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E~oconMobil Global Services Page 11 <br />Colony Shale Oil Project <br />ESR Reclamation Studies <br />Weighing Lysimeter Performance 1990-2003 <br />Project No. 353 <br />focused mainly on simple means to transform the TOSCO II waste into a suitable plant root medium, <br />and to demonstrate success for use in pemutting of a commercial project. Since these were focused <br />on TOSCO II and did not specifically address the issues of moisture migration, the TOSCO and <br />ARCO plots have little to offer to the current issues. It should be noted however, that TOSCO and <br />ARCO's successful field demonstration of revegetation of TOSCO II spent shale, including successful <br />field leaching on a small scale, were the basis for ARCO's original proposal to MLRB to use 12" <br />topsoil cover over leached spent shale as the reclamation plan. Ultimately ARCO accepted a thicker <br />topsoil wver (18"), but (author's recollection) this may have been a concession to MI,RB in light of <br />concerns about the feasibility of field leaching the spent shale in place on a 3:1 pile face. <br />3.3 Extension of Previous Studies to Colony <br />• By the mid-1980s it had become apparent that surface retorting would likely involve a new <br />generation fluid-bed technology. Greenhouse studies carried out by Exxon in 1985-1986 using fluid- <br />bed combusted shale from the ESR pilot plant in Baytown had shown that the material would be <br />difficult to transform into a rooting medium. Although the issue of upward migration of salts still <br />existed, and means to deal with it would have to be demonstrated in field plots, the base case <br />assumption for combusted shale become that a natural topsoil cover would have to sustain the plant <br />community, rather than trying to convert combusted shale and make it into a plant suitable soil. <br />The focus of the ESR studies was therefore directed toward demonstrating in the field that <br />successful revegetation could be achieved using the available topsoil resources on the site, and to try <br />to quantify the amount of deep percolation that might be able to escape the topsoil wne. <br />The previous studies did illustrate the use of instnnnented field plots, or lysimeters, and the <br />use of neutron probes for measuring seasonal variation in moisture content in the soil cover. The <br />concept of testing several variations of covers and using native revegetation species that would be <br />• used on prototype piles was also a useful precendent The calculation of Et using a modified Jensen- <br />LACHEL FELICE & Associates <br />