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Home My WebLink AboutDRB16-0339_Additional Subsurface Investigation_1471292100.pdfKoechlein Consulting Engineers, Inc. Consulting Geotechnical Engineers 12364 W. Alameda Pkwy • Suite 115 • Lakewood, CO 80228-2845 www.KCE-Denver.com LAKEWOOD (303) 989-1223 (303) 989-0204 FAX AVON/SILVERTHORNE (970) 949-6009 (970) 949-9223 FAX August 23, 2007 Greg Gastineau Timberline Commercial Real Estate 12 Vail Road, Suite 600 Vail, Colorado 81657 Subject: Subsurface Investigation Proposed Residence Inn and Timberline Lodge Condominium 1783 North Frontage Road Vail, Colorado Job No. 07-101 As requested an engineer from our office was on site to observe the drilling of two exploratory borings to better define the subsurface conditions below the proposed Residence Inn and Timberline Lodge Condominium, in Vail Colorado. The purpose of this letter is to present a summary of the subsurface conditions encountered in the borings and additional recommendations for the proposed construction. Two exploratory borings were drilled using down hole hammer techniques with a tracked drill rig at the locations shown on the Locations of Exploratory Borings, Fig. 1. Subsurface conditions encountered in exploratory borings were generally similar. The subsurface conditions encountered in exploratory borings TH-1A and TH-2A consisted of approximately 2.0 to 5.0 inches of topsoil overlying a red, brown, dry to very moist, very loose, gravelly, sandy silt to varying depths of 2.0 to 4.0 feet. Below the sandy silt, the subsurface conditions consisted of a red, brown, white, dry to wet, medium dense to very dense, cobbly, silty, gravelly, sand with scattered boulders to varying depths of 23.0 to 47.0 feet. Underlying the gravelly sand to the maximum depth explored of 62.0 feet in boring TH-1A and 42.0 feet in boring TH-2A, the subsurface conditions consisted of a gray to black, dry, hard to very hard, siltstone/shale bedrock. Ground water was encountered at a depth of 53.0 feet in exploratory boring TH-1A. No free ground water was encountered in exploratory boring TH-2A to the maximum depth explored of 42.0 feet at the time of drilling. Detailed logs of exploratory borings are shown in the Boring Logs, Figs. 2 thru 5. Based on the most recent architectural plans provided by Lightowler Johnson Associates, we anticipate that the proposed Residence Inn and Timberline Lodge Condominium will be constructed with two levels of below grade parking under a portion of the structure. Based on Greg Gastineau KOECHLEIN CONSULTING ENGINEERS, INC. August 23, 2007 Consulting Geotechnical Engineers Job No. 07-101 Page 2 of 2 the provided plans, we anticipate that excavations between 15 to 55 feet will be required for the proposed construction. We anticipate that the subsurface conditions at the foundation elevation will consist of either the cobbly, silty, gravelly, sand with scattered boulders or the siltstone/shale bedrock. Foundations constructed at an elevation of 7974 or deeper may be supported by the siltstone/shale bedrock. Foundations constructed at an elevation of 7996 may be supported by the cobbly, silty, gravelly, sand with scattered boulders. Since the foundation system for the proposed structure will be supported by two different kinds of bearing material, we anticipate that the risk of differential movement is high. The bedrock was also very hard and we anticipate that it will require blasting