Alternative Fuel Systems on TSHD Samuel de Champlain

Trailing Suction Hopper Dredge ‘Samuel de Champlain’

The Trailing Suction Hopper Dredge ‘Samuel de Champlain’ has been in the news. She will get a mid-life upgrade with new engines running on LNG1,2. This is good news for the environment as the vessel will have lower emissions of greenhouse gasses. And it is good news for Damen as we see this old lady back again. Already more than ten years ago, we had her also as a customer concerning a gas related retrofit3. That time I was involved in the development and commissioning of that particular system.

Degassing installation on board ‘Samuel de Champlain’

The most peculiar feature of this degassing installation on this ship was that it had to work on the submerged dredge pump. Even as the pump had plenty of NPSH available at that depth, the gas content at certain locations was able to choke the pump. The submerged location posed special requirements on the operational pressures and the dimension of the sludge tank.

Off course, the most simple solution would be to have some gas ejectors on the drag arm and just blow the foam from the degassing scoop overboard altogether. However, that mixture contains (possibly contaminated) silt also, which is unscrupulously released to the environment. The Damen system has some extra components, such as a sludge tank, where the foam is separated in silt and gas. And a separation tank, where the gas is extracted from the clean water. Gas is than released to the atmosphere and the water returned to sea. As the sludge from the sludge tank is injected back to the slurry pipes, it ends up in the hopper and is disposed of with the rest of the silt.

Diagram of a typical Damen degassing system

An often heard complaint is, that the gas is still released to the atmosphere. That is right, but with the other systems it is released in the sea and comes in the atmosphere in bubbles. On top of that, one could also look at the natural process of gas formation4. If it is not dredged the gas would eventually get released by nature itself. With the autumn and winter storms, the bottom gets disturbed enough to release the contained gasses and enter the atmosphere naturally. The dredge only releases the gasses in a concentrated form, where nature does this gradually.

Another question I was asked regularly (and fitting to the opening article): ‘Can we capture the gas to drive the engines?’ That in itself is a good question, as it disposes the gasses beneficially. The degassing installation on board is capable of removing 800 kg/h of gasses from the mixture. If it were LNG, it would provide about a quarter of the energy requirements of this vessel. But, it is not LNG, only part is combustible methane, the rest doesn’t burn or forms sulphuric acid. Yuk! Certainly not something to pour in your expensive engine. It might be easier to just flare the whole mixture4. At least the potent greenhouse gas methane is converted to the less severe carbon dioxide. Any thought anyone?

It was fun to contemplate on this during the return trip from the commissioning. It was already running late (which commissioning doesn’t?) and we were 20 miles out at sea. The captain didn’t want to stop the dredge and he put us in the dingy to return to port. With calm seas and a fast RIB, this was a thrill ride to remember.

Return trip after a job well done


  1. TSHD Samuel De Champlain to be converted to LNG in a European firs; Damen Magazine
  2. Damen Wins Contract for First European TSHD LNG/MGO Conversion; DredgingToday
  3. Retrofit Degassing Lifts Dredger Efficiency; Maritime Journal
  4. Gas flare; Wikipedia

See also

A Reservoir of Dredging Opportunities

Glendo Reservoir in Glendo State Park, Wyoming, USA (Credit: Wikipedia)

OK, sorry, above picture was not taken by us, but could have been in our annual picture book. At this place we had only one mission and that was to watch the 2017 solar eclipse. It took more, than two years of preparation and we were rewarded. With great care we inspected the statistics on cloud cover maps and local geography for the best place to watch this event. The Rocky Mountains in the west block the clouds, the dry planes on the east have a clear horizon, combined with a favourable timing, we selected Glendo State Park, Wyoming, USA to pitch our camp and watch.

Eclipse party at Glendo State Park, Wyoming, USA

We pitched our tents at one of the campsites in the park. This time, the soil had a much higher SPT than at Bad Bear Campground. Although at the top of a hill overlooking the reservoir, the trees prevented to take a good picture of the lake. Hence the Wikipedia picture. The lake was built for power generation, irrigation and recreation. The dam was constructed between 1954 and 1958 as a zoned earth fill structure. Projected lifespan was for a 100 year accumulation. Mmh, clean greenhouse gas free hydroelectricity was eternal, wasn’t it? Well, not so much.1 The dam blocks of some part of the watershed and this will always be a disruption of the natural sediment transport.

General modes of siltation at the usual location in a reservoir

Due to the creation of this artificial lake, there are several areas that have specific siltation problems. At the upper end of the lake, where the river slowly stalls, the bigger particles will settle in the immediate vicinity of the entrance. Smaller, lighter particles will be carried longer, even all the way to the dam. Usually there is a facility near the dam to prevent (re)suspended particles to enter the gates. A common solution is to have a silt trap, a deeper area in front of the dam. The suspended solids behave like a denser fluid and tend to sink in the lower areas and the cleaner, lighter water is skimmed away for sluicing through the dam. Without any action, the reservoir fills up eventually. By now, a lot of reservoirs are already not performing anymore to their specifications.

