SITE INFORMATION AND CORRESPONDENCE

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Bert E. Van Voris 18 - 17 September 2004 Supervising Engineer TDS, mg/L Sodium, mg/L Chloride, mg/L MW-1 W-2 MW-1 W-2 MW-1 W-2 Apr 02 690 690 240 240 67 33 Jun 02 770 790 250 290 110 180 Sep 02 900 870 290 240 180 260 Nov 02 1100 1100 320 330 250 280 Feb 03 1200 980 350 310 290 260 May 03 1400 1000 370 300 340 250 Aug 03 1600 1000 390 290 420 260 Dec 03 1600 900 440 320 430 260 Feb 02 1700 1500 970 340 460 300 May 04 1600 1 1100 1 470 370 460 1 340 The RWD acknowledges but offers no explanation for the increasing trend of TDS, sodium, and chloride in both MW-1 and W-2. On a 24 June 2004 site inspection, Regional Board staff observed wastewater overspray extending far upslope beyond the perimeter of Field 95 and, by extension, MW-1. Other than citing the clayey nature of site soils and the reduced permeability of site soils due to their increasing sodicity from the discharge as evidence for reduced infiltration of applied wastewater to shallow groundwater,the RWD offers no substantive evidence that the discharge is not causing or contributing to the increase in sodium and chloride in these two wells. Due to the increasing sodium and chloride concentrations in some soil profiles, it is apparent that applied salt constituents are migrating through the soil profile and contributing to increased salt concentrations in shallow groundwater. Lacking additional data on groundwater quality upgradient from and beyond the areas directly or indirectly receiving the discharge (i.e., as overspray), it should be concluded that MW-1 is potentially influenced by the discharge and should not be utilized to characterize upgradient ambient groundwater quality. Regarding the RWD's conclusion that impounded wastewater cannot be influencing the quality of groundwater passing through MW-16,the estimated low permeability is based on only two soil borings drilled on a side slope. Evidence of sand and gravel deposits underlying the reservoir area is contained in technical submittals describing the reservoir's construction, which also show a borrow area but provide no information regarding borrow pit depth or whether the excavation penetrated to higher permeable layers. The RWD neither acknowledges the possibility that the elevated concentrations are due to the past and ongoing discharge nor offers any substantive evidence that the elevated concentrations are not attributable to the discharge. It does not take into consideration the potential impact to groundwater caused by the generation of bicarbonate alkalinity and mobilization of calcium and magnesium resulting from the subsoil decomposition of applied organic constituents. The RWD attempts to disregard the concentrating effects of evaporation on the chloride concentration of soil solution released to groundwater. Just because the chloride concentration in groundwater passing through a downgradient well is higher than the discharge does not mean the discharge is not contributing to the chloride in groundwater.