for excavation. Due to the increased risk of differential movement and the presence of very hard bedrock, we recommend that the owner explore alternative subsurface investigation options to determine the depth of bedrock within the proposed construction footprint. We recommend that a geophysical investigation be conducted to better define the depth to bedrock beneath the site. We anticipate that an investigation to determine the in-situ shear-wave velocities of overburden soils and the bedrock through Refraction Microtremor – ReMi testing could help determine rock depth and density. Shear wave testing could be provided by Zonge Geosciences, Inc. under subcontract to Koechlein Consulting Engineers, Inc. We appreciate the opportunity to provide this service. If we can be of further assistance, please contact our office. KOECHLEIN CONSULTING ENGINEERS, INC. Jessica E. Street, E.I. Staff Engineer Reviewed by: Scott B. Myers, P.E. Senior Engineer (3 copies sent) 8030 8025 8020 8015 8010 8005 8000 7995 2 8 5 5 5 8 6 25 43 25 10 10 30 18 0.0 0.3 2.0 TOPSOIL SILT, Sandy, Gravelly, Dry, Loose to medium dense, Brown, Red-brown. SAND, Silty, Gravelly, Scattered boulders and cobbles, Dry to moist, Medium dense to very dense, Brown, Red- brown. Cobbles and boulders to a depth of 8.5 feet. Encountered 1 foot diameter boulder. SAND, Silty, Small gravels, Moist to very moist, Loose to medium dense, Brown, Red-brown.Easier drilling to 13.5 feet, finer grained material. Very little gravel to 17.5 feet. Increased gravel content to 32.0 feet. Boulder from 32.0 to 33.5 feet. TH-1A BORING LOGS PROJECT:Timberline Lodge JOB NO.:07-101 DRILL DATE:July 27, 2007 ELEVATION:8030 JOB NO.07-101 FIG.2ELEVATION(feet)BULK SAMPLESMOISTURECONTENT (%)PERCENT PASSINGNO. 200 SIEVE(%)PROPOSED SLAB-ON-GRADE(feet)DEPTH TO WATER(feet)DEPTH(feet)GRAPHICLOGSOIL DESCRIPTION 7990 7985 7980 7975 7970 7965 7960 8 15 43 69 47.0 53.0 56.0 62.0 Boulder from 37.0 to 38.0 feet. SILTSTONE/SHALE, Slightly moist to moist, Hard to very hard, Tan, Black, Gray. Depth of ground water encountered while drilling. Depth of lowest proposed floor slab. Bottom of Hole. TH-1A BORING LOGS PROJECT:Timberline Lodge JOB NO.:07-101 DRILL DATE:July 27, 2007 ELEVATION:8030 JOB NO.07-101 FIG.3ELEVATION(feet)BULK SAMPLESMOISTURECONTENT (%)PERCENT PASSINGNO. 200 SIEVE(%)PROPOSED SLAB-ON-GRADE(feet)DEPTH TO WATER(feet)DEPTH(feet)GRAPHICLOGSOIL DESCRIPTION 8005 8000 7995 7990 7985 7980 7975 15 24 0.0 0.5 3.0 23.0 35.0 TOPSOIL SILT, Sandy, Gravelly, Slightly moist, Loose to medium dense, Brown, Red-brown. SAND, Silty, Gravelly, Scattered boulders and cobbles, Slightly moist to moist, Medium dense to dense, Brown, Red-brown. Encountered 1 foot diameter boulder to 13.0 feet. SILTSTONE/SHALE, Dry to moist, Hard to very hard, Black, Brown, Gray. Depth of lowest proposed floor slab. TH-2A BORING LOGS PROJECT:Timberline Lodge JOB NO.:07-101 DRILL DATE:July 27, 2007 ELEVATION:8009 JOB NO.07-101 FIG.4ELEVATION(feet)BULK SAMPLESMOISTURECONTENT (%)PERCENT PASSINGNO. 200 SIEVE(%)PROPOSED SLAB-ON-GRADE(feet)DEPTH TO WATER(feet)DEPTH(feet)GRAPHICLOGSOIL DESCRIPTION 7970 7965 7960 7955 7950 7945 7940 42.0 Bottom of Hole. TH-2A BORING LOGS PROJECT:Timberline Lodge JOB NO.:07-101 DRILL DATE:July 27, 2007 ELEVATION:8009 JOB NO.07-101 FIG.5ELEVATION(feet)BULK SAMPLESMOISTURECONTENT (%)PERCENT PASSINGNO. 200 SIEVE(%)PROPOSED SLAB-ON-GRADE(feet)DEPTH TO WATER(feet)DEPTH(feet)GRAPHICLOGSOIL DESCRIPTION