Wis. Stat. § 66.0427
In a town, city or village in a county with a population of 750,000 or more no excavation for building purposes, whether or not completed, may be left open for more than 6 months without proceeding with the erection of a building on the excavation. If an excavation remains open for more than 6 months, the building inspector or other designated officer of the town, village or city shall order that the erection of a building on the excavation begin forthwith or that the excavation be filled to grade. The order shall be served upon the owner of the land or the owner's agent and upon the holder of any encumbrance of record as provided in s. 66.0413(1) (d) . If the owner of the land fails to comply with the order within 15 days after service of the order upon the owner, the building inspector or other designated officer shall fill the excavation to grade and the cost shall be charged against the real estate as provided in s. 66.0413(1) (f) . Section 66.0413(1) (h) applies to orders issued under this section. This section does not impair the authority of a city or village to enact ordinances in this field.
Wis. Stat. § 66.0427