A compressed gas energy storage system may include an accumulator for containing a layer of compressed gas atop a layer of liquid. A gas conduit may have an upper end in communication with a gas compressor/expander subsystem and a lower end in communication with accumulator interior for conveying compressed gas into the compressed gas layer of the accumulator when in use. A shaft may have an interior for containing a quantity of a liquid and may be fluidly connectable to a liquid source/sink via a liquid supply conduit. A partition may cover may separate the accumulator interior from the shaft interior. An internal accumulator force may act on the inner surface of the partition and the liquid within the shaft may exert an external counter force on the outer surface of the partition, whereby a net force acting on the partition is less than the accumulator force.