COMPLIANCE INFO_2024 DRAFT REVISED SITE CHARACTERIZATION WORK PLAN

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z:\projects\sitelogiq\site characterization work plan\reg agency comments\lea comments_dec 2023\rtc attachment_121123.docx RESPONSES TO LEA COMMENTS (RECEIVED DECEMBER 11, 2023) SITE CHARACTERIZATION WORK PLAN (REVISED NOVEMEBER 2023) CLOSED RIVERBANK CITY DUMP 1.Figure 2 in the Work Plan shows the potential limits of waste based on information summarized in Section 3.0. Figure 3 shows the proposed layout of the solar panel project and preliminary locations of the proposed test trenches and potholes. It appears that the limit of the investigation proposed is only confined to the area planned for the solar panels. California Code of Regulations (CCR) Title 27, Section 21190(a) describes the performance standards that must be met for any proposed post closure land use. In order to evaluate compliance with state minimum standards, the entire extent and condition of the disposal area should be determined. The investigation area shown in Figure 3 should be expanded to include the potential waste limit shown in Figure 2. The magnetometer, ground penetrating radar, or geophysical survey that is contemplated in Section 4.0 of the Work Plan should be conducted as a first step to further refine the locations of the potholes and trenches. RESPONSE: The Work Plan has been updated to provide a more detailed background assessment of the extent of waste and procedures to verify the extent. Additional review of the historic topographic maps and aerial photographs was also included along with a field reconnaissance. The berm between the WWTP fence line and Jacob Myers Park appears to be the boundary along the south side. Augur borings are proposed along the berm and at the base of the berm in the floodplain to verify the extent in this direction. In lieu of a geophysical survey, an increase in pothole and augur borings is proposed to 30 (22 potholes and 8 augur locations). The spacing is approximately 50 -foot centers. A geophysical survey will provide no significant useful information not otherwise provided by the potholes and augur borings. Additionally, the increased density obviates the need for trenches. This will minimize the impacts of material backhauling which the LEA has required. 2.Section 4.0 of the Work Plan describes the activities conducted to characterize the site conditions. The thickness, soil type and condition of any cover soil present should also be evaluated. The information will be useful when developing the project’s final design and to ensure that the entire disposal area will be in compliance with state minimum standards. RESPONSE: The thickness, soil type, and condition of any cover soil is part of the evaluation from the potholes and augur borings. This is reflected in Section 4.0 of the Work Plan.