Publisher Summary The Municipal Waterworks of Amsterdam (G.W.) founded a groundwater pumping station in the year 1888. In 1901, another water supply company, the Midden Nederland Water Works (W.M.N.), started in the same area. Already in 1875, the municipality of Hilversum made infiltration works for sewage water east of the town, in an area with small lakes with a distance of about 1500 m southeast of the pumping stations. Together with the natural flow to the northwest, the recharged sewage water flows to the pumping stations and can give troubles in the future. During the past century, new residential and industrial areas were built to the north of the old town of Hilversum. Currently, the border of the town is close to the pumping stations. The groundwater below the town is polluted by sewage water from the leaky sewerage and probably by the direct infiltration of sewage. The water level in the sandy subsoil is about 5–10 m below land surface. From 1934, investigations were made to find a solution for the problem of pollution. In 1977 in the attracted groundwater of G.W., a little amount of trichloroethene (TCE) was discovered.