Water Pump Timing Cover Seal and Shaft O-Rings... Why?

Ok I have been tracing a oil leak down as most of us always seem to be doing lol.

I am sure its coming from the water pump shaft but I bought all the seals just to be safe. I doubt I am going to pull the timing cover though I just don't want to deal with that today.

However when I bought the parts from GM (Yes I went to the dealer, I am sick of tearing things apart here) they showed 2 O-Ring seals on the water pump shaft that goes between the water pump and the gear drive on the timing cover.... I never put any o-rings on to being with and got to thinking...
are they required? What are they for???

I did not think that oil passed through there but I could be wrong.

What is the purpose of these seals why are they there? Any idea's or reasons?

I am going to put them on when i take a look and see how but I am just curious as to why they are there.

If you are talking about item 156 in this pic: http://shbox.com/ci/water_pump.jpg

they are most likely for vibration issues and/or keeping the dirt and moisture out of the splines.

Yes those are the ones I am talking about.