Where the Tobacco and Cedar rivers meet, the ground turns from sand to wet loam lot by lot.
Beaverton began as Grand Forks, named for the meeting of the Tobacco and Cedar rivers, and the Ross family's lumber company founded the town in 1890. It is a small city: about 1,060 people on roughly 1.1 square miles. Of its 582 homes, about 31 percent were built before 1960 and about a fifth in the 1980s alone, which puts the median year at 1975 in the Census Bureau's 2024 estimates. Renters make up about 55 percent of households. The city's own survey of more than 364 home exteriors looked at porches and driveways, and the roughest stretch was Brown Street.
Ross Lake is a 294 acre impoundment of the Cedar and Tobacco rivers, held back by the city's hydroelectric dam, built in 1919 to replace an older wooden one and run today by Public Works. The DNR describes the land around the lake as flat, with soils that are mostly sand and clay, and the USDA maps for the city bear that out. Grattan sand drains fast. Selfridge loamy sand puts about 20 to 40 inches of sand over loamy till, with water 1 to 2 feet down. Parkhill loam can hold water at or just above the surface from December to April.
Water is the constant here. The city's master plan shows a FEMA 1 percent annual chance floodplain right along Ross Lake and both rivers, with 71 parcels inside it. NOAA logged the Tobacco River at Beaverton at a record crest of 14.32 feet on the morning of May 19, 2020. The same plan notes that Tonkin Street floods between M-18 and Church Street each spring, and that some homes pump footing drain water out onto the pavement. That is why our foundation walls get waterproofed on the outside, with drain tile laid before any backfill goes in.
Beaverton writes its own sidewalk recipe into code. Walks must be at least four inches thick, from a five bag mix that reaches 2,500 psi at 28 days, on four inches of tamped sand. Residential walks run five feet wide, pitched a quarter inch per foot toward the street, with 3/8 inch expansion paper at joints and wherever a walk meets a drive or curb. Occupants have 24 hours to clear snow and ice from the walk out front. On private ground, a walk or terrace no more than 12 inches above grade does not count as a structure under the zoning ordinance.
What Beaverton concrete runs into
- Slabs on Parkhill loam heaving where water can stand at the surface from December to April.
- Settling where Selfridge sand drains on top but holds water 1 to 2 feet down.
- Wet basement and crawl walls on the 71 floodplain parcels along Ross Lake and the rivers.
- Walks poured on bare dirt instead of the four inches of tamped sand Beaverton requires.
- Cracks at drives and curbs where the 3/8 inch expansion paper the city calls for was left out.
- Driveways and streets taking footing drain water pumped onto pavement, as the city's plan describes.
