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GEOPROBE OPERATION CATEGORY: " GEO 4.12 March 1998 • Lift the EXTEND lever to bring the derrick assembly back close to the vehicle to lessen the strain on the derrick mount assembly. Proper position is approximately 1 foot behind the rear bumper. • Push down on the FOOT lever until the foot contacts the ground. • Adjust the derrick until it is vertical, using the lever provided to check for true vertical. • Adjust the foot by pushing down on the FOOT lever and raising the rear bumper of the van approximately 1 foot. Do not raise the rear wheels off of the ground. • Lift up on the PROBE lever and raise the derrick to its maximum height. Check that the derrick is true vertical and adjust as necessary. • Shut off the hydraulics by switching the toggle switch on the control panel fully down, and secure the anvil in its cradle with the hammer latch. Never work on or in the hammer while the hydraulics are engaged. • Assemble the desired lead rod and sampling assembly and attach a drive cap to the top of the lead rod. • Place the toggle switch up to the slow position, and place the lead rod below the hammer assembly. The lead rod should be centered and parallel with the derrick. Push down on the PROBE lever while ensuring that the drive cap is seated in the anvil. The Geoprobe 8-A is now ready to advance the sampler into the ground. 5.2.3 Rod Advancement To advance the lead rod to the project depth, the following procedures should be followed when using the Geoprobe 8-A: • With the toggle switch in the center (slow) position, the operator contin- ues to hold the PROBE lever down. The lead rod will need to be steadied with the operator's hand until the anvil is in contact with the lead rod. Only the operator, who is handling the controls, should steady the rod or reach near the hammer assembly. The lead rod will be pushed slowly into the ground. This procedure allows the operator to gauge the soil resistance and avoid deflection. 9