MEMORANDUM TO: The Record FROM: Josh Lewis, Environmental Engineer SUBJECT: Response to Comments from Rocky Mountain Remediation Services, L.L.C. (RMRS) on the Land Disposal Restrictions: Notice of Intent to Grant a Site-Specific Variance to Chemical Waste Management, Inc. I. Request for a treatability study Comment In their comments, RMRS states that it has recently deployed an improved method for treating metals contamination. Early in 1998, it submitted a patent application for the use of a proprietary binder called Envirobond. Studies and full-scale treatment results have shown that Envirobond can be used to stabilize a wide variety of heavy metals including arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver, as well as nickel and zinc. The data show that Envirobond will reduce very high levels of most of these metals, with very high waste loading into the final waste form. Typically, the Envirobond with additives contributes less than 10-15% by weight. Envirobond has been effective on waste streams with more than one contaminant, and in regards to the waste stream discussed in the proposed treatment variance, Envirobond has treated waste containing high levels of arsenic, cadmium, chromium, lead, and in particular, selenium. In addition, Envirobond has been shown to effectively stabilize surrogate samples with selenium as high as 190 mg/L TCLP. RMRS believes Envirobond will easily achieve the proposed levels of 25 mg/L TCLP, and 51 mg/L TCLP, with a much lower reagent to waste ratio (EPA's proposed reagent to waste ratio is 2.7). By using Envirobond, the final volume of waste requiring disposal would be greatly reduced, furthering waste minimization goals. Also, by adding such a small amount of stabilizing ingredients, there is no doubt that "dilution" has not been used to achieve the standard. RMRS research shows that Envirobond achieves compliance with the standard by reacting with the metal in question to form a metallic compound that is insoluble and withstands rigorous leachability testing. Studies have shown that the eight metals of concern: arsenic, barium,cadmium, chromium, lead, mercury, selenium, and silver, pass the TCLP test, and also remain below LDR and UTS levels after multiple extraction procedures that subjected the treated waste to repeated acid extractions. Should Envirobond not achieve the lower LDR or UTS standard, it will still produce a superior product that is below the proposed levels of 25 mg/L TCLP, and 51 mg/L TCLP. Before the EPA makes a final decision on granting the treatability variance, it would be appropriate to do a simple treatability study using Envirobond. Envirobond may make the variance unnecessary, or may allow the EPA to set the variance standard at a level closer to the current regulatory level. Working with the EPA under a Cooperative Research and Development Agreement (CRADA) RMRS has recently completed a technology demonstration a sites in Ohio with extremely high levels of lead. The Ohio EPA desires an in-situ method that will allow contaminated soil to be treated in place. Preliminary data has shown the Envirobond process to be very successful in binding the lead without a complicated lead extraction or soil washing process. RMRS would be interested in evaluating other waste forms with the process. Response The Agency thanks the commenter for the information on Envirobond and the data showing its effectiveness to date. Based on the analytical data submitted, it appears that Envirobond may prove to be successful in treating the two glass manufacturing waste streams. Therefore, we agree that a treatability study is warranted to see if Envirobond can stabilize the wastes to meet, or achieve a result closer to, the current regulatory level of 5.7 mg/L TCLP. See the final rule preamble for a discussion on the results of this treatability study. II. Difficulties with Selenium Stabilization and Analysis Comment In a final comment, RMRS notes that selenium is a difficult metal to accurately analyze for TCLP and to stabilize. RMRS notes that it has used several very good laboratories for TCLP analysis and has found a wide variety in the selenium results. This is especially true if an interfering species such as magnesium or iron is present in the waste. Without a complete characterization of the glass powders in question it is impossible to determine whether interfering species are present, but it appears that the analysis problems may be contributing to the variability in results. Response The Agency agrees that selenium is a hard metal to stabilize, especially when present with other metals, as is the case with the two glass manufacturing wastes that are the subject of this variance. This can contribute to the reported variability in the TCLP results. A number of other factors may also contribute to the variability in laboratory analyses. For example, elemental selenium and many of its compounds are volatile; therefore, samples may be subject to losses of selenium during sample preparation. Also, high concentrations of other metals may cause analytical interferences. Therefore, spike samples and relevant reference materials must be closely monitored to control analytical performance. In conclusion, the Agency agrees that it is difficult, but not impossible, to accurately analyze for selenium using the TCLP.