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215-0030 Hydrologic and Hydraulic StudyStormwater Management Hydrologic and Hydraulic Study Glaccum Property Chanhassen, MN Preliminary June 16, 2015 Glaccum Property Hydrologic and Hydraulic Study June 5, 2015 Alliant Engineering, Inc. Page 1 of 4 215-0030 Introduction Included in this report are the materials necessary to review the stormwater management plan for the proposed Glaccum Property project in Chanhassen, Minnesota. The following information is included:  Study Narrative  Drainage Area Maps  Rate Control HydroCAD Calculation Reports  Volume and Water Quality Control Calculations  Storm Sewer Design Calculations Background This study was conducted to analyze stormwater treatment requirements for a proposed 4 lot residential in Chanhassen, Minnesota and within Minnehaha Creek Watershed boundary. The study will show that the proposed stormwater management facility will nullify the effects of the increased impervious surface resulting from the new development. Following two scenarios are assumed in this study:  Existing conditions – Minimal development  Proposed conditions – Development of the residential project A complete storm water analysis of the 3.12 acre site (1.9 acres disturbed) is included in the study as well as the inclusion of 9.12 acres of offsite catchment that will affect or is affected by the site. The proposed site is bound by Lake Lucy Road to the south, Yosemite Avenue to the west, existing residential to the east and a wetland to the north. Developer is proposing 4 lot single family homes. Drainage maps provided show delineations based on full development. Stormwater management plan for the proposed conditions will meet the guidelines as required by the City of Chanhassen and Minnehaha Creek Watershed District for stormwater quantity and quality. The following criterion was used in designing the stormwater management system:  Post-development peak runoff rate from the site for the 1, 2, 10, 100-year and a 100-year back to back 24-hour Type II storm events (Atlas-14) must not be greater than the existing condition rates in accordance with the City of Chanhassen and Minnehaha Creek WMC.  Proposed water quality treatment must provide a minimum of 60% phosphorous and 90% total suspended solids removal per the City of Chanhassen.  Stormwater management plan must meet the City and Watershed non-degradation policy for storm water runoff quality where post-development nutrient loads cannot exceed those of existing conditions.  Volume control retained on site is equivalent to 1” over new impervious surface in accordance with the City of Chanhassen’s Stormwater Management Plan.  Emergency overflow for flows greater than 100-year event must be provided. Runoff Rate Control All rate control calculations have been performed using the SCS method via HydroCAD software. Five events were modeled including: 1-year, 2-year, 10-year, 100-year, and 100-year back to back Type II 24-hour storm events with ATLAS-14 precipitation amounts of 2.50”, 2.87”, 4.26”, and 7.36” used, respectively. All existing and proposed curve numbers are based on an assumed soil type ‘C’ as indicated in the preliminary geotechnical investigation produced by Braun Intertec. Times of concentrations were estimated and modeled Glaccum Property Hydrologic and Hydraulic Study June 5, 2015 Alliant Engineering, Inc. Page 2 of 4 215-0030 using direct entry. The existing study does include some drainage area from offsite to the north because that area drains into the site’s drainage area. Proposed conditions watershed area will exactly match existing conditions area scenario. Existing Conditions The site is currently one lot with one single family home and associated driveway and out buildings. North side of the property is covered by Lake Lucy floodplain wetland. The wetland limits within the site were delineated Kjholhaug Environmental. The property has variable terrain that primarily drains northerly towards the wetland with a small area along the east side draining to Lake Lucy Road’s ditch. Following subcatchments were used in the existing conditions HydroCAD model:  LW – Onsite area that drains to Lake Lucy Road ditch.  