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HomeMy WebLinkAboutDRB16-0339_Bedrock Evaluation Letter_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 October 4, 2007 Greg Gastineau Timberline Commercial Real Estate 12 Vail Road, Suite 600 Vail, Colorado 81657 Subject:Geophysical Investigation Proposed Residence Inn and Timberline Lodge Condominium 1783 North Frontage Road Vail, Colorado Job No. 07-101 As requested a geophysical survey was conducted to reevaluate the depth to bedrock and its engineering characteristics underneath the construction footprint for the proposed Residence Inn and Timberline Lodge Condominium in Vail Colorado. In addition we reviewed our geotechnical report titled Geotechnical Investigation, Proposed Hotel and Condominium Building, Lots 9, 10, 11, and 12, 1783 North Frontage Road, Vail, Colorado, dated July 14, 2005, Job No. 05-112 and the Subsurface Investigation Addendum Letter dated August 23, 2007, Job No. 07-101. The purpose of this letter is to present the findings of the geophysical investigation and to revise any recommendations for the proposed construction. The geophysical investigation and analysis was provided by Zonge Geosciences, Inc. under subcontract to Koechlein Consulting Engineers, Inc. This investigation was performed by collecting information from ten refraction lines situated across the site to obtain representative data for the subject site. Refraction lines L-1 thru L-5 were oriented approximately north to south, while lines L-6 thru L-10 were oriented approximately east to west. The locations of the refraction lines in relation to the proposed building envelope are shown on The Locations of Refraction Lines, Fig. 1. Due to the close proximity of the subject site to Interstate I-70, which creates noise during the data collection process, and the site topography, it was decided that a combined seismic survey approach would be better suited for the collection of data. The site was analyzed using two-dimensional (2D) refraction tomography and one-dimensional (1D) refraction microtremor (ReMi) testing. Greg Gastineau KOECHLEIN CONSULTING ENGINEERS, INC. October 4, 2007 Consulting Geotechnical Engineers Job No. 07-101 Page 2 of 4 The 2D refraction tomography analysis was conducted to determine variations in the engineering characteristics of the overburden soils, weathered bedrock, and competent bedrock through the analysis of compressional-wave velocity vs. travel time. By analyzing the variations in velocity waves in the different types of subsurface soils and bedrock, a depth to bedrock can be determined. Based on the geophysical data there were variations across the line with high and low spots. The following tables show variations along the refraction survey lines for the elevation of the contact of the overburden soils and the weathered bedrock surface. Tomography Lines1 Elevation of Bedrock (North End) 2 Elevation of Bedrock (South End) 2 Shallowest Elevation of Bedrock3 L1 7974 7942 7974 L2 7965 7940 7980 L3 7968 7944 7980 L4 7973 7952 7988 L5 7974 7950 7978 L6 7975 7956 7980 L7 7980 7980 7988 L8 8008 7995 8008 L9 7972 7974 7976 L10 7960 7966 7976 Notes: 1. Tomography lines L1-L5 are oriented approximately north to south and lines L6-L10 are oriented approximately east to west. 2. Elevation of bedrock based on a 2D refraction data to surface of weathered bedrock. Refer to Appendix A, Figures 3 thru 14 for specific depths of bedrock along the survey line. 3. Indicates shallowest elevation of bedrock encountered along the tomography line. In addition, as recommended in the previously mentioned report, a geophysical investigation was conducted to determine the in-situ shear-wave velocities of overburden soils and the bedrock through Refraction Microtremor – ReMi testing. The initial geotechnical investigation gave the subject site a seismic site classification of Site Class D. Based on the results of the Refraction Microtremor – ReMi testing, the subject site was reevaluated and has a seismic site classification of Site Class C. The following table shows the average shear wave velocity for each line and the shear wave velocity at the foundation elevation across each survey line. Greg Gastineau KOECHLEIN CONSULTING ENGINEERS, INC. October 4, 2007 Consulting Geotechnical Engineers Job No. 07-101 Page 3 of 4 ReMi Line Data Shear Wave Velocity at Foundation Elevation1 (ft/sec) Anticipated Bedrock at Foundation Elevation2 Ripable3 Line 1 1,299 No NA Line 2 2,354 No NA Line 3 2,228 Yes Yes Line 4 2,420 Yes Yes Line 5 3,263 Yes Yes Line 6 2,691 Yes Yes Line 7 2,761 No NA Line 8 1,638 Yes Yes Line 9 2,857 Yes Yes Line 10 2,420 No NA Notes: 1. Refer to Appendix A, Table 1 thru Table 10 for results of the shear wave velocity test vs. depth. 2. We anticipate that bedrock will be encountered at some portion along the line, if not the entire length along the line. Refer to the Preliminary Bedrock Contour Map, Fig. 2 for anticipated bedrock elevations. 