Background/Objectives
On July 6, 2013 an unattended train derailed in the centre of the Town of Lac-Mégantic, Québec, approximately 3 hours east of Montréal. The train’s cargo, Bakken North Dakota formation crude oil contained in 74 rail cars, spilled and resulted in multiple explosions with the fire destroying a portion of the downtown killing 47 residents and creating a major environmental disaster. The spill and resultant explosions and fire destroyed over 30 buildings and municipal infrastructure, impacted soils and groundwater in the immediate spill area as well as surface water and sediments in Mégantic Lake and Chaudière River. Following five months of emergency response activities the site has been stabilized, major urban restoration planning has been completed and a soil, sediment, and groundwater remedy is being implemented.
AECOM was contracted by the Town of Lac-Mégantic and the Québec Ministry of Sustainable Development, Environment and Climate Change to design and oversee construction of all remediation and restoration activities. AECOM’s objectives were to: develop and administer a site-wide Health and Safety Plan, Remediation Plan, impacted building Assessment and Rehabilitation Plan, and oversee and report on all spill site restoration and ancillary commercial renovation activities.
Approach
Site remediation consisted of utilizing existing emergency response soil, groundwater and sediment data to develop a remedial strategy, integrate the strategy into infrastructure and building restoration and demolition activities as well as numerous off-site activities all related to the revitalization of Lac-Mégantic. Impacted soil volumes requiring removal and treatment are anticipated to be 400,000 tonnes and all treated soils are required to meet Québec Level A soil standards. Soils from impacted areas within the “zone incendiée” (area destroyed by fire), around remaining building foundations, storm sewer replacement and miscellaneous other related construction activities will be removed and transported off-site to a treatment area. Several treatment technologies were evaluated including ex-situ biological treatment, soil washing and thermal treatment. Enhanced biological treatment and select off-site thermal treatment were selected. Remediated materials will be reused where appropriate in the site-wide restoration. In addition, a groundwater cut-off trench and strategically located recovery wells situated throughout the site collect and transfer impacted groundwater to a stationary carbon-based treatment system. Additionally, Chaudière River and some Mégantic Lake sediments impacted by the spill will be further delineated and removed.
Results and Lessons Learned
The schedule for the remediation is aggressive with some building demolition, infrastructure replacement, soil and groundwater remediation and restoration extending into 2015. As a result, a strategically staged and sequenced plan has been developed with construction beginning in May 2014. The various components of the plan will ensure clean-up of the downtown area to performance objectives, re-design and installation of required municipal infrastructure, successful treatment of removed soil, groundwater recovery, treatment and monitoring, and flexibility to enable future site development in concert with on-going discussions and consultations with the residents of Lac-Mégantic.
This presentation will provide an update on restorative construction activities, overview of the application of innovative and sustainable remedial technologies and approaches, and provide the basis for the vision of the future of Lac-Mégantic.
Combined Remedy Benefits of Integrated Physical, Chemical and Biological Treatments on a 14 Million Litre Fuel Spill in a Swedish Forest
Kristin Forsberg (kristin.forsberg@rgs90.se) RGS 90, Malmö, Sweden)
Jonny Bergman (jonny.bergman@rgs90.se) (RGS 90, Göteborg, Sweden)
Gareth Leonard (gleonard@regenesis.com) and Jeremy Birnstingl (Regenesis Ltd, Bath, UK)
Background/Objectives. A series of historic spills from a Swedish military storage depot led to an extensive area of groundwater under forest and commercial property being impacted with petroleum fuels. The largest spill event was an explosion resulting in a loss of life and the release of 14 million litres of petroleum products that reached the wider environment, covering an area of approximately 45,000m2. The problem was enhanced by the difficult terrain, which largely consisted of a hillside moraine and boulder fields covered with dense vegetation. An integrated in situ treatment approach proactively combining physical, chemical and biological technologies both spatially and in sequence was selected, with the combined application presenting clear time and cost benefits over the projected use of any one of the technologies used alone.
The principal pollution incident occurred in 1958 following an explosion. 14,000,000 L of gasoline, diesel and jet-fuel were released and flowed down the forested mountainside and into a lake. The initial 1950’s clean-up activities included setting the lake on fire, with the remaining free-product ‘lake’ on shore then covered with soil, left in place and used as a playground.
Approach/Activities. Contemporary remedial options considered have included excavation, multi-phase extraction, in situ chemical oxidation (ISCO), bio-sparging and enhanced natural attenuation. Following costing and feasibility evaluations, integration of physical, chemical and biological technologies both spatially and sequentially was been identified as the most cost-effective and flexibly adaptive strategy. Pilot tests of the component parts (selected as compatible) were conducted separately to identify optimal efficiency bands and dosing requirements, and from this, the spatial arrangement of technologies and sequential switch-points for optimal efficiency were determined. The first stage of full-scale application was conducted through winter of 2013-14. Performance validation (at time of abstract; 6 – 8 months) describes concentration reductions of >95% to non-detect through the majority of the areas treated.
