What do you do with removed contaminated soil?

Q. Why are repositories used to dispose of heavy metals contaminated soil? Agencies use repositories because they are a safe and efficient way to stabilize contaminated soil through consolidation and capping. The 2002 Record of Decision (ROD) calls for using repositories to dispose of contaminated soil. Contaminated soils can also be consolidated at mine and mill sites like the Forest Service’s work at Moon Gulch. Sites like Moon Gulch are different from repositories because they are located at the place where the waste originated and do not take in waste from the local Institutional Controls Program (ICP). On the other hand, a regional repository like Big Creek will take in contaminated soils from yards and the ICP. Q. In the Basin, are there other ways to dispose of heavy metals-contaminated soil? Just because the ROD states that repositories are the preferred method of containing contaminated soils doesn’t mean agencies are not listening to other options suggested by the public. Many people have suggested interesting and creative ways to make the waste disappear. An article in EPA’s latest Basin Bulletin newsletter discusses some of the options presented and why most of them won’t work for this large and complex site. I would like to take the opportunity in this column to reach people who don’t subscribe to the Basin Bulletin. I will describe various options that have been considered and explain if they will work or not for the cleanup. This will take two columns to explain, so stay tuned for the January edition if you don’t see something you brought up at one of the meetings. Here are some of the ideas considered: 1. Leaving Contaminants in Place: Why can’t agencies just leave contaminated soils in place? The agencies do to a large extent. However, because agencies have a public mandate to protect public health and the environment, they remove contaminated soils at the surface where people can be exposed. It would be irresponsible for agencies to leave contaminants in place where there is serious risk of exposure. However, the cleanup does not call for complete removal of all contaminated soils. For example, it calls for stabilization, excavation, and capping to minimize the risk of exposure to contaminated soil. 2. Shipping Off-Site: Agencies have heard some interesting ideas related to this alternative, such as shipping the waste to Yucca Mountain or sending it off the earth completely. Agencies have a responsibility to manage the contaminants within the site if this can be done safely. They have safely stored and contained the waste soil in on-site repositories at the Bunker Hill site for 20 years. Therefore, it would be irresponsible and much more expensive to move the waste to other communities. 3. Putting Soil Down Mine Shafts: Although this may seem like the most obvious alternative, mine-shaft disposal will not work for many reasons. A partial list of the reasons discouraging this method includes: Volume Constraints – Although the contaminants came out of the mines, they have been mixed a hundred-fold or more with river sediment and native soil. One cubic yard of rock removed from the mines may require more than 100 yards of waste storage. There is not enough room available in all the Silver Valley mines combined to hold this much waste material. Water Quality – Most of the old mines are filled with water. Before anyone could re-enter the underground workings, an expensive system of dewatering pumps would need to be operated at each mine. The water produced from dewatering may be contaminated to the point where dumping it into the creeks and rivers would seriously degrade surface water quality. Safety – Many of the old workings have not been occupied for years. To enter the old mines to estimate how much waste they could store would require extensive safety studies. Many of the old workings would require very expensive rehabilitation just to enter them to calculate potential storage volumes, let alone use them to store waste soil. Logistics - The Bunker Hill cleanup operation is performed on a large scale. The repositories commonly receive over 100 20-ton dump trucks per day. This type of operation would require big, heavy-duty roads for safe transport. The mines are scattered all over the Silver Valley, so extensive road improvement or construction in the mountains would be needed to support increased truck traffic. Operational Constraints – Many of the old mines would need extensive surface improvements to handle the truck volume. Additional space would be needed to receive waste soil from trucks and transfer it to underground ore cars. A very large underground material conveyance system would be necessary at each mine to then place the waste soil deep in the old mine shafts. Future Mining Concerns – Mining activity waxes and wanes through the years depending on commodity prices. Currently inactive mines may someday be opportunities for renewed mining activity. Backfilling the mines with waste soil would make it very difficult to re-occupy the mines to start mining activity again. Costs – Underground operations are very costly to move even relatively small amounts of material. Costs to safely develop an old mine to receive waste soil, including dewatering, safety studies, shaft rehabilitation, ventilation system installation, road building, and other underground improvements would be huge in comparison to costs to build large surface repositories. In the next column I will discuss the following waste soil disposal options: phytoremediation, vitrification, making soil into concrete, and “Filling in the Holes” also known as “Community Fill.”