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Stormwater Management Report - 10.14.2002STORMWATER MANAGEMENT REPORT FOR BAYBROOK PROFESSIONAL PARK SUBDIVISION MODIFICATION 10/14/02 Town of Queensbury, New York Warren County Prepared by: NACE ENGINEERING, P.C. 169 HAVILAND ROAD QUEENSBURY, NY 12804 Thomas W. Nace, P.E. October 14, 2002 File: #46148 0 • STORMWATER MANAGEMENT REPORT FOR BAYBROOK PROFESSIONAL PARK SUBDIVISION MODIFICATION 10/14/02 This report is a revision of the previously approved report dated January 2001 and revised March 15, 2001. This current revision reflects the changes made to the subdivision layout to accommodate the final wetland permitting. Stormwater facilities along the section of remaining subdivision road have not been changed from the previous design. However the amount subdivision road tributary to these facilities has been slightly reduced. These changes are reflected in the HydroCAD analysis included herein. INTRODUCTION The site of the proposed Baybrook Professional Park Subdivision is on the east side of Bay Road, opposite Walker Lane, in the Town of Queensbury, NY. The entire site extends through to Meadowbrook Road and contains approximately 86 acres. The proposed subdivision contains 10 lots of various sizes. The western half of the subdivision (lots #1 through #9) will be accessed by a cul-de-sac road off of Bay Road. Future development of the rear of the property (lot #10) will be accessed from Meadowbrook Road. This report addresses drainage issues pertaining only to the development of the subdivision road and infrastructure. Development of the individual lots will include on -site stormwater management to address added impervious areas on the individual lots. EXISTING CONDITIONS The site is a gently sloping meadow. There is a stream (Old Maids Brook) flowing north to south across the west portion of the site. There are three areas of freshwater wetlands on the property. The two major wetlands in the northeast and southwest portions of the property are DEC and ACOE jurisdictional. The third wetland, along the northern portion of Old Maids Brook, is only ACOE jurisdictional. In reviewing the wetland delineation and reviewing the permit application for some minor (less than 0.5 acres total) wetland disturbance on the site, the Corps of Engineers has required that mitigation include created wetlands which will connect the two major wetland areas and effectively cut the site in half The wetland boundaries shown on the design drawings are the final boundaries including the proposed disturbances and created mitigation wetlands. Soils within the area of the proposed subdivision are generally Raynham silt loams. Seven deep test pits were dug in the areas of the proposed subdivision. All of the pits encountered very fine sand, silts or clay loams over clay subsoils. Evidence of seasonal high groundwater was present in all of the test pits at depths varying from 11/2 to 3 feet. 1 Groundcover on the existing site is predominantly overgrown meadow with some brush. There are some forested areas along the southern portion of the site. All existing drainage from the portion of