Project activities will cause both flow alteration, and water quality alteration. Flow alteration will result from water course diversions. The potential environmental effects of flow reduction on freshwater fish and habitat are assessed in Chapter 11. Water quality alteration is discussed in terms of either physical or chemical environmental effects. Physical environmental effects include siltation (measured as total suspended solids) and may result principally from construction activities. Chemical environmental effects include changes to metal concentrations and other parameters resulting from seepage and controlled overflow at the mine rock and tailings basins.
The Project will proceed through a series of phases, each of which may influence the water quality of surrounding watersheds. The phases of the Project are construction, operations, decommissioning and post-decommissioning.
In addition to the Project phases, consideration is also given to accidental
events which may affect water quality. Accidental events are addressed
in Section 10.2.8. Potential accidental events are:
The potential environmental effects in the Assessment Area are summarized in Tables 10.7 and 10.14.
| Potential Environmental
Effect |
Project Phase | Project Activity |
| Flow Alteration |
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| Physical Alteration |
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| Chemical Alteration |
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| Potential Environmental
Effect |
Project Phase | Project Activity |
| Physical Alteration |
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| Potential Environmental
Effect |
Project Phase | Project Activity |
| Flow Alteration |
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| Physical Alteration |
|
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| Chemical Alteration |
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| Potential Environmental
Effect |
Project Phase | Project Activity |
| Physical Alteration |
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| Potential Environmental
Effect |
Project Phase | Project Activity |
| Flow Alteration |
|
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| Physical Alteration |
|
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| Chemical Alteration |
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| Potential Environmental
Effect |
Project Phase | Project Activity |
| Flow Alteration |
|
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| Physical Alteration |
|
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| Chemical Alteration |
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| Potential Environmental
Effect |
Project Phase | Project Activity |
| Physical Alteration |
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| Chemical Alteration |
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| Potential Environmental
Effect |
Project Phase | Project Activity |
| Physical Alteration |
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| Chemical Alteration |
|
|
The following paragraphs present a summary discussion of the IMPACTä model. A detailed discussion is provided in Appendix 10A.
"In the process of dismantling the ovoid we are concerned that chemicals,
dust particles and sediments will settle on vegetation and snow covered
ground in the vicinity of the mine. Snow and water run-off will wash toxic
chemicals into the surrounding water systems and contaminated vegetation
will break through the food chain". (Sarah Webb, Panel Scoping Meeting
in Nain, April 17, 1997)
The principal tool used for modelling the environmental effect of contaminant releases during the various phases of the Project is IMPACTTM - the Integrated Model for the Probabilistic Assessment of Contaminant Transport. IMPACTTM is a probabilistic model that has been developed to calculate effects of contaminant emissions on environmental media (e.g., water, sediment, air). The model uses established mathematical principles to predict concentrations in environmental media and ecological risk to biota and humans. The prediction of concentrations in environmental media such as water is the first step in the prediction of metal exposure and uptake with aquatic and terrestrial food chains.
IMPACTTM has been evaluated as part of BIOMOVS II ( Biosphere Model Validation Study - Phase II), an independent, international, comparative study of models used to predict transport, fate and biological uptake of contaminants in the environment. BIOMOVS II involved modelling of environmental effects using a standard hypothetical data set and included atmospheric, groundwater and surface water pathways. Results of BIOMOVS II evaluation demonstrated that IMPACTTM produces valid and credible predictions of contaminant transport and fate (SRPI 1996).
These sources were described according to parameters in discharge, concentrations of these contaminants, and discharge rates (see Table 10.15). The following metals were modelled using IMPACTTM: copper, nickel, cobalt, lead, zinc, arsenic, aluminum and cadmium. These metals were selected based on review of expected mineralized mine rock and tailings chemistry and their biological sensitivity (CCREM 1987; CCME 1995). In order to predict transport and deposition to the sediment, each metal was characterized in terms of its relative tendency to occur either dissolved in water or attached to particles in the water. The model incorporated source term chemistry predictions, decant and seepage predictions and air quality data. Other metals that were not selected for modelling (as well as those that have been modelled using IMPACT) will be included in a monitoring program that will extend over the duration of the Project. This monitoring program will evaluate the potential concentration changes of those metals in the various receiving watersheds, and will include bio-monitoring (see Chapter 4).
