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Ia MARINE REVIEW. [June 26 CONCRETE BREAKWATER CONSTRUCTION AT BUFFALO. BY MAJOR W. T. SYMONS, CORPS OF ENGINEERS, U. S. A. Reprinted, by permission, with illustrations from the Engineering News. During the last century, when the necessity for breakwaters at some of the lake harbors became recognized, the only ones in existence through- out the world were those of stone and masonry, costing from $500 to $1,500 per lineal foot. Such expensive structures were beyond the financial resources of our people at the time. With true American adaptiveness, however, another type was designed of far less cost, which has done good service. This was composed of a row of timber cribs sunk in place, filled with stone, and surmounted by a continuous superstructure of timber filled with stone and decked over with planking. The cheapness of timber, Lake Side a ( \ \ | Be ye Bee A ma --------------- pan ------------- pa--------------- Pp i ENG. NEWS, 350". > Fig. 1. Typical cross-section of old concrete super- structure for Buffalo breakwater, 1887-1891. and the fact that these structures were built in fresh water and free from the ravages of the teredo and other destructive marine insects, justified the character of the structures. In the aggregate a large amount of this general type of structure has been built at the lake ports. In such struc-. 'tures there are two distinct features--the substructure, or part below water, which, on account of the preservative properties of fresh water on wood, has a very long but indefinite life, and the superstructure, the part above water, the wooden portion of which, being exposed to the action of the elements, decays with greater or less rapidity. This superstructure is also 190" ) <b | Lake Side Harbor Side Fig. 2. Typical cross-section of concrete super- structure for west breakwater, Cleveland harbor. and still is in progress. This work was designed by Col. Jared A. Smith of the corps of engineers. A cross-section of this superstructure as built is shown in Fig. 2. A wooden breakwater with a concrete superstructure may properly be considered as a permanent structure, reasonably secure against decay and deterioration. The question therefore naturally arises, why not put the concrete superstructure on at first? The answer is that most of the lake breakwaters are built on the ordinary lake bottom of clay and sand, and for some years after they are completed settlement and displacement NI5B >k244 -£1.+8.0 Stone Steps, Sf. wide Be ah geateusacceentececiues Phe ere ce entee Lake Side I | Harbor ' Side Stone Filling Fig. 3. Typical cross-section of concrete shell su- perstructure for Dunkirk breakwater. occur, which are generally of unequal character in different portions of the structure. Nearly all wooden breakwaters, piers, etc., present a wavy ap- pearance, due to this unequal settlement and displacement. The wooden superstructure adapts itself to this without serious harm, but a rigid super- structure of masonry would be very seriously injured by it, rendered very unsightly, and perhaps be completely ruined. By the time the wooden -superstructure has rotted off the whole structure will have reached its final settlement and be in a condition of permanent stability and fitted to re- ceive its rigid concrete superstructure. PPPS Filling Stone Filling | { 1 1 1 1 K 2A Int >} ? { Typical Cross Section. Section. Maximum Cross Fig. 4. Maximum and typical cross-sections of concrete superstructure for old breakwater, Buffalo. exposed to the physical destructive action of waves, ice, boats and van- dals, and requires constant repairs, and, finally, when sufficiently weak- ened by decay, complete renewal. In several instances on the lakes where this renewal has been found necessary it has been done by substituting a concrete superstructure for the old wooden and stone one. The first fully-exposed wooden and stone breakwater to be built on the great lakes was at Buffalo, and at Buffalo was also built the first concrete superstructure to replace the old wooden one which had become. dangerously weakened, This was done under the direction of Capt. F. A. An exception to the general system of consecutive construction as outlined above is where the new breakwater is founded on rock or other bottom of sufficient rigidity. Such is the case in two points in the district under my charge. At Dunkirk, N. Y., an extension to the wooden break- water was built by me in 1898, and as it could be founded upon the rock bottom, it was built in the first place of timber crib filled with stone, with a concrete superstructure. Fig. 2 is a section of this breakwater, which has the distinction of being the first concrete shell breakwater superstruc- ture to be built on the lakes or elsewhere, as far as I know. The second fe tev aoe Fig. 5. Junction of timber crib superstructure and concrete super- structure, south harbor breakwater, Buffalo. Mahan, corps of engineers, U. S. A., and consisted of solid concrete, con- forming generally to the shape of the wooden superstructure which it replaced. Concrete blocks were used about the water's edge. A cross- section of this breakwater as constructed is shown in Fig. 1. The heart was of natural cement concrete, the exposed portion of Portland cement concrete. During the years 1887 to 1891, 3,878 lin. ft. of this solid concrete superstructure was built. For some years past the work of replacing the superstructure of the Cleveland, O., breakwater with a solid concrete superstructure has been Fig. 6. Timber superstructure as it appeared after being wrecked by storm. point where a new breakwater was built with timber and stone sub- structure and concrete superstructure was at Buffalo, at the northern por- tion of the harbor, where rock foundation also existed. The concrete shell- superstructure surmounting this breakwater is similar in all material re- spects to that illustrated as used in putting a new superstructure on 1,015 ft. of the old breakwater at Buffalo. When a portion of the old breakwater at Buffalo received a new con- crete superstructure, in 1887-91, a section of 1,015 ft. was left in its original condition, because it was deemed that the substructure was not in a suffi-