Loading...
HomeMy WebLinkAboutB16-0254_Doubletree Drainage Tech Memo 10-17-2016 complete_1496881440.pdfPO Box 97 Edwards, CO 81632 970-926-3373 Alpine Engineering, Inc. DOUBLETREE by HILTON Hotel Conversion DRAINAGE TECHNICAL MEMO: To: Town of Vail CC: Gary Almgren, AEI From: Heiko Mues, AEI Date: October 17, 2016 Drainage: The purpose of this Drainage Technical Memo is to summarize the existing hydrologic conditions found at the existing Doubletree by Hilton hotel (formerly the Holiday Inn) in West Vail and to evaluate the existing storm drainage system and the proposed stormwater quality treatment facilities for the proposed project. The existing Doubletree by Hilton hotel is located on the North Frontage Road east of the West Vail north roundabout between the MacDonalds and the 1st Bank in Vail, Colorado. The parking lot is being repaved and a water quality vault is being proposed to treat stormwater from the site. Portions of the existing storm sewer piping are being replaced. Existing Conditions: The majority of the existing parcel is currently a paved parking lot and has an existing building on it. There is some off-site drainage coming onto the site from the adjacent road and property. There are existing 12” diameter storm sewer pipes and some existing inlets on the site that convey the majority of the parking lot runoff to existing storm sewer pipe in the North Frontage Road that discharges to the west and eventually to Gore Creek. Proposed Conditions: Historic drainage patterns will be maintained with the repaving of the existing parking lot. Some of the existing storm sewer pipe will replaced due to deterioration and clogging due to non-typical piping configurations. The storm system has been evaluated for capacity for the 25 year storm. Rational Method and hydraulic gradient calculations are included. The proposed 12” diameter storm sewer carries the flow without any surcharge coming out of the inlets. Portions of the 100 year storm that are not intercepted by the storm sewer inlets may overflow to the North Frontage Road as appears to have done historically. PO Box 97 Edwards, CO 81632 970-926-3373 Water Quality Treatment: A new water quality treatment vault is being proposed on line at the end of the existing storm sewer pipe system to treat stormwater from the site. An Oldcastle DVS-72 Dual- Vortex Hydrodynamic Separator is being proposed. TR55 calculations for the overall drainage basin have been calculated to the proposed water quality vault and found to be 2.06, 3.54, 4.54 and 5.80 cfs for the 2, 10, 25 and 100 year storms respectively. A DVS-72 Dual-Vortex Hydrodynamic Separator has a total flow capacity of 27 cfs and a treated flow capacity of 2.00 cfs and has been chosen to provide water quality treatment for the site. The chart from Oldcastle showing the flow capacities for the Dual-Vortex Hydrodynamic Separator has been included in the calculations. Heiko Mues, PE Alpine Engineering, Inc. Cell: (970) 390-5594 www.alpinecivil.com Holiday Inn Roof 0.90 DRAINAGE REPORT Drive/Walk 0.89 Date: September 13, 2016 Lawn 0.15 PEAK FLOW DETERMINATION - 25-Year Storm Drainage Inlet Structure Area Tc I Roof Drive Lawn C Q25 (acres) (min) (in/hr) (acres) (acres) (acres) (cfs) 1 Valley Inlet 0.17 5 4.30 0.030 0.140 0.000 0.89 0.65 2 Valley Inlet 0.18 5 4.30 0.060 0.120 0.000 0.89 0.69 3 Valley Inlet 0.05 5 4.30 0.010 0.040 0.000 0.89 0.19 4 Valley Inlet 0.16 5 4.30 0.040 0.120 0.000 0.89 0.61 5 Valley Inlet 1.27 10 3.37 0.140 0.810 0.320 0.70 3.02 6 Valley Inlet 0.52 10 3.37 0.000 0.250 0.270 0.51 0.89 Q25=CIA where,C= Runoff Coefficient I= Rainfall Intensity (in./hr.) A= Drainage Area (acres) Time of Concentration (Tc) is a minimum 5 minutes The Rainfall Intensity is a 25-year event taken from the Town of Vail Intensity-Duration-Frequency Curves RATIONAL METHOD O:\Vail\Holiday Inn West Vail-8948-2016\DWG\Drainage\PEAK-FLOW-25-2016.xls 9/14/2016 WinTR-55 Current Data Description --- Identification Data --- User: HM Date: 9/14/2016 Project: Vail Holiday Inn Units: English SubTitle: Doubletree by Hilton Areal Units: Acres State: Colorado County: Eagle Filename: O:\Vail\Holiday Inn West Vail-8948-2016\DWG\Drainage\TR55\Overall-2.w55 --- Sub-Area Data --- Name Description Reach Area(ac) RCN Tc ------------------------------------------------------------------------------ 1a overall Outlet 2.35 92 .261 Total area: 2.35 (ac) --- Storm Data -- Rainfall Depth by Rainfall Return Period 100-Yr 25-Yr 10-Yr 2-Yr -Yr -Yr -Yr (in) (in) (in) (in) (in) (in) (in) -------------------------------------------------------------------------------- 