23064_DKeffer Pontiac_Phase II ESA_20190729

Phase II Environmental Site
Assessment
Vacant Automotive Dealership
A .,
S EVIL
0 2543
0 ! sue?
2923 South Tryon Street, Suite 100
Charlotte, NC 28203
704,586,0007 main
1001 Tyvola Road
Charlotte, North Carolina
H&H Job No. 5HR-004
July 29, 2019
I9
hart '1• hickman
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#C-1269 Engineering
#C-245 Geology
3921 Sunset Ridge Rd. Suite 301
Raleigh, NC 27607 www.harthi[kman.[om
919.847.4241 main

Phase II ESA
Vacant Automotive Dealership
1001 Tyvola Road
Charlotte, North Carolina
H&H Job No. SHR-004
Table of Contents
1.0 Introduction and Background Information.........................................................................1
2.0 Phase II ESA Methodology.....................................................................................................4
2.1
Utility Clearance....................................................................................................................4
2.2
Groundwater Assessment Activities......................................................................................4
2.3
Soil Assessment Activities....................................................................................................6
2.4
Vapor Intrusion Assessment Activities.................................................................................8
2.5
Quality Assurance/Quality Control.....................................................................................10
3.0 Phase
II ESA Results............................................................................................................12
3.1
Groundwater Analytical Results..........................................................................................12
3.2
Soil Analytical Results........................................................................................................13
3.3
Sub -Slab Vapor / Soil Gas Analytical Results....................................................................14
3.4
Vapor Intrusion Sample Risk Calculations.........................................................................15
3.5
Quality Assurance/Quality Control.....................................................................................16
4.0 Summary
and Conclusions...................................................................................................17
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List of Tables
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Summary of Well Construction and Groundwater Elevation Data
Summary of Groundwater Analytical Results
Summary of Soil Analytical Results
Summary of Subgrade Lift Soil Analytical Results
Summary of Sub -Slab Vapor Analytical Results
Summary of Soil Gas Analytical Results
List of Figures
Figure 1
Site Location Map
Figure 2
Site Map
Figure 3
Sample Location Map
Figure 4
Subgrade Lift Sample Location Map
Figure 5
Shallow Groundwater Potentiometric Map
List of Appendices
Appendix A Preliminary Site Plan
Appendix B Mecklenburg County Subsurface Investigation Permit
Appendix C Soil Boring Logs
Appendix D Laboratory Analytical Reports
Appendix E NCDEQ Risk Calculators
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Phase II ESA
Vacant Automotive Dealership
1001 Tyvola Road
Charlotte, North Carolina
H&H Job No. SHR-004
1.0 Introduction and Background Information
Hart & Hickman, PC (H&H) has prepared this report summarizing Phase II Environmental Site
Assessment (ESA) activities conducted at the vacant automotive dealership located at 1001 Tyvola
Road in Charlotte, Mecklenburg County, North Carolina (Site or subject Site). A Site location
map is provided as Figure 1 and a Site map is provided as Figure 2. The subject Site is comprised
of three parcels of land totaling approximately 12.12 acres in area (Parcel IDs: 16908401,
16908402, and 16908410) that are developed with an approximately 53,946-square foot (SF)
automotive dealership building that is divided into a sales showroom, sales and administrative
offices, parts storage, wash bays, automotive service garage, and paint/body shop. The eastern
portion of the Site contains an approximately 2,240 SF sales and office building and the western
portion of the Site contains an approximately 1,468 SF office building. The northwestern portion
of the Site contains undeveloped wooded land and an unnamed tributary to Kings Branch. The
remainder of the Site consists of asphalt -paved parking, access drives, and landscaped areas.
