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Report (26) �L ti it, COQ IOOSSo Set) 7Zvee- NW Engineers,LLC ENGINEERS 3409 NW John Olsen Place Hillsboro,OR 97124 • .� 1 , Phone(503)601-4401 2-4 n1 r�rh g t,.:'.. Fax(503)601-4402 dr Planning Email stevew@nw-eng.com ,RIL L 2 7 Z016 Website www.nw-eng.com July 27, 2016 City of Tigard Building Division 13125 SW Hall Blvd. Tigard, OR 97223 Attention: To Whom it May Concern RE: 10060 SW Tigard Street Proposed Infiltration System Purpose: This letter is provided to address the proposed infiltration system for a proposed single family residence, Tax Lot 1S1 35CC 3300, located on SW Tigard Street, north of SW Katherine Street. The total site area is 0.35 acres. Existing Conditions: The subject property drains away from the street to the southwest corner of the property. There is no public storm line in SW Tigard St.for the residence to connect to thus the need to do on-site infiltration. Infiltration System Criteria: The roof area of the proposed single family house is 2,606 sq.ft. The on-site driveway is 535 sq.ft. The total area to be conveyed to the infiltration system is 3,141 sq. ft. The system was sized for a 100 year, 24 hour storm event, 4.50 inches and infiltration rate of 2.50 inches/hour. A Geotechnical investigation has found the on-site infiltration rate to be 5 inches/hour. 2 rows of 3 Contech ChamberMaxx chambers will be required to meet the storage requirements. If you :ve any questions please call me at 503-601-4401. Sin•i y, t=ve White, PE Civil Engineer Encl. Cc: Tim Gray Engineering • Planning Director: Greg Thiel,PE Planning Manager: Matthew Newman <SUB > R OF ///\1\s\st:::) INFILTRATION Subcat Reach -on. Link Routing Diagram for Infiltration System(Tigard St) Prepared by NW Engineers,LLC, Printed 7/27/2016 HydroCAD®10.00-12 sin 02505 02014 HydroCAP Software Solutions LLC Infiltration System (Tigard St) Type IA 24-hr 100-year Rainfall=4.50" Prepared by NW Engineers, LLC Printed 7/27/2016 HydroCAD®10.00-12 sin 02505 Q 2014 HydroCAD Software Solutions LLC Page 17 Time span=0.00-36.00 hrs,dt=0.03 hrs, 1201 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Subcatchment SUB-1: ROOF Runoff Area=3,141 sf 100.00% Impervious Runoff Depth=4.26" Tc=5.0 min CN=0/98 Runoff=0.08 cfs 1,116 cf Pond 2P:INFILTRATION Peak EIev=101.89' Storage=259 cf Inflow=0.08 cfs 1,116 cf Outflow=0.01 cfs 1,116 cf Total Runoff Area=3,141 sf Runoff Volume=1,116 cf Average Runoff Depth=4.26" 0.00%Pervious=0 sf 100.00%Impervious=3,141 sf Infiltration St and System Ti y (Tigard � Type IA 24-hr 100-year Rainfall=4.511„ Prepared by NW Engineers, LLC Printed 7/27/2016 HydroCAD®10.00-12 sin 02505 Q 2014 HydroCAD Software Solutions LLC Page 18 Summary for Subcatchment SUB-1: ROOF Runoff = 0.08 cfs @ 7.89 hrs, Volume 1,116 cf, Depth= 4,26" Runoff by SBUH method, Split Pervious/Imperv., Time Span=0.00-36.00 hrs, dt= 0.03 hrs Type IA 24-hr 100-year Rainfall=4.50" Area(sf) CN Description * 3,141 98 Roof 3,141 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment SUB-1: ROOF Hydrograph 0.085 l 0.08 lomat I Runoff 0.075 0.75 r Type IA 24-hr 0.06510 100-year Rainfall=4.50" 0.06 Runoff Area=3,141 sf 0.055 40Runoff Volume=1,116 cf 0.05 , 3 0.045` Runoff Depth=4.26" 0 0,04 0.035 Tc=5.0 min. i% 0.0253 CN=0/98 'ea 0.02 .- /0 0.015 j®�O/✓/ 0.01 ,,,,e' � /✓././s/.�'r//�I'��/�'�//s✓/`�.��/ 0.005 t 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 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours} Infiltration System (Tigard St) Type IA 24-hr 100-year Rain Prepared by NW Engineers, LLC HydroCADO 10.00-12 sin 02505 ©2014 HydroCAD Software Solutions LLC Printed 7/PPage 19 Page 19 Summary for Pond 2P: INFILTRATION Inflow Area= 3,141 sf,100.00% Impervious, Inflow Depth= 4.26" for 100-year event Inflow = 0.08 cfs @ 7.89 hrs, Volume= 1,116 cf Outflow = 0.01 cfs @ 5.04 hrs, Volume= 1,116 cf, Atten=83%, Lag= 0.0 min Discarded = 0.01 cfs© 5.04 hrs, Volume= 1,116 cf Routing by Stor-Ind method,Time Span= 0.00-36.00 hrs, dt=0.03 