Borehole mining (BHM) is a process that incorporates a high-pressure waterjet cutting system and a downhole slurry pumping system through a single hole drilled from the surface into the mineralized rock. The water jet cuts through the material causing the slurry to flow into an extraction pump near the base of the tool and pumped to the surface. As a consequence of this excavation process a cavity will be created [2]. Understanding the relationship between cavity stability and operating parameters is critical in the design of any borehole extraction system. There are numerous technical challenges that must be overcome to advance the concept of in situ extraction of non-soluble tabular resources to a commercial level. vital stage. One of the most important challenges is the technical understanding between cavity formation and stability for a given set of operational characteristics and geomechanical properties of the rock. The first step is to find a numeric code that is easier to use and can also provide reliable results. For this ongoing research the Itasca Flac2D code was selected. The primary objective of this research was to test whether a widely used two-dimensional modeling software package (ItascaFlac2D) had sufficient accuracy to perform a stress analysis within a drilling system as part of a predictive design protocol. To achieve this, data derived from an empirical field study were modeled using Flac2D and the results were compared with those obtained from a case study that used a three-dimensional model (Flac3D). The case study data used in this chapter was obtained from a subsidence study prepared by Barr Engineering Company for Cooperative Mineral Resources (CMR) [1]. CMR attempted to collect samples from two manganese-enriched zones within an oxidized iron formation at a site located near Emily, Minnesota. Through bulk sampling, CMR aimed to evaluate the potential of using a small-scale borehole mining (BHM) system using waterjet technology. CMR considered that the manganese enriched zones in the resource were suitable for BHM excavation methods and, as part of the technical feasibility of the project, a subsidence study was carried out by Barr Engineering. A primary objective of this study was to determine whether subsidence would occur under specific operating conditions and, if so, to develop a potential depth range and radial extents of surface damage in the project area.2) Computer ModelingAs discussed in Previously, there were inherent advantages in this application of using Flac2D over a more sophisticated modeling tool like Flac3D.