DSHW-2024-009532

E N G I N E E R I N G E X C E L L E N C E S I N C E 1 9 7 4
SALT LAKE AREA OFFICE
859 W SOUTH JORDAN PKWY STE 200
SOUTH JORDAN, UTAH 84095 PHONE: [phone]
www.hansenallenluce.com

Mr. Brian Alba May 24, 2024
Operations Manager
ROC Landfill Holdings, LLC
180 South 100 West #158
Pleasant Grove, UT 84062

Re: Second Quarter 2024
Explosive Gas Emissions Monitoring for the
Intermountain Regional Landfill

Dear Mr. Alba:

On May 23, 2024, Hansen, Allen & Luce, Inc. (HAL) completed the Second Quarter 2024
explosive gas emissions monitoring at the Intermountain Regional Landfill “Landfill”. The work
was completed in accordance with the standards outlined in the Utah Administrative Code
R315-302/3. These regulations require methane concentrations below the lower explosive limit
(LEL) for methane, established at 50,000 parts per million (ppm), at the property boundary and
below 25% of the LEL for methane (or 12,500 ppm) within structures located at the landfill.

Prior to conducting the field work, HAL staff calibrated the QED Surface Emissions Monitor (SEM)
5000 using a 500 parts per million (ppm) methane calibration gas standard. Once the SEM 5000
was calibrated, HAL staff completed the monitoring for methane within facility structures and along
the facility property boundary. Structures associated with the landfill consist of the scale house
and offices, maintenance building, and storage containers.

Methane concentrations were detected between 2.5 and 58 ppm at locations across the property.
Methane concentrations did not exceed 25% of the LEL within structures and did not exceed the
LEL along the property boundary.

If you have any questions or comments regarding information contained in this letter, please call.

Sincerely,
HANSEN, ALLEN & LUCE, INC.

__________________________ __________________________
Ted V. Wallace Andrew J. Alvaro
Geologist Environmental Services Director