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HomeMy WebLinkAboutWPO202000019 Calculations 2020-03-30Chattanooga - Colonnade Drive ALBEMARLE COUNTY, VIRGINIA JACK JOUETT DISTRICT DESIGN CALCULATIONS & NARRATIVE WPO # MARCH 23, 2020 .•0•s • 0 % 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 0���:\L7'H s� ��. �� �.1TH.%\ M. SHOULTER � Lie. No. 0402057151 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 Outlet Protection Chart 3 Pre and Post Developed HydroCAD Calculations 4 Virginia Runoff Reduction Method Worksheet Summary Project Narrative: This project includes a new medical office building, parking lot, and associated utilities and site work. The limits of disturbance is 0.85 acres. Water Quality: The site is currently undeveloped. In the proposed condition, there will be 0.61 acres of impervious cover and 0.24 acres of managed turf. Per the Virginia Runoff Reduction Spreadsheet, this will require that 1.09 lbs. of phosphorus be removed per year. Nutrient credits will be purchased to meet stormwater quality requirements. Water Quantity: In existing condition, the site drains towards a stream located adjacent to the eastern property line, just off the site. In the proposed condition, this drainage patterns will be maintained. 155 LF of 72" CMP detention pipe is being installed to meet water quantity requirements. The pipe reduces the 1-year, 24-hour storm to meet the requirements of the energy balance equation. Additionally, the 10-year, 24-hour storm is being detained to less than the pre -developed 10-year, 24-hour storm to meet flood protection requirements. FORM LD 204 STORMWATER INLET COMPUTATIONS SHEET 1 OF 1 LD 204 PROJECT CHATTANOOGA DESIGNER: A.MABEE DATE 3/23/2020 CHECKED: J. SHOWALTER UNITS ENGLISH Sag Inlets Only INLETSOFT BY ENSOFTEC DATE: 3/23/2020 LD-229 STORM SEWER DESIGN COMPUTATIONS STORM FREQUENCY 10 PROJECT: Chattanooga LOCATION: Charlottesville 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) S12E (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. 201 202 STORAGE 0.00 0.00 0.35 5.14 6.50 0.00 2.32 561.28 561.12 15.80 0.01013 12 Circular 1 3.89 0.00380 0.56 0.45 0.27 5.16 0.97 3.06 203 204 202 0.43 0.82 0.35 0.35 5.00 6.54 0.00 2.32 561.81 561.38 42.16 0.01020 12 Circular 1 3.90 0.00380 0.56 0.45 0.27 5.18 0.97 8.14 301 302 STORAGE 0.13 0.90 0.12 0.12 5.00 6.54 0.00 0.77 565.64 565.00 64.11 0.00998 8 Circular 1 1.31 0.00360 0.37 0.20 0.18 3.90 0.60 16.45 401 402 STORAGE 0.00 0.00 1.44 5.23 6.47 0.00 9.39 566.03 564.43 53.18 0.03009 15 Circular 1 12.14 0.01880 0.83 0.86 0.36 10.92 2.68 4.87 403 404 402 1.54 0.67 1.03 1.35 5.11 6.51 0.00 8.77 567.46 566.13 44.36 0.02998 15 Circular 1 12.12 0.01640 0.79 0.82 0.36 10.76 2.59 4.12 405 406 404 0.42 0.76 0.32 0.32 5.00 6.54 0.00 2.08 570.44 568.98 48.61 0.03003 12 Circular 1 6.69 0,00300 0.38 0.28 0.21 7.52 1.26 6.47 411 412 402 0.03 0.53 0.02 0.10 5.06 6.52 0.00 0.63 566.65 566.27 37.63 0.01010 8 Circular 1 1.32 0.00250 033 0.17 0.16 374 0.54 10.07 413 414 412 0.09 0.90 0.08 0.08 5.00 6.54 0.00 0.53 566.88 566.75 12.57 0.01034 8 Circular 1 1.33 0.00170 0.29 0.15 0.15 3.60 0.49 3.49 LD-347 PROJECT: Chattanooga 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. Q. (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 Shaping? Y/N 0.5 Ht (FUM) FINAL H (FtlM) Inlet Water Surface Elevation Top of MH Top of Inlet Elev. APPROX. Adjustment? 