3. Ripper performance in relation to seismic wave velocities was analyzed for use with Multi or Single Shank D9R, D10R, D11R, or Single Shank D11R CD Caterpillar Rippers or an approved equivalent. 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 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. Based on the ReMi survey the bedrock encountered at this site will be ripable. The Geophysical survey also shows a highly variable topography with peaks and depressions filled with overburden soils. Preliminary bedrock contours have been evaluated from the geophysical survey and have been shown on the Preliminary Bedrock Contour Map Fig. 2. Please note that variations in the topography are likely and could result in differences in the encountered bedrock. The subsurface material at the potential foundation elevation for the proposed structure will consist of natural sand and gravel with cobbles and boulders or the siltstone/shale bedrock. Since the foundation system for the proposed structure will be supported by two bearing materials with very different support characteristics, we anticipate that the risk of differential movement is high. In order to reduce the risk of differential movement we recommend that different bearing capacities should be given to the soils and the bedrock. We recommend that the spread footing foundation system bearing on the sands and gravels with cobbles and boulders should be designed for a maximum allowable soil bearing pressure of 6,000 psf. Footings bearing on the siltstone/shale bedrock should be designed for a maximum allowable soil bearing Greg Gastineau KOECHLEIN CONSULTING ENGINEERS, INC. October 4, 2007 Consulting Geotechnical Engineers Job No. 07-101 Page 4 of 4 pressure of 20,000 psf. Because the soils are granular in nature, we anticipate that the majority of the differential settlement will occur during construction. A representative of our office should observe each footing foundation excavation to verify that the foundation is supported by the soils or bedrock in accordance with the structural design. All other foundation recommendations should be followed in accordance with the previously mentioned report. 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: William H. Koechlein President (3 copies sent) TH-5TH-4TH-3TH-7N O R T H F R O N T A G E R O A D M E A D O W R ID G E R O A D TH-1ATH-1TH-6TH-1LEGENDLOCATION OF EXPLORATORY BORING, 2007 INVESTIGATION, JOB NO. 07-101LOCATION OF EXPLORATORY BORING, 2005 INVESTIGATION, JOB NO. 05-112TH-1ATH-2AL1L2L3L4L5L6L7L8L9L10(el. 7942)(el. 7974)(el. 7940)(el. 7965)TH-2(el. 7968)(el. 7944)(el. 7973)(el. 7952)(el. 7974)(el. 7972)(el. 7966)(el. 7960)(el. 7956)(el. 7950)(el. 7974)(el. 7975)(el. 7980)(el. 7980)(el. 8008)(el. 7995)PROPOSED BUILDING ENVELOPEREFRACTION SURVEY LINESNOTESELEVATIONS BASED ON GEOPHYSICAL INVESTIGATION REPORT, ISSUED BY ZONGE GEOSCIENCES, INC. DATED OCTOBER 1 , 2007.FIG. 1LOCATIONS OF REFRACTION LINESJOB NO. 07-101KOECHLEIN CONSULTING ENGINEERS, INC.Consulting Geotechnical Engineers1" = 50' TH-7N O R T H F R O N T A G E R O A D M E A D O W R ID G E R O A D TH-1ATH-1TH-1LEGENDLOCATION OF EXPLORATORY BORING, 2007 INVESTIGATION, JOB NO. 07-101LOCATION OF EXPLORATORY BORING, 2005 INVESTIGATION, JOB NO. 05-1127 9 7 0 7 9 6 0 7 9 8 0 *PRELIMINARY BEDROCK CONTOUR MAP, VARIATIONS COULD OCCUR7 9 4 0 7 9 5 0 7 9 6 0 7 9 8 0 7 9 7 0 7 9 6 0 7 9 7 0 7 9 8 0TH-2TH-5TH-4TH-3TH-6TH-1ATH-2A7 9 9 0 8 0 0 0 PROPOSED BUILDING ENVELOPEFIG. 2PRELIMINARY BEDROCK CONTOUR MAPJOB NO. 07-101KOECHLEIN CONSULTING ENGINEERS, INC.Consulting Geotechnical Engineers1" = 50' KOECHLEIN CONSULTING ENGINEERS, INC. Consulting Geotechnical Engineers APPENDIX A GEOPHYSICAL INVESTIGATION 07156 Koechlein 1 Report 1990 S. Garrison Street, Suite #2 Lakewood, CO 80227 Phone: (720) 962-4444 Fax: 720-962-0417 zongecolo@zonge.com October 1st, 2007 Bill Koechlein Koechlein Consulting Engineers, Inc. 12364 W. Alameda Pkwy, Suite 115 Lakewood, CO 80228 Subject: Geophysical Investigations Report – Proposed Residence Inn and Timberline Lodge Condominiums Project, Vail, Colorado. Dear Mr. Koechlein, This letter report presents results from the geophysical investigation conducted at the Proposed Residence Inn and Timberline Lodge Condominiums Project site. The investigation was located in the town of Vail, Colorado, north of the North Frontage Road and I-70 as shown on Figures 1 and 2. Zonge Geosciences, Inc. (Zonge) performed the geophysical investigation under subcontract to Koechlein Consulting Engineers, Inc. (Koechlein). Field data were acquired on September 13th and 14th, 2007. The objectives of the geophysical investigation are twofold: 1) to map the top-of-bedrock and determine thickness and lateral variability of unconsolidated soil deposits; and, 2) to obtain seismic velocities within the bedrock, if encountered, that may correlate with the mechanical strength and rippability of such materials to aid in the excavation planning for this project site. Based on the geologic setting and the site conditions outlined by Koechlein, Zonge determined a combined seismic survey approach using two-dimensional (2D) refraction tomography and one- dimensional (1D) refraction microtremor (ReMi) soundings would best achieve the project objectives. This report summarizes data acquisition parameters and field methods for the investigation, and also includes brief sections on data processing (1D and 2D), and results/interpretations. SITE DESCRIPTION The area of investigation is located just west of Vail, Colorado, and just north of I-70 (see Figure 1). The seismic lines were placed around the existing buildings at the Roost Lodge, on pavement and in dirt. I-70 and a frontage road where located to the south (see Figure 2). Holes were drilled in the pavement using an impact hammer drill for the placement of each geophone. This area had extremely heavy traffic, including heavy cargo trucks on the highway and frontage road that caused a significant amount of vibrational noise. Zonge Geosciences, Inc. 07156 Koechlein 2 Report Figure 1 – Proposed Residence Inn and Timberline Lodge Condominiums Project location map (indicated by red box). 07156 Koechlein 3 Report Figure 2 – Proposed Residence Inn and Timberline Lodge Condominiums Project site map (seismic line locations indicated with red lines). 07156 Koechlein 4 Report DATA ACQUISITION Seismic refraction and ReMi data were acquired at the project site using a DAQ LinkII seismograph. This system utilizes a state of the art, 24-bit seismograph connected to a field laptop via ethernet cable. Analog data from the geophones are collected in the DAQ seismograph where it is anti-alias filtered, converted to a digital signal, transmitted to the laptop computer and then recorded on the hard drive. DAQ modules have a 24-channel capacity, and one module was needed for this seismic investigation. Twenty-four receivers (geophones) were placed on the ground along each spread. The receivers were Mark Products, 4.5-Hz vertical component geophones, and the same setup was used for both refraction and ReMi data collection. Refraction: A total of ten refraction lines were acquired for this investigation. Approximate line locations and orientations are shown in Figure 2, where each line had channel 1 on the west or south end of the spread. Thus the tomograms are viewed as if the reader is “looking north” or “looking west.” Geophone spacing along each lines 1, 2, 3, 4, 5 and 7 was 5 feet and lines 6, 8, 9 and 10 had 10 foot geophone spacing. Compressional-wave (P-wave) seismic energy was created with a source that consisted of an elastic wave generator (EWG). The EWG used for this project is a truck mounted, hydraulically controlled, 100 pound weight that is lifted and then accelerated onto a metal plate using a large rubber strap to maximize acceleration and the resultant amount of energy imparted into the ground. A 16-pound sledgehammer striking an aluminum plate was also used in shot locations that didn’t require additional energy or couldn’t be safely accessed with the EWG. Up to a maximum of 20 EWG or hammer blows were used to transmit seismic energy across the line of 24 geophones with the maximum number being required for the 2 off- end shot points or during exceptionally noisy periods of the day. Source points were located as shown on the inset illustration; ‘off-end’ shot points were located between 40 and 100 feet beyond each end of each line. This offset was dictated by special limitations including buildings, roads and other obstructions. Refraction shot records were acquired in SEG-2 format, using a 0.25 millisecond (msec) sample rate and 500 msec (½ second) record length. ReMi: The refraction microtremor (ReMi) method uses the same instrumentation and field layout as the refraction survey. However, there are no predefined source points required for this seismic method. The ReMi method uses ambient noise, or vibrational energy, that exists at a site. The existing natural vibrations were enhanced by Zonge personnel with the use of the EWG system, 230 ft TB-1 07156 Koechlein 5 Report random sledge hammer blows, driving a vehicle along the seismic line and walking up and down each line. These small-strain vibrations cause surface wave energy to propagate across the site and be recorded for the ReMi method. At least ten, unfiltered, 30-second ambient vibrational energy records (‘noise’ records) were recorded for each line using a 2 msec sample rate. DATA PROCESSSING Refraction: Refraction tomography is a modern extension of the seismic refraction method, and has been used to study the interior of the earth from scales of miles to tens of feet. The method was introduced in the 1980’s, and uses a similar mathematical approach as the CAT scans (computed automated tomography) used for medical imaging. Tomography is the process of reconstructing spatial variations of a physical property (in this case compressional-wave velocity) from spatially distributed measurements that depend on that property (travel time). It follows that tomographic surveys require the measurement of travel times from large numbers of paths, or “ray-paths” through the media being imaged; in