Environmental Assessment
Volume E-2
Tailings Facility
Project Description
Ambatovy Project
13
January 2006
placement of rip-rap while downstream slope stability between raises will be
provided by placement of erosion-control turf matting on rip-rap.
Stability analyses of generalized embankment cross sections indicates that slopes
of 2H:1V for initial starter embankments will be adequate while a 3H:1V
downstream slope will be required for later years to maintain adequate stability at
higher heights. Downstream construction will be used for the initial starter dam
with centreline construction for ongoing raises to tailings embankments to
minimize ongoing fill requirements.
2.6
TAILINGS DELIVERY AND DEPOSITION
2.6.1
Tailings Delivery System
The tailings delivery pipeline will be 600 mm in diameter (unlined steel) and will
be routed from the tailings pumps in the plant site, exiting the boundary fence in
a southerly direction. At this point the pipe will be buried and will run west
along the plant fence, under the Route Nationale (RN) 2. It follows the RN2 for
about 2,000 m and then turns west through the valley into the tailings dam area
up along the Phase 1/2 water basin to the bifurcation point on the east side. The
main distribution piping will run on the impoundment walls.
The slurry pumping system at the process plant will include two trains (one
running and one standby) of five centrifugal pumps in series to cater for
discharging slurry at the anticipated maximum dam wall elevation.
2.6.2
Tailings Distribution System
The tailings distribution system will include spigot pipes around the complete
perimeter of each of the tailings basins. The placement of spigot pipes across the
upstream crest of embankments as well as around the perimeter of the basins will
allow for controlled discharge of tailings slurry to maximize storage potential and
densities. A distribution pipeline will generally be routed around both sides of
each tailings basin. This will require that a flow control assembly be placed at
the bifurcation point to allow tailings flows to be directed along either
distribution pipe or to a shorter length emergency discharge pipe.
A service road approximately 10 m wide will be provided for inspection and
maintenance of the tailings distribution pipeline around the catchment perimeter.
Some of this road work will be performed during the perimeter embankment
construction.
