SITE INFORMATION AND CORRESPONDENCE_CASE 2

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Ms. Jeanine Townsend .4 - 4 March 2009 study was conducted to establish this dilution credit/mixing zone for the priority pollutant human health criteria." On pages 12-13, revise the carryover paragraph to read: The Central Valley Water Board inappropriately considered the discharge to be a "completely-mixed discharge" without making findings that document an adequate demonstration and verification that the discharge completely mixes. On remand, an appropriate dilution credit should be determined using procedures detailed for incompletely-mixed discharges, which requires site-specific data and an independent mixing zone study, and should contain the appropriate parameters. Anti! the Unless the Central Valley Water Board can make appropriate findings based on the existing record or the Discharger provides study results that are complete and acceptable to the Central Valley Water Board, the discharge should be granted no dilution credit for priority pollutant human health criteria. Chronic Ammonia Effluent Limitation We agree that using a median receiving water pH to calculate the 30-day average chronic criterion may not be adequately protective of the aquatic life beneficial uses of the receiving water. Further evaluation of the ammonia effluent limitations should be conducted and the permit modified accordingly. Chronic Toxicity Effluent Limit We agree that a narrative effluent limitation for chronic toxicity must be added to the permit. However, the Draft Order also requires the permit to be revised to include a re-opener provision to allow implementation of a numeric chronic toxicity limitation when one is available. The adopted permit already includes a re-opener provision (Section VI.C.1.e, p.20) that allows the permit to be re-opened to allow implementation of a numeric chronic toxicity effluent limitation if the State Water Board revises the SIP's toxicity control provisions to require the establishment of numeric chronic toxicity effluent limitations. The reopener language is based on Order WQO 2003-0012 (Los Coyotes/Long Beach), and is the same as the reopener language the State Water Board approved in WQ 2008-0008 (City of Davis). (See, Order WQO 2003-0012, pp. 9-10, and Order WQ 2008-0008, pp. 6-7.) We suggest the following change to the Draft Order starting at the last sentence of the first paragraph of page 17: ... This Permit already includes the appropriate re-opener provision but must also include a similar narrative effluent limitation. On remand, the Central Valley Water Board must include a narrative chronic toxicity limitation in the City's permits aR apprepriate Fe openeF f^F ^ Rurneri In addition, paragraph 4 on page 19 should be changed to read: 4. Amend the Permit to ensure that it contains a narrative chronic toxicity limitation