Loading...
HomeMy WebLinkAboutStudies APPLICANT 4/20/2021STORMWATER ANALYSIS REPORT FOR: NINTH ST PROPERTIES, LLC 431 35TH STREET Map 17-02-31-24, Tax Lots 11900 Springfield, OR 97478 (Pre -Submittal Case # Prepared by SSWEN61NEERS,, CIVIL STRUCTURAL BUILDINGDESIGN SURVEYING LAND USE PLANNING 2350 Oakmont Way, Suite 105 Eugene OR 97401 (541) 485-8383 Contact: Michael A Cox, PE Job #20-7774 _R�rdENB:_ iz� Based on the City of Springfield Engineering Design Standards and Procedures Manual —2012 City of Eugene Stormwater Management Manual 2014 Contents ProjectOverview...................................................................................................1 Methodology............................ ...... .......................... .............................................3 Analysis................................................................................................................3 Engineering Conclusions ......................................................................................4 Attachments: Appendix A: Stormwater Scooping Sheet Appendix B: Stormwater Plan Appendix C: Stormwater Design Calculations Appendix D: Web Soil Survey Map Appendix E: Geotechnical Infiltration Report Appendix F: Stormwater Planting Schedule Exhibit Project Overview Location: 431 35th Street, Springfield, OR. Map and Taxlot: Lot 11900 of Assessor's Map 17-02-31-24 Vicinity Map: T,apn Park ntl E Q t - s4 Development: The property is a 0.93 acre parcel of land comprised of Tax Lot 11900 of Lane County Assessor's Map 17-02-31-24. The subject property is currently under residential use and developed with an existing single-family dwelling and detached garage to remain (431 35th Street). The subject property is bounded on the West by 35th Street, and is bounded on the North, South and East by previously developed private properties. Said adjacent private properties are under separate ownership. The subject property is currently designated "Low Density Residential' per the Comprehensive Plan, and is currently zoned LDR Low Density Residential. The applicant desires to subdivide the subject property into six lots, each of which is proposed to accommodate one single-family dwelling for a total of 6 dwelling units following subdivision approval. This results in a proposed net density of 6.45 dwelling units per acre, which complies with the permitted density range of 6 to14 dwelling units per net acre within the LDR zoning district per Section 3.2-205 of the Springfield Development Code (SDC). The project site lies within 10 year travel time of the Maia potential wellhead (Wellhead Map - 2013 City of Springfield Development & Public Warks — Technical Services Division) with the Q Street Floodwaysubbasin. The public stormwater follows the drainage system in catchments 101135. According to the 10 -Year Future model (Figure 3-10 of the Stormwater Facility Master Plan — 2008), the nearest major piped system has no excess capacity. The stormwater scoping sheet, dated 10/21/2020 indicates that detention is not applicable (See Appendix A). Permits required for the project include local building, electrical, and mechanical. Stormwater discharge is covered under the City of Springfield MS4 NPDES permit. Methodology The downstream capacity of the public system is not sufficient. New impervious surface runoff will not be detained per the Stormwater Scooping Sheet (Appendix A). The stormwater treatment facility will treat all proposed impervious surfaces, with design overflow directed to the existing stormwater system located to the north of the property. Facility layout can be seen on plans found in Appendix B and a planting exhibit (Appendix F) SITE SOIL CLASSIFICATIONS The entirety of the soil at the project site is hydrologic soil group D. Infiltration testing performed by K&A Engineering (Project. 