County drain commissioner, consultant outline Chipman Drain reroute and timelines

Brent Singer, the Shiawassee County drain commissioner, and a consultant from PEA Group described a proposed reroute of the Chipman Drain intended to reduce flooding near the M‑21/Chipman intersection and lower pavement replacement costs. The presenters said the preferred route would move the drain to the north side of the street and connect into an existing 54‑inch Chipman Drain to carry flow more directly to the river.

A PEA Group engineer said stormwater modeling shows the current system of 10‑ to 12‑inch pipes lacks capacity and recommended upsizing. “We ran some storm water modeling, and it needs to be a 24 inch… MDOT has suggested that they would prefer a 36 inch pipe,” the PEA representative said. Presenters estimated construction in summer 2027 and said MDOT indicated it would cover additional cost to upsize above the 24‑inch minimum.

Council members asked how many residences and businesses are affected and whether property owners would face special assessments. The presenters described two statutory approaches to county drains and said this project is a Chapter 20 drain, meaning costs would be shared among municipalities and road agencies in the drainage district — here, the city, Owosso Township and the county — and that a final allocation is pending further hydraulic analysis.

Presenters cautioned that a formal petition for system‑wide improvements could expand the scope and cost substantially (they cited the possibility of a localized $1.5 million project growing to a $15 million system review). City staff and the presenters said the likely next step is continued hydrologic work and potential flow‑share calculations by MDOT before final cost allocations or petitions are filed.