Brush Creek Sites 9-14-15 Geophysical Report w att_v2.pdf

GEOPHYSICAL INVESTIGATION REPORT

Brush Creek – Sites 9, 14, and 15 NRCS – West Virginia Mercer County, West Virginia

NRCS Task Order 12-SPEC-18-F0053 Contract 12SPEC18D0023 Task Order No: 12FPC320F0253

Aterra-Schnabel JV Reference 18proj007 Schnabel Reference 18C35013.010, 18C35013.020, and 18C35013.030 September 12, 2022

300 Brookside Avenue www.aterra-schnabel.com Building 18, Suite 160 T/ 610-405-7708 Ambler, PA 19002

September 12, 2022

Ms. Lauri M. Eipp laureen.eipp@wdc.usda.gov Contracting Officer U.S. Department of Agriculture Natural Resources Conservation Services

Subject: Geophysical Investigation Report for Brush Creek Sites 9, 14, and 15 NRCS Task Order 12-SPEC-18-F0053, Contract 12SPEC18D0023 Mercer County, West Virginia (Aterra-Schnabel Reference 18pro007;

Schnabel Reference 18C35013.010, 18C35013.020, and 18C35013.030)

Dear Ms. Eipp:

Aterra-Schnabel JV is pleased to submit our Geophysical Investigation Report for this project. This report was prepared in accordance with our proposal dated February 10, 2022, (original November 16, 2021; first revision December 17, 2021); and our Task Order signed on March 9, 2022.

We appreciate the opportunity to be of service for this project. Please call us if you have any questions regarding this report.

Sincerely, Aterra-Schnabel JV

Mia A. Painter, PG Associate

Evan B. Binder, PE Associate

CS:JS:MAP:EBB:vm

Distribution:

NRCS – West Virginia (email only) Attn: Mr. Derrick Crane Attn: Mr. Andy Deichert http://www.aterra-schnabel.com/ mailto:laureen.eipp@wdc.usda.gov

Natural Resources Conservation Service – West Virginia Geophysical Investigation Report – Brush Creek Sites 9, 14, and 15

September 12, 2022 Page i Aterra-Schnabel JV Project 18proj007 ©2022 All Rights Reserved

GEOPHYSICAL INVESTIGATION REPORT

NRCS – WEST VIRGINIA

BRUSH CREEK – SITES 9, 14, AND 15

MERCER COUNTY, WEST VIRGINIA

TABLE OF CONTENTS

1.0 INTRODUCTION

Background Objective and Scope of Services Terminology

2.0 RIPPABILITY DISCUSSION

3.0 SITE 9 GEOPHYSICAL INVESTIGATION

Seismic Refraction Data Collection and Analysis Seismic Refraction Results Electrical Resistivity Imaging Data Collection and Analysis Electrical Resistivity Imaging Results

4.0 SITE 14 GEOPHYSICAL INVESTIGATION

Seismic Refraction Data Collection and Analysis Seismic Refraction Results

5.0 SITE 15 GEOPHYSICAL INVESTIGATION

Seismic Refraction Data Collection and Analysis Seismic Refraction Results

6.0 LIMITATIONS

September 12, 2022 Page ii Aterra-Schnabel JV

LIST OF FIGURES

Figure 1: Site Vicinity Map Showing Locations of the Three Sites in Mercer County, West Virginia Figure 2: Site Conditions at Site 9 at Time of Data Collection Figure 3: Site 9 Layout Map (Red Lines Show SR Line Locations; Blue Lines Show ERI Line

Locations) Figure 4: 3D Perspective View of Site 9 Seismic Refraction Results Figure 5: 3D Perspective View of ERI Results, Looking from the South to the North.

Figure 6: Site Conditions at Site 14 at Time of Data Collection Figure 7: Site 9 Line Layout.

Figure 8: 3D Perspective View of Site 14 Seismic Refraction Results Figure 9: Site Conditions at Site 15 at Time of Data Collection Figure 10: Site 15 Line Layout Map Figure 11: 3D Perspective View of Site 15 Seismic Refraction Results

Figure A-1: Site 9 – A Lines Seismic Refraction Results Figure A-2: Site 9 – B Lines Seismic Refraction Results Figure A-3: Site 9 – C Lines Seismic Refraction Results Figure A-4: Site 9 – ERI Results Figure B-1: Site 14 – Seismic Refraction Results Figure C-1: Site 15 – Seismic Refraction Results

LIST OF TABLES

Table A-1: GPS Information for Site 9 Table B-1: GPS Information for Site 14 Table C-1: GPS Information for Site 15

APPENDICES

Appendix A: Site 9 Geophysical Investigation Results and Data Appendix B: Site 14 Geophysical Investigation Results and Data Appendix C: Site 15 Geophysical Investigation Results and Data

September 12, 2022 Page 1 Aterra-Schnabel JV

1.0 INTRODUCTION

Background

This Geophysical Investigation Report presents the findings of the seismic refraction (SR) and electrical resistivity imaging (ERI) surveys performed by Aterra-Schnabel JV at Brush Creek – Sites 9, 14, and 15 for the Natural Resources Conservation Service (NRCS). The sites are in Mercer County, West Virginia.

A Site Vicinity Map is provided in Figure 1.

