Contamination Remediation Case Studies

Transcription

1 Scale Previous use Contaminants Responsibility Assessment and planning Contamination Remediation Case Studies Majority of entire 280-ha site is contaminated, covering 2.3 million tonnes of soil. Around 4 has. of land has contaminated groundwater to a depth of 40m. Industrial estate that left chemicals, glue, fertilizer, engineering works, landfills, and depots on site. Soil - total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAH), arsenic, cyanides, leachable lead, cadmium, copper, mercury, selenium, sulphate Groundwater - PAH, volatile organic compounds (VOC), vinyl chloride Developer Olympic Development Authority Consultant Atkins Contractors north - HBR for stabilization, soil washing, and bioremediation; south - DEC Deme Environmental Contractors for above plus thermal desorption, dredging and sediment treatment Review Environment Agency 3,500 exploratory holes were drilled and 140 archaeology trenches were excavated. Although the approach was global site-wide remediation, each zone has its own remediation plan to separate sites requiring longer build times, each with riskbased remediation strategies and method statements. The goal is to reduce carbon footprint through onsite treatment, reusing, repurposing or recycling 90% through 2 has. of entire 22-ha site is declared contaminated (see Fig 1). A 600,000-m 3 excavation site for an underground car park is also found to have contamination hot spots. Industrial land used as gasworks, shipping and stevedoring facility that left gas wastes, gasometer, tar pits. Soil - copper, lead, zinc, TPH, PAH, bonded and isolated asbestos, benzene, toluene, ethylbenzene, xylenes, ammonia phenol, cyanide, sulphides, phenanthrene, anthracene, coal tar, naphthalene. Groundwater carcinogens/voc Developer Barangaroo Delivery Authority Consultants JBS&G, VeruTEK Contractors Synergy Resource Management (south) and Baulderstone (north-headland Park) Review EPA-accredited Site Auditor (process); EPA/WorkCover (policies); DECCW (Remediation Action Plan) Over 800 test samples were taken over 5 years. Although one Remedial Action Plan was prepared for the whole site, separate remediation action plans were prepared for each zone/phase. Uni of Sydney assessed the asbestos situation. Consultant prepared Air Quality Impact Assessment, Waste and Acid Sulphate Soil Management Plans. Main objectives were to reduce human health and ecological 7.6 has. of entire 200-ha site is contaminated, involving 273,000m 3 of excavated soil to a depth of 1 to 8.3m (see Fig 2) and 150,000L of liquid tarry wastes. Railway and coal/oil gasworks land that left wooden/concrete/steel piles, ammonia plant, tar pits, and tanks. Soil aromatic and aliphatic hydrocarbons (benzene, naphthalene), natural gas, coal/ash wastes, phenols, ammonia, cyanides, sulphates, Goundwater - benzene, naphthalene, cyanide Developer Docklands Authority (now Places Victoria) Consultant Coffey Environments (project management) Contractor Enterra Pty Ltd (50-50 JV between IT Environmental (Australia) Pty Ltd and Abigroup Ltd) Review Superintendent/ environmental auditor Ken Mival (process) Due to concentration of nonaqueous phase liquids (NAPL) both in shallow aquifer and at greater depths, Auditor undertook fate and transport modeling and health risk assessment to determine spread. A risk management approach was adopted in planning for the site s ultimate development, and a clean up to extend practicable approach for removing NAPLs. Goal was to minimise waste through concrete Out of the entire 800-ha site, approximately 70.6 has. or 2 million m 3 of contaminated soil, mostly at shallow depths, in the Port Lands area will be managed over 20 years. Industrial land with tanks for storing coal, petroleum, salt, and area for dumping of sewage/animal waste. Soil heavy metals, asbestos, pesticides, non-metallic inorganic compounds, PAH, VOC, coal tar, sludge, polychlorinated biphenyls, by-products of burning Groundwater localised, with traces of the above contaminants Developer Waterfront Toronto Consultants Golder Associates, OCETA (BLOOM) Contractors DEC and Tetra Tech (pilot facility); GSI Green Soils Inc (full scale operation); Atlas (groundwater remediation) Review Ontario Ministry of Environment (MOE); Stakeholder Advisory Committee Over 500 soil and almost 300 groundwater samples were taken through electromagnetic and ground penetrating radar, and tested to at least 125 contaminants through PCB analysis and radiation. Risk assessment is site-specific. Strategy is to create a pilot soil recycling facility (SRF) to identify treatment options and assess feasibility of onsite treatment and reuse. Plan was to recover at least 80% of soil Studies.docx 1

