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HomeMy WebLinkAboutWPO201900054 Calculations 2020-01-02WAHS Site Improvements ALBEMARLE COUNTY, VIRGINIA SCOTTSVILLE DISTRICT DESIGN CALCULATIONS & NARRATIVE WPO 2019-00054 SEPTEMBER 23, 2019 REVISED: DECEMBER 30, 2019 •�ss•�i TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. Prepared by: Jonathan Showalter, PE Timmons Group 608 Preston Avenue, Suite 200 Charlottesville, VA 22903 434.327.1681 11 1-1PN L7 .1SH 1 14. 5HOW.kLM i.;c. No. 0402057l51 'P 3.2./30/201. q' rd�� '� 1 r�:� � 1. ti:�+C4 ;,`i� Table of Contents Section Title Project Narrative 2.1 LD-204 Inlet Calculations 2.2 LD-229 Pipe Calculations 2.3 LD-347 Hydraulic Grade Line Analysis 2.4 LD269 Culvert Report 3 Virginia Runoff Reduction Method Worksheet Summary Project Narrative: This project included site improvements to Western Albemarle High School including a new Softball Fieldhouse, widened access road, new ADA ramp to the bus loop, and related site work. The limits of disturbance is 0.75 acres. Water Quality: The current site contains an existing field house, narrow driveway, asphalt path, and associated ramps and stairs. 0.75 acres of disturbed area was analyzed for water quality. The site will require 0.30./year to be treated. The required 0.30 lbs/yr will be satisfied by purchasing nutrient credits from a DEQ approved credit bank in accordance with LIS code of Virginia 62.1-44.15:35 Water Quantity: In the developed condition the runoff from the disturbed area will flow off as sheet flow. Level spreaders are provided at points of concentrated discharge to return runoff to sheet flow. this project fulfills the requirements of section 9VAC25-970-66 Section D. FORM LD 204 STORMWATER INLET COMPUTATIONS SHEET 1 OF 1 LD204 PROJECT WAHS Fieldhouse DESIGNER: A.MABEE DATE 12/31/2019 CHECKED: J. SHOWALTER UNITS ENGLISH Sag Inlets Only ®��- III I •I III' ____________________________® --- III I I.I ® I I -------------------------__-® ®® III I I I •I 11 -------------------------__-® --- I III I ' I ®®-------------------------__-® ---_-------®III --®--------®--®----_®-® --- I III -- I I� 1 1 �---------------------__-® --- III --����---------------------__-® ®� III 11 1 I'I 11 -------------------------__-® ---IIII I I ® I I -------------------------__-® INLETSOFT BY ENSOFTEC DATE: 12/31/2019 LD-229 STORM SEWER DESIGN COMPUTATIONS STORM FREQUENCY 10 PROJECT: WAHS Fieldhouse LOCATION: COUNTY: Charlottesville NOAA STATION: Designed by: A.MABEE Checked by: J. SHOWALTER UNITS ENGLISH PIPE NO. FROM POINT TO POINT DRAIN. AREA "A" Acre (3) RUNOFF COEFF. "C., (4) CA TOTAL INLET TIME Minutes (7) RAIN FALL In/Hr (8) RUNOFF INVERT ELEVATIONS LENGTH of Pipe Ft. (12) SLOPE RJR. (13) SIZE (Dia. Or Span/Rise) In. (14) SHAPE Number of Pipes Capacity CFS (15) Friction Slope RJR. NORMALFLOW FLOW TIME Sec. (17) REMARKS (18) INCRE- MENT (5) ACCUM- ULATED (6) Lateral CFS Total Q CFS (9) UPPER END (10) LOWER END (11) Depth of Flow, do Ft. Area of Flow, An S,Ft Hrn Ft. Vn F:e (16) En Ft REFERENCE (1) STA. REFERENCE (2) STA. 201 202 200 0.07 0.43 0.03 0.03 5.00 6.54 0.00 0.20 676.46 673.64 56.46 0.04998 12 Circular 1 8.63 0.00000 0.10 0.04 0.07 4.53 0.42 12.45 301 302 300 0.65 0.47 0.31 0.31 10.00 5.26 0.00 1.61 658.27 656.86 35.24 0.04001 15 Circular 1 12.92 0.00060 0.30 0.22 0.18 7.18 1.10 4.91 401 402 400 0.58 1 0.62 0.36 0.53 5.10 6.51 1 0.00 3.46 667.16 663.96 1 53.28 0.060061 15 Circular 1 15.83 0.00300 0.40 0.34 0.22 10.33 2.05 5.16 403 404 402 0.43 0.40 0.17 0.17 5.00 6.54 0.00 1.13 668.58 667.26 37.80 0.03492 15 Circular 1 12.07 0.00030 0.26 0.18 0.16 6.18 0.85 6.12 499 500 EX-1 0.01 0.90 0.01 0.11 5.32 6.44 0.00 0.74 662.27 662.01 25.99 0.01000 12 Circular 1 3.86 0.00040 0.30 0.20 0.17 3.79 0.52 6.86 501 502 500 0.01 0.90 0.01 0.10 5.24 6.46 0.00 0.68 662.54 662.37 17.14 0.00992 12 Circular 1 3.84 0,00030 0.28 0.18 0.16 3.69 0.50 4.64 503 504 502 0.01 0.90 0.01 0.10 5.17 6.49 0.00 0.62 662.81 662.64 16.89 0.01007 12 1 Circular 1 3.87 10.00030 0.27 0.17 0.16 3.62 0.47 4.67 505 506 504 0.01 0.90 0.01 0.09 5.09 6.51 0.00 0.56 663.08 662.91 16.89 0.01001 12 Circular 1 3.86 0.00020 0.26 0.16 0,15 3.51 0.45 4.81 507 508 506 0.22 0.35 0.08 0.08 5.00 6.54 0.00 0.50 663.35 663.18 17.25 0.00986 12 Circular 1 3.83 0.00020 0.25 0.15 0.14 3.38 0.42 5.10 EXISTING EX- EX 0.16 0.53 0.08 0.20 5.43 6.40 0.00 1.28 661.91 659.40 42.52 0.05903 18 Circular 1 27.65 0.00010 0.22 0.16 0.14 7.96 1.20 5.34 LD-347 PROJECT: WAHS Fieldhouse HYDRAULIC GRADE LINE ANALYSIS INCIDENCE PROBABILITY Year DESIGNED BY: A.MABEE Checked: J. SHOWALTER INLET OR JUNCTION STA. INVERT EL. OUTFLOW PIPE DEPTH OF FLOW OUTFLOW PIPE OUTLET WATER SURFACE ELEV. DIA. PIPE Do (In/mm) DESIGN DISCH. Oo (CFS/CMS) LENGTH PIPE Lo (FtlM) FRICTION SLOPE, Sfo (FT/FT) (M/M) FRICTION LOSS Hf (FtlM) JUNCTION LOSS SURFACE FLOW Adj. Ht 1.3 Ht (FtlM) Inlet Inlet Top of MH Shaping? 0.5 FINAL Water Top of Inlet Adjustment? Ht H Surface Elev. Y/N (FUM) (FtlM) Elevation APPROX. V. Contr. Ho (FtlM) Vi Vi'2/2g Hi (Expn) 0.35'MAX. (Vi2/2g) SKEW Angle K Bend H (FUM) Sum HL (FtlM) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 16 17 18 19 200 1 675.750 202 673.641 1.00 675.750 12 0.196 56.46 0.00003 0.002 4.533 0.080 0.000 0.000 0.000 0.0 0.00 0.000 0.080 0.196 0.104 YES 0.052 0.053 676.567 681.820 O.K. 400 667.400 402 663.960 1.25 667.400 15 3.456 53.28 0.00299 0.159 10.326 0.414 6.176 0.592 0.207 0.0 0.00 0.000 0.621 2.324 0.808 YES 0.404 0.563 667.963 671.000 O.K. 404 667.260 1.25 668.260 15 1.132 37.80 0.00032 0.012 6.176 0.148 0.000 0.000 0.000 0.0 0.00 0.000 0.148 1.132 0.192 YES 0.096 0.108 668.838 672.000 O.K. EX-1 663.000 500 662.010 1.00 663.000 12 0.679 25.99 0.00032 0.008 3.703 0.053 3.692 0.212 0.074 0.0 0.00 0.000 0.127 0.000 0.127 