Figure 1: Site Vicinity Map Showing Locations of the Three Sites in Mercer County, West Virginia

Objective and Scope of Services

This study was completed to support the design of the proposed auxiliary spillway cutoff walls and the toe drains, and additionally, at Site 9 to identify where seepage and/or groundwater flow was occurring. The objective of this study was to: (1) evaluate the depth to rock and rippability of rock at the proposed auxiliary spillway cutoff walls and toe drains at Sites 9, 14, and 15; and (2) evaluate saturated zones and potential seepage pathways to support design of drainage features for the right abutment at Site 9.

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The work presented herein is defined under our proposal dated February 10, 2022, (original November 16, 2021; first revision December 17, 2021); and our Task Order signed on March 9, 2022.

The study includes an SR survey at Sites 9, 14, and 15 to estimate depth to rock and rippability of rock, as well as an ERI survey at Site 9 to estimate saturated zones and potential seepage pathways. This report includes a description of the methods used; conditions encountered; a discussion of the resulting data and interpretations with regard to depth to rock, rippability, and ripping index; annotated presentation of the data; and site location plans.

Terminology

Descriptive nomenclature for dams is based upon one looking downstream in the direction of flow. “Right” and “left” are referenced in this manner. The reservoir side is known as the upstream side, with the opposite slope referred to as the downstream slope. The abbreviation “EL” in this report represents elevation in feet.

Many of the borehole logs show a layer of disintegrated rock overlying the top of competent rock. This layer will have seismic properties more consistent with a soil layer than a rock layer. Therefore, we will generally be referring to the top of competent rock as opposed to disintegrated rock when referring to top of rock, unless specifically noted otherwise.

2.0 RIPPABILITY DISCUSSION

Seismic compression wave (i.e., P-wave) velocity is empirically correlated to the rippability of rock. The Caterpillar Performance Handbook Edition 43 (2013) lists earth materials and correlates seismic velocities to rippability. Table 4-23, “Excavation characteristics of rock,” and Table 4-27, "Correlation of indicators of rock excavatability” (Chapter 4, NRCS Part 631 Geology, National Engineering Handbook) indicate the 7,000 ft/s P-wave velocity contour is critical in determining the headcut erodibility index (kh) value.

The Caterpillar Handbook indicates that a CAT D8R bulldozer equipped with a multi- or single-shank No.

8 stripper can rip rocks such as shale and sandstone with associated seismic velocities of up to about 6,000 to 6,300 ft per second (ft/s). Velocities above these to about 8,200 to 8,400 ft/s are considered marginally rippable, and above these velocities are considered non-rippable. Productivity of rock removal will decrease significantly as the rippability limit is approached.

For this project, we correlated the estimated depth to top of rock based primarily on the test boring results available at each site, as previously reported in the final Geotechnical Investigation Reports submitted for Sites 9, 14, and 15 on May 10, 2019, June 19, 2019 and October 28, 2021, respectively. In addition, we provided the velocity contours of interest based on the information in the NRCS Geology Handbook.

Note that regardless of the method used to estimate rippability, variation depends on conditions such as size and openness of the excavation and maneuverability of the equipment, lithology changes, banding or bedding thickness and orientation, and fracture orientation and frequency.

3.0 SITE 9 GEOPHYSICAL INVESTIGATION

The Brush Creek Watershed Site 9 Dam is located in Mercer County, West Virginia, approximately 4.5 miles northeast of the City of Bluefield on the South Fork of Brush Creek (see Figure 1). The site is primarily a grassy, open area along the embankment, although the southern portion of the site is wooded.

Figure 2 shows the site conditions at the time of data collection.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=31848.wba

September 12, 2022 Page 3 Aterra-Schnabel JV

Figure 2: Site Conditions at Site 9 at Time of Data Collection

A total of 2,285 linear feet (lf) of SR data were collected from April 27 through 29, 2022, along Lines 9-A1, 9-A2-1, 9-A2-2, 9-B1, 9-B2, 9-B3, and 9-C as shown on Figure 3 and Figures A-1, A-2, and A-3. Historical weather data from Weather Underground (https://www.wunderground.com) shows that there was about

0.4 inches of rainfall on April 19, which was 8 days before seismic data collection.

A total of 1,350 lf of ERI data were collected on April 11 and 12, 2022, along Lines 9-D, 9-E, 9-F, and 9- G, as shown on Figures 3 and A-4. The GPS data for each SR and ERI line are given in Appendix A, Table A-1. Historic weather data from Weather Underground shows that there was about 1 inch of rainfall between April 6 and April 7, which was 4 days before collecting the ERI data.

Figure 3: Site 9 Layout Map (Red Lines Show

SR Line Locations; Blue Lines Show ERI Line Locations)

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Seismic Refraction Data Collection and Analysis

SR data were collected using two Geometrics Geode seismographs and 48 10-Hz geophones with a geophone spacing of 5 ft. SR traverses extended beyond the length of the proposed survey lines, where accessible, to provide the required depth coverage along the traverses.

Seismic data processing was conducted using Rayfract Version 4 from Intelligent Resources. The processing involved Schnabel personnel manually picking first-arrival times of seismic energy, incorporating elevations into the data, and generating a model that matches the first arrivals. Gradational velocity changes are common in geologic environments with thicker zones of weathered and fractured bedrock, such as at this site; therefore, we performed a tomographic inversion to estimate these gradational changes in the P-wave velocities. Due to the nature of tomographic inversions, even a sharp geologic boundary will be imaged as a gradient. Therefore, while a specific velocity contour can serve as a tool for interpreting the top of rock, for example, the actual velocity of the rock may be higher than the contour representing the top of the rock.

