The Port Hope Area Initiative (PHAI) is a community-based solution for the long-term management of historic low-level radioactive waste (LLRW) resulting from 60 years of uranium and radium processing operations in the urban setting of Port Hope, Ontario. The Eldorado refinery, on the shores of Lake Ontario, began refining radium-226 from pitchblende ore, later transitioning to the refining of uranium ore. Process residues were deposited at the Welcome Waste Management Facility in the Town of Port Hope until the mid-1950s, switching to the Port Granby Waste Management Facility (PGWMF), which continued to accept waste until the late 1980s. Within the Town of Port Hope, surveys are being conducted at approximately 5,000 individual properties to identify the presence of LLRW resulting from fugitive emissions from the refinery and/or the use of refinery residue as construction backfill within the community. Identification of the presence of LLRW is based on multiple lines of evidence including reviews of historical information, gamma radiation surveys and physical sampling of soil for four signature contaminants. Of the 5,000 properties being surveyed, it is expected that approximately 10% will contain some degree of LLRW requiring physical remediation.

This presentation describes the design phase for remediation of the first group of residential properties to be included in the small-scale sites program of the PHAI. The remedial designs, which include developing Class “A” cost estimates and detailed specifications, are based on a comprehensive review of property survey reports, site inspections and topographic surveys, transportation routes, and consultations with the municipality and homeowners. In developing the design packages for individual properties it was important to understand that this remedial phase represent the final and most intrusive aspect of the PHAI for those homeowners affected. As such, the success of the program is dependent on how well the needs and desires of the community and individual property owners are incorporated into the remedial designs and how well those designs are implemented to remove LLRW and restore properties to their original (or better) condition. Specific design challenges include the extent of soil removals required in many areas, the age of the homes affected and the stability of foundations, and the need to sequence the works to maximize the extent to which residents can remain in their homes.

As community satisfaction is a key metric for the success of the project, constant and effective communication at all stages of the project is necessary to ensure the residents understand the nature and extent of work to be undertaken; any and all inconveniences they can expect during the work; contingencies to deal with those inconveniences (e.g., parking, garbage collection, etc.); measures to protect their health and safety; scheduling; and, what their property will look like at the completion of works. The PHAI Management Office has worked diligently to develop a positive and trusting relationship with the community. The design and execution of this multi-year project needs to work effectively within the communications framework established by PHAI Management Office to ensure that interactions with the community, from face-to-face meetings to discuss remedial designs to construction activities in and around the home, are sensitive to and respectful of the needs of the community and individual homeowners.

The Government of Canada, as part of their duty to reduce nuclear legacy liabilities, has issued a contract to close the Nuclear Power Demonstration (NPD) site in Rolphton, Ontario. Currently in Canada there are no suitable repositories for the disposal of radioactive waste generated during the decommissioning of redundant nuclear reactors. The only options are storage with surveillance or decommissioning of the facility with interim storage of the waste at a dedicated waste store. Of these two options, only storage with surveillance is currently employed in Canada for shutdown nuclear reactors. Without a nuclear waste repository, storage is the only currently available approach to dealing with radioactive wastes.

A review of the characteristics of the NPD reactor and its location has identified that a viable option for disposal would be in situ decommissioning (ISD) with grout used to immobilise and stabilise the wastes in the below grade structure. The Government of Canada has accepted Canadian Nuclear Energy Alliance’s proposal that in situ decommissioning is an acceptable solution for reducing the long-term legacies and liabilities associated with the NPD facility. Currently, the project is going through a federal environmental assessment in accordance with the Canadian Environmental Assessment Act (2012), and will require approval by the Canadian Nuclear Safety Commission in accordance with the Canadian Nuclear Safety and Control Act.

