The Framework for Addressing and Managing Aquatic Contaminated Sites Under the Federal Contaminated Sites Action Plan (FCSAP), hereafter the FSCAP Framework, is a Canadian tool designed to guide the risk management of contaminated sites (
FCSAP 2017). The FSCAP Framework follows 10 steps within five sections: information gathering, screening level assessment (SLA), detailed level assessment, remediation/risk management, and monitoring of remediation/risk management (
Fig. 2). Each step builds upon data, information, and decisions from the preceding level. It combines relevant aspects of human health risk assessment and ecological risk assessment approaches. The FSCAP Framework is similar to frameworks in other countries such as the U.S. and countries in Europe (e.g.,
U.S. Environmental Protection Agency 1998;
den Besten 2007). These guidelines are more flexible to accommodate different measurement endpoints to allow for a large variety of potential stressors, whereas the FSCAP Framework was intended specifically for sediment toxicity.
Step 2—historical review
A contaminated site and a recent dam removal were identified at 4.6 and 6.7 km, respectively, upstream of the train derailment site on Forty-Mile Creek. Both historically impacted sites could also have potentially caused elevated concentrations of contaminants at the downstream train derailment site. The train derailment site was located immediately upstream of the Town of Banff, 100 m west of the main access road into the town from the TransCanada Highway, 200 m west of the Banff train station and rail yard, and 300 m upstream of Forty-Mile Creek’s confluence with the Bow River (
Fig. 1). The Town of Banff is the main service centre in Banff National Park. Forty-Mile Creek is popular for personal watercraft as it connects paddlers from the Town of Banff canoe dock on the Bow River with the Vermillion Lakes upstream of the derailment site. The Town of Banff does not obtain its drinking water from Forty-Mile Creek or the Bow River; however, the Bow River provides drinking water to half the Town of Canmore (total population 14 000) and to nearly 60% of the City of Calgary (total population 1.3 million), located approximately 25 and 125 km downstream of the derailment site, respectively. While there is no harvest of resources from this site due to its location in a national park, the Material Safety Data Sheet for the fly ash indicated potential concerns for human health due to direct exposure. Specifically, the Material Safety Data Sheet for the fly ash identified corrosive, toxic, and irritant hazards (
Boundary Dam Fly Ash 2011). Recommended mitigations to prevent risks to human health included the use of appropriate personal protective equipment, wetting down of work areas to prevent airborne dust, and closing the immediate surrounding areas to human use.
We chose sediment and water trace metals as well as water physico-chemical parameters (pH, turbidity) as contaminants of potential concern (COPCs). Although fly ash contains organic constituents, inorganic contaminants are much more prevalent (
Rowe et al. 2002) and likely easier to use as a COPC given our measurement endpoints (below). The benthic invertebrate community and the aquatic life that inhabited the water column or feed on the benthic community were identified as ecological receptors of potential concern. This included two native trout, westslope cutthroat trout, and bull trout that were assumed to occur in Forty-Mile Creek at the time of the spill (
Mayhood 1995). Forty-Mile Creek became critical habitat for these two species after the spill as Parks Canada gained more knowledge of the distribution of the species and their genetic purity (
Fisheries and Oceans Canada 2019;
Fisheries and Oceans 2020). The exposure pathways by which COPCs may reach and potentially affect receptors of concern were identified as ingestion of COPCs in sediment by benthic invertebrates; absorption of COPCs by direct contact of benthic invertebrates with sediment; absorption and ingestion of COPCs by benthic invertebrates and fishes by direct contact with water; and ingestion of COPCs through consumption of benthic invertebrate or fish prey by insectivores and piscivores. The measurement endpoints were sediment and water threshold concentrations from the Canadian Environmental Quality Guidelines (
FCSAP 2017). These guidelines are scientific benchmarks that synthesize data regarding sediment and water contaminant concentrations and their relationships with adverse biological effects from toxicological studies (
Canadian Council of Ministers of the Environment (CCME) 1999,
2001). More specific information addressing how we used measurement endpoints is provided in step 3.