Seismic Refraction Results

The results from the SR survey for Site 9 are shown in Figures A-1, A-2, and A-3 in Appendix A. Figure A- 1 shows the results for Lines 9-A1, 9-A2-1, and 9-A2-2; Figure A-2 shows the results for Lines 9-B1, 9- B2, and 9-B3; and Figure A-3 shows the results for Lines 9-C1, 9-C2, and 9-C3. The SR results are displayed using color-coded cross-sections with key velocity contours overlaid.

The geologic units, as noted in logs of boreholes located near the lines are overlaid on the geophysical results. Generally, the 5,000 ft/s velocity contour line corresponds closest to the top of competent rock as noted in the borehole logs. It is important to understand that this value represents the top of interpreted rock, not the actual velocity of the rock itself, which may be higher due to the nature of tomographic inversions and because the bulk of the rock is generally more competent, and therefore likely has a higher velocity, than the disintegrated rock/competent rock interface.

On each figure there is a plan-view image that shows the locations of the boreholes and geophysical lines. The symbols along each line are labeled to correspond to the horizontal axis of each line, which is referred to as the downline distance in the discussion of results below.

The results for Line 9-A1 (Figure A-1) show that depth to top of rock, as represented by the 5,000 ft/s contour, varies over the line length. At a downline distance of about 40 ft, the top of rock is interpreted to be within 3 to 5 ft of the ground surface, while only 20 ft farther to the west, at a downline distance of 20 ft, the depth to rock is interpreted to be nearly 20 ft below the ground. Rock is again shallow about 120 ft down the line.

The results for Line 9-A2-1 (Figure A-1) show that rock varies between about 11 to 17 ft below the ground surface. The results for 9-A2-2 show that rock is closer to the surface at a downline distance of about 160 ft.

The results for Lines 9-B1, 9-B2, and 9-B-3 (Figure A-2) show that the interpreted top of rock is about 12 to 18 ft below the ground surface over the line length. However, on Line 9-B3 between downline distances of 0 to 20 ft, rock is up to 30 ft deep; between downline distances of 20 to 60 ft, rock is about 8 ft below the ground surface.

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The results for Lines 9-C1, 9-C2, and 9-C3 are shown on Figure A-3. For most of Line 9-C1, top of rock is interpreted to be about 8 ft from the ground surface; the deepest depth is at a downline distance of 240 ft, where the depth is about 14 ft. Along Line 9-C2, rock is as deep as about 15 ft at a downline distance of 85 ft to within about 4 to 5 ft deep near the surface at about 140 ft down the line; however, this could be caused by increased near surface soil saturation. Along Line 9-C3, rock is as shallow as 6 ft below the surface at the start of the line, but about 25 ft deep at the end of the line.

The seismic data for Site 9 were also imaged as a 3D perspective view that can be helpful for visualization and quality control of the results where the lines intersect. Additionally, this 3D model can be helpful for observing site-wide trends in the results. The view looking from the east to the west is shown in Figure 4.

Figure 4: 3D Perspective View of Site 9 Seismic Refraction Results

Electrical Resistivity Imaging Data Collection and Analysis

Schnabel Personnel conducted an ERI survey on the right abutment at Site 9. A total of 1,350 lf of ERI data were collected using 56 electrodes with a 1.5-m spacing. Data was collected using an AGI Supersting resistivity meter.

The ERI data processing was conducted using EarthImager Version 2.4.4 from AGI. The processing involved Schnabel personnel loading all ERI measurements, filtering out noisy data points, incorporating elevations into the data, and generating a model that matches the observed data via tomographic inversion.

Electrical Resistivity Imaging Results

The ERI results are shown in Figure A-4 in Appendix A. The ERI results are displayed using color-coded cross-sections with key contours overlaid. The location of boreholes located near the lines are noted; the depth to rock is noted from the corresponding borehole logs. On each map there is a plan-view that shows the locations of the boreholes and resistivity lines. The symbols along each line are labeled to correspond to the horizontal axis of each line.

September 12, 2022 Page 6 Aterra-Schnabel JV

Generally, increased soil moisture levels will lead to a decrease in electrical resistivity; however, grain size and material type can also affect resistivity values. Generally, sands and gravels will have a higher resistivity value than silt and clay. Therefore, lower resistivity values are typically indicative of finer materials or wetter materials, where higher resistivity values are typically indicative of coarser or drier materials. When evaluating seepage pathways, both high and low values could be of interest. The low resistivity zones could indicate zones of increased saturation caused by seepage. High resistivity could indicate zones of sand and gravel with higher hydraulic permeability that could be allowing seepage.

The four ERI lines show a wide range of resistivity values. Line 9-D shows a conductive zone underlying the full line. Based on the borehole information from B-34, the top of this conductive zone corresponds to the top of the water table and may not necessarily be related to seepage. The low resistivity zone beneath the full line may be related to the former location of the stream channel, which is reportedly in this approximate location. The low resistivity zone at depth beneath Line 9-G between a downline distance of 60 to 120 ft is also in the approximate same location as the former stream channel. This area may be more highly fractured and permeable than the surrounding bedrock areas.

On Line 9-D there is a smaller low resistivity feature of interest in the embankment that is located at EL 2500 at the start of the line that daylights at the historic wet area observed on the downstream slope at a downline distance of about 100 ft. During the ERI survey, we observed wet soils downstream of this, at a downline distance of about 110 ft. We interpret this low resistivity zone to be a potential source of seepage, though the source appears to be either the reservoir or groundwater. Where the wet area was observed is on top of a high resistivity zone of material; we infer from this that the seeping water daylights at a downline distance of about 100 ft, and then flows on the ground surface above the high resistivity material causing noticeable wet and soft soils just downstream. It should also be noted that the locations where this feature would intersect with SR Lines 9-C2 (140 ft) and 9-C3 (40 ft), both seismic profiles show an increase in near surface velocity, as would be expected if the near surface materials at those points have higher water saturation or an isolated zone of shallow bedrock.