This presentation will describe the proposed ISD approach to decommission the NPD reactor. It will explain how the decision to undertake ISD was reached, including identification of the key challenges faced for a first-of-kind in Canada waste disposal system. Using cement to immobilise and stabilise hazardous waste as an in situ decommissioning method, based on experiences remediating contaminated sites across North America, and the applicability to a nuclear reactor will be discussed. Emphasis will be on the reactor characteristics, design aspects and the stabilisation and immobilisation techniques that meet regulatory requirements, and international best practices to turn a reactor into a nuclear waste disposal facility. The use of a 100-year institutional control period, its implications and how it will be achieved, will be examined. It will then show how ISD is able to provide a high level of safety for protecting people and the environment from harmful effects of ionizing radiation for timescales extending thousands of years into the future. The presentation will conclude with determining the suitability of the approach for the ISD of the NPD reactor, and how it will meet the requirements of all current legislation and will do so by meeting or exceeding the requirements of all current safety standards.

The Faro Mine site is located outside of the Town of Faro at 62’N latitude in a mountainous subarctic region of Yukon, Canada. The open pit mine, which operated for roughly 30 years, was once one of the largest producers of lead and zinc in the world. In 1998, the last owner declared bankruptcy. Today, the Government of Yukon and the Government of Canada are co-proponents in the management and closure planning of one of the most complex abandoned mine clean-up projects in Canada.

In its current condition, the site presents a significant risk to human health and the environment. The mining footprint, which spans approximately 2,500 hectares, includes an estimated 70 million tonnes of tailings and 320 million tonnes of waste rock. A significant amount of the waste has an acid generating potential that exceeds its acid neutralization capability, meaning that in the absence of closure there has been significant degradation of water quality over time. Heavy metals (including iron, manganese, zinc and cadmium) are contaminants of concern, with uncertainties relating to geochemical weathering and reactive transport of weathering products presenting challenges for long-term site management

Using a deterministic load-type model for assessing future conditions for a range of assumed chemical loadings, a closure plan is being developed for the site. The proposed “stabilize in place” approach to remediation will rely on diverting clean water away from potentially contaminated surface water, groundwater and seepages; collecting and treating contaminated water using state-of the-art technology; reducing seepage through acid generating material by stabilizing and covering waste rock and tailings; and, adaptively managing unacceptable levels of contamination in the downstream environment. A seepage interception system will form a last line of defence for protecting the receiving environment. All aspects of the closure will consider complex cold regions phenomena, including seasonally and permanently frozen ground, ground freezing and ground ice formation, ground thawing and associated settlement, and freeze/thaw cycling. Implementation of the closure plan is expected to start in 2022 and take approximately 15 years to complete.

This presentation will summarize select 30% conceptual engineering designs.

Risk assessment (RA), combined with remediation, is a common approach to addressing on-site contamination but it is often difficult to complete RAs at off-site properties due to different conditions and/or ownership. Managing dissolved-phase contamination along property boundaries or adjacent to sensitive receptors, such as residential properties or streams, has long been an area of focus for the environmental industry. Property boundary risk management measures are often required as part of the overall remedial strategy. In the 1990s the first permeable reactive barrier (PRB) was pioneered – an underground permeable “wall” that was a barrier to contaminants but allowed the natural flow of groundwater to continue through unimpeded. The initial PRB using zero-valent iron (ZVI), was termed the “iron wall”, and was very effective and widely applied for the treatment of chlorinated volatile organic compounds (cVOCs). Unfortunately the “iron wall” technology is ineffective for petroleum hydrocarbons (PHCs). For more than 20 years many attempts have been made at creating a PRB for the sustained treatment of PHCs but until recently, each technique has had serious limitations and has not been truly “passive”.

The purpose of this presentation is to showcase two new in situ PRB methods to passively and sustainably treat PHCs flowing across property boundaries.

One method uses an activated carbon (AC)-based technology, and is referred to as “trap and treat”. Previously the use of AC in the subsurface has been limited due to the finite adsorptive capacity of the AC emplaced. However, a new development in the technology allows for both the adsorption and the subsequent treatment of the dissolved-phase PHCs using an efficient anaerobic biodegradation approach. PRBs can now be installed to allow for sustained PHC plume capture and treatment over a long period of time – much longer than would otherwise be possible with just the application of AC. This presentation will showcase the “trap and treat” technology and describe how the technology can be applied along property boundaries, adjacent to streams, or along other sensitive receptors.

