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HomeMy WebLinkAboutEver Vail Preliminary Drainage Report Novemeber 2008 ' , � Preliminary Drainage Report for I-70 South Frontage Road Relocation at � Vail Colorado � � , � -� � _ . ��;., ��:�� � -�� ��� ,�r � � T�. �`� � ' � ��� . � � ����.�:4E. • �i�� �����4# � ��MV 4 ..�� ��: �. "_" rr �Y y, �`�„m ' � � ,� � ' _ �, . Y � � i � , ��' �,'� ' �`i',t '� - - .1-' ��'� �t .� I�i � y� ��¢��.� I� I�:.t � � � � � ,��� . . . k��.. ��;4 ���+�t�i� r� . . � � . .. - � rt, i . ,. � � a ' � .'' . . . ' . A � ` .. 5 �� �,,�, i. ,Y � , . ,.,'h ' - '� y', � . � ' ' '���� �..1 . � � . � . . � � �•�.y r ',�g`�f' � '�..i'.�•'��.'. ., . CDOT Project Number 1702� � f� � � � � - = - - � Edwards Business Centa,Umt A-9 P.O.Box 97 Edwards,Colorado 81632 Phone(970)926-3373 Fax(970)926-3390 ' � ' ' ' ' ' � PRELIMINARY DRAINAGE REPORT � FOR � I-70 SOUTH FRONTAGE ROAD RELOCATION � AT VAIL, COLORADO � � , NOVEMBER 24, 2008 ' ' ' , Prepared for: Vail Resorts Development Company P.O. Box 959 Avon, CO 81620 ' Prepared by: Alpine Engineering, Inc. P.O. Box 97 � Edwards, CO 81632 (970) 926-3373 ' ' ' ' I ' TABLE OF CONTENTS 1. Vicinity Map ' 2. Purpose.......................................................................................................................1 ' 3. Introduction................................................................................................................1 4. Hydrology..................................................................................................................2 , 5. Developed Conditions................................................................................................4 ' 6. Inlet Capacity ............................................................................................................4 7. Water Quality ............................................................................................................5 ' 8. Downstream Impact...................................................................................................5 ' 9. Floodplain..................................................................................................................6 10. Erosion and Sediment Control...................................................................................6 � 11. Tables: Table 1 —Off site Drainage Basin Summary � Table 2—SCS Soils Summary Table 3 —USFS Soils Summary Table 4—Pipe Capacity Summary ' 12. Figures: Figure 1 —U.S. Soil Conservation Service Soils Map ' Figure 2—U.S. Forest Service Soils Map 13. E�ibits: � E�ibit A -FEMA Floodplain Map Exhibit B - Water Quality Vault Details E�ibit C - Sediment Control Details � 14. Appendices: Appendix A—Off-site Drainage Area Calculations Appendix B—On-site Drainage Area Calculations � Appendix C—Hydraulic Calculations Appendix D—Inlet Calculations � 15. Maps: Sheet 1 —Off-Site Drainage Area Map 1"=2,000' Sheet 2—Historic On-site Drainage Area Map 1"=200' , Sheet 3 —Developed On-site Drainage Area Map 1"= 100' Sheet 4—Developed On-site Drainage Area Map 1"= 100' Sheet 5 —Developed Off-site Drainage Area Map 1"=400' � November 2008 Preliminary Drainage Report for South Frontage Road Relocation at Vail,CO i ' � I o � ' � ��� -�/ o �(/,��� ° � 42 � � � � � �,��� � °" �� �� ( 1 ��� � ,�� 0 .� � � \�� r�l �i � � , �1�\� a a � � � , � � � �, , I, � 0 ,� � � � ' ! d2 � � i P' p � � �.... ° � //�/� o � � ��-_ i o �� ��., �'�. i � , . . i I � � �r ' � , ��J : r � ; \� , � : I� , � _...r.. _ -- � , , _�_ i ! 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Q� _�- ►�, � � � � �, � �;, ��t_ �___ __ _ h ' � � o � \ \ � - l �� ---- �lq '�, ` , . . ,� I � � y \ , -- .- �,, ' ❑ _ _ , o � , � 1 i �— _ � � � � W � � 1,1 � 1�, � q x Q q � - �t��;\ ��',p _ , � O � � � '``\1- - -.-� — W � � � � � �� � ` ,� ;� �� ' _ __ _1;-T, I `` � � — ___ __� � ' I � W � � � �� W � `` � � � � ` - - — A � � ,.` ; ` �� � �� • �� � � �` ti`,_ ___�` '--_/ "�IH ' W � ati � [W� � � ` i� W�� �' g'� C., � � _ C�� � o �� W� � N° � � � �1��, w� w W ` '' � � � �,� '\ � � � i w � w `� � ����'�,� � � �� � q � �.