Dive Report & NEED HELP to ID rudder found in Dublin Lake (Dublin, NH) Sept. 19, 2009

[dave4868]

Curious about the layer...could it have been a hydrogen sulfide layer? I recently recovered a major artifact in a freshwater lake and at around 100 + feet ran into a hydrogen sulfide layer. The artifact was embedded (partially) in the mud and it seems much like your rudder/tiller was black. At some points lights were pretty useless and it became all a matter of feel.

BTW - nice report.

Thanks!

I've just done an internet search on hydrogen sulfide layers in water. That may have been what it was.

I was reviewing my log of other dives at this lake and found other encounters with a smoky kind of decreased visibility, all in 2005, one beginning at 85', just after ice-out, and another beginning at 65', in early November. The encounter at 102' was in August of that same year. Water temps were 39F, 48F and 42F respectively, FWIW. We did not encounter it on this recent 89' dive this year (9/19/2009).

The shallower ones may have been stratified, but it was hard to tell, since they appeared more as the side of a cloud. I didn't really get a sense of stratification, since I didn't bother to swim above it. The bottom there was almost flat, unlike the 110' crease which really created a pocket that is probably more likely to trap and concentrate such a layer.

I have a feeling the 110' crease in Dublin Lake doesn't get much "turnover". On sonar, that crease appeared well defined with the depths from 100 to 110' taking an elliptical shape about 150' long by 50' wide. The crease was flanked on three sides by fairly steep slopes reaching up to about 50 to 60'. The fourth side (to the east) is a more gradual slope only coming up to the 80' trough that pretty much runs down the middle of the lake.

Found some interesting pics and links, including some fascinating cave video exerpts:

T-Nation.com | Underwater Lake - Page 1

This in Cenote Angelita cavern in Mexico. It is fresh water down to about 30 meters. At 30 meters there is a "lake" of hydrogen sulfide that sits atop 30 meters of salt water. Makes for a very interesting visual. Especially with the little "island" and tree branches. Came across this and thought it was pretty cool.

Another interesting site about seasonal lake stratification:

seasonal lake statification

This makes things more interesting, as now I can set a dive goal of finding the layer and taking a water sample from it! I'll make sure I have a dive buddy for that dive, so I can have him sniff the sample after the dive to see if it's got hydrogen sulfide in it.

I'll have to start carrying a water sampling container at Dublin Lake! I love having a mission on a dive!

Dave C

 

[jl_va_21]

(Has to be from shore, since I've sold my big boat.)

By any chance did you sell it do to a missing rudder?

 

[dave4868]

By any chance did you sell it do to a missing rudder?

Nope. I sold it due to it missing money! It was too expensive to run a power boat for only a few trips each year....

Dave C

 

[Mr.X]

Thanks!

I've just done an internet search on hydrogen sulfide layers in water. That may have been what it was.


I'll have to start carrying a water sampling container at Dublin Lake! I love having a mission on a dive!

Dave C

Glad to be of help. We also took some samples of our layer. I wish I could publicly share the results of the artifact recovery as they were quite spectacular and made the news in July 09. Oh well...it's all about my anonymity.

It's really important that the vials be sealed/secured at depth and interrupted until analysis. I know this because we took samples and didn't have perfectly leakproof containers. This resulted in the hydrogen sulfide gas off-gassing and leaving behind gin clear liquid!!! Nothing much to show and tell. However, the artifact we recovered was scarred by years of being attacked by the weak acid and what was a deep layer of salt. The lake we dived at one point had been connected to the ocean by a small opening until a large quake isolated it from the ocean.

X

p.s. attached a small pic of the layer. It sits about 20' below this diver.

 

[trappist]

I'm learning everyday !!! I would love to be part of that sample taking

 

[dave4868]

Glad to be of help. We also took some samples of our layer. I wish I could publicly share the results of the artifact recovery as they were quite spectacular and made the news in July 09. Oh well...it's all about my anonymity.

It's really important that the vials be sealed/secured at depth and interrupted until analysis. I know this because we took samples and didn't have perfectly leakproof containers. This resulted in the hydrogen sulfide gas off-gassing and leaving behind gin clear liquid!!! Nothing much to show and tell. However, the artifact we recovered was scarred by years of being attacked by the weak acid and what was a deep layer of salt. The lake we dived at one point had been connected to the ocean by a small opening until a large quake isolated it from the ocean.

X

p.s. attached a small pic of the layer. It sits about 20' below this diver.

Unfortunately, I couldn't quite see the layer in your pic even after adjusting the contrast, hue, saturation, etc.

Good point about the sampling container. I was wondering how quickly the gas would come out of solution.

For visual inspection of a sample, I was thinking of using a small, thick-walled canning jar with a multiple threaded lid that could withstand the positive internal pressure once on the surface.

Otherwise, a clear plastic resealable bag would suffice for bringing up a sample for the "buddy sniff test".....

I think I have a volunteer for that job....

I'm learning everyday !!! I would love to be part of that sample taking

There he is now! What a great dive buddy! I'm assuming he's not going just for the "glory job" of sample "taking"....

Dave C

 

[Mr.X]

Unfortunately, I couldn't quite see the layer in your pic even after adjusting the contrast, hue, saturation, etc.

Good point about the sampling container. I was wondering how quickly the gas would come out of solution.

For visual inspection of a sample, I was thinking of using a small, thick-walled canning jar with a multiple threaded lid that could withstand the positive internal pressure once on the surface.

Otherwise, a clear plastic resealable bag would suffice for bringing up a sample for the "buddy sniff test".....

I think I have a volunteer for that job....

There he is now! What a great dive buddy! I'm assuming he's not going just for the "glory job" of sample "taking"....

Dave C

Sorry about that. I'll have to find a better picture shortly. Or I'll PM you with the details from news articles. Glad you have a volunteer.

Cheers,

X

 

[Mr.X]

Here's one more pic. from the project. It's probably not much better than the first. It shows my team hovering just above the sulfide layer. What's interesting is that minor fin turbulence causes some of the particulate matter to rise up. This occurred even with excellent fin technique.

Please keep us posted on this project. If it occurs during the summer I might be able to lend support with the use of several scooters/video.

 

[dave4868]

Here's one more pic. from the project. It's probably not much better than the first. It shows my team hovering just above the sulfide layer. What's interesting is that minor fin turbulence causes some of the particulate matter to rise up. This occurred even with excellent fin technique.

Please keep us posted on this project. If it occurs during the summer I might be able to lend support with the use of several scooters/video.

That image shows the layer pretty well, thanks.

Nice offer of the scooters and video! I appreciate it. I'll pm you if the goal isn't met more easily.

I probably won't get back into the lake before the ice forms, so I'll wait until the water is open again next year. I'll choose an entry point slightly closer to the 100' hole in the east end and hopefully find the layer.

If the layer isn't found there, I'll plan a dive to shoot for the 110' crease at the other end of the lake, probably from my small boat, but scooters would be another method. That would be more interesting for sure, covering new bottom so quickly. However, it'll be a real effort for me not to get side-tracked if salvage items are spotted.

I may take you up on your offer and PM you next summer. Thanks again!

Dave C

 

[mark_the_singer]

As for the tiller, I think it's either from a Laser II, or other racing class boat. It's not from a sunfish. How big is it? Also, are there any retention systems on the mounting pegs, like holes for a clip?