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HomeMy WebLinkAboutStudies Applicant 11/14/2023 Stormwater Management Plan and Drainage Study 824 S 70th Street Springfield, Oregon For 836 S 70th, LLC 939 Riverstone Lane Springfield, OR 97477 October 31, 2023 DIGITALLY SIGNED © Branch Engineering, Inc. 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 2 3.0 Proposed Development ......................................................................................... 2 4.0 Stormwater Constraints ........................................................................................ 2 5.0 Proposed Development Stormwater Description ....................................... 2 6.0 6.0 Facility Sizing ..................................................................................................... 3 7.0 7.0 Maintenance ....................................................................................................... 3 8.0 8.0 Conclusion........................................................................................................... 3 Appendices Description Appendix A Site Soils and Map Appendix B Basin Map Appendix C Stormwater Calculations Appendix D Stormwater Treatment Manhole Correspondence and Detail 1.0 INTRODUCTION This Stormwater Management Plan (SWMP) report has been prepared for the analysis of subdividing a property located at 824 S 70th Street. The subject site is south of Glacier Drive, north of Ivy Street, and east of S 69th Place. The subject property is identified as Tax Map 18-02-02-23 Tax Lot 4300. The stormwater runoff will be directed to the public stormwater system within the S 70th Street right-of- way. 2.0 EXISTING CONDITIONS The subject property is located in Springfield, Oregon in the Hillside Development Overlay Zone and consists of 1.76 acres of private property. The subject property’s southwesterly boundary abuts the northerly terminus of S 69th Place and the easterly boundary abuts the westerly margin of S 70th Street. The subject property is surrounded on all sides by fully improved properties. There are fences of various heights and character around the site where it abuts other properties. 2.1 TOPOGRAPHY The subject property is sparsely wooded with clusters of trees which have diameters at breast height ranging from 6- to 28-inches and grassed slopes of up to 12.5 percent. The elevations on the subject property range from 710-feet in the southwesterly corner of the site to 678-feet in the northeasterly corner of the site. 2.2 SOILS The Natural Resources Conservation Service (NRCS) Web Soil Survey maps the subject property as containing approximately 92.5% of Urban land-Hazelair-Dixonville complex (127C) and 7.5% Hazelair silty clay loam (52D) which resides in the northeasterly portion of the property. Urban land-Hazelair-Dixonville complex can have key features of both Hazelair and Dixonville soil types, while Hazelair silty clay loam only has Hazelair characteristics. They are differentiated below: · Hazelair is described as a moderately well-drained colluvium derived from sedimentary rock and is in Hydrologic Soil Group D; the soil has a limiting drainage capacity between 0.00- and 0.06-inches per hour. The typical profile of the soil type has silty clay loam between 0- to 11- inches, silty clay from 11- to 15-inches, clay from 15- to 36-inches, and weathered bedrock from 36- to 46-inches; 5 test pits were dug for the associated Geotechnical Report, and no bedrock was found. · Dixonville is described as a well-drained colluvium and residuum derived from basalt and is in Hydrologic Soil Group D; the soil has a limiting drainage capacity between 0.06- and 0.20- inches per hour. The typical profile of the soil type has silty clay loam between 0- to 14-inches, silty clay from 14- to 26-inches, and weathered bedrock from 26- to 36-inches; 