On December 30, 2021, a destructive wildfire, called the Marshall Wildfire, started near State Highway 93 and Marshall Road and burned eastward through the Site. Following the fire, DRMS requested that Tetra Tech complete a preliminary investigation of the conditions across the approximately 7.5-acre southern portion of the Marshall Mesa Underground Coal Fire site which is located near the southwest corner of the Marshall Wildfire impacted area. From March 2022 to August 2023, the investigation expanded to include both the southern AOI and the approximately 17.5-acre area north of the Site or northern AOI. The goal of this continuing investigation is to ascertain subsurface conditions and potential mine fire activity and includes Site-wide (both northern and southern AOI's) microgravity geophysical surveys, drilling and geologic investigation, monitoring well installation and hydrogeologic evaluation, and ongoing subsurface temperature monitoring. This report summarizes findings from the investigations.
