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HomeMy WebLinkAboutWPO201900068 Calculations 2020-02-07Red Hill Elementary School Additions and Renovations ALBEMARLE COUNTY, VIRGINIA SCOTTSVILLE DISTRICT DESIGN CALCULATIONS & NARRATIVE NOVEMBER 25, 2019 REVISED: FEBRUARY f, 2020 TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. Prepared by: Craig Kotarski, PE Timmons Group 608 Preston Avenue, Suite 200 Charlottesville, VA 22903 434.327.1688 .�I Op 1 CRAIG W I KOTARSKI Lic. No. 0402048507 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 3 Virginia Runoff Reduction Method Worksheet Summary Project Narrative: This project includes an addition to Red Hill Elementary as well as added site parking, emergency access lane, ADA ramp and associated site work. The limits of disturbance is 1.39 acres. Water Quality: The current site contains a school building, modular classrooms, and associated parking lots and roadways. 1.39 acres of disturbed area was analyzed for water quality. The site will require 0.50 lb./year to be treated. This required treatment will be met through the purchase of Nutrient Credits. 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 Red Hill Elementary School DESIGNER: A. Mabee DATE 2/6/2020 CHECKED: A. Allison UNITS ENGLISH Saw y --- rrr r - r ® r r, • -------------■------------_-- ---_---����� ---rrrr r r ®rrr -------------■------------_-® INLETSOFT BY ENSOFTEC DATE: 2/6/2020 LD-229 STORM SEWER DESIGN COMPUTATIONS STORM FREQUENCY 10 PROJECT: Red Hill Elementary School LOCATION: COUNTY: North Garden NOAA STATION: Designed by: A. Mabee Checked by: A. Allison 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 Ft./Ft. (13) SIZE (Dia. Or Span/Rise) In. (14) SHAPE Number of Apes Capacity CFS (15) Friction Slope RJR. NORMAL FLOW FLOW TIME Sec. (17) REMARKS (18) INCRE- MENT (5) ACCUM- ULATED (6) Lateral CPS Total Q CPS (9) UPPER END (10) LOWER END (I1) Deptb of Flow, do Ft. Area of Flow, An SgFt H. Ft. V. Ft/See (16) En Ft. REFERENCE (q STA. REFERENCE (2) STA. 101 102 100 0.27 0.35 0.09 0.31 5.11 6.46 0.00 1.98 718.48 717.92 22.43 0.02497 15 Circular 1 10.21 0.00100 0.37 0.31 0.21 6.44 1.02 3.48 103 104 102 0.32 0.66 0.21 0.21 5.00 6.50 0.00 1.37 719.32 718.58 36.73 0.02015 15 Circular 1 9.17 0.00050 0.33 0.26 0.19 5.37 0.78 6.84 201 202 200 0.00 0.00 0.32 5.83 6.24 0.00 1.98 711.64 711.07 11.40 0.05000 12 Circular. 1 7.97 0.00320 0.34 0.24 0.19 8.42 1.44 1.35 203 1204 202 0.17 0.81 0.14 0.14 5.00 6.50 0.00 0.89 1 715.62 714.68 31.36 0.02997 12 Circular 1 6.17 0.00070 0.26 0.16 0.15 5.59 0.74 5.61 211 212 222 0.01 0.90 0.01 0.03 5.37 6.38 0.00 0.17 720.62 715.60 100.41 0.05000 6 Circular 1 1.36 0.00090 0.12 0.04 0.07 4.77 0.47 21.03 213 214 212 0.00 0.00 0.02 5.21 6.43 0.00 0.12 722.74 720.72 40.39 0.05001 6 Circular 1 1.36 0.00040 0A0 0.03 0.06 4.26 0.38 9.49 215 216 214 0.00 1 0.00 0.02 5.14 6.46 0.00 0.12 723.24 722.84 14.29 0.02799 6 Circular 1 1.02 0.00040 0.11 0.03 0.07 3.47 0.30 4.12 217 218 216 0.02 0.90 0.02 0.02 5.00 6.50 0.00 0.12 723.54 723.34 19.31 0+01036 6 Circular 1 0.62 0+00040 0.15 0.05 0.08 2.44 0.24 7.93 221 222 202 0.00 0.00 0.18 5.72 6.28 0.00 1.13 714.84 713.36 42.44 0.03487 12 Circular 1 6.65 0.00110 