A thin line on a parcel map may appear as if it is a road, but when you get into the field you may find nothing but two faint tire tracks.
You need to pay attention to the back road travel routes you have planned between prospective sites. There are fewer bridges on back roads and you often need to ford a river or creek. It can be just a rocky river bottom when the water is low, but if there has been a lot of rain a week before you arrive, these fords may be impassible. I have had to change plans and drive 30 miles out of my way just to get to another site that was just 2 miles on the other side of a swollen creek. Back roads where I have been are often washed out. More than ounce I became a road builded and had to gather boulders and rocks to fill in big gaps.
When you drive off road in many parts of many Western states chances are you are driving on a mixture of bentonite clay. Bentonite is natural occurring clay that comes from the weathering of volcanic ash deposits. It is used as a sealant in drilling operations, in cat litter and even as a diet supplement. I use it in a business to quickly absorb water based spills because it can absorb up to 50 times its own mass of water.
Bentonite is fine for driving or walking on until it gets wet. Even a slight shower can turn the off road trail surface into a pasty mess. It will immediately begin to cake up on your tires and can fill up wheel wells to the point that your tires can stick. If you walk on wet bentonite it will cake up on you boots so that you will be walking around an inch off the ground. Scrape it off and wait for the moisture to soak into your trail.
If Bentonite gets very wet it turns into a slippery goo like Vaseline the locals call “Gumbo.” It can be impossible to drive on with two wheel drive and difficult with four-wheel drive. If you continue to drive on it, our vehicle can slide sideways from the crown of a road and into a ditch.
When the rain stops the bentonite begins to wick the water down into lower layers, and within an hour or two depending on the amount of rain it begins to firm up. Keep testing the surface with your boot until it does not stick or build up. It may still feel damp to the touch but will no longer cause a problem.
If there is even a slight threat of rain, I “bug out” to the closest gravel surface. Many times I have waited on gravel wondering which way the storm will move. Will it pass by or will it hit my dig site? I never try to figure this out at the actual site. If I guess wrong, I could be stranded there until it all dries out. I ounce had to wait two days to get back off road.
In my worst experience, I waited for the rain to stop while I was on a gravel treated road surface. The rain continued to 2 inches. Then, even the gravel aggregates rolled under my tires like roller bearings and I could barely move. After learning the hard way, I now carry a set of chains for the van as if I were planning to drive in deep snow.
My search success has always been dependent on the weather. I schedule my travel flights 60-90 days in advance. But, I am never certain that I can actually get into the field once I arrive to my destination. I have been rained out many times when I am in the field. Three times I have had to cancel my flights altogether. My search areas were so wet I could not get access. Also I have been caught up in a freak snow blizzard and had sit idle in a motel for several days in the nearest town.
Just in case, I now always set up multiple search route strategies for each target area. One is a normal off road route where I try to get my van as close as I can to a search area or dig site. The other plan is for hikes that originate only from a stable gravel road. You need to have alternate plans for those times when you cannot leave a gravel surface due to the wet bentonite. On these occasions, I hike to explore new sites rather than try work in the gumbo mud.
I always check the local weather reports and plan accordingly. I can be 50 miles away from the nearest reporting station so I can expect surprises. I never notice all these things at home. If I look out the window and see rain I just go on to an indoor project. Out on a dig you have no alternate activity. The weather determines your productivity.
If I am at a site on a clear dry day I still watch the weather and the horizons. I find pop-up storms are common. I have been in a deep ravine digging for a few hours, and when I stretched my legs and walked to the top, I was shocked at the dark clouds that were racing toward me. I had to leave all my gear and “bug out” quickly because of the bentonite between me the safe gravel road.