this case, soil and rock materials below the refraction spreads. For this project the tomographic inversions were performed using a simulated annealing algorithm. Due to the noisy nature of this site, and the resulting noise in the data collected on these two lines, a low-pass filter was utilized to remove noise and better identify the first arrivals of refracted energy along each shot record. First-break picks were then made on all of the shot records acquired along each line. Travel times, along with source and receiver positions and elevations were formatted into files and input to the tomography software. Tomographic analysis was carried out using SeisOpt@2D™ (© Optim, Inc., 2006), a commercially available refraction tomography package produced by Optim, LLC (Version 4.0). A two-dimensional cross-section with velocity information at each subsurface point is produced. P-wave velocities can be correlated to the material type. Simulated annealing is a Monte-Carlo estimation process that derives arrival times (P- and/or S- wave) and a velocity model from the data (Pullammanappallil and Louie, 1993; Pullammanappallil and Louie, 1994). The algorithm works by randomly perturbing an arbitrary starting model until the synthetic travel times computed through it match the travel times picked from the data. Unlike linear, iterative inversions, simulated annealing optimization will find the global solution while avoiding local error minimums. The method is insensitive to the starting velocity model, removing the interpreter bias that may be involved in a prospect or project. The fact that SeisOpt@2D makes no assumption about subsurface velocity gradients makes the method ideal for imaging laterally complex subsurface geology. Refraction tomography allows reconstruction of both vertical and lateral velocity variations. The ray-path coverage for all rays traveling through the model is analyzed to determine coverage. A ray is a region in the model that has the highest contribution to the first arrival time. In this survey, the rays probed 20 to 80 feet below the ground surface. The depth of investigation for any refraction survey is dependent on the receiver line length, and the velocity distribution of the subsurface materials, and the offset shot distance. 07156 Koechlein 6 Report ReMi: The ReMi method calculates the shear-wave velocity (Vs) of layers and the respective depths to interfaces beneath the refraction line as described by Louie (2001). The ReMi method is primarily used to calculate shear velocity versus depth at a point (1D) to satisfy building code requirements (International Building Code – IBC). The analysis computes the average shear- wave velocity to a depth of 100-feet (30 m) as described in Section 1615.1.1 of IBC 2000; that is the “Vs100”. ReMi data were collected for both refraction lines at this site. The ‘noise’ records collected at this site were processed using the SeisOpt® ReMi™ software (© Optim LLC, 2005) (Louie, 2001). The ReMi technique is based on two fundamental concepts. The first is that common seismic-refraction recording equipment can effectively record surface waves at frequencies as low as 2 Hz. The second idea is that a simple, two-dimensional slowness-frequency (p-f) transform of a microtremor record can separate Rayleigh surface waves from other seismic arrivals. This separation allows recognition of the true phase velocity and discriminates against energy propagating in other modes without dispersion. The advantages of ReMi from a seismic surveying point of view are several, including the following: It requires only standard refraction equipment; it requires no triggered source of wave energy; and, it will work best in seismically noisy urban settings. Traffic, construction, and wind responses of trees, buildings, and utility standards provide the surface wave energy (“source”) for the recordings. There are three processing steps to derive the Vs profiles: Step 1: Create a velocity spectrum (p-f image) from the noise data. The distinctive slope of dispersive waves is an advantage of the p-f analysis; body waves and airwaves cannot have such a slope. Even if most of the energy in a seismic record is a phase other than Rayleigh waves, the p-f analysis will identify the dispersion of the surface waves. Step 2: Rayleigh-wave dispersion picking - Picking is done along a lowest p-f envelope bounding the dispersed energy appearing on the p-f image. The picks thus discriminate against higher apparent velocities present because ‘noise’ impacts the linear array from all directions. Picking a surface-wave dispersion curve along an envelope of the lowest phase velocities at each frequency has a further desirable effect. Because higher-mode Rayleigh waves have phase velocities above those of the fundamental mode, the refraction microtremor technique preferentially yields the fundamental-mode velocities. Step 3: Shear wave velocity modeling - The ReMi method interactively forward-models the normal-mode dispersion data picked from the p-f images with a code adapted from Saito (1979, 1988) by Yuehua Zeng(1992). This code produces results identical to those of the forward- modeling codes used by Iwata et al. (1998), and by Xia et al. (1999) within their inversion procedure. The modeling iterates on phase velocity at each period (frequency), reports when a solution has not been found within the iteration parameters. The analysis approach and the propagation properties of surface waves allow velocity reversals (low Vs layers at depth) to be modeled successfully. 