waltzt (Mechanical) (OP)
20 Aug 10 14:20
The tank has to be physically modified so that it can never hold 1 million gallons again. Shell vents, overflows, etc can be removed and are not acceptable. I would like to add a cone/cylinder to the bottom of the tank to displace 15,000 gallons, but this alteration "could be altered again" to restore capacity - see below. I am interpreting the requirement below as installing a second floor or lowering the top as the only option. I am just trying to find the lowest cost solution to this issue.
This is our requirement from the EPA:
2.5.3 Definition of Storage Capacity
Under the SPCC rule, if a container has the requisite capacity, it does not matter whether the container is actually filled to the capacity of the container. If a certain portion of the container is incapable of storing oil because of its integral design (e.g., mechanical equipment or other interior components take up space), then the shell capacity of the container is reduced to the volume the container might hold (67 FR 47081).
Generally, the shell capacity is the rated design capacity rather than the working/operational capacity.
2.5.4 Tank Re-rating
Shell capacity should be used as the measure of storage capacity, unless changes are
made to the design shell capacity in a permanent, non-reversible manner. For example, when the integral design of a container has been altered by actions such as drilling a hole in the side of the container so that it cannot hold oil above that point, shell capacity remains the measure of storage capacity because such alteration can be altered again at will to restore the former storage capacity.
When the alteration is an action such as the installation of a double bottom or new floor to the container, the integral design of the container has changed, and may result in a reduction in shell capacity. An addition or modification to a field-erected storage tank should be performed in accordance with industry standards and the original design specifications. Relevant industry standards include American Petroleum Institute (API) Standard 653 "Tank Inspection, Repairs, Alteration, and Reconstruction" (API-653). This standard includes additions or modifications to shell penetrations such as overfill diverters. However, even where such modifications are done in accordance with standards, the tank may not be considered re-rated to a lower capacity; the capacity remains equal to the original rated shell capacity. An owner or operator may reduce the
capacity of a tank only by changing the shell dimensions (i.e., by removing shell plate sections). Since SPCC requirements are based on shell capacity, modifying a vent, overflow, or other tank appurtenances that reduce the working fill capacity does not affect SPCC requirements.