SITE INFORMATION AND CORRESPONDENCE_CASE 2

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REGIONAL WATER BOARD RESPnNSE (SWRCB/OCC File A-1846(a) and A-1846(b)) -7- PETITIONS FOR REVIEW OF We.c DISCHARGE REQUIREMENTS ORDER NO. R5-2007-0036 (NPDES 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 caseis not st3ch a water. RESPONSES TO CSPA'S CONTENTIONS rA-1846(b)] 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 — Salinity Water Q ality Crite rialOb'ectives and Effluent Data Agricukural Secondary Basin Plan Effluent Parameter WQ Goal' MCL' (Bay-Delta Plan)° Avg Max ECmhos/cm Varies' 900, 1600, 700 (1 Apr– 31 Aug) 1753 2410 (N ) 2200 1000 (1 Sep- 31 Mar) TDS (mg/L) Varies 500,5 0000, N/A 1019 2060 Sulfate(mg/L) N/A 250, 0 0 N/A 246 350 Chloride (mg/L) Varies2 250, 0 0 N/A 286 340 1 Agricultural water quality goals based on Water Quality torAgriculture, 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 stated as a recommended level, upper level, and a short-term maximum level. 4 Compliance with the Bay-Della 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