Chapter XXII (2)

All concrete was mixed and placed by hand, the concrete gang consisting generally of 1 sub-foreman, 2 men measuring materials, 2 men mixing mortar, 3 men turning concrete three times, 3 men wheeling concrete, 1 man placing concrete and 2 men ramming concrete. Two gangs were ordinarily employed, each mixing and placing about 20 cu. yds. per day, or 1.43 cu. yds. per man per day. The materials (sand and stone) were measured in bottomless boxes, the following sizes being used:

--Sand Box-- --Stone Box--

Prop. of Mix. Size. Vol. cu. ft. Size. Vol. cu. ft.

1-2½-4[H] 2'9"×2'×1'8" 9.25 5'×4'5½" 14.8 1-3-6[H] 2'9"×2'×2' 11.1 5'×6'8" 22.2 1-2-5 2'9"×2'×1'4" 7.4 5'×6'6-5/8" 18.5 1-2½-6½ 2'9"×2'×1'8" 9.25 5'×7'2½" 24.05

[Footnote H: These mixtures were used for gate house and standpipe foundation work.]

The bottom layer was placed in a continuous sheet; the top layer was laid in 10-ft. squares on the floor and in 8×10-ft. squares on the sides; these squares alternated in both directions, one-half being first laid and allowed to set. In laying the sides the surface was left 1 in. low and then before the concrete had set was brought to plane by a 1-in. layer of 1-2½-4 mixture using stone and stone dust less than 3/8 in. The concrete for the floor was mixed rather wet and rammed until it quaked; on the sides a drier mixture was necessary to prevent flow. The cost of the lining concrete was as follows:

Bottom Layer on Floor: 1-2-5 Mixture: 1.25 bbls. natural cement at $1.08 $1.350 0.34 cu. yd. sand at $1.02 0.347 0.86 cu. yd. stone at $1.57 1.350 4½ ft. B. M. lumber at $20 per M. 0.090 Labor, on forms 0.100 Labor mixing and placing 1.170 Labor general expenses 0.080 ------ Total $4.487

Bottom Layer on Sides: 1-2½-6½ Mixture: 1.08 bbl. Portland cement at $1.53 $1.652 0.37 cu. yd. sand at $1.02 0.377 0.96 cu. yd. stone at $1.57 1.507 Lumber for forms (about 1 ft. B. M.) at $20 0.016 Labor, on forms. 0.121 Labor, mixing and placing 1.213 Labor, general expenses 0.177 ------ Total $5.063

Top Layer on Floor and Sides: 1-2½-4 Mixture: 1.37 bbls. Portland cement at $1.53 $2.09 0.47 cu. yd. sand at $1.02 0.48 0.75 cu. yd. stone at $1.57 1.17 12½ ft. B. M. form lumber at $20 per M. 0.25 Labor, on forms 0.26 Labor, mixing and placing 1.530 Labor, general expenses 0.150 ------ Total $5.93

The side finish with 1-2½-4 concrete of 3/8-in. stone cost $0.154 per sq. yd. 1 in. thick. This work was done by a gang of 3 plasterers and 3 helpers.

The layer of plaster between the concrete layers was put down on 4-ft. strips and finished similarly to the surface of a granolithic walk. This layer consisted of 1-2 mortar finished with a 4-1 mortar. To keep the plaster from cracking it was covered with strips of coarse burlap soaked in water; this precaution was not entirely successful, some cracks appeared and had to be grouted. Three gangs, each consisting of 1 plasterer and 1 helper, did the plastering, each gang laying about 700 sq. yds. per day. The cost of the plaster layer was as follows:

Item. Per 100 sq. ft. Per sq. yd. Per cu. yd. Cement at $1.53 $1.15 $0.103 $7.42 Sand at $1.02 0.13 0.012 0.86 Burlap 0.02 0.002 0.14 Labor 0.92 0.083 6.00 ----- ------ ------ Totals $2.22 $0.200 $14.42

It will be noted that it took over 5 bbls. of cement per cubic yard, and that the labor cost was $6 per cubic yard.

