      For arsenic, the maximum reported concentration was undetected at a value of 0.05 mg/L, a value slightly higher than the maximum allowable TCLP concentration of 0.042 mg/L. The EPA's review of the corresponding laboratory reports indicate that the laboratory reported sample results from the 7/31/2017 characterization sampling round as non-detect based on a practical quantitation limit of 0.05. Subsequent laboratory reports for the 8/31/2017 and 10/4/2017 characterization rounds reported TCLP arsenic results as non-detect at a level of 0.001 mg/L based on a lower method detection limit rather a practical quantitation limit. Since the total arsenic results for all characterization samples are both low and consistent, ranging from 2.02 to 4.77 mg/kg, the EPA believes that the TCLP arsenic results for the 7/31/2017 results are not likely to be materially different than lower non-detect results for the 8/31/2017 and 10/4/2017 sample results. Therefore, the EPA concludes that even though the TCLP arsenic data from the 7/31/2018 laboratory report does not explicitly document satisfaction of the 0.042 mg/L TCLP arsenic delisting criterion, the overall data set clearly supports a conclusion that the TCLP arsenic results do not exceed the maximum allowable concentration of 0.042 mg/L from any of the characterization sampling rounds. The EPA further concludes that the non-detect value of 0.05 mg/L for TCLP arsenic based on a laboratory practical quantitation limit is not a sufficient basis to disqualify Sandvik's waste from being delisted. Sandvik must, of course, ensure that should the EPA grant the requested delisting any required periodic verification sampling and analysis must have appropriate data quality that addressed this issue.

