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Kellogg Garden Products ECO:LOGIC Engineering Groundwater Monitoring Well Installation Work Plan I{ELG04-001 11/10/2004 Site Geology, Soils and Hvdrogeologv Geology Geologic maps of the area indicate that the Kellogg facility is underlain by the Modesto-Riverbank Formation, which can be generally classified as an arkosic alluvium(feldspar rich, of granite origin). Lithologic logs of the existing monitoring well borings and the onsite water supply well indicate that these alluvial deposits are very heterogeneous. They are represented by discontinuous beds of fine sand, silt, and clay, as well as, occasional lenses of gravel. The subsurface geologic materials appear to be primarily fine-grained down to a depth of more than 250 feet, below which beds of coarse sand and gravel yield water to wells in economic quantities. Soils The San Joaquin County Soil Survey indicates that four soils intersect within the within the boundaries of the Kellogg facility. The four soil types are as follows: 112—Bruella sandy loam,hard substratum,0 to 2 percent slopes; 189—Kindon fine sandy loam,0 to 2 percent slopes; 240—San Joaquin loam,thick surface,0 to 2 percent slopes;and, 256—Tokay fine sandy loam,0 to 2 percent slops. Each of these soils is classified as being deep, moderately to well drained, and formed from alluvium derived from granitic rock sources. These soil types are typically used for cultivation of irrigated crops such as orchards or vineyards. The San Joaquin and Burella soil units are characterized by a clay pan or hard substratum that tends to impeded the vertical movement of water through the soil. These soils also tend to have low salinity (electrical conductivities less than 2000µmhos/cm),between 0.5 to 3 percent organic matter, and relatively high clay content ranging from 8 to 50% which can further retard the vertical movement of water. Shallow Groundwater Hydrogeology Existing shallow groundwater information is very limited and restricted to the descriptive logs of onsite monitoring well boreholes and water levels taken from the completed wells. As stated above, the alluvial deposits beneath the site from land surface to the water table are very heterogeneous, represented by discontinuous beds of fine sand, silt, clay, and occasional lenses of gravel. The hydraulic conductivity of the saturated deposits penetrated by the monitoring wells is thought to be low, based on very slow rates of recharge following well purging. One measurement of the vertical hydraulic conductivity of the unsaturated surface soils yielded a value of 1.5 x 10-5 cm/sec, which is generally consistent with the permeability of fine grained sediments. Water supplies in the vicinity are derived from wells that penetrate coarse sand and gravel strata beginning at an approximate depth of 150 to 250 feet below ground surface (bgs). The formation sediments overlying this aquifer are reportedly fine-grained and similar to those penetrated by the monitoring wells at the site. Water levels beneath the site and within the uppermost shallow aquifer are typically between 85 to 112 feet bgs. One onsite product well exists approximately 720 feet north of the contact water pond. This well was constructed in 1988 to a depth of 340 feet with a perforated"drop section"placed in the depth interval between 258 and 298 feet bgs,with the remainder of the well completed as an open hole, and a surface seal to a depth of 78 feet bgs. The closest off-site production well exists approximately 700 feet to the east of the facility. The current groundwater monitoring network consists of four wells (Figure 2) completed at depths ranging from 99 to 115 feet bgs with shallow groundwater generally occurring between 85 to 112 feet bgs. Available groundwater head elevations suggest that a moderate vertical groundwater gradient exists within the saturated alluvial deposits, indicated by a decrease in the head elevation in wells completed at deeper depths. Similarly, the first encountered groundwater, reported for the onsite production well was 84 feet, however decreased to 2