W-1 – Onsite area that drains to the wetland.  W-1(O) – Offsite area that drains across the site and ultimately to the wetland. The area will drain to the existing wetland in the existing conditions. To compare peak discharge rates for the existing and proposed conditions, flows were analyzed compositely as well as both the Lake Lucy Road ditch and Lake Lucy wetland separately. For ease of comparison, the existing analysis nodes will remain consistent in the proposed and existing models. Refer to the existing conditions drainage map and HydroCAD report for additional information and detailed calculations. Site composite existing runoff rate as calculated by HydroCAD are listed in the table below: Event To Lake Lucy Road (cfs) To Wetland (cfs) Wetland NWL (ft) 1 year (2.50” 24hr) 0.76 13.50 999.45 2 year (3.87” 24hr) 0.98 17.17 999.55 10 year (4.26” 24hr) 1.94 32.55 999.98 100 year (7.36” 24hr) 4.32 71.13 1,000.93 Back to Back 100 year (7.36” 24hr) 5.36 88.36 1,002.88 Proposed Conditions The proposed development project includes construction of 4 residential lots and associated roadway as shown in the submittal plan set. Project will include construction of an underground infiltration pipe to provide the rate and volume control and water quality treatment of stormwater. Stormwater runoff from the new roadway and 3 of the front yards will be collected by storm sewer underground infiltration pipe. All of the backyards and the westerly front yard will drain uncaptured toward the wetland. Following subcatchments were used in the proposed conditions HydroCAD model:  R-1 – Onsite area that drains to the wetland.  R-2 – Onsite area that will be captured by storm sewer.  RW-1 – Right of way area that drains to the wetland.  RW-2 – Right of way area that will be captured by storm sewer.  O – Outlot A area (wetland).  W-1(O) – Offsite area that drains across the site and ultimately to the wetland. The area will drain directly to the existing wetland in the proposed condition. The proposed underground infiltration pipe discharge will be routed to the Lake Lucy wetland at the wetland edge. The flow will be regulated by an outlet control structure that will discharge via a 12” pipe. Refer to the submittal plan set for details on the Outlet Control Structure. Glaccum Property Hydrologic and Hydraulic Study June 5, 2015 Alliant Engineering, Inc. Page 3 of 4 215-0030 The proposed stormwater management plan does increase the peak discharge rate into the wetland but because the normal water elevations are insignificantly affected, and runoff to Lake Lucy Road ditch is eliminated, there is no runoff from the site. Refer to the proposed conditions drainage map and HydroCAD report sheets for additional information. Site composite proposed runoff rate as calculated by HydroCAD are listed in the table below: Event To Lake Lucy Road (cfs) / (∆ from Ex.) To Wetland (cfs) / (∆ from Ex.) Wetland NWL (ft) 1 year (2.50” 24hr) 0 / (-0.76) 13.83 / (0.33) 999.48 2 year (3.87” 24hr) 0 / (-0.98) 17.52 / (0.35) 999.59 10 year (4.26” 24hr) 0 / (-1.94) 32.99 / (0.44) 1,000.04 100 year (7.36” 24hr) 0 / (-4.32) 71.83 / (0.70) 1,001.01 Back to Back 100 year (7.36” 24hr) 0 / (-5.36) 88.93 / (0.57) 1,003.06 Stormwater Volume Control and Water Quality The proposed