidal) Alluvial Silts (noncolloidal) Alluvial Silts (colloidal) Coarse Gravel (noncolloidal) Cobbles and Shingles 2.5 2.5 3.0 3.5 5.0 5.0 5.0 5.5 3.5 5.0 6.0 5.5 Sample Problem 8.05a Design of a Grass-lined Channel. Given: Design Q10 = 16.6 cfs Proposed channel grade = 2% Proposed vegetation: Tall fescue Soil: Creedmoor (easily erodible) Permissible velocity, Vp = 4.5 ft/s (Table 8.05a) Retardance class: “B” uncut, “D” cut (Table 8.05c). Trapezoidal channel dimensions: GHVLJQLQJIRUORZUHWDUGDQFHFRQGLWLRQ UHWDUGDQFHFODVV' design to meet Vp. Find: Channel dimensions Solution: Make an initial estimate of channel size $ 49FIVIWVHF IW2 7U\ERWWRPZLGWK IWZVLGHVORSHVRI Z = 3 A = bd + Zd2 P = b + 2d Z2 + 1 R = AP An iterativeVROXWLRQXVLQJ)LJXUHDWRUHODWHÀRZGHSWKWR0DQQLQJ¶Vn SURFHHGVDVIROORZV 0DQQLQJ¶VHTXDWLRQLVXVHGWRFKHFNYHORFLWLHV )URP)LJFSJ5HWDUGDQFH&ODVVG 95 [ d (ft) A (ft 2) R (ft) *n Vt (fps) Q (cfs) Comments 0.8 4.32 0.54 0.043 3.25 14.0 V<Vp OK, Q<Q10 (too small, try deeper channel) 5.13 0.042 3.53 18.10 V<Vp, OK, Q>Q10, OK 1RZGHVLJQIRUKLJKUHWDUGDQFH FODVV% )RUWKHHDVHRIFRQVWUXFWLRQDQGPDLQWHQDQFHDVVXPHDQG try d = 1.5 ft and trial velocity Vt = 3.0 ft/sec d (ft) A (ft 2) R (ft)Vt (fps)n V (fps) Q (cfs) Comments 1.5 11.25 3.0 2.0 1.6 **1.5 0.08 0.11 0.12 0.13 2.5 1.8 1.6 1.5 28 20 18 17 reduce Vtreduce Vt Q>Q10 OK ** These assumptions = actual V (fps.) (chart continued on next page) 8 8.05.10 Rev. 12/93 (continued) Sample Problem 8.05a Design of a Grass-lined Channel. Channel summary: Trapezoidal shape, Z = 3, b = 3 ft, d = 1.5 ft, grade = 2% 1RWH ,Q6DPSOH3UREOHPDWKH³QYDOXH´LV¿UVWFKRVHQEDVHGRQD permissible velocity and not a design velocity criteria. Therefore, the use of 7DEOHFPD\QRWEHDVDFFXUDWHDVLQGLYLGXDOUHWDUGDQFHFODVVFKDUWVZKHQ a design velocity is the determining factor. Tractive Force Procedure The design of riprap-lined channels and temporary channel linings is based on analysis of tractive force. 127( 7KLVSURFHGXUHLVIRUXQLIRUPÀRZLQFKDQQHOVDQGLVnot to be used for design of deenergizing devices and may not be valid for larger channels. To calculate the required size of an open channel, assume the design flow is uniform and does not vary with time. Since actual flow conditions change through the length of a channel, subdivide the channel into design reaches as appropriate. PERMISSIBLE SHEAR STRESS The permissible shear stress, Td, is the force required to initiate movement of the lining material. Permissible shear stress for the liner is not related to the erodibility of the underlying soil. However, if the lining is eroded or broken, the bed material will be exposed to the erosive force of the flow. COMPUTING NORMAL DEPTH 7KH¿UVWVWHSLQVHOHFWLQJDQDSSURSULDWHOLQLQJLVWRFRPSXWHWKHGHVLJQ ÀRZGHSWK WKHQRUPDOGHSWK DQGGHWHUPLQHWKHVKHDUVWUHVV Normal depths can be calculated by Manning’s equation as shown for trapezoidal channels in Figure 8.05d. Values of the Manning’s roughness coefficient for different ranges of depth are provided in Table 8.05e for temporary linings and Table 8.05f for riprap. The coefficient of roughness generally decreases with increasing flow depth. n value for Depth Ranges* Table 8.05e Manning’s Roughness Coefficients for Temporary Lining Materials 0-0.5 ft 0.5-2.0 ft >2.0 ft Lining Type Woven Paper Net Jute Net )LEHUJODVV5RYLQJ 6WUDZZLWK1HW Curled Wood Mat Synthetic Mat 0.016 0.028 0.028 0.065 0.066 0.036 0.015 0.022 0.021 0.033 0.035 0.025 0.015 0.025 0.028 0.021 * Adapted from: FHWA-HEC 15, Pg. 37 - April 1988 Appendices Rev. 12/93 8.05.11 8 8.05.12 Rev. 12/93 Table 8.05f Manning’s Roughness Coefficient n - value n value for Depth Ranges Lining Category Lining Type 0-0.5 ft (0-15 cm) 0.5-2.0 ft (15-60 cm) 2.0 ft (>60 cm) Rigid Concrete Grouted Riprap Stone Masonry Soil Cement Asphalt 0.015 0.040 0.042 0.025 0.018 0.013 0.030 0.032 0.022 0.016 