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HomeMy WebLinkAboutStudies APPLICANT 2/23/2023Stormwater Management Plan and Drainage Study Carver Family, LLC Springfield, Oregon For Carver Family, LLC 112 Timson Drive Folsom, CA 95630 &79232PE ` �4LLY SIGNED OREGON EXPIRES: 12/31/24 February 3, 2023 ENGINEERING= Since 1977 civil - transportation structural • geotechnical SURVEYING w .Branch Engineering.com Contents Page No. 1.0 Introduction............................................................................................................... 1 2.0 Existing Conditions.................................................................................................1 2.1 Topography 1 2.2 Soils 1 2.3 Existing Storm System 1 3.0 Proposed Development.........................................................................................2 4.0 Stormwater Constraints........................................................................................3 5.0 Proposed Development Stormwater Description.......................................3 6.0 Hydrologic and Hydraulic Analysis..................................................................4 6.1 Computer Model 4 6.2 Computer Model Data 4 7.0 Pre -Developed Runoff Rates...............................................................................5 8.0 Post -Developed Runoff Rates.............................................................................5 9.0 Maintenance...............................................................................................................5 10.0 Conclusion..................................................................................................................5 Appendices Description Appendix A Stormwater Management Drainage Basin Map Appendix B Site Soils and Map Appendix C HydroCAD Analysis Existing Site Analysis Post Development Analysis Appendix D Operation and Maintenance Plan O Branch FWneerft, Inc 1.0 INTRODUCTION This Stormwater Management Plan (SWMP) report has been prepared for a Site Plan Review application and construction permits to build an industrial warehouse development at the property currently known as 3654 Kathryn Avenue. The subject site is south of Olympic Street and east of 35- Street. The subject property is identified as Tax Map 17-02-30-43, Tax Lot 6401. The stormwater runoff from the roof drains and a portion of the drive surface will be directed to an existing stormwater drainage trench and a majority of the drive surface will be directed to a treatment swale. The purpose of this report is to document the design and establish maintenance requirements. 2.0 EXISTING CONDITIONS The subject site is located in Springfield, Oregon on the north side of Kathryn Avenue just east of 35m Street, and consists of 3.13 acres of private property. The development site includes the westerly 1.91 acres of the subject site and the drainage ditch located within an easement on the neighboring property to the west (Tax Lot 6400), which encompasses 0.14 acres (totaling 2.05 acres). Of the development site, 0.53 acres consist of existing improvements and 1.52 acres consist of pervious areas including existing stormwater drainage facilities 2.1 TOPOGRAPHY The subject site is underdeveloped with improvements on the easterly 1.75 acres. The developed portion has one main structure, which currently houses an automobile refurbishment and design facility, several storage containers, a 3,800 square foot tent, and associated parking and vehicle circulation area. The undeveloped portion is a grassy/brushy field with a drainage ditch on its southerly side that continues west through the neighboring property. The whole site is quite flat with slopes not exceeding 0.5%(except in existing stormwater facilities), and elevations ranging from 474.7 to 481.7 feet above sea level. 2.2 SOILS The Natural Resources Conservation Service (NRCS) Web Soil Survey maps the development site as containing only Malabon-Urban land complex (76). Malabon-Urban Land Complex is described as a well -drained silty and clayey alluvium and is in Hydrologic Soil Group C. A soils map and individual soil information is provided in Appendix B. 2.3 EXISTING STORM SYSTEM The western portion of the lot is open and vegetated with grass. This area has a private stormwater drainage facility along the southerly edge of the property that continues to the west through the neighboring property (Tax Lot 6400). The facility lies wholly within private property and terminates at the corner of Kathryn Avenue and 35° Street with a ditch inlet. This inlet connects directly into a public stormwater manhole within the 35° Street right-of-way. The facility is grassed, slopes at approximately 0.34%from east to west for 440 -feet, is about 2 -feet -deep with 3:1 (33%) side slopes, and is about 12 -feet -wide. The westerly 100 -feet of the facility widens to 18 -feet with a larger flat bottom. At the time the facility was originally constructed it was designed strictly for