Item 16 - Agreements for A -Tech Consulting, Inc., Dudek, and Leighton Consulting, Inc. for On -Call Various Environmental Services

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0 Proposal for Various Environmental Services Page 20 August 1, 2022 A -Tech prepares a draft report for review by the City and after addressing the comments, the report is suitable for submitting to the regulatory agencies. Site Characterizations/Remedial Investigations If the Phase II ESA confirms the presence of contamination in soil or groundwater, Remedial Investigation is required to determine the best available approach for site cleanup. Complete Phase I and II ESAs and additional investigations resulting from them will effectively characterize the physical, biological, and chemical systems existing at a contaminated site, and develop thorough understanding of the site conditions. Based on the findings of the Phase I and II ESAs and in accordance with ASTM E1689-95 (updated in 2014), A -Tech will develop a Site Conceptual Model (SCM). The SCM is a narrative and/or graphical representation of the current understanding of hydrogeologic conditions and contaminant distribution in the soil -water system beneath the Site. The SCM provides a description of migration pathways of the Chemical of Concerns (COC) and the processes and mechanisms that affect the distribution of COCs in soil vapor, soil, and groundwater. The SCM represents: A geologic cross- section of the Site that effectively identifies the soil profile and types of the soil layers (i.e., clay, silt, sand); Depth to groundwater and the hydraulic gradient within the aquifer; Established background concentrations; COCs concentrations and the extent of their plumes; Contaminant transport pathways and human exposure; and Remediation target zone. After the site is effectively characterized and the SCM is developed, A -Tech will conduct a risk assessment to evaluate the adverse effects of the Site's current conditions on human health and environment. If human health or the ecosystem is threatened by the contamination, Risk -Based Corrective Action must be selected and implemented in accordance with ASTME2081-00 (revised in 2015). A -Tech will conduct a Focused Feasibility Study to evaluate various applicable remedial technologies including no action and propose selection of the most appropriate remedial approach. The flowchart provided in Figure 2 demonstrates the processes and sequence of activities that are involved in successful completion of an environmental remediation project that is initiated by the City's request. A -Tech proposes to evaluate the potential for chemicals associated with the site to cause adverse effects on human health or environmental receptors in the absence of any remedial action. A-Tech's risk assessment approach is designed to fully utilize existing data and information generated during previous investigations at the site in order to minimize the costs and time required to produce a quality document. A-Tech's risk assessments are consistent with the requirements of both the California Department of Toxic Substances Control (DTSC) and the U.S. Environmental Protection Agency (USEPA). The risk assessment will include the selection of chemicals of potential concern (COPCs), use of critical toxicity factors (i.e., reference doses [RfDs] for non -carcinogens and slope factors for carcinogens) in estimating potential health risks and hazards. RfDs and cancer slope factors developed by the DTSC and USEPA will be used for estimating potential health risks. A report detailing the results of this risk assessment will be prepared in a straightforward format for the review and approval by the regulatory agency. The report will include the justification for the selection of exposure pathways and assumptions necessary to support the estimation of potential health risks and hazards. OW A -Tech Consulting, Inc.