0.013 0.028 0.030 0.020 0.016 Unlined Bare Soil Rock Cut 0.023 0.045 0.020 0.035 0.020 0.025 Gravel Riprap 1-inch (2.5-cm) D502-inch (5-cm) D50 0.044 0.066 0.033 0.041 0.030 0.034 Rock Riprap 6-inch (15-cm) D5012-inch (30-cm) D50 0.104 -- 0.078 0.035 0.040 Note: Values listed are representative values for the respective depth ranges. Manning’s roughness coefficients, n, vary with the flow depth. DETERMINING SHEAR STRESS Shear stress, T, at normal depth is computed for the lining by the following equation: T = yds Td = Permissible shear stress where: T = shear stress in lb/ft2 y = unit weight of water, 62.4 lb/ft3 d = flow depth in ft s = channel gradient in ft/ft If the permissible shear stress, Td, given in Table 8.05g is greater than the computed shear stress, the riprap or temporary lining is considered acceptable. If a lining is unacceptable, select a lining with a higher permissible shear stress and repeat the calculations for normal depth and shear stress. In some cases it may be necessary to alter channel dimensions to reduce the shear stress. Computing tractive force around a channel bend requires special considerations because the change in flow direction imposes higher shear stress on the channel bottom and banks. The maximum shear stress in a bend, Tb, is given by the following equation: Tb = KbT where: Tb = bend shear stress in lb/ft2 kb = bend factor T = computed stress for straight channel in lb/ft2 The value of kb is related to the radius of curvature of the channel at its center line, Rc, and the bottom width of the channel, B, Figure 8.05e. The length of channel requiring protection downstream from a bend, Lp, is a function of the roughness of the lining material and the hydraulic radius as shown in Figure 8.05f. Appendices Rev. 12/93 8.05.13 Table 8.05g Permissible Shear Stresses for Riprap and Temporary Liners Permissible Unit Shear Stress, Td Lining Category Lining Type (lb/ft 2) Temporary Woven Paper Net Jute Net )LEHUJODVV5RYLQJ Single Double 6WUDZZLWK1HW Curled Wood mat Synthetic Mat 0.15 0.45 0.60 0.85 1.45 1.55 2.00 d50 Stone Size (inches) Gravel Riprap 1 2 0.33 0.67 Rock Riprap 6 12 15 18 21 24 2.00 3.00 4.00 5.00 6.00 7.80 8.00 Adapted From: FHWA, HEC-15, April 1983, pgs. 17 & 37. Design Procedure- Temporary Liners The following is a step-by-step procedure for designing a temporary liner for a channel. Because temporary liners have a short period of service, the design Q may be reduced. For liners that are needed for six months or less, the 2-year frequency storm is recommended. Step 1. Select a liner material suitable for site conditions and application. Determine roughness coefficient from manufacturer’s specifications or Table 8.05e, page 8.05.10. Step 2. Calculate the normal flow depth using Manning’s equation (Figure 8.05d). Check to see that depth is consistent with that assumed for selection of Manning’s n in Figure 8.05d, page 8.05.11. For smaller runoffs Figure 8.05d is not as clearly defined. Recommended solutions can be determined by using the Manning equation. Step 3. Calculate shear stress at normal depth. Step 4. Compare computed shear stress with the permissible shear stress for the liner. Step 5. If computed shear is greater than permissible shear, adjust channel dimensions to reduce shear, or select a more resistant lining and repeat steps 1 through 4. Design of a channel with temporary lining is illustrated in Sample Problem 8.05b, page 8.05.14. 