project will result in an addition of approximately 0.57 acres of new impervious surface. New impervious surface has been offset by onsite stormwater underground infiltration pipe. Volume control will be provided by infiltration of 1” over new impervious surface and excess NURP storage. The proposed stormwater management plan exceeds the volume control requirements of the City of Chanhassen’s Stormwater Management Plan. See appendix for calculations. The Proposed Underground Infiltration Pipe is also designed to meet the water quality requirements of the City of Chanhassen and will provide the required phosphorus and total suspended solids removal efficiencies. Erosion and Sediment Control Plan Refer to the Stormwater Pollution Prevention Plan (SWPPP) plan sheet for the erosion and sediment control plan for the project. Best Management Practices will be utilized to ensure proper erosion and sediment control. Conclusion Alliant Engineering believes that the proposed design is acceptable for all parties involved. Peak discharge rates for the 1-year, 2-year, 10-year, 100-year and 100-year back to back 24-hour storm events will be decreased from existing rates for the proposed conditions. Adequate runoff volume has been retained on site to mitigate the proposed impervious surface additions. The proposed underground infiltration designs also exceed the required amount of permanent pool volume and meet criteria for proper treatment of the runoff. Nutrient loading to receiving waters will not increase from the existing conditions and the proposed pond phosphorous removal efficiencies meet requirements. Finally, the proposed grading and SWPP plans will utilizes Best Management Practices whenever possible to provide adequate erosion control measures to contain sediment during construction. Please call me at 612-767-9362 with any questions or comments regarding stormwater issues for the Glaccum Property project. Sincerely, Pavel Nikolov, EIT Alliant Engineering, Inc. CC: File 150030 Pond 1.0” Runoff Volume Dead Pool Volume Provided Underground Infiltration Pipe 0.048 af 2,084 cf 0.029 af 1,257 cf Glaccum Property Hydrologic and Hydraulic Study June 5, 2015 Alliant Engineering, Inc. Page 4 of 4 215-0030 APPENDIX - Drainage Maps  Existing Conditions  Proposed Conditions - Rate Control HydroCAD Reports  Existing Conditions  Proposed Conditions - Precipitation Frequency Data - Water Quality and Volume Calculations  Summary Spreadsheet - Storm Sewer Sizing  Sizing Spreadsheet - Preliminary Geotechnical Investigation 1S LW 3S W-1 4S W-1(O) 2P W-1 5L TOTAL Routing Diagram for edrnPrepared by Alliant Engineering, Printed 6/16/2015 HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link edrn Printed 6/16/2015Prepared by Alliant Engineering Page 2HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 3.733 74 >75% Grass cover, Good, HSG C (1S, 3S, 4S) 0.089 89 Gravel roads, HSG C (4S) 0.040 96 Gravel surface, HSG C (1S) 0.348 98 Impervious (1S, 3S) 0.862 98 Unconnected pavement, HSG C (4S) 1.662 98 Water Surface, 0% imp, HSG C (4S) 0.449 98 Water Surface, HSG C (3S) 5.056 70 Woods, Good, HSG C (1S, 3S, 4S) 12.240 79 TOTAL AREA Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2edrn Printed 6/16/2015Prepared by Alliant Engineering Page 3HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: LW Runoff = 5.36 cfs @ 35.98 hrs, Volume= 0.552 af, Depth=11.68" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Area (sf) CN Description 5,169 70 Woods, Good, HSG C * 2,903 98 Impervious 1,756 96 Gravel surface, HSG C 14,872 74 >75% Grass cover, Good, HSG C 24,700 78 Weighted Average 21,797 88.25% Pervious Area 2,903 11.