Construction

We had hoped to start preparing the site for construction work in 2022 following the approved planning application for the project in December 2020. Since then we have been reviewing our plans for the site due to new fire safety measures and the changing costs of materials and labour.

We want to reassure our neighbours that we are still open to dialogue about our plans for land remediation and construction.

 

Land remediation

What we know about the site

The site is known to be affected by historic contamination based on its former use as a gasworks. Extensive site investigation surveys, carried out by both National Grid and St William, have identified hotspots of contamination in a few specific locations (rather than widespread significant contamination across the site).

The primary gas production site was located to the north west (now the Golden Business Park), with the St William landholding historically used for gas storage only. The site has previously undergone remediation by National Grid to remove significant sources of shallow contaminated soils. However, based on the most recent site investigation completed by our specialist environmental consultant, there is still residual contamination at the development site, and this must be addressed as part of the site’s redevelopment for a residential end-use.

Our remediation strategy

There are two elements to our planned land remediation:

  • Selectively removing localised areas (i.e. ‘hotspots’) of contaminated soils and taking it offsite for treatment/disposal. The soil will be taken directly from the site (via the new access road to Orient Way). As previously agreed, there will be no active soil treatment on site, but enabling works to facilitate the relevant development levels will be required, including the backfilling of gasholder voids.
  • The site investigation identified localised residual impacts to groundwater at the site. Treatment of groundwater at these locations will be completed to encourage and stimulate natural processes, promoting environmental improvement longer-term.

Following remediation and construction of the foundations, the site will be capped and new imported soils laid in areas of public open space, to ensure that any residual contamination in the ground is unable to impact the future residents and visitors to the site. This is standard practice for all regeneration schemes on brownfield (previously developed) land.

We are actively considering ways to review and refine the strategy to make it more sustainable and reduce the impact on our neighbours.

The remediation strategy has been prepared by Ramboll UK Limited, an expert environmental consultancy which is highly experienced in working on gasworks sites.

Preventing odour and poor air quality

Air Quality usually refers to the concentrations of chemicals or of particulates present in air, and whether these are a risk to human health or the environment. VOCs (Volatile Organic Compounds) are chemicals released into the air as vapours – many of which are found in common household items and products (such as cleaning products, paint, aerosols etc.), and are sometimes present in the air at background concentrations. Particulates are solid particles and liquid droplets found in the air – common sources can include exhaust fumes, dust, smoke and tyre/brake wear from vehicles.

Odour is largely a potential ‘nuisance’ issue. Whilst the level of odour may be related to the concentration of a chemical in the air, odour impacts are subjective and are different from air quality impacts, and are therefore assessed differently.

During 2021 Ramboll carried out extensive testing to measure the ‘baseline’ air quality and odours on the site. This is so Ramboll can then track any changes that occur during the remediation works, so that any potential increases can be promptly investigated, and subsequently mitigated and controlled.

Trial pits were also dug to investigate shallow soils at the site. The trials data identified that proposed land remediation work has the potential to generate off-site odours and therefore appropriate control measures and monitoring will be implemented by our specialist contractor to mitigate any boundary odour nuisance.

An Air Quality (VOC) and Odour Management Plan has been developed for this . Measures to prevent odour and poor air quality include:

  • Monitoring equipment to measure VOCs, which will provide an alert if there are notable increases against agreed thresholds;
  • Spot check monitoring “sniff testing” at specific locations (work areas);
  • Continuous live monitoring at four boundary sites;
  • Temporary cover systems for potentially odorous material over evenings and weekends;
  • No out of hours excavation or disturbance of contaminated soils;
  • Minimisation of stockpiling and disturbance/ manipulation of contaminated soil;
  • Lorries avoiding schools and residential areas by using the new access from Orient Way unless in special circumstances. (Access requirements will be publicised in advance if required.);
  • Water misting with with suppressant to capture odours at the source (mobile units) or site boundary (static nozzle system). The mist could be scented to help mask the odour.
  • Odour suppressant foam for covering excavation faces or stockpiles in the short term;
  • A selective and planned approach to the excavation of contaminated soils.

The name and contact details of the people accountable for air quality and odour issues will be displayed at the entrance to the development site (eg the Site Environmental Co-ordinator) along with general contact information for St William. A complaints and incidents procedure is outlined in the Plan – and the complaints procedure is outlined at the bottom of this page.

