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.
| Abutment No. 1. | Pier No. 2. | Pier No. 3. | Pier No. 4. | Summary. | ||||||||||||
| Wages per Hour. | No. hrs. | Total Cost | Cost per cu. yd. | No. hrs. | Total Cost | Cost per cu. yd. | No. hrs. | Total Cost | Cost per cu. yd. | No. hrs. | Total Cost | Cost per cu. yd. | Total Hrs. | Total cost. | Av. per cu. yd. | |
| Superintendent | 70 | 24 | $16.80 | $0.03 | 47 | $32.90 | $0.09 | 72 | $50.40 | $0.05 | 16 | $11.20 | $0.03 | 159 | $111.30 | $0.05 |
| Foreman | 35 | 160 | 56.00 | 0.09 | 128 | 44.80 | 0.13 | 324 | 113.40 | 0.12 | 54 | 18.90 | 0.06 | 666 | 233.10 | 0.11 |
| Laborers | 15-20 | 2555 | 383.25 | 0.65 | 2038 | 313.60 | 0.92 | 3513 | 526.95 | 0.56 | 940 | 141.00 | 0.44 | 9046 | 1364.90 | 0.62 |
| Engineman | 30 | 365 | 109.50 | 0.19 | 196 | 58.50 | 0.19 | 244 | 73.20 | 0.08 | 60 | 18.00 | 0.06 | 865 | 259.50 | 0.12 |
| Timekeeper | 40 | 86 | 34.40 | 0.06 | 46 | 18.40 | 0.06 | 81 | 32.40 | 0.04 | 10 | 4.00 | 0.01 | 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: