LSC 305
LAND CONTAMINATION, RESTORATION AND REVEGETATION Croda Site Pictorial and tabulated conceptual site model of the contaminants on the Croda site detailing the potential source, pathways, and receptor and proposed mitigation measures
Registration Number: 090164154 LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305
LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Contents
Content 1.
Introduction 1.1 Introduction 1.2 Background Information and History
Page 2
2.
Baseline Information 2.1 Location 2.2 Site at Present 2.3 Topography 2.4 Geological Conditions
Page 3 - 4
3.
Concept Model 3.1 Definition of Concept Site Model 3.2 Importance of Concept Model 3.3 Concept Site Model
Page 5- 6
4. Contaminants on Site Table 4.1: VOCs Table 4.2: Heavy Metals Table 4.3 Asbestos
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5. Tabulated Linkages 5.1 Potential Pathways and Receptors 5.2 Tabulated Concept Site Model
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6.
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Remediation and Mitigation 6.1 Remediation 6.2 Soil Remediation 6.3 Water Remediation 6.4 Mitigation 6.5 Case Study
7. Conclusion
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Introduction
1. Introduction 1.1 Introduction This report aims to produce a pictorial and tabulated conceptual site model of the contaminants on the Croda site detailing the potential source, pathways, and receptor linkages that may be present which will need to be considered prior to any development that may take place within the boundaries. The methodology used was to conduct a site visit of the area to assess the ground conditions and potential linkages that contaminates could use to infiltrate the land. This will be followed by mitigation measures, including remediation techniques. 1.2 Background Information and History The site history and surrounding land uses that is evident on historical Ordance Surveys (OS) maps indicates that there is prevalent land contamination within the area due to its past usage. This dates back to 1880s when Messrs, Mitchells and Ellison established a coal distillation and processing works. They produced coke which was a durable fuel for furnaces and used in steel production, which was a popular business in Sheffield. There would have been many toxic chemicals (hazardous ring chain molecules) on site including benzene and xylene that would be extracted from the base tar. During the 1920s the site became known as Yorkshire Tar Distillers where it was a prevalent and extensive business that covered the area with many large storage tanks. By 1940s creosote was being provided for timber preservation and later in the 1970’s, the tar production was replaced by that of petroleum, the chemicals used were long chain molecules believed to be less hazardous. In 1975 the company changed hands and was renamed to Croda; the distillation of tar ceased in 1981 and the sole production became that of Bitumen until its final closure in 1998 with the final 45 staff being made redundant. During the production of Bitumen products polymers were added to the product to increase its flexibility and expand its variety of uses from sealants and road emulsions. The lower energy levels during production meant it was safer to handle relative to past chemicals; however large levels of concentrated hydrochloric acid did pose threats to the local environment. In recent years demolition of the works and clearance of buildings and the infrastructure has taken place.
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Baseline Information
2. Baseline Information 2.1 Location The site is based in Swinton, Rotherham and is subdivided into two areas by Carlisle Street that runs through it; these are known as the “North” and “South” areas within this document. The Croda Site is heavily contaminated and lies adjacent to housing areas and is in close proximity to surface water courses. The tar distillation and processing works was first established in the South site, the North site was left undeveloped until the 1940s when it was used as waste material disposal area particularly that of lime process waste and continued until the sites closure. Along the eastern boundary of the site is the Sheffield and South Yorkshire Navigation Canal, with industrial, rough open land beyond that adjacent to the River Don. To the north and south boundaries the land serves an industrial purpose. The western site boundary and beyond lies Rotherham to Doncaster and Wakefield railway lines and residential housing. With regards to physical geology of the site there are no local features of significance due to the location and its history. There is potential for individuals who may walk in the immediate vicinity to be impacted by the contaminants on the site, especially as the current condition of the land is derelict and some people trespass in the boundaries. Therefore receptors are considered to be of local importance as stated in Gleeson Homes and Regeneration Environmental Statement Part 2Technical Paper. Top left: map of site in relation to surrounding context Swinton Bottom left: break down of surrounding land use
