Asheville – It began with the news that well permitting in Buncombe County had increased by 300% this year. These permits were not limited to single-family wells; larger applicants included Mission Hospital and Buncombe County Schools.
In the 1980s, researchers from the University of Southern California gathered data that led them to believe offshore oil drilling was causing earthquakes. Oklahomans often equate correlation with causation, especially after experiencing a surge of earthquakes coinciding with the fracking boom. Additionally, one reason for Mexico City’s well-known sinking is thought to be excessive well-drilling.
Manoochehr Shirzaei at Virginia Tech has been studying this issue for years. Recently, his colleague Leonard Ohenhen’s work has gained attention from mainstream media. Ohenhen’s research concluded that all 28 major U.S. cities are sinking several centimeters each decade, with subsidence affecting two-thirds of the land area in 25 of these cities. This new data was obtained through precision radar measurements from satellites.
Houston is sinking the fastest, with some areas subsiding by one to two centimeters per year. In all cases, the researchers attributed the subsidence to groundwater extraction and correlated it with the expansion of urban centers. They emphasized the risks posed to buildings and infrastructure as different parts of the ground settle at varying rates. Recommended interventions included managing groundwater to prevent excessive drilling in specific areas, engineering structures to accommodate differential subsidence, and monitoring groundwater levels.
Theoretically, groundwater supports the rock above it. If the water drains and the weight of the rock and any structures built on it is sufficient, it may shift or even collapse. Whether this could occur in Asheville depends on whether the local geology can sustain continued withdrawal from a water system that has failed customers for two consecutive winters.
However, it was not just well-drilling that raised concerns. Much of it occurred after a flood, which resulted in numerous sinkholes, landslides, and other geological instabilities.
Another variable of uncertain impact is the water system’s notoriously high levels of “unbilled water.” Residents connected to leaky pipes may experience low water pressure, prompting them to drill wells disproportionately. As the city implements an aggressive plan to repair these leaky pipes, what will happen to aquifers that have been “artificially” supplied?
Experience shows that water wells in Western North Carolina typically need to be around 450 feet deep. However, people are not only drilling for drinking water; property owners are also drilling for geothermal energy, and agencies are drilling to remove contaminated groundwater.
Western North Carolina features diverse terrain. Drilling multiple wells in areas like Sandy Mush or on steep slopes with fissured and crumbling rock may pose greater risks than drilling a single well on fertile land in Hendersonville.
“Buncombe and Henderson counties are located in the Blue Ridge Geologic Belt and Inner Piedmont Geologic Belt,” explained Laura Oleniacz at the North Carolina Department of Environmental Quality. “In these regions, well water is found in joints and fractures of the bedrock layer. Due to the underlying geology, groundwater quantity is low-yielding and highly variable depending on location.”
No geotechnical survey is required to obtain a permit for drilling a private residential well in Buncombe County. Permits are issued by the Department of Health and Human Services, which is concerned about toxic chemical leaks and biohazards—ranging from giardia to dead rats—contaminating drinking water. Neighbors who drill into the same aquifer may face higher costs if they need to drill deeper.
Decision-makers seek data rather than theory. Oleniacz noted that the NCDEQ Division of Water Resources maintains a network of wells for monitoring groundwater. While there are no active stations in Henderson County, Buncombe County has one station located in Bent Creek. She mentioned that water levels were measured in September 2021 and March 2024. “According to DWR staff, water levels at those locations appeared consistent and not in a constant decline. However, due to the region’s geology, water quantity and quality are specific to each well,” she stated.
Shirzaei and his team primarily focus on subsidence in coastal cities like Charleston, which averages only 13 feet above sea level. Ohenhen told NASA Earth Observatory, “Subsidence is a pernicious, highly localized, and often overlooked problem in comparison to global sea level rise, but it’s a major factor that explains why water levels are rising in many parts of the eastern U.S.”