WS-5015_17048_CA_MRP_20190219

TABLE OF CONTENTS

1.0 INTRODUCTION........................................................................................................1
2.0 SITE BACKGROUND ................................................................................................1
3.0 GROUNDWATER SAMPLING EVENT .................................................................3
3.1 Groundwater Flow Direction ....................................................................................3
3.2 Groundwater Sampling .............................................................................................3
4.0 CONCLUSIONS AND RECOMMENDATIONS .....................................................4

TABLES
Table 1 Well Construction Details and Groundwater Elevation Data
Table 2 Groundwater Analytical Data
Table 3 Historical Groundwater Analytical Data

FIGURES Figure 1 Site Topographic Map
Figure 2 Site Map
Figure 3 Potentiometric Map
Figure 4 Constituents of Concern Map

APPENDICES
Appendix A Laboratory Analytical Results

Groundwater Monitoring Report February 19, 2019 NCDEQ Incident No. 17048 NCDOT Elkin Maintenance Facility
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1.0 INTRODUCTION

ATC Associates of North Carolina, P.C. (ATC), on behalf of the North Carolina Department of
Transportation (NCDOT) Roadside Environmental Unit, is submitting this Groundwater
Monitoring Report for the NCDOT Elkin Maintenance Facility located at 150 Northwood Drive in
Elkin, Surry County, North Carolina (Incident #17048). A site topographic map showing the
location of the site is presented as Figure 1 and site map depicting pertinent site features is
presented as Figure 2. The NCDOT continues to occupy the site. This report includes the results
for a groundwater monitoring event performed at the site on December 26-27, 2018.

2.0 SITE BACKGROUND

Presently, the site property is owned and occupied by the NCDOT. The property covers
approximately 7.44 acres and is located in an area characterized by rural and residential use.
Various office building, storage buildings and sheds are located on the property. The subsurface
investigation focus is located on the west-southwestern portion of the property.

In October/November 1990, NCDOT personnel removed seven USTs and one aboveground tank
at the Elkin Maintenance yard. Contamination was discovered associated with one of the
gasoline USTs and one of the diesel USTs. Upon identifying contamination, no additional
impacted soil was excavated at the time of tank closure. The site is still an active UST site
registered as facility ID #0-024854.

In August 2001, Environmental Investigations installed three Type II monitoring wells (MW-1
through MW-3) to determine if groundwater had been impacted. Groundwater samples collected
indicated BTEX (benzene, toluene, ethylbenzene, and xylenes) in the 3 monitoring wells.
Groundwater collected from MW-1 contained 1,700 parts per billion (ppb) of benzene. Based on
the results of groundwater samples from MW-1 through MW-3, a Phase II assessment was begun
in January 2002. One deep monitoring well and three additional shallow monitoring wells were
installed in an attempt to establish the extent of the plume. The Phase I report dated May 31,
Groundwater Monitoring Report February 19, 2019 NCDEQ Incident No. 17048 NCDOT Elkin Maintenance Facility
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2002, identified two up-gradient inactive water supply well within 1,000 feet. The inactive water
supply wells are located approximately 345 feet and 885 feet from the site. MW-4 was identified
to contain 9,700 ppb of benzene. Additional wells and soil borings were recommended to
complete a Comprehensive Site Assessment (CSA) report.

Veetech, PC, installed an additional deep monitoring well and three additional shallow
monitoring wells as part of their CSA. The CSA report dated December 12, 2002 defines the
extent of the plume as being approximately 180 feet by 120 feet and 114 feet deep. The soil was
shown to contain as much as 12,800 ppm of total VOC’s. Depth to groundwater varied from 37
to 50 feet deep across the site. Bedrock was encountered at 104 feet in MW-1B.

