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HomeMy WebLinkAbout2004-10-06 Stormwater Report SPR CHRISTIANSENIg INC. PROFESSIONAL ENGINEERS AND LAND SURVEYORS 160 SU)AViER STREET fiAVERfi1t.L, h,�AS`AGHI)SE:T7S ?3fi3 )-33k3 (978) 373-037.0 FM (978) 372 39C0 August 16, 2004 Mr. William Derry PO Box 2142 So. Hamilton MA Re: Drawing No. 98082035 Dear Bill, At your request I have reviewed the hydrology of the proposed hangar area at Lawrence Municipal Airport and find the following. 1. The peak flow rate of stormwater off the new roof and paved areas will amount to 4.35 cfs for a 100 year storm. 2. A channel running from the site to the existing 12" culvert could carry 192 cfs, if the channel were trapezoidal with a 12 inch base width, 3:1 side slopes and a flow depth of 24 inches. The existing channel conforms to these dimensions, and would be adequate if mowed. 3. The 12 "pipe that drains the area can accommodate 8.44 cfs flowing at a depth of 11 inches. 4. The pipe can flow at this rate without overtopping the surrounding area. I have attached calculation summaries for your reference. Very truly yours Philip Christiansen Lawrence Municipal Airport TYPE Ilf 24-HR Rainfafl=6.40" Prepared by Christiansen &Sergi, Inc, HydroCADID 7.00 s/n 001057 01986-2003 Applied Microcomputer Systems 8/12/2004 Subcatchment 2S: PROPOSED CONDITIONS: DRAINAGE AREA 2 Hydrograph 4.35 cfs I ', ', C1 Runotf TYPE III 24=HR_- 4 Rainfall=6.40" Runoff Area:31,301 sf -- 3- Runoff Volume=0.285 of Runoff Depth=4.75" Flow Length=115' - 2- TC=1.4 min CN=94 14-1 10 11 12 13 14 15 16 17 18 18 20 Time (hours) tmp#1 Channel calculator Given input Data: shape . . . . . . . . . . . . . . . . . . . . . . . Trapezoidal solving far . . . . . . . . . . . . . . . . . . . . . Flowrate slope . . . . . . . . . . . . . . . . . . . . . . . . . . 0.0250 ft/ft manning's n . . . . . . . . . . . . . . . . . . . . . 0.0175 Depth 24.0000 in Height . . . . . . . . . . . . . . . . I . . . . 36.0000 in Bottom width 12.0000 in Left slope . . . . . . . . . . . . . . . . . . . . . . 0.3300 ft/ft Right slope 0.3300 ft �V/H) V/H Computed Results: Flowrate . . . . . . . . . . . . . . . . . . . . . . . . 192.8580 cfs velocity . . . . . . . . . . . . . . . . . . . . . . . . 13,6573 fps Full Flowrate 533,2211 cfs Flow area . . . . . . . . . . . . . . . . . . . . . 14.1212 ft2 Flow perimeter . . . . . . . . . . . . . . . . . . 165.1699 in Hydraulic radius . . . . . . . . . . . . . . . . 12.3113 in Top width . . . . . . . . . . . . . . . . . . . . . . . 157.4545 in Area 30.2727 ft2 Perimeter . . . . . . . . . . . . . . . . . . . . 241.7549 in Percent full . . . . . . . . . . . . . . . . . . . . 66.6667 critical Tnformati on critical depth . . . . . . . . . . . . . . . . . . 34.3414 in critical slope . . . . . . . . . . . . . . . . . . 0.0042 ft/ft critical velocity . . . . . . . . . . . . . . . 6.9676 fps critical area . . . . . . . . . . . . . . . . . 27.6793 ft2 criticalerimeter . . . . . . . . . . . . . . 231.1694 in critical gydraulic radius . . . . . . . 17.2420 in critical top width . . . . . . . . . . . . . . 220.1296 in specific energy . . . . . . . . . . . . . . . . . 4.8987 ft Minimum energy . . . . . . . . . . . . . . . . . . 4.2927 ft Froude number . . . . . . . . . . . . . . . . . . . 