DIVER IDENTIFICATION OF TWO ANOMALIES FOR THE UPPER DISSOLVED OXYGENATION FACILITY, EFFINGHAM COUNTY, GEORGIA

The U.S. Army Corps of Engineers, Savannah District is proposing to deepen the Savannah River Federal Navigation Channel as part of the Savannah Harbor Expansion Project. Studies have determined that the proposed undertaking may have the potential to affect dissolved oxygen levels in the Savannah River, and mitigation will be required to offset potential impacts. The U.S. Army Corps of Engineers, Savannah District has selected the construction of oxygen injection systems as an effective mitigation solution. One of the facilities will be constructed in Effingham County, Georgia upriver from the City of Savannah, on a 49-acre tract owned by Plant McIntosh near Rincon in Effingham County, Georgia. The system will consist of a building constructed on land near the riverbank and an outlet pipe that will extend into the Savannah River. Based on current project design, the area that will be directly impacted by the construction will be limited to 15 acres within the 49-acre tract and approximately 0.48 kilometers (0.31 miles) of the Savannah River to the north and south of the proposed outlet pipe location The remote sensing survey area was located in Effingham County, Georgia and Jasper County, South Carolina.

A Phase I terrestrial and remote sensing investigation of the Area of Potential Effect was conducted in 2013 by AMEC Environment & Infrastructure, Inc. for the Savannah District. Three magnetic anomalies with sonar signatures were identified during the remote sensing of the Savannah River portion located in both Effingham County, Georgia and Jasper County, South Carolina. Based on the nanotesla readings and the sonar images for Anomaly 1, it was determined that this anomaly is associated with a Plant McIntosh intake pipe and bulkhead. The remaining two anomalies, Anomalies 2 and 3, were recommended for additional investigation. Subsequently, and in order to assist the Savannah District with meeting compliance requirements related to the National Environmental Policy Act, Panamerican Consultants, Inc., under subcontract to DCA/GEC A Joint Venture, LLC, conducted a comprehensive submerged cultural resources investigation of the two anomalies in response to the U.S. Army Corps of Engineers’ Scope of Work entitled, Diver Identification of Two Anomalies For the Upper Dissolved Oxygenation Facility, Effingham County, GA, under Contract No. W912HN-12-D-0016, Delivery Order No. 0017.

The project consisted of archival research, a refinement remote sensing survey and subsequent diver investigation of the two potentially significant anomalies. The remote sensing refinement survey was conducted in mid-July. However, subsequent river flooding precluded diving on two attempts during August and September, with diving successfully conducted October 10, 2013 after river levels receded. Results of the archaeological diver assessment indicated both anomalies were negative for cultural resources sites. In concert with probing results, a lack of acoustic targets, and negative subbottom returns, both anomalies are considered to not represent potentially significant cultural resources. Anomaly 2 was a small discrete single-source object. Anomaly 3 was a linear anomaly that crosses the entire survey area; its small size and ephemeral nature argues that it most likely represents wire rope or cable.