Randle Reef is a 60 hectare portion of the Hamilton Harbour bed, heavily contaminated with polycyclic aromatic hydrocarbons and heavy metals. Remediation of contaminated sediment at Randle Reef is currently underway and is expected to be completed by 2022. In order to measure the effectiveness of the remedial effort on the surrounding ecosystem as well as enable the project's success to be critically evaluated, short and long term site-specific monitoring studies are required. As such, research scientists and sediment remediation specialists have collaborated to develop a site-specific, comprehensive series of environmental monitoring plans. The monitoring plans use several metrics to determine the state of the ecosystem prior to, during and post remediation. Monitoring studies have been designed to measure physical, biological and chemical trends over time. These studies will be used to determine the overall effectiveness of the remediation project and ultimately lead to the eventual delisting of Hamilton Harbour from the list of Great Lakes Areas of Concern. This article is a synopsis of the environmental monitoring studies that have been designed to guide and assess the effectiveness of the Randle Reef Sediment Remediation Project.
The governments of Canada and the United States have recognized contaminated sediment issues as a major problem in the Great Lakes ecosystem. In 1985, these two countries identified 43 Areas of Concern (AOCs) where impaired water quality prevented full beneficial use of rivers, bays, harbours and ports (Fox et al., 1996). The Government of Canada is committed to remediating 17 of the AOCs, including Hamilton Harbour which was included in the 1987 Great Lakes Water Quality Agreement (GLWQA; IJC, 1987). Approximately 60 hectares of the Hamilton Harbour bed, known as “Randle Reef,” is severely contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals (Figure 1; Redish, 2002). Total PAH concentrations at Randle Reef are as high as 73,755 mg kg−1 with an average site concentration of 5,000 mg kg−1 (Graham et al., 2012). The contamination is often described as “a spill in slow motion” due to the continuing slow spread of contaminants across the harbour floor. It is a legacy site as contamination dates back over 150 years from different contributors including former coal gasification plants, petroleum refining, steel making and municipal waste disposal activities. The majority of these contributors no longer exist, leaving full ownership of the contamination unclear. Subsequently, the Governments of Canada and Ontario determined that enforcement of the “polluter pay principle” was not possible. The contaminated sediments pose a significant risk to the ecosystem and require management to restore beneficial uses of the area and to meet Canada's obligation under the GLWQA. The Government of Canada, Government of Ontario, local governments and one private company came together to jointly fund the implementation of the Randle Reef Sediment Remediation Project (Project).
The Project involves the construction of a 6.2-hectare Engineered Containment Facility (ECF) on top of the most contaminated sediment in Randle Reef, and then dredging the majority of the surrounding highly contaminated sediment outside the ECF (Figure 2) and placing them within the ECF. The ECF will be constructed using double steel sheet pile walls, with the inner wall having sealed joints.
A thin layer sand cap will be applied to marginally contaminated areas that will not fit within the ECF to facilitate natural recovery and a thin layer of backfill will be placed on top of dredged areas to manage residual contamination remaining after the dredging process. Thin layer capping/backfill is an established process which has been demonstrated at other contaminated sediment remediation projects. The effectiveness of cap material placement in Hamilton Harbour has been assessed in previously conducted pilot studies (Zeman, 2011) which contributed to the overall assessment of capping feasibility. An isolation cap will be applied to the channel created between the ECF and Pier 15 East (currently owned by Stelco Canada) as these sediments are heavily contaminated and dredging is not feasible due to the presence of slag.
The uptake of PAHs from sediment into the food web affects local fish and wildlife populations both directly and indirectly (Harlow and Hodson, 1988). The Project will isolate these contaminants from the ecosystem, thereby eliminating direct pathways of exposure to PAHs and other contaminants by ecological receptors.
Large scale clean-up efforts in the past have generally failed to include effective post-remedial monitoring in order to assess the effectiveness of the remedial efforts (National Research Council, 2007). As such, research scientists and sediment remediation specialists have collaborated to develop a site-specific, comprehensive environmental monitoring plan for Randle Reef. The monitoring plan uses several metrics to determine the state of the ecosystem prior, during, and post remediation. It is imperative that adequate data is collected prior to the remedial effort so that ecosystem changes can be measured and observed. The purpose of this article is to provide a synopsis of the site-specific monitoring programs that have been specifically designed to assess the effectiveness of the Project on the Hamilton Harbour ecosystem.
