Mandan commission adopts new stormwater design manual, begins ordinance rewrite

The Mandan Board of City Commissioners unanimously adopted a new stormwater design standards manual on Jan. 20 and approved first consideration of a companion ordinance to update city stormwater code.

Consultants from Houston Engineering described the manual as an update to the 2011 standards intended to align Mandan’s rules with federal and state MS4 permit requirements and to reduce permit delays by standardizing submittal requirements. Michael Gunsh, project manager with Houston Engineering, said the draft ordinance is written “to amend and reenact section 107,” and that the manual and ordinance were developed concurrently to avoid conflicting definitions and processes.

Why it matters: city staff and consultants said the package clarifies who is responsible for review and enforcement, establishes a fee schedule and an appeals committee, and sets technical thresholds that will affect developers and public‑works projects. The manual’s stated goals include protecting public safety and property, reducing resubmittals and shortening review timelines.

Key details: consultants said a permit would be required for developments that create more than 3,000 square feet of new impervious surface, for land disturbance greater than one acre, or for any activity involving more than 400 cubic yards of earth. Nick Cullen of Houston Engineering summarized the first of the manual’s four pillars: “post construction runoff rates must not exceed the existing condition runoff rates for the 2, 5, 10 and 100‑year 24‑hour rainfall events,” and the manual also requires treatment of the first half‑inch of runoff from impervious areas for water‑quality compliance.

The draft ordinance adds a riverine setback provision matching Morton County practice — 75 feet where a protected bank exists and 100 feet where it does not — and gives the city engineer the program coordinator/enforcement role. Consultants described enforcement tools that include noncompliance fees, permit suspension and cost recovery if the city must clean or repair conditions that damage public infrastructure.

What commissioners did: Commissioner Schoberg moved to adopt the manual as presented and the motion passed by unanimous roll call. Commissioners also approved first reading of Ordinance No. 14‑83, the stormwater ordinance rewrite that codifies related requirements; the ordinance will return for a second reading before taking effect.

What’s next: the manual is effective as adopted by the commission; the companion ordinance proceeds through its required second reading and any additional public notice and amendment process before final adoption.