20066) produced no infiltration over a 24 hour period. Infiltration will not be used on this site. (See Appendix E: Geotechnical Infiltration Report) 2226A—Awbrig-Urban Land Complex Hydrologic Soil Group D (See Appendix D: Web Soil Survey Map, USDA NRCS Web Soil Survey, and accessed 3/3021) STORMWATER BMP— Stormwater planters will be used to treat the complete runoff from the property. Three planters located on the north side of the access road will be used to collect all runoff. Loll and the existing garage on Lot 6 shall be treated at Planter 1, Lots 2 & 5 shall be treated at Planter 2, and Lots 3&4 shall be treated at Planter 3. A portion of the access road will be divided between the three planters for treatment. Planters were designed using the presumptive method using a maximum buildout area including roof and driveway surfaces. Actual size of planters exceeds the required area of the proposed planters. Individual lots shall, at time of construction, demonstrate that the produced impervious area is less than what the proposed planters are capable of. Analysis Design Storms: Water Quality Storm = 0.25 Inches per hour (in/hour) Conveyance Storm = 10Y-10 Min Storm 3.60 in/hour Computation Methods: Rational Method Stormwater Quality Retention Volume Storm Pipe Conveyance Software Used: Excel Design Coefficients: C = 0.90 Impervious Pavement 1.1 = 25Y Adjustment Factor Design Calculations: See Appendix C: Stormwater Design Calculations Flood Control & Conveyance Conveyance of runoff is based on a minimum of 3.0 feet per second flow at 10 year -10 minute design storm conditions and minimum pipe slope of 1.0 percent. Engineering Conclusions Stormwater design and plans conform to the City of Springfield Development Code sections 4.3- 110 and Chapters 3 & 4 of the Springfield Design Standards and Procedures Manual, adopted 2012. Stormwater from all proposed impervious pavement areas will be treated and infiltrated consistent with vegetated stormwater planter design. For conveyance, the system is designed to handle flow beyond the 10 year 10 minute design storm to the planter. An O and M agreement specific to the facilities must be filed. Stormwater facilities constructed must be properly operated and maintained for the life of the facility. Stormwater Plans: See attached Appendix B: Stormwater Plan INN SPRINGFIELD terr-c• 225 FIFTH STREET DEVELOPMENT AND PUBLIC WORKS OREGON SPRINGFIELD, OR 97477 PHONE: 541.726.3753 FAX; 541.726.1021 www.spdngheld-orgov STORMWATER MANAGEMENT SYSTEM SCOPE OF WORK ----------- ._-------------- ------- ------------ Area below this linefilled out Inc Applicant) -------------- –___________________________ (Please return to Clayton McF.achern (an City of Springfield Development and Public Works; Far #736-1021, Phone #736-1036), email; cmcoachern@spring6eldror.gov Project Name: Tentative Subdivision for Ninth St. Properties, LLC Applicant: Jason Goshert, SSW Engineers Inc. Assessors Parcel #: 17-02-31-24, Tax Lot 11900 Date: 10/21/2020 Land Use(s): Residential Phone #: 541-485-8383 Project Size (Acres): 0.93 Acres Fax #: 541-485-8384 Approx. Impervious Area: Roof: +/- 6,800 to 8,500 at Email: jasong@sswengineers.mm ruh, +t_ a ono sf Project Description (Include a copy of Assessor's map): Proposed 6lot residential subdivision for 1 existing dwelling and 5 new / future dwellings. See attached Site Assessment of Existing Conditions and preliminary Land Division Tentative Plan. Drainage Proposal (Public connection(s), discharge locatiori etc. Attach additional sheet(s) if necessary: New impervious areas are proposed to drain to privately maintained on-site vegetated stormwater treatment facilities (and detention facilities if necessary) that collect and discharge treated runoff into the public system via piped connections to the existing 30" public stormwater main which runs along the north side of the proposed subdivision. Stormwater Best Management Practices: dens and/or vegetated planters. r _-_—__-- (Area below this line lined out by the Cily and Returned to the Applicant) --------------- (At a minimum, all boxes checked by the City on the front and back of this sheet shall be submitted f or an a lication to be corn fete (or submittal, although other ce wirements may be necessa .! Drainage Study TvW (FDSPM Section 4 03 2Y (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: 10 year TOT ❑ Hillside Development: NIS ❑ Wetland/Riparian: N/a ❑ Floodway/Floodplain: N/a E]Soil Type: 6-Awbirq Urban Land Complex -likely a E]Other Jurisdictions N/a Downstream Analysis yrdrologic