SITE INFORMATION AND CORRESPONDENCE 1980-1999

Home Browse Search

Cvanide It appears that the Regional Board staff included a total cyanide daily y maximum effluent limitation in the Permit because several samples from 1996 are claimed to exceed the Basin Plan aquatic life objective of 10.0 ug/1. There are a number of misplaced legal and regulatory conclusions that were made in reaching the conclusion that cyanide limitations are necessary. First, the 10 ug/l cyanide objective used to calculate the daily maximum limitation is not applicable to Lodi's discharge. That provision of the Basin Plan specifically applies to Delta waters as defined in the Plan. This area does not include Dredger Cut. Absent a finding that it is reasonable and appropriate to apply the criteria to Dredger Cut, via demonstration of a narrative criteria exceedance, the 10 ug/1 objective may not be applied to Lodi's discharge. Second, there are no known sources of cyanide to the POTW. The high value samples all were reported when the treatment plant was partially nitrifying and there were no sources of pollution that could have caused these levels after advanced treatment. All other test results have been below the detection-level. In fact, all samples for the past three years have been below the detection level. An analysis of the test results clearly leads to the conclusion that the data relied upon are not reliable, which is highly probable because of the many potential sources of interference for measuring cyanide in Lodi's waste stream. "Interference" is common in municipal effluents from similarly designed POTWs due to the formation of chemicals that give false positive results in total cyanide tests. See, Attachment 1, Water Environment & Technology, Vol. 11. No. 11,Nov. 1999, pp 50-51. Given the infrequent nature of the elevated readings and the likelihood of test interference, further testing should be required before imposing a cyanide limitation. There is no reasonable basis for concluding that cyanide is presently being discharged at levels inimical to aquatic life in Dredger Cut. The Regional Board also misapplied the water quality criteria in establishing a monthly average limit based on EPA's proposed California Toxics Rule ("CTR") criteria. The criteria in the CTR were driven by rainbow trout bioassays. There are no trout in • Dredger Cut or White Slough. Considering the important site-specific factors, NPDESPtrmitCommtnts Exhibit 2 Page 3 12/17/99