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Author Topic: Drain the lagoon?  (Read 10771 times)

Scott C. Mitchell

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Drain the lagoon?
« on: September 20, 2017, 02:37:37 PM »

After being a participant on the site for many years, perhaps I'm allowed one crazy idea.  Here it is: drain the lagoon.  If Earhart-related artifacts are thought to have been swept into the lagoon, then searching for them on a dry seabed would be easier than mucking around in a silt-clouded lagoon.  This is what Ameliapedia says about the lagoon:   "The lagoon at Niku is approximately 3 miles long and a mile wide at its widest point. There are two channels that connect the lagoon with the ocean both on the southwestern side of the island, Tatiman Passage (pronounced Taziman) to the north, and Baureke Passage to the south. Baureke passage is on occasion blocked and dry as we found during the Niku IIII expedition in 2001 (and seen in the satellite photo below), but was flowing in 2007 when NIku V visited the island.
The lagoon is generally fairly shallow with an average depth of 15 ft, and a maximum depth of no more than 20 feet."

If Baureke Passage is occasionally dry, that would leave Tatiman Passage as the only entrance to be blocked.  As the drainage mechanism, my mind turns to a series of Archimedes screws along the shore, driven by windpower.  As to the dam construction at the passage, I would leave that to the creative imagination of civil engineers.  Means to protect the environment in general and the flora & fauna of the lagoon would have to be devised.  A scaled down version of this concept might be to drain the lagoon in sections, using cofferdams.  Permissions would have to be petitioned for an environmental change of this scale. 

Two engineering feats inspire my anything-is-possible attitude.   My grandfather was a civil engineer on the Panama Canal.  He told me how the canal seemed impossible because of a cascading river that flowed right through the Panamanian isthmus.  The solution was to dam the river, which provided a reservoir of water that now powers the locks - an elegant solution.  The second are the great towed jetties used in WWII to provide logistical support at the beachheads of the Allies.  With modern composite lightweight materials and the ability to do computer modeling, it would be interesting to see what can be devised on a shoestring budget and with no expectation of lasting construction.

We will pause here for the first round of laughter to subside.

Scott Mitchell

Martin X. Moleski, SJ

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Re: Drain the lagoon?
« Reply #1 on: September 20, 2017, 07:28:03 PM »

After being a participant on the site for many years, perhaps I'm allowed one crazy idea. 

It would be nice if exposure to the site only generated only one crazy idea per person.   ::)

Here it is: drain the lagoon.

I love your challenge to think creatively.  It is definitely a brand new idea, at least in terms of what I have seen on the website and in the Forum.  Well done! 

But the lagoon is a nursery for sharks.  And pouring miles of water out of the lagoon into the neighborhood of the reef would probably raise all kinds of red flags for those who know how beautiful the underwater environment is.  No matter how carefully you worked, the water from the lagoon would have to be silty and, possibly, of a different salinity from the waters around the reef.

A small cofferdam around a site that had lots of evidence of metal would be less expensive and might possibly get through environmental review.  Maybe.   :-\

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Brian Tannahill

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Re: Drain the lagoon?
« Reply #2 on: September 20, 2017, 09:45:57 PM »

I also loved this idea!  I don't think it's feasible but sometimes an impractical idea inspires another idea that is workable.

The time-on-station and the materials needed to drain and then thoroughly search the lagoon would be prohibitively expensive, in my uninformed opinion.  We can reconsider when we locate a few multi-million dollar donors.

But, as Marty said, cofferdams around small areas should be doable.  (Since I know nothing about civil engineering, I don't see any problem with it.)

This is probably all fantasy, but since we haven't had a lot to talk about lately I'm going play with the idea.

Let's flesh this out.  What materials do we need to build a cofferdam 20 feet high?  We have to transport it to Niku, so what does this weigh and how much space does it take up?  Where do we get the materials?  Can we purchase them "locally" in Fiji, or Hawaii, or will they need to be sent over from CONUS?

After writing that last paragraph I spent ten seconds with Google and found this.  You know, this might not be so crazy.

Scott had an idea about draining the entire lagoon with an Archimaedean screw, but I'm thinking of ordinary pumps to drain the water inside the cofferdam.  Pumps are powered by electricity, which means we need generators, so we need gasoline.  I reviewed the specifications for Nai'a and I don't think the operators envisioned using her as a tanker, so we'll probably want to store several dozen 5-gallon gas cans in one of the staterooms, and we'll just have people carry them across the reef and a mile or so up the beach to wherever we're working.

Or we could just use a siphon and a bunch of buckets.

How do we identify the promising areas that we want to inspect?

How large an area can we dam off, and how long will it take to drain an area?

Once an area is drained, what kind of surface do we have?  Would it be solid?  Soft mud?  Quicksand?  I've heard Ric has stories about quicksand.

Do we need to follow archaeological protocols to explore the exposed surface?  Or just grab shovels and go for it?

There are lots of other questions, but I'll stop here.  This could be done -- that is, it's physically possible.  Feasibility is another issue, and we have to get approval, but as I said, I'm considering this a fantasy.  How does that quote go -- "I have abandoned my search for truth, and am now looking for a good fantasy".

Scott C. Mitchell

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Re: Drain the lagoon?
« Reply #3 on: September 21, 2017, 10:43:04 AM »

I agree with Martin's preference with the cofferdam over a complete draining of the lagoon,  All sorts of problems with a complete drain  would have to be anticipated and resolved, like the salinity of the water being pumped into fragile offshore environments.
And using a pump and generator probably would be the way to go.  The concept of using a battery of Archimedes screws powered by the wind may not be practical compared to modern technology.

The idea of using a cofferdam for underwater exploration is hardly original.  Here in Texas, the wreck of the French explorer La Salle's supply ship La Belle was found offshore in Matagorda Bay.  The use of a cofferdam to excavate the wreck in about 30 feet of water was a spectacular success.  A cofferdam in the lagoon would not be as susceptible to the storms and swells of the open ocean.  For the Lagoon Cofferdam, it could be a box of about 20 feet X 60 feet, transported in panels that could be assembled on site.  The actual dimensions would be based on the topography of the lagoon slope.  The box could have inflatable bags on the sides, so it could be easily pushed and towed into position, then the bags deflated and the box allowed to sink to the bottom with the rim still above water.  Pumping out would commence (and probably wouldn't stop for the inevitable leaks).  When that zone is excavated, the bags could be refilled with compressed air, the ring would float, and it could be pushed to another position.   Martin's idea of looking for locations with suspected high metal content makes perfect sense.

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