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/ /tf - I o)U 5w ��s / TUALATIN ' VANCOUVER SALEM-KEIZER 1266 sW MERMAN RO.,SUITE 100•TUNA .OR 07oesAIIIIIIMIIIIIS P(s0ay saws' F:(608)5636182 F.14011451101114115 F0/12$,,,T June 29,2016 Building Department JUN 2016 City of Tigard CiiiY0i - 13125SWHall Blvd.Tigard,OR97223 B(OO) M— T• °ffr9 - ,i RE: Stormwater Lateral Analysis Summit Ridge No. 5, Lots 144 through 149 This letter is intended to summarize our hydraulic analysis of two existing stormwater laterals that will be utilized to collect runoff from Lots 144 through 149 of the Summit Ridge No.5 subdivision. The homebuilder(DR Horton)is proposing/constructing a combination drainage system that utilizes both a fl- inch perforated pipe and a 4-inch solid wall pipe with a 1'x2'burrito wrap within a drain rock trench. The perforated and solid wall pipes will be connected to the existing 4-inch storm drain lateral for Lots 146&147. The solid wall pipes will be utilized to collect roof runoff and yard surface area drains,while the perforated pipe will collect any subsurface drainage. We understand that separate drainage easements will be recorded along the rear of the lots to allow for this shared drainage system. The combination drainage system will convey stormwater runoff from the backyard areas and the proposed roof area for Lots 146&147(assumed to be approximately 2,640 square feet). The roof area for the remainder of the lots(Lots 144,145,148,&149)will be directed towards their respective storm laterals to the north. The existing/proposed 4-inch storm drain laterals were evaluated assuming a minimum 2%slope. A precipitation depth of 3.90-inches,per the Clean Water Service's Design and Construction Standards for Sanitary Sewer and Surface Water Management(R&O 07-20),was utilized for our analysis(24-hr,25-year design storm). The stormwater analysis Indicates that the existing 4-inch lateral pipe provided for Lots 146&147 have sufficient capacity to convey the anticipated stormwater runoff from the proposed private storm drainage system(see attached HydroCAD Stormwater Analysis). Sincerely, est% ek K(49* .L. 6 • -- - a � or 1 i�/ Paul Seilke PE,GE /' AKS ENGINEERING&FORESTRY,LLC A4'tr a, , Attachments: O4 A SfA.%* Exhibit A—Private Storm Trench Detail 2010 4105 20160629 Lots 144-149 Storm Drain HydroCAD Report FINISH GRADE ...,,,-- �o /° °1 %Or VI WOVEN GEOTEXTILE FABRIC C C SCC C I♦ CC O° MIRAFI 140N OR APPROVED C /1 0Th EQUIVALENT Cj 9./� O° •3/4" CLEAN DRAIN ROCK (NO O° CyO'°� O4j�O° FINES; 30% VOIDS MINIMUM) '(� OW'° O`-�,/ I OaoOC�O°� b . °O��O° O� t2.0 !,400,0j000`0 (,---Vc rtffa)gC0000arA 4" SOLID WALL O° 4 PERFORATED STORM DRAIN rCO° STORM DRAIN PIPE O°c�DO � PIPE FOR ROOF AND YARD (MINIMUM 2% SLOPE) m O CSS °0:4 DRAINS (ELEVATION VARIES TO O°,( MAINTAIN MINIMUM 2.0% SLOPE) 12 _ ° sem, _ ),11 I ±1.5' PRIVATE STORM TRENCH DETAIL NTS DATE:06-06-2016 SUMMIT RIDGE NO.5 SUBDIVISION EXHIBIT PRIVATE STORM TRENCH DETAIL A AKS ENGINEERING & FORESTRY, LLCDRwN: DS 12965 SW HERMAN RD, STE 100 CHKD: PAS TUALATIN, OR 97062 AKS JOB: P:503.563.6151 F:503.563.6152 aks-eng.com 4105 DWG:4105 20160606 DR HORTON PRIVATE STORM DRAIN TRENCH 1 LAYOUT1 (3006) D 301 R t> 300R 200R 4 (200S) Lots 147-149 Yard and 4-inch Shared Lat Lot 147 4-inch Lat Lot 146 4-inch Lat Lots 144-146 Yard and Roof Areas Roof Areas Subcat Reach 'on• Drainage Diagram for 4105 Summit No.5-Post-Developed Prepared by AKS