by Dave McCracken

There are few things more disheartening in gold dredging than flipping your dredge upside down in the river! But if you spend some time in river dredge country, talking with experienced dredgers, you will find a good percentage of operators have experienced turning one or more dredges over at one time or another.

Dredges get turned over because of numerous different factors. One common factor  is not having  enough flotation under the dredge. Another is having a dredge design where the dredge is not wide enough. And another common problem is in dredge designs whereby the forward-most floats are not tapered to help deflect the river’s flow.

Often, a dredge which would float just fine in shallow, slack water might not last five minutes in the faster flow of a river.

Gold quite often deposits in the fast water sections of a river. Also, because of the  faster water, these areas often have less gravel and overburden covering the paystreaks.  Consequently, river dredgers often find  themselves dredging in the faster sections of gold bearing rivers—including white water rapids.

It is difficult enough to overcome the underwater problems associated with fast water dredging (knocking out plugups in the suction hose is particularly difficult). A dredger should not also have to worry about  his or her dredge  flipping over at  the same time. Therefore, a certain amount of dredge modification is usually necessary on any store-bought dredge before it is used under fast water conditions.

Normally, dredges are modified for fast water use by adding more flotation—sometimes to the sides, sometimes to the forward part of the dredge. Additional side flotation tends to make the dredge more stable from side to side and generally prevents the flipping problem. However, additional side flotation enormously increases the dredge’s water drag in the fast current. This puts a great deal of pressure on the tie-off lines, and it also makes it more difficult  to get  on and off  the dredge, or work around  the dredge (knocking out plugups)  without  getting swept down river.

It is usually a little more difficult to mount additional flotation as an extension of the front of your dredge, but we have found in our own operations that this is the better overall modification for several reasons. Reduced water drag is very important in swift water conditions. Also, the additional platform in front of the dredge comes in very handy in the operation. And, in the case of larger dredges, if you should ever  want to  mount a winch on the front of your dredge, the extra flotation and frame will already be in place.

Another very common reason for a dredge to flip over during operation is sluice box load up. This is  when rocks and gravel overwhelm the sluice box, start flowing over onto the decks, and eventually cause the dredge to list over to one side and flip. If you have a water flow problem with your recovery system, the problem must be corrected before you operate your dredge without someone at the surface to keep an eye on it. The key is to get enough water flow to keep all of the rocks and material moving through and out of the recovery system. We always make sure we have a little more flow than necessary, because  we  choose not   to have to hire a dredge tender to stay on deck.

Occasionally, even  with  a dredge which is set up  perfectly, just the right rock can lodge in  the sluice box and create an obstruction  which can be the cause of a sluice box load up, and if not caught in time, can flip the dredge over. This is why I say  many  experienced dredgers have had  the experience of  flipping  a dredge.

Tying off the dredge properly in swift water is also an important factor in preventing a flip-over. Obviously, you don’t want your dredge sitting broadside in a super fast current!  It is a matter of applying Murphy’s Law: you must observe the water flow and its effect on the dredge. If it looks chancey, come up with another plan.

When a dredge is flipped over, you generally lose all of the items that float. If the river is swift, these things are usually quite some  distance down river before you get  back up on  the bank and remove your dive gear. I’ll never forget the time we came up from a dive several years ago only to notice that  the five-inch dredge that was operating just down river was underwater and hanging by one pontoon. The guy was dredging when we started our dive, so we assumed he was still underwater, pinned by a rock, or knocked in the head by the dredge when it sank, or something...

However, it turned out that when the dredge flipped over, the dredger came to the surface and saw his other pontoon going downstream fast. He off-loaded his dive gear and swam through  three separate sets of rapids trying to catch the pontoon. He never did catch up with it. He showed back up at the dredge about 45 minutes later, exhausted and demoralized. We  already had dragged  the remainder of his gear out of the river. Several hours later, we located his pontoon about eight miles down river in a back eddy. It only took him several days to get his dredge running again. He installed extra flotation to prevent  further such incidents.

When a dredge is flipped over, after it is set right side up again, the water  needs to be completely removed from inside the engine and compressor. We usually do about half  a dozen oil changes, starting the engine for a  few seconds each time, to remove more water. As long as the oil keeps  turning milky, it is necessary to keep changing it. It is not as hard on an engine if it is not running when it goes underwater! Sometimes it is necessary to remove  the electrical components and blow them out with air or replace them altogether to get spark at the spark plug again.

The air compressor must  have all  water removed from inside, as well as the intake air filters and air lines. If the compressor was running when it was submerged, it will  be necessary to pull out the reed valves and make them straight again or replace them.

And of course, if you were dredging gold, some of that  will have been lost from your sluice box when it flipped over.  So, you will have to decide whether it is worth going  through your cobble and tailing piles to retrieve it.

One important dredge modification worth doing is to secure the sluice box to the frame or deck of your dredge so it will not flap free in the current should the dredge become flipped over. This prevents the box from being damaged or lost altogether. It also makes it a heck of a lot easier to get the dredge flipped back over.

At the end of last season, one of our local commercial dredgers was trying to winch his dredge up through a particularly difficult section of rapids on the Klamath River. He was trying to test a potentially  excellent hot spot that no one else has ventured into  yet. The spot  looked great, and many pounds of gold were recovered just up stream and just down stream. The spot is probably loaded!

He was moving the dredge alone, and just as he was almost around a large rock, the outside edge of his dredge took a dive and the dredge flipped-just like that. This is the way it usually is in fast water; when something  goes  wrong, it happens quickly and decisively. Usually, there is little time to do anything effective about it.

Besides all of the damage to a dredge, the loss of equipment, and the loss of production time, there is  also a large amount of embarrassment  which goes along with  having a dredge floating upside down in the river!

Once we found out about his problem, we put the word out, and experienced dredgers from the area converged on the site to help our friend. It is no small task to right an eight-inch dredge in fast water!

First we had him winch the dredge around the rock and pull it into slower moving water. This did not help the equipment much, because his sluice box was hanging in the current and dragging on the river bottom. His engine was also dragging the bottom.

Then we had several divers use chains and a come-along to lift the sluice box up and secure it to the deck. We used a boat to set up an electric winch on the far bank. We secured the two outside corners of the dredge to the bank on the close side of the river. We secured the winch cable to the opposite corners of the dredge and we flipped the dredge over. What a mess the dredge was! Since it was late fall anyway, this pretty much finished the dredger’s season.  Miners are a hardy bunch; he’ll be back next year, better and smarter than ever!

The moral of the story is that a little prevention goes a long way. Another thing: we are dealing with the forces of nature. We use our observation  and  judgment. We take some chances and we are not always right. Murphy lives! And, when he wins a battle, it doesn’t mean he has to win the war.  There is always another day and another opportunity.

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