07156 Koechlein 7 Report RESULTS / INTERPRETATIONS Geologic and geotechnical borehole information was provided by Koechlein for the area investigated using geophysics. Correlation can be made between geology and seismic velocities calculated and presented here. Interpretations of the data are made based on the 2D velocity distributions and gradients obtained by the tomographic inversions, the 1D trends in shear wave velocities with depth obtained by the ReMi inversions and geologic borehole data. Borehole logs indicate a thin layer of fill materials overlaying undisturbed soils and colluvium. The overburden soils are most likely fairly uniform, with the possibility of small to large boulders within the overburden due to typical erosion processes that occur in this type of alpine valley setting. The unconsolidated materials presumably consist of a mix of silts, quartz and feldspathic sands and/or gravely sands and larger clasts or boulders of similar composition deposited from the erosion of adjacent mountain slopes. Refraction: The 2D refraction results for lines 1 through10 are presented as seismic sections (i.e., distance vs. elevation and velocity distribution) from the tomography analysis on Figures 3 through 12. Elevations were recorded using a hand-level and stadia rod, and were corrected to approximate absolute elevation based on site maps and borehole logs. Velocity scales are the same for all lines, and elevation and distance scales may vary slightly due to varying geophone spacing and depths of investigation. Interpreted depth to weathered bedrock and depth to competent bedrock are indicated on the tomograms with dashed and dotted lines respectively. Approximate locations and elevations of refusal and bedrock encountered during drilling are also annotated on the tomograms. For actual depth to geologic interfaces, Koechlein boring logs should be consulted. Elevation of bedrock, as interpreted by the refraction tomography, is based on a velocity threshold of about 5,000 ft/s (i.e., mid-green color). 5,000 ft/s is a reasonable value for fractured and weathered sedimentary rocks. The potential for low densities and weathering at the soil/bedrock interface can be seen in the 2D sections as the variable section of greens and light blues above the faster velocity regions indicated by yellow and red. Interpretation of the P-wave refraction velocity sections obtained indicates three velocity layers: low-velocity materials interpreted as unsaturated and/or saturated, unconsolidated soils, colluvium and fill (i.e., 1,000-5,000 ft/s), generally shaded in blue or “cool” colors; moderate- velocity materials (i.e.,5,000-6,500 ft/sec) interpreted as weathered and/or fractured rock shaded in green to light yellow; and, relatively high-velocity materials interpreted as competent bedrock (>6,500 ft/s) shaded yellow and red or “hot” colors. Tomographic results were gridded, and the interpreted depth to weathered bedrock line (dashed line) is a digitized pick of the 5,000 ft/s contour. The 2D seismic profiles generally indicate a sharp boundary between the interpreted overburden and bedrock. In addition to standard 2D results presented from refraction tomograms, the approximate and general trend in the interpreted top-of-weathered-bedrock from the tomography solutions is presented in the form of a 3D surface plot seen in Figures 13 and 14. These images were created using the digitized picks of ~5,000 ft/s from each seismic line’s tomogram. Trigonometric calculations were made, utilizing hand-held GPS coordinates of line-ends, to assign an X (easting) and Y (northing) coordinate for each of the 5,000 ft/s picks along each line. These picks were then gridded using the Kriging approach (a robust 3D gridding algorithm similar to 07156 Koechlein 8 Report the minimum-curvature approach), and were then plotted to create a 3D surface. This surface represents the approximate top of 5,000 ft/s and offers the general trend of this P-wave velocity distribution. The color scale represents approximate absolute elevation. Figure 13 presents this velocity contour map from a skewed perspective to show the geometry of the surface, and Figure 14 shows this surface plot in map view with the approximate line locations annotated as they are in Figure 2. The red line on Figures 13 and 14 is an elevation contour plotted on the surface at an elevation equal to that of the proposed floor slab (7974 feet). This indicates areas where the interpreted top-of-weathered-bedrock is above the proposed floor slab elevation, and