The second method to treat PHCs along a property boundary uses slow release oxidants. The use of oxidation in PRBs has been historically limited, especially in fast flowing groundwater regimes, due to the high solubility of oxidants. Lowering the solubility of commonly used oxidants has allowed their use over the longer term in PRBs.

During this presentation each technology and associated case studies will be presented and discussed. The presentation will conclude with general recommendations on installation techniques for PRBs for PHC treatment.

Permeable reactive barriers (PRBs), and related in situ reactive zones (IRZs), offer a sustainable, low-energy way to remediate groundwater in situ over long timeframes while accommodating on-going site use. In the past 20 years, PRBs and IRZs have become relatively mainstream. PRBs have been demonstrated at full scale for, for example, dissolved chlorinated solvents, acid mine drainage, dissolved metals, dissolved hydrocarbons and non-aqueous phase liquids. Installation, repair and rejuvenation techniques have been developed for a range of reactive media and ground conditions.

Failing to understand installation method trade-offs and constraints, however, can lead to procurement processes that omit best solutions from a performance or quality assurance perspective and/or unduly restrict competition between bidders, thereby increasing costs. As one example, poorly considered installed width specifications reduce the number of potential installation contractors, potentially resulting in poor value for the Crown in a nominally competitive tender. As another example, the prescription of an extremely expensive (and wasteful) methodology eliminates the ability of a skilled contractor with a more efficient method from undertaking the installation, even if at their own risk.

Owners and engineers considering permeable/passive barrier installations should understand the advantages, disadvantages and limitations of established construction methodologies, including:
• Cut and cover (i.e., conventional excavation, both supported/shored and unsupported);
• Continuous trenching;
• Biopolymer-supported trenching;
• Soil mixing;
• Injection;
• Caisson drilling;
• Passive wells;
• Passive collection with reactor cells; and,
• Mandrels, vibrating beams, jetting and jet grouting.

Each method, and the existing/conventional equipment associated with each method, has typical operating ranges with respect to project aspects such as soil conditions, groundwater conditions, barrier depth, barrier width, key-in requirements and operational requirements (including, for example, reagent formulation, working width, overhead clearance, slope, bearing capacity and/or temperature). Where there is an interest in developing local capacity, it is also relevant to explore what components of each approach can be procured locally, and which require specialised equipment and/or expertise.

In the case of some techniques, such as the use of continuous trenching machines, the differences between commonly available and experimental equipment, or between demonstrated and theoretical performance, may also be significant, with projects in the “conventional range” attracting more, and more competitive, bidders.

Understanding the relevant performance envelopes prevents inadvertently eliminating options that may provide best value on a performance basis as more and more passive/permeable reactive barriers are installed for sustainable, long-term risk management.

The Air Force Base in Moisie near Sept-Iles (QC), a former Pinetree Line Radar station, was in operation from 1953 to 1988 as part of the North American Aerospace Defense Command (NORAD). The activities of the Base led to soil and groundwater contamination by petroleum hydrocarbons (fuel oil and used oil). Environmental site assessments showed the presence of approximately 10,600 m3 of contaminated soil located between 4 and 10 metres below ground surface, including 4,000 m3 below the watertable. The site is located on a sandy point lying between an important salmon river (Moisie River) and the St-Lawrence Estuary.

The project objectives were to remediate the site to the applicable provincial or federal criteria within a three-year period. Considering that several remediation technologies could be used to meet the project objectives, the adopted procurement approach allowed the industry to select their preferred technology instead of using a more traditional procurement approach that prescribes the technology. The contractor was therefore responsible for design, construction and operation of the remedial system as part of a performance-based contract.