Engineering&Forestry(PAS), Printed 6/29/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC 4105 Summit No. 5 - Post-Developed Prepared by AKS Engineering & Forestry (PAS) Printed 6/29/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 2 Area Listing (selected nodes) Area CN Description (acres) (subcatchment-numbers) 0.304 74 >75% Grass cover, Good, HSG C (200S,300S) 0.061 98 Lot 146 Roof Area (200S) 0.061 98 Lot 147 Roof Area (300S) • 4105 Summit No. 5 - Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS Engineering & Forestry (PAS) Printed 6/29/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 4 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment200S: Lots 144-146 Yard RunoffArea=10,860 sf 24.31% Impervious Runoff Depth>2.04" Tc=5.0 min CN=74/98 Runoff=0.11 cfs 0.042 of Subcatchment300S: Lots 147-149 Yard and Runoff Area=7,646 sf 34.53% Impervious Runoff Depth>2.26" Tc=5.0 min CN=74/98 Runoff=0.09 cfs 0.033 af Reach 200R: Lot 146 4-inch Lat Avg. Depth=0.15' Max Vel=2.96 fps Inflow=0.11 cfs 0.042 af D=4.0" n=0.013 L=33.5' S=0.0200'P Capacity=0.27 cfs Outflow=0.12 cfs 0.042 af Reach 300R: Lot 147 4-inch Lat Avg. Depth=0.10' Max Vel=4.38 fps Inflow=0.09 cfs 0.033 af D=4.0" n=0.013 L=38.5' S=0.0699'/' Capacity=0.50 cfs Outflow=0.09 cfs 0.033 af Reach 301R:4-inch Shared Lat Avg. Depth=0.13' Max Vel=2.79 fps Inflow=0.09 cfs 0.033 af D=4.0" n=0.013 L=162.0' S=0.0200'/' Capacity=0.27 cfs Outflow=0.09 cfs 0.033 af 4105 Summit No. 5 - Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS Engineering & Forestry (PAS) Printed 6/29/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 200S: Lots 144-146 Yard and Roof Areas Runoff = 0.11 cfs @ 7.97 hrs, Volume= 0.042 af, Depth> 2.04" Runoff by SBUH method, Split Pervious/lmperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 8,220 74 >75% Grass cover, Good, HSG C 2,640 98 Lot 146 Roof Area 10,860 80 Weighted Average 8,220 74 Pervious Area 2,640 98 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 200S: Lots 144-146 Yard and Roof Areas Hydrograph 0.125i ■Runoff 012= 0.11 cfs 0.115 o.,, Type IA 24-hr 25-YEAR 0105_ 012 Rainfall=3.90" 0.095 0.09.1Runoff Area=10,860 sf 0.085= 0.08= Runoff Volume=0.042 af 0.075= 0.07:i 65 Runoff Depth>2.04" o 0.06 Tc=5.O min_ LT-0.055-; 0.05' 0.045= CN=74/98 045 0.035= 0.03 0.025 0.02 0.015 0.01-' 0.005 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) 4105 Summit No. 5 - Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS Engineering & Forestry (PAS) Printed 6/29/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 300S: Lots 147-149 Yard and Roof Areas Runoff = 0.09 cfs @ 7.96 hrs, Volume= 0.033 af, Depth> 2.26" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 5,006 74 >75% Grass cover, Good, HSG C 2,640 98 Lot 147 Roof Area 7,646 82 Weighted Average 5,006 74 Pervious Area 2,640 98 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 300S: Lots 147-149 Yard and Roof Areas Hydrograph 0.1 ■Runoff 0.095= 0.09 cfs 009 Type IA 24-hr 25-YEAR 0.085 0.08 Rainfall=3.90" °o 07 Runoff Area=7,646 sf 0.065= Runoff Volume=0.033 af 0.06= 0.055= Runoff Depth>2.26" c 005: LL0.045= Tc=5.0_min_ 0.04 0.035 CN=74/98 0.03= 0.025- 0.02; 0.015- 0.01 0.005= 0 0 1 "1""3"' 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 4105 Summit No. 5 - Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS Engineering & Forestry (PAS) Printed 6/29/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 7 