NCD003162542_Badin Business Park_Corrective Action_20190530

Badin Business Park LLC c/o Alcoa Corporation 201 Isabella Street Suite 500 Pittsburgh, PA 15212-5858 USA Tel: [phone]

May 30, 2019
Mr. Robert C. McDaniel Facility Management Branch Hazardous Waste Section
North Carolina Department of Environmental Quality
217 West Jones Street Raleigh, North Carolina 27603 VIA ELECTRONIC MAIL
Re: Geophysical Evaluation for the Little Mountain Creek Area Badin Business Park (f/k/a Alcoa - Badin Works) Badin, North Carolina EPA ID: NCD 003 162 542

Dear Mr. McDaniel: Badin Business Park LLC respectfully submits the above-referenced report for your review. The report is being provided as a condition of the April 2, 2018, Investigative Work Plan for the Phases 4 and 5
Corrective Measures Study, Alcoa/Badin Landfill, and Former Ball Field.
Should you have any questions or comments, please contact Jason Mibroda of Alcoa at [phone] at your convenience.
Sincerely,
Ronald M. Morosky
Director, Corporate Remediation
Enc. cc: Jason Mibroda, Alcoa

GEOPHYSICAL EVALUATION DOWN GRADIENT OF THE ALCOA BADIN
LANDFILL TO
EVALUATE POTENTIAL SEASONAL VARIABILITY IN ELECTROMAGNETIC
RESPONSE

PREPARED FOR ENVIRONEERING, INC.

by

Geo Solutions Ltd.

GEO SOLUTIONS LIMITED, INC. CONWAY, NORTH CAROLINA

May 2019

TABLE OF CONTENTS
1.0 INTRODUCTION .............................................................................................................................. 1
2.1 Multifrequency Electromagnetic Survey Theory ............................................................................. 2
2.2 Field Implementation ........................................................................................................................ 3
2.3 Method Verification and Data Quality ............................................................................................. 5
3.1 Quarter 1 Results ............................................................................................................................. 5
3.2 Quarter 2 Results ............................................................................................................................. 6
3.3 Quarter 3 Results ............................................................................................................................. 6
3.4 Quarter 4 Results ............................................................................................................................. 7
3.5 Quarterly Comparison ..................................................................................................................... 7
5.0 REFERENCES ................................................................................................................................... 9

LIST OF FIGURES

Figure 1. Site Location Map Figure 2. Site Map of Study Area
Figure 3. Map of Electromagnetic (EM) Profile Locations
Figure 4. Map of the Results of the Quarter 1 EM 32,190 Hz Apparent Conductivity Data
Figure 5. Map of the Results of the Quarter 2 EM 32,190 Hz Apparent Conductivity Data
Figure 6. Map of the Results of the Quarter 3 EM 32,190 Hz Apparent Conductivity Data Figure 7. Map of the Results of the Quarter 4 EM 32,190 Hz Apparent Conductivity Data
Figure 8. Comparison Map of the Four Quarterly Evaluations
Figure 9. Seasonal Trend of Elevated Apparent Conductivity and Size of Elevated Area
LIST OF TABLES
Table 1. Tabulated Quantitative Comparison of Quarterly Results.

LIST OF APPENDICIES
Appendix A. Quality Assurance and Quality Control Profiles for Each Quarterly Evaluation

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1.0 INTRODUCTION
Geo Solutions Limited, Inc. (Geo Solutions) is pleased to submit this report to ENVIRONEERING,
Inc. (ENVIRONEERING) for a geophysical evaluation at Alcoa Badin Landfill and downgradient
area adjacent to Little Mountain Creek, located in Badin, North Carolina. Figure 1 is a site location
map of the study area.
As specified in the April 2, 2018 Investigative Work Plan for the Phase 4 And 5 Corrective
Measures Study, Alcoa/Badin Landfill, And Former Ball Field as prepared by ENVIRONEERING,
an objective was established to delineate the linear extent of elevated constituent levels in the area
downgradient of the landfill and to monitor the effectiveness of a new trench collection system over an extended period of time. To accomplish the objective, Geo Solutions was contracted by
ENVIRONEERING to provide geophysical survey services for this project. The proposed
investigative activities included an electromagnetic (EM) survey as a method to evaluate the
electrical conductance in soil pore water downgradient of the Alcoa/Badin Landfill. This
methodology was supported as a means to correlate between inorganic water chemistry data and data from electrical-based geophysical methods (Benson 1985). These methods can also be used
for time-series measurements to obtain data on concentration dynamics (Benson 1988).