From the nine bidders who responded to the request for proposals, different approaches were presented (in situ, ex situ and combination of both) and the winning contractor was selected based on technical (70%) and cost (30%) evaluation. In order to guarantee results, the successful bidder retained the approach of excavating the soil and remediating the impacted soil using an on-site biopile technology. The contract was awarded in December 2015.

The following challenges had to be addressed:
• Project acceptance by the local population and Innu First Nation;
• Multiple land owners;
• Presence of a 50 m long building located above the excavation area
• Need to dewater the excavation zone to access the contaminated soil below the water table and treat the pumped groundwater;
• Temporary displacement of 87,500 m3 of uncontaminated soil above the contaminated soil during the excavation.

The main portion of the contaminated soil (11,900 m3) was placed in the biopile in September 2016 and reached the remedial criteria within four months of treatment. The second portion (2,407 m3) should be remediated in June 2018.

To date, the project has been completed at 95% and the above challenges have all been addressed. The following topics will be discussed during the presentation: 1) the procurement strategy; 2) the retained approach and the main issues; and, 3) the comparison between the preliminary assumptions and the actual results.

The former Gloucester Landfill site is located on Transport Canada property, adjacent to the Ottawa Macdonald-Cartier International Airport. The Gloucester Landfill site served as a municipal waste disposal site from approximately 1957 to 1980. Beginning in 1969 and until 1980, a portion of the site was used for the disposal of wastes from various federal government departments. These wastes (predominately oils and cleaning solvents in drums or bulk quantities) were disposed of in a Special Waste Compound (SWC).

The former Gloucester Landfill Site has been the subject of numerous hydrogeological studies and environmental evaluations since the late 1970s. During the course of the previous subsurface investigations and chemical analysis programs, it became clear that the primary chemicals of concern were the selected non-halogenated and halogenated volatile organic compounds (VOCs). They are also the substances that represent a relatively large proportion of the waste that were disposed of in the SWC.

The plume emanating from this source is known as the Special Waste Plume (SWP). The source of VOCs is potentially distributed through the saturated zone in the form of ganglia based on historical groundwater analysis results from the SWC. The SWP is present predominantly in the deep aquifer, located below a confining unit in unconsolidated material above the bedrock.

Public Services and Procurement Canada (PSPC), on behalf of Transport Canada (TC), commissionned a pilot groundwater remediation study and the goal of the pilot study was to assess the feasibility of enhanced in-situ bioremediation of chlorinated solvents at the SWC.

Therefore, the goal of the 2016 pilot study activities at the former Gloucester Landfill was to observe enhanced reductive dechlorination (ERD) at a sufficient distance from an injection well for a feasible full-scale design.

Based on the pilot testing completed to date and the technical evaluation, the following is a summary of the main results:

• The pilot study was successful in achieving a “proof of concept” that ERD was occurring in the test area (MW16-01). This conclusion was based on the presence of reducing conditions in the target aquifer, a healthy population of dehalococcoides mccartyi (Dhc), an adequate quantity of dissolved organic carbon, and the destruction of VOCs.
• The pilot study was also successful in determining the key design parameters to evaluate the molasses substrate and to calculate the potential Radius of Influence (ROI) required for the full-scale design.

The 2016 pilot test determined the following:

• Molasses was a very effective substrate and fulfilled the key role of providing a cost effective carbon source with excellent subsurface distribution.
• Based on the weight of evidence including the hydraulic responses, the dissolved carbon distribution and the Dhc presence and growth, the effective ROI is estimated to be 5.5 metres downgradient and 4 m cross-gradient. This is a considered a very good result which allows for a cost effective full-scale design.
• ERD was observed in the monitoring wells adjacent to the injection well following the injections. This conclusion is based on the three lines of evidence provided above.

Based on the success of the pilot study, full-scale design and implementation was approved. Implementation of the full-scale design began in January 2018.

