Wood Group UK Ltd (Wood) is providing land contamination support to Skanska Construction UK Ltd (Skanska) for the Stechford and Saltley (SAS) 13 bridge replacement works in Birmingham. The works are critical to construction of the High Speed 2 (HS2) railway and depot reception lines in the Birmingham area.
Our involvement has predominantly related to the temporary works phase of the scheme, comprising construction of the new bridge fabrication area to enable construction of the new bridge deck prior to it being rolled across the existing main railway lines and then lifted into place. A key aspect of the project involves excavation and relocation of 100,000m3 of contaminated material under the HS2 materials management plan for future use within the wider site area, as well as piling along the existing live rail lines to allow excavation of the existing bridge abutments.
The construction site is within an historically industrial rich area, with previous uses of the site including a hospital, gas works, metal works, scrap yards and cement works.
A legacy of contamination is present within comprising asbestos, heavy metals (notably lead) and hydrocarbons. Invasive species were also present within the site, masking much of the contaminated ground, which required treatment and removal in advance of construction works. The River Rea is in hydraulic continuity with the site as it flows through.
On completion of the Skanska works the site is to be handed over to HS2. As the Skanska works are in advance and separate to the HS2 scheme they wanted to ensure that appropriate account and management of contaminated land was core to their scheme, hence the requirement for use of the NQMS. Wood was therefore brought on board by Skanska to provide a high level of land contamination advisory competency, inclusive of Specialist in Land Condition (SiLC), Society of Brownfield Risk Assessment (SoBRA) accredited risk assessors and Suitably Qualified and experienced Persons (SQP’s). This was critical to enable Skanska to move forward with the project, making full use of the intended construction works to minimize remediation requirements
in a sustainable manner.
Wood’s assessment and support of the project is considered interim within the context of the wider overarching Remediation Strategy developed by HS2 for their deliverable. Wood’s package of work was to focus on contaminant
linkages of concern specific to the Skanska works which are not addressed in the overarching HS2
To complement our deliverables Wood have made use of the National Quality Mark Scheme (NQMS) to provide the assurance that the works are being completed to a good standard and to provide certainty to HS2 of the works completed to
render the site suitable for use in advance of hand over.
A series of land contamination studies and intrusive ground investigations had been undertaken within the site to support the initial design and appraisal of the works and planning for the scheme. As such given the studies had identified a range of chemical and radiological contaminant linkages of concern associated with the proposed development.
Given the breadth and form of works to date Woods initial deliverable comprised an in-depth assessment and review of the existing geoenvironmental data set for the site. The aim of which was to ensure the data was representative and in sufficient form to develop a robust Conceptual Site Model (CSM) taking account of the environmental setting, the ground conditions, the invasive species, soil, water and potential radionuclide contamination. This formed the basis for determining and agreeing each of the stages moving forward to development of the Remediation Strategy.
The assessment was undertaken in advance of the release of the Land Contamination Risk Management (LCRM) from the Environment Agency, however Wood was able to produce it in line with the outline of the document based on the draft version which we commented on. When the final document was released, it was in accordance with the then introduced LCRM guidance.
The previous ground investigation works had identified a potential risk to construction workers from the presence of radionuclides. Wood were able to undertake a critical reassessment of the data and determine that the risk was minimal and that no further works were required to protect the workforce. Therefore, removing the need to remediate the materials and any requirement for offsite disposal/treatment.
Our in depth review of the data and establishment of the initial CSM enabled a focus on key contaminant linkages of concern, thereby driving the project forward. At each stage Skanska were informed of our findings and Wood provided support to the design to assist in maximising sustainability through the scheme
Wood also provided specialist health and safety advice, using our SoBRA accredited risk assessors, with regards to the short-term risk assessment to construction workers to inform the procedures and mitigation to be implemented throughout the construction process. The main contaminants of concern were heavy metals, in particular lead which were at acute levels and also high pH and hydrocarbons. This assessment also assisted in developing and driving the remediation strategy for the site.
Wood delivered guidance on construction control measures during the works. The guidance included the management of asbestos in accordance with Control of Asbestos Regulations 2012, the risk around unexploded ordnance and dust management.
