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WASTE DISCHARGE REQUIREMENTS ORDER R5-2013-0028 -17- DELICATO VINEYARDS, INC. DELICATO FAMILY VINEYARDS SAN JOAQUIN COUNTY shall be less than 2.2 per 100 mL for groundwater designated as supporting the municipal and domestic supply beneficial use. 68. The Basin Plan's narrative water quality objectives for chemical constituents requires, at a minimum, that waters designated as supporting the municipal and domestic supply beneficial use to meet the maximum contaminant levels (MCLs) specified in Title 22 of the California Code of Regulations (hereafter Title 22). The Basin Plan recognizes that the Central Valley Water Board may apply limits more stringent than the Title 22 MCLs to ensure that waters do not contain chemical constituents in concentrations that adversely affect beneficial uses. The Basin Plan's narrative toxicity objective requires that groundwater be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, animal, plant, or aquatic life associated with designated beneficial uses. 69. The Basin Plan states that when compliance with a narrative objective is required to protect specific beneficial uses, the Central Valley Water Board will, on a case- by-case basis, adopt numerical limitations in order to implement the narrative objective. 70. In the absence of specific numerical water quality limits, the Basin Plan methodology is to consider any relevant published criteria. With regard to the agricultural supply beneficial use, general salt tolerance guidelines, such as Water Quality for Agriculture by Ayers and Westcot and similar references, indicate that yield reductions in nearly all crops are not evident when irrigation water has an EC less than 700 pmhos/cm. There is, however, an eight- to ten-fold range in salt tolerance for agricultural crops and the appropriate salinity values to protect agriculture in the Central Valley are considered on a case-by-case basis. It is possible to achieve full yield potential with waters having EC up to 3,000 pmhos/cm if the proper leaching fraction is provided to maintain soil salinity within the tolerance of the crop. 71. For some wastewaters, particularly food processing waste, sodium concentrations may be reduced or controlled by changing from sodium-based cleaning solutions (such as sodium hydroxide) to potassium-based solutions (such as potassium hydroxide). Because potassium is a plant nutrient, land application systems can be designed to maximize potassium uptake by the crop. 72. Chloride moves readily through the soil column with percolation. Chloride will not adsorb to soil as sodium can, and crop uptake of chloride is minimal for most crops. However, plants do take up chloride and excessive chloride in the soil and/or irrigation water can be toxic to crops. Crop sensitivity to chloride varies greatly, but leaching is often used to control chloride to keep crop land in production. Leaching, whether intentional or not, can degrade groundwater quality and may cause water quality objectives for chloride to be exceeded.