group CID soil -infiltration test equired ® N/A ❑ Flow line for starting water surface elevation: ❑ Design HGL to use for starting water surface elevation: ❑ Manhole/Junction to take analysis to: Return to Clayton McEachem @ City of Springfield, email: cmceachern@springfield-or gov, FAX: (541) 7361021 COMPLETE STUDY ITEMS eroffiaa used * Based upon the information provided on defrost of this sheet, the following represents a minimum ofwhat is needed for an application to be complete far submittal with respect to drainage, however, this list should not be used in lieu ofthe Springfield Development Code (SDC) or the City's Engineering Design Manual. Compliance with these requirements does notcwnsthute site approval, Additional site specific information may be required. Note: Cann scoping sheet submittal, ensure completed form has been signed in the space provided below: Interim Design Standards/Water Quality (EDSPM Chapter 3' Req'd N/A ❑/ ❑ All non -building rooftop (NRR) impervious surfaces shall be pretreated (e.g. multi-chambered catchbasin w/oil filtration media) for stormwater quality. Additionally, a minimum of 50% of the NRR impervious surface shall be treated by vegetated methods. Z ❑ Where required, vegetative storm eater design shall be consistent with design standards (EDSPM Section 3.02), set forth in Chapter 2 of the Eugene Slormwater Management Manual. E ❑ For new N13R impervious area less than 15,000 square feet, a simplified design approach may be followed as specified by the Eugene Stormwater Management Manual (Sce2A.1). ® ❑ If a stormwater treatment swale is proposed, submit calculations/specifications for sizing, velocity, flow, side slopes, bottom slope, and seed mix consistent with City of Springfield or Eugene's Stormwater Management Manual. 0 E] Water Quality calculations as required in Section 3.03.1 of the EDSPM. nnly required it proposed area don't meet COE © ❑ standards fo treat ant All building rooftop mounted equipment, or other fluid containing equipment locate rural c of the building, shall be provided with secondary containment or weather resistant enclosure. General Study Requirements EDSPM Section 4.03 7/ ❑ Drainage study prepared by a Professional Civil Engineer licensed in the state of Oregon. Q ❑ A complete drainage study, as requited in EDSPM Section 4.03.1, including a hydrological study map. Z❑ Calculations showing system capacity for a 2 -year storm event and overflow effects of a 25 -year storm event. 0 n The time of concentration (Te) shall be determined using a 10 minute start time for developed basins. U A downstream drainage analysis as described in EDSPM Section 4.01 On-site drainage shall be governed by the Oregon Plumbing Specialty Code (OPSC). Elevations of the HGL and flow lines for both city and private systems where applicable. /1 ❑ Design of Stomt Systems (EDSPM Section 4.04). FA 0 Flow lines, slopes, rim elevations, pipe type and sizes clearly indicated on the plan seb 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 leas. The cover shall be sufficient to support an 80,000 lb load without failure of the pipe structure. © Manning'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. © Existing and proposed contours, located at one foot interval. Include spot elevations and site grades showing how site drains. F/ F-1 Private stormwater easements shall be clearly depicted on plans when private stortnwater flows from one property to another. Drywells shall not receive runoff from any surface w/o being treated by one or more RMPs, with the exception of residential building roofs (EDSP Section 3.01 Additional provisions apply to this as required by the DEQ. Refer to the website: Its://w v.deq.state.or.us/wo/uic/uic.bm for more information. ❑ Detention ponds shall be designed to limit runoff to pre -development rates for the 2 through 25 -yen storm events, onsite soils may limit Infiltration of treatment areas, but should still be maximized as much as possible to limit downstream discharge. *This form shall be included as an attachment, inside the front cover, ofthe sformwater study. 