Loading...
HomeMy WebLinkAboutStudies APPLICANT 6/10/2020380 O Street, Ste 200 Springfield, Oregon 97477 (541) 302-9790 kylemorris@ao-engr.com Drainage Memorandum To: From: Reviewed by: Dale: Taxmap & TL: Re: Project Overview City of Springfield Kyle Moms, PE Scott Moms, PE 5/27/2020 17-03-33-11-00102 A Et O Engineering LLC Kyle Morris r Digitally signed by Kyle Morris, PE PE Date: 2020.05.27 14:11:31 -07'00' Drainage Memorandum for Twenty LLC Partition The applicant is proposing to partition the above listed property into three new parcels. Parcel 1 has an existing duplex structure that is proposed to remain as -is. Parcels 2 & 3 are proposed for new residential dwellings and are to be served by a joint driveway from Dotie Drive. It is proposed to treat and convey stormwater runoff from the proposed joint driveway with an infiltration rain garden. It is also proposed to route runoff from the new roofs through the rain garden. Infiltration An infiltration test was performed on-site on 5!7/2020 by A&O Engineering LLC. Web Soil Survey dassifes the soils on-site as Malabon-Urban Land Complex with a hydrologic soil group C. A hole was dug to approximately 3 feet below ground surface and "bar run" soils were discovered. No groundwater was observed and an Open Pit Falling Head procedure style test was performed. Three trials were run each with a duration of 10 minutes or when all of the water had infiltrated. Below is a graph showing the results from the three different trials run, infiltration test results are attached in the appendix of this memorandum: Infiltration Test s A'S y=21.626x+0.7193 c A Y Z 3.5 =16.9A]x+0.2285 --0—Trial 1 3 --*—Trial2 0 2.5 2 9 Trial W 1.5 y=15.]9x+0.166] ......... Linear (Trial 1) m 3 1 ......••• Linear (Trial 2) 0.5 ••••••••• Linear (Trial 3) a 0.00 0.05 0.10 0.15 0.20 Time Elapsed (Hrs) Figure 1: IMtratimtest trials. The slope of the trendlines shown for each trial were taken as the infiltration rate for each trial. Therefore, the measured infiltration rates were: 27.6 in/hr, 15.8 in/hr and 18.9 in/hr for trials 1-3 respectively. To be conservative the lowest rate is taken as the measured rate. The 2014 Eugene Stormwater Management Manual allows for maximum design infiltration rate of 6 inmr. Thiswould provide a factor of safety of 2.6, therefore the design infiltration rate for the site will be 6 in/hr. Storrnwater Calculation Parameters To perform the stormiwater calculations City of Springfield standards were followed. HydroCAD software was utilized to perform hydraulic and hydrology calculations. Below are the parameters that were used for the stomnwater calculations with their respective sources in (parenthesis). All parameters were taken from the City of Springfield Engineering Design Standards & Procedures Manual unless otherwise noted: Water Quality Precipitation: 0.83" in 24 hours On -Site Design Storm: 2 -Year design storm 2 -Year Precipitation: 3.30" in 24 hours 25 -Year Precipitation: 4.80" in 24 hours Storm Distribution Type: IA-24-hour(NRCS SCS Rainfall Disributions) Manning's n Number: 0.011 Runoff Method: Santa Barbara Urban Hydrograph Method (SBUH) Time of Concentration: Minimum 10 minutes Proposed Storrnwater System It is proposed to construct an infiltration only rain garden to process, treat and convey stomnwater runoff from the joint driveway and future home roofs. Since site soils were shown to have good infiltration characteristics no overflows are proposed for the rain garden. 