During the construction of the North Tailings Basin, physical and flow alteration effects will occur at the North Tailings Basin, Option 5, and Pond 67 watersheds.
During operations, chemical alteration may occur in watersheds as a
result of seepage from tailings pond dams. During post-decommissioning,
controlled overflow from the tailings ponds and open pit may also contribute
to the chemical alteration of North Tailings Basin and Throat Bay watersheds,
and Camp Pond.
Potential accidental events which may affect water quality include:
Factors influencing the geographic extent, severity and duration of environmental effects include time of year (discharge, winter versus spring), nature of the material (solid or liquid, solubility), toxicity of material and location of spill within the watershed. Hazardous materials will be used primarily during the operations phase.
The reversibility of spills would depend on the concentration of the spill material in the receiving water. The high spring flows and high bedload transport will effectively flush the system during the spring following any accident. Although the volume of water in ponds is much greater than in streams, and thus has a greater capacity to dilute the spilled chemical, the turnover time in ponds is much longer. Therefore, a spill in a pond may have an environmental effect that has a longer duration than a spill in a stream.
VBNC has taken and will continue to take all precautions necessary to
prevent spills of hazardous materials. Contingency planning will be in
place to enable a quick and effective response to a spill. Personnel will
be trained in response measures, and spill response equipment will be readily
available in the event of an accidental spill. VBNC enforces and will continue
to enforce strict procedures for the safe transportation of all hazardous
materials on site.
Smoke emissions from the fire would contain particulate matter, CO2, CO, NOx, SO2, volatile organic carbons, poly-cyclic aromatic hydrocarbons or other contaminants. Total particulate matter would increase and contribute metals to the aquatic environment. Runoff would contain ash and sediment and increase alkalinity and TSS. A fire could also increase stream bank erosion and alter the temperature of small waterbodies.
Mitigation and prevention of naturally occurring fires is difficult.
VBNC has taken and will continue to take all precautions necessary to prevent
fire hazards. Contingency planning will be in place to enable a quick and
effective response to an on-site fire. Personnel will be trained in fire
prevention and response, and appropriate fire-fighting equipment will be
readily available in the event of a fire. This capability will also serve
to minimize the environmental effects of fires caused by lightning and
other natural phenomena in the vicinity.
To mitigate environmental effects from accidental pipeline rupture, appropriate safety, spill containment and recovery and environmental protection measures will be incorporated into the pipeline right-of-way design, particularly in proximity to waterbodies. Emergency Spill Response Plans will be developed as discussed in Chapter 4. An Emergency Response Plan with mitigative measures will be developed. These mitigative measures will serve to reduce the environmental effects of any pipeline rupture.
Tailings Pipeline
The tailings slurry from the open pit will be conveyed through a pipeline along the north shore of Camp Pond, Otter Pond and Headwater Pond. The pipeline route will be extended north to the North Tailings Basin during underground operations.
The tailings pipeline is designed so that tailings should not be released
into streams or water bodies in the case of an accidental event. Spilled
tailings slurry will be contained in the containment ditch and/or emergency
dump pockets and will be removed and transported the North Tailings Basin.
Effluent Pipeline Failure - Water Treatment Plant
A 10-km pipeline will convey treated effluent for discharge to Edward's Cove. The water will be treated to MMLER requirements (see Section 10.1.1).
The most environmentally-sensitive areas over which this pipeline traverses
will be at the crossing of Camp Brook, and approximately 1 km north of
the mill site, where the pipeline is in close proximity to Reid Brook.
In the event of a partial break, approximately 20 percent of the pipeline
flow could be released. Assuming a one-hour detection time, about 160 m3
of treated effluent would be released. The average flow in Camp Brook is
approximately 2,100 m3/h, which will provide
at least a ten-fold dilution to any spilled material before it enters Reid
Brook.
Storm events will vary widely in duration and intensity. An emergency spillway is located within each tailings basin. This location is selected based on environmental criteria. Factors influencing the duration and geographic extent of storm events include time of year and location within the watershed.
The consequences of a storm event would depend on the volume of water
released and the time of year. Under a storm event condition, a spillway
will discharge water from Headwater Pond to the Throat Bay watershed. Spillway
discharge at the North Tailings Basin may occur at the Dam N2 location.
These events will happen during periods of high precipitation, so there
will be a higher than normal level of dilution in the watersheds reducing
any environmental effect to the environment.
The release of untreated water would affect the receiving waters, and
the deposition of the tailings would have long term environmental effects
on the sediment and water quality.
A washout would cause bank and stream bed erosion, resulting in the transportation of materials downstream, elevating levels of TSS. No crossings are located directly on Reid Brook. Duration is predicted to be short and reversibility high due to the dynamic nature of brooks, with high spring discharges and spring bedload transportation.
Roads are most susceptible to washouts during the high flow period during and immediately following the spring snow melt. The road design has focused on protection of the aquatic environment by incorporating buffer zones, drainage and erosion control features and culvert design criteria for extreme events. Culverts will be installed with consideration for road and stream gradient, ice conditions and bank stability. High flow situations will also provide increased dilution should a road washout occur, minimizing the overall environmental effect.
