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Home My WebLink AboutPEC140020_Drainage Memorandum_1405442280.pdf July 14, 2014 Mr. Tom Kassmel Town of Vail, Department of Public Works 75 S. Frontage Road Vail, Colorado 81657 Re: Ski and Snowboard Club of Vail Redevelopment: Drainage Analysis Martin/Martin, Inc. Project No.: 14.0498 Mr. Kassmel: Martin/Martin, Inc. has been contracted to do the Civil Engineering design for the redevelopment of the Ski and Snowboard Club of Vail facility located at 598 Vail Valley Drive. Included within the scope is the design of the drainage system. Martin/Martin has completed a preliminary review of the site to understand drainage patterns. Based on ground survey completed by Eagle Valley Surveying, the existing site is estimated to be 35% impervious. Drainage patterns are generally toward the north into Vail Valley Drive then west into an existing set of curb inlets. The existing site does not have any on-site detention or water quality features. Using the Rational Method, the estimated 100-year discharge from the site into Vail Valley Drive is 3.9 CFS. We understand the downstream, public system is presently at capacity. Once redeveloped, the site will continue to have similar drainage patterns in that the driveway, drop-off lanes, and on-grade parking will discharge directly into Vail Valley Drive. The difference will be that it is proposed to capture all of the roof drainage and pipe it below grade. The imperviousness of the redeveloped site will increase to an estimated 52% (17% increase relative to existing). The corresponding discharge is estimated to be 4.3 CFS during the 100-year storm event. However, since it has been requested to limit the redevelopment, 100-year flow rates to match existing, sufficient below-grade detention will be provided. Per the V=KA method of detention volume calculation, it will be necessary to provide approximately 1,500 cubic feet of volume as a result of the 17% increase in overall site imperviousness. The roof drainage will be piped into the detention system. Further design of the site and building must be completed before the required detention volume can be further refined and corresponding release rates established. The following items are attached to this letter: 1. Map identifying the basin limits 2. Rational method calculations 3. Detention volume calculations Let me know if you have any questions. Elk Meadows Subdivision, Lot 1: Drainage Analysis May 15, 2014 P a g e 2 | 2 Sincerely, L. Mark Luna, PE Associate [Attachments] PROJECT INFORMATION PROJECT NAME: PROJECT NO: DESIGN BY: REVIEWED BY: JURISDICTION: REPORT TYPE: DATE: C2 C5 C10 C100 % IMPERV 0.04 0.15 0.25 0.50 0% 0.73 0.75 0.77 0.83 90% 0.89 0.90 0.92 0.96 100% 0.73 0.75 0.77 0.83 90% 1.15 0.33 0.41 0.48 0.65 35.1% AREA (ACRES) C2 C5 C10 C100 0.74 0.04 0.15 0.25 0.50 0% 0.08 0.73 0.75 0.77 0.83 90% 0.32 0.89 0.90 0.92 0.96 100% 0.01 0.73 0.75 0.77 0.83 90% 1.15 0.33 0.41 0.48 0.65 35.1% 1.15 0.33 0.41 0.48 0.65 