During the assessment, one sparge well and three soil vacuum extraction wells were installed for
a pilot test. Veetech subcontracted with Piedmont Industrial Services to conduct a sparge and
vacuum pilot test. Piedmont conducted the test over a two day period and their report is presented
in Appendix A of the Corrective Action Plan (CAP) by Veetech, dated January 8, 2003.
According to Piedmont’s report, the radius of influence for the sparge and vacuum wells was
estimated to be 45 feet and 40 feet, respectively. Based on the pilot test report, Veetech proposed
to install a sparge and vacuum system with three sparge and four vacuum wells. The CAP
proposed to remediate only the area where groundwater contamination exceeds the Gross
Contamination Levels for Groundwater (GCL’s).

Groundwater samples were collected on April 23, 2008 from all existing monitoring wells. These
samples were submitted for analyses by Method 6210D, including methyl tertiary-butyl ether
(MTBE) and isopropyl ether. Two of the monitoring wells, MW-4 and FOMW-1, were found to
contain high levels of gasoline constituents. There wells have benzene levels at 8,400 ppb and
8,600 ppb, respectively. Other wells further down-gradient remain clean. The potentiometric map
was similar to previous maps.

Groundwater Monitoring Report February 19, 2019 NCDEQ Incident No. 17048 NCDOT Elkin Maintenance Facility
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In correspondence dated May 8, 2018, NCDEQ requested that NCDOT complete a groundwater
sampling event at the site. As a result, ATC completed the groundwater sampling event in
December 2018 on behalf of NCDOT. This report presents the findings of that sampling event.

3.0 GROUNDWATER SAMPLING EVENT

3.1 Groundwater Flow Direction
ATC mobilized to the site on December 26, 2018, to sample monitoring wells MW-1 through
MW-8, MW-1A, MW-1B, FOMW-1, and GMW-1. Depth to groundwater measurements were
collected from the wells prior to sampling using an oil/water interface probe. Free product was
not detected in any of the screened monitoring wells. Depth to water measurements ranged from
33.51 feet below ground surface (bgs) in MW-6 to 51.04 feet bgs in MW-1B. Monitoring well
construction details and depth to groundwater data are included as Table 1. A Potentiometric
Map is presented as Figure 3. Based on the referenced Potentiometric Map, groundwater flow
appears to be in a southern direction.

3.2 Groundwater Sampling
Groundwater samples were collected from monitoring wells MW-1 through MW-8, MW-1A,
MW-1B, FOMW-1, and GMW-1 on December 26-27, 2018. The groundwater samples were
collected in laboratory-approved containers, packed in ice and delivered under chain-of-custody
protocol to Prism Laboratories, Inc. in Charlotte, North Carolina. The groundwater samples were
analyzed for volatile organic compounds (VOCs) by EPA Method 6200B and for 1,2-
Dibromoethane (EDB) by EPA Method 504.1.

The laboratory analytical results indicated the presence of benzene, MTBE, isopropyl ether, 1,2-
Dichloroethane, and naphthalene above the 2L Standards. No compounds were detected above
GCLs. Groundwater analytical data is summarized in Table 2 and historically groundwater data
is presented in Table 3. Constituents identified exceeding their respective 2L standards are
presented on Figure 4.
Groundwater Monitoring Report February 19, 2019 NCDEQ Incident No. 17048 NCDOT Elkin Maintenance Facility
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As part of ATC’s quality assurance and quality control (QA and QC) measures, a data review of
the laboratory report was conducted. During the review, it was concluded that samples were
received by the laboratory in acceptable condition. The laboratory report is included as
Appendix A.

4.0 CONCLUSIONS AND RECOMMENDATIONS

Based on the results of the groundwater sampling event conducted on December 26-27, 2018,
ATC concludes the following:
 Groundwater flows to the south across the site;
 Free product was not detected in any monitoring wells; and
 Benzene, MTBE, isopropyl ether, 1,2-Dichloroethane, and naphthalene exceeded 2L
Standards. No compounds exceeded GCLs.

Information presented in the May 31, 2002 Phase I Limited Site Assessment Report prepared by
VEETech, P.C. indicated that no active water supply wells were identified within 1,000 feet of
the site and that drinking water is supplied to the site and surrounding area by the Town of Elkin.
Given this information about water supply, and since concentrations of targeted compounds were
below GCLs, ATC recommends the incident be re-ranked as Low Risk.