5 test pits were dug for the associated Geotechnical Report, and no bedrock was found. A soils map and individual soil information is provided in Appendix A. 2.3 EXISTING STORM SYSTEM There is currently a roadside ditch located on the westerly edge of the pavement inside the S 70th Street right-of-way. Additionally, a 36-inch public stormwater line exists along the easterly edge of the same right-of-way. An 8-inch public stormwater line also exists to the southwest of the site inside the S 69th Place right-of-way, but is uphill from the subject property, and continues westerly away from the site. 3.0 PROPOSED DEVELOPMENT An 8-lot subdivision is proposed. Each lot ranges from 7,300- to 7,600-square feet. It is intended to dedicate and extend S 69th Place (a public road) from its northerly terminus, curving through the site to intersect S 70th Street. Included within the dedicated right-of-way will be a 20-foot-wide roadway with curb and gutters with a 4.5-foot planter strip and 5-foot sidewalk on both sides of the road. The dedicated road will include underground utilities for the lots on its northerly and southerly margin. The frontage along S 70th Street will also be improved to the centerline of the right-of-way. This improvement will consist of 9.5 feet of road pavement with curb and gutters with a 4.5-foot planter strip and 5-foot sidewalk. Based on conversations with staff at the City of Springfield, the site will not include vegetative on-site stormwater quality management facilities. Vegetative treatment facilities require water to slowly move through a growing medium. Having water housed in facilities for longer time spans on slopes exceeding 10 percent may be harmful by promoting erosion and slides in a hillside area. It is assumed that individual lot improvements will either weephole/drain to the road or stub into the stormwater main. In lieu of vegetative treatment, the City of Springfield is requiring the development to be treated via mechanical means. A stormwater treatment manhole is located at the easterly terminus of the site, prior to its outfall into the existing public infrastructure. 4.0 STORMWATER CONSTRAINTS Connection to the existing 36-inch stormwater line within S 70th Street will require trenching across S 70th Street. A Springfield Utility Board transmission line for potable water exists within the right- of=way. The water utility requires that no improvements extend across the street, and the site must continue to drain on the westerly side of S 70th Street.. The average slope across the site prevents the use of infiltration facilities to reduce stormwater discharge. S 69th Place will be extending through the subject property. The easterly half on the existing improvements on S 69th Place will drain to the site without some preventative measure. The location potable water lines within the S 70th Street corridor prevent the installation of stormwater capture systems. 5.0 PROPOSED DEVELOPMENT STORMWATER DESCRIPTION The proposed stormwater development for the subject property will consist of four curb inlets along the northerly portion of the S 69th Place and one on the westerly margin of the existing terminus of S 69th Place. The road will shed water to the north to match the existing direction of the slope on-site, while the improvements on S 70th Street will shed to the west towards the existing ditch just north of the site. Below is an explanation of what pipe size is required to convey runoff. The impervious surface of the proposed road consists of 10,312 square feet of asphalt and 5,725- square feet of sidewalk. All the homes’ impervious areas will be draining to the stormwater system as well as some of the pervious area on the south side of the road. If each lot maximizes its impervious area, there will be an additional 22,400 square feet of impervious