Summary
Key Impacts and Mitigation
Main issues identified through consultation and through the professional
experience of the Malagasy and international EA team included:
•
the need to train local people and optimize employment benefits for
the Malagasy population;
•
in-migration issues from a migrant labour force, including HIV/AIDS;
•
impacts on tombs and cultural sites;
•
impacts on rare tropical forest habitats and the biodiversity they
contain; and
•
water quantity and quality impacts on people and the environment,
including the nearby Torotorofotsy Ramsar site.
Water
The mine layout and water management plan have been designed to
minimize off-site impacts, with special attention to the Torotorofotsy
Wetlands. Early in the design phase, it was decided to protect the
Torotorofotsy Wetlands by keeping project elements away from the basin
draining to the Torotorofotsy. A preliminary assessment determined that
based on economic, social and environmental perspective the reliability
of meeting the water needs for the ore processing plant and downstream
users would best be met through the combined use of the Mangoro River
and mine runoff collection. As a result, the Mangoro River water pipeline
was included to provide water for ore processing, especially in the dry
season. Maximum ore processing water requirements represent less
than 0.3% of the mean annual flow in the Mangoro River, and less than
1.5% of the flow for dry conditions. The goal of the mine water
management plan is to provide enough water for the slurry plant, while
maintaining seasonal flows off-site. There will be some additional wet
season flows during operations, because of vegetation clearing, but
these will be offset by reduced groundwater flow. At closure, the mine
area will be returned to natural runoff conditions through reclamation.
The water released from the runoff collection ponds into the downstream
basins will be designed to meet World Bank suspended solids
concentration criteria of 50 mg/L or less, based on a 1 in 10 year storm
event. For storm events greater than the design storm, suspended
solids levels entering the receiving streams may exceed the 50 mg/L
criteria for short periods. The elevated concentrations, however, will be
diluted by high downstream flows. Due to the sensitive nature of
downstream receiving environments and requests during consultation,
additional sediment modelling is being undertaken to better understand
the probable suspended solids concentrations that could be released
from the ponds during extreme storm events, such as two cyclones in
quick succession. There will be flow monitoring in streams around the
mine during operations, plus regular contact with downstream users on
the acceptability of flows.
Torotorofotsy Wetlands
January 2006
Ambatovy Project — 11
