EPA WQC & HC5 Calculations Sample Clauses

EPA WQC & HC5 Calculations. The US Environmental Protection Agency’s (EPA’s) nationally recommended ambient water quality criteria (AWQC) for Cu are based on the BLM (EPA 2007). The ability to calculate criteria has been included in previous publicly available BLM software versions (2.2.1, 2.2.3) and is included in this version of the BLM Windows® Interface. The freshwater Cu AWQC can be generated by selecting the “EPA WQC” tab button shown in Figure 0-11, and then selecting “Cu” in the “Select Metal” drop-down menu. When the BLM is run in the Cu WQC mode, it generates the EPA (2007) freshwater dissolved Cu WQC (acute and chronic) for each row of input and provides these results in the “WQC” report (see Section 5.10) (Figure 5-13). The report provides the BLM-based final acute value (FAV) and the acute instantaneous water quality criteria (IWQC) (which is calculated as the FAV divided by two; see EPA 2007). The acute and chronic criteria are also known as the criterion maximum concentration (CMC) and criterion continuous concentration (CCC), respectively. If dissolved Cu input data are provided by the user in the BLM input data file, the values are tabulated in the criteria output file and used to calculate acute and chronic toxic units (TUs). These TUs are computed as the ratio of the input dissolved Cu concentration to the IWQC output for each input row, with TU values >1 indicating a potential exceedance of the particular Cu IWQC. Given the basis of EPA’s aquatic life WQC derivations (Xxxxxxx et al. 1985), a TU >1 does not explicitly mean actual toxicity would be expected to occur. Rather, it simply indicates an exceedance of the particular magnitude of the criterion. Figure 0-12. Instantaneous copper criteria report The acute and chronic HC5 option is available for other metals for which BLM-normalized toxicity data have been used to construct a SSD, which was then used to calculate the 5th percentile of organism sensitivity. The BLM-predicted HC5 can be interpreted in a manner similar to EPA’s derivation of aquatic life WQC, but HC5 calculations have not been reviewed and adopted by EPA. For additional information on the terminology and the exact workings of the WQC calculation, the user is advised to refer to EPA (2007). The criteria report shown in Figure 5-13, being in Microsoft® Excel file format, can also be copied for pasting onto any external application or report.