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Home My WebLink AboutOLD TOWN NORTH, NORTH FLATS - PDP & MODIFICATION OF STANDARDS - 28-99D - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTCross Section --Alley S-2 100-yr Event Cross Section for Irregular Channel Project Description Worksheet Alley S-2 100-yr Flow Element Irregular Channel Method Manning's Formula Solve For Channel Depth Section Data Mannings Coefficient 0.016 Channel Slope 0.006000 ft/ft Water Surface Elevation 0.43 ft Elevation Range 0.00 to 0.54 Discharge 9.00 cfs ?fo-sue A 0.55 0.50 0.40 0.30 0.20 0.10 0.00 -0+20.0 -0+15.0-0+10.0-0+05.0 0+00.0 0+05.0 0+10.0 0+15.0 0+20.0 V.20.0N H:1 NTS Project Engineer: JR Engineering x:\3950000.all\3953500\alley s-2.fm2 JR Engineering FlowMaster v7.0 [7.0005] 11/20/06 03:33:01 PM 0 Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 1 of 1 Alley S-2 100-yr Event Worksheet for Irregular Channel Project Description Worksheet Alley S-2 100-yr Flow Element Irregular Channel Method Manning's Formula Solve For Channel Depth Input Data Channel Slope 0.006000 ft/ft Discharge 9.00 cfs Options Current Roughness Method Improved Lotter's Method Open Channel Weighting Method Improved Lotter's Method Closed Channel Weighting Metho. Horton's Method Results Mannings Coefficient 0.016 Water Surface Elevation 0.43 ft Elevation Range 0.00 to 0.54 Flow Area 4.4 ft' Wetted Perimeter 28.96 ft Top Width 28.94 ft Actual Depth 0.43 ft Critical Elevation 0.42 ft Critical Slope 0.007074 ft/ft Velocity 2.05 ft/s Velocity Head 0.07 ft Specific Energy 0.49 ft Froude Number 0.93 Flow Type Subcritical Roughness Segments Start End Mannings Station Station Coefficient -0+20.0 0+18.5 0.016 Natural Channel Points Station Elevation (ft) (ft) -0+20.0 0.54 -0+01.5 0.17 0+00.0 0.00 0+01.5 0.17 0+18.5 0.51 Project Engineer: JR Engineering x:\3950000.all\3953500\alley s-2.fm2 JR Engineering FlowMaster v7.0 [7.0005] 11/20/06 03:32:54 PM 0 Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 1 of 1 JR Engineering, Ltd. 2620 E. Prospect Rd., Ste. 190, Fort Collins, CO 80525 RATIONAL METHOD PEAK RUNOFF (100-YEAR) LOCATION: NORTH FLATS PROJECT NO: 39535.00 COMPUTATIONS BY: ES SUBN4ITTED BY: JR ENGfNEERING, LTD. DATE: 11/20/2006 100 yr storm, Cf = 1.25 DIRECTRUNOFF I CARRYOVER TOTAL REMARKS Des. Point Area Design. A (ac) C Cf tc (min) i (in/hr) Q (100) (cfs) from Design Point Q (100) (cfs) Olt 00)t0t (cfs) 1 MF 0.09 0.91 5.0 10.0 1.01 1.0 2 SF 0.70 0.85 5.0 10.0 7.44 T4 3 ALLEY S-2 0.05 1.00 5.0 10.0 0.57 0.6 Q=CiA Q = peak discharge (cfs) C = runoff coefficient I = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) rota) = 9.0 I = 84.682 / (10+ tc)o 7975 39535.00 FLOW.XLS JR Engineering, Ltd. 2620 E. Prospect Rd., Ste. 190, Fort Collins, CO 80525 RATIONAL METHOD PEAK RUNOFF (10-YEAR) LOCATION: NORTH FLATS PROJECT NO: 39535.00 COMPUTATIONS BY: ES SUBMITTED BY: JR ENGINEERING, LTD. DATE: 11/20/2006 10 yr storm, Cf = 1.00 DIRECT RUNOFF CARRY OVER TOTAL REMARKS Design Point Tributary Sub -basin A (ac) C Cf tc (min) i (in/hr) Q (10) (cfs) from Design Point Q (10) (cfs) Q(10)tot (cfs) MF 0.09 0.73 5.0 4.78 0.31 0.3 SF 0.70 0.68 6.0 4.55 2.17 2.2 ALLEY S-2 0.05 1.00 5.0 4.78 0.22 0.2 Q=CfCiA Q = peak discharge (cfs) C = runoff coefficient Cf = frequency adjustment factor I = rainfall intensity (in/hr) from OF curve A = drainage area (acres) I otas 2.1 I = 41,44 I (10+ tc)° 1174 39535.00 FLOW.XLS LOCATION: PROJ ECT NO: COMPUTATIONS BY SUBMIVULD BY: DATE': 100-yr storm NORTII FLATS 39535.00 ES JR ENGINEERING, LTD. 1 1 /20/2006 Cf = 1.25 TOC-100 STANDARD FORM SF-2 TIME OF CONCENTRATION - 100 YR SUB -BASIN DATA INITIAL /OVERLAND TIME (ti) TRAVEL