Due to a potential for seasonal variability, quarterly baseline geophysical evaluations were
conducted for a period of one year. The quarterly evaluations were used to establish a reference baseline condition. A long-term assessment of conditions may be evaluated through a comparison
of succeeding geophysical evaluations in comparison to baseline conditions.

Figure 1. Site Location Map with study area delineated in yellow.
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2.0 GEOPHYSICAL TECHNIQUES

2.1 Multifrequency Electromagnetic Survey Theory
As presented in the literature reference above, dissolved constituents in soil pore water will increase the electrical conductivity of the soil pore water with respect to background soil pore water
conditions. The soil pore water target, containing dissolved conductive materials, has a
characteristic combination of electrical conductivity, magnetic permeability properties, and
geometrical shape and size. When the target is exposed to a low-frequency electromagnetic field, it produces a secondary magnetic field. By measuring the broadband spectrum of the secondary field, it is possible to obtain a distinct spectral signature that may uniquely identify the target. Thus,
the response spectrum from conductive material is a “fingerprint” of the composition of the target.
This forms the general principles of electromagnetic induction spectroscopy (EMIS) (Won 1998).
The EM method is a non-contact (uncoupled) geophysical method that utilizes a multiple frequency electromagnetic detector (Geophex Model GEM-2). The EM instrument collects electromagnetic
responses in the in-phase (metal detection or magnetic susceptibility mode) and quadrature
(conductivity) mode. The GEM-2 operates in a frequency band between 30 Hz and 93kHZ. The
unit collects data at a rate of 30Hz or 30 data points per second. The GEM-2 detection depth is inversely related to frequency. In other words, a low frequency signal travels farther into the earth and can “see” deep features while a high frequency signal can only travel short distances and
therefore can only “see” shallow features. Therefore, if materials or conductive groundwater at
depth is concentrated in a particular zone, one frequency may “see” the effected area more clearly
than others. Below is a nomogram created by Geophex to display the estimated depth of detection as it relates to frequency and geology.

Multiple frequency electromagnetic evaluations are useful in characterizing targeted materials as well as the distribution of elevated conductivities in soil pore water across a site. Investigative activities at the Alcoa/Badin Landfill included quarterly EM evaluations as a method to detect
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seasonal variability of electrical conductance in soil pore water downgradient of the Alcoa/Badin Landfill.

2.2 Field Implementation

Geo Solutions completed four quarterly evaluations downgradient of the Alcoa Badin Landfill between the toe of the landfill and Little Mountain Creek. The approximate area evaluated during
each quarterly evaluation was twelve (12) acres (Figure 2). The four evaluations were completed
on the following dates: April 19, July 11, and October 15, 2018, and January 31, 2019. The
following documents Geo Solutions’ technical approach employed during each quarterly
geophysical survey to better understand the seasonal variability of the conductivity distribution and to evaluate the best season for long term geophysical monitoring of the site.

• Prior to beginning the first quarterly evaluation, Geo Solutions placed permanent stakes
marking the EM profile endpoints through the area south of the landfill. The stakes were spaced sixty (60) feet apart and ran from the fence near the toe of the landfill to Little
Mountain Creek for a total of twenty (20) profile lines. For navigation assistance, each
stake was marked with a number and alternated in color (red and white) thereby providing
consistency between the quarterly evaluations.

• The GEM-2 was operated in wireless configuration while evaluating the site. The GEM-2
unit was either mounted on PVC tubular sled and towed with a Polaris Ranger all-terrain
vehicle (ATV) or hand carried. The advantage of mounting the GEM-2 on a sled is related
to efficiency of data collection and stability of the unit. When mounted on the sled, the GEM -2 is positioned approximately 0.75 meters from the ground surface (photograph below). In this configuration, data was collected along the gravel road parallel to the
collection trench at the toe of the landfill slope. The GEM-2 was hand carried in the
remaining areas which included the slope of the landfill and the 20 transects in the area
south of the landfill.
• The EM data were collected simultaneously at six varying frequencies (1,470 Hz, 4,110 Hz,
9,810 Hz, 32,190 Hz, 60,000 Hz, and 90,030 Hz). The 32,190 Hz frequency produced the
strongest EM response over the site. This is likely related to the depth of conductive soil pore water. Based on the skin depth nomogram, the 32,190 Hz is most representative of the upper 4 to 6 feet corresponding to the targeted subsurface interval.

