Bored Wells: An Economical Water Solution 2

The principal use of boring for water wells is in unconsolidated formations. Standard equipment will not work on hard rock, although some few special rigs are built to order for consolidated formations. The buckets on these have specially hardened cutting surfaces. A full cycle has the bucket and kelly lowered into the hole; the truck-mounted ring gear rotates the kelly and bucket downward until the bucket is full; the full bucket is raised to the surface, swung either to one side or to the rear of the rig and dumped; the bucket and kelly are returned to the hole for the next bite. This process is repeated until the hole depth reaches a water-bearing strata, usually sand or gravel and hopefully mixed with clay. Drilling continues then to a depth which will create a proper reservoir of water for peak demand within the well.

There is surprisingly little variation in the penetration rate between formations, provided they can be bored in the first place. For best results, the formation must be homogeneous; the work goes much slower when buried obstructions exist. Boulders or cobbles must be picked out of the bottom with a special tool, such as an orange peel bucket or stone tongs. Naturally, it takes time to attach such tools, remove the obstruction, and then replace the bucket. Generally speaking, if you can bulldoze a formation, you can bore it with a bucket rig. Most commonly, areas with clay formations find bored wells predominating. With clay, the formation is least likely to cave in. Caving can be quite a problem in pure sand, although some drillers report success with boring rigs in sand by keeping the hole filled with water at all times. This stiffens the sand and keeps the walls from collapsing. It also is possible to case the hole as you go down in soft formations where cave-ins are a threat. You use a bucket with a reamer attachment which creates a hole of larger diameter than the bucket.

In our area, an auxilliary hoist line is employed to set concrete casing into the hole. The casing setter is manually tripped by means of a rope to release the first 3-foot sections of pipe. This apparatus then automatically positions and releases each successive length of casing pipe. To complete the construction process, grout is placed around the casing from the top, and a reinforced concrete cap is installed. The well is now ready for installation of the pump and connection to the distribution lines for the owner's use.

Where the formation is suited, bored wells can go fairly deep, but most importantly, they go quickly. On speed rests their economic advantages. From 30 to 40 feet per hour is not unusual, and many drillers regularly go down 60 feet per hour. These speeds would involve the use of a kelly only, since addition of drill rods or use of special tools for obstructions will take time away from boring. Boring or augering or rotary bucket drilling can be the most economically efficient method available for large holes to a certain depth. How large and how deep will depend on local conditions and the experience and equipment brought to the job by the driller.