Accidental events are summarized in Table 10.26.
| Project Activity | Watershed Potentially Affected | Physical Alteration | Chemical Alteration |
| Spills of hazardous materials | Reid Brook, North Tailings Basin, Little Reid Brook, Southern Watersheds | X | |
| Fire | all watersheds | X | X |
| Effluent pipeline rupture | Reid Brook, North Tailings Basin Brook, Little Reid Brook | X | |
| Storm events-dam spillway | North Tailings Basin, Throat Bay | X | X |
| Dam failure | Reid Brook, North Tailings Basin, Throat Bay, Pond 67, Option 5 | X | X |
| Road washout and flooding | Reid Brook, Little Reid Brook, Pond 67, Southern Watersheds, North Tailings Basin, Pond 65 | X |
If Project and exploration activities occur together in the same watershed, this may cause a potential cumulative environmental effect. Exploration drilling is anticipated to continue at the Western Extension and Eastern Deeps. Underground exploration will occur at Eastern Deeps. Potential environmental effects associated with drilling rig use may include an increase in TSS and metals.
Non-VBNC exploration and drilling activities have been occurring to
the east of the VBNC Claim Block, within the Throat Bay watershed. No cumulative
environmental effects are anticipated.
These mitigations are discussed in more detail in Sections 10.2.10.1
and 10.2.10.2.
Pond Water Reclaim during Operations
Mill operations represent the largest single water use on-site. VBNC will optimize concentrator water re-cycle both internally within the mill and from the tailings and mineralized mine rock facilities.
Reclaim from Headwater Pond and the North Tailings Basin during operation represents a significant water quality mitigation. Reclaiming water reduces the requirement to withdraw water from other surface water sources for mill operations. Reclaim from the tailings basins often exceeds 100 percent. Greater than 100 percent reclaim is possible due to the additional water available from natural runoff within the Headwater Pond and North Tailings Basin watersheds.
During operation, excess water will be treated and discharged via a pipeline to the marine environment. VBNC will operate at maximum recycle in order to reduce discharges.
Surface Water Diversions
Numerous small surface water diversions will be constructed throughout the mine/ mill area for the purposes of mitigating water quality effects. Surface water diversions have been designed for both the operational phase of the North Tailings Basin and the post-decommissioning phase of Headwater Pond.
At the North Tailings Basin, surface water diversions have been planned at the west and south subwatersheds. These diversions represent a water quality mitigation by reducing the volume of natural water entering the North Tailings Basin. The reduction in these flows decreases the volume of water in the basin requiring treatment and discharge. Diversion dams will be constructed at the west (Dam N4) and south (Dam N5) perimeter of the North Tailings Basin. Water at the west end of the basin will be diverted north, whereas the water at the south end of the basin will be diverted to North Tailings Basin Brook.
At Headwater Pond, the post-decommissioning drainage will be directed east to Throat Bay. A permanent spillway will be constructed at Dam H1, and all runoff from the Headwater Pond subwatershed will be re-directed east. This diversion plan represents an important post-decommissioning water quality mitigation for the Reid Brook watershed.
Seepage Mitigation - Dam Design and Construction
The mitigation of dam seepage is an important engineering design feature of the Project. Seepage control will be implemented through construction of zoned earth embankment dams. The essential elements of these dams are a barrier to retain water and a structure to support the barrier. The barrier is normally a core of low permeability soil and the supporting structure or shells are usually granular material with sufficiently flat slopes and strength to provide stability. Internal drains constructed of suitable sandy soil will control seepage.
The extent of irregular bedrock features cannot be completely determined prior to exposing the rock foundations during construction. The procedure used will therefore involve the removal of all the overburden beneath the core, filter and transition zones. The rock surface will be completely cleaned with a water hose and compressed air. The bedrock surface will be geologically mapped for structure, fractures, stratigraphy and faults in order to plan the grouting program. The core/ bedrock contact will be shaped.
The initial bedrock grouting will involve consolidation or blanket grouting
over the entire area beneath the core and filters. This will seal surface
fractures and fissures. The careful implementation of these seepage mitigation
efforts during dam construction will significantly reduce environmental
effects.
Seepage Collection - Operations and Post-decommissioning
During operations, the dams will be monitored to determine the degree of seepage. Seepage typically emerges at the toe of the dam or downstream through bedrock fractures. If required, seepage will be collected by a pump back system for surface water or by a series of groundwater extraction wells.
Seepage typically emerges at one or several specific locations, and usually drains naturally toward a low point in the toe drain. Toe drain collection ponds are feasible when the low point is accessible and suitable space is available to construct a small pond. Seepage may collect and then may be pumped from the collection pond, back to the tailings/mine rock impoundment. This is usually accomplished by the installation of a sump pump arrangement within the collection pond.
Groundwater extraction wells may be drilled downstream of a dam and a pumping system may be installed.
