Decontamination of Metal Finishing Area

Q. We have a finishing room at one of our plants, and we have outsourced the plating. We also did pickling and bright dip in the room, and we now want to decontaminate it so that we can sell the equipment, or at least dispose of it properly. Our main concerns are cyanide, silver and nickel. All products have been removed from the tanks. The room also has a large pipe vent system going to scrubbers. The plating line consisted of 18 600-gal tanks with a crane system. One of the other systems has a crane mover. We also will want to decontaminate the cyanide destruct tanks and unit in the wastewater room. We plan to decontaminate the floor, remove the berms, scarify the floor and reseal as well as remove walls. Do you have any information that can assist me? D.J.

A. The bottom line for any decontamination project as you described is that whatever material you dispose, it is your responsibility to determine whether or not it is RCRA hazardous, and then to dispose of these properly. You mentioned that the products have been removed from the tanks. There are three options for this material: treat it on-site using your wastewater pretreatment, sell it to another entity, or dispose of it off-site.

Because your plating line used cyanide, a number of listed hazardous wastes under USEPA 40CFR261.31 come into play; these are listed as follows:

F006—wastewater treatment sludges from electroplating operations except from the following processes: 1) sulfuric acid anodizing of aluminum; 2) tin plating on carbon steel, 3) zinc plating (segregated basis) on carbon steel, 4) aluminum or zinc-aluminum plating on carbon steel, 5) cleaning/stripping associated with tin, zinc, and aluminum plating on carbon steel, and 6) chemical etching and milling of aluminum,

F007—Spent cyanide plating bath solutions from electroplating operations,

F008—Plating bath residues from the bottom of plating baths from

electroplating operations where cyanides are used in the process, and

F009—spent stripping and cleaning bath solutions from electroplating operations where cyanides are used in the process.

What this means is that if any of your waste materials mix with any of the above listed hazardous wastes, it is deemed hazardous under USEPA’s mixture rule. Assuming your wastewater pretreatment system is still operational, our experience with clients is that they use their internal labor to decontaminate all of the hard surfaces and tanks interior and exterior taking special attention that waste streams go to their proper sumps (cyanide, chrome, acid/alkalis) and have them treated on-site. Cyanide contaminated equipment is rinsed with a bleach solution, chromate contaminated equipment is rinse with a bisulfite solution, acid contaminated rinsed with a slightly alkaline solution, and alkaline cleaner equipment rinsed with a slightly acidic solution. Everything is then thoroughly rinsed with potable water.

As far as the duct work is concerned, we have seen that our clients have it taken down, crushed, and disposed as a hazardous waste. Why? Too much of a hassle to try to decontaminate. If you decide to do it yourself, we strongly recommend that you sample and analyze a number of samples of the residue on its exterior and interior in order to determine how you will treat the decontamination rinse waters. You do not want cyanide containing residue being flushed into an acidic waste stream.

If your wastewater pretreatment system is not operational, we strongly recommend you contract with a hazardous waste firm to do the job because of all the waste streams generated, containment issues during decontamination, and personal protective equipment needs.

If you do perform some of the work as described above, at some point you will need to contract with a hazardous waste firm to either do the entire job or to finish it, such as removal of duct work, walls, and scarify the floor. Many hazardous waste firms have field service crews that are trained and very knowledgeable about decontamination methods and procedures. Also, they have the training and personal protective equipment to do this work safely and effectively. The removal of ducts, wall, and concrete will create a dusty environment with known toxic materials present; leave their removal to the experts. This firm can assist you with the proper characterization, packaging, labeling, and disposal as the material is generated.

Lastly, while not required by USEPA unless you know there had been a release to the ground, you may want to consider whether or not the subfloor area should be sampled (i.e., soil samples). Depending upon the condition of the floor, trenches, and sumps after you decontaminate them, such as the presence of cracks or excessive corrosion, you may want to have a Phase Two Environmental Site Assessment (EAS) performed. There are professional firms that specialize in Phase Two ESAs. Keep in mind that if the results do show soil contamination, you will be under legal obligation to report it to your state or region EPA and further clean up will likely be warranted. However, most states have clean up thresholds to follow that do not require you to clean up to “squeaky clean” soil.

D.J., this column does not allow me to go into all the specific details and permutations for this type of project. When in doubt, assume waste material is a RCRA hazardous waste and handle accordingly and prepare and keep decontamination documentation for future reference.