area and 18,712 square feet of pervious area entering the system. Note, that the calculated impervious area was taken by using the maximum buildout of the entire proposed site detailed in note 12(a) on the site plan submitted concurrently with this report. Utilizing the areas calculated in the last paragraph and in Section 4.0 above, the total flows during 2-, 10-, and 25-year storm events through the most restrictive stormwater pipe (a 12” diameter pipe with the gentlest slope, see Basin Map in Appendix B for its location) in the new system are listed in the table below: Flow (cfs) Depth of water in 12" pipe (inches) Pipe percent full 2-year 0.84 2.8 18% 10-year 1.14 3.2 22% 25-year 1.29 3.5 24% The most restrictive stormwater pipe is located between the stormwater treatment manhole and the manhole which extends the existing city stormwater system at the intersection of S 69th Place and S 70th Street. Portions of the above impervious areas will not be draining through this pipe, but were used in the model to ensure that any pipe in the system would be able to handle the maximum amount of stormwater runoff from the site. It consists of a 12” diameter, 6.2-foot length of pipe at a 2.9% slope. The existing downstream system consists of a ditch along the westerly margin of S 70th Street ending in a curb inlet that connects to the 36” stormwater pipe within the easterly margin of the S 70th Street right-of-way. The city of Springfield Stormwater Master Plan list this as manhole 1166 (see Basin Map in Appendix B for its location). Future hydraulic performance of this pipe lists the 25-year storm as having a flow of 23 cfs. Adding the additional 1.29 cfs from the proposed system to this value increases the water volume in the pipe from 22% full to 23% full at peak flow. This shows plenty of capacity in the existing system to accommodate the new impervious area runoff. 6.0 FACILITY SIZING All stormwater structures and pipes are to be installed per the City of Springfield’s Engineering Design & Procedures Manual Chapter 4.00. The stormwater treatment manhole was sized per AquaShield’s recommendation based on the flows generated by the site. The correspondence with John Santos at AquaShield is included in this submittal in Appendix D. 7.0 MAINTENANCE The facilities will be maintained publicly as they are located within the public right-of-way and are being installed through a Public Improvement Project (PIP). 8.0 CONCLUSION The above has been reviewed as part of the Public Improvement Plan and is in the final stages of approval by the city engineer. APPENDIX A Site Soils and Map Soil Map—Lane County Area, Oregon Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/21/2022 Page 1 of 348761104876120487613048761404876150487616048761704876180487619048762004876110487612048761304876140487615048761604876170487618048761904876200507710507720507730507740507750507760507770507780507790507800507810507820507830507840507850 507710 507720 507730 507740 507750 507760 507770 507780 507790 507800 507810 507820 507830 507840 507850 44° 2' 20'' N 122° 54' 13'' W44° 2' 20'' N122° 54' 7'' W44° 2' 17'' N 122° 54' 13'' W44° 2' 17'' N 122° 54' 7'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 30 60 120 180 Feet 0 10 20 40 60 Meters Map Scale: 1:694 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:20,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Lane County Area, Oregon Survey Area Data: Version 19, Oct 27, 2021 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jun 12, 2019—Jun 19, 2019 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Soil Map—Lane County Area, Oregon Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/21/2022 Page 2 of 3 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 52D Hazelair silty clay loam, 7 to 20 percent slopes 0.1 7.5% 127C Urban land-Hazelair-Dixonville