Site
Open land Residential Housing Croda Site
Industrial
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Baseline Information 2.2 Site at Present The site at present contains remnants of a range of built structures and also contains areas with habitat value and potential, (newts). The North area was demolished and levelled in late 1990s after being filled with a series of waste products including the run-out of pitch into ash/clinker bunds; residual pitch is still present in the area as well as ash and clinker fill. The north site also suffered from a large spillage from one of the above ground storage tanks, spilling vast amounts of gripta (tar/bitumen blend) over the area and was contained by an earth bund which was removed creating a pond in the area. Contamination has migrated throughout the site in the sand and gravel aquifer. The site is currently designated for housing in local plans after remediation efforts have been completed. 2.3 Topography The site topography is predominantly flat with some raised areas in the north eastern and south western parts of the site. The flat expanse lies approximately 18m above sea level and is believed to be due to the introduction of fill materials. Whereas the higher areas, around 6m higher is due to the presence of sandstone outcrop. During the demolition process of buildings, storage tanks and other structures, piles of rubble have been left. However in the South area some concrete structures remain, as well as extensive areas of hard standing. Much of the remaining areas of the site are covered with a thin layer of low quality soil that supports limited vegetation. Vegetation is better established in the north site where dense shrub growth and small trees can be seen, perhaps a result of the area not being worked as heavily as the south site. However, within the north site contamination at ground level with tar and bitumen is apparent with underlying low permeability has resulted in shallow ponds with varying toxic levels. 2.4 Geological Conditions The solid natural geology beneath the site consists largely of the Upper Carboniferous Middle Coal Measures and consists of complex successions of mudstone, siltstone, sandstone and coal up to 1500m deep. The bedrock is heavily faulted to the northeast/southwest of the site. Exposure of sandstone as a result of a fault is apparent in the southwest of the south site. The Coal Measures outcrop at the surface as weathered sandstone and mudstone. Alluvial Drift deposits can be seen on geological maps; these are associated with the River Don and overlie the solid geology across the area, except in the southwest corner. The deposits comprise of a mix of clay, silt, sand and gravel. Alluvium deposits on the site consist of predominantly fine to coarse gravels and considered by the Environmental Agency to be a minor aquifer of variable permeability. Within the alluvial deposits, groundwater has been identified beneath at depths of 4.5m below ground level. Across the site there are variable Made Ground deposits, this is variable in both composition and thickness, but vary between 0.5 and 2m. These can be zoned into different areas and will follow in tables. The Environmental Agency considers Made Ground to be a non-aquifer.
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Concept Model
3. Concept Model 3.1 Definition of Conceptual Site Model (CSM) “A summary of conditions at a site that identifies the type and location of all potential sources of contamination and how and where people, plants or animals may be exposed to the contamination.” “A representation of a site and its environment that represents what is known or suspected about contaminant sources as well as the physical, chemical and biological processes that affect contaminant transport to potential environmental receptors.” “A conceptual model is a simplified representation of how the real system is likely to behave. It is based on a qualitative analysis of field data. A quantitative conceptual model includes preliminary calculations for key processes.” 3.2 Importance of a CSM Many conceptual site models are used to facilitate the decision process in creating a plan for mitigation and remediation efforts of the contaminated landscape. It is a simple way of compiling, reviewing and updating understanding of the site through formulating hypotheses for testing and further investigation. It is a tool used to support decisions that will achieve the final goals of the project.
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Croda Contamination Report 090164154 Polymer blending
As well as humans and vegetation, wildlife could be adversely affected by contaminants; dogs, fish, birds etc.