'IMPORTANT: ENGINEER PLEASE READ BELOW AND SlCNr As the engineer of record, I hereby certify the above required items are complete and included with the submitted stormwater study and plan set. Signature Date Form Version 5: June 2015 APPENDIX B SITE STORMWATER PLAN 1� �J ® ON F B R IN I NOTES SYMBOLS pZ�i"OVERFLOW 12URCCUT2"CB ' 1YEUB CUT 1 ALLSIORMWATER PIPE ARE PRO UNLESS OTHERWISE 8J PROPOSED LLEANOVi, SEE VC]1 '12 O.C. NOTED "c 8S PROPoSED WWNSAOUT ^�OROVANG MEDIUM 2. RANTING FOR STORMWATER FACILITIES BY OTHERS. � v 1 GROW N0 MEDIUM � — s — PROPOSFC STORM LINE EXISTING SOL PROPOSED PERFORATED STORM LINE m ` ` MAX MAXIMUM LOT IMPERVIOUS SURFACE LOMPALT50 O b"OF i'MPAC �vMEW w CRUSHED ROCK PERAFE OT R SOFT PROPOSED 5lORMWAiEH PLANTER o TOREED LOT] 2A. BO FT 777 CRUsEO ROCK B, PIPE PERFORATED LOTS 25]S BO FT SEE 0 TWIIT OF yn LO259150 FT STORMWATER PLANTER 1 o V jjm/—�-,BN LOU I 515 BO FT COMPAOTBOILORB OF OCOMPACTED : VSHEC ROCK STORMWATER PLANTER 3PLANTER 3 0 / NOTE'. LOT MAX IMPERVIOUS SURFACE ISTHE PROPOSED BUILDING & OR VEWAY SURFACE ®I( X11 I zv wz U., Ce mrs vm vFL-mn va-<easa an L-111 zv i-.xfro o A q7 AT FT E �,.,�F.. m=oT ..rv�� ,e�rt M:I VrFwE. LITYARV. _iM—T } F.�T PT 'Ell RID r:. �=aFT r�aRr..w _ 4 IT DO DU IIS .n.a ALL 1 F. c ..],aR 1aVIA — — — gg �Fa� bU . Fame 1 L— IF�.>Po e Itszes ^ n i n ------ e - vo o BE— aen' .uwizw mw1vei Yry IIII SITE STORMWATER PLAN 1� �J ® ON ENGINEERS. vmrti uF'o Wwn w aMls••Iwsex O J o zJ_W_ J � � aW� ���Wo XXw FaF.-o zOviw zaLh�z 0HON'd Ln (f)O N ❑ d Q Z J EVISIONB SITE STORMWATER PLAN zo-ma MAC xX�47oo F B R IN I O'OVERFLOW pZ�i"OVERFLOW 12URCCUT2"CB ' 1YEUB CUT a'O '12 O.C. "c ^�OROVANG MEDIUM � v 1 GROW N0 MEDIUM � EXISTING SOL m ` ` ---f—oG O NG ME LOMPALT50 O b"OF i'MPAC �vMEW w CRUSHED ROCK PERAFE 3 STORMWATER 'OF —LO PACOPO o TOREED • 777 CRUsEO ROCK B, PIPE PERFORATED SEE 0 TWIIT OF yn PUNTER STORMWATER PLANTER 1 o jjm/—�-,BN COMPAOTBOILORB OF OCOMPACTED : VSHEC ROCK ENGINEERS. vmrti uF'o Wwn w aMls••Iwsex O J o zJ_W_ J � � aW� ���Wo XXw FaF.-o zOviw zaLh�z 0HON'd Ln (f)O N ❑ d Q Z J EVISIONB SITE STORMWATER PLAN zo-ma MAC xX�47oo O'OVERFLOW pZ�i"OVERFLOW ' 1YEUB CUT '12 O.C. "c GROW N0 MEDIUM b` EXISTING SOIL m ` ` ---f—oG O NG ME LOMPALT50 O b"OF i'MPAC CRUSHED ROCK PERAFE 3 STORMWATER PLANTER2 o ENGINEERS. vmrti uF'o Wwn w aMls••Iwsex O J o zJ_W_ J � � aW� ���Wo XXw FaF.-o zOviw zaLh�z 0HON'd Ln (f)O N ❑ d Q Z J EVISIONB SITE STORMWATER PLAN zo-ma MAC xX�47oo O'OVERFLOW _ XG IN, 1R"CURBOVT BE 12 C ---f—oG O NG ME E%15TING 901E yn jjm/—�-,BN COMPAOTBOILORB OF OCOMPACTED VSHEC ROCK STORMWATER PLANTER 3PLANTER 3 0 ENGINEERS. vmrti uF'o Wwn w aMls••Iwsex O J o zJ_W_ J � � aW� ���Wo XXw FaF.-o zOviw zaLh�z 0HON'd Ln (f)O N ❑ d Q Z J EVISIONB SITE STORMWATER PLAN zo-ma MAC xX�47oo �1 SITE GRADING PLAN �0 N SYMBOLS EKIISTING ELVATION TOP OF CURB tX STI NG ELEVATION PROP W EO SECT ELEVATION 32PROPWEDBPOTELEVAIION-TOPOFCURD SQ PdOPWEDSPOT ELWATION - MATCH EXISTING �SE" L PROPOSED SECT ELEVATION -FLOW LINE PROPOSED CUT PROPOSED FILL ESTIMATED CUTIFILL QUANTITY CUT -333 CUBIC YAROS FILI -313 CUBIC YARDS CUT A FILL NCLUDES REMOVAL AND R EPIACEMENT 12 OF CRUSHED COMPACTEO ROCKAND 3 -ASPHALT FOR RE DRIVE AISLE g 0 Y SSW ENGINEERS. I:��� Ax L -I —WR K O J o ZJm aW! W W F- O > m ~WQ�6 I-a~NO W o4~LL H � ZaM z y�9aa y5 O N on=o Q < gz� L NG 2o-nTa d- RAP M MPC :BEI�J�oo APPENDIX C Complete this form for each drainage catchment in the project site that is to be sized per the Presumptive Approach. Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate calculations with the facility. The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF) For infiltration facilities in Class A or B soils where no infiltration testing has been perhomed use an infiltration rate of 0.5 in/hr. For all facilities use a maximum soil infiltration rale of 2.5 in/hr fortopscillg rowing medium. Loose "Yes' from the dropdown boxes below next to the design standards requirements for this facility. Pollution Reduction (PR)Yes Flow Control (FC) No Destination(DT) No -whhfftaromanio moat be,hi as the nutty tyro to meet destination requirements Total Square Footage Impervious Area= Stormwater Surface FiTypeonlln Facility Sizing Spreadsheet sgft Rainfall D 24 Hour Storm, NRCS Type 1A Rainfall Distribution Impervious Area Cl City of Eugene Flow Control Version 2.1 Project Information 7217 Project Name: NINTH ST PROPERTIES Date: 3/17/21 Project Address: 431 35TH STREET Permit Number: SPRINGFIELD. OR 97478 Catchment ID: PLANTER Designer: MICHAEL A COX P.E. Company: SSW ENGINEERS INC Complete this form for each drainage catchment in the project site that is to be sized per the Presumptive Approach. Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate calculations with the facility. The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF) For infiltration facilities in Class A or B soils where no infiltration testing has been perhomed use an infiltration rate of 0.5 in/hr. For all facilities use a maximum soil infiltration rale of 2.5 in/hr fortopscillg rowing medium. Loose "Yes' from the dropdown boxes below next to the design standards requirements for this facility. Pollution Reduction (PR)Yes Flow Control (FC) No Destination(DT) No -whhfftaromanio moat be,hi as the nutty tyro to meet destination requirements Total Square Footage Impervious Area= 7217 sgft Total Square Footage Pervious Area- 0 soft Impervious Area Cl 9BI Flow Control Pervious Area Cl 85 Total Square Footage of Drainage Area= 7217 im Time of Concentration Post Development= 10 min Weighted Average Cis Site Data -Pre Development (Data in this section is only used if Flow Control is required) Pre -Development Cl Time of Concentration Pre -Development= iD min Soil Data Tested Soil Infiltration Role- 5inlhr(See Notes) Destination Design=inlhr Design Soil Infiltration Rale= 25 rrri Soil Infiltration Rate Design Stos ed For Calculations rmUs Re uirement Rainfall De h Desi n Storm Pollution Re duction ,'I, Water Qui Flow Control 1 3 flinches lFlood Control Destination 1 3 flinches lFlood Control Surface Lengl Facility Side Slirm Max. Ponding Depth in Stormwater Facility= Depth of Growing Medium (So 3/3021-12:24 PM Planter Facility Surtace Facility Surface Pont Facility Bottom Facility Bottom Pont Basin Vo Ratio of Facility Area to Impervious Pollution Reduction-Calculation Resul Peak Flow Rate to Stormwater Facility -Mecfs Peak Facility Overflow Rate= 0.000 cfs Total Runoff Volume to Stormwater Facilitycf Total Overflow Volume= 0 cf Max. Depth of Stormwater in Facility=in Drawdown Time=hours We 71Facility Sizing Meets Pollution Reduction Standards? YES Meets Requirement of No Facility Flooding? EE] YES Meets Requirement for Maximum of 18 Hour Dmwdown Time? Flow Control-Calculation Results Peak Flow Rate to Stormwater Facility = 0.140 is ofs Peak Facility Overflow Rate=pool, Total Runoff Volume to Stormwafo r Facility= 2016 of Total Overflow Volume=cf Peak Off -Site Flow Rate Max. Depth of Stormwater in Facility= 6.0 in Filtration Facility Underdrain=ds Drawdown Time= 2.3 [Ours Pre-Develo mens Runoff Data Peak Flow Rate - 0.086 cis Total Runoff Volume= 1265 of FRT-1 Facility Sizing Meets Flow Control Standards? NW Meets Requirement for Post Development offsite Now less or equal to Pre-Development Flow? NW Meets Requirement for Maximum of 18 Hour Drawdown Time? Destination-Calculation Results Peak Flow Rate to Stommwater Facility = IJrA cis Peak Facility Overflow Rate= WA cfs Total Runoff Volume to Stormwater Facility N/A cf Total Overflow Volume= NIA cf Max. Depth of Stormwater in Facility= n Drawdown Time= WA hours N/A Facility Sizing Meets Destination Standards? NIA Meets Requirement of No Facility Flooding? NIA IMeelas Requirement for Maximum of 30 hour Drawdown Time? 3130121-12 24 PM Stormwater Surface Filtype 1 /l Rainfall D Facility Sizing Spreadsheet 24 Hour Storm, NRCS Type 1A Rainfall Distribution City of Eugene Version 2.1 Address: 431 35TH STREET Permit Number: SPRINGFIELD OR 97478 Catchment ID: PLANTER 2 MICHAEL A COX, P.E. SSW ENGINEERS INC Complete this form for each drainage catchment in the project site that is to be sized per the Presumptive Approach. Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate calculations with the facility. The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF) For infiltration facilities in Class A or B soils where no infiltration testing has been pedromed use an infiltration rate of 0.5 ill For all facilities use a maximum soil infiltration rate of 2,5 in/hr for topsoil/growing medium. noose "Yes" from the dropdown boxes below next to the design standards requirements for this facility Pollution Reduction (PR)Yes Flow Control (FC)l No Destination(DT) No 'An mnio-auon faduty must he chosen as the faculty type m meet destination monomania Total Square Footage Impervious Area= 7292 sgft Impervious Area Cl 98 Total Square Footage of Drainage 0 Weighted Average Total Square Footage Pervious Area=osgft Pervious Area Cl85 Time of Concentration Post Development= 10 min F— Pre -Development Cl 85 Time of Concentration Pre -Development= 10 min Tested Soil Infiltration Rate= inlhr(see Now.) Destination Design=®in/hr Design Soil Infiltration Rate= 2.5 in/hr Soil Infiltration Rate Re uirement I Rainfall Depth Design Storm Pollution Reduction 1 4 inches Water Quality Flow Control 1 3.6 inches Flood Control Destination 3.6 inches Flood Control Facility Type= Surface Width= Surface Length= Facility Side Slopes= Max. Pending Depth in Stormwater Facility= Depth of Growing Medium (Soil)= Filtration Stormwater Planter Facility Surface Areal 5 ft Facility Surface Perimeter- 42 fl Facility eoltom Area= 0 to 1 Facility Bottom Perimeter= 6 in Basin Volume= 18 in Ratio of Facility Area to Impervious Area= 210 sgft it sgft ft Of 94 210 94 105.0 0.029 3/30/21-12:24 PM Pollution a uchon-Calculation esu is Peak Flow Rate to Stormwater Facility = 0.051 ofs Peak Facility Overflow Rate= 0.000 cis Total Runoff Volume to Stormwater Facility ]15 of Total Overflow Volume= 0 of Max. Depth of Stormwater in Facility 5.9 in Drawdown Time= 0.2 hours Yes Facility Sizing Meets Pollution Reduction Standards? =Meets Requirement of No Facility Flooding? YES Meets Requirement for Maximum of 18 Hour Drawdown Time? Flow Control -Calculation Results Peak Flow Rate to Stormwater Facility = 0.147 cfs Peak Facility Overflow Rate- 0,129 cfs Total Runoff Volume to Stormwater Facility = 203] of Total Overflow Volume= 942 of Peak Off -Site Flow Rate Max. Depth of Siormwaterin Facility= 6.0 in Filtration Facility Underdrain= 0.012 cfs Drawdown Time= 2.5 hours Pre -Development Runoff Data Peak Flow Rate = 0 08] cfs Total Runoff Volume= 1278 of NW Facility Sizing Meets Flow Control Standards? NW Meets Requirement for Post Development offsite flow less or equal to Pre -Development Flow? NW Meets Requirement for Maximum of 18 Hour Drawdown Time? Destination -Calculation esU t3 Peak Flow Rate to Stormwater Facility = N!A cfs Peak Facility Overflow Rate= N%A cfs Total Runoff Volume to Stormwater Facility NIA cf Total Overflow Volume= NIA cf Max. Depth of Stormwater in Facility- NIAlin Drawdown Time= N/A hours N/A Facility Sizing Meets Destination Standards? ----]N;A Meets Requirement of No Facility Flooding? WA Meets Requirement for Maximum of 30 hour Drawdown Time? 3/30/21-12:24 PM Stormwater Surface Filtrationllnfiltration Facility Sizing Spreadsheet 24 Hour Storm, NRCS Type 1A Rainfall Distribution City of Eugene Name: NINTH ST PROPERTIES Date: 3/17121 Address: 431 35TH STREET Permit Number: SPRINGFIELD. OR 97478 Catchment ID: PLANTER do MICHAEL A COX. P.E. ,y: SSW ENGINEERS INC Complete this form for each drainage catchment in the project site that is to be sized per the Presumptive Approach. Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate calculations with the facility. The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF) For infiltration facilities in Class A or B soils where no infiltration testing has been perfromed use an infiltration rate of 0 5 in/hr. For all facilities use a maximum soil infiltration rale of 2.5 in/hr for topsoil/growing medium. rouse "Yes" from the dropdown boxes below next M the design standards requirements for this facility. Pollution Reduction (PR)Yes Flow Control(FC) No Destination(DT) No 'nn unnerve acility must be chosen as lire faamgrypa to ideal destination requirements Total Square Footage Impervious Area- 6974 sgit Impervious Area CN=l 98 Total Square Footage of Drainage Area= 6974 sit Weighted Average CN= 98 Total Square Footage Pervious Area- 0sft g Pervious Area CN= 85 Time of Concentration Post Development= 10 min Time of Concentration Tested Soil Infiltration Rare -in /hr(See Nem 4) Destination