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 STORAGE 1 565.420 402 564.430 1.25 565.430 15 9.394 53.18 0.01884 1.002 10.922 0.463 10.759 1.797 0.629 0.0 0.00 0.000 1.092 0.000 1.092 NO 1.092 2.094 567.524 570.580 O.K. 404 566.130 1.25 567.524 15 8.771 44.36 0.01642 0.728 10.759 0.449 7.518 0.878 0.307 0.0 0.00 0.000 0.757 0.000 0.757 YES 0.378 1.107 568.631 573.940 O.K. 406 568.980 1.00 569.780 12 2.080 48.61 0.00304 0.148 7.518 0.219 0.000 0.000 0.000 0.0 0.00 0.000 0.219 2.080 0.285 YES 0.143 0.290 570.823 578.320 O.K. 302 565.000 0.67 565.533 1 8 0.765 64.11 0.00357 0.229 3.896 0.059 0.000 0.000 0.000 0.0 0.00 0.000 0.059 0.000 1 0.059 NO 0.059 0.288 566.006 569.470 O.K. 202 561.120 1.00 565.420 12 2.316 15.80 0.00376 0.059 5.163 0.103 5.177 0.416 0.146 0.0 0.00 0.000 0.249 0.000 0.249 NO 0.249 0.309 565.729 569.050 O.K. 204 561.380 1.00 565.729 12 2.316 42.16 0.00376 0.159 5.177 0.104 0.000 0.000 0.000 0.0 0.00 0.000 0.104 2.316 0.135 YES 0.068 0.226 565.955 568.050 O.K. 12 566.270 0.67 567.524 8 0.634 37.63 0.00245 0.092 3.737 0.054 3.601 0.201 0.070 0.0 0.00 0.000 0.125 0.104 0.125 YES 0.062 0.155 567.679 569.000 O.K. H14 566.750 0.67 567.679 8 0.530 12.57 0.00171 0.022 3.601 0.050 0.000 0.000 0.000 0.0 0.00 0.000 0.050 0.000 0.050 NO 0.050 0.072 567.750 570.000 O.K. Outfall Pipe 103 DESIGN OF OUTLET PROTECTION FROM A ROUND PIPE FLOWING FULL MAXIMUM TAILWATER CONDITION ( Tw > 0.5 DIAMETER) 3Do Outlet 1 Min. W = Do + 0.4La Pipe Diameter, Do L I a +1 Tailw r z� 0.5Do �� 80 oc, 70 P - - ok 60 50 jf 40. 20 10 L=9' 0 Recommended Min d5o 6,- 3 5 10 20 50 100 200 500 Discharge, ft3/sec. 3 0 1000 W 00 is 2S Pre -1 (Onsi ) P e -2 (Offsite) K Pre -Developed SubCat Reach On Link Routing Diagram for Pre Prepared by Timmons Group, Printed 3/20/2020 HydroCAD® 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Pre Prepared by Timmons Group Printed 3/20/2020 HydroCAD® 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 1.360 80 >75% Grass cover, Good, HSG D (1S, 2S) 1.200 98 Paved parking, HSG D (2S) 0.250 77 Woods, Good, HSG D (1S) 2.810 87 TOTAL AREA Pre Prepared by Timmons Group Printed 3/20/2020 HydroCAD® 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 3 Soil Listing (all nodes) Area Soil Subcatchment (acres) Group Numbers 0.000 HSG A 0.000 HSG B 0.000 HSG C 2.810 HSG D 1 S, 2S 0.000 Other 2.810 TOTAL AREA Pre Prepared by Timmons Group HydroCAD® 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Printed 3/20/2020 Page 4 Ground Covers (all nodes) HSG-A HSG-B HSG-C HSG-D Other Total Ground Subcatchment (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.000 0.000 1.360 0.000 1.360 >75% Grass cover, Good 1 S, 2S 0.000 0.000 0.000 1.200 0.000 1.200 Paved parking 2S 0.000 0.000 0.000 0.250 0.000 0.250 Woods, Good is 0.000 0.000 0.000 2.810 0.000 2.810 TOTAL AREA Pre Type/1 24-hr 1 YR Rainfall=3.04" Prepared by Timmons Group Printed 3/20/2020 HydroCAD® 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 5 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: Pre -1 (Onsite) Runoff Area=0.850 ac 0.00% Impervious Runoff Depth>1.22" Flow Length=226' Tc=7.5 min CN=79 Runoff=1.72 cfs 0.086 of Subcatchment2S: Pre -2 (Offsite) Runoff Area=1.960 ac 61.22% Impervious Runoff Depth>2.11" Tc=6.0 min CN=91 Runoff=6.87 cfs 0.344 of