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Drainage Study 11-15-2012DRAINAGE STUDY FOR THE Southwest Corner of Yosemite Avenue and 63rd Street Chanhassen, MN November 15, 2012 Prepared For: Steve Ische Premier Land Surveying Prepared By: Kanto Engineering Inc. 10775 Poppitz Lane Chaska, MN 55318 612 -418 -6828 I hereby certify that this plan, report, or specification was prepared by me or under my direct supervision and that I am a dulu icensed en gi e h laws of the State of Minnesota. License No. 269o9 Curtiss J. Kallio DRAINAGE STUDY Scope of Work Kallio Engineering was retained by Steve Ische of Premier Land Surveying to compute the high water elevation of the basin in the southwest corner of Yosemite Avenue and 63d Street in Chanhassen. The City of Chanhassen is requiring the study for a proposed lot split of Lot 1, Block 1, Stoddart Addition. The city will require drainage easements up to the high water elevation. Existing Site The primary outlet of the basin is an existing 15" RCP which drains to a storm sewer system that eventually outfalls to a storm water pond approximately 800 feet to the south. A secondary outlet is a beehive inlet slightly to the north that is connected to a 15" RCP which outlets on the east side of Yosemite Avenue. The emergency overflow for the basin is overtopping of Yosemite Avenue in the same vicinity of the storm drains previously mentioned. The storm drain and overtopping elevations are as follows: Drainage Feature Elevation 15" RCP to storm sewer 1008.1 Beehive inlet to 15" RCP to west of Yosemite 1010.6 Yosemite Avenue Overtopping 1011.8 Note: Existing elevations provided by a Premier Land Surveying The area upstream of the existing pipes is well vegetated horse pasture, wooded area, and single family homes. The existing soil types are clay loans. There is minimal flood storage available immediately upstream of the pipe inlets, but there is a larger perched storage area approximately 280 feet upstream. Calculations The runoff calculations and were performed using HydroCAD software which utilizes SCS TR -20 methodologies. The flood calculations were performed using a Type II 24 -hour rainfall distribution with a 100 -yr rainfall of 6.0 inches. Curve numbers were taken from the table using their respective soil group. The entire storm sewer network from the 15" RCP to the outfall was not analyzed due to the time of concentration of the peak flows to the basin. The time of concentration of the basin will be longer than the curb inlet catchments, which means most of the storm sewer system would be at reduced flows by the time the peak flows of the basin enter the system. The basin areas with their respective impervious area, curve numbers, and time of concentration can be found in the attached HydroCAD report. Results The HydroCAD results produced a peak flow of 15.1 cfs from the basin with a high water elevation of 1011.7 , which is slightly lower than the overtopping elevation of 1011.8. Because this is a land locked basin, it is recommended that any proposed building elevations and lowest building openings be based on the overtopping elevation. According to the city code: • The minimum building opening elevation should be at least 1 foot above the emergency overflow elevation. • The lowest floor elevation should be at least 3 feet above highest known groundwater elevation. • The lowest floor elevation should be at least 3 feet above the high water elevation 1P BASIN (is DRAINAGE TO YOSEMITE Subcat Reach on Link Drainage Diagram for 1241 Existing pared by Kallio