Summary for Reach 200R: Lot 146 4-inch Lat Inflow Area = 0.249 ac, 24.31% Impervious, Inflow Depth > 2.04" for 25-YEAR event Inflow = 0.11 cfs @ 7.97 hrs, Volume= 0.042 of Outflow = 0.12 cfs @ 7.98 hrs, Volume= 0.042 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity= 2.96 fps, Min. Travel Time= 0.2 min Avg. Velocity= 1.77 fps, Avg. Travel Time= 0.3 min Peak Storage= 1 cf @ 7.98 hrs, Average Depth at Peak Storage= 0.15' Defined Flood Depth=451.51', Capacity at Flood Depth= -1,528.36 cfs Bank-Full Depth= 0.33', Capacity at Bank-Full= 0.27 cfs 4.0" Diameter Pipe, n= 0.013 Length= 33.5' Slope= 0.0200 'I' Inlet Invert=447.91', Outlet Invert= 447.24' Reach 200R: Lot 146 4-inch Lat Hydrograph / LITEI !1 1 1 nfc. 1 w 0.12= 0.12 cfs Inflow Arear. ac 0.11 Avg. Depth=0.15' 0.1- 0.09= Max Vel=2.96 fps 0.08: D=4.0" N 0.07: n=0.013 _0 0.06-, L=33.5' u 0.05= 0.04- S=0.0200 '[' 0.033 = 27 cfs 0.02 0.0, 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) 4105 Summit No. 5 - Post-DevelopedType lA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS Engineering & Forestry (PAS) Printed 6/29/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Pace 8 Summary for Reach 300R: Lot 147 4-inch Lat Inflow Area = 0.176 ac, 34.53% Impervious, Inflow Depth > 2.26" for 25-YEAR event Inflow = 0.09 cfs @ 7.97 hrs, Volume= 0.033 af Outflow = 0.09 cfs @ 7.97 hrs, Volume= 0.033 af, Atten= 0%, Lag= 0.1 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity=4.38 fps, Min. Travel Time= 0.1 min Avg. Velocity = 2.56 fps, Avg. Travel Time= 0.3 min Peak Storage= 1 cf @ 7.97 hrs, Average Depth at Peak Storage= 0.10' Defined Flood Depth=455.88', Capacity at Flood Depth= -2,884.33 cfs Bank-Full Depth= 0.33', Capacity at Bank-Full= 0.50 cfs 4.0" Diameter Pipe, n= 0.013 Length= 38.5' Slope= 0.0699 '/' Inlet Invert=451.28', Outlet Invert=448.59' Reach 300R: Lot 147 4-inch Lat Hydrograph / 0.14 I n rig rf s ILI: 0.095= 0.09 cfs Inflow Area=0.176 ac 0.09- 0854 08 Avg. Depth=0.10' 0.075; Max Vel=4.38 fps 0.07 0.0654 0. , .066= D=4.0" H 40.055= n=0.013 3 0.05= LL 0.045= 0.04- L=38.5' 0.035 S=0.0699 'I' 0.03 -z 0.0251 0.025 ' =0.50 cfs 0.02 0.015 0.01 3 0.005 0 ... 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) 4105 Summit No. 5 - Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS Engineering & Forestry (PAS) Printed 6/29/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 9 Summary for Reach 301R: 4-inch Shared Lat Inflow Area = 0.176 ac, 34.53% Impervious, Inflow Depth > 2.26" for 25-YEAR event Inflow = 0.09 cfs © 7.96 hrs, Volume= 0.033 af Outflow = 0.09 cfs @ 7.97 hrs, Volume= 0.033 af, Atten= 0%, Lag= 0.7 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Max. Velocity= 2.79 fps, Min. Travel Time= 1.0 min Avg. Velocity = 1.65 fps, Avg. Travel Time= 1.6 min Peak Storage= 5 cf @ 7.97 hrs, Average Depth at Peak Storage= 0.13' Defined Flood Depth=455.88', Capacity at Flood Depth= -1,543.17 cfs Bank-Full Depth= 0.33', Capacity at Bank-Full= 0.27 cfs 4.0" Diameter Pipe, n= 0.013 Length= 162.0' Slope= 0.0200 '/' Inlet Invert= 454.52', Outlet Invert=451.28' Reach 301R: 4-inch Shared Lat Hydrograph In no rf ■Inflow 0.1= ■Outflow 0.095- 0.09 cfs Inflow Area=0.176 ac 0.09 0.085; o.os= Avg. Depth=0.13' 0.075: Max Ve1=2.79 fps 0.07= 0.065: n 0.06= D-=4.0 n=0.013 x 0.055' 0.05= 0.045' L=162.0' 0.04 0.035= S=0.0200 '/' 0.03 0.025= 0.27 cfs 0.02- 0.015- 0.01 0.005 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)