conveyance of stormwater for the improvements located on the eastern portion of the subject site. Currently, there is no stormwater infrastructure within the northerly half of the Kathryn Avenue right- of-way. All stormwater on the subject site is conveyed through the private stormwater drainage facility into the public main located in the 35- Street right-of-way. This public system consists of a 24 -inch pipe that conveys the water northward to the public main within the Olympic Street right-of-way. Per the City of Springfield Stormwater Basin Master Plan, the subject site is located in both Sub -Basin 9-265 and 9_266. Per the Development Initiation Meeting (811 -22 -000063 -PRE) there are no capacity issues within the public piped system downstream of the site. However, the northerly side of Kathryn Avenue has ponding water during the rainy season due to its lack of stormwater drainage facilities. 3.0 PROPOSED DEVELOPMENT The development site consists of four sub -basins; all of which are mapped on the attached basin map in AppendixA and listed as follows: 1) the stormwater drainage facility (orange outline), 2) the westerly parking area and drive aisle (red outline), 3) the proposed building roof area (green outline), 4) the easterly vehicular circulation and stormwater treatment area (black outline). A longer description of each is below BASIN 1: The stormwater drainage facility will be removed from the frontage of the subject site, but will remain within the property to the west (Tax Lot 6400). This will continue to convey the stormwater from the existing building and pavement located on the subject site to the east that are not part of this development. To achieve this, the existing culvert will be extended to the easterly end of the new stormwater drainage facility. The existing stormwater drainage facilitywill also convey all runoff from the development site as well. BASIN 2: The westerly parking area will include two (2) dual chambered catch basins with drop in filter inserts, as a form of mechanical treatment, that will capture and convey stormwater to Basin 1. This area constitutes 0.48 acres of pavement, which is 41.796 of the development site's non -roof impervious area. BASIN 3: The roof area of the development site will be directed to the stormwater pipes located in Basin 2. The roof area does not need to be treated per the City of Springfield's Engineering Design Standards and Procedures Manual. BASIN 4: The easterly vehicular circulation and stormwater treatment area consists of 3 separate areas each with their own characteristics as part of the development site 1. A portion of the area is composed of pervious landscaping with a centrally located stormwater treatment facility. The facility is a grassy swale designed to convey and treat all the stormwater from Basin 4 and direct it to Basin 1. 2. This area consists of the truck wells and other impervious area that cannot drain to the existing stormwater catch basins located within Basin 4. A strip drain will be located near the bottom of each truck well area. All stormwater will be conveyed to the stormwater treatment facility located in Sub -Basin 4a. It should be noted that the building will have a roof overhang along its easterly side for hydraulic separation for at the base of the truck wells. 3. This area consists of new and existing impervious non -roof area that will be captured by the existing stormwater catch basins located within the development site. The catch basins are currently tied into the existing stormwater pipe network. The connection will be severed from the existing pipe network, and the catch basins' outfall will be directed to the stormwater treatment facility described above. This area constitutes 0.48 acres of pavement, which is 58.3% of the development site's non -roof impervious area. 4.0 STORMWATER CONSTRAINTS Three significant constraints affect the site. One is the existing public infrastructure: elevation of the existing stormwater main located on 35'° Street, its relation to the existing stormwater flowlines on site, and the lack of a stormwater system located within the northerly half of Kathryn Avenue. The second is the flatness of the subject site. The third is the design requirements of the proposed structure. The existing stormwater main in 35m Street has a flowline approximately 5 feet below the asphalt surface. The existing outfall structure's flowline on the subject site is a little less than 4 feet above and approximately 480 feet east of the public stormwater main's flowline. All proposed stormwater systems must fall between these constrain, which limited the types of vegetated treatment that could be considered. City standards require this project to construct and install a public drainage ditch on the northerly side of the existing Kathryn Avenue road pavement. However, connection into the drainage ditch is not possible, as the flowline of the public drainage ditch is above the piped and treatment facility flowlines