Chapter VI

. The following examples of pier and abutment construction cover both large and small work and give a clear idea of current practice.

[Illustration: Fig. 93.--Pier and Cofferdam for a Railway Bridge.]

~COST OF CONSTRUCTING RECTANGULAR PIER FOR A RAILWAY BRIDGE.~--This pier, Fig. 93, was built in water averaging 5 ft. deep. The cofferdam consisted of triple-lap sheet piling, of the Wakefield pattern, the planks being 2 ins. thick, and spiked together so as to give a cofferdam wall 6 ins thick. The cofferdam enclosed an area 14×20 ft., giving a clearance of 1 ft. all around the base of the concrete pier, and a clearance of 2 ft. between the cofferdam and the outer edge of the nearest pile. The cofferdam sheet piles were 18 ft. long, driven 11 ft. deep into sand, and projecting 2 ft. above the surface of the water.

The concrete base resting on the foundation piles was 12×18 ft. The concrete pier resting on this base was 7×13 ft. at the bottom, and 5×11 ft. at the top. The pier supported deck plate girders. There were 100 cu. yds. of concrete in the pier and base.

The cost of this pier, which is typical of a large class of concrete pier work, has been obtained in such detail that we analyze it in detail, giving the costs of cofferdam construction and excavation as well as of mixing and placing the concrete.

Setting up and taking down derrick and platform:

4 days foreman at $5.00 $ 20.00 ¾ days engineman at $3.00 2.25 ¾ days blacksmith at $3.00 2.25 ¾ days blacksmith helper at $2.00 1.50 22 days laborers at $2.00 44.00 ------- Total $ 70.00

Cofferdam-- 7 days foreman at $5.00 $ 35.00 4 days engineman at $3.00 12.00 38 days laborers at $2.00 76.00 1 ton coal at $3.00 3.00 ------- Total labor on 7,900 ft. B. M. at $16.00 $126.00 7,900 ft. B. M. at $20.00 158.00 ------- Total for 58 cu. yds. excavation $284.00

Wet Excavation-- 1.8 days foreman at $5.00 $ 9.00 1.5 days engineman at $3.00 4.50 9 days laborers at $2.00 18.00 ½ ton coal at $3.00 1.50 ------- Total labor on 58 cu. yds. at 57c. $ 33.00

Foundation Piles-- 960 lin. ft. at 10c $ 96.00 4 days setting up driver and driving 24 piles at $20 per day for labor and fuel 80.00 ------- Total $176.00

Concrete-- 100 cu yds. stone at $1.00 $100.00 40 cu. yds. sand at $0.50 20.00 100 bbls. cement at $2.00 200.00 5 days foreman at $5.00 25.00 50 days laborers at $2.00 100.00 5 days engineman at $3.00 15.00 2 tons coal at $3.00 6.00 ------- Total, 100 cu. yds. at $4.66 $466.00

8 days carpenters at $3.00 24.00 2,400 ft. B. M. 2-in. plank at $25.00 60.00 1,000 ft. B. M. 4×6-in. studs at $20.00 20.00 Nails, wire, etc 2.00 ------- Total forms for 100 cu. yds. at $1.06 $106.00

Summary-- Setting up derrick, etc. $ 70.00 Cofferdam (7,900 ft. B. M.) 284.00 Wet excavation (58 cu. yds.) 33.00 Foundation piles (24) 176.00 Concrete (100 cu. yds.) 466.00 Forms (3,400 ft. B. M.) 106.00 --------- Total $1,135.00 Transporting plant 20.00 20 days rental of plant at $5.00 100.00 --------- Total cost of pier $1,252.00

Regarding the item of plant rental, it should be said that the plant consisted of a pile driver, a derrick, a hoisting engine, and sundry timbers for platforms. There was no concrete mixer. Hence an allowance $5 per day for use of plant is sufficient.

It will be noted that no salvage has been allowed on the lumber for forms. As a matter of fact, all this lumber was recovered, and was used again in similar work.

Referring to the cost of cofferdam work, we see that, in order to excavate the 58 cu. yds. inside the cofferdam, it was necessary to spend $284, or nearly $5 per cu. yd. before the actual excavation was begun. The work of excavating cost only 57 cts. per cu. yd., but this does not include the cost of erecting the derrick which was used in raising the loaded buckets of earth, as well as in subsequently placing the concrete. The sheet piles were not pulled, in this instance, but a contractor who understands the art of pile pulling would certainly not leave the piles in the ground. A hand pump served to keep the cofferdam dry enough for excavating; but in more open material a power pump is usually required.

