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CPSA GWET and SVE Systems Decommissioning Activities Work Plan Page 4 Lodi Central Plume Source Area,Lodi,California March 4,2021 Excavation — Limited excavation is proposed to be performed along the sewer line in the western part of the alleyway near Pleasant Avenue, where elevated concentrations of PCE were detected in the soil vapor during the June and August 2019 and February 2021 passive soil gas (PSG) sampling events. Figure 2 shows the anticipated extent of the excavation area along with results of the PSG sampling performed (PSG samples PSG 1/1R, PSG 12/12R, PSG-14 through PSG-18). During the on-site excavation all utility lines including sewer and water that are present within the excavation footprint will be structurally supported to prevent sag and potential breakage.Additionally,the concrete alley approach will all be replaced,as per City of Lodi standards and specifications, after completion of excavation activities. Based on an excavation dimension of approximately 100 feet by 6 feet to a depth of 5 feet, a volume of approximately 115 cubic yards (in-bank) of material will be excavated. Additional soil may be removed depending on observations made during excavation. In addition, excavation sidewall and bottom soil samples will be collected and tested for VOCs to confirm the removal of soil with elevated VOC concentrations. Sidewall samples will be collected from the perimeter of the excavation at lineal intervals of approximately 20 feet and bottom samples every 500 square feet of excavation bottom, and transported under Chain-of-Custody to a California State certified testing laboratory for VOC analysis using EPA Method 8260B. Samples will also be collected if visual examination of the sewer and surrounding backfill suggests that past pipe breaks may have led to discharge of HVOCs to the backfill and surrounding soil. Additionally, we do not expect the width of the excavation to exceed more than two (2) feet beyond the current planned excavation width. During excavation, the remedial piping extending from soil vapor extraction (SVE) well SVE-01,and any other remedial piping,which are within the footprint of the proposed soil excavation, will also be removed. The excavated soil will be stockpiled at the designated area shown on Figure 3. Composite soil samples will be collected per accepted compositing standards and transported under Chain-of-Custody to a California State certified testing laboratory for VOC analysis using EPA Method 8260B to satisfy criteria for acceptance at a soil disposal facility. Based on the results of soil profiling, the soil will be transported to an appropriate landfill for disposal. During excavation activities soil stockpiles will be placed a 10-mil plastic sheets and surrounded by straw waddles to prevent dispersion. When not active,the soil stockpile will be moistened and covered to prevent the generation of dust. Additionally, all surficial asphalt and concrete across the Site will be removed and disposed as inert construction debris to an appropriate facility. Following completion of excavation activities,the excavation will be backfilled with either clean imported soil or controlled density fill (CDF) as per the City of Lodi standards and specifications. 175 N EL MONTE AVENUE,LOS ALTOS,CA 94022 TEL:415-424-3009