HomeMy WebLinkAbout11047_Dollar General Soil Vapor Assessment Rpt 2009.09.04Soil Vapor Assessment Report
Dollar General
Charlotte, North Carolina
Brownfields Project 11047-07-60
H&H Job No. TCC-022
September 4, 2009
2923 South Tryon Street
Suite 100
Charlotte, NC 28203
704-586-0007
3334 Hillsborough Street
Raleigh, NC 27607
919-847-4241
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Table of Contents
Section Page No.
1.0 Introduction ............................................................................................................................ 1 2.0 Previous Assessment Activities ............................................................................................. 2
3.0 Soil Vapor Assessment ........................................................................................................... 3 3.1 Soil Vapor Sampling Methods ............................................................................................. 3
3.2 Soil Vapor Results ............................................................................................................... 5
4.0 Conclusions and Recommendations ..................................................................................... 7
5.0 References ............................................................................................................................... 8
List of Tables Table 1 Summary of Soil Vapor Analytical Detections
List of Figures Figure 1 Site Location Map
Figure 2 Sample Location Map
List of Appendices
Appendix A Laboratory Analytical Data
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Soil Vapor Assessment Report
Dollar General Charlotte, North Carolina H&H Job No. TCC-022
1.0 Introduction Hart & Hickman, PC (H&H) has conducted soil vapor assessment activities at the Dollar General
site located at 1949 E. 7th Street in Charlotte, Mecklenburg County, North Carolina. A site
location map is provided as Figure 1. H&H conducted the activities on behalf of the current
property owner CLHC, LLC (CLHC).
The subject property is comprised of approximately 0.45-acre of land. Dollar General currently
leases a 9,484-square ft commercial building present in the northeastern portion of the subject
property. The commercial building is connected to other retail units within a small strip
shopping center. The building leased by Dollar General is comprised of a showroom, a storage
area, two rest rooms, and an office. The remainder of the property is an asphalt paved parking
lot. The site layout is shown on Figure 2.
After completion of a 2007 Phase I Environmental Site Assessment (ESA) on the subject
property which indicated the presence of former dry cleaners on and in the vicinity of the site.
CLHC submitted a Brownfields Application to the North Carolina Department of Environment
and Natural Resources (DENR). Based upon their review of the 2007 Phase I ESA, DENR
requested soil vapor sampling at the site in support of a Brownfields agreement in a letter dated
March 3, 2009. H&H has provided a brief description of the results of the Phase I ESA in the
following section followed by the methods and results of the soil vapor assessment activities.
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2.0 Previous Assessment Activities
In November 2007, H&H prepared a Phase I ESA on the property and identified two former dry
cleaners that operated on, or near the subject property. The former on-site dry cleaners Valeteria,
Inc. was listed in the reviewed city directories at the address 1953 E. 7th Street from the 1940s
until the mid-1950s. The address indicates that the cleaners previously operated in the southern
portion of the subject property at a location fronting E. 7th Street. Sanitary Cleaners (1959 E. 7th
Street) operated in the off-site building currently occupied by Crisp (a restaurant) located
approximately 70 ft south and topographically upgradient to cross-gradient of the subject
property from the 1950s until the early 1960s. Based upon the presence of the former dry
cleaners on and near the subject site, H&H concluded that there was a potential for soil and/or
ground water impacts at the property.
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3.0 Soil Vapor Assessment
H&H submitted a work plan for the soil vapor assessment on June 8, 2009. DENR subsequently
approved the work plan on June 30, 2009 with additions requesting a 24-hour period between
installation and sampling of soil vapor monitoring points (VMPs), measurement of ambient
indoor air temperature at the start, middle, and end of sampling, and measurement of building
dimensions. H&H conducted the field activities on July 16 and 17, 2009. The methods and
results of the soil vapor assessment activities are provided below.
3.1 Soil Vapor Sampling Methods
H&H installed the three VMPs on July 16, 2009 (labeled VP-1 through VP-3 in Figure 2). VP-1
was installed in the parking lot in the southern portion of the site where the former dry cleaner
was located. H&H collected a deeper soil gas sample at this location because no building is
present, however future development of the site may include a building in this portion of the
property. VP-2 and VP-3 were subslab sample locations collected below the Dollar General
store building.
For the installation of VP-1, a rotary hammer drill was utilized to open a hole through the asphalt
and a hand auger was utilized to install a 3-inch diameter boring through the underlying soil to a
depth of 5-feet below land surface (bls). Soil cuttings from the VP-1 boring were observed to be
orange to red clayey silts and silty clays. For the two interior locations, the rotary hammer drill
was utilized to bore through the concrete slab at the VP-2 and VP-3 locations. The building slab
was observed to be approximately 4 inches thick and underlain by a gravel layer.
