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HomeMy WebLinkAboutWPO201700065 Calculations WPO VSMP 2017-09-08 1 Brown Toyota Site Plan Amendment Stormwater Summary September 8, 2017 Brown Toyota and Mercedes are on four parcels, totaling 10.13 acres. The proposed stormwater management improvements and conservation easement are on two parcels, 14 and 14E. The property, was originally developed in the 1960's and has received additional improvements over the years. Recently, within the past 5 years, some grading expanded a gravel parking area at the rear of the developed portion of the property. The grading increased the gravel area by approximately 11,200 sq. ft. In addition, the grading impacted an area of preserved slopes, as well as created new steep slopes, ultimately decreasing the on-site steep slopes area approximately 0.18 acres. Runoff from the gravel area sheet-flows across the steep slopes area and there are no signs of erosion along the slopes. To address the stormwater requirements created by the additional gravel area, the plan proposes to install the required detention in an adjacent drainage area, where stormwater runoff is being captured in significant quantity. This approach will allow the sheet flow condition to remain, rather than using new curb, and detention in the gravel area, which would require installing new storm piping across the steep slopes. Installation of the detention pipe will disturb approximately 1,375 sq. ft. The work will occur within a paved parking lot and will only involve trench excavation and temporary stockpiling of soil. Per the calculations below, the required allowable runoff for the gravel area is calculated, and that amount is detained in the adjacent drainage system. Gravel Parking Drainage Area APPROVED Pre-development Runoff by the Albemarle County Q(,)Pre Development = 0.15 cfs Community Development Department RV(1)Pre-Development = 0.31" Date Z/ZD/?OS Si' Post-Development Runoff File Ivt0201?00045 Q(1)Post-Development before SWM = 1.14 cfs (1)Post-Development before SWM = 2.02n Q(1)Allowable = I.F. x (Q(1)Pre-Development X RV(1)Pre-Development)/ RV(1)Post-Development before SWM = 0.9 x (0.15 x 0.31)/2.02 = 0.02 cfs Thus, Q(1) must be reduced by Q(1)post-Q(1)Allowable = 1.14-0.02 = 1.12 cfs Grate Drainage Area Q(1)Grate = 3.57 cfs Q(1)Reduction = 1.12 cfs O�9 1 1'NO + Therefore, Q(1)Allowable = Q 1p ( ) ( gate - Q(1)Reduction = 3.57 cfs - 1.12 cfs = 2.45 Cfs. i Per attached calculations: = B.Clark Gath •ht Q(1)Post-Developmentw/SWM = 2.40 cfs (Less than 2.45, OK) `6 %5 * sbg_ SjwNALE Water Quality Per the attached Re-Development spreadsheet, 0.03 lb/yr TP Reduction is required. Per the New Development spreadsheet, the creation of Forest and Open Space Conservation area provides a credit of 0.86 lb/yr TP Reduction. Thus, 0.03 lb/yr TP- 08.6 lb/yr TP = -0.83 lb/yr TP more than required. DEQ Virginia Runoff Reduction Method Re-Development Compliance Spreadsheet -Version 3.0 2011 BMP Standards and Specifications 0 2013 Draft BMP Standards and Specifications Project Name: Brown Toyota Date: 9/8/2017 MM data