Upper carboniferous middle coal measures
Waste disposal, large amount of viscous lime material
North
Contaminants could leach into the soil and down into the various layers migrating further afield and affecting a wider area
Old buildings contain remnants of metals, asbestos and toxic chemicals
Railway
Trains could transport dust particles and toxic waste out of the site
Residential housing
Residents may have direct and indirect contact with contaminants including inhaling toxic vapours/ dust and in future may have dermal contact and ingest contaminants if use of site changes to grow crops potentially
Contamination could leach into the soil and migrate outside of the site and affect crops further afield
Laboratory
Bitumen oxidiser
Gas holder
Storage tanks above and underground containing hazardous and toxic materials could leach into the soil e.g. VOCs
Water runoff into canal and through permeable surfaces into soil
Boiler House
Ground water 4.5m below ground level
Alluvial deposits 1 – 5m
Made ground 0.5 – 2m
Canal
People passing through the site could inhale toxic vapours and dust
Potential Receptors
Potential Pathways
Potential Sources
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3.3 Concept Model
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Contaminants on Site
4. Contaminants on Site Table 4.1: Volatile Organic Compounds (VOC’s) Contaminant VOC’s Benzene
Location/ Source
Threats
Will be present where coking operations took place on site
toxic to humans Coal would be and a carcinogenic changed into coke which was a durable Volatise rapidly fuel and as a byfrom surface soil product of the coking (more so than operations ethylbenzene) hydrocarbons; gas from the coke were Highly mobile in formed and often soil and used to fuel street groundwater lights. environment Would be stripped out Can cause from the base tar explosions, need to be burnt off contained in sealants, solvents, gripta, creosote, tar
Shallow groundwater beneath made ground Perch water Made ground Soil, shallow sand/gravel, lime slurry
Site Use
Underground storage tanks
Xylene
Will be present where coking operations took place on site Shallow groundwater beneath made ground
relatively high water solubility means the compounds will tend to be dissolved in the water phase or evaporated into the air spaces of the soil
Perch water Made ground Soil, shallow sand/gravel, lime slurry Underground storage tanks
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can be transported rather long distances
Coal would be changed into coke which was a durable fuel and as a byproduct of the coking operations hydrocarbons; gas from the coke were formed and often used to fuel street lights. Would be stripped out from the base tar
Comment Recorded concentrations from boreholes within the screened made ground and in sand a gravel units) North area made ground, central zone and some south area, most widespread contaminant Colourless liquid that evaporates rapidly in the air The toxic chemicals were ring chain molecules known as BTEX North area made ground, central zone and some south site highly mobile in the soil and groundwater environment The toxic chemicals were ring chain molecules known as BTEX
Can cause explosions, need to be burnt off
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Contaminants on Site Ethylbenzene
Will be present where coking operations took place on site Shallow groundwater beneath made ground Perch water Made ground Soil, shallow sand/gravel, lime slurry Underground storage tanks
moderately mobile in the soil environment; Ethylbenzene can easily leach from soil given its aqueous solubility, molecular weight and octanol– water partition coefficient Ethylbenzene will volatilise readily from surface soil given its vapour pressure,but less rapidly than this is the most important of the transport processes The solubility and volatility of ethylbenzene is reported to decrease when other hydrocarbon compounds are present Can cause explosions, need to be burnt off
produced in the fractionation of crude oil and in the xylene manufacturing process Ethylbenzene concentrations in soil may be highly elevated as a result of localised spills of petroleum products and during historical production/processing of styrene or “mixed xylenes”, and poor management practice. Ethylbenzene is often a component of complex and weathered mixtures of hydrocarbon compounds and may exist in soils as a degradation byproduct.
North area made ground, central zone and some south site Colourless volatile liquid when open to air Low aqueous solubility Solubility varies in the presence of other petroleum products Upon release into soil, ethylbenzene will tend to sink through the unsaturated zone until it reaches the saturated zone. It has a low aqueous solubility and will tend to collect at the water table as a light non-aqueous phase liquid if present in sufficient concentrations Ethylbenzene will volatilise more readily from soils with a high airfilled porosity such as sands and gravels, volatilisation will be retarded in soils with a high moisture content
The above VOC’s are commonly referred to as BTEX because they have closely related chemical structures, and have similar fate and transport properties. They are often used together in industrial and petroleum products, and commonly occur together in the environment as a result of related pollution.