TABLES DRAFT
TABLE 1
WELL CONSTRUCTION DETAILS AND GROUNDWATER ELEVATION DATA

NCDOT ELKIN MAINTENANCE FACILITY
150 NORTHWOOD DRIVE
WLKIN, SURRY COUNTY, NORTH CAROLINA
NCDEQ INCIDENT #17048
DTW (ft) GW Elev. (Ft.) DTW (ft) GW Elev. (Ft.) DTW (ft) GW Elev. (Ft.) DTW (ft) GW Elev. (Ft.) DTW (ft) GW Elev. (Ft.)
MW-1 2 60.65 98.57 49.67 48.9 49.43 49.14 50.34 48.23 55.2 43.37 50.18 48.39
MW-1A 2 89.00 98.86 50.07 48.79 49.74 49.12 50.78 48.08 55.65 43.21 50.42 48.44
MW-1B 2 114.00 98.86 50.58 48.28 50.6 48.26 51.54 47.32 56.28 42.58 51.04 47.82
MW-2 2 60.20 100.09 50.31 49.78 49.58 50.51 50.67 49.42 55.57 44.52 50.71 49.38
MW-3 2 58.60 100.74 NM NM NM NM 50.58 50.16 55.75 44.99 50.61 50.13
MW-4 2 62.90 98.57 50.02 48.55 49.73 48.84 50.68 47.89 54.09 44.48 50.80 47.77
MW-5 2 62.15 97.63 48.72 48.91 48.42 49.21 49.33 48.3 54.32 43.31 48.95 48.68
MW-6 2 36.70 79.75 NM NM NM NM NM NM 37.95 41.8 33.51 46.24
MW-7 2 54.34 85.94 37.9 48.04 37.81 48.13 38.75 47.19 43.55 42.39 38.41 47.53
MW-8 2 54.75 85.32 36.93 48.39 36.84 48.48 37.58 47.74 42.57 42.75 37.81 47.51
FOMW-1 2 64.00 97.5 NM NM 48.71 48.79 NM NM 55.57 41.93 49.77 47.73
GMW-1 2 54.58 86.15 NM NM NM NM NM NM 44.98 41.17 40.37 45.78
Notes:
2. DTW (Ft.) = Depth to Water in Feet.
1. TOC Elev. = Top of Casing Elevation in Feet.
3. GW Elev. (Ft.) = Groundwater Elevation in Feet.
09/18/03 03/30/04 09/22/04 04/23/08 12/27/18
Well ID TOC Elev. (Ft.)
Well
Diameter
(inches)
Total
Depth
(Ft.)DRAFT
TABLE 2
GROUNDWATER ANALYTICAL DATA

