Three Rivers Golf Course in Kelso was built in the early 1980s on about 3 million cubic yards of silt and river dredgings that included sand and ash from the 1980 eruption of Mount St. Helens, dredged from the Cowlitz River. The fill, 2 to 20 feet deep, drains so well that the course stays playable through wet Northwest winters. Robert Muir Graves designed the public 18.