basford gas works remediation using soil washing technology

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BASFORD GAS WORKS BASFORD GAS WORKS REMEDIATION USING REMEDIATION USING SOIL WASHING TECHNOLOGY SOIL WASHING TECHNOLOGY

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Page 1: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

BASFORD GAS BASFORD GAS WORKSWORKS

REMEDIATION USINGREMEDIATION USINGSOIL WASHING TECHNOLOGYSOIL WASHING TECHNOLOGY

Page 2: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

History of Basford Gas WorksHistory of Basford Gas Works

2.5 miles north-east 2.5 miles north-east Nottingham city centreNottingham city centre

Flood plain River LeenFlood plain River Leen

Operational 1854 – 1972Operational 1854 – 1972

Valuable by-productsValuable by-products

Decommissioned 1972Decommissioned 1972

1995 – 1997 site 1995 – 1997 site investigationsinvestigations

Major ContaminantsMajor Contaminants

Granular soil – soil Granular soil – soil washingwashing

Page 3: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

Objectives of Remediation ProjectObjectives of Remediation Project

Acceptable contamination levelsAcceptable contamination levels

Selective excavationSelective excavation

Soil washingSoil washing

Minimise landfillMinimise landfill

Re-use clean soilRe-use clean soil

Minimise local disruptionMinimise local disruption

Minimise environmental impactMinimise environmental impact

Page 4: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

Project ProcessesProject Processes

Preliminary investigationPreliminary investigation

Identify need for remediationIdentify need for remediation

Test suitability of soil washingTest suitability of soil washing

Detailed site investigationDetailed site investigation

Full scale remediationFull scale remediation

Performance assessmentPerformance assessment

Page 5: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

Soil Washing - ProcessSoil Washing - ProcessRemove debrisRemove debrisMix with waterMix with waterParticle size separationParticle size separation- Contaminants bind to small particles- Contaminants bind to small particles- Small particles bind to larger particles- Small particles bind to larger particles- Washing processes separate small from large- Washing processes separate small from large

Gravity separationGravity separation- Removes high or low specific gravity particles e.g. heavy metal - Removes high or low specific gravity particles e.g. heavy metal containing compoundscontaining compounds

Attrition scrubbingAttrition scrubbing- Removes surface contaminant from coarse particles- Removes surface contaminant from coarse particles

Sequential washingSequential washing

Page 6: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

Soil Washing - ApplicabilitySoil Washing - Applicability

Originally developed to remove PAH’s Originally developed to remove PAH’s and PCPand PCPAlso applies to:Also applies to: - Fuels- Fuels

- Pesticides- Pesticides- Various industrial - Various industrial

chemicals chemicals

- Metals- Metals

Removes a wide range of organic and Removes a wide range of organic and inorganic contaminants from coarse inorganic contaminants from coarse grained soilsgrained soils

Page 7: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

Soil Washing as a solution at Soil Washing as a solution at Basford GasworksBasford Gasworks

Efficient technique for contaminant types Efficient technique for contaminant types (mainly hydrocarbons) and soil(mainly hydrocarbons) and soilWaste minimisation technique, reduced lorry Waste minimisation technique, reduced lorry movement offsite (23,000 to 8,000 movement offsite (23,000 to 8,000 movements)movements)14,500 movements saved compared to 14,500 movements saved compared to traditional dig and dumptraditional dig and dumpSignificant recovered quantities of ash & Significant recovered quantities of ash & clinker (steel and breezeblock clinker (steel and breezeblock manufacturing) using soil washingmanufacturing) using soil washing

Page 8: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

Efficiency of Soil WashingEfficiency of Soil Washing

80.5% of input recovered as 80.5% of input recovered as clean for re-useclean for re-useThat unclean usually contained That unclean usually contained high coarse organic content high coarse organic content within gravel fractionwithin gravel fractionMost contaminants located in Most contaminants located in filter-cake - the higher the input filter-cake - the higher the input contaminant concentration the contaminant concentration the more effectively it is washedmore effectively it is washed15,000t of excavated 15,000t of excavated contaminated soil blended with contaminated soil blended with filter-cake to stabilize itfilter-cake to stabilize it Soil Washing Plant

Page 9: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

Material ProcessingMaterial Processing

161,650 tonnes of material 161,650 tonnes of material supplied supplied Processing rate of 370t of clean Processing rate of 370t of clean output/dayoutput/day125,761t of clean material (sand & 125,761t of clean material (sand & gravel fractions) and 32,240t of gravel fractions) and 32,240t of filter cakefilter cake76% excavation was re-used 76% excavation was re-used (compared to 11% for traditional (compared to 11% for traditional methods)methods)Site restored to original ground Site restored to original ground levels (+/- 0.3m) with the addition levels (+/- 0.3m) with the addition of 81,402t clean fillof 81,402t clean fill

Clean soil from Washing Plant

Page 10: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

Alternative SolutionsAlternative Solutions

No recommended alternativesNo recommended alternatives

Dig and dump would have been cheaper Dig and dump would have been cheaper – did not meet the requirements– did not meet the requirements

(Cost of soil washing was £21.11/t)(Cost of soil washing was £21.11/t)

Selective excavation (low cost, low Selective excavation (low cost, low technology) was also used in technology) was also used in conjunction with soil washing (higher conjunction with soil washing (higher cost, higher technology)cost, higher technology)

Page 11: BASFORD GAS WORKS REMEDIATION USING SOIL WASHING TECHNOLOGY

SummarySummary

Only solution to fulfil all objectivesOnly solution to fulfil all objectivesShowed that soil washing was effective on a Showed that soil washing was effective on a variety of contaminantsvariety of contaminantsReduced volumes transported offsiteReduced volumes transported offsiteMinimised disruption to local communityMinimised disruption to local communitySignificant quantities of recycled materialsSignificant quantities of recycled materials30% less energy compared to road haulage 30% less energy compared to road haulage 200,000t of contaminated material excavated, 200,000t of contaminated material excavated, this represents a substantial saving in landfill this represents a substantial saving in landfill void spacevoid spaceBetter results as voluntary projectBetter results as voluntary project