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County approves zoning text amendment requiring groundwater monitoring where solar farm piers approach groundwater
Summary
The commission approved a zoning text amendment adding groundwater-monitoring requirements for solar energy conversion systems when galvanized piers would be within four feet of groundwater; the change responds to public concerns about zinc leaching from corroding galvanized piers.
The Douglas County Commission approved a zoning text amendment that adds groundwater-monitoring and testing requirements for solar energy conversion systems when galvanized piers are proposed within four feet of the shallowest measured groundwater level.
Mary Miller, city-county planner, said staff originally recommended denial after researching zinc behavior in soil but that the Planning Commission recommended approval to apply a cautious, site-specific monitoring approach. "Zinc is very immobile in soil. So if it corrodes and it's in the soil, zinc likes to stay right where it is," Miller told the board, while adding that uncertainty remains where piers are very near groundwater.
Under the adopted changes, an applicant for a solar facility must provide baseline groundwater and soil testing and, if piers are proposed within four feet of the groundwater table at any time of year, install monitoring wells. The monitoring plan must describe installation, sampling and proposed mitigation. The draft language uses the EPA secondary drinking water guideline of 5 milligrams per liter of zinc as a monitoring threshold; if groundwater zinc reaches that level the applicant must increase sampling frequency and test private wells within a quarter-mile downstream of the monitoring wells with the permission of owners. If elevated concentrations are found, applicants are required to document mitigation measures.
Dan Fuller, who requested the amendment, urged caution. He cited his experience with steel and galvanizing and warned that driving piers through sandstone can accelerate corrosion. "That's what kind of piqued my interest when I figured out that there was going to be 172,000 piers potential," Fuller told commissioners.
Public commenters and local advocates urged a precautionary approach and asked for monitoring to protect private wells. Michael Allman of Sustainability Action Network recommended following the Planning Commission’s precautionary principle and requiring extensive monitoring wells.
Planner Miller said staff found no documented cases of groundwater pollution from corroding galvanized piers but that there are many site-specific variables — soil pH, resistivity, groundwater depth and geology — that affect corrosion and mobility. The Planning Commission’s unanimous recommendation for approval reflected a desire to address the unknowns cautiously and to require monitoring in higher-risk situations.
Commissioner Dorsey moved to approve the amendment; Commissioner Jean Dorsey seconded. The motion passed on voice vote. The amendment applies to future solar CUP applications and does not retroactively change approvals for previously authorized projects, including the Kansas Sky CUP and the Stoll solar facility, unless an operator seeks an amendment or reapplies.
The county will use the monitoring results to evaluate whether additional requirements or mitigation are needed in future projects. Monitoring costs will be site specific and are expected to be part of an applicant's studies submitted with a conditional use permit application.