~RELINING A RESERVOIR, CHELSEA, MASS.~--The following account of relining the Powder Horn Hill Reservoir at Chelsea, Mass., is taken from a paper by Mr. C. M. Saville. This reservoir which holds about 1,000,000 gallons is oval in shape, 98×175 ft. at the top, 68×148 ft. at the bottom and 15 ft. deep, with side slopes about 1 on 1. The work was done by day labor. For sake of completeness the costs of excavation and back-filling are given here as well as the concrete costs.

The top of the bank was too narrow to allow the use of carts and an 18-in. gage railroad was decided upon as most convenient for handling materials. A 65-ft. boom derrick with a 70-ft. mast was used for removing the excavated material and for depositing concrete. The derrick was operated by a 15-h.p. double drum hoisting engine, was held in place by six wire guy ropes, and had a reach such that only one moving was necessary after it was placed. The engine and derrick were set up on the floor of the reservoir, and the work of excavation was begun at about the middle of the south side. In order to facilitate the work, a platform supported on A frames was set up. These frames were spaced about 15 ft. apart and rested on the bottom and slope of the reservoir, being held in place by bolts driven into the floor.

The paving blocks on the top of the slope were removed and piled up to be taken away. The old lining and the material excavated from the bank were shoveled into the scale pan of the derrick, hoisted to the cars on the top of the bank, and then run by gravity to a dump a short distance down the hillside. Here the cars were run out on a rough trestle, the load dumped, and the empties hauled back to the work by a rope carried through pulleys to the winch head on the hoisting drum of the engine.

For the storage of some of the materials, two small portable storehouses were set up--one 8×10×7 ft., the other 11×16 x 7 ft. The bulky portions, such as cement, sand, and stone, were delivered as necessary, a few days' supply only being kept on hand. A branch from the railroad was so arranged that it passed the storehouses and stone piles, while the sand was piled close to the concrete mixing board. The intention on the work was to do nothing by hand that could possibly be done by steam, except that all of the concrete was mixed by hand. As great a proportion of water was used as could be done without causing the material to slide when rammed in place.

The lower layer of concrete was of the proportion by volume of 1 cement, 2½ sand, and 6½ crushed stone (sizes from ¾ to 1½ ins.). This was rather a lean mixture, and as it could not be rammed enough to flush all over, the surface was finished where necessary by a thick mortar made in the proportion of 1 cement to 6 sand, and applied with heavy brushes. Before placing any of the concrete, the bank back of the old concrete left in place was thoroughly rammed with iron railroad tampers, and the edge of the old concrete was scrubbed with water and a stiff brush and then coated with 1 to 4 grout, which was allowed to fill in the angle between the concrete and the slope. Just before placing the concrete the earth bank was well wet in order that moisture might not be drawn from the concrete while it was soft.

In order to make the new lining as waterproof as possible, a layer of asphalt was placed on top of the lower layer of concrete and brought up on the exposed edge of the old layer at the bottom of the new work. This, it was expected would make an elastic and watertight joint between the new and the old work.

Venezuela asphalt, "Crystal Brand," was used, being poured upon the top of the concrete layer and allowed to run down the slope, care being taken that the concrete was entirely and perfectly covered. After the first layer of asphalt was cool, a second layer was similarly applied, and the resulting sheet was about ¼ in. thick. Any inclination to crawl down the slope when exposed to the sun was readily stopped by throwing on a pailful of cold water. A most particular part of this work was to get the asphalt as hot and liquid as possible and yet not burn it. All of the concrete was protected from the sun and kept damp by being covered with strips of burlap, which were moistened by sprinkling.

The upper layer of concrete was composed of a much richer mixture of concrete than that used in the bottom layer, the proportions by volume being 1 cement, 1¼ sand, 1¼ stone dust, and 4 broken stone of the sizes mentioned above. On account of the steep slope it was possible to do only a little ramming, and the material was laid as wet as possible. To make this layer more impervious and also to obtain a smooth surface, the concrete was left about an inch below and a finish coat applied by expert granolithic finishers. This coating was applied as soon as it was possible to do so after the main layer was in place, but on account of the steepness and the liability of the wet concrete to flow, care had to be taken not to begin work too soon.

