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Home My WebLink AboutCC - Storm Drainage Calcs ESE CONSULTANT S ESE 03 W.Sheryl Dr Inc. $103 W.Sheryl Drive ENGINEERING • PLANNING • SURVEYING • ENVIRONMENTAL Meridian,Idaho 83642 TEL: 208-424-0020 STORMWATER MANAGEMENT REPORT FOR DAYSPRING SUBDIVISION NO. 3 Q4��C NAL 9461370 m o OF 10 J. 21 fa �„ m mjN 0j. _ Anna Leigh Hirning Professional Engineer Idaho License No.9461370 m _ March 2026 LOCATEDIN: CITY OF MERIDIAN ADA COUNTY, IDAHO TABLE OF CONTENTS SUBJECT SECTION Project Overview 1 Stormwater Management Design 2 Stormwater Equations 3 Primary Conveyance & Stormwater Facility Calculations 4 Intensity-Duration-Frequency Curve 5 Pipe Flow Calculations 6 Drainage Basin Map 7 SECTION 1 - Project Overview Dayspring Subdivision No.3 is a part of a multi-phase mixed use development located in the City of Meridian,Ada County, Idaho. The development is situated along the south side of West Ustick Road, between North Black Cat Road and North McDermott Road. The applicant proposes to develop fifty-seven (57) single family residential lots with this phase of the project. The development includes the construction of homes and infrastructure to include roads, sidewalks, a stormwater management facility, utilities, and other improvements typical of residential construction. Existing Conditions The project site is currently bound by a single-family residential development to the east(Tricia's Crossing Subdivision) and vacant agricultural land to the west and south. The project site itself is comprised of existing irrigated farmland with several abandoned houses and ancillary buildings, and irrigation delivery ditches. The existing terrain is relatively flat with slopes generally less than one percent. The site slopes down gradient from north to south. Geotechnical Characteristics A Geotechnical Engineering Report was prepared by ALLWEST for the Dayspring Subdivision (f.k.a. Porter Complex Development), dated September 2, 2020. The soils were generally described as surficial lean clay with sand or sandy lean clays with thickness of 1 to 3 feet, overlaying varying layers and mixtures of native silty and sandy soils. Underlying the silty and sandy soils, were generally observed poorly graded gravels with silt and sand to test pit depths of up to 13' bgs. Groundwater Groundwater was observed by ALLWEST during testing in June of 2020 at depths ranging from 7.5' -13.5' bgs. Additional groundwater monitoring performed by Geotek commenced in August 2024 and is ongoing. There are currently 30 active piezometers onsite, and groundwater is observed at depths ranging from 3.2'-12.3' bgs. Geotek's results are summarized in the attached report dated January 2026. Soil Infiltration ALLWEST performed soil infiltration tests at 8 (eight) locations within the project site which resulted in rates ranging from a low of 