COMBINING GEOPHYSICAL METHODS FOR DETECTING THE STRUCTURAL REMAINS OF FORT LA PRÉSENTATION, OGDENSBURG, NY

In what would later become Ogdensburg, NY, The French established a settlement on the banks of the St Lawrence River on November 21, 1748. This initial settlement was attacked and burned the following year by Native Americans. In 1751, a more solid fortification was constructed of 150 ft on a side, characterized by four stone bastions, constructed using the piece-sur-piece technique and connected to each other by a wooden palisade, this would become known as Fort La Presentation (FLP). The site went through many modifications due to the occupation and abandonment of FLP throughout history by the French, British and finally the Americans. After its days as a defensive structure, the Rome, Watertown, and Ogdensburg Railroad used the area as a rail terminal. Subsequently an oil storage facility was built by Standard Oil (later ExxonMobil), which was in operation until the 1980s. Today, the exact location of the fort has been lost to history, research has been conducted to locate it. In the fall of 2007, a team from SUNY Potsdam attempted to excavate the area. However, because oil contamination was severe, the excavations were limited to less than a meter. These types of challenges make geophysical methods a viable alternative. The main objective of this project is to locate the structural remains of FLP, through a non-invasive approach. We tested several different geophysical techniques including ground penetrating radar, electrical resistivity, and earth resistivity tomography. Electrical resistivity, through the use of a GF CMD-4 and CMD mini 6L allowed us to identify the areas with low resistivity that indicates the areas where excavations were carried out in 2012 to remediate contaminated soils as well as identify areas with patterns of soil compaction, which could indicate the location of buildings or roads. A MALA GX 450 MHz GPR system was used to further our understanding of the subsurface and has been marginally useful due the oil contamination and site disturbance. Earth resistivity tomography surveys are planned for August and September and hope to reveal original shorelines of the area and a better understanding of the longer-term site evolution.