The top finishing coat was made in the proportion of 1 part cement, 1-2/3 part sand, and 3-1/3 parts stone dust. In order to help in bonding, the last ramming on the concrete was done with rammers studded with pieces of iron about 1 in. long and ½ in. deep.

The finishing was done in three operations: The material was spread on the concrete and thoroughly worked into it by the finishers, using rough wooden floats; after this it was gone over and partially smoothed down with a thin steel float; and finally it was worked to give the finished appearance and an impervious surface.

The under layer of concrete was placed in a continuous sheet. The upper layer was put down in alternate strips, 10 ft, long (the whole length of the layer) and 5 ft. wide. These blocks were built up in forms, which were not removed until the concrete had set. Finally, the back or edge of the block toward the bank was well wet and thoroughly plastered, to prevent, as far as possible, the infiltration of any water. The plaster was mixed in the proportion of 1 part cement to 4 parts sand. When the forms were wholly removed, the space between the concrete and the bank was refilled, to within about 6 ins. of the top, with a clayey material previously excavated, and the space was filled and graded to the top of the bank with loam. During the work two holidays intervened; the men were also transported to and from the work. Charges were made for these items, amounting to $209.77, and this sum, together with the cost of installing the plant ($716.03) are proportionally charged against the work as follows:

Per cent. Total. Per cu. yd. Excavation 70.3 $651 $2.17 Lower concrete 12 111 1.16 Upper concrete 15.4 143 1.11 Back fill 2.3 21 .28

The detailed cost of repairing the reservoir lining is given in the following tabulations:

Excavation.

Rate. Per cu. yd. Foreman 9 5/9 days $4.00 $0.13 Engineman 12 3/9 days 3.00 .12 Carpenter 2 days 2.67 .02 Laborers 9 6/9 days 2.25 .07 Laborers 110 2/9 days 2.00 .73 Laborers 46 5/9 days 1.75 .27 Derrick 12 3/9 days 3.75 .15 Rails and cars 11 2/9 days 0.40 .02 Stove coal 3.05 tons 6.50 .07 Egg coal .95 tons 6.25 .02 ---- Total, 300 cu. yds. 1.60

Estimated proportionate charge for plant installation and holidays 2.17 ---- Grand total 3.77

Lower Layer Concrete. Rate. Per cu. yd. Foreman 3-7/9 days $4.00 $0.16 Engineer 2-3/9 days 3.00 0.07 Carpenters 7 days 2.67 0.20 Laborers 1-7/9 days 2.25 0.06 Laborers 89 days 2.00 1.87 Laborers 4 days 1.75 0.07 Derrick and engine 2-3/9 days 3.75 0.08 Rails and cars 2-2/9 days 0.40 0.01 Cement 106-3/8 bbls. 1.35 1.50 Sand 37.4 cu. yds. 1.10 0.43 Broken stone 117.9 tons 1.35 1.67 Egg coal .41 tons 6.25 0.03 Lumber 1.3 M. ft. 21.00 0.28 ---- Total, 95.5 cu. yds. $6.43

Estimated proportionate charge for
plant installation and holidays 1.16
----
Grand total $7.59

Upper Layer Concrete. Rate. Per cu. yd. Foreman 6-7/9 days $4.00 $0.21 Engineer 1-8/9 days 3.00 0.04 Carpenter 18-5/9 days 2.67 0.38 Laborers 1-7/9 days 2.25 0.03 Laborers 119-5/9 days 2.00 1.85 Derrick and engine 1-8/9 days 3.75 0.05 Rails and cars 8-3/9 days 0.40 0.03 Cement 176½ bbls. 1.35 1.86 Sand 30.2 cu. yds. 1.10 0.26 Stone dust 41.6 tons 1.50 0.48 Broken stone 122.8 tons 1.35 1.28 Egg coal .2 tons 6.25 0.00 Lumber 4 M. ft. 21.00 0.65 Burlap 300 yds. 0.04½ 0.10 Nails 170 lbs. 0.05 0.03 ----

Total, 129.2 cu. yds. $7.25
Estimated proportionate charge for
plant installation and holidays 1.11
----
Grand total $8.36