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.6 260 0.0231 0.57 Lag/CN Method, Summary for Subcatchment 3S: W-1 Runoff = 23.12 cfs @ 36.00 hrs, Volume= 2.526 af, Depth=11.85" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Area (sf) CN Description 52,525 70 Woods, Good, HSG C 19,578 98 Water Surface, HSG C * 12,242 98 Impervious 27,060 74 >75% Grass cover, Good, HSG C 111,405 79 Weighted Average 79,585 71.44% Pervious Area 31,820 28.56% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 9.0 Direct Entry, Summary for Subcatchment 4S: W-1(O) Runoff = 68.57 cfs @ 36.06 hrs, Volume= 9.025 af, Depth=11.88" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2edrn Printed 6/16/2015Prepared by Alliant Engineering Page 4HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Area (sf) CN Adj Description 162,566 70 70 Woods, Good, HSG C 72,397 98 98 Water Surface, 0% imp, HSG C 37,549 98 98 Unconnected pavement, HSG C 120,661 74 74 >75% Grass cover, Good, HSG C 3,877 89 89 Gravel roads, HSG C 397,050 79 78 Weighted Average, UI Adjusted 359,501 90.54% Pervious Area 37,549 9.46% Impervious Area 37,549 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 15.0 Direct Entry, Summary for Pond 2P: W-1 Inflow Area = 11.673 ac, 13.64% Impervious, Inflow Depth = 11.87" for Bk-Bk 100 yr event Inflow = 88.36 cfs @ 36.04 hrs, Volume= 11.550 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Starting Elev= 999.00' Surf.Area= 92,936 sf Storage= 220,377 cf Peak Elev= 1,002.88' @ 48.84 hrs Surf.Area= 166,121 sf Storage= 723,480 cf (503,103 cf above start) Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 996.00' 1,506,240 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 996.00 55,574 937.1 0 0 55,574 1,000.00 107,513 2,029.6 320,513 320,513 313,562 1,002.00 155,414 1,946.5 261,460 581,973 340,155 1,004.00 180,253 1,931.4 335,360 917,333 346,217 1,006.00 202,937 1,997.4 382,966 1,300,299 367,222 1,007.00 208,958 2,016.1 205,940 1,506,240 373,523 Device Routing Invert Outlet Devices #1 Primary 1,006.00'123.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=999.00' (Free Discharge) 1=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2edrn Printed 6/16/2015Prepared by Alliant Engineering Page 5HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Summary for Link 5L: TOTAL Inflow Area = 12.240 ac, 13.56% Impervious, Inflow Depth = 0.54" for Bk-Bk 100 yr event Inflow = 5.36 cfs @ 35.98 hrs, Volume= 0.552 af Primary = 5.36 cfs @ 35.98 hrs, Volume= 0.552 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs 1S R-1 2S R-2 4S W-1(O) 7S RW-2 8S RW-1 9S O 3P W-1 7P Storage Pipe 6L TOTAL Routing Diagram for pdrnPrepared by Alliant Engineering, Printed 6/16/2015 HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link pdrn Printed 6/16/2015Prepared by Alliant Engineering Page 2HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Area Listing (all nodes) Area (acres) CN Description (subcatchment-numbers) 3.984 74 >75% Grass cover, Good, HSG C (1S, 2S, 4S, 7S, 8S) 0.089 96 Gravel surface, HSG C (4S) 0.862 98 Impervious (4S) 0.234 98 Paved roads w/curbs & sewers, HSG C (7S) 0.271 92 Paved roads w/open ditches, 50% imp, HSG C (8S) 0.211 98 Unconnected pavement, HSG C (1S) 0.206 98 Unconnected roofs, HSG C (2S) 2.106 98 Water Surface, HSG C (4S, 9S) 4.276 70 Woods, Good, HSG C (1S, 4S, 8S) 12.240 80 TOTAL AREA Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2pdrn Printed 6/16/2015Prepared by Alliant Engineering Page 3HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment 1S: R-1 Runoff = 11.94 cfs @ 36.01 hrs, Volume= 1.313 af, Depth=11.51" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Area (sf) CN Adj Description 9,204 98 98 Unconnected pavement, HSG C 19,724 70 70 Woods, Good, HSG C 30,725 74 74 >75% Grass cover, Good, HSG C 59,653 76 74 Weighted Average, UI Adjusted 50,449 