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Drainage Report
C C h h a a n n h h a a s s s s e e n n A A p p a a r r t t m m e e n n t t s s Stormwater Management Study Chanhassen, MN Prepared For: Oppidan 5125 County Road 101, Suite 100 Minnetonka, MN 55345 Prepared By: Alliant Engineering, Inc. 233 Park Avenue South, Suite 300 Minneapolis, MN 55415 March 15, 2013 Chanhassen Apartments Drainage Report March 15 st , 2013 Alliant Engineering, Inc. | 212-0103 1 Introduction Included in this report are the ma terials necessary to review the stormwater management plan for the proposed multi-family apartments in Chanhass en, Minnesota. We have provided all pertinent calculations in this report for the City of Ch anhassen with the following information included: Drainage Report Drainage Area Maps HydroCAD Reports which include: o Rate Control Calculations (2-yr, 10-yr, 100-yr, 100-yr Snow Melt) o NURP Water Quality Calculations Storm Sewer Sizing Worksheet (10-Year Sizing) Background This hydrologic study was conducted to analyze th e stormwater treatment requirements for a proposed apartment complex and adjacent infrastr ucture in Chanhassen, Minnesota located just west of Galpin Boulevard and south of W 78 th Street. The purpose of the report is to design a stormwater management facility that is capable of handling the effects of the proposed complex and increased impervious cover. This st udy compares the following two scenarios: Existing conditions Proposed conditions The stormwater analysis was completed for the 7.868 acre property. This s ite also contains one delineated wetland which covers 0.142 acres. Drai nage maps in the appendix show delineations based on existing conditions and the proposed deve lopment. The stormwater management plan for the proposed conditions will meet the guidelin es as required by the City of Chanhassen for stormwater quantity and quality. The following criterion was used in designing the stormwater management system: Rate Control: Post-development peak runoff rates from the site for the 2, 10 and 100-year 24-hour Type II storm events must not be greater than the existing condition rates. Post-development peak runoff rates from the site for the 100-year 10-Day Snow Melt must not be greater than the existing condition rates. Volume/Water Quality Control: Water quality pond meeting NURP standards: o A permanent pool volume (“dead storage”) below the principal spillway (normal outlet) shall be provided that is greater than or equal to the runoff from a 2.5-inch 24-hour storm over the entire contributing drainage area, assuming full development. o A permanent pool average depth (basin volume/basin area) shall be > 4 feet, with a maximum depth of < 10 feet. o An emergency spillway (emergency outlet) that is adequate to safely pass the 100-year frequency, critical-duration rainfall or runoff event. o Basin side slopes above the normal water le vel should be no steeper than three feet horizontal to one foot vertical (3H:1V), and preferably flatter. A basin shelf with a minimum width of 10 feet and 1 foot deep below the normal water level is needed to Chanhassen Apartments Drainage Report March 15 st , 2013 Alliant Engineering, Inc. | 212-0103 2 enhance wildlife habitat, reduce potential safety hazards, and improve access for long-term maintenance. o To prevent short-circuiting, the distance betw een the major inlets and normal outlet shall be maximized. o Riprap shall be provided below the channel grade and above the outfall or channel bottom to insure that riprap will not be unde rmined by scour or rendered ineffective by displacement o Trash and floatable debris skimming device shall be placed on the outlet of detention basin to provide treatment up to the 1-year frequency event. Wetland Elements: Water level fluctuations (peak elevation and dura tion) for wetlands shall be limited to two feet and duration not to exceed 48 hours so as to pr event the destruction of wildlife habitat and wetland vegetation. Sedimentation basins or sediment removal devi ces shall be provided prior to discharge into wetlands. Runoff Rate and Volume Control All rate control calculations have been performed using the SCS method via HydroCAD software. Three events were modeled including: the 2-year, 10-year and 100-year, Type II 24-hour storm events with precipitation amounts of 2.8, 4.2, and 6.0 inches, resp ectively. All existing and proposed curve numbers are based on assumed soil types ‘B’ and ‘C’ obtained from the NR CS web soil survey. Existing Conditions The site is currently a vacated lot, once used as a miniature golf course and driving range. There are remnants of impervious areas throughout the easte rn and southern portions of the parcel. The majority of runoff from the site drains into the existing wetland. The re maining runoff generated on site drains into catch basins along Galpin Boulevard and W 78 th St., and ultimately discharges into the existing stormwater pond located to the west of the property. The following is a description of the HydroCAD sub catchments that were used in the existing conditions model: EW-1s – 5.510 acre area which drains into the existing wetland. The wetland is connected to another wetland located across W 78 th St via an outlet pipe. This subcatchment area is further divided by two soil classifications, soil types ‘B’ and ‘C’. The majority of the site was modeled as a type ‘B’, however, the soil around the existing wetland was modeled as type ‘C’. It should also be noted that a small portion of runoff from W 78 th St. ROW discharges into the existing wetland. D-1s – 2.689 acre area which drains offsite to storm sewers on Galpin Boulevard and W 78 th St., and discharges into the existing pond. The total area res ponsible for offsite drainage was modeled as one subcatchment. In addition, this subcatchment area contains almost all of the remnant impervious area. Refer to the existing conditions drainage map a nd HydroCAD report sheets for additional information and detailed calculations. To compare peak discharge rates and volumes for the existing and proposed conditions, flows were analyzed at the two site discharge points. For ease of comparison, the existing subcatchments drain to HydroCAD links that will remain consistent in the pr oposed and existing models. Refer to the existing Chanhassen Apartments Drainage Report March 15 st , 2013 Alliant Engineering, Inc. | 212-0103 3 conditions drainage map and HydroCAD report sh eets for additional information and detailed calculations. 