Back Plaster. Rate. Per cu. yd. Plasterer 3-8/9 days $5.40 $0.08½ Plasterer 8/9 days 6.00 0.02 Plasterer 5-5/9 days 4.50 0.09 Laborers 9-3/9 days 2.25 0.08½ Laborers 3/9 days 2.00 0.00 Cement 6 bbls. 1.35 0.03 Sand 3.3 cu. yds. 1.10 0.01 ---- Total, 262 sq. yds. 0.32

Surfacing. Rate. Per cu. yd. Plasterer 7-6/9 days $5.40 $0.09 Plasterer 2-1/9 days 6.00 0.03 Plasterer 9-4/9 days 4.50 0.09 Laborers 12-8/9 days 2.25 0.06 Laborers 2-4/9 days 2.00 0.01 Cement 22¼ bbls. 1.35 0.06 Sand 5.07 cu. yds. 1.10 0.02 Stone dust 14 tons 1.50 0.04 ---- Total, 460 sq. yds. $0.40

Asphalt. Rate. Per cu. yd. Foreman 1/9 day $4.00 $0.00 Asphalt man 11 days 2.00 0.05 Laborers 6 days 2.00 0.02½ Asphalt kettle 11 days 1.50 0.03½ Asphalt 3.9 tons 30.00 0.25 Asphalt mops 3.00 0.01 ---- Total, 464 sq. yds. $0.37

Back Filling.

Rate. Per cu. yd. Foreman 1-3/9 days $4.00 $0.07 Laborers 23-3/9 days 2.00 0.62 Laborers 9 days 1.75 0.21 Rails and cars. 2-2/9 days 0.40 0.02 Loam 27-5/9 cu. yds. 1.25 0.46 ----- Total, 75 cu. yds. $1.38

Estimated proportionate
charge for installing plant and holidays $0.28
-----
Grand total $1.66

Installing Plant.

Total. Foreman 15-4/9 days $4.00 $61.78 Sub-foreman 1 day 3.00 3.00 Engineer 8-4/9 days 3.00 25.33 Carpenter 3 days 2.67 8.00 Watchman 42 days 2.00 84.00 Laborers 17-4/9 days 2.25 38.36 Laborers 149-8/9 days 2.00 299.78 Double team 10½ days 5.00 52.50 Single team 6 days 2.00 12.00 Single team 1 day 3.50 3.50 Teaming (total) 53.00 Derrick and engine. 11-4/9 days 3.75 49.92 Rails and cars 8-2/9 days 0.40 3.29 Broken stone 7.05 tons 1.35 9.52 Egg coal .6 ton 6.25 3.75 Kerosene 30 gal. 0.11 3.30 Oil 4 gal. 0.25 1.00 Spikes 220 lbs. 0.05 11.00 ------- Total $723.03

The cost of the concrete work in the lower and upper layers can be still further detailed as shown below:

Lower Layer Concrete. 95.5 cu. yds., 1-2½-6½ concrete.

Materials: Rate. Per cu. yd. Atlas cement 1.11 bbl. $1.35 $1.50 Sand .39 cu. yd. 1.10 0.43 Broken stone (.97 cu. yd.) 1.23 tons 1.35 1.66 Miscellaneous, plant, coal, etc. 1.28

Labor:
Mixing and placing $2.09
Carpenter work on forms at $24.00 per M. .34
-----
Total per cu. yd. in place $7.30

Upper Layer Concrete. 129.2 cu. yds., 1-1¼-1¼-4 concrete.

Materials: Rate. Per cu. yd. Atlas cement 1.37 bbl. $1.35 $1.85 Sand .24 cu. yd. 1.10 0.26 Stone dust (.25 cu. yd.) .32 ton 1.50 0.48 Broken stone (.75 cu. yd.) .96 ton 1.35 1.30 Lumber 0.31 M. ft. 21.00 0.65 Miscellaneous, plant, etc. 1.32

Labor:
Mixing and placing 1.85
Carpenter work on forms at $21.00 per M. 0.66
-----
Total per cu. yd. in place $8.37

The following approximate labor costs are also given: Transporting, erecting and removing derrick, $260.85. Equivalent time: Foreman, 6 days; engineer, 4 days; laborer, 85 days.

Transporting, laying and removing track, $125.03. Equivalent time: Foreman, 4 days; laborer, 40 days.