2 Acceptance criteria Screening Soil remediation techniques Groundwater remediation techniques cut and fill strategy. risks and reuse soil for reclamation. recycling, soil screening/treatment. to add to 1 million m 3 of clean fill. Comply with Environment Agency s criteria based on future land use. Reduce leachability of contaminants to below detection limits (by 90%). For ex-situ contaminated soils treatment, minimum reduction in leachate concentrations was 80%. Materials were pre-screened and some crushed to remove any biodegradable, oversized and metallic objects. Soils with chemical exceedences were screened to less than 50mm to allow to pass through secondary treatment plants. Used soil washing, soil stabilisation/ solidification (S/S), bioremediation and on-site burial. Thermal desorption was also used to increase volatility of contaminants so that they can be separated from the solid matrix, then collected or thermally destroyed. For ex-situ treatment, single powder reagent combined with two liquid additives was used. In-situ treatment consists of chemical and geotechnical immobilisation (based on mix formulation sans cement) to reduce leachability of contaminants. Once soil is cleaned/stabilised, a 60cmdeep layer of highly remediated soil was spread across site. Dredging, sediment treatment, and in-situ bioremediation were used. Bioremediation took place for periods of up to 12 months per application and by injecting into boreholes Archaea to degrade Comply with EPA s normal clean-up criteria. Soil allowed to contain max 1% asbestos, as long as buried more than 0.5m. Soil to be reused should not contain asbestos fibers. Water not to exceed criteria for discharge into Sydney Harbour. Materials which cannot be stabilised and reused on site are taken off site by safe means and appropriately deposited in a licensed waste facility. Wastewater will be dewatered and resulting sludge will be disposed offsite to landfill. Due to the high risk nature and low public support for ex-situ treatment, the Surfactant-Enhanced In Situ Chemical Oxidation (SISCO) method will be used. This involves controlled injection into soils with a chemical consisting of water, hydrogen peroxide, sodium persulfate, catalysts and food-grade surfactants. This effectively degrades contaminants into nontoxic by-products. One of its main advantages is that it avoids bringing the contaminated material to the surface. It is not clear whether treated soil will still be reused for reclaiming originally the Headland Park and latterly Port Kembla. Contaminated groundwater is treated through Synergy s custombuilt multi-barrier water treatment and dewatering system. Dewatering helps reduce volume of water by over 90%, enabling conventional Comply with established health and ecological risk-based soil acceptance criteria for specific sites and depths. These were based on published data on contamination attenuation rates and criteria developed by the Gas Industry. Concrete was crushed and reused on site. Wastewater dewatered to separate residues. Soil screened to remove reusable solids then fines were either treated/reused onsite or disposed off-site to landfill. Heavy contaminants were dealt with offsite. Originally, capping, containment, and installation of a deep cut-off perimeter wall was proposed. However, CBA showed the benefit of these methods was minimal compared to complete removal. Exsitu treatment was preferred, using lime and permanganate, and Fenton s reagent (catalysed hydrogen peroxide) to reduce PAH concentrations in soil by chemical oxidation. Liquid tarry wastes and remaining underground structures were removed. See Fig 3 for remediation process adopted. Note than lime may only be effective for certain metals and permanganate for chlorinated compounds. No active groundwater remediation was undertaken on site. NAPLs were separated from groundwater in a water processing plant, which has a tank with baffles to remove gross volumes and drainage to remove Comply with MOE contamination guidelines with cleanup criteria for maximum allowable concentrations under different land use scenarios, and the Environmental Protection Act and Brownfields Legislation for reuse of contaminated sites. Soils are graded and separated according to size using water and mechanical means. Machines expel contaminated soils in the form of a thick, dark slurry. Screened soils containing hazardous waste are transferred to licensed landfill site. Pilot techniques used for approx 20,000m 3 and in 2 mos. include soil washing and 16 alternatives (stabilisation, solidification, thermal, bioremediation, recycling of some soils in asphalt, and reuse of some materials in brick making etc.) Fieldbased tests proved advantageous as process can be adjusted instantly, where necessary. Study by OCETA showed that recycling was beneficial to environment and society than the dig and dump approach. GSI uses bioremediation technique that involves spraying soil with bacterial compounds to convert hydrocarbons into non toxic fatty acids, carbon dioxide, and water. Techniques used include an aquabarrier (a water-filled dam that uitilises a patented internal baffle for stability) to contain and filter tremie concrete runoff; eductor and wellpoint dewatering systems with Studies.docx 2