NCDOT ELKIN MAINTENANCE FACILITY
150 NORTHWOOD DRIVE
WLKIN, SURRY COUNTY, NORTH CAROLINA
NCDEQ INCIDENT #17048
FOMW-1 GMW-1 MW-1 MW-1A MW-1B MW-2 MW-3 MW-4 MW-5 MW-6 MW-7 MW-8
12/27/2018 12/26/2018 12/27/2018 12/27/2018 12/27/2018 12/27/2018 12/26/2018 12/27/2018 12/27/2018 12/26/2018 12/26/2018 12/26/2018
Benzene 1 5,000 <0.048 <0.048 0.94 63 0.67 0.46 J <0.048 980 <0.048 <0.048 <0.048 <0.048
Toluene 600 260,000 <0.044 <0.044 <0.044 2.2 <0.044 2.5 <0.044 8.4 <0.044 <0.044 <0.044 <0.044
Ethylbenzene 600 84,500 <0.061 <0.061 <0.061 1.2 <0.061 11 <0.061 130 <0.061 <0.061 <0.061 <0.061
Xylenes, total 500 85,500 <0.15 <0.15 <0.15 1.2 J <0.15 47 <0.15 90 <0.15 <0.15 <0.15 <0.15
Methyl-tert-Butyl Ether 20 20,000 0.26 J <0.042 36 28 <0.042 <0.042 <0.042 5,000 <0.042 <0.042 <0.042 <0.042
Isopropyl Ether 70 70,000 3.4 <0.050 300 170 26 <0.050 <0.050 5,200 <0.050 <0.050 <0.050 <0.050
1,2,4-Trimethylbenzene 400 28,500 <0.054 <0.054 0.63 0.82 <0.054 15 <0.054 69 <0.054 <0.054 <0.054 <0.054
1,2-Dichloroethane 0.4 400 <0.066 <0.066 1 3.9 7 <0.066 <0.066 23 <0.066 <0.066 <0.066 <0.066
1,2-Dibromoethane (EDB)0.02 50 <0.0025 <0.0024 <0.0025 <0.0025 <0.0024 <0.0025 <0.0025 <0.0025 <0.0025 <0.0024 <0.0025 <0.0025
1,3,5-Trimethylbenzene 400 25,000 <0.076 <0.076 <0.076 <0.076 <0.076 5.2 <0.076 <0.76 <0.076 <0.076 <0.076 <0.076
4-Isopropyltoluene 25 11,700 <0.089 <0.089 <0.089 0.46 J <0.089 <0.089 <0.089 7.8 <0.089 <0.089 <0.089 <0.089
Chloroform 70 70,000 <0.076 0.97 <0.076 <0.076 <0.076 7.2 <0.076 <0.76 <0.076 <0.076 0.27 J <0.076
Isopropylbenzene (Cumene)70 25,000 <0.054 <0.054 <0.054 3.6 <0.054 0.68 <0.054 6.6 <0.054 <0.054 <0.054 <0.054
Methyl Isobutyl Ketone 100 100,000 <0.078 <0.078 <0.078 <0.078 <0.078 <0.078 <0.078 13 <0.078 <0.078 <0.078 <0.078
Naphthalene 6 6,000 <0.19 <0.19 <0.19 11 <0.19 2.7 <0.19 40 <0.19 <0.19 <0.19 <0.19
n-Butylbenzene 70 6,900 <0.076 <0.076 <0.076 0.97 <0.076 0.29 J <0.076 <0.76 <0.076 <0.076 <0.076 <0.076
n-Propylbenzene 70 30,000 <0.087 <0.087 <0.087 0.87 <0.087 2.5 <0.087 16 <0.087 <0.087 <0.087 <0.087
sec-Butylbenzene 70 8,500 <0.076 <0.076 <0.076 2.3 <0.076 <0.076 <0.076 <0.76 <0.076 <0.076 <0.076 <0.076
tert-Butylbenzene 70 15,000 <0.088 <0.088 <0.088 0.87 <0.088 <0.088 <0.088 <0.88 <0.088 <0.088 <0.088 <0.088
Notes:
1. < # - Not detected above the metod detection limit.
2. J = Indicates constituent was detected above laboratory detection limit but below laboratory reporting limit.
3. Concentrations are reported in micrograms per liter (µg/l).
4. Concentrations in bold print equal or exceed the April 1, 2013 NCDEQ 15A 2L NCAC Groundwater Standard (NC2L).
5. GCL = Gross Contamination Level.
6. Concentrations shaded equal or exceed the GCL.
ANALYTE NC2L GCL
DRAFT
TABLE 3
HISTORICAL GROUNDWATER
ANALYTICAL DATA