complex, 3 to 12 percent slopes 1.8 92.5% Totals for Area of Interest 2.0 100.0% Soil Map—Lane County Area, Oregon Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/21/2022 Page 3 of 3 Lane County Area, Oregon 127C—Urban land-Hazelair-Dixonville complex, 3 to 12 percent slopes Map Unit Setting National map unit symbol: 234l Elevation: 200 to 2,000 feet Mean annual precipitation: 30 to 60 inches Mean annual air temperature: 50 to 55 degrees F Frost-free period: 160 to 235 days Farmland classification: Not prime farmland Map Unit Composition Urban land:35 percent Hazelair and similar soils:25 percent Dixonville and similar soils:20 percent Minor components:3 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Urban Land Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8 Hydric soil rating: No Description of Hazelair Setting Landform:Hills Landform position (two-dimensional):Summit, shoulder, toeslope Landform position (three-dimensional):Interfluve, nose slope, base slope Down-slope shape:Linear Across-slope shape:Linear Parent material:Colluvium derived from sedimentary rock Typical profile H1 - 0 to 11 inches: silty clay loam H2 - 11 to 15 inches: silty clay H3 - 15 to 36 inches: clay H4 - 36 to 46 inches: weathered bedrock Properties and qualities Slope:3 to 12 percent Depth to restrictive feature:20 to 40 inches to paralithic bedrock Drainage class:Moderately well drained Capacity of the most limiting layer to transmit water (Ksat):Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table:About 12 to 24 inches Map Unit Description: Urban land-Hazelair-Dixonville complex, 3 to 12 percent slopes---Lane County Area, Oregon Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/21/2022 Page 1 of 3 Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 4.8 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: D Ecological site: R002XC010OR - Claypan Low Hill Group Forage suitability group: Moderately Well Drained < 15% Slopes (G002XY004OR) Other vegetative classification: Moderately Well Drained < 15% Slopes (G002XY004OR) Hydric soil rating: No Description of Dixonville Setting Landform:Hills Landform position (two-dimensional):Summit, shoulder, toeslope Landform position (three-dimensional):Interfluve, nose slope, base slope Down-slope shape:Linear Across-slope shape:Linear Parent material:Colluvium and residuum derived from basalt Typical profile H1 - 0 to 14 inches: silty clay loam H2 - 14 to 26 inches: silty clay H3 - 26 to 36 inches: weathered bedrock Properties and qualities Slope:3 to 12 percent Depth to restrictive feature:20 to 40 inches to paralithic bedrock Drainage class:Well drained Capacity of the most limiting layer to transmit water (Ksat):Moderately low to moderately high (0.06 to 0.20 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 4.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3e Hydrologic Soil Group: D Ecological site: R002XC011OR - Low Hill Group Forage suitability group: Well drained < 15% Slopes (G002XY002OR) Other vegetative classification: Well drained < 15% Slopes (G002XY002OR) Hydric soil rating: No Map Unit Description: Urban land-Hazelair-Dixonville complex, 3 to 12 percent slopes---Lane County Area, Oregon Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/21/2022 Page 2 of 3 Minor Components Panther Percent of map unit:3 percent Landform:Swales Hydric soil rating: Yes Data Source Information Soil Survey Area: Lane County Area, Oregon Survey Area Data: Version 19, Oct 27, 2021 Map Unit Description: Urban land-Hazelair-Dixonville complex, 3 to 12 percent slopes---Lane County Area, Oregon Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/21/2022 Page 3 of 3 Lane County Area, Oregon 52D—Hazelair silty clay loam, 7 to 20 percent slopes Map Unit Setting National map unit symbol: 237c Elevation: 200 to 2,000 feet Mean annual precipitation: 