Approach and data review
In order to assess the effectiveness of the Project, the following approach will be undertaken:
Examining data from past monitoring programs that were used to assess the extent and severity of the contamination;
Examining data from monitoring programs that will be undertaken during project implementation to ensure that the project itself is not causing impacts to the surrounding environment or exasperating problems; and
Utilizing data from monitoring programs that will compare pre-project baselines to the future conditions to assess how successful the remediation efforts were in restoring the degraded ecosystem in the Randle Reef area.
Past monitoring programs
The Randle Reef area has a long history of sediment sampling dating back to the late 1970s when this contaminated site was first discovered. Sediment sampling in the 1980s and 1990s focused on assessing the sediment chemistry and toxicity in the areas closest to Pier 15 East (Murphy et al. 1990 and 1995). These studies identified sediment with total PAH concentrations exceeding 800 mg kg−1 and demonstrated toxicity. However, due to lack of precision in the geographical position, these results were of limited use in the characterization, delineation and prioritization of contaminated sediment at the Randle Reef site.
In 1990, Murphy et al. performed sediment chemical and biological studies of the harbour and Randle Reef area analyzing the chemistry of 81 sediment cores as well as subjecting the sediment to bioassays. They found that total PAHs at concentrations >200 mg kg−1 in the sediment resulted in the death of 50% of the Daphnia magna and Hexagenia. Murphy et al. (1990) recommended a cleanup criterion of 200 mg kg−1 total PAHs and concluded that PAH concentrations appeared to be a better guide for a cleanup standard in Hamilton Harbour than metal concentrations based on the correlation between PAH concentrations and toxicity. The toxicity work by Murphy has been superseded by additional more comprehensive work that is described later in this article. The Murphy study concluded that 48,300 m3 of sediment exceeded 200 mg kg−1 providing an early indication of the amount of sediment that may require remediation.
Subsequent studies (described below) continued to investigate the lateral and vertical extent of the contamination, and contributed to the understanding of the extent and variability of the contaminant distributions in the soft sediments and in the underlying clay layer. Extensive core and grab sampling in the Randle Reef area was conducted in 1996 and summarized and referenced in two documents (MDA, 1999; Zeman and Patterson, 2003). The data set created by these studies improved the delineation of the extent of the contaminated sediments and the estimated total volume. One of the most important studies in moving forward with the remediation design was the 2002 Benthic Assessment of Sediment (BEAST) work conducted by Environment and Climate Change Canada (ECCC; Milani and Grapentine, 2016). The BEAST methodology involves the assessment of sediment quality based on multivariate techniques using data on the physical and chemical attributes of the sediment and overlying water, benthic community structure and the functional response of laboratory organisms in toxicity tests (Reynoldson et al., 1995). Data from 80 test sites were compared to biological criteria developed for the Laurentian Great Lakes; however, the benthic community assessment around Randle Reef was problematic due to lack of appropriate reference areas for comparison as well as the presence of other potential stressors such as vessel propeller disturbance and seasonal low hypolimnetic oxygen concentrations (Milani and Grapentine, 2016). As a result, initial prioritization of areas for remediation focused on laboratory toxicity tests and the associated sediment contaminant levels. The findings of these studies were used with background conditions in the harbour and on-going atmospheric inputs to establish the site specific clean-up criterion of 100 mg kg−1 total PAHs for the site (Graham et al., 2013d). This work also helped determine an initial volume estimate of the Randle Reef contaminated sediment where Total PAH exceeded 100 mg kg−1 and metals exceeded the severe effect level (SEL) threshold specified in the Province of Ontario's Sediment Quality Guidelines. These toxicity results and the cleanup criterion were then utilized to prioritize the sediment for remediation into five groups: Priority 1, 2, 3, 4 and non-priority (Table 1 and Figure 2). This key study follows the most up to date approaches in the assessment of contaminated sites where multiple lines of evidence (including toxicity, benthic community impairment and biomagnification potential) are utilized in addition to the traditional and most common metric of sediment bulk chemistry results (Chapman, 2008; Chapman and McDonald, 2005).
The design of the ECF utilized this prioritization to ensure that the facility is able to contain all the Priority 1 and 2 sediments (approximately 97% of the total contaminant mass [BBL, 2006]), plus at least 20% of the Priority 3 sediments. Remaining Priority 3 sediments will be managed with a thin-layer sand cap. Priority 4 sediments will be left undisturbed for natural attenuation and recovery.
