European regulations (Directive EEC/15.07.91) provide that marketing of live bivalve molluscs intended for human consumption must comply with strict bacteriological criteria. In order to comply with these requirements along the Nord/Pas de Calais coast and to preserve shellfish culture activities, a transfer through a depuration plant is the only solution at the present time. IFREMER, with the support of the Nord/Pas-de-Calais regional authorities, conducted an initial study on the use of UV for mussel depuration and on the design of a shellfish depuration plant. This study was used as a basis by TECHMAR Company to design a project for a modular type plant, under contract from the Nord/Pas-de-Calais Region. The basic module consists of two ponds with a daily depuration capacity of 1,900 kg of shellfish (maximum 3,800 kg in 48 hours). The necessary infrastructures include a pumping station, buffer and reserve tanks, facilities for filtration, sterilization and oxygenation (and temperature control if needed), a treatment building and auxiliary buildings. Capital investment for a standard module which can be integrated into an existing building is estimated at 450 KF. For a complete plant (building + equipment) capable of treating 2,000 tons of shellfish annually, the estimated budget is approximately 3,900 KF, to which should be added the cost of the pumping station as well as the layout and integration into the site selected for construction. Figures from the operating budget forecast indicate a treatment cost of approximately 63 centimes per kilogram, for a total of 2,000 tons treated annually. A first plant of this type should be installed in Wimereux in 1992. The financial package for this operation is nearly complete. The planned facilities include a shipping center located on the shellfish growing site and designed to house a dozen shipping companies.