4

Photograph showing typical deployment of GEM-2 EM Profiler mounted on sled.

Photograph showing typical deployment of GEM-2 EM profiler in walking mode.
• Data was collected at the rate of thirty samples per second. The position of each sample
point was measured utilizing a Hemisphere Model A-325 GPS unit which is augmented by
the Wide Area Augmentation System (WAAS) and is capable of submeter accuracy that provided real-time location data. The GEM-2 communicated to a handheld data collector on board the Polaris Ranger ATV via Bluetooth.

• Prior to beginning and before ending the EM survey, a quality assurance and quality control
(QA/QC) profile was completed to test the response of the GEM-2 EM profiler. The QA/QC profile was 50-feet long with a steel plate in the center. Each QA/QC profile can
be found in Appendix A of this report.

• Geo Solutions competed the EM evaluation as parallel profiles along the gravel road and the toe of the landfill, and along the staked profiles through the area south of the landfill
(Figure 3). An effort was made to complete the same transects at each quarterly evaluation.
The sample spacing along each profile is a function of rate of travel of the sled or the pace
of walking. Here, the average sample spacing along each profile was less than 1 foot.

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• The EM data was transferred from the GEM-2 to a laptop computer using the WinGEM
Version 3 software provided by the manufacturer. During the transfer process, the
WinGEM software assigns Universal Transverse Mercator metric coordinates to each data
collection station, and calculates the apparent conductivity, sum of conductivity, and
magnetic susceptibility for each frequency collected using the system software. These data were then transferred to a Microsoft Excel spreadsheet and reviewed for data anomalies
such as poor GPS confidence levels that would likely result in poor coordinate assignments.
These data were used to compile a series of maps illustrating various responses using a
simple mapping program (Golden Software’s Surfer Mapping System Version 15).
2.3 Method Verification and Data Quality

Changes in the EM response from the landfill to the area south of the landfill were observed at each
quarterly evaluation with the landfill having more elevated EM response as compared to the area
south of the landfill. This would indicate that the data quality is of high integrity it is expected that the landfill would have more conductive soils and pore water than the downgradient area. QA/QC
profiles collected prior to beginning and after completed each quarterly evaluation indicate the
GEM-2 was working properly during each quarterly evaluation (Appendix A).
3.0 EM QUARTERLY RESULTS
The objective of the surveys was to delineate the linear extent of elevated constituent levels in the
area downgradient of the landfill and to monitor the effectiveness of a new trench collection system
over an extended period of time. To accomplish the objective, quarterly EM surveys were
completed to establish a baseline for monitoring the effectiveness of the new trench collection system.

3.1 Quarter 1 Results

Field data collection for the Quarter 1 evaluation was completed on April 19, 2018. Site soil conditions were moist during the survey with an isolated area of standing water on the west end of
the survey area south of the landfill. Figure 4 displays the results of the 32,190 Hz apparent
conductivity for Quarter 1 evaluation. The contrast between apparent conductivity values during
this quarterly survey was excellent with a notable contrast between background site conditions and
areas of elevated apparent conductivity values. The orange and red hues indicate areas of elevated apparent conductivity values while the yellow and green hues indicate background site conditions.

The demarcation between elevated apparent conductivity values and background site conditions
appears at approximately a value of 50 millisiemens per meter (mS/m). The total area containing
elevated apparent conductivity values was approximately 101,822 ft2. Apparent conductivity values increase to over 100 mS/m at the collection trench. Background conditions approaching 0 mS/m
were observed along Little Mountain Creek indicating that soil pore water containing elevated
apparent conductivity values was not intersecting Little Mountain Creek.