The above costs are the actual costs, and do not include the contractor's profits. His bid on the work was as follows:

Piles delivered 12 cts. per ft. Piles driven $5 each Cofferdam $37 per M. Wet excavation $1.00 per cu. yd. Concrete $8.00 per cu. yd.

In order to ascertain whether or not these prices yielded a fair profit, it is necessary to distribute the cost of the plant transportation and rental over the various items. We have allowed $120 for plant transportation and rental, and $70 for setting up and taking down the plant, or $190 in all. The working time of the plant was as follows:

Per cent. Prorated Days. of time. plant cost. Cofferdam 7 39 $74 Excavation 2 11 21 Foundation piles 4 22 42 Concrete 5 28 53 -- --- ---- Totals 18 100 $190

As above given, the labor on the 7,900 ft. B. M. in the cofferdam cost $126, or $16 per M.; but this additional $74 of prorated plant costs, adds another $9 per M., bringing the total labor and plant to $25 per M., to which must be added the $20 per M. paid for the timber in the cofferdam, making a grand total of $45 per M. This shows that the contractor's bid of $37 per M. was much too low.

The labor on the excavation cost 57 cts. per cu. yd., to which must be added the prorated plant cost of $21 distributed over the 58 cu. yds., or 36 cts. per cu. yd., making a total of 93 cts. per cu. yd. This shows that the bid of $1 per cu. yd. was hardly high enough.

The labor on the 24 foundation piles cost $80, or $3.33 each. The prorated plant cost is $42, or $1.75 per pile, which, added to $3.33, makes a total of $5.08. This shows that the bid of $5 Per pile for driving was too low. However there was a profit of 2 cts. per ft., or 80 cts. per pile, on the cost of piles delivered.

The concrete amounted to 100 cu. yds. Hence the prorated plant cost of $53 is equivalent to 53 cts. per cu. yd. Hence the total cost of the concrete was:

Per cu. yd. Cement, sand and stone $3.20 Foreman (at $5) 0.25 Labor (at $2) 1.00 Engineman (at $3) 0.15 Coal (at $3) 0.06 Carpenters (at $3) 0.24 Forms (at $23.50, used once) 0.80 Wire, nails, etc 0.02 Prorated plant cost 0.53 ----- Total $6.25

Since the contract price for concrete was $8 per cu. yd., there was a good profit in this item.

~BACKING FOR BRIDGE PIERS AND ABUTMENTS.~--Six piers and two abutments of the City Island bridge were constructed in 1906 at New York city, of masonry backed with 1-2-4 concrete below and 1-3-5 concrete above high water. The piers and abutments were all sunk to rock or hard material by means of timber cofferdams. Table XVI gives the labor cost of mixing and placing the concrete backing for one abutment and three piers, after the materials were delivered on the scows. The concrete was mixed by a rectangular horizontal machine mixer and deposited by 2-cu. yd. bottom dump buckets handled by derrick scows and stiff leg derricks. The high cost of concreting on Pier 2 was due to the fact that the concrete was improperly deposited and had to be removed and the higher cost in Abutment 1 was probably due to the fact that the abutment was so long and narrow that it was difficult to handle the bucket.

TABLE XVI.--COST OF CONCRETE BACKING FOR MASONRY PIERS.

[Transcriber's note: Table split to be less than 80 column width]

Abutment No. 1. Pier No. 2. Wages Cost Cost per No. Total per No. Total per Hour. hrs. Cost. cu. yd. hrs. Cost. cu. yd. Superintendent 70 24 $16.80 $0.03 47 $32.90 $0.09 Foreman 35 160 56.00 0.09 128 44.80 0.13 Laborers 15-20 2555 383.25 0.65 2038 313.60 0.92 Engineman 30 365 109.50 0.19 196 58.50 0.19 Timekeeper 40 86 34.40 0.06 46 18.40 0.06

Pier No. 3. Pier No. 4. Wages Cost Cost per No. Total per No. Total per Hour. hrs. Cost. cu. yd. hrs Cost. cu. yd.

