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Mr. Robert Meleg - 3 - 22 July 2003 Public Works Director objectives state groundwater shall not contain chemical constituents in concentrations that adversely affect any beneficial use, including any exceedance of maximum contaminant levels (MCLS) specified in Title 22, California Code of Regulations (CCR), as necessary for domestic supply. The Basin Plan requires application of the most stringent objective for each constituent to protect the beneficial uses (i.e., domestic drinking water, agricultural supply, etc.). To protect the specific beneficial uses of groundwater, narrative water quality objectives are translated into numerical limits (i.e., MCLs specified in Title 22, etc.). To project agricultural beneficial use, appropriate limitations for groundwater include, at a minimum, EC of 700 µmhos/cm, sodium of 69 mg/L, and chloride of 106 mg/L. Underlying groundwater already exceeds some of these limitations and, despite what is stated in the RWD, exceeds some of the groundwater limitations derived from Title 22 MCLS (even in wells not impacted by offsite sources). Groundwater underlying the WWTF exceeds the primary MCL limit of 2.2 MPN/100 mL for total coliform organisms (TCO), and the secondary MCL limits of 0.05 mg/L for manganese, 0.3 mg/L for iron, and 900 µmhos/cm for EC. The groundwater data also shows a chemical oxygen demand in the groundwater ranging from 1 to 53 mg/L,and total organic carbon ranging from 11 to 46 mg/L. Although both upper concentrations are downgradient of MW-6 (impacted from offsite domestic septic tank systems), monitoring wells such as MW-5, directly downgradient of the WWTF's disposal ponds and within the area influenced by effluent mounding, are also i pacted. For example, MW-5 has concentrations of selected constituents as follows: iron (0.42 mg/L), manganese (6.1 mg/L), total organic carbon (16 mg/L), sodium(380 mg/L), EC (1,244 µmhos/cm), and TCO (26 MPN/100 mL). This data constitutes evidence of degradation and the lack of assimilative capacity in soils underlying disposal ponds to effectively reduce the concentrations of decomposable waste constituents in the percolating wastewater. The RWD acknowledges that the Regional Board may impose more stringent 5-day biochemical oxygen demand(BODS), total suspended solids (TSS), total nitrogen, and coliform limitations when it drafts waste discharge requirements for the new expansion. The RWD also indicates that uncertainties by Regional Board staff over the potential far groundwater degradation by the WWTF and its discharge, if any, and the relative value of the recent improvements on groundwater limitations are based upon limited data reflecting the WWTF prior to, or during the improvements. Adequate time and improved information are needed to reach conclusions regarding the impact of the WWTF and its discharges on groundwater quality. Recent monitoring for additional constituents in groundwater influenced by the discharge clearly shows exceedances of applicable water quality limits and degradation by oxygen demanding substances. Continued groundwater monitoring for key constituents will confirm this. It is unlikely that recent improvements will adequately protect groundwater quality, which is clearly already degraded by the discharge. Because the existing groundwater has been impacted, the proposed discharge must not exacerbate the impacts. The discharge's impact to groundwater must be reduced to levels that will protect the beneficial uses of the groundwater and be consistent with Regional Board plans and policies. Iron and sodium concentrations based on May and June 2003 samples averaged. Manganese,total organic carbon,EC and TCO based on one June 2003 sample.