COLD WATER DREDGING

"Dredging in the frigid waters of the Trinity River in Northern California."
 

Can you recall ever standing alongside an unheated swimming pool or just next to the water's edge on the beach, trying intently to muster the nerve to jump into the cold water? Perhaps you even tried to build up to the big leap by counting, "One, two, three.. .jump!" -- only to find yourself still standing at the edge of the water after the countdown and feeling like your body is not quite under your control. This can often be the case when you are dredging in cold water. The key to successful cold water  dredging is having the proper equipment -- particularly those items needed to keep your body from getting too cold and uncomfortable.


              "Cozy campsite set up for winter dredgers"

Wetsuits
Wetsuits are designed to allow water to get inside the suit. Your body heat then warms the water up, insulating you from the colder water outside the suit. In really cold water, the main problem with a wetsuit is that initial frigid shock that smacks your body as the cold water rushes into your suit when you first enter the water. This happens every time you re-enter the water after knocking out a plug-up in the jet tube or every time you take a break. This "cold water shock" has an accumulative affect on the body; and even the toughest people often find themselves going "one, two, three" on the bank and have trouble making their bodies jump back into the water.

Some wetsuit divers lessen the pain of cold water shock by having a hot tub of water on the bank. They pour the hot water into their suits just before re-entering the water to help bring up their body temperature. Hot water systems that provide a steady flow of hot water into a wetsuit are much better -- but we will address that topic in a minute.

There are different types of wetsuits, some which are designed especially for cold water use. Cold water wetsuits are generally made of thicker rubber, have few or no zippers, and almost always have the hood directly attached to the wetsuit top. There is also the "shortie," which is like a pullover wetsuit sleeveless T-shirt with or without a hood attached. A shortie can be worn underneath a regular wetsuit to create added warmth. In addition to the added thickness of rubber around your upper torso, a hooded-shortie prevents the cold water shock from running down your neck and back!

Dry-suits
For cold water dredging or diving, dry-suits are definitely a step above wetsuits. A dry-suit is designed to keep ALL of the water out. Basically, there are two different types of dry-suits available on the market: Those that use the rubber or nylon shell as insulation, and those that require additional insulation to be worn inside the suit. Both types work well, and it is a matter of individual preference as to which kind is best.

Dredging activity is extremely hard on any type of suit. There are many different models and makes of dry-suits available. Some are designed more for sport diving rather than dredging and hard work. Dry-suits generally are much more expensive than wetsuits. However, you cannot rightfully put a price on comfort and warmth when you are spending many hours underwater working for a living. If you are cold and uncomfortable, you will not get in as much dredging time; and you will not make as much gold (money). So, my advice is to spend the extra money on getting a quality dry-suit if you are going to buy one.

Dry-suits generally require more maintenance than wetsuits. Mainly, the seals at the extremities and the zipper must be properly maintained. Most dry-suits have zippers which should be coated with bees wax every several uses and sprayed with silicone each time the suit is used. The seals should be sprayed just before each use. This allows them to slip on more easily, and prevents unnecessary stretching. The zipper is the heart of a dry-suit and must be handled with care. You have to be careful not to get sand in it, and not to sit on it or rub it heavily while moving rocks around in the hole. Some dredgers glue a rubber flap over their dry-suit zippers to further protect them from dredging wear and tear. Most manufacturers stress having a second person zip it closed rather than doing it yourself, because often you cannot pull the zipper straight when it is behind you, as many dry-suit zippers are. If you damage the zipper, the suit is no good until you get the zipper replaced.

You will find that even the smallest puncture holes in a dry-suit need to be patched when diving or dredging in extremely cold water. Otherwise, you are constantly uncomfortable with cold water entering the suit from that location.

Hot Water Systems
As far as I'm concerned, if you are going to dredge extensively in cold water, a hot water system is definitely the way to go! Water is usually heated with a heat-exchanging device mounted to the dredge engine. The dredge pump is tapped to provide a water supply, which runs through the heat-exchanger, then through a steam trap, and then down through a hose to pour a constant volume of warm water into the dredger's wetsuit. Some dredgers are using propane continuous-demand hot water heaters, but most use heat exchangers mounted to their engine exhaust systems.

Hot water heat-exchangers are available on the market. They are also reasonably easy to build. Most homemade exchangers are built with a long length of copper tubing which is either wrapped around the existing exhaust system or is coiled inside a separate housing through which the engine's exhaust is channeled.

