DEPARTMENT OF TRANSPORTATION DIVISION: MATERIALS REPORT COVER SHEET

Transcription

1 LD-450 5/12/09 DEPARTMENT OF TRANSPORTATION DIVISION: MATERIALS REPORT COVER SHEET Soil Survey Report October 27, 2017 Authored By: Stephen A. Chaos, Travis S. Higgs, P.E. VDOT Materials Division Salem District Geotechnical Engineer Responsible for Pages: All UPC No.: ( , P101) Rte. 460 Bypass Ramp A to Rte. 460 Bus. - Montgomery County

2 VIRGINIA DEPARTMENT OF TRANSPORTATION SALEM DISTRICT MATERIALS SECTION October 27, 2017 Rte. 460 Bypass Ramp A to Rte. 460 Bus. Project , P101 Christiansburg, Montgomery County UPC# , Adv. Date 6/2018 MEMORANDUM To : Mr. Tim M. Dowdy Subject: Soil Survey Report DESCRIPTION: Eastbound exit ramp from Route 460 Bypass Ramp A to Franklin Street (Route 460 Business). TOPSOIL / ROOT MAT Since the project has been rough graded in the recent past, there has been little time for topsoil to develop within the project limits. As such, from field observations and measured depths in borings, the topsoil averages 2 inches in depth throughout the project. The root mat averages 12 inches throughout the project area. SOIL TYPES Residual soil was encountered in borings and observed in the existing graded slopes within the project area. This soil was described as yellowbrown, lean clay with silt and traces of sand and gravel. The residual soil was encountered from the surface in all borings and continued to a depth below proposed grade or to bedrock (auger refusal above grade). It varied in moisture from moist to (very) wet. Seven Standard Penetration Tests in the residual soil varied from 0 to 5 blow counts for 1 foot of penetration, resulting in density description of soft to very soft. A bulk sample of soil was collected from auger cuttings and tested for CBR (see the attached test report # for details). It should be noted that the optimum moisture listed on the CBR test report is 19.8%, whereas field moistures varied from 23% to 60%. The low SPT blow counts and extremely high moisture content will be addressed in the UNSUITABLE MATERIAL / SUBGRADE STABILIZATION portion of this report. Due to the rough grading which has occurred within the project area, some fill material may be encountered during construction. The fill material can be expected to have the exact components of the residual soil, possibly intermingled with chunks and gravel from the carbonate bedrock which underlays the site. Further, it is likely that residual soil will be encountered as seams in the carbonate bedrock at the time of construction.

3 ROCK DATA Bedrock underlying the project area consists of the Elbrook formation of Cambrian age. From published literature, the Elbrook formation is composed of light to dark gray, fine to medium grained, limestone and dolostone with traces of shale. Bedrock was exposed in outcrops and encountered in borings above the grade elevation between stations and (See Attachment A for outcrop surface area). Although not encountered in borings or observed in cut sections beyond the aforementioned stations, it is possible that bedrock may be encountered elsewhere within the project area as ledges or pinnacles (which are characteristic of karst environment). If it becomes necessary to utilize blasting to excavate bedrock encountered during construction, controlled blasting techniques should be utilized. Note that there are private dwellings, businesses, and utilities adjacent to the project area which could be damaged by construction activities, i.e. ground vibration and air blast. In order to alleviate the Department from liability, water sources should be documented and structures which could be damaged by construction activities (ground vibration, etc.) should be inspected and documented prior to construction. Considering the limitations of practical investigation processes and the irregular weathering properties of carbonate bedrock, the quantity and condition of bedrock in cut sections are difficult to estimate. In order to more accurately predict the volume of bedrock within the project area, Schnabel Engineering was hired to conduct geophysical testing. See the investigation report #17C provided by Schnabel Engineering dated October 10, NOTE: Attachment A and boring logs included in this report were provided to Schnabel Engineering prior to their investigation as background information and reference, and are included herein so that bidders have access to all data collected for this project. From Schnabel s testing in conjunction with test borings conducted by VDOT, it was calculated that bedrock could compose roughly 19% of the total excavation, producing a 13% shrinkage correction for the project. Note that a sink hole has been documented approximately 25 feet right of station on plan sheet 4. Although no other sink holes were observed in the project area, it is possible that others may be discovered at the time of construction. In order to remediate this and any unforeseen sink holes or karst related cavities, a Sink Hole Guide has been attached. The Sink Hole Guide includes a diagram of a typical cavity with written instructions for excavation and stabilization; however, due to the anomalies associated with any particular karst collapse feature, the methods detailed may have to be modified to accommodate any particular differences encountered. SLOPE RECOMMENDATIONS The subsurface investigation included solid auger and hollow-stem auger borings for this project. Moisture samples were collected from auger cuttings and much of the soil was found to be very wet during the investigation. Several borings were left open for more than 24 hours to determine if an unconfined groundwater table was encountered, but no water accumulated in any of the borings. If, at the time of construction, any soil is found to be more than 30% over lab optimum, it should not be placed in the embankment structure unless allowed to dry to accepted tolerances. Based on the composition of the residual soil (relatively high clay content), it may take substantial time to dry when exposed to the 2