0.25 in/hr to a high of greater than 20 in/hr. An infiltration rate of 1 in/hr was utilized for design purposes. SECTION 2 - Stormwater Management Design Design Criteria The Stormwater Management Plan described herein has been designed according to the Ada County Highway District Policy Manual. The proposed Stormwater Management Design has been prepared to meet the following requirements and guidelines: ♦ The Rational Method (Q=CiA) has been utilized to calculate peak flows. Runoff coefficients were used per the ACHD Policy Manual. Rainfall intensities were determined using the ACHD adopted Intensity-Duration-Frequency Curve located in Section 5 of this report. Calculations for the requisite time of concentration (Tc) value are enclosed. The overland flow and gutter flow segments of the Tc were calculated based on the equations provided in the ACHD Policy Manual and enclosed within this report for reference. ♦ Pipe flow calculations are provided to demonstrate that the primary stormwater conveyance system is sized to adequately handle stormwater flows based on the 100-yr storm event. ♦ The residential lot grading was designed to drain approximately the front half of the lot towards the street and is included in the stormwater basin calculations. Stormwater that falls within the back of the lots will be retained on site. Yard drains will be installed in the rear yards during home construction and final landscaping to facilitate infiltration of lot drainage. ♦ High groundwater observed through the site necessitated the use of Vertical Sand Filters for the storage and infiltration of the 100-year storm event. An infiltration rate of 1 inch per hour has been used for the design of the vertical sand filters. Sand and grease traps are provided for pretreatment for the vertical sand filters which have been designed so the bottom of facility elevation is higher than the anticipated seasonal groundwater. ♦ Within Phase 3,there are five (5) proposed vertical sand filters. Basin 3.1 is located within a future common lot on the west side of N Dayspring Way Basin 3.2 is located within Common Lot 9C, Block 14 on the west side of N Barnstead Way, Basin 3.3 is located within Common Lot 5C, Block 13 on the north side of W Ridgeside St, Basin 3.4 is located within Lot 17C, Bock 11 on the south side of W Ridgeside St, and Basin 3.5 is located within 6C, Blockon the west side of N Bebee River Way. ♦ Stormwater generated within the front halves of Lots 3 & 4, Block 13, 4,5,21 & 22, Block 12, and Lot 3, Block 11 and adjacent roadways have been accounted for in the Dayspring Subdivision No. 2 stormwater facilities. ♦ Phase 3 includes two(2)temporary stormwater retention ponds that have been sized for the 100-year event and designed to provide a minimum of 3' between the bottom of facility elevation and the anticipated seasonal groundwater. Basins 3.6 & 3.7 are