H&H recently conducted a Phase I ESA at the Site and identified the following Recognized
Environmental Conditions (RECs):
• The Site has been occupied by various automotive dealerships and used for service, repair,
and paint/body shop operations from 1976 through 2018. Historically, the subject Site has
been identified as a Resource Conservation and Recovery Act (RCRA)-Small Quantity
Generator (SQG) of ignitable (D001) and spent non -halogenated solvent (F003 and F005)
hazardous wastes. Several RCRA violations have been reported at the Site. The RCRA
violations were cited for a lack of proper paperwork including a contingency plan, open
drums of various wastes, unlabeled waste drums, and spilled waste observed on the sides
and base of the drums. Regulatory compliance was met during subsequent inspections,
and no further regulatory actions were taken. As the Site is currently vacant, hazardous
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waste management practices were not observed during the Site reconnaissance and no
historical waste management documents were provided for review. Based on the length of
time automotive operations were conducted at the Site (approximately 42 years), historical
hazardous waste generation at the Site, the fact that several RCRA violations have been
issued to the Site, and the lack of hazardous waste management documentation, H&H
considered the potential for impact to the subject Site from historical automotive service,
repair, and paint/body operations to be a REC.
• H&H observed evidence of 23 subgrade hydraulic lifts located throughout the service
garage. Of the 23 subgrade hydraulic lifts, 17 were single -piston lifts and 6 were double -
piston lifts. The installation date of the subgrade lifts is unknown; however, it is likely the
lifts were installed when the facility was constructed in the late 1970s. Lift inspection
and/or maintenance records were not available for review. No apparent previous
environmental assessment has been conducted associated with the subgrade lifts. Based
on the length of time the lifts were likely in use and the lack of service and/or maintenance
records, H&H considered the potential for impact to the subject Site associated with the
subgrade hydraulic lifts to be a REC.
• H&H observed two oil/water separators (OWSs) located in the southwest and southeast
portions of the Site. Fluids from floor drains located in the service garage and wash bay in
the main Site building flow into the OWS located in the southwestern portion of the Site
prior to discharge to the municipal sewer system. Fluids from a floor drain located in a
wash bay in the eastern Site building flow into the OWS located in the southeastern portion
of the Site prior to discharge to the municipal sewer system. The OWS installation dates
are not known; however, it is likely the OWSs were installed when the buildings were
constructed in the late 1970s and early 1980s, respectively. No service or maintenance
records were available for review. Based on the likely age of the OWSs (approximately
42 years and 37 years) and the lack of service and/or maintenance records, H&H considered
the potential for impact to the subject Site from the OWSs to be a REC.
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• Properties in the immediate vicinity of the Site have been used for various commercial
purposes since the late-1970s to the present. Based on file review activities, chlorinated
solvents (including trichloroethene [TCE] and tetrachloroethene [PCE]) and petroleum -
related compounds (primarily benzene) have been detected in groundwater at nearby
properties located topographically upgradient of the subject Site at concentrations above
the North Carolina Administrative Code 02L Groundwater Quality Standards (2L
Standards) and/or North Carolina Department of Environmental Quality (NCDEQ) Vapor
Intrusion Groundwater Screening Levels (GWSLs). H&H considered the potential for
impact to the subject Site (including the potential for vapor intrusion associated with future
Site development) from nearby historical commercial use and the documented presence of
groundwater impacts at nearby topographically upgradient properties to be a REC.
Based on the results of the Phase I ESA, Site history, and current redevelopment plans, H&H
prepared a Phase II ESA scope of work to assess the potential for impact to the subject Site from
historical Site operations, upgradient contaminant sources, and to evaluate potential risks
associated with future Site development. The scope of work included the collection of
groundwater, soil, soil gas, and sub -slab vapor samples for laboratory analysis. A copy of the
preliminary Site plan is presented in Appendix A. A discussion of methods, analytical results, and
conclusions of the Phase II ESA activities are provided in the following sections.
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2.0 Phase II ESA Methodology
The assessment activities were performed in general accordance with the NCDEQ — Inactive
Hazardous Sites Branch (IHSB) Guidelines for Assessment and Cleanup dated October 2015, the
NCDEQ Division of Waste Management (DWM) Vapor Intrusion Guidance dated March 2018,
and most recent version of the U.S. Environmental Protection Agency (EPA) Region IV Science
and Ecosystem Support (SESD) Field Branches Quality System and Technical Procedures
guidance.
As required by Mecklenburg County, H&H obtained a Subsurface Investigation Permit (SIP No.