Results/Lessons Learned. Identification of optimal bands of application based on pilot study performance and cost-projection enabled each technology to be applied at its maximum efficiency, providing an overall ‘treatment-train’ synergy. The projected cost of integrated technology application was calculated at between 25 – 55% of the cost of any of the same technologies used alone, representing cost savings of between $1.7M – $6.5M on the overall project. The projected time for completion was also shortened by several years, although the actual extent of this is harder to reliably determine. In the final design, excavation was not required. The remediation left no visible impacts; important both for aesthetics, military security, and macro-environmental impact – the forest was left in place.
This talk provides qualitative and quantitative examples of the cost and practicality benefits that may be secured through proactive technology integration by way of a large, multi-faceted, formal case study. It is anticipated that this talk will be of interest to end-users, remediation practitioners and regulators alike.
The presence of DNAPL is often limiting factor for the removal of chlorinated aliphatic hydrocarbons from the subsurface. Residual DNAPL usually results in the rebound effect causing repeated increase of contaminants concentrations. Surfactants (surface active agents) are chemical compounds with specific molecular structures typically composed of a strongly hydrophilic head and a hydrophobic tail. In a DNAPL-contaminated aquifer, this specific property of surfactants can increase DNAPL solubility and lower DNAPL-water interfacial tension to the point that physical mobilization takes place. Application of surfactants thus can enhance the remedial action. Surfactants flushing is a mature technology in the petroleum-engineering field. The technology has been shown to be effective also for DNAPL sites recently. A surfactant flushing system typically consists of a network of injection and extraction wells. A mixture of injected fluid and mobilized contaminant is captured through extraction wells that requires further treatment. This treatment could be technically demanding (e.g. due to the tendency of surfactants to form foam). Considering that coupling of surfactants application with another remedial technology seems to be suitable. In-situ chemical oxidation (ISCO) is promising technology for the combination with surfactants. In addition, the main weakness of ISCO application to treat DNAPL thus could be solved.
The pilot test of combined application of surfactants and ISCO was performed at the DNAPL-contaminated site in the western part of the Czech Republic. From the geological point of view, the site bedrock is formed by mica-schist. The shallow aquifer is bound to the zone of weathered bedrock and overlying sandy to clayey loams. The aquifer permeability is relatively low represented by hydraulic conductivity of 10-6 to 10-7 m/s.
The test comprised three phases: 1) separate application of surfactant (i.e. without subsequent injection of oxidant); 2) separate application of oxidant (i.e. without preceding application of surfactant); 3) combined application of surfactant and oxidant. Concentrations of chlorinated aliphatic hydrocarbons, surfactant and other relevant parameters were monitored during the pilot test.
The application of surfactant resulted in the multiply increase of concentrations of chlorinated hydrocarbons (up to 13 times) confirming the efficiency of surfactant to mobilize the residual DNAPL. The subsequent injection of oxidant showed immediate reduction of chlorinated hydrocarbons mobilized by surfactants.
The results of pilot test indicate the applicability of combined use of surfactants and in-situ chemical oxidation at the DNAPL-contaminated sites but also some limitations of this approach.
The performed work was granted by Czech Ministry of Industry and Trade.
The context
Halton Borough Council (HBC) is procuring a £686M road crossing of the River Mersey between Widnes and Runcorn, known as the Mersey Gateway Project, one of the UK government’s Top 40 priority projects in the National Infrastructure Plan. Part of the advance works has been the remediation of Catalyst Trade Park, a 5.6ha site to be covered by an embankment and road junction associated with the new bridge.
The challenge
Historically, the site was an alkali works and then ICI’s ‘Widnes Experimental Site’. It was
contaminated with chlorinated solvents (at concentrations so high ‘neat’ solvents were
present), arsenic and radioactive materials. These contaminants posed significant cost and
programme risks if remediation was left for the main construction works. The remediation was a ‘critical path’ item so completion on time and prompt ‘sign off’ were key expectations of HBC and Merseylink, the Preferred Bidder. The remediation had to be delivered between
central Government conditional financial approval and ‘financial close’. Given the complexity of the site’s geology and the technically challenging nature of the contaminants a goal of ‘betterment’ rather than ‘target’ values was successfully negotiated by Ramboll with the regulators.
The solution
Without set targets to achieve, the problem for the project team was to achieve and demonstrate ‘betterment’ to the regulators within a specific timeframe. Ram,boll’s approach to this problem enabled a previously challenging concept, remediation of chlorinated solvents, to be delivered at considerably lower risk in terms of certainty, costs and programme. Ramboll and Celtic (the remediation contractor) designed, installed, then successfully demonstrated that substantial “betterment” had been achieved. This resulted from technical excellence through innovation, flexibility and optimisation in design with the technical deployment of a combination of remediation techniques, the complex nature
of the site and the contaminants, including the ‘neat’ solvents, meant that a simple “off-the-shelf” remediation solution would not suffice. Celtic and Ramboll collaborated closely with HBC and the regulators to develop the remediation solution that combined the efficiencies of four separate techniques (groundwater abstraction, multiphase extraction of contaminated water, vapours, in-situ chemical oxidation and ‘neat’ solvent recovery) to achieve the maximum and most cost effective mass recovery possible within programme. ‘Betterment’ was maximised by continuously monitoring performance parameters and site conditions so that the system could be optimised and adapted as changing circumstances required. The regulators were invited to attend monthly progress meetings and encouraged to become
part of the ‘project team’, steering the works to a successful conclusion.