the site to be developed runs off into Old Maids Brook as it crosses the site. This brook flows into the wetland along the southern portion of the site and eventually finds its way across the adjacent Bay Meadows Golf Course and into Halfway Brook. DRAINAGE METHODOLOGY Since the existing soils are relatively impermeable and the groundwater is high, it is not practical to use subsurface infiltration to disperse of the storm runoff from the subdivision. Therefore, a storm sewer system is proposed to collect the runoff. These storm sewers will outfall into Old Maids Brook. The outfalls will incorporate detention basins to allow the collected stormwater to outlet into the brook at approximately the same rate that it presently reaches the brook. These basins will be shallow and will incorporate a rip -rap surfaced overflow spillway. The basins will be sized to store the runoff from a 50 year design stone. New culverts will be installed at one location where the proposed subdivision road cross Old Maids Brook. These culverts have been sized by analyzing the entire upstream drainage basin of Old Maids Brook. Drainage areas for this drainage basin are shown on the plan included with the culvert analysis. This plan also labels the components of the drainage system as they are modeled in the HydroCAD analysis. CALCULATIONS - All computations SCS TR-20 HydroCAD. - 50 year storm event — Type II rainfall=4.8" — for detention basin and storm sewer sizing - 25 year storm event - Type II rainfall = 4.5" — for culvert sizing - Soil conditions — very fine sands, silts & clay loams — SCS soil group C Runoff rate and volume computations for the 50 year storm event have been completed for both the pre -developed and developed conditions. Detention basins have been sized to maintain adequate freeboard during a 50 year design storm. Road culverts have been sized to provide adequate capacity for a 25 year design storm without submerging the inlet or storing water at the upstream end of the culvert. See attached HydroCAD analysis for all computations. CONCLUSIONS Detention Pond #2 Pre -developed peak runoff rate - 0.78 cfs Post development peak runoff rate - 0.72 cfs `A 0 Detention Pond #4 Pre -developed peak runoff rate - 0.32 cfs Post development peak runoff rate - 0.37 cfs TOTAL SITE Pre -developed peak runoff rate - 1.10 cfs Post development peak runoff rate - 1.09 cfs Based upon the attached HydroCAD analysis, the detention basins have sufficient capacity to manage all runoff generated by the subdivision roads during a 50 year storm event and total post development runoff will be maintained at pre -developed level. STORMWA'TER MANAGEMENT REPORT FOR BAV13ROOK PROFESSIONAL PARK SUBDIVISION MODIFICATION 10/14/02 HydroCAD RESULTS EXISTING CONDITIONS 0 0 46148 - BAYBROOK - EXIST. COND. - 10-2002 MOD. Type 1124-hr Rainfall=4. 60 " Prepared by {enter your company name here} Page 1 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Type II 24-hr Rainfall=4.80" Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 2S: AREA TRUBUTARY TO POND #2 Tc=50.3 min CN=65 Area=0.920 ac Runoff= 0.78 cfs 0.103 of Subcatchment 4S: AREA TRIBUTARY TO POND #4 Tc=64.8 min CN=65 Area=0.460 ac Runoff-- 0.32 cfs 0.051 of Runoff Area = 1.380 ac Volume = 0.154 of Average Depth = 1.34" 46148 - BAYBROOK - EXIST. COND.