The former black fuel (mazut) storage area in Valmiera is contaminated by oil products. However, until now, no research was done on evaluation of the contaminated area influence on quality of groundwater and pollution of soil. In 2016-2017, the company ”Vides konsultāciju birojs” has investigated the area in order to obtain information on the contamination. Latvian Environment, Geology and Meteorology Centre together with Riga Technical University have established the local hydrogeological model for the research on the groundwater contamination and its migration in the groundwater flow. The model base was extracted from the hydrogeological model of Latvia (LAMO4). It is found out that contaminated groundwater may reach the river Gauja in 60 years. During the first 15 years in sandy loam only 40 metres can be covered. The rest 45 years are spent to reach the river that is located 1.8 km from to base. During the first 15 years, due to dilution, the concentration of contaminants drops 60 times. During this time period, intensive contaminant destruction may take place. Results of hydrogeological modelling convince that groundwater contamination has only slight influence on the base area environmental quality. Descriptions on the building and using the hydrogeological and contaminant transportation models can be useful for modellers dealing with groundwater contamination problems