Public works . 40 feet long is on a 2 per cent, grade and the concrete piersand abutments have pile foundations built in colTer-dams excavated below the river bottom. The super-structure consists of 17 regular 79-foot plate girderspans and one plate girder 77 foot Scherzer basculespan with a clearance of about 26 feet above highwater. The main girders are spaced 21 feet aparton centers. The footingsare protected with a riprap, and the floor of thebascule span is paved withwooden blocks. The fixedspans have reinforced con-crete pavement. SHEirr PILE COFFERDAMS. At low water the depth
Public works . 40 feet long is on a 2 per cent, grade and the concrete piersand abutments have pile foundations built in colTer-dams excavated below the river bottom. The super-structure consists of 17 regular 79-foot plate girderspans and one plate girder 77 foot Scherzer basculespan with a clearance of about 26 feet above highwater. The main girders are spaced 21 feet aparton centers. The footingsare protected with a riprap, and the floor of thebascule span is paved withwooden blocks. The fixedspans have reinforced con-crete pavement. SHEirr PILE COFFERDAMS. At low water the depthof the river in the channelis 7 feet and the velocity 4miles per hour. In highwater the depth is 22 feetand the velocity 6 piers were construct-ed in cofferdams made ofWakefield sheet piles builtup of 2xl2-inch planksdriven to a maximumdepth of 14J4 feet belowlow water level and a pen-etration of from 6 to 15feet. The sheet piles weredriven by a 2,100-pounddrop hammer aided by anhydraulic jet and were. pulled by a two-part wire rope tackle aided by thesame jet. The cofferdams ,were unwatered and the riverbottom was excavated to the bottoms of the footingsby one Nye steam-driven sand pump with a 4-inchintake that carried about 20 per cent, of the sandwith a rise of 20 feet for the suction and 10 feet forthe discharge; one Domestic gasoline pump with a4-inch diaphragm that carried 50 per cent, sand andgravel with a 15-foot suction, and one Cameron testpump with a 3-inch intake, a 12-foot suction and8-foot discharge that handled only clear water. Thepumps were shifted from pier to pier, about 80 feet,by hand, requiring 6 menone hour for the Nyepumps, and four men 10minutes for the Domesticpumps. FALSEWORK. For the construction ofthe substructure the con-tractor built two servicetracks parallel and adja-cent to the axis of thebridge. These were carriedon falsework with three-pile bents 21 feet apart,spaced to clear the bent had one pile 2feet 6 inches, one pile
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectmunicip, bookyear1896
