This Data Release contains supporting data to evaluate fine sediment infiltration into gravels in identified locations of Chinook spawning habitat at three sites on the Sauk River, located in western Washington. Fine sediment infiltration into the river substrate that salmonid fish species use to spawn has been shown to increase mortality during the incubation and pre-emergence phase when salmonids are still residing in the subsurface gravels. The contents of this data release include; 1) geographic coordinates for the three site locations along the Sauk River, 2) hourly dissolved oxygen concentration in the subsurface at the three site locations, and 3) grainsizes, defined as fraction finer than a given sieve size of sediment for bulk subsurface samples and sediment held within infiltration boxes and bags.