Design/Performance
An innovative remediation system was designed to recover technically challenging solvents;
combining the efficiencies of four techniques to achieve the required balance of ‘neat’ solvent
recovery and groundwater treatment, integrated into a single highly flexible and adaptable system. Performance parameters were automatically measured and relayed to the team and the system was continually adapted to maximise the ‘betterment’ achieved. Whilst the system focused on treating groundwater and soils, a secondary system was used to recirculate treated groundwater and encourage ‘neat’ solvent into recovery wells where
it could be extracted. The system proved very successful and ‘neat’ solvent was identified within a week of commencing operations. Whereas initial expectations were that hundreds of kilos of solvent might be recovered, 17 tonnes were ultimately extracted, significantly exceeding the regulator’s expectations. Multi-phase extraction was used to aggressively recover neat solvents from the base of treatment boreholes. The success of the system was measured against the goal of achieving ‘asymptotic’ conditions in terms of recovery of solvents, to demonstrate maximum practicable recovery.
Benefits
The main benefit of undertaking sustainable remediation was recovering a significant volume
of a highly toxic persistent contaminant, improving groundwater quality and reducing environmental risks to the River Mersey and to local people. Secondly, the remediation works successfully unlocked the site development constraints allowing the development to proceed. Also, significant cost and time delays to the project were avoided by ensuring that the Regulator did not designate the site as a ‘Contaminated Site’ under Part IIA regulations.
The “Fixed price” gave economic certainty to HBC. In turn HBC gained the advantage of
significantly reducing (effectively removing) the ‘risk price’ the Preferred Bidder might have put against the contamination issue which was expected to have been many times greater than the £2.2M cost of the remediation. The early completion also removed a significant potential programme risk from the Project. During 14 months, 90% operational time was
achieved based on 24/7 working. The work was delivered on budget within the strict programme. Ultimately regulatory sign-off was achieved within a week, as Regulators had confidence that the remediation work was completed diligently. The pro-active approach adopted in implementing the remediation design enabled a robust approach to health and safety to be maintained during high profile works. The benefits that this delivered included no lost time incidents during the entire programme. Celtic was awarded “Performance beyond Compliance” certification under the Considerate Constructors Scheme and their approach to H&S was commended by the CDM-C.
The remediation of aged source zone affected by residual chlorinated solvents DNAPL represent one of the main challenge in aquifer contamination. When biological reductive dechlorination is considered as a feasible remediation approach, effective delivery and distribution of electron donors other than bioavailability of contaminants in heterogeneous aquifers are some of the primary limitations in most hydrogeological settings. Traditional injection approaches are often limited by preferential migration of injected fluids through better permeable zones, while delivery through less permeable and contaminated layers is usually limited.
By this regards, Groundwater Circulation Wells (GCWs) could advantageously improve the distribution of soluble electron donors by creating a three-dimensional groundwater controlled circulation pattern, especially efficient in anisotropic settings where significant differences exist between horizontal and vertical hydraulic conductivity.
In this work we report on the remediation activity carried out at an operative industrial site in North Italy, heavily contaminated by different chlorinated aliphatic hydrocarbons, including 1,1-DCA, TCE, 1,2-DCE and VC at concentration up to 100 mg/L. The site is characterized by the presence of a persistent source zone in an hydrogeological complex saturated zone characterized by fine to middle sands with intercalation of less permeable sandy silts to clayey silts layers.
Microbiological characterization by FISH and qPCR techniques along with results from extensive microcosm investigation with different electron donors have clearly indicated the possibility to enhance the active biological reductive dechlorination (RD) until the complete dechlorination of the occurring CAH to ethene. Among the different tested electron donors, poly-hydroxy-butyrrate (PHB), a biodegradable polymer easily fermented to volatile fatty acids and molecular hydrogen, have been experimentally verified as effective in stimulating biological RD at the investigated site. Moreover, coupling biological RD with ZVI have been considered and tested as the option to efficiently remove the spectrum of CAH present at the site.
Based on the laboratory investigation and site characterization, a 30 meter deep GCW, with three screen sections, was designed and installed at the site for a pilot testing. Groundwater is pumped, at a rate up to 2.5 m3/h, towards two screen sections of the GCW and is reinjected into the aquifer by another screen section after passing through an above ground installed PHB (releasing electron donor) and ZVI reactor. The pumping rate can be adjusted to the progress of microbiological remediation and also the spreading of biostimulants in the subsurface can be varied. For sampling purposes and to monitor the remediation progress two Multilevel Sampling System (MLWS) and a multi cluster well are installed in the sphere of influence of the GCW .
Key performance issues from hydraulic, technical and operational standpoints will be discussed and evaluated during the presentation.