The Port Lands is a 356-hectare area bounded by the Keating Channel/Don River and Lake Shore Boulevard in the north, the Toronto Inner Harbour in the west, Leslie Street in the east and Lake Ontario and Tommy Thompson Park in the south. Formerly the largest natural wetland in Lake Ontario, the area was infilled in the early 1900s to make more land available to serve Toronto’s growing industrial sector and for shipping. While still used for industrial and port purposes today, these brownfield lands are generally underutilized, lack adequate municipal services necessary for other uses, and also fall within the flood plain of the Don River. Plans are underway to flood protect and revitalize this valuable part of the city through re-naturalizing the mouth of the Don River and extending the river south and west through the Port Lands. Successful completion of this work will require addressing multiple complex issues associated with the construction of a river through a brownfield site – something that has never before been done.

This presentation will explore some of the challenges associated with the redevelopment of the Port Lands, and the different strategies being applied to address those challenges, including:
• Permits and Approvals – navigation of a complex regulatory framework for work that has not previously been done and falls “outside the box” of standard regulatory approvals;
• Delineation of Site Impacts and Understanding of Site Risks – application of models and specialized testing to characterize the distribution of site contamination and assess the potential for elevated risks to human and ecological receptors under future constructed conditions;
• Presence of Non-Aqueous Phase Liquid (NAPL) – evaluation of options for remediating NAPL impacts versus managing impacts in place, particularly along the length of the planned new Don River;
• Soil Management – development of a site soil reuse strategy to facilitate alignment with anticipated future excess soil regulation and stakeholder sustainability objectives, given the anticipated >1 million cubic metres of soil to be produced via site construction; and,
• Odour Management – approach for evaluating the potential for adverse effects from odours during site construction, and the strategy for minimizing these impacts.

The Port Lands is a 356 hectare (880 acre) area at the edge of Toronto’s Inner Harbour. Formerly one of the largest natural wetlands in North America, the area was infilled in the early 1900s to make more land available to serve Toronto’s growing industrial sector and for shipping. While still used for industrial and port purposes today, these brownfield lands are generally underutilized, contaminated, lack adequate municipal services necessary for other uses and also fall within the flood plain of the Don River. Plans are underway to flood protect and revitalize this valuable part of the city by building a new river outlet to Lake Ontario.

To build the river and flood protect the area, over 1 million cubic metres of soil will be excavated. A portion of the soil will be reused to construct flood protection walls. Poor environmental and geotechnical conditions complicate the soil removal and creation of a new river valley. Waterfront Toronto initiated a process in 2016 to test innovative but proven technologies in the following categories:
• In situ remediation and/or stabilization of non-aqueous phase liquid (NAPL);
• In situ soil stabilization to improve geotechnical conditions; and,
• Ex situ soil remediation, amendment and dewatering technologies.

Ten bench scale studies were completed and six pilot tests are underway to evaluate and maximize options for soil reuse. Waterfront Toronto has been testing in situ technologies that would remediate or stabilize the presence of NAPL within the project area prior to the initiation of the excavation work. A key component of the project is also to prevent any NAPL migration to the future river valley, reduce over-excavation for channel design slopes, and treat excavated and dredged soil to levels that would allow its reuse within the project area. It is anticipated that most of the excavated and dredged material will have to be dewatered, sorted, and remediated to reduce contaminant concentrations and/or amended to improve its geotechnical conditions.

The tested technologies include:
• In situ remediation (self-sustaining treatment for active remediation (STAR) – in situ smoldering);
• Electro-thermal treatment (surfactant enhanced product recovery (SEPR)-surfactant-enhanced in situ chemical oxidation (S-ISCO) – surfactant enhanced removal with chemical oxidation);
• Ex situ remediation (enhanced bioremediation, soil washing and STARx);
• Risk management (block and adsorb and stabilization); and,
• Geotechnical improvement (urea-based soil stabilization).

Treatability, constructability and life cycle costs have been identified as the primary factors influencing the selection of the remediation or improvement technology(ies). Results of the bench scale and pilot tests will be presented and the decision process in selecting the final remedy will be discussed.