30 to 60 inches Mean annual air temperature: 50 to 55 degrees F Frost-free period: 160 to 235 days Farmland classification: Farmland of statewide importance Map Unit Composition Hazelair and similar soils:85 percent Minor components:3 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Hazelair Setting Landform:Mountains, mountains Landform position (two-dimensional):Footslope Landform position (three-dimensional):Mountainbase Down-slope shape:Linear Across-slope shape:Linear Parent material:Colluvium derived from sedimentary rock Typical profile H1 - 0 to 11 inches: silty clay loam H2 - 11 to 15 inches: silty clay H3 - 15 to 36 inches: clay H4 - 36 to 46 inches: weathered bedrock Properties and qualities Slope:7 to 20 percent Depth to restrictive feature:20 to 40 inches to paralithic bedrock Drainage class:Moderately well drained Capacity of the most limiting layer to transmit water (Ksat):Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table:About 12 to 24 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 4.8 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: D Ecological site: R002XC010OR - Claypan Low Hill Group Forage suitability group: Moderately Well Drained < 15% Slopes (G002XY004OR) Map Unit Description: Hazelair silty clay loam, 7 to 20 percent slopes---Lane County Area, Oregon Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/21/2022 Page 1 of 2 Other vegetative classification: Moderately Well Drained < 15% Slopes (G002XY004OR) Hydric soil rating: No Minor Components Panther Percent of map unit:3 percent Landform:Swales Hydric soil rating: Yes Data Source Information Soil Survey Area: Lane County Area, Oregon Survey Area Data: Version 19, Oct 27, 2021 Map Unit Description: Hazelair silty clay loam, 7 to 20 percent slopes---Lane County Area, Oregon Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 3/21/2022 Page 2 of 2 APPENDIX B Basin Map APPENDIX C Stormwater Calculations B1Maximum Proposed ConditionsEFExisting FlowP1Restrictive SW PipeP2Existing 36" PipeRouting Diagram for 21-287 Tent. HydroCADPrepared by Branch Engineering, Printed 10/31/2023HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLCSubcatReachPondLink Thurston Oaks Full Buildout Type IA 24-hr WQ Rainfall=0.83"21-287 Tent. HydroCAD Printed 10/31/2023Prepared by Branch Engineering Page 1HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Summary for Subcatchment B1: Maximum Proposed Conditions Runoff = 0.14 cfs @ 8.00 hrs, Volume= 0.050 af, Depth= 0.46" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24-hr WQ Rainfall=0.83" Area (sf) CN Description * 18,712 86 Minimum pervious areas Lots 1-4 * 22,400 98 Maximum impervious area Lots1-8 * 5,725 98 New sidewalk inside S 69th Place * 10,312 98 New asphalt inside S 69th Place 57,149 94 Weighted Average 18,712 32.74% Pervious Area 38,437 67.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Reach P1: Restrictive SW Pipe Inflow Area = 1.312 ac, 67.26% Impervious, Inflow Depth = 0.46" for WQ event Inflow = 0.14 cfs @ 8.00 hrs, Volume= 0.050 af Outflow = 0.14 cfs @ 8.00 hrs, Volume= 0.050 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 3.57 fps, Min. Travel Time= 0.0 min Avg. Velocity = 2.07 fps, Avg. Travel Time= 0.0 min Peak Storage= 0 cf @ 8.00 hrs Average Depth at Peak Storage= 0.10' Bank-Full Depth= 1.00' Flow Area= 0.8 sf, Capacity= 7.17 cfs 12.0" Round Pipe n= 0.011 Length= 6.2' Slope= 0.0290 '/' Inlet Invert= 683.58', Outlet Invert= 683.40' Thurston Oaks Full Buildout Type IA 24-hr 2YR Rainfall=3.30"21-287 Tent. HydroCAD Printed 10/31/2023Prepared by Branch Engineering Page 2HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Summary for Subcatchment B1: Maximum Proposed Conditions Runoff = 0.84 cfs @ 7.98 hrs, Volume= 0.294 af, Depth= 2.69" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24-hr 2YR Rainfall=3.30" Area (sf) CN Description * 18,712 86 Minimum pervious areas Lots 1-4 * 22,400 98 Maximum impervious area Lots1-8 * 5,725 98 New sidewalk inside S 69th Place * 10,312 98 New asphalt inside S 69th Place 57,149 94 Weighted Average 18,712 32.74% Pervious Area 38,437 67.