70002635) from the Mecklenburg County Land Use and Environmental Services Agency
(LUESA) prior to installing temporary monitoring wells at the Site. A copy of the subsurface
investigation permit is provided in Appendix B.
H&H conducted the Phase II ESA activities from June 24 to 28, 2019 and conducted additional
assessment activities on July 17, 2019. The 23 subgrade hydraulic lifts and associated components
were removed and disposed off -Site in July 2019.
2.1 Utility Clearance
Prior to conducting Phase II ESA activities, H&H contacted North Carolina One -Call, the public
utility locator, to mark subsurface utilities located on the Site. H&H also contracted with Probe
Utility Locating (Probe), a private utility locator, to screen proposed boring locations for subgrade
utilities which were not identified by the public locator. Additionally, H&H directed the drilling
contractor to hand clear each boring to a depth of approximately five feet below ground surface (ft
bgs) to further screen boring locations for the presence of subsurface utilities.
2.2 Groundwater Assessment Activities
Under the direction of H&H, seven temporary monitoring wells (TW-1 through TW-7A) were
installed by Mid South Environmental, LLC (Mid South) of Salisbury, North Carolina and sampled
for laboratory analysis. The temporary monitoring wells were advanced with a track -mounted
Geoprobe 661ODT drill rig utilizing direct push technology (DPT) drilling methods. The
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temporary monitoring well locations are depicted on Figure 3 and the soil boring logs are presented
in Appendix C. The well construction and sampling details are summarized below.
RCRA
Boring
VOCs by
PAHs by
Metals by
Area of Concern /
Well ID
Depth
EPA
EPA
EPA
Sample Location
(ft)
Method
Method
Methods
8260
8270
6020/7471
TW-1
20
X
X
X
Oil/Water
Separators
TW-2
20
X
X
X
Downgradient of
TW-3
23
X
X
Service Garage and
Paint/Body Shop
TW-4
25
X
X
TW-5
20
X
X
Background
(Upgradient)
TW-6
17
X
X
TW-7A
20
X
X
Table Notes:
VOCs = Volatile Organic Compounds
PAHs = Polynuclear Aromatic Hydrocarbons
The temporary monitoring wells were constructed using 1-inch diameter PVC riser with a 10 ft
section of 0.010-inch slotted PVC screen set to bracket the water table. A filter sand pack was
then installed from the bottom of the well boring to approximately two ft above the well screen,
and a bentonite seal was installed above the filter sand pack. Please note that shallow perched
water was encountered at boring TW-7; therefore, H&H instructed the driller to advance another
boring at a nearby location (TW-7A).
Prior to sampling, H&H developed the temporary monitoring wells by removing at least three well
volumes using a peristaltic pump. Once three well volumes were removed, the temporary wells
were purged using low flow methods until field parameters of temperature, pH, specific
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conductivity, and oxidation reduction potential (ORP) stabilized and turbidity was less than or near
10 nephelometric turbidity units (NTUs).
Following stabilization of field parameters, groundwater samples were collected using low -flow
sampling techniques and "soda straw" sampling method for VOCs. Following sample collection,
samples were submitted to Pace Analytical Services, LLC (Pace), a North Carolina certified
laboratory (NC Certification No. 381), for the above analyses. The RCRA metals include arsenic,
barium, cadmium, chromium, lead, mercury, selenium, and silver.
Following sampling completion, the top of casing elevations of the wells was determined using
survey methods to the nearest 0.01 ft, which were referenced to an assumed datum of 100.00 ft at
the TW-5 top of casing. A summary of temporary well construction and groundwater elevation
data is presented on Table 1.
2.3 Soil Assessment Activities
To evaluate soils which may be disturbed during future Site redevelopment activities and/or most
likely to pose a direct contact exposure concern, H&H advanced and sampled 10 soil borings
across the Site and collected one sample per boring for laboratory analysis (SB-1 through SB-10).
Additionally, H&H advanced one soil boring adjacent to each single -piston subgrade lift and two
soil borings adjacent to each double -piston subgrade lift (total of 29 borings) and collected one
sample from each boring for laboratory analysis (L-1 through L-23). The soil boring locations are
depicted on Figures 3 and 4.