located at the west end of W Belle Meade Dr. within proposed temporary storm drain easements and will be removed and replaced with the development of future phases. SECTION 3 - Stormwater Equations Stormwater Conveyance ACHD Policy Manual 8011.2) Q = iA where= Q - Discharge rate (ofs) _ Coefficient of Runoff(dimensionless) i = Rainfall intensity (in/hr) for a duration equal to the time of concentration (Tc) over the contribuking area and for the design frequency. A = Site area (acres) Tc = Time of concentration Coefficient of Runoff(ACHD Policy Manual 8011.2.1) Estimated Runoff Coefficients for Various Surfaces Type of Surface Runoff Coefficients "C" Business Downtown areas 0.70-0.95 Urbannelghtwhoods 0.50-0.70 Residential Single Family 0.35.0.50 Multifamily 0.60.0.75 Residential1Fural) 0.25.0.40 ApartmentDwellingAreas 0.70 Industrial and Commerclal Light areas 0.80 Heavy areas 0.90 Parks,{emeterles 0.10-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20.0.40 UnlmpFaved areas 0.10.0.30 StFBBtS Asphalt 0.95 Gan{Fete 0.95 Brick 0.95 Roofs 0.95 Grant 0.75 Fields:Sandy sail Soll Type Slope A B { Flat 0.2% 0.04 0.07 0.11 0.1S Average,2.6% 0.09 0.12 0.15 4.20 Steep' % 0.13 0.18 0.2n :'.?a Adapted from ASCE Design Storm Runoff Volume (ACHD Policy Manual 8011.3.2) V=CiA(3600) V: Design storm runoff volume required for storage C: Coefficient of Runoff is Rainfall Intensity per IDF Curve 1-hour 100-year storm event, i=0.96 1-hour 2-year storm event, i=0.26 A: Total catchment area(acres) Time of Concentration Tc=Tc-G+Tc-s Tc : Total time of concentration LG Tc-c — 60 • VG Tc-G : Gutter time of concentration LG : Length of gutter flow VG : Gutter flow velocity VG=K„k Sr0.5 Ku : Empirical coefficient(3.281) k : Intercept coefficient(0.619) Sr : Slope (percent) 0.007(nL)0-8 Tc—S — (p2)0.5So.4 Tc-s : Overland time of concentration L : Length of overland(sheet) flow n : Manning's Roughness Coefficient(0.24) P2 : 2-year 24-hour rainfall (1.2 in.) S : Slope (ft/ft) Manning's Roughness Coefficient(ACHD Policy Manual 8011.5.3) Typical Range of Manning's Coefficient (n) for Channels and Pipet, CandUii Matoridl Mann ing's n' Closed Conduits Concrete pipe 0.010- 0.015 CMP 0.017 -0.037 Plastic pips(SM001h) 0.009-0.015 Plastic ppe(corrugated) D_018-0.025 PavemenUgutter sections OmM-0.016 ma to Open Chenriel5 Concrete 0.01 i -0.015 Rubble or riprap 0_d20-d_D35 V aget a ban d.020=0.150 Base Soil 0.01fi-0.025 Rack Cut 0.025-0.045 Natural channels(minor streams, lop avudth at none saga <30 m(100 h)) Fairiy regular s,wjo a 0.025- 0.050 Irregular 9Ocban with N!S 0.040-0.150 'Lower values are usually For well-constructed and maintained 1;&mDotherj pipes and channels Table 3-2. Manning's Roughness Coefficient(n)for Overland Sheet Flow,`' Surface Description n Smooth asphalt 0.011 Smooth concrete 0.012 Ordinary concrete lining 0.013 Good wood 0.014 Brick with cement mortar 