Environmental Assessment
Volume E-4.3
Tailings Facility
Fish and Aquatic Resources
Ambatovy Project
181
January 2006
Table 4.3-6 Predicted Aquatic Habitat Loss as a Result of the Displacement of
Streams and Wetlands by Tailings Facility Construction
(a)
Habitat Type
Number and Mean Width (m)
(b)
Channel Length (m) Est. Wetted Area (ha)
Streams 1
st
order
50 (0.50)
24,901.9
1.25
Streams 2
nd
order
13 (2.39)
4,547.4
1.09
Streams 3
rd
order
4 (2.70)
4,982.7
1.35
Streams 4
th
order
1 (5.31)
1,697.2
0.90
(a)
Within tailings footprint and boundaries of three sub-basins of the Ambolona watershed.
(b)
Mean width in 2
nd
, 3
rd
, 4
th
order streams calculated from survey site habitat observations (average of high and low
flows); no on-site data available for 1
st
order streams, width estimated.
Service Corridors and Infrastructure
Ancillary facilities (i.e., the access road and the tailings pipeline from the process
plant and the water discharge pipeline) can disturb riparian and aquatic habitat
and fauna in study area watercourses by instream construction activities and by
surface runoff (i.e., sediment from erosion). Along the proposed tailings service
corridor three permanent watercourses will be crossed. A majority of the
watercourses within the service corridor exhibit highly modified habitats, and
will exhibit a low sensitivity to minor disturbance. Based on habitat
characteristics and the IHIA model for site TMT001 (the lower Ambolona
tributary, which will be crossed by the service corridor) the stream habitat
condition was rated as Class E (extensive modification of riparian and instream
ecosystems). A similar habitat condition and sensitivity to construction is
expected for other watercourses along this corridor.
Construction effects from instream activity during crossings of these
watercourses will be primarily a short-term disturbance of riparian and instream
habitat. Watercourse crossing guidelines will be followed to prevent or mitigate
harmful effects on aquatic habitat (addressed in Volume E, Section 7,
Environmental Management Plans) and impacts are not anticipated from
construction activities associated with the service corridor. However long-term,
permanent local disturbance could occur depending on the type and size of road
crossing (culvert, bridge) used for roads, and its effect on stream hydrology and
channel morphology.
Change in Downstream Water Flow and Quality
Clearing of the tailings area, diversion of streams, and operation of the tailings
facility will affect surface water quantity and quality (runoff and effluent tailings)
in the streams draining the project area. These changes may alter riparian and
instream aquatic habitat and affect the presence and abundance of critical habitat
for aquatic biota in portions of the receiving watersheds. Five regionally endemic
