Laserfiche WebLink
November 18, 1996 <br />Geotechnical Smdy Evaluation <br />Page 2 <br />Specific Comments <br />Paee 1; "Site and Subsurface Conditions" <br />The additional study addresses the backfilling of cuts similar to those of the two highest benches. It <br />generally assumes cut slopes of 2h:ly in original predisturbance slopes of 3h:ly. This appears <br />appropriate for the two cuts analyzed. It does not appear to be an appropriate assumption for many other <br />cuts which will be generated by the proposed construction at the site. For instance, the numerous <br />switchback tight-radius tutus necessary to accommodate the proposed access road will probably result in <br />excavation of high cut. slopes with facial slopes steeper than 3h:ly in areas with predisturbance slopes <br />greater than 3h:ly. The application will have to specifically project the operational and reclaimed slopes <br />[o be constructed and reclaimed before we can judge the propriety of these modeled assumptions. For <br />steeper reclaimed slopes, it will be necessary to analyze the actual projected configurations. As an <br />alternative, typical encountered situations could be analyzed assuming a range of reclaimed slope <br />gradients and bench configurations. <br />Paee 2 <br />As in their earlier laboratory analyses of specimens collected at the site, Maxim Technologies has chosen <br />to perform unconsolidated-undrained (U-U) triaxial tests. In our earlier adequacy memorandum we <br />commented: <br />"The report author correctly observes that the best course of action in analyzing the stability of <br />the landslide mass is to assume worst case conditions. Further, the author observes that <br />consolidated-drained (C-D) materials testing is often preferred for geotechttical design and <br />analysis. The author states: "Our approach was to conduct U-U (Unconsolidated-Undrained) <br />tests, review the results, and determine if C-D testing would likely obtain different or more <br />conservative results". With no discussion of comparative U-U and C-D laboratory and\or <br />analytical results, however, Maxim Technologies state that the U-U results were satisfactory. <br />This conclusion will require complete justification. <br />Maxim Technologies still has not justified its selection of laboratory methodology. <br />Maxim Technologies completed compazative analyses to determine the recompacted soils sensitivity to <br />varying degrees of compaction. Specifically, Maxim analyzed the shear strength of this material a[ 85% <br />and 90% relative density. <br />Page 2; "Slone Stability Anaylsis" <br />In analyzing the projected stability of the reclaimed cut benches, Maxim Technologies limited its analysis <br />to a "conventional circular stability analysis". With its original report, Maxim Technologies referenced <br />a major, recent rock slope failure which occurred just to the east of the proposed portal azea. At other <br />locations in the report the entire bedrock section is referred to as meta-stable. The slide in question <br />occurred in the early 1980's in response to the bulldozing of several light access prospect drilling roads <br />by Coors Energy while exploring the property. The affected bedrock section is clinkered by subcorp coal <br />