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Foothill Sanitary Landfill Page 14 of 53 San Joaquin County DPW - Solid Waste Joint Technical Document Revised 6/09/2020 encountered in the six borings consisted of moderately cemented clay/claystone and cemented silt/siltstone with in-place hydraulic conductivities on the order of 10-6 to 10-7 cm/sec. These same soils had remolded hydraulic conductivities as low as 10-9 cm/sec. The remaining soils consisted of cemented silty sand/silty sandstone with in-place hydraulic conductivities on the order of 10-3 cm/sec and remolded hydraulic conductivities between 10-4 to 10-5 cm/sec (Appendix D). During a Geologic Investigation (Kleinfelder 1990), seven soil borings (B-1 through B-7) were advanced to depths ranging from 30 to 65 feet in the east, southeast, and southern areas of the site. The soils encountered in the seven borings consisted of cemented clay/claystone, cemented silt/siltstone, and cemented sand/sandstone with in-place hydraulic conductivities ranging from 10-3 to 10-5 cm/sec. Remolded soils had hydraulic conductivities ranging from 10- 4 to 10-6 cm/sec. The results of the laboratory testing are tabulated in a report dated January 2, 1991 (Appendix E). 4.10.2.2. Groundwater First encountered groundwater at the site varies from about 200 to 300 feet below ground surface. Groundwater elevations generally range from about 36 feet MSL on the southern side of the site to about 61 feet MSL on the northern side of the site +/- 1 foot of seasonal variation. The average groundwater elevation at the site is about 45 feet MSL (2015 WDR). Groundwater flow velocity is approximately 90 feet per year based on a hydraulic gradient of 0.0027 foot per foot (Figure 12). 4.10.2.3. Surface Waters The site is about 1.5 miles south of the Calaveras River and 4 miles east of Mormon Slough, which branches off from the Calaveras River near Bellota about 3.5 miles northwest of the site. Surface drainage from the site flows into a network of streams and creeks that meander toward the southwest, ultimately emptying into Mormon Slough at two points near Linden and east Stockton, respectively. Mormon Slough is partially tributary to the Stockton Diverting Canal, which drains into the Calaveras River, a tributary of the San Joaquin River. The remainder of Mormon Slough flows directly into the San Joaquin River in Stockton (2015 WDR).