Commissioners approve stormwater study for Kansas Sky with conditions for final basin plans

Douglas County commissioners voted to accept the final stormwater management report for the Kansas Sky Energy Center, subject to further staff review and approval of detailed construction plans for two proposed detention basins.

Chad Voigt, the county engineer, said his parallel review found the applicant's drainage calculations to be within acceptable assumptions and reported that the study shows a 2% net decrease in runoff across the roughly 1,100-acre project area. "The outcome of the current calculations shows a 2% decrease in runoff for the 1,100 acre area," Voigt said, adding that the applicant provided basins where localized increases were identified to avoid impacts to adjacent properties.

Mike Ivey and Westwood (the project's engineering consultant) described modeling methods used for the report: HEC‑HMS (U.S. Army Corps of Engineers Hydrologic Modeling System), NOAA Atlas 14 precipitation data, and NRCS TR‑55 curve numbers adapted for site conditions. Westwood presented the analysis by seven ultimate discharge locations on the site and explained where detention basins or vegetated conveyances would mitigate increases.

Several township officials, drainage-district trustees and adjacent landowners urged a short deferral for independent third-party review, citing local flooding history, concerns about the adequacy of culverts and road crossings, and potential impacts during the vegetation-establishment period. Grant Township, Kaw Valley Drainage District and multiple farmers requested 30–60 days for independent review; township representatives emphasized the statutory role of the drainage district to protect downstream lands and asked for time to hire engineering expertise.

Staff and the county engineer said the report satisfies the county's solar-specific standards and the Maple Grove watershed expectations. Voigt recommended approval contingent on final construction plans for two detention basins being reviewed and approved by staff and inspected during construction to ensure the as-built conditions match the calculations.

Commissioner Reed moved to approve the stormwater study for CUP-23-00312 (Kansas Sky Energy Center) “contingent upon staff review and approval of detailed construction plans for the proposed detention basins.” A second was recorded and the motion passed. The approval requires the applicant to provide final basin construction documents and for county staff to inspect basins during construction to verify compliance.