The most important aspect of any drilling job, whether limited or unlimited access, is safety. With a bigger rig and taller tower, it can be much more obvious when drilling near overhead power lines as to whether or not you are too close to them. With a smaller rig, it may not be so easy. Minimum distances from overhead electrical lines should be enforced by both the drill crew and the consultant. Also, any drillers should have the backbone to say no if they believe they aren’t at a safe working distance. No job is too important that it should be undertaken less than the minimum distance from overhead lines without specific safety precautions taken by the power company. That may include covering overhead lines with sheathing to prevent arcing or even shutting down power, if possible, to the lines closest to the work area.
In the vast majority of limited access situations that I encounter, there are no specific dangers beyond the usual ones found on any drilling site: trips and slips, cuts, overhead dangers and staying clear of the augers or cathead while they are rotating. But there are still many jobs out there with many dangers, so you shouldn’t let your guard down.
Working on or near railroad tracks is a good example. Track mounted rigs may cause damage to the rails, so smaller equipment that can be loaded onto a rail truck and driven out to the work area is a good option. Having flagmen working for the railroad supervising the work and letting workers know if there is a train approaching are mandatory on jobs like this for obvious reasons, and it goes without saying that the safety of the people is a much higher priority than saving a rig from destruction.
Working at the top of slopes is another example where extra precautions are necessary. This doesn’t just include making sure you don’t fall down the hill, but rather what is the reason you’re there, are there signs of imminent failure? Has the slope already failed? A few years back, I worked on a job where the residents in four or five houses on a street that backed on to a ravine woke up one morning to the sounds of their backyards sliding away down the hill. The slide was so severe that foundations were exposed right to the bottoms of footings. It seemed like a miracle that the houses themselves were still in place. The particular house that I worked behind had a concrete pad acting as a patio that had survived the slide, and that was our work area.
We ended up bringing both our track-mounted drill and a Big Beaver auger drill to the site. We were unable to get our track rig into the backyard and I’m VERY glad that we couldn’t. Although it wasn’t visible around the outside of the concrete pad, there was a void of several inches underneath. I have my doubts that it would have been able to support the 4,500 pounds of our track-mounted drill, as the slab itself was only a few inches thick. I don’t think I’d enjoy having bad dreams of the disastrous consequences if the concrete pad failed and the slope had given away. We ended up using the Beaver and drilling to 40 feet, installing a piezometer in one hole and then augering to 40 feet in another hole to install an inclinometer.
Have an Escape Plan
Confined spaces, now that’s really limited access drilling—inside closets, walk-in freezers and in the bottom of elevator shafts just to name a few. A lot of these rooms aren’t all that big. You’ve got two people in there, plus a drill of some sort. I worked on a job where one of the holes was in a small storage room, right in the door way. It was a small area, less than 12 feet by 12 feet. There was very little wooden framing as it was just in the back corner of a store, and it wasn’t needed as structural support. In the event of an emergency, my escape route was through the drywall. If I can easily punch through it, then it won’t do much to stop my 240 pounds from making a hole large enough to get through it.
I guess the point here is, like in many confined space situations you need to have an escape plan ready in case of an emergency. I’m not sure if going through the wall was a valid escape plan or not, but it seemed like a good idea at the time. If there hadn’t been buried lines under the floor, an obviously better option would have been to move the borehole a few feet further in or out of the room to keep the doorway clear, but unfortunately it was the only choice. Had I not had the option to break through the drywall in the event of an emergency, we would have opted out of drilling the monitoring well in there.