Step 3—initial testing program
The SLA, as described in the FSCAP Framework, is expected to provide answers to the following questions: (1) Is sediment toxicity possible, based on comparison to generic sediment quality guidelines? (2) Is biomagnification likely based on the presence of elevated concentrations of organic chemicals that biomagnify?; and (3) Are these or other COPCs present at concentrations above reference concentrations? The second question was intended to account for COPCs that may not be elevated above guidelines, but that could pose a risk because of biomagnification (
FSCAP 2017). Although various organic compounds have been associated with coal combustion residues (e.g.,
Ribeiro et al. 2014), the analysis of organic contaminants was beyond the scope of this case study because we did not collect biological tissue samples (e.g.,
Mathews et al. 2014). Therefore, we modified the response to these SLA questions to not include question #2. If the answers to question 1 were “yes” and the answer to question 3 was also “yes” for one or more COPCs, the specific COPC was upgraded to a contaminant of concern, meaning the site was considered a potential risk with further action required (
FSCAP 2017). No further action was required if the answers to the above questions were “No.” The rationale for the comparison to a reference site included both the fact that inorganic substances occur naturally and may be naturally enriched in some areas (e.g., naturally mineralized areas), and the fact that reference conditions may not be totally pristine (
FCSAP 2017).
We sampled fly ash by scooping material directly from the rail car into a 500 mL polypropylene container. Twelve spatially replicated sediment samples were collected once, 2 weeks following the incident ( 1 January 2015), from a 200 m reach immediately downstream of the derailment site (S-DN1
40Mile to S-DN12
40Mile). Twelve samples were also collected from an upstream reference reach, randomly spaced starting at 500 m upstream and ending at 1.5 km upstream of the derailment site (S-RF1
40Mile to S-RF12
40Mile;
Fig. 1), but downstream of the landfill and dam. Samples were located by walking back and forth in the vicinity of each site over the frozen river and stopping randomly at sampling locations within the reach. The ice was cored using a 20 cm dia. hand ice auger (Nils; U.S.). Sediment was collected by reaching through 30–90 cm of water and scooping surface sediment (approx. top 10 cm layer) into a 500 mL polypropylene container. The contents were then immediately dumped into a polypropylene bag provided by the analytical laboratory (Maxxam Environmental Services, Calgary, AB). The following trace metals were analysed from the fly ash using inductively coupled plasma/mass spectrometry (ICP-MS; Agilent 7700 ICPMS): Ag, Al, As, soluble boron (B), Ba, Be, Cd, Co, Cr, Cr
6+, Cu, Fe, Hg, Mo, Ni, Pb, Sb, Se, Sn, Tl, U, V, and Zn. Sediment concentrations of the same trace metals were also analysed using ICP-MS, but due to an error, Al and Fe were not included in the testing package. Samples were dried at 55 °C, sieved and digested in a nitric-hydrochloric acid and de-ionized water mixture to solubilize the solid matter and remove organic material.
We sampled and metered water daily on Forty-Mile Creek starting at 14:00 on 27 December 2014, 33 h following the train derailment, until 2 January 2015. We sampled daily again for 1 week, beginning on 23 January 2015, 5 weeks following the incident. We sampled daily for 1 week, again a third time, beginning on 14 March 2015, 14 weeks following the incident. Water was sampled from a site 150 m downstream from the derailment site (W-DN1
40Mile), 300 m downstream of the derailment site (W-DN2
40Mile), and a reference site 1.7 km upstream of the derailment, but downstream of the landfill and dam (W-RF
40Mile;
Fig. 1). Water was also sampled and metered from the Bow River at the same schedule as Forty-Mile Creek, from sites 800 m downstream of the derailment site (W-DN1
Bow), 17 km downstream of the derailment site (W-DN2
Bow), and an upstream reference site 9.2 km upstream of the derailment site (W-RF
Bow;
Fig. 1). Selection of sampling sites included consideration of road accessibility because sampling occurred during winter. Therefore, we sampled water from all sites at least once/day for a total of 21 days. Water samples were collected by wading into the water while moving away from the shoreline and plunging 250 mL high-density polyethylene bottles, provided by the laboratory (Maxxam Environmental Services, Calgary, AB), into the water facing upstream. Bottles were rinsed with the flowing water three times before taking the samples. Water samples were analyzed for the following trace metals based on a general total metals package: Al, Ag, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Tl, Ti, U, V, and Zn using ICP-MS and -OES (Varian Vista Pro ICPOES and Agilent 7700 ICPMS) by Maxxam Analytics (Calgary, Alberta, Canada). However, not all these trace metals were evaluated (See Initial Testing Program below). We also recorded physico-chemical parameters (turbidity and pH) using a portable device (YSI ProDSS multiparameter meter; YSI Inc., Yellow Springs, OH, U.S.) at W-DN1, W-DN2 and W-RF in both Forty-Mile Creek and the Bow River at the time of water sampling.
