Construction of Masonry Dams by Chester Wason Smith

Author:Chester Wason Smith
Language: eng
Format: epub, pdf
Publisher: McGraw-Hill book company, inc.
Published: 1915-03-25T05:00:00+00:00

During two years operation by the Government January i, 1912, to December 31, 1913, 30,337 train miles have averaged a cost of $2.34 per train mile, the minimmn for one month being $1.53 per train mile. The total ton miles of freight amounted to more than three-quarters of a million, and 45,000 passengers were carried. Thus in this case the cost of haul was reduced from 47 cents per ton mile to about 9 cents, a saving of $6.46 per ton over the 17 miles. Assume charged against this saving the entire cost of 19 miles at $20,000 or $380,000, plus say $20,000 depreciation on rolling stock, making a total of $400,000. Then for a total volume of freight of about 61,900 tons the investment in the railroad is justified to say nothing of the values attaching to prompt delivery of freight and to good passenger service. Only surveys and a careful examination could determine the feasibility and cost of such a railroad. Allowable grades might be obtainable only at prohibitive expense and the cost of grading and bridging might vary widely from the above example. In addition to the grading and bridging the cost for ties, rails and laying would be $8,000 to $10,000 per mile.

In connection with a possible railroad consider the question of quarry location, and whether, if the quarry be at some distance from the dam, one railroad will not serve to transport stone as well as other

freight and thereby furnish a further economic justification for the railroad. It might be that the choice between two or more possible quarry sites might be influenced by the possibility of combining the two reasons for building a railroad. As the total tonnage bears on the question of road or railroad, so does the yardage to be handled influence the amount and kind of plant at the site of the work. Other considerations are the manner of doing the work, which in turn depends upon the general design, the amount of water to be handled during construction, the length of the working season between interrupting floods or winter weather, the total time allowable for the work, etc. Generally speaking it would be silly to put as much plant upon a 50,000-cu. yd. dam as would be advisable upon a 300,-000-cu. yd. dam. On the other hand if there were but two months in spring and two months in fall between severe winter weather and a summer season of floods, it might well be necessary to put on a plant of many times the capacity that would be advisable if there were no interruptions from winter or from floods.

Another question which might affect the amount of advisable expenditure for plant is the amount of salvage to be reasonably expected in the particular case, considered in connection with the reduced operating cost which might follow from certain proposed additional equipment. Before discussing this question, however, let us briefly examine the principles governing depreciation and net plant account chargeable to similar jobs under different conditions of location and accessibility.

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