The cache is located at the confluence of N46 and W119. There is a web site dedicated to confluences and you can read at this webpage (https://www.confluence.org/confluence.php?id=573) about previous attempts to get to this location. The hike to the cache should only be attempted by the fit and able bodied.
The Columbia river is nearby and the geologic story for the area is quite remarkable. The ice age floods carved a channel through here and the area is called Wallula Gap. More on that here at the National Park Service’s website (Wallula Gap National Natural Landmark (U.S. National Park Service) (nps.gov))
The closest roads from the Tri-Cities that get you nearest the cache are Ayers and Les Blair. Presumably named after pioneering farmers that once lived on these roads. These are both gravel roads that in my experience have always been driveable in a 2WD vehicle.
But if you have a boat the easiest access would be to get near the geocache via the Columbia River. You’d still have a bit of a hike however as the latitude and longitude confluence is a bit off the river and up a steep slope.
I used to hunt in this area but gave up hunting many years ago. But I still like to return to the Wallula Gap area to hike around. In talking to the then farmer (who unfortunately has gone to jail for fraud), this area around the GZ is all open to hunting as part of the water rights for taking water from the Columbia River to irrigate the land.
The geocache container is an aluminium drink bottle further wrapped in aluminium foil in an effort to discourage rodents from chewing the bottle’s lid. The cache is in a pile of rocks intended to protect it from extreme heat that will occur when at some point a wildfire burns through this area. Please be mindful of protecting the geocache from wildfire heat and cover the container with a good number of rocks. The pile of rocks at the base of a bluff is easy to spot, and I was able to get N46.00.000 and W119.00.000 on my GPS exactly on this pile of rocks.
The cache contains a logbook and a foreign coin. Bring your own pen. Attempting the cache in spring before the wild oats have grown and before the summer heat has set in is recommended. Please trade another foreign coin so that a finder can have a unique keepsake, should they want it, for their efforts to get to this cache. There is no easy way to this geocache so it will be a memorable geocache should you take up the challenge.