Environmental Assessment
Volume B-3.3
Mine
Soils
Ambatovy Project
34
January 2006
Tropical laterite soils are naturally low in nutrients and have a low pH which also
creates potential metal toxicity problems for plant growth. Topsoil may not
always be able to be salvaged before mining and stored for future use, so further
loss of nutrients will occur.
Assessment Methods
The assessment methodology included an analysis of potential linkages between
mine activities and soil resources, the analysis of effects identified by the Key
Question and a classification of residual effects associated with the Key
Question.
Soil types directly affected by the mine were quantified by Geographic
Information System (GIS) analysis using the following process:
•
The GIS quantified areas of soil types to be disturbed within the mine
footprint.
•
Impact ratings were determined based on the net permanent loss of
unique soils (ferricrete) during the construction phase, the overall
change in area of soils following reclamation and closure, and a
qualitative assessment of potential changes in soil quality following
reclamation and closure.
3.3.3.3 Assessment Criteria
The criteria used to rate soil residual impacts are outlined in Table 3.3-2.
Table 3.3-2 Assessment Criteria for Soils
Direction
Magnitude
Geographic Extent
Duration
Reversibility
Frequency
positive
,
negative
or
neutral
for the
measurement
endpoints
negligible
: no
measurable effect (<1%)
low
: <10%
moderate
: 10 to 20%
high
: >20%
local
: effect restricted
to the LSA
regional
: effect extends
beyond the LSA into the
region
beyond
regional
: effect
extends beyond the
region
short-term
:
<3 years
medium-term
: 3 to
30 years
long-term
:
>30 years
reversible
or
irreversible
low
: occurs
once
medium
:
occurs
intermittently
high
: occurs
continuously