2.3209 Flow condition . . . . . . . . . . . . . . . . . . supercritical Page 1 ' 1 tmp#1 Manni ng Pipe Calculator Given Input Data. shape . . . . . . . . . . . . . . . . . . . . . . . Circular solving for . . . . . . . . . . . . . . . . . . . . . Flowrate Diameter . . . . . . . . . . . . . . . . . . . . . . . . 12.0000 in Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.0000 in slope . . . . . . . . . . . . . . . . . . . . . . . . 0.0234 ft/ft Manning's n . . . . . . . . . . . . . . . . . . . . . 0.0090 computed Results: Flowrate . . . . . . . . . . . . . . . . . . . . . . . . 8.4419 cfs Area . . . . . . . . . . . . . . . . . . . . . . . . . 0.7854 ft2 Wetted Area . . . . . . . . . . . . . . . . . . . 0.7541 ft2 Wetted Perimeter . . . . . . . . . . . . . . . . 30.6709 in Perimeter . . . . . . . . . . . . . . . . . . . . . . . 37.6991 in Velocity 11.1941 fps Hydraulic�Radius . . . . . . . . . . . . . . . . 3. 5407 in Percent Full . . . . . . . . . . . . . . . . . . . 91.6667 % Full flow Flowrate . . . . . . . . . . . . . . 7.8723 cfs Full flow velocity . . . . . . . . . . . . . . 10.0233 fps Page 1 Culvert Calculator tmp#1 Entered Data: shape . . . . . . . . . . . . . . . . . . . . . . . Circular Number of Barrels . . . . . . . . . . . . . . . 1 solving for . . . . . . . . . . . . . . . . . . . . . Headwater chart Number . . . . . . . . . . . . . . . . . . . . 1 scale Number . . . . . . . . . . . . . . . . . . . . 1 Chart Description . . . . . . . . . . . . . . . CONCRETE PIPE CULVERT; NO BEVELED RING ENTRANCE scaly Decsription . . . . . . . . . . . . . . . SQUARE EDGE ENTRANCE WITH HEADWALL Overtopping . . . . . . . . . . . . . . . . . . . . . off Olowrate . . . . . . . . . . . . . . . . . . . . . . . 8.4400 cfs Manning`sn 0.0120 Roadway Elevation 124.0000 ft Inlet Elevation 117.8500 ft outlet Elevation . . . . . . . . . . . . . . . . 112.7000 ft Diameter . . . . . . . . . . . . . . . . . . . . . . . . 12.0000 in Length . . . . . . . . . . . . . . . . . . . . . . . . . . 200.0000 ft Entrance Loss . . . . . . . . . . . . . . . . . . . 0.0000 Tailwater . . . . . . . . . . . . . . . . . . . . . . . 0.1000 ft Computed Results: Headwater . . . . . . . . . . . . . . . . . . . . . . . 123.8365 ft outlet control Slope . . . . . . . . . . . . . . . . . . . . . . . . . 0.0257 ft/ft Velocity . . . . . . . . . . . . . . . . . . . . . . . 10.8907 fps Messages: outlet head > Inlet head. Computing Outlet Control headwater. outlet not submerged. Normal Depth: 12.0000 in Critical Depth: 11.5234 in Flow is subcritical . Normal depth > critical depth. Tailwater depth < normal depth. M2 drawdown profile. Tailwater depth <= critical depth. Depth computed with direct step method starting at critical depth. Headwater: 123.8365 ft DIS- HEAD- INLET OUTLET CHARGE WATER CONTROL CONTROL FLOW NORMAL CRITICAL OUTLET TAILWATER Flow ELEV. DEPTH DEPTH TYPE DEPTH DEPTH VEL. DEPTH VEL. DEPTH cfs ft ft ft in in fps ft fps ft 1.69 119.13 0.53 1.28 NA 4.28 12.00 3.79 0.36 0.00 0.10 3. 38 124.00 1.11 6.15 NA 6.32 12.00 5.10 0.53 0.00 0.10 5.06 119.88 2.03 0,00 NA 8.25 11.04 8.79 0.69 0.00 0.10 6.75 1.21.17 3.32 0.00 NA 12.00 12.00 8.60 1.00 0.00 0.10 8.44 122.$2 4.97 0.00 NA 12.00 12.00 10.75 1.00 0.00 0.10 10.13 124.00 6.15 0.00 NA 12.00 12.00 12.90 1.00 0.00 0.10 Page 1