Constructing the Big Buffalo Filtration Plant
Some of Problems That Have Been Met and Overcome in Great Work—Large Concrete Buckets Employed-Capacity Doubled
AS no doubt many of the chiefs will insist the new filtration works of Buffalo during their stay in the convention city the following description will prove of considerable interest and will assist them in understanding the immensity of the work that is being carried on in improving the water of Buffalo:
The new $4,000,000 filtration plant in Buffalo, N. Y., is being constructed on lines that have a decided flavor of the original. The large quantities of concrete handled, the method of getting around the engineering difficulties encountered, and the use of political methods to put the plant over in the first place, all make it something out of the ordinary.
The water now is not actually dangerous, as it is subjected to a careful chlorination treatment, but it is distinctly unpleasant, and the need of a filtration plant is obvious.
Long ago, the city engineers realized this need, but the taxpayers were averse to spending money for anything, no matter how necessary, and a regular siege was needed to persuade them to agree. The city made legitimate use of the methods more often used by gang politicians to lay before the public the advantages of having a new filtration plant.
Movie films were prepared, showing the differences between filtered and unfiltered water; dodgers were distributed, and a corps of city engineers and others mustered into service as speakers. In general, all the machinery of a lively political campaign was employed. The effort was successful, the bonds were issued and the new filtration plant begun.
Extent of the Work
Contract No. 1, covering all the concrete work on the new plant was let to the Thompson-Starrett Company of New York, and they are now in charge of the work. The contract covers the building of a coagulating basin 408 x 304 feet, the clear water basin, 515 x 330 feet, conduits leading the water between the various basins and the pumping station, the substructures and foundation of the pumping station. The work is of reinforced concrete throughout, and aggregates something like 60,000 cubic yards of that material.
To handle this immense amount of concrete special equipment was necessary. A plant for handling it was erected at the north of the job itself, near the dock wall, and fortunately located between the harbor and the railroad siding so that materials could be handled to it either by land or water.
Method of Mixing Cement
Beside a cement storage building, this plant consists of a four-story wooden building, about 50 feet high and 28 x 52 feet at the base. At its top are two storage bins; on the third floor is a charging hopper and cement storage room ; on the second floor two 1 1/2-yard capacity motor driven cement mixers, and a discharge hopper. The ground floor is occupied by the tracks for a narrow gauge railway, used for transporting the concrete to the work. A motor driven elevator is used for lifting the cement from the ground floor to the charging hoppers.
Huge Concrete Buckets Employed
A remarkable feature of the work is the concrete buckets. Instead of the usual yard or half-yard of concrete, they carry five yards of it—a really great advance in handling this material. The big buckets, loaded, weigh approximately twelve tons. The narrow-gage railway that carries them from the mixing plant to the job is operated by gasoline locomotives, and once on the job, the huge buckets are handled to the points of discharge by means of a cableway.
The two cableways themselves are engineering works of no mean importance. The span over which they handle the huge concrete buckets, and have handled steel, forms, and all other materials for the job, is 800 feet. Naturally, in transporting loads of twelve tons and upward over a span of 800 feet, the towers of the cableways had to be something better than the customary portable wooden towers of knockdown type.
Large Steel Towers for Cableways
These towers were built of steel especially for the job, and operate along the east and west faces of the work on tracks. They are 85 feet high, and 36 x 50 feet at the base, with a lifting capacity of 18 tons. They have handled all the material placed on the job so far, and by means of their use, the site has been kept clear of all temporary structures except the forms for the concrete.
The use of extremely large buckets and cableways has resulted in great economy of time and material, in spite of the greater initial outlay. The system has proven itself very efficient, and the only fault to be found with it is the personal factor of carelessness. When workmen are so careless as to allow the 12ton buckets to swing against the forms, these are naturally wrecked.
Problem of Water in Excavated Ledges
Aside from this no engineering difficulties were encountered except in flooring the clear water reservoir. The original plan, based on the depth at which rock was found, was that a thin layer of concrete should be laid over the rock. When excavation was complete, however, the rock was found in broken ledges, through which water was seeping in such a quantity as to seriously endanger the work.
Grouting would have done nothing more than to force the water back into the seams, giving a vigorous upward pressure on the bottom of the floor at all times, a pressure the floor and the weight of the columns and roof were by no means prepared to stand.
How the Difficulty Was Met
The difficulty was overcome by the ingenious method of constructing a series of French drains of loose rock at the seams where the seepage was occurring and leading them to a central point. The thickness of the floor was slightly increased at the same time. All along the drains vertical galvanized wrought iron pipes were let through the floor slabs in order that the drains might be observed in action. When the work is completed, these will be plugged or used as points for the application of grout, as the drains will no longer be necessary. The clear water reservoir will seldom, if ever, be emptied, and the pressure of the water in it will easily counterbalance any upward pressure from the seepage.
The work on the new filtration plant is about 75 per cent, completed. It is expected that the plant will be in operation by the fall of 1925. The filter units of the plant will be 33 x 50 feet, with a rated capacity of four million gallons per 24 hours, and capable of 50 per cent, overload. It is not expected that the plant will be worked to its fullest capacity by the present use of water in Buffalo, but as this is rapidly increasing, there is no doubt that it will all be needed in a few years.
Plans for Doubling Capacity in Future
The treated water conduit at the east of the coagulating basin is provided with a horizontal floor midway between the top and bottom, in order that the filter plant may be extended to double its present capacity at some future date without in any way interfering with its operation.
A similar arrangement is made in the settled water conduit leading to the gallery flumes.