0 Page 2 Hydraulic Calculations Hydraulic calculations were performed to ensure the infiltration rain garden is sized accordingly to be contained within the stormwater facilities. HydroCAD software was utilized to perform the hydrologic calculations and the HGL determinations. In the table below is a summary of the proposed rain garden physical characteristics. The facility will have an 18" growing medium and 12" rock chamber for additional storage. Table 1: Rain Garden Physeal Charaaenstics The HGLs of the rain garden were checked to ensure no damage would occur on any of the structures. Below is a table summary of each storm event. Table 2. Rai, Garden Elevations and HGLs Bottom Bottom Side Depth Growing Rock Rock Facility Length Width Slopes [ft] Medium Depth Chamber Chamber [ft] [ft] [ft] Len [ft] Width [ft] Grassy 19 5 3:1 1 1.5 19 5 Swale The HGLs of the rain garden were checked to ensure no damage would occur on any of the structures. Below is a table summary of each storm event. Table 2. Rai, Garden Elevations and HGLs As shown in the table above stormwater is completely contained within the rain garden and will not cause damage to surrounding infrastructure. All stormwater runoff is completely infiltrated even during the 25 -Year flood event. Another component is detaining peak flowrates. Since the proposal is to infiltrate all stormwater runoff from the new impervious areas detention requirements are met. Conclusion The proposed stormwater system will serve the development adequately. Water quality will be provided by the vegetative contact time by allowing for infiltration during the water quality storm event. Also, detention requirements are met through all runoff being infiltrated. The proposed system will not cause any damage to the proposed development or surrounding infrastructure. Appendix • HydroCAD calculations for Twenty LLC Partition • Storm Scoping Sheet • Infiltration Test Results 0 Page 3 FL Elev. Flood Ek!v.2-YR HGL 25 -YR HGL Facility [ft] [ft] [ft] [ft] Rain 438.00 439.00 438.23 438.73 Garden As shown in the table above stormwater is completely contained within the rain garden and will not cause damage to surrounding infrastructure. All stormwater runoff is completely infiltrated even during the 25 -Year flood event. Another component is detaining peak flowrates. Since the proposal is to infiltrate all stormwater runoff from the new impervious areas detention requirements are met. Conclusion The proposed stormwater system will serve the development adequately. Water quality will be provided by the vegetative contact time by allowing for infiltration during the water quality storm event. Also, detention requirements are met through all runoff being infiltrated. The proposed system will not cause any damage to the proposed development or surrounding infrastructure. Appendix • HydroCAD calculations for Twenty LLC Partition • Storm Scoping Sheet • Infiltration Test Results 0 Page 3 Dis 2S 3S O O Impervious Driv \Vsouthtuserth House Infiltration Rain Garden Subcat Reach on Link Routing Diagram lar Storm Design &B-20 Prepared by (enter your company name here), Printed 5/27/2020 HyJaDAO®10,00.269n 04993 O 2020 HydroCAD Soa eSolutions LLC Storm Design 5-8-20 Prepared by {enter your company name here) Printed 5/27/2020 HvdroCAM 10.00-28 s/n 04993 02020 HvdroCAD Software Solutions LLC pane 7 Area CN (acres) Area Listing (selected nodes) Description (su bcatch m ent-n umbers) 0.114 98 Impervious Area (1 S, 3S) 0.037 98 Impervious Roof (2S) 0.151 98 TOTALAREA Storm Design 5-8-20 Prepared by {enter your company name here) Printed 5/27/2020 HvdroCAM 10.00-28 s/n 04993 02020 HvdroCAD Software Solutions LLC pane 3 Area Soil (acres) Group 0.000 HSGA 0.000 HSG B Soil Listing (selected nodes) Subcatchment Numbers 0.000 HSG C 0.000 HSG D 0.151 Other 1S, 2S, 3S 0.151 TOTAL AREA Storm Design 5-8-20 Prepared by {enter your