How to HighBank
The high banker is one of my favorite pieces of equipment for prospecting. It's fairly light, very versatile, can process a lot of material fairly fast and is well suited to work in conjunction with the metal detector. With a high banker you have the ability to work right in the river, or you can work up on the hillside.
Before you leave the house you need to carefully choose your location. Be sure you have the ability to pack in the high banker, pump and power supply (fuel canister or battery) as well as your prospecting tools in and out. Keep in mind you’ll need to plan for enough time to pack everything into the site and back out before dark. The hike in to your target location will dictate how many hours you will be able to process material before you have to clean up and pack out. If you’re going solo you will most likely have to make a couple trips to get all of your equipment into the site, and back out again, so take that into account when selecting your work site.
The size of your high banker will dictate whether or not you will need someone to help pack it in. If you have a small 1 1/2" model like I do, you can pack everything in one trip. The downside is you can't process a large amount of gravel. A larger unit will allow you to process much more gravel, but the downside is you'll have to make several trips or you'll need a couple of people.
Once you’ve got everything packed into the work site, the first step is to find a suitable place to setup the high banker. Things you need to consider before you setup are as follows;
1. Distance to the area you want to prospect - The closer the high banker is set up to the work site, the better. Try to setup the high banker in an area that is as close to the source of the material as possible. This allows you to process much more gravel because you won't spend all your time packing material up or down stream. You want to set up as close to your work area as your pump (and the length of its hoses) will allow.
2. Water source - For proper operation of the high banker, you need to have a sufficient quantity of clean water. The water can be muddy, but no sand. Even a small amount of sand will wear out a pump’s internal components very quickly. When selecting a location to place the pump, you will need to choose a spot as close to the water line as possible. Pumps can push water much better than they can pull it. Pulling water uphill just a few feet can significantly reduce the pump’s efficiency. Even though you might have enough hose, the higher the pump is placed above the water line, the lower the head pressure, which will result in greatly reduced volumes of water in the header box. The less water pumping into the header box, the less volume of material you will be able to run through it. In my experience, if the pump is six feet above the water line you will lose as much as half of your flow. So keep the pump (and high banker) as close to the water as possible.
3. Distance from the pump to the box – Horizontal distance is not as important as the elevation. Pumps are rated by gallons per minute (GPM) and head pressure. Head pressure rating indicates the actual elevation or the height that it will pump uphill. If your pump is rated 35 GPM and a head pressure of 90; that means it will pump 35 gallons per minute at the pump discharge unrestricted, at the water line. At 90 feet in elevation above the pump, water will quit flowing altogether, but at 85 feet it would be just a dribble.
You also have to figure hose drag into the equation. As a rule of thumb, I figure for every 10 feet of horizontal hose, you lose one unit of head pressure. With the above mentioned pump set up 30 feet away from your high banker and 15 feet below the header box, you would have approximately 24 gallons per minute flowing into your header box. All high bankers have a minimum gallons per minute rating that they require to operate correctly. When the setting up your high banker this is one of the most important variables because if your high banker is not operating efficiently you could be washing the gold right out the back of your box.
4. Discharge from the box - When selecting a location for the high banker, you also have to make sure that there is a place for the tailings to go. You can move a lot more gravel if you only have to shovel it once. Make sure there is plenty of area in front of the high banker for the tailings to accumulate. You also need space behind the header box for the large, classified gravels to pile up when they fall out of the wash box.
5. Tread lightly - If possible, try to locate your high banker in a spot that has a natural settling pond or an area that can easily be converted into one. If you have a primary settling pond that flows into a secondary pond, you can pump out of the secondary pond and recirculate the same water so that you’re recycling the same muddy water. Always strive to keep from mudding out the river downstream and try to respect the other people who may be enjoying the river below you.
Once you have satisfied the above requirements and have selected a good setup location you can set up the high banker.
Setting Up The Box
When setting up the high banker, make sure that it is level from side-to-side. A small bubble level attached to the hopper works great. You need to make sure when the water is flowing through the box that it is flowing evenly across the riffles. Too much water on one side can create a high pressure channel that can blow gold right out of the box.
The angle of the box (front to back) is a balancing act between keeping the slope shallow enough to keep the fine gold, and steep enough to keep the riffles from plugging. I begin by setting my box up on a roughly 30 degree angle. Then I fire up the pump and run some gravel through the box. Once the water has cleared up enough for you to see the riffles, take a look at the carpet between the riffles. If you are unable to see the carpet, the box is too flat. If you can see all the carpet between the riffles, the box is to steep. I try to set my box up so that the top third of the carpet always has gravel on it.
Processing the Gravel
Now that the high banker is setup and ready to start processing material, you can start feeding gravel into it. It's best to feed the gravel at a constant rate. Try not to overload the hopper/header box. If you put too much gravel into the hopper at one time you will overload the grizzly and lose some gravel out the back of the box before it has a chance to wash off all the gold. You need to make sure the lower section of the grizzly only has large clean rocks passing out the back of it. Make sure that all the rocks are washed clean and any clumps of gravel are broken up. Keep an eye on the rocks that are coming off of your grizzly, you don't want to lose any large nuggets. If the area you are working has a history of producing large nuggets, it's a good practice to go over the tailings with a metal detector when you're done to make sure you haven’t missed any large nuggets or quartz with gold seams inside.
One of the great things about the high banker is the ease of cleanup. You can stop at any time and check your box for gold. When shutting down, the one thing you want to be sure of is turning the water on and off slowly. If the flow into the box starts or stops too abruptly it could dislodge your gold from behind the riffles and wash it out the back of the box.
To clean your concentrates out of the high banker you need a container large enough to capture the material from the box. Try to find a bucket or container that is wider than the end of the box so that you don’t lose anything that may fall out of the box during cleanout. Put the container on the discharge end of the box after lowering your pump down to an idle. Make sure your container can't move and is able to capture all the concentrate as well as the carpet. Remove the perforated plate at the top of the box. Then go ahead and unlatched the riffles to raise them up. This will allow your carpet and most of the concentrates to slide into the container. Don’t worry if the bucket or container begins overflowing with water during cleanout, the concentrates (and gold) will stay at the bottom of the container.
With the pump at an idle you should have enough water to flush the box clean so that everything is flushed into the container. Be sure to rinse the riffles off. Once all of the concentrates and carpet have been flushed into the container, go ahead and remove the container from the front of the box. All you need to do now is wash out the carpet inside the container so that all of the concentrates and gold fall into the bottom of the container, make sure to scrub carpet really well and try to do all of the scrubbing under the water line. Once the carpet is clean and you have cleaned off the riffles, you can now reassemble the box .
Panning the Concentrates
Now you are ready to pan out your concentrates. Pour the concentrates from the clean out container into your gold pan. Make sure to get every last drop of material out of the container because more often than not, the last grams of concentrate will have a the highest volume of very fine gold so make sure to splash some water up into the container to clean out every single bit of material.
Panning out the concentrates can literally be done anywhere with a standing body of water so if the sun is setting you should probably get packed up and get back to your vehicle before night closes in. You can even pan them out at home in a large bin or tote so you can pan the concentrates twice to make sure you don’t lose anything. It takes longer to pan out concentrates than a regular pan of gravel due to the high density of the black sands and gold, so don’t gamble with your safety at the end of a long day of hard work. Get to safety and then take your time panning out the concentrates. It is a good idea to save your black sands. I will discuses what to do when you have accumulated enough to make working them worth while in a later article.