Total capacity of all reclamation reservoirs over time (Credit: US Bureau of Reclamation)

There are several options to perform reservoir maintenance.2 The most spectacular method is flushing. The reservoir is drained quickly, over a special by pass channel.3 The idea is, that as the water table is lowered, the cross section of the water body decreases and the velocity increases. Hopefully, the current increases enough to pick up material and by pass it along the dam.

Flushing of a reservoir dam (Credit: US Army Corps of Engineers)

As a right minded dredger, I am always a bit disappointed that there is no dredge present to solve the sedimentation problem in a more sophisticated way. In a way, I have some experience in actually building a power dam dredge. But that will be another historical narrative.

Let me conclude this series of reviews from our annual picture album with the one single picture that was the cause and culmination of our special holiday in the United States: the Great American Eclipse.

2017 Solar Eclipse at Glendo State Park, Wyoming


  1. Hydroelectric power’s dirty secret revealed, New scientist
  2. Formulating Guidelines for Reservoir Sustainability, USBR
  3. Annual sediment flushing exercise scheduled at Cherry Creek Reservoir, USACE

See also


The Origin of Clay, When Dredging Becomes Sticky

Clay forming Fountain Paint Pot, Yellowstone National Park, Wyoming, USA

This mud pot gave me a revelation on the origin of clay. I was aware, that clay is a completely different mineral than sand. For starters, sand is based on silicon dioxide and clay on some complex aluminium compound. Sand is mechanically worn down rock, usually quartz. But I never got around to understand where clay came from. Here, a small sign at the side of the mud pot revealed a complete different mechanism: chemical alteration of rock by hydrothermal action.

Sign at the Fountain Paint Pot, Yellowstone National Park, USA

Now, it became clear to me, how all the funny properties of clay arise from this generating process. Unlike weathered sand, clay grains are nice symmetric hexagonal crystals. And these crystals grow under changing conditions for temperature, chemistry and pressure. Exactly the environment in these mud pots. The sulphuric acid leaches the chemicals from the rock matrix, in Yellowstone usually Feldspar, the water bubbles to higher levels, transporting and mixing the ions and cooling down along the way. Just like salt crystallises in brine, the clay shakes out like tiny particles, about 2µm. These flakes coalesce into a new sediment: clay1.

Hexagonal sheets of a clay mineral (kaolinite) (SEM image, ×1340 magnification) (Credit: Wikipedia)

The specific mineral of clay, e.g. kaolinite, is a hydrated oxide. And the hydrate allows the charge of these semi-ions to be moved around. As same charges repel and drive themselves apart, the edges and corners of the little crystal will become negatively charged. Now, there are a bunch of discs that have a preference to stick to each other like masonry. Between the discs, there is not much space making the water content low. But, one can add water and the sediment will swell, but there will still be contact between the ends and centres of the disc. Even with this spongy structure, there is still some consistency. It behaves like a plastic substance, you can deform it and it will stay like that.

The plasticity of clay can be measured by rolling the clay in a sausage and measure the water content at which it crumbles. That is a lower limit. An upper limit of plasticity has to be determined by testing the effect of shaking a bowl with clay. Both methods are described2 in ASTM D4318. The difference of water content between the lower plastic limit and the higher liquid limit is the plasticity index. The higher the plasticity index, the more difficult it is to cut this material. It is like cutting warm butter, material is moved around, but you are not severing chunks of the bulk.

Synthesis of clay and the relevant properties for dredging

Whenever you hear dredge people boast about difficulties in dredging, usually it involves clay also. The cutting itself, it is very hard to cut the material out of the sediment. When the chunks come loose, the chunks will stick to the cutter head and the will get completely smeared over and no new material can be cut or sucked up. After that, the clay chunks will tumble down the discharge pipeline. Under certain conditions, the chunks will snowball and form bigger balls. Finally, the clay gets at the reclamation area and will cause problems with the drainage. Remember, fines clog the pores between the grains and prevent the flow of drain water. And clay particles are very fine and they glue the bigger grains together.

Knowing the properties of clay, it is obvious, that normal cutting tools for sand dredging, do not work in a clay environment. Based on the special properties of clay, we once developed a special clay tool for a specific project3. And it worked4. It was fun. And it will be another story.

DOP pumps with special clay cutter head at the ‘Markthallen’ project in Rotterdam


  1. Metasomatism, Wikipedia
  2. Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils, ASTM D4318
  3. DOP150 creates underground car park,
  4. Prestigieus project Markthal Rotterdam vraagt om innovatieve oplossingen, Autograaf 42-p.8, MvO Groep

See also