I am designing a water treatment facility in a velocity-related and acceleration-related seismic zone 1 (in Ontario).  The facility is supported entirely on H Piles.

In one reference the Ontario Building Code says to include the full weight of tanks and their contents, while in another is says that "When the mass of a tank plus contents is greater than 10% of the supporting floor, the lateral forces shall be determined by rational analysis."

With the weight of the reservoir tanks included, the base shear is extremely large, and will require a greater number of piles (all battered).

It has been brought to my attention that there is a reference possibly by the AWWA (D100?) that indicates that the sloshing water actually provides a damping effect.  I am interested in reading this reference, or any other relevant information, so that I can quantify the damping effect (if applicable).

Thanks for your help in advance.