QUARTZ-HILL, ALASKA - A CASE-HISTORY OF ENGINEERING AND ENVIRONMENTALREQUIREMENTS FOR STD IN THE USA

The Quartz Hill molybdenum prospect, with an. estimated tailings dispo sal rate of up to 80,000 tons per day, was developed through prelimina ry engineering design, environmental impact assessments, and permit ap plications during the 1970s and 1980s. The intent was to meet the stri ngent environmental requirements of several federal and state regulato ry agencies. The case history of mine development, extending over two decades, provides a unique set of details usable by future large-scale coastal and island mine prospects in the U.S. and elsewhere. Two fjor ds provided options for submarine failings disposal (STD) with convent ional deaeration and seawater mix chamber. An outfall was designed, an d would be located, to produce a density current descending to fjord b ottom. Innovative modeling of near-field and far-field tailings disper sal, and resuspension potential, was developed and applied. Of about $ 102,000,000 invested on the development, approximately $31,000,000 was given to environmentally related work. From the assessments, it was a greed that land disposal of tailings would cause more environmental da mage than STD. There was disagreement, however between regulatory agen cies over the preferred site for STD. Discharge permits were drafted, but the applications were finally denied by the Environmental Protecti on Agency (EPA) in 1990. In 1991 the developer sold its interest in th e prospect to another company.