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Whetstone <br />Associates4 Technical Memorandum <br />2. GROUTING MATERIALS AND METHODS <br />The pressure testing and grouting were performed using the contractor's proprietary iGroutTM <br />system, which allows the geologist or engineer to monitor operations and record a digital log of flow <br />and pressures. The drill rig and grouting apparatus were set up in the valley floor, between Sump 10 <br />and the mine office. The grout holes were collared in alluvium and fill with PVC collars and drilled <br />vertically at least 40 feet into bedrock using a ROC D3 percussion drill with a 2.5 -inch -diameter <br />hammer bit. Prior to grouting, the rock permeability was investigated by pressure -testing each hole <br />using an inflatable straddle packer or single packer system. The pressure tests involved injecting <br />water into the packed -off interval and monitoring flow rates and injection pressures. A total of 13 <br />holes were pressure -tested over 10 -foot intervals using an upstage straddle packer system and the <br />remaining holes were tested over a longer interval (Section 3.4). The standard test pressure was 0.5 <br />psi per foot of depth over the natural hydraulic pressure at the borehole collar. The iGroutTM reports <br />for each water test interval are provided in Attachment 1. <br />Bedrock was pressure -grouted using neat Type I/II Portland cement with no additives. Grouting was <br />performed using an upstage method, i.e., from the bottom of the hole to the surface in 10 -foot <br />intervals using a single packer at the top of the interval. The Portand cement grout was mixed in <br />batches on-site using a high -shear colloidal mixer and then sent to the hole location through 1 -inch <br />high pressure grouting lines. Grout was injected into the interval until the refusal criterion of <3 <br />lugeons, was met. A lugeon is defined as the loss of fluid in liters per minute and per meter length <br />borehole at an over -pressure of 1 MPa, which is equivalent to a hydraulic conductivity of <br />approximately 1.5 x 10"3 cm/sec. After refusal was achieved, the packer was deflated, pulled up 10 <br />feet in the hole, and inflated to begin grouting on the next interval. <br />The general procedures were as follows: <br />1. Drill through the fill material to the top of bedrock and install PVC casing. The PVC collars <br />were installed using a Hatte drill and 5 -inch hammer bit. <br />2. Drill at least 40 feet into bedrock using ROC D3 drill with a 2.5 -inch hammer bit. <br />3. Flush the drill hole with water until return water is clear. <br />4. Insert straddle packer and perform water injection/pressure tests at 10 -ft intervals to evaluate <br />the permeability of the rock. <br />5. Mix the Portland cement grout, insert the single packer, inject grout under pressure using the <br />iGroutTM machine to monitor pressure and grout take. <br />6. Begin with an initial grout mix of 2:1 water to cement by weight (w:c) for each stage <br />grouted. Thicken the grout mix after every 100 gallons of grout pumped, from 2:1 to 1.5:1 to <br />1:1 and finally to 0.75:1 until refusal is achieved. Cease injection when grout take falls <br />below 3 lugeons at the maximum pressure. <br />7. Deflate packer, move the packer system uphole. <br />8. Repeat Steps 4 through 7 until all stages of grouting are completed. <br />The iGroutTM system monitored and recorded the time, injection pressure, flow rate, and total <br />volume injected at specified time intervals (typically 1 — 2 minutes). The data were used to calculate <br />4109C.150730 <br />