Hi BOb,

On Wed 2037-Aug-05 05:10, Bob Ackley (1:300/3) wrote to Richard Webb:

 BA>> I don't know how they did it in San Francisco.  In downtown SF, some
 BA>> of the  city's trolleys were already subways and BART was put in
 BA>> below them. 

 RW> That's one good way to do it.  WHat really sorta makes me
 RW> shake my head is different proposals I've heard over the
 RW> years for a subway system in L.A.  Yah just what you need so close to
 RW> a major fault line >

BA> The tube that BART trains run under the bay in crosses the San
BA> Andreas fault. So, FTM, do the Dumbarton, San Mateo and Oakland-San
BA> Francisco bridges. 

YEp, at least on a bridge I"ve got a fighting chance if the
whole thing shakes and rolls .



BA> The San Mateo was similar construction until many years ago when the
BA> state replaced
BA> it with what is essentially an elevated freeway, with a nice
BA> overpass over that ship
BA> channel (for years the steel drawbridge section remained isolated -
BA> the road on both
BA> sides had been removed - right next to that overpass - it was too
BA> expensive to dismantle), all concrete (which doesn't do well in salt
BA> water or under lateral stress).
YEp I can see that.    HOpe they replaced it with something
that had a bit of flexibility  Of some interest is that the last time I crossed the San Mateo
BA> Bridge (30 or so years
BA> ago) I noted that the roadway was about ten feet above the rooftops
BA> of Foster City (a
BA> development built entirely on crud dredged up from the bottom of the
BA> bay and piled on
BA> top of what had been mud flats - that sort of fill turns to mud and
BA> jelly during earthquakes, not the sort of thing one wants to build
BA> anything on). 

YEp, and bet those houses sold for high dollars too.  WOnder if it still
survives.  IF so I bet they can't rebuild
anymore there, at least if the authorities are smart.

Regards,
Richard


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