3 Infrastructure and equipment Results Monitoring and future concerns ammonia, or other reagents like Regenesis Advanced Oxygen Release Compound with patented Controlled-Release Technology for other contaminants. Direct-push injection is highly efficient, with no operating costs or site disturbance. 2 automated soil hospitals, one soil washing plant and 4 other plants for both soil washing and stabilisation. Bioremediation bio-pile system which has ex-situ automated batch mixing plants and ammonia oxidising bioreactor. More permanent cut-off walls to lessen contamination. Output materials from plants include sand, gravel, fine silts and clays, and fine/coarse organic matter and ashes/coal materials. Treated soils were less vulnerable to weathering.. 90% of contaminated soil reused, saving 68m of landfill cost 20m gallons of groundwater treated. Real-time monitoring stations were installed across site, allowing rapid response to pollution incidents. The site remains classified as a contaminated brownfield site with claims of reburied radioactive wastes. Future contractors are warned that excavated material is considered contaminated unless proven otherwise. Construction of private gardens or growing edible crops are also not allowed. transport and disposal of the dewatered sludge offsite to landfill, providing cost savings, and reducing the frequency of transport movements. Treated water is either returned to the harbour or reused on site for dust suppression. Water treatment and extraction plant onsite with custom-made industrial tanks designed and supplied by Bushmans. Sludge plant to dewater waste generated by the extraction plant. Machinery being used by Baulderstone to extract and treat sandstone for reuse onsite. More than 150m litres of water has been treated, over 112 million litres of which is extracted groundwater. Analysis on the SISCO pilot trial is underway. Treatability tests show that most contaminants can be destroyed within 8 to 21 days. Potential by-products include carbon dioxide, water, and oxygen. A number of soil and groundwater monitoring/pump-out wells have been identified. There is regular asbestos monitoring and reporting. Works plans are always subject to planning approval processes. As remediation is ongoing, there is no report yet released on how future use will be managed. sinkers, and a secondary tank with 2 hydro cyclones that use centrifugal effects to remove sand and silt particles and remaining oily water. The remaining liquids were tested and disposed off to sewer under a trade waste agreement. Soil washing plant. Water processing plant with 2 holding tanks. Clay cut-off walls to minimise recontamination from outside. Annular drainage system installed in the base of gasholders and tar pit as hydraulic containment to lower the water table and reverse gradients. 35% of excavated material recycled (80,000m 3 concrete and 10% soils). 190,000m 3 sent to landfill Imported fill for backfill. Created 50,000 truck movements. Lime was successful with about 15% returned as backfill. Bioremediation was disappointing. 40 million litres of water treated. Monitoring wells and annular drainage systems were installed. A soil and groundwater management plan was adopted in 2001 to provide for construction and future monitoring of trigger levels for chemicals of concern. Use of lime was found to have caused an increase in concentration of cyanides, raised alkalinity, and increased ph conditions, resulting in claims for damage to cars. seawall anchor system and sheet pile face (see Fig 4); enviro/weir tanks for reduction of total suspended solids in pumped water, final discharge, or VOC treatment; and carbon vessels for the reduction and removal of VOCs. 2 pilot mini-soil processing plant on 8.2 has. (DEC used same equipment for London) Full community soil recycling plant Boundary groundwater interceptor trench with temporary treatment unit Collection pond that receives rain runoff, reusing it as process or dustsuppressing water. 62% remediated, 25% assessed but not remediated, 14% not assessed. Full SRF would create $65m worth of societal, environmental and health benefits over 10 years reduced traffic accidents, noise, congestion, pavement wear and tear, truck traffic (80%) and fuel consumption, GHG emissions (75%), landfill. An Area Wide Initiative study was made to set out groundwater, ecological, and recovery monitoring protocols and trigger levels. Dust control, air and runoff control measures are in place. Modern underground corrosion resistant storage tanks with automated interstitial monitoring have been constructed to provide certainty that further contamination will not occur. Studies.docx 3

4 Timeline Cost of remediation Awards 2006 contractors appointed 2007/2008 construction/operation 2009 completed (10 months early) Contract was for 2 years, 9 months. Remediation was part of the 364m enabling works budget. 12.7m ( 1,400/m 2 ) was spent on Banner Chemicals, which involved on-site burial. HBR contract included 0.4m ex-situ treatment, 1.35m ammonia oxidising bioreactor, and 5.35m for 2 washing plants. Use of various treatment methods proved less expensive than pure S/S. Government paid for all these. Best use of a combination of remediation techniques BB Remediation Awards trial applied/consulted 2011 trial approved 2013 trial commenced/analysed Remediation to complete in 3 years. A$98m (A$4,900/m 2 ), plus $30m for off-site disposal of 200,000m 3 soil Ground leases from the developer will initially pay for these. Eventually, parties whose actions resulted in contamination are responsible. Jemena Ltd (gasworks owner) is in dispute with state government, following expert advice that current construction caused spread of contaminants. Water Treatment and Extraction System - Finalist National Infrastructure Awards started clean-up 2005 completed 2006 Audit Statement issued Significant activity occurred in A$44.35m for fixed price design and construct contract to max 5m depth. Average unit rate A$136/tonne Final cost was higher due to lower depths, delays to site access, industrial disputes, wage claims, and disagreements on work programmes. State government paid for this. Note that governance is now shared by the City and government None that is specific to remediation. Early 2010 pilot consulted/built Late 2010 pilot results released 2011 GSI assumed full operation Remediation to complete in 10 yrs. CA$60m (CA$30/m 3 ) federal funding $350,000 Green Municipal Fund federal grant received in April 2012 Under the agreement with GSI, Waterfront Toronto and its partners will send contaminated soil to the SRF, provided GSI offers rates competitive with tipping fees charged by Greater Toronto Area landfills and other remediation firms. Pilot SRF - Canadian Urban Institute Brownie Award 2010 for technological innovation Figure 1. Barangaroo Sydney Contaminated Site Figure 2. Melbourne Docklands Contaminated Site Studies.docx 4

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6 Figure 3. Melbourne Docklands Soil Treatment Process Figure 4. Toronto Waterfront Eductor and Wellpoint Dewatering Systems Studies.docx 6