As the long-running saga of the re-licensing of the Conowingo Dam continues, one major document relevant to that proceeding has been released – an environmental impact statement covering the Conowingo and two other projects along the Susquehanna River. The document was released March 11 by the Federal Energy Regulatory Commission, the body currently reviewing the federal re-licensing of the Exelon facility.
The context for the report is summarized in its cover content:
This final EIS documents the view of governmental agencies, non-governmental organizations, affected Indian tribes, the public, the license applicants, and Federal Energy Regulatory Commission (Commission or FERC) staff. It contains staff evaluations of the applicants’ proposals and the alternatives for relicensing each of the Susquehanna River Projects.
Before the Commission makes a licensing decision, it will take into account all concerns relevant to the public interest. The final EIS will be part of the record from which the Commission will make its decision. The final EIS was sent to the U.S. Environmental Protection Agency and made available to the public on or about March 11, 2015.
The lengthy (nearly 900 page) document details a multitude of exhibits relevant to the major project. One element summarizes sediment issues in the area behind the Conowingo Dam (excertped form page 112):
The LSRWA study (Corps and MDE, 2014) investigated the sediment trapping capacity of the lower Susquehanna River reservoirs, including Conowingo Pond, and the potential effects on the Chesapeake Bay; details of the LSRWA study are described in section 220.127.116.11, Geology and Soils, Environmental Effects. Essentially, that study concludes that Conowingo Pond has reached its sediment capacity and is now in a state of dynamic equilibrium where high-flow events scour sediment (and associated nutrients) from the reservoirs, followed by periods with lower flows when sediment accumulates within the storage space created by the high-flow events. On average, sediment and nutrient loads delivered to the Chesapeake Bay via the Susquehanna River equal the load delivered into the three lower river reservoirs.