Preventing dust

An Air Quality Dust Management Plan has been developed to mitigate potential impacts from dust emissions during the construction. Measures to reduce dust include:

  • 2.4 metre hoarding (solid fence) on the boundary;
  • Sheeting/screening to prevent dust blowing from temporary stockpiles;
  • Wheel washing of vehicles exiting the site;
  • Coordination with other high risk construction sites within 500 metres;
  • Water cannon / misting units to control dust at source of operation;
  • Damping down of dusty areas and haul road with water;
  • Workers will be required to change dirty boots before leaving site to reduce transport of dust
  • Real time dust monitoring using continuous monitors at the site boundary
  • Offsite visual checks for dust to inform use of control measures

 

How can we monitor what is happening?

Air Quality data will be summarised on a weekly basis in a transparent and plain-English Environmental Monitoring Report, compiled by St William’s third-party environmental monitoring consultant. This report will be published on the project website each week and will set out:

  • Air Quality (Dust) & Volatile Organic Compound levels gathered from live boundary monitoring equipment across four locations.
  • This will be presented from the previous seven days, indicating if the pre-agreed Air Quality levels have been exceeded and note how any such incident was resolved by St William.

A newsletter will be produced each month. This newsletter will include an overview of upcoming works, completed works, programme, key dates and any community events.

There will be an opportunity for members of the public to sign up to an electronic mailing list to receive a copy of the newsletter via email.

Each newsletter will be posted on the project website, and a printed copy of the newsletter will be delivered to residents immediately adjacent to the site as well as Sybourn School and Lammas School.

 

Who has approved the plans?

  • An Environmental Health Officer from Waltham Forest Council’s has approved all of the plans – which were conditions of the planning application
  • The Environment Agency has been consulted and has approved relevant plans
  • We have challenged Ramboll (our consultants) to review the plans to ensure they remain appropriate and in line with best practice.

 

Complaints procedure

St William will maintain a complaint register including the date and time of the complaint, as well as contact details for the complainant. The origin of the complaint will also be recorded (e.g. direct or via local or other regulatory authority). Details recorded will include a description of the nuisance, duration, if it is constant or intermittent and whether the source is identifiable.

  • St William will investigate complaints by undertaking site inspections and recording site activities, mitigation measures employed, implementing remedial measures and updating management plans where necessary.
  • St William will investigate potential alternative (e.g. off-site) sources of odours and record evidence of these (i.e. photos or “sniff” testing) if identified.
  • St William will respond to complainants with details of the findings of any investigations undertaken and also any mitigation/control measures implemented.
  • St William will report back to senior management and operatives on the investigation findings, including any mitigation / control measure applied. The complaints register will be made available for review by the local authority if requested.

 

Find out more

  • Environmental Management Plan – the overall approach to managing the environmental impact of construction, including construction traffic management, environmental control measures and site rules. (This was approved as part of Condition 4 associated with the planning application)
  • Remediation Strategy – how we plan to deal with the contamination of the land (this is the most recent version of the strategy, (You can view the version from December 2021 approved as part of Condition 16 associated with the planning application)
  • Air Quality (VOC) and Odour Management Plan – how we plan to mitigate the release of chemicals (Volatile Organic Compounds) into the air, and how we plan to minimise the release of odours (smells). (This was approved as part of Condition 11 associated with the planning application)
  • Air Quality Dust Management Plan – how we plan to minimise the release of dust and particulates into the air. (This was approved as part of Condition 12 associated with the planning application)

Questions and answers

We know our neighbours have many questions about the plans for land remediation and construction. We have collected as many questions as we can and answered them here. If you have any other questions, please don’t hesitate to contact us.

 

What will be different about St William’s approach to land remediation at Lea Bridge Gasworks compared to some other sites?

Compared to some of the larger more complex sites, Lea Bridge Gasworks is relatively small, and the former infrastructure was predominantly related to gas storage only. Therefore, most of the contamination is generally restricted to a few specific shallow areas of the site. The site has previously been remediated by National Grid, removing a significant volume of contaminated material. This means it is practical for any remaining shallow soils that require remediation (i.e. not suitable for direct on-site re-use) to be removed from the site, and no active soil treatment needs to take place on the site. St William and its specialist remediation contracting and environmental consultancy supply chain has extensive experience in the remediation and redevelopment of gasworks sites, helping inform our approach and consideration to our stakeholders and local residents.