The IMPACT TM model scenario did not consider iron, pH or ammonia, which are expected to be associated with the North Tailings Basin and Headwater Pond. The concentrations and potential environmental effects of these parameters were modelled separately using source term chemistry and receiving environment information.
|
|
||||
| Parameter | Operations | Post-Decommissioning | ||
| Pond Water
(mg/L) |
Pore Water
(mg/L) |
Pond Water (mg/L) | Pore Water
(mg/L) |
|
| Nickel | <0.010 to 1.000 | <0.010 to 1.000 | 0.394 | <0.010 to 0.500 |
| Copper | <0.010 to 0.100 | <0.010 to 0.100 | 0.001 | <0.010 to 0.100 |
| Cobalt | <0.010 to 0.100 | <0.010 to 0.100 | 0.0097 | <0.010 to 0.100 |
| Arsenic | <0.010 | <0.010 | - | <0.010 |
| Aluminum | <0.100 | <0.100 | 0.071 | <0.100 to 1.000 |
| Zinc | <0.010 to <0.100 | <0.010 to 0.100 | 0.0031 | <0.010 to 0.1000 |
| Cadmium | <0.0005 to <0.005 | <0.0005 to 0.005 | - | <0.0005 to 0.005 |
| Lead | <0.002 to 0.100 | <0.002 to 0.050 | - | <0.002 to 0.050 |
| Iron | <0.100 to 1.000 | 0.100 to 1.000 | <1.000 | 1 to 10 |
| Ammonia | 2 to 9 | - | 2 to 9 | - |
| pH | 8.0 to 9.5 | 6 to 8 | 6 to 8 | 6 to 8 |
|
|
||||
| Parameter | Operations | Post-Decommissioning | ||
| Pond Water
(mg/L) |
Pore Water
(mg/L) |
Pond Water (mg/L) | Pore Water
(mg/L) |
|
| Nickel | <0.010 to 1.000 | <0.010 to 1.000 | 0.245 | <0.010 to 0.500 |
| Copper | <0.010 to 0.100 | <0.010 to 0.100 | 0.0006 | <0.010 to 0.100 |
| Cobalt | <0.010 to 0.100 | <0.010 to 0.100 | 0.0061 | <0.010 to 0.100 |
| Arsenic | <0.010 | <0.010 | - | <0.010 |
| Aluminum | <0.100 | <0.100 | 0.041 | <0.100 to 1.000 |
| Zinc | <0.010 to 0.100 | <0.010 to 0.100 | 0.0019 | <0.010 to 0.1000 |
| Cadmium | <0.0005 to 0.005 | <0.0005 to 0.005 | - | <0.0005 to 0.005 |
| Lead | <0.002 to 0.100 | <0.002 to 0.050 | - | <0.002 to 0.050 |
| Iron | <0.100 to 1.000 | 0.100 to 1.000 | <1.00 | 1 to 10 |
| Ammonia | 6 to 10 | - | - | - |
| pH | 8.0 - 9.5 | 6 to 8 | - | 6 to 8 |
| 1 These predictions were based on source modelling for Headwater Pond and North Tailings Basin during the operations and post-decommissioning phases of the Project. | ||||
The rates of water flow through each of the defined surface water polygons were calculated based on unit area runoff coefficients and the catchment area for each defined polygon.
Water quality was also modelled in IMPACTTM on a short term basis to account for seasonal variability. Mean monthly flow rates were incorporated only for water polygons receiving metal loadings via seepage. These are the only polygons where contaminant loading would remain constant, due to relatively constant seepage rates, while inflow or dilution water would vary on a seasonal basis.
Seasonal environmental effects were evaluated to determine the downstream concentrations under low (worst case) and peak flow. Mean monthly flow rates, were incorporated only for water polygons receiving contaminant loadings via seepage pathways.