TIME / GUTTER OR CHANNEL FLOW (ft) tc CHECK (URBANIZED BASIN) FINAL tc REMARKS DESIGN PONIT SUBBASIN(s) (1) Area (ac) (2) C (3) C'Cf Length (ft) (4) Slope (%) (5) ti (min) (6) Length (ft) (7) Slope (%) (8) n Manning rough. Val. (ft/s) (9) It (min) (10) tc= ti+tt (11) Total (It) (12) tc=(1/180)+10 (min) (13) (min) (14) 1 MF 0.09 0.73 0.91 40 2.0 1.7 90 0.6 0.016 1.6 0.96 2.7 130 10.7 5.0 2 SF 0.70 0.68 0.85 50 2.0 2.5 160 0.6 0.016 1.6 1.71 4.2 2101 11.2 5.0 3 ALLEY S-2 0.05 1.00 1.00 10 2.0 0.5 90 0.6 0.016 1.6 0.96 1.4 100110.6 5.0 EQUATIONS: tc=ti+tt ti=[1.87(1.1-CCf)L0.5)/S1/3 tt = Wel. Velocity from Manning's Eqquation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tt and urbanized basin check min. tc = 5 min. due to limits of OF curves Page 2 JR Engineering, Ltd. 2620 E. Prospect Rd., Ste. 190, Fort Collins, CO 80525 LOCATION: PROJECTNO: COMPUTATIONS BY: SUBMITTED BY: DATE: 10-yr storm NOWITI FLATS 39535.00 I? S JR f NGINEFRING, LTD. 1 1 /20/2006 Cf = 1.00 STANDARD FORM SF-2 TIME OF CONCENTRATION - 10 YR SUB -BASIN DATA INITIAL /OVERLAND TIME (ti) TRAVEL TIME / GUTTER OR CHANNEL FLOW (tt) tc CHECK (URBANIZED BASIN) FINAL tc REMARKS DESIGN PONIT SUBBASIN(s) (1) Area (ac) (2) C (3) Length (ft) (4) Slope (%) (5) ti (min) (6) Length (ft) (7) Slope (%) (8) n Manning rough. Vel. (ft/s) (9) It (min) (10) tc= ti+it (11) Total (ft) (12) tc=(1/180)+10 (min) (13) (min) (14) MF 0.09 0.73 40 2.0 3.3 90 0.6 0.016 1.6 0.96 4.3 130 10.7 5.0 SF 0.70 0.68 50 2.0 4.2 160 0.6 0.016 1.6 1.71 6.0 210 11.2 6.0 ALLEY S-2 0.04591 1 10 2.0 0+51 90 0.6 0.016 1.6 0.96 1.41 100 10.61 5.0 EQUATIONS: tc=tl+tt tl=[1.87(1.1- CC,) L0.5S1/3 It = Wel. Velocity from Manning's Eqquation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + It and urbanized basin check min. tc = 5 min. due to limits of IDF curves 39535.00 FLOW.XLS SUMMARY DRAINAGE SUMMARY TABLE Design Point Tributary Sub -basin Area (ac) C (10) C (100) tc (10) (min) tc (100) (min) Q(10)tot (cfs) Q(100)tot (cfs) DRAINAGE STRUCTURE /REMARKS MF 0.09 0.73 0.91 5.0 5.0 0.3 1.0 SF 0.70 0.68 0.85 6.0 5.0 2.2 7.4 ALLEY S-2 0.05 1.00 1.00 1 5.0 5.0 0.2 1 0.6 9.0 TOTAL TO ALLEY S-2 Page 5 Client: .4 14 Project: .K,U Subject: Vir"L By: �Chk. By: -Povv Is - Job No: D- - Date: 28 4 J-R ENGINEERINC A Westrian Company Sheet No: of f ___3__ I I IT E-11 LLL F _� T � -� I _ _I 1A, SLY F 110 AA V 9 T - ------ - - -- --- ------ - --------- 1. - -I F- -- t F- 646-01-98 Shear Engineering Corporation 12/21/2001 ;dah Old Town North 9:15 AM grmine Runoff Coefficients for Single Family and Town Home Lots ,e Family Lots aDimensions 40.00 ft x 1 85.00 Ift s 3400.00 sf = 0.08 ac. s` Im A C A*C W P A*%Im P sf 8na,ding Area 1910 0.95 1814.50 100% 1910 Drive/ walks Area 405 0.95 384.75 100;- 405 Lawn Area = remainder 1085 0.10 108.50 0w 0 p-Jy^ Lot Area (A) = 3400 sf 2315 Total A*C = 2307.75 C2 = (Total/A) 0.68 % Impervious 68.09� L100 = 1.25*C2 0.85 - C100 cannot be > 1 Roof Drives and walks L x W = Area ft ft sf L x W = Area ft ft sf 40.00 4.00 1160.00 15.00 3.00 1 45.00 8.00 25.00 1200.00 34.00 40.00 11360.00 25.00 22.00 1 550.00 Total 11910.00 Total 1405.00 Tow^l Home Lots Lot Dim__-ion-s-----�70.00 ft x 18.00 ft P_rea = 1260.00 sf = 0.03 ac. A C A*C Imp A*Imp sf Building Area 970 0.95 921.50 100% 970 Drive/ walks Area 102 0.95 96.90 100% 102 La"fm Area = remainder 188 0.10 18.80 0% 0 Avg Lot Area (A)= 1260 1 19JL Total A*C = 1037.20 % Impervious 85.08% C2 = (Total/A) 0.82 C100 = 1.25*C2 1.00 - C100 cannot be > 1� Roof Drives and walks L x W = Area L x W= Area ft ft sf ft ft sf 38.00 18.00 664.00 18.00 4.00 72.00 22.00 13.00 286.00 10.00 3.00 30.00 970.00 S.