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Re: Steel Water Tank Foundation

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        I prefer this design too but for small tanks like the one Richard Lewis is working on the steel ring works very well also.
H. Daryl Richardson
----- Original Message -----
Sent: Thursday, September 28, 2006 10:53 AM
Subject: RE: Steel Water Tank Foundation

My personal preference is a Type ! foundation per AWWA D100, i.e. a concrete ringwall foundation.  The ringwall is designed for both the vertical loads (roof and shell reactions plus tributary water weight) and for lateral earth pressure due to the tank surcharge on the contained soil.  I use at-rest earth pressure since the ring tension will limit lateral deflection.
Bill Sherman

From: Michelle Motchos [mailto:mmotchos(--nospam--at)]
Sent: Thursday, September 28, 2006 9:27 AM
To: seaint(--nospam--at)
Subject: RE: Steel Water Tank Foundation

The AWWA has a standard (ANSI/AWWA D100-96)  "Welded Steel Tanks for Water Storage" that covers the design of the tank and foundation including seismic and is the publication referenced as a consensus standard in ASCE 7 for non-building structures.
The type of base is dependent on the tank size, overturning, and supplier/owner preference.   In the project I was involved in, the tank supplier provided the engineered foundation plans as part of their submittal.  The Standard discusses both options but I don't have much experience in them to offer further commentary.

Michelle Motchos, PE
Stevens & Wilkinson of South Carolina, Inc.

Columbia, Sc

From: Rich Lewis [mailto:seaint04(--nospam--at)]
Sent: Thursday, September 28, 2006 11:05 AM
To: seaint(--nospam--at)
Subject: Steel Water Tank Foundation

I was asked to research a foundation design for a large steel water tank.  The tank is about 50 feet diameter and 24 feet tall.  It looks like a typical oil field tank.  Are there publications that give foundation design recommendations for large diameter tanks?  What is the best source of design criteria?


The owner has stated that typically they put down sand and gravel and sit the tank directly on that.  Then they build a steel ring around the tank, beyond the tank perimeter,  to contain the soil underneath.  Is this a common procedure?  I would have expected a concrete ring footing below the tank.


If a concrete ring footing is used, does it only carry gravity load, or is it subject to tension forces from horizontal forces from the soil as well?


Thanks for any insight you can give.