| Cost of Side Walls. | |
| Materials— | Per cu. yd. |
| 1.33 bbl. cement at $2.00 | $2.66 |
| 0.5 cu. yd. sand at 0.18 | 0.09 |
| 0.75 cu. yd. stone at 0.55 | 0.41 |
| ——— | |
| Total | $3.16 |
| Labor on concrete— | |
| 0.01 day foreman at $5.00 | $0.05 |
| 0.03 day foreman at $3.00 | 0.09 |
| 0.03 day engineman at $3.00 | 0.09 |
| 0.35 day laborer at $1.75 | 0.61 |
| ------- | ——— |
| 0.42 Total | $0.84 |
| Labor, removing timber, building forms, excavating, etc.— | |
| 0.02 day foreman at $5.00 | $0.10 |
| 0.05 day foreman at $3.00 | 0.15 |
| 0.40 day laborer at $1.75 | 0.70 |
| ------- | ——— |
| 0.47 Total | $0.95 |
| Miscellaneous— | |
| 0.02 day engineer and superintendent at $5.00 | $0.10 |
| Falsework and forms, timber and iron | 0.07 |
| Tools, light, etc. | 0.10 |
| Interest and depreciation of $1,800 plant at 20% per annum 0.09 | |
| Train service, 0.03 day work train at $25 | 0.75 |
| Summary concrete side walls— | Per cu. yd. |
| Materials | $3.16 |
| Labor on concrete | 0.84 |
| Labor removing timber, etc. | 0.95 |
| Train service | 0.75 |
| Miscellaneous | 0.34 |
| ——— | |
| Total | $6.04 |
In the two side walls there were 2.59 cu. yds. of concrete per lin. ft. of tunnel, hence the cost of the side walls was $6.04 × $2.59 = $15.64 per lin. ft. of tunnel. The concrete arch varied in thickness, averaging from 14 to 20 ins. at the springing line to 8 to 14 ins. at the crown. The arch averaged 1.2 cu. yds. per lin. ft. of tunnel. About 20 cu. yds. of arch were placed per day. The arch concrete was mixed 1-3-5 and the cost was as follows:
It will be noted that the "train service" is an item that really should be considered as a part of the cost of the materials, for the cost of the sand and stone is the cost f. o. b. cars at the sand pit and at the quarry, to which should be added the cost of hauling them to the tunnel—to-wit, the "train service."
Summing up, we have the following as the cost per lineal foot for lining this single-track tunnel with concrete: Per lin. ft.
| 2.59 cu. yds. side walls at | $6.04 | $15.64 |
| 1.20 cu. yds. arch at | 10.33 | 12.40 |
| ——— | ——— | ——— |
| 3.79 cu. yds. Total | $9.38 | $28.04 |
It should be remembered that the higher cost of the arch concrete is due in large measure to the fact that 1.8 cu. yds. of dry rock packing above the arch are included in the cost of the concrete. Strictly speaking, this dry rock packing should not be charged against the arch concrete, and, segregating it, we have the following:
| Per lin. ft. | ||
| 2.59 cu. yds. concrete side walls at | $6.04 | $15.64 |
| 1.20 cu. yds. concrete arch at | 8.18 | 9.82 |
| 2.16 cu. yds. dry rock at | 0.55 | 1.19 |
| Labor placing 2.16 cu. yds. at | 0.64 | 1.39 |
| ——— | ||
| Total | $28.04 |
This is a much more rational analysis of the cost and a still further reduction in the cost of the arch concrete might be made by prorating the train service item ($1.50 per cu. yd. concrete). At least half of this train service should be charged to the dry rock backing, for there are 1.25 cu. yds. of sand and broken stone to 1.80 cu. yds. of dry rock backing.
The amount of this dry rock backing, or packing, varies greatly in different parts of a tunnel. In the first half of this tunnel it averaged 1.8 cu. yds. per lin. ft., while in the second half it averaged nearly 2.4 cu. yds. per lin. ft.