Environmental Assessment
Volume E-3.7
Tailings Facility
Hydrogeology
Ambatovy Project
61
January 2006
10 mg/L) may extend about 1,000 m downgradient (east of) the tailings facility.
A smaller area concentrated immediately downgradient the tailings facility is
predicted to contain manganese at concentrations ranging from 10 mg/l to
50 mg/l. This represents a high magnitude change.
The magnitude of change of both groundwater flows and groundwater quality
resulting from the tailings facility during operation and closure phases is high,
based on the percent change predicted for each, relative to baseline conditions.
While each high magnitude rating is given a correspondingly high environmental
consequence rating based on the assessment methodology, these impacts are
related solely to physical changes to the environment. Consequent impacts of the
changes in groundwater flow and quality on surface water and human use are
evaluated in other report sections.
Table 3.7-6 Residual Impact Classification for Hydrogeology
Phase
Direction Magnitude Geographic
Extent
Duration Reversibility Frequency Environmental
Consequence
Issue: Impacts to Groundwater Levels
construction
n/a
negligible
local
short-
term
reversible
high
negligible
operation/
closure
negative
high
local
long-
term
reversible
high
high
Issue: Impacts to Surface Water Flows
construction negative
negligible
local
short-
term
reversible
high
negligible
operation/
closure
negative
low
local
long-
term
reversible
high
low
Issue: Impacts to Groundwater Quality
construction
neutral
negligible
local
short-
term
reversible
high
negligible
operation/
closure
negative
high
local
long-
term
reversible
high
high
(a)
(a)
Related solely to physical changes. Consequent social effects addressed in Volume D, Section 5.1.
Changes in groundwater flow and quality may influence groundwater use if there
are shallow groundwater wells within the affected area, and this is addressed in
the social impact assessment (Volume D, Section 5.1). The social impact
assessment identified proposed mitigation such that the residual environmental
effects on human use is of low environmental consequence.
Resultant changes in surface water flows are addressed within the hydrology
section (Volume E, Section 3.8) and resultant changes in surface water quality in
the water quality section (Volume E, Section 3.10).