4 atmosphere and the schedule of construction may need to be adjusted accordingly. The basis for precluding wet soil from the embankment structure is outlined in Section (h) of the 2016 Road and Bridge Specifications. Should it become necessary to utilize borrow (off site) material to construct the embankment sections, such material should have engineering properties as good or better than the minimum design CBR of 5.0. Based on test borings and field observations, it is recommended that a 2:1 or flatter design be utilized for all embankment slopes and cut slopes throughout the project. Top rounding of cut slopes is recommended to facilitate maintenance and minimize erosional energy. It is further recommended that all cut and embankment slopes be seeded as soon as possible to minimize the risk of erosion. The aforementioned slope designs should offer optimum stability in soil, for cut and embankment sections. It should be noted that all embankment structures proposed should be continuously benched against the existing man-made and natural slopes in accordance with Section (h) of the 2016 Road and Bridge Specifications. UNSUITABLE MATERIAL / SUBGRADE STABILIZATION Observations and in-situ testing revealed that the foundation soil for the pavement is of consistent composition but generally very soft and very wet. (See the attached borings logs for SPT blow counts and moisture content). Due to the unsuitable foundation soil and its proximity to bedrock beneath the proposed pavement; an additional stabilization layer of Number 1 Aggregate has been added to pavement design. The stabilization layer will require the excavation of unsuitable soil and bedrock to the prescribed depths. Should this or any excavated material from the project be more than 30% over optimum moisture, it should be dried prior to placement elsewhere in an embankment or wasted. Note that the Number 1 Aggregate stabilization layer should extend 1 foot wider on both sides than the entire width of the proposed pavement structure for the entire length of proposed new location pavement and be underlain with geotextile drainage fabric. Please see the PAVEMENT DESIGN portion of this report for details on the aforementioned recommendation. EMBANKMENT FOUNDATIONS Field observations and test borings revealed no areas of unsuitable embankment foundation. It should be noted that all embankment structures should be continuously benched against the existing man-made and natural slopes in accordance with Section (h) of the 2016 Road and Bridge Specifications. PAVEMENT DESIGN Existing Average Pavement Structure of Route 460 EB Shoulder and Partial Offramp: Average Asphalt Thickness (inches) = 9.9 Asph. Stab. Open Graded Drainage Layer (inches) = 2.5 Cement Treated Aggregate (inches) = 7 Deficiencies Consistent debonding and stripping in the top 4.25 of cores 3

