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WASTE DISCHARGE REQUIREMENTS ORDER R5-2013-0028 -22- DELICATO VINEYARDS, INC. DELICATO FAMILY VINEYARDS SAN JOAQUIN COUNTY d. Sodium. The process wastewater is currently not monitored for sodium, but sodium is known to be a key salinity constituent in winery wastewater. Data for the three background monitoring wells indicate that background sodium concentrations average no more than 86 mg/L. However, groundwater monitoring data from 2001 through 2011 consistently shows elevated sodium concentrations downgradient of the existing LAAs (up to 366 mg/L on average), and the downgradient sodium concentrations have apparently not decreased over time. The most stringent potential water quality objective for sodium is the agricultural water quality goal of 69 mg/L. However, that goal is intended to protect the most salt sensitive crops, such as beans, nuts, and deciduous fruits. Additional information about the crops that could be grown in the area, soil calcium, soil exchangeable sodium percentage (ESP), and soil Sodium Adsorption Ratio (SAR) would be needed to determine the numeric water quality objective for sodium to protect the agricultural beneficial uses of groundwater'. Therefore, this Order requires that the Discharger submit the information required to make this determination. Based on the planned modifications to the wastewater management system and expanded LAAs that this Order requires, concentrations of sodium in shallow groundwater are expected to decrease over time, but it is not possible to predict the level of improvement that can achieved or when it might occur. Therefore, this Order sets a groundwater limitation for sodium that prohibits any statistically significant increase in sodium concentrations in any compliance monitoring well and includes a time schedule in the Provisions that requires the Discharger to complete the proposed improvements, evaluate the effectiveness of salinity reduction measures implemented to date, and evaluate the feasibility of additional salinity reduction measures to reduce sodium concentrations in groundwater. This Order also requires that the Discharger evaluate existing and potential future local agricultural uses of groundwater to support determination of a site-specific water quality objective. e. Chloride. The process wastewater is currently not monitored for chloride, but chloride is known to be a key salinity constituent in winery wastewater. Data for the three background monitoring wells indicate that background chloride concentrations average no more than 23 mg/L. However, groundwater monitoring data from 2001 through 2011 consistently shows elevated chloride concentrations downgradient of the existing LAAs (up to 123 mg/L on average), and the downgradient chloride concentrations have apparently not decreased over time. The level of apparent degradation that has occurred is not likely causing beneficial use impacts unless the groundwater is used to irrigate the most chloride sensitive crops, such as strawberries and avocados2. ' Ayers, R. S. and D. W.Westcot, Water Quality for Agriculture, Food and Agriculture Organization of the United Nations- Irrigation and Drainage Paper No. 29, Rev. 1, Rome (1985), Section 4.1.2. 2 Ibid, Section 4.1.1.