NCDOT ELKIN MAINTENANCE FACILITY
150 NORTHWOOD DRIVE
WLKIN, SURRY COUNTY, NORTH CAROLINA
NCDEQ INCIDENT #17048
Date Benzene Toluene Ethylbenzene
Xylenes,
total
Methyl-tert-
Butyl Ether
Isopropyl
Ether
1,2 Dichloro-
ethane
NC 2L 1 600 600 500 20 70 0.4
GCL 5,000 260,000 84,500 85,500 20,000 70,000 400
08/24/01 1,700 770 46 470 BDL BDL BDL
05/09/02 680 BDL BDL BDL BDL BDL BDL
09/18/03 522 BDL BDL BDL BDL 56 BDL
03/30/04 53.4 BDL BDL BDL BDL 52 BDL
09/22/04 9.3 BDL BDL BDL BDL 66.3 BDL
04/23/08 220 BRL BRL BRL 0.77 150 3.9
12/27/2018 0.94 BRL BRL BRL 36 300 1
02/01/02 8,000 4,700 700 3,500 BDL 800 BDL
05/09/02 7,500 9,400 1,100 4,600 BDL 490 BDL
09/18/03 BDL BDL BDL BDL BDL BDL BDL
03/30/04 139 BDL BDL BDL BDL 33 BDL
09/22/04 BDL BDL BDL BDL BDL BDL BDL
04/23/08 850 12 370 51.3 13 140 45
12/27/2018 63 2.2 1.2 1.2 J 28 170 3.9
05/09/02 85 1.3 1.8 6 BDL 85 BDL
09/18/03 23.4 BDL BDL BDL BDL 80.4 BDL
03/30/04 15.5 BDL BDL BDL BDL 94.3 BDL
09/22/04 4.5 BDL BDL BDL BDL 55.7 BDL
04/23/08 BRL BRL BRL BRL BRL 54.0 15
12/27/2018 0.67 BRL BRL BRL BRL 26 7.0
08/24/01 18 64 18 82 BDL BDL BDL
05/09/02 5 12 4.7 16 BDL BDL BDL
09/18/03 5.1 49.4 17.6 144 BDL BDL BDL
03/30/04 6.4 48 16.8 140 BDL BDL BDL
09/22/04 8.3 11.6 BDL 66 25.7 BDL BDL
04/23/08 20 120 68 305 BRL BRL BDL
12/27/2018 0.46 J 2.5 11 47 BRL BRL BRL
08/24/01 BDL 33 77 160 BDL 70 BDL
05/09/02 BDL BDL BDL BDL BDL 40 BDL
09/18/03 NA NA NA NA NA BDL BDL
09/22/04 2.7 21.3 BDL 81.1 BDL 13.5 BDL
04/23/08 BRL BRL BRL 3.1 BRL 2 0.66
12/26/2018 BRL BRL BRL BRL BRL BRL BRL
02/01/02 9,700 15,000 1,100 7,800 1,800 8,200 BDL
05/09/02 10,000 16,000 1,400 7,200 1,900 9,500 BDL
09/18/03 9,900 6,030 1,050 6,000 1,850 8,130 BDL
03/30/04 12.7 BDL BDL 6.08 94.8 766 BDL
09/22/04 7.79 BDL BDL BDL BDL 455 9.9
04/23/08 8,400 290 1,900 3,870 170 240 BDL
12/27/2018 980 8.4 130 90 5,000 5,200 23
02/01/02 0.72 BDL 1.3 1.5 BDL 1.9 BDL
05/09/02 BDL BDL BDL BDL BDL BDL BDL
09/18/03 10.1 7.9 BDL 5.5 BDL 18.0 BDL
03/30/04 BDL BDL BDL BDL BDL BDL BDL
09/01/04 BDL BDL BDL BDL BDL BDL BDL
04/23/08 BRL BRL BRL BRL BRL 6.7 2.4
12/27/2018 BRL BRL BRL BRL BRL BRL BRL
MW-2
MW-3
MW-4
MW-5
Well ID
MW-1
MW-1A
MW-1B DRAFT
TABLE 3
HISTORICAL GROUNDWATER
ANALYTICAL DATA

