DERR-2024-006595

Underwood Environmental Consulting, Inc.
1

January 3, 2024

Mr. Mark Crim
Department of Environmental Quality
Division of Environmental Response and Remediation
P.O. Box 144840
Salt Lake City, Utah 84114-4840

Re: Soil Vapor Sampling
Former Calvinco Co. (Intermountain Lock)
3106 South Main Street
South Salt Lake, Utah
Facility ID #4000124, Release Site OBL

Dear Mr. Crim,

In the DERR’s March 28, 2023 letter outlining additional sampling requirements, the Stage 2 portion of the letter
requires a plan for sub-slab vapor testing if an SSCL for “Indoor Air Exposure” is exceeded. Results from the
May 2023 sampling event revealed two locations (MW-7 and MW-5) in which soil fractionation results exceeded
the SSCL for the C7-C8 Aliphatic Hydrocarbon range. No other exceedances were found in soil or groundwater
samples tested.

On behalf of the property owner, Underwood Environmental requests that “near-slab” vapor sampling be utilized
in lieu of sub-slab samples. The concerns expressed by the property owner as well as the consultant are related
to the intrusive nature of drilling through the building’s foundation. Some of the concerns are summarized below:

• The current Intermountain Lock (IML) building was constructed as an “earthquake proof” building. The
foundation may therefore contain special features which could be compromised by penetration of the
vapor sampling device. Additionally, several underground utilities enter the building through the
showroom area the exact locations of which are unknown. Damage to flooring materials would also occur.
• Drilling and sampling inside the building might also alarm employees who could perceive a greater risk
than actually exist. This could be disruptive to the business.
• Creating a hole in the foundation might over time become a pathway in itself despite standard procedures
used when abandoning the sample points.
• According the owner there have never been complaints of hydrocarbon odors inside the building.

In consideration of these concerns and based on similar projects performed for the DERR, we respectfully request
a stepwise approach to evaluating potential vapor intrusion. If warranted, near-slab soil vapor testing could be
performed to evaluate for subsurface soil vapor potential. Locations for near-slab sample point installation would
be negotiated with the DERR and detailed in a sampling plan including a rendering of the building’s ground level
layout as requested.

Underwood Environmental Consulting, Inc.
2

Respectfully,
Underwood Environmental Consulting, Inc.
L. Earl Underwood, P.G.
Sr. Geologist, CC-0018