Additionally, three background soil samples were collected to assess naturally occurring
concentrations of metals in soil at the Site. The locations of the background soil borings were
determined in the field and were collected from areas that did not appear to have been impacted
from historical operations. The background soil borings were advanced in the historically
undeveloped area in the northern portion of the Site (see Figure 3). The soil boring and sampling
details are summarized below.
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RCRA
TPH-
Area of
Boring
VOCs by
PAHs by
Metals by
DRO by
Concern /
Sample ID
Depth
EPA
EPA
EPA
EPA
Sample
(ft)
Method
Method
Methods
Method
Location
8260
82�70
6020/7471
8015
Oil/Water
SB-1 & SB-2
20
X
X
X
X
Separators
Air
Compressor /
SB-3
10
X
Oil Stained
Area
Shop Floor
SB-4 through
5
X
X
X
Drains
SB-9
Aboveground
Storage Tank
SB-10
10
X
X
X
Area
Subgrade
L-1 through
15
X
Hydraulic Lifts
L-23
Background
BG-1 through
5
X
BG-3
Table Notes:
TPH = Total Petroleum Hydrocarbons
DRO = Diesel Range Organics (C 10 — C28)
Soil samples were collected using either a decontaminated stainless -steel hand auger or by DPT
utilizing a decontaminated five ft long Macro -Core® sampler with disposable acetate liners.
Following collection, soil samples were described for lithologic purposes, inspected for the
presence of staining and odors, and field -screened for the presence of organic vapors with a
calibrated photo -ionization detector (PID). Based upon field screening results, H&H collected one
soil sample from each boring location for laboratory analysis. If there was field evidence of
potential impacts, then the sample exhibiting the greatest potential for impact was submitted for
laboratory analysis. If no evidence of potential impact was observed, then the soil sample for
laboratory analysis was collected from within the upper ten ft of soil column which is the area
most likely to be disturbed during future redevelopment activities and/or most likely to pose a
direct contact exposure concern. Boring logs with lithologic descriptions and field screening
results are provided in Appendix C.
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Following collection, the soil samples were placed in dedicated laboratory -supplied sample
containers, labeled with the sample identification, date, and requested analysis, and placed in a
laboratory supplied cooler with ice. The samples were delivered to Pace under standard chain of
custody protocols for the above analyses.
2.4 Vapor Intrusion Assessment Activities
To evaluate the potential for vapor intrusion associated with current Site conditions and the
proposed Site buildings, H&H installed and sampled five temporary sub -slab vapor points (SSV-
1 through SSV-5) and four temporary exterior soil gas points (SG-1 through SG-4) at the Site. The
sub -slab vapor and soil gas sample locations are depicted on Figure 3 and the sampling details are
summarized below.
Sample
VOCs by
Area of Concern /
Sample ID
Sample
Depth
EPA
Sample Location
Type
eft)
Method
TO-15
Paint/Body Shop
SSV-1
Sub -Slab
0.5
X
Paint/Body Shop
SSV-2
Sub -Slab
0.5
X
Service Garage and Future
SSV-3
Sub -Slab
0.5
X
Building #3
Service Garage and Future
SSV-4
Sub -Slab
0.5
X
Building #2
Future Building #1
SSV-5
Sub -Slab
0.5
X
Southeast Portion of Site
SG-1
Soil Gas
8
X
(Future Commercial)
Future Building #1
SG-2
Soil Gas
10
X
Future Building #3
SG-3
Soil Gas
8
X
Future Building #4
SG-4
Soil Gas
7
X
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The sub -slab vapor and soil gas points were installed and sampled in general accordance with the
NCDEQ DWM Vapor Intrusion Guidance dated March 2018 and as described below.
