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Report (55) /Pi S 7-)'. CP /� ) 1,3&5---e St() �'✓ICG C"k Acol OFFICE COPY512 AK Tran a 0 2016 E1) ENGINEERING$FORESTRY JUN 2 12965 SW Herman Road#100, Tualatin, OR 97062 'IIYOF I/GARD B JI i,,1 DIVISION To: Jessicajo Echanis FROM: Paul Sellke DR Horton AKS Engineering & Forestry 4380 SW Macadam Ave Suite 100 12965 SW Herman Road #100 Portland, OR 97239 Tualatin, OR 97062 PaulS@aks-eng.com 503-563-6151 PROJECT Summit Ridge No. 5 6/7/2016 4105 SUBJECT: Lot 159 Lateral Stormwater ID#: 00072 Analysis PURPOSE: For your use VIA: Email REMARKS: Hi Jessicajo: Attached is the stormwater analysis for the existing Lot 159 lateral which shows that a 4-inch pipe has sufficient capacity. Do not hesitate to call or email with any questions. Thanks, Paul Sellke, PE, GE Project Engineer AK AKS ENGINEERING & FORESTRY, LLC 12965 SW Herman Road, Suite 100 I Tualatin, OR 97062 P: 503.563.6151 Ext. 219 I F: 503.563.6152 I www.aks-eng.com I PauIS(a>aks- enq.com Offices in: Tualatin, OR I Salem-Keizer, OR I Vancouver, WA DESCRIPTION OF CONTENTS QTY DATED TITLE NUMBER SIZE 4105 20160607 Summit Ridge, Lot 1 6/7/2016 159 Private Lateral Stormwater Eval.pdf COPIES: DCGardner@drhorton.com Page 1 of 1 TUALATIN ' VANCOUVER ' SALEM-KEIZERAI( WWW.AKS-ENG.COM 12965 SW HERiuH RD.,Sum 100•7UALATIN,OR 97062 P.(803)5636151 F:(503156361= ENCIINIEMIUNG a PDINast'Rv June 7, 2016 Building Department City of Tigard 13125 SW Hall Blvd.Tigard,OR 97223 RE: Stormwater Lateral Analysis Summit Ridge No. 5, Lots 159 through 164 This letter is intended to summarize our hydraulic analysis of an existing stormwater lateral that will be utilized to collect runoff from Lots 159 through 164 of the Summit Ridge No.5 subdivision. The homebuilder(DR Horton)is proposing/constructing a combination drainage system that utilizes both a 4- 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 Lot 159. 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 a separate drainage easement 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 usable backyard areas (approximately 8,560 square feet)and the proposed roof area for Lots 159(assumed to be approximately 2,640 square feet). The roof area for Lots 160 through 164 will be directed towards their respective storm laterals to the north. The existing 4-inch storm drain lateral was evaluated assuming a 2%slope, per the approved construction plans. 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 Lot 159 has sufficient capacity to convey the anticipated stormwater runoff from the proposed drainage system(see attached HydroCAD Stormwater Analysis). Sincerely, 'gyp PRGKF v�5��1 NEF�i / t- 61688P Ifra42 Paul Sellke PE, f / E f-41 // • AKS ENGINEERING&FORESTRY,LLC p Ge2 r 09,1°43 *it A SE`N'DS. Attachments: Exhibit A—Private Storm Trench Detail ' JUNE ao. was 4105 20160606 Lots 159-164 Storm Drain HydroCAD Report . FINISH GRADE 707P;i e Ol •-W4 WOVEN GEOTEXTILE FABRIC /�Y�Io �� 0. MIRAFI 140N OR APPROVED y� .���•„•io EQUIVALENT I�47,w; 0��.� " ,•W W �I�0 I0;1 3/4 CLEAN DRAIN ROCK (NO 0°.•.Wi••W'. ip FINES; 30% VOIDS MINIMUM) • .II ° •�� 0, •47,4 jai 0,0 Idro•mw• ••�i.�• t2.0' .24/WP11140 411 OPgo.. o 4" SOLID WALL 0a�./=i I•�O. 4" PERFORATED STORM DRAIN �•� .�,• e1 PIPE FOR ROOF AND YARD STORM DRAIN PIPE i.�� . •mo , � � ,.