Superintendent 70 72 $50.40 $0.05 16 $11.20 $0.03 Foreman 35 324 113.40 0.12 54 18.90 0.06 Laborers 15-20 3513 526.95 0.56 940 141.00 0.44 Engineman 30 244 73.20 0.08 60 18.00 0.06 Timekeeper 40 81 32.40 0.04 10 4.00 0.01

Summary. Wages Total Total Av. Hrs. cost. per cu. yd. Superintendent 70 159 $111.30 $0.05 Foreman 35 666 233.10 0.11 Laborers 15-20 9046 1364.90 0.62 Engineman 30 865 259.50 0.12 Timekeeper 40 223 89.20 0.04

~PNEUMATIC CAISSONS, WILLIAMSBURG BRIDGE.~--Mr. Francis L. Pruyn, Assoc. M. Am. Soc. C. E., gives the following costs of concreting the pneumatic caissons for the Brooklyn tower of the Williamsburg bridge at New York city. The work comprised the mixing and placing of some 13,637 cu. yds. of concrete in two caissons. Table XVII shows the itemized costs for one caisson and Table XVIII shows them for the other caisson. The methods of work were as follows:

After each caisson was built it was towed to its proper site, where it was held in place by temporary pile dock built completely around it. On these docks the concrete was placed; a 2 cu. yd. cubical mixer of the usual pattern being used for mixing. The concrete materials, consisting of sand, stone and cement was handled direct from barges alongside, into the mixer. The concrete was placed by a derrick located in the center of the caisson, which was a bad feature as the caisson was usually out of level and considerable difficulty was experienced in swinging the derrick. On the South caisson ¾ cu. yd. bottom dump buckets were used in placing the concrete, on the North caisson the size of these was increased to 1½ cu. yd. which reduced the cost of placing 15 cts. per cu. yd. There were placed in the South caisson 3,827 cu. yds. in 32 days of actual working time--120 cu. yds. per day of 10 hrs. The gross time was 2 months. On the North caisson 5,693 cu. yds. were placed in 46 days worked--124 cu. yds. per day. The gross time was 4 months.

The rates of labor were as follows per 10-hour day:

Foreman $5.00 Assistant foreman 2.50 Hoisters 2.50 Fireman 1.60 Laborer 1.50

Proportions concrete were 1: 2.5: 6.

The low price of sand in the North caisson was brought about by the finding of good building sand in the excavation for the anchorage, which work was done by the same contractor.

When the caissons had been sealed the iron material shafts were removed. This left holes 5 ft.×6 ft. extending from the roof of the caisson up to Mean H.W. which were filled with concrete. These shaft holes were 80 ft. deep on the South caisson and 100 ft. deep on the North caisson. They were partially filled with water and the concrete had to be placed with considerable care. Wooden chutes were used on the South caisson; they rested on the caisson roof, were filled with concrete and then raised allowing concrete to flow out at the bottom. The shaft holes were too deep on the North caisson for chutes and 20 cu. ft. bottom dump buckets were used. They had to be lowered to bottom of shaft each trip before dumping, a slow operation, which greatly added to the cost. Proportion for concrete 1-2.5-6.

The proportion for concrete in working chamber was the same as for all other concrete. The specifications called for 6 in. of mortar, of 1 part of cement to 2½ parts of sand, between the concrete and all bearing areas; that is, under the cutting edge and directly under the roof of the working chamber. The concrete was mixed in the cubical mixer and dumped on the bottom door of the material lock, the top door of the lock was then closed, the bottom door opened and the concrete fell through the shaft to the working chamber. It was then shoveled by the sand hogs into place. A 6-in. space was left below all bearing surfaces into which damp mortar was tightly rammed. Concreting the South caisson took 10¼ working days of 24 hours, the gangs working night and day in twelve 2-hour shifts; 1,566 cu. yds. of concrete and mortar were placed, or at the rate of 140 cu. yds. per 24 hours. The gross time including Sundays was 14½ days. The sand hogs worked in shifts of 2 hours each and received $3.50 for the two hours work. The twelve foremen received 1 dollar more: the average gang consisted of 12 sand hogs.

On the North caisson the organization was much better, owing to the experience gained on the first caisson; and in spite of the fact that the sand hogs, on account of the increased depth, received $4.00 for 1½ hours' work, or an increase of $22.00 per man per 24 hrs. over that on the South caisson, the work was done for less money. There were placed 1,566 cu. yds. of concrete in 7 working days of 24 hrs., or at the rate of 224 cu. yds. per day. The gross time was 11½ days including Sundays. The average number of men in the sand hog gangs was 18, with one foreman, who received $5 for 1½ hours work.