The sub -slab vapor points were installed by utilizing a hammer drill and 1 1/2-inch diameter drill bit
to advance a pilot hole into the concrete slab to a depth of approximately 13/4 inches below the
surface. A drill guide was then placed in the pilot hole, and a 5/8-inch diameter drill bit was
utilized to advance the boring through the concrete slab. Following concrete borehole
advancement, loose concrete cuttings were removed from the boring using a bottlebrush and high
efficiency particulate air (HEPA) vacuum. A Cox -Colvin Vapor Pin (vapor pin) assembly (brass
sampling point and silicone sleeve) was seated in each borehole using an installation/extraction
tool and hammer. The vapor pins were installed as flush -mount sample points capable of being
secured with a stainless -steel cover that screws onto the sampling point and is seated within the
pilot hole annulus.
The soil gas monitoring points were installed utilizing DPT methods to advance the borings into
the vadose zone to depths ranging from approximately seven to 10 ft bgs (approximately three to
five ft above the estimated depth to groundwater). A stainless -steel screen point fitted with'/4-inch
diameter Teflon® tubing was then advanced within the boreholes to the maximum depth of the
boring. Filter sand was placed around the annular space of the sample points and extended to
approximately one-ft above the bottom of the borehole. The sampling point was completed by
placing hydrated bentonite from the top of the filter sand to the ground surface. Using a syringe,
the soil gas sample points were purged of a minimum of three times the volume of the annular
space plus the tubing volume. Because the soil gas points were installed utilizing DPT methods,
the soil gas points were allowed to stabilize for a minimum of two hours after installation prior to
collecting the soil gas samples.
Prior to collecting the sub -slab vapor and soil gas samples, a leak check was conducted at each
location by constructing a shroud around the monitoring point and flooding the air within the
shroud with helium gas. Using a syringe, a sample was collected from the gas in the shroud into
a Tedlar® bag and analyzed for helium concentrations using a helium gas detector. Vapor from
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the monitoring points was purged and sampled outside of the shroud into a separate Tedlar® bag
and analyzed using the helium gas detector to ensure that helium concentrations were less than
10% of the concentration measured within the shroud.
Following a successful field leak check, the sub -slab and soil gas vapor points were purged to
remove a minimum of three volumes. Samples were then collected into one -liter Summa canisters
for laboratory analysis by connecting the Teflon® sample tubing to an airflow regulator using a
brass nut and ferrule assembly to create an air tight seal. The airflow regulator was calibrated by
the laboratory to allow the Summa canisters to fill slowly at a rate not greater than 200 milliliters
per minute. The vacuum pressure in each Summa canister upon completion of the sampling event
was between four and six inches of mercury. Upon completion of sample collection, the air flow
regulator was removed from the Summa canister and the samples were submitted to ConTest
Analytical Laboratory (ConTest), a nationally accredited laboratory, under standard chain of
custody protocols for analysis of VOCs by EPA Method TO-15. Upon receipt of the samples, the
laboratory recorded the final vacuum pressure for each Summa canister received.
2.5 Quality Assurance/Quality Control
H&H utilized standard quality assurance/quality control (QA/QC) processes during the Phase II
ESA activities. Non -dedicated sampling equipment, including DPT tooling, the water level meter,
and the hand auger, were decontaminated using Liquinox detergent prior to and between each
sampling location. H&H and the drilling subcontractors wore nitrile gloves while handling
samples, and the sub -slab, soil gas, and groundwater samples were collected using dedicated
tubing. Soil and groundwater samples were collected in laboratory -provided containers and placed
on ice immediately upon collection.
For field and laboratory QA/QC purposes, H&H collected one duplicate sample per media. The
duplicate samples were analyzed for the same compounds as the parent samples. H&H collected
one duplicate groundwater sample from TW-1, duplicate soil samples from borings SB-1, L-7A,
and L-11, and one duplicate sub -slab sample from SSV-4.
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A laboratory supplied trip blank was placed into the laboratory supplied cooler that was used for
water samples analyzed for VOCs and accompanied field personnel during water sample collection
activities. The trip blank was analyzed for VOCs by EPA Method 8260. Additionally, H&H
requested a Level II QA/QC data package from the laboratory and requested the laboratory to
report values to the laboratory -specified method detection limits using J-flags.
