Early identification of problems can extend the operational life of a well.
By Michael Schnieders, PG, PH-GW
Think about the cars alongside you on the road. Are they maintained for optimal, efficient operation or just enough to remain in use? How about the homes in your town? Are they nicely painted, properly insulated, and all major appliances in good working order?
I’m going to guess there was at least a moment of hesitation in there or the flash of an image of a house in need of repair or perhaps an automobile you’d be hesitant to park next to.
Unfortunately, many potable well systems fall into this same category—maintained just enough to keep them running and meeting the state’s minimum testing requirements. No category of wells is immune to this with residential, municipal, and industrial candidates aplenty.
Per Merriam-Webster, maintenance is defined as the process of maintaining or preserving something; the upkeep of property or equipment. When applied to a potable well, what does this mean? That answer can change from owner to owner, state to state, and even contractor to contractor with a variety of benchmarks and terms.
For some, it could focus on efficiency and the cost to produce the needed water. This often manifests as the tracking of specific capacity (SC). A well’s specific capacity is equal to the discharge rate (in gallons per minute) divided by the amount of drawdown (in feet).
A lot goes into that calculation and the change may reflect changes in the well, the aquifer, or both.
Use of the specific capacity as a benchmark for maintenance can differ based on the well size as a larger high-capacity well can still meet demand even with a greater decline, while the realization may be faster and more significant in a smaller well of lower capacity. A good rule of thumb is a 20% loss in specific capacity is significant and a solid indication that the well should be evaluated for maintenance.
To some owners, impacts on the use or treatability of the produced water are an effective means of monitoring the need for maintenance. Discoloration, high turbidity, taste, and odor issues can alter the use and application of the water or cause a need for more advanced treatment prior to use.
While not an exhaustive list, these few changes can often indicate more significant developments are occurring downhole.
Discoloration, such as the sudden onset of red water, can mean iron bacteria are present or chemical corrosion is occurring—or both. In addition to aesthetic impacts, the occurrence of red water can challenge filtration and disinfection.
High turbidity—reflective of increased aeration, sediment, or congested water chemistry—can impact the water quality, treatment, and handling of the water. Taste and odor, even subtle changes, can cause a number of challenges for owners of small and large wells alike.
In public water supply wells regularly tested, water quality is often used as an indication of the need for maintenance. While seen as a “run to failure” method, it is commonly employed, especially in smaller wells and in rural systems.
In short, it means the well is operated until a maximum contaminant level (MCL) is reached per testing guidelines set forth by the individual state, which is typically a reflection of the U.S. Environmental Protection Agency National Primary and Secondary Drinking Water Standards.
A common example is the use of total coliform testing as the primary means of evaluating the presence of bacteria. Coliforms are a large group of bacteria including many opportunistic pathogens, including E. coli and other common soil bacteria. Oftentimes, the well had other microbial issues developing, but it wasn’t until a coliform occurrence that the extent of the problem was understood.
Addressing the Problem
Maintenance can involve a wide variety of activities with a well, both above and below ground. Well maintenance begins with understanding what the problem is and where the problem is located.
When conducting maintenance, we want to address the problem while not worsening the issue or causing new problems to develop. Some problems are tied to operation while others may be a symptom of the original construction or changes in the aquifer. Sometimes there’s a clear cause and effect, while at other times there are a multitude of issues impacting the well.
When it comes to maintenance, it is a good idea to start with the 100-foot test—looking at changes that have occurred around the wellhead and watershed which may impact the well or aquifer.
Moving closer to the well, inspect the controls and pipeline, ensuring everything is in good working order and there are no signs of damage or degradation. Testing the pump to gauge production capability, specific capacity, and wire-to-water efficiency helps provide a benchmark of well performance. This also provides us with an excellent opportunity to collect samples for testing as well as to evaluate the presence of sediment, turbidity, gas entrainment, or other physical and visual developments.
Testing should focus more on conditions that impact operation and use of the well and less on water quality unless there is a specific concern of contamination. This would include assessing basic parameters such as pH, conductivity, oxidation reduction potential, alkalinity, and hardness, while also looking at common mineral scale components such as iron, calcium, manganese, and sulfates.
Biologically, evaluate the total microbial population and identify the level of anaerobic activity. Additionally, if you suspect nuisance bacteria such as iron bacteria or sulfate-reducing bacteria, incorporate those parameters into the testing.
Although there are many similarities, each well is designed, constructed, and operated differently. Each well will have challenges that are at times similar to others but are unique to that well and reflect the way it was designed, completed, operated, and maintained (or not).