Engineered Diffusion/Redox Barrier Post-decommissioning - Headwater Pond
During decommissioning, elevated metal concentrations may occur if there
is oxidation at the tailings pond water interface and if there is a high
flux rate from the pore water to the pond water. Mitigation could include
the construction of an engineering diffusion or redox barrier. Diffusion
barriers will inhibit metal release to the pond water. A redox barrier
can serve as both a diffusion barrier and to create reducing conditions
which precipitate metals from the pond. It should be noted that, at this
time, it cannot be determined whether a barrier will be required.
In summary, downstream residual environmental effects are predicted from three main source areas: Headwater Pond, North Tailings Basin, and the open pit. The residual environmental effects from these sources are predicted to occur during operations and to continue at specific downstream locations through the post-decommissioning phase. With the exception of major (significant) residual environmental effects to Headwater Pond and the North Tailings Basin, residual environmental effects are predicted to be predominantly negligible (not significant) to moderate (significant), as defined below.
The residual environmental effects of the Project on Headwater Pond and the North Tailings Basin will be major (significant). There will be very substantial physical and chemical alterations to both of these ponds as a result of deposition of tailings and mineralized mine rock.
In Canada, surface water quality is often evaluated relative to established guidelines. The Canadian Water Quality Guidelines were established in 1987 for the Protection of Fish and Aquatic Life (CCREM 1987), and were recently updated (CCME 1995). The guidelines were developed to provide basic scientific information on the effects of water quality on biota so that existing and potential water quality issues may be identified. In addition, the guidelines provide information for the development of site-specific water quality objectives. The document recognizes that many of the guidelines recommended in the Canadian Water Quality Guidelines (CWQG) will need to be modified, when used to develop specific water quality objectives, to account for site-specific variation in conditions (CCREM 1987). The CWQG states: "The guidelines should therefore not be regarded as blanket values for national water quality."
Within the Water Assessment Area, the presence of near surface sulfide mineralization naturally causes concentrations of some metals to be above CWQG. These concentrations have likely been occurring for thousands of years due to natural weathering processes. It is evident that the populations (fish and invertebrates) inhabiting these areas can tolerate these conditions. The CWQG are based on laboratory tests run on a variety of species, and then usually established based on chronic effects to the most sensitive species. The Water Assessment Area is located within a subarctic zone; thus, the species composition of the aquatic environment is not directly comparable to many parts of Canada where guidelines are applied.
In keeping with the intent of the CCME guidelines and in light of the site-specific baseline concentrations and local species composition, VBNC will develop and apply site-specific receiving water quality objectives. This includes determination of input terms for site toxicity testing, characterization of toxicity controlling factors (e.g., pH, hardness), and consideration of the existing biological community. The primary goal in developing site specific objectives will be to establish limits that will ensure the protection of fish and aquatic life in the Water Assessment Area.
To assess residual environmental effects based on the predicted water quality for the modelled scenarios at the various phases of the Project, evaluation criteria have been developed which are based on toxicity threshold data for site-specific species. The National Ambient Water Quality Criteria (NAWQC) documents from the US EPA were reviewed to obtain acute and chronic threshold values for species found at the site. This document also forms the basis of the CWQG. For the purpose of rating significance of residual environmental effects, four criteria have been developed:
A major (significant) residual environmental effect is one where the acute toxicity threshold for a parameter is exceeded on an annual average basis for the most sensitive site species.
A moderate (significant) residual environmental effect is one where the chronic toxicity threshold for a parameter is exceeded on an annual average basis for the most sensitive site species (i.e., chronic sub-lethal effects).
A minor (not significant) residual environmental effect is one where predicted average annual concentrations are below chronic threshold values for less sensitive site species. Generally, the upper limit of the minor effect range is based on the lowest reported chronic value for identified site species. When existing metal concentrations exceed this value, the upper limit for the minor effect is less than the reported maximum chronic value.
A negligible (not significant) residual environmental effect is one where there is no, or only a slight increase, in annual average concentration above background, and the levels are below the threshold limit for chronic toxicity.
This evaluation does not relate directly to biotic effects (e.g., bioaccumulation, toxicity) as site-specific conditions and populations must be assessed. These issues are considered in Chapters 11 to 18.
Several of the watersheds being examined have background aluminum levels which correspond to the minor (not significant), or in one case, moderate (significant) residual environmental effect levels. This means that relatively small contributions from the Project might change a minor (not significant) residual environmental effect to a moderate (significant) residual environmental effect. For example, Pond 64 in the Throat Bay watershed already has a background level which is moderate (0.110 mg/L). The conservative nature of the evaluation criteria being used to determine water quality effects is demonstrated in this example as Pond 64 currently supports a fish population.
The basis for the specific rationale for each parameter evaluated is provided below, together with supporting toxicity data and background concentrations.
Nickel: Published chronic toxicity values for nickel for salmonids range from 0.230-0.535 mg/L (Nebeker et al. 1985, as cited in US EPA 1985a) at low hardness. Similarly, published chronic threshold values for caddisfly (an invertebrate and food for brook trout) range from 0.295-0.734 mg/L (Nebeker et al. 1985, as cited in US EPA 1985a). However, chronic thresholds reported for the invertebrate Daphnia magna are substantially lower at 0.010-0.021 mg/L (Chapman et al. 1982a; 1982b; as cited in US EPA 1985a) for soft water. Acute toxicity values for nickel range from 0.51 mg/L for Daphnia magna to 2.48 mg/L for a fish species (no data available for site-specific fish).
