The Ilukste oil transit station pipelines diesel fuel from Belorus to the town Ventspils in Latvia. In 1970-1996, the station also filled fuel (oil) in railway tanks and oil leakages occurred. Due to these leakages, groundwater under the railway terminal routes was contaminated. The groundwater flow enters the nearby Ilukste river. Fortunately, oil discharged over ground from a steep bank before the river. To prevent the oil inflow into the river, a special pond was dug for its intercepting. Later, in order to divert the oil discharge underground, the horizontal drain for catching oil was installed before the pond. In 1996, remediation of the oil contaminated station area started and followed up until now. The work was supervised and financed by the station owner LatRosTrans Ltd. Since 2000, the site sanitation was performed by the company VentEko. Right now, due to close long term cooperation between the owner and the performer companies and also due to appliance of effective remediation equipment, the contaminated area of the station site is practically cleaned from the mobile oil fraction. About 165m3 of oil were recovered by using pumping from wells and mainly due to the oil natural run off into the drain located before the pond. Unfortunately, about 100m3 of trapped oil for a long time will contaminate groundwater due to the oil dissolution in water. For this reason, the equipment that cleans groundwater intercepted by the horizontal drain must be preserved and renovated. In 1997, scientists of Riga Technical University (RTU) established the hydrogeological model of the contaminated area. Due to use of the model and the special program ARMOS, the disposition of the oil leakage source was found. The oil plume self-cleaning for about 25 years was predicted due to oil natural run off. In 2018, RTU assessed results of the sanitation. It was found out that the site remediation process had reached its final stage, as productivity of the oil recovery was getting low. Comparison of the real sanitation results with the predicted course of the oil plume natural run off showed that they differed mainly due to repeated oil leakages at of the railway terminal routes. The case confirmed considerable value of results that were obtained by modelling during the initial stage of the site remediation work. In the paper, essence of the prognosis that was obtained by appliance of the program ARMOS is explained and the results of the site remediation are considered.