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Reach P1: Restrictive SW Pipe Inflow Area = 1.312 ac, 67.26% Impervious, Inflow Depth = 2.69" for 2YR event Inflow = 0.84 cfs @ 7.98 hrs, Volume= 0.294 af Outflow = 0.84 cfs @ 7.98 hrs, Volume= 0.294 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 6.11 fps, Min. Travel Time= 0.0 min Avg. Velocity = 3.42 fps, Avg. Travel Time= 0.0 min Peak Storage= 1 cf @ 7.98 hrs Average Depth at Peak Storage= 0.23' Bank-Full Depth= 1.00' Flow Area= 0.8 sf, Capacity= 7.17 cfs 12.0" Round Pipe n= 0.011 Length= 6.2' Slope= 0.0290 '/' Inlet Invert= 683.58', Outlet Invert= 683.40' Thurston Oaks Full Buildout Type IA 24-hr 10YR Rainfall=4.30"21-287 Tent. HydroCAD Printed 10/31/2023Prepared by Branch Engineering Page 3HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Summary for Subcatchment B1: Maximum Proposed Conditions Runoff = 1.14 cfs @ 7.97 hrs, Volume= 0.400 af, Depth= 3.66" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24-hr 10YR Rainfall=4.30" Area (sf) CN Description * 18,712 86 Minimum pervious areas Lots 1-4 * 22,400 98 Maximum impervious area Lots1-8 * 5,725 98 New sidewalk inside S 69th Place * 10,312 98 New asphalt inside S 69th Place 57,149 94 Weighted Average 18,712 32.74% Pervious Area 38,437 67.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Reach P1: Restrictive SW Pipe Inflow Area = 1.312 ac, 67.26% Impervious, Inflow Depth = 3.66" for 10YR event Inflow = 1.14 cfs @ 7.97 hrs, Volume= 0.400 af Outflow = 1.14 cfs @ 7.97 hrs, Volume= 0.400 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 6.67 fps, Min. Travel Time= 0.0 min Avg. Velocity = 3.73 fps, Avg. Travel Time= 0.0 min Peak Storage= 1 cf @ 7.97 hrs Average Depth at Peak Storage= 0.27' Bank-Full Depth= 1.00' Flow Area= 0.8 sf, Capacity= 7.17 cfs 12.0" Round Pipe n= 0.011 Length= 6.2' Slope= 0.0290 '/' Inlet Invert= 683.58', Outlet Invert= 683.40' Thurston Oaks Full Buildout Type IA 24-hr 25YR Rainfall=4.80"21-287 Tent. HydroCAD Printed 10/31/2023Prepared by Branch Engineering Page 4HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Summary for Subcatchment B1: Maximum Proposed Conditions Runoff = 1.29 cfs @ 7.97 hrs, Volume= 0.453 af, Depth= 4.14" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-36.00 hrs, dt= 0.01 hrs Type IA 24-hr 25YR Rainfall=4.80" Area (sf) CN Description * 18,712 86 Minimum pervious areas Lots 1-4 * 22,400 98 Maximum impervious area Lots1-8 * 5,725 98 New sidewalk inside S 69th Place * 10,312 98 New asphalt inside S 69th Place 57,149 94 Weighted Average 18,712 32.74% Pervious Area 38,437 67.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Reach P1: Restrictive SW Pipe Inflow Area = 1.312 ac, 67.26% Impervious, Inflow Depth = 4.14" for 25YR event Inflow = 1.29 cfs @ 7.97 hrs, Volume= 0.453 af Outflow = 1.29 cfs @ 7.97 hrs, Volume= 0.453 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 6.92 fps, Min. Travel Time= 0.0 min Avg. Velocity = 3.87 fps, Avg. Travel Time= 0.0 min Peak Storage= 1 cf @ 7.97 hrs Average Depth at Peak Storage= 0.29' Bank-Full Depth= 1.00' Flow Area= 0.8 sf, Capacity= 7.17 cfs 12.0" Round Pipe n= 0.011 Length= 6.2' Slope= 0.0290 '/' Inlet Invert= 683.58', Outlet Invert= 683.40' Thurston Oaks Full Buildout Type IA 24-hr 25YR Rainfall=4.80"21-287 Tent. HydroCAD Printed 10/31/2023Prepared by Branch Engineering Page 5HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Summary for Reach P2: Existing 36" Pipe Inflow Area = 21.410 ac,100.00% Impervious, Inflow Depth = 4.56" for 25YR event Inflow = 23.00 cfs @ 7.96 hrs, Volume= 8.142 af Outflow = 