Some studies have focused on chemical screening of the dissolved fraction of trace metals (e.g.,
Ruhl et al. 2009). This assessment used Canada’s national environmental guidelines, which are applicable to total concentrations, not the dissolved fraction. These guidelines were designed to inform practitioners about the biological risk thresholds of certain contaminants. Furthermore, dissolved-phase concentrations alone would not account for the potential future speciation of trace metals from total to dissolved concentrations.
Trace metal concentrations from fly ash sampled directly from the derailment site were compared to the CCME sediment quality guidelines for the protection of aquatic life (
CCME 2001), using both the interim sediment quality guidelines (SQG-ISQG) and probable effect levels (SQG-PEL). The SQG-ISQG represents the concentration above which adverse biological effects may occur, while the SQG-PEL represents the concentration above which adverse biological effects occur frequently (
CCME 2001). Any parameter that exceeded the reporting detection limit (RDL) was further evaluated using sediment data. We compared the concentrations of sediment trace metals identified from the previous step to the SQG-ISQG and SQG-PEL. When a CCME SQG was not available, we adopted the Government of Alberta sediment quality guidelines for the protection of aquatic life, again both ISQGs and PELs (
Government of Alberta 2018). Any trace metals that exceeded SQG-ISQG and SQG-PELs and upstream reference concentrations were identified as sediment contaminants of concern. Sediment trace metal concentrations that exceeded reference concentrations, but had no guidelines were identified as uncertainties. Trace metals that were identified as contaminants of concern or uncertainties were further evaluated using water data.
We screened for potential impacts to drinking water and aquatic resources by comparing concentrations of trace metals identified in the previous step and physico-chemical parameters to the Canadian guidelines for drinking water quality (GDWQ;
Health Canada 2019) and CCME Canadian water quality guidelines for the protection of aquatic life (CWQG;
CCME 1999). We used long-term, rather than short-term guidelines, because long-term guidelines are more conservative and are intended to protect all forms of aquatic life for indefinite exposure periods, whereas short-term guidelines are intended to protect a fraction of individuals from severe effects such as lethality and is used for transient situations (
CCME 2007). The federal environmental quality guidelines were used when a CWQG was not available (
Environment and Climate Change Canada 2007). The Government of Alberta surface water quality guidelines (
Government of Alberta 2018) were adopted when no CWQG or federal environmental quality guidelines were available. Water parameters that exceeded any of the water quality guidelines and exceeded concentrations from the upstream reference site were identified as water contaminants of concern.
The median daily concentrations were used as a measure of central tendency, and the Q
3 was used as an upper measure of spread as most parameters were not normally distributed. On days when multiple water samples were metered or collected, the mean value for that day was used to ensure there were no days with higher weighting in the overall analyses. A significant number of trace metal concentrations were below laboratory RDLs and were often reported as being less than an analytical threshold (i.e., “censored”). Censored observations complicate the routine calculations of descriptive statistics, testing differences among groups and regression coefficients (
Helsel 2012). Therefore, we used nonparametric survival analyses to estimate summary statistics for both sediment and water (Kaplan-Meier method;
Helsel 2012). Nonparametric survival analysis is likely to have greater power than parametric procedures when working with skewed data (
Helsel 2012). When censoring exceeded 50% of the data for any one parameter, the median for that site could not be computed and the median values were reported as less than the RDL. The 3rd quartile was reported as not applicable (N/A) when there was not enough non-censored data to compute a quartile. To statistically compare sediment and water data between sites, another non-parametric survival analysis method was used (the Generalized Wilcoxon Score Test;
Helsel 2012). This method is appropriate for censored data because it uses ranks to make comparisons between two or more groups and can thus handle a higher percentage of censored values (
Helsel 2012).