1048 an average altitude of 90 meters above sea level. During the surveys carried out, ash fillings of 0.45 m were found, with a maximum thickness of 4.5 m, while the average and median were 1.64 m and 1.7 m, respectively. The total volume of ash and soil mixed with ash was approximately between 610,000 and 690,000 m³. 4.2 Problem The landfill is characterized by the regular production of exposed ash that is continuously moistened to prevent it from dispersing into the air. A cover was sought to seal it off. The results of the soil sample analyses showed concentrations of certain metals (Se, Cu, V, Co, Hg) above the reference values established by Italian standards for industrial soil. Therefore, a human health risk assessment was carried out in accordance with the procedure set out in the document “Methodological Guide for the Management of Soils with Potential Contaminants” Human health risks due to exposure to soil with concentrations above the reference values were calculated to determine the need for action. Based on the results of the risk assessment, current and future exposure for site recipients meets the risk criteria. Therefore, the concentration measured in the soil was consistent with the industrial exposure scenario. As established in the Guide, no further action or studies were necessary (end of process). Based on the risk assessment performed, it was concluded that for a future industrial exposure scenario, the site will not generate or present a risk to the health of the population, under the terms established in paragraph a) of Article 11 of Law No. 19,300, since the magnitude of the risk is acceptable. However, it was necessary to minimize the impact of the ash on the environment caused by possible erosion by wind and runoff from scarce rainfall. Figure 17 – Ash landfill 4.3 Solution The closure phase for each cell ends once the surface of the tank that comprises it has been waterproofed and cleaned up. These will be closed in the order of their designation. The waterproofing and remediation package for the surface of the cell includes: • Levelling of the surface • Compaction of the surface • Installation of an HDPE geocell filled with soil cement on the filling surface of the cell. 4.4 Coverage Installation Procedure. The installation of the final cover began by placing a leveling soil over the ash, both on the sloped and flat areas. Next, 5 cm high HDPE geocells were installed. This material is a three-dimensional confinement structure composed of honeycomb-shaped cells with perforated walls and indented rhombic corrugation, made of high-density polyethylene (HDPE). Its function is to retain the fill with high shear resistance, in this case the soil cement. Figure 18 shows the extension of the geocell. For ease of construction, 10mm diameter and 1m long steel rods were used to anchor the geocell to the ground.
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