Hermiston is a city in Umatilla County, Oregon, United States, near the junction of I-82 and I-84. U.S. Route 395 also goes through the center of the city. Hermiston is seven miles south of the Columbia River, Lake Wallula, and the McNary Dam. The Umatilla Chemical Depot and the Umatilla Chemical Agent Disposal Facility are five miles west of the city, northeast of the intersection of I-84 and I-82. As of 2010, the estimated population is 16,745 residents.