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AWWA has lagged behind the ASCE 7-95 on wind design.  The ASCE 7-95 is
predicated on a 3 second gust.  I believe the AWWA D-100 is still predicated
on a fastest mile wind.
I ran into a similar situation for a liquefied natural gas plant.  I
insisted on the ASCE 7-95 for wind.
I would use the ASCE 7-95 for wind, but the AWWA D-100 is better for
seismic.  Look at the probability of excedance, and you may even conclude
that you need a higher velocity.  You might also want to convert the
Saffir-Simpson scale velocities to 3 second gusts.  It will give you the
information about what level of hurricane you could resist.
Harold Sprague, P.E.
harold.sprague(--nospam--at) <mailto:harold.sprague(--nospam--at)>  

-----Original Message-----
From: Randy Russ [mailto:rruss(--nospam--at)]
Sent: Thursday, November 19, 1998 9:15 AM
To: seaint(--nospam--at)
Subject: ASCE vs AWWA

I have been comissioned to design a foundation for a 225' water tower. The
tower will be designed by a tank vendor with proper professional
registration. They are using AWWA D100 standards. I am using ASCE 7 to
determine proper wind forces on the foundation. 
I am not that familiar with AWWA. AWWA states that the actual wind velocity
should be used but should not be less than 100 MPH. It gives no means to
determine what velocity should be used and it gives no means to determine
when a different velocity should be used.
ASCE 7 gives good info on this subject. I am designing the foundation for
120 MPH ASCE 7-95. I suggested that my client put into his specs to use ASCE
7 and/or AWWA. He refuses. He also refuses to put in a higher AWWA wind
speed even though this is < 100 miles from the Gulf Coast.
The foundation will be designed with ASCE 7 or AWWA (whichever is most
stringent). Do I drop the subject and hope for the best or do I insist that
the client change his performance spec for the tank.
Most of y'all are earthquake hounds but how about a little feedback for us
hurricane folk? 
This project is out in the boonies and there are no local governing codes.