Engineering LLC 11/15/2012 FHyd7,Ar, ® 7 .10 sin 002095 © 2005 HydroCAD Software Solutions LLC 1241 Existing Type// 24 -hr 100 YR Rainfall= 6.00" Prepared by Kallio Engineering LLC Page 2 HydroCAD@ 7.10 s/n 002095 @ 2005 HydmCAD Software Solutions LLC 11/15/2012 Subcatchment 1S: DRAINAGE TO YOSEMITE Runoff = 16.86 cfs @ 12.30 hrs, Volume= 1.788 af, Depth= 2.90" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.10 hrs Type II 24 -hr 100 YR Rainfall= 6.00" Area (ac) CN Description 0.550 98 Impervious,_ Average Tc Length Slope Velocity Capacity Description 17.1 200 0.0600 0.2 Sheet Flow, Grass: Dense n= 0.240 P2= 2.80" 2.0 150 0.0600 1.2 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 14.8 440 0.0050 0.5 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 33.9 790 Total Subcatchment 1S: DRAINAGE TO YOSEMITE Hydrograph 18 16.86 cfs - - ❑ Hunoff 16 17- Type II 24 -hr 100 YR- ,5 Rainfall =6.00r, a - -- -_r -- _ Runoff Area -7.400 ac 12- Runoff Volume =1.788 of 16 -..... Runoff Depth= 2.90 " - -- .2 6 Flow Length =790' Tc =33.9 min- - 6. 5 CN =71 - i 3 22 24 26 28 30 32 34 36 38 40 42 44 46 48 Time (hours) 1241 Existing Type 1124 -hr 100 YR Rainfall =6.00" Prepared by Kallio Engineering LLC Page 3 HydroCADO 7.10 s/n 002095 © 2005 HvdmCAD Software Solutions LLC 11/15/2012 Pond 1P: BASIN Inflow Area = 7.400 ac, Inflow Depth = 2.90" for 100 YR event Inflow = 16.86 cis @ 12.30 hrs, Volume= 1.788 of Outflow = 15.07 cfs @ 12.42 hrs, Volume= 1.788 af, Atten= 11 %, Lag= 6.7 min Primary = 15.07 cfs @ 12.42 hrs, Volume= 1.788 of Routing by Stor -Ind method, Time Span= 0.0048.00 hrs, dt= 0. Peak Elev= 1,011.68'@ 12.42 hrs Surf.Area= 0.098 a or�5orraDe 0.073 of �) Plug -Flow detention time= 1.6 min calculated for 1.784 of (100% of inflow) Center -of -Mass det. time= 1.6 min ( 860.2 - 858.5 ) Volume Invert Avail.Storage Storage Description #1 1,008.10' 0.109 of Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (acres) (acre -feet) (acre -feet) 1,008.10 0.000 0.000 0.000 1,010.00 0.010 0.009 0.009 1,011.00 0.030 0.020 0.029 0,029+ 08 �0•fB- o,02�= O O77AT C 1,012.00 0.130 0.080 0.109 Device Routing Invert Outlet Devices #1 Primary 1,008.10' 15.0" x 18.0' long Culvert RCP, end - section conforming to fill, Ke= 0.500 Outlet Invert= 1,007.92' S= 0.01007 Cc= 0.900 n= 0.025 Corrugated metal #2 Primary 1,010.60' 22.0" Horiz. Orifice/Grate Limited to weir flow C= 0.600 #3 Device 2 1,004.50' 15.0" x 50.0' long Culvert RCP, end - section conforming to fill, Ke= 0.500 Outlet Invert-- 1,004.00' S= 0.0100'/' Cc= 0.900 n= 0.012 Concrete pipe, finished #4 Primary 1,011.80' 100.0' long x 30.0' breadth Broad - Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Primary OutFlow Max =15.01 cfs_@1�42 hrs HW= 1,011.67' (Free Discharge) Culvert (Barrel Controls 8.2 cfs _@ 7.3 fps) Lifice /Grate (Passes 6.1 13.13 cis potential flow) -13= Culvert (Inlet Contro 6.10 cfs @ 5.0 fps) = Broad - Crested Rectangular Weir( Controls 0.00 cfs) 1241 Existing Type 1124 -hr 100 YR Rainfall= 6.00" Prepared by Kallio Engineering LLC Page 4 H droCAD® 7.10 s/n 002095 © 2005 H droCAD Software Solutions LLC 11/15/2012 u 3 0 LL 1 Pond 1P: BASIN - ❑Inflow ,16.86 Cfs 10 Primary 1 Inflow Area =7.400 ac 5.07 Cfs nr_ ��_.._ AAA &e1 Time (hours) Drainage Area Map - Basin in the Southwest Corner of Yosemite Ave. and 63rd St. w � Rte" a�i#. �ir��,- - — — — '�F• _ =^fir,' '. �',. ' rJre.abn�m GIROSTWi sve �� yam• _ \j\ _ _ _ L BEEHIVE INLET!' - OF pls, RIM 1010.6 YOSEMITE . _ t_ IV fi Id 1 INV. I DUCK LN m � 11 o r r i WiOECT NU 1291 o W W _ I I 91EFi SGIF IH iRt � � 1 51ffEI5