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Contaminants on Site Table 4.2: Heavy Metals Contaminant Heavy Metals Arsenic
Location/ Source
Threat
Site Use
Comment
Shallow groundwater/ Perched waters
Movement of metals through soil is reduced by presence of clay minerals and organic matter
Within old buildings on site that were used in the production of tar/ bitumen
Common in southeast of south site
Soil leachate/ made ground Waste/ lime tips Near transport routes – railway line/sidings, canal
Becomes more soluble at higher pH levels
Metal oxides used in carbonisation process as catalysts and corrosion inhibitors
Present as trace elements in bog ore from coal, coal, spent oxide and foul lime
Lead
Common round old process areas, former coal storage sites and areas used for disposal of spent oxide/ other process residues including made ground Shallow groundwater Soil leachate/ made ground
Movement of metals through soil is reduced by presence of clay minerals and organic matter
Within old buildings on site that were used in the production of tar/ bitumen
Common in southeast of south site
Waste/ lime tips Near transport routes – railway line/sidings, canal
Solubility of some metals may increase under acidic conditions Toxic/ phytotoxic metal
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Contaminants on Site Present as trace elements in bog ore from coal, coal, spent oxide and foul lime
Copper
Common round old process areas, former coal storage sites and areas used for disposal of spent oxide/ other process residues including made ground Shallow groundwater Soil leachate/ made ground
Soft, easily dissolved
Movement of metals through soil is reduced by presence of clay minerals and organic matter
Within old buildings on site that were used in the production of tar/ bitumen
Common in southeast of south site
Waste/ lime tips Near transport routes – railway line/sidings, canal Present as trace elements in bog ore from coal, coal, spent oxide and foul lime
Solubility of some metals may increase under acidic conditions Toxic/ phytotoxic metal
Common round old process areas, former coal storage sites and areas used for disposal of spent oxide/ other process residues including made ground
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Contaminants on Site Table 4.3: Asbestos Contaminant Asbestos
Location/ Source Waste area, general waste Ground layer and in soil and rubble
Threat If becomes airborne is carcinogenic
Site Use Asbestos was used in roof tar cements so may have been used in mixtures along with polymers to make it more durable and flexible with sealants
Comment It is not water soluble or mobile in soil
Would have been used in commercial buildings and machinery
Top left: vandalism on site, fires release toxic vapours into the atmosphere Top right: view across site; canal, railway, site and housing in distance Bottom middle: effluent treatment plant, water purifying tanks
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Tabulated Linkages
5. Tabulated Linkages 5.1 Potential Pathways and Receptors Potential Pathway Dermal contact with soil
Intake via ingestion of soil
Potential Receptor Site users following development Small mammals As above, if any vegetables/ crops are grown in the soil Small mammals
Intake via inhalation of vapours/dust
Underground services
Migration through soil/ groundwater
Trespassers Site users following development Unlikely, local residents off site if water pipes are contaminated Local residents off site if water pipes are contaminated
Comment Short term exposure during development process
This pathway would be present if the necessary remediation measures are not followed through depending on what the new usage of the site will be (proposed housing development may entail small allotment space) Vapours will be released from onsite trespassers making fires on contaminated ground Some contaminants may migrate through service pipes and effect human receptors Could affect human receptors off site if they grow vegetables/ crops in contaminated soil
Fish in canal Could migrate on surface of soil in surface runoff during periods of heavy rainfall Could migrate further during flooding
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Tabulated Linkages 5.2 Tabulated Conceptual Model Receptors and Pathways
Human health Dermal contact Ingestion Inhalation of vapours/ gas Inhalation of dust Ingestion of water from affected surfaces Buildings Direct contact with foundations
Controlled waters Groundwater
VOC’s (benzene, ethylbenzene, xylene)
Heavy Metals (arsenic, lead, copper)
Asbestos
x x
x
x
Comment
VOC’s may be inhaled when trespassers ignite fires on the ground soil turning them into toxic chemicals
Asbestos particles may be present in rubble of old buildings and if disturbed released into the air Metal compounds in building rubble metal solubility is complex dependant on factors including pH and organic matter content of the soil Xylene is highly mobile in the soil and groundwater environment Asbestos it is not water soluble or mobile in soil
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Remediation, Mitigation and Conclusion