One additional area of slightly elevated apparent conductivities was observed on the west side of the survey area; however, this was attributed to standing water in the area. Three elevated areas of
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elevated conductivity along the slope of the landfill were noted and are believed to be related to the former seep collection areas. Several anomalous areas of elevated apparent conductivity of up to
1,000 mS/m were observed which were related to the remaining collection infrastructure at the site
including the leachate collection force main subsurface piping.
3.2 Quarter 2 Results
Field data collection for the Quarter 2 evaluation was completed on July 11, 2018. Site soil
conditions were moist during the survey with an isolated area of standing water on the west end of
the survey area south of the landfill. Figure 5 displays the results of the 32,190 Hz apparent
conductivity for the Quarter 2 evaluation. The contrast between apparent conductivity values during this quarterly evaluation was excellent with a notable contrast between background site
conditions and areas of elevated apparent conductivity values.

As with the previous quarterly evaluation, the demarcation between elevated apparent conductivity
values and background site conditions appears at approximately a value of 50 mS/m. The total area containing elevated apparent conductivity values was approximately 130,529 ft2, which is
28,707 ft2 larger than the Quarter 1 evaluation. Apparent conductivity values increase to over 100
mS/m at the collection trench. The three elevated areas along the slope of the landfill were noted
during the Quarter 2 survey as previous. Background conditions approaching 0 mS/m were
observed along Little Mountain Creek indicating that soil pore water containing elevated apparent conductivity values was not intersecting Little Mountain Creek.

One additional area of slightly elevated apparent conductivities was observed on the west side of
the survey area; however, this was attributed to standing water in the area. Several anomalous areas
of elevated apparent conductivity of up to 1,000 mS/m were observed which were related to the collection infrastructure at the site. These results of the survey are very similar to the Quarter 1
survey however, the contrast between the background site conditions and areas of elevated apparent
conductivity were greater. As shown on Figure 5, the elevated conductivity observed in areas in
the south of the landfill are consistent with the three former seep collection areas.
3.3 Quarter 3 Results

Field data collection for the Quarter 3 evaluation was completed on October 15, 2018. Site soil
conditions were moist during the survey with small areas of standing water on the western side of
the survey area. Little Mountain Creek appeared to have flooded between the Quarter 2 and Quarter 3 surveys as evidence by the presence of woody debris and high-water marks on trees in the
floodplain. Figure 6 displays the results of the 32,190 Hz apparent conductivity for the Quarter 2
evaluation.

The demarcation between elevated apparent conductivity values and background site conditions appears at approximately a value of 50 (mS/m). The total area containing elevated apparent
conductivity values was approximately 123,754 square feet, which is 6,775 ft2 smaller than the
second quarterly evaluation. Apparent conductivity values increase to over 100 mS/m at the
collection trench. As present in the first two quarters, three areas of elevated apparent conductivity
associated with the former seep collection areas were observed. Background conditions
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approaching 0 mS/m were observed along Little Mountain Creek indicating that soil pore water containing elevated apparent conductivity values was not intersecting Little Mountain Creek.

Several anomalous areas of elevated apparent conductivity of up to 1,000 mS/m were observed
which were related to the collection infrastructure at the site. These results of the survey are most
similar to Quarter 2 with the 50 (mS/m) contour reaching approximately the same distance to Little Mountain Creek. The distribution pattern of the contoured data was not a uniform as Quarter 2 and
an area along the western end of the slope of the landfill was slightly more conductive than previous
quarters.
3.4 Quarter 4 Results
Field data collection for the Quarter 4 evaluation was completed on January 31, 2019. Site soil
conditions were moist to wet during the survey with small areas of standing water throughout the
area south of the landfill especially on the western side of the study area. This quarterly survey
provided the best access into the area south of the landfill due to the vegetation being dormant. Figure 7 displays the results of the 32,190 Hz apparent conductivity. The contrast between apparent
conductivity values during this quarterly survey was excellent with a notable contrast between
background site conditions and areas of elevated apparent conductivity values.

The demarcation between elevated apparent conductivity values and background site conditions appears at approximately a value of 50 (mS/m). The total area containing elevated apparent
conductivity values was approximately 83,607 ft2, which is 40,147 ft2 smaller than the third
quarterly evaluation. Apparent conductivity values increase to over 100 mS/m at the collection
trench. The three suspected seep areas along the slope of the landfill were observed during the
Quarter 4 evaluation. Background conditions approaching 0 mS/m were observed along Little Mountain Creek indicating that soil pore water containing elevated apparent conductivity values
was not intersecting Little Mountain Creek.

