DERR-2025-000545

485 West 1400 North ● Orem, Utah 84057 ● [phone] ● Fax [phone]

Compliance Specialist
Assessments ● Remediation

December 19, 2024

Ms. Hillary Mason
Utah Dept. of Environmental Quality
Division of Environmental Response and Remediation
195 North 1950 West, 1st Floor
Salt Lake City, UT 84116

Re: Report on Installing Monitoring Wells and Collecting Soil and Groundwater Samples
On August 21-26, 2024 at the Delle Auto Truck Stop located at I-80 Mile Marker 70
Grantsville, Utah
Facility ID #8000119, Release Site NMZ

Dear Ms. Mason:

On August 21-22, 26, 2024 a Hamilton Environmental representative installed six (6) monitoring
wells and collected soil and groundwater samples at the Delle Auto Truck Shop site located at I-
80 mile marker 70, Grantsville, Utah. Appendix A - Figure 1 shows Site Map with approximate
sampling locations of the monitoring wells.

Monitoring Well Installation

On August 21-22, 2024 Monitoring Wells 12-17 were installed using a drilling methodology. The
wells were installed by Earth Core Drilling. The installation of the wells was under the supervision
of a State of Utah UST Consultant (Jay Hamilton CC 0062).

Collection of Soil Samples and Data

Soil samples were collected to assist in defining the horizontal and vertical extent of the possible
contamination plume. All soil samples were screened in the field with a photoionization detector
(PID) (see Attachment A – Table 1) . Soil samples were submitted for analysis to Chemtech-Ford
Laboratory, a Utah BLI-certified laboratory (see Attachment B). The samples were placed on ice
and submitted under chain of custody for analysis of MBTEXN and TPH-GRO and THP-DRO
using EPA Method 8260 D. Sampling was conducted by a Utah Certified Soil and Groundwater
Sampler (Jay Hamilton GS 0251).

Unified Soil Classification was conducted on soil samples collected from Monitoring Well -14 at
the following depths:

MW- 14 0-5 feet ML - Sandy fat clay w/gravel
MW- 14 5-10 feet CL – Sandy lean clay
MW- 14 10-15 feet SC – Clayey sand
MW- 14 20-25 feet SC - Clayey sand
MW- 14 25-30 feet SC - Clayey sand

See USC results from Chemtech – Ford are in Attachment B

MWs 12-17 were installed using an auger drill. The soil cuttings from wells were stored on site.
The cuttings were placed on 8 mil plastic and covered with the plastic and secured so wind would
not uncover the soil. A three foot soil berm was placed around the covered soil pile (see Attachment
C–Site Photos. The location of the berm is approximately 200 feet southeast from the convenience
store. The owner of Delle owns approximately 500 acres with no residential structures on the
property.

Results of Soil Sampling
The Soil laboratory analytical results indicate that none of the wells had petroleum concentrations
that exceeded the Initial Screen Levels (ISL) (see Attachment B-Table 2 and Table A below).

Collection of Groundwater Samples and Data

Prior to sampling, fluid level measurements were collected from Monitoring Wells 12-17. Depth-
to-water readings are listed in Table B. Groundwater samples were also collected from the
following wells: MWs 1-5, and MWs 8-11. Monitoring Wells 8-17 were developed on August 22
and August 25, 2024 using a purge pump.

Free-product was observed in MW-1 (0.8 feet), MW-2 (3+ feet) and MW-3 (0.08 feet) (see Site
Photos). MW 6 was unable to be found after several hours using a metal detector and MW-7 and
been destroyed during site construction.

MWs 4-5. 8-17 were sampled using disposable polyethylene bailers and the appropriate 40 ml
glass bottles. The samples were placed on ice and transported under chain-of-custody to
Chemtech-Ford Laboratories, an accredited National Environmental Laboratory Accreditation
Program (NELAP) in Utah. The groundwater samples were analyzed for MTBE, benzene, toluene,
ethylbenzene, xylenes, naphthalene (MBTEXN), and total petroleum hydrocarbons (TPH) analysis
employing EPA Method 8260 B/Cand D, 8015C, 5030A.