The following nickel evaluation criteria were established with reference to the relevant species chronic and acute threshold toxicity data noted in the literature and highlighted above. A negligible (not significant) residual environmental effect is less than 0.01 mg/L. A minor (not significant) residual environmental effect range of 0.010-0.020 mg/L represents baseline concentrations which would present a potential for some environmental effect on Daphnia magna but would protect other invertebrates and fish. A moderate (significant) residual environmental effect of 0.020-0.50 mg/L was selected as the concentration range representing potential for chronic environmental effects to fish and invertebrates but below acute threshold levels. A major (significant) residual environmental effect level of greater than 0.50 mg/L was selected. The literature suggests potential for lethal effects to fish and invertebrates at this concentration.
Copper: Published chronic toxicity values for brook trout range from 0.003-0.005 mg/L (McKim et al. 1978) and 0.022-0.043 mg/L (Sauter et al. 1976 ) at low hardness. Similarly, published chronic threshold values for Daphnia magna, an invertebrate, range from 0.007-0.043 mg/L (Chapman et al. 1982a; 1982b as cited in US EPA 1985b) for soft water. Baseline concentrations in the Reid Brook watershed and other local watersheds were observed at concentrations above 0.003 mg/L, with peak concentrations in the Reid Brook watershed of 0.0198 mg/L. Resident brook trout communities were observed in these same locations. Acute toxicity values for copper ranged from 0.010 mg/L for Daphnia magna to 0.015 mg/L for trout species (no data available for site-specific fish).
The following copper evaluation criteria were established with reference to the relevant species chronic and acute threshold toxicity data noted in the literature and highlighted above. A negligible (not significant) residual environmental effect is less than 0.003 mg/L. A minor (not significant) residual environmental effect range of greater than 0.003-0.005 mg/L represents baseline to a concentration which would present some potential for an environmental effect on brook trout. However, other studies (Sauter et al. 1976) suggest higher concentrations for brook trout effects (0.022 to 0.043 mg/L). Baseline conditions were measured above the lower limit for brook trout. A moderate (significant) residual environmental effect level of 0.005-0.010 mg/L was selected. This concentration range represents potential for chronic effects to fish and invertebrates but below acute threshold levels. A major (significant) residual environmental effect level of less than 0.010 mg/L was selected, as concentrations above this level represent the potential for lethal environmental effects to fish and invertebrates.
Cobalt: There is no CWQG or NAWQC guideline for cobalt and as such there is limited supporting toxicity data. A study on fathead minnow (a standard sublethal test species) indicated a chronic threshold of 0.286 mg/L and an acute threshold of 3.6 mg/L (Kimball 1978).
The following cobalt evaluation criteria were established with reference to the relevant species chronic and acute threshold toxicity data noted in the literature and highlighted above. A negligible (not signficant) residual environmental effect is less than 0.05 mg/L. A minor (not significant) residual environmental effect range of greater than 0.05-0.100 mg/L represents baseline to a concentration below the chronic threshold value. A value of half the published chronic threshold was selected to provide a safety factor due to of the limited data available. A moderate (significant) residual environmental effect level of 0.10-1.0 mg/L was selected as the concentration range representing potential for chronic effects to fish and invertebrates but below acute threshold levels. Again, a value lower than the published acute threshold of 3.6 mg/L was used as the upper limit for moderate (significant) residual environmental effect to account for the limited information. A major (significant) residual environmental effect level of greater than 1.0 mg/L was selected, as concentrations above this level represent the potential for lethal effects to fish and invertebrates.
Arsenic: Published chronic toxicity values range from 0.300 for salmonid species (Nichols et al. 1984) to 0.914 mg/L for Daphnia magna (Call et al. 1983; Lima 1984). Baseline concentrations in the Reid Brook watershed and other local watersheds were below the LOQ of 0.002 mg/L. Acute toxicity values for arsenic ranged from 0.812 mg/L (Sanders and Cope 1966) for a cladoceran invertebrate species to 13.34 mg/L for a trout species (CCREM 1987).
The following arsenic evaluation criteria were established with reference to the relevant species chronic and acute threshold toxicity data noted in the literature and highlighted above. Based on these observed thresholds the evaluation criteria were established. A negligible (not significant) residual environmental effect is less than 0.01 mg/L. A minor (not significant) residual environmental effect range of 0.01-0.300 mg/L represents baseline concentrations to the lower chronic effect threshold. A moderate (significant) residual environmental effect level of 0.300-0.800 mg/L was selected as it represents potential for chronic effects to invertebrates and fish but is below acute threshold levels for all known site species. A major (significant) residual environmental effect level of greater 0.800 mg/L was selected, as concentrations above this level represent the potential for lethal effects to invertebrates.
