Residual and Cumulative Impacts

1.     Nutrient loading in sewage and contamination downstream

2.     Loss of ecosystem

3.     Disturbance of wildlife


1. Nutrient loading in sewage and contamination downstream

Cumulative Impacts
            Mining operation will increase potential nutrient loading that could introduce contamination downstream.  The accumulation of nutrients could be due to many physical impacts:

·        Siltation

·        Erosion

·        Discharge effluents

·        Effluent from the tailing impoundment

·        Other economic projects
                                                -Mining project

            Siltation is also known under the name of sedimentation.  It is probable that the leaching of rocks during the mining operation increase sediment runoff.  In theory, the dam should stop any water coming from the open pit.  Siltation could also occur due to the modification of water quantity.  Sedimentation will come from chemical interactions with the water component.  Filter plant will reject effluent directly in the Iskut River potentially increasing the amount of organic matter in the water.  Organic matter reacts with metals and binds tightly resulting in a different chemical conformations allowing sedimentation.  Sedimentation usually makes the metals less bioavailability which reduce the risk.  However, it might reduce carbon availability for organisms or even change the river flow in some sensitive areas.

            The erosion could come from groundwater wells, waste rocks and roads erosion.  The blasting could also increase the erosion rate.  A breakdown blasting could also increase the erosion rate.  A breakdown in the filter plant discharge could lead in rejection of higher contaminated water than the Mining Act accepts.  The effluent of tailings impoundment was first supposed to be discharge in Galore Creek.  The plan has been charged to include a bigger dam downstream the tailings impoundment to stop the water.  This way the acid rock drainage effects will be reduced.  However, the water over the tailing impoundment dam will be diverse in the Galore Creek.

Discharge effluents
            Discharge effluents in the Galore Creek and in the Iskut River can increase siltation and erosion.  Effluents are under the Mining Act restrictions.  Therefore, the metals, dissolved and total carbon concentration will be regulated.  However, direct discharges will cause sublethal and lethal mortality amount the aquatic population.

             The effluent reject via the filter plant could bring copper concentration down to almost 6 km of the Iskut River during the heavy rainfall period.  It is 5.9 km further than usual distance.  The volume of water in the Stikine River considerably made the effects negligible.

Effluent from the tailing impoundment
            Direct discharges of tailing impoundment could result in great decrease of water quality.

Other economic projects
            Previous mining had no residual impacts on the water quality because even if they were located on the lower portion of Iskut River.  Other future mining projects could become cumulative impacts.  In the future, the development of a forestry and agriculture cumulated with mining operations could increase in degradation of water quality.  As mentioned in the socio-economics section, forestry development never ends in a concrete plan.  Agriculture was not in the region further plan.

Overall effects

            Metals are known to bioaccumulation within the food web increasing in concentration at each level.  Therefore, trace metals such as copper could represent a potential threat to the wildlife and First Nations which consume their products of hunting and fishing.  As the baseline study indicated a high concentration of metals already present and a high tolerance of wildlife to those concentrations.  However, organic carbon is already in low concentration in the river with high metal concentration.  Lower carbon concentration by reducing the flow could definitely affects the survival of the aquatic resources.

            The proponent would not add any mitigation measures to the one already installed.  The mitigation implanted is a monitoring program for siltation, for erosion, for quality of discharged effluents and for water quality.  Further mitigation was considered unnecessary due to expected natural improvement for the tailings facilities after closure and the acid rock drainage waste rock will be controlled by sub-aquatic facilities already.  Their model predicted only 10 years before improvement of water quality.

2. Loss of ecosystem

                   A permanent lost of terrestrial ecosystem will occur during construction, operation and post-closure of the mine.  The location of the impact is the Galore Creek valley.  It will be caused by the submergence of the pits and tailing area.  This impact might be accentuated with the potential introduction of invasive species.  The water quality and the lost of land might fragile the ecosystem enough to allow exotic and invasive species to take over the advantages.  Those species will be advantaged because the absence of parasites will increase their chance of survival in a destabilized area compared to indigenes population that will have to fight their parasites in addition to survive in a disturbed area.

           Copper Canyon, Foremore and RDN properties could impacts on the lost of ecosystem due to exploration activities.  Exploration required the clearing of land in order to drill to extract sample.  A proposed development of Shaft Creek mine could also result in even more land lost in the area.  However, the impacts still is negligible.  Recreational activities are just not important due to low frequencies.  Inexistent access facilities reduce possible tourism, but Galore Creek mining project did provide higher access to the region.  Destabilisation might be greater with the introduction of traffics and human presence.  If forest project go on, the ecosystem will be even more vulnerable to invasion due to greater lost of land. 


            Loss of ecosystems is a significant impact that require many mitigation processes.  The proponents implemented revegetation of exposed mineral soil.  This process should be concealed with strict access control of the territories.  The proponents also suggested the consultation of Environmental counsellors in order to determine measures to prevent the establishment of invasive plant species.  They will  put reclamation activities in place after mine closure.  Potential invasive plant problems shall be monitored with a monitoring program.

3. Disturbance of wildlife

            The grizzly bear and mountain goat are both susceptible to residual cumulative impacts. 

Grizzly Bear
            The effects of quality and quantity water could have on salmon population could spread over grizzly bear.  In addition, the loss of ecosystem might increase the stress over the population.  Porcupine River valley activities also create important quantity of noises, but the impact is not predictable.  A fourth human activities might have also influence the grizzly survival.  Human recreation activities could increase with the access road.  Human activities include:

·        Fishing

·        Guide-outfitting non-resident harvest

·        Resident and First Nations harvest

·        Mineral exploration

·        Recreation and tourism

·        Forestry


Mountain Goat
            Mountain goat reactions to human activities are difficult to estimate because few data are available on their behaviour.  The effects assessment still declared residual effects on mountain goats.  The disturbance will affect their reproductive success.  The Eskay Creek mine, the proposed Forrest Kerr hydroelectric project, and the proposed Schaft Creek mine are additional factors to the previous human activities listed in the grizzly bear section.  Population will certainly reduce in certain areas.

LAST UPDATED: Sunday, April 13th, 2008.


NRSC 437 Lecture notes