Laserfiche WebLink
Whetstone <br />,j <br />Associatesw Technical Memorandum <br />boreholes were completed on June 22, 2015. F15 and F16 were pressure tested on June 25, 2015 <br />and F 17 was pressure tested on June 29, 2015. <br />Beginning on June 8, 2015, after pressure tests were completed on primary boreholes, Hayward <br />Baker began grouting the boreholes to refusal (<3 lugeons grout take). Grouting was conducted <br />using an upstage method in 10 -foot stages. Hayward baker used an initial grout mix of 2:1 w:c by <br />weight for each stage grouted. The grout mix was thickened after every 100 gallons of grout <br />pumped from the initial 2:1 to 1.5:1 then to 1:1 and finally to 0.75:1 w:c until refusal was achieved. <br />If communication to the surface was observed before refusal was met, Hayward Baker would try to <br />stop the communication by moving the packer up approximately one foot and continuing grouting to <br />refusal. If communication couldn't be stopped, the crew would advance to the next stage and <br />resume grouting beginning with 2:1 grout. Grouting of the original 14 primary boreholes was <br />completed on June 22, 2015. F16 was completed on June 26, 2015, F15 was completed on June 29, <br />2015 and F 17 was completed on July 1, 2015. <br />On June 18, 2015 Hayward Baker began drilling the secondary holes to TD (Table 2). Secondary holes <br />were completed in the same fashion as the primary boreholes being drilled vertically to approximately <br />40 feet below the top of bedrock with a 2.5 -inch bit. Drilling of the secondary boreholes was completed <br />on June 22, 2015. <br />On June 22, 2015 Hayward Baker began pressure testing secondary boreholes (Table 3) to evaluate <br />effectiveness of primary grouting, and grouting secondary boreholes (Table 4). The pressure testing <br />and grouting procedure for the secondary boreholes was the same as for the primary boreholes. <br />Secondary pressure tests were completed on June 29, 2015 and grouting of the secondary holes was <br />completed on June 30, 2015. <br />4. CONCLUSIONS <br />The grouting program effectively sealed 30 holes in the Illinois Fault zone at the Schwartzwalder <br />Mine. Holes were drilled 38.73 to 50.58 feet into bedrock (45.94 to 57.39 feet bgs), pressure tested, <br />and grouted to refusal (<3 lugeons). <br />The grout -take analysis indicates that permeability decreased as the grouting program progressed. <br />The secondary holes took approximately 40% less grout than the primary holes (Figure 2). The <br />primary holes took an average of 77 gallons of grout per stage (7.5 gal/ft), while the secondary holes <br />took an average of 46 gallons of grout per stage (4.90 gal/ft). Further, the reduction in grout take <br />could be seen as specific primary holes were drilled between previously grouted primary holes (e.g., <br />F8 between F7 and F9). Cross sections of the grouted area are shown in Figure 3 and Figure 4. <br />4109C.150730 13 <br />