Construction works, like any anthropogenic activity, have a negative impact on natural complexes. High levels of air, water and soil pollution are observed in areas of construction. This occurs at all construction stages: during the design and survey work, during the construction of roads and quarries, directly during the work on the construction site. Each stage of construction results in a new pollutant appearing each time. The greatest problem is the contamination of soils and sub-soils: soil dumps on construction sites, using bulk construction supplies, storing various supplies on the construction site, washing off bulk materials into the areas adjacent to the construction site, and the contamination of soil with fuel. The paper presents the results of the study describing the process of penetration of oily liquids, exemplified by kerosene, diesel fuel and gasoline. Studies were conducted in the laboratory. Sand is used as soil in accordance with the similarity criterion. Each type of fuel underwent series of tests with different volumes 50, 100 and 150 ml. The minimum number of tests in the series – 6. The minimum testing time for each series – 24 hours. The results of the study were analyzed and presented in the form of tables and graphs. The study revealed the following. Initially, the process of penetration is the same for all liquids tested. With the minimum tested volume, the average penetration depth for gasoline was 16.7 cm, for kerosene – 12 cm, and for diesel fuel – 21.5 cm. With the maximum tested volume, the average penetration depths were 21 cm, 21 cm and 21.5 cm, respectively. The studies also showed that, at the initial period, diesel fuel penetrates the sub-soil more slowly compared to all other tested liquids. This is due to a higher level of viscosity. The paper considers ways to reduce the impact of soil contamination on biota, as well as ways to eliminate this negative impact, leading to an increase in the efficiency of land improvement works, which take place after construction.