Prior to sub -slab vapor and soil gas sample collection, H&H conducted a five-minute sampling
system shut-in test for each sample to verify an airtight seal between Summa canister and airflow
regulator. All Summa canisters passed the five-minute sampling system shut-in test prior to
sampling.
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3.0 Phase II ESA Results
The results of analysis of the groundwater samples are summarized in Table 2, the results of
analysis of the soil samples are summarized in Tables 3 and 4, the results of the analysis of the
sub -slab vapor samples are summarized in Table 5, and the results of analysis of the soil gas
samples are summarized in Tables 6. Laboratory analytical data reports and chain -of -custody
records are included in Appendix D.
3.1 Groundwater Analytical Results
Laboratory analytical results were compared to the 2L Standards and the NCDEQ Residential and
Non -Residential GWSLs.
Groundwater flow at the Site was generally determined to be to the west towards the unnamed
tributary to Kings Branch. A shallow groundwater potentiometric map is provided as Figure 5.
vnc-,
The results of analysis of the groundwater samples indicate that 1,2-dichloroethane (1,2-DCA)
was detected in upgradient background well TW-6 at a concentration of 4.3 micrograms per liter
(µg/L) which is above the 2L Standard of 0.4 µg/L, but below the Residential and Non -Residential
GWSLs of 22 µg/L and 98 µg/L, respectively. Additionally, 1,2-DCA was detected in TW-4,
located west of the dealership building (and generally downgradient of TW-6) at a concentration
of 1.8 µg/L.
No other VOCs were detected at concentrations exceeding 2L Standards and no VOCs were
detected at concentrations exceeding GWSLs.
PAHs
One PAH (2-methylnaphthalene) was detected at an estimated concentration of 3.1 J µg/L in TW-
7A, which is below the 2L Standard of 30 µg/L. GWSLs have not been established for 2-
methylnaphthalene. No PAHs were detected at concentrations above 2L Standards or GWSLs.
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Metals
Analytical results indicate that multiple metals, including barium, chromium (total), lead, and
mercury were detected at concentrations above laboratory detection limits but below 2L Standards
and GWSLs.
3.2 Soil Analytical Results
Soil analytical results were compared to the NCDEQ IHSB Protection of Groundwater,
Residential, and Industrial/Commercial Preliminary Soil Remediation Goals (PSRGs) dated May
2019 and the NCDEQ Underground Storage Tank (UST) Section Action Levels. Metals
concentrations were first compared to Site -specific background levels before comparison to the
PSRGs.
TPH-DRO
Analytical results indicate that TPH-DRO was detected at concentrations above the NCDEQ
Action Level of 100 milligrams per kilogram (mg/kg) at nine of the 23 subgrade lift locations,
including: L-1 (3,680 mg/kg), L-4A (3,160 mg/kg), L-10 (127 mg/kg), L-11 (2,480 mg/kg), L-15
(903 mg/kg), L-17 (2,890 mg/kg), L-18A (903 mg/kg), L-20 (682 mg/kg), and L-21 (281 mg/kg).
TPH-DRO was detected at a concentration of 99.8 mg/kg at L-713, which is just below the NCDEQ
Action Level of 100 mg/kg.
VOCs
Analytical results indicate that no VOCs were detected in any of the soil samples at concentrations
exceeding PSRGs. Several low-level petroleum -related VOCs were detected in soil sample SB-5
located adjacent to a floor drain in the paint/body shop, but at concentrations below PSRGs.
PAHs
Analytical results indicate that one PAH (1-methylnaphthalene) was detected in soil sample SB-5
at an estimated concentration of 0.26 J mg/kg which is above the Protection of Groundwater PSRG
of 0.11 mg/kg, but below the Residential and Industrial/Commercial PSRGs of 18 mg/kg and 73
mg/kg, respectively. No other PAHs were detected at concentrations above PSRGs.
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Metals
Analytical results indicate that no metals were detected at concentrations above PSRGs and Site -
specific background levels.
Laboratory analytical results indicate that arsenic was detected in each of the two oil/water
separator soil samples (SB-1/DUP-1 and SB-2) at concentrations of 0.849 mg/kg and 1.44 mg/kg,
which are above the Residential PSRG of 0.68 mg/kg but below the Site -specific background range
of 2.45 mg/kg to 3.12 mg/kg.
