Removal of Waste from Site – Hackney Substation, London
JOB: HACKNEY SUBSTATION, LONDON
CLIENT: NATIONAL GRID PLC
ENGINEER: NJP ENVIRONMENTAL LLP
DATE: MAY 2017
*a much higher cost than our average price for assessing for removing waste material from site, due the number of trial pits and asbestos screening tests requested by the Client.
The council leased a plot of land, part of Millfield Park to the National Grid. National Grid levelled the land off by importing material onto the site, on top of a geotextile terram. When the land was to be returned to the council, the imported material was to be removed from site and the material was believed to contain asbestos and other hazardous properties.
A waste classification assessment was required to determine whether the material was classed as non-hazardous or hazardous, with the aim of delineating any areas of non-hazardous and hazardous material and recommending the appropriate landfill site/sites. As the cost of sending non-hazardous material to landfill start from £25 per tonne and hazardous anywhere from £105 per tonnes up to many hundreds plus a £40 per load fee, any segregation would significantly reduce landfill costs for the Client.
The comprehensive site investigation was requested by the Engineer and included:
- 102 No. trial pits on a 5m x 5m grid (a much more compact grid than would normally be necessary)
- 102 No. asbestos screenings
- Contamination analysis
- Waste classification assessment
- Waste acceptance criteria (WAC) analysis.
CONCLUSIONS AND RECOMENDATIONS:
A waste classification assessment using the contamination analysis results determined the majority of the material on site to be classed as non-hazardous, however in one area, the imported material was classed as hazardous due to high levels of benzo(a)anthracene.
White cement (chrysotile) asbestos was found in one of the samples at a depth of 0.40m. However, asbestos quantification showed this to be a minimal amount of asbestos and the imported material within this area was below the hazardous properties threshold and the material was classed as non-hazardous.
The results of the WAC analysis required the majority of the imported material to be disposed of to a non-hazardous landfill rather than an inert landfill with a small proportion being sent to a hazardous landfill site.
Further testing would allow for the material to be precisely delineated into hazardous and non-hazardous material, providing the Client with an estimated minimum cost saving of £282,000.
|Minimum Estimated Disposal Costs to Landfill
|Without a Comprehensive Ground Investigation||3500||0||374,500*|
|With a Comprehensive Ground Investigation||60||3440||92,500|