1L – Discharges from the wetland to the northwest via an existing pipe connection. 2L – Discharges offsite to catchbasi ns on Galpin Boulevard and W 78 th St., and flows into the existing pond west of the property on the north side of T.H. No. 5. Proposed Conditions The proposed project includes the construction of a multi-family apartment complex and associated parking lots. Both a ground level parking lot and a basement level parking garage are proposed. The proposed development includes roughly 2.65 acres of im pervious surface. The apartment complex and parking lot will drain into a detention pond located just to the west of the parking lot via catch basins and proposed stormsewer. The detenti on pond will be utilized to control runoff volumes as well as provide the required water quality volume. An outlet contro l structure will be regulating discharge into the wetland from the pond. The following is a list of the HydroCAD subcatchments that are used in the proposed conditions model: P-1s – 4.416 acres of primarily impervious area that sheet drains to the catch basins located at both entrances to the parking garage plus one at the western end of the parking lot. EW-1s – 0.678 acre pervious area consisting primarily of the berm and lawn area surrounding the wetland, plus approximately 270 ft of W 78 th St. ROW runoff that discharges into the wetland. An outlet control structure will regulate discharge from the site to levels below the existing conditions. Please see the plan shee t for details on the outlet control structure. D-1s – 3.027 acre offsite drainage area that wi ll continue to ente r the existing storm sewers along Galpin Boulevard and W 78 th St. and ultimately end up in the stormwater pond to the west of the property. The proposed stormwater management plan decrease s the composite peak discharge rates to below existing conditions for all of the modeled events. Refer to the proposed c onditions drainage map and HydroCAD report sheets for additional information. Existing & Proposed runoff rates and volumes as ca lculated by HydroCAD are listed in the table below: Peak Discharge Rates (cfs) Discharge Point 2 ‐Year 10 ‐Year 100 ‐YR RF 100 ‐YR SM Existing Proposed Existing Proposed Existing Proposed Existing Proposed 1L 0.07 0.07 0.87 0.47 3.66 2.89 5.13 4.11 2L 2.62 2.31 6.46 6.17 12.20 12.05 3.22 3.61 Chanhassen Apartments Drainage Report March 15 st , 2013 Alliant Engineering, Inc. | 212-0103 4 Stormwater Quality Detention Pond Data Pond NURP Design The proposed detention pond has been designed to meet the standards for the City of Chanhassen. More specifically, the pond must provide a ‘dead pool’ volum e that meets or exceeds the runoff from the 2.5” NURP rainfall event over the entire contributing waters hed. The 2.5” rainfall event generates 13,417 CF of runoff volume for the P-1s watershed. The propos ed detention pond provides a dead pool water quality volume of 20,930 CF exceeding the requirement. Th e pond has a maximum depth of 8 feet and an average depth of 4.14’ excluding the pond bench. A 15” RCP submerged inlet acts as a skimmer to control trash and floatables prior to entrance to the wetland. A stabilized emergency overflow is set at 958.12 to the wetland with a top of berm set at 960.00. Basin side slopes are set at 3:1 slopes. The pond has a 10’ bench around the perimeter below the NWL of the pond. The 100-yr HWL for the pond will be 958.11’. Please see the attached HydroCAD m odel for the 2.5” water quality event. Wetland Elements The onsite wetland will utilize an outlet control structure to meet rate control requirements. Within the OCS, a 1.7” orifice controls the 2-yr rainfall event, while the 10-yr and 100-yr events are controlled by a weir wall. A sharp- crested vee will be placed at an invert elevation 956.5’ and a rectangular section will be set at 957.5’. The 100-yr HWL level of the wetland is 957.33’. Wetland Summary 2 ‐Year Existing Proposed Difference Inundation Time (hr) 70.25 114.5 44.25 Bounce (ft) 955.59 956.30 0.71 The maximum bounce is limited to less than 2 feet fo r all events, whereas the inundation time is under the maximum allowed 48 hour time for the 2-yr event. Erosion and Sediment Control Plan The following Best Management Practices (BMP’s) are proposed for the project. Temporary erosion control devices indicated on the grad ing and erosion control plans to provide sediment control during project construction: Silt fence Rock construction entrance Inlet sediment barriers at catch basins Permanent erosion control devices shown to be installed include: Rip rap at storm sewer pipe outlets Turf reinforcement mat at pond spillway Turf establishment including seeding, sodding, etc. Chanhassen Apartments Drainage Report March 15 st , 2013 Alliant Engineering, Inc. | 212-0103 5 Conclusion Alliant Engineering believes that the proposed design is acceptable for all parties involved. The peak off-site discharge rates for the 2-year, 10-year and 100-year 24-hour storm events will be decreased from existing rates for the proposed conditions. The proposed pond design exceeds the required amount of permanent pool volume and meets depth, surface area and length criteria for proper treatment of the runoff. The wetland water level fluctuations are l ess than the maximum two feet, and the inundation time is less than 48 hours for the 2-yr event. Lastly , the proposed grading and erosion control plan utilizes Best Management Practices whenever possible to pr ovide adequate erosion control measures to contain sediment during construction. Please call me at 612-767-9342 with any questions or comments regarding stormwater issues for the Chanhassen Apartments. Sincerely, Charles Butterworth, EIT Alliant Engineering, Inc. CC: File 120103 Chanhassen Apartments Drainage Report March 15 st , 2013 Alliant Engineering, Inc. | 212-0103 6 APPENDIX Drainage Maps HydroCAD