TABLE XVII.--ITEMIZED COST OF CONCRETING SOUTH CAISSON FOR BROOKLYN TOWER OF THE WILLIAMSBURG BRIDGE: COST OF CONCRETING CAISSONS ABOVE ROOF.

South Caisson (3,827 cu. yds.). Materials. Quantity. Rate. Amount. Cement 4,480 bbls. $1.57 $7,034.00 Sand 1,288 cu. yds. .60 773.00 Broken stone 3,421 cu. yds. 1.50 5,132.00 Water 36.00 ------- ------ --------- Total 3,827 cu. yds. $3.39 $12,975.00

Labor. Mixing and placing 3,827 cu. yds. $0.90 $3,432.00 Plant charges 2,280.00 Plant labor 742.00 ------- ------ --------- Total plant 3,827 cu. yds. $0.79 $3,022.00 ------- ------ --------- Total cost 3,827 cu. yds. $5.08 $19,429.00 General expenses, 10% 3,827 cu. yds. .51 1,943.00 ------- ------ --------- Grand total 3,827 cu. yds. $5.59 $21,372.00

COST OF CONCRETING SHAFTS. South Caisson. Materials. Quantity. Rate. Amount. Concrete 612½ bbls. $1.57 $962.00 Sand 193 cu. yds. .40 77.00 Stone 493 cu. yds. 1.10 542.00 ------- ------ --------- Total 541 cu. yds. $2.92 $1,581.00 Labor. Handling, mixing and placing 541 cu. yds. $0.96 $519.00 Plant charges, etc. 541 cu. yds. 1.06 576.00 ------- ------ --------- Total 541 cu. yds. $4.94 $2,676.00 General expenses, 10% 541 cu. yds. .49 267.00 ------- ------ --------- Grand total 541 cu. yds. $5.43 $2,943.00

COST OF CONCRETE IN WORKING CHAMBERS. South Caisson. (1,435 cu. yds.) Materials. Quantity. Rate. Amount. Cement for concrete 1,666 bbls. $1.57 $2,615.00 Cement for mortar 459 bbls. 1.57 720.00 Sand for both 670 cu. yds. .40 268.00 Broken stone 1,181 cu. yds. 1.10 1,299.00 ------- ------ --------- Total materials 1,435 cu. yds. $3.42 $4,902.00 Labor. Top labor, mixing and placing 1,435 cu. yds. $1.09 $1,575.00 Pneumatic labor 1,435 cu. yds. 4.93 7,117.00 Compressor house labor 1,435 cu. yds. .19 275.00 ------- ------ --------- Total labor 1,435 cu. yds. $6.21 $8,967.00

Plant. Coal at $2.40 per ton 1,435 cu. yds. .10 140.00 Concrete plant 1,435 cu. yds. .79 1,145.00 Pneumatic plant 1.435 cu. yds. 1.05 1,522.00 -------- ------ --------- Total plant 1,435 cu. yds. $1.94 $2,807.00 Totals 1,435 cu. yds. $11.57 $16,676.00 General expenses, 10% 1,435 cu. yds. 1.16 1,667.00 -------- ------- ---------- Grand total 1,435 cu. yds. $12.73 $18,343.00

TABLE XVIII.--ITEMIZED COST OF CONCRETING NORTH CAISSON FOR BROOKLYN TOWER OF THE WILLIAMSBURG BRIDGE:

COST OF CONCRETING CAISSON ABOVE ROOF (5,692 cu. yds.)

Materials. Quantity. Rate. Amount. Cement 6,707½ bbls. $1.57 $10,531.00 Sand 2,133 cu. yds. .40 845.00 Broken stone 4,938 cu. yds. 1.10 5,432.00 Water 51.00 ------- ------ --------- Total 5,692 cu. yds. $2.96 $16,859.00 Labor. Mixing and placing 5,692 cu. yds. $0.73 $4,159.00 Plant charges 2,952.00 Plant labor 517.00 ------- ------ --------- Total 5,692 cu. yds. $0.61 $3,469.00 Total cost 5,692 cu. yds. $4.30 $24,487.00 General expenses, 10% 5,692 cu. yds. .43 2,448.00 Grand total 5,692 cu. yds. $4.73 $26,935.00

COST OF CONCRETING SHAFTS.

