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Author Topic: The Lagoon as a Collection Basin  (Read 19242 times)

Andrew M McKenna

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Re: The Lagoon as a Collection Basin
« Reply #15 on: June 22, 2012, 09:48:18 AM »

Bill (I assume it is Bill Magnus, yes?)

I'll see if I can find out what is available.

Andrew
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Walt Holm

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Re: The Lagoon as a Collection Basin
« Reply #16 on: June 29, 2012, 12:55:02 PM »

Hi All:

   I haven't posted to the forum in the past, but since this is a topic I've been so heavily involved in, I figured I should chime in here.

   As the original poster noted, the lagoon has always been a tantalizing place to look, because if Electra debris has washed into it, it won't ever wash back out again.  The lagoon is very shallow and so is searchable with relatively small and low-cost equipment, as opposed to the big (and expensive) gear that's on its way to Niku right now.

   There have been at least 4 previous searches in the lagoon:

- In 1997 (IIRC) the lagoon area in the vicinity of Bauareke Passage was searched with some kind of magnetometer/ metal detector equipment gear set up in a skiff.

- In 2001 Andrew McKenna, Van Hunn and I spent about a week diving in the area between the Tatiman Passage sandbar and Taraia Point, which is the spit of land due east of Tatiman Passage.  The reason for searching this area was that TIGHAR had collected anecdotes from colonists that there had been aircraft debris in the vicinity of Taraia Point.  The results of the visual search were nada- the lagoon bottom in that area is very clean, and the silt is only, say, six inches deep or so, so large aircraft parts could not be buried in the silt.

   Towards the end of the expedition virtually the entire team spent a day doing visual searching and metal detecting work in and around Taraia Point.  Results were again negative.  I ran a metal detector out to chest-deep water around the point, and only got one good hit- it turned out to be a porcelain-covered steel bowl, buried maybe six inches deep, in chest-deep water.  Why this was at Taraia point is a bit of a mystery, but it did show that small metal objects could get buried in the silt there.

- In 2003 Van, John Clauss, Howard Alldred and I spent a day and a half doing an intensive visual search in Tatiman Passage for the "Wheel of Fortune".  Other than an encounter with an adolescent blacktip reef shark being overly territorial, it was uneventful.

- In 2010 Jesse Rodocker, John Clauss and I worked in the lagoon whenever conditions were not appropriate for running the ROV in the ocean.  We had an Iver 2 AUV fitted with a sidescan sonar that took a high-resolution map of probably 80% of the lagoon.  We filled in the rest of the map by towing a Starfish 450 sonar behind a skiff.  We reviewed the sonar data and Jesse and I dove on maybe 25 or thirty sites that looked interesting; all turned out to be coral heads.

So what would be appropriate to do in the future?  Obviously the results of this summer's Niku 7 expedition will affect everything that takes place afterwards, so this is somewhat idle speculation.  But I for one haven't given up on the lagoon- there doesn't appear to be any large- or even medium-sized airplane pieces there, but there could still be plenty of small pieces of aluminum there.  Here's a plan that I would recommend:

- This summer John Clauss and I are going to be visiting White's Electronics in Oregon to talk with them about all things metal-detector related.  Among the items on my discussion list are towed metal detectors that could be run around the lagoon, as well as metal detectors for finding large, deeply buried objects.  We have spent a lot of time metal detecting on the Tatiman Passage sandbar, with largely negative results.  But there is still the possibility that there is metal stuff buried deeper in the sandbar, below the detection range of our existing detectors. 

- The lagoon sonar data from 2010 needs to be reviewed.  We looked at the data while on the ship, but a review of the data in a more relaxed environment might turn up some areas that we want to revisit.

- If in the future we go back to Niku with a land team, and we get the OK to do some work in the lagoon, we should bring a search-and-recovery style high-frequency sidescan with us.  The Starfish 450 unit we had in 2010 is a general-purpose unit and doesn't have the resolution needed to pick out small objects in the lagoon.  Thus the inability to discern between coral heads and man-made objects.  The sidescan data from the AUV is much clearer, but there are probably areas in that data that we would want to revisit as well.

Starfish now makes a much higher resolution unit, the 990, that is pretty much ideal for the kind of searching we are doing in the lagoon.  So I'd bring a sonar like that, re-map all of the periphery of the lagoon (the areas that were done with the 450 in 2010), and revisit any areas of interest from the AUV sonar data.

- If towed metal detecting proves to be practical, spend some time in Tatiman passage and in the lagoon with the appropriate equipment.

- Spend some time on the northeast shore of the lagoon, NW and SE of Taraia point, doing some work with hand-held metal detectors out to chest-deep water.

