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<br />• <br />ExxonMobil Global Services <br />Colony Shale Oil Project <br />ESR Reclamation Studies <br />Weighing Lysimeter Performance 1990-2003 <br />Project No. 353 <br />Page 7 <br />shale, the permeabilities could reduce well below what was then viewed as "impervious" (10 - <br />7 crn/sec). <br />The need to compact the combusted shale to achieve the extremely low permeabilities <br />appears to also apply to the cementation strength gain of these materials. Madrid and Nelson <br />(1986) provide a good discussion of the factors involved in pozzolanic reactions, including the <br />similarities to Portland cement and the calcium-silicate-hydrates referred to as tobermorite gel. <br />The spent shale they investigated was the fine fiaction from the Lurgi process, which like the <br />ESR process reached temperatures high enough to calcine the carbonate minerals. They <br />postulated that the cementing mechanism involves interlocking growth of hydration product <br />crystals and tobermorite gel on the surface of the retorted shale fragments, but there are limits <br />to the distance the tobermorite gel can bridge. This explains the influence of compactive <br />effort on compressive strength. The same cell growth would cause a reduction in <br />permeability, so it is not unreasonable that the observed permeability reduction would also be <br />dependent on compaction. <br />The above considerations led Exxon to develop an ESR reclamation research program <br />in the mid-1980's, making use of available spent shale produced by Exxon's 5-ton per day <br />fluid bed combusting retort at Baytown, Texas. The reclamation studies started with <br />greenhouse testing of various vegetative cover profiles, plant species, and spent shale <br />amendment techniques in 1985, and culminated in the construction of the field plots in 1988 <br />and the monitoring program conducted since 1990. The goals were to determine the <br />minimum topsoil cover thickness needed to assure a suitable permanent vegetative cover, to <br />better define the parameters that controlled infiltration and percolation through a soil cover, <br />and to define the quality of the runoff and leachate from a prototype pile. <br />The field program that became the ESR test plots was designed to reflect what was <br />then viewed as the best practicable design'of an economical commercial pile. Details relating <br /> <br />LACHEL FELICE & Associates <br />