Rig Setup Near a 7.2-kV Line on Soft Fill
A two-person crew is setting up a truck-mounted rotary rig on a 10% side slope beside a cottage. The borehole is 18 ft from a 7.2-kV overhead line. The ground under the right rear outrigger is soft fill over an old septic tank; the left outrigger is on firm till. The helper plans to stand at the hole and hand-guide the casing into the chuck while the driller operates the top drive. Thunderstorms are forecast within 2 hours. The driller wants to 'get the surface casing in before the storm' and skip cribbing because the outrigger 'looks okay.' The site is 150 ft from the road, and the truck can access only through a narrow gate.
1. List the hazards and the controls before the bit turns.
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Hazards: overhead 7.2-kV line 18 ft away; rig mast and casing can swing into the 10-ft minimum approach distance; soft fill over an old septic tank under the right rear outrigger; 10% side slope; helper hand-guiding casing at the chuck; approaching lightning. Controls: relocate the rig or de-energize the line; use a spotter and maintain at least 10 ft from the line, more if the mast can move closer; crib and spread the right rear outrigger on stable ground, not on the septic fill, and re-check level; barricade the hole; prohibit hand-guiding and use a casing guide or controlled line; hold a tailgate briefing and designate stop-work authority. If the rig cannot be set level and stable, move it.
2. What should the operator do if the mast contacts the power line?
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Stay in the cab; do not touch the rig, the ground, or anyone nearby. Call 911 and the utility. Warn others to stay at least 30 ft away. If the operator must leave because of fire, jump clear with feet together and shuffle away, never touching the rig and ground at the same time. Do not try to move the rig off the line unless directed by the utility. The helper should not approach the rig.
3. How should the crew handle the approaching thunderstorm?
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Stop drilling, lower the mast, move the crew away from the rig and the borehole, and do not resume until 30 minutes after the last thunder. Lightning can travel through the rig, casing, and groundwater; the rig is not a safe shelter. The crew should not try to 'finish the surface casing' because the storm is close. Document the stop in the daily log and secure the hole with a cover.