0.014 Vitrified clay 01015 Cast iron 0.015 Corrugated metal pipe 0,024 Cement rubble surface M24 Fallow (no residue) 0.05 Cultivated soils Residue cover s 20% 0_06 Residue cover> 20°fo 0.17 Range(natural) 0_13 Grass Short grass prairie 0.15 Dens@ grasses 0.24 Bermuda grass 0.41 Woods' Light underbrush 0.40 Dense underbrush 4_$4 -When selecting n, consider cover to a height of about K mm. This is only part of the plant cover that will obstruct sheet Flow, SECTION 4 Primary Conveyance & Stormwater Facility Calculations BASIN CATCHMENT AREA 3.1 BASIN CHARACTERISTICS Basin Area: 0.73 Acres Runoff Coefficient, C: 0.65 Rainfall Intensity, is 0.96 in/hr Infiltration Rate, r: 1.0 in/hr TIME OF CONCENTRATION Overland Flow Gutter Flow Sub-Catchment Length, L Slope, s TC-5 Elev 1 Elev 2 Length, LG Slope, Sp Gutter Velocity,VG Tc-G Total Tc (ft) M (min.) (ft) (ft) (ft) M (ft/sec) (min.) (min.) 3.1A 40.0 1.00 14.8 2544.0 2542.8 265 0.44 1.34 3.3 18.1 3.113 40.0 1.00 14.8 2544.0 2542.8 271 0.44 1.35 3.3 18.1 CONVEYANCE Sub-Catchment C Area, A i2 i25 i100 Q2 Q25 Q100 (acres) (in/hr) (in/hr) (in/hr) (cfs) (cfs) (cfs) 3.1A 0.65 0.30 0.53 1.40 1.95 0.10 0.27 0.38 3.113 0.65 0.43 0.53 1.40 1.95 0.15 0.39 0.55 Total 0.73 0.25 0.66 0.93 SAND & GREASE TRAP No. of S&G Baffle Throat Vault Size Traps Spacing Width Throat Area Flow Rate, Q100 Throat Velocity, V Flow Rate Check Velocity Check (galon) (inch) (inch) (ft) (cfs) (fps) Q100< 3.33 cfs V<0.5 fps 1000 1 20 48 6.67 0.93 0.14 TRUE TRUE STORAGE VOLUMES (Vertical Sand Filter) Chamber 1 Req'd Volume, V2-YR L1 W1 d1 Pipe Volume, VP1 Volume, VR1 Storage Volume,V1 (ft) (ft) (ft) (ft) (ft) (ft) (ft) 444 90 3.5 4.5 157 504 661 Chamber 2 Rock Void Design Infiltration Bed Infiltration Time to Drain Req'd Volume, V100-YR L2 W2 dz Pipe Volume, VPZ Volume, VRz Rate, I Volume,VZi Storage Volume,VZ 90% (ft) (ft) (ft) (ft) (ft) (ft) (in/hr) (ft) (ft) (hrs) 1,640 90 10 4.5 70 1,592 1.0 75 1,737 19.68 BASIN CATCHMENT AREA 3.2 BASIN CHARACTERISTICS Basin Area: 2.08 Acres Runoff Coefficient, C: 0.50 Rainfall Intensity, is 0.96 in/hr Infiltration Rate, r: 1.0 in/hr TIME OF CONCENTRATION Overland Flow Gutter Flow Sub-Catchment Length, L Slope, s TC-5 Elev 1 Elev 2 Length, LG Slope, Sp Gutter Velocity,VG Tc-G Total Tc (ft) M (min.) (ft) (ft) (ft) M (ft/sec) (min.) (min.) 3.2A 40.0 1.50 12.6 2544.0 2541.0 517 0.59 1.55 5.5 18.1 3.2B 15.0 2.00 5.1 2542.9 2541.0 394 0.49 1.43 4.6 9.7 CONVEYANCE Sub-Catchment C Area, A i2 i25 i100 Q2 Q25 Q100 (acres) (in/hr) (in/hr) (in/hr) (cfs) (cfs) (cfs) 3.2A 0.50 1.12 0.53 1.40 1.95 0.30 0.78 1.09 3.2B 0.50 0.96 0.69 1.85 2.58 0.33 0.89 1.24 Total 2.08 0.63 1.67 2.33 SAND & GREASE TRAP No. of S&G Baffle Throat Vault Size Traps Spacing Width Throat Area Flow Rate, Q100 Throat Velocity, V Flow Rate Check Velocity Check (galon) (inch) (inch) (ft) (cfs) (fps) Q100< 3.33 cfs V<0.5 fps 1000 1 20 48 6.67 