Hydrology
· Background
· Surface water
· Groundwater
Background
A number of watersheds were identify during scoping phase :
· Galore
· Scud
· Iskut
· Stikine River
· Porcupine Riber
Galore River will be directly impact during all the phases of the project. It is on the mining tailings site. Galore River falls into Scud River.
Stikine River is a major stream that receives influents from Scud River. Stikine pass the US boundary. It is located Western area.
Scud River receives the influent from the Galore River and finish into the Stikine River. It is located in Northem area of the project.
Iskut River flows into the Iskut Hot Springs Provincial Park. It is linked with the Stikine River. It is located at eastern side of the project near the filter plant, diffuser system, concentrate pipeline and diesel pipeline.
Porcupine River is located downstream of the aerodrome location. No effects were anticipated on this stream except potential accidents in the aerodrome. Aerodrome is located at the complete Southern-Western area of the project.
Surface water-Quantity
The mining process requires important amount of water especially for the tailing impoundments. The baseline study mixed Tahltan traditional knowledge and scientific data. During 2005, four flow volumes were investigated: annual, monthly, high and low flows. Five locations were also targeted and separated:
· Mining area
· Filter plant
· Aerodrome
· Tunnel
· Access corridor
1. Galore River
A -Impact-Pollutants and diversion channels
Annual flow volumes were monitored. Monthly flows differed a lot between seasons. From November to April, only 10% of the annual runoff totals are registered. During months of June to August (summer season), 65% of the total runoff was monitored.
There is a very in equal quantity of water available depending of the season. In addition, the volume of water could impact on the mineral dilution coming from the tailing proponents agreed that the surface water of the tailing facilities should only be discharged at the beginning of May.
It will results in a potential increase of mineral in May due to low dilution at that period, but it was calculated as a minor impact.
Many modifications will occur with Galore River during all the phases of the project. During construction, diversion channels will be constructed in order to no flow the main construction sites.
In the first year of operation, the dam will stop most of the upstream watersheds and temporary bring the water to diversion channel. A small watershed area will be mainted in the tailings area to be stored in the second dam reservoir. The second dam is also called the tailing dams because it will retain the tailings residues under water.
The studies reveal a drop in only 10% compared to the baseline. However, in the case of a blockage in the diversion channel, the drop could be up to 80% compared to the baseline.
Mitigation of diversion channel
The infrastructure was designed to be accessible rapidly in order to fix problems of diversion channels easily.
Mitigation
They will monitor the quality of water especially in May. If the water does not respect the British Columbia Water Act and Canada Water, they will wait before. They will maintain the quantity water with main channels that will pump groundwater.
B -Impact-High flow
Three mechanisms are known to impact and maybe cause high flow conditions:
· Rapid snowmelt (during summer months)
· Rain failing on melting snow (during spring, summer and winter months)
· Heavy rainfall (September to October)
C- Impact – Low flows
Low flows are a major concern due to needs in water during the processe and to requirement of water to dilute the discharges. It happens usually in winter where the flow is already only 10% of the entire annual flow.
Residual impacts
The flow volumes of the Galore River will be altered and no mitigation is possible.
2- Stikine River
Impact
Stikine River receives influents from the Scud River. No modification in water quantity level should be noted.
One other potential impact on water quantity could be created by the access corridor and the pipeline rupture
Paragraph.
3- Scud River
Impact
Galore River flows into Scud River. The permanent diminution of Galore River water quantity will directly impact Scud River water quantity. However, the impact should not be too important because it will result in less than 10% of the flow modification. No mitigation is required.
Paragraph.
4- Iskut River
Impact
The main impact on the Iskut River is the filter plant. The water flow is around 80 m^3 at the filter plant location. The water quantity should not be impact. Water will be imported in the Iskut River during the discharge of the filter plant.
5- Porcupine River
Impact
Porcupine River has an annual flow of 46 m^3. It should have exactly absolutely no impact at all on the water quantity. No mitigation is required.
I. Access corridor
Impact- Installations
The Access corridor is passing through most of the region. Most of the River streams could be affected. The high water flow could impact the access road and wash out the bridges and road.
