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3. Monitoring Results Quarterly groundwater level and quality monitoring commenced in March 1994 to characterize pre- mining groundwater conditions in the area and facilitate the continued evaluation of local groundwater conditions. Also,as part of Teichert's approved plan to dry-pit mine, groundwater level monitoring provides the necessary information to establish and maintain a buffer between the base of mining and groundwater. Mining of the Lone Tree ll mining phase began in 1998 and has proceeded to varying depths in different portions of the phase:to an approximate depth of 80 feet in the initial mined area r (currently used as a siltation pond) and to the permitted mining depth of 150 feet in the currently mined area. r 3.1 Groundwater Levels Long-term fluctuations of shallow groundwater levels in the area are depicted by the hydrograph for Well r 4S/6E-5A 1 (Figure 4), which has been monitored semi-annually by the California Department of Water Resources(DW R) since 1960(typically in the winter, i.e.. Janua February,or March;and in late summer/early fall, i.e., in September or October)and quartr��IIlyi for Teichert's quarry excavation _ monitoring program sine 1994. The lowest water level, i. 6 feet above mean sea level(msl),was recorded in early 1962, at the end of two consecutive criticyears. Water levels recovered subsequently to a high of 87.9 feet(msl) in December 1969. During this early period, seasonally high water levels ranged from approximatef 83 to 8�feet(msl)and seasonally low elevations typically ranging from 78 to 82 feet(msl). Water levels declined about 5 feet during the 1976-77 drought and then quickly recovered in the late 1970s and early 1980s to reach the highest water levels on record during the wet period of 1983-86(i.e.,91.2 feet,msl in October 1984). During the 1987-92 drought, water levels r declined to levels below those observed during the 1976-77 drought and,since then, have not recovered to earlier elevations. The quarterly record,starting in 1994, shows that water levels recovered some, to a high of almost 81 feet(msl) in 1998 (i.e., at the end of 4 consecutive wet years). Since then, seasonally r high water levels have slightly declined almost every year to below 75 feet(msl). Prior to the 1987-92 drought, seasonal water levels fluctuated commonly 5-8 feet. Since 1994, seasonal water level fluctuations have mostly ranged between 2-3 feet. DWR's semi-annual record indicates that seasonally high water levels are most typically observed in late summer and early fall;not during the wet season in r winter and early spring. This pattern is substantiated by the quarterly water level record dating back to 1994. r Groundwater levels in the shallow wells located west and northwest of Well 4S/6E-5A I,are 3 to 6 feet higher but show the same seasonal fluctuations and overall water level trends during the period of record (Figure 5). Specifically,the quarterly record,starting in 1994, shows that post-drought water levels recovered some;and highest water levels were observed in 1998. Since then,seasonally high water levels r have slightly declined almost every year at the same rate as water levels have declined in Well 4S/6E- 5A1. Individual hydrographs for network wells are provided in Attachment 1. The median depth to groundwater in the shallow aquifer zone has ranged from about 81 feet in the northwest portion of the monitored area(i.e.,Hall and Faulkner wells)to about 155 feet in the southeast (Well 4S/6E-6A1)(Table 1). Corresponding groundwater elevations are shown in Table 2. ,. Groundwater levels observed in the deep wells are typically lower,and they exhibit greater seasonal and annual fluctuation than levels in the shallow wells(Figure 6). Water levels in the deep zone have ranged in depth from about 190 to 340 feet, with up to 40 to 60 feet of seasonal fluctuation. In the early 2000s, r ©LLI WFF & SCGLIAF INI 4 CONSULTING ENGINEERS r