• Phase I ESA is a preliminary investigation conducted to identify potential or existing environmental contamination liabilities on a property. It involves a review of historical records, regulatory databases, and a site inspection, along with interviews with current and past property owners or occupants. The goal is to identify Recognized Environmental Conditions (RECs) that may warrant further investigation. Phase I ESAs follow the ASTM E1527 standard and do not include sampling or laboratory analysis. If RECs are found, a Phase II ESA may be recommended to assess the extent of contamination.

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• Phase II ESA is a detailed investigation conducted when a Phase I ESA identifies potential environmental concerns, known as Recognized Environmental Conditions (RECs). It involves collecting and analyzing samples of soil, groundwater, soil gas, surface water, sediment, and sometimes building materials to determine the presence and extent of hazardous substances. Guided by a site-specific sampling plan and safety protocols, field activities may include drilling, installing monitoring wells, and collecting vapor samples. The results are compared to regulatory standards to assess environmental risk and determine if further action, such as remediation, is needed. The final report includes site maps, lab data, and recommendations based on the findings.

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• Phase III ESA, also known as the Remedial Investigation and Feasibility Study (RI/FS), is conducted when contamination has been confirmed and further action is required. This phase involves a detailed investigation to delineate the nature and extent of contamination, assess potential risks to human health and the environment, and evaluate cleanup options. It includes developing and analyzing remedial alternatives, coordinating with regulatory agencies, and preparing a cleanup plan that meets applicable environmental standards. The goal is to identify the most effective and feasible remediation strategy for the site.

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• Regulatory Compliance Review ensures that environmental site assessments and related activities adhere to all applicable local, state, and federal environmental laws. In Washington State, this includes compliance with the State Environmental Policy Act (SEPA), the Model Toxics Control Act (MTCA) for contaminated site cleanup, and emerging regulations such as those targeting PFAS, climate disclosure, and chemical use restrictions. The review process involves evaluating whether site activities meet current legal standards, coordinating with regulatory agencies, and preparing documentation to demonstrate compliance. This step is critical for minimizing legal liability and ensuring that any environmental risks are managed according to evolving regulatory expectations.