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<br />Mr. Steve Wathen <br />Division of Minerals and Geology <br />Page 3 <br />section 16, the realigned subdrain would <br />provide the best means of directing it safely <br />under the fill, therefore, providing for added <br />fill stability. <br />3) We agree with Mr. Pendleton's observations. CTL/Thompson <br />did not believe the revised configuration would have a <br />material effect on the stability of the spoil pile. <br />4) We agree with Mr. Pendleton's observations. No <br />additional verification of geologic conditions beneath <br />the toe of the fill were warranted. <br />Colowyo has however, implemented extra steps to provide <br />for added stability at the toe of the fill. Although not <br />required in the construction plan, after topsoil was <br />removed we excavated the area further to bedrock by <br />removing a veneer of weathered clays and colluvial <br />deposits. We have also increased the width of the rock <br />drain at the toe of the fill to approximately 40 feet in <br />width or over twice the design width. Colowyo has <br />essentially overbuilt this section of the subdrain to <br />enhance the stability of the fill, particularly at the <br />toe. We intend to submit the details of this overbuilt <br />subdrain at the time of the required inspection report <br />for the "placement of underdrainage system". <br />5) We have included herein a drawing entitled "Section 16 <br />Fill Underdrain Location" showing the realigned <br />underdrain system. Page IIa-2 of Exhibit 19 (rev. March <br />1992) provides the detail and commitment to construct a <br />controlled underdrain from the head to the toe of the <br />fill. The December 16, 1991 letter from CTL/Thompson <br />included also in Exhibit 19 reconfirms this commitment. <br />As noted above, much of the subdrain construction has <br />been overbuilt as compared to design. The other details <br />of underdrain construction will be submitted to the <br />Division with the specific report required at the <br />conclusion of "placement of underdrainage systems". <br />In closing, I would like to reiterate the discussions we made <br />during your November 10, 1992 inspection. It is Colowyo's <br />intention to meet or exceed the design requirements for the Section <br />16 Fill. To date we have exceeded some of the design requirements <br />for the subdrain and all inspection reports and certifications will <br />provide the detail of the final as-built construction. We would <br />also agree that if modifications to the construction of the fill <br />are necessary and the modifications do not meet the minimum <br />requirements of the approved design then review and approval by the <br />Division would be appropriate at that time. <br />