5 Minimum Existing Structural Number = 5.36 It should be noted that the existing shoulder and partial offramp from Route 460 EB have the same pavement structure. Recommended Rehabilitation of Existing Route 460 EB Shoulder and Existing Partial Offramp: Mill existing pavement 4.5-inches Replace with 3.0-inches BM-25.0A and 1.5-inches SM-9.5D ph WATER Assumed Pavement Design Inputs for Offramp New Pavement Sections: ADT (2017 est.) = 6,000 Traffic Growth Rate (%) = 1.5 Design Lane (%) = 100 Directional Split (%) = 100 Trailer Trucks (%) = 1 Single Unit Trucks (%) = 1 ESAL Factor for Cars = ESAL Factor for Trailer Trucks = 1.05 ESAL Factor for Single Unit Trucks = 0.46 Design Life of Pavement = 30 years CBR = 5.0 ESALs = 1,257,480 Recommended Pavement Design for Route 460 EB Offramp and Shoulders New Pavement Sections: Surface: 1.5-inches (175 lbs/sy) Asphalt Concrete, Type SM-9.5D Base: 6.0-inches Asphalt Concrete, Type BM-25.0A Subbase: 6.0-inches Aggregate Base Material, Type I, No. 21-B Pavement Stabilization: 8.0-inches No. 1 Aggregate Geotextile: Geotextile Drainage Fabric (in accordance with section (c) of the 2016 Road and Bridge Specifications Note that the Number 1 Aggregate pavement stabilization layer and geotextile should extend 1 foot wider on both sides than the entire width of the proposed pavement structure for the entire length of proposed new location pavement. It can be assumed from field observation that surface water ph should be neutral to slightly acidic for this project. UNDERDRAINS To prevent water degradation of subgrade and pavement, a Modified UD is recommended near station (See Attachment B for location diagram and Attachment C for details). Note that the recommended Modified UD needs to be designed to allow for outfall drainage. 4

6 MATERIALS UNIT WEIGHTS Asphalt Concrete: Surface Asphalt - approximately 115 lbs./yd 2./in. Base Asphalt - approximately 119 lbs./yd 2./in. Crushed Aggregate: No. 21-B Aggregate - approximately lbs./ft 3. No. 57 Aggregate - approximately 95.1 lbs./ft 3. No. 1 Aggregate - approximately lbs./ft 3. Riprap - approximately 130 lbs./ft 3. Travis. S. Higgs, PE District Pavement Design and Geotechnical Engineer SAC/WHP/TSH CY: Project File Geology Wade H. Pence III, PG District Engineering Geologist 5

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17 Summary of Pavement Coring 16

18 Pavement Design Calculations 17

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20 GEOPHYSICAL SERVICES REPORT Geophysical Survey Route 460 Ultimate Ramp Virginia Department of Transportation VDOT Project # Montgomery County, Virginia Schnabel Project Number: 17C October 10, 2017

21 October 10, 2017 Mr. Wade Pence III, PG Engineering Geologist Virginia Department of Transportation Salem District Materials Section 731 Harrison Avenue Salem, VA Subject: UPC# , Contract Geophysical Survey - Route 460 Ultimate Ramp, Christiansburg, Montgomery County, Virginia, VDOT Project # , M501 Schnabel Project 17C Dear Mr. Pence: SCHNABEL ENGINEERING, LLC (Schnabel) is pleased to submit our geophysical services report for this project. This study was performed in accordance with our proposal dated September 21, 2017, as authorized by Mr. David Lee (VDOT) via dated September 21, PROJECT DESCRIPTION The site is located in Christiansburg, VA, where North Franklin Street (Business 460) merges with U.S. Route 460. We understand that VDOT has plans to construct a ramp between the two routes, which will include cuts of up to 20 feet below existing grade. Borings completed by VDOT encountered rock (auger refusal) at depths ranging from 10 feet to about 22 feet below existing grade. A boring location plan provided by VDOT indicated an area of bedrock outcrops approximately between Station and Station , and extending out from the project baseline. We understand that it was unclear as to whether these outcrops were in-place or were float material. VDOT requested our assistance in evaluating the depth to rock and providing estimates of rock quantity that would require removal for construction. OBJECTIVE AND SCOPE OF SERVICES Our proposal dated September 21, 2017, defined the scope of services for this project. The scope of services generally included collecting ERI geophysical data along two lines generally parallel to the project baseline, one being essentially along the baseline, and the other being 25 feet northwest of this line. In addition to the ERI data, our scope included collecting seismic refraction data along three traverses, two of which were coincident to the two ERI lines, and a third located 25 feet southeast of the