company name Ground Covers (selected nodes) Printed 5272020 HSG -A HSG -B HSGC HSG -D Other Total Ground Subcatchment (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.114 Impervious Area 1S,3S 0.037 Impervious Roof 2S 0.151 TOTAL AREA 0.000 0.000 0.000 0.114 0.000 0.000 0.000 0.000 0.037 0.000 0.000 0.000 0.000 0.151 Storm Design 5-8-20 Type IA 24 -hr 01-WQ Rainfall=0.83" Prepared by {enter your company name here} Printed 5/27/2020 HydroCAM 10.00-26 s/n 04993 02020 HydroCAD Software Solutions LLC Paae 5 Time span=0.00-32.00 hrs, dt=0.05 hrs, 641 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchmentl S: Impervious Drive Runoff Area=3,109 sf 100.00%Impervious Runoff Depth=0.63" Tc=10.0 min CN=0/98 Runoff --0.01 cfs 0.004 of Subcatchment2S: South House Runoff Area=1,601 sf 100.00%Impervious Runoff Depth=0.63" Tc=10.0 min CN=0/98 Runoff --0.01 cfs 0.002 of Subcatchment3S: North House Runoff Area=1,848 sf 100.00%Impervious Runoff Depth=0.63" Tc=10.0 min CN=0/98 Runoff --0.01 cfs 0.002 of Pond 4P: Infiltration Rain Garden Peak Eler436.01' Storage=0.000 of Inflovr--0.02 cfs 0.008 of Outflow=0.01 cfs 0.008 of Total Runoff Area = 0.151 ac Runoff Volume = 0.008 of Average Runoff Depth = 0.63" 0.00% Pervious = 0.000 ac 100.00% Impervious = 0.151 ac Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 01-WQ Rainfall=0.83" Printed 5272020 LLC Paae 6 Summary for Subcatchment 1S: Impervious Drive Runoff = 0.01 cfs @ 7.98 hrs, Volume= 0.004 af, Depth= 0.63" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 01-WQ Rainfall=0.83" Area (sf) CN Description 3,109 98 100.00°x6 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 1S: Impervious Drive Xydrograph 6.612_____________ ■auaex 0.611 0.01 cfs ----;- ;- --�-- 6.611 Type-WZ4=iii- 6.01 .01 °'01 01-WQ Rai 6. nfa[C=0rH3"-- Runoff Area=3,109 sf 6.666 - °.006 Runoff Volume=0.004 6.66, of 0." ' Runoff Depth=0.63`-`-- LL 0.665 ' Tc=10.-0-mirv- 0.005 0.004 /_�_w_1Y/�_�_p_p__ ------------- ------------------------------ M=0/98 - 0.004 0.003 0003 0.002 0.002 0.001 0.001 0.000 0 0 1 2 3 4 5 6 7 8 9 Time (hours) 21 22 23 24 25 26 27 28 29 30 31 32 Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 01-WQ Rainfall=0.83" Printed 5272020 LLC Paae 7 Summary for Subcatchment 2S: South House Runoff = 0.01 cfs @ 7.98 hrs, Volume= 0.002 af, Depth= 0.63" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 01-WQ Rainfall=0.83" Area (sf) CN Description 1,601 98 100.00°x6 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 2S: South House Hydro¢q,h ------------------------- T_,_,_,_-__,__, 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 Time (hours) ' Type IA -24 -Fr 9.995 9.995 ' ------------------------------------------ 01-WQ Rainfall=0.83" ------------------------------------------ Runoff Area=1,601 sf Runoff Volume=0.002 of Runoff Depth=0.63"- 9.993 ' Tc=10.0 min 9.992 ------------- CN=0/98- 9.992 ------------------------- 9.99, 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 Time (hours) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 01-WQ Rainfall=0.83" Printed 5272020 LLC Paae 8 Summary for Subcatchment 3S: North House Runoff = 0.01 cfs @ 7.98 hrs, Volume= 0.002 af, Depth= 0.63" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 01-WQ Rainfall=0.83" Area (sf) CN Description 1,848 98 100.00°x6 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 3S: North House Hydrograph 909A �� ❑Runoff °°°' Type IA 24 -hr 0006 ainfall=0.83"- 01-WQ Rainfall--11.83"- 0.90.