Mitigation
The infrastructure was build to resist an instantaneous peak for the next 100 years.
Impact- road
The road could diminish the hydrology flow in less than 1% of the baseline studies. It could impacts on the following aspect of the hydrology:
· Surface runoff
· Infiltration
· Evapo-transpiration
· Temperature
· Snow accumulation
· Snowmelt
Mitigation
The effects are so low that no mitigation was considered necessary. The water quantity will already be monitored. In fact, the Galore River is only 0,3% of the Stikine River.
II: Pipeline Rupture
Impact
Pipeline rupture could add 1240 m3 at a flow rate of 0,03 m3/second
Mitigation
Mitigation was already planned for pipeline rupture in infrastructure section. In term of water quanityt, it is negligible.
Surface water-quality
In order to respect to the B.C. Water Quality guidelines, the baseline study included the following analysis of samples:
· Physical parameters
· Nutrients
· Dissolved anions
· Total organic carbon
· Total cyanide
· pH
· Total & dissolved metals
The key sites for water quality study were the two sites where discharges will occur: Galore and Iskut River.
All the sites analyzed were:
· Mine area (Galore and Skut watersheds only)
· Filter plant area (Iskut River sites)
· Lakes and wetlands along the access corridor
Water quality was identified as VECs due to its key role in the environment. It was a subject of concern for the government due to its trans-boundary effects with United States of America in Alaska.
Also, the Tahltan community was concern by the surface water quality because it might impact the food web. Iskut and Galore River are hot used to drink water or any particular activity like swimming. The concern was that water quality could contaminate the traditional food and herbs of the surrounding region. No sportive activity such as conoe are performed on those river. The Galore and Iskut water quality was included in compensations. There is navigable stream, no town that could be affected by the flooding and hydrology changes. The annual flow at the Stikine River will only be altered of 2% which would not affect Alaska.
Water quality is also important in the case of environmental health indicators. It could reveal potential problems on flora and fauna.
Five main issues were identified as potential contamination:
1. Contaminant loading
2. Discharges
3. Surface runoff
4. Siltation
5. Associated water chemistry effects
1 . Contaminant loading
Impacts could be the result of three kinds of loading:
A. Metal leaching/ acid rock drainage
B. Leaching of nitrogen residues generated from blasting
A. Metal leaching / acid rock drainage
Impact
All the acid rock formation and the metal leaching impact are described in risk assessment section of this website. It could come from open pits, tunnel and grade ore stockpile.
Mitigation
The underwater storage facility and the dam should mitigate all the effects of the Acid generation.
B. Leaching of Nitrogen Residues Generated from Blasting
B. Leaching of Nitrogen Residues Generated from Blasting
Impact
Introduction of ammonia into the environment could result on water quality. Ammonia is a nutrient for plants and miroorganisms. The inputs are the tailings and water rock impoundment to Galore Creek. Permit levels could also be impacted if the proper measures are not installed to assure low nitrogen input.
This impact was investigated due to previous experiences of Canadian mines development. Ammonia salts usually come from the explosives storages areas.
Mitigation
The baghouses will be installed and storage silos with non-corrosive stages liners. The buildings also included installation of an impermeable apron with a sump at the loading/uploading area. The proponents installed a spill management plan in addition to all those measures.
2- Discharge
2- Discharge
Two main discharges are found in the project:
I. Mine Site
II. Filter Plant
I. Mine Site
Impact
The tailings impoundments discharge will only start in May. If the dilution is inadequate, the dam is build to maintain storage for two more months.
Month of May should be the worst in term of water quality. It is mainly created by the amount of mineral gypsum (CaSO4) that is a result of rock tailings.
The baseline study revealed important concentration of metals in the water.
Mitigation
The water discharge of the mining site will be submitted to the B.C. and Canadian Water Act guidelines. The total suspended solids will be monitored in order to respect the 15 mg/L regulated by Metal Mining Effluent Regulations.
II. Filter Plant Discharge
The filter plant proceeds this way:
3- 4- and 5- Suface Runoff, Siltation and Associated water chemistry effects
Impact
The surface runoff and sedimentation process could possibly modify the water quality. The erosion rate might increase which will add suspended particles in the water. Associated water chemistry effects could be dramatic changed in pH or organics ions concentration.