The average groundwater depth below ground surface (bgs) during the sampling event was 19.84
feet (see Table B).

TABLE B

WELL 8/22/2024
GWD (FT)
MW-1 Free Product
MW-2 Free Product
MW-3 Free Product
MW-4 20.88
MW-5 20.15
MW-6 Can’t locate
MW-7 Destroyed
MW-8 19.6
MW-9 20.15
MW-10 20.75
MW-11 13.89
MW-12 20.28
MW-13 20.78
MW-14 19.24
MW-15 18.45
MW-16 19.24
MW-17 18.66

See Appendix A–Figure 2 for groundwater contours..
Analytical results of the August 21-22, 2024 groundwater sampling can be reviewed in Appendix
A - Table 3. Laboratory analytical reports from the August 21-22, 26, 2024 sampling event are
provided in Appendix B.

Results of Groundwater Sampling

The Groundwater laboratory analytical results indicate that the following wells had petroleum
concentration that exceeded the Initial Screen Levels (ISL) (see Table C).

Table C

WELL Benzene
February 3-5, 2022)
(mg/L)

MW-1 Free Product
MW-2 Free Product
MW- 3 Free Product
MW- 4 *0.052
MW-5 *0.067
MW-10 *0.010
MW-14 *0.007
MW-15 *0.110

* Samples collected that exceed Initial Screening Level (ISL) for benzene.

Conclusions – Soil and Groundwater Sampling

Soil - Analytical Reports from August 21-22, 2024 soil sampling appears to indicate that
petroleum concentrations did not exceed the ISL in MWs 12-17.

Groundwater – Analytical Reports from the August 21-22, 26, 2024 groundwater sampling
appears to indicate that petroleum concentrations exceeded the ISL in MWs 1(FP), 2 (FP), 3(FP),
4 (0.052mg/L), 5 (0.067), 10 (0.010), 14 (0.007) and 15 (.110) It should be noted that it appears
the groundwater from MWs 10 may not exceed the Tier 1 Screening Criteria.

Tier Screen Criteria

These levels only apply when there are no buildings, property lines or utility lines within 30 feet
of source, and no water wells or surface water within 500 feet of source.

Recommendations – Groundwater Sampling

Hamilton Environmental recommends that the groundwater at the Delle site be monitored in three
months. Hamilton Environmental recommends that during the next sampling event that MWs 8,
and 11 need not be sampled. The free product in MWs 1, 2 and 3 should be removed as soon as
possible. It appears that the plume has been delineated except in the area of MW 14 (0.007 mg/L)
and MW 15 (0.110mg/L). To delineate the contamination in MWs 14 and 15 it would be necessary
to drill an additional well 800 feet to the north. The drill rig could not move any further to the north
toward the UDOT Right-of-way because of geologic barriers. The approximate 800 feet would
include the UDOT Right-of- Way on the south of I-80 Freeway, the I-80 freeway and another
UDOT Right of Way on the north side of the Freeway.. With the relative amounts of
contamination in Monitoring Well #14 (0.007 mg/L) and in Monitoring Well #15 (0.110 mg/L)
the contamination may be under the Freeway.

If you have any questions, please call me at [phone]

Sincerely,

Jay Hamilton
Project Manager

cc: Steve Saunders

Attachments
Appendix A:
Figure 1 – Site Map and Sampling Locations
Figure 2 – Groundwater Contours
Table 1 – PID Log
Table 2 – Soil Data and Analytical Results
Table 3 - Groundwater Data and Analytical Results
Appendix B:
Groundwater Analytical Reports and Chain-of-Custody
Appendix C:
Site Photographs
Appendix D:
Geologic Logs

APPENDIX A

Figure 1 – Site Map
Figure 2 – Groundwater Contours

Table 1– PID Logs
Table 2– Soil Data and Analytical Results
Table 3 – Groundwater Data and Analytical
Results

APPENDIX B

Groundwater Analytical Reports and Chain-of-Custody

APPENDIX C

SITE PHOTOS

APPENDIX D

GEOLOGIC LOGS