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ti11NING & ENVIRONMENTAL SEf~VICES LLC <br />A portion of the boreholes used for contact grouting also served as formation <br />grout holes in later drilling stages. <br />An additional "ring" of formation-only grout holes was added to each location <br />after the preliminary design, to further reduce the probability of significant <br />leakage. <br />Typical layout of grouting pipes is shown in the drawing sets under Tab 5. <br />Detailed daily grouting logs can be found at Tab 14. Grout takes were minimal, <br />which indicates that the joints in the rockmass were generally low permeability, <br />which is very favorable. <br />3.6 Borehole groutin <br />For the Pierce adit, additional grout pipes were placed to effect the abandonment <br />of a 6-inch diameter borehole going to an upper level, and to fill the 4-inch HDPE <br />pipe located in the borehole. This borehole was grouted on January 29, 2008. <br />Field calculations based on pressure head indicate that the borehole was grouted <br />to approximately 71 feet of elevation above the injection point, midway in the adit. <br />• <br /> <br />13 <br />Figure 10: Placement of grout pipes for borehole abandonment <br />