2.9 2.4 2.0 1.4 .0 .0 .0 Storm Data Source: User-provided custom storm data Rainfall Distribution Type: Type II Dimensionless Unit Hydrograph: <standard> ================================================================================== HM Vail Holiday Inn Doubletree by Hilton Eagle County, Colorado Watershed Peak Table Sub-Area Peak Flow by Rainfall Return Period or Reach 100-Yr 25-Yr 10-Yr 2-Yr Identifier (cfs) (cfs) (cfs) (cfs) ---------------------------------------------------------------------------------- SUBAREAS 1a 5.80 4.54 3.54 2.06 REACHES OUTLET 5.80 4.54 3.54 2.06 ================================================================================== HM Vail Holiday Inn Doubletree by Hilton WinTR-55, Version 1.00.10 Page 1 9/14/2016 1:33:15 PM Eagle County, Colorado Sub-Area Summary Table Sub-Area Drainage Time of Curve Receiving Sub-Area Identifier Area Concentration Number Reach Description (ac) (hr) -------------------------------------------------------------------------------- 1a 2.35 0.261 92 Outlet overall Total Area: 2.35 (ac) ================================================================================== HM Vail Holiday Inn Doubletree by Hilton Eagle County, Colorado Sub-Area Time of Concentration Details Sub-Area Flow Mannings's End Wetted Travel Identifier/ Length Slope n Area Perimeter Velocity Time (ft) (ft/ft) (sq ft) (ft) (ft/sec) (hr) -------------------------------------------------------------------------------- 1a SHEET 100 0.1500 0.410 0.247 SHALLOW 42 0.0950 0.050 0.002 SHALLOW 214 0.0600 0.025 0.012 CHANNEL 303 Time of Concentration .261 ======== ================================================================================== HM Vail Holiday Inn Doubletree by Hilton Eagle County, Colorado Sub-Area Land Use and Curve Number Details Sub-Area Hydrologic Sub-Area Curve Identifier Land Use Soil Area Number Group (ac) -------------------------------------------------------------------------------- 1a Open space; grass cover > 75% (good) C .59 74 Paved parking lots, roofs, driveways C .28 98 Paved; curbs and storm sewers C 1.48 98 Total Area / Weighted Curve Number 2.35 92 ==== == ================================================================================== WinTR-55, Version 1.00.10 Page 2 9/14/2016 1:33:15 PM ©2009  Kristar Enterprises, Inc. 360 Sutton Place, Santa Rosa, CA, 95407, (800) 579‐8819  REV DVCC 111009  FloGard® Dual‐Vortex Hydrodynamic Separator    Characteristics and Capacities (English)  Model ID Depth  Below  Invert  Treated Flow  Capacity1  Total  Flow  Capacity3  Max.  Pipe  Size  Sediment  Storage  Oil/  Floatable Storage   ft ft 67 µm  cfs  110  µm  cfs  Peak2  cfs  cfs in yd3 gal  DVS‐36 3 3.75 0.12 0.35 0.50 4 12 0.3 18  DVS‐48 4 5.00 0.25 0.75 1.25 9 18 0.7 43  DVS‐60  5 6.25 0.45 1.30 2.50 16 24 1.3 83  DVS‐72 6 8.25 0.70 2.00 4.25 27 36 2.2 141  DVS‐844 7 9.50 1.00 3.00 6.50 40 42 3.5 294  DVS‐96 8 10.75 1.40 4.20 9.50 57 48 5.3 337  DVS‐1204 10 13.50 2.50 7.30 16.80 99 48 9.7 917  DVS‐1444 12 16.00 3.90 11.60 26.40 154 60 15.5 1825    Characteristics and Capacities (Metric)  Model ID Depth  Below  Invert  Treated Flow  Capacity1  Total  Flow  Capacity3  Max.  Pipe  Size  Sediment  Storage  Oil/  Floatable  Storage   m m 67 µm  L/s  110  µm  L/s  Peak2  L/s  L/s mm m3 L  DVS‐36 0.9 1.14 3.5 10 14 113 300 0.23 68  DVS‐48 1.2 1.52 7 21 35 255 450 0.54 163  DVS‐60  1.5 1.91 13 37 71 453 600 1.00 314  DVS‐72 1.8 2.51 20 57 120 765 900 1.70 534  DVS‐844 2.1 2.90 30 85 184 1133 1050 2.70 1113  DVS‐96 2.4 3.28 40 120 269 1614 1200 4.00 1276  DVS‐1204 3.0 4.11 70 205 475 2800 1200 7.40 3471  DVS‐1444 3.7 4.88 110 330 750 4360 1500 11.90 6908    1Treated Flow Capacity is based on 80% removal of suspended sediment with the approximate mean particle size  shown.  The appropriate flow capacity should be selected based on expected site sediment characteristics.  2 Maximum flow prior to bypass.  3 Total design flow to the system should not exceed the Peak Flow Capacity.  4Call Kristar representative for availability in your area.    Notes: Systems may be sized based on a water quality flow (i.e. 1‐inch design storm) or on net annual sediment load removal depending on  local regulatory requirements.   Contact Kristar for the most accurate and cost effective sizing for your project location.  When sizing system based on a water quality flow, the required flow to be treated must be less than or equal to the Treated Flow  Capacity for the selected unit.  Additional Treated Flow Capacities based on different mean particle sizes are available upon request.