Caring for dump and disposing of surplus by rough grading, $70.28. Equivalent time: Foreman, 1 day; laborer, 33 days.

The total cost of the work was $3,503.66, divided up as follows:

Excavation $ 480.79 Lower layer concrete 614.15 Upper layer concrete 937.94 Back plaster 84.73 Surfacing 186.04 Asphalting 170.94 Back filling 103.27 Installing plant 716.03 Transportation and holidays 209.77 --------- Grand total $3,503.66

~LINING JEROME PARK RESERVOIR.~--The bottom of the reservoir that was lined covered 250 acres, and the concrete lining was 6 ins. thick. The lining was laid in alternate strips 16 ft. wide between forms set to grade. The concrete was mixed in 18 Ransome mixers provided with charging hoppers and mounted on trucks without boilers. Steam was supplied to the mixer engines from the boilers of the contractor's locomotives. One locomotive supplied steam for three or four mixers. Tracks were laid in parallel lines across the reservoir bottom from 150 to 200 ft. apart. Sand and stone were hauled in on these tracks. The sand was dumped in stock piles at intervals; the stone was shoveled from the cars directly into the charging hopper and the sand was delivered by wheelbarrows to the same hopper. Four men shoveled the stone for each mixer. To deliver the concrete from the mixer to the work required six men with wheelbarrows. Two men leveled off the concrete discharged by the barrows and two other men floated the surface by means of a straight-edge spanning the 16-ft. strips and riding on the forms. By using a wet but not sloppy concrete and moving the straight-edge back and forth a good surface was secured. The gang mixing and placing consisted of 20 men for each mixer and 18 gangs laid approximately 1½ acres per 10-hour day. The gang organization and wages were as follows:

Item. Per 10 hours. 4 men shoveling stone at $1.50 $ 6.00 2 men wheeling sand at $1.50 3.00 2 men delivering cement at $1.50 3.00 1 man dumping mixer at $1.50 1.50 1 man tending engine and water at $1.50 1.50 6 men wheeling concrete at $1.50 9.00 2 men spreading concrete at $1.50 3.00 2 men leveling concrete at $1.50 3.00 1 foreman 3.00 ------ Total per day $33.00

These costs do not include the fraction of a day's labor for fireman or the cost of fuel.

~RESERVOIR FLOOR, CANTON, ILL.~--The following costs are given by Mr. G. W. Chandler for lining the bottom of a 160×80-ft. reservoir with corners of 20-ft. radius and vertical brick sidewalls. A 1-3½-7½ crushed stone concrete was used; it was mixed by hand in batches of 2.7 cu. ft. cement, 9 cu. ft. sand and 20¼ cu. ft. stone. The sand and stone were measured separately, the sand and cement mixed dry, then shoveled into a pile with the rock, well wetted, shoveled over again and then shoveled into wheelbarrows. The stone had 40 per cent. voids and the sand 30 per cent. voids. The lining was 10 ins. thick including a ¾-in. coat of 1-2¼ mortar spread and worked smooth with a trowel. The cost per cubic yard of the lining in place was as follows:

0.856 bbl. cement at $2.50 $2.14 10.1 bu. sand (100 lbs. per bu.) at 5¾ cts 0.58 0.857 cu-yd-stone at $2.17 1.86 Labor, mixing and placing at 19 cts. per hr. 0.80 ----- Total $5.38

~RESERVOIR FLOOR, PITTSBURG, PA.~--The following methods and costs of laying a reservoir floor are given by Mr. Emile Low, M. Am. Soc. C. E., for the Hiland Reservoir constructed at Pittsburg, Pa., in 1884, by contract. There were 7,681 cu. yds. of concrete in the floor which was 5 ins. thick and laid on a clay puddle foundation.

Natural cement costing $1.35 per barrel was used. The broken stone varied in weight from 147 to 152 lbs. per cu. ft.; it was quarried and hauled 20 miles by rail and then unloaded into small cars and hauled ½ mile to the reservoir. The cost of the stone per cubic yard delivered was:

Quarrying, per cu. yd. $0.45 Breaking, per cu. yd. 0.35 Transporting, per cu. yd. 0.50

Total $1.30

The sand was obtained on the site at the cost of excavation, or 1¼ cts. per bushel.

