WS-3748_12330_CA_LTRRPT_20200921

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DRAFT

September 21, 2020 Mr. Herbert Berger, P.G. NCDEQ, Division of Waste Management, UST Section
1646 Mail Service Center
Raleigh, North Carolina 27699-1646
Reference: Letter Report Kodell’s Grocery
7150 NC Highway 89 Westfield, Stokes County, North Carolina NCDEQ Incident No. 12330
NCDEQ Contract: N17006 ECS Project 49:3394-C
Dear Mr. Berger: As authorized by your acceptance of ECS Southeast, LLP (ECS) Task Authorization Request (TAR) No. 3 dated May 29, 2020. ECS has completed the Letter Report for the above referenced site. Included in this report is a description of the field activities, the results obtained, and our conclusions and recommendations. PROJECT UNDERSTANDING
The Kodell’s Grocery site is located at 7150 NC Highway 89 in Westfield, Stokes County, North Carolina (Figures 1 and 2). Based on information provided to ECS, three 1,000-gallon gasoline
underground storage tanks (USTs) and one 500-gallon kerosene UST were removed from the site in January 1994. Soil samples collected after the USTs were removed indicated impact by Total Petroleum Hydrocarbons Gasoline Range Organics (TPH GRO) beneath the former
gasoline and kerosene tanks. On February 17, 2010, monitoring well MW-1 was installed at the site. Monitoring wells MW-2, MW-3, and MW-4 were installed at the site on May 27, 2010. The locations of the monitoring wells are shown on Figure 2. A sample was collected from monitoring wells MW-1 on March 4, 2010, and samples were collected from monitoring wells MW-1 through MW-4 on June 14, 2010. Laboratory analysis of the samples detected compounds above the North Carolina 2L Ground Water Quality Standards (NC2LGWQS) in samples collected from monitoring wells MW-1 and MW-3. Since 2010 and prior to ECS’ involvement on the site, the monitoring wells were sampled twice,
in 2012 and most recently in 2014. Laboratory analysis of the samples detected compounds above the NC2LGWQS in samples collected from monitoring wells MW-1 and MW-3. Based on water table elevation data, the groundwater is flowing to the north-northwest. The horizontal
extent of contamination has been determined. Receptor surveys have determined that nine water-supply wells are located within 1,000 feet of
Letter Report Kodell’s Grocery
Westfield, Stokes County, North Carolina NCDEQ Incident: 12330 NCDEQ Contract: N17006
ECS Project 49:3394-C September 21, 2020
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the site and determined public water is not available in the vicinity of the site. Four of the water supply wells located within 500 feet of the release (WSW-0460, WSW-9974, WSW-1737, and WSW-2242) have been sampled three times. The laboratory analysis has not detected
hydrocarbons associated with the petroleum release; however, trihalomethanes, associated with chlorination, have been detected in the water well located behind (south) of the school. It is ECS’s opinion that the trihalomethanes are a result of disinfecting the well with chlorine. On February 9, 2015, personnel from ECS mobilized to the site to install, measure top-of0casing elevation, and sample one additional Type II groundwater monitoring well (MW-5) on the north downgradient side of the site. Laboratory analysis of the groundwater samples collected from monitoring well MW-5 detected benzene, ethylbenzene, naphthalene, styrene, toluene, 1,2,4-trimethylbenzene, and total xylenes at concentrations exceeding the NC2LGWQS. The concentrations do not exceed the applicable Gross Contamination Levels (GCLs). Additionally, 1,3,5-trimethylbenzene and n-propylbenzene were detected above the laboratory method detection limit, but below their NC2LGWQS. Based on the laboratory
analytical results, the horizontal extent of the groundwater contamination has not been defined. ECS recommended installing two monitoring wells downgradient of MW-5 to further define the extent of contamination.
In October 2015, ECS observed and documented the installation and sampling of two monitoring wells (MW-6 and MW-7) at the site. Additionally, monitoring wells MW-1, MW-3, and
MW-5 were sampled. Petroleum hydrocarbons were detected in groundwater samples collected from monitoring wells MW-1, MW-3, and MW-5 at concentrations above the NC2LGWQS, but below the GCLs. Targeted constituents were not detected above the laboratory detection limit in monitoring wells MW-6 and MW-7. On November 22, 2016, ECS personnel collected groundwater samples from three monitoring wells (MW-1, MW-3, and MW-5). Laboratory analysis of the groundwater samples collected from monitoring wells detected multiple targeted constituents above the NC2LGWQS, but below the GCLs. ECS collected groundwater samples from monitoring wells MW-1 through MW-5 on January 2,
2019. Laboratory analysis of groundwater samples collected from monitoring wells MW-1, MW-3, and MW-5 detected multiple petroleum hydrocarbons at concentrations above the NC2LGWQS, but below the GCLs. Laboratory analysis of the groundwater samples collected
from monitoring wells MW-2 and MW-4 did not detect targeted constituents above the laboratory detection limits. On April 14, 2020, ECS collected groundwater samples from monitoring wells MW-1 through MW-7. In addition, ECS returned to the site on April 23, 2020 and collected a
sample from water supply well WSW-9947. Review of the laboratory analytical report indicated multiple petroleum hydrocarbons at concentrations greater than the respective NC2LGWQS, but less than the respective GCLs, in the samples collected from monitoring wells MW-1, MW-3, and MW-5. Additional compounds were indicated at concentrations greater than the laboratory method detection limits in the sample collected from monitoring wells MW-1, MW-2, MW-3, and MW-5, but less than their respective NC2LGWQS. Compounds were not detected at concentrations greater than the laboratory method reporting limit in the samples collected from monitoring wells MW-4, MW-6, and MW-7. Review of the laboratory analytical report for the water supply well sample did not indicate analyzed compounds at concentrations greater than the laboratory method reporting limit.

APPENDIX A