Link 3L: Pre -Developed Inflow=8.48 cfs 0.430 of Primary=8.48 cfs 0.430 of Total Runoff Area = 2.810 ac Runoff Volume = 0.430 of Average Runoff Depth = 1.84" 57.30% Pervious = 1.610 ac 42.70% Impervious = 1.200 ac Pre Type/1 24-hr 1 YR Rainfall=3.04" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 1S: Pre -1 (Onsite) Runoff = 1.72 cfs @ 11.99 hrs, Volume= 0.086 af, Depth> 1.22" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1 YR Rainfall=3.04" Area (ac) CN Description 0.600 80 >75% Grass cover, Good, HSG D 0.250 77 Woods, Good, HSG D 0.850 79 Weighted Average 0.850 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 100 0.1474 0.28 Sheet Flow, Grass: Dense n= 0.240 P2= 3.70" 0.5 45 0.0444 1.47 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.0 81 0.0690 1.31 Shallow Concentrated Flow, Woodland Kv= 5.0 fos 7.5 226 Total Subcatchment 1 S: Pre -1 (Onsite) Hydrograph ❑ Runoff 1 72 cfs Type II 24-hr R Rllainfall=3.b4I 61 'Runbff Area=0.850 ad I Runoff lVmlume=0.086 of w -4 — I— 4 —I— I I I �un Off p IDe th>1. 26` 1 I I I I I I I Q I U.RIdw Length=226' Tc=7.,5 min I I I I L 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Pre Type/1 24-hr 1 YR Rainfall=3.04" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 2S: Pre -2 (Offsite) Runoff = 6.87 cfs @ 11.97 hrs, Volume= 0.344 af, Depth> 2.11" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1 YR Rainfall=3.04" Area (ac) CN Description 1.200 98 Paved parking, HSG D 0.760 80 >75% Grass cover, Good, HSG D 1.960 91 Weighted Average 0.760 38.78% Pervious Area 1.200 61.22% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, N 3 0 U. 7 0 Subcatchment 2S: Pre -2 (Offsite) Hydrograph I I I Type Ili 24-hr 1 R Rainfall=34Q4" 1 'Runoff Aced=1-960 arc I I I I I I I I I Runoff lVmlume=0.344 of -Oun9ff llDepih>-2-.'1111'' I I Tc--6.,0 fni n_ I I I I I I I I I I I III III I 1 �+^N;:91 I I I I I I I I I I I I I 1 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Runoff Pre Type/1 24-hr 1 YR Rainfall=3.04" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 8 Summary for Link 3L: Pre -Developed Inflow Area = 2.810 ac, 42.70% Impervious, Inflow Depth > 1.84" for 1 YR event Inflow = 8.48 cfs @ 11.97 hrs, Volume= 0.430 of Primary = 8.48 cfs @ 11.97 hrs, Volume= 0.430 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs N U 3 0 LL Link 3L: Pre -Developed Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow ❑ Primary Pre Type 11 24-hr 2 YR Rainfall=3.68" Prepared by Timmons Group Printed 3/20/2020 HydroCAD® 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 9 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: Pre -1 (Onsite) Runoff Area=0.850 ac 0.00% Impervious Runoff Depth>1.70" Flow Length=226' Tc=7.5 min CN=79 Runoff=2.42 cfs 0.121 of Subcatchment2S: Pre -2 (Offsite) Runoff Area=1.960 ac 61.22% Impervious Runoff Depth>2.71" Tc=6.0 min CN=91 Runoff=8.71 cfs 0.443 of Link 3L: Pre -Developed Inflow=10.99 cfs 0.563 of Primary=10.99 cfs 0.563 of Total Runoff Area = 2.810 ac Runoff Volume = 0.563 of Average Runoff Depth = 2.41" 57.30% Pervious = 1.610 ac 42.70% Impervious = 1.200 ac Pre Type 11 24-hr 2 YR Rainfall=3.68" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment 1S: Pre -1 (Onsite) Runoff = 2.42 cfs @ 11.99 hrs, Volume= 0.121 af, Depth> 1.70" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 2 YR Rainfall=3.68" Area (ac) CN Description 0.600 80 >75% Grass cover, Good, HSG D 0.250 77 Woods, Good, HSG D 0.850 79 Weighted Average 0.850 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 100 0.1474 0.28 Sheet Flow, Grass: Dense n= 0.240 P2= 3.70" 0.5 45 0.0444 1.47 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.0 81 0.0690 1.31 Shallow Concentrated Flow, Woodland Kv= 5.0 fos 7.5 226 Total Subcatchment 1 S: Pre -1 (Onsite) Hydrograph I I I L I I I I I I I I I I 2 I I I I I I I I I I I I I a - + -4 I I I I I I I I I I I I I I I I I I I I I I I ❑Runoff i I I i i I I Type II 24-hr - -Z- ! ainfalf=3.-681 'Runbff Area=0.850 ad I I I I I I I Runoff lVmlume=0.121 of Ou;nOff 11Depth>1.1'701' I RIdw itength=226' Tc=7.15 min I I I L 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Pre Type 11 24-hr 2 YR Rainfall=3.68" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment 2S: Pre -2 (Offsite) Runoff = 8.71 cfs @ 11.97 hrs, Volume= 0.443 af, Depth> 2.71" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 2 YR Rainfall=3.68" Area (ac) CN Description 1.200 98 Paved parking, HSG D 0.760 80 >75% Grass cover, Good, HSG D 1.960 91 Weighted Average 0.760 38.78% Pervious Area 1.200 61.22% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, N 3 LL Subcatchment 2S: Pre -2 (Offsite) Hydrograph L I I I I I I I 1 _I_ I I I L _ I I _ I_ L I I I J 1 I I I I L I I I I I J I I J 1 I I L I I I J I I I I I I I I I I I I I J 1 I I — I I I J I I 1 I I I I I ' I I I I I I V I I I I L J _ I_ L —I- -1 L J - I- 1 _Type I11-24 hr �2 1�1ailnfallT38�' 'Runbff Awes=1.960 aid 1LJI11L— JI RunmfflVol umle=;0.445 of -0-u;n-Lf 11Depih>-2J71'� 1-1-Tc-=6..10��tt iet -1 _ L J —C N� -91 - I I I I I I I J I— 1 1 L J I— J I I I I I I I I I I I I J—I-1—I—L - J I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Runoff Pre Type 11 24-hr 2 YR Rainfall=3.68" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 12 Summary for Link 3L: Pre -Developed Inflow Area = 2.810 ac, 42.70% Impervious, Inflow Depth > 2.41" for 2 YR event Inflow = 10.99 cfs @ 11.97 hrs, Volume= 0.563 of Primary = 10.99 cfs @ 11.97 hrs, Volume= 0.563 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 3L: Pre -Developed A Hydrograph i I —1 I I I — —I— I I I — — — I I I I I I I I I I I I I I I I 12 7 —1— T —1 — — - —I— I- —I c F 7 7 -1 71F -1 / L 1 )__1 10.99 cfs 1 fI aV 11 Yi Sa=2_181- I I I I I I I I I I I I I I I I I I I I 10i T 1 F 7 1 F-1 1 F -1 1 T-1 F T F-1—— 9 i I I I I I I I I I I I I I I I I I I I I 81 7-1—F-1—I—-1-1-r-1-1— —I—-1-1—T_-—I—rt—I—F-1—— N 7 _I_ _I —— _I_ 1 _I_ _ _I_ 1 _I —— 1 _I_ 1 _I — — u 3 6 7 —1— 1- —1 —1— rt —1— r -I —I— — I— I —I— T_ I —I— rt —I— F -1 — — LL 5 i I I I I I I I I I I I I I I I I I I I I 4- 3 i I I I I I I I I I I I I I I I I I I I I 2 rt —I— fi —1 —1— -1 —1— r- -1 —1 — 1 —1— fi I —I— rt —I— r I — — 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) F Inflow ❑ Primary Pre Type 1124-hr 10 YR Rainfall=5.57" Prepared by Timmons Group Printed 3/20/2020 HydroCAD® 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 13 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment1S: Pre -1 (Onsite) Runoff Area=0.850 ac 0.00% Impervious Runoff Depth>3.29" Flow Length=226' Tc=7.5 min CN=79 Runoff=4.61 cfs 0.233 of Subcatchment2S: Pre -2 (Offsite) Runoff Area=1.960 ac 61.22% Impervious Runoff Depth>4.53" Tc=6.0 min CN=91 