Evaluation of the Wilkeson-Carbonado coal field, Pierce County, Washington, for hydraulic coal mining

Abstract

This report includes a review and analysis of the relevant geological information that is available on the Wilkeson-Carbonado coal field in Pierce County, Washington.The coal deposits are in the Puget Group of Eocene age, which has been intensely folded and faulted, and in places intruded by igneous rocks. Much of the coal-bearing sequence is concealed by glacial deposits and a dense forest growth, so exposures of bedrock are rare. Detailed geologic knowledge of the coal-bearing sequence is confined to areas of extensive mining, and very little is known about the geology of the intervening areas or the relation of the geology of one mine area to another. About 40 coal beds, which vary from a few inches to 23 feet in thickness, occur in a dominantly siltstone-sandstone sequence more than 8,000 feet thick. The Wilkeson-Carbonado coal field has significant reserves of metallurgical coal, probably 60 to 125 million tons. Most of the easily accessible coal has been mined, and part of the remaining estimated coal resources may be uneconomical to mine because of prior mining. Coal in the Wilkeson-Carbonado coal field ranges in rank from high-volatile A bituminous to low-volatile bituminous. The coal in the beds in the upper part of the coal-bearing sequence is generally noncoking, however, coal in the lower part of the sequence has good coking qualities.The coal has a low sulfur content, generally less than 1 percent; the ash content is rather high, ranging from 8 to 23 percent. Most of the coal is fractured and brittle enough to be classed as friable. About 21 million tons of coal has been produced from the 12 beds that were workable under past market conditions.Water supply and quality in the Carbon River and South Prairie Creek drainages appear to be adequate for hydraulic coal mining, assuming a recycled water supply. However, the selection of a site in the Wilkeson-Carbonado coal field for hydraulic mining experiments, or the possible development of a producing mine using hydraulic mining concepts, will require careful consideration of many adverse geologic conditions.The steeply dipping and fault terminated coal beds present many mining difficulties that will require ingenuity and resourceful engineering to make hydraulic mining a successful venture.It is recommended that very detailed investigations of the geology and hydrology of the Wilkeson-Carbonado coal field be made prior to selection of a mine site and to verify the feasibility of hydraulic mining.

Evidence for the Heterogeneity of the Pore Structure of Rocks from Comparing the Results of Various Techniques for Measuring Hydraulic Properties

“…The used block originates from an outcrop in Pierce County, Washington (USA). The light gray to brown, compact, poorly sorted sandstone has an average composition of 50 % quartz and 35 % feldspar, and approximately 10 % porosity (Ahrens et al 2018;Arndt and Kent 1980;Duda 2011;Moen 1967). The pore space of WS consists of equant pores between grains but also inter-and intragranular microcracks (Ahrens et al 2018).…”

Evaluating porosity estimates for sandstones based on X-ray micro-tomographic images

“…Some of the algorithms are designed for bimodal distributions, while others are applicable to multimodal threshold problems with n classes and n-1 thresholds. We expect two distinct classes 10 in the intensity distributions according to the significant density contrast of air with 1.2 kg/m 3 and rock forming minerals e.g.…”

“…For unimodal histograms, the algorithm detects and selects the point of maximum curvature as threshold level. However, for many of the unimodal histograms recorded here the algorithm selected the point of maximum 10 curvature at a threshold level with an intensity larger than g mode1 . Therefore, it failed to separate pore intensities from grain intensities and we did not employ this algorithm.…”

“…CC BY 4.0 License.Wilkeson sst (WS) is a light gray to brownish, carboniferous sandstone from a quarry in the Wilkeson-Carbonado coal field in the southwest of Washington State,USA (GardJr., 1968). The sandstone is composed of about 50 % quartz and 35 % feldspar highly altered to sericite(Arndt et al, 1980). Minor lithic fragments are black chert and quartzite.…”

Effects of coal mine drainage on the water quality of small receiving streams in Washington, 1975-77

“…The mines were reopened in the 1950's, but were abandoned in 1963. The geology of these coal seams is described in detail by Arndt and Kent (1980). They stated that the sulfur content of the Nos.…”