North Hyde Substation

Under the Minor Civils Framework agreement JSM were appointed as Principal Contractor to carry out the remediation works at a client’s 275kV substation in North Hyde, Middlesex.

The project objective for this remediation work was to provide a solid solution to mitigate risks to human health associated with the presence of asbestos in the shallow soils within the live 275kV substation compound.


The scope of works covered :

  • Principal Contractor Duties under CDM
  • The excavation of the existing surface material layer to 225mm below ground level
  • classification of excavated material
  • safe disposal of excavated material
  • The compaction of formation level
  • CBR testing of formation level soils
  • The installation of geotextile membrane indicator layer
  • Supply and installation of imported sub-base material
  • CBR testing of sub-base material
  • Supply and installation of substation gravel surface layer


The 1.72 ha. site was located on an active substation that is operated by the client and a 3rd party DNO. Following a Detailed Quantitative Risk Assessment (DQRA) the area was declared as requiring remediation as soil samples returned positive for asbestos fibres. Asbestos fragments were also found on surface level in the form of cement bound asbestos tiles.

A specialised asbestos contractor was called in to guarantee JSM was in full compliance with the Control of Asbestos Regulations 2012. These regulations also include guidelines on the correct disposal of the asbestos.

JSM aimed to minimise the amount of hazardous waste that was sent to landfill during this project. 99.95% of the 1538.23m² waste removed was diverted from landfill as it was classified as non-hazardous.

Various environmental measures were undertaken to ensure the project’s success. These were intended to protect site personnel, surrounding environments and other invested or potentially affected parties. Measures included constant Asbestos fibre monitoring, dust monitoring, noise monitoring and vibration monitoring. No excessive readings where recorded throughout the construction works.

Throughout the works the local residences, local authority and businesses were kept well informed and no issues or complaints were raised. In addition to this, no environmental incidences or near misses occurred during this project.

In 2018, JSM were shortlisted in the National Grid Property Awards for their efforts on this project.