RA-1999_12313_CA_O_20200210_ Email from aTC Vapor Intrusion Testing Update

From:Gabe Araos
To:Petermann, Mark
Subject:[External] FW: Snack Shack #245
Date:Monday, February 10, 2020 5:22:08 PM
Attachments:image001.png
SnackShack#245_20200210_SS-1_RiskCalc.pdf
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Mark,

I wanted to update you on the vapor intrusion sampling at Snack Shack. ATC collected both sub-slab
soil gas samples and indoor air samples in January 2020. The sub-slab sample (SS-1) indicated the
presence of toluene, total xylenes, 1,2,4-trimethylbenzene, styrene, tetrachloroethylene and
dichlorodifluoromethane but these compounds did not exceed the Division of Waste Management
(DWM) Soil Gas Screening Levels (SGSLs) for Non-Residential vapor intrusion. To confirm the
potential risk from these compounds, ATC then utilized the DSCA Soil Gas Risk Calculator for non-
resident. Based on the risk calculator (see attached), the cumulative carcinogenic risk for SS-1 was
calculated at 3.2E-09 and it did not exceed the mitigation standard of 1.0E-04. In addition, the
hazard quotient was calculated at 1.8E-03 and it did not exceed the mitigation standard of 1. Based
on the risk calculations, there is no risk of vapor intrusion to non-residents at the site and we will
instruct the lab not to run the indoor air samples. This is the typical procedure utilized during DSCA
vapor intrusion assessments. Let me know if you have any questions or comments.

Thanks

Gabriel Araos, P.E. | PRACTICE GROUP MANAGER | ATC Group Services LLC Direct [phone] | Cell [phone] | Office [phone]
2725 E. Millbrook Road, Suite 121 | Raleigh, NC [e-mail] | www.atcgroupservices.com
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From: Jeremy Robbins <[e-mail]>
Sent: Monday, February 10, 2020 3:53 PM
To: Gabe Araos <[e-mail]>
Subject: Snack Shack #245

Gabe,

I have attached the SS-1 Non-Residential risk calculator to this email.

Jeremy Robbins, P.G. | STAFF GEOLOGIST | ATC Group Services LLC Direct [phone] | Cell [phone]
2725 East Millbrook Road Suite 121 | Raleigh, NC [e-mail] | www.atcgroupservices.com
This email and its attachments may contain confidential and/or privileged information for the sole use of the intended
recipient(s). If you are not the intended recipient, any use, distribution or copying of the information contained in this
email and its attachments is strictly prohibited. If you have received this email in error, please notify the sender by
replying to this message and immediately delete and destroy any copies of this email and any attachments. The views
or opinions expressed are the author's own and may not reflect the views or opinions of ATC.