Reports (includes rate control and NURP calculations) Storm Sewer Sizing Worksheet (10-Year Sizing) D-1s Direct Offsite EW-1s Existing Wetland EW-1 Existing Wetland 1L NW Wetland 2L Existing Pond Drainage Diagram for 120103-edrn Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcat Reach Pond Link Chanhassen Apartments Existing Conditions 120103-edrn Page 2 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Area Listing (all nodes)Area (acres)CN Description (subcats)5.54261>75% Grass cover, Good, HSG B (D-1s,EW-1s)1.80874>75% Grass cover, Good, HSG C (EW-1s)0.84998Paved parking & roofs (D-1s,EW-1s) 8.199 Chanhassen Apartments Existing Conditions Type II 24-hr 2yr Rainfall=2.80"120103-edrn Page 3 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment D-1s: Direct Offsite Runoff=2.62 cfs @ 12.03 hrs, Volume=0.155 af, Depth=0.69"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr Rainfall=2.80"Area (sf)CNDescription 36,19598Paved parking & roofs 80,95761>75% Grass cover, Good, HSG B 117,15272Weighted Average 80,957Pervious Area 36,195Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)10.0 Direct Entry, Subcatchment EW-1s: Existing Wetland Runoff=1.74 cfs @ 12.18 hrs, Volume=0.192 af, Depth=0.42"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr Rainfall=2.80"Area (sf)CNDescription 78398Paved parking & roofs 160,46061>75% Grass cover, Good, HSG B 78,76674>75% Grass cover, Good, HSG C 240,00965Weighted Average 239,226Pervious Area 783Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)13.2500.02000.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80"7.14850.02681.15 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 20.3535Total Pond EW-1: Existing Wetland Inflow Area =5.510 ac, Inflow Depth = 0.42" for 2yr event Inflow=1.74 cfs @ 12.18 hrs, Volume=0.192 af Outflow=0.10 cfs @ 19.36 hrs, Volume=0.192 af, Atten= 95%, Lag= 431.0 min Discarded=0.03 cfs @ 19.36 hrs, Volume=0.143 af Primary=0.07 cfs @ 19.36 hrs, Volume=0.049 af Chanhassen Apartments Existing Conditions Type II 24-hr 2yr Rainfall=2.80"120103-edrn Page 4 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Peak Elev= 955.59' @ 19.36 hrs Surf.Area= 12,835 sf Storage= 5,467 cf Plug-Flow detention time= 1,472.3 min calculated for 0.192 af (100% of inflow)Center-of-Mass det. time= 1,472.8 min ( 2,394.3 - 921.6 )VolumeInvertAvail.StorageStorage Description #1955.00'75,572 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)955.006,170362.0006,170 956.0018,950570.011,97811,97821,604 958.0046,695926.063,59575,57264,011 DeviceRouting InvertOutlet Devices #1Discarded0.00'0.100 in/hr Exfiltration over Surface area #2Primary955.48'24.0" x 108.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 954.48' S= 0.0093 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections Discarded OutFlow Max=0.03 cfs @ 19.36 hrs HW=955.59' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.03 cfs)Primary OutFlow Max=0.07 cfs @ 19.36 hrs HW=955.59' TW=0.00' (Dynamic Tailwater)2=Culvert (Barrel Controls 0.07 cfs @ 1.53 fps)Link 1L: NW Wetland Inflow Area =5.510 ac, Inflow Depth = 0.11" for 2yr event Inflow=0.07 cfs @ 19.36 hrs, Volume=0.049 af Primary=0.07 cfs @ 19.36 hrs, Volume=0.049 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Link 2L: Existing Pond Inflow Area =2.689 ac, Inflow Depth = 0.69" for 2yr event Inflow=2.62 cfs @ 12.03 hrs, Volume=0.155 af Primary=2.62 cfs @ 12.03 hrs, Volume=0.155 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Existing Conditions Type II 24-hr 10yr Rainfall=4.20"120103-edrn Page 5 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment D-1s: Direct Offsite Runoff=6.46 cfs @ 12.02 hrs, Volume=0.359 af, Depth=1.60"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr Rainfall=4.20"Area (sf)CNDescription 36,19598Paved parking & roofs 80,95761>75% Grass cover, Good, HSG B 117,15272Weighted Average 80,957Pervious Area 36,195Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)10.0 Direct Entry, Subcatchment EW-1s: Existing Wetland Runoff=6.31 cfs @ 12.15 hrs, Volume=0.526 af, Depth=1.15"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr Rainfall=4.20"Area (sf)CNDescription 78398Paved parking & roofs 160,46061>75% Grass cover, Good, HSG B 78,76674>75% Grass cover, Good, HSG C 240,00965Weighted Average 239,226Pervious Area 783Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)13.2500.02000.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80"7.14850.02681.15 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 20.3535Total Pond EW-1: Existing Wetland Inflow Area =5.510 ac, Inflow Depth = 1.15" for 10yr event Inflow=6.31 cfs @ 12.15 hrs, Volume=0.526 af Outflow=0.91 cfs @ 12.98 hrs, Volume=0.526 af, Atten= 86%, Lag= 49.9 min Discarded=0.04 cfs @ 12.98 hrs, Volume=0.153 af Primary=0.87 cfs @ 12.98 hrs, Volume=0.373 af Chanhassen Apartments Existing Conditions Type II 24-hr 10yr Rainfall=4.20"120103-edrn Page 6 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Peak Elev= 955.86' @ 12.98 hrs Surf.Area= 16,748 sf Storage= 9,489 cf Plug-Flow detention time= 636.2 min calculated for 0.526 af (100% of inflow)Center-of-Mass det. time= 636.8 min ( 1,519.4 - 882.6 )VolumeInvertAvail.StorageStorage Description #1955.00'75,572 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)955.006,170362.0006,170 956.0018,950570.011,97811,97821,604 958.0046,695926.063,59575,57264,011 DeviceRouting InvertOutlet Devices #1Discarded0.00'0.100 in/hr Exfiltration over Surface area #2Primary955.48'24.0" x 108.