Although not as clear in Line 9-D, on Line 9-E there is an interruption in the highly resistive surface that occurs between about 70 and 90 ft down that indicates a somewhat similar, if more subdued, anomaly as seen on Line 9-D. This feature could also be related to the same seepage observed on Line 9-D in the embankment. The historic zone of wetness on the embankment ends between Lines 9-D and 9-E, and the subtle, low resistivity zone in Line 9-E could be a 3D effect from wet embankment material, or it could be a zone that has a lesser amount of seepage.

Line 9-E shows a low resistivity zone at depth that we interpret to indicate groundwater, which is also observed at the intersection with Line 9-G. This low resistivity zone does not appear to daylight on the embankment at this location, but it could indicate a seepage pathway from the abutment to the historic wetland area.

The results from Line 9-G show a somewhat similar feature at about EL 2480 between the start of the line and 120 ft down the line. This line runs parallel to the embankment, so it is not possible to tell if this extends upward into the embankment.

Line 9-F shows generally higher resistivity value than the rest of the lines and shows no features that clearly indicate potential seepage. Most of the line is located on the native abutment materials, which may account for the higher resistivity values.

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As with the SR results, we can display the ERI results in a 3D perspective view (Figure 5). Due to software limitations, the color scale for 3D is not a direct match to the 2D images shown in Figure A-4;

however, the trends discussed are visible, including the potential seepage pathway seen in Lines 9-D and 9-E.

Figure 5: 3D Perspective View of ERI Results, Looking from the South to the North

4.0 SITE 14 GEOPHYSICAL INVESTIGATION

The Brush Creek Watershed Site 14 Dam is in Mercer County, West Virginia, almost 9 miles northeast of the City of Bluefield and about 4 miles southwest of the City of Princeton on the North Fork of Brush Creek (see Figure 1). The site is primarily grassy, open area along the embankment, although the southwest portion of the site is wooded (Figure 6).

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Figure 6: Site Conditions at Site 14 at Time of Data Collection

A total of 1,135 lf of SR was collected on April 7, 2022, along Lines 14-A, 14-B, 14-C, and 14-D, as shown on Figures 7 and B-1. Additionally, the GPS data for each line are given in Appendix B, Table B1. Data collection took place within a day of a rainfall that, according to Weather Underground, was about an inch combined between April 6 and April 7, 2022.

Figure 7: Site 14 Line Layout.

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Seismic Refraction Data Collection and Analysis

Schnabel personnel conducted an SR survey to evaluate the depth to rock and rippability of rock at the proposed auxiliary spillway cutoff walls and toe drains. Two Geometrics Geode seismographs were used with up to 48 10-Hz geophones with a geophone spacing of 5 ft. SR traverses extended beyond the length of the proposed survey lines, where accessible, to provide the necessary depth coverage along the traverses.

Seismic data processing was conducted using Rayfract Version 4 from Intelligent Resources. The processing involved Schnabel personnel manually picking first-arrival times of seismic energy, incorporating elevations into the data, and generating a model that matches the first arrivals. Gradational velocity changes are common in geologic environments with thicker zones of weathered and fractured bedrock, such as at this site; therefore, we performed a tomographic inversion to estimate these gradational changes in the P-wave velocities.

Seismic Refraction Results

The results from the SR survey for Site 14 are shown in Figure B-1 in Appendix B. The geologic units, as noted in logs of boreholes located near the lines are overlaid on the geophysical results. Generally, the 5,000 ft/s velocity contour line corresponds closest to the top of competent rock as noted in the borehole logs. It is important to understand that this value represents the top of interpreted rock, not the actual velocity of the rock itself, which may be higher due to the nature of tomographic inversions and because the bulk of the rock is generally more competent, and therefore likely has a higher velocity, than the disintegrated rock/rock interface.

On each figure there is a plan-view image that shows the locations of the boreholes and seismic lines.

The symbols along each line are labeled to correspond to the horizontal axis of each line, which is referred to as the downline distance in the discussion of results below.

The results for Line 14-A (Figure B-1) show that top of rock, as represented by the 5,000 ft/s contour, is generally flat over the line length at a depth of about 18 to 20 ft. At a downline distance of about 30 to 80 ft there is a zone where the near surface soil velocity values increase from less than 2,500 ft/s to greater than 3,000 ft/s. Generally, this could be an indication of increased soil saturation, but, in this case, it also corresponds to the road that this line crosses and is possibly related to increased soil compaction related to the road construction.

The results for Line 14-B show more variation in the depth to rock. At the start of the line, the depth to rock is about 20 ft, which stays mostly stable until about 100 ft down the line, where there the depth to rock appears to be about 10 ft below the surface. From there, the depth to rock increases again to about 20 ft, before being as shallow as about 6 ft at the end of the line. There is a zone of lower velocity rock between about 130 and 170 ft downline. This could indicate a zone of increased fracturing or weathering within the rock.

The results for Line 14-C show that the top of rock is generally about 14 to 20 ft below the ground surface over the full line, and is shallowest at about 90 ft down the line.

