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inappropriate amendment of the Basin Plan to apply the Delta zinc objective to Dredger <br /> Cut. <br /> 1. Clean Techniques _ <br /> The Regional Board has concluded that limitations are necessary based upon <br /> historical metals readings from 1992 through 1997. Data since August 1998, which were <br /> not used in the analysis, show that even total recoverable measurements were not above <br /> 100 ug/1. The historical effluent data is suspect because "clean techniques"were not <br /> used. The recently published draft policy developed to implement the Inland Surface <br /> Waters Plan discusses the need to use "available, valid, relevant, representative data and <br /> information" in determining the need for water quality-based permit limits. Without <br /> reliable data, it is inappropriate to determine whether an effluent limitation is necessary to <br /> comply with water quality criteria or protect beneficial uses. In the case of metals, EPA <br /> has stated that it is necessary to use clean sampling techniques when measuring metals in <br /> the parts-per-billion ("ppb") range and ultra-clean techniques when measuring in the <br /> parts-per-trillion ("ppt") range. <br /> Through various publications, EPA has informed states and the regulated <br /> community that metals data are often unreliable due to widespread analytical <br /> contamination. Without the use of clean techniques, the metals data simply are not <br /> reliable. The Regional Board recognized the importtance of this technique in relation to <br /> mercury, stating that "the accuracy of the analyses is questionable without implementing <br /> `clean technique' for sample collection, handling and analysis." (Permit at 5, ¶25.) In <br /> fact the Regional Board required the use of ultra-clean techniques "for the purpose of <br /> establishing a performance-based effluent limitation." Given that the more recent data do <br /> not indicate any concern regarding zinc levels (absent consideration of dilution) and the <br /> historical data is virtually certain to be contaminated, deferral of the limitation and <br /> improved monitoring is appropriate. <br /> 2 Application of EPA Recommended Translator Yields Higher Limitations <br /> A key assumption regarding the Regional Board's imposition of restrictive zinc <br /> limitations is that dissolved objectives are being exceeded. In reaching this conclusion, <br /> NPDESPermitComments Exhibit 2 Page 5 12/17/99 <br />