In 1873 some arrangement was made by which the government undertook to build the foundations of the Copperas Creek lock, at a cost of about $80,000; the State was to complete the lock and build the dam. Operations on the lock-pit were commenced by the government September 1, 1873, and continued until the end of September, 1874, when the foundations were finished, the work turned over to the State, and has since then been completed. In the fall of 1877, Capt. G. J. Lydecker, Corps of Engineers, was assigned to the charge of the work, relieving Col. J. N. Macomb, and dredging operations, under the contract then in force, were continued to the end of the last fiscal year (June 30, 1878), when the contract was closed; since that date no work has been done. The extent to which navigation has been improved may be briefly stated as follows: The State works at Henry and Copperas Creek fur nish a reliable 7-foot navigation for a distance of about 100 miles. On that part of the river below Copperas Creek a present navigable depth of 4 feet has been obtained over the worst bars by dredging, building wing-dams, &c., but other bars remaining unimproved will not carry more than 23 feet during extreme low-water; consequently through nav gation is limited to that depth during low-water season. All work on the river has been done by contract. Its extent and the amount paid therefor to contractors may be summarized as follows: (For details, see Statement A.) The aggregate length of dredged channels is 123,320 linear feet, vary ing in width from 40 to 50 feet, most of them being under the full width designed. The dredged material was largely used in forming dikes and dams for contracting the river or closing lateral channels, in addition to the brush and stone dams referred to above. The total amount appropriated for the improvement from 1869 to June Balance available July 1, 1878.... $549,150.00 471, 016 58 78, 133 42 The principal facts gleaned from the preceding historical sketch of the improvement may be recapitulated as follows: The plan of improvement, adopted by the board of engineers after extensive surveys in 1866 and 1867, was a lock and dam (slack-water) system, designed to furnish a reliable 7-foot depth. Appropriations sufficient to carry out this plan were not made, whereupon the State of Illinois undertook the work of building the necessary locks and dams, substantially on the plan adopted by the board, and up to date have finished two of these works (viz, at Henry and Copperas Creek), the general government building the lock foundation at the latter place. As auxiliary to the State work, the gen eral government commenced (in 1869) dredging channels through the various bars between Henry and Copperas Creek, to a depth sufficient to give 7 feet navigation when the dam at Copperas Creek was finished, intending to continue down the river, and in this way provide for the required depth, with diminished height of dams. This plan was soon modified (in 1870) to dredging channels, 4 feet deep, through the worst bars, taking them in the order of their importance as obstructions to navigation, so as to enlarge the navigability of the river as rapidly as possible. In connection with this work, wing-dams were built, side channels closed by brush and stone dams, &c. These different changes were "rendered necessary," only because Congress did not appropriate sufficient money at any one time to warrant a start on the plan recommended, while parties interested in the navigation of the river called for immediate relief. The only work done by the general government, applied to carrying out the plan adopted by the board, was the construction of the Copperas Creek lock foundation, and dredging in the pool above; the total expenditure for these purposes was about $150,000. All other expenditures, amounting to $321,016.58, were on the plan of dredging open channels, building wing-dams, &c., to give immediate relief to navigation; hence this may be regarded as the "general plan adopted." In addition to what precedes, I am called upon to state "whether any material changes are in your (my) judgment necessary, and whether, in any plan for the radical improvement, the work already accomplished may not form a component part." It is my opinion, for the reasons to be given, that some material changes in the general plan adopted are necessary, in order to accomplish, at an early date, the ultimate object; but that the work already done may form a component part, and aid in the execution of any plan for a more perfect and radical improvement. The objections to the present plan of operations may be stated in general terms as follows: Slow progress towards the attainment of the completed improvement, temporary character and excessive cost, of the results obtained. I do not know the nature of the agreement by which the State and general government co-operate in the work; whether it is a well-defined and binding affair, or simply an indefinite understanding. In either case it is one of the principal causes operating to retard the progress of the work. The interests involved in its completion are not local simply, but widespread, and it is my belief that the improvement would be attained more speedily, and the various