From: on behalf of Panel Registry Subject: FW: TNG registration of ...

Stratus Consulting Memorandum (4/16/2010)
related contaminants at concentrations 8 times higher than the water quality standard. The
creek that drains the mine workings turned iridescent blue from released copper salts. In
addition, floods in 1993 breached the TSF 13 times, releasing an estimated
265,000 tonnes of tailings into the Gila River (Kuipers et al., 2006; Lipton, 2009).
3.3 Tailings Dam Failures
Tailings dam failures are not uncommon (see, e.g., Davies, 2002; WISE Uranium Project, 2009).
The U.S. Commission on Large Dams (USCOLD), the International Commission on Large
Dams (ICOLD), and the United Nations Environmental Programme (UNEP) have each compiled
tailings dam failures over the years. USCOLD compiled a list of 185 tailings dam failure
incidents as of 1994, and UNEP and ICOLD compiled a list of 221 tailings dam failure incidents
(WISE Uranium Project, 2009). Dr. Maest will briefly summarize these data.
She will also present a recent analysis of tailings dam failures in the European Union (EU), in
which the authors conclude that most failures occur at operating mines that fail to adequately
design for floods (Rico et al., 2008a). Data from the EU and other sources suggest that a failure
of the TSF dam at Prosperity would result in a tailings plume extending many hundreds of
kilometers downstream (Rico et al., 2008b), impacting the Taseko, Chilcotin, Chilco, and Fraser
rivers.
Dr. Maest may include specific examples of tailings dam failures, such as:
�� The 1990 Matachewan Mines tailings dam failure in Ontario (Baker et al., 1996), in
which an estimated 190,000 m 3 of tailings were released into Davidson Creek and the
Montreal River, filling the Davidson Creek floodplain with tailings, depositing an
estimated 90,000 m 3 of tailings into the bed sediments of the Montreal River, and
creating a plume of suspended fine tailings that was visible until the Montreal River
entered Lake Temiskaming 168 km downstream.
�� The 2000 Baia Mare tailings dam failure in Romania, in which a dam designed by Knight
Piésold failed after only 8 months of operation, killing an estimated 1,240 tonnes of fish,
extirpating endangered salmon and sturgeon from one river, and affecting drinking water
for 2 million people. The EU commission that investigated the spill blamed it in part on a
poor water balance model that did not account for the expected range of water inputs, as
well as a faulty dam design by Knight-Piésold (Baia Mare Task Force, 2000).
�� The 1975 failure of a tailings dam in the Upper Blackfoot River in Montana, which
destroyed aquatic habitat and riparian vegetation for several kilometers. Now 35 years
later, the area is still nearly devoid of aquatic life (Holmes and Lipton, 2007).
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