YES 0.064 0.072 663.072 665.521 O.K. 502 662.370 1.00 663.170 12 0.679 17.14 0.00032 0.006 3.692 0.053 3.618 0.203 0.071 0.0 0.00 0.000 0.124 0.058 0.124 YES 0.062 0.068 663.238 665.520 O.K. 504 662.640 1.00 663.440 12 0.621 16.89 0.00027 0.005 3.618 0.051 3.511 0.191 0.067 0.0 0.00 0.000 0.118 0.058 0.118 YES 0.059 0.063 663.503 666.120 O.K. 506 662.910 1.00 663.710 12 0.563 16.89 0.00022 0.004 3.511 0.048 3.383 0.178 0.062 0.0 0.00 0.000 0.110 0.059 0.110 YES 0.055 0.059 663.769 666.120 O.K. 508 663.180 1.00 663.980 12 0.504 17.25 0,0001 8 0.003 3.383 0.044 0.000 0.000 0.000 0.0 0.00 0,000 0.044 0.504 0.058 YES 0.029 0.032 664.012 665.320 O.K. PROJECT WAHS Site Improvements SHEET UNITS OF ENGLISH CULVERT DESIGN FORM LD-269 DESIGNER: A. Mabee DATE: 9/24/2019 REVIEWER: J. Showalter ROAD COUNTY Albemarle (Zone 2) CULVERT 101 VA NOAA Station Charlottesville HYDROLOGICAL DATA Method: RATIONAL Drainage Area: 0.12 Acres Time of Concentration 5 Minutes DESIGN FLOWS Shldr. Elsf= Eli= Lr S= SKEW= Elev. Lt. ELBWd= 667.62 0.00 ft 667.84 ft 11.34 ft 3.00% 00 Roadway Width 0 ft ROADWAY ELEVATION 0.00 It It ft -------- 7 ------------------------------------------------------------ 1Hwi ------ ------- Stream Bed -- DEPRESSION 0 in. `"-' -- "n" Bed 0.013 Etc= Road Length -- H10 TW 667.50 0 Suface Type PAVED Freeboard= #VALUE! It Shldr. Elev. Rt. It TW DEPTH 0.12 ft TW VEL. 0.96 fps Channel Inv.El.. 667.50 It It R.I. (years) FLOW (cfs) Design 0.31 2 Check 0.24 10 Max. 0.31 CULVERT DESCRIPTION: TYPE: Single/Multiple Conforming Inlet Edge Description: Smooth Tapered Inlet Throat TOTAL FLOW Q cfs FLOW PER BARREL QIN cfs HEADWATER CALCULATIONS CONTROL HEADWATER ELEV It OUTLET VEL fps MINIMUM SHOULDER ELEV. it COMMENTS INLET CONTROL OUTLET CONTROL Single / Multiple Conforming / Broken Back Culverts HWi/D HWi It FALL ft ELHWi It TW ft do ft (dc+D)/2 ft ho It ke H it ELHWo ft MATERIAL SHAPE Size (in) N Mannings n Concrete Circular 12 1 0.01 0.31 0.3 -0.22 -0.22 0.00 667.62 0.12 0.23 0.62 0.61 0.20 -667.84 0.27 667.62 0.38 0.24 0.2 -0.24 -0.24 0.00 667.60 0.10 0.20 0.60 0.60 0.20 -667.84 0.26 667.60 0.25 0.31 0.3 -0.22 -0.22 0.00 667.62 0.12 0.23 0.62 0.61 0.20 -667.84 0.27 667.62 0.38 Broken Back Culvert TAILWATER DATA: TAILWATER RESULTS: ROADWAY DATA: ROADWAY OVERTOPPING: LENGTH Elev. SKEW' Channel Shape Trapezoidal " = 0.035 Discharge cfs Elevation ft Flow ft Velocity fps Shear force PSF , It Roadway Width, 0 Discharge Discharge cfs CfS Overtopping Elevation ft Bottom Width, It Side Slope Lt: (HA V) Side Slope Rt: (HA V) Channel Slope, ft/ft 2.50 Surface Type PAVED 2.00 Design 667.62 0.12 0.96 0.07 Top of Road Elevation, If 0 Design 0 667.62 2.00 Check 667.60 0.10 0.87 0.06 Length of Road, ft 0 Check 0 667.60 0.0100 Max. 1 667.62 1 0.12 1 0.96 1 0.07 Max. 0 667.62 Distance I I I I I I I Elevation E:� q TECHNICAL FOOTNOTES: (1) USE Q/NB FOR BOX CULVERTS (4) ELhi = HWi + ELi (INVERT OF INLET CONTROL SECTION) (6) ho = TW or (dc + D/2) (WHICHEVER IS GREATER) (2) HWi/D = HW/D OR HWi/D FROM DESIGN CHARTS (5) TW BASED ON DOWNSTREAM CONTROL OR FLOW (7) H = [1 + ke + (29n2L)/Rt 331v2/2g (3) FALL = HWI - (ELHWd - ELsf); FALL IS ZERO FOR CULVERTS ON GRADE DEPTH IN CHANNEL SUBSCRIPT DEFINITIONS: COMMENTS / DISCUSSION: CULVERT BARREL SELECTED HWd DESIGN HEADWATER i INLET SIZE: n: HWi HW IN INLET CONTROL o OUTLET SHAPE: MATERIAL: HWo HW IN OUTLET CONTROL sf Streambed ENTRANCE: @ culvert face CULVERTSOFT by ENSOFTEC, INC. PROJECT WAHS Site Improvements CULVERT DESIGN FORM LD-269 ROAD COUNTY Albemarle (Zone 2) SHEET OF DESIGNER: A. Mabee DATE: 9/24/2019 CULVERT 101 VA UNITS ENGLISH REVIEWER: J. Showalter NOAA Station Charlottesville H.W. ELEV V/S DISCHARGE 667.E 667.6—.._.._.._..--.._.._.._..--.._.._.._..--.._.._.._.._._.._. 667.6 W Ed367.6 3 M67.6 667.E 667.6 r 0 0 0 0 0 0 0 0 DISCHARGE TW DEPTH V/S DISCHARGE 0.1 0.1 = 0.1—.._.._.._..—...... ...... —_.._.._.._.._..._.._.._.._.�.._.._.._.._..._.._.._.. ..�.._.._.._.._.. o0.1-.._.._.._..-I_. .._.._.._ .._.._.._.._..._ _.._.._.I� .._.._.._..._.. _.._...._ _.._.._.. 0.1 0 0 0 0 0 0 0 0 DISCHARGE CULVERTSOFT by ENSOFTEC, INC. OUTLET VELOCITY V/S DISCHARGE 0.4 0.4 0.3 U 0.3 O J > 0.2 w 0.2 Q 0.1 0.1 0.0 0 0 0 0 0 0 0 0 DISCHARGE TW VELOCITY V/S DISCHARGE 1.0 1.0 1.0 0.9 0.9_.._.._.._...._........ _..-j.._.._.._.._.._..l-.._.._.._.._..-L.._.._.._.._...._.._.._.. .._.I_.._.._.._.._.. w 0.9 > 09 3 T � F T 0.9 0.9...... 0.9 0 0 0 0 0 0 0 0 DISCHARGE data input cells Project Name: WAHS Site Improvements 9/23/2019 constant values Date: Linear Development Project? No calculation cells Site Information Post -Development Project (Treatment Volume and Loads) Enter Total Disturbed Area (acres) 0.75 Check. BMP Design Specifications List. 2013 Draft Stds & Specs Linear project? No 0.13 Land cover areas entered correctly? . - - 0.30 Total disturbed area entered? �I Pre-ReDevelopment Land Cover (acres) A Soils B Soils C Soils D Soils Totals Forest/Open Space (acres) -- undisturbed forest/open space 0.00 Managed Turf (acres) -- disturbed, graded for yards or other turf to be mowed/managed 0.49 0.49 Impervious Cover (acres) 0.26 0.26 0.75 Post -Development Land Cover (acres) A Soils B Soils C Soils D Soils Totals Forest/Open Space (acres) -- undisturbed, protected forest/open space or reforested land 0.00 0.00 Managed Turf (acres) -- disturbed, graded for 0.36 yards or other turf to be mowed/managed 0.36 Impervious Cover (acres) 0.39 0.39 Area Check OK. OK. OK. 0.75 Constants Runoff Coefficients (Rv) Annual Rainfall (inches) 43 A Soils B Soils C Soils D Soils Target Rainfall Event (inches) 1.00 Forest/Open Space 0.02 0.03 0.04 0.05 Total Phosphorus (TP) EMC (mg/L) 0.26 Managed Turf 0.15 1 0.20 1 0.22 0.25 Total Nitrogen (TN) EMC (mg/L) 1.86 Impervious Cover 0.95 1 0.95 1 0.95 