 

What soil and air testing will be happening?

Extensive soil (site investigation) and air testing (baseline monitoring) has already taken place, to delineate and define how contaminated the soil and groundwater is, and to establish the background levels of air quality and odour.

During the proposed land remediation and enabling works phase, weekly reports will detail results from air quality monitors on the site boundary.

When more sensitive work is taking place (e.g. excavating known soil ‘hotpots’) there will be additional testing to monitor changes in real time. If significant increases are detected, investigations will take place and work paused whilst suitable mitigation and control measures are implemented in accordance with the Air Quality (VOC) and Odour Management Plan.

 

What is in the soil? What did investigations find?

The contaminants detected at the site are generally typical of most brownfield sites proposed for redevelopment, such as railway sidings, industrial sites and former gas works.  The contamination comprises a mixture of organic (hydrocarbon based) and inorganic substances.

Are odours likely?

As with many brownfield sites and construction projects, there is a potential for odours to be generated during remediation and enabling works. Odour is defined as a construction nuisance, is highly subjective and not a risk to health. St William understands that anxiety around this issue can be a cause for concern to local residents. Any odour generated from site activities will be closely monitored in conjunction with the approved Air Quality (VOC) and Odour Management Plan. If odours are deemed to be generating an off-site nuisance, these will be investigated promptly and any mitigation measures and controls reviewed to prevent further nuisance issues.

 

Does odour equal poison?

No. Odour nuisance is highly subjective and not considered a risk to human health, however there are chemicals that contribute to poor air quality that also have an odour that can sometimes represent a risk to human health. An odour does not necessarily mean that the concentrations of contaminants present represent a toxicological health risk and conversely, there can be health risks from certain contaminants without there being a distinctive odour, such as vehicle emissions.

Will your works cause contamination to groundwater and the River Lea?

Our investigations have indicated that the groundwater under the site is already contaminated by the site’s previous use as a gasworks and gas storage. Our remediation work will reduce the contamination in the soils and groundwater, and provide environmental improvement to the surrounding area long term. Groundwater beneath the site could form part of the base flow to the River Lea.  The planned remediation of groundwater at the site has therefore been designed to be protective of the River Lea, and ultimately mitigate contaminant migration risk.

How will you minimise the impacts from the demolition of the gasworks, including potential unpleasant odours and dangerous chemicals?

  • Extensive environmental monitoring (noise / dust / VOC / odour / vibration)
  • Temporary covers/sheeting over odorous materials
  • No excavation or disturbance of potentially odorous soils during out of hours work
  • Lorries avoiding schools and residential areas by using the new access from Orient Way
  • Water misting with odour suppressant at the site boundary and at source
  • Odour suppressant foam for short term odour control at the excavation face or stockpile
  • A selective and planned approach to the excavation of contaminated soils.


Will contaminated soil be cleaned on site?

No, contaminated soil that does not meet the re-use criteria will be removed from the site via road haulage and treated at a specialist off-site facility (where possible) for beneficial re-use. This promotes best practice under the waste hierarchy and meets St William’s sustainability targets to reduce our environmental impact.

How will you minimise construction disruption on the surrounding streets?

A new access to the site has been constructed from Orient Way. All construction traffic will use this access so the Clementina Estate will not be exposed to this construction disruption. Only in special circumstances will access from the Clementina Estate be required, and this will be publicised in advance if required.

We think there is a noticeable gas odour on some days – does your assessment agree?

The baseline ‘sniff tests’ recorded odours including exhaust fumes and background urban pollution at low/ medium intensities and were assumed to relate to off-site sources. From our sniff tests and air quality monitoring we concluded that odours and VOCs are present at low level background concentrations prior to any works starting on-site.

Why can’t I have monitoring equipment in my home?

Monitoring equipment will be set up at locations around the boundary of the site, meaning that issues would be identified without needing to intrude into neighbours’ homes. VOCs and particulates can often be found inside people’s homes from common household objects and substances, therefore these could be picked by monitoring equipment in the home.

Will air monitoring continue during the whole construction period?

Monitoring for VOCs and odour will be carried out during the remediation and earthworks only. Dust monitoring will take place throughout the entire construction period.

Will remediation traffic and construction traffic come through the Clementina Estate?

No, we have built an access road from Orient Way – only in special circumstances will access from the Clementina Estate be required, and this will be publicised in advance if required.

