Georgia Ports Authority is committed to upgrading, modernizing, and expanding its facilities in order to meet the demand in the container market, and is constantly pursuing new methods and technologies to increase productivity and facility capacity. While a number of expansion alternatives exist to address the forecasted container cargo amount through the year 2045, it is reasonable to expect increased productivity and operational changes to provide further capacity at existing facilities.

Historical Operating Practices

Underkeel Clearance. During the interview with the Master Pilot, he revealed that current pilot regulations require that the ships not depart the docks at Garden City Terminal until there is at least a 4-foot difference (underkeel allowance) between the draft of the vessel at the dock and the authorized depth plus additional depth due to tides. When the ship is underway at a speed of 10 knots, the ship would "squat" 2.4 feet lower in the water than when at rest. Therefore, the 4-foot underkeel allowance provides for a net underkeel clearance of only 1.6 feet.

Ship pilots also indicate they are normally unable to make full use of only 4 feet of the high tides because of the short time high tides are available, and because it requires about 3 to 3-1/2 hours to reach the sea buoy and natural deep water due to tidal currents. With an existing channel depth of 38 feet mlw and a high tide of 4 feet, the requirement for a total underkeel allowance of 4 feet would permit ships of up to 38-foot drafts to depart from Savannah Harbor when making maximum practical use of high tides. The actual data on drafts of ships departing Savannah Harbor in 1989 shows that the normal maximum operating draft was constrained at a maximum draft of 38 feet, with only 5 outbound trips exceeding 38foot drafts, which confirms the information on actual operating practice provided by the pilots.

The economic analysis was based upon actual practice concerning underkeel clearances. This resulted in an assumption that with authorized channel depths of 38, 40, and 42 feet mlw, the normal maximum operating drafts for vessels leaving or entering Savannah Harbor would be constrained at 38, 40, and 42 feet respectively when making full use of the maximum practical usable high tide of 4 feet.

Light Loading. Light-loading practices of container ships using Savannah Harbor for the year 1988 are shown in Table 22. The data indicate a consistent pattern of light loading of containerships. About 92 percent of the trips were made with vessels light loaded to some extent. Light loading will often appear to Occur on vessels that are at or near capacity in terms of number of

containers. Light loading occurs under these circumstances as the result of empty containers being transported between ports, or due to low density cargo for that particular voyage.

However, this should not be interpreted to mean that containerships never load to their registered drafts. Historically, a fraction of all ships, including the largest containerships, have been observed operating fully laden in Savannah.

TABLE 22

NUMBER OF CONTAINER VESSEL TRIPS LIGHT LOADED BY DESIGN DRAFT
SAVANNAH HARBOR 1988

Analysis of the bulk fleet used in the grain export trade to the Far East and Europe (mainly the Soviet Union) indicates that the typical vessel has a capacity of 39,000 DWT and maximum draft of 36 feet. Bulk grain vessels sail fully loaded from the terminal in Savannah Harbor to their final destinations. Vessel operating practices of the bulk grain fleet are discussed in greater detail in the Economics Appendix.

NEED FOR PROJECT MODIFICATION

The engineering and economic studies have clearly indicated the need for deepening of the authorized channel in Savannah Harbor and Kings Island Turning Basin.

There

Deepening the harbor channel to 40 feet or more would provide substantial benefits from an increase in bulk grain vessel traffic and container vessel traffic from the Far East and Europe. would also be benefits from the reduction in tidal delays now experienced by vessels which must wait for favorable tide conditions before entering or departing the harbor.

These constraints will become more critical in the future as the average vessel size in the world fleet grows. Large containerships, for example, are projected to constitute as much as half the future fleet with a deepening project in place. However, if the harbor is not deepened, Savannah will come under increasing pressure from ports and harbors with infrastructure better suited to the large, efficient vessels which will dominate trade in the next century.

There are no unusual factors, issues, or constraints which would result in prohibitively high costs associated with channel deepening.

The Georgia Ports Authority strongly supports channel deepening. The local sponsor is also willing to cost share in a deepening project. The proposed expansion and upgrading of port facilities by the Georgia Ports Authority will accommodate projected vessel traffic through the year 2045.

Therefore, the feasibility study continued the previous development and evaluation of alternatives for channel deepening, which included various channel depths and methods of disposal of dredged material. The alternatives also included the need for concurrent deepening of the Kings Island Turning Basin, due to maneuvering problems being experienced with the current authorized depth.

FORMULATION AND EVALUATION OF ALTERNATIVES

DEVELOPMENT AND EVALUATION OF ALTERNATIVES

Introduction

The problem analysis showed a need for deepening of the authorized harbor channel from its present depth of 38 feet. Several alternative methods for channel deepening were developed, which included various depths and methods of disposal of the dredged material.

The following discussion presents the plan selection that derived from the various alternatives considered during the Preformulation Phase of the study. It also presents the final array of alternatives studied in more detail during the Formulation (Feasibility) Phase of the study. The discussion concentrates on the three plans, and variations thereof, that were considered in detail during the final Feasibility Phase.

This section is divided into four parts:

(1) A description of the alternatives that were considered during the Preformulation Phase, but eliminated from detailed review;

(2) A description of each of the final array of alternatives considered in detail, including the without action plan and the selected plan;

(3)

(4)

An evaluation and comparison of the alternatives
considered in detail, and;

The identification of the National Economic Development
(NED) Plan and the selected plan.

Summary of Screening of Alternatives

Table 23 illustrates the iterative development, evaluation, and screening of various channel deepening alternatives since the initial plan formulation phase of the study. It also shows the various depths and disposal areas considered for each alternative, since these were the primary differences between alternatives.

During the preformulation study, Plan 7 was developed which would place maintenance dredging from the bar channel on Tybee Beach. It was not economically feasible and was dropped from further study. During the feasibility study, this plan was restudied for using new work material on Tybee Beach, but it was also not economically feasible and was not subjected to a detailed evaluation.

Plans Eliminated from Further Study

During the initial plan formulation phase of the study, six alternatives and variations for deepening Savannah Harbor were considered. Two of these alternatives, Plans 3 and 5, were considered for deepenings of 2, 4, and 6 feet. The others were only evaluated for a 2-foot deepening. Plan numbers, such as Plan 3, refer to the original plan numbering scheme in the Preformulation Report.

Initial evaluation of these alternatives was discussed in the Savannah Harbor Comprehensive Study Preformulation Report dated January 1983. This evaluation eliminated Plans 3, 4, and 6 from further consideration for the reasons discussed below.