are thus provided for, two to be located at the 360-ft lock and two at the Missouri shore end of the dam for Alternate B, or at the site of the 600-ft lock for Alternate B'. This scheme is deemed feasible with proper construction procedures but, again, these additional risks and uncertainties should be considered in evaluating rehabilitation vs replacement. 3. Alternates C and C' New 1200-Ft (and 600-Ft) Lock(s) and Dam Two Miles Downstream The Corps recommends constructing a new dam and a new 1200-ft long lock about two miles downriver from the present dam at an estimated cost of $391,000,000, based upon January 1976 prices. Alternate C, Table II, calls for an additional 600-ft lock with all other provisions the same as the Corp-recommended plan for a single 1,200-ft replacement structure, Alternate C', Table III. Problems, risks, and uncertainties will be minimized with this plan. The new structure will fulfill all the requirements for presentday design standards, eliminating the continuing problems with the existing locks and dam. 1. Provision for a 1200 and 600-Ft Lock A summary of estimated costs for the satisfactory alternatives, each providing one 1200-ft and one 600-ft lock, as discussed in subsections above is given in Table II. All costs are based on January 1976 price levels. 88-866 - 77-71 The least costly choice is Alternate A, constructing a new lock along the Missouri bank and rehabilitating both the dam and the 600-ft lock. The estimated cost for this is $420,000,000. There are certain risks associated with this plan, however, as discussed earlier in this report. The order of magnitude cost of a new lock in the existing dam and rehabilitating the existing 600-ft lock and the remainder of the dan is $440,000,000. Included in this fugure are provisions for maintaining the same swellhead through the dam after the new lock is built. The estimated cost of a complete replacement about two miles downriver is $470,000,000, which will also provide for a 1200-ft and 600-ft lock. This cost is based on Corps of Engineers estimates at January 1976 price levels. A summary of estimated costs for the satisfactory alternatives, each providing one 1200-ft lock as discussed in subsections above, is given in Table III. All costs are based on January 1976 price levels. The least costly choice is Alternate A', constructing a new lock along the Missouri bank, rehabilitating the dam, and closing the existing locks. The estimated cost for this is $365,000,000. The estimated cost for a new 1200-ft lock in the existing dam, rehabilitating the dam, and closing the existing locks is $375,000,000. The estimated cost for the 1200-ft lock replacement facility downstream is $391,000,000. TABLE II ESTIMATED COSTS FOR PROVIDING NEW LOCKAGE CAPACITY 7. Add four new gate bays for maintain ing the same swellhead 3. Railroad and highway modi 16,000 (remove portion of dam) |