Holbeck Delivery Unit

Background

The wider depot has been used for the storage and maintenance of trains for over 100 years; initially steam then diesel.  The development area has predominantly been used as an engine shed for general repair work, offices and storage.

Proposed redevelopment involves repurposing of the existing building, with improvements to the associated car parking area.  Repurposing requires conversion of a former engineering building into offices and storage spaces, with both internal and external alterations to the building layout and structure.

Key considerations

Lithos were commissioned to provide a geoenvironmental appraisal of the site, specifically designed to address land quality questions raised by Leeds City Council with respect to risks to groundwater and surface water.  As most of the excavated soils were to be removed from site, Lithos were also asked to undertake a detailed WM3 waste code assessment to support duty of care obligations.

What we did

Detailed ground investigation suggested a complex groundwater regime, with deeper drift groundwater impacted by hydrocarbons from an unknown source.  Careful review of dip data confirmed drift soils and deeper bedrock were not in hydraulic continuity and that drift groundwater was unlikely to be discharging to surface water.  Superimposing below ground infrastructure on the scaled conceptual site model provided the Contractor with a clear indication of where groundwater might be encountered, and where dewatering would be needed.

Data collected during the ground investigation was used to divide made ground and natural soils into suitable sub-populations which were then characterised in line with the Environment Agency’s Technical Guidance WM3.  Classification and assessment of waste soils under WM3 is a complex process.  Whilst tools such as HazWaste Online are available to support assessment, consideration must also be given to understanding the characteristics of the waste as a whole in order to allow a suitable waste code to be applied.  This includes identifying sample populations, relevant chemicals and confirming the statistical confidence in data sets; all are critical if the 7-step approach set out in WM3 is to be followed.  Lithos’ waste code assessment also provides practical advice on the segregation and management of waste soils in order to reduce the volume of hazardous waste generated.

The outcome

Our detailed Phase I desk study review of site activities enabled us to justifiably discount some hazardous classifications (such as persistent organic pollutants) without the need for expensive laboratory testing.