Existing data on site history can provide useful information on potential causes and sources of groundwater contamination. Data that should be collected include old maps and aerial photographs, interviews with present and former employees at the plant site, records of operations, records of product losses and spills, waste disposal practices, and the list of contaminants generated over the operating history of the site. The inventory must also include a history of the raw materials used and wastes disposed of over the years as industrial processes changed. Particular attention should be paid to potential sources of ground-water contamination such as locations of abandoned and active landfills and wastewater impoundments, buried product pipelines, old sewers, tanks, cesspools, dry wells, product storage areas, product loading areas, storm water collection areas, and previous spill areas.
In addition, foundation borings or construction details of supply wells can provide firsthand information on the types and characteristics of subsurface soils and ground-water at the site. Chemical data may be available from the results of previous monitoring activities at the site or at adjacent properties. These data should be analyzed and plotted on base maps and used to estimate background groundwater and soil quality.
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