Once information on source terms were entered into the model and each polygon was characterized in terms of its physical attributes, the polygons were linked to allow for transport of metals downstream and prediction of concentrations in those downstream polygons. The flow pattern for the surface water courses reflected the baseline flow patterns on the site except where the Project design will alter these.
Concentrations of the selected metals were predicted in these time steps in fifteen freshwater polygons representing areas downstream of discharge sources. Predicted concentrations were compared to chronic toxicity thresholds established for fish and invertebrate species present on the site. Locations which exceeded thresholds were identified for the various time frames reported.
After the Project is decommissioned and regulated point-of-discharge standards are achieved without treatment, the diversions will be removed and the natural water flows will be restored.
With respect to water quality predictions, the IMPACTTM model has been designed to simulate the significant and complex physical, biological and chemical interactions within the environment based on the above inputs, and to predict water quality effects downstream.
Tailings and mine rock source term chemistry has been determined by predicting short and long term pore water chemistry within the tailings, and the rate of flux of metals into the overlying pond water from the tailings and mine rock. These predictions are based on the site water management plan, mill operations, tailings/ mine rock composition and climatic/precipitation conditions. The output of the source term model provides a range of potential concentrations for the various parameters. The outputs were then verified based on existing field data from other mine sites. The maximum concentration value predicted for each parameter was selected for IMPACTTM model input.
Predicted incremental increases were added to the existing or background median value for each watershed. As discussed in Section 10.1, many of the metals analyzed in the baseline surveys were below the laboratory LOQ values. In such cases, the predicted incremental increases in concentrations were added to the LOQ value resulting in an overestimate of the predicted total concentrations of those metals.
Groundwater modelling methods were used to develop dam seepage estimates. The final stage (maximum water level) conditions at both the Headwater Pond and North Tailings Basin locations were modelled. Seepage estimates are based on interpretation of bedrock and dam permeability following construction, and are considered to be realistic and achievable.
Local streamflow and pond bathymetry data has been collected in the field and interpreted for the purposes of estimating receiving water flows and potential downstream dilution effects. Field flow data is highly variable on streams potentially affected by the Project. The model inputs are therefore based on interpreted realistic flows and pond dilutions. These IMPACTTM model inputs are also considered realistic, yet conservative.
Airborne particulate effects have been determined based on the modeling of the Total Suspended Particulate (TSP) deposition rates on the environment. The airborne effects on water quality are assessed in the mine/mill area. Conservative assumptions with respect to particle composition, distribution and loading have been used as IMPACTTM inputs.
In summary, the model predictions provided are often based on multiple
input parameters that are realistic, yet conservative. The predictions
are therefore intended to represent realistic conservative conditions.
The environmental monitoring program, to be conducted throughout all phases
of the Project, will allow verification of the environmental effects predicted
by the model and also allow direct field measurement of the various input
parameters.
Summary of Potential Environmental Effects Resulting from Iron Oxidation, pH and Ammonia
Ammonia levels may be elevated in both the North Tailings Pond and Headwater Pond as a result of the explosives used in the mining process. Ammonia is toxic to freshwater species when it is present in its non-ionic form, which occurs at relatively high pH (greater than 8.0). The concentrations of ammonia are predicted to be below 0.180 mg/L and pH is not predicted to be above 7.0. Thus, ammonia is not predicted to have any residual environmental effects .
The natural pH of the watersheds being examined range from pH 6.0- 7.0. In general the effects of the Project will be to decrease the pH slightly. This depression will occur mainly post-decommissioning. During the operations, tailings pH is likely to be high (greater than 8.0) and effluent from the tailings ponds will be treated (including pH adjustment) before discharge to Edward's Cove or Kangeklualuk Bay.
Iron (ferrous ions) in the tailings ponds can oxidize to ferric ions in oxygenated water and this results in the generation of acid along with insoluble ferric hydroxide. Iron is a major constituent of the ore, but will be relatively insoluble and modelling has predicted that iron concentrates in all water systems will not increase incrementally above 0.012 mg/L in any watershed. There is unlikely to be sufficient iron present in the effluent to cause any staining, often associated with deposition of iron hydroxide in streams.
