"The tank had been previously emptied of pumpable liquids, leaving a small amount of liquid waste inside, the agency said. Systems in the area capture and remove contaminants that reach the groundwater and ensure the protection of the Columbia River, the agency said."
[/size][size=78%] It'd be nice to know how many gallons are left from the original 123,000 gallon volume max capacity. With a lot of headspace, temperature changes can create set up "dew" from remaining liquid up on the bare interior tank walls. This will fluctuate levels. Odds on, there were probably leaks in this old tank prior to being pumped down.[/size]