these may be areas where rock is encountered during excavation. It is important to understand that this surface plot does not necessarily represent the true surface of bedrock, and that the areas between lines may have shallow bedrock that hasn’t been detected by the refraction survey or plotted due to seismic line locations. Some of the tomograms show vertical bands of ~3,000-4,000 ft/s (light blue-green) surrounded by lower velocity regions (darker blue). These vertical bands are a result of concentrated ray- path coverage calculated during the inversion process, and they suggest the presence of a sharp transition in P-wave velocity with depth (slow soils over fast rock). This can be seen on many of the tomograms, where the interpreted top-of-weathered-rock (dashed line) is just above the interpreted top-of-competent-rock (dotted line). There are some discrete areas of faster velocities (~4,000 ft/s) distributed at relatively shallow depths as seen on the tomograms. These could be a result of variable soil compaction, the presence of excessive cobbles and boulders or saturated soils that have increased the average propagation velocity of P-waves within these zones. Several inversions were performed on the data to ensure that the results presented here are the best fit models for each Line. REMI: ReMi soundings (i.e., 1D S-wave velocity values versus depth) were computed beneath each of the 10 seismic lines, and the models are assigned to the center of each line. The 1D sounding data are derived by averaging the ambient noise across the 24 channel receiver array and represent the bulk properties of the soil and/or rock beneath the ‘entire’ array. ReMi calculations are based on determining the lower-bound for the surface wave dispersion which provides a conservative (i.e., lowest possible) shear-wave velocity for each layer modeled in the 1D result. The resultant ReMi models are presented on Figures 15 through 24 and in Tables 1 through 10. Calculated Vs100 values are annotated on these Figures and included in the tables. The average Vs100 value for the 10 lines is =1563.9 ft/s. The ReMi results indicate a sequence of overburden deposits with S-wave velocity ranging between about 200 and 2,000 ft/sec. These observed S- wave velocities are in a reasonable range for unconsolidated colluvial deposits. The two models generally indicate an increase in S-wave velocity with depth, but there are velocity inversions in some of the models, where low-velocity layers are modeled. Trends in the S-wave velocities, that are interpreted to indicate bedrock, are seen as the sudden increases in velocity at depth for the ReMi models. This is generally interpreted to indicate the interface between weathered and competent bedrock. These trends in S-wave velocity models generally match the relevant P- wave tomograms fairly well, but some of the ReMi models appear to indicate the depth to competent rock rather than the top-of-weathered-rock when compared to the P-wave refraction tomograms. These discrepancies are most likely due to the orientation of the lines with respect to the highway which was the primary source of surface waves at the project site. Note that the 07156 Koechlein 9 Report velocities and layer thicknesses derived by the ReMi method are averaged over the 230-foot seismic line, and the P-wave tomograms are believed to represent the distribution of velocities and interpreted geologic interfaces more accurately. Four observations provide confidence in the geophysical results: 1) There is good correlation between refraction tomography (P-wave) and ReMi (S-wave) seismic results and borehole data provided by Koechlein; 2) Multiple tomographic inversions were performed and yielded repeatable results and consistent trends in velocity distributions that support the provided interpretation; 3) The trends in interpreted top-of-weathered-bedrock are similar between adjacent lines, and the 3D surface plot of this interpreted interface has a strong downward trend dipping to the south (as expected); 4) The seismic data quality ranged from fair to good, and was improved by the use of selective filtering in the frequency domain. If you have any questions regarding the field procedures, seismic analysis techniques, or the 2D refraction tomography or 1D ReMi results and interpretations presented herein, please do not hesitate to contact us. We appreciate working with you and look forward to providing you with geophysical services in the future. Respectfully Submitted, Justin Rittgers Phil Sirles Geophysicist Managing Geophysicist Zonge Geosciences, Inc. Zonge Geosciences, Inc. 07156 Koechlein 10 Report Table 1 - Line 1 ReMi Data Depth, ft Vs, ft/s 0.0 418.6 -4.8 418.6 -4.8 963.9 -20.8 963.9 -20.8 1299.1 -72.1 1299.1 -72.1 2893.1 -91.9 2893.1 -91.9 3481.7 -100.0 3481.7 Line 1 Vs100' = 1,303 ft/sec Table 2 - Line 2 ReMi Data Depth, ft Vs, ft/s 0.0 217.0 -1.9 217.0 -1.9 819.0 -5.0 819.0 -5.0 1096.9 -42.8 1096.9 -42.8 1348.3 -52.2 1348.3 -52.2 2353.9 -100.0 2353.9 Line 2 Vs100' = 1,347 ft/sec 07156 