Materials. Quantity. Rate. Amount. Cement 614½ bbls. $1.57 $965.00 Sand 204 cu. yds. .40 82.00 Stone 521 cu. yds. 1.10 574.00 ------- ------ --------- Total 576 cu. yds. $2.82 $1,621.00 Labor. Mixing and placing 576 cu. yds. 1.70 982.00 Plant charges, etc. 576 cu. yds. 1.36 795.00 ------- ------ --------- Total 576 cu. yds. $5.88 $3,398.00 General expenses, 10% 576 cu. yds. .59 339.00 ------- ------ --------- Grand total 576 cu. yds. $6.47 $3,737.00

COST OF CONCRETING WORKING CHAMBERS (1,566 cu. yds.).

Materials. Quantity. Rate. Amount. Cement for concrete 1,559 bbls. $1.51 $2,446.00 Cement for mortar 442 bbls. 1.51 $694.00 Sand for both 630 cu. yds. .40 252.00 Broken stone 1,380 cu. yds. 1.10 1,518.00 ------- ------ --------- Total 1.566 cu. yds. $3.14 $4,910.00 Labor. Top labor, mixing and placing 1,566 cu. yds. $0.78 $1,198.00 Pneumatic labor 1,566 cu. yds. 4.91 7,694.00 Compressor house labor 1,566 cu. yds. .11 180.00 ------- ------ --------- Total labor 1,566 cu. yds. $5.80 $9,072.00

Plant. Coal at $2.40 per ton 1,566 cu. yds. .06 87.00 Concrete plant 1,566 cu. yds. .86 1,352.00 Pneumatic plant 1,566 cu. yds. .81 1,272.00 ------- ------ --------- Total plant 1,566 cu. yds. $1.73 $2,711.00 ------- ------ --------- Totals 1,566 cu. yds. $10.67 $16,693.00 ------- ------ --------- General expenses, 10% 1,566 cu. yds. 1.06 1,669.00 ------- ------ --------- Grand total 1,566 cu. yds. $11.73 $18,362.00

~COST OF FILLING PIER CYLINDERS.~--The following costs were obtained in mixing and placing concrete in steel cylinder piers. The sand and gravel were wheeled 100 ft. to the mixing board at the foot of the cylinder, mixed and shoveled into wooden skips, hoisted 20 ft. by horsepower and dumped into the cylinder. The foreman worked on the mixing board and the men worked with great energy. The costs were as follows:

Item-- Per day. Per cu. yd. 6 men wheeling materials and mixing at 15 cts. per hour 9.00 $0.45 2 men dumping skips and ramming at 15 cts. per hour 3.00 0.15 1 team and driver at 40 cts. per hour 4.00 0.20 1 foreman at 30 cts. per hour 3.00 0.15 ----- ---- Totals $19.00 $0.95

~PIERS, CALF KILLER RIVER BRIDGE.~--The following methods and costs of building two new piers and extending three old piers with concrete are given by Mr. J. Guy Huff. The work was done by the railway company's masonry gangs. Figure 94 shows the arrangement of the several piers and the character of the work on each and Fig. 95 gives the detail dimensions of the three main piers.

The sand and aggregate, consisting of blast furnace slag, were unloaded from cars to platforms on a level with the top of rail, placed about 100 ft. south from the south end of the bridge. A cubical 1/6 cu. yd. mixer was used. This was operated by a gasoline engine, and was located on a platform about 50 ft. south of the south end pier. A tank near the mixer to supply water was elevated enough to get the desired head, and was kept filled by a pump run by another gasoline engine located down by the river bank. The cement house was located between the mixer platform and slag pile.

[Illustration: Fig. 94.--Diagram Arrangement of Piers, Calf Killer River Bridge.]

[Illustration: Fig. 95.--Details of Pier for Calf Killer Elver Bridge.]

Slag and sand were delivered to the mixer by means of wheelbarrows. The mixer was so placed that it would dump onto a platform, and the concrete could then be shoveled into a specially designed narrow-gage car. This car ran on one rail of the main track and an extra rail outside. A turnout for clearing passing trains was provided at both ends of the bridge. The track over the bridge from the mixer had a descending grade of about 1 per cent., so that with a little start the concrete car would roll alone down to the required points on the bridge. Only in returning the empty cars to the mixer was it necessary to push them by hand, and then only for a distance of never more than 400 ft.

