Abstract – In Latvia, the Ventspils sea port oil terminal area is heavily contaminated by various petroleum products. The groundwater table of the area must be lowered by using a drainage system. Water that is pumped of from the system must be cleaned before it is returned to an environment. For a rather long time (since 2001), the system has not been used regularly, due to a high cost of the water treatment. The groundwater table has mounted up to inadmissible levels. The hydrogeological model has been created. It has been found out that it is possible to use considerably lower water withdrawal rates of the steady regime. If no special regimes of restarting are taken, it will take a rather long time for an idle system to reach its steady state.