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La r r y M . A l l e n , P LS Ja mi e W . V a n A g t m a e l G r e g J . Z a r t ma n , P . E S A L E M – C o r p o r a t e O f f i c e 2 5 6 4 1 9 t h S t r e e t S E S a l e m , O r e g o n 9 7 3 0 2 P 5 0 3 . 3 9 9 . 3 8 2 8 F 8 6 6 . 2 3 2 . 6 7 9 0 www.leiengineering.com MEMORANDUM To: West Coast Home Solutions, LLC From: Greg J. Zartman, P.E. Date: October 15, 2025 Pages: 28 Job Number: 60-32 – Hermanson Preserve Subject: Preliminary Stormwater Analysis for the Hermanson Preserve Subdivision Dear West Coast Home Solutions, This memorandum presents a preliminary analysis for the stormwater analysis for a detention and treatment facility for the conveyance system for the planned Hermanson Preserve Subdivision in Woodburn, Oregon following the City of Woodburn Stormwater Drainage Master Plan (Stormwater Standards). This planned subdivision is located west of Highway 99E and North of Bell Passi Road NE, Tas Lot 00100 of Marion County Assessor’s Map 06 1W 18D. The Stormwater Standards state the flood control treatment will be provided such that stormwater runoff from the post-development 25-year design storm is reduced to flow from the 5-year pre- development design storm. Moreover, the designed facility will also provide conveyance for overflow from the 100-year design storm. To provide this flood control treatment, a dry detention pond with a control structure is planned in the northwest portion of the development. See attached composite utility sheet UT-2. HydroCAD version 10.2 was used to perform the preliminary analysis of the planned dry detention pond with inputs taken from the Stormwater Standards. Preliminary runoff basins were delineated for the subdivision (Main Subdivision) and pond tract (Pond Tract). For the Main Subdivision basin, lots were assumed to be composed of 70% impervious surfaces and all roads were designated as impervious areas. For the Pond Tract the area of the pond planned to detain water was delineated as impervious and all other surfaces as impervious. This result is that 78% of the site was modeled as impervious surfaces and 22% of the site as pervious. Total site area is 806,821 square feet. During the 5-year pre-development design storm, 1.64 cfs of runoff is anticipated to leave the site. During the 25-year post-development design storm, 13.22 cfs of stormwater runoff enters the dry detention pond. A 4.8-inch orifice in the control structure limits runoff from the facility to 1.62 cfs with total detention volume of 87,438 cubic feet. Approximately 150,000 cubic feet of detention is potentially available at the planned pond location. See attached HydroCAD computations. ---PAGE BREAK--- Page 2 of 2 During the 100-year design storm, runoff from the subdivision to the facility is 16.63 cfs with 3.44 cfs leaving the facility through the 18” overflow and then is conveyed out of the control structure with an 18” conveyance pipe. See attached HydroCAD computations. The planned dry detention pond meets the stormwater treatment requirements specified in the Stormwater Standards for the planned subdivision following, as preliminarily designed. Please don’t hesitate to call or email me with any questions. Thank you. Sincerely, LEI ENGINEERING & SUREYING OF OREGON, LLC Greg J. Zartman, P.E. Principal Engineer ---PAGE BREAK--- LOT 66 LOT 65 LOT 64 LOT 63 LOT 62 LOT 61 LOT 67 LOT 68 LOT 70 LOT 71 LOT 72 LOT 73 LOT 74 LOT 75 LOT 76 TRACT G TRACT H TRACT F TRACT I LOT 69 LOT 96 LOT 46 L LOT 82 LOT 81 LOT 94 LOT 80 LOT 87 LOT 86 LOT 83 LOT 84 LOT 79 LOT 93 LOT 92 LOT 91 LOT 90 LOT 89 LOT 88 LOT 85 LOT 95 LOT 52 LOT 51 LOT 50 LOT 49 LOT 48 LOT 47 TRACT E LOT 58 LOT 57 LOT 56 LOT 55 LOT 54 LOT 53 LOT 59 LOT 77 LOT 78 LOT 60 UT-1 G. MALDONADO G. MALDONADO J. VAN AGTMAEL PLS G. ZARMAN PE · THE LOCATION OF UTILITIES SERVING THE PROPERTY HAVE BEEN DETERMINED BY OBSERVED EVIDENCE, TOGETHER WITH MARKINGS PROVIDED BY UTILITY