Middleton told federal rule keeps city in MS4 stormwater program; council hears cost estimate of up to $600,000 a year

City officials told the Middleton City Council on June 4 that federal and state interpretations of the Clean Water Act mean the city will remain regulated under the municipal separate storm sewer system (MS4) program even after the 2020 census excluded Middleton from the Nampa urbanized area — and that complying with the permit could cost far more than the city’s current stormwater budget.

Jason Van Gilder, Middleton’s public works director, and the city’s legal counsel explained the background and the city’s options during an informational presentation that the council did not vote on. Van Gilder said Middleton currently operates a minimal stormwater utility funded mostly by a small fee and staff support from the streets department. "Right now our stormwater fee is about a dollar fifty or so per house, per month," he told the council.

Attorney Mark Hilty summarized the regulatory problem: Middleton was designated as a regulated small MS4 when the city was included in the Nampa–Caldwell urbanized area in earlier census calculations.…