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<br />. . <br /> <br />001943 <br /> <br />3 <br /> <br />. <br /> <br />. <br />CRB RecommendationNo. 3: <br /> <br />Reclamation's plan for providing drainage of the deep trough on the downstream left abutment is <br />to excavate an open cut channel through the barrier that divides the' trough and stream channel. <br />The excavated channel would have an invert elevation to match the downstream end of the <br />trough and an invert slope equal to or greater than the trough slope. To insure drainage, the <br />trough and open cut channel would be backfilled with a 10-foot depth of zone 3 material that <br />extends the drain downstream until the zone 3 blanket drain is encountered. With this <br />modification, the CRB believes that drainage design for the left abutment trough is adequate. <br /> <br />Reclamation response: <br /> <br />Reclamation concurs in this recommendation. Drawing Nos. 69-D-1578 & -1579, <br />enclosed in Appendix C, depict Reclamation's plans for draining the trough on the left <br />abutment. These drawings are not yet final as as-excavated topography has not been <br />completed. However, the drawings show Reclamation's intent for this design feature. <br /> <br />CRB Recommendation No.4 <br /> <br />. <br /> <br />The zone 2 filter blanket and overlying zone 3 blanket are designed to drain any foundation <br />seepage water passing downstream of the grout curtain. The CRB believes that it is important <br />that the joints and fractures in the Lewis Shale be cleaned of any shale powder resulting from <br />desiccation or traffic that would tend to clog these features and reduce drainage from the <br />foundation into the filter blanket. If mechanical excavation and cleaning is found to be <br />inadequate to accomplish the necessary joint cleaning, further methods such as air jetting and <br />brooming should be used. Clean joints and fractures in contact with zone 2 filter blanket should <br />facilitate rapid dissipation of foundation seepage pressures. <br /> <br />Reclamation response: <br /> <br />Reclamation's final decision concerning cleanup of the foundation for Zone 2 in the <br />valley portion of the Lewis Shale contact is documented in Foundation Approval <br />Decision Memorandum No. DEC-RB-8311-l8, dated July XX, 2005, enclosed here in <br />Appendix C. As documented, the foundation over a majority of the Zone 2 contact area <br />was cleaned by blowdown and hand cleanup. Most of the joints in this area were open <br />and exposed. <br /> <br />A portion of the Zone 2 contact had slaked and/or been disturbed by construction <br />equipment resulting in a thin covering of the foundation material. This area was cleaned <br />just prior to Zone 2 material placement by using a 50% visible fresh rock criteria with a <br />backhoe equipped with a 'butterbar'. Reclamation believes that the resultant surface will <br />readily transmit any seepage from the foundation into the Zone 2 blanket and will also <br />not result in a plane of weak material. <br /> <br />. <br />