Washington County septic services.

Washington County permits septic (SSTS) work except in the city of Dellwood — listed by MPCA's 2025 annual report as running its own SSTS program, at least as strict as the county's (Minn. R. 7082.0040) — confirm which office holds your address. The county's own ordinance, required by Minn. Stat. § 115.55, may be stricter than the state rules; ask for its written list of differences (subd. 2(c)). The report lists the county among the 59 requiring a compliance inspection at property transfer.

Part of Washington County lies in the Lower St. Croix Riverway, whose districts Minnesota rules define directly (Minn. R. 6105.0360). Inside them, riverway ordinances set their own septic standards: a soil absorption system sits at least 200 feet back from the river in rural districts (100 in urban ones) and 40 feet from any bluffline, and is barred where groundwater or bedrock comes within four feet of the system bottom (Minn. R. 6105.0390). Check the riverway boundary before planning.

The dominant constraint here is seasonal soil saturation close to the surface (26.5% of rated soils), followed by rocky layers that earn reduced treatment credit under the state rules (13.6%). NRCS's Minnesota-specific ratings put 49.4% of rated ground in the very or extremely limited classes for a conventional below-grade trench and 47.4% for a mound.