Analytical results indicate that low-level concentrations of hexavalent chromium were detected in
each of the three background samples (BG-1 through BG-3) at concentrations above the
Residential PSRG of 0.31 mg/kg, but below the Protection of Groundwater PSRG (3.8 mg/kg) and
the Industrial/Commercial PSRG (6.5 mg/kg). The portion of the Site that the background samples
were collected has historically been undeveloped wooded land since at least 1938.
3.3 Sub -Slab Vapor / Soil Gas Analytical Results
Laboratory analytical results of the sub -slab vapor and soil gas samples were compared to the
NCDEQ DWM Residential and Non -Residential Sub -Slab and Exterior Soil Gas Screening Levels
(SGSLs) dated February 2018. These screening levels are very conservative and are based upon
a lifetime incremental cancer risk (LICR) of 1 x 10"5 for potential carcinogenic effects and/or a
Hazard Index (HI) of 0.2 for potential non -carcinogenic effects. Vapor intrusion mitigation for
occupied structures is not typically considered unless the LICR exceeds the acceptable risk range
of 1 x 10-4 to 1 x 10-6 for potential carcinogenic effects and a HI of 1 for potential non -carcinogenic
effects.
Laboratory analytical data indicates that PCE was detected at concentrations above the Residential
SGSL of 280 micrograms per cubic meter (µg/rn) in sub -slab vapor sample SSV-4 and its
duplicate (DUP-1) at concentrations of 560 µg/m3 and 620 µg/m3, which are below the Non -
Residential SGSL of 3,500 µg/m3. SSV-4 was collected from the southern portion of the service
garage. Additionally, the VOC naphthalene was detected in sub -slab sample SSV-2, located in
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the southern portion of the paint/body shop, at a concentration of 26 µg/m3 which is above the
Residential SGSL of 21 µg/m3 but below the Non -Residential SGSL of 260 µg/m3.
No other VOCs were detected in the sub -slab samples above SGSLs and no VOCs were detected
in the soil gas samples at concentrations above SGSLs.
3.4 Vapor Intrusion Sample Risk Calculations
To further evaluate the detected VOCs, H&H input the concentrations of the compounds detected
in each soil gas and sub -slab vapor sample into the NCDEQ Risk Calculator (May 2019 Version).
Calculations were completed for both residential and non-residential use scenarios of the soil gas
to indoor air exposure pathway to calculate cumulative potential carcinogenic and non -
carcinogenic risks for the sub -slab vapor and soil gas samples. Copies of the calculations are
provided in Appendix E and a summary of the calculated LICRs and HIs for each sample is
provided below:
Sample ID
Resident
Risk
Exceeded?
Non -Residential Worker
Risk
Exceeded?
Calculated
LICR
Calculated
HI
Calculated
LICR
Calculated
HI
SSV-1
5.9E-08
0.011
NO
4.5E-09
0.00084
NO
SSV-2
1.0E-05
0.27
NO
7.6E-07
0.022
NO
SSV-3
4.2E-07
0.1
NO
3.2E-08
0.0083
NO
SSV-4/DUP-1
1.9E-06
0.45
NO
1.5E-07
0.036
NO
SSV-5
3.9E-07
0.11
NO
3.0E-08
0.0084
NO
SG-1
3.7E-06
0.067
NO
2.8E-07
0.0053
NO
SG-2
3.9E-06
0.23
NO
3.0E-07
0.018
NO
SG-3
3.5E-06
0.092
NO
2.7E-07
0.0073
NO
SG-4
6.9E-07
0.032
NO
5.2E-08
0.0025
NO
As indicated above, the calculated LICRs were within the acceptable risk range of 1 x104 to 1 x
10"6 and the calculated HIs were less than 1 under both residential and non-residential use
scenarios.