0.28 0.18 0.16 6.32 0.90 6.71 223 224 222 0.08 0.90 0.07 0.15 5.24 6.42 0.00 0.99 717.92 715.15 79.09 0.03502 8 Circular 1 2.45 0.00600 0.30 0.15 0.15 6.65 0.98 11.90 225 226 224 0.09 0.90 0.08 0.08 5.00 6.50 0.00 0.53 720.86 718.02 81.01 0.03506 8 Circular 1 2.45 0.00170 0.21 0.09 0.12 5.60 0.70 14.47 LD-347 PROJECT: Red Hill Elementary School HYDRAULIC GRADE LINE ANALYSIS INCIDENCE PROBABILITY ®Year DESIGNED BY: A. Mabee Checked: A. Allison INLET OR JUNCTION STA. INVERT EL. OUTFLOW PIPE DEPTH OF FLOW OUTFLOW PIPE OUTLET WATER SURFACE ELEV. DIA. PIPE Do (In/mm) DESIGN DISCH. 00 (CFS/CMS) LENGTH PIPE Lo (Ft/M) FRICTION SLOPE, St. (FT/FT) (M/M) FRICTION LOSS Hf (Ft/M) JUNCTION LOSS SURFACE FLOW Adj. Ht 1.3 Ht (Ft/M) Inlet Inlet Tap of MH Shaping? 0.5 FINAL Water Top of Inlet Adjustment? Ht H Surface Be, Y/N (Ft/M) (Fi/M) Elevation APPROX. Vo Contr. Ho (FUM) Vi Vi"2/2g Hi (Expn) 0.35'MAX. (Vi2/29) SKEW Angle K Bend H (Ft/M) Sum HL (Ft/M) 1 2 3 4 5 6 7 8 9 10 11 (12) (13) 14 15 16 16 17 18 19 100 1 1 1 1 719.360 102 717.920 1.25 719.360 15 1.983 22.43 0.00099 0.022 6.442 0.161 5.372 0.448 0.157 0.0 1 0.00 0.000 0.318 0.000 0.318 YES 0.159 0.181 719.541 722.070 O.K. 104 718.580 1.25 719.580 15 1.372 36.73 0.00047 0.017 5.372 0.112 0.000 0.000 0.000 0.0 0.00 0.000 0.112 1.372 0.146 YES 0.073 0.090 719.670 724.000 O.K. 200 712.230 202 711.070 1.00 712.230 12 1.979 11.40 0.00323 0.037 8.418 0.275 6.321 0.620 0.217 0.0 0.00 0.000 0.492 0.000 0.492 NO 0.492 0.529 712.759 719.000 O.K. 222 713.360 1 1.00 1 714.160 12 1.134 42.44 1 0.00106 1 0.045 6.321 0.155 6.648 0.686 0.240 0.0 0.00 0.000 0.395 0.000 0.395 1 NO 0.395 0.440 715.119 718.920 O.K. 212 715.600 0.50 716.000 6 0.174 100.41 0.00086 0.086 4.774 0.088 4.258 0.282 0.099 0.0 0.00 0.000 0.187 1 0.000 0.187 NO 0.187 0.273 720.741 723.910 O.K. 214 720.720 0.50 721.120 6 0.117 40.39 0.00039 0.016 4.258 0.070 3.468 0.187 0.065 0.0 0.00 0.000 0.136 0.000 0.136 NO 0.136 0.151 722.839 725.470 O.K. 216 722.840 0.50 723.240 6 0.117 14.29 0.00039 0.006 3.468 0.047 2.436 0.092 0.032 0.0 0.00 0.000 0.079 0.000 0.079 NO 0.079 0.084 723.354 725.780 O.K. 218 723.340 0.50 723.740 6 0.117 19.31 0.00039 0.007 2.436 0.023 0.000 0.000 0.000 0.0 0.00 0.000 0.023 0.000 0.023 NO 0.023 0.031 723.771 725.930 O.K. 714.680 1.00 715.480 12 0.891 31.36 0.00065 0.021 5.591 0.121 0.000 0.000 0.000 0.0 0.00 0.000 0.121 0.891 0.158 NO 0.158 0.178 715.877 720.020 O.K. E226 715.150 0.67 715.683 8 0.989 79.09 0.00597 0.472 6.648 0.172 5.600 0.487 0.170 0.0 0.00 0.000 0.342 0.000 0.342 YES 0.171 0.643 718.215 723.400 O.K. 718.020 0.67 1 718.553 8 1 0.527 81.01 0.00169 0.137 5.600 0.122 0.000 0.000 0.000 0.0 0.00 0.000 1 0.122 0.000 0.122 NO 0.122 0.259 721.070 725.830 O.K. data input cells Project Name: Red Hill Elementary School January 22, 2020 constant values Date: Linear Development Project? No calculation cells Site Information Post -Development Project (Treatment Volume and Loads) Enter Total Disturbed Area (acres) 0.92 Check. BMP Design Specifications List. 2013 Draft Stds & Specs Linear project? No '® Land cover areas entered correctly? �I Total disturbed area entered? Pre-ReDevelopment Land Cover (acres) A Soils B Soils C Soils D Soils