The perfect little canyon to do some backpack dredging
Some folks will tell you the 2" dredge is merely a toy. Something which isn't a serious tool for finding gold. It may be true the 2" can't move a lot of material, nor can it reach any kind of depth, buy you can sure get them into a whole lot of places where you couldn't get a bigger dredge and you can have one heck of a lot of fun working the rugged, remote canyons.
Although most of the people who work the big rivers sneer at the person running around with a backpack dredge, the odds are pretty good at the end of the season you may end up with as much gold as they did by being patient and persistent and sampling, sampling, sampling. There's actually a lot of people who use dredgers 2.5" and smaller. According to the California Department of Fish and Wildlife permit database fully 20% of all dredgers who held permits in 2009 used this size dredge, nearly 1,000 of us.
Using a backpack dredge allows you to prospect areas you'd never consider if you were having to pack in a couple hundred pounds of gear on your back. Prospecting is typically a series of steps which begins with research. Each step involves a greater commitment of time and resources. After an initial assessment of a creek using a pan it's time to bring in a backpack dredge and determine whether its worth filing a claim.
I've run a lot of dredges, and have thousands of hours on a nozzle and enough time under water the fish know me by name, but my favorite dredge is still the backpack dredge. When I'm running a 5" it starts to feel like work, I'm just taking apart a hole and running gravel. After a few hours of that you can get a little bored and think about moving the dredge to somewhere else. With a 5" I'm just running material. Sure, the material has gold and at the end of the day I have a nice sluicebox, but I'm always thinking the pay should be a little richer.
Although I enjoy working the backpack dredges I don't like to carry more weight than I need to. Like most of us I just want to get there, and get a dredge engine running.
I have various sized dredges, kind of like a golf bag. You have different clubs for different purposes. You tend to pull out your favorite club, sometimes for a shot which doesn't really fit. It's the same with dredges. If you're going to be doing this you should have an assortment of tools including different sized dredges. One size doesn't fit all, and bigger isn't always better.
I used to have two 5" dredges. I'd have one on the upper part of the claim, and another one on the lower part of the claim that way I could work one area, then move to another without having to move the dredge. When you're working alone in the canyons you find yourself coming up with innovative ways to work. The fives got to be too much work for me alone and it was either get a partner or get a smaller dredge. I got a 4" dredge. Nice dredge by the way. I can't move as much material as the 5" but just the ability to work consistently without fighting the dredge almost makes up for the volume loss.
Some say a 4" is a little bitty dredge, I suppose it is, but when it's on your back it doesn't feel like a tiny dredge. Maybe when I was in my 20's a 6.5hp engine would have been easy, but in my 50's it's a lot of weight. It takes me 4 trips just to move the pontoons. Quick math: If you're hiking into a canyon 1/2 mile from your truck and it has an 800' drop then each trip is 1 mile and 1600' of elevation change. Four trips to move pontoons is 3200' of up and down and 4 miles. If I can pack a 2.5" in one shot then that's better.
I, and most dredgers, consider the 2" dredge a step up from panning, but it has the ability to clean the bedrock which a shovel and pan doesn't have. The 2.5" is a whole lot better than a 2", it just seems like you can move an awful lot more. The 3" is too close in size and weight to the 4" to make it worth your while, although it's typically the first size which you can run air with.
Don't even think about moving overburden with a 2" dredge. Sure, it's possible, but you'll spend more time throwing cobbles out of the way than actually moving material. The trick with the small dredges is to work the shallow stuff, not the stuff the bigger dredges are better at. You're not competing against bigger dredges, you're just sampling.
The backpack dredge is an underwater sampling tool. I'll use it work from the bank down as low as I can go, which is the reach of your arm. The most overburden I'll work is 18", then I'll move somewhere else.
The true advantage of these backpack dredges is exactly what they're called. Your ability to put it all on your back and get into a canyon in one shot, maybe two, but you'll get in, and out in a day. Or you can get in and work your way up a creek for a few weeks sampling as you go.
Portability is the key. Every part you have to carry is more you have to strap to your back or carry. With the 2" I like the old type which floats on an inner-tube. I like the same set up for the 2.5" and I prefer the old "crash box" to the flare jet. With the crash box you just need enough water for the foot valve, but with the flare jet you need enough water for the tube to drop down. Often, there's not enough water for that.
A 2.5" Dahlke flare jet at work on a creek with enough water to run something bigger than a 2", but smaller than a 4"
The below pictures is the type of canyons I look for to run the backpack size dredges. Steep sides, hard to get to and skinny water with little overburden. The spring floods act like a firehose and just flush everything out of the canyon, but you're not looking for pay layers, you're under water sniping and your goal is to find the cracks which the gold has hung up in.
It's the kind of creek someone with a bigger dredge would bypass. Too hard, too steep and not enough width to even float one. This particular creek was buried by tailings in the 1800s. These tailings were over 40' deep in some places and although the old miners, and the Chinese, worked them they never saw the creek clean like I see it. They could dig to bedrock, but they didn't have it all available to them.
My experience with these rocky slot canyons is they'll hold pickers and nuggets, but not too much fine gold. The fine gold gets washed away with the tailings.
The payoff from a day on a small creek with a small dredge
In the above picture you can see the results of working this slot canyon. Even with a small dredge I still have a hard time finding enough water to run the pump. When you can find enough water you'll have a great afternoon picking the gold out of the cracks with a pair of tweezers. I often just use the nozzle like a vacuum cleaner to simply just clean the bedrock, then spend the time picking up the gold by hand.
These rugged canyons are hot, tough to get into and pretty wild. They take a lot of work. I've worked a lot of them and find I often have to find my own way in. There are rarely trails where you want to go and they tend to run a stretch, then you encounter a steep cliff or waterfall which is almost impossible to work around and you'll have to go back up to get down.
A backpack dredge can be a lot of work, and it's doubtful you'll ever do the one ounce days you hear about. The gold is spotty and hard to find, but for an adventure that results in some nice gold, you can't beat it.