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<br />Mr. William Paddock <br />December 3. 1993 <br />Page - 3 <br /> <br />. <br /> <br />~, <br /> <br />Perform Spring, 1995. <br /> <br />Phase IV . Abutment Grouting <br /> <br />If seepage flows are excessively high through the vertical and lateral drainage system <br />and the flow path is clearly defmed, an abutment grouting program will be recommended. <br />This grout cunain may extend from approllimately station 3+00 to station 4+00. Fifty feet <br />of this length would underlie the dam core. The cunain would extend along the dam <br />centerline and the access road onto the left abutment. Additional field work will be done <br />during Phase I to more accurately define tile extent of this potential cunain. <br /> <br />The initial curtain would consist of grout holes at 4 to 5 foot centers extended to a <br />depth of about 50 feet. The intent of the grouting will be to reduce the seepage flow to <br />modest levels - not to eliminate seepage completely. It can be expected that conditions <br />will change with time following grouting and seepage may increase at a later date. At that <br />time, a second row of grout holes would be recommended. The grout pattern would <br />consist of ten vertical holes through the embankment core and ten inclined holes (60 <br />degrees) into the abutment. <br /> <br />The estimated total cost for this phase of the work is: <br /> <br />$50,000.00 <br /> <br />Perform Summer, 1995 or 1996. <br /> <br />If the entire scope of work is carried out the total estimated cost is $272,500.00. <br />We suggest a reserve of $300,000 to cover all aspects of the project How extensive the <br />program is to be will depend on the performance of the dam as measured by the seepage <br />and stability analyses. Water levels in the piezometers and the piezometer level responses <br />to reservoir fluctuations will have to be monitored frequently. You may wish to consider <br />the relative merits of manual readings vs. temporary instrumentation for tIlese purposes. <br />Instrumentation costs could add an additional $30,000 to the costs. <br /> <br />Harza has contaCted several vendors for input to the above estimates. As each task <br />is approached, firm fIX cost proposals should be obtained from each. We have included <br />funding for engineering analysis and reports at each phase. We recommend that out year <br />costs be escalated by 10 percent per year. <br /> <br />Because each stage of the work will require monitoring for performance, this work <br />will have to be extended over 1994, 1995 and possibly 1996. It is our opinion, dependent <br />on the results of the seepage and stability analyses and concurrence with the State of <br />Colorado, that following installation of the vertical drains, full reservoir use should be <br />allowed. In any case, depending on water availability, the reservoir levels should be cycled <br />to evaluate performance of the system. <br /> <br />Page' 14 of 15 <br />