input cells constant values Linear Development Project? No calculation cells Site Information final results Post-Development Project(Treatment Volume and Loads) • • --------------------------- -- Enter Total Disturbed Area(acres) -31 0.41 I Check: BMP Design Specifications List: 2013 Draft Stds&Specs Maximum reduction required:~ 10% Linear project? No The site's net increase in impervious cover(acres)is: 0.26 Land cover areas entered correctly? ✓ Post-Development TP Load Reduction for Site(lb/yr):! 0.46 Total disturbed area entered? ./ Pre-ReDevelopment Land Cover (acres) A Soils B Soils C Soils D Soils I Totals Forest/Open Space(acres)--undisturbed, 0.26 protected forest/open space or reforested land 0.26 Managed Turf(acres)--disturbed,graded for 0.00 yards or other turf to be mowed/managed 0.00 Impervious Cover(acres) 0.00 0.00 0.26 I Post-Development Land Cover (acres) A Soils B Soils C Soils D Soils I Totals I Forest/Open Space(acres)--undisturbed, 0.00 protected forest/open space or reforested land 0.00 Managed Turf(acres)--disturbed,graded for 0.00 yards or other turf to be mowed/managed 0.00 _ Impervious Cover(acres) 0.26 0.26 Area Check OK. OK. OK. OK. I 0.26 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 t 0.95 Target TP Load(lb/acre/yr) 0.41 P1(unitless correction factor) 0.90 LAND COVER SUMMARY-- PRE-REDEVELOPMENT LAND COVER SUMMARY--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) 0.26 0.00 Forest/Open Space 0.00 Forest/Open Space 0.00 _ Cover(acres) Cover lacresl ____ Weighted Rv(forest) 0.03 0.00 Weighted Ry(forest) 0.00 Weighted Rv(forest) 0.00 %Forest 100% 0% %Forest 0% %Forest 0% Managed Turf Cover(acres) 0.00 3.00 Managed Turf Cover 0.00 Managed Turf Cover 0.00 lacresl lacresl Weighted Rv)turf) 0.00 0.00 Weighted Rv(turf) 0.00 Weighted Rv(turf) 0.00 %Managed Turf 0% 0% %Managed Turf 0% %Managed Turf 0% Impervious Cover ReDev.Impervious New Impervious Cover Impervious Cover(acres) 0.00 0.00 0.26 0.00 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 0% 0% %Impervious 100% %Impervious 0% Total Site Area(acres) 0.26 0.00 Final Site Area(acres) 0.26 Total ReDev.Site Area 0.00 lacresl Site Rv 0.03 0.00 Final Post Dev Site Rv 0.95 ReDev Site Rv 0.00 Treatment Volume and Nutrient Load Final Post-Development Post-ReDevelopment Post-Development Pre-ReDevelopment Treatment Volume (acre-ft) 0.0007 0.0000 Treatment Volume 0.0206 Treatment Volume 0.0000 Treatment Volume 0.0206 (acre-ft) (acre-ft) (acre-ft) Final Post-Development Post-ReDevelopment Post-Development Pre-ReDevelopment Treatment Volume (cubic feet) 28 0 Treatment Volume 897 Treatment Volume 0 Treatment Volume(cubic 897 (cubic feet) (cubic feet) feet) Pre-ReDevelopment TP Load Final Post- Post-ReDevelopment post-Development TP (Ib/yr) 0.02 0.00 Development TP Load 0.56 Load(7P) 0.00 Load(Ib/yr) 0.56 (Ib/yr) (Ib/yr)• Pre-ReDevelopment TP Load per acre Final Post-Development TP 1 Post-ReDevelopment TP (lb/acre/yr) 007 Load per acre 2.17 Load per acre (Ib/acre/yr) I (lb/acre/yr) Baseline TP Load(lb/yr) Max.Reduction Required (0.41 lbs/acre/yr applied to pre-redevelopment area