Lake Washington -- the Harpoon 9/12/10

We have a wonderful community here in Seattle. When a friend of mine sent out an e-mail asking if some folks wanted to do some tech diving on wrecks in Lake Washington this weekend, within about 24 hours, he had not only his boat full, but ours! So today, nine dives prepared to do the PV-2 Harpoon, which lies off Magnuson Park (which used to be an Naval airfield) in 140 feet of water.


The PV-2 was a bomber and patrol aircraft in WWII. This one crashed on a training dive, going into the water just off the end of the runway. Both pilots escaped, but the airplane ended up going nose first into the silt. Over time, the tail has fallen off, and lies beside the rest of the plane. (I have heard that the viz can be so bad there, that people have descended INTO the open fuselage without realizing they were on the wreck, and given Lake Washington, I can believe it.)

We were diving off our boat, and one of the divers from the other one came over to boat tend for us during our dive. We were the first team in, so we had no feedback on viz, or where the shot was. I had a spool, in case we had to search (if we were far enough to need a reel, at that depth, we were going home!)

Kirk and Peter and I geared up and got in the water without incident, but once at the top of the shot, we discovered Kirk's primary light wouldn't stay lit. One of the wonderful things about our community is the amount of resources that gets to a dive site -- within a few minutes, we had another can light, and the game was back on. So, down we went, through initially warm and clear water, but once we went through the thermocline, the vis steadily deteriorated. I am happy to say that I did actually see the bottom of the shot before I hit the silt (easy to do in the lake, where there is often no well-defined bottom, but rather viz that gets worse and worse until you realize it's solid).

But although we all started looking at about 120, none of us saw any trace of the wreck. It was with some apprehension that I tied my spool into the upline and began to search . . . for the plane, which may have been as much as five feet away! The dark paint on it, combined with the low viz, made it amazingly hard to find until we found it, and then I think we all felt a little stupid. (But I noticed the next team ran line to it, too.)

I had no idea at all what part of the plane we found, or what I tied into, and that degree of orientation was to persist through the entire first lap of the wreck. Kirk was leading, as he had been there before, and I was #2. The first 15 minutes of the dive consisted of, "Rusted metal to my left, check; Kirk and Peter located, check; depth and time okay, check gas." Rinse and repeat. I remember looking at something that looked like a tail, and wondering how we had gotten there. And then, finally, we were on the fuselage, and I knew that's what it was, because it was vertical, and it was a relief to see something whose orientation made any kind of sense. We went up and peered into the interior, and admired the twin guns, and then went back down and did another lap. This time, I at least realized we swam the length of a wing

These dives in the lake are interesting dives for me. I'm not quite sure I would term them fun, but they are fabulous exercises in all the things I'm weak on or don't much like -- very dark, very low visibility, and often very disorienting. There were periods of swimming through thick murk with no visual reference (Kirk had gone behind the wing, and his light was gone, and we were far enough off the main structure that I couldn't see it). There was lots of structure that couldn't be used for spatial orientation, because I basically didn't know how it lay. If I hadn't had the cave training I've had, I think I would have aborted the dive within five minutes, but as it was, I had the skills and the training (and the team) to do the full tour.

In contrast with the dive itself, the deco was almost a relief. Although I had to pull the team in tight at the beginning, to be able to see people's faces and hands, and be sure my signals were getting through, by the time we were at 100 feet, viz had improved markedly, and the rest of the deco was relaxed and easy.

Lessons from this dive: If you are diving in a very low viz, the leader needs to move slowly and check back regularly. It takes VERY little time to lose the person behind you. Also, you have to be very close together to see one another's hand signals or eyes; communication with lights is limited to very simple things, so running ascents and the like needs to be done very close together until the viz opens up.

The best part of the dive? Having my buddy, Kirk (who has been my diving and training buddy since just after Fundies, and has seen me struggle) tell me I made the ascent and deco look as though it was easy.

Max depth 140
Bottom time 28 minutes
Mix 21/35 bottom, 50%
Deco: RD 1:1

As always, great writeup. Thank you.

Quick question of your opinion ... (I've only been on that wreck once)

I don't know if you had a chance to look at the fuselage where the tail used to be attached, but when I was there, it looked too perfect to have been torn off in the crash.

Considering the condition of the rest of the wreck, that the plane is virtually vertical, and how nicely the tail seems to be sitting beside the rest of the plane (Right at the end of one wing, in almost perfect alignment), do you think it's possible that the tail could have had some 'help' in it's efforts to remove itself from the rest of the plane??

A good read as always. Thanks for posting Lynne!

Thanks for the report Lynne. Sounds like an interesting and challenging dive in some respects.

Henrik

It looked, to my entirely untutored eye, as though the tail came off at a mechanical junction in the plane's structure. You're right; the edges are very sharp and straight. I think it would be very difficult for anyone using tools underwater to get that kind of result, but I'm not a commercial diver, so I could certainly be wrong.

thanks for posting lynne.
ww

sunkmail:

Quick question of your opinion ... (I've only been on that wreck once)

I don't know if you had a chance to look at the fuselage where the tail used to be attached, but when I was there, it looked too perfect to have been torn off in the crash.

Considering the condition of the rest of the wreck, that the plane is virtually vertical, and how nicely the tail seems to be sitting beside the rest of the plane (Right at the end of one wing, in almost perfect alignment), do you think it's possible that the tail could have had some 'help' in it's efforts to remove itself from the rest of the plane??

Click to expand...

It wasn't torn off in the crash, for quite a few years it was attached and the stern wheel was as shallow as 100ft or so (mud is at about 138ffw). It broke off eventually and is lying behind the port side wing now. There have always been rumors that someone was trying to "salvage" the tail but I'm pretty sure it just broke off. The clean edges are along the seams of the plating. The planes of Lake Washington are alot more fragile than the wooden wrecks because even in fresh water the intentionally lightweight steel components (to save weight) do rust and there's galvanic corrosion with the aluminum as well. And in the case of the Valient the canvas & plywood skin is the consistency of wet cardboard. Small soft shot weights are mandatory to avoid punching holes in these wrecks or ripping them to pieces.

Glad you got a chance to see this one Lynne

there is thought that it might have been 'caught' by a downrigger or net or something and 'helped' in that sense, and just separated at a weak seam.

I hear that in the Great Lakes they alternatively use a length of chain as in theory it's even less harmful than a solid shot weight, but i have not tried it.

Really enjoyed your report, Lynne! Thanks for sharing