The results from Line 14-D show that the depth to rock starts at about 25 ft deep on the southeast portion of the line, with the rock becoming shallower to the northwest, where it is only about 15 ft deep at the line end. However, the agreement between the depth to rock as estimated with the 5,000 ft/s contour does not

September 12, 2022 Page 10 Aterra-Schnabel JV agree well with the borehole logs from B-244 and B-242. This can be explained by the fact that B-242 notes bedrock as medium strong to very weak, moderately weathered to severely weathered sandstone, while B-244 shows strong to medium, fresh to slightly weathered shale. This change in lithology down the line makes estimating a single velocity value more challenging.

The seismic data for Site 14 were also imaged as a 3D perspective view that can be helpful for visualization and quality control of the results where the lines intersect. Additionally, this 3D model can be helpful for observing site-wide trends in the results. The view looking from the east to the west is shown in Figure 8.

Figure 8: 3D Perspective View of Site 14 Seismic Refraction Results

5.0 SITE 15 GEOPHYSICAL INVESTIGATION

The Brush Creek Watershed Site 15 Dam is located in Mercer County, West Virginia, about 9.5 miles northeast of the City of Bluefield and about 6 miles southwest of the City of Princeton on the North Fork of Brush Creek (see Figure 1). The site is partially grassy, open area along the embankment and spillway, but part of Line 15-Alt and 15-A were located within heavy brush, including heavy multi-floral rose that required extensive clearing before data collection could be conducted (See Figure 9).

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Figure 9: Site Conditions at Site 15 at Time of Data Collection

A total of 1,020 lf of SR data were collected from April 4 through 6, 2022, along Lines 15-A, 15-B1, 15-B2, 15-Alt, and 15-E as shown on Figures 10 and C-1. Additionally, the GPS data for each line is given in Table C1 in Appendix C. Historical weather data from Weather Underground shows that there was about 1 inch of rainfall on May 27.

Figure 10: Site 15 Line Layout Map

Seismic Refraction Data Collection and Analysis

Schnabel personnel conducted an SR survey to evaluate the depth to rock and rippability of rock at the proposed auxiliary spillway cutoff walls and toe drains. Two Geometrics Geode seismographs were used with up to 48 10-Hz geophones with a geophone spacing of 5 ft for the embankment lines (Lines 15-B1

Derrick.Crane Cross-Out March (updated per comment response from ASJV 6/7/23)

Additionally ASJV states "We expect prior rainfall will have minimal to no effect on the results. "

September 12, 2022 Page 12 Aterra-Schnabel JV and 15-B2) and 2.5 ft for the spillway lines (Lines 15-Alt, 15-E, and 15-A). SR traverses extended beyond the length of the proposed survey lines, where accessible, to provide the necessary depth coverage along the traverses.

Seismic data processing was conducted using Rayfract Version 4 from Intelligent Resources. The processing involved Schnabel personnel manually picking first-arrival times of seismic energy, incorporating elevations into the data, and generating a model that matches the first arrivals. Gradational velocity changes are common in geologic environments with thicker zones of weathered and fractured bedrock, such as at this site; therefore, we performed a tomographic inversion to estimate these gradational changes in the P-wave velocities.

Seismic Refraction Results

The results from the SR survey for Site 15 are shown in Appendix C, Figure C-1. The SR results are displayed using color-coded cross-sections with key velocity contours overlaid. The geologic units, as noted in logs of boreholes located near the lines are overlaid on the geophysical results.

On each figure there is a plan-view image that shows the locations of the boreholes and seismic lines.

The symbols along each line are labeled to correspond to the horizontal axis of each line, which is referred to as the downline distance in the discussion of results below.

Comparing the SR results to the borehole logs indicates there is variation in the rock type, weathering, and strength that affects estimating a velocity contour to represent top of rock. For BH-257, located near the intersection of Lines 15-Alt and 15-E in the auxiliary spillway, the top of rock corresponds to a velocity value of 3,000 ft/s; however, for B-561 and AP-351 located in the embankment, the top of rock corresponds to a velocity value of 5,000 ft/s. The rock encountered at BH-257 is described as very weak, while the rock encountered in B-651, for example, is described as moderately strong. Therefore, within the auxiliary spillway, we interpret the 3,000 ft/s contour line as an estimate for the top of rock, while in the embankment the 5,000 ft/s contour is our estimate for top of rock. It is important to understand that these values represent the top of interpreted rock, not the actual velocity of the rock itself, which may be higher due to the nature of tomographic inversions and because the bulk of the rock is generally more competent, and therefore likely has a higher velocity, than the disintegrated rock/rock interface.

The results for Line 15-A show a generally flat laying velocity structure, with a depth to the 3,000 ft/s contour being about 8 to 15 ft and to the 5,000 ft/s contour being about 20 ft. There are no boreholes close to this line, so it is unknown if the 5,000 ft/s or 3,000 ft/s contour is best used as an estimate for top of rock; however, based on intersecting SR lines from close borings, we recommend considering the 3,000 ft/s contour to represent top of rock in the auxiliary spillway.

The results for Line 15-Alt indicate that rock is very shallow along the top of the auxiliary spillway (southwest portion of the line), and then gets deeper as the line extends down the hill. Assuming the correlation with B-257 holds for the line length, the 3,000 ft/s contour represents the top of rock along Line 15-Alt. There is thicker, low velocity material on the slope of the hillside compared to that at the top (start of the line) or very bottom (end of the line), ranging from about 5 to 14 ft based on the 3,000 ft/s contour.

It should be noted that Line 15-Alt extends down a steep slope and could encounter different rock conditions at the bottom of the slope than at the top, as observed elsewhere on this site.

