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2021 ANNUAL GROUNDWATER MONITORING REPORT TEICHERT AGGREGATES AND GRANITE CONSTRUCTION VERNALIS AREA The presence of the observed nitrate concentrations is likely related to both the historical agricultural land use in the area prior to the commencement of aggregate mining by Teichert Aggregates and also continuing farming practices.This includes the nitrate concentration increases in the Brown's#1 well. Metal concentrations(i.e., copper, iron, and zinc) in shallow groundwater samples(i.e.,from the Hall and Faulkner wells)are typically low and frequently below their respective reporting limits. Iron and zinc detections are more frequent at the Faulkner well than at the Hall well. In the deep wells Tracy#1 and#3, metal concentrations are typically low and frequently below their respective reporting limits. Metal concentrations (i.e., particularly iron and manganese) are more frequently detected and more variable in the other deep wells (i.e., Brown's New, Brown's#1, Granite #3, and Granite#5). Total coliform bacteria have been nondetect from the Hall and Faulkner domestic wells with few exceptions. Most recently,total coliform bacteria were detected at the reporting limit of 1.1 MPN/100 mL in the August 2008 sample retrieved from the Hall well. Fecal coliform organisms were nondetect. The sporadic presence of coliform bacteria can be due to sample contamination at the time of collection,the introduction of coliform bacteria to the well structure during well and pump maintenance work, or the detachment of bacterial biofilm from the well structure in combination with naturally occurring coliform organisms. 5 SUMMARY Quarterly groundwater level and quality monitoring of two identified aquifer zones (a shallow and a deep zone)commenced in 1994 and mining of the Vernalis Central area commenced in 1998. Water level data, collected semi-annually from 1960 through 2020 by the California Department of Water Resources,are also available for one shallow zone well. Groundwater levels in the shallow wells have declined to the lowest levels since the period of record began in 1994. Groundwater elevation contour maps indicate relatively steady shallow groundwater flow in southeasterly to easterly directions over the period of record. Groundwater levels observed in the deep wells are typically lower than in the shallow zone and exhibit greater seasonal and annual fluctuation than groundwater levels in the shallow wells due to increased aquifer confinement and pumping stresses. In the early 2000's,groundwater levels in the deep zone noticeably declined, likely in response to reported increased pumping stress and overall dry conditions. In the mid 2000's,substantial recovery of groundwater levels occurred, however,seasonally high-water levels remained below those observed in the mid to late 1990s.Since 2013,groundwater levels have approximately declined an average of 70 feet. The groundwater quality record documents stable conditions in both the shallow and deep aquifer zones.Shallow groundwater is generally of Ca-Na/HCO3-CI or Na-Ca/HCO3-CI type and deep groundwater is of Ca-Na/HCO3-SO4 or Ca-Na/SO4-HCO3 type.The overall content of soluble minerals is LUHDORFF&SCALMANINI CONSULTING ENGINEERS 8