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 954.48' S= 0.0093 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections Discarded OutFlow Max=0.04 cfs @ 12.98 hrs HW=955.86' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.04 cfs)Primary OutFlow Max=0.87 cfs @ 12.98 hrs HW=955.86' TW=0.00' (Dynamic Tailwater)2=Culvert (Inlet Controls 0.87 cfs @ 2.10 fps)Link 1L: NW Wetland Inflow Area =5.510 ac, Inflow Depth = 0.81" for 10yr event Inflow=0.87 cfs @ 12.98 hrs, Volume=0.373 af Primary=0.87 cfs @ 12.98 hrs, Volume=0.373 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Link 2L: Existing Pond Inflow Area =2.689 ac, Inflow Depth = 1.60" for 10yr event Inflow=6.46 cfs @ 12.02 hrs, Volume=0.359 af Primary=6.46 cfs @ 12.02 hrs, Volume=0.359 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Existing Conditions Type II 24-hr 100yr Rainfall=6.00"120103-edrn Page 7 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment D-1s: Direct Offsite Runoff=12.20 cfs @ 12.02 hrs, Volume=0.671 af, Depth=2.99"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr Rainfall=6.00"Area (sf)CNDescription 36,19598Paved parking & roofs 80,95761>75% Grass cover, Good, HSG B 117,15272Weighted Average 80,957Pervious Area 36,195Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)10.0 Direct Entry, Subcatchment EW-1s: Existing Wetland Runoff=13.88 cfs @ 12.14 hrs, Volume=1.080 af, Depth=2.35"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr Rainfall=6.00"Area (sf)CNDescription 78398Paved parking & roofs 160,46061>75% Grass cover, Good, HSG B 78,76674>75% Grass cover, Good, HSG C 240,00965Weighted Average 239,226Pervious Area 783Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)13.2500.02000.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80"7.14850.02681.15 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 20.3535Total Pond EW-1: Existing Wetland Inflow Area =5.510 ac, Inflow Depth = 2.35" for 100yr event Inflow=13.88 cfs @ 12.14 hrs, Volume=1.080 af Outflow=3.71 cfs @ 12.56 hrs, Volume=1.080 af, Atten= 73%, Lag= 25.0 min Discarded=0.05 cfs @ 12.56 hrs, Volume=0.161 af Primary=3.66 cfs @ 12.56 hrs, Volume=0.918 af Chanhassen Apartments Existing Conditions Type II 24-hr 100yr Rainfall=6.00"120103-edrn Page 8 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Peak Elev= 956.29' @ 12.56 hrs Surf.Area= 22,221 sf Storage= 17,959 cf Plug-Flow detention time= 350.2 min calculated for 1.079 af (100% of inflow)Center-of-Mass det. time= 350.9 min ( 1,211.0 - 860.1 )VolumeInvertAvail.StorageStorage Description #1955.00'75,572 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)955.006,170362.0006,170 956.0018,950570.011,97811,97821,604 958.0046,695926.063,59575,57264,011 DeviceRouting InvertOutlet Devices #1Discarded0.00'0.100 in/hr Exfiltration over Surface area #2Primary955.48'24.0" x 108.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 954.48' S= 0.0093 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections Discarded OutFlow Max=0.05 cfs @ 12.56 hrs HW=956.29' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.05 cfs)Primary OutFlow Max=3.66 cfs @ 12.56 hrs HW=956.29' TW=0.00' (Dynamic Tailwater)2=Culvert (Inlet Controls 3.66 cfs @ 3.07 fps)Link 1L: NW Wetland Inflow Area =5.510 ac, Inflow Depth = 2.00" for 100yr event Inflow=3.66 cfs @ 12.56 hrs, Volume=0.918 af Primary=3.66 cfs @ 12.56 hrs, Volume=0.918 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Link 2L: Existing Pond Inflow Area =2.689 ac, Inflow Depth = 2.99" for 100yr event Inflow=12.20 cfs @ 12.02 hrs, Volume=0.671 af Primary=12.20 cfs @ 12.02 hrs, Volume=0.671 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Existing Conditions Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 120103-edrn Page 9 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment D-1s: Direct Offsite Runoff=3.22 cfs @ 119.11 hrs, Volume=1.560 af, Depth=6.96"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 Area (sf)CNDescription 36,19598Paved parking & roofs 80,95761>75% Grass cover, Good, HSG B 117,15272Weighted Average, Adjusted for AMC to CN = 98 80,957Pervious Area 36,195Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)10.0 Direct Entry, Subcatchment EW-1s: Existing Wetland Runoff=6.41 cfs @ 119.23 hrs, Volume=3.196 af, Depth=6.96"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 Area (sf)CNDescription 78398Paved parking & roofs 160,46061>75% Grass cover, Good, HSG B 78,76674>75% Grass cover, Good, HSG C 240,00965Weighted Average, Adjusted for AMC to CN = 98 239,226Pervious Area 783Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)13.2500.02000.06 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 2.80"7.14850.02681.15 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 20.3535Total Pond EW-1: Existing Wetland Inflow Area =5.510 ac, Inflow Depth = 6.96" for 100yr SM event Inflow=6.41 cfs @ 119.23 hrs, Volume=3.196 af Outflow=5.19 cfs @ 119.57 hrs, Volume=3.192 af, Atten= 19%, Lag= 20.5 min Discarded=0.06 cfs @ 119.57 hrs, Volume=0.638 af Primary=5.13 cfs @ 119.57 hrs, Volume=2.554 af Chanhassen Apartments Existing Conditions Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 120103-edrn Page 10 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Peak Elev= 956.46' @ 119.57 hrs Surf.Area= 24,205 sf Storage= 21,813 cf Plug-Flow detention time= 539.7 min calculated for 3.192 af (100% of inflow)Center-of-Mass det. time= 529.7 min ( 7,876.5 - 7,346.8 )VolumeInvertAvail.StorageStorage Description #1955.00'75,572 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)955.006,170362.0006,170 956.0018,950570.011,97811,97821,604 958.0046,695926.063,59575,57264,011 DeviceRouting InvertOutlet Devices #1Discarded0.00'0.100 in/hr Exfiltration over Surface area #2Primary955.48'24.0" x 108.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 954.48' S= 0.0093 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections Discarded OutFlow Max=0.06 cfs @ 119.57 hrs HW=956.46' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.06 cfs)Primary OutFlow Max=5.13 cfs @ 119.57 hrs HW=956.46' TW=0.00' (Dynamic Tailwater)2=Culvert (Inlet Controls 5.13 cfs @ 3.36 fps)Link 1L: NW Wetland Inflow Area =5.510 ac, Inflow Depth = 5.56" for 100yr SM event Inflow=5.13 cfs @ 119.57 hrs, Volume=2.554 af Primary=5.13 cfs @ 119.57 hrs, Volume=2.554 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Link 2L: Existing Pond Inflow Area =2.689 ac, Inflow Depth = 6.96" for 100yr SM event Inflow=3.22 cfs @ 119.11 hrs, Volume=1.560 af Primary=3.22 cfs @ 119.11 hrs, Volume=1.560 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs D-1s Direct Offsite EW-1s Existing Wetland P-1s Proposed Pond EW-1 Existing Wetland P-1 Proposed Pond 1L NW Wetland 2L Existing Pond Drainage Diagram for 120103-pdrn Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcat Reach Pond Link Chanhassen Apartments Proposed Conditions 120103-pdrn Page 2 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Area Listing (all nodes)Area (acres)CN Description (subcats)4.14061>75% Grass cover, Good, HSG B (D-1s,P-1s)1.32774>75% Grass cover, Good, HSG C (D-1s,EW-1s,P-1s)2.65298Paved parking & roofs (D-1s,P-1s) 8.119 Chanhassen Apartments Proposed Conditions Type II 24-hr 2yr Rainfall=2.80"120103-pdrn Page 3 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment D-1s: Direct Offsite Runoff=2.31 cfs @ 12.06 hrs, Volume=0.153 af, Depth=0.61"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr Rainfall=2.80"Area (sf)CNDescription 28,85298Paved parking & roofs 95,72261>75% Grass cover, Good, HSG B 7,27374>75% Grass cover, Good, HSG C 131,84770Weighted Average 102,995Pervious Area 28,852Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)12.0 Direct Entry, Subcatchment EW-1s: Existing Wetland Runoff=0.77 cfs @ 12.03 hrs, Volume=0.044 af, Depth=0.78"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr Rainfall=2.80"Area (sf)CNDescription 29,48074>75% Grass cover, Good, HSG C 29,480Pervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)10.0 Direct Entry, Subcatchment P-1s: Proposed Pond Runoff=4.95 cfs @ 12.14 hrs, Volume=0.384 af, Depth=1.04"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 2yr Rainfall=2.80"Area (sf)CNDescription 86,68898Paved parking & roofs 84,61961>75% Grass cover, Good, HSG B 21,04774>75% Grass cover, Good, HSG C 192,35479Weighted Average 105,666Pervious Area 86,688Impervious Area Chanhassen Apartments Proposed Conditions Type II 24-hr 2yr Rainfall=2.80"120103-pdrn Page 4 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)20.0 Direct Entry, Pond EW-1: Existing Wetland Inflow Area =5.093 ac, Inflow Depth = 1.01" for 2yr event Inflow=1.69 cfs @ 12.46 hrs, Volume=0.428 af Outflow=0.09 cfs @ 24.20 hrs, Volume=0.428 af, Atten= 94%, Lag= 704.3 min Discarded=0.03 cfs @ 24.20 hrs, Volume=0.216 af Primary=0.07 cfs @ 24.20 hrs, Volume=0.212 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Peak Elev= 956.30' @ 24.20 hrs Surf.Area= 0.281 ac Storage= 0.285 af Plug-Flow detention time= (not calculated: outflow precedes inflow)Center-of-Mass det. time= 1,951.5 min ( 3,058.0 - 1,106.5 )VolumeInvertAvail.StorageStorage Description #1954.99'1.639 af Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(acres)(feet)(acre-feet)(acre-feet)(acres)954.990.0004.00.0000.0000.000 955.000.142362.00.0000.0000.239 956.000.268445.00.2020.2020.362 958.000.359502.00.6250.8270.463 960.000.456556.00.8131.6390.570 DeviceRouting InvertOutlet Devices #1Discarded0.00'0.100 in/hr Exfiltration over Surface area #2Primary955.48'24.0" x 108.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 954.48' S= 0.0093 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections #3Device 2955.48'1.7" Vert. Orifice/Grate C= 0.600 #4Device 2956.50'90.0 deg x 0.5' long x 1.00' rise Sharp-Crested Vee/Trap Weir C= 2.50 #5Device 2957.50'5.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Discarded OutFlow Max=0.03 cfs @ 24.20 hrs HW=956.30' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.03 cfs)Primary OutFlow Max=0.07 cfs @ 24.20 hrs HW=956.30' TW=0.00' (Dynamic Tailwater)2=Culvert (Passes 0.07 cfs of 3.75 cfs potential flow)3=Orifice/Grate (Orifice Controls 0.07 cfs @ 4.17 fps)4=Sharp-Crested Vee/Trap Weir ( Controls 0.00 cfs)5=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Chanhassen Apartments Proposed Conditions Type II 24-hr 2yr Rainfall=2.80"120103-pdrn Page 5 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Pond P-1: Proposed Pond Inflow Area =4.416 ac, Inflow Depth = 1.04" for 2yr event Inflow=4.95 cfs @ 12.14 hrs, Volume=0.384 af Outflow=1.57 cfs @ 12.49 hrs, Volume=0.384 af, Atten= 68%, Lag= 21.1 min Primary=1.57 cfs @ 12.49 hrs, Volume=0.384 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Starting Elev= 956.00' Surf.Area= 7,971 sf Storage= 20,930 cf Peak Elev= 956.69' @ 12.49 hrs Surf.Area= 8,729 sf Storage= 26,725 cf (5,795 cf above start)Plug-Flow detention time= (not calculated: initial storage excedes outflow)Center-of-Mass det. time= 270.6 min ( 1,133.6 - 863.0 )VolumeInvertAvail.StorageStorage Description #1948.00'62,054 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)948.00168111.000168 950.001,067179.01,1061,1061,764 952.002,294229.03,2844,3893,438 954.003,817277.06,04710,4365,436 955.004,680298.04,24114,6776,439 956.007,971361.06,25320,9309,759 958.0010,248398.018,17139,10112,119 960.0012,750436.022,95262,05414,775 DeviceRouting InvertOutlet Devices #1Primary956.00'15.0" x 25.0' long Culvert RCP, rounded edge headwall, Ke= 0.100 Outlet Invert= 955.88' S= 0.0048 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior Primary OutFlow Max=1.57 cfs @ 12.49 hrs HW=956.69' TW=955.37' (Dynamic Tailwater)1=Culvert (Barrel Controls 1.57 cfs @ 3.25 fps)Link 1L: NW Wetland Inflow Area =5.093 ac, Inflow Depth = 0.50" for 2yr event Inflow=0.07 cfs @ 24.20 hrs, Volume=0.212 af Primary=0.07 cfs @ 24.20 hrs, Volume=0.212 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Proposed Conditions Type II 24-hr 2yr Rainfall=2.80"120103-pdrn Page 6 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Link 2L: Existing Pond Inflow Area =3.027 ac, Inflow Depth = 0.61" for 2yr event Inflow=2.31 cfs @ 12.06 hrs, Volume=0.153 af Primary=2.31 cfs @ 12.06 hrs, Volume=0.153 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Proposed Conditions Type II 24-hr 10yr Rainfall=4.20"120103-pdrn Page 7 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment D-1s: Direct Offsite Runoff=6.17 cfs @ 12.05 hrs, Volume=0.369 af, Depth=1.46"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr Rainfall=4.20"Area (sf)CNDescription 28,85298Paved parking & roofs 95,72261>75% Grass cover, Good, HSG B 7,27374>75% Grass cover, Good, HSG C 131,84770Weighted Average 102,995Pervious Area 28,852Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)12.0 Direct Entry, Subcatchment EW-1s: Existing Wetland Runoff=1.78 cfs @ 12.02 hrs, Volume=0.098 af, Depth=1.74"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr Rainfall=4.20"Area (sf)CNDescription 29,48074>75% Grass cover, Good, HSG C 29,480Pervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)10.0 Direct Entry, Subcatchment P-1s: Proposed Pond Runoff=10.36 cfs @ 12.13 hrs, Volume=0.783 