The method of proportioning and mixing the concrete was as follows: Platforms 10×16 ft. of 2-in. plank were laid on the puddle foundation and by these were set 5×4×1½-ft. boxes on legs. Into these boxes 1 bbl. of cement and 2 bbls. of sand were emptied and thoroughly mixed dry, then mixed with water to a thin grout. Five barrels of stone were placed on the platform and thoroughly wetted; the grout was then emptied over the stone and the two turned over three times with shovels. The concrete was rammed until the mortar flushed to the surface. The following costs cover various periods as follows:

Two Days Work (101 cu. yds.): Total. Per cu. yd.
27 laborers, 2 days, at $1.25 $72.90 $0.7217
1 foreman, 2 days, at $2.50 5.00 0.0495
------ -------
Total $77.90 $0.7712

One Month's Work (1,302 cu. yds.):
642 days, laborers, at $1.35 $ 866.70 $0.6649
17 days, water boy, at $0.60 10.20 0.0078
22 days, foreman, at $2.50 55.00 0.0421
------ -------
Total $931.90 $0.7148

Two Days Work (101 cu. yds.): Total. Per cu. yd.
27 laborers, 2 days, at $1.25 $72.90 $0.7217
1 foreman, 2 days, at $2.50 5.00 0.0495
------ -------
Total $77.90 $0.7712

One Month's Work (1,302 cu. yds.):
642 days, laborers, at $1.35 $ 866.70 $0.6649
17 days, water boy, at $0.60 10.20 0.0078
22 days, foreman, at $2.50 55.00 0.0421
------ -------
Total $931.90 $0.7148

Total Work (7,861 cu. yds.):

Quarrying stone $0.45 Transporting stone 0.50 Breaking stone 0.35 1-1/3 bbl. natural cement 1.80 8 bu. sand 0.10 Water 0.05 Labor mixing and laying at $1.25 0.75 Incidentals 0.05 ----- Total $4.05

The contract price was $6 per cu. yd.

~CONSTRUCTING A SILO.~--The form construction shown in Fig. 286 was employed in building a silo 28 ft. high, 22 ft. 3 ins. interior diameter, and having 6-in. walls. The bottom of the silo was made 9 ins. thick and set 2 ft. below the surface. The reinforcement consisted of ten 2½×3/16-in. rings spaced equally in the lower half and of woven wire fencing in the upper half. The iron rings were hoops removed from an old wooden silo. The concrete was a 1-6 mixture of Portland cement and sandy gravel. Figure 286 is a section through the forms. There were twenty T-shaped posts, which extended perpendicularly from the ground to a height of 28 ft., being secured at top and bottom by a system of guy ropes and posts. The rings, of which there are four, two inside and two outside, were built of weather boards with their edges reversed. Four thicknesses of board were used in each ring. The curbing consisted of 2×8-in. sticks 4 ft. long. Wedges driven between the vertical posts and the rings held the latter in place. When the forms were to be removed the wedges were knocked out and the rings sprung enough to permit the removal of the curbing. The rings were then pushed up and fastened in place for another section. The average rate of progress was one 4-ft. section per day. The forms were filled in the afternoon and moved up the following forenoon. Five-foot sections could have been built just as readily.

The work was all done by farm laborers hired by the month and 100 man-days of such labor were required, excluding seven days work of a mason brushing and troweling the surface. The cost of the work, not including the old hoop iron or the old lumber used in forms, was as follows:

Item. Total. Per cu. yd. Cement $100.00 $2.62 Gravel and sand 35.00 0.92 1 20-rod roll of fencing 5.20 0.01 New lumber 18.00 0.47 100 days labor at $1.75 175.00 4.60 7 days mason troweling at $3.50 24.50 0.64 ------- ----- Total, 38.2 cu. yds. $357.70 $9.26

The external area of the silo is 1,950 sq. ft., which makes the cost of brushing and troweling 1¼ cts. per sq. ft. There were about 2,300 ft. B. M. of lumber used in the forms, or about 61 ft. B. M. per cu. yd. of concrete.

