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PLANS, SPECIFICATIONS, AND COSTS.
ference with traffic. The necessary water for flushing this material would, of course, be supplied from the central pumping plant on the river or from the Roaring Brook gravity supply.
SAND FROM DISTANT POINTS.
Another important source of supply of material which we believe would be practicable would be sand and loam that the transportation companies should bring in from distant points along their railroads, where it can be most economically procured, in returning empty coal cars. This material would have to be dumped over a suitably arranged hopper and flushed into the mines with culm and other material.
A comparatively cheap and effective means for transportation of flushing material on the city streets to the shallow shafts and bore holes suggested would be to arrange with the traction company to haul the stuff in suitably designed hopper-bottom cars from the central crushing plant during the time of light traffic at night.
We would suggest the establishment of about four crushing plants so designed as to be easily knocked down and moved to other locations. The material to be handled by these plants should be taken from points where grading of humps and hills will result in the improvement of highways, parks, and private or public lands.
In this connection we would refer to the very extensive grading operations carried on in Seattle, Wash. A large section of the business center of that city was regraded mainly by the hydraulic method. Hills 100 feet high were cut or washed away, buildings were shored up or torn down, and the general level of the regraded section was lowered 10 to 30 feet. The material was flushed into Puget Sound by streams of water, and large areas of new land were formed over the low tide marshes along the bay shore. The expense was met by a general city-improvement tax.
PLANS, SPECIFICATIONS, AND COSTS.
The general nature and wide scope of this report necessarily limit us to general plans, specifications, and estimates of cost. The rendering of detailed plans and specifications and of exact estimates of cost can be made only after careful and exact surveys under particularly ascertained conditions; such surveys should be obtained from the engineers who are to be in charge of the execution of the work recommended in this report, in case it shall be entered upon by the authorities. We therefore explain by way of specifications what will be necessary in our opinion, what we recommend to be done to ameliorate the present conditions, and the approximate cost thereof.
We have made careful investigations of the resisting power of the various devices thus far used for supporting the roof at various 97821°—Bull. 25—12-----5