MSD staff outline pilot to target 500 large sites with permit-and-surcharge for excess stormwater

Metropolitan Sewer District (MSD) staff on April 7 proposed a targeted pilot to reduce excess wet-weather flow by focusing on roughly 500 large nonresidential properties in the combined-sewer area and using a two-step approach: a general stormwater permit and, after planning and mitigation opportunities, a possible surcharge for excess flow.

In a presentation to the board, MSD presenter Diana said the program aims to improve rate equity and incentivize on-site stormwater management by concentrating on the largest contributors rather than imposing a new charge districtwide. "The proposal we're discussing today focuses on reducing excess wet weather flow, particularly from the largest contributors, to help manage system performance and costs over time," she said.

Staff said the pilot would target nonresidential properties with more than 2 acres of impervious surface — about 500 sites that together account for roughly 2,300 impervious acres in the combined area. By comparison, MSD cited about 99,239 residential properties discharging to the combined system totaling about 4,000 impervious acres. MSD staff said that concentration makes targeted action potentially more effective.

How it would work: MSD would first require affected properties to enroll under a new general pretreatment/stormwater management permit. The permit would…