Jefferson County, WI Environmental Rules: Stormwater Management (2026)

Section 16-35, part of the subdivision-platting article in Chapter 16, requires subdividers to install the "required improvements" the county specifies before development proceeds: grading (§ 16-35(b)), street surfacing (§ 16-35(c)) and, for stormwater specifically, § 16-35(e)'s drainage facilities. " If the required stormwater sewers exceed 24 inches in diameter to handle the contemplated flow, § 16-35(e)(2) prorates the extra cost between the subdivider and either the county board or the broader tributary drainage area, so a developer is not always responsible for the full cost of oversized drainage infrastructure.

The related design-standards section, § 16-34(i)(2), separately requires a subdivision traversed by a watercourse or drainageway to include an adequate drainage easement approved by the engineer, and directs that "stormwater drainage shall be maintained by landscaped open channels of adequate size and grade" where necessary. Because § 16-36(a) bars any construction or installation of improvements until the preliminary plat is approved and the engineer authorizes work in writing, a subdivider cannot install stormwater facilities, or receive a building permit under § 16-36(b), ahead of that approval. Enforcement runs through the county's plat-approval process rather than a standalone stormwater permit or fine.