Aluminum: The toxicity of aluminum is dependent upon ambient pH. Where pH levels are below 6.5, toxicity increases. The average baseline pH levels are 6.5-6.85 and the Project is not expected to cause a decrease in pH. Therefore the evaluation criteria used for this assessment are based on pH levels of above 6.5. Mean baseline concentrations range from 0.054 mg/L in the Reid Brook watershed to 0.115 mg/L in the Little Reid Brook watershed. A published acute threshold for Daphnia magna at pH 6.5 is 0.68 mg/L (Lamb and Bailey 1981). Chronic toxicity values for pH above 6.5 were not available, although CCME recommends a value of 0.10 mg/L for the protection of fish and aquatic life.
The following aluminum evaluation criteria were established with reference to the relevant species chronic and acute threshold toxicity data noted in the literature and highlighted above. A negligible (not significant) residual environmental effect is less than 0.075 mg/L. A minor (not significant) residual environmental effect range is greater than 0.075-0.10. A moderate (significant) residual environmental effect level of 0.10-0.68 mg/L was selected as it represents potential for chronic effects to fish and invertebrates but is below acute threshold levels for fish. A major (significant) residual environmental effect level of greater than 0.68 mg/L was selected, as concentrations above this level represent the potential for lethal effects to fish and invertebrates.
Zinc: Published chronic toxicity values for brook trout range from 0.534-1.360 mg/L (Holcombe and Andrew 1978) at low hardness. Published chronic threshold values for Daphnia magna, are somewhat lower ranging from 0.070-0.102 mg/L (Biesinger and Christensen 1972, as cited in CCREM 1987) for soft water. Baseline concentrations in the Voisey's Bay drainage and other local watersheds were observed at concentrations above 0.005 mg/L. Resident Brook trout communities were observed in these same locations. Acute toxicity values for zinc range from 0.097 mg/L (Chapman 1978) to 0.905 mg/L (US EPA 1980) for salmonid species and 0.100 (Biesinger and Christensen, 1972) to 0.280 mg/L (Cairns et al. 1978) for Daphnia magna. The apparent overlap in acute and chronic threshold is attributed to species tolerance levels and controlling factors such as hardness and pH .
The following zinc evaluation criteria were established with reference to the relevant species chronic and acute threshold toxicity data noted in the literature and highlighted above. The negligible (not significant) residual environmental effect is less than 0.01 mg/L. A minor (not significant) residual environmental effect range of 0.01-0.03 mg/L represents baseline to concentrations below the lower chronic threshold. The upper limit for the minor (not significant) residual environmental effect range is equal to CCME; this lower value was used in place of the higher chronic threshold of 0.07 mg/L because of the close range of the chronic (0.07 mg/L) and acute (0.09 mg/L) thresholds. A moderate (significant) residual environmental effect level of 0.03-0.10 mg/L was selected as it represents potential for chronic effects to fish and invertebrates but is below acute threshold levels. A major (significant) residual environmental effect level of greater than 0.100 mg/L was selected, as these concentrations represent potential for lethal effects to fish and invertebrates.
Cadmium: Published chronic toxicity values for brook trout range from 0.001-0.003 mg/L (Sauter et al. 1976, as cited in US EPA 1985c) at low hardness. Published chronic threshold values for Daphnia magna, are 0.00008-0.0003 mg/L (Chapman et al. 1982a; 1982b, as cited in US EPA 1985c) for soft water. Baseline concentrations in the Reid Brook watershed and other local watersheds were below the LOQ of 0.0003 mg/L. Acute toxicity values for cadmium range from 0.001-0.018 mg/L (Chapman 1975; 1978; Holcombe et al. 1983) for brook trout and salmonid species, respectively to 0.28 mg/L for the amphipod Hyalella azteca (Reinbold and Pescitelli 1982, as cited in US EPA 1985c) to 0.0099 mg/L for Daphnia magna (Chapman et al. 1982a; 1982b, as cited in US EPA 1985c).
The following cadmium evaluation criteria were established with reference to the relevant species chronic and acute threshold toxicity data noted in the literature and highlighted above. The negligible (not significant) residual environmental effect is less than 0.0007 mg/L. A minor (not significant) residual environmental effect range of 0.0007-0.001mg/L represents baseline concentrations to the lowest chronic threshold for brook trout. The upper limit of the minor (not significant) residual environmental effect range is within the range of baseline concentrations but may still represent a minor (not significant) residual environmental effect due to the chronic threshold of Daphnia magna. A moderate (significant) residual environmental effect level of 0.001-0.010 mg/L was selected as it represents potential for chronic effects to invertebrates and protection for fish but is below acute threshold levels for all known site species. A major (significant) residual environmental effect level of greater than 0.010 mg/L was selected as concentrations representing the potential for lethal effects to invertebrates.
Lead: Published chronic toxicity values for brook trout range from 0.058-0.119 mg/L (Holcombe et al. 1976) at low hardness. Published chronic threshold values for Daphnia magna were somewhat lower ranging from 0.009-0.017 mg/L (Chapman et al.1982a; 1982b. as cited in US EPA 1985d) for soft water. Baseline concentrations in the Reid Brook watershed and other local watersheds were observed at concentrations at the LOQ of 0.0001 mg/L. Acute toxicity values for lead range from 0.124 mg/L (Spehar et al. 1979, as cited in US EPA 1985d) for an amphipod to 0.612 mg/L (Chapman et al. 1982a; 1982b, as cited in US EPA 1985d) for Daphnia magna to 4.10 for brook trout (Holcombe et al. 1976).