on site. Due to the subject site having an average slope of 0.596 falling from the northeast corner to the southwest corner, the slopes of the proposed stormwater system (pipes and swales) are limited between 0.396 and 0.496 for the main transmission lines. This constraint forces all pipes to be 12" if their grade is less than 0.5% in order to achieve cleansing velocity per chapter 13 of the ODOT Hydraulics Manual. The proposed structure having truck wells and ramps, along with a flush parking lot to the west required the building to be a certain elevation to prevent excessive grades leading from the street to the building entrance and still allow for the strip drains near the bottom of the truck wells to flow to the stormwater treatment facility without the need for a sump pump. 5.0 PROPOSED DEVELOPMENT STORMWATER DESCRIPTION The stormwater facilities will be designed to meet Chapter 3 of the City of Springfield's Engineering Design Standards and Procedures Manual for water quality. The proposed development consists of a swale located between the proposed building and the Kathryn Avenue right-of-way. The swale is only designed to convey and treat the non -roof impervious area in Basin 4 of the development site. It consists of a 106-foot4ong by 2 -foot -wide bottom with 3:1 (3396) side slopes. Per Chapter 4 of the City of Eugene Stormwater Management Manual, a set of design requirements must be met during the water quality design storm (0.83 inches / 24 hours, per the City of Springfield's Engineering Design Standards and Procedures Manual) to consider the swale as a treatment facility. The following is a list of those standards, and how the proposed stormwater treatment facility meets those standards. Description of Standard Design Swale Proposed Swale Max. flow depth 4 inches 3.6 inches Max. water velocity 0.9 feet per second 0.13 feet per second Min. hydraulic residence time 9 minutes 15.2 minutes Min. longitudinal slope 0.50% 0.35% Manning's Number (grassed) 0.25 0.25 The Proposed Swale meets or exceeds the Design Swale standards in all but the minimum longitudinal slope. This is due to the first of the described constraints in the Stormwater Constraints section above. However, due to the other constraints and the soils on site, this option met more standards than any other facility type for treatment. 6.0 HYDROLOGIC AND HYDRAULIC ANALYSIS 6.1 COMPUTER MODEL In preparing this Stormwater Management Plan for the project site, Branch Engineering utilized the HydroCAD 10.0 software. This is a computer program used to model, analyze and design hydrosystems of drainage basins. HydroCAD computes Santa Barbara Urban Hydrographs (SBUH) using rainfall data supplied by the designer. The SBUH method is a recognized analysis method by the City of Springfield and Oregon DEQ and is appropriate for a project site of this size. Once the appropriate data is input to HydroCAD, each drainage basin has a hydrograph and runoff flow for the desired storm event 6.2 COMPUTER MODEL DATA HydroCAD needs data supplied from the designer that describes the drainage basin in order to create the hydrograph. Below is the data that is needed to describe each drainage basin. o Storm Event For the purposes of this design, the design storm events are as follows: Water Quality Event 0.83 inches / 24 hours 2 -year Storm Event 3.30 inches / 24 hours 10 -year Storm Event 4.30 inches / 24 hours 25 -year Storm Event 4.80 inches / 24 hours o Impervious Area Pavement, sidewalks, hardscapes and rooftops are all impervious surfaces. Each drainage basin's impervious area was calculated using the proposed site plan. o Pervious Area Lawns and open space are pervious areas. Each drainage basin's pervious area is all that area that is not impervious. o Runoff Curve Numbers Each drainage basin has a Runoff Curve Number for the impervious areas and the pervious areas. The Runoff Curve Number is based on the type of surface and the Hydrologic Group of the soils. Table 2-2a of Urban Hydrology for Small Watersheds (commonly referred to as TR -55) has the curve number for impervious area as 98 and 89 for pervious. o Time of Concentration The time of concentration was estimated at 10 minutes for each sub basin, as each sub basin is less that one acre in size. For such a small area, this is a reasonable assumption 7.0 PRE -DEVELOPED RUNOFF RATES As described in the existing stormwater system section above, the downstream system that the development site drains to has no capacityissues. This section and the next are here to provide clarity to the changes to the runoff rate from pre- to post -developments. The development site, as described in Section 2.0 above, has existing parking, vehicle circulation area, undeveloped land and a stormwater drainage facility all of which currently drain into the city storm system. Using HydroCAD stormwater modeling software, it has been determined that the existing conditions of the development site has peak pre -developed runoff rates of 0.82 cis, 1.29 cfs, and 1.54 cis during the 2 -year, 10 -year, and 25 -year design storms, respectively. See Subcatchment EC (Bxisting Conditions) in Appendix C for the HydroCAD results and the Pre - Developed Runoff Rate results. 