2011-12-06_REPORT - P2009025 (2)

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Whetstone Associates • Technical Memorandum 3. Attach the piezometer to its own signal cable, keeping accurate serial number tags at the terminal (upper) end of the cable. Record the serial number that appears on the multilevel housing and on a label that is wrapped around the top of the signal cable. Note that serial numbers are important for data reduction and must not be lost. Take care of the label wrapped around the top of the signal cable. Take care of this label during and after installation. 4. Lower the section of grout pipe into the hole that will extend beyond the lower -most VWP (to 20 feet off the bottom of the hole). 5. At the correct location, attach the deepest VWP to the sacrificial grout pipe with its filter tip facing upwards so that air bubbles cannot form in front of the diaphragm. (The diaphragm of the piezometer is about 4 inches (102mm) below middle of the upper coupling.) 6. Tape securely with waterproof tape. Keep the cable straight and tape it securely to the pipe at 5 -ft intervals. 7. Lower the placement pipe, signal cables, and VWP assembly into the core hole. Keep accurate count of pipe lengths and tape the remaining piezometers to the pipe at the specified intervals. The bottom of the grout pipe (placement pipe) must not be allowed to touch the bottom of the core hole during VWP installation 8. Back -fill the borehole with grout in accordance with the requirements for Permanent Abandonment of Prospecting Drill Holes specified in the Hard Rock, Metal and Designated Mining Rules (Section 5.4.2, September 2010). The grout is to be mixed using a commercially available grout plant with high shear mixer, agitated storage tank, and positive displacement injection pump to ensure that it can be placed in a continuous lift without gaps or water pockets. Grout mixing in a stock tank or other improvised container will not be accepted. The general mixing procedure will be to first add the cement to water followed by the bentonite. 9. The field engineer shall monitor pressure from the VWPs during grouting to ensure that the instruments are not over pressurized. When possible, the boreholes and VWPs will be grouted in a single pass from the bottom up using the sacrificial grout pipe. Deeper installations may require grouting in two stages with a second tremie pipe' to keep from over pressuring the instruments The calibration sheet for each VWP gives a table of pressure ranges and the associated Hz readings. A quick comparison of the reading with the calibration sheet will determine if the pressure is within range. 10. Grout will be pumped into the core hole until it reaches a level of approximately 10 feet bgs. The upper 10 feet of the borehole will be sealed using a neat cement mixture with a maximum water to cement ratio of six gallons water to one 94 lb bag of cement. 11. The VWP wires will terminate above ground at a Quattro Logger. The logger will be placed in a waterproof enclosure with waterproof connectors and protected from cows and vehicles using steel t- posts. 12. Note that readings taken immediately after installation will be high, but will decrease as the grout cures. Datum readings can be taken hours to days after installation, depending on the permeability of the soil. The lag time caused by the grout itself is measured in minutes. ' If a second tremie pipe is required, it must be run into the hole at the same time as the original sacrificial grout pipe to avoid damaging the WVP wires. The second tremie pipe will be used to grout in a second stage and will be removed from the hole as the second stage of grout is emplaced. 2 The vibrating wire piezometers have a over - pressure rating of 1.5 x range, but not over an extended period of time. The diaphragm could become deformed and the sensor would be permanently damaged. 4153A.110422 2