Environmental Assessment
Volume B-6
Mine
Reclamation and Closure Plan
Ambatovy Project
401
January 2006
The following mitigation will be applied as appropriate to prevent the siltation of
reclaimed watercourses:
•
prohibit the operation of construction equipment close to the banks of
watercourses where there is a risk of bank sloughing, failure of the
vehicle crossing or flooding of the work area;
•
excavate cross ditches to divert runoff away from watercourses;
•
construct berms containing overburden, timber, lumber, sandbags, rock,
straw bales on approach slopes and/or banks to divert runoff off the site
and onto well-vegetated lands; and
•
place sand bags strategically to help stabilize and add height to banks to
prevent flooding of nearby areas especially where vegetation has been
removed.
6.7.1.1 Using Vetiver for Erosion Control
Vetiver (Vetiveria zizanioides) is a native grass from India that is being used
throughout the tropics for erosion control (NRC 1993). It has been used in
Madagascar for erosion control by farmers and industry for over a decade and is
also suggested for erosion control of mine dumps in the country (Grimshaw
1997). Users in the tropics for erosion control have reported that planting
Vetiver hedgerows will reduce soil loss up to 90% and water runoff up to 60%
(Grimshaw 1997).
The NRC (1993) has suggested that Vetiver has the following unique traits:
•
controls erosion when planted in a hedge across the slope just one plant
wide;
•
certain types bear infertile seed ensuring it does not encroach and
spread;
•
the plants are hardy and have been documented to survive drought,
grazing, fire and floods. They are not tolerant to freezing;
•
they are deep-rooted plants with roots having a high tensile strength
allowing them the hold the soil against erosion;
•
inexpensive to establish and require low maintenance; and
•
grow in diverse soil types include saline, acid and low fertility.
For this project, trials of Vetiver are proposed for the initial waste dumps that are
established to evaluate the potential of this species for the overall mining
program.