Several anomalous areas of elevated apparent conductivity of up to 1,000 mS/m were observed
which were related to the collection infrastructure at the site. As compared to the other 3 quarterly evaluations, Quarter 4 displayed the weakest contrast between areas of elevated apparent
conductivity and background site conditions. The Quarter 4 evaluation was most similar to Quarter
1.
3.5 Quarterly Comparison

A comparison of each quarterly evaluation is presented on Figure 8. Here, the 50 mS/m contour
which we have chosen as an indicator for elevated conductivity for each quarterly evaluation has been delineated to compare the seasonal distribution of the apparent conductivity response in the
areas adjacent to Little Mountain Creek. Quarter 2 and 3 have the largest area at or above 50 mS/m
over the area south of the landfill which would suggest the dissolved constituent levels in the soil
pore space is more concentrated during the warm season. Moreover, the Quarter 4 evaluation, which was collected during the seasonally wetter Winter, showed the weakest apparent conductivity values and had the smallest area above 50 mS/m over the area south of the landfill.

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A statistical analysis of the 50 mS/m or greater footprint areas of each season was completed. Data presented in Table 1 below can be used to quantitively compare the seasonal results based on the
50 mS/m demarcation between background and elevated apparent conductivity. The Summer and
Fall evaluations provided the highest average apparent conductivity values while the Winter was
significantly lower than the other seasons. This season variability should be considered if a long-
term monitoring program is established.
Table 1. Season Comparison of Elevated area south of the Alcoa/Badin Landfill
Quarterly
Evaluation
Date
Surveyed Size of Elevated Area (ft2)
Average Apparent Conductivity
Value (mS/m) Within Elevated
Area
1 4/19/2018 101,822 98.42
2 7/11/2018 130,529 101.43
3 10/15/2018 123,754 102.42
4 1/31/2019 83,607 90.39

4.0 CONCLUSIONS

The objective of the quarterly surveys at the Alcoa Badin Landfill was to delineate the linear extent
of elevated constituent levels as a function of elevated apparent conductivity and to establish a
baseline for monitoring the effectiveness of the new trench collection system. Below are the
conclusions of the quarterly evaluations and recommendations for future testing.

• Based on a comparison of the quarterly EM evaluations, the Summer and early Fall provided
the best contrast between background site conditions and the areas of elevated apparent
conductivity. Subsequent EM evaluations for long-term monitoring should be conducted
during this time period. The Quarter 4 evaluation, which was collected during the seasonally wetter Winter, displayed the weakest contrast.
• The distribution of the apparent conductivity response into the area adjacent to Little
Mountain Creek appears to correlate well with locations of the former seep collection areas or known areas of dissolved constituents within the boundary of the landfill.
• All four quarterly evaluations suggest that as a function of elevated EM apparent
conductivity response, dissolved constituents in the pore water do not appear to intersect
Little Mountain Creek.

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5.0 REFERENCES
I.J. Won, D.A. Keiswetter, and E. Novikova, 1998, Electromagnetic induction spectroscopy,
Journal of Environmental and Engineering Geophysics, v. 3, Issue 1, pp. 27-40.

Benson, R.C., M.S. Turner, W.D. Vogelsong and P.P. Turner, Correlation between field geophysical measurements and laboratory water sample analysis, Proceedings of the Conference
on Surface and Borehole Geophysical Methods in Ground Water Investigations, National Water
Well Association, Worthington, OH, pp. 178–197, 1985.

Benson, R.C., M.S. Turner, P.P. Turner and W.D. Vogelsong, In situ, time-series measurements for long-term ground-water monitoring, in Ground Water Contamination: Field Methods, ASTM STP
963, Collins, A.G. and Johnson, A.I. Eds., American Society for Testing and Materials,
Philadelphia, PA, 1988, pp. 58–72.

