Which clue may indicate that a site has a history as a waste disposal area?

The presence of visual signs of soil discoloration is a significant clue that a site may have a history as a waste disposal area. Soil discoloration often results from the breakdown of waste materials, which can alter the natural color and characteristics of the soil. Contamination from hazardous substances or leachate can lead to visible changes such as darkening, staining, or unusual coloration of the soil, which are indicators of previous pollution or waste disposal activities.

While diverse bird species might suggest a thriving ecosystem, it does not specifically indicate previous waste disposal activity. Thorough landscaping typically shows human intervention and care, which would not align with a history as a waste disposal site. Unusual traffic patterns can suggest various activities but do not provide direct evidence of prior waste-related use. Thus, soil discoloration stands out as the most definitive clue related to a history of waste disposal.