The following lead evaluation criteria were established with reference to the relevant species chronic and acute threshold toxicity data noted in the literature and highlighted above. The negligible (not significant) residual environmental effect is less than 0.001 mg/L. A minor (not significant) residual environmental effect range of 0.001-0.009 mg/L represents baseline concentrations and is below the chronic effect threshold. A moderate (significant) residual environmental effect level of 0.009-0.124 mg/L was selected as it represents potential for chronic effects to fish and invertebrates but below acute threshold levels. A major (significant) residual environmental effect level of greater than 0.124 mg/L was selected as the concentrations representing the potential for lethal effects to fish and invertebrates.
The range of values used for establishing residual environmental effects
significance criteria are presented in Table 10.27.
| Metal | Negligible | Minor | Moderate | Major |
| Ni | <0.01 | >0.01-0.02 | >0.02-0.5 | > 0.5 |
| Cu | <0.003 | >0.003-0.005 | >0.005-0.01 | > 0.01 |
| Co | <0.05 | >0.05-0.1 | >0.1-1.0 | >1.0 |
| As | <0.01 | >0.01-0.3 | >0.3-0.8 | > 0.8 |
| Al | <0.075 | >0.075-0.10 | >0.10-0.68 | > 0.68 |
| Zn | <0.01 | >0.01-0.03 | >0.03-0.1 | > 0.1 |
| Cd | <0.0007 | >0.0007-0.001 | >0.001-0.01 | > 0.01 |
| Pb | <0.001 | >0.001-0.009 | >0.009-0.124 | > 0.124 |
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use
(Capacity) of Renewable Resourcea |
||
| Construction | physical alteration | minor
(not significant) |
n/a | n/a | ||
| Operation | physical and chemical alteration | major
(significant) |
high | low | ||
| Decommissioning | physical and chemical alteration | major
(significant) |
high | low | ||
| Post-Decommissioning | chemical alteration | major
(significant) |
moderate | low | ||
| a likelihood
and sustainable use of renewable resources are only defined for environmental
effects that are significant (moderate or major) (CEAA: 1994: 84, 187)
n/a = not applicable |
||||||
Major (significant) residual environmental effects will occur at Headwater Pond and the North Tailings Basin as a result of the placement of tailings during the operation phase. The likelihood of a major (significant) residual environmental effect is rated high during operation and decommissioning. This rating is based on professional judgement that the probability of occurrence is high and that there is high scientific certainty that the residual environmental effect will occur. The sustainable use of water is rated low for operation and decommissioning because existing fish populations will not be sustained, but some populations of lower aquatic trophic levels will be sustained at decommissioning. During post-decommissioning water quality will improve after the deposition of tailings and mine rock ceases. The development of a natural layer of pond bottom sediment and the replacement of tailings pond water with natural runoff will ameliorate the water quality within the basin. The likelihood of a major (significant) residual environmental effect occurring post-decommissioning is rated as moderate. The rating is based on professional judgement that the probability of occurrence is moderate and there is little scientific uncertainty that the residual environmental effect will occur. The effect on sustainable use is rated as low as previously discussed.
The residual environmental effects remaining after mitigation downstream
of Headwater Pond in the Reid Brook watershed are presented in Table
10.29.
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use
(Capacity) of Renewable Resourcea |
||||
| Construction | physical and chemical alteration | minor
(not significant) |
n/a | n/a | ||||
| Operation | physical and chemical alteration | moderateb (significant) | moderate | moderate | ||||
| Decommissioning | physical and chemical alteration | minor
(not significant) |
n/a | n/a | ||||
| Post-Decommissioning | chemical Alteration | minor
(not significant) |
n/a | n/a | ||||
| Accidental events | physical and chemical alteration | major
(significant) |
low | low | ||||
| a likelihood
and sustainable use of renewable resources are only defined for environmental
effects that are significant (moderate or major) (CEAA: 1994: 84, 187)
n/a = not applicable b residual environmental effects are limited to Camp Pond and Camp Brook during open pit operations |
||||||||
The residual environmental effects on the Reid Brook watershed are confined to Camp Pond and Camp Brook. The residual environmental effects are predicted to be moderate (significant) for copper and minor (not significant) for nickel and aluminum during the open pit phase, while all other phases show only negligible (not significant) to minor (not significant) concentrations for the parameters. The residual environmental effects in Reid Brook will be negligible (not significant). The residual environmental effects result primarily from the deposition of dust into Otter Pond, Camp Pond and Camp Brook from the open pit mining. This dust is mainly derived from ore, and is the result of truck traffic to and from the mine, and hauling ore to the crusher. The ore will consist mainly of pentlandite, chalcopyrite, and pyrrhotite (see Chapter 3). These sulphide minerals are insoluble in water and have extremely low solubility in hydrochloric acid. Thus, the bio-availability of the metals (nickel, copper, cobalt) in the ore is low.