Additional sediment sampling in 2003 and 2004 (summarized in the Basis of Design and Basis of Design Addendum reports [BBL, 2006]) provided what was thought to be the last major effort in delineating the extent of the contamination prior to finalizing the design. The combination of all of these studies provided a substantial data set that delineated the extent of the contamination in the area surrounding the initial Randle Reef hotspot. By 2004 the estimate of contaminated sediment that required management was up to 675,000 m3.
A layer of silty clay underlies the contaminated sediment at the Randle Reef Site and historical sampling indicated that this substrate is not contaminated. However, a supplementary geotechnical program in 2013 discovered some of the silty clay layers were deeper than originally thought. It was not known if the sediment located above this silty clay was contaminated at depth. The initial remediation plan (BBL, 2006) was to conservatively dredge all the way to the silty clay; however, this was not feasible due to the ECF containment volume. ECCC therefore embarked on additional sediment chemistry investigations in 2013 and 2014 in selected areas where the silty clay layer was deeper than thought. The purpose was to identify if vertical “clean lines” in substrates above the silty clay existed. Sampling, using 3 m long cores, was conducted to assess the sediment against site specific remediation criteria identified for the site (Graham, 2013b). These data, combined with existing geophysical data (sub-bottom profiling), found that in many cases the denser sands and silts above the silty clay substrate met the site specific clean-up criterion. This resulted in revised target elevations for dredging and subsequently reduced dredging volumes. Following completion of all the investigative work at this site, 695,000 m3 of contaminated sediment was deemed to require management (PWGSC, 2015).
Monitoring programs designed to assess environmental effects of in-water work
Monitoring programs are being conducted to ensure that the project is not causing unacceptable adverse impacts on the aquatic environment during implementation. Monitoring for water quality parameters such as turbidity, total suspended solids (TSS) and chemistry (PAHs and metals) will be conducted. The monitoring discussed in this section, was guided by potential concerns identified in the environmental assessment conducted under the Canadian Environmental Assessment Act (1992) (Environment Canada, 2012). Environmental Impact assessments are used in Canada and many other countries to identify potential risks caused by the implementation of projects as well as to recommend mitigations. By following this technique, the monitoring complies to the accepted approach in Canada (Environment Canada and Ministère du Développement durable, de l'Environnement et de la Lutte contre les changements climatiques du Québec, 2015).
TSS is always a concern during any dredging as it is detrimental to fish and fish habitat (Birtwell et. al., 2008; Wilber and Clark, 2001). Turbidity is used as a field surrogate for TSS as turbidity can be measured in real time, while TSS cannot (Palermo et al., 2008). For environmental dredging projects, it is standard industry practice to establish an acceptable turbidity limit above background at a set distance from the dredging operations (ITRC, 2014; Bridges et al., 2008). In order to use turbidity at contaminated sediment remediation sites, a site specific relationship between turbidity and TSS is required (Palermo et al., 2008; Thackston and Palermo, 2000).
In advance of the Project, the following three items were explored to assess TSS release from in-water construction activities:
Site specific relationship between turbidity and TSS;
Determination of the acceptable water quality criterion during dredging; and
The estimated quantity of TSS (if any) generated from the driving and removal of steel sheet piles. (Occasionally sheets require removal due to alignment issues or buried obstacles.)
This equation will be verified in the field during project implementation and adjusted as necessary based upon actual operational conditions.
TSS criterion during dredging
Traditionally, water quality impacts associated with dredging focused largely on the physical impacts of suspended solids on fish such as impact on the gills, behavioural changes, habitat modification and short-term reproductive effects (Birtwell et al., 2008; Wilber and Clark, 2001). It is expected that these types of negative effects to fish are low at Randle Reef due to poor fish habitat at this greatly degraded site.