22 Virginia Department of Transportation Geophysical Survey Route 460 Ultimate Bypass project baseline. The locations of the lines are shown on Figure 1. The objective of these services was to evaluate the depth to rock and estimate rock quantities requiring removal. GEOPHYSICAL EXPLORATION Field Methodology Schnabel personnel arrived onsite on September 24, Upon arrival, we observed stationing for the baseline, and we were able to locate most of the VDOT borings previously completed. We observed several outcrop areas, and the rock appeared to be thin-bedded limestone with a shallow dip. The orientations of the dips observed on the various outcrops appeared to be similar, suggesting the outcrops were in-place. Schnabel personnel collected electrical resistivity imaging (ERI) data at the site along two lines on September 24, The spacing between the ERI lines was 25 feet. ERI line 2 was positioned with its origin (0 meters) at Station , and passing through Station ERI Line 1 was positioned 25 feet northwest of, and generally parallel to, ERI Line 2. Figure 1 shows the locations of the geophysical lines. We collected the ERI data using an Advanced Geosciences, Inc. SuperSting R8 resistivity meter with a dipole-dipole electrode array. We collected the ERI data with 31 electrodes spaced 6.6 ft (2 meters) apart, for an active array length of about 196 ft (60 meters). The ERI data were recorded digitally by the SuperSting and downloaded to a computer for analysis. Schnabel personnel collected seismic refraction data at the site along three lines on September 25, Two of the seismic lines were coincident with ERI lines 1 and 2, but were shorter in length since the seismic refraction method doesn t require the additional line length that ERI surveys require for the same horizontal coverage. The third seismic refraction line was located 25 feet southeast of, and parallel to, ERI/seismic Line 2. We collected the seismic refraction data using a 24-channel geophone array and 8-Hz geophones. The geophones were spaced 6.6 feet (2 meters) apart for an active array length of about 151 feet (46 meters). The energy source for the seismic refraction surveys was a sledgehammer striking a steel plate. We recorded data for five shot locations: two end shots, two intermediate shots, and one center shot. The seismic data were recorded digitally on a 24-channel Geode seismograph connected to a laptop computer. The relative elevations of several locations along each survey line were measured using an optical level and rod. A relative elevation was also obtained for VDOT boring B-5, and all other relative elevations were referenced to a ground surface elevation of 2,107 ft at VDOT boring B-5. This elevation was obtained from a map of existing site contours provided by VDOT. We expect the elevations to be within about 0.5 ft accuracy. Locations of the ERI traverses were obtained using a sub-meter Trimble Geo7X DGPS system, and the locations are within about 2 ft accuracy. References to direction and location in this report are based on the US State Plane 1983 System, Virginia South 4502 Zone, using the NAD 83 datum, with units in US survey ft. October 10, 2017 Page 2 Schnabel Engineering, LLC Project 17C All Rights Reserved

