ARCHIVED REPORTS_2021 CURRENT CONDITIONS RPT

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24 May 2021 Project No. 14-3002 Page 10 of 23 2.8.3. Stratigraphy and Groundwater The lithology of the Site from surface grade to approximately 14 feet bsg (18 feet bsg in AOC2) is comprised of fine-grained silty sands and fine- to coarse-grained sands. Clay was encountered in most borings and wells between 14 and 15 feet bsg (between 18 and 19 feet bsg in AOC2) and extending to 20 feet bsg in some locations. In most borings, silty sand grades into poorly graded sand between approximately 6 and 9 feet bsg in AOC1 and between approximately 9 and 12 feet bsg in AOC2 (Figures 6 through 9 and 17 through 21). Groundwater was generally encountered in the poorly graded sands between 10 and 11 feet bsg (AOC1) and between 14 and 15 feet bsg (AOC2). The surface elevation of the former power plant area is approximately 3.5 to 5.0 feet higher than the surrounding area. Based on groundwater data collected from Site monitoring wells in April 2021, depth to groundwater was measured between approximately 10.5 and 11.5 feet bsg and groundwater elevations ranged between 4.32 feet and 5.01 feet above the North American Vertical Datum (NAVD88). Groundwater was inferred to be flowing to the southwest at an average hydraulic gradient of 0.001 foot per foot (ft/ft) across the Site (Figure 23). Depth to water and groundwater elevations are summarized in Table 11. 2.9. OTHER SITE CONDITIONS AGI reviewed the California Department of Fish and Wildlife’s National Diversity Database (CNDDB) to identify any threatened or endangered species at the Site. No threatened or endangered species were identified in the location of the subject property. The closest species occurrence was approximately 1,500 feet north of the Site (Swainson’s Hawk). The CNDDB Summary Table and Multiple Occurrence Pages are provided in Appendix E. AGI searched the National Preservation Society’s (NPS): National Register of Historic Places; list of National Historic Landmarks; and California’s Office of Historic Preservation. The subject property was not listed or identified on any of the above registers or lists. According to an Environmental Data Resources, Inc. (EDR) Database reviewed for the subject property, there are no wetlands or waterways at the subject property and the property is not within a 100-year or 500-year flood zone. Additionally, no crops or livestock are on or immediately surrounding the subject property. The property is currently vacant and there are no residences, schools, or daycares facilities on the subject property. According to the 2015 Urban Water Management Plan for the City of Lathrop, the closest city of Lathrop municipal water well is over one mile from the subject property.