The key to a hot water system is to provide an ABUNDANCE of hot water. If you do not have plenty of hot water for all of the divers working on a system, then you will most likely end up pumping cooler water into each diver's suit-which can be worse than having a wetsuit with no hot water system. You can never have too much hot water -- because you do not necessarily have to use it all.

Most ordinary wetsuits are adequate as hot water suits -- particularly with the addition of a hooded shortie vest. Dry-suits normally do not make good hot water suits, unless they are modified. The seals prevent the hot water from exiting the suit. The excess water inside the suit then cools down and makes the diver cold. Removal of the seals on a dry-suit would probably make it a good hot water system -- but this seems a waste of money when a far less expensive wetsuit would accomplish the same purpose.

The main problem dredgers have had with hot water systems in the past is being scalded by extreme hot water or steam. This problem has been solved in recent years by adding a steam trap to the system. Some prefer to call this a "mixing container." On our larger systems, we generally use the Keene plastic air tank for this. On smaller systems, a mixing container can be made out of PVC plastic tubing. Basically, the mixing container's purpose is as a holding tank for water and steam. Then, if extreme hot water or steam is created in the system, it will have a chance to mix with the cooler water in the tank before being pumped down to the diver. The mixing container should be mounted vertically on your dredge with the input coming from the top, and the output to the diver being on the bottom of the container. This way, steam is never allowed to escape from the container. Some systems contain a low pressure relief valve at the top of the container to allow air and steam to release.

 The mixing container must be large enough to absorb a shot of extremely hot water, but not so large that it allows the water to cool down before it is pumped to the diver. The mixing container allows the diver to feel the rise in water temperature much more slowly, so that the hot water hose can be removed from the wetsuit before it gets uncomfortably hot! Sometimes, the water can be so hot coming out of a heat exchanger, that a special steam hose must be used.

If the water coming out of the heat exchanger is too hot to pump directly to a diver -- which is often the case -- a source of cold water can also be tapped from the pump and directed into the mixing tank. By regulating the amount of cold water, you can adjust the temperature of the water being pumped down to the diver. This also increases the volume of hot water available to all of the divers.

The hot water is generally pumped down to the diver through the same kind of hose being used for air line. The hot water line and air line are usually taped together to prevent tangling and additional underwater confusion. The hot water line can simply be slipped into your wetsuit down through the neck. Or, you can devise a splitter system which will direct some of the warm water to your chest, hood, each bootie, and each glove. This is the best way to do it. However, the splitter system can often be avoided simply by having a hot water system which provides so much volume, that the hot water is forced out into these same extremities.

If you do not have hot water directed to your hands, it is usually necessary to use three-finger wetsuit mittens when dredging in extremely cold water. Otherwise, your hands will tend to go numb from the cold. Three finger mittens are bulky; they prevent you from picking up larger cobbles with one hand,; and they generally slow you down. With a good source of hot water to the hands, you can often get by with a good set of rubber work gloves with the openings rubber-banded around your wrists to prevent cold water from entering.

It is necessary to warm up your dredge engine to normal operating speed for at least several minutes to properly set the temperature of the water directed to the divers from the mixing container. If a dredger stands on the deck of his or her dredge for a few minutes with hot water pouring into the suit, there is usually no shock at all when entering the cold water. As a matter of fact, it can be a pleasure to enter the cold water after you run your body temperature up to the uncomfortable hot stage.

A hot water system should be removed from the dredge when not being used, like during the warm summer months. Otherwise, the heat and vibration will tend to wear the heat-exchanger out unnecessarily. Also, even when not in use, if a hot water system is attached, water should be allowed to flow through it any time the engine is running. This will prevent unnecessary overheating of the heat-exchanger. If you are tapping your dredge pump for a supply of water, be sure the water output is either closed off or underwater when priming your pump. Otherwise, there may be an air leak which can prevent priming.

The nice thing about a hot water system is that it will supply a continuous feed of hot water into your suit. This way, your body's energy reserves are not being constantly used up to keep warm. As a result, you can be comfortable and get in more dredging time. However, you can also be so warm that your body doesn't want to work -- like being in a hot shower. The solution to this lies in how far down you zip your wetsuit jacket! Believe me, "too warm" is a much easier problem to solve underwater than "too cold."