Ehhh, that's about all my ideas for now.  As they say, no plan survives initial contact with the enemy, so until the results of the deep-water search come in, it's pretty much idle musings....

-Walt
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John Ousterhout

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Re: The Lagoon as a Collection Basin
« Reply #17 on: June 29, 2012, 08:28:56 PM »

Would you (reasonably) be able to use the same high-definition sidescan on the reef, if/when conditions are appropriate?  I suspect that light aluminum objects that wash into the lagoon, might wash back out pretty easily, sometime over the years.
Cheers,
JohnO
 
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Walt Holm

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Re: The Lagoon as a Collection Basin
« Reply #18 on: July 02, 2012, 12:31:24 PM »

Well no, not really.  The Starfish sonar units are made for relatively shallow water, where you can dive as well.  Since the visibility on the reef is amazing, a diver is going to see all kinds of stuff that a sidescan will not.  The reason you're pretty much stuck with sonar or metal detecting or whatever in the lagoon is that the visibility there is so bad.

Below diveable depths, you need a different kind of sidescan setup.  It's very hard to get close to the reef face without pranging your towfish against it.  The current expedition is using an AUV to get in reasonably close, but even so it will be interesting to see whether they can get in tight enough to see small stuff.  The sonar being used (an Edge-Tech 2200-S at 400 kHz IIRC) is not optimal for seeing really small stuff.  If there's an Electra down there they'll see it.  An Electra center section, sure, as long as there's not big rocks around.  An engine,  ehh, that depends upon what it's sitting on.  Pieces of skin, likely not.
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Matt Revington

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Re: The Lagoon as a Collection Basin
« Reply #19 on: August 22, 2012, 10:10:10 AM »

Dave here is copied text from a post by Walt Holm in June

Re: The Lagoon as a Collection Basin
« Reply #16 on: June 29, 2012, 12:55:02 PM »
Quote
Hi All:

   I haven't posted to the forum in the past, but since this is a topic I've been so heavily involved in, I figured I should chime in here.

   As the original poster noted, the lagoon has always been a tantalizing place to look, because if Electra debris has washed into it, it won't ever wash back out again.  The lagoon is very shallow and so is searchable with relatively small and low-cost equipment, as opposed to the big (and expensive) gear that's on its way to Niku right now.

   There have been at least 4 previous searches in the lagoon:

- In 1997 (IIRC) the lagoon area in the vicinity of Bauareke Passage was searched with some kind of magnetometer/ metal detector equipment gear set up in a skiff.

- In 2001 Andrew McKenna, Van Hunn and I spent about a week diving in the area between the Tatiman Passage sandbar and Taraia Point, which is the spit of land due east of Tatiman Passage.  The reason for searching this area was that TIGHAR had collected anecdotes from colonists that there had been aircraft debris in the vicinity of Taraia Point.  The results of the visual search were nada- the lagoon bottom in that area is very clean, and the silt is only, say, six inches deep or so, so large aircraft parts could not be buried in the silt.

   Towards the end of the expedition virtually the entire team spent a day doing visual searching and metal detecting work in and around Taraia Point.  Results were again negative.  I ran a metal detector out to chest-deep water around the point, and only got one good hit- it turned out to be a porcelain-covered steel bowl, buried maybe six inches deep, in chest-deep water.  Why this was at Taraia point is a bit of a mystery, but it did show that small metal objects could get buried in the silt there.

- In 2003 Van, John Clauss, Howard Alldred and I spent a day and a half doing an intensive visual search in Tatiman Passage for the "Wheel of Fortune".  Other than an encounter with an adolescent blacktip reef shark being overly territorial, it was uneventful.

- In 2010 Jesse Rodocker, John Clauss and I worked in the lagoon whenever conditions were not appropriate for running the ROV in the ocean.  We had an Iver 2 AUV fitted with a sidescan sonar that took a high-resolution map of probably 80% of the lagoon.  We filled in the rest of the map by towing a Starfish 450 sonar behind a skiff.  We reviewed the sonar data and Jesse and I dove on maybe 25 or thirty sites that looked interesting; all turned out to be coral heads.

So what would be appropriate to do in the future?  Obviously the results of this summer's Niku 7 expedition will affect everything that takes place afterwards, so this is somewhat idle speculation.  But I for one haven't given up on the lagoon- there doesn't appear to be any large- or even medium-sized airplane pieces there, but there could still be plenty of small pieces of aluminum there.  Here's a plan that I would recommend:

- This summer John Clauss and I are going to be visiting White's Electronics in Oregon to talk with them about all things metal-detector related.  Among the items on my discussion list are towed metal detectors that could be run around the lagoon, as well as metal detectors for finding large, deeply buried objects.  We have spent a lot of time metal detecting on the Tatiman Passage sandbar, with largely negative results.  But there is still the possibility that there is metal stuff buried deeper in the sandbar, below the detection range of our existing detectors. 