Shallow groundwater was also an issue along with the containment and disposal of surface water runoff from the stockpile generation as part of the excavation and removal of the contaminated materials. As such Wood provided advice and guidance for the surface water management as we are very familiar with the HS2 guidance and requirement which needed to be met. Wood also provided advise for the compliance with the Water Framework Directive with accordance with the overarching HS2 technical standard.
The Environment Agency indicated that a Water Resources and Flood Risk Management Plan was required for the site. The purpose of such a document was to review the water resources and flood risk context of the site, highlight sensitive features, draw on other assessments to identify risks to these sensitive features and identify mitigation and management procedures. An initial background information review generated a preliminary Water Resources and Flood Risk Management Plan which assessed the impact to the River Rea and the general water environment from both Skanska’s and HS2’s works.
Wood undertook an options appraisal aligned to the requirements of LCRM, which detailed a capping
layer as the most appropriate remediation solution for the scheme.
This built from the necessity of Skanska to construct the development platform. Key considerations specific to the site and wider scheme, taken account of within the Option Appraisal comprised:
The options appraisal formed an alternative assessment and a new take on the proposed remediation of the development, maximising the form of development to act as the remediation solution. As a result, it facilitated a change in the remediation technique to be employed and allowed greater retention of materials on the site which greatly supported the sustainability goals for the development. Skanska and Wood
followed the Sustainable Remediation Forum (SuRF-UK) guidance to focus on Sustainable Remediation solutions.
A containment cover system was considered to be the most suitable option in the context of the scheme. It offers a good interim remediation option in relation to the overarching HS2 remediation strategy that is achievable within the required timescales and directly aligns to the Skanska temporary works. This approach has greatly reduced materials movement, timescales and the need for large scale import.
Following acceptance of the options appraisal, by Skanska, Wood developed the remediation strategy to work alongside the overarching remediation strategy for the HS2 development across the wider Washwood Heath development site. This ensured that Skanska complied
with the overarching strategy and also appropriate guidance/legislation to ensure the site is suitable for the proposed commercial end use. The strategy followed the format provided within LCRM.
The Wood remediation strategy was critically assessed by HS2 to ensure it met with their expected high standards and that the strategy was fit for purpose from all parties perspective, with particular regard the HS2 overarching Remediation Strategy. It was critical to gain HS2 approval to ensure no future queries were raised with regards the remediation techniques being implemented. HS2 were in full agreement with our Remediation Strategy and recognised the importance of utilising the NQMS.
In advance of each deliverable forming the Remediation Strategy the Wood Suitably Qualified and experienced Person (SQP) assessed and ensured the Wood technical teams capability through the Wood competency matrix, which directly aligns to the requirement of the National Brownfield Skills Framework (NBSF). The Wood SQP delegated specialist elements within the deliverable for Wood Technical specialist, such as radiological appraisal. Overall, the Wood SQP ensured the Remediation Strategy is in line with the requirements of the NQMS.
The Remediation Strategy was documented as technically adequate under the NQMS to provide visible
identification that it had been checked for quality by SQP. The NQMS Declaration Reference for the
Remediation Strategy is 1220- D0496.
In bringing Wood into the scheme to support them Skanska have been able to bring forward their works,
with the certainty that remediation is appropriate and sustainable. Wood has taken account of the LCRM staged approach to assessment of contaminated land to provide an outcome which has met with both Skanska and HS2 high standards for the scheme.
Wood is currently present during the works to provide verification of the remediation to ensure compliance with the remediation strategy. The verification process is through presence of a wood competent site chemist and comprises:
• Chemical testing to demonstrate the materials suitability (through either a material management plan
for site won materials or using Table 6.1).
• Visual inspection of material prior to placement to identify whether the material is contaminated.
• Material tracking information.
• Thickness of cover, with photographic evidence collected during placement being suitable.
• Presence of demarcation layer, with photographic evidence collected during placement being suitable.
With the Wood site presence, they are also available on hand to provide advice and guidance to Skanska on any matters relating to the remediation strategy and any general environmental matters. The remediation verification report will also be subject to the rigours of the NQMS.