According to the recent U.S. Drought Monitor, approximately 65% of the contiguous United States is currently experiencing “abnormally dry” to “exceptional drought” conditions. In my part of the country, a recent projection indicates that a reservoir supplying a significant portion of our municipal water supply could dry up within 3-4 years if severe drought conditions persist. Although an “Aquifer Storage and Recovery” program was previously developed to enhance the available supply of groundwater, it is only designed to replenish the drinking water aquifer from excess river flow during flood conditions—a rare occurrence during a severe drought.
I am not capable of allocating percentages of fault for this persistent drought between anthropic climate change and extreme climatic occurrences that are “normal” in the context of geologic time. However, I am persuaded by the argument that “climate change,” by whatever definition you choose to give it, is a problem not only of causation and prevention, but also of adaptation. A previous posting on the need to prioritize adaptation to climate change states the argument well. Is it time we give more thought to groundwater replenishment as an adaptation tool?
My practice includes representing clients at various hazardous substance release sites, under both state and federal law. The default remedy for contaminated groundwater at many of these sites remains extraction and treatment (commonly using air stripping technology) to both contain and clean up the extracted groundwater to “unrestricted use” quality. At most of these sites, however, treated groundwater is discharged to a ditch, creek or similar conveyance where the value of the groundwater as a critical natural resource is largely lost.
An environmental consultant at one such site recently calculated that, over the period of two years, the pump and treat system had removed and discharged to a nearby ditch approximately 110 million gallons of treated groundwater. During a period of severe drought, the system was depleting a drinking water aquifer by over two feet annually. In addition, it was estimated that the quantity of groundwater being treated, and largely wasted, was equivalent to the water used by 1,850 residents (27% of the population) of the city in which the site is located.
Beneficial reuse of “contaminated” water resources is obviously not a new concept, particularly the reuse of nonpotable water. Examples include the reuse of treated nonpotable water for industrial, municipal and agricultural purposes. Potable water reuse is less common for reasons related to water quality requirements, technical issues, cost and community and regulatory acceptance.
Notwithstanding the obstacles and additional costs, it may now be time for environmental professionals, regulators and attorneys to more systematically and creatively consider potable reuse options at contaminated groundwater sites. This would include an evaluation of discharging treated groundwater through infiltration basins, infiltration galleries and injection wells to replenish the drinking water aquifer from which it was extracted. Consideration should be given to partnering site regulators and responsible parties with nearby municipalities to revitalize drinking water aquifers or supplement other potable water resources. Another issue worthy of discussion is community acceptance, which may be more likely when treated contaminated groundwater is beneficially reused indirectly through aquifer replenishment, rather directly through discharge into water supply pipes.
I submit that all too often we accept without much thought the default option of permitted surface discharge of groundwater that has been treated to “non-detect”. Potable reuse through groundwater recharge and restoration involves significant cost and technical issues. But in our effort to add weapons to the climate change adaptation arsenal, all interested parties should more carefully consider such options notwithstanding the challenges.