23 Virginia Department of Transportation Geophysical Survey Route 460 Ultimate Bypass ERI Data Analysis The ERI data files were reviewed in EarthImager 2D software and edited as needed to remove data spikes. Elevation data were then incorporated into the software, and the data were mathematically inverted to produce 2-dimensional subsurface resistivity model profiles along the lines. The errors associated with the modeling of the ERI data ranged from 3 to 6%. The error represents the software s comparison of its version of the data calculated during the inversion process, to the actual field data. Generally, the lower the modeling error, the higher the match between the ERI profile and the actual subsurface conditions. In general, the modeling errors on the order seen in these data sets indicate good quality data. The ERI data are interpreted by comparing the relative modeled resistivity values with approximate known values for the expected geological conditions and known subsurface information. In general, lower resistivity values are indicative of wetter soil, more highly conductive soil such as clays, and/or weathered and fractured bedrock. Higher resistivity values are indicative of drier soils, less conductive soils such as silts, sands and gravels, and/or less weathered bedrock. On sites where fill or debris materials may be present, resistivity values may vary considerably over short distances. Seismic Refraction Data Analysis Seismic data processing involved manually picking first-arrival times of seismic energy using the Pickwin module of SeisImager 2D software. Further processing was performed in the Plotrefa module of SeisImager 2D software, with elevations incorporated into the data. The data were initially inverted using a time-term inversion method to allow for assigning arrival times to subsurface layers, and 2-dimensional, 2-layer models of compressional wave velocities were produced. The time-term models were then used as input to perform tomographic inversion to estimate gradational changes in the compressional wave velocities beneath the survey lines. Compressional waves are directly related to the density of the material and can often be correlated to how hard the material is for excavation and foundation purposes as well. Results Figure 2 and Figure 3 show the resistivity and seismic refraction profiles for Line 1 and Line 2, respectively. The horizontal scales for the ERI model and seismic refraction model are the same, so that the two models for each line can be directly compared. Figure 4 shows the seismic refraction profile for Line 3. Three VDOT borings that were reasonably close (<5 ft) to the geophysical lines are plotted on the nearest profile. The borings generally encountered soils of lean clays with silt, trace sand, and weathered limestone gravel. All three borings (B-3, B-4, B-5) encountered auger refusal on what was interpreted to be limestone bedrock. The two ERI profiles generally show similar variations in resistivity from northeast to southwest. The blue colors on the resistivity profiles likely represent higher-moisture clay soils, as evidenced by the information from VDOT boring B-4. The darker green colors likely represent a combination of higherweathered and fractured bedrock, and soil zones. The yellow to red colors likely represent less- October 10, 2017 Page 3 Schnabel Engineering, LLC Project 17C All Rights Reserved

24 Virginia Department of Transportation Geophysical Survey Route 460 Ultimate Bypass weathered to massive bedrock. The ERI profiles generally confirm that the observed outcrops are portions of in-place bedrock, and the bedrock surface is likely variable. We have highlighted several velocity contours on the seismic velocity models that we interpret to be significant to this investigation. Our interpretations are based on the seismic and resistivity survey results, soil boring information, our experience, and seismic velocity information published in the Caterpillar Performance Handbook Edition 47 (2017). In addition to rock density (correlated to compression wave velocity), rock penetration and removal is highly dependent on the type of bedrock, orientation of bedding planes or other discontinuities in the bedrock, the type of equipment used, the level of effort employed to remove the rock and what is deemed to be an acceptable productivity (i.e. productivity levels will decrease significantly with increased compression wave velocities although material may still be removed if it has near horizontal discontinuities that an excavator or ripping tooth can penetrate). Furthermore, material can more easily be removed in mass excavations where equipment can be maneuvered as opposed to excavation on a slope or a narrow utility trench. The standard of practice is to correlate rock removing potential (i.e., ripping capacity) with a Caterpillar D8R dozer using multi or single shank. However, in some situations, material can be excavated to similar depths with a large excavator (e.g. Caterpillar 336 or larger) with an appropriate bucket with rock teeth. We provide the following interpretations of materials and seismic velocities: Rippable soils: Less than 3,000 ft/s are residual soil materials. Generally rippable materials: Less than 5,500-6,000 ft/s are likely a combination of residual soil materials and weathered limestone rock. This material can typically be penetrated with standard 3 ½ ID hollow stem augers used for geotechnical investigations, although local areas of pinnacled limestone bedrock may be encountered as auger refusal. Marginally to non-rippable materials: Greater than 5,500-6,000 ft/s are relatively hard disintegrated limestone rock to competent limestone rock. Auger refusal is typically encountered within this material and split spoons will generally have less than two inches of penetration over 100 blows. While there is good agreement between auger refusal depths noted for borings B-4 and B-5, and the top of marginally to non-rippable materials, there appears to be significant discrepancy with the auger refusal noted for boring B-3. This may be due to the boring encountering a bedrock cutter between pinnacles. For purposes of this project, we recommend considering the top of rock to be the 3,000 ft/s contour on the seismic refraction profiles. We have included the planned grade on the seismic refraction profiles by obtaining elevations from the VDOT cross-sections at 25-foot spacings along the alignment baseline. Estimating Rock Volume We plotted the interpreted top of bedrock onto the VDOT cross-sections where the geophysical survey lines would intersect each section. Figures 5 through 8 show the cross-sections and estimated bedrock surfaces. On each section, we extrapolated the interpreted top of bedrock beyond the outermost geophysical lines (1 and 3) to the respective edge of planned cut, as shown in red on Figures 5 through 8. We constructed polygons on each cross-section between the interpreted top of bedrock and the planned grade, as shown in green on Figures 5 through 8. We calculated the area of each polygon as a bedrock October 10, 2017 Page 4 Schnabel Engineering, LLC Project 17C All Rights Reserved