A common question people ask is, "Should I get a hot water system, or a dry-suit?" The answer to this lies in what you intend to do. I suggest having both systems available, depending on your activity. For production dredging and sampling in extremely cold water, I would use a hot water system. For swimming across the river to stretch a rope, or for swimming down the river with mask and snorkel to look at the bottom in extremely cold water, I would recommend a dry-suit.

Other Things To Know About Cold Weather Dredging
If you are working in freezing temperatures above water, there are certain things that should be done on your dredge each day before knocking off. Your pump should have a drain plug tapped into the bottom. This way, you can drain the water at the end of each day to prevent your pump from freezing solid. It is not a bad idea to bring some hot water with you everyday in a thermos, because sometimes the pump will freeze a little even with the water drained. Be careful not to crack the pump housing by pouring too much scalding water directly over it when it is freezing cold.

Also, in freezing weather, the concentrates and water must be completely cleaned out of your recovery system at the end of each day. Otherwise, they will freeze solid and prevent the system from working until it thaws out the following day -- if it thaws!

Your concentrates from the day should be stored well underwater to prevent them from freezing on the bank. Your mask, hood and gloves should be brought back to camp each evening and kept warm. Otherwise, you have the misery of putting them on when they're ice cold -- unless you have a hot water system on your dredge.

Winter Dredging
Even if you are able to handle most of the cold water problems with the use of good equipment, another factor winter dredgers often have to deal with is higher and faster water. While the higher water will allow you to mine further up on the edges of the river, in many areas it will prevent you from mining out in the faster and deeper water areas-which may provide easy mining during the summer months. If, due to the faster, higher water, you are not able to get out and sample in certain sections of the river, you will not be able to run a full testing program on that section of river; and you will miss pay-streaks. So, it can also be more difficult to locate deposits during the faster and higher water months of the year.

On the other hand, if the river edges are paying, the winter months may be the only time they are available for dredging. The location of deposits are going to vary from one location to the next.

While wetsuits, hot water suits and dry-suits do make for good insulation underwater, they generally provide poor insulation to the cold air above water when you are wet. Therefore, it is good to have a warm winter jacket to wear over your diving suit while taking breaks on the surface.

If you are mining in extremely cold conditions, it really helps to have a warm and comfortable camp. A person can put up with some pretty cold and difficult conditions if he or she knows there is a warm shower and hot meal coming later that evening. There are few things worse than freezing all day and then going back to stay in a wet and cold camp!

How Tough Are You?
It takes a pretty tough person to dredge in extremely cold conditions. Even with the best equipment, there is still a substantial amount of cold water exposure on your hands and face. You spend quite a bit of time working on the dredge, tying off lines, swimming the river, cleaning up concentrates, making repairs, etc. This all adds up to exposure which can be painful or uncomfortable. Some people are gung-ho enough to dredge in extremely cold water on a short-term basis. Few people are willing to do it long-term.

We all have the potential to be tough enough to dredge in extremely cold water. What it always comes down to is whether or not we desire to be that tough! A lot of people think they are, and then realize they are not willing to be that tough! Talk is cheap! I was mining with several guys in 34o water one winter. One of the divers and I were sampling for a new deposit while the other two guys were actively dredging out a rich deposit we had already located. They were pulling several ounces of nugget-gold out each day, while we were knocking out sample holes. One day, we helped get the production operation started and then headed out to do our sampling. We soon realized we forgot our lunch, turned around and drove back to where our partners were dredging. We weren't gone five minutes, and they had already gotten out of the water and were in the truck with the heat turned on -- drinking hot coffee! These were tough guys; that water was cold!

A partner and I were dredging in Alaska in October when things started to freeze. We'd had a very good season, but I wanted to put more ounces into my bottle before returning home. Ice had already formed on the edges of the river, and my partner had been ready to leave weeks before. I was determined to spend one more week dredging, because the gold was good and I had plans for what I was going to do with it. One day, with a week to go, I could not make my body go underwater again. "One, two, three, go!" -- but my body refused. So, it just wasn't worth it, anymore! I walked over and tugged on my partner's air line and asked him if he was ready to go -- home, that is. We were on the road later that afternoon in a warm truck with the heat blasting. In that area of Alaska, three feet of snow fell that night!

There is a point where the body just takes over and says, "No!" And, this is probably the point where it is smart for you to listen. Good luck!  

"Eric Bosch and Dave McCracken displaying nuggets pulled while diving together."