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�J From: <Liden.Douglas@epamail.epa.gov> To: <learyp@rb5s.swrcb.ca.gov>, <FagerneR@rb5s.swrcb.ca.gov>, <landauk @ rb5s.swrcb.ca.gov> Date: 12/15/99 2:06PM Subject: White Slough Permit Pat/Robert: I took a brief look at the White Slough WPCP Permit (NPDES No. CA 0076243). Overall, I thought you did a very thorough job setting the WQBELs and writing the justification for these limits in the findings. I am concerned, however, by the lack of any WQBELs for mercury. While I realize that it is difficult to establish WQBELs due to uncertainty in criteria and in monitoring results,the little data they do have (a hit of 0.63 ug/1), combined with the knowledge of what other similar POTWs discharge and the fact that this pollutant is currently . listed as causing impairment due to fish tissue levels, certainly indicate that the discharger could contribute to an exceedance of the narrative standards. The issue, I believe, is not whether they need a limit, but rather how to establish one. My suggestion: 1. A final limit referenced in the FINDINGS and fact sheet of zero loading unless a TMDL has been established and a different WLA has been determined; 2. An interim mass limit based on th.e 0.2 ug/I detection level multiplied by average flow; 3. Interim requirements as mentioned in our draft guidance and in the Tosco letter (attached); The rationale for these limits and this finding can be found in our draft guidance (you have already included the necessary P2 requirements); and 4.The reopener clause that you have already included allowing for tighter interim performance-based limits, if necessary. Again,the detail and organization of the findings and the fact sheet were excellent and we appreciate the high level of effort expended on this permit. We are pleased by the requirements for monitoring using the 1613 method and for aggressive the source control requirements for mercury. However, I don't think that these requirements are sufficient to meet the- definition of WQBELs under 122.44, and would send a message to dischargers that have gathered data using ultra-clean methods in the past that they are now being penalized for this effort. Simply adding a final limit in the findings and some additional interim requirements such as participation in TMDL development as well as a feasibility study for achieving offsets or otherwise eliminating mercury loads in addition to an interim mass cap should suffice. Feel free to give me a call if you have any questions at (415) 744-1920. Thanks. -Doug Liden (footnotes are attached to documents.)(See attached file: guidance.WPD)(See attached file:toscoltr3.wpd) CC: <Oda.Terry@ epamail.epa.gov>