LEGEND
Site Map
GEOPHYSICAL EVALUATION
Alcoa Badin Landfill, Badin NC
0 150 300 450
Map Scale (ft)
Collection Trench
Survey Boundary
1"=150'
FIGURE 2
Approximate Location
of Little Mountain Creek
LEGEND
MULTIFREQUENCY EM
GEOPHYSICAL EVALUATION
EM Profiles
Alcoa Badin Landfill, Badin NC
0 150 300 450
Map Scale (ft)
FIGURE 3
Collection Trench
1"=150'
Indicates Location of
MFEM Data Point
Collection Trench
Approximate Location
of Little Mountain Creek
FIGURE 4
LEGEND
Apparent Conductivity
Data
32190 Hz
-78
-70
-62
-54
-46
-38
-30
-22
-14
-6
2
10
18
26
34
42
50
58
66
74
1000
MULTIFREQUENCY EM
GEOPHYSICAL EVALUATION
Quarter 1.
Surveyed: April 19, 2019
Alcoa Badin Landfill, Badin NC
0 150 300 450
Map Scale (ft)
Standing Water
1"=150'
Collection Trench
Approximate Location
of Little Mountain Creek
LEGEND
Apparent Conductivity
Data
32190 Hz
-78
-70
-62
-54
-46
-38
-30
-22
-14
-6
2
10
18
26
34
42
50
58
66
74
1000
MULTIFREQUENCY EM
GEOPHYSICAL EVALUATION
Quarter 2
Surveyed: 07/11/2018
Alcoa Badin Landfill, Badin NC
0 150 300 450
Map Scale (ft)
1"=150'
Collection Trench
FIGURE 5
Standing Water
LEGEND
Apparent Conductivity
Data
32190 Hz
-78
-70
-62
-54
-46
-38
-30
-22
-14
-6
2
10
18
26
34
42
50
58
66
74
1000
MULTIFREQUENCY EM
GEOPHYSICAL EVALUATION
Quarter 3.
Surveyed: 10/15/2018
Alcoa Badin Landfill, Badin NC
0 150 300 450
Map Scale (ft)
FIGURE 6
Collection Trench
1"=150'
Standing Water
Approximate Location
of Little Mountain Creek
LEGEND
Apparent Conductivity
Data
32190 Hz
MULTIFREQUENCY EM
GEOPHYSICAL EVALUATION
Quarter 4.
Surveyed: 01/31/19
Alcoa Badin Landfill, Badin NC
0 150 300 450
Map Scale (ft)
FIGURE 7
Collection Trench
1"=150'
-78
-70
-62
-54
-46
-38
-30
-22
-14
-6
2
10
18
26
34
42
50
58
66
74
1000
Standing Water
Approximate Location
of Little Mountain Creek
LEGEND
MULTIFREQUENCY EM
GEOPHYSICAL SURVEY
Comparison of the Four Quarters
Alcoa Badin Landfill, Badin NC
0 150 300 450
Map Scale (ft)
FIGURE 8
Collection Trench
1"=150'
Quarter 1. April
Quarter 2. July
Quarter 3. October
Quarter 4. January
Delineation of the
50 mS/m Contour
Approximate Location
of Little Mountain Creek
88.00
90.00
92.00
94.00
96.00
98.00
100.00
102.00
104.00
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
2/19/2018 4/10/2018 5/30/2018 7/19/2018 9/7/2018 10/27/2018 12/16/2018 2/4/2019 3/26/2019 Mean Apparent Conductivity (ms/m)Area (ft2)Date
Figure 9. Seasonal Trend of Elevated Apparent Conductivity and Size of
Elevated Area
Area
Apparent Conductivity
APPENDIX A. Quality Assurance and Quality Control (QA/QC) Profiles

Quarter 1. QA/QC

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QA/QC Profile 1
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QA/QC Profile 2
Quarter 2. QA/QC

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QA/QC Profile 1
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QA/QC Profile 2
Quarter 3. QA/QC

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0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 4832190 Hz Apparent Conductivity (mS/m)Distance (ft)
QA/QC Profile 1
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QA/QC Profile 2
Quarter 4. QA/QC

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0 4 7 11 15 19 22 26 30 33 37 41 44 4832190 Hz Apparent Conductivity (mS/m)Distance (ft)
QA/QC Profile 1
0.00
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0 5 10 14 19 24 29 33 38 43 4832190 Hz Apparent Conductivity (mS/m)Distance (ft)
QA/QC Profile 2