Runoff=14.11 cfs 0.740 of Link 3L: Pre -Developed Inflow=18.51 cfs 0.974 of Primary=18.51 cfs 0.974 of Total Runoff Area = 2.810 ac Runoff Volume = 0.974 of Average Runoff Depth = 4.16" 57.30% Pervious = 1.610 ac 42.70% Impervious = 1.200 ac Pre Type 1124-hr 10 YR Rainfall=5.57" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 14 Summary for Subcatchment 1S: Pre -1 (Onsite) Runoff = 4.61 cfs @ 11.99 hrs, Volume= 0.233 af, Depth> 3.29" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YR Rainfall=5.57" Area (ac) CN Description 0.600 80 >75% Grass cover, Good, HSG D 0.250 77 Woods, Good, HSG D 0.850 79 Weighted Average 0.850 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 100 0.1474 0.28 Sheet Flow, Grass: Dense n= 0.240 P2= 3.70" 0.5 45 0.0444 1.47 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.0 81 0.0690 1.31 Shallow Concentrated Flow, Woodland Kv= 5.0 fos 7.5 226 Total Subcatchment 1 S: Pre -1 (Onsite) Hydrograph 5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ■Runoff 4 61 cfs I I I i I I I 1 1 1 1 1 (Type II 24-hr 4 I fly*nRaifall=3. 7 I I I I I I I I I I I I I 1 1 1 1 1 1 1Runbff Area=0.850 ad I I I I I I I I I I I I I I I I I 1 t 1 fi 1 1 I —Runoff iVo ume=o-23 -a w 3 Ou;nOff 11Depth>1. 9�• U. 1 1 1 1 1 1 FlawlLengt-h=226' 1 1 1 1 1 2 1 11 1 1 1 Tc$7.15 min I I I I I I I I I I I I L _1_ 1 _1_— _7_ 1 I I I I I I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Pre Type 1124-hr 10 YR Rainfall=5.57" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 15 Summary for Subcatchment 2S: Pre -2 (Offsite) Runoff = 14.11 cfs @ 11.96 hrs, Volume= 0.740 af, Depth> 4.53" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10 YR Rainfall=5.57" Area (ac) CN Description 1.200 98 Paved parking, HSG D 0.760 80 >75% Grass cover, Good, HSG D 1.960 91 Weighted Average 0.760 38.78% Pervious Area 1.200 61.22% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: Pre -2 (Offsite) Hydrograph 15 I I -I- I I I I I I I I I I I I I I I I I I 14.11 cfs- I I I I I I i i l l l l 14 ---L-1- -1-L- I- -L -I I I TypeaU24-hr 13 1 1 1 1 1 1 I -1 I I I I I - - 119Yj q 12 1 1 1 1 1 1 - Rainfafl *5 —71 11 ' Ru nbff Awed=1.960 at � - 1- rt -1- fi -1 - r � - 1- rt-. 1.-„,�rt,�-1-ry 10 1 1 1 1 IRun*WVb1u e=;n.740 -a Z. 9 _ I_ _ _ _I _ _ I_ _ 1 1 1 _ 1 1�p1 � 4 "1 T _4n" `t' 1 1 8 0 , ----------------- --------------- -I - - 1- Tci�6.'0 Ih'lii� 1 1 rt rt --fi 1 1 rt 16.10 1r 6 --I1 4 1 1 --I1 4 I -- 1 -4 1 i-G"1 5 4 1 1 1 1 3 2 T T 1-F-1 F 7 T -1-r T I F �-I-t-I-- I-�-I- 1-f- 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Runoff Pre Type 1124-hr 10 YR Rainfall=5.57" Prepared by Timmons Group Printed 3/20/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 16 Summary for Link 3L: Pre -Developed Inflow Area = 2.810 ac, 42.70% Impervious, Inflow Depth > 4.16" for 10 YR event Inflow = 18.51 cfs @ 11.97 hrs, Volume= 0.974 of Primary = 18.51 cfs @ 11.97 hrs, Volume= 0.974 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 3L: Pre -Developed Hydrograph _I_ 20 i L _ _ -1 - I- 1 - I - L L _ 18.51 cfs _ L -i — I - L/�_J I- L -I - L L 19 i -1- -1 - 1- 4 -1- � _ 1as1 ors - Infl o1w-A ea=118 FW ac 18 i -4 -1- 4- -1 -1- -1- - -1 - I- -4 - I - 4- -1- 4 - I - -I- 17 i rt -1- fi -1 - - rt -1 f � -1 rt -I- fi - -1- rt -1- � -I- 16 i rt I F I F-1-1-r--1- --1 I T_J 1 7 1 F-1 15 i 14 i I F I 1 1 13 i N 