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ATTACHMENT 1 1-6 <br /> NITROGEN EFFLUENT LIMIT EVALUATION <br /> ORDER WQ 2014-0153-DWQ <br /> GENERAL WASTE DISCHARGE REQUIREMENTS <br /> FOR SMALL DOMESTIC WASTEWATER TREATMENT SYSTEMS <br /> Step B — Nitrogen Effluent Limit Evaluation <br /> If a Regional Water Board's Basin Plan addresses the area where the site is located, the <br /> nitrogen control measures shall be consistent with the Basin Plan. <br /> If the Step A evaluation indicated additional treatment for nitrogen control may be <br /> necessary, continue the evaluation at "Step B, Nitrogen Effluent Limit Determination." <br /> B1 Nitrogen Limits Required? The initial evaluation of the need for nitrogen control <br /> (discussed in Item A5) shall include comparison of the wastewater effluent quality to <br /> groundwater quality and the potential for the wastewater discharge to cause or <br /> contribute to a condition of pollution or nuisance. The benefits of nitrogen control <br /> should be balanced with the cost of implementing nitrogen control. <br /> Measures implemented to protect groundwater quality (e.g. equipping a pond with a <br /> synthetic or low permeability liner to reduce infiltration, using supplemental water to <br /> reduce LAA loading rates, or agronomic application of nitrogen) should be considered <br /> when determining the need for nitrogen effluent limits. <br /> B2 Low-Threat (Adequate Attenuation)? In low-threat situations, the 50 percent nitrogen <br /> removal (in effluent prior to discharge) is appropriate. Low-threat situations are those <br /> where additional nitrogen removal will occur in the dispersal area (e.g. land application <br /> crop uptake, denitrification, shallow dispersal area, etc.) or where adequate <br /> attenuation exists based on other conditions such as depth to groundwater. <br /> B3 High-Threat (Limited Attenuation)? In high-threat situations, the 10 milligrams per liter <br /> (mg/L) effluent limit is appropriate. High-threat situations are those where limited <br /> nitrogen removal will occur in the dispersal area or in limited attenuation situations <br /> (e.g. shallow depth to groundwater, fractured aquifer, potential for groundwater to <br /> migrate to surface water bodies with limited attenuation, etc.). <br /> September 23, 2014 <br />