- 9.90.RunoffArea=1,848 Runoff Area=1,848sf 9.994 Runoff Volume=0.002 of Runoff Depth=0.63" 9.993 ' Tc=10.0 min r< 9.993 ' ------------ _ 0/98 9.992 ------------- - 9.992 ----------- - 9.991 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 39 31 32 Time (hours) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 01-WQ Rainfall=0.83" Printed 5272020 Summary for Pond 4P: Infiltration Rain Garden Inflow Area = 0.151 ac,100.00% Impervious, Inflow Depth = 0.63" for 01-WQ event Inflow = 0.02 cfs 7.98 hrs, Volume= 0.008 of Outflow = 0.01 cfs 7.65 hrs, Volume= 0.008 af, Atten= 43%, Lag= 0.0 min Discarded = 0.01 cfs 7.65 hrs, Volume= 0.008 of Routing by Stor-Ind method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Peak Elev= 436.01' @ 8.38 hrs Surf.Area= 0.002 ac Storage= 0.000 of Flood Elev= 439.00' Surf.Area= 0.017 ac Storage= 0.006 of Plug -Flow detention time= (not calculated: outflow precedes inflow) Center -of -Mass det. time= 4.5 min ( 734.3 - 729.9 ) Volume Invert Avail.Storage Storage Description #1 438.00' 0.004 of 5.00'W x 19.001 x 1.00'H Open Storage Z=3.0 #2 436.50' 0.001 of 5.00'W x 19.001 x 1.50'H Growing Media Z=3.0 0.008 of Overall x 10.0% Voids #3 435.50' 0.001 of 5.00'W x 19.001 x 1.00'H Rock Chamber 0.002 of Overall x 35.0% Voids 0.006 of Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 435.50' 6.000 in/hr Infiltration over Surface area iscarded OutFlow Max=0.01 cfs @ 7.65 hrs HW=435.54' (Free Discharge) 1-1 =Infiltration (Exfltration Controls 0.01 cfs) Storm Design 5-8-20 Type IA 24 -hr 01-WQ Rainfall=0.83" Prepared by {enter your company name here} Printed 5/27/2020 HydroCAM 10.00-28 s/n 04993 ©2020 HydroCAD Software Solutions LLC Paae 10 Pond 4P: Infiltration Rain Garden 0.02cfs 0.04 - ------ - ---- Inflow Area=0.159-ac-- -L-L-L-----L--- Peak Elev=436.01' 0.018' - ----- - - - 7 =b. 00 V _Mora Q � 0.01 cfs � 0.014 --------------------------------------------- ----- ---- *----i-- _ _ �_________ �f �i_______y-----F-F-i-----F--- 0.004 0.002 a 0 1 2 3 4 5 fi ] 8 9 10 11 12 13 14 15 ifi 9 18 19 20 21 22 23 24 2fi 2fi 27 28 29 30 31 32 Time (lwre) ■ me ■ Dwmea Storm Design 5$-20 Type IA 24 -hr 02 -Yr Rainfall=3.30" Prepared by {enter your company name here} Printed 5/27/2020 HydroCAM 10.00-26 s/n 04993 02020 HydroCAD Software Solutions LLC Paae 11 Time span=0.00-32.00 hrs, dt=0.05 hrs, 641 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment l S: Impervious Drive Runoff Area=3,109 sf 100.00%Impervious Runoff Depth=3.07" Tc=10.0 min CN=0/98 Runoff=0.05 cfs 0.018 of Subcatchment2S: South House Runoff Area=1,601 sf 100.00%Impervious Runoff Depth=3.07" Tc=10.0 min CN=0/98 Runoff=0.03 cfs 0.009 of Subcatchment3S: North House Runoff Area=1,848 sf 100.00%Impervious Runoff Depth=3.07" Tc=10.0 min CN=0/98 Runoff --0.03 cfs 0.011 of Pond 4P: Infiltration Rain Garden Peak Elev=438.23' Storage=0.002 of Inflovr--0.11 cfs 0.038 of Outflow=0.09 cfs 0.038 of Total Runoff Area = 0.151 ac Runoff Volume = 0.038 of Average Runoff Depth = 3.07" 0.00% Pervious = 0.000 ac 100.00% Impervious = 0.151 ac Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 02 -Yr Rainfall=3.30" Printed 5272020 .LC Paae 12 Summary for Subcatchment 1S: Impervious Drive Runoff = 0.05 cfs @ 7.98 hrs, Volume= 0.018 af, Depth= 3.07' Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 02 -Yr Rainfall=3.30" Area (sf) CN Description 3,109 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 1S: Impervious Drive Hydro¢g1h -------------------------Type-IA-2-4=hr 9.95 0.00.5 02 -Yr Rainfall=3.30" 0.04 RunoffArea=3,109 sf Runoff Volume=0.018 of 00] Runoff Depth=3.07" 0025 Tc=10.0 min 002 CN=0/98 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 39 31 32 Time (hours) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 02 -Yr Rainfall=3.30" Printed 5272020 .LC Paae 13 Summary for Subcatchment 2S: South House Runoff = 0.03 cfs @ 7.98 hrs, Volume= 0.009 af, Depth= 3.07" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 02 -Yr Rainfall=3.30" Area (sf) CN Description 1,601 98 100.00°x6 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 2S: South House Hydrograph 9.N '_ _'_ _ ■ aueerr 9.928 - 0.03 cfs ' Type -IA'24 -hi - 9.9M 0.024 02 -Yr Rainfall=3.30" 9.922 - Runoff Area=1;601- sf- - 0.