Implications for TMDL Development from Proposed Harbor Modifications

Major harbors of the United States must support a wide variety of users and typically attract many differing interests. The majority of the stakeholders have an interest in overall water quality and many participate in the development of a TMDL. Increasingly, harbors in the US and around the world are seeking to balance the environmental and socioeconomic interest through comprehensive watershed management planning and stakeholder participation. Significant Harbor modifications are regulated by the USACE under Section 404 of the Clean Water Act; where as TMDLs are regulated by EPA and the states under Section 303. Although these are different regulatory authorities and responsibilities, they are addressing the same interests in resource protection and management. In Savannah Harbor, the USACE, EPA and States of Georgia and South Carolina have coordinated with each other and supported various aspects of harbor planning and TMDL development. This cooperation has led to a comprehensive effort to balance the harbor user's needs and support technically defensible decision making.The Georgia Ports Authority (GPA) and USACE Savannah District are evaluating the feasibility of several proposed Harbor modifications, including ecosystem restoration projects and deepening a portion of Savannah Harbor for consideration as a Federal Navigation Project. The USEPA is responsible for the determination of a water quality standard and TMDL for dissolved oxygen (D.O.) in Savannah Harbor. In coordination with these agencies and other stakeholders, water quality models are being used to support the evaluation of the effects of deepening the existing navigation channel, which would extend a maximum of 35 miles from an inner Harbor port to almost 15 miles offshore. The impacts to DO and other estuarine resources will be evaluated using a calibrated 3-D, hydrodynamic model that will predict changes to salinity and dissolved oxygen due to the various alternative Harbor modifications. The water quality model will also be used to develop a TMDL for DO in the Savannah Harbor. Through extensive stakeholder coordination, a comprehensive methodology for the development and calibration of a water quality model to support these evaluations has been developed.The water quality model will be used to define the relative impact of the deepening upon the DO concentrations throughout the system under various conditions and in the development of a TMDL. The physical processes, which must be considered, include the following:Reduced reaeration over the water column due to increased depths, which will primarily impact the bottom concentrations;Alterations to the transport of BOD material throughout the system;Alterations to the levels of stratification which may reduce bottom layer reaeration; andIncreased salinities, which may alter the saturation concentrations.In response to varying and sometimes conflicting interests and concerns, the Georgia Ports Authority, USACE, USEPA, other state and federal resource agencies, and public interest and environmental groups jointly formed the Stakeholders Evaluation Group (SEG) to address concerns raised about the potential impacts of the proposed deepening. The purpose of the SEG is to identify scientific studies necessary to adequately characterize the estuarine resources, evaluate potential affects of various modifications and to reach consensus on final mitigation planning. SEG members include representatives from over 150 of the applicable Federal, State, local, and private interest groups, including numerous environmental organizations.This paper and presentation will outline the process used to develop a working team of stakeholders, regulators and scientists who oversee the project, and the results of the project to date. This process is one that provides an excellent example of coordination and resource sharing for any group planning a comprehensive watershed study involving multiple users and stakeholders.