Progress of C-Farm tank retrievals
Active retrieval of all single-shell tanks (SSTs) in the C-Farm is complete. Work is underway to complete all post-retrieval sampling and end of retrieval data reports. Less than 66,000 gallons of waste remains in the C-Farm SSTs, almost all of which is sludge.
AX-Farm and A-Farm tanks
Now that C-Farm retrieval is complete, installation is underway for equipment including active ventilation for retrieving waste from the four AX-Farm tanks (almost 500,000 gallons of total volume). The current plan is to then retrieve from the A-Farm tanks (900,000 gal total volume). Two of the six A-Farm SSTs (A-104 and A-105) are leaking tanks that will provide special challenges for retrieval.
We received a report on Friday, May 19, 2017 that Hanford work crews inspecting tank AZ-101 had discovered high contamination readings between the walls of the double-shell tank (DST). We immediately called for the Department of Energy to do an inspection to figure out the cause of the contamination. We’re concerned that it could have been a sign the tank is leaking. The tank is filled with 750,000 gallons of highly toxic, radioactive waste. We are actively engaged and closely monitoring this situation, including going on site for a first-hand perspective and information.
Interim Measures Project
There are two interim barriers at Hanford tank farms. They are at T and TY farms. They cover small sections of the farms with known leaking tanks. The T and TY barriers were 2-year demonstration projects, whose objective was to evaluate barriers’ effectiveness in drying the vadose zone under the barriers. T barrier was the first one constructed, using a polyurea plastic as barrier material. TY barrier was constructed second, using modified asphalt. While the asphalt TY barrier has held up very well, the yellow polyuria T barrier has not. However, both barriers continue to demonstrate drying of the vadose zone well past the intended 2-year demonstration period.
SX Farm interim barrier
Two years ago Ecology approved construction of two small barriers covering portions of the SX farm. During the last year Ecology and DOE agreed that another section (termed an “SX barrier expansion”) should be added in order to achieve barrier coverage over the whole farm. If possible, the three sections (i.e., the whole barrier) should be constructed at the same time. An evapotranspiration basin that will serve the SX barrier was built in 2017, and DOE plans to construct the barrier in 2018.
Next interim barriers objectives and locations
Ecology and Energy are negotiating installation of more interim barriers to proactively minimize risks to human health and the environment from releases of contaminants from tank farms. There are about 160 tanks that still need retrieval. It will take many more years to retrieve all tanks, and tanks that are presently sound may deteriorate and leak their contents into the soil. The objective of future interim barriers is to proactively minimize risks to human health and the environment.
Future interim barriers will be installed over tank farms in the following order: TX, U, S, BY, A, AX, BX, B, T, TY. These farms have been prioritized planning those with the highest known inventories of technetium 99 (Tc99) and other contaminants that require water for travel in the vadose zone first, while also considering other risk factors. Barriers are effective up to their depth of influence, which is a function of geology, weather, temperature, and chemical and physical properties of released waste materials, and other factors. For tanks that are currently sound but may start leaking due to aging, interim barriers would prevent rain or snow melt intrusion from coming in contact with leaked contaminants. Barriers will prevent or slow down spreading in the vadose zone, and ultimately into the groundwater, of contaminants that are transported by water, Tc99 in particular.