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0 <br /> WASTE DISCHARGE REQUIREMENTS ORDER R5-2013-0028 -18- <br /> DELICATO VINEYARDS, INC. <br /> DELICATO FAMILY VINEYARDS <br /> SAN JOAQUIN COUNTY <br /> 73. Groundwater monitoring at the facility since 2001 has demonstrated that the <br /> previous and current discharge has degraded groundwater quality to levels that <br /> could affect plant growth if the shallow groundwater were to be used for irrigation <br /> of salt-sensitive crops. However, the planned changes in the discharge, which are <br /> required by this Order, are expected to prevent future increases in groundwater <br /> salinity and the existing salinity levels should decrease over time through <br /> attenuation. <br /> 74. Excessive application of high organic strength wastewater to land can create <br /> objectionable odors, soil conditions that are harmful to crops, and degradation of <br /> underlying groundwater with nitrogen species and metals, as discussed below. <br /> Such groundwater degradation can be prevented or minimized through <br /> implementation of best management practices which include planting crops to take <br /> up plant nutrients and maximizing oxidation of BOD to prevent nuisance <br /> conditions. <br /> 75. Unless groundwater is very shallow, groundwater degradation with nitrogen <br /> species such as ammonia and nitrate can be prevented by minimizing percolation <br /> below the root zone of the crops and ensuring that the total nitrogen load does not <br /> exceed crop needs over the course of a typical year. Where there is sufficient <br /> unsaturated soil in the vadose zone, excess nitrogen can be mineralized and <br /> denitrified by soil microorganisms. <br /> 76. With regard to metals, excessive BOD loading rates can deplete oxygen in the <br /> vadose zone and lead to anoxic conditions. At the ground surface, this can result <br /> in nuisance odors and fly-breeding. When insufficient oxygen is present below the <br /> ground surface, anaerobic decay of the organic matter can create reducing <br /> conditions that convert metals that are naturally present in the soil as relatively <br /> insoluble (oxidized) forms to more soluble reduced forms. This condition can be <br /> exacerbated by acidic soils and/or acidic wastewater. If the reducing conditions do <br /> not reverse as the percolate travels down through the vadose zone, these <br /> dissolved metals (primarily iron, manganese, and arsenic) can degrade shallow <br /> groundwater quality. Many aquifers contain enough dissolved oxygen to reverse <br /> the process, but excessive BOD loading over extended periods may cause <br /> beneficial use impacts associated with these metals. <br /> 77. Typically, irrigation with high strength wastewater results in high BOD loading on <br /> the day of application. It is reasonable to expect some oxidation of BOD at the <br /> ground surface, within the evapotranspiration zone and below the root zone within <br /> the vadose (unsaturated) zone. The maximum BOD loading rate that can be <br /> applied to land without creating nuisance conditions or leaching of metals can vary <br /> significantly depending on soil conditions and operation of the land application <br /> system. <br /> 78. Maximum BOD loading calculations were prepared for current wastewater <br /> discharge at 56 MGY with 23 acres of LAAs and for the proposed facility <br />