PIER CONSTRUCTION, PORT COLBORNE, ONT.—In constructing the new harbor at Port Colborne, Ont., on Lake Erie, the piers consisted of parallel rows of timber cribs set the width of the pier apart and filled in and between with stone blasted and dredged from the lake bottom in deepening the harbor. The tops of the cribs terminated below water level and were surmounted by concrete walls set on the outer edges. These walls were filled between with stone and the top of the filling was floored part way or entirely across, as the case might be, with a thick concrete slab. The footings of the walls to just above the water level were made of concrete blocks 4½×4×7 ft., constructed as shown by Fig. 81. The wall above the footing course and the floor slab were of concrete molded in place. The concrete work consisted of molding and setting concrete blocks and of molding concrete wall and slab in place.
The blocks were molded on shore, shipped to the work on scows and set in place by a derrick. Figure 82 shows the construction of the forms for molding the blocks; the bottom tie rods passed through the partitions forming the ends of the molds. The sides were removed in 48 hours and used over again. Figure 83 shows the hooks used for handling the molded blocks. Considerable trouble was had in setting these blocks level and close jointed, owing to the difficulty of leveling up the stone filling under water.
Fig. 84.—Scow Plant for Mixing and Placing Concrete, Port Colborne Harbor Pier.
The mass concrete was mixed and placed by the scow plant, shown by Fig. 84. The scow was loaded with sufficient sand and cement for a day's work and towed to and moored alongside the pier. Forms were set for the wall on top of the block footing. These forms were placed in lengths of 60 to 75 ft. of wall and resembled the block forms with partitions omitted. The bottoms of the rear uprights were held by being wedged into the grooves in the blocks, and the bottoms of the front uprights were held by bolts resting on top of the blocks. The tops of the uprights were held together across the wall by tie bolts. The forms being placed, the mode of procedure was as follows:
The crusher fed directly into a measuring box. After some 6 ins. of stone had run into the box the door of the crusher spout was closed. A wheelbarrow load of sand was spread over the stone in the box and over this were emptied and spread two or three bags of cement. Another layer of stone and then of sand and of cement were put in and these operations repeated until the box was full. The box was then hoisted and dumped into the hopper of a gravity mixer of the trough type which ran along a track on the scow and fed directly into the forms. The gang worked consisted of 1 foreman, 1 derrickman and 18 common laborers. This gang placed from 65 to 75 cu. yds. of concrete per day at a labor cost of 50 cts. per cu. yd.
Fig. 85.—Cross-Section of Concrete Pier, Superior, Wis.
CONCRETE BLOCK PIER, SUPERIOR ENTRY, WIS.—The methods and cost of constructing a concrete pier 3,023 ft. long and of the cross-section shown by Fig. 85 at Superior entry, Wisconsin, are given in the following paragraphs.
Molds and Molding.—About 80 per cent. of the concrete was deposited in molds under water, according to a plan devised by Major D. D. Galliard, corps of engineers. In brief the concrete was built in place in two tiers of blocks, the lower tier resting directly on piles and being entirely under water and the upper tier being almost entirely above water. As shown by Fig. 85, a pile trestle was built on each side of the proposed pier and a traveler for raising and lowering the molds spanned the space between trestles.