Without a professional to assist you, there might be a mistake, an item missed, etc. I'd go back to the "boss" and explain. While some guidance here might help, we do not have all the details. One thing fur sure, be sure that the earth or compacted fill outside that ring foundation is well compacted to a distance at least out from the foundation equal to the depth of that material below the ring foundation. Even though what the tank sits directly on might not compress, any weaker material outside and within that dimension mentioned above can allow the ring to settle and slip out down and away from the tank. Then a major failure is going to happen.