�� � '� � co� � �' `i'�'° w�i � , � '• � . . . �d , � � 2. PURPOSE The purpose of this preliminary drainage report is to provide a preliminary , hydraulics report to accompany the FIR plan submittal to CDOT. 1 3. INTRODUCTION ' The Town of Vail and Vail Resorts are proposing to relocate the I-70 South � Frontage Road in the west part of Lionshead in Vail, Colorado. The area of relocation is adjacent and south of Interstate 70 from approximately Interstate 70 road station 125+00 � to 150+00 in the vicinity of mile post 175. The site is in the Northeast 1/4 of Section 12, ' Township 5 South, Range 81 West of the Sixth Principal Meridian, the Northwest 1/4 of I Section 7, Township 5 South, Range 80 West of the Sixth Principal Meridian and the �, � Southwest 1/4 of Section 6, Township 5 South, Range 80 West of the Sixth Principal I � Meridian in the Town of Vail, in Eagle County, Colorado. Red Sandstone Creek is the major drainage way that passes under the South ' Frontage Road. It flows from north to south and under Interstate 70 in an 84"diameter ' corrugated metal pipe (CMP). Red Sandstone Creek passes under the existing South Frontage Road in twin 14-foot concrete box culverts. Red Sandstone Creek flows to ' Gore Creek in an open channel. Both Red Sandstone Creek and Gore Creek have detailed FEMA floodplain studies. ' There are three separate 24"CMP culverts that carry Interstate 70 drainage and � drainage north of Interstate 70 to the area proposed for the South Frontage Road relocation. � � , November 2008 Preliminary Drainage Report for South Frontage Road Relocation at Vail,Colorado 1 � � � 4. HYDROLOGY Red Sandstone Creek and Gore Creek have FEMA floodplains and hydrology for , these streams is included in the Flood Insurance Study (FIS) for each stream. A culvert is proposed to carry Red Sandstone Creek under the relocated South Frontage Road and ', � � floodplain and culvert calculations for this concrete arch culvert are provided under , ' separate cover by others. � There are drainage basins of 19 acres, 31 acres and 164 acres north of Interstate 70 that outfall to the relocated South Frontage Road via culverts under Interstate 70. The ' hydrology for these drainage basins has been calculated using the U.S. Soil Conservation Service, Urban Hydrology for Small Watersheds, Technical Release Number 55, June � 1986, which is known as TR55. These drainage basins have been delineated on the Off- � site Drainage Area Maps and calculations may be found in Appendix A. Results have � been summarized in Table 1. TR55 was used to calculate Runoff Curve Number(RCN), the Time of , Concentration (Tc) and flow rates (Q). The 24-hour precipitation values were taken from , the NOAA Atlas 2,Volume III Isopluvials of 24-hour precipitation maps and were found to be 1.4, 1.8, 2.0, 2.4, 2.8 and 2.9 inches for the 2, 5, 10, 25, 50 and 100 year storms ' respectively. Flows were calculated using the actual soil types as obtained from the U.S. Soil Conservation Service Soil Survey of Aspen-Gypsum Area, Colorado, Parts of Eagle, ' Garfield and Pitkin Counties and the U.S. Forest Service, Hol Cross Area Soil Surve , Y Y � White River National Forest, Glenwood Springs, Colorado. A soils summary may be found in Tables 2 and 3. The appropriate hydrologic soil type was used for each area. � There are four hydrologic soil groups (A, B, C or D)that soils may be classified into as a � , November 2008 Preliminary Drainage Report for South Frontage Road Relocation at Vail,Colorado 2 � , , means of estimating runoff from precipitation. They are grouped according to their runoff—producing characteristics from long-duration storms. � Please refer to Figure 1 and Figure 2 for Soils Maps and Tables 2 and 3 for soil ' names and hydrologic soil groups. Group B soils have a moderate infiltration rate and consist mainly of moderately deep or deep, moderately well drained soils that have ! moderately fine texture to moderately course texture. Made Land(ML) is man-made � material, including buildings, pavement, fill, and other disturbed areas. It is mostly impervious. The soils group adjacent to the Made Land was assumed for the Made Land � since it probably consists of primarily native material. � The Developed On-site Drainage Area Map shows the proposed storm sewer II � system and the drainage areas to the proposed inlets. The flows for the smaller on-site � areas have been calculated using the Rational Method for the 10 and 100 year frequency � storms. Weighted runoffcoefficients were calculated using Table 3-1 from the Denver Urban Drainage and Flood Control District(UDFCD) Storm Drainage Criteria Manual ' for the types of cover found at the project. Table 3-1 is included in Appendix B. The , Rainfall Intensity-Duration Curve from the Town of Vail was used for a time of concentration of 5 minutes to obtain the intensity. A copy of the Rainfall Intensity- � Duration Curve is included in Appendix B. The calculated flows will be used to analyze the proposed inlets. ' The proposed pipe sizes were evaluated using the Hydraflow for Storm Sewers � 2008 computer program. Only the main trunk storm sewer lines were evaluated using the overall storm sewer flows. The lateral lines had small drainage areas and an 18"diameter � pipe was assumed to have adequate capacity. The combined 100 year flow for area OS2- � on, which includes basin OS2 and on-site basins 9-15 from the