Sunday, April 11, 2010

Sunday Quiz

The Wandsworth one way system is a well known London traffic black spot which drivers are only too happy to get through as quickly as possible.

However I lingered long enough to take a pic of this contraption in the Thames near Wandsworth Bridge.

Any guesses, educated or not as to:
a) what is this?
b) what is it doing?
c) and why?


will said...

it's a spud barge, spuds being the legs that hold it in place, making it an idea platform for any work performed by the crane. they could be lowering pipe, for example. when the work is finished, a tug will attach and spuds will be raised (ie, the barge refloated) to wherever it's next needed.

Tillerman said...

a) Jack up barge
b) drilling boreholes
c) doing a survey for Thames Water as part of the Tideway Tunnel Project.

O Docker said...

I actually knew this without Mr. Google's help.

They used one of these a few years ago to help dismantle an old SF Bay bridge that had been replaced.

And there's the same day shape that appeared on the survey boat in one of your earlier quizzes, I think its official meaning is, "It would take too long to explain what I'm doing, so just go around me."

Tillerman said...

It strikes me as rather odd that the barge is using the day shape for a "vessel restricted in her ability to maneuver" and not that for "vessel aground". I know that the definition of "vessel restricted in her ability to maneuver" includes survey vessels, but surely the barge is technically "aground" when the legs are down?

I actually didn't not know this was not odd without none of Mr. Google's help.

O Docker said...

I have no idea what rules apply in the Thames estuary, but here is the relevant USCG rule 27 (vessel not under command):

A vessel engaged in dredging or underwater operations, when restricted in her ability to maneuver, shall exhibit the lights and shapes prescribed (ball, diamond, ball) and shall in addition ...when at anchor, the lights or shapes prescribed in this paragraph instead of the lights or shapes prescribed in Rule 30, for anchored vessels.

Oh great, now you've made me go and ask Mr. Google, after all.

Tillerman said...

Wandsworth is not in what would normally be considered the Thames Estuary. I'm so sure I'm right on this that I almost wrote this sentence without Mr. Google's help.

But is this barge anchored or aground? Surely if the legs are down its weight is supported on the river bed, which sounds like the same as being aground to me. I actually wrote this whole paragraph without Mr. Google's help.

O Docker said...

Hmm, it sounds more like being anchored to me - they conciously chose the place and the time, presumably, and are attached to the bottom with gear deployed for that purpose.

But right there is a good reason why I try to avoid discussions about rules and regulations. Before long, you're using words like 'deploy'.