84.57% Pervious Area 9,204 15.43% Impervious Area 9,204 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.0 Direct Entry, Summary for Subcatchment 2S: R-2 Runoff = 4.50 cfs @ 35.98 hrs, Volume= 0.483 af, Depth=12.68" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Area (sf) CN Description 8,957 98 Unconnected roofs, HSG C 10,948 74 >75% Grass cover, Good, HSG C 19,905 85 Weighted Average 10,948 55.00% Pervious Area 8,957 45.00% Impervious Area 8,957 100.00% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.0 Direct Entry, Summary for Subcatchment 4S: W-1(O) Runoff = 68.57 cfs @ 36.06 hrs, Volume= 9.031 af, Depth=11.89" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2pdrn Printed 6/16/2015Prepared by Alliant Engineering Page 4HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Area (sf) CN Description 162,566 70 Woods, Good, HSG C 72,397 98 Water Surface, HSG C * 37,549 98 Impervious 120,661 74 >75% Grass cover, Good, HSG C 3,877 96 Gravel surface, HSG C 397,050 79 Weighted Average 287,104 72.31% Pervious Area 109,946 27.69% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 15.0 Direct Entry, Summary for Subcatchment 7S: RW-2 Runoff = 3.67 cfs @ 35.96 hrs, Volume= 0.385 af, Depth=13.43" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Area (sf) CN Description 10,188 98 Paved roads w/curbs & sewers, HSG C 4,811 74 >75% Grass cover, Good, HSG C 14,999 90 Weighted Average 4,811 32.08% Pervious Area 10,188 67.92% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 8S: RW-1 Runoff = 5.01 cfs @ 35.98 hrs, Volume= 0.528 af, Depth=12.44" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Area (sf) CN Description 11,808 92 Paved roads w/open ditches, 50% imp, HSG C 3,988 70 Woods, Good, HSG C 6,411 74 >75% Grass cover, Good, HSG C 22,207 83 Weighted Average 16,303 73.41% Pervious Area 5,904 26.59% Impervious Area Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2pdrn Printed 6/16/2015Prepared by Alliant Engineering Page 5HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.0 Direct Entry, Summary for Subcatchment 9S: O Runoff = 5.56 cfs @ 35.90 hrs, Volume= 0.536 af, Depth=14.48" Runoff by SCS TR-20 method, UH=SCS, Weighted-Q, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2 Area (sf) CN Description 19,342 98 Water Surface, HSG C 19,342 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.0 Direct Entry, Summary for Pond 3P: W-1 Inflow Area = 12.240 ac, 30.67% Impervious, Inflow Depth = 11.98" for Bk-Bk 100 yr event Inflow = 88.93 cfs @ 36.03 hrs, Volume= 12.223 af Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 100%, Lag= 0.0 min Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Routing by Stor-Ind method, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs Starting Elev= 999.00' Surf.Area= 92,936 sf Storage= 220,377 cf Peak Elev= 1,003.06' @ 48.84 hrs Surf.Area= 168,295 sf Storage= 752,784 cf (532,408 cf above start) Plug-Flow detention time= (not calculated: initial storage exceeds outflow) Center-of-Mass det. time= (not calculated: no outflow) Volume Invert Avail.Storage Storage Description #1 996.00' 1,506,240 cf Custom Stage Data (Irregular) Listed below (Recalc) Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 996.00 55,574 937.1 0 0 55,574 1,000.00 107,513 2,029.6 320,513 320,513 313,562 1,002.00 155,414 1,946.5 261,460 581,973 340,155 1,004.00 180,253 1,931.4 335,360 917,333 346,217 1,006.00 202,937 1,997.4 382,966 1,300,299 367,222 1,007.00 208,958 2,016.1 205,940 1,506,240 373,523 Device Routing Invert Outlet Devices #1 Primary 1,006.00'123.