COMPANIES; 811 OREGON UTILITY NOTIFICATION CENTER. THE LOCATION OF THE UTILITIES, SHOWN HEREON, DETERMINED BY ABOVE GROUND EVIDENCE AND ILLUSTRATED WITH HELP FROM CITY MAPS, IS APPROXIMATE. NO AS-BUILT SURVEYS HAVE BEEN PROVIDED OR REVIEWED AT THIS TIME. LEI MAKES NO WARRANTIES TO THE LOCATION OF THE UTILITIES. THE CONTRACTOR SHALL CALL FOR PRIVATE UTILITY LOCATES AND FIELD VERIFY ALL UTILITIES BEFORE CONSTRUCTION ACTIVITIES. · THE BOUNDARY SHOWN ON THIS MAP IS FOR ENGINEERING PURPOSES ONLY. NO MONUMENTATION SHALL BE SET AND THIS MAP SHALL NOT BE FILED WITH THE COUNTY AS RECORD. GENERAL NOTES: SCALE IN FEET 0 50' 100' CHECKED DRAWN DESIGN 2564 19TH STREET SE Salem, Oregon 97302 (503) 399-3828 ENGINEERING & SURVEYING www.leiengineering.com OF OREGON PREPARED FOR: FILE PATH: P:\60 (West Coast Home Solutions)\60-32 Hermanson Preserve\dwg\Preliminary Plan Set\60-32_Preliminary Plan Set.dwg 2025-10-9 7:47 AM APPROVED LAYOUT SHEET PROJECT NO. SCALE REUSE OF DOCUMENTS: THIS DOCUMENT, AND THE IDEAS AND DESIGNS INCORPORATED HEREIN, AS AN INSTRUMENT OF PROFESSIONAL SERVICE, IS THE PROPERTY OF LEI ENGINEERING AND SURVEYING OF OREGON, LLC AND IS NOT TO BE USED, WHOLE OR IN PART, FOR ANY OTHER PROJECT WITHOUT THE WRITTEN AUTHORIZATION OF LEI ENGINEERING. ©LEI ENGINEERING NO. DATE REVISION BY APVD PRELIMINARY UT-1 · THE LOCATION OF UTILITIES SERVING THE PROPERTY HAVE BEEN DETERMINED BY OBSERVED EVIDENCE, TOGETHER WITH MARKINGS PROVIDED BY UTILITY COMPANIES; 811 OREGON UTILITY NOTIFICATION CENTER. THE LOCATION OF THE UTILITIES, SHOWN HEREON, DETERMINED BY ABOVE GROUND EVIDENCE AND ILLUSTRATED WITH HELP FROM CITY MAPS, IS APPROXIMATE. NO AS-BUILT SURVEYS HAVE BEEN PROVIDED OR REVIEWED AT THIS TIME. LEI MAKES NO WARRANTIES TO THE LOCATION OF THE UTILITIES. THE CONTRACTOR SHALL CALL FOR PRIVATE UTILITY LOCATES AND FIELD VERIFY ALL UTILITIES BEFORE CONSTRUCTION ACTIVITIES. · THE BOUNDARY SHOWN ON THIS MAP IS FOR ENGINEERING PURPOSES ONLY. NO MONUMENTATION SHALL BE SET AND THIS MAP SHALL NOT BE FILED WITH THE COUNTY AS RECORD. GENERAL NOTES: GREENWAY TERRACE HERMANSON LANE (PRIVATE) STORM WATER FACILITY DEER RUN LN LOT 40 LOT 41 CAM'S SUBDIVISION TAXLOT 051W18D000200 TAXLOT 051W18D000300 HERMANSON PRESERVE PUD WEST COAST HOME SOLUTIONS, LLC 60-32 09 OF 14 1" = 50' COMPOSITE UTILITIES 1 UT-1 POND PLACE PRELIMINARY 10.0' PUE 16.0' UTILITY EASMENT 10.0' PUE 10.0' PUE 10.0' PUE 10.0' PUE 10.0' PUE SEE SHEET UT-3 FOR DETAILS ---PAGE BREAK--- LOT 4 LOT 6 LOT 7 LOT 9 LOT 13 LOT 25 LOT 26 LOT 27 LOT 28 LOT 29 LOT 30 LOT 31 LOT 32 LOT 33 LOT 34 TRACT A TRACT D TRACT F LOT 5 LOT 8 LOT 12 LOT 10 LOT 11 LOT 1 LOT 2 LOT 3 LOT 14 LOT 15 LOT 39 LOT 22 LOT 36 LOT 21 LOT 20 LOT 37 LOT 19 LOT 18 LOT 38 LOT 40 LOT 41 LOT 17 LOT 16 LOT 24 TRACT B LOT 23 LOT 100 TRACT C LOT 99 LOT 98 LOT 97 LOT 96 LOT 46 LOT 45 LOT 44 LOT 42 LOT 43 LOT 82 LOT 81 LOT 94 LOT 80 LOT 87 LOT 86 LOT 83 LOT 84 LOT 79 LOT 93 LOT 92 LOT 91 LOT 90 LOT 89 LOT 88 LOT 85 LOT 95 LOT 52 LOT 51 LOT 50 LOT 49 LOT 48 LOT 47 LOT 58 LOT 57 LOT 56 LOT 55 LOT 54 LOT 53 LOT 59 LOT 35 UT-2 G. MALDONADO G. MALDONADO J. VAN AGTMAEL PLS G. ZARMAN PE · THE LOCATION OF UTILITIES SERVING THE PROPERTY HAVE BEEN DETERMINED BY OBSERVED EVIDENCE, TOGETHER WITH MARKINGS PROVIDED BY UTILITY COMPANIES; 811 OREGON UTILITY NOTIFICATION CENTER. THE LOCATION OF THE UTILITIES, SHOWN HEREON, DETERMINED BY ABOVE GROUND EVIDENCE AND ILLUSTRATED WITH HELP FROM CITY MAPS, IS APPROXIMATE. NO AS-BUILT SURVEYS HAVE BEEN PROVIDED OR REVIEWED AT THIS TIME. LEI MAKES NO WARRANTIES TO THE LOCATION OF THE UTILITIES. THE CONTRACTOR SHALL CALL FOR PRIVATE UTILITY LOCATES AND FIELD VERIFY ALL UTILITIES BEFORE CONSTRUCTION ACTIVITIES. · THE BOUNDARY SHOWN ON THIS MAP IS FOR ENGINEERING PURPOSES ONLY. NO MONUMENTATION SHALL BE SET AND THIS MAP SHALL NOT BE FILED WITH THE COUNTY AS RECORD. GENERAL NOTES: SCALE IN FEET 0 50' 100' CHECKED DRAWN DESIGN 2564 19TH STREET SE Salem, Oregon 97302 (503) 399-3828 ENGINEERING & SURVEYING www.leiengineering.com OF OREGON PREPARED FOR: FILE PATH: P:\60 (West Coast Home Solutions)\60-32 Hermanson Preserve\dwg\Preliminary Plan Set\60-32_Preliminary Plan Set.dwg 2025-10-9 7:47 AM APPROVED LAYOUT SHEET PROJECT NO. SCALE REUSE OF DOCUMENTS: THIS DOCUMENT, AND THE IDEAS AND DESIGNS INCORPORATED HEREIN, AS AN INSTRUMENT OF PROFESSIONAL SERVICE, IS THE PROPERTY OF LEI ENGINEERING AND SURVEYING OF OREGON, LLC AND IS NOT TO BE USED, WHOLE OR IN PART, FOR ANY OTHER PROJECT WITHOUT THE WRITTEN AUTHORIZATION OF LEI ENGINEERING. ©LEI ENGINEERING NO. DATE REVISION BY APVD PRELIMINARY UT-2 · THE LOCATION OF UTILITIES SERVING THE PROPERTY HAVE BEEN DETERMINED BY OBSERVED EVIDENCE, TOGETHER WITH MARKINGS PROVIDED BY UTILITY COMPANIES; 811 OREGON UTILITY NOTIFICATION CENTER. THE LOCATION OF THE UTILITIES, SHOWN HEREON, DETERMINED BY ABOVE GROUND EVIDENCE AND ILLUSTRATED WITH HELP FROM CITY MAPS, IS APPROXIMATE. NO AS-BUILT SURVEYS HAVE BEEN PROVIDED OR REVIEWED AT THIS TIME. LEI MAKES NO WARRANTIES TO THE LOCATION OF THE UTILITIES. THE CONTRACTOR SHALL CALL FOR PRIVATE UTILITY LOCATES AND FIELD VERIFY ALL UTILITIES BEFORE CONSTRUCTION ACTIVITIES. · THE BOUNDARY SHOWN ON THIS MAP IS FOR ENGINEERING PURPOSES ONLY. NO MONUMENTATION SHALL BE SET AND THIS MAP SHALL NOT BE FILED WITH THE COUNTY AS RECORD. GENERAL NOTES: STORM WATER FACILITY HAWLEY ST GREENWAY TERRACE PACIFIC HIGHWAY 99E LOT 5 LOT 4 LOT 3 LOT 2 LOT 1 LOT 1 LOT 14 LOT 13 LOT 12 LOT 11 LOT 10 TAXLOT 051W18DA09500 TAXLOT 051W18D000201 TAXLOT 051W18D000200 HERMANSON PRESERVE PUD WEST COAST HOME SOLUTIONS, LLC 60-32 10 OF 14 1" = 50' COMPOSITE UTILITIES 2 UT-2 10.0' PUE MILL CREEK PARK ADDITION #4 MILL CREEK PARK ADDITION #2 10.0' PUE 10.0' PUE 10.0' PUE 10.0' PUE 10.0' PUE 10.0' PUE 10.0' PUE 10.0' PUE 10.0' PUE 16.0' SEWER EASEMENT HERMANSON LANE (PRIVATE) HERMANSON LANE (PRIVATE) HERMANSON LANE (PRIVATE) ---PAGE BREAK--- LOT 6 LOT 65 LOT 64 LOT 63 LOT 62 LOT 61 TRACT G TRACT H TRACT I UT-3 G. MALDONADO G. MALDONADO J. VAN AGTMAEL PLS G. ZARMAN PE · THE LOCATION OF UTILITIES SERVING THE PROPERTY HAVE BEEN DETERMINED BY OBSERVED EVIDENCE, TOGETHER WITH MARKINGS PROVIDED BY UTILITY COMPANIES; 811 OREGON UTILITY NOTIFICATION CENTER. THE LOCATION OF THE UTILITIES, SHOWN HEREON, DETERMINED BY ABOVE GROUND EVIDENCE AND ILLUSTRATED WITH HELP FROM CITY MAPS, IS APPROXIMATE. NO AS-BUILT SURVEYS HAVE BEEN PROVIDED OR REVIEWED AT THIS TIME. LEI MAKES NO WARRANTIES TO THE LOCATION OF THE UTILITIES. THE CONTRACTOR SHALL CALL FOR PRIVATE UTILITY LOCATES AND FIELD VERIFY ALL UTILITIES BEFORE CONSTRUCTION ACTIVITIES. · THE BOUNDARY SHOWN ON THIS MAP IS FOR ENGINEERING PURPOSES ONLY. NO MONUMENTATION SHALL BE SET AND THIS MAP SHALL NOT BE FILED WITH THE COUNTY AS RECORD. GENERAL NOTES: SCALE IN FEET 0 50' 100' CHECKED DRAWN DESIGN 2564 19TH STREET SE Salem, Oregon 97302 (503) 399-3828 ENGINEERING & SURVEYING www.leiengineering.com OF OREGON PREPARED FOR: FILE PATH: P:\60 (West Coast Home Solutions)\60-32 Hermanson Preserve\dwg\Preliminary Plan Set\60-32_Preliminary Plan Set.dwg 2025-10-9 7:47 AM APPROVED LAYOUT SHEET PROJECT NO. SCALE REUSE OF DOCUMENTS: THIS DOCUMENT, AND THE IDEAS AND DESIGNS INCORPORATED HEREIN, AS AN INSTRUMENT OF PROFESSIONAL SERVICE, IS THE PROPERTY OF LEI ENGINEERING AND SURVEYING OF OREGON, LLC AND IS NOT TO BE USED, WHOLE OR IN PART, FOR ANY OTHER PROJECT WITHOUT THE WRITTEN AUTHORIZATION OF LEI ENGINEERING. ©LEI ENGINEERING NO. DATE REVISION BY APVD PRELIMINARY UT-3 · THE LOCATION OF UTILITIES SERVING THE PROPERTY HAVE BEEN DETERMINED BY OBSERVED EVIDENCE, TOGETHER WITH MARKINGS PROVIDED BY UTILITY COMPANIES; 811 OREGON UTILITY NOTIFICATION CENTER. THE LOCATION OF THE UTILITIES, SHOWN HEREON, DETERMINED BY ABOVE GROUND EVIDENCE AND ILLUSTRATED WITH HELP FROM CITY MAPS, IS APPROXIMATE. NO AS-BUILT SURVEYS HAVE BEEN PROVIDED OR REVIEWED AT THIS TIME. LEI MAKES NO WARRANTIES TO THE LOCATION OF THE UTILITIES. THE