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2020 ANNUAL GROUNDWATER MONITORING REPORT TEICHERT AGGREGATES AND GRANITE CONSTRUCTION VERNALIS AREA 2 GROUNDWATER MONITORING ACTIVITIES Teichert's permits requires a minimum of 10 wells to be located around the general perimeter of the permitted mining area for quarterly groundwater level monitoring. In addition, the permit requires 5 wells (two upgradient from the project site,two downgradient from the project site, and 1 on site)for groundwater quality monitoring. Groundwater quality monitoring shall include, at a minimum,general mineral analyses, and nitrate. Wells used for domestic purposes shall also be tested for bacteria.The permit does not specify a frequency for groundwater quality monitoring activities.Since the inception of the monitoring program in 1994 and through 2009,groundwater quality sampling was conducted on a quarterly schedule together with groundwater level measurements.Groundwater quality monitoring was reduced to a semi-annual schedule in 2010.The required reporting frequency of monitoring results is annual. The wells for the monitoring network were selected based on a reconnaissance groundwater investigation conducted by LSCE in 1991 and 1992 (LSCE, 1992). Results indicated that the depth to groundwater ranged between 80 feet beneath the valley floor to the northeast and 250 feet beneath the mountain flanks to the southwest. In addition, a confining clay was identified beginning at an approximate depth of 250 feet beneath the Vernalis Central Phase 1 and 8 that appeared to divide the underlying aquifer into shallow and deep zones.This clay is most likely the Corcoran Clay Member of the Tulare Formation, which has been reported to extend beneath much of the San Joaquin Valley, including the present monitoring network area (Hotchkiss, 1972). Further,the investigation indicated that the direction of groundwater flow in the shallow zone was to predominantly the southeast. Since 1994, groundwater levels have been obtained from a total of sixteen wells(Figure 2).The Thoming irrigation well was destroyed in early 2013. Since 2006,water level measurements in the irrigation well 4S/6E-6A1 have been precluded by an obstruction at a depth of approximately 100 feet(bgs). Since fall 2018, water level measurements in the Koster irrigation well have been precluded by instrumentation of the California Department of Water Resources that lodged in the well casing.Since 2016, water level measurements in the Rustan well have been infrequent due to site access limitations.South Tracy#3 has an obstruction at approximately 271 ft bgs and is only accessible for water levels that are above the obstructed depth. Prior to 2019, port access at the Granite#3 well had been difficult and only a few measurements had been obtained since this well was incorporated into the network in 2006. During spring 2019, the pump was removed from Granite#3 and water levels since then have been obtained. In fall 2017, Granite#4 and Brown's New well were rehabilitated.Since the rehabilitation, the sounding port at Granite#4 has been obstructed at approximately 370 ft bgs (approximately 285 ft bgs starting in 2020)and is only accessible for water levels that are above the obstructed depth. An airline was installed in the Brown's New well to obtain water levels, but it was destroyed by wildlife in spring 2018 making the well inaccessible for water level measurements.The airline was repaired, and pressure readings were obtained in 2019 and spring 2020. In summer 2020, the pump was temporarily removed, and a water level was obtained. By fall 2020,the pump was re-installed, however there was no longer an airline and no access to the well for water level measurements. In 2019, the Granite#5 production well LUHDORFF&SCALMANINI CONSULTING ENGINEERS 2