COMPLIANCE INFO_2024 FINAL SITE CHARACTERIZATION WORK PLAN

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3 Site Characterization Work Plan SWT Engineering Z:\PROJECTS\SiteLogIQ\Site Characterization Work Plan\Text\Riverbank_Site Charac. Work Plan (Feb 2024)_Final.doc Post-Disposal  1969 UCSB  1993 UCSB  2019 UCSB  2023 (May) Google Earth Topographic Maps: The following available historical topographic maps were compiled and reviewed from the USGS Topoview website https:www.ngmdb.usgs.gov/topoview/viewer/#1/-1/- 9: Pre-Disposal  1916  1953 Post-Disposal  1969  2019  2021 Assessor Parcel Information: Assessor Parcel Information was obtained from a Title Report and in the San Joaquin County Assessor Parcel Maps website (https://www.sjgov.org/department/assessor/property-information/homeowners/parcel-maps). As indicated in Section 1.0, the location of the project, which is located on the south end of the City of Riverbank WWTP, falls within APN 247-260-02 (see Appendix A). 3.0 REVIEW OF RECORDS Aerial photographs included in Appendix A do not show disposal activities but may be used along with topographic maps to indicate likely timeframes as to the location and timing of disposal activities and changes in land use. The 1916 topographic map indicates the location of a large WWTP pond, which was expanded to the south between 1953 and 1957 and to the west between 1963 and 1969. Topographic maps from 1916 and 1953 show a trending north-northeast depression, likely access for a former rail line spur to the river, which is up to 10-15 feet deep. The State Department of Public Health inspection indicated an open dump with partial burning in November 1956. Open burning of solid waste was a commonly accepted practice in the 1950’s and 1960’s, in some cases up to the early 1970’s. The 1969 topographic map indicates most of the remaining depression filled. Therefore, the likely timeframe of disposal activities was from the mid-1950’s to late- 1960’s. Topographic maps indicate a variable shallow slope area with little change in relief (up to 10-15 feet) over time. Currently, a berm 10-15 feet in height separates the WWTP fence line from the Jacob Myers Park to the south. The berm (see Figure 4) roughly correlates with the historic break in slope from the elevated WWTP property to the lower floodplain, which is now occupied by Jacob Myers Park. Therefore, it is unlikely that the disposal site extends to the Park (see Section 4 for measures proposed to verify the extent to the Park).