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<br />r • <br />MINE ID # OR PROSPECTING ID # M-77-215 <br />INSPECTION DATE 5-13-98 <br />(Page 2) • <br />INSPECTOR'S INITIALS SSS <br />This partial inspection was conducted to evaluate the 9360 portal seal grout injection <br />program around the first monolithic concrete plug. <br />Grouting began 5-11-98 using the radially placed pipes that were set into the concrete seal <br />block. These pipes are drilled out to approximately 1.5 feet into native material around the <br />block prior to grout injection in each pipe. Grout is injected to a target 30 psi when <br />possible. By 5:00 p.m, on 5-13-98, five pipes were grouted. Two pipes were pressured up to <br />only 20 psi. while the other three reached 30 psi. The two lower pressure holes were the <br />upper inside corners of the seal. it is believed that these holes connected to the adit inby <br />the block through a path which would not hold thirty psi. The mine drainage from behind the <br />block became cloudy with grout during injection of these two holes. <br />The grouting process seems to be working well, as evidenced by grout emerging through loose <br />material around the face of the concrete block and as far as two timber sets away from the <br />block. Grout being injected into the lower, left, inside corner of the concrete block <br />emerged from the lower, right, outside corner before pressuring up to 30 psi. The grout <br />appears to be penetrating the loose material when under pressure. The grout being used is <br />a conbextra terracem or ultracem. The two are inter-changed when required, to achieve the <br />desired pressure injection result. The grouting crew would verify injection pressure, <br />injection rate, grout thickness, grout type, and even try stopping the process for several <br />minutes before continuing the injection, in attempting to achieve the desired injection <br />pressure. This is a difficult task, due to the nature of the unconsolidated material around <br />the block. <br />The mine drainage volume was approximately 120 gpm. The operator indicated that the <br />discharge had been as high as 150 gpm. All but approximately 10-15 gpm was being evaporated <br />off through the sprinkler distribution system which had 48 sprinkler heads operational at the <br />time of the inspection. The other 10-15 gpm. was being discharged into the infiltration <br />trench. The operator was being careful not to seal the trench with grout filled water. No <br />discharge was observed leaving the site. <br />Saddle timber sets have been installed between each existing full timber set for the entire <br />length of the accessible portion of the adit. <br />The concrete block appeared to have good contact with the timber set on the outer face. <br />There were no appreciable voids visible in the concrete block, indicating that the injected <br />concrete most likely filled the seal area as expected. <br />The stainless steel pipe for the tracer injection system was in place through the left side <br />of the plug. <br />I ~ E Contact Addr ess cc: Tom Gillis, DMG <br /> ^ CE <br />NAME Alan Cox ^ BL <br />OPERATOR Homestake Mining Company ^ FS <br />STREET 650 California Street ^ HW <br />CITY/STATE/ZIP San Francisco. California 94108 ^ FiM4INID (CH) <br /> ^ SE <br /> ^ WQCD (CH) <br /> ^ OTHER <br />