SITE INFORMATION AND CORRESPONDENCE_CASE 2

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REGIONAL WATER BOARD RESPONSE (SWRCB/OCC File A-1846(a) and A1646(b)) -7- PETITIONS FOR REVIEW OF W�= DISCHARGE REQUIREMENTS ORDER NO. R5-2007-0036 (NPDEa NO. CA0079154) AND TIME SCHEDULE ORDER NO. R5-2007-0037 CITY OF TRACY, WASTEWATER TREATMENT PLANT however, the Order would authorize very minimal, if any, lowering of receiving water quality given the increased level of treatment required by the Order. The third part of the test applies to so-called "Outstanding National Resource Waters", but the receiving water in this case-Ts rtof su-Ch a water. RESPONSES TO CSPA'S CONTENTIONS fA-1846(b)1 The following are the Regional Water Board's responses to discrete contentions raised in CSPA's petition. For convenience, the responses are correlated to the issues as they appear in the petition. CSPA — CONTENTION A: The Order does not contain a protective or legal effluent limitation for Electrical Conductivity. The discharge from the Facility contains total dissolved solids (TDS), chloride, sulfate, and electrical conductivity (EC). These are water quality parameters that are indicative of the salinity of the water. Their presence in water can be growth limiting to certain agricultural crops and can affect the taste of water for human consumption. The Basin Plan contains a chemical constituent objective that incorporates State Maximum Contaminant Levels (MCLs), contains a narrative objective, and contains site-specific numeric water quality objectives for EC (See Table 1). Table 1 — Sali ity Water Q ality Criteria/Objectives and Effluent Data Agricultural Secondary Basin Plan Effluent Parameter WQ Goal MCLS (Bay-belta Plan)4 Avg Max EC (Nmhos/cm) Varies 900, 1600, 1000 00 ( r ) 1753 2410 2200 (1 Sep– 31 Mar) TDS (mg/L) varies 500, 1 0 0 N/A 1019 2060 15 Sulfate (mg/L) N/A 2560000 N/A 246 350 Chloride (mg/L) varies 250, 0 0 NIA 286 340 1 Agricultural water quality goals based on Wafer Quality for Agriculture, Food and Agriculture Organization of the United Nations—Irrigation and Drainage Paper No. 29, Rev. 1 (R.S.Ayers and D.W. Westcot, Rome, 1985) 2 The EC level in irrigation water that harms crop production depends on the crop type, soil type, irrigation methods, rainfall, and other factors. An EC level of 700 pmhos/cm is generally considered to present no risk of salinity impacts to crops. However, many crops are grown successfully with higher salinities. 3 The secondary MCLS are slated as a recommended level, upper level, and a short-term maximum level. 4 Compliance with the Bay-Delta Plan water quality objectives is determined at three monitoring locations in the South Delta. Final water quality-based effluent limitations (WQBELs) based on the secondary MCL, Basin Plan numeric objectives, or the agricultural water quality goal would likely require construction