°2 Runoff Volume=0.009 of 0.018 0.016 Runoff Depth=3.07"__ E °°" Tc=10.0 min - 0012 CN=0/98 9.91 ------------ 9.998 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 39 31 32 Time (hours) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 02 -Yr Rainfall=3.30" Printed 5272020 .LC Paae 14 Summary for Subcatchment 3S: North House Runoff = 0.03 cfs @ 7.98 hrs, Volume= 0.011 af, Depth= 3.07' Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 02 -Yr Rainfall=3.30" Area (sf) CN Description 1,848 98 100.00°x6 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 3S: North House Hydro¢g1h 9.a34 ---- - _______'__'__'__ ■rweerr ' 0.03 cfs Type -IA-24 9.93 °°M 02 -Yr Rainfall=3.30" 9.926 Runoff Area=1,848 sf 9.924 Runoff Volume=0.011-af-- Runoff Depth=3.07" aa� 001fi Tc=10.0 min 9.914 9.912 9.91 9.998 9.09fi 9.994 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 Time (hours) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 02 -Yr Rainfall=3.30" Printed 5272020 Summary for Pond 4P: Infiltration Rain Garden Inflow Area = 0.151 ac,100.00% Impervious, Inflow Depth = 3.07" for 02 -Yr event Inflow = 0.11 cfs 7.98 hrs, Volume= 0.038 of Outflow = 0.09 cfs 8.17 hrs, Volume= 0.038 af, Atten= 22%, Lag= 11.4 min Discarded = 0.09 cfs 8.17 hrs, Volume= 0.038 of Routing by Stor-Ind method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Peak Elev= 438.23' @ 8.17 hrs Surf.Area= 0.014 ac Storage= 0.002 of Flood Elev= 439.00' Surf.Area= 0.017 ac Storage= 0.006 of Plug -Flow detention time= (not calculated: outflow precedes inflow) Center -of -Mass det. time= 22.9 min ( 693.5 - 670.6 ) Volume Invert Avail.Storage Storage Description #1 438.00' 0.004 of 5.00'W x 19.001 x 1.00'H Open Storage Z=3.0 #2 436.50' 0.001 of 5.00'W x 19.001 x 1.50'H Growing Media Z=3.0 0.008 of Overall x 10.0% Voids #3 435.50' 0.001 of 5.00'W x 19.001 x 1.00'H Rock Chamber 0.002 of Overall x 35.0% Voids 0.006 of Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 435.50' 6.000 in/hr Infiltration over Surface area iscarded OutFlow Max=0.09 cfs @ 8.17 hrs HW=438.23' (Free Discharge) 1-1 =Infiltration (Exfltration Controls 0.09 cfs) Storm Design 5$-20 Type IA 24 -hr 02 -Yr Rainfall=3.30" Prepared by {enter your company name here} Printed 5/27/2020 HydroCAM 10.00-26 s/n 04993 ©2020 HydroCAD Software Solutions LLC Paae 16 Pond 4P: Infiltration Rain Garden 0.11 cfs - - - - --fnfl',ow-Area=U.151'1-ac - ----------Peak- Efpv=438 33'- 0.09 cf6 Storage -O.002 af- ■ m� ■ Dwmea Storm Design 5-8-20 Type iA 24 -hr 25 -Yr Rainfaii=4.80" Prepared by {enter your company name here} Printed 5/27/2020 HydroCADOR 10.00-26 s/n 04993 ©2020 HydroCAD Software Solutions LLC Paae 17 Time span=0.00-32.00 hrs, dt=0.05 hrs, 641 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchmentl S: Impervious Drive Runoff Area=3,109 sf 100.00%Impervious Runoff Depth=4.56" Tc=10.0 min CN=0/98 Runoff -0.08 cfs 0.027 of Subcatchment2S: South House Runoff Area=1,601 sf 100.00%Impervious Runoff Depth=4.56" Tc=10.0 min CN=0/98 Runoff -0.04 cfs 0.014 of Subcatchment3S: North House Runoff Area=1,848 sf 100.00%Impervious Runoff Depth=4.56" Tc=10.0 min CN=0/98 Runoff -0.05 cfs 0.016 of Pond 4P: Infiltration Rain Garden Peak Elev=438.73' Storage=0.004 of Inflov -O.16 cfs 0.057 of Outflow=0.10 cfs 0.057 of Total Runoff Area = 0.151 ac Runoff Volume = 0.057 of Average Runoff Depth = 