Gas membranes and “compliance” with BS8485

This information sheet looks at whether a gas membrane can comply with BS8485. It is the responsibility of the designer to select a suitable gas membrane for a particular site taking into account the project specific factors. The designer should be appropriately qualified and must also justify the choice of membrane in a design report. A membrane cannot “achieve compliance with BS8485” since BS8485 is not a material specification. The sheet discusses the information that designers require to allow an appropriate choice of membrane. It also discusses the influence of plunger size on puncture and impact tests and the effect of cement on corrosion in aluminium foil membranes.

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Using purge and recovery tests in ground gas risk assessment

Purge and recovery tests involve removing gas from a monitoring well and recording the recovery in gas concentration immediately afterwards. The tests were often used in the early 1990s to assess gas emission rates, but were replaced by direct flow rate measurement from boreholes once accurate flow meters with a low detection limit became available. They are still used by some but BS8576: 2013 recommends that the tests (which it refers to as recharge tests) are not used to replace flow rate measurements. This is because there are concerns over the accuracy of the results, which need careful interpretation and can give misleading indications of gas risk in certain situations. This paper identifies the situations where the results are likely to be reliable or unreliable. It describes how the results in appropriate situations can be used to determine diffusion coefficients for use in detailed gas risk assessment.

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Guidance on waterproof basement construction and ground gas

Waterproof basement construction is, in many cases, inherently resistant to ground gas ingress. A simple process to design waterproof basements that also provide gas resistance is explained in this Ground Gas Information Sheet. The method does not require any special site investigation or characterisation of gas risk to be completed, over and above that which would normally be completed for any development. Detailed Quantitative Risk Assessment is only likely to be required where higher risk gas sources are present or if the gas protection system requires value engineering to rationalise it (or remove it altogether).

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Screening approach for landfill gas migration around landfill sites

Landfill gas migration risk may need to be considered when dealing with planning applications for new building development close to landfill sites, for Part IIA assessments of landfill sites or when considering the surrender of environmental permits. Installing monitoring wells outside the site in areas close to receptors or completing other monitoring (eg. internal monitoring) can be difficult, costly and cause unnecessary stress to nearby residents. It may also result in blight on properties. This paper describes a risk based framework that can be used to screen the landfill gas migration risk around old landfills.

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Dissolved methane monitoring for ground gas risk assessment

Ground gas monitoring data for risk assessment should ideally be obtained from monitoring wells installed in the unsaturated zone.

Where groundwater is present in gas monitoring wells it may contain dissolved methane that can influence the measured gas concentrations in the well headspace.

The source of the dissolved methane can be from a diverse range of sources including residual gas from historic landfill, groundwater in Alluvial soils or methane released as a result of shale gas production.

This paper provides information on the influence of dissolved methane on headspace gas concentration and shows how monitoring of dissolved methane can be used to help interpret ground gas monitoring results.

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USING TERNARY PLOTS

Ternary plots are commonly used to allow interpretation of ground gas monitoring results.

There are various ways of plotting data in ternary graphs. This paper explains two different approaches that can be used and the implications that need to be considered when interpreting the data.

It also provides advice on using ternary plots to help characterise the ground gas regime and risk where only low concentrations of carbon dioxide and/or methane have been recorded in monitoring wells without elevated flow rates.

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EPG Latest News (July 2018)

Structural Waterproofing Designs

As projects at Downe Leisure Centre; Lombard Street, London; Ulster University, Belfast and Surrey University in Guildford near completion, several others are underway incorporating structural waterproofing designed by EPG including Phase 3A of Battersea Power Station Redevelopment (Keltbray/SRM), mixed developments at Chatham Waters and Liverpool Waters (Forrest/Peel Holdings) and Queen Victoria House in Bristol (SMS).

SUDS & Blue Roofs

EPG continues to expand the use of innovative SUDS designs including blue-green roofing with numerous new and ongoing appointments including Keybridge House, Nine Elms (Mount Anvil); Elephant & Castle (Lend Lease); Dylon, Sydenham (Crest Nicholson); The Gates, Durham (SRM)

Contaminated Land Redevelopment

Sir Robert McAlpine has recently appointed EPG to undertake the next phase of the Pinewood Studios development at Iver Heath after the successful implementation of the Phase 1 remediation measures last year. EPG’s continued growth in the remediation sector reflects our ongoing commitment to delivering cost-effective solutions, based on robust detailed qualitative risk assessments and our unrivalled expertise in the gas contamination risk evaluation and mitigation provision.

