2906_DavidsonMidwayConvenienceCenter_SeepReleaseResults_DIN26966_20161102

November 2, 2016

Ms. Jackie Drummond
NCDEQ - Division of Waste Management
Asheville Regional Office
2090 U.S. 70 Highway
Swannanoa, NC 28778-8211

RE: Seep Release Results
Davidson County Midway Convenience Center
Davidson County, North Carolina

Dear Ms. Drummond:

Smith Gardner, Inc. (S+G) on behalf of Davidson County is pleased to present this brief letter
report summarizing the Seep Response Investigation at the Davidson County Midway
Convenience Center. S+G followed the approved Seep Response Plan related to the August
11th email from Jason Watkins regarding seeps observed during a site inspection. It should
also be noted that Davidson County has reportedly added secondary containment to the
compactors to prevent future releases.

Soil Sample Collection and Analysis

S+G personnel mobilized to the site on September 8th and again on October 7, 2016 to collect
soil samples from the two seep areas, and to collect a background sample.

In accordance with the work plan, on September 8th, S+G collected a discreet grab samples
from at or near the ground surface, from the two seep areas (S-1 and S-2). Due to the
naturally occurring inorganic metals in the soils of North Carolina, S+G also collected a
background sample, BG-1, upgradient and away from the seep areas to evaluate the
concentrations of naturally occurring constituents. Sampling locations are shown on Figure
1. Sample results indicated elevated concentrations of inorganic constituents.

On October 7th approximately 4.5 feet of soil was excavated in both the S-1 and S-2 locations.
A second round of samples, including background samples, were collected from the in place
soils for laboratory analysis.

For both events samples were collected in the laboratory provided bottles and were shipped
to the laboratory under proper chain-of-custody (COC). Prism Laboratories, Inc., in
Charlotte, NC, a North Carolina certified laboratory (NC Certification No.: 402) performed the
analysis. Collected samples were analyzed for the Appendix I list of constituents (40 CFR 258
Appendix I). Laboratory analysis for the October date is included as Attachment 1.

Results were compared with the background sample and the NCDEQ IHSB Preliminary Soil
Remediation Goals (PRGs). The October sample results indicate that the soils were not
Ms. Drummond
November 2, 2016
Page 2 of 2
impacted by site activities. The only volatile organic compound detected was acetone at low
concentrations in samples S-1, S-2 and BG-1. Cobalt and vanadium, in samples S-1, S-2,
and BG-1, were detected at concentrations above their PRGs. Thallium was detected slightly
above the PRGs in S-1 and S-2, and just below the PRG in the background sample. These
inorganic constituents are naturally occurring in North Carolina soils. Concentrations
between the background location, BG-1, and other locations did not indicate a substantial
difference in inorganic concentrations for the analyzed parameters. Sample results from the
October event are presented in Table 1.

Summary and Conclusions

Inorganic constituents are naturally occurring in North Carolina soils. Background sample
concentrations were generally consistent with the concentrations from the samples
collected in observed seep areas; indicating the metals concentrations are naturally
occurring.

No organic constituents were reported at concentrations above the PRGs in soil samples.

Based on the soil laboratory analysis, the leachate release does not appear to have adversely
affected the natural environment at the site. If you have any questions or require additional
information, please contact us at 919-828-0577 or by email below.

Sincerely,
SMITH GARDNER, INC.

Madeline M. German, P.G. Joan A. Smyth, P.G.
Project Geologist Senior Hydrogeologist
[e-mail] [e-mail]

Attachments - Figure 1
Table 1
Prism Laboratory Report

cc: Rex Buck – Davidson County
Steven Sink – Davidson County
Susan Heim - NCDEQ

H:\Projects\Davidson County (NC)\Midway Convenience Center Seep Investigation 9-16\Midway Seept Release
Results_Davidson.docx
S-2
BG-1
S-1
Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/AirbusDS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, andthe GIS User Community
G :\C A D \D a v i d s o n \D a v d c o 1 6 -5 \s h e e t s \D A V D C O -A 0 8 1 6 .m x d
DRAWN:APPROVED:SCALE:FIGURE NO.:PROJECT NO.:DATE:
C.T.J.J.A.S.1AS SHOWN Oct. 2016 DAVDCO 16-5
SOIL SAMPLING LOCATIONS
MIDWAY CONVENIENCE CENTER
DAVIDSON COUNTY, NORTH CAROLINA
³
0 50 100 150 200Feet

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Table 1
Detected Constituents
Davidson Midway Convenience Center
October 7,, 2016
By: JS
Date: `0/25/16
Detected Constituents
NCDENR IHSB
Preliminary Soil
Remediation
Goals (PRGs)
(mg/kg)
S-1
(mg/kg dry)
S-2
(mg/kg dry)
BG-1
(mg/kg dry)
Arsenic 5.8 1.2 J 1.3 J 0.81 J
Barium 580 100 110 37
Beryllium 63 0.96 0.99 0.31
Chromium 360000 20 20 7.8
Cobalt 0.9 4.1 3.8 1.8
Copper 700 5.7 1.8 2.9
Lead 270 32 22 9.3
Nickel 130 10 BH 9.8 BH 3.8 BH
Selenium 2.1 BRL 0.15 J 0.16 J
Thallium 0.28 0.54 0.47 0.21 J
Vanadium 6 42 47 16
Zinc 1200 47 35 20 J
Acetone 24 0.03 0.021 0.05
NOTES:
J - Constituent detected but below the Reporting Limit (RL); therefore, the results is an estimated concentration.
BH - Method Blank > 1/2 Reporting Limit, but sample concentrations are greater than 10X the Method Blank.
Bold and Shaded - Concentration above listed standard
BRL = Not Detected above the Laboratory Established Reporitng Limit
Data from Prism Laboratories, Inc., Work Order No: 6100164 dated 10/20/16
IHSB Prelim. Soil Remediation Goals - NCDEQ Inactive Hazardous Sites Branch Preliminary Soil Remediation Goals
for protection of groundwater updated October 2016

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