The single-shell tank – 241-T-111 – has a long history of a suspected but unconfirmed leak.
T-111 is part of Hanford's T-Farm, one of the site's oldest tank farms used to store Hanford's highly radioactive and chemically hazardous waste generated from decades of plutonium production.
- The tank was put into service in 1945.
- It was suspected of leaking as far back as 1974. Subsequent reviews of the tank waste volumes have concluded that it's not possible to determine whether it is or isn't leaking, It remains a suspected leaker.
- A surface barrier, to prevent precipitation from driving soil contamination to groundwater, was installed in 2008. It covers all or part of nine of the 16 tanks in T-Farm, but does not cover T-111.
In 2013, Energy evaluated the liquid level data trends for all of the single-shell tanks and found T-111 had one of the highest decrease rates. At the time, then Energy Secretary Steven Chu notified Gov. Inslee of the presumed leak.
Energy took interim steps, actively ventilating the tank to reduce liquids, which occurred intermittently from July 2015 to April 2019. The waste levels decreased during that time, presumably due to evaporation.
However, since ventilation stopped in April 2019, in-tank monitors show liquid levels have continued to decrease, despite the ventilation being discontinued.
The in-ground monitoring we’re requesting would place probes into the soil around T-111 and T-farm to measure how well the soil conducts electric impulses. That in turn detects whether moisture is being added to the soil and would determine whether the tank is actively leaking.
The formal leak assessment would empanel a group of experts to review the data collected from T-111 over the decades. The panel would determine whether, in its collective expert opinion, the tank is leaking or whether other factors are more likely to account for the fluctuation of levels within the tank.