The decommissioning of the b-zone with ecological engineering : 1994 final report
Date
1995-01-31
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Abstract
Within the decommissioning scenarios for the B-Zone waste rock pile, a passive
treatment approach for seepages which might emerge from the recontoured and
revegetated pile is being considered. The muskeg areas to be used are within the
waste management area, located between the waste rock pile and the pit or lvison Bay.
Design criteria for a scale-up of the process to relegate As and Ni to sediments in these
areas are based on 3 years of laboratory and field work. In collaboration with CANMET
biotechnology, the forms of As and Ni which would be retained in the wetland
sediments were determined and found to be environmentally stable under prevailing
condition. Both elements are primarily complexed as organic particulates which are
formed in association with the decomposition of added organic materials. In this form,
the As and Ni settle to the sediment where they are transformed into insoluble metal
precipitates as favourable Eh and pH conditions are encountered in the deeper portions
of the sediment. Estimates of removal rates based on the experiments are 0.046 to 0.25 g.m-*.day-’ for
As and 0.05 to 0.36 gm*.day” for Ni. Loading from the waste rock pile seepages are
estimated as 153-398 kg.yr-’ for As and Xl-1,397 kg.yr-’ for Ni for 1992 to 1994 based
on 7 % of precipitation reporting as run-off.
An open water muskeg in the vicinity has an area of 2.4 ha and therefore theoretically
sufficient to accommodate the annual loadings from the pile. Design criteria for scaleup
are presented.
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Keywords
waste rock pile, decommissioning, seepage, recontourning, revegetation, muskeg sediments, arsenic, nickel