2.33 0.35 TRUE TRUE STORAGE VOLUMES (Vertical Sand Filter) Chamber 1 Req'd Volume, V2-YR L1 W1 d1 Pipe Volume, VP1 Volume, VR1 Storage Volume,V1 (ft) (ft) (ft) (ft) (ft) (ft) (ft) 973 100 5.5 4 175 810 985 Chamber 2 Rock Void Design Infiltration Bed Infiltration Time to Drain Req'd Volume, V100-YR L2 W2 dz Pipe Volume, VPZ Volume, VRz Rate, I Volume,VZi Storage Volume,VZ 90% (ft) (ft) (ft) (ft) (ft) (ft) (in/hr) (ft) (ft) (hrs) 3,594 100 22 4 78 3,489 1.0 183 3,750 17.64 BASIN CATCHMENT AREA 3.3 BASIN CHARACTERISTICS Basin Area: 2.41 Acres Runoff Coefficient, C: 0.50 Rainfall Intensity, is 0.96 in/hr Infiltration Rate, r: 1.0 in/hr TIME OF CONCENTRATION Overland Flow Gutter Flow Sub-Catchment Length, L Slope, s TC_5 Elev 1 Elev 2 Length, LG Slope, Sp Gutter Velocity,VG Tc_G Total Tc (ft) M (min.) (ft) (ft) (ft) M (ft/sec) (min.) (min.) 3.3 70.0 1.00 23.1 2545.1 2541.6 659 0.54 1.50 7.3 30.5 CONVEYANCE Sub-Catchment C Area,A i2 i25 i100 Q2 Q25 Q100 (acres) (in/hr) (in/hr) (in/hr) (cfs) (cfs) (cfs) 3.3 0.50 2.41 0.4 1.06 1.48 0.48 1.28 1.78 Tota 1 2.41 0.48 1.28 1.78 SAND & GREASE TRAP No. of S&G Baffle Throat Vault Size Traps Spacing Width Throat Area Flow Rate, Q100 Throat Velocity, V Flow Rate Check Velocity Check (galon) (inch) (inch) (ft) (cfs) (fps) Q100< 3.33 cfs V<0.5 fps 1000 1 20 48 6.67 1.78 0.27 TRUE TRUE STORAGE VOLUMES (Vertical Sand Filter) Chamber 1 Req'd Volume, V2-YR L1 W1 d1 Pipe Volume, VP1 Volume, VR1 Storage Volume,V1 (ft') (ft) (ft) (ft) (ft') (ft') (ft) 1,128 170 3.5 4 298 833 1,131 Chamber 2 Rock Void Design Infiltration Bed Infiltration Time to Drain Req'd Volume, V100-YR L2 W2 d2 Pipe Volume, VP2 Volume, VR2 Rate, I Volume,V21 Storage Volume,V2 90% (ft) (ft) (ft) (ft) (ft) (ft) (in/hr) (ft) (ft) (hrs) 4,164 170 15 4 133 4,027 1.0 213 4,372 17.64 BASIN CATCHMENT AREA 3.4 BASIN CHARACTERISTICS Basin Area: 2.66 Acres Runoff Coefficient, C: 0.50 Rainfall Intensity, is 0.96 in/hr Infiltration Rate, r: 1.0 in/hr TIME OF CONCENTRATION Overland Flow Gutter Flow Sub-Catchment Length, L Slope, s TC_5 Elev 1 Elev 2 Length, LG Slope, Sp Gutter Velocity,VG Tc_G Total Tc (ft) M (min.) (ft) (ft) (ft) M (ft/sec) (min.) (min.) 3.4 70.0 1.00 23.1 2544.3 2541.6 511 0.53 1.48 5.7 28.9 CONVEYANCE Sub-Catchment C Area,A i2 i25 i100 Q2 025 Q100 (acres) (in/hr) (in/hr) (in/hr) (cfs) (cfs) (cfs) 3.4 0.50 2.66 0.41 1.09 1.53 0.55 1.45 2.03 Tota 1 2.66 0.55 1.45 2.03 SAND & GREASE TRAP No. of S&G Baffle Throat Vault Size Traps Spacing Width Throat Area Flow Rate, Q100 Throat Velocity, V Flow Rate Check Velocity Check (galon) (inch) (inch) (ft) (cfs) (fps) Q100< 3.33 cfs V<0.5 fps 1000 1 20 48 6.67 2.03 0.31 TRUE TRUE STORAGE VOLUMES (Vertical Sand Filter) Chamber 1 Req'd Volume, V2-YR L1 W1 d1 Pipe Volume, VP1 Volume, VR1 Storage Volume,V1 (ft') (ft) (ft) (ft) (ft') (ft') (ft) 1,245 100 7 4.5 175 1,190 1,365 Chamber 2 Rock Void Design