-10-2002 MOD. Type 1124-hr Rainfall=4.80" Prepared by (enter your company name here) Page 2 HvdroCAD® 6.00 s/n 000768 © 1986-2001 Annlied Minrnnmmnufer Rvsfams iniuionno Subcatchment 2S: AREA TRUBUTARY TO POND #2 Runoff = 0.78 cfs @ 12.54 hrs, Volume= 0.103 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr Rainfall=4.80" Area (ac) CN Description 0.920 65 MEADOW Tc Length Slope Velocity Capacity Description 48.7 300 0.0120 0.1 Sheet Flow, ACROSS GRASS Grass: Dense n= 0.240 P2= 2.40" 1.6 160 0.0120 1.6 Shallow Concentrated Flow, ACROSS GRASS TO STREAM Grassed Waterwav Kv= 15.0 fps 50.3 460 Total Subcatchment 4S: AREA TRIBUTARY TO POND #4 Runoff = 0.32 cfs @ 12.74 hrs, Volume= 0.051 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr Rainfall=4.80" Area (ac) CN Description 0.460 65 MEADOW Tc Length Slope Velocity Capacity Description 64.8 350 0.0080 0.1 Sheet Flow, ACROSS GRASS Grass: Dense n= 0.240 P2= 2.40" 0 L1 STORMWATER MANAGEMENT REPORT FOR 13AYIIIZOOK PROFESSIONAL PARK SUBDIVISION MODIFICATION 10/ 14/02 HydroCAD RESULTS DEVELOPED CONDITIONS c N O N E 2 o N o N j 0 3 � O n Z e o O o ^ 7 U LL N mr� Y m¢ O co O >o C N m N Co } nm a a E° d 00 0 o co�co w °o , v �o q �o Ln ° ` C N C VO L m o cm CD {Q Cu0 cc m N U o o = c J 0 U d co co 46148 - BAYBROOK SUBDIVISION 10-14-02 MOD. Prepared by {enter your company name here} Type lI 24-hr Rainfall=4.80" Page 1 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, LIH=SCS, Type II 24-hr Rainfall=4.80" Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 3S: WILLOWBROOK ROAD - CB #9/10 TO END Tc=5.0 min CN=82 Area=0.460 ac Runoff= 2.36 cfs 0.103 of Subcatchment 4S: WILLOWBROOK DRIVE CB#5/6 TO #9/10 Tc=6.9 min CN=82 Area=0.520 ac Runoff= 2.52 cfs 0.117 of Subcatchment 5S: WILLOWBROOK - BAY ROAD TO CB#5/6 Tc=7.5 min CN=81 Area=0.400 ac Runoff= 1.85 cfs 0.087 of Reach 3R: CB #10 TO POND #4 Inflow= 2.36 cfs 0.103 of Length= 165.0' Max Vel= 4.5 fps Capacity= 3.28 cfs Outflow= 2.25 cfs 0.103 of Reach 4R: CB#6 TO CB#8 Inflow= 1.85 cfs 0.087 of Length= 170.0' Max Vel= 4.3 fps Capacity= 3.28 cfs Outflow= 1.79 cfs 0.087 of Reach 5R: CB#8 TO POND #2 Inflow= 4.27 cfs 0.203 of Length= 30.0' Max Vel= 6.7 fps Capacity= 4.63 cfs Outflow= 4.26 cfs 0.203 of Pond 2P: POND #2 Peak Storage= 4,227 cf Inflow= 4.26 cfs 0.203 of Primary= 0.72 cfs 0.161 of Outflow= 0.72 cfs 0.161 of Pond 4P: POND #4 Peak Storage= 2,031 cf Inflow= 2.25 cfs 0.103 of Primary= 0.37 cfs 0.098 of Outflow= 0.37 cfs 0.098 of Runoff Area = 1.380 ac Volume = 0.307 of Average Depth = 2.67" 46148 - BAYBROOK SUBDIVISION 10-14-02 MOD. Type /I24-hrRainfall=4.80° Prepared by (enter your company name here} Page 2 HvdroCAD® 6.00 s/n 000768 © 1986-2001 ADDlied Microcomputer Svstems 1n/15nnm Subcatchment 3S: WILLOWBROOK ROAD - CB #9/10 TO END Runoff = 2.36 cfs @ 11.96 hrs, Volume= 0.103 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr Rainfall=4.80" Area (ac) CN Description 0.260 98 PAVEMENT 0.200 61 GRASS 0.460 82 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 