Elevated levels of pH in Headwater Pond and the North Tailings Basin, will be reduced in the receiving waters, which will reduce any environmental effect from ammonia or iron, given the low concentrations of each in the tailings ponds. The ammonia levels in the tailings ponds will decrease to low levels soon after blasting activity ceases.
As the concentrations of these three components of Headwater Pond waters and North Tailings Basin waters are low, it is unlikely that there will be any environmental effect from these components on receiving water quality and there is no further discussion of iron, ammonia or pH.
A summary background discussion of water quality parameters is presented
in Appendix 10B.
Mineralized mine rock and tailings will be placed in Headwater Pond. The deposition plan is shown on Figure 10.12.
Flow Alteration
The main construction-related flow alteration issue involves the pump down of Headwater Pond. The objective of the pump down is to minimize the volume of water ultimately requiring treatment and to provide flexibility with respect to dam construction.
The pump down of Headwater Pond will involve the extraction of about 50 percent of the natural pond volume (7.5 million m3). This water will be pumped into Otter Pond during two construction seasons and result in increased flows to Camp Brook and, ultimately, Reid Brook. The pump down will be carried out from mid-June (following peak runoff) to mid-August to reduce the environmental effects on the downstream environment. This will result in an increased flow in Camp Brook in mid-July from about 1-2 m3/sec. Environmental effects will therefore be short term and reversible.
The diversion of approximately 25 percent of the Camp Brook Subwatershed
to Edward's Cove will occur during operations. These diversions include:
The maximum annual withdrawal from Camp Pond for process use is estimated at 1.1 million m3 per year (see Chapter 3.). The drawdowns at Camp Pond will principally influence the peak (maximum) water levels during the spring. The water levels during the low flow period will remain unchanged during open pit operations with minimal changes (less than 0.2 m) during underground operations. The drawdown during Project startup should range from about 0.2-0.3 m and will be dominated by the removal of Headwater Pond from the watershed. During open pit mining the drawdown will range from about 0.3-0.4 m due to the extraction of freshwater from Camp Pond and the removal of Headwater Pond from the watershed. During underground mining, conditions at Camp Pond will be similar to the open pit phase.
During post-decommissioning, the drainage within the open pit area will be restored to the natural condition. All pumping systems, pipelines and the sedimentation ponds will be removed by transferring sediment to Headwater Pond (if required), removing and re-grading the pond sites. The mill site will be regraded so that the open pit area drains into either Camp Pond or Reid Brook.
Dewatering of the open pit will terminate near the end of operations. The projected time frame required for the open pit to refill is approximately five years (recharge rate is approximately 2.2 million m3/year). These waters will be directed to Camp Pond.
Headwater Pond will remain permanently removed from the Reid Brook watershed, and will be directed to the east. During post-decommissioning, surface waters within the mine/mill area will be re-directed back to Reid Brook and water extraction from Camp Pond will cease. Therefore, the flow to Reid Brook from the Camp Pond sub-watershed will be slightly greater than during the operational phase.
Physical Alteration
During the construction phase, an increase in total suspended solids (TSS) may occur in the Reid Brook watershed. This will be associated with either construction around the mine/mill area, or Headwater Pond Dam H2 construction.
In the mine/mill area, water diversions and water management facilities (sedimentation ponds) will be constructed prior to proceeding with the major earthworks (i.e., overburden stripping and concentrator site preparation). A sequential sedimentation pond construction program will begin with construction of the Mill Site Sedimentation Pond, followed by the Surge Pond and South Sedimentation Pond. During construction, these facilities will be operated to allow appropriate residence times, therefore facilitating settlement of suspended solids prior to release. These waters will be assessed so that they meet appropriate surface water discharge criteria.
Construction phase water management planning involves pumping water, as required, from the South Sedimentation Pond and Surge Pond to the Mill Site Sedimentation Pond. These waters will combine with the local area drainage from the concentrator site and will be decanted, as required, to Camp Pond during construction. Short term and reversible siltation environmental effects are therefore anticipated to be restricted to Camp Pond during the construction phase. Siltation control structures will reduce the volume of silt entering Camp Pond.
