Tukwila ground, weather, and permits
The city’s shoreline inventory describes young river alluvium on the valley floor, often capped by fill, over older alluvium that reaches about 90 feet thick near Tukwila. A shallow aquifer there connects directly to the river and flows toward it. The uplands are broadly mapped as Alderwood gravelly sandy loam, with till that restricts downward flow of groundwater. The city’s plan flags numerous steep, potentially unstable slopes, plus coal formations, some of them mined, southwest of Interurban Avenue South.
The Permit Center in Community Development handles building permits, while Public Works sets the right-of-way and surface water requirements. The city’s wall handout puts the permit line at 4 feet, measured to the bottom of the footing, or 2 feet when the wall carries a surcharge, and exempts no wall in a critical area. Slopes of 15 percent or more, mapped flood areas along the river, and coal mine hazards each add review. Before pricing a job, we pull the hazard layers and permit path for your parcel.
Nearby, we also build in Renton, Kent, Burien, White Center, and West Seattle, and we serve the rest of Pierce and South King County.