Environmental Assessment
Volume B-3.9
Mine
Water Quality
Ambatovy Project
120
January 2006
The following impact pathways have been assessed relative to changes in water
and sediment quality:
Water Removal from the Mangoro River
Water will be pumped from the Mangoro River for mine water requirements.
Construction of the intake will include erosion control measures to minimize the
amount of sediment entering the Mangoro River. The hydrology assessment
predicted a maximum reduction of 0.5% to annual average flows and 1.4% to
the lowest 10-year flow at the intake pipe in the Mangoro River. These
predicted changes in flow and the erosion control measures will result in
negligible changes in water and sediment quality in the Mangoro River.
Air Emissions Impact on Surface Water Quality
Nitrogen and sulphur dioxides will be released through air emissions from the
combustion of fossil fuels within the mine area. These types of air emissions
have the potential to cause acidification (lowering of the pH) in natural ponds
located within the undisturbed area of the mine. However, there is insufficient
water quality data from these natural ponds to complete an assessment of
acidification potential. Additional monitoring of these ponds, including on-site
azonal vegetation protection areas, will be completed before construction.
Acidification of the receiving watercourses around the mine is not expected to
occur based on baseline pH values (6.8 to 7.2) and predicted alkalinity (21 to
45 mg/L as CaCO
3
). Therefore, acidification of receiving watercourses was not
assessed further.
Seepage
The water quality of seepages from the mine areas, during operations and post-
closure, has the potential to be different compared to baseline groundwater
concentrations. However, the amount of seepages is expected to be minimal, as
described in the Hydrogeology Section 3.7 (Volume B). Based on the current
understanding of the groundwater system, seepages are not expected to affect
surface water and sediment quality in downstream receiving watercourses and
water bodies.