~GROINED ARCH RESERVOIR ROOF.~--The following data are given by Mr. Allen Hazen and Mr. William B. Fuller, in Trans. Am. Soc. C. E. 1904. The concrete was mixed in 5-ft. cubical mixers in batches of 1.6 cu. yds. at the rate of 200 cu. yds. per mixer day. One barrel of cement, 380 lbs. net, assumed to be 3.8 cu. ft., was mixed with three volumes of sand weighing 90 lbs. per cu. ft., and five volumes of gravel weighing 100 lbs. per cu. ft. and having 40 per cent voids. On the average 1.26 bbls. of cement were required per cu. yd. The conveying plant consisted of two trestles (each 900 ft. long) 730 ft. apart, supporting four cableways. The cables were attached to carriages, which ran on I-beams on the top of the trestles. Rope drives were used to shift the cableways along the trestle. Three-ton loads were handled in each skip. The installation of this plant was slow, and its carrying capacity was less than expected. It was found best to deliver the skips of concrete to the cableway on small railway track, although the original plan had been to move the cableways horizontally along the trestle at the same time that the skip was traveling.

The cost of mixing and placing the concrete was as follows:

Per cu. yd.
Measuring, mixing and loading $0.20
Transporting by rail and cables 0.12
Laying and tamping floors and walls including setting forms 0.22
-----
Total $0.54

The cost of laying and tamping the concrete on the vaulting was 14 cts. per cu. yd. The vaulting is a groined arch 6 ins. thick at the crown and 2½ ft. thick at the piers.

The lumber of the centering for the vaulting was spruce for the ribs and posts, and 1-in. hemlock for the lagging. The centering was all cut by machinery, the ribs put together to a template, and the lagging sawed to proper bevels and lengths. The centers were made so that they could be taken down in sections and used again. The cost of centering was as follows:

Labor on centers covering 62,560 sq. ft.

Foreman, 435 hrs. at 35 cts. $ 152.25 Carpenters, 4,873 hrs. at 22½ cts. 1,096.42 Laborers, 3,447 hrs. at 15 cts. 517.05 Painters, 577 hrs. at 15 cts. 86.55 Teaming, 324 hrs. at 40 cts. 121.60 --------- Total labor building centers, 313 M. at $6.37 $1,973.87

Materials for centers covering 62,560 sq. ft.

313,000 ft. B. M. lumber, at $18.20 $5,700.00 3,700 lbs. nails, at 3 cts. 111.00 8 bbls. tar, at $3 24.00 --------- Total $5,835.00

These centers covered two filters, each having an area of 121-1/3×258 ft. There were six more filters of the same size, for which the same centers were used. The cost of taking down, moving and putting up these centers (313 M.) three times was as follows:

Foreman, 2,359 hrs. at 35 cts. $ 825.65 Carpenters, 12,766 hrs. at 22½ cts. 2,872.35 Laborers, 24,062 hrs. at 15 cts. 3,609.30 Team, 430 hrs. at 40 cts. 172.00 3,000 ft. B. M. lumber, at $20 60.00 3,000 lbs. nails, at 3 cts. 90.00 ---------

Total cost of moving centers to cover 196,660 sq. ft. $7,629.30

The cost of moving the centers each time was $8.10 per M., showing that they were practically rebuilt; for the first building of the centers, as above shown, cost only $6.37 per M. In other words, the centers were not designed so as to be moved in sections as they should have been. Although the centers were used four times in all, the lumber was in fit condition for further use. The cost of the labor and lumber for the building and moving of these centers for the 8 filter beds, having a total area of 259,220 sq. ft., was $15,438, or 6 cts. per sq. ft.

~GRAIN ELEVATOR BINS.~--In constructing cylindrical bins 30 ft. in diameter and 90 ft. high for a grain elevator the forms shown by Fig. 287 were used. For the inside wall a complete ring of lagging 4 ft. high nailed to circular horizontal ribs of 2×8-in. planks was used. For the outside wall two, three or four segments fitting the clear spaces between adjoining tanks were used, these panel segments being also 4 ft. high. The inside and outside rings were held together by yokes constructed as shown, and bolted to the inner and outer ribs. A staging built up inside the tank carried jack screws, on which were seated the inner legs of the yokes.