The results for Line 15-E show that the top of rock, as defined by the 3,000 ft/s contour, varies between 6 ft deep on the northeast side and up to 12 ft deep on the southeast side.

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The results from Lines 15-B1 and 15-B2, the lines located along the toe of the embankment, show that rock is generally about 10 to 16 ft and 15 to 18 ft below the ground surface for Lines 15-B1 and 15-B2 respectively, based on the 5,000 ft/s contour line. At about 160 ft down the line on Line 15-B1, the velocity at the surface increases to over 2,000 ft/s, indicating possible increased surface moisture at that location.

The seismic data for Site 15 were also imaged as a 3D perspective view that can be helpful for visualization and quality control of the results where the lines intersect. Additionally, this 3D model can be helpful for observing site-wide trends in the results. The view looking from the southeast to the northwest is shown in Figure 11.

Figure 11: 3D Perspective View of Site 15 Seismic Refraction Results

6.0 LIMITATIONS

The data provided in this report are based on the information obtained from geophysical surveys performed by Aterra-Schnabel JV. The report also includes other physical data and information as indicated in investigations and work by others. Conditions at the sites may vary between the discrete locations observed at the time of our field investigations, the investigations by others, and from the methods and equipment used to conduct the respective subsurface investigations. The nature and extent of variations and physical properties may not become evident until future construction and/or additional investigation activities.

We have endeavored to complete the services identified herein in a manner consistent with that level of care and skill ordinarily exercised by members of the profession currently practicing in the same locality and under similar conditions as this project. No other representation, express or implied, is included or intended, and no warranty or guarantee is included or intended in this report or other instrument of service.

Results produced by the SR method are limited to the inherent physics of seismic waves traveling through earth materials. These limitations include: (1) the fact that material boundaries require a contrast in seismic velocity to be defined by the method; (2) low velocity materials cannot be identified below high velocity materials; (3) modeling thin dipping beds may look like a smooth gradational blurring of these boundaries or may be undulating; (4) assumptions that the seismic ray-paths are traveling below the

September 12, 2022 Page 14 Aterra-Schnabel JV seismic line at the ground surface, and not along a faster out-of-plane pathway; and (5) non-uniqueness, meaning that earth materials are not defined by a particular seismic velocity, differing materials may have the same velocity, and multiple conditions can produce the same results. Additional factors that affect the correlation of seismic refraction results with subsurface conditions include the resolution, which is based on the line spacing; geophone and shot spacing; and the amount of noise (traffic noise, wind, rain, or other vibrational energy sources) in the seismic data, which introduces subjectivity in selecting the data for input into the model.

September 12, 2022 Aterra-Schnabel JV

APPENDIX A

SITE 9 GEOPHYSICAL INVESTIGATION

RESULTS AND DATA

Figure A-1: Site 9 – A Lines Seismic Refraction Results Figure A-2: Site 9 – B Lines Seismic Refraction Results Figure A-3: Site 9 – C Lines Seismic Refraction Results Figure A-4: Site 9 – ERI Results

Table A-1: GPS Information for Site 9

Site 9 - A Lines Seismic Refraction

NRCS NE Brush Creek Additional Engineering Services

Mercer County, WV

SCHNABEL PROJECT NO. 18C35013.020

© Schnabel Engineering 2022 All Rights Reserved

FIGURE A-1

5000 5000

7000 70008000

8000 80009000

9000 9000

10000

10000

10000

10000

B-232 B-233

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 Downline Distance (feet)

El ev at io n (fe et

5000 5000

7000 7000 8000 8000

9000 9000

10000 10000

B-236

0 20 40 60 80 100 120 140 160 180 200 220 240

Downline Distance (feet)

El ev at io n (fe et

50007000 70008000 80009000

10000

10000

0 20 40 60 80 100 120 140 160 180 200 220 Downline Distance (feet)

El ev at io n (fe et

Line 9-A1

Line 9-A2-1

Line 9-A2-2

Northwest Southeast

West East

0 10 20 30 40

Seismic Profile Scale 1 inch = 40 feet

West East

Line B1 Intersection Line B2 Intersection Line B3 Intersection

Line B1 Intersection Line B3 Intersection

Line B1 Intersection Line B2 & A2-2

Intersection Line B3 Intersection

Line intersections Key

Top of strong to medium strong rock

10000

Ve lo cit y

(ft /s

Seismic Velocity Values and Interpretations

Rippability Estimates from Table 4-27 of NRCS National Engineering Handbook

9-C1

9-C2

9-C3

9-A1

9-A2-1

9-A2-2 9-B1 9-B2

9-B3

Notes:

Coordinates in UTM Zone 17N, Feet

White symbols with red text correspond to distance along velocity cross-sections.

Blue lines show ERI locations

Line B2 & A2-2 Intersection

GF-4

GF-202

GF-201

GF-1

GF-2

GF-3

1589200 1589300 1589400 1589500 1589600 1589700 1589800

Easting (feet)

No rt hi ng

(f ee t)

9-C1

9-C2

9-C3

9-A1

9-A2-1

9-A2-2 9-B1 9-B2

9-B3

0 50 100

1 inch = 150 feet

Notes:

Coordinates in UTM Zone 17N, Feet

White symbols with red text correspond to distance along velocity cross-sections.