23.00 cfs @ 7.96 hrs, Volume= 8.142 af, Atten= 0%, Lag= 0.1 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 14.53 fps, Min. Travel Time= 0.1 min Avg. Velocity = 8.06 fps, Avg. Travel Time= 0.2 min Peak Storage= 135 cf @ 7.96 hrs Average Depth at Peak Storage= 0.83' Bank-Full Depth= 3.00' Flow Area= 7.1 sf, Capacity= 138.79 cfs 36.0" Round Pipe n= 0.015 Concrete sewer w/manholes & inlets Length= 85.0' Slope= 0.0576 '/' Inlet Invert= 663.85', Outlet Invert= 658.95' Thurston Oaks Full Buildout Type IA 24-hr 25YR Rainfall=4.80"21-287 Tent. HydroCAD Printed 10/31/2023Prepared by Branch Engineering Page 6HydroCAD® 10.00-20 s/n 10784 © 2017 HydroCAD Software Solutions LLC Summary for Reach P2: Existing 36" Pipe Inflow Area = 22.722 ac, 98.11% Impervious, Inflow Depth = 4.54" for 25YR event Inflow = 24.29 cfs @ 7.96 hrs, Volume= 8.595 af Outflow = 24.29 cfs @ 7.96 hrs, Volume= 8.595 af, Atten= 0%, Lag= 0.1 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-36.00 hrs, dt= 0.01 hrs / 2 Max. Velocity= 14.76 fps, Min. Travel Time= 0.1 min Avg. Velocity = 8.19 fps, Avg. Travel Time= 0.2 min Peak Storage= 140 cf @ 7.96 hrs Average Depth at Peak Storage= 0.85' Bank-Full Depth= 3.00' Flow Area= 7.1 sf, Capacity= 138.79 cfs 36.0" Round Pipe n= 0.015 Concrete sewer w/manholes & inlets Length= 85.0' Slope= 0.0576 '/' Inlet Invert= 663.85', Outlet Invert= 658.95' APPENDIX D Stormwater Treatment Manhole Correspondence and Detail 1Andrew StroutFrom:Santos, John <jsantos@aquashieldinc.com>Sent:Wednesday, April 26, 2023 8:15 PMTo:Andrew StroutSubject:RE: Springfield, Oregon Subdivision - Stormwater Quality ManholeAttachments:AS-2 BYP CW PCS.pdf; AS-2 BYP CW PCS ACAD.dwg; Aqua-Swirl I&M Manual 10-17.pdf.pdf; PCS Aqua-Swirl Specification 2015-10-23.pdfImportance:HighHello Andrew, here is the informaon that you requested for specifying the AquaSwirl hydrodynamic separator. Based on the flow rate you have provided, I would recommend the AquaSwirl Concentrator model AS-2 with a maximum water quality flow rate of 0.25cfs based on WADOE GULD approval. The MSRP is about $10,500 FOB jobsite with only a 6 week lead me from receipt of the distributors purchase order and the approved shop drawings. A8ached you will find the standard drawings in PDF and CAD, maintenance document and specificaon example for your use. Sincerely, John Santos Western Business Development Manager AquaShield, a Komline Company 9580 Oak Ave. Parkway, Ste. 7-203 Folsom, CA 95630 Cell: (916) 850-9879 E-Mail: jsantos@aquashieldinc.com www.aquashieldinc.com 2This email including any files transmitted with it is intended solely for the above-mentioned recipient and it may contain confidential or privileged information. If you have received it in error, please notify the sender immediately and then destroy any copies of it. The email signature block does not constitute a signature for any contract binding Komline-Sanderson Corporation. From: Andrew Strout Sent: Saturday, April 15, 2023 6:33 AM To: Santos, John <jsantos@aquashieldinc.com> Subject: Springfield, Oregon Subdivision - Stormwater Quality Manhole Hi John, Sorry it took me so long to get back to you. The development has a maximum cfs of 0.13 during the water quality storm (0.83 inches per 24 hour period, SBUH Method). The Manhole in queson has the following properes: CAUTION: This email originated from outside the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. 