4.56" 0.00% Pervious = 0.000 ac 100.00% Impervious = 0.151 ac Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 25 -Yr Rainfall=4.80" Printed 5272020 .LC Paae 18 Summary for Subcatchment 1S: Impervious Drive Runoff = 0.08 cfs @ 7.98 hrs, Volume= 0.027 af, Depth= 4.56" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 25 -Yr Rainfall=4.80" Area (sf) CN Description 3,109 98 100.00°x6 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 1S: Impervious Drive Hydrogr9 h 9.985 ---- - - - - -- --------------------------- --- -_-- i__r_ ■aueerr _-------- _________________i_i__i__i_i_ 0.08 cfs 0.975 Type-IA-2-4- ype IA_24-0.07 0.07 25 -Yr Rainfall=4.80" 9.965 9.96 Runoff Area=3,109 sf _ Runoff Volume=0.027 of 9.945 Runoff Depth=4.56" Tc=10.0 min -- 9.935 ------------- CN=0/98 9.93 a.a2s" a0.02 9.91. 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 Time (hours) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 25 -Yr Rainfall=4.80" Printed 5272020 .LC Paae 19 Summary for Subcatchment 2S: South House Runoff = 0.04 cfs @ 7.98 hrs, Volume= 0.014 af, Depth= 4.56" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 25 -Yr Rainfall=4.80" Area (sf) CN Description 1,601 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 2S: South House Hydrograph y 6.624 6.622 6.62 - -- 6.618 6.614 6.612 - ---------- -- - - - - - - - -- FE11 Type IA -2 -4 -Kr _ 25 -Yr Rainfall=4.80"- Runoff Area=1,601 sf - Runoff Volume=0.014 of Runoff Depth=4.56" Tc=10.0 min -- CN=0/98-- ----------------------------- 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 39 31 32 Time (hours) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 25 -Yr Rainfall=4.80" Printed 5272020 .LC Paae 20 Summary for Subcatchment 3S: North House Runoff = 0.05 cfs @ 7.98 hrs, Volume= 0.016 af, Depth= 4.56" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Type IA 24 -hr 25 -Yr Rainfall=4.80" Area (sf) CN Description 1,848 98 100.00°x6 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Subcatchment 3S: North House Hydro¢q,h 6.65 ■ Rumff 6.a4a 0.05 cfs --------- 6.a4fi 6.644 Type IA= Whir 0042 ' 25 Rainfall -4.80`-'= 6.6 ' -Yr 6.630 Runoff Area=1,848 sf 6.634 ' °M _ Runoff Volume=0.016 of 6.63 Runoff Depth=4.56" 6.62fi ° 6.624 ' /� Tc=10_0-Olio G 6.622 6.62 = ------------------------------------------� N '98 6.618 ------------- -------VFY=(FJ0. 0.01fi ' 6.614 6.612 6.61 ' 6.660 0.60fi 4 15 16 17 18 19 29 21 22 23 24 25 26 27 28 29 39 31 32 Time (hours) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 25 -Yr Rainfall=4.80" Printed 5272020 Summary for Pond 412: Infiltration Rain Garden Inflow Area = 0.151 ac,100.00% Impervious, Inflow Depth = 4.56" for 25 -Yr event Inflow = 0.16 cfs 7.98 hrs, Volume= 0.057 of Outflow = 0.10 cfs 8.32 hrs, Volume= 0.057 af, Atten= 40%, Lag= 20.6 min Discarded = 0.10 cfs 8.32 hrs, Volume= 0.057 of Routing by Stor-Ind method, Time Span= 0.00-32.00 hrs, dt= 0.05 hrs Peak Elev= 438.73' @ 8.32 hrs Surf.Area= 0.016 ac Storage= 0.004 of Flood Elev= 439.00' Surf.Area= 0.017 ac Storage= 0.006 of Plug -Flow detention time= 22.6 min calculated for 0.057 of (100% of inflow) Center -of -Mass det. time= 22.6 min ( 684.3 - 661.7 ) Volume Invert Avail.Storage Storage Description #1 438.00' 0.004 of 5.00'W x 19.001 x 1.00'H Open Storage Z=3.0 #2 436.50' 0.001 of 5.00'W x 19.001 x 1.50'H Growing Media Z=3.0 0.008 of Overall x 10.0% Voids #3 435.50' 0.001 of 5.00'W x 19.001 x 1.00'H Rock Chamber 0.002 of Overall x 35.0% Voids 0.006 of Total Available Storage Device Routing Invert Outlet Devices #1 Discarded 435.50' 6.000 in/hr Infiltration over Surface area iscarded OutFlow Max=0.10 cfs @ 8.32 hrs HW=438.73' (Free Discharge) 1-1 =Infiltration (Exfltration