H&H installed a stainless steel AMS dedicated soil gas vapor point fitted with ¼-inch diameter
Teflon tubing through each borehole. The tip installed at the VP-1 location was advanced to 5.5-
feet bls, and the tips installed at the VP-2 and VP-3 locations were set approximately 2 to 3-
inches beneath the slab within the underlying gravel layer. The probes were set using an AMS
Gas Vapor Probe Kit and slide hammer. H&H then poured filter sand through each borehole
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around the vapor tip to approximately 4 to 6 inches above the VP-1 tip and approximately 3-
inches below the top surface of the concrete slab at the VP-2 and VP-3 locations. H&H
subsequently completed each borehole by installing bentonite slurry from the top of the sand to
the surface of the borehole.
On July 17, 2009, after allowing the bentonite slurry to set for a 24-hour period, H&H personnel
collected vapor samples from each VMP using 6-liter Summa canisters. Prior to mobilizing to
the site, H&H measured and recorded the initial vacuum in each Summa canister using a vacuum
gauge provided by the lab. In the field, each VMP was purged using a 60 mL syringe with a
three-way valve to evacuate air in the probe annular space and tubing. After purging the VMP,
H&H connected the Summa canister to a flow regulator (set by the lab to limit the vapor intake
rate to approximately 6-liters per hour) and checked the sample train for leaks. Subsequently,
H&H connected the flow regulator to the VMP tubing using a ferrule to form an air-tight seal.
The canister’s air intake valve was then opened to begin collection of the vapor sample.
H&H personnel recorded the initial vacuum pressure indicated by a vacuum gauge on the flow
controller at the commencement of sampling. After more than one hour when each regulator
indicated less than 5 inches mercury vacuum, the canister’s valve was closed, and the flow
controller was disconnected from both the VMP and the canister. H&H measured and recorded
the final vacuum in each Summa canister using the vacuum gauge supplied by the laboratory. In
addition, as requested by DENR, H&H recorded the air temperature near the indoor sub-slab
VMPs at the beginning, middle, and end of the sampling activities. H&H has provided a
summary of the temperature readings in Table 1.
For quality control and evaluation of analytical reproducibility, H&H collected a duplicate
sample at VP-1 (labeled VP-1 Duplicate). The duplicate sample was collected at the same time
as VP-1 using a “T” sample configuration.
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Upon completion of the VMP sampling, the Summa canisters were shipped under chain-of-
custody procedures to Air Toxics, Ltd. in Folsom, CA for analysis of VOCs by EPA Method
TO-15. As requested by DENR, the laboratory’s full TO-15 parameter list was reported for each
sample.
3.2 Soil Vapor Results
The results of the soil vapor sample analyses are summarized in Table 1, and the laboratory
analytical data sheets are provided in Appendix A. H&H compared the concentrations of
compounds detected in the soil vapor samples to the DENR Inactive Hazardous Sites Branch
(IHSB) Residential Soil Gas Screening Concentrations (RSGSCs) and the Industrial/Commercial
Soil Gas Screening Concentrations (ICSGSCs). Please note that the IHSB soil gas screening
concentrations are very conservative and are derived from the EPA Regional Screening Level
(RSL) indoor air concentrations assuming an attenuation factor of 0.1 between subslab soil vapor
and indoor air. However, literature indicates that the attenuation factor between soil vapor and
indoor air is much greater. For example, Johnson, et al. (2002) indicates that empirical
attenuation factors are in the range of 0.0001 to 0.000001, and Johnson (2002) indicates that a
reasonable range of attenuation factors is 0.01 to 0.0001. The IHSB RSGSCs and ICSGSCs are
based upon a lifetime incremental cancer risk (LICR) of 1 x 10-5
In the case that an IHSB soil gas screening concentration was not available for a compound,
H&H compared the concentration of that compound to the Target Shallow Soil Gas
Concentration (TSSGC) in EPA (2002). The EPA TSSGCs used for comparison were based
upon a LICR of 1 x 10
for carcinogens and a hazard
index of 0.2 for non-carcinogens.
-5 for carcinogens and a hazard index of 0.2 for non-carcinogens for
consistency with the IHSB RSGSCs and ICSGSCs. Because the EPA TSSGCs for non-
carcinogens are based upon a hazard index of 1, the TSSGCs for non-carcinogens were
multiplied by 0.2 for consistency with the IHSB SGSCs.
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As indicated in Table 1, the laboratory detected multiple compounds in the soil gas; however, no
concentrations exceeded the conservative screening levels. Therefore, the vapor intrusion
pathway does not pose an unacceptable risk to current or future building occupants and further
screening evaluation of the data is not warranted.
