SITE INFORMATION AND CORRESPONDENCE 2000-2018

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FACT SHEET ORDER NO. 5-f-031 ATTACHMENT C -9- CITY OF LODI WHITE SLOUGH WATER POLLUTION CONTROL PLANT SAN JOAQUIN COUNTY 18 samples. Effluent limitations for lead have been included in this Order based on the converted chronic criteria. Full compliance with the lead limitations are not required by this Order until 1 May 2004. Mercury: Effluent monitoring for mercury has shown the median concentration to be non- -detectable at <0.2 µg/1, and the highest measured to be 0.63 µg/1. The accuracy of the analyses is questionable without implementing "clean technique" (EPA Method 1631) for sample collection, handling, and analyses. The current EPA Ambient Water Quality Criteria for continuous concentration of mercury (30-day average, chronic criteria) is 0.77 µg/1, and the proposed California Toxics Rule concentration is 0.050 µg/1. Mercury is listed under the California 303(d) list as a pollutant causing impairment in the Sacramento-San Joaquin Delta. This listing is based partly on elevated levels of mercury in fish tissue. Because the Sacramento-San Joaquin Delta has been listed as an impaired water body for mercury based on fish tissue impairment, the discharge must not cause or contribute to increased mercury levels in fish tissue. In view of the uncertainty of applicable water quality criteria, and the accuracy of existing sampling results, this permit contains an interim performance-based effluent limit of 1.36 lbs/year for mercury. This interim mass limit was developed taking one-half of the average effluent m--rcury concentration (<0.2 µg/1) and applying that to the average daily flow of 5.6 mgd dischareed to Dredger Cut for 8 months out of the year and including a 20% allowance in mass loading to account for unforeseen variability in concentrations. The limit will not become effective until 1 January 2004, or one year after establishment and approval of a watershed mercury loading offset program. This Order requires monitoring for mercury using a "clean technique"EPA Method 1631. The Discharger is required to develop a program for identification and control of mercun, discharges within the collection system. If mercury is found to be causing toxicity, or if a TMDL (Total Mass Daily Loading) program is adopted for the Delta, this permit will be reopened and modified or revised to address the issue of mercury concentrations or loading. Zinc: The Basin Plan's numerical water quality objective for dissolved zinc is a maximum concentration of 100 µg/l, which is equivalent to a total recoverable concentration of 101 c:Jl. EPA's ambient water quality criteria for protection of freshwater aquatic life are a continuous concentration of 133 µg/l (4-day average, chronic criteria), and a maximum concentration of 133 µg/1 (expressed as a 1-hour average, acute criteria), using a water hardness of 113 mill. These criteria were originally developed using metals concentrations expressed as total recoverable metals, but have been converted to be expressed as dissolved metals. For zinc, the acute CF=0.978 and the chronic CF=0.986. 40CFR 122.45(c) requires that permit limits be expressed as total recoverable metal. A reasonable assumption is that the metal concentration in the receiving water is biologically available to the same extent as during the toxicity testing. Therefore, the wat,-r quality criteria, expressed as dissolved metal, has been divided by the conversion factor, and presented in the table, above, for the purpose of comparing the measured effluent concentrations with the criteria. Sampling results shown that effluent concentrations of zinc have exceeded the converted acute and chronic criteria, and also the Basin Plan water quality objective if converted to a total recoverable metal concentration. The Basin Plan objective is the most stringent. An effluent