ing dike. These works make the revetment above the Interstate Bridge reasonably safe against flanking. The effect of extending Dikes Nos. 5 and 6 to the line of the training dike prolonged, and constructing Dike No. 7, has not been accurately determined. The center of gravity of section of the reach between Dike No. 7 and a point 1,600 feet below, however, is now apparently farther away from the bank than prior to constructing the above works. This makes the revetment of that part of the bank less liable to being undermined. There has been no material change in position of the channel at the Interstate Bridge. It is still under the middle fixed span at low stages, and under the north arm of the drawspan at high stages. REVETMENT CONSTRUCTION AND REPAIR. During the interval between the suspension of work in the fall of 1895 and its resumption in 1896 the revetment of 1892, between Dike No. 7 and a point about 1,450 feet below, was damaged at four different places, aggregating about 790 linear feet, by being undermined. This was caused by the flow, after following the training dike, concentrating and forming a gorge section in front of the bank referred to, the subaqueous mattress settling and the bank behind it caving as the section in front of the mattress deepened by scour. With the exception of 360 feet immediately above the old launching ways, the mattress was held by its anchor cables and appeared to be intact. For the above distance and the adjacent 160 feet below it, occupied by the launching ways, where no subaqueous mattress had been placed, a mattress 520 feet long by 66 feet wide from low water was woven. The slope of the upper bank was also restored by filling voids, formed by caving, with layers of fascines and stone. The last-described class of repairs was also made to the other parts of the upper bank, which had caved. The above revetment repairs were made during the fall and early winter of 1896. The details of extent and net cost of revetment work are given in Exhibit B. As there is no safe ice harbor in the vicinity of Council Bluffs, the old launching ways were reconstructed and a set of tracks, with sufficient capacity to store the plant, erected, in as inexpensive a manner as possible. The old ways' incline was found to be occupied by a number of unserviceable flatboats belonging to private individuals, and several weeks elapsed before the owners of the boats could be gotten to remove them. As soon as this was done work on the ways was begun. They were completed October 31. The laying up of plant on the storage tracks was begun November 1, and was practically completed November 7. The ring in the Atalanta's boiler, which was burned while towing plant up the river, was replaced, and slight repairs made to the hulls of the boats. The river was closed by ice November 28 at a stage of 2 feet below standard low water. Operations were suspended December 19 and all employees discharged except an overseer and two watchmen to take care of property. A movement of the ice occurred January 19, by which the top diagonal bracing at the stream end of Dike No. 5 was lifted and the piles canted. This damage was repaired in February and the ice cut away along the lower hundred feet of the training dike to relieve it from stress of moving ice. The river opened at the boatyard March 16, at a stage of about 44 feet above standard low water, without doing any damage to the dikes. The ice from gorges below Sioux City, Iowa, passed the boatyard between March 20 and 23. Very inclement weather delayed completing necessary repairs to the calking of the plant until March 28, when the launching of plant was begun. Launching was completed April 3, after which the part of the ways above water and the storage tracks were dismantled and, with the other property pertaining to the work, loaded on barges for shipping down the river. The operations were concluded May 10, on which date the towing of plant to Nebraska City was completed. Very respectfully, your obedient servant, Capt. HIRAM M. CHITTENDEN, SAML. H. YONGE, Division Engineer. Corps of Engineers, U. S. A., |