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Groundwater Salinity Impacts For the purpose of estimating the salinity impact ^� ,� egate percolate concentration of 776 mg/l was calculate erage of total percolate. The total volume of percolate is approximately 9.26 x 106 ft3/year. The percolate will be intercepted by 1.65 x 106 ft3 of shallow groundwater with an average salinity of 684 mg/1 . Assuming ideal mixing conditions the average salinity will be 762 mg/l after mixing. Thus groundwater salinity in the shallow ..aquifer of the Victor formation will increase by about 11% in the immediate vicinity of the plant. The water level data for the monitoring wells indicate that the hydraulic gradient at the site may be significantly greater than 10 ft/mile. Therefore the calculated salinity increase of 11% should be considered as an upper limit of impact on groundwater quality. A plot of the conductance of groundwater samples from the monitoring wells is shown in Figure 6. It is clear that groundwater salinity has remained constant since 1985. The local stratigraphy divides the components of the upper aquifer system into two units. The shallow groundwater which is impacted directly by the wastewater disposal operation already has a relatively high concentration of salts due to the agricultural practices of the area. Based on the regional average groundwater gradient it appears that the shallow groundwater will be only slightly affected by QAP irrigation practices. The primary source of G groundwater for domestic, municipal and industrial uses is the preferred aquifer in the Laguna formation. This aquifer is not impacted directly by the percolate derived from irrigation. Hydraulic continuity between the shallow groundwater and the underlying groundwater in the Laguna formation is diminished by the presence of a region of low hydraulic conductivity separating the two. Evidence for the existence of an aquitard comes from well log data. In addition water quality data indicates that groundwater in the Laguna formation is isolated from the shallow groundwater. Due to the local stratigraphy and regional geohydrology the land disposal of wastewater from the plant does not appear to significantly impact groundwater quality. A recent study (11) investigated the time required for infiltrated water to migrate downward to the groundwater. Based on a geographic data base included in the study a "Recharge Time Index" can be calculated. According to these calculations it appears that it will take approximately twelve years for the infiltrate at the surface to reach the groundwater in the vicinity of the cannery. tvkd �,� .fi,,A Summary and Conclusions The California Regional Water Quality Control Board Order No. 88-094 stipulates that QAP will provide an analysis of the potential for groundwater impacts due to the elevated total dissolved solids content of its wastewater. The constituents of primary concern are the inorganic salts since the organic fraction is removed by incorporation into the soil humus. 1-13 RP033-L