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=999.00' (Free Discharge) 1=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs) Type II 24-hr Bk-Bk 100 yr Rainfall=7.36" x 2pdrn Printed 6/16/2015Prepared by Alliant Engineering Page 6HydroCAD® 10.00 s/n 01427 © 2013 HydroCAD Software Solutions LLC Summary for Pond 7P: Storage Pipe Inflow Area = 0.801 ac, 54.85% Impervious, Inflow Depth = 13.00" for Bk-Bk 100 yr event Inflow = 8.09 cfs @ 35.97 hrs, Volume= 0.868 af Outflow = 8.03 cfs @ 35.97 hrs, Volume= 0.834 af, Atten= 1%, Lag= 0.5 min Discarded = 0.00 cfs @ 2.87 hrs, Volume= 0.020 af Primary = 8.03 cfs @ 35.97 hrs, Volume= 0.814 af Routing by Stor-Ind method, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs / 3 Peak Elev= 1,021.92' @ 35.97 hrs Surf.Area= 528 sf Storage= 2,151 cf Plug-Flow detention time= 145.7 min calculated for 0.834 af (96% of inflow) Center-of-Mass det. time= 97.6 min ( 1,629.0 - 1,531.4 ) Volume Invert Avail.Storage Storage Description #1 1,015.00' 1,257 cf 48.0" Round Pipe Storage Inside #2 L= 100.0' S= 0.0020 '/' #2 1,014.50' 328 cf 5.00'W x 100.00'L x 4.70'H Rock Bedding 2,350 cf Overall - 1,257 cf Embedded = 1,093 cf x 30.0% Voids #3 1,012.00' 457 cf 6.00'D x 16.18'H MH 2 -Impervious #4 1,011.80' 317 cf 6.00'D x 11.20'H OCS 3 2,359 cf Total Available Storage Device Routing Invert Outlet Devices #1 Primary 1,002.40'12.0" Round Culvert L= 42.0' RCP, rounded edge headwall, Ke= 0.100 Inlet / Outlet Invert= 1,002.40' / 1,001.98' S= 0.0100 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf #2 Device 1 1,019.00'12.0" Round Culvert L= 44.2' RCP, rounded edge headwall, Ke= 0.100 Inlet / Outlet Invert= 1,019.00' / 1,007.07' S= 0.2699 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf #3 Discarded 1,011.80'0.200 in/hr Exfiltration over Surface area Phase-In= 0.01' Discarded OutFlow Max=0.00 cfs @ 2.87 hrs HW=1,014.50' (Free Discharge) 3=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=8.01 cfs @ 35.97 hrs HW=1,021.91' (Free Discharge) 1=Culvert (Passes 8.01 cfs of 17.63 cfs potential flow) 2=Culvert (Inlet Controls 8.01 cfs @ 10.20 fps) Summary for Link 6L: TOTAL Inflow Area = 12.240 ac, 30.67% Impervious, Inflow Depth = 0.00" for Bk-Bk 100 yr event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-100.00 hrs, dt= 0.01 hrs NOAA Atlas 14, Volume 8, Version 2 Location name: Excelsior, Minnesota, US* Latitude: 44.8849°, Longitude: -93.5599° Elevation: 1065 ft* * source: Google Maps POINT PRECIPITATION FREQUENCY ESTIMATES Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoffery Bonnin NOAA, National Weather Service, Silver Spring, Maryland PF_tabular | PF_graphical | Maps_&_aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Duration Average recurrence interval (years) 1 2 5 10 25 50 100 200 500 1000 5-min 0.355 (0.275-0.459) 0.421 (0.326-0.545) 0.535 (0.413-0.694) 0.635 (0.488-0.827) 0.781 (0.583-1.05) 0.900 (0.656-1.22) 1.02 (0.722-1.41) 1.16 (0.782-1.62) 1.34 (0.872-1.92) 1.48 (0.940-2.14) 10-min 0.520 (0.403-0.672) 0.617 (0.477-0.798) 0.784 (0.605-1.02) 0.930 (0.714-1.21) 1.14 (0.854-1.54) 1.32 (0.960-1.78) 1.50 (1.06-2.07) 1.69 (1.15-2.38) 1.96 (1.28-2.81) 2.17 (1.38-3.13) 15-min 0.634(0.491-0.820)0.752(0.582-0.973)0.956(0.738-1.24)1.14(0.871-1.48)1.40(1.04-1.87)1.61(1.17-2.18)1.83(1.29-2.52)2.06(1.40-2.90)2.39(1.56-3.42)2.65(1.68-3.82) 30-min 0.892 (0.691-1.15) 1.06 (0.824-1.38) 1.36 (1.05-1.77) 1.62 (1.24-2.11) 2.00 (1.49-2.69) 2.31 (1.68-3.13) 2.63 (1.85-3.63) 2.97 (2.01-4.18) 3.45 (2.25-4.94) 3.83 (2.42-5.52) 60-min 1.16(0.899-1.50)1.38(1.07-1.79)1.78(1.37-2.30)2.14(1.64-2.78)2.69(2.02-3.65)3.16(2.31-4.30)3.66(2.59-5.07)4.21(2.86-5.94)4.99(3.26-7.17)5.62(3.56-8.11) 2-hr 1.43 (1.12-1.83) 1.69 (1.33-2.17) 2.19 (1.71-2.81) 2.66 (2.06-3.42) 3.38 (2.58-4.56) 4.01 (2.97-5.42) 4.69 (3.36-6.46) 5.44 (3.74-7.63) 6.53 (4.32-9.33) 7.42 (4.75-10.6) 3-hr 1.59 (1.26-2.02) 1.88 (1.48-2.39) 2.43 (1.91-3.10) 2.97 (2.32-3.80) 3.83 (2.95-5.16) 4.58 (3.42-6.18) 5.41 (3.91-7.43) 6.34 (4.39-8.86) 7.69 (5.12-10.9) 8.80 (5.67-12.5) 6-hr 1.88(1.50-2.35)2.20(1.75-2.77)2.84(2.26-3.58)3.48(2.75-4.39)4.50(3.52-6.02)5.41(4.10-7.25)6.43(4.70-8.75)7.56(5.30-10.5)9.23(6.22-13.0)10.6(6.92-15.0) 12-hr 2.13 (1.72-2.64) 2.52 (2.03-3.14) 3.26 (2.62-4.06) 3.96 (3.16-4.94) 5.04 (3.96-6.61) 5.97 (4.56-7.87) 6.99 (5.15-9.38) 8.12 (5.74-11.1) 9.74 (6.62-13.6) 11.1 (7.29-15.5) 24-hr 2.50 (2.04-3.06) 2.87 (2.34-3.52) 3.58 (2.91-4.40) 4.26 (3.45-5.26) 5.35 (4.26-6.96) 6.31 (4.87-8.23) 7.36 (5.49-9.79) 8.53 (6.11-11.6) 10.2 (7.05-14.2) 11.6 (7.76-16.1) 2-day 2.91(2.40-3.53)3.26(2.69-3.96)3.95(3.25-4.81)4.63(3.78-5.65)5.72(4.61-7.35)6.69(5.23-8.64)7.76(5.86-10.2)8.96(6.49-12.0)10.7(7.46-14.7)12.2(8.20-16.7) 3-day 3.15 (2.62-3.80) 3.54 (2.94-4.27) 4.28 (3.54-5.17) 4.99 (4.11-6.05) 6.11 (4.94-7.77) 7.09 (5.58-9.08) 8.17 (6.21-10.7) 9.37 (6.83-12.5) 11.1 (7.78-15.1) 12.5 (8.51-17.1) 4-day 3.35(2.80-4.01)3.78(3.15-4.53)4.58(3.81-5.50)5.32(4.40-6.42)6.48(5.25-8.17)7.47(5.90-9.50)8.56(6.52-11.1)9.75(7.13-12.9)11.5(8.06-15.5)12.9(8.76-17.5) 7-day 3.87 (3.27-4.60) 4.40 (3.71-5.22) 5.33 (4.47-6.34) 6.16 (5.14-7.36) 7.40 (6.03-9.18) 8.43 (6.69-10.6) 9.53 (7.31-12.2) 10.7 (7.88-14.0) 12.4 (8.76-16.6) 13.7 (9.42-18.5) 10-day 4.39 (3.72-5.17) 4.97 (4.22-5.86) 5.98 (5.05-7.07) 6.87 (5.77-8.15) 8.16 (6.67-10.0) 9.21 (7.34-11.4) 10.3 (7.95-13.1) 11.5 (8.49-14.9) 13.1 (9.32-17.5) 14.4 (9.95-19.4) 20-day 5.98(5.14-6.97)6.70(5.75-7.80)7.88(6.74-9.21)8.88(7.55-10.4)10.3(8.46-12.4)11.4(9.15-13.9)12.5(9.70-15.6)13.6(10.2-17.4)15.1(10.9-19.9)16.3(11.4-21.7) 30-day 7.38 (6.39-8.53) 8.23 (7.12-9.52) 9.61 (8.28-11.1) 10.7 (9.20-12.5) 12.3 (10.1-14.6) 13.4 (10.9-16.2) 14.6 (11.4-18.0) 15.7 (11.8-19.9) 17.2 (12.4-22.4) 18.3 (12.9-24.2) 45-day 9.18(8.00-10.5)10.3(8.94-11.8)12.0(10.4-13.8)13.3(11.5-15.4)15.1(12.5-17.8)16.4(13.3-19.6)17.6(13.8-21.6)18.8(14.2-23.6)20.2(14.7-26.1)21.2(15.1-28.0) 60-day 10.7 (9.40-12.2) 12.1 (10.6-13.8) 14.1 (12.3-16.1) 15.7 (13.6-18.0) 17.7 (14.8-20.7) 19.2 (15.6-22.8) 20.5 (16.2-24.9) 21.7 (16.5-27.1) 23.2 (16.9-29.8) 24.2 (17.2-31.8) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top PF graphical Page 1 of 3Precipitation Frequency Data Server 6/3/2015http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=44.8849&lon=-93.5599&data=... Back to Top Maps & aerials Small scale terrain Large scale terrain Map data © 2015 GoogleReport a map error50 km   Page 2 of 3Precipitation Frequency Data Server 6/3/2015http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=44.8849&lon=-93.5599&data=... Large scale aerial Back to Top US Department of Commerce National Oceanic and Atmospheric AdministrationNational Weather Service Office of Hydrologic Development1325 East West Highway Silver Spring, MD 20910 Questions?: HDSC.Questions@noaa.gov Disclaimer Map data © 2015 GoogleReport a map error2 km   Imagery © 2015 TerraM etricsReport a map error2 km Page 3 of 3Precipitation Frequency Data Server 6/3/2015http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=44.8849&lon=-93.5599&data=... LA K E  LU C Y  RO A D  SU B D I V I S I O N La n d  Co v e r  an d  Vo l u m e  Ma n a g e m e n t  Re q u i r e m e n t  Ca l c u l a t i o n Ty p e  "C "  So i l s  As s u m e d Ex i s t i n g  Co n d i t i o n s Dr a i n a g e  Ar e a [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] LW 2 4 7 0 1 0 . 5 6 7 2 9 0 3 0 . 0 6 7 1 7 5 6 0 . 0 4 0 5 1 6 9 0 . 1 1 9 1 4 8 7 2 0 . 3 4 1 0 0 . 0 0 0 W ‐1 1 1 1 4 0 4 2 . 5 5 7 1 2 2 4 2 0 . 2 8 1 0 0 . 0 0 0 5 2 5 2 5 1 . 2 0 6 2 7 0 6 0 0 . 6 2 1 1 9 5 7 8 0 . 4 4 9 3. 1 2 5 15 1 4 5 Of f s i t e W ‐1( O ) 3 9 7 0 5 0 9 . 1 1 5 3 7 5 4 9 0 . 8 6 2 3 8 7 7 0 . 0 8 9 1 6 2 5 6 6 3 . 7 3 2 1 2 0 6 6 1 2 . 7 7 0 7 2 3 9 7 1 . 