The latest ACI 318 code has now referred all concrete water containing structures to the ACI 350 code This has really played havoc with our base sizes. The elimination of zones and the addition of different earthquake values for each base based on the reservoir’s specific location has made it difficult to use turnkey plans like we used to. Base sizes now vary so much based on soils and location that they can no longer be listed. The foundation size can not be nailed down until a soils report is obtained and an exact construction location is pin pointed. Please note that the dynamic (earthquake) loads on water reservoirs when compared to their static loading will be at a much higher ratio than would be expected in a normal non liquid containing structure. This is due to the live load or ‘slosh’ affect of water moving within the tank during an earthquake. Have a soils engineer keep the numbers as high as the soils will allow. This will keep us from having to increase the base size unnecessarily, adding additional costs.
Please give us a call early on to discuss the specific requirements of the reservoir size and location you are considering.