Well Maintenance

Why Well Maintenance Makes Good Sense

By Matt McGinnisEngineer, Cotey Chemical Corp.

Diagram Regular maintenance will keep the plugging material thin, relatively soft and easier to remove.

Maintain: to keep up, to keep in a certain condition, to keep in good repair. What is the importance of good water well maintenance? Like our teeth, our vehicle, or our house, if we don't maintain our water wells we could be asking for trouble. Anyone who has had to have an engine overhauled or replaced or had to buy a new vehicle will agree that proper maintenance always pays off. Again, ask someone who's been required to have a root canal or a tooth extracted; every-day brushing takes on a whole new meaning. So, although often inconvenient, we do maintenance with the belief that if we don't, something worse will happen. And it stands to reason that the more we're convinced of this, the more committed we'll be toward maintenance.

With that in mind, this article is specifically about water well maintenance. But, instead of beginning with the reasons why it makes sense, let's begin with some foundational information about well plugging. It's then possible that the reasons to do maintenance will become more obvious and this article can be shortened to allow for more leisure activity – like helping the wife with honey-do's around the house.

The reasons water well pathways become occluded are both simple and frustratingly unpreventable. Since groundwater resides in the ground, all of it contains minerals – some more than others. Whenever this water moves through any medium the minerals in the water will be deposited on the medium itself. Additionally, as the velocity of the water increases, the rate of deposition increases. This accounts for much of the mineral deposits found in wells all over the country. But, there are two main categories of water well plugging material and minerals is just one of them. The other plugging material may be categorized as biological. Similar to minerals, all groundwater also has natural-occurring bacteria. Once a well is drilled and therefore oxygen and nutrients added, bacteria begin to multiply and colonize. As this happens, slime is formed and used as both a protective mechanism and a food pantry for the bacteria. And, interestingly enough, biological slimes and bacteria counts also increase proportional to the increases in velocity. Since the velocities in moving groundwater are highest around the well bore when the pump is operating, mineral and biological deposits are greatest in that area. Suffice it to say, from the moment a water well pump is turned on, deposition begins.

Mineral deposits are, probably without much argument, the most difficult to remove. They can be traced to three main sources: red or brown deposits usually caused by iron-based minerals, brown and black deposits usually caused by magnesium-based minerals and white or yellow deposits usually caused by calcium carbonate (limestone) or dolomite. Interestingly, much of the hard mineral deposits found in wells across the country are biologically precipitated – meaning they are captured and then deposited by biofouling slimes. Regardless of how they are formed, what makes mineral deposits so hard to remove is, well, they are hard. This cement-like structure is particularly formidable when in places difficult to access like the gravel pack, the water-bearing formation and in low-flow zones. The most difficult of this already arduous challenge is when deposits are found both farther back in the formation and in low-flow zones.

Biological deposits, while maybe not as difficult to remove as mineral, have their own unique challenges. Foremost among those is that natural-occurring bacteria is everywhere, as already mentioned – even in the cleanest of all ground water. One test took 60 samples from 4 different wells and found 4500 different types of bacteria. When these tiny animals are united with a food source, and anything can be a food source, including drip oil, tin cans, natural-occurring minerals, metal casing, and even chlorine (eventually), they multiply faster than rabbits, building slime as they go, ultimately clogging any and all water pathways and covering everything in the well bore. Most of these subsurface bacteria are aerobic, meaning they have to have oxygen to live. But, since we've already introduced air into their environment via the punched hole in the ground, that little problem is solved.

There are over 16 million water wells in this country. Each one of them will suffer some water flow impediment problems due to mineral and biological deposition. Once this happens a decision must be made: drill a new well, attempt comprehensive rehabilitation or consider well maintenance.

Drilling a new well can be overwhelming for both emotional well being and the pocket book. Consider alternatives before taking this drastic step. Well rehabilitation, discussed in last months edition of WWJ, is a good alternative to drilling. The decision to do comprehensive rehab is often only based on changes in specific capacity of the water well. While monitoring specific capacity is a reliable practice and should be done for every well, it will often fail to tell the whole story.

Some theorize, as mentioned in the last article, that there exists a proportional link between changes in specific capacity and well plugging, ie. if there's a 20% decrease in specific capacity the well is 20% plugged. This is not true in many cases and definitely not true when the well has excess production capacity – the ability to produce more water than what is required. There may be one zone that supplies most of the water needed from the well. As this zone becomes obstructed another zone begins compensating without any notable changes to the specific capacity. The well will continue to foul, yet the specific capacity will not reflect the real problems because the well is covering for itself. By the time a decision is made to rehabilitate the well, significant amounts of material have had time to gather and harden and will be more difficult, if not impossible, to remove. Moreover, the greater the buildup of plugging material, the greater the possibility of not restoring the lost capacity and the greater the risk of losing the well altogether. For these reasons, many in the industry are becoming stronger proponents of regular well maintenance.

Once a well is newly completed or recently rehabilitated, begin scheduling regular maintenance treatments. This will allow the well to be cleaned when the plugging material is thin, relatively soft and easier to remove. Regular preventative maintenance also allows the well owner to schedule the treatments during slow times, treat the well without pulling the pump, use less chemical since the buildup is slight and extend the overall life of the well – ultimately saving a great deal of time and money. Add all these benefits to a more relaxed and less anxious well owner (knowing the well is in good shape) and you get a decision that makes the most sense of all the options. I guess it could be said that water well maintenance makes "CENT$", and that would be right...on the money.