Fisheries and Oceans Canada
BC Ministry of Environment
Squamish Nation
Impact Assessment

Fish Assessment | Benthos Assessment | Ecological Assessment | Water Quality

Fish Assessment

Following the spill, B.C. Ministry of Environment (MoE) fisheries biologists, technicians and contracted staff documented fish survival and compared fish density information to available previous data.

Fish mortalities were collected from the Cheakamus River downstream of the spill, with activities including:

  • recording mortalities by species and location;
  • collecting length data to determine age classes of impacted fish;
  • collecting scale samples to further supplement brood year identification; and,
  • freezing and storing of samples for further examination, if required.

Fish Impact Assessment (MoE and DFO) (pdf)

MoE Estimated Impacts on Salmon and Trout Populations:

- 25% of juveniles from 2004 spawning population
- 50% of 2005 spawning population

- juveniles not affected
- 2005 spawning population not affected

- 50% of juveniles from 2004 spawners
- 2005 spawning population not affected

- juveniles not affected
- between 3 - 10% of 2005 spawning population

- 90% of mainstem juveniles from 2003 to 2005 spawners
- 2006 and 2007 steelhead spawning populations not affected

Estimated Impacts on Other Fish

Ninety percent of resident fish in the mainstem Cheakamus River may have been affected by the spill including:

  • Dolly Varden/Bull Trout
  • Rainbow Trout
  • Lamprey (2 species)
  • Sculpins (bullheads - 2 species)
  • Sticklebacks

Juveniles rearing in tributary streams at the time of the spill were not affected.

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Benthos Assessment

The Reference Condition Approach (RCA) is being used to provide an indication of the impact realized by the benthic macroinvertebrate community structure in the Cheakamus River over a three-month period after the spill. The RCA approach has been adopted by Environment Canada who developed field and lab protocols published by the Canadian Aquatic Biomonitoring Network (CABIN). Environment Canada has collected samples from several sites in the Fraser and Georgia Basins, including the Cheakamus River in the areas upstream of the spill (i.e. near Daisy Lake). These reference sites are being compared to CN sampling sites upstream and downstream of the spill.

Biweekly measurements in the zone of influence and at a control site were collected by CN after the derailment to provide samples for comparison to regional reference sites. Comparisons of predicted and observed benthic community structure will provide an indication of spatial and temporal distribution of variation in the benthic community in the three-month period immediately after the derailment.

In addition, a colonization basket study was completed in 2006 by CN to replicate a previous Cheakamus assessment completed in 1997 and 1999-2000. This assessment involved placing wire mesh baskets at specific locations in the Cheakamus River and then harvesting the baskets after a six-week incubation period, and comparing benthic invertebrate taxa in terms of density, biomass, community structure, and relative abundance. Comparisons of pre and post spill data from colonization baskets are being completed to further describe potential changes and recovery of invertebrates.

Results from these assessments are currently being analyzed and will be used to determine the direction of future recovery efforts for benthic invertebrates.

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Ecological Assessment

A screening level qualitative assessment of ecological effects has been conducted for CN to understand the potential effect the spill could have had on receptors other than fish in order to identify and target the need for ecosystem restoration activities.

Given the broad scope of the project and the limited amount of available data (i.e., exposure data, such as concentration of NaOH in environmental media, NaOH ecotoxicity toward specific species) it is not possible to conduct a comprehensive ecological risk assessment for each species present in the ecosystem. The screening level assessment focused on the functions of populations and communities within the ecosystem. This recognizes populations are less sensitive than their most sensitive individual member and some effects may be observed at the population level without impairing the functions of the ecosystem as a whole.

Qualitative methods using subjective ecological effects ranking categories, such as high, medium and low, were used to describe the likelihood of adverse effects rather than providing a numerical estimate of effects. To minimize subjective influence, the interpretation of ecological effects contain a clear explanation of the lines of evidence leading to the conclusions, including a description of the uncertainties and assumptions used. Additionally, matrices were used to provide a structured framework for the characterization of ecological effects. The assessment used existing information from baseline and monitoring reports and from previous scientific literature.

This screening level assessment of ecological effects consists of three main steps: problem formulation, analysis and characterization of the likelihood of adverse ecological effects. Results from the ecological effects assessment will be used to determine the direction of future recovery efforts for other components of the Cheakamus River ecosystem.

For more details, view the

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Water Quality

River Sampling

Water quality professionals tested and monitored the following:

  • Water quality in the Cheakamus and Squamish Rivers, August 5 - 8, 2005
  • Water quality in the Cheakamus during site remediation activities, August 10 - 26, 2005
  • Water quality in the Cheakamus after rainfall events, August 17 - October 28, 2005

Monitoring was conducted over a variety of meteorological conditions and river levels. The parameters monitored included: pH and conductivity, sodium, total dissolved and total suspended solids, total and dissolved organic carbon.


The Cheakamus River was cleared for recreation after 24 hours by Vancouver Coastal Health on August 6, 2005. Water quality downstream of the derailment site was determined to be similar to that upstream.

Well Sampling

Forty-eight wells within 100 metres of the Cheakamus River were sampled on August 6 and 7, 2005. The parameters monitored included pH and conductivity, sodium, total dissolved and total suspended solids.

The sampling was coordinated by Environment Canada, Vancouver Coastal Health Authority, Triton Environmental Consultants Ltd., and Quantum Environmental Services.

Drinking water from wells was cleared for drinking by the Vancouver Coastal Health Authority after 48 hours on August 8, 2005.

No additional detailed water quality sampling is required.

Water Quality Report September 2007 (pdf)
Water Quality Report Appendices September 2007 (pdf)

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