As such, maintenance should be well- and problem-specific. In many situations, just about any attempt at maintenance will result in benefits to the well’s production. The longevity of the improvements and the potential for damage to the structure are where we see vast differences in maintenance efforts. Well maintenance is often termed well rehabilitation, reflecting the focus of efforts to “rehabilitate” troubled wells.
Rehabilitating the System
Although often interchanged, there are three main categories of well rehabilitation: disinfection, cleaning, and development.
Disinfection is the most commonly employed treatment effort. Disinfection occurs at the completion of construction of the well, following modification of the well or pump work, at the end of cleaning efforts, and periodically in an effort to target bacterial issues. Disinfection commonly uses chlorine or other oxidative chemistries in an effort to reduce the active microbial population downhole and within the adjacent aquifer.
Cleaning is typically a combined chemical and mechanical effort that targets mineral scale, biomass, or combinations of both. Chemical cleaning is generally acid-based, but may also include dispersants, surfactants, inhibitors, and in some rare cases, may utilize caustic solutions.
Development, or in existing wells redevelopment, is a method of treatment that specifically targets drilling fluids and fine sediment following construction, or after many years of formation influence and sediment migration. Development relies heavily on mechanical efforts, but can also utilize chemicals designed to target mud, clay, and silt.
Mechanical methods for well cleaning differ from region to region and contractor to contractor. Mechanical cleaning can be used as a means of pretreatment, the main cleaning method, or coupled with the use of chemicals. Common mechanical methods include brushing, surging or swabbing, jetting, and the use of more invasive methods such as gas injection or explosives.
The selection and employment of the mechanical method should be based on the well design (including any liners or modifications), the structural integrity of the well, the nature of the fouling mechanisms, and the use and type of chemicals.
It is important the selection of mechanical method complements the well, not just in size but in condition and level of aggressiveness desired. A splayed cable brush can be very useful in addressing hard carbonate or sulfate scale within an agricultural well, but that same high-tensile strength cable used for the bristles can damage casing and increase the amount of reactive surfaces and the mobilization of iron. On the flip side, a poorly sized nylon brush or a bristle that exhibits too much flex may not provide enough energy to address the problem at hand.
Chemicals utilized in well maintenance vary considerably as well. Similar to mechanical means, not all chemicals are the same. As noted above, there are a variety of chemicals available for use in well cleaning.
The selection of the right chemistry should include much the same guidelines as selecting the right mechanical tool: Will it address the identified fouling mechanism? Will it limit damage to the well structure and aquifer? Is it safe for the crew and environment? Does it complement the selected mechanical method? Can we manage evacuation and disposal of the introduced chemicals?
Regulatory-wise, you want to make sure the products are safe for use in a potable well system. This question is answered by confirming the product is NSF Standard 60 approved for use in potable wells.
Each chemical and mechanical means of maintenance has specific means of employment within the well. Any questions or concerns should be addressed in advance of arriving at the well site. With regards to all maintenance efforts, it is necessary to ensure you adequately purge (evacuate) the well following any mechanical or chemical application. This ensures all introduced or disrupted materials are removed from the well and aquifer setting.
Three easy means of evaluating whether you’ve been effective at purging the materials include: visual turbidity, conductivity, and pH. When compared to your original observations, these three means of evaluation should confirm whether the well has been adequately flushed.
Some within the industry feel the disrupted scale or introduced chemicals can be neutralized downhole in an effort to reduce costs. But research has shown by allowing the materials to remain, both chemical and biological fouling often returns at a much faster rate, potentially impacting the well more significantly than original.
Water well maintenance is an often oversimplified, poorly timed, and rushed endeavor. Unfortunately, the “run to failure” attitude prevails in our industry—not just in the residential well market, but in the municipal field as well.
Like annual maintenance to your home’s HVAC system, routine maintenance to your well helps avoid premature failure or costly repairs. Moving a well owner’s mindset (and our own) to a position of being proactive—instead of reactive—can pay dividends over the life of the well, even more so if it is the sole resource or key component of their supply.
Early identification of problems and judicial employment of the right method saves time and money, while extending the operational life of the well.
Michael Schnieders, PG, PH-GW, is a professional geologist currently serving as the principle hydrogeologist and president of Water Systems Engineering Inc. in Ottawa, Kansas. Schnieders’ primary work involves water resource investigation and management, specializing in the diagnosis and treatment of fouled well systems. Schnieders was the 2017 McEllhiney Distinguished Lecturer in Water Well Technology. He can be reached at firstname.lastname@example.org.