Controls 0.10 cfs) Storm Design 5-8-20 Prepared by {enter your company name Type IA 24 -hr 25 -Yr Rainfall=4.80" Printed 5272020 Pond 4P: Infiltration Rain Garden 0.18 0.16 cfs-----'� -'� -'� ---- -I 0.17 --- 4n#low-Ar411.15-1--- -ac-- 0.16 0.15 - Peak Elev=43873' Peak 014 0.13 Storage= =0.0104 of -i-- - -i-,-- 0.12 0A1 0.10 cfs -r _- _________- _____�__� 0.1 0,09 fi.ofi fi.a a.ofi a.o4 aw ■ m. ■ Dwmea PUBLIC WORKS DEPARTMENT / Engineering Division Phone: (541) 726-3753 Fax: (541) 736-1021 STORMWATER MANAGEMENT SYSTEM SCOPE OF WORK --- (Area below this line filled out by Appheard) --- (Please rebsum to MdtStouder @ Cfty of5),rhWfm1dPub1k Works Eh&eerty; For # 736-1021, Phone # 736-1035.) Project Name: Land Partition for Twenty, LLC Applicant: A&O Engineering LLC Assessors Parcel M 17-03-33-11-00102 Date: 4/30/2020 Land Use (s): Low Density Residential Phone #: (541) 302.9790 Project Siz(Acres): 0.36 Fax M Approm Impervious Area: 7,000 5P Email: kylemorris@ao-engr.com Project Description (Include a copy of Assessor's map): The proposed project is to partition the property into more residential lots. A joint drivewaywill be constructed to serve the new residences. Drainage Proposal (Public connection(s), discharge location(s), etc. Attach additional sheet(s) if necessary: It is proposed to construct vegetative stormwater treatment facilities (rein gardens, swales or storm planters) to treat and convey stormwater runoff from the joint driveway. Infiltration will be utilized as much as possiblewith an overflow to the new Date Drive through aweephole in the curb. Runoff from the new residences will either beweepholed or processed through the stormwater facility. Proposed Stormwater Best Management Practices: A vegetated facility (swale, rein garden or planter) is proposed to treat stormwater runoff from the impervious pavement. Infiltration will be utilized from this facility if possible and the overflow will route into the Dotie Drive ROW as discussed above. — (Area below this line tiled outbr the Cts madRetuued to the Applicant) — (At a punumum, all boxes checked by the City on tic frond and back ofthis sheet shall be submitted for an application to be con ylete for submittal, although other requirements may be necessary.) Drainage Study Type (EDSPM Section 4.03.2): (Note, UH may be substituted for Rational Method) ® Small Site Study—(use Rational Method for calculations) ❑ Mid -Level Development Study- (use Unit Hydrograph Method for calculations) ❑ Full Drainage Development Study— (use Unit Hydrograph Method for calculations) Environmental Considerations: ❑ Wellhead Zone: n/a ❑ Hillside Development: n/a ❑ Wetland/Riparian: n/a ❑ Floodway/Floodplain: n a ❑ Soil Type: 76-malabon urban land ❑ Other Jurisdictions: n/a Downstream Analysis: ® N/A Downstream analysis will be necessary if increased from roof and driveway can't be infiltrated on site ❑ Flow line for starting water surface elevation: ❑ Design HGL to use for starting water surface elevation: ❑ Manhole/Junction to take analysis to: Return to Matt Stouder C& City of Springfield, email: mstouder el.s rin field.or.us FAX: 541 7361021 9 of 10 COMPLETE STUDY ITEMS I Far lid iaio.owr. e Bared upon the infornudion provided on the front ofdtis sheet, tic following represents a nuninwm of what is needed far an application to be complete for submittal with respect to drainage; however, ads list should act be used in lieu ofthe Springfield Development Cc& (SDC) or the City's Engineering Design Maraol. Compliance with these requirements does not constitute site approval, Additional site specific alibso nation nary be required. Able: Upon scoping sheet subnuttal, ensure completedform has