Koechlein 11 Report Table 3 - Line 3 ReMi Data Depth, ft Vs, ft/s 0.0 217.0 -1.9 217.0 -1.9 852.1 -5.3 852.1 -5.3 1110.1 -13.3 1110.1 -13.3 1130.0 -47.8 1130.0 -47.8 1348.3 -53.5 1348.3 -53.5 2228.2 -100.0 2228.2 Line 3 Vs100' = 1,325 ft/sec Table 4 - Line 4 ReMi Data Depth, ft Vs, ft/s 0.0 706.6 -1.7 706.6 -1.7 786.0 -6.4 786.0 -6.4 1262.3 -7.9 1262.3 -7.9 620.6 -10.2 620.6 -10.2 1208.4 -13.4 1208.4 -13.4 1295.4 -48.0 1295.4 -48.0 2420.1 -95.8 2420.1 -95.8 2506.1 -100.0 2506.1 Line 4 Vs100' = 1,560 ft/sec 07156 Koechlein 12 Report Table 5 - Line 5 ReMi Data Depth, ft Vs, ft/s 0.0 1023.7 -1.4 1023.7 -1.4 904.0 -9.6 904.0 -9.6 1596.1 -11.6 1596.1 -11.6 463.7 -14.0 463.7 -14.0 2447.7 -26.5 2447.7 -26.5 1718.6 -37.9 1718.6 -37.9 1493.9 -49.3 1493.9 -49.3 3262.5 -100.0 3262.5 Line 5 Vs100' = 1,932 ft/sec Table 6 - Line 6 ReMi Data Depth, ft Vs, ft/s 0.0 289.8 -1.7 289.8 -1.7 408.8 -8.0 408.8 -8.0 1077.1 -11.8 1077.1 -11.8 779.3 -16.7 779.3 -16.7 1057.2 -37.4 1057.2 -37.4 825.7 -61.0 825.7 -61.0 2691.4 -68.3 2691.4 -68.3 2962.6 -100.0 2962.6 Line 6 Vs100' = 1,080 ft/sec 07156 Koechlein 13 Report Table 7 - Line 7 ReMi Data Depth, ft Vs, ft/s 0.0 1116.8 -4.5 1116.8 -4.5 457.0 -5.7 457.0 -5.7 1868.4 -6.8 1868.4 -6.8 559.7 -11.1 559.7 -11.1 2081.8 -15.5 2081.8 -15.5 2761.7 -20.7 2761.7 -20.7 3713.5 -24.3 3713.5 -24.3 982.3 -27.4 982.3 -27.4 2082.8 -63.7 2082.8 -63.7 3732.7 -100.0 3732.7 Line 7 Vs100' = 1,992 ft/sec Table 8 - Line 8 ReMi Data Depth, ft Vs, ft/s 0.0 456.4 -3.3 456.4 -3.3 978.1 -11.8 978.1 -11.8 1637.8 -36.2 1637.8 -36.2 2428.0 -57.0 2428.0 -57.0 3008.1 -61.3 3008.1 -61.3 2636.2 -82.7 2636.2 -82.7 5513.6 -86.4 5513.6 -86.4 5592.9 -100.0 5592.9 Line 8 Vs100' = 1,924 ft/sec 07156 Koechlein 14 Report Table 9 - Line 9 ReMi Data Depth, ft Vs, ft/s 0.0 719.2 -1.7 719.2 -1.7 1019.9 -6.1 1019.9 -6.1 600.7 -13.8 600.7 -13.8 850.0 -14.8 850.0 -14.8 1963.6 -27.1 1963.6 -27.1 1447.6 -31.7 1447.6 -31.7 627.2 -40.9 627.2 -40.9 2856.8 -100.0 2856.8 Line 9 Vs100' = 1,731 ft/sec Table 10 - Line 10 ReMi Data Depth, ft Vs, ft/s 0.0 719.2 -1.7 719.2 -1.7 647.0 -6.1 647.0 -6.1 845.5 -13.8 845.5 -13.8 850.0 -14.8 850.0 -14.8 1156.5 -27.1 1156.5 -27.1 1447.6 -31.7 1447.6 -31.7 1010.9 -52.0 1010.9 -52.0 2420.1 -100.0 2420.1 Line 10 Vs100' = 1,445 ft/sec 07156 Koechlein 15 Report REFERENCES Iwata, T., Kawase, H., Satoh, T., Kakehi, Y., Irikura, K., Louie, J. N., Abbott, R. E., and Anderson, J. G., 1998, Array microtremor measurements at Reno, Nevada, USA (abstract): Eos, Trans. Amer. Geophys. Union, v. 79, suppl. to no. 45, p. F578. Louie, J, N., 2001, Faster, Better: Shear-wave velocity to 100 meters depth from refraction microtremor arrays: Bulletin of the Seismological Society of America, v. 91, p. 347-364. Pullammanappallil, S.K., and Louie, J.N., 1993, Inversion of seismic reflection traveltimes using a nonlinear optimization scheme: Geophysics, v. 58, p. 1607-1620. Pullammanappallil, S.K., and Louie, J.N., 1994, A generalized simulated-annealing optimization for inversion of first arrival times: BSSA, v. 84, p. 1397-1409. Saito, M., 1979, Computations of reflectivity and surface wave dispersion curves for layered media; I, Sound wave and SH wave: Butsuri-Tanko, v. 32, no. 5, p. 15-26. Saito, M., 1988, Compound matrix method for the calculation of spheroidal oscillation of the Earth: Seismol. Res. Lett., v. 59, p. 29. Xia, J., Miller, R. D., and Park, C. B., 1999, Estimation of near-surface shear-wave velocity by inversion of Rayleigh wave: Geophysics, v. 64, p.691-700. 07156 Koechlein 16 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataNSFigure 3Ground SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec) Figure 3 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 1 refraction tomogram. Timberline 07156 Koechlein 17 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataNSFigure 4TH-2Ground SurfaceInterpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec)Depth of Refusalor BedrockRespectively (from Test Holes)orInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec) Figure 4 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 2 refraction tomogram Timberline 07156 Koechlein 18 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataSNFigure 5Ground SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,5000 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec) Figure 5 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 3 refraction tomogram Timberline 07156 Koechlein 19 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataNSFigure 6Ground SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec) Figure 6 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 4 refraction tomogram Timberline 07156 Koechlein 20 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataNSFigure 7Ground SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec) Figure 7 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 5 refraction tomogram Timberline 07156 Koechlein 21 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataEWFigure 8TH-4Ground SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec)Depth