Built in 1954, the tank was found to be leaking in 1988. At that time, approximately 113,000 gallons of liquid were removed from the tank, and the leak stopped. In December 1997, unusual fluctuations were observed in measurements of the tank's liquid level. The analysis at that time showed that the tank was not leaking, but engineers continued to study the tank. In effect, sections of the tank act as giant barometers, experiencing a nearly four-inch cycling in liquid level with changes in barometric pressure.
Liquids rise and fall in different areas of the tank.
Pumping of the remaining liquid in Tank SX-104 began in September 1997 as part of DOE's program to stabilize all 149 of the Hanford tanks having only a single shell. Sixty-seven of the single shell tanks have leaked or are suspected of having leaked in the past. However, there is no evidence that any of the 149 single shell tanks currently are leaking, and there is no leak history associated with any of Hanford's 28 double-shell tanks. Rick Raymond, LMHC deputy director of TWRS technical operations and engineering, explained that plugging occurred even after the waste was diluted and the lines were heated to improve flow. The analysis shows that when the liquid is pumped from the tank into the buried transfer line, it is cooled by the surrounding soil.