The likelihood of elevated copper concentrations occurring in Camp Pond and Camp Brook during the open pit operation is moderate. This rating is based on professional judgement that the probability of occurrence is moderate and that there is little scientific uncertainty that the residual environmental effect will occur.
The residual environmental effects remaining after mitigation in the
Southern Watersheds are presented in Table 10.30.
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use (Capacity) of Renewable Resourcea |
| Construction | physical alteration | minor
(not significant) |
n/a | n/a |
| Operation | physical alteration | minor
(not significant) |
n/a | n/a |
| Decommissioning | physical alteration | minor
(not significant) |
n/a | n/a |
| Accidental Events | physical and chemical alteration | major
(significant) |
low | low |
| a likelihood
and sustainable use of renewable resources are only defined for environmental
effects that are significant (moderate or major) (CEAA: 1994: 84, 187)
n/a = not applicable |
||||
The residual environmental effects remaining after mitigation downstream
of Dam N2 in the North Tailings Basin watershed are presented in Table
10.31.
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use (Capacity) of Renewable Resourcesa |
| Operationb | physical and chemical alteration | minor
(not significant) |
n/a | n/a |
| Decommissioning | chemical alteration | negligible
(not significant) |
n/a | n/a |
| Post-Decommissioning | physical and chemical alteration | moderate
( significant) |
moderate | moderate |
| Accidental Events | physical and chemical alteration | major
(significant) |
low | low |
| a likelihood
and sustainable use of renewable resources are only defined for environmental
effects that are significant (moderate or major) (CEAA: 1994: 84, 187)
b construction activities will occur in the Operation phase |
||||
The residual environmental effect downstream of Dam N2 is predicted to be minor (not significant) during operations as a result of potential siltation events, but becomes moderate (significant) after decommissioning when the water from the Basin will be discharged into North Tailings Basin Brook. The residual environmental effect will extend the length of the watershed and will result from increased nickel and aluminum concentrations from the background.
The likelihood of elevated nickel and aluminum concentrations occurring in North Tailings Basin Brook after decommissioning is moderate. This rating is based on professional judgement that the probability of occurrence is high, and that there is little scientific uncertainty that the residual environmental effect will occur.
The residual environmental effects remaining after mitigation in the Pond 65 watershed are presented in Table 10.32.
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use (Capacity) of Renewable Resourcesa |
| Operationb | physical alteration | minor
(not significant) |
n/a | n/a |
| Decommissioning | physical alteration | minor
(not significant) |
n/a | n/a |
| Accidental events | physical and chemical alteration | minor
(not significant) |
n/a | n/a |
| a likelihood
and sustainable use of renewable resources are only defined for environmental
effects that are significant (moderate or major) (CEAA: 1994: 84, 187)
b construction activities will occur in the operation phase |
||||
The residual environmental effects remaining after mitigation in Throat Bay watershed are presented in Table 10.33.
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use (Capacity) of Renewable Resourcesa |
| Construction | physical alteration | minor
(not significant) |
n/a | n/a |
| Operation | chemical alteration | negligible
(not significant) |
n/a | n/a |
| Decommissioning | chemical alteration | negligible
(not significant) |
n/a | n/a |
| Post-Decommissioning | chemical alteration | moderate (significant) | moderate | moderate |
| Accidental Events | physical and chemical alteration | major
(significant) |
low | low |
| a likelihood and sustainable use of renewable resources are only defined for environmental effects that are significant (moderate or major) (CEAA: 1994: 84, 187) | ||||
The residual environmental effect resulting from seepage from Headwater Pond to the Throat Bay watershed during operations is negligible (not significant). After decommissioning the decant will result in a moderate (significant) residual environmental effect on water quality to Pond 64, and a minor (not significant) residual environmental effect beyond Pond 64, primarily resulting from an increase in nickel concentrations. The Throat Bay watershed has relatively high levels of aluminum occurring naturally. The contribution of the Project to aluminum concentrations is very small.
The likelihood of elevated nickel concentrations occurring downstream of Headwater Pond at Dam H1 is moderate. This rating is based on professional judgement that the probability of occurrence is high and that there is little scientific uncertainty that the residual environmental effect will occur.
The residual environmental effects remaining after mitigation in the
Option 5 watershed are presented in Table 10.34.
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use (Capacity) of Renewable Resourcesa |
| Operationb | physical and chemical alteration | minor
(not significant) |
n/a | n/a |
| Decommissioning | physical and chemical alteration | minor
(not significant) |
n/a | n/a |
| Post-Decommissioning | chemical alteration | negligible
(not significant) |
n/a | n/a |
| Accidental Events | physical and chemical alteration | minor
(not significant) |
n/a | n/a |
| a likelihood
and sustainable use of renewable resources are only defined for environmental
effects that are significant (moderate or major) (CEAA: 1994: 84, 187)
b construction activities will be conducted in the Operation phase |
||||
The residual environmental effects remaining after mitigation in the Pond 65 watershed are presented in Table 10.35.