af, Depth=2.13"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr Rainfall=4.20"Area (sf)CNDescription 86,68898Paved parking & roofs 84,61961>75% Grass cover, Good, HSG B 21,04774>75% Grass cover, Good, HSG C 192,35479Weighted Average 105,666Pervious Area 86,688Impervious Area Chanhassen Apartments Proposed Conditions Type II 24-hr 10yr Rainfall=4.20"120103-pdrn Page 8 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)20.0 Direct Entry, Pond EW-1: Existing Wetland Inflow Area =5.093 ac, Inflow Depth = 2.07" for 10yr event Inflow=4.69 cfs @ 12.37 hrs, Volume=0.880 af Outflow=0.50 cfs @ 15.37 hrs, Volume=0.880 af, Atten= 89%, Lag= 180.2 min Discarded=0.03 cfs @ 15.37 hrs, Volume=0.264 af Primary=0.47 cfs @ 15.37 hrs, Volume=0.617 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Peak Elev= 956.80' @ 15.37 hrs Surf.Area= 0.303 ac Storage= 0.431 af Plug-Flow detention time= (not calculated: outflow precedes inflow)Center-of-Mass det. time= 1,491.0 min ( 2,634.9 - 1,144.0 )VolumeInvertAvail.StorageStorage Description #1954.99'1.639 af Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(acres)(feet)(acre-feet)(acre-feet)(acres)954.990.0004.00.0000.0000.000 955.000.142362.00.0000.0000.239 956.000.268445.00.2020.2020.362 958.000.359502.00.6250.8270.463 960.000.456556.00.8131.6390.570 DeviceRouting InvertOutlet Devices #1Discarded0.00'0.100 in/hr Exfiltration over Surface area #2Primary955.48'24.0" x 108.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 954.48' S= 0.0093 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections #3Device 2955.48'1.7" Vert. Orifice/Grate C= 0.600 #4Device 2956.50'90.0 deg x 0.5' long x 1.00' rise Sharp-Crested Vee/Trap Weir C= 2.50 #5Device 2957.50'5.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Discarded OutFlow Max=0.03 cfs @ 15.37 hrs HW=956.80' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.03 cfs)Primary OutFlow Max=0.47 cfs @ 15.37 hrs HW=956.80' TW=0.00' (Dynamic Tailwater)2=Culvert (Passes 0.47 cfs of 8.51 cfs potential flow)3=Orifice/Grate (Orifice Controls 0.08 cfs @ 5.38 fps)4=Sharp-Crested Vee/Trap Weir (Weir Controls 0.38 cfs @ 1.59 fps)5=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Chanhassen Apartments Proposed Conditions Type II 24-hr 10yr Rainfall=4.20"120103-pdrn Page 9 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Pond P-1: Proposed Pond Inflow Area =4.416 ac, Inflow Depth = 2.13" for 10yr event Inflow=10.36 cfs @ 12.13 hrs, Volume=0.783 af Outflow=4.40 cfs @ 12.39 hrs, Volume=0.782 af, Atten= 58%, Lag= 15.4 min Primary=4.40 cfs @ 12.39 hrs, Volume=0.782 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Starting Elev= 956.00' Surf.Area= 7,971 sf Storage= 20,930 cf Peak Elev= 957.30' @ 12.39 hrs Surf.Area= 9,414 sf Storage= 32,181 cf (11,251 cf above start)Plug-Flow detention time= 1,092.8 min calculated for 0.302 af (39% of inflow)Center-of-Mass det. time= 339.1 min ( 1,181.4 - 842.2 )VolumeInvertAvail.StorageStorage Description #1948.00'62,054 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)948.00168111.000168 950.001,067179.01,1061,1061,764 952.002,294229.03,2844,3893,438 954.003,817277.06,04710,4365,436 955.004,680298.04,24114,6776,439 956.007,971361.06,25320,9309,759 958.0010,248398.018,17139,10112,119 960.0012,750436.022,95262,05414,775 DeviceRouting InvertOutlet Devices #1Primary956.00'15.0" x 25.0' long Culvert RCP, rounded edge headwall, Ke= 0.100 Outlet Invert= 955.88' S= 0.0048 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior Primary OutFlow Max=4.39 cfs @ 12.39 hrs HW=957.29' TW=955.84' (Dynamic Tailwater)1=Culvert (Barrel Controls 4.39 cfs @ 4.29 fps)Link 1L: NW Wetland Inflow Area =5.093 ac, Inflow Depth = 1.45" for 10yr event Inflow=0.47 cfs @ 15.37 hrs, Volume=0.617 af Primary=0.47 cfs @ 15.37 hrs, Volume=0.617 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Proposed Conditions Type II 24-hr 10yr Rainfall=4.20"120103-pdrn Page 10 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Link 2L: Existing Pond Inflow Area =3.027 ac, Inflow Depth = 1.46" for 10yr event Inflow=6.17 cfs @ 12.05 hrs, Volume=0.369 af Primary=6.17 cfs @ 12.05 hrs, Volume=0.369 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Proposed Conditions Type II 24-hr 100yr Rainfall=6.00"120103-pdrn Page 11 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment D-1s: Direct Offsite Runoff=12.05 cfs @ 12.04 hrs, Volume=0.708 af, Depth=2.81"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr Rainfall=6.00"Area (sf)CNDescription 28,85298Paved parking & roofs 95,72261>75% Grass cover, Good, HSG B 7,27374>75% Grass cover, Good, HSG C 131,84770Weighted Average 102,995Pervious Area 28,852Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)12.0 Direct Entry, Subcatchment EW-1s: Existing Wetland Runoff=3.26 cfs @ 12.02 hrs, Volume=0.180 af, Depth=3.18"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr Rainfall=6.00"Area (sf)CNDescription 29,48074>75% Grass cover, Good, HSG C 29,480Pervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)10.0 Direct Entry, Subcatchment P-1s: Proposed Pond Runoff=17.95 cfs @ 12.12 hrs, Volume=1.354 af, Depth=3.68"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr Rainfall=6.00"Area (sf)CNDescription 86,68898Paved parking & roofs 84,61961>75% Grass cover, Good, HSG B 21,04774>75% Grass cover, Good, HSG C 192,35479Weighted Average 105,666Pervious Area 86,688Impervious Area Chanhassen Apartments Proposed Conditions Type II 24-hr 100yr Rainfall=6.00"120103-pdrn Page 12 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)20.0 Direct Entry, Pond EW-1: Existing Wetland Inflow Area =5.093 ac, Inflow Depth = 3.61" for 100yr event Inflow=8.00 cfs @ 12.35 hrs, Volume=1.533 af Outflow=2.92 cfs @ 13.13 hrs, Volume=1.533 af, Atten= 64%, Lag= 46.5 min Discarded=0.03 cfs @ 13.13 hrs, Volume=0.271 af Primary=2.89 cfs @ 13.13 hrs, Volume=1.262 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Peak Elev= 957.33' @ 13.13 hrs Surf.Area= 0.327 ac Storage= 0.599 af Plug-Flow detention time= (not calculated: outflow precedes inflow)Center-of-Mass det. time= 913.1 min ( 1,947.4 - 1,034.3 )VolumeInvertAvail.StorageStorage Description #1954.99'1.639 af Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(acres)(feet)(acre-feet)(acre-feet)(acres)954.990.0004.00.0000.0000.000 955.000.142362.00.0000.0000.239 956.000.268445.00.2020.2020.362 958.000.359502.00.6250.8270.463 960.000.456556.00.8131.6390.570 DeviceRouting InvertOutlet Devices #1Discarded0.00'0.100 in/hr Exfiltration over Surface area #2Primary955.48'24.0" x 108.