12 0.0200 0.8 Sheet Flow, ACROSS ROAD TO WING Smooth surfaces n= 0.011 P2= 2.40" 4.7 230 0.0070 0.8 0.02 TrapNee/Rect Channel Flow, WING SWALE TO CB Bot.W=0.00' D=0.50' Z= 0.0 & 0.2 '/' n= 0.013 5.0 242 Total Subcatchment 4S: WILLOWBROOK DRIVE CB#5/6 TO #9/10 Runoff = 2.52 cfs @ 11.98 hrs, Volume= 0.117 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type II 24-hr Rainfall=4.80" Area (ac) CN Description 0.290 98 PAVEMENT 0.230 61 GRASS 0.520 82 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 12 0.0200 0.8 Sheet Flow, ACROSS ROAD TO WING Smooth surfaces n= 0.011 P2= 2.40" 6.6 320 0.0070 0.8 0.02 TrapNee/Rect Channel Flow, WING SWALE TO CB Bot.W=0.00' D=0.50' Z= 0.0 & 0.2 7' n= 0.013 6.9 332 Total Subcatchment 5S: WILLOWBROOK - BAY ROAD TO CB#5/6 Runoff = 1.85 cfs @ 11.99 hrs, Volume= 0.087 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type 11 24-hr Rainfall=4.80" 46148 - BAYBROOK SUBDIVISION 10-14-02 MOD. Type 11 24-hr Rainfall=4.80" Prepared by (enter your company name here) Page 3 HydroCADO 6.00 s/n 000768 © 1986-2001 Applied Microcomputer Systems 10/15/2002 Area (ac) CN Description 0.220 98 PAVEMENT 0.180 61 GRASS 0.400 81 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 12 0.0200 0.8 Sheet Flow, ACROSS ROAD TO WING Smooth surfaces n= 0.011 P2= 2.40" 7.2 350 0.0070 0.8 0.02 TrapNee/Rect Channel Flow, WING SWALE TO CB Bot.W=0.00' D=0.50' Z= 0.0 & 0.2 '/' n= 0.013 7.5 362 Total Reach 3R: CB #10 TO POND #4 Inflow = 2.36 cfs @ 11.96 hrs, Volume= 0.103 of Outflow = 2.25 cfs @ 11.97 hrs, Volume= 0.103 af, Atten= 5%, Lag= 1.2 min Routing by Stor-Ind+Trans method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Max. Velocity= 4.5 fps, Min. Travel Time= 0.6 min Avg. Velocity = 1.5 fps, Avg. Travel Time= 1.9 min Peak Depth= 0.62' Capacity at bank full= 3.28 cfs 12.0" Diameter Pipe n= 0.010 Length= 165.0' Slope= 0.0050 7' Reach 4R: CB#6 TO CB#8 Inflow = 1.85 cfs @ 11.99 hrs, Volume= 0.087 of Outflow = 1.79 cfs @ 12.00 hrs, Volume= 0.087 af, Atten= 4%, Lag= 1.0 min Routing by Stor-Ind+Trans method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Max. Velocity= 4.3 fps, Min. Travel Time= 0.7 min Avg. Velocity = 1.4 fps, Avg. Travel Time= 2.0 min Peak Depth= 0.54' Capacity at bank full= 3.28 cfs 12.0" Diameter Pipe n= 0.010 Length= 170.0' Slope= 0.0050 '/' Reach 5R: CB#8 TO POND #2 Inflow = 4.27 cfs @ 11.99 hrs, Volume= 0.203 of Outflow = 4.26 cfs @ 11.99 hrs, Volume= 0.203 af, Atten= 0%, Lag= 0.1 min Routing by Stor-Ind+Trans method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Max. Velocity= 6.7 fps, Min. Travel Time= 0.1 min Avg. Velocity = 2.3 fps, Avg. Travel Time= 0.2 min 46148 - BAYBROOK SUBDIVISION 10-14-02 MOD. company name here) 38 © 1986-2001 Applied t Peak Depth= 0.76' Capacity at bank full= 4.63 cfs 12.0" Diameter Pipe n= 0.010 Inflow = Outflow = Primary = 4.26 cfs @ 0.72 cfs @ 0.72 cfs @ Length= 30.0' Slope= 0.0100'/' Pond 2P: POND #2 11.99 hrs, Volume= 0.203 of 12.24 hrs, Volume= 0.161 af, 12.24 hrs, Volume= 0.161 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type 1124-hr Rainfall=4.80" Page 4 Atten= 83%, Lag= 15.2 min Peak Elev= 2.24' Storage= 4,227 cf Plug -Flow detention time= 137.6 min calculated for 0.160 of (79% of inflow) Storage and wetted areas determined by Prismatic sections Elevation (feet) Surf.Area (sq-ft) Inc.Store (cubic -feet) Cum.Store (cubic -feet) 0.00 0 0 0 0.30 1,510 227 227 1.30 2,056 1,783 2,010 2.30 2,651 2,353 4,363 2.80 2,900 1,388 5,751 Primary OutFlow (Free Discharge) L1=Orifice/Grate 2=Orifice/Grate # Routing Invert Outlet Devices 1 Primary 0.00' 2.0" Vert. Orifice/Grate C= 0.600 2 Primary 1.50' 5.5" Vert. Orifice/Grate C= 0.600 Pond 4P: POND #4 Inflow = 2.25 cfs @ 11.97 hrs, Volume= 0.103 of Outflow = 0.37 cfs @ 12.19 hrs, Volume= 0.098 af, Atten= 83%, Lag= 12.9 min Primary = 0.37 cfs @ 12.19 hrs, Volume= 0.098 of Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Peak Elev= 1.96' Storage= 2,031 cf Plug -Flow detention time= 115.8 min calculated for 0.098 of (95% of inflow) Storage and wetted areas determined by Prismatic sections Elevation (feet) Surf.Area (sq-ft) Inc.Store (cubic -feet) Cum.Store (cubic -feet) 0.00 0 0 0 0.50 914 229 229 1.50 1,296 1,105 1,334 2.50 1,727 1,512 2,845 3.00 2,040 942 3,787 46148 - BAYBROOK SUBDIVISION 10-14-02 MOD. Prepared by {enter your company name here} HvdroCAD® 6.00 s/n 000768 © 1986-2001 ADDlied Microcomnt Primary OutFlow (Free Discharge) L1=Orifice/Grate 2=0rifice/Grate Type 11 24-hr Rainfall=4.80" Page 5 # Routing Invert Outlet Devices 1 Primary 0.00' 2.0" Vert. Orifice/Grate C= 0.600 2 Primary 1.50' 4.0" Vert. Orifice/Grate C= 0.600 STOItNMATER I JANAGL1 TENT REPORT FOR BAYBROOK PROFESSIONAL PARK SUBDIVISION MODIFICATION 10/l4/02 HydroCAD RESULTS STREAM CULVERT SIZING REVISED 3115101 (Rainfall amount corrected to 4.5 inches) ��J�.Ni�yF �C1rcv�s -- u ' I 3. ROq I t 7:; �. < 35 % I e / 'Z i 'tr Adirondack Coi�ulnity f* 4�7 ,004ge LZ J r' •� , o 350 :, O l olfo r�sq Ro?o5'0� i u yet � � :. p f\ W', Golf Course 4 ) Data for BAYBROOK SURD.- EXISTING WATERSHED Page 1 TYPE II 24-HOUR RAINFALL= 4.50 IN Prepared by NACE ENGINEERING, P.C. 18 Mar 01 HydroCAD 5.11 000576 (c) 1986-1999 Applied Microcomputer Systems WATERSHED ROUTING ISTIZ&-t-' i r�uL-V)&,r-r S;'(aI s z 0 0 O o 0�0 OSUBCATCHMENT REACH POND LINK SUBCATCHMENT 1 = SUBCATCH 1 - -> REACH 1 SUBCATCHMENT 2 = SUBCATCH 2 -> REACH 2 SUBCATCHMENT 3 = SUBCATCH 3 -> REACH 3 REACH 1 = UPPER STREAM -> REACH 2 REACH 2 = MIDDLE STREAM -> REACH 3 REACH 3 = LOWER STREAM -> POND 1 POND 1 = NEW CULVERT WITH UPSTREAM STORAGE -> Data for BAYBROOK SUBO.- EXISTING WATERSHED Page 2 TYPE II 24-HOUR RAINFALL= 4.50 IN Prepared by NACE ENGINEERING, P.C. 18 Mar 01 u droCAD 5 11 000576 (c) 1986-1999 Applied Microcomputer Systems SUBCATCHMENT 1 SUBCATCH 1 PEAK= 6.01 CFS @ 12.85 HRS, VOLUME= 1.86 AF ACRES CN SCS TR-20 METHOD 97.30 45 WOODS, BRUSH, SOME DEVELOPMENT TYPE II 24-HOUR RAINFALL= 4.50 IN SPAN= 10-20 HRS, dt=.1 HRS Method Comment Tc (min) TR-55 SHEET FLOW Segment ID: 45.3 Woods: Light underbrush n=.4 L=300' P2=2.4 in s=.04 SHALLOW CONCENTRATED/UPLAND FLOW Segment ID: 9.6 Woodland Kv=5 L=500' s=.03 '/' V=.87 fps SUBCATCHMENT 2 SUBCATCH 2 Total Length= 800 ft Total Tc= 54.9 PEAK= 38.56 CFS @ 12.63 HRS, VOLUME= 6.79 AF ACRES CN 105.00 52 25.00 70 130.00 55 WOODS, BRUSH