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Collection
M 009: |
R
E P 0 R T
Relating To
SITES FOR PROPOSED COAL MINE OPENINGS
On
THE PORTER FUEL COMPANY'S PROPERTIES,
Situated Near
DURANGO, La Plata County, COLORADO,
AND OTHER INFORMATION.
By JOHN McNEIL, M. E. Consulting Engineer,
Equitable Building,
Denver, Colorado,
OCTOBER, 1909.
To:
D. O. CLARK, ESQ.,
Vice-President & General Manager,
Union Pacific Coal Company,
Omaha, Nebraska,
Dear Sir:
I n t r o d u c t o r y
In obedience to your wishes, I went over The Porter Fuel Co.’s properties at Durango, La Plata Co., Colorado, in a general manner, my observations, however, being more particularly confined to selecting sites for proposed openings to furnish probable tonnages of coal required, should future necessities press, for the same.
On reaching Durango, your Superintendent, Mr. Gifford, met me and courteously announced his willingness to aid in the work. He presented me with much useful information, plats of the property, and afforded me every facility to expedite my examination; and he also accompanied me over the field in the execution of the same,
Three proposed points of attack to open mines, were selected, the locations being, viz: At Porter, the newly acquired Ute Mines, and at a point situated some distance south of the American Smelting & Refining Co’s smelter on the flat near the river; and I herewith present to you, concisely, in this report, the results of our findings.
The Site Selected For An Opening At Porter: My idea is to open up a mine here by an improved system of "Long-Wall", working on No. 3 Seam (commencing numerically from the bottom) on which a prospect tunnel (being the most southerly opening) is driven in 1200 feet, showing a uniform vein of coking coal from 3' to 3' 3" in thickness.
The tunnel referred to consists of a single level, or drift opening, driven in from the surface outcrop on the strike of the seam, consequently (no parallel air course), there is no means of conducting an adequate supply of air throughout and on to the face of the work.
The opening is driven 24 feet wide, and an attempt has been made to conduct the ventilation by the building of a wall of rock and debris shot down from the roadway to make sufficient height for the purpose of haulage; but as you may imagine, such a wall loosely thrown together, the result is that the air current, in its travel, gradually leaks through until there is almost an absence of air at the face.
Mr. Gifford informed me that he had made an effort to open out from this tunnel, cross entries and rooms, but it was claimed, owing to the hardness of the coal and inadequate ventilation, the workmen, after a fair trial to mine the seam at the current rate of prices paid in the operation of the other mines at Porter, gradually became discouraged, and it became very difficult to get miners to continue the work.
Doubtless, the lack of efficient ventilation contributed much to the cause of such dissatisfaction. There is nothing, in my opinion, that disgruntled a miner more readily than the inhalation of bad air.
This opening was sealed up at the time of my inspection and I could not enter, but on a previous visit, I made a careful examination of the conditions there, and thus speak advisedly. I was then fully convinced, that owing to the thinness of the coal seam, its characteristic of hardness and the physical conditions of the roof and floor, would make it difficult to mine the coal by the ordinary method of room and pillar, at the current rate of prices paid at Porter; while the same characteristics and physical features offered ideal conditions for the successful operation of an improved method of "Long-Wall" work, either by Advancing or Retreating Systems, but preferably the former.
In a former report to you, on another coal field, I illustrated and described a "Long-Wall" Plan of mining coal from thin coal seams by the mode of Advancing; but for convenience in your files and to more directly aid Mr. Gifford in the application of the work, should you decide to adopt the system, I will herewith briefly portray the most salient features connected with such mode of extracting coal, and please find map illustrating the same; also a diagram showing mode of mining by "Semi-Long-Wall" Retreating, attached at the end of this report.
The "Long-Wall" System Of Mining Coal, fully described, would require a lengthy article, but my remarks on the same here will be stated briefly, and should more detailed information be desired later, in putting the system into practice, you will find me at your command with plans and detailed advice, to the best of my ability.