- The lagoon sonar data from 2010 needs to be reviewed.  We looked at the data while on the ship, but a review of the data in a more relaxed environment might turn up some areas that we want to revisit.

- If in the future we go back to Niku with a land team, and we get the OK to do some work in the lagoon, we should bring a search-and-recovery style high-frequency sidescan with us.  The Starfish 450 unit we had in 2010 is a general-purpose unit and doesn't have the resolution needed to pick out small objects in the lagoon.  Thus the inability to discern between coral heads and man-made objects.  The sidescan data from the AUV is much clearer, but there are probably areas in that data that we would want to revisit as well.

Starfish now makes a much higher resolution unit, the 990, that is pretty much ideal for the kind of searching we are doing in the lagoon.  So I'd bring a sonar like that, re-map all of the periphery of the lagoon (the areas that were done with the 450 in 2010), and revisit any areas of interest from the AUV sonar data.

- If towed metal detecting proves to be practical, spend some time in Tatiman passage and in the lagoon with the appropriate equipment.

- Spend some time on the northeast shore of the lagoon, NW and SE of Taraia point, doing some work with hand-held metal detectors out to chest-deep water.

Ehhh, that's about all my ideas for now.  As they say, no plan survives initial contact with the enemy, so until the results of the deep-water search come in, it's pretty much idle musings....

-Walt
« Last Edit: August 22, 2012, 12:35:48 PM by Martin X. Moleski, SJ »
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Tom Swearengen

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Re: The Lagoon as a Collection Basin
« Reply #20 on: August 22, 2012, 12:40:33 PM »

Dave---We talked to Andrew and Walt at the symposium, and asked very similiar questions about the lagoon. What I can reall is there are place where a plane 'could' hace landed and survived. other places have jagged coral heads that are submerged that would do some pretty detructive damage to a fuselege of an aircraft. Seems I do remember reading somewhere on here that PBY's did sucessfully land in the lagoon in support of the loran station, although i may be mistaken.
Even though is seems like a good idea, not knowing what is under the surface would be weighing on my mind IF I were looking for a place to set th plane down. The beach, or the reef. might be better.

I think Andrew & Walt can speak better about the underwater topograpy of the lagoon, as well as the black tips.
tom
 
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richie conroy

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Re: The Lagoon as a Collection Basin
« Reply #21 on: August 22, 2012, 04:46:30 PM »

Just to add to this discussion, the only object i know to have survived the journey from Nessie and Norwich City area, into lagoon is the water tank, which ended up not far from the seven site  :)
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richie conroy

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Re: The Lagoon as a Collection Basin
« Reply #22 on: August 22, 2012, 05:01:30 PM »

Amelia's lively hood, depended on the Electra making the round the world flight, The cost of fishing the Electra out the lagoon is not worth thinking about, MY opinion is if they could land safely on reef, they had a chance of refueling an taking to the air again to howland.

Also if they landed in lagoon they would have no chance of radioing for help, So i think the pluses of a reef landing out weigh the lagoon landing theory. 
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Tom Swearengen

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Re: The Lagoon as a Collection Basin
« Reply #23 on: August 23, 2012, 01:13:43 PM »

Walt brings up some really good points. Points that come from someone that has BEEN THERE, and knows the territory. It occured to me the the 'standard' metal detection, and sonar devices just might not be appropriate for this island. The reef slope topography shows this. I assume the lagoon is similar with coral heads, and other things that we dont know about.
Perhaps, a group of those members that have been in the lagoon, like Walt and Andrew, could get together with Whites, Phoenix, or others, and come up with something that serves the purpose. Obviously, you cant build one piece of equipment that handles all possibilities, but maybe they can.
The lagoon 'could' hold other secrets that we arent aware of. IMHO, we should search it too.
Tom
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Gloria Walker Burger

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Re: The Lagoon as a Collection Basin
« Reply #24 on: August 25, 2012, 06:17:43 PM »

Tom said
Quote
The lagoon 'could' hold other secrets that we arent aware of. IMHO, we should search it too.

I agree that the lagoon bears further scrutiny.

I hope this isn't too dumb a question, but if there were bones swept into the lagoon, how could they be discovered? By dredging? The naked eye? I can't see a metal detector helping unless there is metal in a tooth :)

Gloria
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Ric Gillespie

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Re: The Lagoon as a Collection Basin
« Reply #25 on: August 28, 2012, 07:41:21 AM »

I hope this isn't too dumb a question, but if there were bones swept into the lagoon, how could they be discovered?

Bones would probably not survive in water.
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