square miles of Chicago and the territory of the tributary water sheds, will hardly be carried away by the drainage canal. Possibly the conditions in the south branch may be bettered, but the current in the main river and the north branch may be easily diverted toward the lake by a surcharge of storm water much as it is under present conditions. The influence of the winds and barometric changes, also operate to produce possible contamination of the lake. A drop of one foot in the lake level from these causes is quite common, and a fluctuation of two feet in fifteen or twenty minutes is by no means rare. What will the effect of such a drop in the lake level be upon the main river, the north branch and even a portion of the south branch? I confess I fail to see how the drainage canal is to be used at all times with entire safety, in this respect. But there are so many debatable questions with reference to the sanitary aspects of the drainage canal that it is not wise to enter into them here. My reference to the matter was made solely by way of illustration. The main point intended to be brought out by this paper being that by more rapid methods of artificial intermittent filtration recently tried, large cities of Chicago's class, without available land for land methods of sewerage disposal, are not debarred from careful investigation of intermittent filtration. XXXVII OBSTRUCTIVE BRIDGES AND DOCKS IN THE CHICAGO RIVER. By G. A.. M. LILJENCRANTZ, Mem. W. S. E. Read June 1. 1898. Having been requested to present some notes on the Chicago river and the various obstructions to navigation which are found therein, I shall treat this subject under three separate heads, viz: 1. The river as it is; 2. The river as it will be, and 3. The river as it might be. next. THE RIVER AS IT IS. It is well known to everybody that the Chicago river has been and is of enormous value to the commerce of the city, through its large and extensive lake traffic, which compares favorably with that of any of the largest cities in the country, and this expresses it even more modestly than need be, not to overstate the truth. But it should be remembered that, in a place of such rapid growth and progress as Chicago, that which appears great and ample one day has generally proved small and insufficient the The dimensions of the river some thirty years ago were ample for the commerce and traffic of that time. So were the bobtail one-horse street cars for the street traffic, and the jog trot of the old horse gave comparative satisfaction as to speed. Four and five story buildings were then considered commodious for stores and offices. In such matters as well as in numerous others -too many to here enumerate-the greatest advances have been made since, however. We now ride in electric and cable cars; sixteen and eighteen-story buildings are no longer a rarity, and we find several that are even higher. Thus has almost everything in the city been "kept up with the times"-except the river. To be sure, it has been improved. Miles of docks have been built, periodical dredging has been done; improved bridges built, many of which are of excellent design and furnished with the best and most modern equipment for maneuvering, but the question is: Has it also been "kept up with the times?" Has the improvement of the river been kept abreast with other improvements in this great and rapidly growing city? And another question which, in the writer's mind, is still more serious: Are existing conditions such as to admit of an improvement of the river that will be commensuate with a metropolis of three or four million inhabitants, as Chicago no doubt will be but a few decades hence? For is not the growth of Chicago, at the present stage of development, similar to the coasting of a sled down an icy hill, in that it can not be stopped? When studying the conditions we find much cause for discouragement. Fig. 389. The improvement of the river for the purposes of navigation may be considered as of two different kinds or classes, which I may be permitted to term, respectively, the vertical and the horizontal improvement, the former called for by increased draft of vessels, the latter by the constantly increasing horizontal dimensions of the craft of modern times. Thus, the vertical improvement aims at securing a depth of channel sufficient for the passage of modern lake vessels at this port. Increased depth has been secured to some extent by occasional dredging, but it is again regularly decreased by the unceasing deposits from the numerous sewers emptying into both branches of the river, as well as by constant sweeping and dumping of refuse in various ways into the channel, requiring frequent redredging. But this removable material forms the least serious obstacle in the way of the vertical improvement. Not less than three tunnels cross the river, with their crowns at an elevation which, at the time they were built, allowed