Part 20 (1/2)

Blacksmith Work-- 1 laborer at $2 $0.0086 1 blacksmith at $3.25 0.0141 1 waterboy at $0.75 0.0032 ------- Total per cubic yard $0.4473 Add 75% of cost of administration 0.1388 ------- Total labor per cu. yd. $0.5861

The total cost of each cubic yard of concrete in place was estimated to be as follows:

Per cu. yd.

Ten-elevenths cu. yd. pebbles at $1.085 $0.9864 Ten-twenty seconds cu. yd. sand at $0.00 0.0000 1 26 bbls. cement at $1.77 2.2302 Labor as above given 0.5861 Cost of plant distributed over total yardage 0.8400 ------- Total $4.6427

It will be noted that the sand cost nothing as it was dredged from the trench in which the pier was built, and paid for as dredging. The cost of the plant is distributed over this south pier and over the proposed north pier work on the basis of only 20 per cent. salvage value after the completion of both piers. It is said, however, that 80 per cent. is too high an allowance for the probable depreciation.

~DAM, RICHMOND, INDIANA.~--The dam shown in cross-section in Fig. 89 was built at Richmond, Ind. It was 120 ft. long and was built between the abutments of a dismantled bridge. The concrete was made in the proportion of 1 bbl. Portland cement to 1 cu. yd. of gravel; old iron was used for reinforcement. The foundations were put down by means of a cofferdam which was kept dry by pumping. On completion it was found that there was a tendency to scour in front of the ap.r.o.n and accordingly piling was driven and the intervening s.p.a.ce rip-rapped with large stone. Labor was paid as follows per day: Foreman, $3; carpenter, $2.50; cement finisher, $2; laborers, $1.50. The concrete was mixed by hand and wheeled to place in wheelbarrows. The cost of the work was as follows:

Materials-- Per cu. yd.

204 bbls. cement at $1.60 $1.485 Sand and gravel 0.800 Lumber 0.610 Tools, hardware, etc. 0.445 ------ Total materials $3.34

Labor-- Clearing and excavating $0.96 Setting forms and mixing concrete 1.01 Pumping 0.27 ----- Total labor $2.24 Total materials and labor $5.58

[Ill.u.s.tration: Fig. 89.--Concrete Dam at Richmond, Ind.]

~DAM AT ROCK ISLAND a.r.s.eNAL, ILLINOIS.~--The dam was in the shape of an L with one side 192 ft. and the other side 208 ft. long; it consists of a wall 30 ft. high, 3 ft. wide at the top and 6 ft. wide at the bottom with a counterfort every 16 ft., 26 in all. Each counterfort extended back 16 ft. and was 4 ft. thick for a height of 6 ft. and then 3 ft.

thick. There were 3,500 cu. yds. of concrete in the work, which was done by day labor under the direction of the U. S. Engineer in charge.

The forms consisted of front and back uprights of 810-in. stuff 24 ft.

high, connected through the wall by -in. rods which were left in the concrete. The lagging was 212-in. plank dressed down 1 ins. placed inside the uprights. These forms were built full height in 16-ft.

sections with a counterfort coming at the center of each section. Each section contained 95 cu. yds. of concrete and was filled in a day's work. The concrete was a 1-4-7 mixture wet enough to quake when rammed.

Run of crusher limestone was used of which 50 per cent. pa.s.sed a 1-in.

sieve, 17 per cent. a No. 3 sieve and 9 per cent. a No. 8 sieve. The concrete was mixed in c.o.c.kburn Barrow & Machine Co.'s screw-feed mixer which discharged into 2-in. plank skips 2 ft. wide 5-1/3 ft. long and 14 ins. deep, holding cu. yd. These skips were taken on cars to a derrick crane overhanging the forms and by it hoisted and dumped into the forms.