Totals Forest/Open Space (acres) -- undisturbed, 0.16 protected forest/open space or reforested land 0.16 Managed Turf (acres) -- disturbed, graded for 0.57 yards or other turf to be mowed/managed 0.57 Impervious Cover (acres) 0.19 0.19 0.92 Post -Development Land Cover (acres) A Soils B Soils C Soils D Soils Totals Forest/Open Space (acres) -- undisturbed, 0.00 protected forest/open space or reforested land Managed Turf (acres) -- disturbed, graded for 0.48 yards or other turf to be mowed/managed 0.48 Impervious Cover (acres) 0.44 0.44 Area Check OK. OK. OK. 0.92 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 0.20 0.22 0.25 Total Nitrogen (TN) EMC (mg/L) 1.86 Impervious Cover 0.95 0.95 0.95 0.95 TargetTP Load (lb/acre/yr) 0.41 Pj (unitless correction factor) 0.90 COVERLAND • •COVER SUMMARY 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 Forest/Open Space 0.00 Post -Development New Impervious Forest/Open Space Cover (acres) 0.16 0.00 Forest/Open Space 0.00 Cover (acres) Cover (acres) Weighted Rv(forest) 0.03 0.00 Weighted Rv(forest) 0.00 Weighted Rv(forest) 0.00 %Forest 0% Managed Turf Cover 048 %Forest 17% 0% %Forest 0% Managed Turf Cover(acres) 0.57 0.48 Managed Turf Cover 048 (acres) (acres) Weighted Rv (turf) 0.20 %Managed Turf 72% ReDev. Impervious New Impervious Cover 0.19 0.25 Weighted Rv(turf) 0.20 0.20 Weighted Rv (turf) 0.20 %Managed Turf 62% 72% %Managed Turf 52% Impervious Cover (acres) 0.19 0.19 Impervious Cover 0.44 (acres) Cover (acres) I (acres) Rv(impervious) 0.95 0.95 Rv(impervious) 0.95 Rv(impervious) 0.95 Rv(impervious) 0.95 %Impervious 21% 28% %Impervious 48% %Impervious 28% Total Site Area (acres) 0.92 0.67 Final Site Area (acres) 0.92 Total ReDev. Site Area 0.67 (acres) Site Rv 0.33 0.41 Final Post Dev Site Rv Final Post- 0.56 Treatment ReDev Site Rv 0.41 Volume and Nutrient Load Post -Development Treatment Volume and Nutrient Load Post-ReDevelopment Pre-ReDevelopment Treatment Volume 0.0249 0.0230 Development 0.0428 Treatment Volume 0.0230 Treatment Volume 0.0198 (acre-ft) Treatment Volume (acre-ft) (acre-ft) (acre-ft) Post-ReDevelopment Final Post- Post -Development Pre-ReDevelopment Treatment Volume 1,086 1,004 Development 1,866 Treatment Volume 1,004 Treatment Volume (cubic 862 (cubic feet) Treatment Volume (cubic feet) feet) (cubic feet) Post-ReDevelopment Post -Development TP Pre -Re Development TP Load Final Post- (Ib/yr) 0.68 0.63 Development TP Load 1.17 Load (TP) 0.63 0.54 Load (Ib/yr) (Ib/yr) (Ib/yr)* Pre-ReDevelopment TP Load per acre Final Post -Development TP Post-ReDevelopment TP (lb/acre/yr) 0.74 0.94 Load per acre Load per acre 0.94 (Ib/acre/yr) (lb/acre/yr) Max. Reduction Required Baseline TP Load (lb/yr) (0.41 Ibs/acre/yr applied to pre -redevelopment area excluding 0.27 (Below Pre- 10% pervious land proposed for new impervious cover) ReDevelopment Load) TP Load Reduction IAdjusted Land Cover Summary: TP Load Reduction Pre ReDevelopment land cover minus pervious land cover (forest/open space or Required for q 0.06 Required for New 0.44 managed turf) acreage proposed for new impervious cover. Redeveloped Area Impervious Area (Ib/yr) (eloped 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) 0.50