The plan before you, I designed and put into practice in the Rockville Colliery, when with the Atchison, Topeka & Santa Fe Coal Dept., now nearly 28 years ago (the coal seam there is 3' to 3' 6" thick), and during that time, approximately 1,000 acres have been extracted from the property, and by modern means of underground haulage, the mine is still being successfully operated with a large daily output,
Referring to the map: It will be noticed that the coal seam is worked on one continuous face around the mine and the haulage roads "branch" through the "gobs" of the worked-out areas. The rocks and debris from the "brushing" of the roof to allow the passage of cars, are built into pack walls at least 4 yards wide on each side of the roadways, but more particularly on the cross-roads to cut-off rooms and on main headings. See map.
The pressure of the superincumbent strata presses on the working face of the coal, thus the great weight and pressure of the same causes the coal to "work" and is, therefore, easily mined, but very little, if any powder being required.
As the coal is worked out, the roadways are kept "brushed" (top shot down), up in the near proximity to the coal face, to admit the pit cars to reach the coal to be loaded as it is extracted, the roof gradually "creeps" down on the pack walls and "gobs".
All "back" timber should be drawn out so the roof may gradually "creep" down on the "pack walls" and "gobs" so that in time the debris and "Pack walls" will be crushed down and packed by the weight of the superincumbent strata until it becomes almost as compact as the over and under lying rocks. After this "creeping" or settling of the roof is over, the roadways will show but little "movement" and will stand almost like tunnels through solid rock.
The advantages of "Long-Wall" mining of thin coal seams, are many but the chief reasons for its adoption wherever it can be followed, are, briefly stated, as follows:
Effective ventilation the air current being always at the face where the workmen are engaged.
Almost a prohibition of powder in mining the coal.
Economy in the cost of mining. The great advantage of extracting the entire coal seam, thus a 3-ft. seam will yield 5,000 tons per acre, while by the "Room and Pillar", system, a 5-ft. seam seldom yields more.
It will be seen that no narrow work such as driving entries, cross-cuts or turning rooms is required.
The ventilating current being always up to the face of the work, there is no danger of explosive gas accumulating where the men are at work, and as the roof and floor all excavated and unpacked portions of the abandoned workings soon "creep" together, there are thus no cavities of any material area left to allow gas to accumulate in any dangerous volume.
The writer recommended and put into practice some 20 Years ago, the "Long-Wall" system at Rock Creek, Texas, where the seam of coal is only 18" to 2' in thickness, and the same was operated quite successfully.
It is more convenient and economical too, to have all "brushing" and repairing of haulage roads done during the night, and men accustomed to such work are of great assistance, as there is some skill required in the proper building of pack walls, taking down the top, "cribbing", etc.
The cost of mining No. 3 coal seam under the existing conditions described, I place not to exceed $1.25 per ton run-of-mine coal f.o.b. cars or coke ovens, if a reasonable daily tonnage can be disposed of.
The distance of wall face between roadways, should be as much as practicable, for the fewer the roads to be "brushed" and kept up, the cheaper we may expect the coal, as the "brushing" and "ripping" of roadways form the greater item of expense in such a system of mining.
In some cases, where the vein is too thin to allow the passage of the pit car along the wall face, small buggies with low wheels, or sleds shod with iron, are used by the miner to convey coal from the far ends of the working face to the roadway where the coal is loaded into the pit cars.
It is desirable that the vein of coal be worked steadily ahead as much as possible so as to be constantly moving under fresh roof, and with this in view, only sufficient wall face should be opened as will suit the output required, as in this system of work (like all others), it is expensive to have surplus workings open. 2,000 feet of wall face in a seam 3 ft. in thickness, should, with experienced miners, yield an output of approximately 600 tons daily. It should also be borne in mind that seams reasonably free from "faults" are best suited to this mode of extracting coal.
In all thin coal seams, only low, small pit cars should be used (we often see mistakes in this connection), for economy cars should always be made to suit the underground roadways yet, we often see roadways made to suit the pit car. Cars with a low "bed" and low wheels and a carrying capacity of 1,500 to 1,700 pounds will be found much more economical in a 3-ft. coal seam than a larger car.
[this is the end of our transcription of the first 8 pages of this report, which is available in its entirety in collection M 009]
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