Design=®in/hr Design Soil Infiltration Rate= 2.5 in/ Soil Infiltration Rate Re uirement Rainfall De th Desi n Storm Pollution Reduction 1 4 inches Water Qualit Flow Control 3.6inches Flood Control Deafin. I 3.8 inches IFlood Control Surface Wid Surface Leng Facility Sid. Slop, Max. Pending Depth in Stormwater Facility= Depth of Growing Medium (Sc 3/30/21-12:25 PM Facility Su Facility Surface Facility Br Facility Bottom Ratio of Facility Area to Pollution a uchon- alcu anon Results Peak Flow Rate to Stormwater Facility = 0.049 cis Peak Facility Overflow Rate= 0.000 cis Total Runoff Volume to Stormwater Facility 684 of Total Overflow Volume= 0 cf Max. Depth of Stormwaterin Facility= 59 in Drawdown Time= 0.2 hours =Facility Sizing Meets Pollution Reduction Standards? YES Meets Requirement of No Facility Flooding? YES Mesta Requirement for Maximum of 18 Hour Drawdown Time? Flow Control-Calculation Results Peak Flow Rate to Stormwater Facility = 0.135 cfs Peak Facility Overflow Rate= 0.123 ds Total Runoff Volume to Stormwater Facility =dof Total Overflow Volume= 905 cf Peak Off -Site Flow Rate Max. Depth of Stormwater in Facility=in Filtration Facility Underdrain= 0.012 cls Drawtlown Lme=hours Pre-Development Runoff Data Peak Flow Rate= 0.083 cis Total Runoff Volume = 1223 cf =Facility Sizing Meets Flow Control Standards? 7 Meets Requirement for Post Development offsite flow less orequal to Pre-Development Flow? MA Mesta Requirement for Maximum of 18 Hour Drawdown Time? Destination-Calculation esul[s Peak Flow Rate to Stormwater Facility = N!A cis Peak Facility Overflow Rate= N/A cis Total Runoff Volume to Stormwater FacilityAcf Total Overflow Volume= N/4 d Max. Depth of Stpmrwater in Facility=in Drawdown Time=Hours NTA' Facility Sizing Meets Destination Standards? N.A Meets Requirement of No Facility Flooding? NA IMeets Requirement for Maximum of 30 hour Drawdown Time? 3/30/21-12'25 PM N�i �iii���u�°����n° ���� u ��s ��� �n ���� �� liini �■ni ,iI um n � i■n hmi �' im ■�i � � � n� I;I ISI �Y■ Y� IYI ■■I ■1! 11 IIII 11 ■111 ■III 11 �1 Y �I� II�I�II �ii� mei uin ni�i� iiii� i���� APPENDIX D M... Sl M dE %E iLl M.@ S dti N M m M 2 N N � Z a� � m �N k^ m O zQ 2U M.S i65 vII1 dIL � / .©<�, {1; ƒ■ ■ /0 _ -2- \\\( Eo k{ § \/ § \ ( !q 3 4# .©<�, {1; ƒ■ ■ /0 _ Soil Map—Lane County Area, Oregon Map Unit Legend 431 35th Sl, Springfield, Oregon Map Unit Symbol Map Unit Name Acres in AOI Percent of AOl 2226A to land complex, 0 2.2 100.0% l0 2 percent slopes Totals for Area of Interest 2.2 USOn Natural Resources Web Soil Survey 3/30/2021 '� Conservation Service National Cooperative Soil Survey Page 3 of 3 APPENDIX E K& A ENGINEERING, INC. 91051 S. WILLAMETTE STREET7 P. O. Box 8486, Coau RG, OR 97408 A (541) 684-9399 KAENGINEERS.COM en g n e e ri n g November 30, 2020 Project: 20066 Ninth St. Properties, LLC 17605 NW Autumn Ridge Dr. Beaverton, OR 97006 Subject: Infiltration Test Summary 431 35'^ Street, Springfield, Oregon. PURPOSE AND SCOPE At the request of the Lane County, K & A Engineering, Inc. has completed one (1) infiltration test for the purpose of determining allowable infiltration rates for the design of stormwater facilities associated with the subject development. The scope of our services included one (1) infiltration tests, conducted on November 19, 2020 and this Written Report. INFILTRATION TEST RESULTS Locations and Depths One (1) shallow infiltration test were made at the subject project site to characterize the Infiltration rates for design and specification of stormwater retention/detention facilities for the project. The test location and depth (3 -feet) were specified by the project architect. The test location has been labelled as IT -1. The test was made at an approximate depth of 3 -ft below the existing ground surface. See the attached Site Plan drawing for approximate location. Procedure • 6 -inch diameter borings were pre -drilled to a 3 -foot depth using 6 -inch solid stem auger and our geotechnical drill. • 5 -inch diameter PVC casing was placed in the holes and pushed approximately 6 -inches into the soil at the bottom of the hole to form the requisite soil plug. • Water was placed in the casing to a minimum height of 1 -foot