The derrick was moved along a track at the foot of the wall as the work progressed. The concrete was spread and rammed in 6-in. layers. The men were paid $1.50 per 8-hour's work and the work cost including footing, as follows:

Item-- Total. Per cu. yd.

Cement $1,500.00 $0.429 Sand 400.00 0.114 Storing and hauling cement 460.00 0.131 Taking sand from barge to mixer 96.00 0.027 Crus.h.i.+ng stone 1,450.00 0.414 Mixing concrete 4,825.00 1.378 Placing concrete 1,670.00 0.477 Lumber for forms, etc. 600.00 0.171 Erecting and taking down forms 2,450.00 0.700 ---------- ------ Totals $13,451.00 $3.841

~DAM AT McCALL FERRY, PA.~--The dam was 2,700 ft. long and 48 ft. high of the cross-section shown by Fig. 90 and with its subsidiary works required some 350,000 cu. yds. of concrete. The plant for mixing and placing the concrete was notable chiefly for its size and cost. Parallel to the dam, which extended straight across the river, and just below its toe a service bridge consisting of a series of 40-ft. concrete arch spans was built across the river. This service bridge was 50 ft. wide and carried four standard gage railway tracks besides a traveling crane track of 44 ft. gage. This very heavy construction of a temporary structure was necessitated by the frequency of floods against which only a solid bridge could stand; it was considered cheaper in the long run to provide a bridge which would certainly last through the work than to chance a structure of less cost which would certainly go out with the floods. The concrete service bridge was designed to be destroyed by blasting when the dam had been completed. The method of construction was to build the dam in alternate 40 ft. sections, mixing the concrete on sh.o.r.e, taking it out along the service bridge in buckets on cars and handling the buckets from cars to forms by traveling cranes.

[Ill.u.s.tration: Fig. 90.--Steel Forms for McCall Ferry Dam.]

The concrete mixing plant is shown by Fig. 91. Cars loaded with cement, sand and stone were brought in over the tracks carried on the wall tops of the bins and were unloaded respectively into bins A, B and C, of which there were eight sets. Each set supplied material by means of measuring cars to a 1 cu. yd. Smith mixer. Two sets of cars were used for each mixer so that one could be loading while the other was charging. The mixers discharged into 1 cu. yd. buckets set two on a car and eight cars were hauled to the work in train by an 18-ton ”d.i.n.ky.” At the work the buckets were picked up by the traveling cranes and the concrete dumped into the forms. Figure 90 shows the construction of the steel forms. Six sets of forms were used. Each set consisted of five frames s.p.a.ced 10 ft. apart and braced together in the planes parallel to the dam, and each set molded 40 ft. of dam. The lagging consisted of wooden boxes 8 ft. wide and 10 ft. long. For the vertical face of the dam these boxes were attached by bolts to the vertical post, for the curved face they were bolted to a channel bent to the curve and held by struts from the inclined post of the steel frame.

[Ill.u.s.tration: Fig. 91.--Concrete Mixing Plant for McCall Ferry Dam.]

In construction the footing and the body of the dam to an elevation of 5 ft. above the beginning of the curve were built continuously across the river; above this elevation the dam was built in alternate 40-ft.

sections. The strut back to the service bridge shown in the lower right hand corner of Fig. 90, shows the manner of bracing the first 30-ft.

section of the inclined post to hold the lagging for the continuous portion. The lagging was added a piece at a time as concreting progressed. The ends of each set of frames for a 40-ft. section were for the isolated sections closed by timber bulkheads carrying box forms to mold grooves into which the concrete of the intermediate sections would bond.

[Ill.u.s.tration: Fig. 92.--Traveler for Concreting Dam, Chaudiere Falls, Quebec.]

The concrete used was a 1-3-5 mixture, the stone ranging in size from 2 to 5 ins. Rubble stone from one man size to ton were bedded in the concrete. The capacity of the concrete plant was 2,000 cu. yds. per day or about 250 cu. yds. per mixer per 10-hour day.