Infiltration Bed Infiltration Time to Drain Req'd Volume, V100-YR L2 W2 d2 Pipe Volume, VP2 Volume, VR2 Rate, I Volume,V21 Storage Volume,V2 90% (ft) (ft) (ft) (ft) (ft) (ft') (in/hr) (ft) (ft) (hrs) 4,596 100 25.5 4.5 78 4,559 1.0 213 4,849 19.47 BASIN CATCHMENT AREA 3.5 BASIN CHARACTERISTICS Basin Area: 1.90 Acres Runoff Coefficient, C: 0.50 Rainfall Intensity, is 0.96 in/hr Infiltration Rate, r: 1.0 in/hr TIME OF CONCENTRATION Overland Flow Gutter Flow Sub-Catchment Length, L Slope, s TC-5 Elev 1 Elev 2 Length, LG Slope, Sp Gutter Velocity,VG Tc-G Total Tc (ft) M (min.) (ft) (ft) (ft) M (ft/sec) (min.) (min.) 3.5A 70.0 1.00 23.1 2544.3 2542.1 438 0.50 1.44 5.1 28.2 3.5B 70.0 1.00 23.1 2544.3 2542.1 438 0.50 1.44 5.1 28.2 CONVEYANCE Sub-Catchment C Area, A i2 i25 i100 Q2 Q25 Q100 (acres) (in/hr) (in/hr) (in/hr) (cfs) (cfs) (cfs) 3.5A 0.50 0.87 0.42 1.10 1.54 0.18 0.48 0.67 3.5B 0.50 1.03 0.42 1.10 1.54 0.22 0.57 0.79 Tota 1 1.90 0.40 1.05 1.46 SAND & GREASE TRAP No. of S&G Baffle Throat Vault Size Traps Spacing Width Throat Area Flow Rate, Q100 Throat Velocity, V Flow Rate Check Velocity Check (galon) (inch) (inch) (ft) (cfs) (fps) Q100< 3.33 cfs V<0.5 fps 1000 1 20 48 6.67 1.46 0.22 TRUE TRUE STORAGE VOLUMES (Vertical Sand Filter) Chamber 1 Req'd Volume, V2-YR L1 W1 d1 Pipe Volume, VP1 Volume, VR1 Storage Volume,V1 (ft) (ft) (ft) (ft) (ft) (ft) (ft) 889 207 2 5.75 364 807 1,171 Chamber 2 Rock Void Design Infiltration Bed Infiltration Time to Drain Req'd Volume, V100-YR L2 W2 dz Pipe Volume, VPZ Volume, VRz Rate, I Volume,VZi Storage Volume,VZ 90% (ft) (ft) (ft) (ft) (ft) (ft) (in/hr) (ft) (ft) (hrs) 3,283 207 6.5 5.75 162 3,030 1.0 112 3,304 26.35 TEMPORARY BASIN CATCHMENT AREA 3.6 BASIN CHARACTERISTICS Basin Area: 0.28 Acres Runoff Coefficient, C: 0.55 Rainfall Intensity, is 0.96 in/hr STORAGE VOLUMES Temporary Basin Req'd Volume Botom Top Area Basin V100YR Depth Area Volume (ft3) (ft) (ftz) (ftz) (ft) 532 - 0 617.00 1046.0 831.5 TEMPORARY BASIN CATCHMENT AREA 3.7 BASIN CHARACTERISTICS Basin Area: 0.07 Acres Runoff Coefficient, C: 0.55 Rainfall Intensity, is 0.96 in/hr STORAGE VOLUMES Temporary Basin Req'd Volume Botom Basin V100YR Depth Area Top Area Volume (ft) (ft) (ft2) (ft) (ft) 135 _._ 221.00 347.0 142.0 SECTION 5 Intensity-Duration-Frequency Curve ACHD Intensity-Duration-Frequency Intensity(inches per hour) Design Storm 2 5 10 25 50 100 Tc(hr) Tc(min) 0.17 10 0.69 1.15 1.48 1.85 2.20 2.58 0.25 15 0.59 0.97 1.22 1.56 1.86 2.18 0.33 20 0.49 0.81 1.01 1.30 1.54 1.81 0.42 25 0.43 0.71 0.89 1.14 1.35 1.58 0.50 1 30 0.41 0.67 0.85 1.08 1 1.29 1.51 0.58 35 0.34 0.56 0.70 0.90 1.07 1.25 0.67 40 0.31 0.51 0.64 0.82 0.98 1.15 0.75 45 0.29 0.48 0.60 0.77 0.91 1.07 0.83 50 0.27 0.45 0.56 0.72 0.85 1.00 0.92 55 0.26 0.43 0.54 0.69 0.82 0.96 1 60 0.26 0.43 0.54 0.69 0.82 0.96 2 120 0.16 0.25 0.31 0.39 0.46 0.54 3 180 0.13 0.19 0.23 0.29 0.34 0.40 6 