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 954.48' S= 0.0093 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections #3Device 2955.48'1.7" Vert. Orifice/Grate C= 0.600 #4Device 2956.50'90.0 deg x 0.5' long x 1.00' rise Sharp-Crested Vee/Trap Weir C= 2.50 #5Device 2957.50'5.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Discarded OutFlow Max=0.03 cfs @ 13.13 hrs HW=957.33' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.03 cfs)Primary OutFlow Max=2.88 cfs @ 13.13 hrs HW=957.33' TW=0.00' (Dynamic Tailwater)2=Culvert (Passes 2.88 cfs of 14.09 cfs potential flow)3=Orifice/Grate (Orifice Controls 0.10 cfs @ 6.43 fps)4=Sharp-Crested Vee/Trap Weir (Weir Controls 2.78 cfs @ 2.50 fps)5=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Chanhassen Apartments Proposed Conditions Type II 24-hr 100yr Rainfall=6.00"120103-pdrn Page 13 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Pond P-1: Proposed Pond Inflow Area =4.416 ac, Inflow Depth = 3.68" for 100yr event Inflow=17.95 cfs @ 12.12 hrs, Volume=1.354 af Outflow=7.50 cfs @ 12.38 hrs, Volume=1.353 af, Atten= 58%, Lag= 15.4 min Primary=7.50 cfs @ 12.38 hrs, Volume=1.353 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Starting Elev= 956.00' Surf.Area= 7,971 sf Storage= 20,930 cf Peak Elev= 958.11' @ 12.38 hrs Surf.Area= 10,373 sf Storage= 40,191 cf (19,261 cf above start)Plug-Flow detention time= 520.5 min calculated for 0.873 af (64% of inflow)Center-of-Mass det. time= 234.9 min ( 1,061.4 - 826.6 )VolumeInvertAvail.StorageStorage Description #1948.00'62,054 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)948.00168111.000168 950.001,067179.01,1061,1061,764 952.002,294229.03,2844,3893,438 954.003,817277.06,04710,4365,436 955.004,680298.04,24114,6776,439 956.007,971361.06,25320,9309,759 958.0010,248398.018,17139,10112,119 960.0012,750436.022,95262,05414,775 DeviceRouting InvertOutlet Devices #1Primary956.00'15.0" x 25.0' long Culvert RCP, rounded edge headwall, Ke= 0.100 Outlet Invert= 955.88' S= 0.0048 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior Primary OutFlow Max=7.49 cfs @ 12.38 hrs HW=958.10' TW=956.52' (Dynamic Tailwater)1=Culvert (Barrel Controls 7.49 cfs @ 6.10 fps)Link 1L: NW Wetland Inflow Area =5.093 ac, Inflow Depth = 2.97" for 100yr event Inflow=2.89 cfs @ 13.13 hrs, Volume=1.262 af Primary=2.89 cfs @ 13.13 hrs, Volume=1.262 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Proposed Conditions Type II 24-hr 100yr Rainfall=6.00"120103-pdrn Page 14 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Link 2L: Existing Pond Inflow Area =3.027 ac, Inflow Depth = 2.81" for 100yr event Inflow=12.05 cfs @ 12.04 hrs, Volume=0.708 af Primary=12.05 cfs @ 12.04 hrs, Volume=0.708 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Proposed Conditions Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 120103-pdrn Page 15 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment D-1s: Direct Offsite Runoff=3.61 cfs @ 119.14 hrs, Volume=1.756 af, Depth=6.96"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 Area (sf)CNDescription 28,85298Paved parking & roofs 95,72261>75% Grass cover, Good, HSG B 7,27374>75% Grass cover, Good, HSG C 131,84770Weighted Average, Adjusted for AMC to CN = 98 102,995Pervious Area 28,852Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)12.0 Direct Entry, Subcatchment EW-1s: Existing Wetland Runoff=0.81 cfs @ 119.11 hrs, Volume=0.393 af, Depth=6.96"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 Area (sf)CNDescription 29,48074>75% Grass cover, Good, HSG C 29,48074Weighted Average, Adjusted for AMC to CN = 98 29,480Pervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)10.0 Direct Entry, Subcatchment P-1s: Proposed Pond Runoff=5.14 cfs @ 119.22 hrs, Volume=2.561 af, Depth=6.96"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 Area (sf)CNDescription 86,68898Paved parking & roofs 84,61961>75% Grass cover, Good, HSG B 21,04774>75% Grass cover, Good, HSG C 192,35479Weighted Average, Adjusted for AMC to CN = 98 105,666Pervious Area 86,688Impervious Area Chanhassen Apartments Proposed Conditions Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 120103-pdrn Page 16 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)20.0 Direct Entry, Pond EW-1: Existing Wetland Inflow Area =5.093 ac, Inflow Depth = 6.96" for 100yr SM event Inflow=4.65 cfs @ 119.39 hrs, Volume=2.952 af Outflow=4.14 cfs @ 119.78 hrs, Volume=2.912 af, Atten= 11%, Lag= 23.5 min Discarded=0.03 cfs @ 119.78 hrs, Volume=0.571 af Primary=4.11 cfs @ 119.78 hrs, Volume=2.340 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Peak Elev= 957.49' @ 119.78 hrs Surf.Area= 0.334 ac Storage= 0.651 af Plug-Flow detention time= 1,112.9 min calculated for 2.911 af (99% of inflow)Center-of-Mass det. time= 1,017.7 min ( 8,636.7 - 7,619.1 )VolumeInvertAvail.StorageStorage Description #1954.99'1.639 af Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(acres)(feet)(acre-feet)(acre-feet)(acres)954.990.0004.00.0000.0000.000 955.000.142362.00.0000.0000.239 956.000.268445.00.2020.2020.362 958.000.359502.00.6250.8270.463 960.000.456556.00.8131.6390.570 DeviceRouting InvertOutlet Devices #1Discarded0.00'0.100 in/hr Exfiltration over Surface area #2Primary955.48'24.0" x 108.0' long Culvert RCP, end-section conforming to fill, Ke= 0.500 Outlet Invert= 954.48' S= 0.0093 '/' Cc= 0.900 n= 0.013 Concrete pipe, bends & connections #3Device 2955.48'1.7" Vert. Orifice/Grate C= 0.600 #4Device 2956.50'90.0 deg x 0.5' long x 1.00' rise Sharp-Crested Vee/Trap Weir C= 2.50 #5Device 2957.50'5.