6 6 2 12 . 2 4 0 Pr o p o s e d  Co n d i t i o n s Dr a i n a g e  Ar e a [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] [f t 2 ] [a c r e ] O 19 3 4 2 0 . 4 4 4 0 0 . 0 0 0 0 0 . 0 0 0 0 0 . 0 0 0 0 0 . 0 0 0 19 3 4 2 0. 4 4 4 RW ‐1 22 2 0 7 0 . 5 1 0 1 1 8 0 8 0 . 2 7 1 0 0 . 0 0 0 3 9 8 8 0 . 0 9 2 6 4 1 1 0 . 1 4 7 0 0 . 0 0 0 RW ‐2 14 9 9 9 0 . 3 4 4 1 0 1 8 8 0 . 2 3 4 0 0 . 0 0 0 0 0 . 0 0 0 4 8 1 1 0 . 1 1 0 0 0 . 0 0 0 R ‐1 59 6 5 4 1 . 3 6 9 9 2 0 4 0 . 2 1 1 0 0 . 0 0 0 1 9 7 2 4 0 . 4 5 3 3 0 7 2 5 0 . 7 0 5 0 0. 0 0 0 R ‐2 19 9 0 5 0 . 4 5 7 8 9 5 7 0 . 2 0 6 0 0 . 0 0 0 0 0 . 0 0 0 1 0 9 4 8 0 . 2 5 1 0 0 . 0 0 0 3. 1 2 5 40 1 5 7 Of f s i t e W ‐1( O ) 3 9 7 0 5 0 9 . 1 1 5 3 7 5 4 9 0 . 8 6 2 3 8 7 7 0 . 0 8 9 1 6 2 5 6 6 3 . 7 3 2 1 2 0 6 6 1 2 . 7 7 0 7 2 3 9 7 1 . 6 6 2 12 . 2 4 0 25 0 1 2 S F O r   0. 5 7 A C I"  in f i l t r a t i o n  vo l u m e  re q u i r e d  = 2 0 8 4 C F Or 0. 0 4 8 A F Pr o p o s e d  Un d e r g r o u n d  In f i l t r a t i o n  Vo l u m e  Pr o v i d e d  (p e r  MC W D ) PI P E 1 2 5 7 Pr o p o s e d  En h a n c e m e n t  of  Pr e v i o u s  Ar e a  Vo l u m e  Cr e d i t  (p e r  MC W D )  Ar e a  Pr e s e r v e d   [f t 2 ] 20 3 5 8 21 0 5 C F E x c e e d s  Re q u i r e m e n t Wa t e r Wa t e r To t a l  in c r e a s e d  on s i t e  im p e r v i o u s  su r f a c e  = Gr a v e l  w/ o  RW Im p e r v i o u s  RW To t a l  Ar e a Pe r v i o u s  (G r a s s ) Pe r v i o u s  (G r a s s ) Gr a v e l  w/ o  RW Im p e r v i o u s Wo o d s Wo o d s 12 5 7 Ba s i n To t a l  Vo l u m e   [f t 3 ] Vo l u m e  Re d u c t i o n  pr o v i d e d  = Tu e s d a y ,  Ju n e  16 ,  20 1 5 To t a l  Ar e a To t a l  Vo l u m e  Re d u c t i o n   Cr e d i t 84 8 To t a l  Vo l u m e  Re d u c t i o n   Cr e d i t ST O R M S E W E R D E S I G N W O R K S H E E T - P O S T - D E V E L O P M E N T C O N D I T I O N S ALLIANT ENGINEERING, INC. PR O J E C T N A M E : G L A C C U M P R O P E R T Y 233 PARK AVENUE SOUTH PR O J E C T N U M B E R : 1 5 0 0 3 0 SUITE 300 PR E P A R E D B Y : P L N MINNEAPOLIS, MN 55415 Re v i s i o n 6 - 1 6 - 1 5 Rim=CL-0.605 4' MIN BUILD DE S I G N S T O R M F R E Q U E N C Y = 1 0 Y E A R S IM P R U N O F F I N T E N S I T Y P . D I A . P . S L O P E P. M a t MA N N I N G ' S P . C A P . P . V E L O C I T Y P I P E C A P . O V E R F R O M T O R I M C o v e r S T R . C A S T B U I L D P i p e FR O M T O T O T A L I M P E R V I O U S I N C R . C U M . % C I N C R . C U M . P I P E C U M . i I N C R . C U M . D [ I N ] S [ F T / F T ] n Q [ C F S ] M A X [ F T / S ] L E N G T H [ F T ] Q [ C F S ] I N V E R T I N V E R T E L E V [ FT] T Y P E T Y P E [ F T ] C l a s s CB 1 0 0 M H 2 36 8 7 8 19 7 7 6 0. 8 4 7 0 . 8 4 7 5 4 % 0 . 5 8 0 . 4 8 7 0 . 4 8 7 15 . 0 0 15 . 0 0 4 . 7 7 2 . 3 2 3 2 . 3 2 3 12 0 . 0 2 0 0 RC P 0. 0 1 3 5 . 0 4 6 . 4 2 36.4 2.7153 1023.00 1022.27 1027.00 2.80 2 4 x 3 6 R-3067-V 4.00 5 MH 2 * O C S 3 00 0. 0 0 0 0 . 0 0 0 0 % 0 . 2 0 0 . 0 0 0 0 . 0 0 0 1 5 . 0 0 1 5 . 0 0 4 . 7 7 0 . 0 0 0 0 . 0 0 0 48 0 . 0 0 2 0 HD P E 0. 0 1 1 7 5 . 9 2 6 . 0 4 100.0 75.9191 1015.00 1014.80 1028.18 8.98 7 2 R-1642 13.18 A D S OC S 3 * C B M H 4 00 0. 0 0 0 0 . 8 4 7 0 % 0 . 2 0 0 . 0 0 0 0 . 0 0 0 1 5 . 0 0 1 5 . 0 0 4 . 7 7 0 . 0 0 0 0 . 0 0 0 12 0 . 2 7 0 0 RC P 0. 0 1 3 1 8 . 5 1 2 3 . 5 7 44.2 18.5129 1019.00 1007.07 1023.00 2.80 7 2 R-4342 12.20 5 CB M H 4 F E S 5 00 0. 0 0 0 1 . 6 9 3 0 % 0 . 2 0 0 . 0 0 0 0 . 4 8 7 0 . 0 0 1 5 . 0 0 4 . 7 7 0 . 0 0 0 2 . 3 2 3 12 0 . 0 1 0 0 RC P 0. 0 1 3 3 . 5 6 4 . 5 4 42.0 1.2396 1 0 0 2 . 4 0 1 0 0 1 . 9 8 1011.00 7.40 4 8 R-4342 8.60 5 *M A N H O L E S H A V E 3 ' D E E P S U M P S Q [ C F S ] MH / C B A R E A [ A C ] T I M E O F C O N C . [ M I N ] AR E A [ S F ] A * C