Siting and having standards for construction practices can impact well life.
By Eric Duderstadt and Michael Schnieders, PG, PH-GW
To say groundwater sustainability is a complex and wide-ranging issue may well be an understatement. While the scope of the issue extends globally, regional differences in water sources make the goal of sustainability highly variable.
Further complicating matters, the manner in which wells are constructed and subsequently maintained fluctuates immensely dependent on state-to-state standards, budgets, and contrasting philosophies amongst owners, operators, and engineers.
Many in our industry focus on sustainability as an issue based on well use and aquifer resiliency. And while those are important factors, what about smart well design? Site-specific construction? Regular operation and proactive maintenance?
The definition of “sustainability” used by the U.S. Geological Survey (Sustainability of Ground-Water Resources) is as follows: “development and use of groundwater resources to meet current and future beneficial uses without causing unacceptable environmental or socioeconomic consequences.”
To that end, to correctly develop a groundwater resource a well must first be properly sited and constructed. Failure to achieve one of these initial steps poses serious risk to the likelihood of providing acceptable quantity and quality of the resource moving forward.
Selecting an appropriate location for drilling a water well often takes a great deal of technical preparation to consider the geology present, the depth of the water table, recharge characteristics, and the topography of the area. Additionally, knowledge of surrounding land uses with regards to possible contaminant sources as well as population density limit the risk for contamination and help ensure resources are sufficient to meet the needs of the area.
Identifying and understanding the potential influences to the wellfield and area of recharge which could impact your well system is vital to characterizing and managing the resource. Part of this is understanding current conditions while a major portion is preventive measures to address “what might be” in the future.
The most cost effective location is the one providing the best quality water, easiest to tie in with existing infrastructure, and offering the least chance of being impacted by localized surface or hydrogeologic influences.
A new well design should be developed after a thorough and detailed testing program and understanding of the site. Many wells have been taken out of service because one of the most fundamental concepts of well design has been ignored: A deep well is no safer than a shallow well if surface waters or waters from shallow zones are not properly sealed out.
State minimum standards were intended to regulate the design and construction of potable wells in order to protect public health and safety as well as the environment. Unfortunately, many systems were installed years before current regulations were in place and enforced. This leaves many wells susceptible to contamination due to insufficient grout, poor material selection, improper siting, or substandard construction practices.
As such, even now, design and construction with a “minimum” in mind instead of “necessary” can impact the operational lifespan of the well as well as the health and viability of the aquifer.
Another challenge with state regulations is the common behavior of aquifers and watersheds to spread beyond political boundaries. In short, stringent design and wellhead protection efforts in one state can be negated in an adjoining state with more lax requirements or absent enforcement. Regional, watershed, or aquifer-specific guidelines show greater success at preserving and protecting water resources while providing the industry with better guidelines for construction and use.
The issue of sustainable water practices slowly continues to impact legislation, including the adoption of the Sustainable Groundwater Management Act for the state of California in 2014. While this and similar measures move efforts forward in one state, they often fall short in their single-state focus.
Incorporating a broader focus and bringing more stakeholders to the table appears better suited for real success, such as efforts championed by the Susquehanna River Basin Commission in Harrisburg, Pennsylvania, which brings together multiple states (Pennsylvania, New York, and Maryland) tied together by a unifying aquifer and recharge system.
Historically, maximum yield was expected from the well and when multiple zones contributed to the yield, they also contribute to the quality. As water quality standards tighten and the number of constituents of emerging concern increases, we are taking a closer look at zone-specific water quality. By going to a zone-specific design, typically better-quality water is supplied to the system.
Once the portion of the aquifer being developed is identified, the next concern needing to be addressed is over-pumping. When specific zones are utilized in an area historically where all zones have been targeted for production, it is unreasonable to expect the same pumping rate.
It is best to design a new well so as not to exceed the hydraulic conductivity of the targeted zone. Detailed evaluation and assessment of water needs and uses coupled with design changes can result in reduced demand on potable wells.
Once a suitable location is determined, correctly sizing the well or wellfield is imperative so that a well can operate more optimally without impacting an aquifer or creating detrimental conditions.
In years past, it was a common practice to overdesign a well, thus ensuring a strong production capability for the well despite poor development or inevitable well fouling. While this practice can stave off maintenance needs in the early years, as the well ages, efficiencies decline more significantly—requiring more invasive treatment responses.
It is important to look at the water system to determine what infrastructure changes might be needed to better serve the customers and reduce long-term costs. Oftentimes, the higher demand can be mitigated by a balancing of well yields with system storage. In these cases, a smaller well can be used if system storage is increased or if blending capabilities are enhanced.
Once a groundwater source is established and a properly designed well or wellfield is installed, the manner in which the resource is utilized is of equal importance. Wells that are properly operated and maintained are much more likely to achieve the expected production rates and produce an acceptable quality of water long term, compared to those that do not.
As an example, a survey of nearly 2000 water samples collected from potable water wells across the United States was taken to examine biological activity with regards to maintenance, operation, and fouling potential. Results from the survey showed that wells that are not on active operating schedules, on average, display bacterial populations roughly three times greater than those that do.
Thus, the research suggests that more continuous flow through properly sized and exercised wells deters bacterial growth, propagation, and cell attachment to surfaces, further limiting the potential for fouling and maintenance requirements.
However, as with all things mechanical, wells and their components are subject to wear with use over time. It’s important that when the time comes, rehabilitation efforts follow a scientific approach and are supported through a systematic review of the conditions and issues influencing the well.
As a result, rehab work can be geared toward specific fouling mechanisms or structural issues in play. Additionally, those efforts can proportionate to the issues at hand and utilize the proper tools for the job. Failing to utilize the proper application of tool and techniques can easily result in efforts that are too heavy-handed which may lead to more long-term problems.
Identifying the need for maintenance should also take on a more proactive approach vs. reactive to issues that are already occurring. If maintenance is not regularly conducted and parts aren’t replaced with the proper frequency, even the most extensive efforts or most expertly constructed wells can become too degraded to effectively re-establish.
Sustainability is a much bigger issue than is commonly acknowledged. Decisions must account for system needs as well as well design and construction, use, and operation. Providing sustainable adequate water quantity and appropriate water quality for a given need, without compromising the future ability to do so, must undoubtedly include good construction and proper operation of wells.
As this issue continues to gain attention, future implementation of strategies, data collection, and collaborative efforts between decision-makers will surely follow. These decisions should cross disciplinary boundaries as well as political borders.
As we move forward, it’s important to understand the numerous factors that impact our wells, the systems they are a part of, and the aquifer and watersheds which make them possible. Through better understanding of the resource, the decisions we make regarding well use and operation, maintenance, abandonment, and replacement will be better suited toward securing a vulnerable resource for generations to come.
Part of this will require educating ourselves of the factors that influence our wells, and part of this will be educating our customers and the general public.
Eric Duderstadt is a water chemist and microbiologist with Water Systems Engineering Inc. in Ottawa, Kansas, where he works as a consultant. He is a corrosion technologist with the National Association of Corrosion Engineers, specializing in chemical and microbiological corrosion of water systems. He can be reached at email@example.com.
Michael Schnieders, PG, PH-GW, is a hydrogeologist and senior consultant for Water Systems Engineering in Ottawa, Kansas. He served as the NGWA McEllhiney Lecturer in 2017, has authored numerous articles on well maintenance, and specializes in the diagnosis and treatment of troubled well and water treatment systems. He can be reached at firstname.lastname@example.org.