ENVIRONMENTAL ASSESSMENT OF CHANGED CONDITIONS FOR THE AND ADDENDUM TO THE JULY 1991 FINAL EIS FOR THE 1.00 Background. On November 15, 1991 the Savannah District mailed the Final EIS on the Savannah Harbor Comprehensive Study Harbor Deepening to the Environmental Protection Agency for filing in the Federal Register. Subsequently, it was learned that authorization had been issued for the closing of New Cut and the permanent discontinuance of operation of the Back River tide gate. This authorization was issued pursuant to Section 1135 of the Water Resources Development Act of 1986, as amended. Construction of the Section 1135 project will result in a change in the without project condition for the Savannah Harbor Deepening Project. In addition, the District has discovered several items in the Final EIS which have changed due to new information and project plan refinement. In view of this new information, the District determined that an Environmental Assessment was needed to address the environmental impacts of these changes and to determine if the changes were significant enough to require a supplemental EIS. 2.00 Scope and Authority. 2.01 Scope. The purpose of this document is to evaluate the impacts of the changed conditions on the Savannah Harbor Deepening Project to determine if the changes will modify the selection of the preferred alternative and whether a supplemental EIS is needed. 2.02 Authority. The Savannah Harbor Comprehensive Study was authorized by a resolution adopted by the Senate Committee on Public Works on 10 July 1972. The House of Representatives Committee on Public Works adopted a similar resolution for the study on 12 October 1972. The following changes 3.00 Description of Changed Conditions. a. The affected environment (without project condition) has changed due to closure of New Cut and the permanent discontinuance of operation of the Back River tide gate. b. Due to plan refinement the volumes of material to be dredged under each alternative plan has been revised. A 2 foot deepening would result in the dredging of 715,780 cubic yards of material from the inner harbor/Kings Island Turning Basin and 255,405 from the bar channel. A 4 foot deepening would require the dredging of 4,375,142 cubic yards from the inner harbor/Kings Island Turning Basin and 1,551,915 from the bar channel. c. The contractor would ce allowed to use equipment other than hopper dredges in the bar channel to avoid having to perform all work during the winter. However, all material dredged from the bar channel would still be transported to the ocean disposal site. d. Cost estimates for project alternatives have changed due to project plan refinement and impacts of the Section 1135 Project. e. Project may result in the need to remove a pipeline owned by the Union Camp Corporation and would result in impacts to some privately owned property. f. The costs and environmental impacts of deepening and maintaining the berths at which project benefits were claimed need to be discussed as a secondary impact of project construction. No such dredging would be required for a 2 foot deepening. A 4 foot deepening would require approximately 90,000 cubic yards of material to be dredged from these berths (See Figures 1 and 2) and placed in Disposal Area 2A. Maintenance of the berths ould continue to be conducted with no increase in the volumes of material expected to be dredged. g. All plans have been modified to gradually reduce proposed project widths and dredging depths i.. the channel both up and downstream of the CSS Georgia with a maximum narrowing at the CSS Georgia of 100 feet and no dredging below -42′ mlw at the site. Only one-way traffic would be allowed in the wreck vicinity. This would avoid impacts to the wreck which may have resulted from the deepening project. The currently proposed narrowed channel at the CSS Georgia is indicated on Figure 3. The configuration of this channel section would be further investigated prior to construction to insure there would be no impacts to the CSS Georgia or Old Fort Jackson due to erosion. 4.00 ALTERNATIVES 4.01 Introduction. This chapter of the EIS presents the selected plan and all alternatives considered in a comparative form, concentrating on four plans which were considered in detail, so that each alternative can be compared with the others. In this way each alternative's relative benefits and detriments to the total environment can be determined. The chapter is divided into four sections: (1) a description of the alternatives that were considered, but were eliminated from detailed review; (2) a description of each alternative, including the selected plan; (3) an evaluation and comparison of the alternatives considered in detail; and (4) the identification of the National Economic Development (NED) Plan, Locally Preferred Plan, and Selected Plan. 4.02 Plans Eliminated From Further Study. During the plan formulation phase of this study, six alternatives for deepening Savannah Harbor were developed. Two of these alternatives, Plans 3 and 5, were considered for deepenings of 2, 4, and 6 feet. others were only evaluated for a 2 feet deepening. Initial The |