sufficient draft for the navigation of that day, but which now form the gravest obstructions to the much larger vessels of deeper draft of the present time; and I wish to repeat a remark I made at a meeting of this society in 1894, when a paper on the last built of these tunnels, the one at Van Buren street allowing only 18 feet draft of vessels, was read, viz: "The time will come, and before many years have past, when these tunnels must be lowered, if Chicago is to remain at the head among the lake ports." These tunnels, if allowed to remain, limit the extent of the vertical improvement, of which more will be said under the next heading. Docks are frequently built with more consideration as to cheapness in first cost than to future needs and are thus made only of strength enough for the existing depth of water, and are accordingly subject to undermining, whenever the channel is considerably deepened. An extensive vertical improvement, even if the obstructive tunnels did not exist, would accordingly involve great expense to individual owners, in addition to the direct improvement by dredging, and to make such improvement practically permanent it will be necessary to dispose of the sewage by a different method from that now employed, or provide for continuous maintenance by dredging. Let us next look at the difficulties we encounter in planning a horizontal improvement. Vessels of even the greatest dimensions in use until about 1890, and which still constitute the great part of the lake fleet, easily pass any part of the navigable river, but some of those built within the last few years find it impracticable to enter either of the branches of the river, or, loaded, to pass the first the first of the "artificially constructed reefs, so to speak, the LaSalle street tunnel. The manner in which a long vessel has to move to make this passage possible is illustrated on the sketch marked "A-2," Fig. 390, showing tne river between Clark and Wells streets, with the tunnel half way between.* The available channel is here in the middle of the stream. A vessel with 48 feet beam and 432 feet long (which is the length of the longest boat now navigating the lakes) is on that sketch represented as coming through the north draw of Clark street bridge, turning to the deeper channel in the middle, over the tunnel. It is compelled to proceed thence across to the south draw of the bridge at Wells street, because the turn to the north draw of that bridge is practically impossible, for there is only 500 feet between the two bridges, and the center channel has a depth of seventeen feet at low-water over the restricted width of only 62 feet on the line of center piers of bridges. The cross-sections on sketch "A-3", Fig. 391, will further illustrate this deplorable condition. The principal obstructions along the two branches of the river are shown on other sketches accompanying these notes, by representing thereon the horizontal contours of a vessel of the dimensions mentioned, attempting to make a trip up the river, and meeting with the several obstructions on its passage. Thus, the sketch "A-4", Fig. 392, shows the narrow draws of Randolph, Washington and Madison street bridges, the chief obstruction of the first of these being, however, the clumps of piles at the west abutment. Sketch "A-5", Fig. 373, shows the bridges at Taylor and Twelfth streets, with the intermediate Wisconsin Central Railroad bridge. The vessel can pass through the east draw of the railroad bridge, but through none of the other draws of these bridges. The dock south of Twelfth street bridge would prevent the passage also, even if the east draw of this bridge were passable. The Canal street bridge, shown on sketch "A-6," Fig. 394, has a center draw and would admit the passage of the long vessel were it not for the obstructive dock to the north and west of the bridge. At Twenty-Second street, sketch "A-7," Fig. 395, both the draws are too narrow. The Chicago and Alton R. R. bridge, North of Archer Avenue, sketch "A-8", Fig. 396, is a striking example of how some bridges are constructed without the least regard for the demands of navigation. Too narrow are also the draws of the three bridges, placed in close proximity at Kinzie street, in the north branch of the river, as well as at Indiana street bridge, all of which are shown on sketch "A-9", Fig. 397. Nothing larger than a tug can pass the east draws of the first named three bridges, which, in fact, had never even been dredged until in April of this year. At Division Street bridge neither draw can be used, nor can those of the North Avenue bridge, shown on sketch “A-10", Fig. 398, by such large vessels. *The sketches illustrating the conditions of the river, and accompanying this paper, were copied from those accompanying the report of Major W. L. Marshall. Corps of Engineers, to Chief of Engineers, U. S. Army, for the fiscal year ending June 30, 1897. |