8.0 POST -DEVELOPED RUNOFF RATES The proposed stormwater system, as described in Section 3 Proposed Development and Section 5 Proposed Development Stormwater Description, drains to the same point that the existing stormwater system currently drains to. Using HydroCAD stormwater modeling software, the table below shows the peak post -development runoff rates compared to the peak pre -developed runoff rates Design storm Peak Pre -developed Runoff Rates (cfs) Peak Post -developed Runoff Rates (cfs) Difference (cls) 2 -year 0.82 1.53 0.71 10 -year 1.29 2.01 0.72 25 -year 1.54 2.25 0.71 See Appendix C for the HydroCAD results of the post -developed runoff. ' 1 11:1\\:\ The facilities will be maintained privately since they receive water only from private improvements and will be constructed under a Building Permit. Maintenance will be per the City of Springfield's Stormwater Management Manual. Repairs to storm facilities shall be made in accordance with City of Springfield Public Works Department. Detailed Operations and Maintenance information is included in Appendix D. 10.0 CONCLUSION Compliance has been established for the stormwater system designed herein for the new site improvements. Water quality is accomplished through a grassy swale which treats 58.396 of the development site's non -roof impervious area and dual chambered catch basins with drop in filter inserts, as a form of mechanical treatment, will treat 41.796 of the development site's non -roof impervious area. The proposed runoff from the site does not need to meet pre -development flow rates as the existing conveyance system downstream has adequate capacity. /_\»:1►IQ KV90 Stormwater Management Drainage Basin Map APPENDIX B Site Soils and Map APPENDIX C HydroCAD Analysis Existing Site Analysis Post Development Analysis Operation and Maintenance Plan TABULATION OF COVERAGE TABULATION OF COVERAGE ONLY INCLUDES THE LIMITS OF m DISTURBANCE. DEVELOPMENT SITE .a ` TM: 17-02-30-43, TL 5401 + TOTAL SITE AREA 2.05 AC EXISTING CONDITIONS IMPERVIOUS AREA PARKING AND CIRCULATION 0.53 AC PERVIOUS AREA 1.52 AC PROPOSED CONDITIONS ,,. IMPERVIOUS AREA ROOF, PARKING AND SIDEWALKS 1.81 AC PERVIOUS AREA 0.24 AC ® INCREASE IN IMPERVIOUS AREA 1.28 AC ------ `°` BASIN 1 or 'Mor - ® PRIVATE STORMWATER DRAINAGE FACILITY ® ORANGE OUTLINE 0.14 AC _----_ar. BASIN 2 a WESTERLY PARKING AREA 'pa1 '� e —Ion— RED OUTLINE 0.48 AC eas . BASIN 2 y E I sRur BUILDING ROOF AREA —I — GREEN OUTLINE 0.66 AC d a "'amA+nr torn;. -I '£ —(E)SO — BASIN 4 all WmA .:— 5�„e as EASTERLY VEHICULAR CIRCULATION AND ® STORMWATER TREATMENT FACILITY ° 41 _ a ki ' BLACK OUTLINE 0.77 AC o- h. iBASIN 3 g no.as az000se 4 d�rt� _ /ID'ICATBP' I�q.�l + x :Io BASIN 2� rrsui.w :. BASIN 4 — 11 is F on rh � 1 e•,� it u a'21111 u 0 fl<NMW •.� ° YRwetu [rmnu e c`1 — BASIN 1 — � '4 �: 9 -- emam z z w ,can — m ,as sraa 0.°xmH+S mwa smGnRx n _ re nN4 nn <,aco,"x21 g eu.xfgnm. tvu{ —,r rt, — KATfIRYV It MhtW q mHiA q° --(q +M�q°----Iq OHW x21 sae cq+w—ur.. m..�Rw.—E ..—Iq..—cEw.gr—Ip.x �p IwN—crn.—mw-a�qM,+ >na„.. all saw ar++�K ° °x. n� rn nrw carp .vn lA g n v rn— y hb revr � � I � �' M1gp n� en xY¢smv mmur s+r¢r uvn 10 a` � I 100 ru ror ewr ry�ii wvesl m4 11 o90 MINEERING= °nun:R°rtxnon f°`S U RV E Y I HG nlcal nr.mnnn, !H U I— J 0 m J ^ � J is; Zw Z 0 Q I m Q LLo Z 0 LLI = w oma U .nW pllMS dr.grar ROC war- 21-749 STORMWATER BASIN MAP sr rt or rr = Sal Map—Lane County Area, Oregon ; (Carron Family, LLC - SMP) W R 9 9 9 9 0 9 I 6 � aa�xa"ry snmo sr� snsa snmo s>vm snvo sma soma stay saw a t Wpy le: 1:909RPnkdmAlmEsape(11"xes�tl 6. p N Nis a m m a m a -A a a m m zoo M�POJahn: WDM 3or CmrrmwtlYala:1W584 FAgeEa: NM]me10N 1W584 LiNatural Resources IM1Fb Sol Survey 5/23/2022 Conservation Serme Nalmal Cooperative S lSurvey Page 1 a3 Shc Map—Lane County Area, Oregon (Carver Family, LLC - SVMAP) _SD, Natural Resources Mill Sol Survey 5232D22 all Conservation Service National Cooperative Shc Survey Page 2 of 3 MAP LEGEND MAP INFORMATION Area at lmerasr tA09 Spot Area The sal surveys that comprise your AOI were mapped at Area of Interest(AOI) 1:20,090. Q Stany Spat Soils Vey Sony Spa Waming: Shc Map may not be vapid al Mrs scale. 