At its twenty-second ordinary (June 1998) and extraordinary (November 1998) sessions, the Bureau was informed of the events resulting from the eruptions of Mount Ruapehu in 1995 and 1996. The volcano’s Crater Lake has been drained and a large build-up of ash has blocked the Lake’s outlet. When Crater Lake refills, probably within the next few years, a rapid collapse of the ash dam could occur followed by a major lahar. The management authorities are faced with the dilemma of either letting nature take its course, putting both human life and some natural values at risk, or taking action to open up the outlet. The option to excavate a trench through the ash at the crater outlet should not significantly affect the natural values for which the site is inscribed. However, interference with the summit area has implications for the recognition and respect for the spiritual, traditional and cultural values to the Maori people which justified the site’s inscription under cultural criterion (vi). The Ngati Rangi and the Ngati Tuwharetoa Maori Tribes are opposed to the idea of engineering works at the Crater Lake. The Minister for Conservation has called for a comprehensive environmental and cultural assessment identifying the risks associated with and possible impacts of the mitigation options.
In a letter dated 31 March 1999 from the New Zealand Department of Conservation, the Centre was provided with an update on the decisions concerning management of the ash build-up at the Crater Lake outlet on Mount Ruapehu. A Draft Assessment of the Environmental Effects report was released for public comment in late October 1998 and consultations have taken place with Maori people, other agencies and the public. Furthermore, the Department of Conservation is investigating possible components of a suitable alarm system to warn members of the public about large lahars from Crater Lake and informal discussions have begun to establish an emergency management group to address such hazards. Continuous monitoring has shown that as of 22 March 1999, the Crater Lake was 22% full and 54 metres below the old overflow level. According to current projections, the Crater Lake will not fill until the year 2003.
IUCN confirmed to the Bureau that the New Zealand Government is proceeding with great caution not to offend Maori sensibilities over the option of excavating a trench through the 1995 and 1996 ash build-up blocking the outlet to the Crater Lake of Mount Ruapehu. IUCN also informed the Bureau that the report on public consultations on the Draft Assessment of the Environmental Effects report will be sent to the Minister of Conservation, who will make a decision as to what action to take, following receipt of an opinion on the legal implications of cutting a trench or letting nature take its course. ICOMOS commented on the relevance of the case of managing the ash-build up at Tongariro National Park to other cases where in the future there would be an equal need to negotiate a management solution between two cultures.
The Bureau requested the Centre, IUCN and ICOMOS to maintain contact with the State Party to monitor the ash build-up at the Crater Lake and submit a report to its twenty-fourth session in the year 2000.