360 0.09 0.12 0.14 0.18 0.21 0.25 12 720 0.06 0.08 10.10 0.12 0.14 0.16 24 1440 0.04 0.06 1 0.06 0.08 0.09 0.10 Intensity Duration Frequency 3 - 2 -x-5 -x-to 2.5 -�25 t so 2 f 100 s v u 1.5 c T a+ x� a 1 c \X�X ��\X�X� _ 0.5 - _ \x-- -X X-X-X _ =�,3 10 15 20 25 30 35 40 45 50 55 60 120 180 360 720 1440 Duration (minutes) SECTION 6 Pipe Flow Calculations Channel Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Thursday, Feb 19 2026 100 YR - SDCB MA TO SDMH 3.1 Circular Highlighted Diameter (ft) = 1.00 Depth (ft) = 0.37 Q (cfs) = 0.930 Area (sqft) = 0.27 Invert Elev (ft) = 100.00 Velocity (ft/s) = 3.51 Slope (%) = 0.50 Wetted Perim (ft) = 1.31 N-Value = 0.010 Crit Depth, Yc (ft) = 0.41 Top Width (ft) = 0.97 Calculations EGL (ft) = 0.56 Compute by: Known Q Known Q (cfs) = 0.93 Elev (ft) Section Depth (ft 102.00 2.00 101.50 1.50 101.00 1.00 100.50 0.50 100.00 0.00 99.50 -0.50 0 1 2 3 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Thursday, Feb 19 2026 100 YR - SDCB 3.1 B TO SDCB 3.1A Circular Highlighted Diameter (ft) = 1.00 Depth (ft) = 0.28 Q (cfs) = 0.550 Area (sqft) = 0.18 Invert Elev (ft) = 100.00 Velocity (ft/s) = 3.02 Slope (%) = 0.50 Wetted Perim (ft) = 1.12 N-Value = 0.010 Crit Depth, Yc (ft) = 0.31 Top Width (ft) = 0.90 Calculations EGL (ft) = 0.42 Compute by: Known Q Known Q (cfs) = 0.55 Elev (ft) Section Depth (ft 102.00 2.00 101.50 1.50 101.00 1.00 100.50 0.50 v 100.00 0.00 99.50 -0.50 0 1 2 3 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Thursday, Feb 19 2026 100 YR - SDCB 3.2A TO SDMH 3.2 Circular Highlighted Diameter (ft) = 1.00 Depth (ft) = 0.63 Q (cfs) = 2.330 Area (sqft) = 0.52 Invert Elev (ft) = 100.00 Velocity (ft/s) = 4.47 Slope (%) = 0.50 Wetted Perim (ft) = 1.83 N-Value = 0.010 Crit Depth, Yc (ft) = 0.66 Top Width (ft) = 0.97 Calculations EGL (ft) = 0.94 Compute by: Known Q Known Q (cfs) = 2.33 Elev (ft) Section Depth (ft 102.00 2.00 101.50 1.50 101.00 1.00 IL 100.50 0.50 100.00 0.00 99.50 -0.50 0 1 2 3 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Thursday, Feb 19 2026 100 YR - SDCB 3.2B TO SDCB 3.2A Circular Highlighted Diameter (ft) = 1.00 Depth (ft) = 0.43 Q (cfs) = 1.240 Area (sqft) = 0.33 Invert Elev (ft) = 100.00 Velocity (ft/s) = 3.81 Slope (%) = 0.50 Wetted Perim (ft) = 1.43 N-Value = 0.010 Crit Depth, Yc (ft) = 0.47 Top Width (ft) = 0.99 Calculations EGL (ft) = 0.66 Compute by: Known Q Known Q (cfs) = 1.24 Elev (ft) Section Depth (ft 102.00 2.00 101.50 1.50 101.00 1.00 100.50 0.50 100.00 0.00 99.50 -0.50 0 1 2 3 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Thursday, Feb 19 2026 100 YR - SDCB 3.3 TO SDMH 3.3 Circular Highlighted Diameter (ft) = 1.00 Depth (ft) = 0.53 Q (cfs) = 1.780 Area (sqft) = 0.42 Invert Elev (ft) = 100.00 Velocity (ft/s) = 4.19 Slope (%) = 0.50 Wetted Perim (ft) = 1.63 N-Value = 0.010 Crit Depth, Yc (ft) = 0.57 Top Width (ft) = 1.00 Calculations EGL (ft) = 0.80 