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Profleet Truck Lube and Tire Service August 15, 2018 15453 N. Thorton Rd Project No. 1188 Lodi, California Page 2 to 960 milligrams per kilogram (mg/kg). TPH-mo values ranged from 90 to 15,000 mg/kg. The laboratory report is provided in Attachment E. After reviewing the lab results, FES returned to the site on August 3, 2018 to remove an additional 12 to 18 inches (6 cubic yards) from the perimeter of the CMU wall. Photo 4 in Attachment D shows this soil after it was placed in a 20 cubic yard roll -off bin. This roll -off bin is partially filled and will remain onsite so that Profleet will continue to fill the bin with oily waste for 60 days until that bin is full. The bin will be transported as non-RCRA hazardous waste to U.S. Ecology near Beaty, Nevada. We will forward the completed manifest to you as soon as it is returned by the disposal facility. After soil removal was complete, FES collected three soil samples from the base of the shallow excavation and analyzed them for CAM 17 metals, TPH as diesel (TPH-d) and TPH as motor oil (TPH-mo). CAM 17 metals results are within the background range of values for this geographic area. TPH-d values ranged from 2.5 to 15 milligrams per kilogram (mg/kg). TPH-mo values ranged from 45 to 275 mg/kg. The laboratory report is provided in Attachment F. TPH values were reduced significantly by this removal action. Environmental Screening Levels' (ESLs) allow dischargers and regulators to quickly focus on the most significant problems at contaminated sites and streamline the investigation and cleanup process while protecting surface water, groundwater quality, human health (direct exposure), aquatic habitats, terrestrial biota. Additionally, they protect against leaching from soil and subsequent degradation of groundwater, vapor intrusion into buildings and nuisance conditions. Under most circumstances, the presence of a chemical in soil, soil gas or groundwater at concentrations below the ESL can be assumed to not pose a significant threat to human health, water resources of the environment. Additional evaluation will generally be necessary at site where a chemical is present at concentrations above the corresponding ESL. Active remediation may or may not be required depending on site-specific conditions and considerations. The ESLs may especially be beneficial for use at site where the preparation of a more formal environmental assessment may not be warranted due to time and cost considerations. The ESLs provide tiered approach to environmental risk assessments. Under Tier 1, sample data are directly compared to ESLs for a more conservative conceptual site model (e.g., residential land use and potable groundwater). Under Tier 2, selection of specific ESLs is further refined with respect to site- specific considerations such as land use and groundwater use potential. This provides an intermediate but still relatively rapid and cost-effective option for preparing more site-specific risk assessments. The use of exposure scenarios and assumptions that depart significantly from those used to develop the ESLs constitutes a site-specific Tier 3 evaluation. It is important to note that ESLs are not used to regulate sites. Their use by dischargers and regulators is optional. The presence of chemicals at concentrations in excess of ESLs does not necessarily indicate adverse effects on human health or the environment, rather that additional evaluation is warranted. Lastly, ESLs should not be used as criteria to determine when chemical concentrations at a site must be reported to a regulatory agency. The Tier 1 ESL for TPH-d in soil is 230 mg/kg and the ESL for TPH-mo is 5,100 mg/kg. Soil sample results from the second round of soil sampling on August 3, 2018 are significantly below Tier 1 ESLs. Since Tier 1 ESLs are based on very conservative assumptions, the residual I Users Guide: Derivation and Application of Environmental Screening Levels, San Francisco Bay Regional Water Quality Control Board, Interim Final, February 22, 2016. 2 Assumes residential land use, groundwater is a drinking water resource, groundwater depth is shallow, soil is assumed to be sand, soil exposure depth is shallow.