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HomeMy WebLinkAboutWPO201900068 Calculations 2019-11-26Red Hill Elementary School Additions and Renovations ALBEMARLE COUNTY, VIRGINIA SCOTTSVILLE DISTRICT DESIGN CALCULATIONS & NARRATIVE NOVEMBER 25, 2019 .'lost*� 0 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 U CR.MCiW I K9rARSK1 Lie. No. 0402048507 �vAL 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 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 0.94 acres. Water Ouality• The current site contains a school building, modular classrooms, and associated parking lots and roadways. 0.94 acres of disturbed area was analyzed for water quality. The site will require 0.50 lb./year to be treated. A surplus removal of 0.44 lb./year has been achieved on the Scottsville Elementary School Addition WP0201900051. 0.44 lb./year of that surplus removal will be applied to this project. In addition, a surplus removal of 0.15 lb./year has been achieved on the Woodbrook Elementary School WP0201600074. 0.06 lb./year of that surplus removal will be applied to this project. Per 9VAC25-870-69 Section A part 5, the Albemarle County School Board owns all associated parcels. 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 11/25/2019 CHECKED: J. Showalter UNITS ENGLISH IILET ° o� ¢ e f'i ai g 3 C y y� a �' a Li SagInlets Only a 79 U ❑ 104 D1-213 6 0.180 0.90 0.162 0.000'RIGH7 0.140 0.35 0.049 0.211 4 0.844 0 0.844 0.0400 0.0208 2.365 2.000 0.8457 0.0833 8 0.1665 7.751 2.000 0.774 0.931 0.786 0.058 2.090 206 DI-3B 6.000 0.140 0.90 0.126 ff.48 Back/Lt. 0.000'RIG 0.030 0.35 0.0105 Back/Lt. 0.137 4 0.548 0 0.0400 0.0208 1.779 2.000 1.1242 0.0833 Back/Lt. 0 4 0 0 Ahead/Rt. 0.548 1 0.0400 1 1 1 1 1 1 1 1 1 1 6 1 1 0.548 1 1 1.020 1 0.166 0.0138 12.0028923 1 3.020 1 4.086 Weir Elow INLETSOFT BY ENSOFTEC DATE: 11/25/2019 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: 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 CPS (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. 101 102 100 Q27 0.35 0.09 0.31 5.09 6.47 0.00 1.98 718.48 717.92 22.43 0.02497 15 Ciroular 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 29.94 0.02472 15 Circular 1 10.16 0.00050 0.31 0.24 0.18 5.78 0.83 5.18 201 1202 1200 1 0.00 1 0.00 0.32 5.89 6.23 1 0.00 1.97 713.96 713.47 1 49.21 0.009961 12 Circular 1 3.56 0.00320 0.53 0.43 0.26 4.65 0.87 10.59 203 204 202 0.00 0.00 0.16 5.76 6.26 0.00 1.05 714.59 714.06 35.15 0.01508 12 Circular 1 4.38 0.00090 0.33 0.23 0.19 4.58 0.66 7.68 205 206 204 0.17 0.81 0.14 0.14 5.00 6.50 0.00 0.89 715.62 714.82 53.59 0.01493 12 Circular 1 4.35 0.00070 0.31 0.20 0.17 4.36 0.60 12.30 211 212 204 0.01 0.90 0.01 0.03 5.41 6.37 0.00 0.17 720.69 715.67 100.26 0,05007 6 Circular 1 1.36 0,00090 0.12 0.04 0.07 4.77 0.47 21.00 213 214 212 0.00 0.00 0.02 5.23 6.43 0.00 0.12 722.55 721.39 38.74 0.02994 6 1 Circular 1 1.05 10.00040 0.11 0.03 0.07 3.55 0.31 10.91 215 216 214 a00 0.00 0.02 5.13 6.46 0.00 0.12 723.24 722.71 21.20 0.02500 4 1 