Open dumps remain the predominant form of municipal solid waste disposal in many Amazonian municipalities, posing significant risks to soil and water resources due to uncontrolled leachate generation. This study evaluates soil physicochemical properties in an active open dumpsite located in Lábrea, Amazonas State, Brazil, aiming to assess soil quality and infer its potential role in leachate attenuation and contaminant mobility. Eight sampling points were collected at a depth of 0–40 cm and analyzed for pH, organic matter content, and soil texture. The results revealed acidic conditions (pH 4.4–5.8), high organic matter contents (16–39 g kg⁻¹), and a predominance of silt and clay fractions. The fine-textured soil suggests reduced permeability and a potential attenuation capacity for leachate percolation; however, the low pH may enhance the mobility of trace elements and increase environmental vulnerability. The relatively homogeneous spatial distribution of soil properties indicates consistent influence of waste disposal across the site. Although the results suggest some natural attenuation capacity, the combined effects of acidity and continuous waste input highlight the risk of contaminant transport to groundwater. This study provides baseline data for an under-researched Amazonian context and supports the need for integrated monitoring, including contaminant analysis and hydrogeochemical assessment, to guide sustainable waste management strategies.