CONTRACTOR SHALL CALL FOR PRIVATE UTILITY LOCATES AND FIELD VERIFY ALL UTILITIES BEFORE CONSTRUCTION ACTIVITIES. · THE BOUNDARY SHOWN ON THIS MAP IS FOR ENGINEERING PURPOSES ONLY. NO MONUMENTATION SHALL BE SET AND THIS MAP SHALL NOT BE FILED WITH THE COUNTY AS RECORD. GENERAL NOTES: HERMANSON PRESERVE PUD WEST COAST HOME SOLUTIONS, LLC 60-32 11 OF 14 1" = 50' COMPOSITE UTILITIES 3 UT-3 TAX LOT: 051W19B000100 TAX LOT: 051W18C000600 TAX LOT: 051W19B000200 CONNECTION TO EXISTING CITY PUBLIC WATER LINE PRELIMINARY EXISTING CITY PUBLIC WATER LINE EXISTING SANITARY SEWER LINE CONNECTION TO CITY PUBLIC SEWER MAIN MILL CREEK TAXLOT 051W18D000400 LOT 40 CAM'S SUBDIVISION 20.0' SEWER EASEMENT LOT 41 TAX LOT: 051W18CD002200 TRACT F SEWER EXTENSION THROUGH OPEN SPACE DEDICATED TO THE CITY BY "MILL CREEK MEADOWS" SUBDIVISION INSTALL IN FILL FOR PROPOSED DEER RUN LANE DEER RUN LN GREENWAY TERRACE ---PAGE BREAK--- 1S Main Subdivision 3S Pond Tract 4S Main Subdivision (PRE) 5S Pond Tract 8P Pond 7L Pre-Development Routing Diagram for Hermison Preliminary Analysis - 050525 Prepared by LEI Engineering & Surveying, Printed 5/7/2025 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Subcat Reach Pond Link ---PAGE BREAK--- Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 2 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Rainfall Events Listing (selected events) Event# Event Name Storm Type Curve Mode Duration (hours) B/B Depth (inches) AMC 1 5-Year Type IA 24-hr Default 24.00 1 2.80 2 2 25-Year Type IA 24-hr Default 24.00 1 3.60 2 3 100-Year Type IA 24-hr Default 24.00 1 4.40 2 ---PAGE BREAK--- Type IA 24-hr 5-Year Rainfall=2.80" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 3 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Main Subdivision [49] Hint: Tc<2dt may require smaller dt Runoff = 9.39 cfs @ 7.91 hrs, Volume= 139,221 cf, Depth= 2.19" Routed to Pond 8P : Pond Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 5-Year Rainfall=2.80" Area (sf) CN Description * 378,742 98 Lots impervious (70%) * 162,318 74 Lots pervious (30%) * 222,000 98 Roads 763,060 93 Weighted Average 162,318 74 21.27% Pervious Area 600,742 98 78.73% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev Subcatchment 1S: Main Subdivision Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 10 9 8 7 6 5 4 3 2 1 0 Type IA 24-hr 5-Year Rainfall=2.80" Runoff Area=763,060 sf Runoff Volume=139,221 cf Runoff Depth=2.19" Tc=5.0 min CN=74/98 9.39 cfs ---PAGE BREAK--- Type IA 24-hr 5-Year Rainfall=2.80" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 4 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Pond Tract [49] Hint: Tc<2dt may require smaller dt Runoff = 0.48 cfs @ 7.92 hrs, Volume= 7,233 cf, Depth= 1.98" Routed to Pond 8P : Pond Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 5-Year Rainfall=2.80" Area (sf) CN Description * 14,361 74 Ladscaping * 29,400 98 Pond 43,761 90 Weighted Average 14,361 74 32.82% Pervious Area 29,400 98 67.18% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev Subcatchment 3S: Pond Tract Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 0.52 0.5 0.48 0.46 0.44 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type IA 24-hr 5-Year Rainfall=2.80" Runoff Area=43,761 sf Runoff Volume=7,233 cf Runoff Depth=1.98" Tc=5.0 min CN=74/98 0.48 cfs ---PAGE BREAK--- Type IA 24-hr 5-Year Rainfall=2.80" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 5 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: Main Subdivision (PRE) Runoff = 1.53 cfs @ 8.17 hrs, Volume= 49,851 cf, Depth= 0.78" Routed to Link 7L : Pre-Development Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 5-Year Rainfall=2.80" Area (sf) CN Description 763,060 74 Pasture/grassland/range, Good, HSG C 763,060 74 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 23.1 250 0.0200 0.18 Sheet Flow, Sheet Flow Grass: Short n= 0.150 P2= 2.50" 0.8 100 0.0200 2.12 Shallow Concentrated Flow, SCF Grassed Waterway Kv= 