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2 <br /> ♦ 1993 UCSB <br /> ♦ 2019 UCSB <br /> ♦ 2023 (May) Google Earth <br /> The following historical topographic maps were compiled and reviewed from the USGS <br /> Topoview website https:www.ngmdb.usgs.gov/topoview/viewer/#1/-1/-9.: <br /> ♦ 1916 <br /> ♦ 1953 <br /> ♦ 1969 <br /> ♦ 2019 <br /> ♦ 2021 <br /> 3.0 REVIEW OF RECORDS <br /> Aerial photographs included in Appendix A do not indicate a timeframe as to when disposal <br /> activities may have occurred or show significant changes in site use and vegetation. The <br /> WWTP is present in the 1957 aerial photograph and 1953 topographic map, and by 1963 <br /> had significantly expanded. Topographic maps indicate a variable shallow slope area with <br /> little change in relief (up to 10-15 feet) over time. Topographic maps from 1916 and 1953 <br /> show a north-northeast trending trench, which is most likely a former irrigation canal at the <br /> west end of the site from 10-15 feet deep that is not present in 1957. It is likely that the <br /> former canal was filled between 1953 and 1957. This former canal appears to be the area <br /> of waste fill and is located where the 565-kW ballasted ground mount array is to be placed <br /> on the old landfill area. The former canal area extends to the outside the limits of the WWTP <br /> operations to Jacob Myers Park which is within the parcel boundary and owned by the City of <br /> Riverbank. Figure 3 shows the approximate limits of waste of the disposal site with respect <br /> to the proposed Solar array. <br /> Preliminary assumptions concerning the nature, extent, and potential threat to public health <br /> and safety environment are that the Riverbank City Dump is shallow (probably < 15 feet <br /> deep), has limited extent, and poses a very low potential threat to public health and safety <br /> and the environment. Figure 2 shows the approximate lateral extent of the waste within the <br /> property boundary (approximately 0.76 acres). Assuming an average depth of 12 feet, the <br /> total volume of waste is approximately 14,800 cubic yards. The waste is likely mainly inert <br /> debris and land clearing materials (soil and vegetation) associated with WWTP construction <br /> activities, with deminimis degradable materials that could generate landfill gas or leachate. <br /> The LEA Site Identification Form (dated June 20, 2011) ranks the threat posed by the Site as <br /> "C", which is a low threat to public health and safety and the environment with minimal <br /> action needed to prevent human contact with waste. Current land use is non-irrigated open <br /> space and storage and staging activities associated with WWTP operations. <br /> 4.0 SITE CHARACTERIZATION WORK PLAN <br /> Based on the available information, potholes and/or trenches to 10-15 feet deep are <br /> proposed to determine the vertical and lateral extent of waste fill. The proposed excavation <br /> locations are shown on Figure 3 and will be marked prior to implementation. The location of <br /> Site Characterization Work Plan SWT Engineering <br /> Z:\PROJECTS\SiteLoglQ\Site Characterization Work Plan\Text\Riverbank_Site Charac.Work Plan_072823.doc <br />