- ' �-rati0nal r ocks Typ Page 3 of 44 1 102.00 LOCATION: North Flats PROJECT NO: 39535.00 COMPUTATIONS BY: E. SCHNEIDER SUBMITTED BY: JR ENGINEERING, LTD. DATE: 9/28/2006 Updated Determination of Runoff Coefficients for Town Home Lots Town Home Lots Block Dimensions Area 182 ft 15470 sf A sf x = C 85 0.355 A*C ft ac %I A*%I Roof Area Asphalt Area Paver Area Sidewalk/concrete Area Lawn Area = remainder 6463.2 0.95 6140.0 100 6463.16 2039.E 0.95 1937.6 100 2039.62 2910.0 0.95 2764.5 100 2910 36.0 0.95 34.2 100 36 4021.2 0.10 402.1 0 0 Avg Block Area (A)= Total A*C= C2 = (Total/A) C100 = 1.25*C2 15470.0 % Impervious 11448.78 74.01 11278.5 0.73 0.91 Reference: "Final Drainage and Erosion Control Report for Old Town North Phase I" Prepared by Shear Engineering Corporation, March, 2002 Conclusions: % Impervious of Town Home area decreased from original calculations (85% to 74%) 0siand ar Street — ` - I---- - LEGEND TOWN HOME BLOCK AREA TOWN HOME ROOF AREA --� TOWN HOME ASPHALT AREA TOWN HOME PAVER/CONCRETE AREA 30 15 0 30 SCALE: 1" = 30' TYPICAL TOWN HOME BLOCK TO DETERMINE AREAS FOR %I NORTH FLATS SEPTEMBER 28, 2006 SHEET 01 OF 01 J•R ENGINEERING A WrUlan Company 2620 East Prospect Road, Suite W • Port Couiri, CO 8053 07A—AGt-mma. c,,, o�a_omn . September 29, 2006 J R ENGINEERING A Westrian Company Mr. Wes Lamarque City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80522 RE: Drainage impact for changes to the Old Town North Phase 1 Development Dear Wes: We are pleased to submit for your review and approval this letter showing the drainage impacts from the proposed changes to the townhome area of the Old Town North Phase 1 development. This area, named North Flats, is the multi -family area located to the east and west of Blondel Street. The area will include eight, two story, five-plex townhome units. Analysis of the proposed versus previously approved conditions, as stated in the "Final Drainage and Erosion Control Report for Old Town North Phase 1" dated March, 2002 and prepared by Shear Engineering Corporation, has indicated the percent imperviousness for the townhome area would decrease by 11%. Therefore, stormwater runoff flows would remain at or below previously approved conditions. Please refer to the attached spreadsheet and drawing for calculations and information. The area that includes alley S-2 was checked to ensure that during the major storm event, flooding of the building located to the west of the southern half of alley S-2 would not occur. The area was chosen for analysis because it is the area that takes the most flow during the major storm event. Our calculations indicate that during the major storm event, flooding would not occur and the water surface elevation would remain below the finish floor elevation of the adjacent building and within the existing drainage easement. Please refer to the attached spreadsheet for these calculations. JR Engineering has reviewed and concluded that the impact to the local drainage basin is improved and negative impacts are not anticipated to the surrounding areas due to the proposed improvements. All computations within this letter have been completed in compliance with the most recent rainfall data and the City of Fort Collins Storm Drainage Design Criteria. We appreciate your time and consideration in reviewing this submittal. If you have any questions or need additional information please call (970) 491-9888. Prepared by: 9�k� Erika Schneider Project Engineer Reviewed by: Joseph C. Sparone P.E. Project Manager 0�'°,aoo uC 2620 East Prospect Road, Suite 190, Fort Collins, CO 80525 X:\3950000.all\3953500\Word\Letters\Drainage Letter.doc 970-491-9888 • Fax: 970-491-9984 • wJrengineering.com