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2020 ANNUAL GROUNDWATER MONITORING REPORT <br /> TEICHERT AGGREGATES AND GRANITE CONSTRUCTION <br /> VERNALIS AREA <br /> 4 SUMMARY <br /> Quarterly groundwater level and quality monitoring of two identified aquifer zones(a shallow and a <br /> deep zone) commenced in 1994 and mining of the Vernalis Central area commenced in 1998. Water <br /> level data, collected semi-annually from 1960 through present by the California Department of Water <br /> Resources, are also available for one shallow zone well. <br /> Groundwater levels in the shallow wells have declined to the lowest levels since the period of record <br /> began in 1994. Groundwater elevation contour maps indicate relatively steady shallow groundwater <br /> flow in southeasterly to easterly directions over the period of record. Groundwater levels observed in <br /> the deep wells are typically lower than in the shallow zone and exhibit greater seasonal and annual <br /> fluctuation than groundwater levels in the shallow wells due to increased aquifer confinement and <br /> pumping stresses. In the early 2000's,groundwater levels in the deep zone noticeably declined, likely in <br /> response to reported increased pumping stress and overall dry conditions. In the mid 2000's, substantial <br /> recovery of groundwater levels occurred, however, seasonally high-water levels remained below those <br /> observed in the mid to late 1990s. Since 2013,groundwater levels have approximately declined an <br /> average of 50 feet. <br /> The groundwater quality record documents stable conditions in both the shallow and deep aquifer <br /> zones. Shallow groundwater is generally of Ca-Na/HCO3-CI or Na-Ca/HCO3-CI type and deep <br /> groundwater is of Ca-Na/HCO3-SO4 or Ca-Na/SO4-HCO3 type.The overall content of soluble minerals is <br /> slightly higher in shallow zone groundwater than in deep zone groundwater. Elevated nitrate <br /> concentrations in groundwater, documented since pre-mining times to the present, are most likely <br /> attributable to historical and ongoing agricultural land use in the area. In summary, the existing data <br /> record shows no indication that mining operations have changed groundwater quality to date. <br /> LUHDORFF He SCALMANINI <br /> CONSULTING ENGINEERS 9 <br />