�1 �• DRAINS (ELEVATION VARIES TO (MINIMUM 2% SLOPE) ' .;I �•� �� t MAINTAIN MINIMUM 2.0% SLOPE) rw.01.44,01 ±1.5' 1 PRIVATE STORM TRENCH DETAIL NTS DATE:06-06-2016 SUMMIT RIDGE NO.5 SUBDIVISION EXHIBIT PRIVATE STORM TRENCH DETAIL A AKS ENGINEERING & FORESTRY, LLC DRWN: DS 12965 SW HERMAN RD, STE 100S( 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 I LAYOUT1 1006 > 100R Lots 159-164 Yard and Lot 159 4-inch Lat Roof Areas Subca\ Reach mon. Link Drainage Diagram for 4105 Summit No.5-Post-Developed Prepared by AKS Engineering& Forestry(PAS), Printed 6/7/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC 4105 Summit No. 5 - Post-Developed Prepared by AKS Engineering & Forestry (PAS) Printed 6/7/2016 HydroCADO 8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 2 Area Listing (selected nodes) Area CN Description (acres) (subcatchment-numbers) 0.197 74 >75% Grass cover, Good, HSG C (100S) 0.061 98 Lot 159 Roof Area (100S) 0.257 TOTAL AREA 4105 Summit No. 5 - Post-Developed Prepared by AKS Engineering & Forestry (PAS) Printed 6/7/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 3 Soil Listing (selected nodes) Area Soil Subcatchment (acres) Goup Numbers 0.000 HSG A 0.000 HSG B 0.197 HSG C 100S 0.000 HSG D 0.061 Other 100S 0.257 TOTAL AREA 4105 Summit No. 5 - Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS Engineering & Forestry (PAS) Printed 6/7/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Pape 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 Subcatchment100S: Lots 159-164 Yard RunoffArea=11,200 sf 23.57% Impervious Runoff Depth>2.02" Tc=5.0 min CN=74/98 Runoff=0.12 cfs 0.043 af Reach 100R: Lot 159 4-inch Lat Avg. Depth=0.15' Max Vel=2.98 fps Inflow=0.12 cfs 0.043 af D=4.0" n=0.013 L=26.0' S=0.0200'P Capacity=0.27 cfs Outflow=0.12 cfs 0.043 af Total Runoff Area=0.257 ac Runoff Volume=0.043 af Average Runoff Depth = 2.02" 76.43% Pervious= 0.197 ac 23.57% Impervious = 0.061 ac 4105 Summit No. 5 - Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS Engineering & Forestry (PAS) Printed 6/7/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 100S: Lots 159-164 Yard and Roof Areas Runoff = 0.12 cfs @ 7.98 hrs, Volume= 0.043 af, Depth> 2.02" 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 8,560 74 >75% Grass cover, Good, HSG C 2,640 98 Lot 159 Roof Area 11,200 80 Weighted Average 8,560 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 100S: Lots 159-164 Yard and Roof Areas Hydrograph 0.13: p Runoff 0.125 0.12 cfs 012 0.115: Type IA 24-hr 25-YEAR 0.11 0.105; Rainfall=3.90" 0.1 0.095; Runoff Area=1`1,200 sf 0.09y Runoff Volume=0.043 af 0.08= 00.075'007= Runoff Depth>2.02" 3 0.065 0 0.06; Tc=5.0 min a 0.055: 0 .0 5' CN=74/98 0.045 0.04', 0.035', 0.03i id r is✓` � s�/`E`��'s�j�!° 0.025', 0.02', f,✓rt 0.0151 0.01- � > 0.0050 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 6/7/2016 HydroCAD®8.50 s/n 005096 ©2007 HydroCAD Software Solutions LLC Page 6 Summary for Reach 100R: Lot 159 4-inch Lat Inflow Area = 0.257 ac, 23.57% Impervious, Inflow Depth > 2.02" for 25-YEAR event Inflow = 0.12 cfs @ 7.98 hrs, Volume= 0.043 af Outflow = 0.12 cfs @ 7.98 hrs, Volume= 0.043 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= 2.98 fps, Min. Travel Time= 0.1 min Avg. Velocity= 1.78 fps, Avg. Travel Time= 0.2 min Peak Storage= 1 cf @ 7.98 hrs, Average Depth at Peak Storage= 0.15' Bank-Full Depth= 0.33', Capacity at Bank-Full= 0.27 cfs 4.0" Diameter Pipe, n= 0.013 Length= 26.0' Slope= 0.0200 '/' Inlet Invert=406.91', Outlet Invert=406.39' Reach 100R: Lot 159 4-inch Lat Hydrograph / ■Inflow 0.13: I n 17 rfs I E Outflow 0.12 cfs Inflow Area=0.257 ac 0.12- 0.,,- Avg. Depth=0.15' Max Vel=2.98 fps ° 0.08- D=4.0" 0.07= n=0.013 o 0.06: L=26.0' 0.05- S=0.0200 '/' 0.04- 0.03- =i 27 cfs 0.02- 0.01 4-6" -4"-6-1';':;"'*1-7.2"--r-4" Time (hours)