During the Pebble copper-gold-molybdenum (Cu-Au-Mo) deposit
discovery drilling, drilling waste was directly disposed of on the landscape or
passed through unlined sumps prior to disposal. The ore and host rock are high
in sulphides, which are weathered by metal leaching to sulfuric acid. Oxidized
cuttings were visually noticeable and verified to have a pH of 2.7-4.3 by
laboratory and field research. Cu and Mo reached or were at the high end of the
natural history at these locations. Cu was within the range of 545 mg / kg to
4865 mg / kg, with one exception. At all sites with drill cuttings on the soil,
dead vegetation was observed. There has also been observed dead vegetation on Covers
of sump rock, unrelated to drilling waste. Places where vegetation had not been
preserved were between the ages of four and thirteen. The possible surface and
groundwater effect has not been determined. It could lead to better site
management to understand the source and nature of damage from cuttings. In
order to determine the rate of chemistry shifts, drill cuttings sump contents
require more sampling and whether groundwater downgradient from sumps is being
affected. Finally, more research should be carried out to determine if sulfidic
drill waste accumulated in isolated bodies of water, such as glacial kettles,
is having an effect. In order to ensure clean control samples, testing sites
should be examined before and after drilling.
Author (s) Details
David M. Chambers,
Center for Science in Public Participation, Bozeman, MT 59715, USA.
Dr. Kendra Zamzow,
Center for Science in Public Participation, Chickaloon, AK 99674, USA.
View Book :- https://bp.bookpi.org/index.php/bpi/catalog/book/279
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