If not once a week, at least, twice a month, we receive email from students, missionaries and other house owners, seeking information regarding water wells. Therefore below, is our brief report on drilling and water wells construction. Hope this may be of help to you.
Best
Ed. Elliott

Drillers General Classification of Formation and Well Construction.

Overburden;
Earth, soils, sands, gravel and formation above the bedrock, some of the general terms used are, topsoil, silt, sand, gravel, clay, till, hardpan. Water can be found, in sands and gravel. Water found in silts, may not be usable. All overburden wells, require a steel pipe (casing) to protect the water bearing formation from the formation above it. In some wells, plastic pipe (casing) is used, rather than steel, this depends on the drilling method. To increase the water flow, a well screen is generally installed into the water bearing formation.

Bedrock;
Solid rock formations encountered, after the overburden, some rock formations are, granite, sandstone, siltstone, mudstone, shale, conglomerates, schist, gneiss and many others. Water can be found, in the cracks of the rock formations, and also in the fault zones. Some of the yields, can be, a few gallons per hour to several hundred gallon per minute, largely depending on the cracking or faulting of the rock formation. Basic construction of the well is as follows, steel casing is installed from surface to the rock, and maybe embedded into the rock. Plastic casing maybe used, depending on the drilling method. A sealant should be used between the outside of the casing, and overburden formation, and the bedrock. Avoiding, the movement of unfit water from the overburden , into the rock formation. Then, an open unprotected hole is drilled through the rock formations until water is encountered. In some wells, the rock is not stable enough, to allow an open hole construction, a steel or plastic liner is then installed top to bottom.

Drilling Methods
Two of the most popular methods, will be discussed, briefly. The comments are, in general, and to help the, "do it yourselfers," in deciding what method to employ or uses in their low budget projects. Drilling on a commercial bases, a lot more consideration would have to be given to each method. Air drilling will not be discussed, because of the general high cost of the drill and equipment.

Cable Tool Method;
Drilling using the percussion method, raising and dropping of a heavy tool.
1) Most drills are small, low cost, driven by small economical gas or diesel engine, can be trailer mounted, or mounted on small single axle trucks.
2) Very low operating cost and maintenance cost.
3) Not counting casing and well consumables, a very small inventory of spare parts or drilling supplies are needed.
4) Slow but steady drilling rate.
5) Quite easy to gain the knowledge on how to operate.
6) Can drill most overburden, slow but with eases, rock drilling is very slow, and may get to the point of just about "no production days" in very hard rocks.
7) Hard labour not required, if volunteer labour is used, a crew of four is sufficient.
8) With patience, wells can be drilled to great depths, and the water well developed to produce adequate fresh clean water.
9) Drills a straight hole

Conclusion;
A low cost drill, economical to run, needs few spare parts, easy to train crews to operate, drills most formations, slow but steady, does a clean job of finding water.

Drill support equipment needed.
1) Service truck with water tank of 200 gallons.
2) Both electric welder and gas cutting set.
3) Average hand tool box of assorted tools.

Rotary Drill;
The method, of turning a drill bit, or augers. The "Auger Drilling" is without a circulation medium, drill cutting are return to surface, by the flights of the augers. The "Mud Drilling" is with a circulation medium, such as a mixture of bentonite, water and additives, which returns, the drill cutting to surface. High pressure pumps are used to circulation the drilling mud.

Augers;
1) Requires larger engines, to turn augers, large enough to drill water wells.
2) Heavier fuel consumption.
3) High cost of auger replacement and auger bits.
4) Requires a large inventory of drilling consumables, such as bits, shanks, augers.
5) Drilling to shallow depth only.
6) Will not drill some unconsolidated formations.
7) Hard to develop, the water source.
8) More knowledge is required to operate.
9) Hole alignment, is difficult to keep straight.

Conclusion;
Higher cost for the drill, higher cost to operate, needs plenty of inventory, limited to shallow depth only, unable to drill some formations, needs experience crew. Not recommend for water well work.

Drill support equipment needed;
1) Service truck, 12 foot deck
2) Welder and cutting set.
3) Small compressor to develop the water well.
4) Good selection of hand tools.

Mud;
1) Require larger engine, for horsepower, to turn drill bit, drill pipe and mud pump.
2) Fuel consumption is high.
3) Requires a large inventory of spare parts, and drilling consumables, drill bits, drill pipe, mud pump parts and hoses.
4) Needs good supply of parts for breakout wrench, and drilling tools.
5) Needs good supply of drilling bentonite and additives
6) Higher cost per foot for drilling.
7) Hole alignment, is difficult to keep straight.
8) Needs very experiences crews.
9) Developing the water source is difficult.

Conclusion;
High cost for the drill and tools, high cost to operate and high replacement cost on tools, needs a very good supply of drilling consumables and spare parts, needs a very experience crew, hard to develop the water sources., will drill very fast in soft formations and can drill hard formation slow.

Drill support equipment needed;
1) Service truck, 18 foot deck, with 500 gallon water tank, and 100 gallon fuel tank.
2) Welder and cutting set.
3) Small compressor to develop the water well.
4) Good selection of hand tools.