Mitigation
The erosion and the suspended particles will both be monitored. In the case of insufficient water quantity to dilute properly, groundwater will be pump and be added to the effluent.
Goundwater
Groundwater will be used in the tailing process and to dilute the discharge waters. Two majors concerns were investigated:
· Quantity
· Quality
Goundwater-quantity
Impact
The open pit dewatering should pum 50 000 m3/ day depending on the requirements for seepage and pumping wells capacity. The pump for processing used 23 000 m3/ day. In all only 6000 m3/day should be discharged in the tailings impoundment.
The impact is not significant because it corresponds to only 0.15 m3/ day. This calculation is based on the 2,67 m average of annual precipitation. The impact will not change the direction of the groundwater. It will continue toward Scud River.
At the post-closure, groundwater pumping should stop. Even if it will never come back to the exact same baseline conditions, most of the impacts could be reverse back.
Mitigation
Mitigation will occur by monitoring. The water is required in the mining project which means they do not have much alternative. The impacts on surface water would be much greater than groundwater. They chose the option with the less environmental impacts.
Groundwater-quality
The groundwater quality was tested on four wells during the year 2004 and from 10 more wells during 2005.
The parameters were:
· Physical aspects
· Nutrients
· General ions
· Dissolved trace metals
· Total trace metals
· pH
· Electrical conductivities (EC)
Nutrients tested were nitrite at 0.0127 mg/L, phosphorus at 0.76 mg/L and nitrate at 0.0787 mg/L. The pH was 7.56 to 8.20. The electrical conductivities are also a measure of the metal ions concentration. It revealed in wide range in major ion concentrations.
List of the components found during the test and their relative level:
Dissolved (not detectable)
· Beryllium
· Bismuth
· Lithium
· Mercury
· Phosphorus
· Silver
Dissolved (contain higher levels than drinking water should have)
· Aluminium (0.3 mg/L)
· Iron (0.339 and 0.453 mg/L)
· Manganese (0.45200 mg/L)
· Nickel (0,00149 mg/L)
Dissolved (detectable, but lower than the Mining Act requirement)
· Antimony
· Arsenic
· Boron
· Cadmium
· Chromium
· Cobalt
· Lead
· Molybdenum
· Nickel
· Thallium
· Tin
· Titanium
· Uranium
· Vanadium
· Zinc
Dissolved (below the maximum allowable content in drinking water)
· Calcium
· Magnesium
· Potassium
· Sodium
· Strontium
The total organic carbon concentration was between undetectable level and 8.7 mg/L. The average was 1.19 mg/L. Almost all the site was under 2 mg/L except one site that was 8.7 mg/L. They concluded that particular sample was contaminated with sediment.
During the mining operation, 10 wells will bring water down and 15 will bring water up.
The two concerns of groundwater quality are:
· Blasting and use of explosives
· Metal leaching/ Acid rock drainage
Impact of Blasting and use of explosives
This section was already discussed in the surface water quality.
Impact of Metal leaching / Acid rock drainage
Total metal concentration could increase due to leaching of the rock surfaces. The water could modify the mobility of trace metals, but this impact is expected to be low. Most of this section was already discussed in the risk assessment section.
Mitigation
The monitoring program will follow the progress of groundwater quality until the situation is considered safe. Before, the post-closure, the proponents planned more modeling.
Critique
Water is an important component of the ecosystem that can be easliy modified. Enormous amounts of water are required during a mining project. The project will definately modify the hydrology of the Galore River in terms of quantity and quality. The Iskut River will be impacted as well in terms of quality. All the mitigation measures have been put in place to assure there is no contamination of the Tahltan traditional food. This part of the EIA was done in respect to all the stakeholder's concerns and with respect to the environment.
WRITTEN BY: ANDRÉE-ANNE ROULEAU
LAST UPDATED: Sunday, April 18th, 2008.
References:
http://www.eao.gov.bc.ca/epic/output/html/deploy/epic_document_239_23630.html