25 Virginia Department of Transportation Geophysical Survey Route 460 Ultimate Bypass area for the cross-section. Using the calculated areas, we estimated the volume of bedrock between the VDOT cross-sections in accordance with the Average End-Area Method: VV = LL xx (AA 1 + AA 2 ) 2 where: L = distance between adjacent cross-sections (25 feet) A 1 and A 2 = rock cut area from first profile and second cross-section, respectively The calculated rock cut areas are summarized in the table below. Summary of Rock Cut Areas VDOT Cross-section Estimated Rock Cut Area (ft 2 ) (assumed) , , Using the rock cut areas and the spacing of 25 feet between adjacent cross-sections, we calculated an estimate of rock volume. The calculation results are summarized in the table below. Summary of Estimated Rock Volume Calculations VDOT Cross-sections Distance between Calculated Rock Rock Cut Areas (ft 2 ) Used Cross-sections (ft) Volume (ft 3 [yd 3 ]) ,150 [265] , ,950 [1,035] , , ,987 [1,259] , ,125 [708] ,887 [366] ,112 [375] ,688 [285] ,525 [56] Total Estimated Rock Volume = 117,424 [4,349] October 10, 2017 Page 5 Schnabel Engineering, LLC Project 17C All Rights Reserved

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27 Virginia Department of Transportation Geophysical Survey Route 460 Ultimate Bypass Attachments: Figure 1 Site Vicinity Map Figure 2 Line 1 Geophysical Profiles Figure 3 Line 2 Geophysical Profiles Figure 4 Line 3 Geophysical Profile Figure 5 Estimated Bedrock Areas Figure 6 Estimated Bedrock Areas Figure 7 Estimated Bedrock Areas Figure 8 Estimated Bedrock Areas October 10, 2017 Page 7 Schnabel Engineering, LLC Project 17C All Rights Reserved

28 gnuyda 460 Belmont Belmont Farms M o n t g o m e r y C o u n t y Yellow Sulphur Springs 460 ^_!(!(!(!(!(!(!( Yellow Sulphur 460 Site Location Christiansburg ³ ' 0' 10/5/2017 G:\2017\Blacksburg\17C VDOT Route 460 Ultimate Ramp Geophysics\03-SE Products\07_GIS\R460_VICIN.mxd 193' !( 193'!( ' LINE B-4 LINE 2 Source: Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community, ESRI MediaKit 2010 Projection: NAD 1983 StatePlane Virginia South FIPS 4502 Feet LINE 3 VDOT B-5 ROUTE 460 ULTIMATE RAMP VA. DEPT. OF TRANSPORTATION MONTGOMERY COUNTY, VIRGINIA PROJECT NO. 17C Legend 0' VDOT B-3!( VDOT Boring ERI Line Seismic Refraction Line Scale: 1:360 SITE VICINITY MAP Feet FIGURE 1 Schnabel Engineering, All Rights Reserved.