Where researchers have actually examined effects beyond physical impacts, the Dredging Elutriate Test (DRET) is usually applied. This test which is outlined in Palermo et al. (2008) simulates the contaminant loadings as well as potential toxicity at the dredge head. It then requires modelling to estimate the potential impacts at a distance from the dredge head. The introduction of modelling adds additional uncertainty to the predictions. In order to provide a comprehensive, robust and defendable water quality criterion for the Project, potential chemical and toxicological impacts of dredging Randle Reef contaminated sediment to the water column were examined by a modified DRET process (Graham et al., 2014; Watson-Leung et al., 2017). Briefly, the modified process created sediment and water elutriates at 25, 50 and 75 mg l−1 TSS covering the range of TSS that are typically specified for environmental dredging projects (Graham et al., 2014). These levels were quantified with respect to the corresponding concentration of dissolved and total contaminant loadings expected to the water column. In addition, elutriates using contaminated sediment from the site were created and Daphnia magna, Pimephales promelas, Chironomus dilutus and Hyalella azteca were exposed in standard laboratory toxicity tests. By qualifying effects at a range of TSS levels that are commonly used as stop work criteria in dredging projects (without any toxicological basis), this approach avoided additional uncertainties with modelling from the dredge head to the receptor. Based on the data collected, scientists from ECCC along with an external peer reviewer concluded that a TSS value of up to 75 mg l−1 above background could be supported for this Project as a short-term maximum criterion. However, to encourage slow methodical dredging that minimizes disturbance and resuspension as well as generated residuals, ECCC is setting a lower criterion. The criterion is 25 mg l−1 TSS above ambient conditions, 100 m from the in-water work. In addition, criteria from other sites were examined and compiled to ensure that the selected criterion was practical and reasonable. It was recommended that verification of this lab study be undertaken with field measurements once the Project commences.
TSS during pile driving
To our knowledge there is no published information about the creation of suspended solids during pile driving and extraction. Project specific information does exist to a limited extent in unpublished consultant reports and generally imply that TSS increases were low and localized but dependent upon the methods used. As a result, ECCC measured turbidity during a pile driving test program in 2012 and 2013 (Graham et al., 2013a). This program was used to assess the difficulty in driving steel sheet piles to the depths that would be required in the Project itself.
No apparent increase in turbidity was observed from the monitoring locations, located at 15 m increments down-current from the piles during installation. These results were expected as vibratory pile driving is not a highly disruptive activity and any turbidity generated would be expected to be localized and rapidly diluted in the water column. During pile removal at a 3 m distance from the pile, a slight increase in turbidity from the pre-removal profile was observed in the last metre above the harbour bottom. The maximum increase was 6 Nephelometric turbidity units (NTUs) above the pre-extraction level; however, the general increase was about 1-3 NTUs in the last metre with the higher increase occurring to the leeward side of the pile. It was concluded that no discernable increase could be measured in a relatively short distance from the pile.
Based on the monitoring conducted, turbidity will not be a problem for water quality. All components of the remediation work that have the ability to re-suspend sediments will be monitored and subject to the established water quality criterion. This study demonstrated that TSS would not be a problem with sheet pile installation or removal (if required).
Monitoring plans to assess the long term impacts of the cleanup on the surrounding ecosystem
Large scale clean-up efforts in the past have generally failed to include effective post-remedial monitoring to assess the effectiveness of remedial efforts (National Research Council, 2007). This report highlights that a baseline of appropriate indicators of effectiveness must be established prior to the remediation in order to have a post remediation baseline. The indicators must be started well enough in advance that the pre-remediation baseline data is adequate. Finally the report findings indicate that most projects have too small an array of monitoring. A number of different indices are needed to provide a comprehensive examination. This Project has been designed to ensure that its effectiveness can be evaluated. It will use six indicator studies which are described in this section. The indicator study program has existed since 2005. It started with a larger list that was refined down to 6 studies, after some indices were found to be unsuitable. The amount of data and sampling events does vary from study to study however. The following baseline studies will be utilized after the Project is complete to critically assess the effectiveness of the remediation.
Suspended sediment loading
Remediation of Randle Reef is expected to reduce loadings of PAHs and metals in suspended sediments in the Harbour; this will in turn improve overall ecosystem health. In previous studies using suspended sediment traps, ECCC has shown that contamination arising from re-suspended coal tar-contaminated sediments can be distinguished from contamination entering the Harbour from other sources based on chemical profiles (Sofowote, 2008). Suspended sediments have been monitored in Hamilton Harbour, including locations near Randle Reef, for the past 28 years (prior to the indicator study program for the Project) and will continue to be sampled during project implementation and post-remediation. The traps used are described in Charlton (1983) and are deployed for one month at different depths. It is expected the program will reflect improved suspended sediment quality and a concomitant shift in the tracer compound profiles to a lower ratio of coal tar-related compounds in comparison to those profiles related to on-going sources once the Project is complete.
