The Awwa Research Foundation has completed a project regarding application of well condition assessment and rehabilitation techniques. The emphasis of the project is the renovation of wells with regard to water yield. Techniques that were potentially suitable for renovation of wells with respect to contamination and clogging of the well screens also were to be identified and addressed. Similarly, well-maintenance procedures to prevent reduced water yield or decreased water supply were to be investigated.
The decline in production efficiency of water-supply wells has been a long-term concern. Typical responses to this problem include redevelopment of wells, aquifer fracturing, drilling of new wells, or employing various rehabilitation techniques. Unfortunately, redevelopment of wells often is a temporary remedy because aquifer fracturing can destroy the well installation, installation of new wells is expensive, and rehabilitation techniques are not always successful in restoring wells to their former yields. There have been recent advances in water treatment techniques, as well as in subsurface well-rehabilitation techniques, that should be studied in detail to determine their strengths, weaknesses and potential applications. The quality of water in wells often is compromised by deterioration of the wellhead or well-casing materials. The deterioration of these portions of a well installation may allow a direct hydraulic connection of two separate water-bearing layers, or it can allow surface water and surface-water runoff to channel down along the well casing and directly impact the aquifer water quality. A number of recent outbreaks of enteric disease in the United States and the United Kingdom have been traced to compromised wellheads and well casings.
The researchers succeeded in testing a number of techniques for well rehabilitation methods in a variety of settings. All techniques are well documented and available for those involved with the water-well industry to review and learn from by visiting www.awwarf.org. This is the first effort to publish several well-documented case studies. Indeed, the team was frustrated at the lack of published studies that were available for incorporation into this project.
Clearly, there are many more chemical treatments and processes listed in this report than were possible to use during the tests. The researcher’s goals were to select a cross section of the types of treatments and chemicals. It is possible that there are sufficient differences in particular blends that are similar between companies that would result in different outcomes. The selection of chemicals was somewhat arbitrary, and the fact that some were not utilized has no bearing on their quality and ability to achieve good results. Therefore, the authors encourage using the knowledge gained from this study to make informed decisions on the selection of a treatment.
The comparison of methods was not a simple task. The researchers strongly caution anyone from comparing one technique to another in different settings. It is even difficult to compare methods within the same well field because the cause of the deterioration can be unique to the particular design of the well, local chemistry of the water, the local microbiology and pumping rates of the well. Important aspects to be gained from the case studies include expanding the water well industry’s familiarity with the variety of treatment technologies that are available, the types of pre-rehabilitation analysis that should be undertaken, the selection of appropriate methods, the application of the treatments, and the record-keeping.
In addition to presenting detailed reports on the field tests, the report contains several important conclusions. These conclusions include recommendations on tracking well performance, when to rehabilitate, technology selection, techniques to evaluate the success of rehabilitation, and preventative maintenance.