Bering Sea Gold Dredging

Over the past two years we have been inundated with Emails and calls concerning dredging in the Bering Sea. With the obvious media attention and current economic situation, Alaska is a hard place to ignore especially if you are a displaced California miner. The Bering Sea beach placers can be a lucrative prospect with the biggest downside being an average 30 day season due to weather and ocean conditions. We have compiled our field notes, experience and equipment design from the past 40 years of Alaskan dredging to aid you. I’m going to make the assumption that you are a competent dredger and that you have a working knowledge of dredges. Outfitting a dredging operation for Alaska can be a daunting task. You most likely have studied numerous geologic reports, read everything online that you could find and of course watched the television reality shows. But the question remains. What do I need to be successful? Before we get into the fine details you should ask yourself a few questions:

 1) Can I risk the time and capital of a project of this scope?
 2) Am I physically and mentally healthy to endure the extremely hard and tedious labor?
 3) Do I have the tenacity and perseverance to continue with the project even if the mineral find is small?
 4) Last but most important, am I undertaking this venture as a mining operation or a get rich quick scheme?

If you answered “yes” to the above mentioned questions than you have made the rational decision to go ahead a form a realistic mining plan. To fully try and help you, I must approach the exploration plan as if it was researched by our company. Notice I used the term “exploration plan” instead of mining plan. The biggest mistake we see are individuals who choose to stay in one spot hoping to eventually hit the pay streak.  In the Bering Sea if you don’t see gold after running one ton of material move on to the next location. This venture is a business, therefore run it like a business. Common business sense while dredging dictates that every 12” of overburden you take off you lose $100 per hour in doing so. Four feet of sand overburden equals $400 loss. Dredging the Alaskan offshore placer deposits is a straight forward concept. The more gravel you process in the right area, the more gold you will produce. When planning your operation the key component is logistics, logistics, logistics. Our dredging operations take us to some of the most remote regions of Africa and the Amazon. Logistics can be a nightmare and must be planned for. Nome and the Alaskan frontier are no different. If you are prepared to invest a substantial amount of money in your project than it makes sense to fly to Nome and observe a dredging season before you place a single dredge in the water. You should diligently research the price of diesel, living costs including food, transport and berthing fees.  Ask questions of the seasoned miners and pay close attention to how many working weather days occur.  

Dredge
The dredge component of your operation can either be the most daunting challenge or the easiest. In our opinion, when designing or buying a dredge keep it simple. Electronics, motors, gadgets and lack of spares are the major factors in dredge shutdown. If you are using an open platform dredge without an enclosure keep your electronics to a minimum. The smallest hose we would use is an 8” diameter hose with a 10” being the norm. In the ocean we are not so much concerned about the rock size but the suction lift of the hose. The 8-10” hose readily sucks the gravel with less of the need for using a pry bar, compared to the smaller 6” hose. The downside to using bigger hoses is the restriction in flex. Effort is needed to move the bigger hoses underwater but can be helped by attaching your hose to floating buoys or by putting your hose through inflated inner tubes to lessen the weight

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Recovery
Although it is the standard recovery system for Nome, sluices are not the choice for optimum recovery. If you can imagine for a moment the typical gold recovery circuit and the ideal recovery conditions it would be similar to a land based recovery model. As the material enters into the scrubber it is effectively cleaned and sized. The concept is to have your cleaned fractions go to the proper recovery system. For instance you would not want your ½ inch material mixed with your ⅛ inch material going into your mineral jigs, sluices or centrifuge. The different sized material would collide and interrupt the settling pattern of the gold we are trying for. Yet, this is precisely the methods currently used. The ideal recovery solution at sea would be for the material to:

• slow down after exit from the taper
• settle and classify itself
• transfer to individual recovery zones

The concept might sound impossible especially with the rolling sea conditions, absence of mineral jigs or centrifuges and a small dredge platform but fortunately we have implemented these basic recovery techniques and so far are they working well. Essentially how the system works is as the material exits the taper it should flow over a static double deck screener. We use a top screen of ¼ inch and a bottom screen of ⅛ inch. The screener is set an angle so the oversize material flows out with gravity.  Each screen has a collection chute so the fractions go to separate holding bins. At this point the dredger has a choice to either collect and save the fines to process on land or to process on deck. On deck processing is the preferred method since most dredgers don’t have the floatation capacity and space to hold two tons of material. Since the fines are small we have a small submersible slurry pump in each bin that conveys the material to the proper recovery unit. Depending on the size of your dredge the recovery units can be volume controlled sluices or for us we use a system of small lidded jigs and a centrifuge. By all means our dredges are not starter units. I am currently designing a similar on-deck dredge processing unit for South America so I will hopefully have a few pictures of the fabrication process to share.
 
Wyatt Yeager MSc
wyattyeager@gmail.com