At Headwater Pond, the grouting of Dam H2 foundation at the west end of Headwater Pond will result in short term siltation type effects to Otter Pond. These environmental effects are anticipated to be short term and reversible. Control measures will be implemented to reduce siltation. Road construction along the north shore of Camp Pond and Otter Pond may also result in localized siltation within these ponds. Environmental effects will be reduced through the construction of siltation control systems, where appropriate.
During operations, sedimentation will be controlled and monitored. The main areas of potential environmental effect during operations are Camp Pond and Camp Brook, during spring periods of high runoff. Increases in TSS are also anticipated from airborne sediment generated from the movement of trucks equipment in the open pit.
Decommissioning Project activities will involve re-grading. These activities are anticipated to result in short term TSS increases to surface waters and are reversible.
Chemical Alteration
During construction, the permanent sewage treatment plant will be constructed at the mill site. A sequencing batch reactor type plant will be designed to accommodate 700 people. The treated effluent discharge will be directed to Camp Pond and will comply with the Newfoundland and Labrador Environmental Control (Water and Sewer) Regulations (Schedule A) pursuant to the Department of Environment Act. The sewage treatment facility will discharge approximately 315 m3/day into Camp Pond (at peak 700 workers X 0.450 m3/day/person). This flow will not measurably affect the overall site water balance or the water levels in Camp Pond. Although the discharge will comply with the provincial regulations, increased levels of nutrients will result (nitrogen and phosphorus compounds). As discussed in Section 10.1, phosphorus and nitrogen compounds are currently at low levels, co-limiting primary productivity in Camp Pond. However, these environmental effects will be short term and reversible as discharge of sewage to Camp Pond will only occur during construction.
During operations, the water quality will be affected as a result of deposition of airborne particulates at Camp Pond and seepage through Dam H2 at the west end of Headwater Pond discharging into Otter Pond. The water levels in Headwater Pond will vary during operations. It is anticipated that, as a result of the pump down, seepage will be inward towards Headwater Pond during the initial years of operation. The water level will gradually rise, reaching an operational maximum elevation of 100 m above sea level at about year 8. Estimates for seepage for Dam H2 are provided in Table 10.16.
| Year | Seepage (L/min) |
| 1 to 3 | 0 |
| 4 to 8 | 12 |
| 9 to 25 | 12 |
| post year 25 | 12 |
These basin waters are anticipated to have alkaline pH, elevated levels of sulphate and low levels of most trace metals. The pore water within the tailings is expected to be the principal source of seepage waters.
A water level of 100 m above sea level will be maintained throughout the operational phase of the Project. The water quality effects on Camp Pond have been selected for discussion purposes, due to its location and geographical relevance to the Project.
During post-decommissioning, predicted water quality effects associated
with this watershed will be based on two sources:
Following decommissioning, elevated concentrations of all metals are predicted in Camp Pond.
The modelling results for the concentrations of metals and other reagents in Camp Pond at various phases of the Project are presented in Table 10.17 and are assessed in Section 10.3.
| Water Quality Parameter | Existing Median (mg/L) | Increase at Constructiona | Increase at Open Pit Operations (Total)b | Increase at End of Operations
(Total) |
Increase at Post-Decommissioning
(Total) |
| Nickel | <0.002 | Nil | 0.01
(0.012) |
0.001
(0.003) |
0.013
(0.015) |
| Copper | <0.002 | Nil | 0.006
(0.008) |
Nil | 0.003
(0.005) |
| Cobalt | <0.001 | Nil | Nil | Nil | 0.002
(0.003) |
| Arsenic | <0.002 | Nil | Nil
|
Nil | 0.001
(0.003) |
| Aluminum | 0.067 | 0.001
(0.068) |
0.024
(0.091) |
0.001
(0.068) |
0.013
(0.080) |
| Zinc | <0.003 | Nil | Nil
|
Nil | 0.006
(0.009) |
| Cadmium | <0.0003 | Nil | Nil
|
Nil | 0.0001
(0.0004) |
| Lead | 0.0001 | Nil | Nil
|
Nil | 0.0013
(0.0014) |
| Iron | 0.05 | not modelled | not modelled | 0.003
(0.053) |
0.003-0.006
(0.053-056) |
| Ammonia | <0.05 | not modelled | not modelled | Nil | Nil |
| a the incremental
increase is indicated as nil if it is an order of magnitude less than the
LOQ
b the total (increase plus existing median) is indicated in parentheses |
|||||
Freshwater diversions are not anticipated during any phase of the Project.