been signed in the space provided below: Interim Design Standards/Water Quality (EDSPM Chapter 3) Req'd N/A ® ❑ All non -building rooftop (NBR) impervious surfaces shall be pre-treated (e.g. multi-chambered catchbasinw/oil filtration media) for stonmwater quality. Additionally, a minimum of 50% of the NBR impervious surface shall be treated by vegetated methods. ® ❑ Where required, vegetative stonsweter design shall be consistent with interim design standards (EDSPM Section 3.02), set forth by the Bureau of Environmental Services (BES) or Clean Water Services (CWS). �] ❑ For new NBR impervious area less than 15,000 square feet, a simplified design approach may be followed as specified by the BES for vegetative treatment. ® ❑ If a mormovater treatment swale is proposed, submit calculations/specifications for sizing, velocity, flow, side slopes, bottom slope, and seed mix consistent with either BES or CWS requirements. ® ❑ Water Quality calculations as required in Section 3.03.1 of the EDSPM ® ❑ All building rooftop mounted equipment, or other fluid containing equipment located outside of the building, shall be provided with secondary containment or weather resistant enclosure. General Study Requirements (EDSPM Section 4.03) ❑ Drainage study prepared by a Professional Civil Engineer licensed in the state of Oregon. ❑ A complete drainage study, as required in EDSPM Section 4.03.1, including a hydrological study map. ❑ Calculations showing system capacity for a 2 -year storm event and overflow effects of a 25 -year storm event. ❑ The time of concentration (Tc) shall be determined using a 10 minute start time for developed basins. Review of Downstream System (EDSPM Section 4.03.4.C) ❑ 0 A downstream drainage analysis as described in EDSPM Section 4.03A.C. On-site drainage shall be governed by the ��r{{ Oregon Plumbing Specialty Code (OPSC). ❑ yJ Elevations of the HGL and flow lines for both city and private systems where applicable. Design of Storm Systems (EDSPM Section 4.04) W❑ Flow lines, slopes, rim elevations, pipe type and sizes clearly indicated on the plan set. ® ❑ Minimum pipe cover shall be 18 inches for reinforced pipe and 36 inches for plain concrete and plastic pipe materials, or proper engineering calculations shall be provided when less. The cover shall be sufficient to support an 80,000 lb load without failure of the pipe structure. ❑ Meaning's "n" values for pipes shall be consistent with Table 4-1 of the EDSP. All storm pipes shall be designed to achieve a minimum velocity of three (3) feet per second at 0.5 pipe full based on Table 4-1 as well. Other/Misc ❑ Existing and proposed contours, located at one foot interval. Include spot elevations and site grades showing how site drains ® ❑ Private stommater easements shall be clearly depicted on plans when private stommater flows from one property to another ❑ Drywells shall not receive runoff from any surface w/o being treated by one or more BMPs, with the exception of residential building roofs (EDSP Section 3.03.4.A). Additional provisions apply to this as required by the DEQ. Refer to thewebsite: w ..deg.state.or.ushvg/Umndwa/uichome.hcm for moreinfonnation. ❑ Detention ponds shall be designed to limit nmoff to pre -development rates for the 2 through 25 -year stomp events `Thisform shall be bschuted as an nttachmen4 inside thefrout cover, of the stormwrder shut, `IMPORTANT: ENGINEER PLE4SEREAD BELO WAND SIGN.' As the engineer of record, I hereby certify the above required items are complete and included with the submitted stonmwater study and plan set. Signature: Kyle Morris Date: 5/27/2020 10 of 10 7 O J C W J C n 0 0 v C N J W C Q O O W _ _ - o 3 a v Q 0 0 v 3