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3.5 Quality Assurance/Quality Control
For field and laboratory QA/QC purposes, H&H collected one duplicate groundwater sample from
TW-1, duplicate soil sample from borings SB-1, L-7A, and L-11, and one duplicate sub -slab
sample from SSV-4. The duplicate samples were analyzed for the same compounds as the parent
samples. The results of analysis of the duplicate samples are provided in the attached tables and
generally indicate good analytical repeatability for the duplicate samples.
A laboratory supplied trip blank was placed into the laboratory supplied cooler that was used for
water samples and accompanied field personnel during groundwater sample collection activities.
The trip blank was analyzed for VOCs by EPA Method 8260. One compound, methylene chloride
was detected at an estimated concentration of 0.86 J µg/L, which is below the 2L Standard of 5
µg/L and the Residential and Non -Residential GWSLs of 940 µg/L and 4,000 µg/L, respectively.
Please note that methylene chloride is a commonly utilized laboratory solvent; therefore, it's likely
the low-level detection is the result of laboratory cross -contamination.
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4.0 Summary and Conclusions
H&H completed Phase II ESA activities at the vacant automotive dealership located at 1001
Tyvola Road in Charlotte, Mecklenburg County, North Carolina. The assessment activities were
conducted to assess the potential for impact to the subject Site from historical Site operations,
upgradient contaminant sources, and to evaluate potential risks associated with future Site
development, including the potential for vapor intrusion. The Phase II ESA activities were
conducted on June 24 to 28, 2019 and on July 17, 2019 and included the collection of soil,
groundwater, sub -slab vapor, and soil gas samples for laboratory analysis. A summary of the
results of the Phase II ESA is provided below.
Groundwater Summary
• The results of analysis of the groundwater samples indicate that 1,2-DCA was detected at
concentrations above the 2L Standard in one background/upgradient well (TW-6) and one
well located west of the service garage and paint/body shop (generally downgradient of
TW-6). No other compounds were detected in the groundwater samples at concentrations
above 2L Standards and no compounds were detected in the groundwater samples at
concentrations above the GWSLs.
Soil Summary
• Analytical results indicate that TPH-DRO was detected at concentrations above the
NCDEQ Action Level in 9 of the 23 former subgrade lift locations. The former subgrade
lifts with identified impacts above the Action Level include Lift #1, #4, #10, #11, #15, #17,
#18, #20, and #21 (see Figure 4). The subgrade lifts and associated components were
removed from the Site in July 2019. However, petroleum -impacted soils identified at the
above lift locations remain in -place at the Site.
• The results of analysis of the soil samples indicate one PAH (1-methylnaphthalene) was
detected at an estimated concentration slightly above the Protection of Groundwater PSRG
(0.26 J mg/kg compared to 0.11 mg/kg). No compounds were detected in soil at
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concentrations above the Residential or Commercial/Industrial PSRGs and background for
metals.
Vapor Intrusion Summary
• Laboratory analytical data indicates that PCE was detected at concentrations above the
Residential SGSL in sub -slab vapor sample SSV-4 and its duplicate (southern portion of
service garage) at concentrations above the Residential SGSL but below the Non -
Residential SGSL. Additionally, naphthalene was detected in sub -slab sample SSV-2,
located in the southern portion of the paint/body shop, at a concentration slightly above the
Residential SGSL but below the Non -Residential SGSL.
• To further evaluate the detected compounds, H&H input the concentrations of the
compounds detected in each sub-slab/soil gas sample into the NCDEQ Risk Calculator.
The results of the cumulative risk calculations indicate the potential carcinogenic and non -
carcinogenic risks associated with the sub-slab/soil gas detections are within the range of
acceptable limits under both future residential and non-residential use scenarios.
Conclusions
• Based upon the results of our assessment activities, there are petroleum -impacted soils that
remain in -place in the service garage associated with the former subgrade lifts that warrant
environmental management during future development activities.
• Based upon the results of our assessment activities, groundwater impact at the Site is
limited and is likely the result of migration from an off -Site and hydraulically upgradient
source.
• Because the cumulative risk calculations for the sub -slab and soil gas samples indicate
acceptable carcinogenic and non -carcinogenic risks under both residential and non-
residential exposure scenarios, vapor mitigation controls do not appear warranted for future
buildings at the Site at this time.
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Tables
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