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Discarded OutFlow Max=0.03 cfs @ 119.78 hrs HW=957.49' (Free Discharge)1=Exfiltration (Exfiltration Controls 0.03 cfs)Primary OutFlow Max=4.11 cfs @ 119.78 hrs HW=957.49' TW=0.00' (Dynamic Tailwater)2=Culvert (Passes 4.11 cfs of 15.22 cfs potential flow)3=Orifice/Grate (Orifice Controls 0.11 cfs @ 6.71 fps)4=Sharp-Crested Vee/Trap Weir (Weir Controls 4.00 cfs @ 2.70 fps)5=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Chanhassen Apartments Proposed Conditions Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 120103-pdrn Page 17 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Pond P-1: Proposed Pond Inflow Area =4.416 ac, Inflow Depth = 6.96" for 100yr SM event Inflow=5.14 cfs @ 119.22 hrs, Volume=2.561 af Outflow=4.02 cfs @ 119.49 hrs, Volume=2.559 af, Atten= 22%, Lag= 15.8 min Primary=4.02 cfs @ 119.49 hrs, Volume=2.559 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Starting Elev= 956.00' Surf.Area= 7,971 sf Storage= 20,930 cf Peak Elev= 957.76' @ 119.61 hrs Surf.Area= 9,958 sf Storage= 36,665 cf (15,734 cf above start)Plug-Flow detention time= 1,790.7 min calculated for 2.078 af (81% of inflow)Center-of-Mass det. time= 315.7 min ( 7,662.3 - 7,346.5 )VolumeInvertAvail.StorageStorage Description #1948.00'62,054 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)948.00168111.000168 950.001,067179.01,1061,1061,764 952.002,294229.03,2844,3893,438 954.003,817277.06,04710,4365,436 955.004,680298.04,24114,6776,439 956.007,971361.06,25320,9309,759 958.0010,248398.018,17139,10112,119 960.0012,750436.022,95262,05414,775 DeviceRouting InvertOutlet Devices #1Primary956.00'15.0" x 25.0' long Culvert RCP, rounded edge headwall, Ke= 0.100 Outlet Invert= 955.88' S= 0.0048 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior Primary OutFlow Max=4.02 cfs @ 119.49 hrs HW=957.75' TW=957.47' (Dynamic Tailwater)1=Culvert (Outlet Controls 4.02 cfs @ 3.28 fps)Link 1L: NW Wetland Inflow Area =5.093 ac, Inflow Depth = 5.51" for 100yr SM event Inflow=4.11 cfs @ 119.78 hrs, Volume=2.340 af Primary=4.11 cfs @ 119.78 hrs, Volume=2.340 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Chanhassen Apartments Proposed Conditions Type II 24-hr 240.00 hrs 100yr SM Rainfall=7.20", AMC=4 120103-pdrn Page 18 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Link 2L: Existing Pond Inflow Area =3.027 ac, Inflow Depth = 6.96" for 100yr SM event Inflow=3.61 cfs @ 119.14 hrs, Volume=1.756 af Primary=3.61 cfs @ 119.14 hrs, Volume=1.756 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs P-1s Proposed Pond P-1 Proposed Pond Drainage Diagram for 120103-pdrn Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcat Reach Pond Link Chanhassen Apartments NURP Calculations 120103-pdrn Page 2 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Area Listing (selected nodes)Area (acres)CN Description (subcats)1.94361>75% Grass cover, Good, HSG B (P-1s)0.48374>75% Grass cover, Good, HSG C (P-1s)1.99098Paved parking & roofs (P-1s) 4.416 Chanhassen Apartments NURP Calculations Type II 24-hr NURP Rainfall=2.50"120103-pdrn Page 3 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Subcatchment P-1s: Proposed Pond Runoff=3.90 cfs @ 12.14 hrs, Volume=0.308 af, Depth=0.84"Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs Type II 24-hr NURP Rainfall=2.50"Area (sf)CNDescription 86,68898Paved parking & roofs 84,61961>75% Grass cover, Good, HSG B 21,04774>75% Grass cover, Good, HSG C 192,35479Weighted Average 105,666Pervious Area 86,688Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs)20.0 Direct Entry, Pond P-1: Proposed Pond Inflow Area =4.416 ac, Inflow Depth = 0.84" for NURP event Inflow=3.90 cfs @ 12.14 hrs, Volume=0.308 af Outflow=1.09 cfs @ 12.55 hrs, Volume=0.308 af, Atten= 72%, Lag= 24.4 min Primary=1.09 cfs @ 12.55 hrs, Volume=0.308 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-300.00 hrs, dt= 0.05 hrs / 3 Starting Elev= 956.00' Surf.Area= 7,971 sf Storage= 20,930 cf Peak Elev= 956.57' @ 12.55 hrs Surf.Area= 8,588 sf Storage= 25,631 cf (4,701 cf above start)Plug-Flow detention time= (not calculated: initial storage excedes outflow)Center-of-Mass det. time= 221.3 min ( 1,091.0 - 869.7 )VolumeInvertAvail.StorageStorage Description #1948.00'62,054 cf Custom Stage Data (Irregular) Listed below (Recalc)ElevationSurf.AreaPerim.Inc.StoreCum.StoreWet.Area (feet)(sq-ft)(feet)(cubic-feet)(cubic-feet)(sq-ft)948.00168111.000168 950.001,067179.01,1061,1061,764 952.002,294229.03,2844,3893,438 954.003,817277.06,04710,4365,436 955.004,680298.04,24114,6776,439 956.007,971361.06,25320,9309,759 958.0010,248398.018,17139,10112,119 960.0012,750436.022,95262,05414,775 DeviceRouting InvertOutlet Devices #1Primary956.00'15.0" x 25.0' long Culvert RCP, rounded edge headwall, Ke= 0.100 Chanhassen Apartments NURP Calculations Type II 24-hr NURP Rainfall=2.50"120103-pdrn Page 4 Prepared by Alliant Engineering 3/18/2013 HydroCAD® 8.00 s/n 004060 © 2006 HydroCAD Software Solutions LLC Outlet Invert= 955.88' S= 0.0048 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior Primary OutFlow Max=1.09 cfs @ 12.55 hrs HW=956.57' TW=955.29' (Dynamic Tailwater)1=Culvert (Barrel Controls 1.09 cfs @ 2.95 fps) STORM SEWER DESIGN WORKSHEET - PROPOSED CONDITIONS PROJECT NAME: Chanhassen Apartments ALLIANT ENGINEERING, INC.PROJECT NUMBER: 120103 233 PARK AVENUE SOUTH SUITE 300 PREPARED BY: CB MINNEAPOLIS, MN 55415 REVISION DATE 3-15-13 (CB)DESIGN STORM FREQUENCY = 10 YEARS MH/CBAREAIMP IMPRUNOFF INCR. CUMTcTc INTENSITY INCREMENTAL TOTAL PIPE PIPE SLOPE PIPE CAP.PIPE CAP. V PIPEINVERTINVERTRIM ELEV COVER STRUCTUREPIPECASTING FROMTO INCR. TOTAL SF % C AC AC PIPE CUM.TIME i Q Q DIA S QCHECK MAX LENGTHFROMTO CHECK TYPETYPE =====================================================================================================================================================================================================================================================================================================================CB-1A CBMH-4 0.354 0.354 5,932 38%0.490.1740.174 8.00 8.006.111.061.06 120.0045 2.401.333.05 342.00958.30 956.76961.001.502x3N-12 ADS3067-V CB-2A CBMH-3 0.217 0.217 5,255 56%0.620.1340.134 8.00 8.006.110.820.82 120.0045 2.401.583.05 120.00957.80 957.26961.002.002x3N-12 ADS3067-V CBMH-3CBMH-4 2.340 2.911 73,310 72%0.741.7202.0271.879.875.669.7411.48 210.0060 12.310.835.12 8.00 956.51956.46962.604.1448N-12 ADS3067-V CBMH-4FES-5 0.000 2.911 0 0%0.210.0002.0270.039.895.660.0011.47 210.0063 12.611.145.24 26.00 956.16956.00962.604.4948RCP3067-V