Blue lines show ERI locations

Easy Ripping

Very Hard Ripping

Hard Ripping

Extremely Hard Ripping to Blasting

Borehole Key

GF-202

Schnabel Boreholes

Gennett Fleming Boreholes

5000 5000 7000 70008000 80009000 900010000

10000

B-235

0 20 40 60 80 100 120 140 160 180 200 220 Downline Distance (feet)

El ev at io n (fe et

50007000 70008000 80009000

10000

10000

0 20 40 60 80 100 120 140 160 180 200 220 Downline Distance (feet)

El ev at io n (fe et

Site 9 - B Lines Seismic Refraction

NRCS NE Brush Creek Additional Engineering Services

Mercer County, WV

SCHNABEL PROJECT NO. 18C35013.040

© Schnabel Engineering 2022 All Rights Reserved

10000

10000

0 20 40 60 80 100 120 140 160 180 200 220 Downline Distance (feet)

El ev at io n (fe et

Line 9-B1

Line 9-B2

Line 9-B3 0 10 20 30 40

Seismic Profile Scale 1 inch = 40 feet

Line A1 Intersection

Line A2-2 Intersection

Line A2-1 Intersection

Line A1 Intersection

Line A2-1 & A2-2 Intersection

Line B3 Intersection

Line B3 Intersection

Line A1 Intersection

Line A2-1 Intersection

Line A2-2 Intersection

Line B2 Intersection

Line B1 Intersection

North South

Northeast Southwest

Northeast Southwest

Line intersections Key

Top of strong to medium strong rock

10000

Seismic Velocity Values and Interpretations

Rippability Estimates from Table 4-27 of NRCS National Engineering Handbook

FIGURE A-2

GF-4

GF-202

GF-201

GF-1

GF-2

GF-3

1589200 1589300 1589400 1589500 1589600 1589700 1589800

Easting (feet)

No rt hi ng

(f ee t)

9-C1

9-C2

9-C3

9-A1

9-A2-1

9-A2-2 9-B1 9-B2

9-B3

0 50 100

1 inch = 150 feet

Notes:

Coordinates in UTM Zone 17N, Feet

White symbols with red text correspond to distance along velocity cross-sections.

Blue lines show ERI locations

Easy Ripping

Very Hard Ripping

Hard Ripping

Extremely Hard Ripping to Blasting

Borehole Key

Schnabel Boreholes

Site 9 - C Lines

NRCS NE Brush Creek Additional Engineering Services

Mercer County, WV

SCHNABEL PROJECT NO. 18C35013.040

© Schnabel Engineering 2022 All Rights Reserved

North South

10000

10000

10000

AP-331

AP-332 B-634

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320

Downline Distance (feet)

El ev at io n

(fe et

10000

10000

AP-332 B-634

0 20 40 60 80 100 120 140 160 180

Downline Distance (feet)

El ev at io n (fe et

10000

10000

0 20 40 60 80 100 120 140 160 180

Downline Distance (feet)

El ev at io n (fe et

Line 9-C1

Line 9-C2

Line 9-C3 0 10 20 30 40

Seismic Profile Scale 1 inch = 40 feet

North South

North South

Line C2 Intersection

Line C2 Intersection

Line C1 Intersection

Line C3 Intersection

Line intersections Key

Top of strong to medium strong rock

10000

Seismic Velocity Values and Interpretations

Rippability Estimates from Table 4-27 of NRCS National Engineering Handbook

FIGURE A-3

GF-4

GF-202

GF-201

GF-1

GF-2

GF-3

1589200 1589300 1589400 1589500 1589600 1589700 1589800

Easting (feet)

No rt hi ng

(f ee t)

9-C1

9-C2

9-C3

9-A1

9-A2-1

9-A2-2 9-B1 9-B2

9-B3

0 50 100

1 inch = 150 feet

Notes:

Coordinates in UTM Zone 17N, Feet

White symbols with red text correspond to distance along velocity cross-sections.

Blue lines show ERI locations

Easy Ripping

Very Hard Ripping

Hard Ripping

Extremely Hard Ripping to Blasting

Borehole Key

GF-4

Schnabel Boreholes

Site 9 - ERI ResultsNRCS NE Brush Creek Additional Engineering Services

Mercer County, WV

SCHNABEL PROJECT NO. 18C35013.020

© Schnabel Engineering 2022 All Rights Reserved

FIGURE A-4

9090 125125 175175 300

0 20 40 60 80 100 120 140 160 180 200 220 240 260 Distance Distance (ft)

El ev at io n

(ft

90 90

175 175

500700

0 20 40 60 80 100 120 140 160 180 200 220 240 260 Distance Distance (ft)

El ev at io n (ft

0 20 40 60 80 100 120 140 160 180 200 220 240 260 Distance Distance (ft)

El ev at io n (ft

West East

505050

175 175

300 300

700 90

0 20 40 60 80 100 120 140 160 180 200 220 240 260 Distance Distance (ft)

El ev at io n (ft

Line 9-D

Line 9-E Line 9-F

Line 9-G

0 10 20 30 40

ERI Profile Scale 1 inch = 40 feet

Line intersections Key

Historical Wetland Area

Wet/Soft Soil During Survey

West East

GF-4GF-4

GF-1

GF-2

GF-3

1589200 1589300 1589400 1589500 1589600 1589700 1589800 Easting (feet)

No rt hi ng

(f ee t)

9-G

9-F

0 50 100

1 inch = 150 feet

Notes:

Coordinates in UTM Zone 17N, Feet

White symbols with red text correspond to distance along velocity cross-sections.