relocated South Frontage ' � November 2008 Preliminary Drainage Report for South Frontage Road Relocation at Vail,Colorado 3 1 ' � Road is 23.5 cfs. The combined flow for area OS4-on, which includes OS3 and OS4 and on-site basins 1-8 from the relocated South Frontage Road is 30.6 cfs. Known flows were ' input into Hydraflow at the upper end of the system or where a large contributing off-site � drainage basin entered the system. Drainage area OS 1 was calculated for the proposed storm sewer on the south side of the existing South Frontage Road but was not evaluated ' with Hydraflow. The flow from OS 1 is 23 cfs. Hydraulic Gradient calculations and � profiles generated by Hydraflow to evaluate pipe capacity may be found in Appendix C. � 5. DEVELOPED CONDITIONS � The project proposes to relocate the South Frontage Road to be adjacent and parallel to Interstate 70. Drainage from Interstate 70 will be captured by a proposed � storm sewer system in the relocated South Frontage Road. Historic drainage patterns will � be maintained in the developed project by generally directing drainage to Gore Creek or Red Sandstone Creek in its historic drainage directions. The existing box culverts in the ' South Frontage Road at Red Sandstone Creek will be removed and allow restoration of , Red Sandstone Creek in this area. A concrete arch culvert is proposed to span Red Sandstone Creek adjacent to Interstate 70 where the relocated South Frontage Road is ' proposed to cross Red Sandstone Creek. Sheet 3, Developed On-site Drainage Area Map, shows the preliminary storm sewer layout. ' � 6. INLET CAPACITY Inlet capacity has been evaluated for the proposed relocated South Frontage Road. � Flows to each proposed inlet were calculated in Appendix B, On-Site Drainage Area � Calculations using the Rational Method. The"Type R Curb Inlet Interception Rate on , November 2008 Preliminary Drainage Report for South Frontage Road Relocation at Vail,Colorado 4 � � � Continuous Grade"nomograph from the CDOT Drainage Design Manual was used to calculate the capacity of the on-grade inlets. HEG 12 was used to calculate the capacity � of the two sump inlets. Calculations and a summary of inlet capacity may be found in II Appendix D. I , � 7. WATER QUALITY � The relocated South Frontage Road is proposed to have water quality structures adjacent to the road that will treat pollutants from the relocated South Frontage Road. � One example of potential water quality vaults would be the Contech Vortechs products. � Details of these vaults may be found in Appendix A. � 8. DOWNSTREAM IMPACT DThe proposed South Frontage Road relocation moves existing South Frontage Road from its current location to be adjacent to the Interstate 70 right-of-way. Storm � sewer outfalls will be diverted into Red Sandstone or Gore Creek. A conceptual storm � sewer layout has been provided on Sheet 3 of the maps at the end of this report. The drainage basins for Red Sandstone and Gore Creek are quite large in comparison to the � proposed development site. The peak runoff from the development site is expected to be much earlier than the overall drainage basin and would not increase the peak runoff in the � overall drainage basin. Therefore, detention of stormwater is not recommended for this � site and no downstream impact as a result of stormwater flows from the proposed development is expected. � � � November 2008 Preliminary Drainage Report for South Frontage Road Relocation at Vail,Colorado 5 ' � � 9. FLOODPLAIN � There is a FEMA floodplain on both Gore Creek and Red Sandstone Creek. The � FEMA floodplain map is included in Exhibit A of this report. Modifications to the Red Sandstone Creek will include the relocated South Frontage Road crossing. The area � where Red Sandstone Creek passes under the existing South Frontage Road in box � culverts will also be revised since the box culverts will be removed. There are no floodplain impacts on Gore Creek expected as a result of the proposed development. � Floodplain modeling of modifications to Red Sandstone Creek will be submitted in a , separate report by others. � 10. EROSION AND SEDIMENT CONTROL � A sediment control plan will be prepared for the project to limit the transportation of sediments to Gore Creek and Red Sandstone Creek during construction. Devices that amay be used during construction to prevent sediment-laden runoff from leaving the site � include stabilized construction entrances, silt fence, straw bales, stone outlet structures, sediment traps and a removable pumping station. Details of these devices may be found �� in E�ibit C. � � � � � November 2008 Preliminary Drainage Report for South Frontage Road Relocation at Vail,Colorado 6 ' � ' ' 'I I ' ' � TABLES � � � � � � � � � � � � '