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Hong Kong Disneyland
Page 8 of 10

Stage 1 of the Penny's Bay land reclamation project  is now over 80% complete.  Commissioned by the Hong Kong Civil Engineering Department, Hong Kong based Scott Wilson Ltd. is the main contractor and the Dutch company HAM Group and Hong Kong Construction Holdings are performing the actual dredging work.   Stage 1 will ultimately result in the land for, among other things, a water recreation area, an arboretum, a ferry terminal, a train station, retail shops, restaurants, one thousand or so hotel rooms, and last but not least, a Disneyland.

To get a better idea of what we're looking at now, let's take a brief look back at the steps of the process we missed.  This is a ground-breaking bit of ground making for Hong Kong, or anywhere for that matter.  Considering  what's involved in this reclamation, the accelerated timetable of the project is unprecedented.  Work began at the site in May of 2000 and the creation of just short of 500 acres is on schedule to be completed in December of this year.  In that time, a total of more than 2 billion cubic feet of earth will be moved to the site.  The area will still be called Penny's Bay, but the bay will be gone.

As is the unfortunate necessity with virtually all of Hong Kong's reclamation projects, before the land could be built up, the floor of  Penny's Bay had to be dredged down.  The soft sediment of the bay floor was removed down to the hard clay layer below it in order give this future piece of real estate a firm footing.  That sediment was more than 100 feet think in some areas and not much less than that everywhere else.   In all, nearly 1.5 billion cubic feet of mud was removed.

This was done using eleven Trailer Suction Hopper Dredgers (TSHD), a Cutter Suction Dredger, a Grab Dredger, and a Water Injection Dredger.

TSHD, often called "hoppers", are self-propelled ships which pick up material using their slow forward momentum  to drag one or two large scoops at the end of suction pipes (like giant vacuum cleaners) along the marine mud.  Many of the TSHD used at Penny's Bay were the largest in the world, with the ability to pick up material from a depth of up to 250 feet.

Due to the tight schedule, a system was devised in which smaller TSHD would cut  channels through areas too shallow for the jumbos (as the big ships are called).  Then the jumbos, with their high capacity scoops and holds, could be employed in areas where they would have otherwise run aground.

Side note- Remember that ariel shot of Hong Kong International Airport?  The scale of its land reclamation revolutionized the industry.  It's called the "dredging contract of the 20th century" because up it was the largest reclamation project of the century and, until recently, of all time. (It has now been surpassed by Singapore's Jurong Island project.)  It was the Hong Kong International Airport reclamation which  necessitated the development of the jumbo TSHD, in the first place.

When a TSHD had filled its hold at Penny's Bay, it headed out to sea to one of the "allocated dumping areas".  To insure that there was no cheating, a tamper proof "black box? system, linked to a GPS unit, recorded the location of the ship when it opened its giant bottom doors and dumped its hold full of mud.

Beside their ability to dredge up especially large amounts of material, the jumbo TSHD also had the ability to travel out to the open sea dumping areas in conditions that were often too rough for the smaller ships to safely navigate. Considering the project's tight schedule, this was especially advantageous.

For use in shallower water, another ship, a smaller one called a Cutter Suction Dredger, was also used.  This ship stays in place and uses a large cutter head to bore down into the submarine surface so its suction device can vacuum up the loose material.  Even solid rock isn't a problem for this ship.

Also used in shallower areas, a vessel called a Water Injection Dredger, was employed.  It was the first time this relatively new technology was used in Hong Kong.  This dredger uses high power water jets, submerged to the floor of the bay at the end a boom.  The jets lift material from the bottom and send it in a dense current to a predetermined location. Pretty high-tech stuff.

The idea behind the Grab Dredger isn't nearly so modern.  Actually the technique they employ has been used for well over 100 years. A crane onboard the ship lowers a scoop, or "grab", down to the sea floor on chains and hauls up a load of dirt.  The advantage of this ship is that the only thing that limits how deep it can dredge is the length of its chains.

Although fill work was undertaken in some areas while silt removal was still occurring in others, by November of 2001 the silt was gone and it was time to turn full attention to making land.  That land would rise above the water an average height of approximately 20 feet.  Again, up to 100 feet of material had been removed to get down to firm clay, and the average water depth was roughly 16 feet before the silt removal...  The amount of earth that needed to be moved to Penny's Bay was similar in size to a 130 foot tall hill with an area of five Disneylands.

