Processes applied for preliminary treatment of wastewater from refineries and petrochemical plants create the oily sludge, containing high percentage of water and only a bit less of hydrocarbons. This sludge is collected in storage tanks, because no application for it can be found. Our researches had as a first step the aim to convert this fluid sludge into solid substance (product) by adding of quicklime and then utilize the product in the road construction as a bottom layer of the road. The product should be added in the amount of a few percent comparing to the rest of soil. The second step of the research was an assessment of an impact of the product used for construction of experimental sections of roads and squares on environment by monitoring of surface and ground water quality in their vicinity. If the contribution of the product in total amount of the road material is less than 8% the influence is kept under limits.