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4.0 Conclusions and Recommendations
In July 2009, H&H collected soil vapor samples from the Dollar General site. The results of the
soil vapor sampling indicated that there were no compounds detected that exceeded generic
screening levels. Based upon the results of the soil gas sampling, the vapor intrusion pathway
does not pose an unacceptable risk to current or future building occupants. As such, H&H does
not recommend further assessment activities at the site in support of the Brownfields Agreement.
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5.0 References
EPA (2002). Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from
Groundwater and Soils. EPA530-F-02-052, November 2002.
Johnson, Paul (2002). Identification of Critical Parameters for the Johnson and Ettinger (1991) Vapor Intrusion Model. American Petroleum Institute, May 2002.
Johnson, P.C., R.A. Ettinger, J. Kurtz, R. Bryan, and J.E. Kester. (2002). Migration of Soil Gas
Vapors to Indoor Air: Determining Vapor Attenuation Factors Using a Screening-Level Model
and Field Data from the CDOT-MTL Denver, Colorado Site. American Petroleum Institute, May 2002.
Table 1
Summary of Vapor Analytical Detections
Dollar General
Charlotte, NC
Hart & Hickman Project No. TCC-022
S:\AAA-Master Projects\The Conformity Corporation - TCC\TCC-022 Dollar General\Brownfields\Soil Vapor Table Freon 11EthanolAcetone2-PropanolCarbon DisulfideMethylene Chloride2-Butanone (Methyl Ethyl Ketone)ChloroformBenzeneTolueneTetrachloroetheneChlorobenzeneEthylbenzenem,p-Xyleneo-XylenePropylbenzene4-Ethyltoluene1,2,4-Trimethylbenzene1,4-DichlorobenzeneVP-1 07/17/09 TO-15 <4.6 13 50 20 8.8 140 18 <4.0 16 35 <5.6 8.0 5.2 18 16 4.7 8.3 11 <4.9
VP-1 (Dup)07/17/09 TO-15 <4.5 14 66 27 <2.5 190 23 <3.9 21 47 <5.5 10 6.8 23 21 6.4 11 14 5.2
VP-2 07/17/09 TO-15 <4.3 13 37 <7.5 4.0 <2.6 8.7 6.0 <2.4 6.8 <5.2 <3.5 <3.3 3.8 4.1 <3.7 <3.7 <3.7 <4.6
VP-3 07/17/09 TO-15 9.2 6.3 15 <7.6 32 <2.7 3.8 <3.8 <2.5 4.4 8.2 <3.6 <3.4 <3.4 <3.4 <3.8 <3.8 <3.8 <4.6
6.2E+03 NE 2.8E+05 NE 6.2E+03 2.6E+03 4.4E+04 5.3E+02 1.6E+02 NE 2.1E+02 4.4E+02 4.9E+02 1.4E+04*1.4E+04*2.8E+02*NE 6.2E+01 1.1E+02
1.5E+03 NE 6.4E+04 NE 1.5E+03 5.2E+02 1.0E+04 1.1E+01 3.1E+01 1.0E+04 4.1E+01 1.0E+02 9.7E+01 NE NE NE NE 1.5E+01 2.2E+01
TimeTemperature (oC)TimeTemperature (oC)Initial 1450 25.1 1500 24.9
Midpoint 1530 25.0 1540 24.9
Final 1555 25.1 1625 25.0
Notes:Analytical Methodµg/m3
IHSB Industrial/Commercial Vapor
Intrusion Soil Gas Screening Level Sample IDSampling Date (mm/dd/yy)1. Only those analytes detected in at least one sample are shown in this table
2. NE = Value not established, µg/m3 = micrograms per cubic meter
3. * Indicates Target Shallow Soil Gas Concentrations from Table 2b of EPA (2002). LICR = 1E-05 for carcinogens and 0.2 for non-carcinogens. Value is displayed only for compounds with
no established IHSB Residential or Industrial/Commercial Soil Gas Screening Level.
IHSB Residential Vapor Intrusion
Soil Gas Screening Level Stage of SamplingVP-2 VP-3
Ambient Air Temperature Meaurements Near Indoor
VPs During Sample Collection
TITLE
PROJECT
SITE LOCATION MAP
DOLLAR GENERAL
CHARLOTTE, NORTH CAROLINA
DATE:
JOB NO:
REVISION NO:
FIGURE NO:
8-19-09 0
1TCC-022
0 2000 4000
APPROXIMATE
SCALE IN FEETN
U.S.G.S. QUADRANGLE MAP
QUADRANGLE
7.5 MINUTE SERIES (TOPOGRAPHIC)
CHARLOTTE, NC 1967
REVISED/INSPECTED 1988
SITE