15.0 fps 23.9 350 Total Subcatchment 4S: Main Subdivision (PRE) Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 1 0 Type IA 24-hr 5-Year Rainfall=2.80" Runoff Area=763,060 sf Runoff Volume=49,851 cf Runoff Depth=0.78" Flow Length=350' Slope=0.0200 Tc=23.9 min CN=74/0 1.53 cfs ---PAGE BREAK--- Type IA 24-hr 5-Year Rainfall=2.80" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 6 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Pond Tract Runoff = 0.11 cfs @ 8.04 hrs, Volume= 2,859 cf, Depth= 0.78" Routed to Link 7L : Pre-Development Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 5-Year Rainfall=2.80" Area (sf) CN Description 43,761 74 Pasture/grassland/range, Good, HSG C 43,761 74 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0200 0.15 Sheet Flow, Sheetflow Grass: Short n= 0.150 P2= 2.50" 0.9 119 0.0200 2.12 Shallow Concentrated Flow, SCF Grassed Waterway Kv= 15.0 fps 12.0 219 Total Subcatchment 5S: Pond Tract Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 0.125 0.12 0.115 0.11 0.105 0.1 0.095 0.09 0.085 0.08 0.075 0.07 0.065 0.06 0.055 0.05 0.045 0.04 0.035 0.03 0.025 0.02 0.015 0.01 0.005 0 Type IA 24-hr 5-Year Rainfall=2.80" Runoff Area=43,761 sf Runoff Volume=2,859 cf Runoff Depth=0.78" Flow Length=219' Slope=0.0200 Tc=12.0 min CN=74/0 0.11 cfs ---PAGE BREAK--- Type IA 24-hr 5-Year Rainfall=2.80" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 7 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Pond 8P: Pond [44] Hint: Outlet device #2 is below defined storage Inflow Area = 806,821 sf, 78.10% Impervious, Inflow Depth = 2.18" for 5-Year event Inflow = 9.87 cfs @ 7.91 hrs, Volume= 146,454 cf Outflow = 1.40 cfs @ 16.64 hrs, Volume= 146,454 cf, Atten= 86%, Lag= 523.8 min Primary = 1.40 cfs @ 16.64 hrs, Volume= 146,454 cf Routing by Stor-Ind method, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Peak Elev= 104.38' @ 16.64 hrs Surf.Area= 16,500 sf Storage= 55,070 cf Plug-Flow detention time= 476.0 min calculated for 146,454 cf (100% of inflow) Center-of-Mass det. time= 475.9 min ( 1,163.0 - 687.1 ) Volume Invert Avail.Storage Storage Description #1 100.00' 93,997 cf Pond (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 100.00 8,620 0 0 106.50 20,302 93,997 93,997 Device Routing Invert Outlet Devices #1 Primary 99.00' 18.0" Round Outlet Pipe L= 40.0' Ke= 0.500 Inlet / Outlet Invert= 99.00' / 97.72' S= 0.0320 Cc= 0.900 n= 0.010 PVC, smooth interior, Flow Area= 1.77 sf #2 Device 1 98.00' 4.8" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 106.25' 18.0" Horiz. Overflow C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=1.40 cfs @ 16.64 hrs HW=104.38' (Free Discharge) 1=Outlet Pipe (Passes 1.40 cfs of 18.32 cfs potential flow) 2=Orifice/Grate (Orifice Controls 1.40 cfs @ 11.17 fps) 3=Overflow ( Controls 0.00 cfs) ---PAGE BREAK--- Type IA 24-hr 5-Year Rainfall=2.80" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 8 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Pond 8P: Pond Inflow Primary Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 11 10 9 8 7 6 5 4 3 2 1 0 Inflow Area=806,821 sf Peak Elev=104.38' Storage=55,070 cf 9.87 cfs 1.40 cfs ---PAGE BREAK--- Type IA 24-hr 5-Year Rainfall=2.80" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 9 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Link 7L: Pre-Development Inflow Area = 806,821 sf, 0.00% Impervious, Inflow Depth = 0.78" for 5-Year event Inflow = 1.64 cfs @ 8.15 hrs, Volume= 52,710 cf Primary = 1.64 cfs @ 8.15 hrs, Volume= 52,710 cf, Atten= Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Link 7L: Pre-Development Inflow Primary Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 1 0 Inflow Area=806,821 sf 1.64 cfs 1.64 cfs ---PAGE BREAK--- Type IA 24-hr 25-Year Rainfall=3.60" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 10 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Main Subdivision [49] Hint: Tc<2dt may require smaller dt Runoff = 12.57 cfs @ 7.91 hrs, Volume= 186,228 cf, Depth= 2.93" Routed to Pond 8P : Pond Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-Year Rainfall=3.60" Area (sf) CN Description * 378,742 98 Lots impervious (70%) * 162,318 74 Lots pervious (30%) * 222,000 98 Roads 763,060 93 Weighted Average 162,318 74 21.27% Pervious Area 600,742 98 78.73% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev Subcatchment 1S: Main Subdivision Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Type IA 24-hr 25-Year Rainfall=3.60" Runoff Area=763,060 sf Runoff Volume=186,228 cf Runoff Depth=2.93" Tc=5.0 min CN=74/98 12.57 cfs ---PAGE BREAK--- Type IA 24-hr 25-Year Rainfall=3.60" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 11 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Pond Tract [49] Hint: Tc<2dt may require smaller dt Runoff = 0.65 cfs @ 7.92 hrs, Volume= 9,814 cf, Depth= 2.69" Routed to Pond 8P : Pond Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-Year Rainfall=3.60" Area (sf) CN Description * 14,361 74 Ladscaping * 29,400 98 Pond 43,761 90 Weighted Average 14,361 74 32.82% Pervious Area 29,400 98 67.18% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev Subcatchment 3S: Pond Tract Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type IA 24-hr 25-Year Rainfall=3.60" Runoff Area=43,761 sf Runoff Volume=9,814 cf Runoff Depth=2.69" Tc=5.0 min CN=74/98 0.65 cfs ---PAGE BREAK--- Type IA 24-hr 25-Year Rainfall=3.60" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 12 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: Main Subdivision (PRE) Runoff = 3.28 cfs @ 8.07 hrs, Volume= 83,263 cf, Depth= 1.31" Routed to Link 7L : Pre-Development Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-Year Rainfall=3.60" Area (sf) CN Description 763,060 74 Pasture/grassland/range, Good, HSG C 763,060 74 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 23.1 250 0.0200 0.18 Sheet Flow, Sheet Flow Grass: Short n= 0.150 P2= 2.50" 0.8 100 0.0200 2.12 Shallow Concentrated Flow, SCF Grassed Waterway Kv= 15.0 fps 23.9 350 Total Subcatchment 4S: Main Subdivision (PRE) Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 3 2 1 0 Type IA 24-hr 25-Year Rainfall=3.60" Runoff Area=763,060 sf Runoff Volume=83,263 cf Runoff Depth=1.31" Flow Length=350' Slope=0.0200 Tc=23.9 min CN=74/0 3.28 cfs ---PAGE BREAK--- Type IA 24-hr 25-Year Rainfall=3.60" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 13 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Pond Tract Runoff = 0.23 cfs @ 8.02 hrs, Volume= 4,775 cf, Depth= 1.31" Routed to Link 7L : Pre-Development Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-Year Rainfall=3.60" Area (sf) CN Description 43,761 74 Pasture/grassland/range, Good, HSG C 43,761 74 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0200 0.15 Sheet Flow, Sheetflow Grass: Short n= 0.150 P2= 2.50" 0.9 119 0.0200 2.12 Shallow Concentrated Flow, SCF Grassed Waterway Kv= 15.0 fps 12.0 219 Total Subcatchment 5S: Pond Tract Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 0.26 0.25 0.24 0.23 0.22 0.21 0.2 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Type IA 24-hr 25-Year Rainfall=3.60" Runoff Area=43,761 sf Runoff Volume=4,775 cf Runoff Depth=1.31" Flow Length=219' Slope=0.0200 Tc=12.0 min CN=74/0 0.23 cfs ---PAGE BREAK--- Type IA 24-hr 25-Year Rainfall=3.60" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 14 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Pond 8P: Pond [44] Hint: Outlet device #2 is below defined storage Inflow Area = 806,821 sf, 78.10% Impervious, Inflow Depth = 2.92" for 25-Year event Inflow = 13.22 cfs @ 7.91 hrs, Volume= 196,042 cf Outflow = 1.62 cfs @ 19.29 hrs, Volume= 196,042 cf, Atten= 88%, Lag= 682.8 min Primary = 1.62 cfs @ 19.29 hrs, Volume= 196,042 cf Routing by Stor-Ind method, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Peak Elev= 106.17' @ 19.29 hrs Surf.Area= 19,713 sf Storage= 87,438 cf Plug-Flow detention time= 641.1 