interests best subserved, if the whole cost and direction of operations for the improvement of the river were assumed by the general government, and it is eminently right that this should be done, when the national importance and general commercial value of the route are considered. The State government will have much more than its share of the expenses if it enlarges the Illinois and Michigan Canal to give to the through line the width and depth designed; the estimated cost of this part of the work being about $16,250,000. If the ultimate improvement is to be obtained by carrying out the slackwater system, it would be far better to build the necessary locks and dams 'at once, and not do any more dredging in the pools resulting from their construction, until they are completed; afterwards, this dredging could be done where needed, at less expense, and the work would be permanent, or as nearly so as possible. On this plan we can speedily, economically, and surely secure the radical improvement desired; one which would furnish a certain and reliable navigation at all times, for vessels drawing 6 feet; and if the necessary appropriation can be obtained, I would urge its adoption as the basis for next season's operations. The work already done will modify in some of its details the project proposed by the board of engineers. Without going extensively into these details here, it may be sufficient to state that instead of three more locks and dams, it is my opinion that only two will be necessary, the last dam on the river being located in the vicinity of Columbiana Flats, about 31 miles above the mouth of the river. The fall of the river in these 31 miles (as shown by profile of 1867) is 3 feet, or only 0.1 foot per mile. The depth of water is considerably over 7 feet for most of the distance, and but little dredging would be required to give this depth throughout, while the conditions are such that channels of any desired width could be made, and they would be permanent. The total cost to complete, by this system, should not exceed $1,000,000. Whatever dredging is necessary should be done by machinery, owned and operated by the government. My annual report for 1878 contains this recommendation and the reasons therefor. I may add to what is stated therein, that from an examination of the statements accompanying this report, it would appear that the average cost of dredging, includ ing the elaborate surveys and engineering operations necessary in following out the contract system heretofore in use, was over 40 cents per cubic yard. I would also note that my predecessors in charge of the work have, on different occasions, recommended the purchase or construction of a dredging outfit, to be operated by the government. The question as to what is our best course, if we cannot have the means to build the locks and dams, remains to be answered. In this case we should prepare for obtaining the best practicable improvement by dredging, and the construction of wing-dams and dikes. It is im possible to state positively to what extent the river may be improved by this method, though I should look for something much better than a channel 160 feet wide and 4 feet deep, the limits indicated in the report of the board; but it must be remembered that the board had under consideration the whole length of river, up to La Salle, while we have now in question only that part from Copperas Creek lock to the mouth, where the slope is less than on the upper section, and the low water discharge is considerably greater. The distance from the lock to Grafton is 137 miles, with a total fall (low-water surface, profile of 1867) of 21 feet, giving a mean fall of 0.15 foot per mile; the aggregate lengths of bars and shoals on which the depth at low-water is less than 6 feet is about 70 miles, or a little more than one-half the entire distance. It is unfortunate that the surveys and records thereof, at least such as are accessible to me, do not supply all the data required for a complete discussion of the questions before us; they furnish everything necessary to show that a slack-water system can be readily and cheaply obtained, but little that is required for a careful consideration of other methods of improvement. For that now under consideration we should know with some certainty the low-water discharge at different places on this section of the river; but from the records in my possession, I can find no reliable information on this point, and I have been unable to have it determined, for the reason that no low-water state has been reached since my connection with the work began. From such facts as I have been able to gather, it cannot be assumed as exceeding 2,000 cubic feet per second. A channel 200 feet wide and 6 feet deep, with a slope of 0.2 foot per mile, would discharge*1,504 cubic feet per second, whence it is By de Prony's formula: * V=100 √RI-0.15-1.31 feet, By Eytelweim's formula: whence discharge=1,562 cubic feet. to be inferred that such a channel could be made and maintained through the different bars, if the low-water cross-sections outside of the channel limits are properly reduced by low dams. The amount of dredging would be very great, not short of 8,000,000 cubic yards probably; with suitable