Eagan, MN Environmental Rules: Stormwater Management (2026)

Eagan's stormwater management ordinance, City Code § 4.34, imposes post-construction requirements on any project needing a permit under the section that adds 10,000 square feet or more of new or fully reconstructed impervious surface. Under § 4.34(F)(1)(a), new nonlinear development must retain on site 1.1 inches of runoff calculated from the impervious surface created, and § 4.34(F)(1)(b) applies the same 1.1-inch retention standard to redevelopment and reconstruction projects. Linear projects such as roadways, sidewalks and trails must capture the larger of 0.55 inches of runoff from new impervious surface or 1.1 inches from the net increase in impervious area.

Where infiltration is restricted, for example near contaminated soils, drinking-water source areas, or high-infiltration-rate soils, an applicant must work through a three-step alternative design sequence before the city will approve a different approach. Section 4.34(F)(3) also sets rate control standards: on-site facilities must maintain predevelopment peak runoff rates for the 50 percent, ten percent and one percent probability 24-hour storm events, calculated under NOAA Atlas 14 rainfall data and the NRCS TR-55 methodology. Section 4.34(G) requires oil and grease removal technology on the first 1.1 inches of runoff at any site with 40 or more parking stalls, high-traffic areas like drive-through lanes, or businesses such as gas or service stations with grease or oil pollution potential.

Property owners must maintain private stormwater facilities under § 4.34(I), including an annual inspection by a qualified person and removal of accumulated sediment, and sign a recorded stormwater management agreement before the city issues a permit. Violating these standards is a misdemeanor under § 4.34(J), with the city able to order corrective work and recover its costs.