Physical Alteration
Siltation at stream crossings and in the area of Pond 73 may occur during road and airstrip construction. These environmental effects will be controlled during construction. The environmental effects are therefore short term and reversible.
Siltation may be anticipated in Pond 73 during airstrip operations. Regular application of water to the gravel airstrip may be required to reduce the amount of airborne particulate matter. The installation of a geofabric filter fence may be required to reduce the concentrations of silt in this pond during operations.
Site re-grading may result in siltation events during decommissioning. Siltation controls will be implemented as required.
Chemical Alteration
No chemical water quality effects are anticipated in this watershed during any phase.
Flow Alteration
During construction, flow alterations will be limited to temporary diversions
of small local streams for the purposes of completing roads and dams. Alteration
to streamflows will also occur as a result of the construction of surface
water diversions to the north and south around the North Tailings Basin.
| Year | Seepage (L/min) |
| 9 to 11 | 0 |
| 12 to 18 | 6.5 |
| 18 to 25 | 15 |
| Post Year 25 | 15 |
The North Tailings Basin closure plan will include a final stage flooded elevation of 149 m and maintenance of water treatment facility until the termination of decommissioning. The pH of the basin will remain alkaline during operations. During post-decommissioning this water will be replaced from upstream sources and will ultimately reflect natural conditions. The pore water will remain in a steady state condition, representative of the operating conditions.
On the basis of the seepage rates through Dam N2 and the reduced flow rates in North Tailings Basin Brook, estimates of water quality immediately downstream of Dam N2 in North Tailings Basin Brook were made. The results of the modelling of metal concentrations and other parameters in North Tailings Basin Brook is shown in Table 10.19 and are assessed in Section 10.3.
| Water Quality Parameter | Existing Median (mg/L) | Increase at End of Operations (Total)a,b | Increase at Year 50 (Total) |
| Nickel | <0.002 | 0.002
(0.004) |
0.228
(0.230) |
| Copper | <0.002 | Nil | 0.001
(0.003) |
| Cobalt | <0.001 | Nil | 0.006
(0.007) |
| Arsenic | <0.002 | Nil
|
0.001
(0.003) |
| Aluminum | 0.063 | Nil | 0.066
(0.129) |
| Zinc | 0.004 | Nil
|
0.002
(0.006) |
| Cadmium | <0.0003 | Nil | Nil |
| Lead | 0.0001 | 0.0001
(0.0002) |
0.0009
(0.0010) |
| Iron | 0.028 | 0.003
(0.031) |
0.003 - 0.004
(0.031 - 0.032) |
| Ammonia | <0.05 | 0.003 - 0.012
(0.05 - 0.06) |
Nil |
| a the incremental
increase is indicated as nil if it is an order of magnitude less than the
LOQ
b the total (increase plus existing median) is indicated in parentheses |
|||
Flow Alteration
Diversions and flow alteration are not anticipated during the construction
and operation phases. Following decommissioning, significant increases
in flow are anticipated in the Throat Bay watershed. The Headwater Pond
watershed will be directed east through Throat Bay. The increase in flows
to the east will range from near zero during winter to approximately 0.5-0.6
m3/sec during spring.
Physical Alteration
The grouting of the dam foundation at the east end of Headwater Pond is unlikely to result in siltation-related environmental effects to Pond 64. However, the access road to the airstrip will involve several stream crossings at the western section of the watershed. Siltation control measures will be implemented during construction. These environmental effects are anticipated to be short term and reversible. No siltation is anticipated during operations.
