A conservative estimate would probably place the annual gate travel of each gate at about 100 miles, which is a severe strain on old gates, of which practically no care can be taken save a hasty annual overhauling in the winter. The axles usually break just inside their journal boxes, while the wheel breakages follow no particular rule. Similar breakages do not occur on later gates, whose axles, however, are very much heavier and have loose wheels. No special reason has been discovered for these breakages at Dam No. 1, save that the axles are probably too light for the work. As the breakages occur gradually, frequent examinations are made by divers; broken axles supported by chains or otherwise, and broken wheels removed, etc. Beyond this, little or nothing can be done until the annual winter repair season, unless a gate becomes entirely disabled. Usually, they can be made to run through the season. However, in 1910 the upper gate became so badly disabled as to necessitate its suspension in October. Since Pool No. 2 can be made to maintain within about 2 feet, the normal pool stage at Pittsburg navigation was not seriously affected by the temporary lowering of Dam No. 1. At time of suspension the condition of upper gate in detail was as follows, beginning at outer end: Truck No. 1. In good condition. Truck No. 2. In good condition. Truck No. 3. Lower wheel broken. Truck No. 6. In good condition. Truck No. 7. In good condition. Truck No. 8. In good condition. Truck No. 9. Axle broken. Truck No. 10. Both wheels broken. Truck No. 11. Axle and both wheels broken. Truck No. 12. Both wheels broken. Truck No. 13. Axle and both wheels broken. Thus, of a total of fifteen axles five were broken, and of thirty wheels thirteen were broken. In addition, there were also several broken journal boxes and eight upper gate posts were entirely or partly rusted through at the water line. While the wheels were not entirely broken into pieces, yet they were so badly damaged as to require replacing with new ones. That a lock gate in such con dition should still be capable of making a lockage seems altogether unbelievable. Where wheels are fixed to axles, as in this case, the gates must be raised about 40 inches and adjacent valve frames removed in order to release and replace trucks. The field work of all repairs of this nature is always performed by the lock forces. In Dam No. 6, Ohio River, there were originally constructed two bear-trap gates, each 120 feet wide by 13 feet 2 inches vertical height (among the largest ever built). Their design-steel frames filled in with wood-involved the first radical departure from wooden hear-trap construction, theretofore deemed essential to their successful operation on account of buoyancy. They were given a test trial, in 1904, and found to be so flexible as to forecast but a brief existence. In fact, their collapse at any time was considered imminent. However, it was decided to use them as long as practicable. When down, during their latter stages, it was always a question whether or not they would rise again. Finally, in 1909, both lower leaves broke in two about midway between piers. Although still serviceable and performing their functions reasonably well, their reconstruction was undertaken immediately and completed early the following season. This rebuilding consisted mainly in the removal of the wood filling and covering of the steel frames with buckle plates, so that in their pre ent state the gates involve the essential features of the later steel bear traps and are equally satisfactory. While under reconstruction the remainder of dam was in raised position part of the time, and could have been kept in operation practically all the time. Except the structural steel work, for which a contract was let, the work was performed by the operating force. This, it will be observed, furnishes another instance showing the extent to which an important structural feature of a dam may be injured or disrupted and yet be made to continue in active service. RENEWALS Notwithstanding that in time every part of the movable dam structures will require rebuilding, the extensive use of modern steel in many of their important features will hasten the need for renewals alarmingly, rendering these an essential factor in maintenance and operation. In order to avert vexatious interruptions to navigation, if not indeed costly disasters to both it and the Government, perhaps the most difficult question in this connection will be the determination of the proper time for abandonment and re construction of certain important parts. For instance, the life of steel lock gates is likely to be short, and to insure continuous navigation their removal must be anticipated a year in advance. So, in a measure, too, the replacing of hear-trap gates, service bridges, maneuvering boats, etc. As a more notable example will come the reconstruction of Dam No. 1. This was the initial, and to a considerable extent experimental, structure, erected thirty years ago, and lacks many of the essential qualifications of the more modern dams. Furthermore, it has been subjected to severe usage, causing many breakages in the floor, sill, anchor bolts, etc.; is equipped with an objectionable hurter; has no protection structure along downstream edge and, above all, under the 9-foot navigation scheme. furnishes only a 3-foot head over Pool No. 2, rendering its operation exceedingly difficult under certain stage conditions. These defects, it is believed, can together be remedied most satisfactorily and economically by rebuilding. Experience has pretty fully demonstrated the impracticability of maintaining a system of locks and dams without interrupting navigation while accomplishing important repairs and constructions under contract. Ordinarily, contractors are suspicious of repair jobs and bid accordingly. It is evident the risks contingent on the preservation of navigable pools during construction operations are inconsistent with reasonable contract prices to the Government. Then, too, contractors do not look with favor on winter river operations, which of necessity are most advantageous to slackwater repairs. and renewals. Hence, it has been found desirable to perform all work possible by the operating forces and additional hired labor, letting only shop and such field work as will not prove detrimental to movable dam operations. Whilst omitting mention of many important maintenance and operating requirements applying to Ohio River movable dams the foregoing will doubtless suffice to emphasize the necessity for superior qualifications in those responsible for their direct supervision. The lockmaster in charge of a million-dollar structure and operating plant, although not left entirely to his own discretion, must nevertheless combine more than ordinary executive ability, sound judgment, and resourcefulness with practical experience as an all-round riverman, machinist, mechanic, concrete worker, and general construction overseer capable of performing any character of river work under unfavorable and abnormal conditions within exacting time and economical cost limitations. And, above all, he must be fearless within reasonable limits and absolutely trustworthy and reliable. So, also, in order that the work be accomplished properly, must his assistants be equipped, at least in measure, with similar qualifications. Movable dam operations have now extended over a period of more than three years on a series of seven consecutive dams in the Pittsburg engineer district, while with a lesser number combined with their construction more than thirty years experience is had. With an increase in number of dams will also, doubtless, arise new problems applying especially to the enlarged system. Others, too, affecting individual structures will no doubt develop. Yet it is probable that the majority of difficult questions have already been met and by giving attention to occasional new conditions as they occur the perfecting of the entire Ohio River system will eventually be accomplished. Meanwhile, the greatest danger to the works would seem to lie in an assumption that the situation has been so fully mastered as to render failure impossible. So long as nature is known not to have exhausted her resources to produce new conditions or combinations eternal vigilance will probably furnish the surest safeguard to the preservation of these navigation interests. A SYSTEM FOR FILING AND INDEXING BY Capt. J. A. WOODRUFF Corps of Engineers In order to keep track of the numerous books, pamphlets, catalogs, mimeographs, etc., that are sent to the officers of the Corps of Engineers, some system of indexing and filing is necessary. The system described below was originally devised by Maj. H. B. Ferguson, Corps of Engineers, in 1903, assisted by Maj. W. D. Connor, Corps of Engineers, and the author. The system is so simple, flexible, and convenient that it is believed a description of it may be of some aid to the officers of the Corps, especially the junior officers, in arranging their professional papers. The index is kept on cards, 3 by 5 inches, in a file or cabinet. It is probably best to commence with a single-drawer cabinet which will hold about 1,000 cards. The following decimal classification may be used: |