Circular 1 0.30 10.004001 0.14 0.04 0.08 3.25 0.31 6.52 217 218 216 0.02 0.90 0.02 0.02 5,00 6.50 0.00 0.12 723.54 723.34 19.31 0.01036 4 Circular 1 0.21 0.00340 0.18 0.05 0.09 2.49 0.27 7.77 221 222 202 0.08 0.90 0.07 0.15 5.24 6.43 0.00 0.99 718.04 713.92 91.50 0.04503 8 Circular 1 2.78 0.00600 0.28 0.14 0.15 7.29 1.10 12.55 223 224 222 0.09 0.90 0.08 0.08 5.00 6.50 0.00 0.53 122.61 720.86 70.04 0.02499 8 Circular 11 2.07 10.001701 0.23 1 0.11 1 0.13 1 4.96 1 0.61 114.12 LD-347 PROJECT: Red Hill Elementary School 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 (Ft/M) FRICTION SLOPE, Sfo (FT/FT) (M/M) FRICTION LOSS Hf (Ft/M) JUNCTION LOSS SURFACE FLOW Adj. Ht 1.3 Ht (Ft/M) Inlet Inlet Top of MH Shaping? 0.5 FINAL Water Top of Inlet Adjustment? Ht H Surface Ele, Y/N (Ft/M) (Ft/M) Elevation APPROX. Vo Contr. Ho (FtlM) Vi Vi'2/2g Hi (Expn) 0.35'MAX. (Vi2/2g) 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 1 719.360 102 717.920 1.25 719.360 15 1.984 22.43 0.00099 0.022 6.443 0.161 5.779 0.519 0.182 0.0 0.00 0.000 0.343 0.000 0.343 YES 0.171 0.193 719.553 722.110 O.K. 104 718.580 1.25 719.580 15 1.372 29.94 0.00047 0.014 5.779 0.130 0.000 0.000 0.000 0.0 0.00 0.000 0.130 1.372 0.169 YES 0.084 0.098 719.678 724.020 O.K. 200 714.670 202 713.470 1.00 714.670 12 1.973 49.21 0.00321 0.158 4.646 0.084 7.291 0.825 0.289 0.0 0.00 0.000 0.373 0.000 0.373 NO 0.373 0.530 715.200 716.950 O.K. 222 713.920 0.67 715.200 8 0.989 91.50 0.00597 0.546 7.291 0.206 4.960 0.382 0.134 0.0 0.00 0.000 0.340 0.000 0.340 YES 0.170 0.716 718.315 724.880 O.K. 224 720.860 0.67 721.393 8 0.527 70.04 0.00169 0.119 4.960 0.096 0.000 0.000 0.000 0.0 0.00 0.000 0.096 0.000 0.096 NO 0.096 0.214 722.839 725.770 O.K. 204 714.060 1.00 715.200 12 1.048 35.15 0.00090 0.032 4.577 0.081 4.359 0.295 0.103 0.0 0.00 0.000 0.185 0.000 0.185 NO 0.185 0.216 715.417 718.150 O.K. 206 714.690 1.00 715.490 12 0.891 53.59 0.00065 0.035 4.359 0.074 0.000 0.000 0.000 0.0 0.00 0.000 0.074 0.891 0.096 NO 0.096 0.131 715.797 719.580 O.K. 212 715.670 0.50 716.070 6 0.174 1 100.26 0.00086 0.086 4.774 0.088 3.552 0.196 0.069 0.0 0.00 0.000 0.157 0.000 0.157 NO 0.157 0.243 720.811 723.910 O.K. 214 721.390 0.50 721.790 6 0.117 38.74 0.00039 0.015 3.552 0.049 3.482 0.188 0.066 0.0 0.00 0.000 0.115 0.000 0.115 NO 0.115 0.130 722.662 725.050 O.K. 216 722.700 0.33 722.967 4 0.117 21.20 0.00395 0.084 3.482 0.047 2.485 0.096 0.034 0.0 0.00 0.000 0.081 0.000 1 0.081 NO 0.081 0.164 723.476 725.780 O.K. 218 723.340 0.33 723.607 4 0.117 1 19.31 0.00337 0.065 2.485 0.024 0.000 0.000 0.000 0.0 0.00 0.000 0.024 0.000 1 0.024 NO 0.024 0.089 723.717 725.930 O.K. Project Name: Red Hill Elementary School CLEAR ALL constant values Date: 11/25/2019 Linear Development Project? No calculation cells Site Information Post -Development Project (Treatment Volume and Loads) Enter Total Disturbed Area (acres) 0.94 Check: BMP Design Specifications List: 2013 Draft Stds & Specs Maximum reduction required:' Linear project? No The