Research Updates

Following on from the recent publication of Guidance on the construction of SuDS (CIRIA C768), authored by Sue Illman and Steve Wilson; EPG’s Rod Green heads up our continued commitment to research with several partners looking at the potential use of SUDS in refugee camps, which is sponsored by The Humanitarian Innovation Fund.

In a similar vein EPG is collaborating with the BRE, Goundworks London and Polypipe to develop a sensory garden to support a much broader project with a team comprising BRE, Halsall Lloyd Partnership, Liverpool John Moores University and Loughborough University researching the role of the built environment in the treatment and management of dementia. BRE officially opened ‘Chris and Sally’s’ dementia house at their Innovation Park in Watford on 4th July. A pop-up rain-garden designed by EPG will later be incorporated into a permanent relaxation and activity space.

Training in Iceland

Steve Wilson recently travelled to Reykjavik to deliver a SUDS workshop to local practitioners and it was so well received that a follow up workshop is to be arranged later this year.

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SPOSH identified in industrial units

A local authority is in the process of formally determining 16 industrial units on landfill gas grounds.

17 March 2016 / Contaminated land

North Lincolnshire Council has written to 16 industrial premises in Scunthorpe warning them landfill gas concerns pose significant possibility of significant harm

The Council is in the process of formally determining the sites and has confirmed it rates them Category 1 or Category 2.

The 40ha site was an ironstone quarry used for municipal waste landfill by Humberside County Council and its predecessors between 1945 and 1978.

Commercial units were built on the site between the 1960s and 1980s and 8ha of it is public open space.

The Council undertook an initial Phase 1 desk study in 2011.

A ground investigation report was prepared by the The Environmental Protection Group Ltd in 2013 and it concluded there is a significant possibility of significant harm from landfill gas and human health risks from direct contact pathways via exposure to near surface capping soils within a public open space.

A separate report on asbestos in the capping soils

was carried out by LQM the same year which concluded asbestos risks would not fall within Part 2A, although risks might need consideration under other legal contexts.

The Council has written to the 16 properties it considers to be Category 1 or 2 to warn them action is needed and to 36 others rated Category 3 to say monitoring is needed and annual checks will be carried out.

Checks were carried out on nearby residential properties in Lilac Avenue and Warwick Avenue in the 1990s and the Council says protection measures were put in place.

Further Information contact North Lincolnshire Council

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More SUDS schemes in Jersey

Following on from numerous successful projects on Jersey, EPG has designed zero discharge SUDS schemes for two schools at St Martin’s School and Grouville School for States of Jersey utilising a variety of techniques.
At St Martin’s School numerous integrated systems including pervious block paving, modular plastic sub-base replacement were used and roof discharges were via modular shallow diffusers into reservoir pavements. EPG worked in close collaboration with lead engineers T&G Consultants Ltd and the main contractor was Marett Construction Ltd.

At Grouville School a combination of modular narrow infiltration trenches in conjunction with a plastic gravel paved reservoir pavement was installed by contractor DB Cummins.

Jersey-based specialist SUDS company Permeable Paving Solutions Ltd supplied the systems and supervised the installations at both sites.

St. Martin’s School

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Roof water discharged into reservoir pavement open graded sub-base via modular diffusers

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Pervious concrete block paving finish under construction.

Grouville School Car Park

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Modular soakaway trench system

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Plastic modular gravel filled pervious paving system

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Illman Young and EPG awarded CIRIA contract to produce updated SUDS Construction Guidance

EPG is pleased to announce that CIRIA has appointed Illman Young and EPG to produce updated SUDS construction guidance to compliment the updated SUDS Manual, which is soon to be issued.

Ensuring that SUDS construction works on site are completed correctly so that they deliver both the visual quality and functional performance intended is fundamental to any project.  The target audience for this guidance will encompass all those who will have a direct input or influence during the construction works on site, and the handover of the design to the site team, and their ongoing inspections required during construction.

Sue Illman will lead the research and production of the guidance with the support of Steve Wilson and various staff from Illman Young, EPG and other industry experts.

EPG are very pleased to continue their longstanding involvement in the production of CIRIA SUDS guidance.

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