Gordon Wilson Construction Director Sighthill TRA Contract 1 - - PowerPoint PPT Presentation

Gordon Wilson

Construction Director

Sighthill TRA Contract 1

Sighthill TRA Contract 1

Remediation Specialists : Major Projects in Scotland

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Detailed Quantitative Risk Assessment (DQRA)

Sighthill Sighthill Sighthill Sighthill TRA Contract 1 TRA Contract 1 TRA Contract 1 TRA Contract 1

Key CSM Changes: Separate Galligu and Non-Galligu Sources Risk to deep groundwater only assessed, taking into account potential for biodegradation Basal Seal not considered necessary following review of impact on deep ground water Risk to human health considered sources at surface and at depth

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Practicable Human Health Remedial Target Criteria (RTC) derived for cover layers (exposed at surface and at depth) and for Made Ground outside of Galligu containment area. Water Environment dQRA identified widespread risk from sulphide and sulphate in Galligu source to groundwater supporting a containment solution. Water Environment dQRA identified isolated organic, metal and inorganic exceedances in non-Galligu areas. Soil-Leachate Water Environment RTC derived for allowing for a small amount of

• rganic biodegradation. Applicable to cover layers and all areas outside of Galligu

containment area. Reduction in hotspots identified requiring remediation

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Site Clearance Site wide Materials Management Remediation of identified hotspots outside of Galligu area Galligu Containment - Slurry Wall around main Galligu area Galligu Containment – Geosynthetic Clay Liner (GCL) Membrane Emplacement of suitable cover layers

Remediation Areas

Sighthill TRA Contract 1

Principal Quantities 20,000m2/1800m long slurry wall 125,000m2 GCL 1,000,000m3 Materials Management 25,000m3 Hotspot Treatment by Stabilisation

Sighthill TRA Contract 1

Galligu What is it? That depends! Waste product from production of Sodium Carbonate (Soda Ash) Different production processes Different make up Different degrees of weathering Different appearances Different properties

Sighthill TRA Contract 1

Sighthill Contract 1

Slurry Wall Min 600mm wide 1800m length variable depth up to 18m determined by probing Cement/Bentonite/GGBS Specification for the Construction

• f Slurry Trench Cut off Walls

Target permeability

Sighthill TRA Contract 1

Geosynthetic Clay Liner –GCL Woven/Non woven fibre reinforced Needle punched Polypropylene fibres Polyethylene coating Sodium Bentonite impregnated Hydration from soil moisture Minimum soil cover on placement

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Hotspots of arsenic, lead, sulphide, polycyclic aromatic hydrocarbons and total petroleum hydrocarbons identified Options appraisal identified stabilisation as most suitable option for remediation of discrete hotspots Stabilisation imobilises contaminants reducing leachability. Treated material to be placed under cover layers mitigating risks to human health Estimated Quantities 50% reduction through DQRA and delineation

Sighthill TRA Contract 1

Treatment by Stabilisation Leachability criteria SEPA Mobile Plant License Trials to determine additives Conditioning/Incorporation Control/Tracking Verification

Sighthill TRA Contract 1

Verification EA NEN 7375:2004 Tank Test Restrained samples All round exposure Periodical replenishment of eluate Analysis 0.25,1.0,2.25,4,9,16,32days Up to 64 days

Sighthill TRA Contract 1

Environmental Monitoring Hydrogen Sulphide Dust Vibration Noise Ground Water

Sighthill TRA Contract 1

Post Completion Monitoring Bi monthly gas and groundwater for 24 months -general Monthly gas monitoring -shallow wells over containment area Odour survey -Hydrogen Sulphide on 50m grid for 12 months

Sighthill TRA Contract 1

Services CDM Coordination -3 other contractors Archaeology Stone Circle Demolition Pedestrian management Ecology Local residents

Sighthill TRA Contract 1