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use (Capacity) of Renewable Resourcesa |
| Operationb | physical and chemical alteration | moderate
(significant) |
moderate | moderate |
| Decommissioning | chemical alteration | moderate
(significant) |
moderate | moderate |
| Post-decommissioning | chemical alteration | moderate
(significant) |
moderate | moderate |
| Accidental Events | physical and chemical alteration | minor
(not significant) |
n/a | n/a |
| a likelihood
and sustainable use of renewable resources are only defined for environmental
effects that are significant (moderate or major) (CEAA: 1994: 84, 187)
b- construction activities will occur in the operation phase |
||||
The residual environmental effect of seepage from the North Tailings Pond on the Pond 67 watershed is predicted to be moderate (significant) during the operations phase of the Project, as a result of elevated nickel levels. The moderate (significant) residual environmental effect is confined to immediately downstream of Dam N3, while the rest of the watershed will experience only minor (not significant) residual environmental effects. The level of nickel will decrease (minor (not significant) residual effect) after decommissioning. The level of aluminum will increase after decommissioning, resulting in a moderate (significant) residual environmental effect immediately downstream of Dam N3.
The likelihood of elevated nickel and aluminum concentrations occurring
downstream of Dam N3 is moderate. This rating is based on professional
judgement that the probability of occurrence is high and that there is
little scientific uncertainty that the residual environmental effect will
occur.
The residual environmental effects remaining after mitigation in Little Reid Brook watershed and port site drainage are presented in Table 10.36.
| Project Phase | Residual Environmental Effect | Significance | Likelihooda
(Probability) |
Sustainable Use (Capacity) of Renewable Resourcesa |
| Construction | physical alteration | minor
(not significant) |
n/a | n/a |
| Operation | physical alteration | minor
(not significant) |
n/a | n/a |
| Decommissioning | physical alteration | minor
(not significant) |
n/a | n/a |
| Accidental Events | physical and chemical alteration | major
(significant) |
low | low |
| a likelihood and sustainable use of renewable resources are only defined for environmental effects that are significant (moderate or major) (CEAA: 1994: 84, 187) | ||||
Downstream water quality will only be affected by seepage through dams
at Headwater Pond and the North Tailings Basin. Excess water will be treated
and directly discharged to the marine environment. Minor (not significant)
to moderate (significant) residual environmental effects will occur near
or at the end of mine production, to limited areas of the Pond 67 watershed.
Camp Pond and Camp Brook will experience moderate (significant) residual
environmental effects during the open pit operations. The spatial extent
of these residual environmental effects during open pit operations and
end of operation is illustrated in Figures 10.14 and 10.15, respectively.
The residual environmental effects of downstream surface water concentrations of metals is dependent upon season and size of receiving waterbody. In areas where there is a large waterbody, such as downstream of Dam H2 (Otter Pond), there is less variation than at a stream. Stream concentrations are highly dependent upon season. For example, during low flow periods in mid-winter, metal concentrations can increase. However, during spring freshet and summer, these concentrations are near background. Seasonal residual environmental effects on fish are discussed in Chapter 11.
The likelihood of the residual environmental effects predicted for Pond 67, Camp Pond and Camp Brook is moderate and is based on conservative assumptions that were used to predict concentrations. As a transport medium, the pathway to aquatic biota is dependent upon the hardness of the water, which affects the bio-availability of metals. The hardness of the water will be elevated at seepage areas; this will affect the bio-availability of the metals, making them less toxic. In addition, the presence of precipitated iron hydroxides may reduce their bio-availability and toxicity. The sustainable use of water is rated moderate because the potential effects to water quality at the upstream sources will affect the sustainable use of water in those locations. However, the residual environmental effects are limited to these locations and the sustainable use of water will not be affected elsewhere in the Assessment Area.
Moderate (significant) residual environmental effects will principally result from increased concentrations of nickel and aluminum in North Tailings Basin Brook, and downstream of Dam H1 in the Throat Bay watershed as a result of pond overflow. Aluminum occurs at naturally high concentrations, within North Tailings Basin Brook, Throat Bay and Pond 67 watersheds. High natural concentrations of aluminum may be attributed to the bedrock geology in this area. Therefore, even a small increase in aluminum concentrations may result in moderate (significant) residual environmental effects.
The likelihood of residual environmental effects is moderate and is based on conservative assumptions that were used to predict concentrations. As a transport medium, the pathway to aquatic biota is dependent upon the hardness of the water, which affects the bio-availability of metals.
The sustainable use of water is rated as moderate because the potential
effects to water quality at the upstream sources will affect the sustainable
use of water in those locations. However, water quality effects are limited
to these locations and the sustainable use of water will not be affected
elsewhere on the site.
Water quality will be monitored in accordance with the federal Metal Mining Liquid Effluent Regulations (1977) and the provincial Environmental Control (Water and Sewage) Regulations (1980). Water discharged from Headwater Pond, the North Tailings Basin, the mill, and sedimentation ponds will be monitored on a regular basis for compliance with regulated limits.
The follow-up program for water quality monitoring is described in Chapter 4.
Water Quality Commitments
Elevated concentrations of metals are predicted at several locations downstream of the Project. VBNC has committed to the long term protection of water quality across the site, particularly Reid Brook, Camp Pond and Camp Brook, and Otter Pond (downstream of Dam H2):
