The 7874 foot tunnel, engineered by Hamilton Smith Jr. from the Malakoff Diggings, has its outlet in Humbug Creek 1 mile upstream. In the late 1870s, tailings from the Malakoff Diggings filled the river channel to a depth of 60 feet. Remnants of these tailings may still be seen along the banks of the South Yuba River downstream from this point.