As part of a plan to end the disposal of unpurified wastewater of Rotterdam and surrounding area, some underground treatment plants will be built. This plan was developed after previous plans had been turned down on account of financial, town-planning and environmental objections.
Since 1970, when in the Netherlands a Law "Pollution Surface-Water" came into force with a view to protect the quality of surface-water of lakes, rivers etc., sewage treatment plants were built at many places in the country. For some other areas plans were prepared to realize such installations in the nearby future. Within these plans also studies have been made to solve the wastewater problems of Rotterdam at the borders of the river Nieuwe Maas and the surrounding area. (Fig. 1 and Fig. 2) In connection with international agreements the plans have to be realized before 1985. Already in 1973 several ideas were developed to treat the wastewater of the Rotterdam region. One of the first plans attended to the erection of a centralized treatment plant with a capacity of over 1.000.000 population equivalents (p.e.), east of Rotterdam. On account of the high costs of investment of the necessary pressure pipelines from the pumping-stations to this plant as well as the high annual running costs of the wastewater-transport, this plan was abandoned rather soon. In 1976 a new plan was developed by the water-authority to which the management of the water quality in this region is directed. Three treatment plants were to be built, one with a capacity of about 300.000 p.e. west of Vlaardingen (De Groote Lucht), another one with a capacity of about 600.000 p.e. east of Rotterdam at the same site as the plant in the previous plans (Kralingseveer) and a third one with a capacity of about 325.000 p.e., south of Rotterdam near the intersection of 2 motorways (Vaanplein) (Fig. 2) Especially against the latter plant that would be used to treat the wastewater of the southern part of Rotterdam and surrounding area, objections were made by the local council of Rotterdam. These objections concerned town- and landscape-planning, the pollution of the environment by odors and aerosols and the very high costs of a comprehensive reconstruction of the existing sewerage system which would be necessary. In the years 1977 and 1978 the Public Works of Rotterdam designed an alternative plan which took away these objections by the construction of a few underground plants in old harbors. Although the water-authority rejected this alternative at first, also because of the unconventional nature of the design, a compromise arose in 1979. Local council as well as water-authority agreed with the erection of 2 conventionally built treatment plants and 2 underground plants in the Dokhaven and the Maashaven for about 400.000 p.e. and about 170.000 p.e. respectively (Fig. 2). In this paper the choice of the location Dokhaven and the way in which the design was developed, will be described. At the moment unpurified wastewater of the southern part of Rotterdam is disposed of from 4 outlets at the southern embankment of the river Nieuwe Maas.