Over the piers on the bridge in the center of the concrete car track openings were sawed to let the concrete pass to the forms below. To get the concrete into the forms, there were used zig-zag chutes with arms about 10 ft. long, which sections were removed as the concrete in the forms was increased. These chutes were a convenience by their ends alternating from one side to the other as the arms were removed in coming up.

The cost of the concrete work was as follows:

Unloading Material. Rate Total days Per cu. yd. per day. worked. Total. concrete. Foreman $3.40 5 $17.00 $0.04 11 laborers 1.36-8/10 52 71.14 .15 ----- Total for unloading material $0.19 Building Forms, Bins, Etc. Foreman $3.40 18 $61.20 $0.14 9 carpenters 2.25 166 373.50 .81 New lumber, 23.7 M. ft. at $17.80 421.86 .92 Old lumber, 6 M. ft. at $8.33 49.98 .11 ----- Total for building forms, bins, etc. $1.98

Cofferdam Excavation (45 cu. yds.) Foreman $3.40 8 $27.20 $0.06 9 laborers 1.15 6/10 74½ 86.12 .19 ----- Total for cofferdam excavation $0.25 Cofferdam Concrete (37 cu. yds.) Foreman $3.40 8 $27.20 $0.06 11 laborers 1.36 3/10 79 107.68 .23 Cofferdam lumber, 2.25 M. ft. at $20.00 45.00 .09 ---- Total for cofferdam concrete $0.38 Concrete Mixing and Placing. Foreman $3.40 30 $102.00 $0.22 9 laborers 1.15 6/10 282 325.99 .71 Cement, 452 bbls. at $1.55 701.00 1.52 Slag, 437 cu. yds. at $0.20 87.40 .19 Sand, 220 cu. yds. at $0.30 66.00 .14 ----- Total for mixing and placing $2.78 Taking Down Forms and Clearing Up. Foreman $3.40 13 $44.20 $0.09 11 laborers 1.17 1.43 107.31 .36 ----- Total for taking down forms, etc. $200.00 $0.45 Engineering and supervision .43 ----- Grand total, 460 cu. yds. concrete $6.46

The wages given are the average wages. The men worked a 10-hour day. The concrete was a 1-3-6 mixture. The cofferdam work was done in connection with the construction of the fourth pier, this pier being the only one coming in the bed of the river to be built entirely new. The work on this was started in water about 6 ft. deep. The 37 cu. yds. of concrete is included in the total of 460 cu. yds. in the above tabulation. By itself the cost of the cofferdam work, not including cost of cement, sand and slag was as follows:

Per cu. yd. Total. Concrete. Lumber $ 45.00 $1.21 Labor, excavating 113.32 3.06 Labor, concrete 134.88 3.64 ----- Total 37 cu. yds. concrete $7.91

[Illustration: Fig. 96.--Details of Piers for K. C., M. & O. Ry. Bridge.]

~METHOD AND COST OF CONSTRUCTING 21 BRIDGE PIERS.~--The following account of the methods and cost of constructing 21 concrete piers for a railway bridge consisting of 20 50-ft. plate girder spans has been compiled from records kept by Mr. W. W. Colpitts, Assistant Chief Engineer, Kansas City, Mexico & Orient Ry. The shape and dimensions of the piers are shown by Fig. 96 and Fig. 97 shows the construction of the forms. Sheet pile cofferdams to solid rock were used for constructing the foundations.

[Illustration: Fig. 97.--Forms for Piers for K. C., M. & O. Ry. Bridge.]

The 1-3-5 concrete was mixed in a Smith mixer having a batch capacity of 9 cu. ft. The mixer was located on the slope of the embankment approach, with the main track at its rear and facing a temporary material track. This temporary track turned out from the main track about 500 ft. beyond the mixer and extended diagonally down the embankment approach on a 3 per cent. grade and across the river bottom alongside the pier sites. The portion of the track in the river bottom was supported on bents of spliced ties, jetted to the rock, and wired to the cofferdam to avoid the danger of loss in case of high water. The sand and crushed rock were delivered by cars from the main line track, immediately above the mixer, and the cement was stored in a shanty at one side of the mixer. The concrete materials and machinery were, in this manner, very conveniently located for rapid work and well above the high water line. The concrete was transported to the pier sites in improvised dump boxes, set on push cars. These dump boxes were hinged longitudinally and discharged directly into the cofferdams. The grade of the temporary track carried the push cars by gravity to the cofferdams and they were returned by teams, for which purpose a straw and brush road had been built paralleling the track. As the work progressed farther into the stream, more cars were added properly to balance the work. While the concrete in the base was still fresh, a number of steel reinforcing bars, 8 ft. in length, were set in place along each end to insure a good bond between the base and shaft.