DEVELOPED AREA SCS TR-20 METHOD TYPE II 24-HOUR RAINFALL= 4.50 IN SPAN= 10-20 HRS, dt=.1 HRS Method Comment Tc (min) TR-55 SHEET FLOW Segment ID: 45.3 Woods: Light underbrush n=.4 L=300' P2=2.4 in s=.04 SHALLOW CONCENTRATED/UPLAND FLOW Segment ID: 9.6 Woodland Kv=5 L=500' s=.03 '/' V=.87 fps SUBCATCHMENT 3 SUBCATCH 3 Total Length= 800 ft Total Tc= 54.9 PEAK= 66.65 CFS @ 12.42 HRS, VOLUME= 8.01 AF ACRES CN SCS TR-20 METHOD 43.10 80 DEVELOPED AREAS INC. ROADS TYPE II 24-HOUR RAINFALL= 4.50 IN SPAN= 10-20 HRS, dt=.1 HRS Method Comment Tc (min) TR-55 SHEET FLOW Segment ID: 39.7 Grass: Dense n=.24 L=300' P2=2.4 in s=.02 SHALLOW CONCENTRATED/UPLAND FLOW Segment ID: 7.9 Kv=6 L=400' s=.02 '/' V=.85 fps Total Length= 700 ft Total Tc= 47.6 • 0 Data for BAYBROOK SUBD.- EXISTING WATERSHED Page 3 TYPE II 24-HOUR RAINFALL= 4.50 IN Prepared by NACE ENGINEERING, P.C. 18 Mar 01 HydroCAD 5.11 000576 (c) 1986-1999 Applied Microcomputer Systems REACH 1 UPPER STREAM Qin = 6.01 CFS @ 12.85 HRS, VOLUME= 1.86 AF Qout= 5.16 CFS @ 13.31 HRS, VOLUME= 1.77 AF, ATTEN= 14`0, LAG= 27.7 MIN DEPTH END AREA DISCH (FT) (SO -FT) (CFS) 0.00 0.00 0.00 .30 1.98 1.82 - .60 4.32 5.98 .90 7.02 12.20 1.29 11.07 23.42 1.80 17.28 43.72 2.40 25.92 76.48 3.00 36.00 119.75 6' x 3' CHANNEL SIDE SLOPE= .5 n= .05 LENGTH= 2000 FT SLOPE= .0055 FT/FT STOR-IND METHOD PEAK DEPTH= .54 FT PEAK VELOCITY= 1.3 FPS TRAVEL TIME = 24.9 MIN SPAN= 10-20 HRS, dt=.1 HRS REACH 2 MIDDLE STREAM Qin = 40.73 CPS @ 12.68 HRS, VOLUME= 8.57 AF Qout= 36.05 CFS @ 12.92 HRS, VOLUME= 8.33 AF, ATTEN= 11%, LAG= DEPTH END AREA DISCH (FT) (SO -FT) (CFS) 0.00 0.00 0.00 .30 1.98 2.33 .60 4.32 7.65 .90 7.02 15.61 1.29 11.07 29.96 1.80 17.28 55.93 2,40 25.92 97.84 3.00 36.00 153.19 REACH 3 6' x 3' CHANNEL SIDE SLOPE= .5 n= .05 LENGTH= 3000 FT SLOPE= .009 FT/FT LOWER STREAM 14.4 MIN STOR-IND METHOD PEAK DEPTH= 1.41 FT PEAK VELOCITY= 2.9 FPS TRAVEL TIME = 17.4 MIN SPAN= 10-20 HRS, dt=.1 HRS Qin = 84.98 CFS @ 12.56 HRS, VOLUME= 16.33 AF Qout= 82.97 CFS @ 12.66 HRS, VOLUME= 16.17 AF, ATTEN= 2%, LAG= 6.2 MIN DEPTH END AREA DISCH (FT) (SO -FT) (CFS) 0.00 0.00 0.00 .30 1.98 2.33 .60 4.32 7.65 .90 7.02 15.61 1.29 11.07 29.96 1.80 17.28 55.93 2.40 25.92 97.84 3.00 36.00 153.19 6' x 3' CHANNEL SIDE SLOPE= .5 n= .05 LENGTH= 1600 FT SLOPE= .009 FT/FT STOR-IND METHOD PEAK DEPTH= 2.18 FT PEAK VELOCITY= 3.6 FPS TRAVEL TIME = 7.4 MIN SPAN= 10-20 HRS, dt=.1 HRS • ii Data for BAYBROOK SUBD.- EXISTING WATERSHED Page 4 TYPE II 24-HOUR RAINFALL= 4.50 IN Prepared by NACE ENGINEERING, P.C. 18 Mar 01 HydroCAD 5.11 000576 (c) 1986-1999 Applied Microcomputer Systems POND 1 NEW CULVERT WITH UPSTREAM STORAGE Qin = 82.97 CFS @ 12.66 HRS, VOLUME= 16.17 AF Qout= 82.99 CFS @ 12.68 HRS, VOLUME= 16.13 AF, ATTEN= 0%, LAG= 1.3 MIN ELEVATION AREA INC.STOR CUM.STOR STOR-IND METHOD (FT) (SF) (CF) (CF) PEAK STORAGE = 4265 CF 0.0 100 0 0 PEAK ELEVATION= 3.2 FT 1.0 500 300 300 FLOOD ELEVATION= 4.0 FT 2.0 1500 1000 1300 START ELEVATION= 0.0 FT 3.0 3000 2250 3550 SPAN= 10-20 HRS, dt=.1 HRS 4.0 6000 4500 8050 Tdet= 1.6 MIN (15.97 AF) # ROUTE INVERT OUTLET DEVICES 1 P 0.0' 42" CULVERT X 2 n=.01 L=80' S=.005'/' Ke=.5 Cc=.9 Cd=.6 TW=2.2' 0 f&