site's net increase in impervious cover (acres) is: Land cover areas entered correctly? Post-Developmentr r Total disturbed area entered? �I Pre-ReDevelopment Land Cover (acres) A Soils B Soils C Soils D Soils Forest/Open Space (acres) -- undisturbed, protected forest/open space or reforested land 0.21Managed Turf (acres) -- disturbed, graded foryards n0.21 or other turf to be mowed/managed 0.54Impervious Cover (acres) 0.19 E 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 0.00 Managed Turf (acres) -- disturbed, graded for 0.50 yards or other turf to be mowed/managed 0.50 Impervious Cover (acres) 0.44 0.44 Area Check OK. OK. OK. OK. 0.94 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 Target TP Load (Ib/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 Post -Development New Impervious Forest/Open Space Cover (acres) 0.21 0.00 Forest/Open Space 0.00 Forest/Open Space 0.00 Cover (acres) Cover (acres) 0.00 0% 0.50 Weighted Rv(forest) 0.03 0.00 Weighted Rv(forest) 0.00 Weighted Rv(forest) %Forest 22% 0% %Forest 0% %Forest Managed Turf Cover (acres) 0.54 0.50 Managed Turf Cover 0.50 Managed Turf Cover (acres) (acres) 0.20 72% 019 New Impervious Cover 0.25 Weighted Rv(turf) 0.20 0.20 Weighted Rv (turf) 0.20 Weighted Rv (turf) %Managed Turf 57% 72% %Managed Turf 53% %Managed Turf Impervious Cover (acres) 0.19 0.19 Impervious Cover 0.44 ReDev. Impervious (acres) Cover (acres) (acres) Rv(impervious) 0.95 0.95 Rv(impervious) 0.95 Rv(impervious) 0.95 Rv(impervious) 0.95 %Impervious 20% 28% %Impervious 47% %Impervious 28% Final Site Area (acres) 0.94 Total ReDev. Site Area 0.69 (acres) Final Post Dev Site Rv 0.55 ReDev Site Rv 0.41 Treatment Volume and Nutrient Load Final Post- Post-ReDevelopment Post -Development Development 0.0432 Treatment Volume 0.0234 Treatment Volume 0.0198 Total Site Area (acres) 0.94 0.69 Site Rv 0.31 0.41 Treatment Volume and Nutrient Load Pre-ReDevelopment Treatment Volume 0.0246 0.0234 (acre-ft) Treatment Volume (acre-ft) (acre-ft) (ant Final Post- Post-ReDevelopment Post -Development Pre-ReDevelopment Treatment Volume 1,070 1,018 Development 1,880 Treatment Volume 1,018 Treatment Volume (cubic 862 (cubic feet) Treatment Volume (cubic feet) (cubic feet) feet) Final Post- Post-ReDevelopment Post -Development TP Pre-ReDevelopment TP Load 0.67 0.64 Development TP Load 1.18 Load (TP) 0.64 0.54 (Ib/yr) Load (Ib/yr) (Ib/yr) (Ib/yr)• Final Post -Development TPJL Post-ReDevelopment TP Pre-ReDevelopment TP Load per acre (Ib/acre/yr) Load per acre 1.26 Load per acre 0.93 (Ib/acre/yr) (lb/acre/yr) Baseline TP Load (lb/yr) Max. Reduction Required (0.41 Ibs/acre/yr applied to pre -redevelopment area excluding 0.28 (Below Pre- 10% pervious land proposed for new impervious cover) ReDevelopment Load) IAdjusted Land Cover Summary: TP Load Reduction 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) (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 Ibs/acre/year). ' pme nt Requirement TP Load Reduction Required (Ib/yr) 0.50