The Prince of Wales Fort, in Churchill Manitoba, was constructed in the early 18th century by the Hudson Bay Trading Company (HBC) in an effort to secure the fur trade in northern Canada. The fort is a Vauban style rubble masonry construction, and is the most northerly fortification of this kind. In the 1920’s the fort received recognition as a National Historic Site by the Historic Sites and Monuments Board of Canada, at which time monitoring and repairs began under the leadership of Parks Canada. As a result of the fort’s northern latitude it has been subjected to extreme temperatures and freeze thaw cycles causing a gradual break down of the mortar within the escarp walls. Recently, climate change has led to an increase in the average local temperature shifting the thermal gradient within the earth rampart. During spring and summer, high volumes of ground water have drained through the walls washing out much of the degraded mortar. The result is a partially grouted rubble wall, encased with ashlar face stones. These deteriorating core conditions have caused significant lateral deflections in several areas and failure in others. The core wall material will be analyzed by modeling it as an irregular granular material. Using this approach, different levels of cohesion can be used to determine the in-situ mortar conditions and the strength of the structure.