0.95 TargetTP Load (lb/acre/yr) 0.41 Pj (unitless correction factor) 0.90 COVERLAND •• • POST DEVELOPMENT Land Cover Summary -Pre Land Cover Summary -Post (Final) Land Cover Summary -Post Land Cover Summary -Post Pre-ReDevelopment Listed Adjusted Post ReDev. & New Impervious Post-ReDevelopment Post -Development New Impervious Forest/Open Space Cover (acres) 0.00 0.00 Forest/Open Space 0.00 Forest/Open Space 0.00 Cover (acres) cover (acres) Weighted Rv(forest) 0.00 %Forest 0% Managed Turf Cover 0.36 Weighted Rv(forest) 0.00 0.00 Weighted Rv(forest) 0.00 %Forest 0% 0% %Forest 0% Managed Turf Cover(acres) 0.49 0.36 Managed Turf Cover 0.36 (acres) (acres) Weighted Rv (turf) 0.20 New Impervious Cover 0.13 Weighted Rv(turf) 0.20 0.20 Weighted Rv (turf) 0.20 %Managed Turf 65% 58% %Managed Turf 48% %Managed Turf 58% Impervious Cover (acres) 0.26 0.26 Impervious Cover 0.39 ReDev. Impervious 0.26 (acres) Cover (acres) (acres) Rv(impervious) 0.95 0.95 Rv(impervious) 0.95 Rv(impervious) 0.95 Rv(impervious) 0.95 %Impervious 35% 42% %Impervious 52% %Impervious 42% Total ReDev. Site Area 0.62 Total Site Area (acres) 0.75 0.62 Final Site Area (acres) 0.75 (acres) ReDev Site Rv 0.51 Volume and Nutrient Load Post -Development Site Rv 0.46 0.51 Final Post Dev Site Rv Final Post- 0.59 Treatment Treatment Volume and Nutrient Load Post-ReDevelopment Pre-ReDevelopment Treatment Volume 0.0288 0.0266 Development 0.0369 Treatment Volume 0.0266 Treatment Volume 0.0103 (acre-ft) Treatment Volume (acre-ft) (acre-ft) (acre-ft) Post-ReDevelopment Final Post- Post -Development Pre-ReDevelopment Treatment Volume 1,252 1,158 Development 1,606 Treatment Volume 1,158 Treatment Volume (cubic 448 (cubic feet) Treatment Volume (cubic feet) feet) (cubic feet) Post-ReDevelopment Post -Development TP Pre-ReDevelopment TP Load Final Post- (lb/yr) 0.79 0.73 Development TP Load 1.01 Load (TP) 0.73 Load (lb/yr) 0.28 (lb/yr) (lb/yr)* Post-ReDevelopment TP Pre-ReDevelopment TP Load per acre Final Post -Development TP (lb/acre/yr) 1.05 1.17 Load per acre Load per acre 1.17 (lb/acre/yr) (lb/acre/yr) Max. Reduction Required Baseline TP Load (lb/yr) (0.41 lbs/acre/yr applied to pre -redevelopment area excluding 0.25 (Below Pre- 10% land proposed for new impervious cover) ReDevelopment Load) TP Load Reduction Required for 0.07 i Adjusted Land Cover Summary: Pre ReDevelopment land cover minus pervious land cover (forest/open space or TP Load Reduction Required for New 0.23 managed turf) acreage proposed for new impervious cover. Redevelo ed Area p Impervious Area (Ib/yr) (Ib/yr) Adjusted total acreage is consistent with Post-ReDevelopment acreage (minus acreage of new impervious cover). Column I shows load reduction requriement for new impervious cover (based on new development load limit 0.41 lbs/acre/year). Post -Development Requirement for Site Area TP Load Reduction Required (Ib/yr) 0.30