Environmental Assessment
Volume E-3.2
Tailings Facility
Geology and Geochemistry
Ambatovy Project
27
January 2006
manganese and sulphate. The high calcium and sulphate concentrations are
consistent with the presence of significant amounts of gypsum.
Sequential leach testing of two tailings samples demonstrates that values for pH
vary only slightly over the three leaches. Trace metal concentrations generally
are low. Chromium is not detected in any of the leachates at concentrations
above its detection limit of 0.001 mg/L. Nickel in consecutive leachates shows
consistent decreases in concentration, as do manganese and sulphate.
Exceedances of Malagasy and/or World Bank open pit mining effluent standards
(Volume I, Appendix 2.1) are observed for manganese, sulphate and conductivity
in all entrained tailings solutions. Since sulphate is the dominant dissolved
constituent and occurs at significant concentrations, elevated values for
conductivity are observed as well. For the leachates from the sequential testing,
the exceedances also are limited to manganese, sulphate and conductivity. This
is in contrast to exceedances observed for the mine rock and ore, which were
generally related to chromium, nickel and iron (Volume B, Section 3.2).
Due to the limited ability of static leach tests to simulate ambient site conditions,
the presence of exceedances does not imply that such exceedances will indeed be
observed on-site. For instance, the attenuation potential of certain lithologies
will result in reduced concentrations relative to those observed during the leach
testing. Monitoring of on-site groundwater and surface water quality will assist
in further identifying the potential for metal leaching under operating and closure
conditions.
3.2.3
Impact Assessment
3.2.3.1 Assessment Methods
Geology
There are no valid impact pathways for geology at the tailings facility. No
existing geologic resources will be removed or sterilized by the development of
this facility. The only potential loss is that of aggregates (granular resources)
which are covered by tailings. However, the economic value of such granular
deposits are low, and other potential sources are available in the region, this
aspect is further addressed in the Socioeconomics Section (Volume E,
Section 5.1). No impact assessment is required for the tailings facility for
geology.
