Laserfiche WebLink
9/30/93 <br />Responses to Comments <br />San Luis Reclamation Evaluation Report <br />Page 16 <br />Comments From Dr. Harry Posey <br />Comment: <br />In summary, it does not appear that BMRI's sampling methodology <br />was designed to adequately evaluate the composition of the <br />interstitial fluids in the tailings. Most of the tailings were <br />retrieved from units above the standing water table dnd above <br />most of the units deposited during the time when high cyanide <br />concentrations were reporting to the tailings. <br />Response: There appears to be some confusion about the <br />presence of a standing water table in the San Luis <br />tailings. This confusion may be caused in part by <br />the characterization of the sampled tailings <br />material in the logs as saturated or supersaturated. <br />This characterization is based on geotlechnical <br />definition of these terms as discussed in section 1 <br />above. The concept of thin layer depositipn is to <br />dewater the tailings as they are placed. The <br />dewaterinq is accomplished by both a1loWing the <br />water to run off the tailings beach into the pond co ~~~„(~~ <br />and by an underdrain system which extends beneath yt 5 uh~~,E <br />the entire facility. The purpose of the underdrain sSrr" <br />is to prevent a head from forming, i.e. the ",~,.~ <br />development of a standing water table. As a result, S-~ y ,o,.,, 7 <br />the design of the San Luis facility prevents a ~.'~" <br />standing water table and the data confirms that ~ ~~ <br />there is no "standing water table" in the tailings 1 <br />facility. ~ <br />Comment: <br />Secondly, it appears that the tailings do have a net acid <br />generating potential, and the implications of that dlegree of <br />potential acid generation needs to be put in qualitative terms. <br />Response: It is unclear to BMRI why the DMG believes that the <br />tailings do have a net acid generating potential. <br />The geochemical test data presented in the Deport do <br />not substantiate this statement. As discussed in <br />the report both static and kinetic acid generating <br />tests were performed. <br />As discussed in Section 4 of the Preamlple, the <br />static test method evaluates the total sulfur <br />present in the tailings material. The evaluation of <br />total sulfur is conservative, since the number <br />assumes that all sulfur is present as sulfides and <br />