Compute by: Known Q Known Q (cfs) = 1.78 Elev (ft) Section Depth (ft 102.00 2.00 101.50 1.50 101.00 1.00 100.50 _ 0.50 100.00 0.00 99.50 -0.50 0 1 2 3 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Thursday, Feb 19 2026 100 YR - SDCB 3.4 TO SDMH 3.4 Circular Highlighted Diameter (ft) = 1.00 Depth (ft) = 0.57 Q (cfs) = 2.030 Area (sqft) = 0.46 Invert Elev (ft) = 100.00 Velocity (ft/s) = 4.37 Slope (%) = 0.50 Wetted Perim (ft) = 1.71 N-Value = 0.010 Crit Depth, Yc (ft) = 0.61 Top Width (ft) = 0.99 Calculations EGL (ft) = 0.87 Compute by: Known Q Known Q (cfs) = 2.03 Elev (ft) Section Depth (ft 102.00 2.00 101.50 1.50 101.00 1.00 100.50 - 0.50 100.00 0.00 99.50 -0.50 0 1 2 3 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Thursday, Feb 19 2026 100 YR - SDCB 3.5A TO SDMH 3.5 Circular Highlighted Diameter (ft) = 1.00 Depth (ft) = 0.47 Q (cfs) = 1.460 Area (sqft) = 0.36 Invert Elev (ft) = 100.00 Velocity (ft/s) = 4.00 Slope (%) = 0.50 Wetted Perim (ft) = 1.51 N-Value = 0.010 Crit Depth, Yc (ft) = 0.51 Top Width (ft) = 1.00 Calculations EGL (ft) = 0.72 Compute by: Known Q Known Q (cfs) = 1.46 Elev (ft) Section Depth (ft 102.00 2.00 101.50 1.50 101.00 1.00 100.50 0.50 100.00 0.00 99.50 -0.50 0 1 2 3 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Thursday, Feb 19 2026 100 YR - SDCB 3.5B TO SDCB 3.5A Circular Highlighted Diameter (ft) = 1.00 Depth (ft) = 0.34 Q (cfs) = 0.790 Area (sqft) = 0.24 Invert Elev (ft) = 100.00 Velocity (ft/s) = 3.32 Slope (%) = 0.50 Wetted Perim (ft) = 1.25 N-Value = 0.010 Crit Depth, Yc (ft) = 0.38 Top Width (ft) = 0.95 Calculations EGL (ft) = 0.51 Compute by: Known Q Known Q (cfs) = 0.79 Elev (ft) Section Depth (ft 102.00 2.00 101.50 1.50 101.00 1.00 100.50 0.50 100.00 0.00 99.50 -0.50 0 1 2 3 Reach (ft) SECTION 7 Drainage Basin Map \ _ DAYSPRING SUBDIVISION NO. 2 \ ` I I ❑ ® 22 ' 19 ® I I I FUTURE PHASE 3.2 — _ —.os° I 18 ❑ I I ❑ 21 - - -- 9C LEGEND 3.2A 3.2E 1 96 4 BASIN BOUNDARY LINE 3 1 10 I I I a 7 ❑ ❑7 20 ❑ SUB—BASIN BOUNDARY LINE a.sA 3.ae BLOCK 14 08 I I I TIME OF CONCENTRATION I 11 3 16 ❑7 I } 19 I 3.1 BASIN NUMBER 3 3.1 A . 12 I IJI ,0.73. BASIN AREAI I 5 O 31A 15 8 SUB—BASIN NUMBER Q 9 oc m 3 o.ao o SUB—BASIN AREA Z BLOCK 13 Z I BLOCK 12 18 I I ® ® ROADWAY INLET 3 3 13 I I 14 I 9LU I LIJ 13 10 m c I ❑ 11 � I I II) I 16 I I W BELLE MEAD DR FUTURE PHASE I I I 7 L II I � 5C I I I 12 13 15 ❑ ❑ II ❑ 3.3 23 • •41 ° 14C 3.6 8 .28 W RIDGESIDE ST / / 3.4 22 20C 19 8 � 17Ci 6 15 14 13 2 1 10C N 24C 21 FEET BLOCK 11 ❑9 I I I 100 0 50 100 — SAFFORD LATERAL GRAPHIC SCALE ---------------------- 1 inch A00 ft.Horizontal � TOP T^o -- CESCE 00H,%UL4La14Z DAYSPRING SUBDIVISION NO. 3 Toll Brothers ENGINEERING PLANNING SURVEYING ENVIRONMENTAL DRAINAGE CATCHMENT PLAN ESE Consultants,Inc. 3103 W.Sheryl Drive•Suite 100•Meridian,ID 83642 February 19, 2026 - Meridian, Idaho AMERICA'S LUXURY HOME BUILDER* T:208-424-0020