Surface water quality
Remediation of Randle Reef is expected to result in a small reduction in the loadings of PAHs and metals in the area of the Harbour adjacent to the reef. By establishing the weekly ambient concentrations over a number of years (will be 7 by the time dredging starts), variability resulting from metrological events, changing contributions of different sources, and physical processes in the harbour can be determined. This allows for a baseline to be established to compare changes resulting from the successful remediation of these sediments.
Water samples were extracted from 1 metre below the water surface. Both whole water sampling, centrifuged water and suspended sediment sampling were completed to distinguish concentration variability independent of turbidity which has been noted to occur in other areas of Hamilton Harbour (Burniston et al., 2016). Interim target concentrations for remedial activities and monitoring objectives can be more appropriately established by obtaining an appropriate baseline for water quality. Once the Project is complete, the effect on water quality in the area can be assessed in relation to the remediation project. The pre-project baseline concentrations were established using five years of surface water monitoring data in both the Randle Reef area, as well as locations throughout the entire harbour.
Benthic invertebrate assessment
The Benthic Invertebrate Assessment examined; (a) how the contaminants in Randle Reef impact benthic organisms, and (b) how those contaminants enter the food chain. This study uses four lines of evidence to assess the benthic invertebrates in Randle Reef; sediment chemistry, benthic community structure, sediment toxicity and bioaccumulation (to laboratory exposed organisms). The baseline studies were an initial step for a long-term monitoring strategy for the harbour (Milani and Grapentine, 2006a,b). The studies demonstrated a degraded benthic community in the Randle Reef area. The goals of these baseline studies were initially to examine the spatial extent of contamination, and in the future to determine (a) impacts of Randle Reef sediment removal, and (b) recovery of benthic conditions from the current degraded condition. The severity of the toxicity and benthic community response over time will be determined and maps generated to indicate benthic conditions. Findings from the completed work to date show:
Sediments at a distance of 1 to 1.2 km from the proposed ECF demonstrated adverse effects on the health of the benthic invertebrate community.
Total PAHs bioaccumulated in mayflies, but had no direct relationship to sediment PAH concentrations; and
Sediments from within the Priority 1 and 2 areas demonstrated toxicity.
This study will be repeated at the completion of the Project and then again in the future (every five years) to determine the recovery of site conditions over time.
Fish and Semi-Permeable Membrane Device Response study
The Fish and Semi-Permeable Membrane Device (SPMD) Response study will determine the success of the remediation by monitoring the concentrations of PAHs in water from Randle Reef and Hamilton Harbour using SPMDs, cell line exposures to SPMD extracts, as well as fish embryo-larval exposures. Randle Reef sediments have been studied to determine effects on fish in the lab (by assessing liver mixed function oxygenase [MFO] enzymes and embryo-larval survival, growth and deformities). Assessing MFOs in fish liver followed the methods outlined in Parrott et al. (2011). Changes in fish exposed to sediments were related to the measure of PAHs in Randle Reef sediments. To date, sediments from Randle Reef have been found to increase fish hepatic MFO enzymes in rainbow trout, and increased mortality and deformities in embryo-larval stages of fathead minnows (unpublished data). SPMDs concentrated freely-dissolved PAHs from the water column. SPMD results have been variable year-to-year suggesting movement of PAHs with water circulation in the Harbour. Extracts of SPMDs caused increases in fish MFO enzymes in a fish cell line. All these endpoints will be re-assessed in future years, after the Project is completed and improvements are expected.
The tumours-in-wild-fish study has examined the frequency of preneoplastic and neoplastic lesions in the liver of brown bullhead from the Hamilton Harbour Area of Concern (Baumann, 2010). Tumour rates were compared to a reference location (Jordan Harbour), as well as an overall reference database generated over many years. Detailed methods can be found in Baumman (2010). In general, this study utilized sliced liver tissues that were stained with Harris hematoxylin and eosin, followed by microscopic examination for lesions with a Zeiss Photomicroscope. Based on these data, the fish in Hamilton Harbour showed evidence of increased overall liver tumour rates of about 5.5%. Additional sampling has been conducted to obtain younger fish from Hamilton Harbour and analysis is ongoing. Sampling is planned at the mid-point of the Project, as well as following completion of the Project to monitor rates in the population. These types of studies have been used previously to demonstrate recovery at PAH-contaminated sites before and after dredging (Yang et al., 2009, Baumann et al., 2008) and will be used to assess the effectiveness of this Project.
