technical report on the nechalacho deposit, thor lake project ...

Surface Hydrology
The Thor Lake drainage basin is characterized by numerous lakes, marshes and streams. The
lakes vary in size and bathymetry. Connectivity between lakes is limited to small streams. Lake
level and stream flow measurements were made during 2008 and 2009 for the Murky, Thor and
Fred lakes. Lake levels decreased in the summer, and rose moderately in September due to
increased rainfall. Recorded stream flows in 2009 averaged less than 0.1 m 3 /s for the Murky
Lake outlet, less than 0.2 m 3 /s for the Fred lake outlet and less than 0.3 m 3 /s for the Thor Lake
outlet. A reverse in flow between Thor and Long lakes was observed by Stantec.
EBA identifies potential effects to surface hydrology and suggests some mitigation measures.
Effects include reduction in discharge from Thor Lake, and increased spring time flow through
Drizzle and Murky lakes. Mitigation measures include compliance with MVLWB terms and
conditions, and recycling of water.
Fisheries and Aquatics
Baseline studies included investigation of water quality, aquatic ecology, and fisheries values in
nine watercourses and 25 lakes that will be directly or indirectly affected by project
development. Water samples collected at 23 lakes indicate that the mean pH ranges from 7.07
to 8.62, with a large range of conductivity and hardness, and low nutrient levels. Sediment
characteristic varied across the study area, though generally showed high phosphorus, organic
carbon and nitrogen content. Iron, arsenic, silver, nickel and copper concentrations in sediments
were found to be higher than CCME guidelines.
Fisheries studies were conducted in 19 lakes, of which 11 were considered fish-bearing. The
most common species found were the northern pike, lake whitefish, lake cisco, slimy sculpin,
and ninespine stickleback, all of which were present in Thor, Long, Elbow, A and Redemption
lakes. Catch per unit effort was calculated for the five species of fish. Fish health assessments
included length, weight, examination for parasites, analyses for mercury, metals and rare earth
elements. Parasite frequency was found to be low among large-bodied species, and highest in
lake whitefish.
EBA identifies potential effects to fish habitat and suggests some mitigation measures. Effects
include changes in flow patterns and lake levels as a result of the water consumption and loss
of fish habitat due to the construction of the tailings management facility and barge-dock
system. Mitigation measures include recycling of water, construction of a seasonal pipeline from
Drizzle Lake to Thor Lake to supplement winter water levels in thor Lake, and to reduce high
storm event discharges, the adherence to Best Management Practices and compliance with
permit terms.
Technical Report 43-101 – March 13, 2011 Page 18-96
Prepared by Avalon Rare Metals Inc.