The core problem facing the Viola community and its neighbors, including Rochester and the Mayo Clinic, stems from the proposed Lemon Hill Solar Project’s location within a highly vulnerable geological setting, the fragile karst region. Viola and its surrounding area share a single connected aquifer system, meaning that actions taken locally affect families and institutions across the entire region. The Minnesota DNR and leading geologists have repeatedly issued warnings, classifying groundwater in the karst region as highly vulnerable to contamination. This inherent risk means that in a fragile karst area, the margin for error is thin, and the costs of failure could fall on future generations.
The specific mechanism of contamination is facilitated by the unique characteristics of karst geology. Karst landscapes allow surface contaminants to move rapidly into wells and springs, particularly following heavy rain or freeze–thaw cycles. Unlike typical soil, which provides natural filtration, pollutants in karst can travel from the surface directly into aquifers in hours—sometimes even minutes—without adequate natural barriers. Furthermore, large-scale construction in such areas is known to elevate sinkhole risk and destabilize subsurface systems. This is critical because once karst aquifers become contaminated, remediation is often considered extraordinarily difficult, if not entirely infeasible.
The immediate cause of heightened risk is the sheer scale and method of installation proposed for the Lemon Hill Solar Project. The plans call for driving a massive number of steel piles—estimated between 230,000 and 360,000—directly into this fragile karst geology. The introduction of hundreds of thousands of fractures to the bedrock cannot be withstood by the karst region, according to concerns confirmed by the Minnesota DNR and multiple scientists and hydrologists. These piles, driven deep into the ground across roughly three square miles of prime farmland, are the features that create long-term conduits allowing surface water and pollutants to bypass soil filtration and reach the critical aquifer.
A critical factor that ensures these dangerous conduits will open and widen over time is the climate of Minnesota, specifically the **freeze–thaw cycles** or frost heave. Frost heave occurs when moisture in the soil freezes and expands, forming ice lenses that lift the soil. As this process, known as frost jacking, occurs, it repeatedly pushes and pulls on anything driven into the ground, including the solar piles. Evidence from solar farms in cold climates, such as Ontario, confirms that frost heave causes significant pile movement, with typical movement around one inch and documented cases reaching approximately 1.5 inches. This ongoing misalignment cumulatively opens tiny, hairline gaps along the steel piles.
In karst geology, the combination of frost heave and shallow-embedded piles results in a greater number of pathways, faster contaminant movement, and a higher contamination risk. These open pathways allow various hazardous materials to enter the shared drinking water supply. Potential contaminants include farm chemicals like nitrates, pesticides, and herbicides, which can travel faster through karst geological pathways. Additionally, catastrophic storm damage, such as from tornadoes or hail, could shatter solar panels, potentially releasing hazardous substances or deadly toxins into surface runoff and surrounding soils that are directly connected to the karst features. The resulting severe contamination risk constitutes a public health and economic harm that threatens the entire region.