Following decommissioning, potential siltation related to the removal of diversion structures and the decommissioning of roads is anticipated. These environmental effects will be mitigated through the installation of engineered siltation controls.
Chemical Alteration
Chemical environmental effects are not anticipated during construction. During operations, seepage loss rates through perimeter Dam H1 (Headwater Pond) are estimated in Table 10.20. The tailings pond water and pore water are anticipated to have alkaline pH, elevated levels of sulphate and low levels of metals. The seepage through and under the dam enters the Throat Bay watershed.
| Year | Seepage (L/min) |
| 1 to 3 | 0 |
| 4 to 8 | 6 |
| 9 to 25 | 6 |
| Post Year 25 | 6 |
The Headwater Pond closure plan will include a final stage flooded elevation of 10 m above sea level. During post-decommissioning water quality will approach natural conditions as runoff displaces the tailings pond water. The pore water will remain in a steady state condition, representative of the operating conditions.
On the basis of the seepage rates and the projected Headwater Pond water
quality, estimates of water quality directly downstream of Dam H1 were
made. The existing conditions are provided for Pond 64, approximately 1000
m downstream of Dam H1. The results of the modelling for metal concentrations
and other parameters in directly downstream from Dam H1 are shown in Table
10.21 and are assessed in Section 10.3.
| Water Quality Parameter | Existing Median (mg/L) | Increase at End of Operation (Total)a,b | Increase at Year 50 (Total) |
| Nickel | <0.002 | 0.006
(0.008) |
0.080
(0.082) |
| Copper | <0.002 | 0.001
(0.003) |
0.001
(0.003) |
| Cobalt | <0.001 | 0.001
(0.002) |
0.008
(0.009) |
| Arsenic | <0.002 | Nil | Nil |
| Aluminum | 0.110 | 0.001
(0.111) |
0.060
(0.170) |
| Zinc | 0.003 | 0.001
(0.004) |
0.001
(0.004) |
| Cadmium | <0.0003 | Nil
|
0.0001
(0.0004) |
| Lead | 0.0001 | 0.0003
(0.0004) |
Nil |
| Iron (Pond 64) | 0.054 | 0.003
(0.057) |
0.003-0.015
(0.057-0.069) |
| Ammonia | <0.05 | Nil | Nil |
| a the incremental
increase is indicated as nil if it is an order of magnitude less than the
LOQ
b the total (increase plus existing median) is indicated in parentheses |
|||
No alterations of flows are anticipated within this watershed during construction. During operations, the west subwatershed of the North Tailings Basin will be diverted into this watershed. This will result in an increase of the average annual flows at the outlet of Pond 58 from approximately 0.19-0.34 m3/sec during operation.
Following decommissioning, the watershed upstream of the North Tailings Basin will be returned to natural conditions, and the diversion to the Option 5 watershed will be removed. The flows through the Option 5 watershed will return to the natural, pre-development flow rates.
Physical Alterations
Grouting of the dam foundation at the north end of the North Tailings Basin (Dam N6) will result in short term siltation effects to Pond 58. Siltation downstream of the north diversion channel area is also possible. All siltation-related environmental effects will be reduced through the placement of control measures. These environmental effects are therefore anticipated to be short term and reversible.
Minimal siltation is anticipated during operations and post-decommissioning. Engineering controls will be implemented to limit the discharge of TSS during all phases of the Project.
Chemical Alteration
Chemical alteration of water quality is not anticipated in this watershed
during the construction phase (the North Tailings Basin will be constructed
during the operation phase). During operations, seepage loss of basin water
through the perimeter Dam N6 will enter the Option 5 watershed. Estimates
for seepage are presented in Table 10.22.
| Year | Seepage (L/min) |
| 9 to 11 | 0 |
| 12 to 18 | 7.5 |
| 19 to 25 | 14.4 |
| Post Year 25 | 14.4 |
On the basis of the seepage rates through Dam N6 and the projected North
Tailings Basin water quality, estimates of water quality were predicted
for Pond 58 of the Option 5 watershed (Table 10.23) and are assessed in
Section 10.3.