Will an independent air quality benchmark be carried out before any land remediation takes place?

Yes. The monitoring we plan for dust and air quality, which will include VOCs, will be carried out by a specialist environmental consultant. Baseline monitoring at multiple locations around the site boundary and wider community network will be conducted prior to works commencing on-site. This process ensures that any changes from the baseline conditions during construction can be tracked, and where required controls implemented to mitigate any construction nuisances, such as dust and odour.

How long until remediation begins?

This is subject to achieving planning permission for the current scheme, but we would like to start at the end of 2024.

Can you do a year of baseline monitoring as a test base?

St William aim to carry out extensive baseline air quality monitoring. A detailed plan describing baseline monitoring techniques and associated testing locations will be presented and shared with Stakeholders and local residents to show our commitment to managing and monitoring construction nuisances during the regeneration of Lea Bridge Gasworks.

Why aren’t we testing for PM 2.5?

We will be testing for PM 2.5. The following construction nuisances shall be tested for; Noise, Vibration, Odour / VOCs and Dust. We will be undertaking monitoring for PM10 dust and PM2.5, however the threshold is set by Local Planning Authorities at PM10 only.

Will the air quality monitors pick up the smaller particles?

The monitoring regime for Lea Bridge will include particulate monitoring for dust, and VOC monitoring based on two testing techniques. These are; live monitoring for Total VOCs, and passive monitoring via Tenax tubes to define multiple organic compounds at extremely low concentrations in the atmosphere.

Are decontamination standards higher for residential buildings than industrial buildings?

Yes – The remediation strategy for Lea Bridge Gasworks will be delivered to a Residential end-use. This standard is more protective of the environment and human health than a commercial or industrial end-use.

Have decontamination standards changed since the land was decontaminated for the Orient Way warehouses were to be constructed?

Yes – a number of changes have been made since the Orient Way land, west of the Lea Bridge Site, was remediated in 2006. This includes the introduction of Land Contamination Risk Management (LC:RM), which is the updated (2020) Government Guidance for how a contaminated Site is assessed and any subsequent Remediation Strategy developed. The LCRM guidance also defines how the Site Remediation works are validated on completion by the Environment Agency, as the Statutory Consultee to the Local Planning Authority.

Will you share the results of the remediation?

Yes – The Remediation works will be delivered by a specialist contractor, overseen by our Environmental Consultant team. The works are monitored throughout and the results are provided in a detailed Verification and Validation report under Land Contamination Risk Management Guidance. The report is subsequently submitted to the Council and Environment Agency (as the statutory consultee) for approval. The Validation report provides the required evidence that the works have met the agreed specification (Council- approved Remediation Strategy). No occupation of a building or phase is permitted until the associated Condition for contaminated land has ultimately been discharged through the planning regime.   This verification report will be published on the planning portal for access by the public once it has been through the above process.

Will you work with the Lea Bridge Station Sites development on drainage and decontamination?

The drainage strategy is a self sufficient strategy to deal with the application site. If the Lea Bridge Station sites comes forward to construction we will liaise closely with them on the drainage strategy and any decontamination.

Will the piling for buildings D&E be deeper because they are higher? Will this affect contamination of groundwater?

The approved Remediation Strategy takes into consideration the risk to groundwater contamination, and includes a form of groundwater treatment to facilitate environmental betterment of the current Site conditions. Our foundation works risk assessment outlines the chosen foundation solution based on the building typology and proposed heights. We do not anticipate any significant change from the previous assessment. However, if there is a change this will be incorporated into a new risk assessment. The piling methodology is based on the Environment Agency approved technique for working on brownfield contaminated Sites.

Is the team aware that the water table is very high?

Yes, the team are aware of this.  As part of the consented scheme a full assessment of the drainage and flood risk was carried out.  This has been reviewed to assess the impact of the increased proposals.  The consented and revised scheme would improve the flood protection for the area.  The impact will be assessed within the application.

What will be the effect on the water table of contaminated ground / decontamination?

The water table will not change based on the proposed development. The proposed Remediation Strategy (which includes a form of groundwater treatment) and Foundation Works Risk Assessment are regulatory approved documents to facilitate long term betterment of the current groundwater conditions.

What are the timeframes for construction?

This is subject to planning permission but we would like to start at the end of 2024 to commence the remediation and enabling works for approximately one year. Construction would be complete in five years.

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