MINING CONDITIONS UNDER CITY OF SCRANTON, DA.
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It is also deemed important to refer particularly to No. 23 School, where the Rock and the Big bed pillars now in place should not under any circumstances be disturbed, neither under the school lot nor for some distance outside of it, as shown by the maps formerly submitted to the school board by the North End Coal Co. We also suggest that the openings under this school property should be flushed full of sand, culm, or other material.
The best manner of applying an effective remedy for this serious menace is difficult to determine, because the openings are so large, on account of the thickness of the seams, and there is the difficulty of procuring the material for this purpose.
DUNMOEE BEDS.
The deeper-lying Dunmore beds under the major portion of the city, constitute a class by themselves. They are in many places so thin that during mining much top or bottom rock has been removed in all the gangways and along roads in the chambers to make room for cars and mules. This rock with the large quantity of interstratified refuse that is usually present in the coal beds nearly fills the mined-out space when stowed in the chambers, and thus constitutes a check to quick or total subsidence. Then, too, the thickness of the rock over the coal is generally so great that local caves in the workings are not likely to affect the surface. The greatest menace to the surface property from these deep thin beds is through a general subsidence—a creep or squeeze extending over large areas. Even then the settlement will be gradual, and as a rule so uniform as to cause little or no damage to surface property, except where the uniformity of the subsidence is interrupted or prevented by the presence of very large pillars or solid blocks of unmined coal, in which event, buildings located on the surface over or near the margin of such large pillars will be liable to considerable damage by the side pull, or
uneven subsidence.
In consequence of these facts we would advise as a measure of preventing damage to surface improvements over these deeper beds that the Dunmore beds be mined in the usual manner under large blocks of coal now held as reservations in any of the coal beds overlying the Dunmore and not at present mined nor intended to be mined.
RECAPITULATION.
Thus, to recapitulate, we have three general sets of conditions which naturally divide the coal workings into as many separate classes, to wit:
1. The surface beds, viz, on the west side, the Eight-foot, Five-foot, and Four-foot; on the east side, the Big, New County, Clark, and Dunmore No. 2, of which the latter are surface beds under different parts of the south side and central city sections.