hrs Peak Elev= 101.89'© 11.49 hrs Surf.Area=230 sf Storage=259 cf Plug-Flow detention time= 184.1 min calculated for 1,116 cf(100% of inflow) Center-of-Mass det. time= 184.1 min (841.6-657.5) Volume Invert Avail.Storage Storage Description #1 100.50' 199 cf Contech ChamberMaxx x 4 Inside#2 Effective Size=49.6"W x 30.0"H =>6.92 sf x 7.12'L=49.3 cf Overall Size= 51.4"W x 30.3"H x 7.58'L with 0.47'Overlap Row Length Adjustment= +0.32'x 6.92 sf x 1 rows #2 100.00' 288 cf 6.30'W x 9.12'L x 4.00'H Prismatoid x 4 919 cf Overall- 199 cf Embedded= 720 cf x 40.0%Voids 487 cf Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 100.00' 2.500 in/hr Exfrltration over Surface area Qiscarded Outflow Max=0.01 cfs @ 5.04 hrs HW=100.04' (Free Discharge) 1=Exfiltration (Exfiltration Controls 0.01 cfs) Infiltration System (Tigard St) Type IA 24-hr 100-year Rainfall=4.50" Prepared by NW Engineers, LLC Printed 7/27/2016 HydroCADOD 10,00-12 sin 02505 ©2014 HydroCAD Software Solutions LLC Page 20 Pond 2P: INFILTRATION Hydrograph /// 0.085 to Inflow ()reds l Discarded 0.08 Inflow Area=3,141 Sf 0.075 0.07 Peak EIev=101.89' 0.065 10 0.06 gigStorage=259 of 0.055 nit 0.05 V 0.045kr 0 0.04 a 0 0.035 ifr,�, 0.03 `F �"` 0.025 „ 4. 0.02 , .0,..+* .,a.,. 0.015 ,4,01 cfa 0-7 l9r 7gr ' m's ^0.01 0.005 it .r°r /, ,.' s°..A'e..rr'. 0 1 2 3 4 5 6 7 8 9 10 11 1213 14 15 1617 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ■ ' D �" TM PRETREATMENT .. Design Your Own Detention System ' \� 1k /� SYSTEM \y MEALIER PIPE �, .INSPEC TOR PORT . ` is' '' design " ilii ., a' r,,; ' %`,:--; CC1441181011.11* For t SOLUTIONS we and pricing end completeddworksheet to: t W�, � �r�, dyods@contech-cpi.com ,.. 'K '� e>., / _ *`�', is Project Summa ` / Date: ''''''42,4_,.." y '. �; „ MAHDAROOPEN ' Project Name: : :0. 43 T k- CHAMBER ,� '? '5.....s y � INTEGRATEOENO City,State: ;171=71.1.7,a. "','; " 3 'z,..''''4 WAIL CHAMBER County: '' A ''' Designed By: a . ` ova, as . ,, ,. ,. PAVEMENT ,,. , , ,- 1 1 FINISHED GRADE Company: ELEVATION ' g" ' ;7'-X-'411'; Enter Information in Telephone: �` i { 1 Blue Cells �c j ChainberMaxx Calculator BACKFILL TO GRADE* i•-s"MM Kt, y Storage Volume Required(cf): o- qq A f 1 +=�„{yyfk=Cr+.4. i PFE: ++ , fig COVER OVE Chamber Invert Depth Below Asphalt(ft): "+ .r++_y .,�,3+s+, Limiting Width(ft): e v i., " it r� `--t C '. t. U 02-#.40, 30.3" �, , Porous Stone Backfill Included For Storage: °t, , �� ,_¢ w Depth A:Porous Stone Above Chamber(in): 6.11-''� Wa#erwa Area(ft2) "'' RISE F u_ Depth C:Porous Stone Below Chamber(in) p "� y ,;, / 5"MIN uj I 10.78 \ys ! Stone Porosity(0 to 40%): :40'''., ,:;f_'-'14c +j' .- fC jds.4 f,`r_e,..r, . System Sizing } Use Custom Layout(at right)for layout adjustment Additional Units Required z 0 Custom Layout Required Chambers: 6 Chambers To adjust layout,select thea 'I ate number of chambers m the light blue boxes below. Chamber Storage: 300 cf Porous Stone Storage: 280 cfitai� W , ��; � 4' "�,., Total Storage Provided: 32 ' g 580 cf 119.2% of Req d Storage Rectangular Footprint(W x L): 11 ft x 28.8 ft CONTECH Materials ChamberMaxx Middle Units: 2 Chambers @ 71"installed length ChamberMaxx Start Units: 2 Chambers @ 8'installed length ChamberMaxx End Units: 2 Chambers @ 7'5"installed length Manifold Fittings(1 manifold): 1 ea Tees and lea Elbow Scour Protection Netting: 11 ft long x 7.5'wide Approximate Truckloads: 1 Trucks Construction Quantities 1 Total Excavation: 68 cy(assumes 4"asphalt) Stone Backfill: 26 cy stone Remaining Backfill To Asphalt: 27 cy backfill per specifications i Non-Woven Geotextile: 73 sy for top and sides of excavation 0 1 2 3 4 5 .6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 **Construction Quantities are approximate and should be verified upon final design Cells C 2007 CON t)_CH Stormwater Solutions F------'----------_-__-____.______---_-----____________________ ` --__---_� | / / . / . / / / | . / / `` . ., ` | ` | `� \. | `` \ ` / \ . ` ` /^ ' � / ` / . 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