excluding pervious 0.00 (Below Pre- 10% land proposed for new impervious cover) ReDevelopment Load) 'Adjusted Land Cover Summary: TP Load Reduction Pre ReDevelopment land cover minus pervious land cover(forest/open space or Required for TP Load Reduction managed turf)acreage proposed for new impervious cover. Redeveloped Area 0.00 Required for New 0.46 (Ib/yr) Impervious Area(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) 0.46 Nitrogen Loads(Informational Purposes Only) Final Post-Development TN Load Pre ReDevelopment TN Load(Ib/yr) 0.13 (Post-ReDevelopment&New Impervious) 4.03 (Ib/yr) V OC V O SP I N A w N N ti S P 3 Q "' a O C1 v g A a _ - o O w -, c 8 i O d CJ 7 '•1 O 2 in N v u N v u 3 w s 'rp n.- n v w a' F• r+ R 3 OO 7 n m o .d. c m v, in y s Q u n m m' a w o 3 3 3 y .. o v o v+ 3 o d £ O O1 ° £ as m o. 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Ln Ln to Z '^ 0 —I ry m A 8 ro 2,- cc Cc H w 73 0 d I 5. m , = iv o i c CI 3 en ro a ro .7N I N Brown Toyota PIPE PRE Type 1124-hr 1"24-hour Rainfall=3.00" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 1 Summary for Subcatchment 9S: DA GRATE PRE [49] Hint: Tc<2dt may require smaller dt Runoff = 3.57 cfs @ 11.95 hrs, Volume= 0.167 af, Depth> 2.21" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1" 24-hour Rainfall=3.00" Area (sf) CN Description 35,389 98 Paved parking, HSG B 4,085 61 >75% Grass cover, Good, HSG B 39,474 94 Weighted Average 4,085 10.35% Pervious Area 35,389 89.65% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, tc Subcatchment 9S: DA GRATE PRE Hydrograph 3.57 cfs El Runoff _ Type II 24-hr - 1" 24-hour Rainfall-3.00" 3 Runoff Area=39,474 sf - Runoff Volume-0.167 of 1/7 - Runoff Depth>2.21" 2- Tc-5.0 min - CN=94 1- 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 16 17 18 19 20 Time (hours) Brown Toyota PIPE PRE Type 1124-hr 10-year Rainfall=5.50" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 9S: DA GRATE PRE [49] Hint: Tc<2dt may require smaller dt Runoff = 6.96 cfs @ 11.95 hrs, Volume= 0.343 af, Depth> 4.54" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-year Rainfall=5.50" Area (sf) CN Description 35,389 98 Paved parking, HSG B 4,085 61 >75% Grass cover, Good, HSG B 39,474 94 Weighted Average 4,085 10.35% Pervious Area 35,389 89.65% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, tc Subcatchment 9S: DA GRATE PRE Hydrograph 6.96 cfs _❑ Runoff` 7= Type II 24-hr 6 10-year Rainfall=5.50" Runoff Area=39,474 sf y 5= Runoff Volume=0.343 af 4_ Runoff Depth>4.54" o = Tc=5.0 min 3y CN=94 0 0 .// / - 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 16 17 18 19 20 Time (hours) 9S DAG ATE PP double 36 INCH pipe :Subcat Reach Pon Routing Diagram for Brown Toyota PIPE 2 Prepared by Windows User, Printed 5/11/2017 HydroCAD®10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Brown Toyota PIPE 2 Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 0.094 61 >75% Grass cover, Good, HSG B (9S) 0.812 98 Paved parking, HSG B (9S) 0.906 94 TOTAL AREA Brown Toyota PIPE 2 Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 3 Soil Listing (all nodes) Area