min calculated for 195,838 cf (100% of inflow) Center-of-Mass det. time= 641.7 min ( 1,323.3 - 681.5 ) Volume Invert Avail.Storage Storage Description #1 100.00' 93,997 cf Pond (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 100.00 8,620 0 0 106.50 20,302 93,997 93,997 Device Routing Invert Outlet Devices #1 Primary 99.00' 18.0" Round Outlet Pipe L= 40.0' Ke= 0.500 Inlet / Outlet Invert= 99.00' / 97.72' S= 0.0320 Cc= 0.900 n= 0.010 PVC, smooth interior, Flow Area= 1.77 sf #2 Device 1 98.00' 4.8" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 106.25' 18.0" Horiz. Overflow C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=1.62 cfs @ 19.29 hrs HW=106.17' (Free Discharge) 1=Outlet Pipe (Passes 1.62 cfs of 21.56 cfs potential flow) 2=Orifice/Grate (Orifice Controls 1.62 cfs @ 12.89 fps) 3=Overflow ( Controls 0.00 cfs) ---PAGE BREAK--- Type IA 24-hr 25-Year Rainfall=3.60" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 15 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Pond 8P: Pond Inflow Primary Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Inflow Area=806,821 sf Peak Elev=106.17' Storage=87,438 cf 13.22 cfs 1.62 cfs ---PAGE BREAK--- Type IA 24-hr 25-Year Rainfall=3.60" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 16 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Link 7L: Pre-Development Inflow Area = 806,821 sf, 0.00% Impervious, Inflow Depth = 1.31" for 25-Year event Inflow = 3.51 cfs @ 8.07 hrs, Volume= 88,038 cf Primary = 3.51 cfs @ 8.07 hrs, Volume= 88,038 cf, Atten= Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Link 7L: Pre-Development Inflow Primary Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 3 2 1 0 Inflow Area=806,821 sf 3.51 cfs 3.51 cfs ---PAGE BREAK--- Type IA 24-hr 100-Year Rainfall=4.40" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 17 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: Main Subdivision [49] Hint: Tc<2dt may require smaller dt Runoff = 15.80 cfs @ 7.91 hrs, Volume= 234,112 cf, Depth= 3.68" Routed to Pond 8P : Pond Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 100-Year Rainfall=4.40" Area (sf) CN Description * 378,742 98 Lots impervious (70%) * 162,318 74 Lots pervious (30%) * 222,000 98 Roads 763,060 93 Weighted Average 162,318 74 21.27% Pervious Area 600,742 98 78.73% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev Subcatchment 1S: Main Subdivision Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Type IA 24-hr 100-Year Rainfall=4.40" Runoff Area=763,060 sf Runoff Volume=234,112 cf Runoff Depth=3.68" Tc=5.0 min CN=74/98 15.80 cfs ---PAGE BREAK--- Type IA 24-hr 100-Year Rainfall=4.40" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 18 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 3S: Pond Tract [49] Hint: Tc<2dt may require smaller dt Runoff = 0.83 cfs @ 7.92 hrs, Volume= 12,471 cf, Depth= 3.42" Routed to Pond 8P : Pond Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 100-Year Rainfall=4.40" Area (sf) CN Description * 14,361 74 Ladscaping * 29,400 98 Pond 43,761 90 Weighted Average 14,361 74 32.82% Pervious Area 29,400 98 67.18% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Post-Dev Subcatchment 3S: Pond Tract Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Type IA 24-hr 100-Year Rainfall=4.40" Runoff Area=43,761 sf Runoff Volume=12,471 cf Runoff Depth=3.42" Tc=5.0 min CN=74/98 0.83 cfs ---PAGE BREAK--- Type IA 24-hr 100-Year Rainfall=4.40" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 19 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 4S: Main Subdivision (PRE) Runoff = 5.34 cfs @ 8.06 hrs, Volume= 120,549 cf, Depth= 1.90" Routed to Link 7L : Pre-Development Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 100-Year Rainfall=4.40" Area (sf) CN Description 763,060 74 Pasture/grassland/range, Good, HSG C 763,060 74 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 23.1 250 0.0200 0.18 Sheet Flow, Sheet Flow Grass: Short n= 0.150 