The site shall retain all stormwater associated with a three (3) inch daily rainfall on non-absorptive surfaces, in addition to all otherwise applicable County stormwater requirements, per a detailed Stormwater Pollution Prevention Plan filed with the application. Post-development peak stormwater release rates shall not exceed pre-development peak rates for the 2-year, 10-year, 50-year, and 100-year storm events. For runoff calculation under the Iowa Stormwater Management Manual, all compacted gravel switchyards, substation and transformer pads, battery storage foundations, and similar outdoor infrastructure shall be treated as one hundred percent (100%) impervious.

Within five (5) statute miles of the Dubuque Regional Airport, no open-water retention pond or other standing-water feature shall be constructed or maintained, and required retention shall be met by underground or dry systems; stormwater design shall avoid hazardous wildlife attractants per Article IX. Elsewhere, detention shall use dry basins designed to drain fully within forty-eight (48) hours.

There shall be no discharge of process water, cooling blowdown, or contact stormwater to surface water or groundwater except after treatment in full compliance with applicable permits.

Erosion, Sediment, and NPDES Compliance. All roadwork and site development shall comply with the applicant's National Pollutant Discharge Elimination System (NPDES) permit as required by the Iowa Department of Natural Resources and with the Dubuque County Erosion and Sediment Control and Stormwater Ordinance; the Stormwater Pollution Prevention Plan shall be filed with the County before any construction and kept current through construction.