12 c 10 i L _I L _I L 1 _I L J _I_L I_ L J _ 1 L J LL 9 i 1 I J 1 � -I-I- J 1- 1 -- 8 i1I_+I _j -I JI-_+I��-- 7 i _t I fi 1 I_t 1 t-� 1I fiJ 1 fi 16 i rt-1-r-1-I-rt-1-ram-II-7--1-7-1-r7-1 5 i4 7 T 7 r-- r - 3 i 1 1 1 2 1 i 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Inflow ❑ Primary Post Type/1 24-hr 1 YR Rainfall=3.04" Prepared by Timmons Group Printed 3/23/2020 HydroCAD® 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 1 Summary for Link 6L: POA Inflow Area = 2.810 ac, 64.41 % Impervious, Inflow Depth > 2.16" for 1 YR event Inflow = 7.42 cfs @ 12.03 hrs, Volume= 0.505 of Primary = 7.42 cfs @ 12.03 hrs, Volume= 0.505 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs N V 3 0 LL Link 6L: POA Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ❑ Inflow ❑ Primary Post Type 11 24-hr 2 YR Rainfall=3.68" Prepared by Timmons Group Printed 3/23/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 2 Summary for Link 6L: POA Inflow Area = 2.810 ac, 64.41 % Impervious, Inflow Depth > 2.76" for 2 YR event Inflow = 11.17 cfs @ 12.01 hrs, Volume= 0.647 of Primary = 11.17 cfs @ 12.01 hrs, Volume= 0.647 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs f f f Link 6L: POA Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow ❑ Primary Post Type 1124-hr 10 YR Rainfall=5.57" Prepared by Timmons Group Printed 3/23/2020 HydroCADO 10.00-20 s/n 06538 © 2017 HydroCAD Software Solutions LLC Page 3 Summary for Link 6L: POA Inflow Area = 2.810 ac, 64.41 % Impervious, Inflow Depth > 4.58" for 10 YR event Inflow = 18.38 cfs @ 12.00 hrs, Volume= 1.074 of Primary = 18.38 cfs @ 12.00 hrs, Volume= 1.074 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Link 6L: POA Hydrograph / L_I_L_I_1_1_I_LL_I_1_1_L-1_1_L-_1_L_I_LL 20 / -4 -1- -k -1 - 1- 4 -1- -4 - f8s8 as _ 4 Iuu,,� 4 4 1/j�/��(''u/�u� -_/II- 19 / -4 -1- -1 - 1- 4 -1- { 4 - 18.38 cfs Q1 - In fl o Y r a=Zi1 V , V c1c 18 / -t -1- fi -1 - 1- -t -1- � -j -1- - I- I -I- t- --] - I- -t I - - 17 / -T -I- -r -I - I- rt -I- r I -I- r- -1 16 / T 1 - 15 / _7 14 / 1 1 13 / N 12 u 11 / -i _I_ L _I _ 1_ 1 _I_ L � _1 L -1 1_ 1 _I_ L _1 310 0 LL 9/ -4 1-k 1 1 4 -1- -4 1- 4 1 �--1 1 4 1� -- 6 / 7 1 F 1 1 7 I L -I- - -I- T- -1 F 7 -1- F -1 5 / 4 / I I I I I I I I I I I I I I I I I 3I' / 1111111111111111pp, 2 / 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow ❑ Primary ' DEQ Virginia Runoff Reduction Method New Development Compliance Spreadsheet - Version 3.0 ( 2011 BMP Standards and Specifications 1 0 2013 Draft BMP Standards and Specifications I ' Project Name: Chattanooga - Colonnade Drive data input cells Date: 3/23/2020 constantvalues BMP Design Specifications List: 2013 Draft Stds & Specs calculation cells Site Information Post -Development Project (Treatment Volume and Loads) 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 Managed Turf (acres) -- disturbed, graded for 0.24 yards or other turf to be mowed/managed 0.24 Impervious Cover (acres) 0.61 0.61 0.85 ICnnstants Annual Rainfall (inches) 43 Target Rainfall Event (inches) 1.00 Total Phosphorus (TP) EMC (mg/L) 0.26 Total Nitrogen (TN) EMC (mg/L) 1.86 Target TP Load (Ib/acre/yr) 0.41 Pj (unitless correction factor) 0.90 Runoff Coefficients (Rv) A Soils B Soils C Soils D Soils Forest/Open Space 0.02 0.03 0.04 0.05 Managed Turf 0.15 0.20 0.22 0.25 Impervious Cover 0.95 0.95 0.95 0.95