Hanford is a flat area near the Columbia River, close to the TriCities at the south end of I82. And it's not close to I82. The Firing Range covers the hills between Yakima and Ellensburg. If you came up US97 this is probably the part you traveled. It's a highspeed rolling stretch of freeway, with an impressive downhill at the north end.
It gets heavy truck traffic because it is a cross over between I80/84 and I90. Traffic headed to Seattle and Vancouver from the east has to take the northerly I90/94 route, or a central I80/84/82/90 route.
US97 in Washington is one of the more varied highways in the country. It starts with climb from the Columbia to Satus Pass. Then a drop through the Yakima Indian Reservation to the Yakima agricultural area (I82). then it crosses the ridge to Ellensburg, and higher ridge to US2. Blewett Pass is nearly as high as US2 Stevens Pass, though it never gets as much snow. Then it follows the Columbia River and its orchard country. And finally the open Okanogan valley till it reaches the bustling BC 97 orchard and resort country.