Dunn County approves temporary asphalt plant at Downing Quarry with conditions

The Dunn County Board of Adjustment on Oct. 8 approved Mathey Construction’s conditional-use request to operate a temporary asphalt plant at the Downing Quarry to serve the Wisconsin Department of Transportation Highway 128 paving project, voting 5–1.

The board attached conditions including limiting plant production operations to 6 a.m. to 8 p.m. Monday through Saturday, requiring the applicant to offer emergency‑responder outreach within the first three weeks of operation, provide a local point of contact for neighbors, and notify county staff when the plant is delivered, placed into operation and removed.

Tammy (zoning staff) told the board the proposed site is a previously disturbed portion of the Downing Quarry (address listed as 1131 County Road W), a 32‑acre parcel. The mobile plant would primarily serve WisDOT project 8650-0074 (State Highway 128, from U.S. Highway 12 to State Road 170) and could also supply Dunn and Saint Croix county highway departments and local municipalities. Staff said the quarry has operated since 1968 and is permitted under chapter 20 of the Dunn County zoning ordinance for mining and reclamation. Staff noted that state agencies — the Wisconsin Department of Transportation, Department of Natural Resources and Department of Agriculture, Trade and Consumer Protection — regulate aspects of asphalt production including mix quality, air emissions, stormwater and fuel storage.

Candy Anderson, representing Mathey Construction, Monarch Paving and Milestone Materials, said mobile asphalt plants typically remain on a single site about 6–8 weeks but requested authority for the 2026 construction season to allow flexibility for weather and project…