0 Soil Map Unit Polygons 9 VJrf Spot p Enlargement of maps beyond the scale of mapping can cause ,.,. Soil Map Unic Lines misunderslantling of the tletail of mapping and accuracy of soil 4 Other line placement. The maps do not show the small areas of Soil Map Unit Points soils that could have been shown at a more detailed Special Line Feelcontrasting Special Point Features scale. Lg Blowout water Features Streams and Canals Please rely on the bar scale on each map sheet for map ® Boraw Pit measurements. Trenspartatian Clay Spot Rails Source of Map: Natural Resources Conservation Service 0 Closed Depression Web Soil SurveyLIRL: Interstate Highways Coordinate System: Mill Mercator(EPSG:3B5]) Graces Pit US Routes Maps from the Web Soil Survey are based on the Web Mercator Gravely Spa Malor Roads projection, which preserves and shape but schdistorts and area, projection that preserves area, such as the ion that ® Landfill Local Roads Abersdistance o Albers equal-area conic projection, should be used if more Lara Flaw accurate calculations of distance or area are req uired, Background aga Marsh or swamp . Aerial Photography This productis generated from the USDA­gRCS certified data as of Ne version dates) listed below. * Mine or Query SSurvey Area: Lane County Area, Oregon ® Miscellaneous Ydscer Suavely 21 y Area Data: Version 19, OctOc12T, 2021 ® Perennial VMmer Shc map units are labeled (as space allows) for map scales y, Rock Outcrop 1:50,ODD or larger. A Saline Spot Dates) aerial images were photographed: Jun 12, 20191 19, 2019 Sandy Spot The odhophoto or other base map on which the soil lines were Severely Eroded Spot compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor Sinkhole shifting ofmap and boundaries may be evident. �p Slide or Slip Sodic Spot _SD, Natural Resources Mill Sol Survey 5232D22 all Conservation Service National Cooperative Shc Survey Page 2 of 3 Sal Map�ane Connly Area, Oregon Map Unit Legend Carver Family, LLC - SMP LSIA Natural Resources Web Soil Survey 5/23/2022 iMi Conservation Serme National Cooperative Soil Survey Page 3 of3 Map Unit Symbd Map Unit Name Acres in AOI Percent of AOI 76 Malabori lrban land cornplex 2.0 100.0% Totals for Area of Interest 20 100.0% LSIA Natural Resources Web Soil Survey 5/23/2022 iMi Conservation Serme National Cooperative Soil Survey Page 3 of3 Map Unit Description: Malabon-Urban land complex --lane Cmnty Area, Oregon Carver Family, LLC - SMP Lane County Area, Oregon 76—Malabon-Urban land complex Map Unit Setting National map unit symbol. 238t Elevation. 300 to 650 feet Mean annual precipitation: 40 to 60 inches Mean annual air temperature: 52 to 54 degrees F Frost -free period. 165 to 210 days Farmland classification. Farm land of statewide importance Map Unit Composition Malabon and similar soils. 50 percent Urban land. 45 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Malabon Setting Landform: Terraces Landform position (three-dimensional): Tread Down-slope shape: Linear Across -slope shape: Linear Parent material. Silty and clayey alluvium Typical profile H1 - 0 to 12 inches. silty clay loam H2 - 12 to 42 inches: silty clay H3 - 42 to 60 inches: clay loam Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Drainage class. Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high (0.20 to 0.57 inlhr) Depth to watertable: More than 80 inches Frequency of floodirg: None Frequency of ponding: None Available water supply, 0 to 60 inches. High (about 11.4 inches) Interpretive groups Lard capability classification (irrigated): 1 Lard capability classification (nonirrigated): 1 Hydrologic Sal Group: C Ecological site: R002XCOO6OR -Stream Terrace Group Forage suitability group: Well drained < 15% Slopes (G002XY002OR) Other vegetative classification. Well drained < 15% Slopes (G002XY002OR) LSM Natural Resources Wiab Soil Survey 5/23/2022 irk Conservation Serves National Cooperative Soil Survey Pagel oft Map Unit Desorption: Malabon-Urban land complex --lane County Area, Oregon Carver Family, LLC - SMP Hydric soil rating: No Description of Urban Land Interpretive groups Land capability classification (irrigated): None specified Lard capabildy classification (nonirrigated): 8 Hydric sal rating. No Data Source Information Soil Survey Area: Lane County Area, Oregon Survey Area Data: Version 19, Oct 27, 2021 LSM Natural Resources Mb Soil Survey 5/23/2022 211 Conservation Service National Cooperatirve Soil Survey Page 2 oft 1B Zg 3B 4B Basin 1 - tormwater Bas 2 - Westerly Drainag Facility arking Area asin 3 - Roof Area Basi 4 -Easterly Vehi lar Circulation a d Stormwater reatment Area 6R 5R Outfall Channel Stormwater Treatment Facility Routing Diagram for Concept 1 Subcat Reacb on Link Prepared by Branch Engineering, Printed 1/17/2023 HydroCAD® 10.00-20 s/n 10784 0 2017 HydroCAD Software Solutions LLC Carver Family, LLC Concept 1 Type IA 24 -hr 2 yr Rainfall=3.30" Prepared by Branch Engineering Printed 1/162023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 1 Summary for Subcatchment EC: Existing Conditions Runoff = 0.82 cfs @ 8.03 hrs, Volume= 0.289 af, Depth= 1.69" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 2 yr Rainfall=3.30" Area (sf) CN Description * 56,867 74 Undeveloped area * 23,036 98 Existing Asphalt * 9,278 98 Existing Stormwater Drainage Facility 89,181 83 Weighted Average 56,867 63.77% Pervious Area 32,314 36.23% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Carver Family, LLC Concept 1 Type IA 24 -hr 10 yr Rainfall=4.30" Prepared by Branch Engineering Printed 1/162023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 