Invitation to tender, deadline 3rd April, 2008 for the geological and geotechnical study for the Los Hatillos tunnel, as part of the environmental upgrading project of metropolitan San José. Twenty-two core drillings, for a total of 765 metres, will be necessary. The geology is grey sound lava, with some interconnected, relatively dense small cavities. The mechanical condition is regular. As part of the environmental upgrading project of metropolitan San José, a 1,825 m water transfer tunnel is planned to transport waste waters from the Tiribí­ and Marí­a Aguilar sewers, situated south of the metropolitan area, to the Torres river basin where they will join the waste waters of the Rivera and Torres sewers prior to be conveyed to the Los Tajos treatment plant located near La Carpio. The tunnel's minimum cover will be 7 m at the beginning of the path and 43 m approx. halfway of it. This water tunnel will feature an internal diameter of 2.2 m and will be lined with concrete, either precast concrete segments or jacked concrete pipes. Contact Instituto Costarricense de Acueductos y Alcantarillados (AyA), tel. +506 2425491, fax +506 2425442. Read E-News Weekly 13/2006. Visit www.aya.go.cr/proveedor/datos_licitacion.php?id=2008LA-00008-PRI 11/08.