The big TSHD were the star of the show in this phase of the operation, as well.  This time they were used in reverse fashion.

Unlike the sedimentary mud of Penny's Bay, the sand from the shipping channels of Hong Hong is acceptable fill material. The TSHDs would pick up that sand and dump it near the site.  From there, a Cutter Suction Dredger, would again pick up the sand and either transport the material the rest of the way to the shallow waters of the site or pump it there through a large floating pipeline, run from the ship to the site. (Clearing the shipping channels and creating new land at the same time... How elegant, in a massive engineering project sort of way.)  Do to the massive amount of sand needed, it was also taken from the near-by seabeds of mainland China.

But the TSHD have another interesting time saving ability.  Called "rainbowing", the ships' immensely powerful pumps can shoot focused arches of material directly from their holds, through nozzles at their bow, a distance of nearly 250 feet to the reclamation site.   Due to environmental concerns over the uncontrolled spread of material, rainbowed fill was only aimed at areas which were already above the water line, or within containment barriers.

Speaking of containment, an important technique which was employed extensively at Penny's Bay is called "Containment Bunding".  First an artificial lagoon or a fully enclosed pond  is created by pumping materiel by pipeline to the location.  Then it's filled through the use of rainbowing and additional pipeline pumping.

Well, there's the skinny of how the land we're looking at came to be, so now back to...

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Again, we're at over 80% complete.

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But the percentage of the total soil at the site is well over that. The last of it is being brought in by these mud barges.

If you look closely at this picture, slightly above center and to the left, you'll see the top of what could be a smaller TSHD, but looks more like the project's lone Water Injection Dredger.

In this picture and the next, the site's 2.5 mile long "silt curtain" can be seen just off the shoreline.

Silt curtains are sheets of synthetic material which are anchored to the bay floor using concrete blocks and are held up at the surface by tubular floating units. Their intended purpose is to reduce the spread of silt beyond the site.

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Notice the barge being tugged in to the right of this picture. These "little" guys are taking on all they can handle.
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But what's this forest of metal rising up out of the center of the reclamation?

No, it's not vertical construction. That's still about five months away.

Those cranes are holding Vibroflot.

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Vibroflot are large cylindrical devices used to compact the soil.
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A Vibroflot is sunk down through the sand to a depth of 50 to 100 feet, depending on how much the sand needs to be compacted. It gets there by shooting high powered jets of water out of its downward pointing end, loosening the sand below it and sinking the heavy device down until it reaches its intended depth. Once there, it releases jets of water out of its sides, causing the sand to pack tightly around it. When that process is complete, its tome for this odd machine to really get to work.

Using a powerful electric motor, it begins to vibrate with a horizontal force of over 100,000 pounds. It is then slowly, step by step, lifted out of the hole.

This process is repeated and repeated and repeated. Ultimately it results in soil of a density that would have taken years to occur naturally.

The Vibroflot sounds like pretty fancy technology, doesn't it? Well, it was developed in Germany over 70 years ago. (Those Germans!)

"Vertical drains" also play a key role in accelerating the settling of the site. This process involves burying pipes in the ground vertically, with their top ends even with the surface. A synthetic sheet of material which is layered in such a way as to allow water to flow sideways through it is put down over the area, and then it is "surcharged".

Surcharging involves simply piling up dirt that is of a greater weight than the structure that will eventually replace it, and then letting it sit. The weight forces water in the fill up through the pipes and it drains out through the sides of the synthetic sheet. This has the effect of removing water from the ground at a rate of up to ten time fast than it would occur naturally.

Four months is the standard minimum period of surcharging at the Penny's Bay site.

Consequently, some of the mounds that can be seen in these pictures give an indication of where structures will be located.

All this work is necessary, but, in the case of this site, there's absolutely no room for movement (so to speak). The Walt Disney Company has it clearly spelled out in writing. During negotiations they insisted on and received a "zero settlement" promise from the SAR. That's a tough one to keep... but every measure is being taken in an attempt to do so.

 

 

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