of Refusalor BedrockRespectively (from Test Holes)or Figure 8 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 6 refraction tomogram Timberline 07156 Koechlein 22 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataEWFigure 9Ground SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec)TH-2ADepth of Refusalor BedrockRespectively (from Test Holes)TH-6or Figure 9 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 7 refraction tomogram Timberline 07156 Koechlein 23 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataEWFigure 10TH-2AGround SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec)Depth of Refusalor BedrockRespectively (from Test Holes)or Figure 10 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 8 refraction tomogram Timberline 07156 Koechlein 24 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataEWFigure 11TH-2Ground SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec)Depth of Refusalor BedrockRespectively (from Test Holes)or Figure 11 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 9 refraction tomogram Timberline 07156 Koechlein 25 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataEWFigure 12Ground SurfaceInterpreted Top-of-Bedrock from Seismic Tomography (~6,500 ft/sec)Interpreted Top-of-Weathered-Bedrock from Seismic Tomography (~5,500 ft/sec) Figure 12 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 10 refraction tomogram Timberline 07156 Koechlein 26 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataFigure 13Elevation Contour of Proposed Floor-Slab (~7974 ft)Surface Plot of Interpreted Bedrock Elevation (~5,000 ft/s) Figure 13 – Proposed Residence Inn and Timberline Lodge Condominiums Project, 3D Surface plot of 5,000 ft/s velocity-contour. Elevation (ft) Timberline 07156 Koechlein 27 Report Koechlein EngineeringRooster Lodge ProjectSeismic Refraction DataFigure 14ApproximateLine LocationsElevation Contour of Proposed Floor-Slab (~7974 ft)Surface Plot of Interpreted Bedrock Elevation (~5,000 ft/s) Figure 14 – Proposed Residence Inn and Timberline Lodge Condominiums Project, 3D Surface plot of 5,000 ft/s velocity-contour with seismic line locations.Elevation (ft) Timberline 07156 Koechlein 28 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 1000 2000 3000 4000 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1303 ft/s 07156 Koechlein, Line 1: Vs Profile Figure 15 Figure 15 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 1 ReMi model. 07156 Koechlein 29 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 500 1000 1500 2000 2500 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1347 ft/s 07156 Koechlein, Line 2: Vs Profile Figure 16 Figure 16 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 2 ReMi model. 07156 Koechlein 30 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 500 1000 1500 2000 2500 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1325 ft/s 07156 Koechlein, Line 3: Vs Profile Figure 17 Figure 17 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 3 ReMi model. 07156 Koechlein 31 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 500 1000 1500 2000 2500 3000 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1560 ft/s 07156 Koechlein, Line 4: Vs Profile Figure 18 Figure 18 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 4 ReMi model. 07156 Koechlein 32 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 1000 2000 3000 4000 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1932 ft/s 07156 Koechlein, Line 5: Vs Profile Figure 19 Figure 19 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 5 ReMi model. 07156 Koechlein 33 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 1000 2000 3000 4000 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1080 ft/s 07156 Koechlein, Line 6: Vs Profile Figure 20 Figure 20 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 6 ReMi model. 07156 Koechlein 34 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 1000 2000 3000 4000 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1992 ft/s 07156 Koechlein, Line 7: Vs Profile Figure 21 Figure 21 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 7 ReMi model. 07156 Koechlein 35 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 1000 2000 3000 4000 5000 6000 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1924 ft/s 07156 Koechlein, Line 8: Vs Profile Figure 22 Figure 22 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 8 ReMi model. 07156 Koechlein 36 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 500 1000 1500 2000 2500 3000 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1731 ft/s 07156 Koechlein, Line 9: Vs Profile Figure 23 Figure 23 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 9 ReMi model. 07156 Koechlein 37 Report -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0 500 1000 1500 2000 2500 3000 Shear-Wave Velocity, ft/s Depth, ftVs100' = 1445 ft/s 07156 Koechlein, Line 10: Vs Profile Figure 24 Figure 24 – Proposed Residence Inn and Timberline Lodge Condominiums Project, Line 10 ReMi model.