| Water Quality Parameter | Existing Median (mg/L) | Increase at End of Operation (Total)a, b | Increase at Year 50
(Total) |
| Nickel | <0.002 | 0.001
(0.003) |
0.001
(0.003) |
| Copper | <0.002 | Nil | Nil |
| Cobalt | <0.001 | Nil | Nil |
| Arsenic | <0.002 | Nil | Nil |
| Aluminum | 0.073 | Nil | 0.001
(0.074) |
| Zinc | 0.008 | Nil | Nil |
| Cadmium | <0.0003 | Nil | Nil |
| Lead | 0.0001 | Nil | 0.0001
(0.0002) |
| Iron | 0.011 | 0.003 - 0.012
(0.014 - 0.023) |
0.003 - 0.006
(0.014 - 0.017) |
| Ammonia | <0.05 | Nil | Nil |
| a the incremental
increase is indicated as nil if it is an order of magnitude less than the
LOQ
b the total (increase plus existing median) is indicated in parentheses |
|||
Flow alteration is not anticipated during construction. Dam N3 will eliminate seasonal discharge from the North Tailings Basin to Pond 67. Post-decommissioning flow alteration is not anticipated.
Physical Alteration
During construction, siltation of the downstream ponds are anticipated as a result of dam foundation bedrock grouting at Dam N3. Siltation will be controlled during construction and reduced during operations and post-decommissioning. These environmental effects are anticipated to be short term and reversible.
Chemical Alteration
Downstream water quality chemical effects are not anticipated during construction.
Seepage through perimeter Dam N3 (North Tailings Basin) will enter the
Pond 67 watershed. Estimates for seepage at Dam N3 are presented in Table
10.24.
| Year | Seepage (L/min) |
| 9 to 11 | 0 |
| 12 to 18 | 8.3 |
| 19 to 25 | 17.4 |
| Post Year 25 | 17.4 |
The limited dilution available in the small watershed immediately downstream of Dam N3 may result in downstream environmental effects.
On the basis of seepage rates through Dam N3 and the projected North
Tailings Basin water quality, estimates of water quality downstream of
Dam N3 were predicted. The existing conditions are presented for Pond 67,
approximately 300 m east of Dam N3. The predicted operations and post decommissioning
water quality immediately downstream of Dam N3 are summarized in Table
10.25, and are assessed in Section 10.3.
| Water Quality Parameter | Existing Median (mg/L) | Increase at End of Operations (Total)a,b | Increase at Year 50
(Total) |
| Nickel | <0.002 | 0.028
(0.030) |
0.014
(0.016) |
| Copper | <0.002 | 0.003
(0.005) |
0.003
(0.005) |
| Cobalt | <0.001 | 0.003
(0.004) |
0.003
(0.004) |
| Arsenic | <0.002 | Nil | Nil |
| Aluminum | 0.082 | 0.003
(0.085) |
0.03
(0.112) |
| Zinc | 0.007 | 0.003
(0.010) |
0.003
(0.010) |
| Cadmium | <0.0003 | 0.0001
(0.0004 |
0.0001
(0.0004) |
| Lead | 0.0001 | 0.001
(0.0011) |
0.001
(0.0011) |
| Iron | 0.025 | 0.003-0.012
(0.025-0.037) |
0.003 - 0.006
(0.028 - 0.031) |
| Ammonia | 0.05 | 0.014 - 0.180
(0.064 - 0.230) |
Nil |
| a the incremental
increase is indicated as nil if it is an order of magnitude less than the
LOQ
b the total (increase plus existing median) is indicated in parentheses |
|||
The temporary diversion of local streams at the port site may be required during construction. These streams will be returned to their natural state following construction. Little Reid Brook will not be diverted.
Physical Alteration
The only potential environmental effect that may occur in this watershed is potential siltation events at stream crossings and at the port site. These events will be controlled during construction. Minor siltation is expected during decommissioning. These environmental effects are short term and reversible.
Chemical Alteration
Chemical alteration is not anticipated in Little Reid Brook during any
phase of the Project.