Wild fish health
The wild fish health studies provide an assessment of whether there are potential differences in the growth, reproduction, and survival of the fish population between those exposed (Hamilton Harbour) and reference areas (Jordan Harbour). Detailed wild fish collections, using electrofishing were undertaken in the fall of 2005 and in the spring of 2007, at two sites selected from a preliminary field survey. Fish health was investigated using a series of measurement endpoints such as deformities, erosions and lesions and endocrine function. In terms of reproductive status, steroidogenesis and histological staging of ovarian development were evaluated. Other analysis included Vitellogenin (Vtg) in fish plasma and mixed-function oxidase (MFO) activity in the liver.
Current unpublished data indicate:
Brown bullheads (the sentinel species) collected from Randle Reef were older than brown bullheads collected from the Jordan Harbour reference area.
Growth rates appear to be slower at the Randle Reef site for both sexes and more pronounced in males when compared to the reference site.
No significant differences in the amount of energy invested into reproduction were found during either of the two sampling periods.
Increased liver size in both sexes of bullhead collected from Randle Reef during the fall of 2005 corresponds to increases in ethoxyresorufin-Odeethylase (EROD) activity in the liver.
There were no corresponding increases in production of the 17β-estradiol hormone by the ovarian tissue from the same fish, but there were significant increases in production of testosterone by exposed females.
Estrogenic exposures are not occurring in brown bullhead in the Randle Reef area. Although in the spring of 2007 sampling, female brown bullhead from Randle Reef had reduced circulating levels of Vitellogenin suggesting some possible disruption.
These observations will be examined through remediation, as well as following completion of the Project.
This article provides a synopsis of the site-specific monitoring programs specifically designed to assess the effectiveness of the Project on the Hamilton Harbour ecosystem and demonstrates how these programs are in line with current practices and the state of the science. A similar approach could be applied to other sediment remediation projects to ensure that the (a) remediation is comprehensive, (b) the remediation process itself minimizes harm to the ecosystem and (c) there is a way to critically evaluate the success of the remediation once complete.
Pre-remediation studies undertaken (sediment sampling for chemistry, toxicity and benthic health assessment) have been used to delineate the bounds of remediation, prioritize sediments for remediation and assess potential adverse effects of remedial methods to be used. Initial sediment sampling at this site focused on investigating the extent and severity of the problem, however, despite seemingly comprehensive sampling, the engineering design identified data gaps, especially with a need for more samples at depth. As a result, further delineation studies had to be undertaken. This demonstrates the importance of an extensive and comprehensive sampling regime and inter-communication among the various disciplines involved. Toxicity studies were utilized to determine a cleanup criterion and prioritize the sediments for remediation following current approaches for assessing contaminated sediments (Chapman, 2008), while the additional sampling conducted supported the completion of the final design.
Monitoring during Project implementation will be undertaken to demonstrate that the remedial activities are not causing unnecessary impacts to the surrounding environment. This will include water quality monitoring for turbidity, TSS and water chemistry. Preliminary studies have already been undertaken in order to predict possible effects from the construction of the ECF within the contaminated area and during dredging. These preliminary studies show that minimal to no effects are expected during the pile driving for construction of the ECF and that a TSS limit of 25 mg l−1 (above ambient background) 100 m from the dredge is protective of the surrounding environment.
Several environmental monitoring studies will be used to assess the effectiveness of remediation. In keeping with the state of the science on evaluating sediment remediation projects, these studies have been carefully selected to ensure a wide array of measures and that adequate data is available prior to remediation. Baseline data required to measure any changes post-remediation include the response of the biological community to the remediation such as benthic invertebrate assessment, fish and SPMD response, fish tumours and wild fish health. In addition, water quality and suspended sediment loading post-remediation will also be measured. These studies will be undertaken for several years post-remediation in order to determine any temporal trends.
Comparisons of ‘Pre-remediation’ and ‘Post-remediation’ effects in the ecosystem will critically evaluate the benefit of the Project on the local ecosystem within Hamilton Harbour. This is an important step that has not been present in many remediation projects of the past and is especially important when public funds are utilized.
While not part of the scope of this article, it should be noted that several long-term monitoring programs are planned to ensure the integrity of the ECF as a containment structure as well as the performance of the isolation cap used at the site.