Soil Subcatchment (acres) Group Numbers 0.000 HSG A 0.906 HSG B 9S 0.000 HSG C 0.000 HSG D 0.000 Other 0.906 TOTAL AREA Brown Toyota PIPE 2 Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC 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 0.094 0.000 0.000 0.000 0.094 >75% Grass cover, Good 9S 0.000 0.812 0.000 0.000 0.000 0.812 Paved parking 9S 0.000 0.906 0.000 0.000 0.000 0.906 TOTAL AREA Brown Toyota PIPE 2 Type 1124-hr 1"24-hour Rainfall=3.00" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 5 Time span=0.00-20.00 hrs, dt=0.05 hrs, 401 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 9S: DA GRATE Runoff Area=39,474 sf 89.65% Impervious Runoff Depth>2.21" Tc=5.0 min CN=94 Runoff=3.57 cfs 0.167 of Pond 10P: double 36 INCH pipe Peak Elev=2.36' Storage=0.021 of Inflow=3.57 cfs 0.167 of Primary=2.40 cfs 0.166 of Secondary=0.00 cfs 0.000 of Outflow=2.40 cfs 0.166 of Total Runoff Area = 0.906 ac Runoff Volume = 0.167 of Average Runoff Depth =2.21" 10.35% Pervious = 0.094 ac 89.65%Impervious = 0.812 ac Brown Toyota PIPE 2 Type 1124-hr 1"24-hour Rainfall=3.00" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 9S: DA GRATE [49] Hint: Tc<2dt may require smaller dt Runoff = 3.57 cfs @ 11.95 hrs, Volume= 0.167 af, Depth> 2.21" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 1" 24-hour Rainfall=3.00" Area (sf) CN Description 35,389 98 Paved parking, HSG B 4,085 61 >75% Grass cover, Good, HSG B 39,474 94 Weighted Average 4,085 10.35% Pervious Area 35,389 89.65% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, tc Subcatchment 9S: DA GRATE Hydrograph 3.57 cfs _❑ Runoff` Type II 24-hr 1" 24-hour Rainfall=3.00" 3 Runoff Area=39,474 sf Runoff Volume=0.167 af Runoff Depth>2.21" 2 Tc=5.0 min �° CN=94 10 ,0,. 0 1 2 3 4 5 6 7 8 9 1011 121314151617181920 Time (hours) Brown Toyota PIPE 2 Type 1124-hr 1"24-hour Rainfall=3.00" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 7 Summary for Pond 10P: double 36 INCH pipe Inflow Area = 0.906 ac, 89.65% Impervious, Inflow Depth > 2.21" for 1" 24-hour event Inflow = 3.57 cfs @ 11.95 hrs, Volume= 0.167 of Outflow = 2.40 cfs @ 12.02 hrs, Volume= 0.166 af, Atten= 33%, Lag= 4.2 min Primary = 2.40 cfs @ 12.02 hrs, Volume= 0.166 af Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 2.36' @ 12.02 hrs Surf.Area= 0.014 ac Storage= 0.021 af Plug-Flow detention time= 6.2 min calculated for 0.166 af (99% of inflow) Center-of-Mass det. time= 4.8 min ( 755.7 - 751.0 ) Volume Invert Avail.Storage Storage Description #1A 0.00' 0.014 af 9.50'W x 65.00'L x 4.00'H Field A 0.057 af Overall - 0.021 af Embedded = 0.036 af x 40.0% Voids #2A 0.50' 0.021 af CMP_Round 36 x 6 Inside#1 Effective Size= 36.0"W x 36.0"H => 7.06 sf x 20.00'L = 141.1 cf Overall Size= 36.0"W x 36.0"H x 20.00'L 2 Rows of 3 Chambers 7.50' Header x 7.06 sf x 1 = 52.9 cf Inside 0.035 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Primary 0.00' 8.0" Vert. Orifice/Grate C= 0.600 #2 Secondary 3.90' 12.6' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Primary OutFlow Max=2.36 cfs @ 12.02 hrs HW=2.31' (Free Discharge) L1=Orifice/Grate (Orifice