6. Remediation and Mitigation 6.1 Remediation Any remediation techniques are advised to be carried out prior to the new housing development proposed for the site, to mitigate the risks that are posed to human health, controlled waters, buildings and structures and flora and fauna. A series of complimentary techniques should be engaged to break down and/or contain any hazardous materials; this will then break linkages and pathways between source and receptor. The variety of techniques engaged will help ensure the highest possible level of contaminants are broken down and that any future uses of site should be free from any health risks. In granting of planning permission for new development, PPS 23 states that remediation must remove unacceptable risk to human health and make the site fit for its intended use. 6.2 Soil Remediation Remaining rubble, building debris containing metals and asbestos should be removed from the site as part of ex-situ remediation Soil that has high concentration level of contaminants that shows potential for the contaminates to migrate further through groundwater or that would become unstable during construction, particularly the area of high lime volumes that become flexible with energy should be subject to solidification – stabilisation treatment o Either ex-situ or in-situ o Mix the soil with reagent to reduce contaminant mobility o For organic and heavy metal contamination The majority of the site should be capped to help break the pathways of contamination within the soil. This will form part of the new soil structure and be covered with other layers of hard standing. o This has a long life span of containing contaminants and forming a barrier o Acts as a barrier to ground gas migration of VOC’s that may still remain o Barrier to dermal contact with contaminated soil o Reduces migration into water system Soil vapour extraction can be used to remove VOCs by passing air through the sub surface in conjunction with chemical oxidation that is suitable for most organic compounds as it adds reagent to subsurface to destroy contaminant by oxidation 6.3 Water Remediation A water treatment option is pump and treat as it breaks short term path o Not long term o Applicable to water soluble and mobile NAPL contaminants Permeable Reactive Barriers (PRBs) should be used for water treatment as they can be used in-situ and along the canal o Can have a phased operation for different contaminants e.g. different reactive medium determined by contaminant from hydrocarbons to metals o However this is a costly option Perched groundwater and other areas of contaminated water should be removed through a phased system of different techniques; o Recovered groundwater should be treated on site and then discharged into local water sewage system when clear to off-site area A natural remediation measure that can be used within the canal as well as any open water that may be introduced in the new development is that or reed bed planting
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Remediation, Mitigation and Conclusion 6.4 Mitigation The range of issues that need to be taken into account include the following during the remediation process as stated in Guidance for the Safe Development of Housing on Land Affected by Contamination: • costs and benefits (including finance considerations and liability); • effectiveness of meeting remediation objectives (including site-specific criteria, timeliness, durability, risk-based and non risk-based objectives); • wider environmental effects (including disruption to amenity, emissions, sustainability); • regulatory requirements (meeting certain conditions or obtaining a licence or permit); • practical operational issues (for example, site access, availability of services, agreed access); and • aftercare issues (for example, the need to maintain and inspect remediation systems or to establish longer term groundwater or gas monitoring). Other mitigation measures that may be incorporated for aesthetic reasons at a lower cost may involve the introduction of new planting schemes, once soil has been cleaned, this would help to screen parts of the site that may still be contaminated with large debris piles. As previously stated the planting of reeds along the canal not only improves the visual aesthetics but also serves as a cleaning agent to any contaminants that may migrate into the canal if barriers break. 6.5 Case Study Knottingley remediation strategy is an important case study as the site has many of the same challenges seen at the Croda site: suffered from offsite migration of contaminants in groundwater, leaching of contaminants from the waste mass to the groundwater, has Great Crested Newts inhabiting the site and is a desirable area for housing development. The remediation tactics they employed were that of increased hard surfacing, engineered drainage system, sorting of material onsite among others.
7. Conclusion In conclusion, the remediation strategy will be costly but can be phased over time, and therefore meet the Government’s objectives of ‘bringing damaged land back into beneficial use’ (PPS23) by removing the unacceptable risks to human health and the environment. However the guidance note set out in PPS23 should be adhered to; to seek to ensure that the cost burdens faced by individuals, companies and society as whole are proportionate, manageable and economically sustainable.
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LAND CONTAMINATION, RESTORATION AND REVEGETATION LSC 305 Bibliography Bibliography • •
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Government. (NA). Coal Works. Available: http://publications.environmentagency.gov.uk/PDF/SCHO0195BJKP-E-E.pdf. Last accessed 15th April 2012. Government. (NA). Soil Guidelines for Ethylbenzene. Available: http://www.environmentagency.gov.uk/static/documents/Research/SCHO0309BPQK-e-e.pdf. Last accessed 20th April 2012. Government. (NA). Guidance for safe housing development on contaminated land. Available: http://publications.environment-agency.gov.uk/PDF/SR-DPUB66-E-E.pdf . Last accessed 17th April 2012. Eugris. (NA). BTEX. Available: http://www.eugris.info/FurtherDescription.asp?e=6&Ca=2&Cy=0&T=Benzene,%20toluene,% 20ethylbenzene,%20and%20xylene. Last accessed 17th April 2012. Gleeson Homes and Regeneration . (NA). Environmental Statement Part 2 Technical Paper 2: Geology and Ground Conditions. Available: http://roam.rotherham.gov.uk/PlanNet/documentstore%5CGY%20AND%20GROUND%20CO NDITIONS_01_1.PDF. Last accessed 20th April 2012. WOODFORD GROUP PLC. (2008). SITE SPECIFIC REMEDIAL TARGET CONCENTRATIONS FOR CONTROLLED WATERS . Available: http://roam.rotherham.gov.uk/PlanNet/documentstore%5CSPECIFIC%20REMEDIAL%20TAR GET_01_1.PDF. Last accessed 20th April 2012.
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