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D R A F T January 4, 2012 salinity requirements."" The State Water Board is unable to assess, based on the current record, whether site-specific factors in this case would justify higher EC concentrations; however, the Central Valley Water Board can evaluate this issue on remand. Further, as mentioned previously, the City contends that the elevated EC levels may be due to regional groundwater conditions, which have been influenced by the predevelopment intrusion of brackish to saline water in the Delta region. There is little information in the record on concentrations of wastewater constituents in the storage ponds. Limited data indicates that TDS and EC values in the pond exceed water quality objectives for groundwater during much of the year. Nitrate concentrations as N, on the other hand, have been relatively low. From 2002 to 2004, average monthly nitrate concentrations in the storage ponds varied from roughly 1 to 7 mg/L as N. On the other hand, ammonia concentrations in the ponds are relatively high, and the City has indicated that transformation of ammonia to nitrate in the storage ponds and subsurface may be occurring.4' Leakage of wastewater from the ponds along with subsequent nitrification could lead to nitrate concentrations in groundwater well above the maximum contaminant level. Based on the available evidence in the record, the Board concludes that at least some of the Facility's activities have adversely affected groundwater underlying the site. The groundwater mounding provides physical evidence of a release from the Facility. Groundwater monitoring data from wells downgradient from the unlined ponds show nitrate and EC levels that exceed the applicable Basin Plan objectives. Although it is unclear whether the pre- discharge EC values in the groundwater underlying the Facility were elevated, it appears that the EC concentrations currently existing within the downward-and-outward flowing groundwater mound could have been caused by the ongoing downward percolation of wastewater discharged within the Facility. The Board concludes that wastewater releases from the unlined storage ponds may have resulted in nitrate and EC concentrations above the applicable Basin Plan objectives in the underlying groundwater. Therefore, the City's discharge of wastewater to the unlined ponds does not qualify for an exemption from Title 27 at the present time. As explained previously, there is insufficient evidence in the record to assess whether naturally occurring concentrations of some constituents, such as EC, in groundwater underlying the Facility exceed the applicable Basin Plan objectives. Thus far, the City has not provided sufficient information to demonstrate that naturally occurring concentrations of salts exceed the 44 See discussion in State Water Board Order WQ 2004-0010(Woodland), pp.4-8. 45 Final Report, fn.31, ante, at pp. 6-11; Report of Waste Discharge,fn. 1, ante, p.45. 16.