P2= 2.50" 0.8 100 0.0200 2.12 Shallow Concentrated Flow, SCF Grassed Waterway Kv= 15.0 fps 23.9 350 Total Subcatchment 4S: Main Subdivision (PRE) Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 5 4 3 2 1 0 Type IA 24-hr 100-Year Rainfall=4.40" Runoff Area=763,060 sf Runoff Volume=120,549 cf Runoff Depth=1.90" Flow Length=350' Slope=0.0200 Tc=23.9 min CN=74/0 5.34 cfs ---PAGE BREAK--- Type IA 24-hr 100-Year Rainfall=4.40" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 20 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: Pond Tract Runoff = 0.38 cfs @ 8.01 hrs, Volume= 6,913 cf, Depth= 1.90" Routed to Link 7L : Pre-Development Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type IA 24-hr 100-Year Rainfall=4.40" Area (sf) CN Description 43,761 74 Pasture/grassland/range, Good, HSG C 43,761 74 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 11.1 100 0.0200 0.15 Sheet Flow, Sheetflow Grass: Short n= 0.150 P2= 2.50" 0.9 119 0.0200 2.12 Shallow Concentrated Flow, SCF Grassed Waterway Kv= 15.0 fps 12.0 219 Total Subcatchment 5S: Pond Tract Runoff Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 0.42 0.4 0.38 0.36 0.34 0.32 0.3 0.28 0.26 0.24 0.22 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Type IA 24-hr 100-Year Rainfall=4.40" Runoff Area=43,761 sf Runoff Volume=6,913 cf Runoff Depth=1.90" Flow Length=219' Slope=0.0200 Tc=12.0 min CN=74/0 0.38 cfs ---PAGE BREAK--- Type IA 24-hr 100-Year Rainfall=4.40" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 21 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Pond 8P: Pond [44] Hint: Outlet device #2 is below defined storage Inflow Area = 806,821 sf, 78.10% Impervious, Inflow Depth = 3.67" for 100-Year event Inflow = 16.63 cfs @ 7.91 hrs, Volume= 246,583 cf Outflow = 3.44 cfs @ 10.83 hrs, Volume= 246,583 cf, Atten= 79%, Lag= 175.2 min Primary = 3.44 cfs @ 10.83 hrs, Volume= 246,583 cf Routing by Stor-Ind method, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Peak Elev= 106.49' @ 10.83 hrs Surf.Area= 20,279 sf Storage= 93,732 cf Plug-Flow detention time= 573.7 min calculated for 246,583 cf (100% of inflow) Center-of-Mass det. time= 573.7 min ( 1,251.1 - 677.4 ) Volume Invert Avail.Storage Storage Description #1 100.00' 93,997 cf Pond (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 100.00 8,620 0 0 106.50 20,302 93,997 93,997 Device Routing Invert Outlet Devices #1 Primary 99.00' 18.0" Round Outlet Pipe L= 40.0' Ke= 0.500 Inlet / Outlet Invert= 99.00' / 97.72' S= 0.0320 Cc= 0.900 n= 0.010 PVC, smooth interior, Flow Area= 1.77 sf #2 Device 1 98.00' 4.8" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads #3 Device 1 106.25' 18.0" Horiz. Overflow C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=3.43 cfs @ 10.83 hrs HW=106.49' (Free Discharge) 1=Outlet Pipe (Passes 3.43 cfs of 22.09 cfs potential flow) 2=Orifice/Grate (Orifice Controls 1.66 cfs @ 13.17 fps) 3=Overflow (Weir Controls 1.78 cfs @ 1.59 fps) ---PAGE BREAK--- Type IA 24-hr 100-Year Rainfall=4.40" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 22 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Pond 8P: Pond Inflow Primary Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Inflow Area=806,821 sf Peak Elev=106.49' Storage=93,732 cf 16.63 cfs 3.44 cfs ---PAGE BREAK--- Type IA 24-hr 100-Year Rainfall=4.40" Hermison Preliminary Analysis - 050525 Printed 5/7/2025 Prepared by LEI Engineering & Surveying Page 23 HydroCAD® 10.20-6a s/n 10330 © 2024 HydroCAD Software Solutions LLC Summary for Link 7L: Pre-Development Inflow Area = 806,821 sf, 0.00% Impervious, Inflow Depth = 1.90" for 100-Year event Inflow = 5.71 cfs @ 8.06 hrs, Volume= 127,462 cf Primary = 5.71 cfs @ 8.06 hrs, Volume= 127,462 cf, Atten= Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Link 7L: Pre-Development Inflow Primary Hydrograph Time (hours) 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Flow (cfs) 6 5 4 3 2 1 0 Inflow Area=806,821 sf 5.71 cfs 5.71 cfs