In general, the work of putting in the bases was organized so that about the same time was required in filling a cofferdam with concrete, in excavating the sand from the next, and in driving the sheet piling for the third. These three operations were thus carried on simultaneously and, although interruptions in one part of the work or the other occurred frequently, the gangs were interchangeable and no appreciable loss was suffered, except in time, because of such delays.

In piers 19 and 20, where the rock was from 17 to 19 ft. below the surface, some difficulty was encountered due to the presence of fissures in the rock, from which it was necessary to remove the sand to fill with concrete. In such cases, the larger leaks were stopped as much as possible by driving sheet piles against the outside face of the cofferdam and into the fissures, and the smaller leaks by manure in canvas bags rammed into the openings.

Upon the completion of all the bases, the forms for several shafts were set in position and the work of filling with concrete proceeded as in the case of the bases, except that a derrick erected on a flat car and stationed at the pier was utilized to raise the dump boxes in depositing the concrete in the forms. As soon as the concrete in one shaft had set sufficiently to permit of it, the forms were removed and placed on the pier ahead. Four sets of forms were used for the shafts.

The following are the average prices paid for materials and labor:

Materials.--Lumber for forms, etc., $16.50 per M. ft., B. M.; cement, Kansas Portland, $1.50 per bbl.; broken limestone, 45c per cu. yd.; sand, Arkansas River, 15c per ton.

Labor.--General foreman, $110 per month; assistant foreman, $75 per month; timekeeper, $60 per month; riveters, 35c per hour; blacksmith, 30c per hour; blacksmith assistant, 20c per hour; carpenters, 22½c and 25c per hour; enginemen, 25c per hour; firemen, 20c per hour; night watchman, 20c per hour; laborers, 17½c and 20c per hour; team (including driver), 40c per hour. The prices quoted for lumber, cement, limestone and sand are prices f. o. b., Louisiana, Iola, Kan., El Dorado, Kan., and Wichita, Kan.

The total and unit cost of constructing the concrete piers and abutments and of erecting the steel superstructure are given in the following tabulation. Altogether there was about 2,300 cu. yds. of concrete in the substructure, most of which, as stated above, was a 1-3-5 mixture.

Machinery and Supplies. Concrete mixer, 20% of cost $ 152.10 Supplies, freight, hauling, setting up 505.04 -------- Total $ 657.14 Centrifugal sand pump, 20% of cost $ 27.00 Supplies, freight, hauling, setting up 277.50 Rent of traction engine to operate 83.25 -------- Total $ 387.75 Water pump and pipe, 20% of cost $ 29.00 Supplies, freight, hauling, setting up 177.32 -------- Total $ 206.32 Pile driver engine, 20% of cost $ 100.00 Supplies, freight, hauling, setting up 243.65 -------- Total $ 343.65 -------- Grand total $1,594.86 Cofferdams. Materials, lumber and nails $1,285.26 Freight and train haul 306.33 Labor making piles 696.82 Labor driving piles 1,384.05 --------- Total $3,672.46

The sheet piling took 63,500 ft. B. M. of lumber; the cost per 1,000 ft. B. M. for the sheet piling was then:

Materials, lumber and nails $ 20.08 Freight and haulage 4.82 Labor making piles 10.97 Labor driving piles 21.80 -------- Total $ 57.67

Forms, Platforms and Runways. Lumber, hardware, etc. $ 224.59 Freight and train haul. 40.20 Labor making, removing and placing. 556.51 --------- Total $ 821.30 Concrete Materials. Cement, freight, unloading and storing. $4,617.48 Sand, freight, unloading, etc. 1,336.05 Broken stone, freight, unloading, etc. 2,026.92 --------- Total $7,980.45

This gives us for 2,300 cu. yds. of concrete a cost of $3.47 per cu. yd. for materials, including freight, storage, and unloading charges of all kinds. A line on the proportion of the cost contributed by these latter items may be got by taking the prices of the materials f. o. b. at the places of production and assuming the proportions for a 1-3-5 concrete. According to tables in