Title: The Leyden Dilemma!
Speaker: Stephen A. Krajewski, Industrial Ergonomics, Inc.
Date: October 18, 2002
Publication: The Outcrop, October 2002, p. 4-5
The Leyden No. 1, 2 and 3 Mines are located in Sections 26, 27 and 34 in Township 2 South, Range 70 West just west of the town of Leyden, Colorado approximately 12.5 miles northwest of downtown Denver. The three underground mines operated from 1903 through 1950, and produced approximately 6.5 million tons of low-sulfur, lignite coal with heating values of 9,500 BTU/lb. Leyden coal was burned to generate electricity for the Denver Tramway Company (DTC). The mines ceased operations when DTC went out of business.
Operations that began in 1902 revealed that the Leyden “A” coal seam had an average thickness of 9′; a northeast strike and gentle southeast dip; few, thin non-coal partings; a gently undulating floor; and, an argillaceous shale roof. Geologically, the coal occurs in the Lower Member of the Upper Cretaceous Laramie Formation; paleo-environmentally, it was deposited in a back-levee, poorly drained swamp on a southeastward draining delta plain.
Conventional room and pillar mining was used to develop the coal. Mining was completed using electric chain and compressed air punching machines, and animal (mules) and rope-powered haulage equipment. To promote coal miner safety and to minimize the cost of excess timbering, only 7 foot of coal was mined. Room and entry pillars were pulled during retreat operations.
Production from Leyden No.3 mine occurred from 1918 through May of 1950. The No. 3 mine was in the Leyden “B” coal seam that is stratigraphically 50′ below the Leyden “A” seam mined in the No. 1 & 2 Mines. Coal thickness in the No. 3 mine varied from 6′ to 16′; and sandstone roof was common. As mining progressed to the northwest and south, seam dip and coal parting thickness increased; and, numerous small-displacement faults were encountered. Coal mining was completed using room and pillar methods similar to those used in the Leyden 1 & 2 Mines. Haulage in the mines changed from mules and rope haulage when the mines first opened to electric track haulage in the later years. Pillars were pulled throughout most of the mined area.
Review of the historic data indicates that the mines were operated safely, were non-gassy mines, and did not produce water that had to be pumped to the surface for disposal. Also, the “A” and “B” coal seams did not have significant non-coal partings or sulfur, so a minimum amount of waste rock was produced in surface screening and loading operations at the tipple. Finally, the mines were deep enough so that subsidence into mined areas did not reach the surface. In general, the mines did not produce significant environmental problems while operating or in subsequent years since production stopped.
In 1958, Public Service Company of Colorado (PSCCO) began evaluating the feasibility of converting the 150 million cubic foot void in the Leyden mines into an underground gas storage field. After initial tests proved favorable, the Leyden shafts were sealed and a well field consisting of thirty-two injection, production and monitoring wells were drilled to access the mined area. Approximately 2.5 billion cubic feet of natural gas at 250 psig was pumped into the underground mines during the warmer months, and drained off during colder months when demand in the Denver area increased. Gas within the underground mines and overlying subsidence zone is held in place by hydrostatic pressure of ground water in the overlying rocks. Injection and production operations continued on an annual basis until recently. The Leyden field is the only gas storage project in the world that operated in an abandoned, underground coal mine.
This talk will show how computer aided design (CAD) and geographic information system (GIS) software can be used to integrate mine maps, aerial and satellite photos, topo maps, and outcrop and drill hole data; and, to reconstruct and visualize historic mining operations in 3D. This data can then be integrated into effective land use plans to mitigate uncontrolled urban sprawl.