Controls 2.36 cfs @ 6.77 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=0.00' (Free Discharge) -2=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Brown Toyota PIPE 2 Type 1124-hr 1"24-hour Rainfall=3.00" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 8 Pond 10P: double 36 INCH pipe - Chamber Wizard Field A Chamber Model = CMP_Round 36(Round Corrugated Metal Pipe) Effective Size= 36.0"W x 36.0"H => 7.06 sf x 20.00'L = 141.1 cf Overall Size= 36.0"W x 36.0"H x 20.00'L 36.0" Wide + 18.0" Spacing = 54.0" C-C Row Spacing 3 Chambers/Row x 20.00' Long +3.00' Header x 1 = 63.00' Row Length +12.0" End Stone x 2 = 65.00' Base Length 2 Rows x 36.0" Wide + 18.0" Spacing x 1 + 12.0" Side Stone x 2 = 9.50' Base Width 6.0" Base + 36.0" Chamber Height + 6.0" Cover= 4.00' Field Height 6 Chambers x 141.1 cf + 7.50' Header x 7.06 sf = 899.7 cf Chamber Storage 2,470.0 cf Field - 899.7 cf Chambers = 1,570.3 cf Stone x 40.0% Voids = 628.1 cf Stone Storage Chamber Storage + Stone Storage = 1,527.8 cf = 0.035 of Overall Storage Efficiency = 61.9% Overall System Size = 65.00' x 9.50' x 4.00' 6 Chambers 91.5 cy Field 58.2 cy Stone fk 1 Brown Toyota PIPE 2 Type 1124-hr 1"24-hour Rainfall=3.00" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 9 Pond 10P: double 36 INCH pipe Hydrograph 3.57 cfs n Inflow --/ Inflow Area-0.906 ac Outflow Peak Elev=2.36' LI Primary Storage-0.021 of i--1 Secondary 3- 2.40 cfs 2- ir. PO 1- 00 0.00 cfs iiiiiiiiiiiiii�iiiiiiiiiiiiiiiiiii 0 �o yrr.8 r����ltd,/�1/,!�r��Afr ., ,r.,,, 0 2 4 6 8 10 12 14 16 18 20 Time (hours) Brown Toyota PIPE 2 Type 1124-hr 10-year Rainfall=5.50" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 10 Time span=0.00-20.00 hrs, dt=0.05 hrs, 401 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 9S: DA GRATE Runoff Area=39,474 sf 89.65% Impervious Runoff Depth>4.54" Tc=5.0 min CN=94 Runoff=6.96 cfs 0.343 af Pond 10P: double 36 INCH pipe Peak EIev=4.20' Storage=0.035 af Inflow=6.96 cfs 0.343 af Primary=3.31 cfs 0.314 af Secondary=4.27 cfs 0.028 af Outflow=7.56 cfs 0.342 af Total Runoff Area = 0.906 ac Runoff Volume = 0.343 of Average Runoff Depth = 4.54" 10.35% Pervious= 0.094 ac 89.65% Impervious= 0.812 ac Brown Toyota PIPE 2 Type 1124-hr 10-year Rainfall=5.50" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment 9S: DA GRATE [49] Hint: Tc<2dt may require smaller dt Runoff = 6.96 cfs @ 11.95 hrs, Volume= 0.343 af, Depth> 4.54" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr 10-year Rainfall=5.50" Area (sf) CN Description 35,389 98 Paved parking, HSG B 4,085 61 >75% Grass cover, Good, HSG B 39,474 94 Weighted Average 4,085 10.35% Pervious Area 35,389 89.65% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, tc Subcatchment 9S: DA GRATE Hydrograph 6.96 cfs _D Runoff 7•". Type II 24-hr 6 10-year Rainfall=5.50" : Runoff Area=39,474 sf To' 5= Runoff Volume=0.343 af 4_.: Runoff Depth>4.54" _o Tc=5.0 min 3= CN=94 2= 0 1 2 3 4 5 6 7 8 9 1011 121314151617181920 Time (hours) Brown Toyota PIPE 2 Type 1124-hr 10-year Rainfall=5.50" Prepared by Windows User Printed 5/11/2017 HydroCAD® 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 