35.1% TOTAL SITE COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS TOWN OF VAIL PRELIMINARY (PEC) - EXISTING 07/02/14 JURISDICTIONAL STANDARD SKI CLUB VAIL 14.0498 J. YARNELL L. M. LUNA ROOF LANDSCAPE ASPHALT/CONCRETE DRIVES AND WALKS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS ROOF ASPHALT/CONCRETE LANDSCAPE SUB-BASIN COMPOSITE 1 DRIVES AND WALKS TOTAL SITE COMPOSITE 7/10/2014 7:54 AM COMPOSITE_C-VALUES H:\14.0498-VAIL SKI CLUB\ENG\DRAINAGE\Rational - Existing.xlsm CALCULATED BY:JOB NO:CHECKED BY:PROJECT:DATE:FINALtcAREA LENGTH SLOPEtiLENGTH SLOPE VEL.ttCOMP.TOT. LENGTHac ft ft/ft min ft ft/ft fps Mintcft min min(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)1 1 0.41 1.15 120 0.2080 5.0 385 0.0420 20 4.10 1.6 6.6 505.0 12.8 6.6*Velocity (V) = CvSw0.5TABLE RO-2*Table RO-2, UDFCD (V.1), Chapter 5, Page RO-6in which: Cv = Conveyance Coefficient (See Table Above)Sw = Watercourse Slope (ft/ft)J. YARNELLL. M. LUNA07/02/14INITIAL/OVERLANDTIME OF CONCENTRATION SUMMARY(tt)TRAVEL TIME14.0498SKI CLUB VAILSTANDARD FORM SF-2(RATIONAL METHOD PROCEDURE)(URBANIZED BASINS)tc CHECKREMARKSType of Land SurfaceConveyance Coefficient, CvNearly Bare Ground10Grassed Waterway155Short Pasture and Lawns7Paved Areas and Shallow Paved Swales20Heavy Meadow2.5Tillage / FieldBASINDESIGN POINTC5tc=(L/180)+10CvDATASUB-BASINTIME (ti)TOC7/10/2014 7:54 AMH:\14.0498-VAIL SKI CLUB\ENG\DRAINAGE\Rational - Existing.xlsm CALCULATED BY:J. YARNELLJOB NO:14.0498CHECKED BY:L. M. LUNAPROJECT:SKI CLUB VAILDATE:07/02/14DESIGN STORM:100-YEARONE-HR PRECIP:1.64(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)1 1 1.15 0.65 6.6 0.75 5.14 3.85I. One-Hr Precipitation Values for the Town of VailReturn Period: 2-YEAR 5-YEAR 10-YEAR 100-YEARDepth In Inches: 0.58 0.75 0.91 1.64*Equation RA-3, UDFCD (V.1), Chapter 4, Page RA-6*Rainfall Intensity:In Which: I = Rainfall Intensity (Inches Per Hour)P1 = 1-Hour Point Rainfall Depth (Inches)tc = Time Of Concentration (Minutes)BASIN DESIGN POINTDIRECT RUNOFFTOTAL RUNOFFtc (MIN)S(CxA) (AC)I (IN/HR)Q (CFS)REMARKSAREA (AC)RUNOFF COEFFtc (MIN)STANDARD FORM SF-3STORM DRAINAGE SYSTEM DESIGN(RATIONAL METHOD PROCEDURE)CxA (AC)I (IN/HR)Q (CFS)100-YEAR7/10/2014 7:54 AMH:\14.0498-VAIL SKI CLUB\ENG\DRAINAGE\Rational - Existing.xlsm PROJECT INFORMATION PROJECT NAME: PROJECT NO: DESIGN BY: REVIEWED BY: JURISDICTION: REPORT TYPE: DATE: C2 C5 C10 C100 % IMPERV 0.04 0.15 0.25 0.50 0% 0.73 0.75 0.77 0.83 90% 0.89 0.90 0.92 0.96 100% 0.73 0.75 0.77 0.83 90% 1.15 0.45 0.50 0.56 0.70 51.9% AREA (ACRES) C2 C5 C10 C100 0.50 0.04 0.15 0.25 0.50 0% 0.36 0.73 0.75 0.77 0.83 90% 0.11 0.89 0.90 0.92 0.96 100% 0.19 0.73 0.75 0.77 0.83 90% 1.15 0.45 0.50 0.56 0.70 51.9% 1.15 0.45 0.50 0.56 0.70 51.9% TOTAL SITE COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS TOWN OF VAIL PRELIMINARY (PEC) - PROPOSED 07/02/14 JURISDICTIONAL STANDARD SKI CLUB VAIL 14.0498 J. YARNELL L. M. LUNA ROOF LANDSCAPE ASPHALT/CONCRETE DRIVES AND WALKS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS ROOF ASPHALT/CONCRETE LANDSCAPE SUB-BASIN COMPOSITE 1 DRIVES AND WALKS TOTAL SITE COMPOSITE 7/10/2014 7:54 AM COMPOSITE_C-VALUES H:\14.0498-VAIL SKI CLUB\ENG\DRAINAGE\Rational - Proposed.xlsm CALCULATED BY:JOB NO:CHECKED BY:PROJECT:DATE:FINALtcAREA LENGTH SLOPEtiLENGTH SLOPE VEL.ttCOMP.TOT. LENGTHac ft ft/ft min ft ft/ft fps Mintcft min min(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)1 1 0.50 1.15 120 0.2080 4.4 385 0.0420 20 4.10 1.6 5.9 505.0 12.8 5.9*Velocity (V) = CvSw0.5TABLE RO-2*Table RO-2, UDFCD (V.1), Chapter 5, Page RO-6in which: Cv = Conveyance Coefficient (See Table Above)Sw = Watercourse Slope (ft/ft)J. YARNELLL. M. LUNA07/02/14INITIAL/OVERLANDTIME OF CONCENTRATION SUMMARY(tt)TRAVEL TIME14.0498SKI CLUB VAILSTANDARD FORM SF-2(RATIONAL METHOD PROCEDURE)(URBANIZED BASINS)tc CHECKREMARKSType of Land SurfaceConveyance Coefficient, CvNearly Bare Ground10Grassed Waterway155Short Pasture and Lawns7Paved Areas and Shallow Paved Swales20Heavy Meadow2.5Tillage / FieldBASINDESIGN POINTC5tc=(L/180)+10CvDATASUB-BASINTIME (ti)TOC7/10/2014 7:54 AMH:\14.0498-VAIL SKI CLUB\ENG\DRAINAGE\Rational - Proposed.xlsm CALCULATED BY:J. YARNELLJOB NO:14.0498CHECKED BY:L. M. LUNAPROJECT:SKI CLUB VAILDATE:07/02/14DESIGN STORM:100-YEARONE-HR PRECIP:1.64(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)1 1 1.15 0.70 5.9 0.81 5.31 4.27I. One-Hr Precipitation Values for the Town of VailReturn Period: 2-YEAR 5-YEAR 10-YEAR 100-YEARDepth In Inches: 0.58 0.75 0.91 1.64*Equation RA-3, UDFCD (V.1), Chapter 4, Page RA-6*Rainfall Intensity:In Which: I = Rainfall Intensity (Inches Per Hour)P1 = 1-Hour Point Rainfall Depth (Inches)tc = Time Of Concentration (Minutes)BASIN DESIGN POINTDIRECT RUNOFFTOTAL RUNOFFtc (MIN)S(CxA) (AC)I (IN/HR)Q (CFS)REMARKSAREA (AC)RUNOFF COEFFtc (MIN)STANDARD FORM SF-3STORM DRAINAGE SYSTEM DESIGN(RATIONAL METHOD PROCEDURE)CxA (AC)I (IN/HR)Q (CFS)100-YEAR7/10/2014 7:54 AMH:\14.0498-VAIL SKI CLUB\ENG\DRAINAGE\Rational - Proposed.xlsm PROJECT INFORMATION PROJECT NAME: PROJECT #: POND NAME: DATE: Required Detention Volume: *Equations SO-1 through SO-5, UDFCD (V.2), Chapter 10, Pg. SO-9 Where: Vi =Required Volume Where Subscript i = 100-, 10- or 5-Year Storm (acre-ft) Ki =Empirical Volume Coefficient I = Fully Developed Tributary Catchment Imperviousness (%) A = Tributary Catchment Area (acres) I = 17.0 (%) A = 1.2 (acres) K100 =0.029 K10 =0.014 K5 =0.010 V100 =0.033 (ac-ft) V10 =0.016 (ac-ft) V5 =0.012 (ac-ft) NRCS Hydrologic Soil Group: C & D Max 5-Year Release Rate = 1.1 (cfs) Max 10-Year Release Rate = 1.6 (cfs) Max 100-Year Release Rate = 3.9 (cfs) Maximum Unit Flow Release Rates (cfs/acre) from On-Site Detention Facilities *Table SO-1, UDFCD (V.2), Chapter 10, Page SO-8 SKI CLUB VAIL 14.05 BELOW-GRADE 01/14/14 0.07 0.13 0.50 0.17 NRCS Hydrologic Soil GroupDesign Return Period (Years) 5 10 100 0.30 1.00 A B C & D 0.13 0.23 0.85 7/10/2014 7:53 AM Detention Volume H:\14.0498-VAIL SKI CLUB\ENG\DRAINAGE\Pond_Design_KA.xlsm