2 Summary for Subcatchment EC: Existing Conditions Runoff = 1.29 cfs @ 8.01 hrs, Volume= 0.435 af, Depth= 2.55" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 10 yr Rainfall=4.30" Area (sf) CN Description * 56,867 74 Undeveloped area * 23,036 98 Existing Asphalt * 9,278 98 Existing Stormwater Drainage Facility 89,181 83 Weighted Average 56,867 63.77% Pervious Area 32,314 36.23% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Carver Family, LLC Concept 1 Type IA 24 -hr 25 yr Rainfall=4.80" Prepared by Branch Engineering Printed 1/162023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 3 Summary for Subcatchment EC: Existing Conditions Runoff = 1.54 cfs @ 8.01 hrs, Volume= 0.511 af, Depth= 2.99" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 25 yr Rainfall=4.80" Area (sf) CN Description * 56,867 74 Undeveloped area * 23,036 98 Existing Asphalt * 9,278 98 Existing Stormwater Drainage Facility 89,181 83 Weighted Average 56,867 63.77% Pervious Area 32,314 36.23% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Carver Family, LLC Concept 1 Type IA 24 -hr VVQ Rainfall=0.83" Prepared by Branch Engineering Printed 1/162023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 4 Summary for Subcatchment 1B: Basin 1 - Stormwater Drainage Facility Runoff = 0.02 cfs @ 7.97 hrs, Volume= 0.007 af, Depth= 0.63" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr WQ Rainfall=0.83" Area (sf) CN Description * 5,895 98 Stormwater Drainage Facility 5,895 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 2B: Basin 2 -Westerly Parking Area Runoff = 0.08 cfs @ 7.97 hrs, Volume= 0.025 af, Depth= 0.63" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr WQ Rainfall=0.83" /_TMTMII=0101 20,575 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 3B: Basin 3 -Roof Area Runoff = 0.11 cfs @ 7.97 hrs, Volume= 0.034 af, Depth= 0.63" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr WQ Rainfall=0.83" 28,233 98 28,233 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Carver Family, LLC Concept 1 Type IA 24 -hr 144Q Rainfall=0.83" Prepared by Branch Engineering Printed 1/162023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 5 Summary for Subcatchment 4B: Basin 4 -Easterly Vehicular Circulation and Stormwater Treatment Ai Runoff = 0.13 cfs @ 7.97 hrs, Volume= 0.040 af, Depth= 0.63" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr WO Rainfall=0.83" Area (sf) CN Description * 33.482 98 Easterly Vehicular Circulation and Stormwater Treatment Area 33,482 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Reach 5R: Stormwater Treatment Facility Inflow Area = 0.769 ac,100.00% Impervious, Inflow Depth = 0.63" for WO event Inflow = 0.13 cfs 7.97 hrs, Volume= 0.040 of Outflow = 0.11 cfs 8.10 hrs, Volume= 0.040 af, Atten= 10%, Lag= 7.8 min Routing by Dyn-Scor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 0.13 fps, Min. Travel Time= 15.2 min Avg. Velocity = 0.05 fps, Avg. Travel Time= 36.8 min Peak Storage= 103 cf @ 8.10 hrs Average Depth at Peak Storage= 0.30' Bank -Full Depth= 1.00' Flow Area= 5.0 sf, Capacity= 1.25 cfs 2.00' x 1.00' deep channel, n= 0.250 Side Slope Z -value= 3.0'f Top Width= 8.00' Length=118.0' Slope= 0.0035 'f Inlet Invert= 476.20', Outlet Invert= 475.79' Summary for Reach 6R: Outfall Channel Inflow Area = 2.024 ac,100.00% Impervious, Inflow Depth = 0.63" for WO event Inflow = 0.31 cfs 8.03 hrs, Volume= 0.106 of Outflow = 0.31 cfs 8.03 hrs, Volume= 0.106 af, Atten= 0%, Lag= 0.0 min Carver Family, LLC Concept 1 Type IA 24 -hr IAKQ Rainfall=0.83" Prepared by Branch Engineering Printed 1/162023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 6 Routing by Dyn-Scor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Carver Family, LLC Concept 1 Type IA 24 -hr 2 yr Rainfall=3.30" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 7 Summary for Subcatchment 1B: Basin 1 - Stormwater Drainage Facility Runoff = 0.10 cfs @ 7.94 hrs, Volume= 0.035 af, Depth= 3.07' Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 2 yr Rainfall=3.30" Area (sf) CN Description * 5,895 98 Stormwater Drainage Facility 5,895 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 2B: Basin 2 -Westerly Parking Area Runoff = 0.37 cfs @ 7.94 hrs, Volume= 0.121 af, Depth= 3.07' Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 2 yr Rainfall=3.30" /_TMTMII=0101 20,575 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 3B: Basin 3 -Roof Area Runoff = 0.50 cfs @ 7.94 hrs, Volume= 0.166 af, Depth= 3.07' Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 2 yr Rainfall=3.30" 28,233 98 28,233 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Carver Family, LLC Concept 1 Type IA 24 -hr 2 yr Rainfall=3.30" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 8 Summary for Subcatchment 4B: Basin 4 -Easterly Vehicular Circulation and Stormwater Treatment Ai Runoff = 0.60 cfs @ 7.94 hrs, Volume= 0.196 af, Depth= 3.07" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 2 yr Rainfall=3.30" Area (sf) CN