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There are two localities in Monterey County where coal beds have been exploited, Stone Canyon and Priest Valley. (See Pl. I.) At the Stone Canyon mine (formerly known as Slack Canyon coal mine) the thickness of the coal bed is from 12 to 14 feet. The entire thickness is clean coal without shale partings. This coal bed has been traced, by means of tunnels, pits, and borings, for 4,300 feet along the strike, and to a depth of 526 feet at the incline of the Stone Canyon mine. The analyses made (see table on p. 21) indicate that the coal is a lignite and that it contains a large percentage of volatile matter. The roof of this mine is a hard, yellowish sandstone, which outcrops above the coal bed in massive strata several hundred feet thick. The floor is of soft, friable clay shale, much crushed and full of slickensides. It is of considerable thickness, and west of the mine appears to rest directly upon the San Luis formation, but to the east it rests on sandstone similar to that above the coal bed. The whole series of sandstone, shale, and coal is tilted up at high angles, with northward dips ranging from 80° to 90° along the outcrop. A very large amount of sulphureted hydrogen escapes from the coal bed below the water plane, making it difficult for men to work in the incline.
This mine is in an isolated region on the summit of Mount Diablo Range, 2,600 feet above sea level, and 20 miles from a railroad. The construction of a branch railroad will be expensive and difficult, although a line could be built to within 3 or 4 miles of the mine at a reasonable cost, and the coal delivered to this point by a cable incline operated by gravity.
In Priest Valley and on Wartham Creek there are coal beds which have been prospected at various times (see Pl. I), especially those at the Drabble mine, on Wartham Creek. These mines are now idle, and it is evident from an examination of the mine and region that the coal is of poor quality and too far from market to be of value at present (see table of analyses on next page). The coal beds exposed in the Drabble mine extend northwestward under Priest Valley, where they are folded into a synclinal trough. The same series of beds appears on the southwest side of the valley, dipping northeastward, and also on the northeast side of the valley, dipping southwestward. The coal here is not so good as that at the Drabble mine.
Coal beds are also reported to occur at intervals northwest of Priest Valley, in the Mount Diablo Range, but from reports none of these deposits seemed to be of any economic value and they were not visited.
a Information given by F. J. Horswell, Superintendent. bEighth Ann. Rept. California State Mining Bureau, 1888, p. 404. c Twelfth Ann. Rept. California State Mining Bureau, 1894, p. 51. a Ibid., p. 61.
Table of arialyses of coal from Drabble and Stone ('un yon mines.
In October, 1901, Mr. W. W. Cockins, jr., was detailed to study the ground water of the lower Salinas Valley. Data were collected regarding the depth of wells, amount of water, cost, etc. From his observations, supplemented by the work of the Bureau of Soils of the l'nited States Department of Agriculture, the table on pages 22-30 has been compiled.
The location of the wells is shown on Pl. II. In a small bow-shaped area west of Salinas the wells formerly flowed slightly; the boundaries of this artesian tract are indicated on the map. Some of these wells flow at present when not drawn down by pumping. The artesian water is struck in a bed of coarse gravel that lies about 150 feet below the surface. In passing northeastward up the valley this stratum is found at a greater depth and the artesian water rises, but fails to reach the surface. The distance from the surface to the water from the artesian stratum is shown on the map by heavy lines, the line numbered 10 indicating that the ground water will rise to within 10 feet of the surface, but in order to reach the gravel bed it will be necessary to sink 150 to 160 feet plus 10 feet, or 160 to 170 feet, etc. There are not enough deep wells to trace the entire outline of this basin, but the direction taken by the various curves of depth indicate that the gravel bed may thin out in passing up the valley and that they probably extend northwestward beyond Castroville to the Bay of Monterey.