Soil and aquifer pollution, caused by hydrocarbon liquid spilling, is induced by misguided operational practices and inefficient safety guidelines. According to the Environmental Brazilian Institute (IBAMA), during 2013 alone, over 472.13 m3 of diesel oil leaked into the environment nationwide for reported cases only. Thus, there is an indisputable need in adopting appropriate environmental safeguards, especially for areas intended for hydrocarbon fluids' production, treatment, transportation and storage. According to local environmental legislation (ABNT-NBR 7505-1:2000), compacted soil (mineral) barriers used in structural contingency levees, such as storage tanks, are required to present a maximum water permeability coefficient, k, of 1x10-06 cm/s. However, as pointed by several studies, water cannot be adopted as the reference fluid to determine the performance of containment structures against organic fluids. Mainly, due to the great discrepancy observed in polarity values (dielectric constant) between water and most organic fluids. Previous studies, within this same research group, proposed optimal range values for a soil's index properties in order to elaborate mineral barriers focused for organic fluid containment. Nevertheless, at some places, it is not possible to find appropriate soils with the required characteristics near the construction/production site leading to increase manufacturing/freight costs and environmental risks. For these cases, the use of an organic product as an additive (amendment) to enhance the mineral-barrier containment performance is considered as a feasible and attractive alternative. This paper evaluates the effect of activated charcoal (AC) amendment within a clayey soil to attempt reduce permeability values towards a hydrocarbon fluid. Variables such as compaction energy, carbon texture and addition content (0%, 10% and 20%) were analyzed through laboratory falling-head permeability tests using distilled water and commercial diesel as percolating fluids. The hereby results showed that AC with high a specific area reduced permeability values remarkably towards commercial diesel fuel, suggesting that organic-mineral barriers are effective for this purpose providing an alternative technology and a broad