29 ERI Line 1 ELEVATION (FEET) NE (offset 27' SE) (offset 29' SE) Massive Bedrock (offset 31' SE) Weathered and Fractured Bedrock (offset 31' SE) VDOT B-4 Wet Soil A.R (offset 31' SE) (offset 29' SE) outcrops (offset 25' SE) Less Weathered Bedrock Weathered and Fractured Bedrock VDOT B-6 (offset 20' SE) at 196' Wet Soil DISTANCE (FEET) Resistivity (ohm-m) SW Compressional wave velocities 3,000 ft/s contour 6,000 ft/s contour Seismic Refraction Line 1 ELEVATION (FEET) NE (offset 29' SE) Planned Grade (offset 31' SE) Generally rippable bedrock and soil (offset 31' SE) VDOT B (offset 31' SE) Rippable soil (offset 29' SE) outcrops (offset 25' SE) VDOT B-6 (offset 20' SE) at 196' Rippable soil Generally 2095 rippable 2090 Marginally to bedrock and soil Marginally to non-rippable 2085 A.R. non-rippable bedrock bedrock DISTANCE (FEET) Rippable soil SW Generally rippable bedrock and soil Marginally to non-rippable bedrock Compressional Wave Velocity (ft/s) ROUTE 460 ULTIMATE RAMP VA. DEPT. OF TRANSPORTATION MONTGOMERY COUNTY, VIRGINIA

30 ERI Line 2 NE (offset 3' SE) (offset 5' SE) outcrop (offset 3' NW) (offset 6' SE) (offset 5' SE) outcrops (offset 3' SE) (offset 4.5' NW) SW Wet Soil Wet Soil ELEVATION (FEET) Massive Bedrock Weathered and Fractured Bedrock Less Weathered Bedrock Weathered and Fractured Bedrock Less Weathered Bedrock Weathered and Fractured Bedrock Compressional wave velocities 3,000 ft/s contour 6,000 ft/s contour DISTANCE (FEET) Seismic Refraction Line 2 ELEVATION (FEET) NE (offset 3' SE) outcrop (offset 5' SE) (offset 3' N) (offset 6' SE) Generally rippable bedrock and soil Marginally to non-rippable bedrock Planned Grade Rippable soil (offset 3' SE) (offset 5' SE) outcrops DISTANCE (FEET) Generally rippable Rippable soil bedrock and soil 3000 Generally rippable bedrock and soil Rippable soil SW Resistivity (ohm-m) Marginally to non-rippable bedrock Compressional Wave Velocity (ft/s) ROUTE 460 ULTIMATE RAMP VA. DEPT. OF TRANSPORTATION MONTGOMERY COUNTY, VIRGINIA

31 Seismic Refraction Line 3 ELEVATION (FEET) NE (offset 20' NW) (offset 20' NW) VDOT (offset 20' NW) B-3 VDOT B-5 Planned Grade Rippable soil (offset 22' NW) (offset 26' NW) Generally rippable Marginally to 2095 bedrock and soil 2090 non-rippable A.R bedrock A.R DISTANCE (FEET) SW Rippable soil Generally rippable bedrock and soil Marginally to non-rippable bedrock Compressional Wave Velocity (ft/s) ROUTE 460 ULTIMATE RAMP VA. DEPT. OF TRANSPORTATION MONTGOMERY COUNTY, VIRGINIA

32 1,664 ft ft 2 Estimated top of bedrock (dashed where inferred) Estimated bedrock area ROUTE 460 ULTIMATE RAMP VA. DEPT. OF TRANSPORTATION MONTGOMERY COUNTY, VIRGINIA

33 475 ft 2 1,055 ft 2 Estimated top of bedrock (dashed where inferred) Estimated bedrock area ROUTE 460 ULTIMATE RAMP VA. DEPT. OF TRANSPORTATION MONTGOMERY COUNTY, VIRGINIA

34 493 ft ft 2 Estimated top of bedrock (dashed where inferred) Estimated bedrock area ROUTE 460 ULTIMATE RAMP VA. DEPT. OF TRANSPORTATION MONTGOMERY COUNTY, VIRGINIA

35 95 ft 2 27 ft 2 Estimated top of bedrock (dashed where inferred) Estimated bedrock area ROUTE 460 ULTIMATE RAMP VA. DEPT. OF TRANSPORTATION MONTGOMERY COUNTY, VIRGINIA