Description * 33.482 98 Easterly Vehicular Circulation and Stormwater Treatment Area 33,482 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Reach 5R: Stormwater Treatment Facility Inflow Area = 0.769 ac,100.00% Impervious, Inflow Depth = 3.07" for 2 yr event Inflow = 0.60 cfs 7.94 hrs, Volume= 0.196 of Outflow = 0.57 cfs 8.06 hrs, Volume= 0.196 af, Atten= 5%, Lag= 7.1 min Routing by Dyn-Scor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 0.20 fps, Min. Travel Time= 9.7 min Avg. Velocity = 0.09 fps, Avg. Travel Time= 23.0 min Peak Storage= 331 cf @ 8.06 hrs Average Depth at Peak Storage= 0.69' Bank -Full Depth= 1.00' Flow Area= 5.0 sf, Capacity= 1.25 cfs 2.00' x 1.00' deep channel, n= 0.250 Side Slope Z -value= 3.0'f Top Width= 8.00' Length=118.0' Slope= 0.0035 'f Inlet Invert= 476.20', Outlet Invert= 475.79' Summary for Reach 6R: Outfall Channel Inflow Area = 2.024 ac,100.00% Impervious, Inflow Depth = 3.07" for 2 yr event Inflow = 1.53 cfs 7.99 hrs, Volume= 0.517 of Outflow = 1.53 cfs 7.99 hrs, Volume= 0.517 af, Atten= 0%, Lag= 0.0 min Carver Family, LLC Concept 1 Type IA 24 -hr 2 yr Rainfall=3.30" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 9 Routing by Dyn-Scor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Carver Family, LLC Concept 1 Type IA 24 -hr 10 yr Rainfall=4.30" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment 1B: Basin 1 - Stormwater Drainage Facility Runoff = 0.14 cfs @ 7.94 hrs, Volume= 0.046 af, Depth= 4.06" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 10 yr Rainfall=4.30" Area (sf) CN Description * 5,895 98 Stormwater Drainage Facility 5,895 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 2B: Basin 2 -Westerly Parking Area Runoff = 0.48 cfs @ 7.94 hrs, Volume= 0.160 af, Depth= 4.06" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 10 yr Rainfall=4.30" /_TMTMII=0101 20,575 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 3B: Basin 3 -Roof Area Runoff = 0.66 cfs @ 7.94 hrs, Volume= 0.220 af, Depth= 4.06" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 10 yr Rainfall=4.30" 28,233 98 28,233 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Carver Family, LLC Concept 1 Type IA 24 -hr 10 yr Rainfall=4.30" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Pagel l Summary for Subcatchment 4B: Basin 4 -Easterly Vehicular Circulation and Stormwater Treatment Ai Runoff = 0.78 cfs @ 7.94 hrs, Volume= 0.260 af, Depth= 4.06" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 10 yr Rainfall=4.30" Area (sf) CN Description * 33.482 98 Easterly Vehicular Circulation and Stormwater Treatment Area 33,482 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Reach 5R: Stormwater Treatment Facility Inflow Area = 0.769 ac,100.00% Impervious, Inflow Depth = 4.06" for 10 yr event Inflow = 0.78 cfs 7.94 hrs, Volume= 0.260 of Outflow = 0.75 cfs 8.05 hrs, Volume= 0.260 af, Atten= 4%, Lag= 6.8 min Routing by Dyn-Scor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 0.22 fps, Min. Travel Time= 9.0 min Avg. Velocity = 0.09 fps, Avg. Travel Time= 21.2 min Peak Storage= 406 cf @ 8.05 hrs Average Depth at Peak Storage= 0.79' Bank -Full Depth= 1.00' Flow Area= 5.0 sf, Capacity= 1.25 cfs 2.00' x 1.00' deep channel, n= 0.250 Side Slope Z -value= 3.0'f Top Width= 8.00' Length=118.0' Slope= 0.0035 'f Inlet Invert= 476.20', Outlet Invert= 475.79' Summary for Reach 6R: Outfall Channel Inflow Area = 2.024 ac,100.00% Impervious, Inflow Depth = 4.06" for 10 yr event Inflow = 2.01 cfs 7.99 hrs, Volume= 0.686 of Outflow = 2.01 cfs 7.99 hrs, Volume= 0.686 af, Atten= 0%, Lag= 0.0 min Carver Family, LLC Concept 1 Type IA 24 -hr 10 yr Rainfall=4.30" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Paae 12 Routing by Dyn-Scor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs /2 Carver Family, LLC Concept 1 Type IA 24 -hr 25 yr Rainfall=4.80" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 13 Summary for Subcatchment 1B: Basin 1 - Stormwater Drainage Facility Runoff = 0.15 cfs @ 7.94 hrs, Volume= 0.051 af, Depth= 4.56" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 25 yr Rainfall=4.80" Area (sf) CN Description * 5,895 98 Stormwater Drainage Facility 5,895 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 2B: Basin 2 -Westerly Parking Area Runoff = 0.54 cfs @ 7.94 hrs, Volume= 0.180 af, Depth= 4.56" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 25 yr Rainfall=4.80" /_TMTMII=0101 20,575 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 3B: Basin 3 -Roof Area Runoff = 0.74 cfs @ 7.94 hrs, Volume= 0.246 af, Depth= 4.56" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 25 yr Rainfall=4.80" 28,233 98 28,233 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Carver Family, LLC Concept 1 Type IA 24 -hr 25 yr Rainfall=4.80" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 14 Summary for Subcatchment 4B: Basin 4 -Easterly Vehicular Circulation and Stormwater Treatment Ai Runoff = 0.88 cfs @ 7.94 hrs, Volume= 0.292 af, Depth= 4.56" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24 -hr 25 yr Rainfall=4.80" Area (sf) CN Description * 33.482 98 Easterly Vehicular Circulation and Stormwater Treatment Area 33,482 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Reach 5R: Stormwater Treatment Facility Inflow Area = 0.769 ac,100.00% Impervious, Inflow Depth = 4.56" for 25 yr event Inflow = 0.88 cfs 7.94 hrs, Volume= 0.292 of Outflow = 0.84 cfs 8.05 hrs, Volume= 0.292 af, Atten= 4%, Lag= 6.6 min Routing by Dyn-Scor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 0.23 fps, Min. Travel Time= 8.7 min Avg. Velocity = 0.10 fps, Avg. Travel Time= 20.5 min Peak Storage= 442 cf @ 8.05 hrs Average Depth at Peak Storage= 0.83' Bank -Full Depth= 1.00' Flow Area= 5.0 sf, Capacity= 1.25 cfs 2.00' x 1.00' deep channel, n= 0.250 Side Slope Z -value= 3.0'f Top Width= 8.00' Length=118.0' Slope= 0.0035 'f Inlet Invert= 476.20', Outlet Invert= 475.79' Summary for Reach 6R: Outfall Channel Inflow Area = 2.024 ac,100.00% Impervious, Inflow Depth = 4.56" for 25 yr event Inflow = 2.25 cfs 7.99 hrs, Volume= 0.770 of Outflow = 2.25 cfs 7.99 hrs, Volume= 0.770 af, Atten= 0%, Lag= 0.0 min Carver Family, LLC Concept 1 Type IA 24 -hr 25 yr Rainfall=4.80" Prepared by Branch Engineering Printed 1/172023 HydroCAD® 10.00-20 sln 10784 © 2017 HydroCAD Software Solutions LLC Paae 15 Routing by Dyn-Scor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs /2 4.5.10 Swale O & M Plan Swales are filtration stormwater conveyance facilities that provide flow control and stormwater quality benefits. Swales are long and narrow vegetated and grassed depressions used to collect and convey stormwater runoff which allows pollutants to settle and filter out as the water flows through the facility. All facility components, vegetation, and source controls shall be inspected for proper operations and structural stability, at a minimum, quarterly for the first 2 years from the date of installation, 2 times per year thereafter, and within 48 hours after each major storm event. Training and/or Written Guidance information for operating and maintaining Swales shall be provided to all property owners and tenants. A copy of the 0 & M Plan shall be provided to all property owners and tenants. Inspection Logs shall be kept by the facility owner demonstrating the following items have been inspected and are being maintained properly: • Access to Swales shall be safe and efficient. Obstacles preventing maintenance personnel and/or equipment access to the components of the facility shall be removed. • Channelization and causes for altered water flow shall be identified and corrected upon discovery. Stormwater should exit the vegetative filter as sheet flow, unless a collection drainpipe is used. • Debris and Litter shall be removed to prevent channelization, clogging, and interference with plant growth. Fallen leaves and debris from deciduous plant foliage shall be raked and removed. • Erosion Damage shall be identified and controlled when native soil is exposed or erosion channels are forming. • Grassed Swales shall be mowed to 4"-9" high and grass clippings shall be removed no less than 2 times per year. • Infiltrating Swales shall be excavated and cleaned, and gravel or soil shall be replaced to correct low infiltration rates. The Swale should drain within 48 hours of a storm event. • Wets shall maintain a calm flow of water entering the Swale and shall be cleared when conveyance capacity is plugged to ensure unrestricted stormwater flow to the rain garden. • Mulch shall be replenished as needed to ensure healthy plant growth. • Nuisance and Prohibited Vegetation from the Eugene Plant List (such as blackberries and English Ivy) shall be removed when discovered. Invasive vegetation contributing up to 25% of vegetation of all species shall be removed and replaced. • Outlets shall be cleared when 50% of the conveyance capacity is plugged. Stormwater Management Manual 425 Eugene 2014 Sedimentation build-up near or exceeding 2" in depth shall be hand -removed with minimum damage to vegetation using proper erosion control measures. Sediment shall be removed if it is more than 4 inches thick or so thick as to damage or kill vegetation. • Slopes shall be stabilized to prevent erosion and failure using appropriate measures when native soil is exposed. • Vegetation shall be healthy and dense enough to provide filtering while protecting underlying soils from erosion. Dead vegetation shall be removed to maintain less than 10% of area coverage or when vegetative filter function is impaired. Vegetation shall be replaced immediately to control erosion where soils are exposed and within 3 months to maintain cover density. Spill Prevention Measures shall be exercised on site when handling substances that contaminate stormwater. Releases of pollutants shall be corrected as soon as identified. Non -Chemical Pest Control measures shall be taken to prevent development of insects, mosquitoes, and rodents. Stormwater Management Manual 426 Eugene 2014