above the bottom of the borehole. • Measurement of drawdown commenced within approximately 4 -hours of initial filling. • Observations continued for a period of 24 -hours after initial filling Subsurface conditions Subsurface soils, based on visual inspection of the soil cuttings during the advancement of the auger, consist of (approximately): Infiltration Test Results k*a 431 35ih Street, Springfield OR November 30, 2020-K& A Engineering, Inca Project No.: 20066 englneeriag • Undocumented FILL: 1.5 -feet of dark gray,damp, soft organic SILT with woody debris, over • Organic CLAY: 1.5 -feet of dark brown, damp, soft, silty -CLAY. In general, the soil layer at the depth of infiltration test can be described as silty -CLAY. Infiltration Observations Infiltration was observed in the casing over a period of 24 -hours. No changes in the water column height inside the casing could be detected over the test period SUMMARY AND RECOMMENDATIONS Test indicates extremely poor infiltration capacity of the organic silty -CLAY at the depth tested and we recommend that these soils are not suitable for conventional on-site storm water disposal systems such as soakage trenches. We recommend that detention or retention facilities can be used but should not be designed to incorporate any significant infiltration back into soils at the site, at least at this depth. Based on our research of logs for nearby wells', groundwater is likely to be found as shallow as 10 -feet. Further testing at greater depths may find increased infiltration capacity, but additional testing should also be accompanied by at least one deep boring to determine actual groundwater levels at the site. Deep infiltration testing, if successful, requires deeper stormwater handling facilities, which cost more to construct. K & A Engineering, Inc. should be contacted if further exploration and testing is desired to improve the viability of on-site stormwater disposal or storage. 'Oregon Water Resources Department Well Report Query, See Well Report Query (state.or.us) Page 12 Infiltration Test Results7 431 35`^ Street, Springfield OR A November 30, 2020 K &A Engineering, Inc. - Project No.: 20066 engineering LIMITATIONS AND USE OF GEOTECHNICAL RECOMMENDATIONS This report has been prepared forthe exclusive use of Ninth St. Properties, LLC for the subject project. The geotechnical testing, analysis, and recommendations forthis report meet the standards of care of competent geotechnical engineers providing similar services at the time these services were provided. We do not warrant or guarantee site surface subsurface conditions. Infiltration testing in this case was made without investigating the depth of groundwater, which can have a significant effect on seepage characteristics. We made reasonable assumptions of groundwater depth from well log report of nearby sites. The scope of our services does not include construction safety precautions, techniques, sequences, or procedures, except as specifically recommended in this report. Our services should not be interpreted as an environmental assessment of site conditions. Thank you for the opportunity to be of service. Please call me if you have any questions. Sincerely, Michael Remboldt, P.E., G.E. K & A Engineering, Inc. ;SPED PROFF''9 GINE �2 � F y 19.474. 9 u OREGON �, Eo TFhggER 4p � DENNIS VE r u:: f'LY➢7 Page 13 APPENDIX F + -(- JUNCUS EFFUSUS (COMMON RUSH) 4" POTS - 12" O.C. + 318" TO 314" ROUND ROCK NON-FLOATABLE MULCH 4" TO 8" COBBLES AT INLET LOCATIONS PIPE INLET OVERFLOW PIPE INLET PLANTER 1 CO . . . a 83'-22' 1 m �-12" INLET IN CURB m @ 12' O.C., TYP. 47,-041" O E F • PLANT�R/3 08, INLET ..��,. LL...PCANTER2 i. PIPE INLET It -12" INLET IN CURB NOTES @ 12' O.C., TYP. - PLANTINGS PER CITY OF SPRINGFIELD, OREGON: ENGINEERING DESIGN STANDARDS AND PROCEDURES MANUAL (2012) APPENDIX 6B, ZONE A; MOIST TO WET CONDITIONS & CITY OF EUGENE STORMWATER MANAGEMENT MANUAL (2014); APPENDIX D, ZONE A STORMWATER PLANTING SCHEDULE EX1 J SCALE: V=5-0" ieo zo-ma ENGINEERS LAND DIVISION TENTATIVE PLAN FOR: *SSW NINTH ST. PROPERTIES, LLC CIVIL STRUCTURAL BUILBINGRESIBN SURVEYING IANBUSEPLMNING MAP 17-02-31-24, TAX LOT 11900 43135TH STREET SPRINGFIELD OR 97478