Red lines show seismic locations

9-D 9-E

North South

Northeast Southwest

Finer soil and/or wetter soil or rock

Resistivity Generalized Interpretation Coarser soil and/or drier soil or rock

30 100 300

B-34

B-34

AP-331 B-634

water level ---

B-632 water level artesian

Line G Intersection

Line G Intersection

Line F Intersection

Line F Intersection

Line D Intersection

Line E Intersection

Line D Intersection

Line E Intersection

Line F Intersection

Line G Intersection

Wet/soft Soil During Survey

Historical Wetland Area

Historical Wetland Area

Wet/soft Soil During Survey

OS 3 ft N

Borehole Key

Schnabel Boreholes

APPENDIX B

SITE 14 GEOPHYSICAL INVESTIGATION

Figure B-1: Site 14 – Seismic Refraction Results

Table B-1: GPS Information for Site 14

10000

P- W av e

Ve lo cit y

(ft /s

Site 14 - Lines A-D Seismic Refraction

NRCS NE Brush Creek Additional Engineering Services

Mercer County, WV

SCHNABEL PROJECT NO. 18C35013.030

© Schnabel Engineering 2022 All Rights Reserved

FIGURE B-1

Northeast Souhwest

North South

Line D Intersection

Line intersections Key

Top of strong to medium strong rock

Seismic Velocity Values and Interpretations

Rippability Estimates from Table 4-27 of NRCS National Engineering Handbook

9-C1

9-C2

9-C3

9-A1

9-A2-1

9-A2-2 9-B1 9-B2

9-B3

Notes:

Coordinates in UTM Zone 17N, Feet

White symbols with red text correspond to distance along velocity cross-sections.

Blue lines show ERI locations

9-C1

9-C2

9-C3

9-A1

9-A2-1

9-A2-2 9-B1 9-B2

9-B3

Notes:

Coordinates in UTM Zone 17N, Feet

White symbols with red text correspond to distance along velocity cross-sections.

Blue lines show ERI locations

BH-061

BH-231

BH-232

BH-233

BH-234

BH-701

BH-702

1595100 1595200 1595300 1595400 1595500 1595600 1595700

Easting (feet)

No rt hi ng

(f ee t)

0 50 100

1 inch = 150 feet

5000 5000 5000 5000

7000 7000 7000

8000 8000 8000

9000 9000

10000

10000

10000 10000

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 Distance (feet)

El ev at io n (fe et

14-A

14-B

Line 14-A

10000 10000

B-243

B-642

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 Distance (feet)

El ev at io n (fe et

9000 10000

0 20 40 60 80 100 120 140 160 180 200 220 Distance (feet)

El ev at io n (fe et

Southeast Northwest

10000

10000

B-242 B-244

0 20 40 60 80 100 120 140 160 180 200 220 Distance (feet)

El ev at io n (fe et

Line 14-B

Line 14-C

Line 14-D

14-C

14-D

Southeast Northwest

Line C Intersection

Line A Intersection

Line A Intersection

Easy Ripping

Very Hard Ripping

Hard Ripping

Extremely Hard Ripping to Blasting

Borehole Key

BH-231

Schnabel Boreholes

NRCS

APPENDIX C

SITE 15 GEOPHYSICAL INVESTIGATION

Figure C-1: Site 15 – Seismic Refraction Results

Table C-1: GPS Information for Site 15

Site 15

NRCS NE Brush Creek Additional Engineering Services

Mercer County, WV

SCHNABEL PROJECT NO. 18C35013.040

© Schnabel Engineering 2022 All Rights Reserved

3000 3000

10000

0 20 40 60 80 100 120 140 160 180 200 Distance (feet)

El ev at io n (fe et

10000

B-257

0 20 40 60 80 100 120 140 160 180 200 220 240 260 Distance (feet)

El ev at io n (fe et

10000

10000

AP-351B-651

B-652

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 Distance (feet)

El ev at io n (fe et

10000

10000

B-651

0 20 40 60 80 100 120 140 160 180 200 220 240 Distance (feet)

El ev at io n (fe et

3000 3000 5000 5000

7000 7000 8000 8000

10000

B-257

0 20 40 60 80 100 120 140 160 180 200 Distance (feet)

El ev at io n (fe et

Line 15-A

Line 15-Alt

Line 15-E

Line 15-B1

Line 15-B2

Line Alt Intersection

Line Alt Intersection

Line E Intersection

Line A Intersection

Line B2 Intersection

Line B1 Intersection

West East

West East

Northwest Southeast

Northwest Southeast

Southwest Northeast

0 10 20 30 40

Seismic Profile Scale 1 inch = 40 feet

GF-3

BH-221

1586150 1586200 1586250 1586300 1586350 1586400 1586450 1586500 1586550 1586600 1586650 1586700 1586750 1586800 1586850 1586900 1586950 Easting (feet)

No rt hi ng

(f ee t)

15-B2

15-B1

-A lt

15-E

15-A

0 50 100

1 inch = 100 feet

Notes:

Coordinates in UTM Zone 17N, Feet

White symbols with red text correspond to distance along velocity cross-sections.

Line intersections Key

10000

Ve lo cit y

(ft /s

Top of very weak rock (as seen in auxillary spillway)

Top of strong to medium strong rock

Seismic Velocity Values and Interpretations

Rippability Estimates from Table 4-27 of NRCS National Engineering Handbook

FIGURE C-1

Easy Ripping

Very Hard Ripping

Hard Ripping

Extremely Hard Ripping to Blasting

Borehole Key

BH-221

Schnabel Boreholes

Gennett Fleming Boreholes

NRCS

6.0 LIMITATIONS