machinery and systematic work (i. e., completing each channel before commencing on another, instead of moving from place to place simply to supply the present wants of navigation), it could be done at 15 cents per cubic yard; but even at this rate the first cost of the dredging would be $1,200,000; the auxiliary wing-dams would cost at least $50,000 more, and the subsequent annual cost of maintaining the improvement could not safely be estimated at less than $15,000. It is possible that the amount of dredging might be diminished by an increased expenditure for dams and dikes, but at present I have no data to show that any sav ing in cost could be effected in this way, and it is not believed that the construction of channels materially smaller than the one indicated would meet the ultimate requirements of the route. The time in which the improvement could be accomplished on this plan cannot be stated definitely, nor can any positive statement be made as to its permanence; it is highly probable, however, that most of the work would stand well, deteriorating slowly and gradually; but in some localities it would be liable to sudden and complete destruction at any time. Comparing, now, this with the slack-water system, it is seen that the latter has the advantage in every important feature. It will cost less, can be accomplished within a shorter period of time, its results would be certain, and the improvement would be permanent. It may be proper to note here that those at present interested in the local navigation of this part of the river seem strongly opposed to the slack-water system, and really look upon the structures at Copperas Creek and Henry as obstructions to navigation. The point is, their boats are adapted to a low-water navigation, and they would prefer an open channel of 4 feet rather than have the additional depth and pay the tolls now exacted for the passage of the locks, the owners of boats and barges claiming that these tolls are excessively high, constituting almost a prohibitory tariff on their business. If, however, the construction of the remaining locks should be undertaken by the general government, there would be a decided change in this respect; the tolls then collected being reduced to the amount necessary for maintaining and operating these works only, would be a small matter, and would cause no complaint, when the great advantages to be derived from the improvement are recognized. But as it is now the locks on the river are under the same management as the Illinois and Central Canal, and the tolls from the former are undoubtedly applied, in part at least, to maintain the latter. It would seem that such a tax on the river commerce is not only unjust, but unnecessary, as much so as it would be to tax vessels navigating the Hudson River and apply part of the proceeds to defraying the expense of the Erie Canal. The following are the conclusions to which this report leads: 1st. That the slack-water system is the one on which the improvement of the river should be completed. 2d. That the completion of this system, aided by dredging, should be undertaken by the general government at once, or as soon as practicable. 3d. While it is believed that a radical improvement can be effected by dredging, its cost would exceed that of the slack-water system, the improvement would be less certain, and would require considerable annual expenditure for maintenance. 4th. That all dredging can be better and much more economically done by machinery owned and operated by the government. 5th. The work already done may form a component part of either of the above-mentioned plans. In view of the above, I have the honor to submit the following recom mendations: 1st. That an appropriation of at least $400,000 be urged for the fiscal year ending June 30, 1880, to be applied to building one lock and dam, and such dredging as may be necessary to obtain the required depth after the dam is constructed. 2d. That from the appropriation now available there be purchased or built an outfit with which to carry on future dredging operations; said outfit to consist of one first-class dredge, two dump-scows, two deckscows, and one tow-boat, the total cost of which would probably be about $30,000. This outfit would be required for either system of im provement. For extensive dredging operations, the outfit should be increased to number at least three dredges, with scows, &c., complete. 3d. That no more dredging be done until next season, unless it should be found necessary to do a little work for the restoration of channels, and for maintaining navigation during extreme low-water; and that such work, if any is called for, may be done by hired labor and machinery and purchases in open market; but that the engineering party be employed in careful examinations and surveys, in order to show what changes have taken place in the various dredged channels since their improvement, amend existing maps to correspond to the present condition of the river from Copperas Creek to Grafton, and supply all the data needed for future operations, whether for the construction of locks and dams or dredging. I am, very respectfully, your obedient servant, Brig. Gen. A. A. HUMPHREYS, Chief of Engineers, U. S. A. G. J. LYDECKER, |