12 Summary for Pond 10P: double 36 INCH pipe [93] Warning: Storage range exceeded by 0.20' [88] Warning: Qout>Qin may require smaller dt or Finer Routing Inflow Area = 0.906 ac, 89.65% Impervious, Inflow Depth > 4.54" for 10-year event Inflow = 6.96 cfs @ 11.95 hrs, Volume= 0.343 af Outflow = 7.56 cfs @ 11.96 hrs, Volume= 0.342 af, Atten= 0%, Lag= 0.5 min Primary = 3.31 cfs @ 11.97 hrs, Volume= 0.314 of Secondary = 4.27 cfs @ 11.96 hrs, Volume= 0.028 af Routing by Stor-Ind method, Time Span= 0.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 4.20' @ 11.97 hrs Surf.Area= 0.014 ac Storage= 0.035 af Plug-Flow detention time= 5.5 min calculated for 0.341 af (100% of inflow) Center-of-Mass det. time= 4.5 min ( 738.5 - 734.1 ) Volume Invert Avail.Storage Storage Description #1 A 0.00' 0.014 af 9.50'W x 65.00'L x 4.00'H Field A 0.057 af Overall - 0.021 af Embedded = 0.036 af x 40.0% Voids #2A 0.50' 0.021 af CMP Round 36 x 6 Inside #1 Effective Size= 36.0"W x 36.0"H => 7.06 sf x 20.00'L = 141.1 cf Overall Size= 36.0"W x 36.0"H x 20.00'L 2 Rows of 3 Chambers 7.50' Header x 7.06 sf x 1 = 52.9 cf Inside 0.035 af Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Primary 0.00' 8.0" Vert. Orifice/Grate C= 0.600 #2 Secondary 3.90' 12.6' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Primary OutFlow Max=3.25 cfs @ 11.97 hrs HW=4.08' (Free Discharge) L1=Orifice/Grate (Orifice Controls 3.25 cfs @ 9.32 fps) Secondary OutFlow Max=3.80 cfs @ 11.96 hrs HW=4.10' (Free Discharge) L2=Sharp-Crested Rectangular Weir (Weir Controls 3.80 cfs @ 1.48 fps) Brown Toyota PIPE 2 Type 1124-hr 10-year Rainfall=5.50" Prepared by Windows User Printed 5/11/2017 HydroCAD®10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 13 Pond 10P: double 36 INCH pipe - Chamber Wizard Field A Chamber Model = CMP_Round 36 (Round Corrugated Metal Pipe) Effective Size= 36.0"W x 36.0"H => 7.06 sf x 20.00'L = 141.1 cf Overall Size= 36.0"W x 36.0"H x 20.00'L 36.0" Wide + 18.0" Spacing = 54.0" C-C Row Spacing 3 Chambers/Row x 20.00' Long +3.00' Header x 1 = 63.00' Row Length +12.0" End Stone x 2 = 65.00' Base Length 2 Rows x 36.0" Wide + 18.0" Spacing x 1 + 12.0" Side Stone x 2 = 9.50' Base Width 6.0" Base + 36.0" Chamber Height + 6.0" Cover = 4.00' Field Height 6 Chambers x 141.1 cf + 7.50' Header x 7.06 sf = 899.7 cf Chamber Storage 2,470.0 cf Field - 899.7 cf Chambers = 1,570.3 cf Stone x 40.0%Voids = 628.1 cf Stone Storage Chamber Storage + Stone Storage = 1,527.8 cf = 0.035 of Overall Storage Efficiency = 61.9% Overall System Size = 65.00' x 9.50' x 4.00' 6 Chambers 91.5 cy Field 58.2 cy Stone Brown Toyota PIPE 2 Type 1124-hr 10-year Rainfall=5.50" Prepared by Windows User Printed 5/11/2017 HydroCAD© 10.00-16 s/n 08839 ©2015 HydroCAD Software Solutions LLC Page 14 Pond 10P: double 36 INCH pipe Hydrograph ■ Inflow 7.56 cfs (1 Outflow 8 Inflow Area-0.906 � 4 � p Primary Peak Elev-4.20' 7 Storage-0.035 of _ Secondary 6 13 0 - 4.27 cfs J., Ulb 0 4 =. u. 3i 1 " 0 ///////f////////////////////////////////////. ////////////////////f////////// 0 2 4 6 8 10 12 14 16 18 20 Time (hours)