8 8.05.14 Rev. 12/93 Sample Problem 8.05b Design of a Temporary Liner for a Vegetated Channel Given: Q2 = 16.6 cfs %RWWRPZLGWK IW Z = 3 n = 0.02 (Use basic n value for channels cut in earth (Table 8.05b) Vp IWVHFPD[LPXPDOORZDEOHYHORFLW\IRUEDUHVRLO SJ Channel gradient = 2% Find: Suitable temporary liner material Solution: 8VLQJ0DQQLQJ¶VHTXDWLRQ b(ft) d(ft) A(ft 2) R(ft) V(fps) Q(cfs) Comments 3.0 2.82 0.42 5.88 16.60 V>Vp, (needs protection) Q Q 2, OK 9HORFLW\!ISVFKDQQHOUHTXLUHVWHPSRUDU\OLQHU &DOFXODWHFKDQQHOGHVLJQZLWKVWUDZZLWKQHWDVWHPSRUDU\OLQHU n = 0.033 (Table 8.05e). Td = 1.45 (Table 8.05g, pg. 8.05.13) b(ft) d(ft) A(ft 2) R(ft) V(fps) Q(cfs) Comments 3.0 0.76 4.05 4.10 16.60 V<Td, OK Calculate shear stress for Q2 conditions: 7 \GV ZKHUH \ XQLWZHLJKWRIZDWHU OEIW 3) G ÀRZGHSWKLQIW s = channel gradient in ft/ft 7 7 7d, OK 7HPSRUDU\OLQHU VWUDZZLWKQHW *In some cases the solution is not as clearly defined; the use of a more conservative material is recommended. DESIGN OF RIPRAP LINING-MILD GRADIENT The mild gradient channel procedure is applicable for channel grades less than 10%. The method assumes that the channel cross section has been designed properly, including undercut and that the remaining problem is to provide a stable riprap lining. Side slope stability. As the angle of the side slope approaches the angle of repose of the channel lining, the lining material becomes less stable. The stability of a side slope is given by the tractive force ratio, K2, a function of the side slope and the angle of repose of the rock lining material. The rock size to be used for the channel lining can be determined by comparing the tractive force ratio, an indicator of side slope stability, to the shear stress on the sides and shear stress on the bottom of the channel. The angle of repose for different rock shapes and sized is shown in Figure 8.05g. The required rock size (mean diameter of the gradation, d50) for the side slopes is determined from the following equation: d50 (sides) = K1 d50 (bottom) K2where: K1 = ratio of shear stress on the sides, Ts, and bottom, T, of a trapezoidal channel (Figure 8.05h), K2 = tractive force ratio (Figure 8.05i). Appendices Rev. 12/93 8.05.15 8 8.05.16 Rev. 12/93 Appendices Rev. 12/93 8.05.17 Selection of riprap gradation and thickness. Riprap gradation should have a smooth size distribution curve. The largest stone size in the gradation should not exceed 1.5 times the d50 size. The most important criterion is that interstices formed by larger stones be filled with smaller sizes in an interlocking fashion, preventing the formation of open pockets. These gradation requirements apply regardless of the type of filter design used. In general, riprap constructed with angular stone performs best. Round stones are acceptable as riprap provided they are not placed on side slopes steeper than 3:1. Flat, slab-like stones should be avoided since they are easily dislodged by the flow. An approximate guide to stone shape is that neither the breadth nor the thickness of a single stone be less than one-third its length. The thickness of a riprap lining should equal 1.5 times the diameter of the largest rock size in the gradation. Filter design: When rock riprap is used, an appropriate underlying filter material must be selected. The filter material may be either a granular, gravel or sand filter blanket, or a geotextile fabric. 8 8.05.18 Rev. 12/93 For a granular filter blanket, the following criteria must be met: d15¿OWHU d85 base < 5 5 <d15¿OWHU d15 base < 40 d50¿OWHU d50 base < 40 Where “filter” refers to the overlying riprap or gravel and “base” refers to the underlying soil, sand or gravel. The relationship must hold between the filter blanket and base material and between the riprap and filter blanket. The minimum thickness for a filter blanket should not be less than 6 inches. In selecting a filter fabric, the fabric should have a permeability at least equal to the soil and a pore structure that will hold back the base soil. The following properties are essential to assure performance under riprap: • For filter fabric covering a base with granular particles containing 50 percent or less (by weight) of fine particles (less than U.S. Standard Sieve No. 200): a. d85 base (mm)/EOS* filter cloth (mm) > 1. b. Total open area of filter is less than 36%. • Filter fabric covering other soils: a. EOS less than U.S. Standard Sieve No. 70. b. Total open area of filter less than 10%. *EOS - Equivalent Opening Size to a U.S. Standard Sieve Size Design Procedure- Riprap Lining, Mild Gradient The following is a step-by-step procedure for designing a riprap channel lining with mild gradients. This procedure is designed for smaller channels that are generally used as erosion control measures, and is not intended for conveyance channels. Additional design information for lined channels may be obtained from the National Technical Information Services (NTIS) by obtaining a copy of the National Cooperative Highway Research Program Report No. 108, titled “Tentative Design Procedure for Riprap - Lined Channels”. Step 1. Select a riprap size, and look up the Manning’s n value (Table 8.05f) and permissible shear stress, Td (Table 8.05g). Step 2. Calculate the normal flow depth in the channel, using Manning’s equation (Figure 8.05d). Check that the n value for the calculated normal depth is consistent with that determined in step 1. Step 3. Calculate shear stress at normal depth. APPENDIX 8 Riprap and Stone for Erosion Control [Ref. 8] Section 1043 10-62 All stone shall meet the approval of the Engineer. While no specific gradation is required, 1 there shall be equal distribution of the various sizes of the stone within the required size 2 range. The size of an individual stone particle will be determined by measuring its long 3 dimension. 4 Stone or broken concrete for rip rap shall meet Table 1042-1 for the class and size 5 distribution. 6 TABLE 1042-1 ACCEPTANCE CRITERIA FOR RIP RAP AND STONE FOR EROSION CONTROL Required Stone Sizes, inches Class Minimum Midrange Maximum A 2 4 6 B 5 8 12 1 5 10 17 2 9 14 23 No more than 5.0% of the material furnished can be less than the minimum size specified nor 7 no more than 10.0% of the material can exceed the maximum size specified. 8 SECTION 1043 9 AGGREGATE FROM CRUSHED CONCRETE 10 1043-1 GENERAL 11 Aggregate from crushed concrete is a recycled product made by crushing concrete obtained 12 from concrete truck clean out, demolition of existing concrete structures or pavement, or 13 similar sources and transported from a crushing facility. It does not include concrete 14 pavements that are rubblelized, broken or otherwise crushed in place on the roadway. 15 The crushed material must meet all sources approval requirements described in Sections 1005 16 and 1006 with the exception of the sodium sulfate test requirement. Deleterious materials 17 shall not be more than 3%. 18 Sampling and acceptance for the determination of gradaction, LL and PI will be performed as 19 described in the Aggregate QC/QA Program Manual and the Aggregate Sampling Manual. 20 1043-2 AGGREGATE BASE COURSE 21 The material shall meet the ABC gradation. The LL of the material shall be raised 5 points to 22 no more than 35. 23 1043-3 AGGREGATE SHOULDER BORROW 24 The material shall meet Section 1019. 25 1043-4 CLEAN COARSE AGGREGATE FOR ASPHALT 26 The material shall meet the gradation of a standard size in Table 1005-1. Use of the material 27 shall be approved by the Engineer, and the mix shall meet all requirements. 28 1043-5 CLEAN COARSE AGGREGATE FOR CONCRETE 29 The material shall meet the gradation of a standard size in Table 1005-1. Use of the material 30 is restricted to Class B concrete mixes only. Use of the material shall be approved by the 31 Engineer, and the concrete shall meet all requirements. 32 SECTION 1044 33 SUBSURFACE DRAINAGE MATERIALS 34 1044-1 SUBDRAIN FINE AGGREGATE 35 Subdrain fine aggregate shall meet No. 2S or 2MS in Table 1005-2. 36 NCDOT 2012 Standard Specifications