NCDOT ELKIN MAINTENANCE FACILITY
150 NORTHWOOD DRIVE
WLKIN, SURRY COUNTY, NORTH CAROLINA
NCDEQ INCIDENT #17048
Date Benzene Toluene Ethylbenzene
Xylenes,
total
Methyl-tert-
Butyl Ether
Isopropyl
Ether
1,2 Dichloro-
ethane
NC 2L 1 600 600 500 20 70 0.4
GCL 5,000 260,000 84,500 85,500 20,000 70,000 400
Well ID
02/01/02 BDL BDL BDL 1.0 BDL BDL BDL
05/09/02 BDL BDL BDL BDL BDL BDL BDL
09/18/03 NA NA NA NA NA BDL BDL
04/23/08 BRL BRL BRL BRL BRL BDL BDL
12/26/2018 BRL BRL BRL BRL BRL BRL BRL
05/22/02 BDL BDL BDL BDL BDL BDL BDL
09/18/03 BDL BDL BDL BDL BDL BDL BDL
03/30/04 BDL BDL BDL BDL BDL BDL BDL
09/22/04 BDL BDL BDL BDL BDL BDL BDL
04/23/08 BRL BRL BRL BRL BRL BDL BDL
12/26/2018 BRL BRL BRL BRL BRL BRL BRL
05/22/02 BDL BDL BDL BDL BDL BDL BDL
09/18/03 BDL BDL BDL BDL BDL BDL BDL
03/30/04 BDL BDL BDL BDL BDL BDL BDL
09/22/04 BDL BDL BDL BDL BDL BDL BDL
04/23/08 BRL BRL BRL BRL BRL BDL BDL
12/26/2018 BRL BRL BRL BRL BRL BRL BRL
04/03/02 2 BDL BDL 2 25 BDL BDL
09/18/03 BDL BDL BDL BDL BDL BDL BDL
03/30/04 BDL BDL BDL BDL BDL BDL BDL
04/23/08 8,600 4,800 920 5,200 5,700 10,000 83
12/27/2018 BRL BRL BRL BRL 0.26 J 3.4 BRL
09/18/03 NA NA NA NA N/A N/A BDL
04/23/08 BRL BRL BRL BRL BRL BRL BDL
12/26/2018 BRL BRL BRL BRL BRL BRL BRL
Notes:
1. < # - Not detected above the specified limit
2. J = Indicates constituent was detected above laboratory detection limit but below laboratory reporting limit
3. Concentrations are reported in micrograms per liter (µg/l).
4. Concentrations highlighted and in bold print equal or exceed the April 1, 2013 NCDEQ 15A 2L NCAC Groundwater Standard (NC2L).
5. BDL = Below Detection Limit.
6. BRL = Below Reporting Limit.
7. GCL = Gross Contamination Level.
8. Concentrations shaded equal or exceed the GCL.
FOMW-1
GMW-1
MW-6
MW-7
MW-8
DRAFT

FIGURES

DRAFT
site
DRAFT
PROJECT NO.
NOTES:1. Features shown are not an authoritative location, nor are theypresented to a stated accuracy.
DATE
TITLE
SCALEREV. BYPREP. BYCAD FILECOORDINATE SYSTEM:NAD 1983 NORTH CAROLINA STATE PLANE FIPS 3200, USSURVEY FEET
[phone]Raleigh, North Carolina, 27604ATC Associates of North Carolina, P.C.DRAFT
PROJECT NO.
NOTES:1. Features shown are not an authoritative location, nor are theypresented to a stated accuracy.2. Groundwater measurements were collected on 12/26/18 and12/27/18.3. * = MW-1B was not used to construct contours.
DATE
TITLE
SCALEREV. BYPREP. BYCAD FILECOORDINATE SYSTEM:NAD 1983 NORTH CAROLINA STATE PLANE FIPS 3200, USSURVEY FEET
[phone]Raleigh, North Carolina, 27604ATC Associates of North Carolina, P.C.DRAFT
PROJECT NO.
NOTES:1. Features shown are not an authoritative location, nor are theypresented to a stated accuracy.2. Concentrations presented equal or exceed the April 1, 2013
NCDEQ 15A 2L NCAC Groundwater Standard.3. Concentrations are reported in micrograms per liter (µg/L).
DATE
TITLE
SCALEREV. BYPREP. BYCAD FILECOORDINATE SYSTEM:NAD 1983 NORTH CAROLINA STATE PLANE FIPS 3200, USSURVEY FEET
[phone]Raleigh, North Carolina, 27604ATC Associates of North Carolina, P.C.DRAFT

APPENDIX A

LABORATORY ANALYTICAL RESULTS DRAFT
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