3 4 I wanted to double check, the inlet and outlet of the manhole, they can be the same, correct? I haven’t updated the drawing to the reflect that. I wanted to get wri8en confirmaon first. Let me know what other items you may need, and when you could get me a meline on when I could receive the detail pertaining to this system. Thank you, Andrew Strout, EIT Engineering Technician Project Manager BRANCH ENGINEERING, INC. 310 5th Street, Springfield, OR 97477 p: 541.746.0637 ex. 106 5www.branchengineering.com Eugene-Springfield OR | Corvallis-Albany OR Projected View SCALE 1:80 Plan View SCALE 1:40 Elevation View SCALE 1:40 2733 Kanasita Drive, Suite 111, Chattanooga, TN 37343 Phone (888) 344-9044 Fax (423) 826-2112 www.aquashieldinc.com Structure #: Drawn By: Scale: Date: OFlores 9/15/2022 Rvwed Rvw. Date U.S. Patent No. 6524473 and other Patent PendingStandard Detail As Shown Aqua-Swirl® Concentrator el. Varies Inlet/Outlet Invert el. Varies el. Varies Grade (Rim) el. Varies OutletInletAS-2 BYP CW AS-2 STD Aqua-Swirl® Polymer Coated Steel (PCS) Stormwater Treatment System 12 in [305 mm] Manhole Frame & Cover Detail For Non-Traffic Areas Only NTS 48 in [1219 mm] Min. Gravel Backfill Concrete Wrap Compressible Expansion Joint Material to a minimum 1/2-inch [13 mm] thickness around top of riser to allow transfer of inadvertent loading from manhole cover to concrete slab. Riser Soil Cover Frame 1/2 in [13 mm] 1/2 in [13 mm] Place small amount of concrete [3,000 psi [20 MPa] (min)] to support and level manhole frame. DO NOT allow manhole frame to rest upon riser. Backfill (90% Proctor Density) 8 in [203 mm] 4 1/2 in [114 mm] Unless other traffic barriers are present, bollards shall be placed around access riser(s) in non-traffic areas to prevent inadvertent loading by maintenance vehicles. Manhole Frame & Cover Detail For Traffic Loading Areas NTS Cover Frame 48 in [1219 mm] Min. Backfill (90% Proctor Density) 3,000 psi [20 MPa] (min) Concrete #4 [13 mm] Rebar @ 6 in [152 mm] Each Way 30 in [762 mm] Riser 1/2 in [13 mm] 4 1/2 in [114 mm] 14 in [356 mm] 1/2 in [13 mm] Thick Expansion Joint Material If traffic loading (HS-25) is required or anticipated, a 4-foot [1.22 m] diameter, 14-inch [356 mm] thick reinforced concrete pad must be placed over the Stormwater Treatment System Riser to support and level the manhole frame, as shown. The top of riser pipe must be wrapped with compressible expansion joint material to a minimum 1/2-inch [13 mm] thickness to allow transfer of wheel loads from manhole cover to concrete slab. Manhole cover shall bear on concrete slab and not on riser pipe. The concrete slab shall have a minimum strength of 3,000 psi [20 MPa] and be reinforced with #4 [13 mm] reinforcing steel as shown. Minimum cover over reinforcing steel shall be 1-inch [25 mm]. Top of manhole cover and concrete slab shall be level with finish grade. Please see accompanied Aqua-Swirl® specification notes. See Site Plan for actual system orientation. Approximate dry (pick) weight: 1000 lbs [500 kg]. Backfill shall extend at least 18 inches [457 mm] outward from Swirl Concentrator and for the full height of the Swirl Concentrator (including riser) extending laterally to undisturbed soils. (See MH Detail Below) Pipe coupling by Contractor. 12 in [305 mm] long Stub-out by Manufacturer. Octagonal Base Plate Pipe coupling by Contractor. 12 in [305 mm] long Stub-out by Manufacturer. Varies Varies Internal Baffles Riser n30 in [n765 mm] 42 in [1067 mm] 42 in [1067 mm] 38 in [965 mm] 60 in [1524 mm] 5 in [127 mm] MH Frame n30 in [n762 mm] n12 in [n305 mm] n12 in [n305 mm] Rim elevations to match finish grade. n30 in [n762 mm] 1 1 As an alternative, 42 in [1067 mm] diameter, HS-20/25 rated precast concrete rings may be substituted. 14 in [356 mm] thickness must be maintained. AS-2 BYP inlet/outlet pipe size ranges from 8 in [203 mm] to 15 in [381 mm]. AS-2 chamber height may vary from 52 in [1321 mm] to 60 in [1524 mm], depending on inlet/outlet pipe size. Orientation may vary from a minimum of 90° to a maximum of 180°. Manhole Frame and Cover by Manufacturer. (See Details) 180° Lifting Lugs Lifting Lugs 2 3 4 2 3 4 2 Band Coupler by Manufacturer. (as needed) Backfill Bedding Undisturbed soil 18 in [457 mm] 6 in [152 mm]