MBC has been working on the Cashmere High School redevelopment for over five years, with Arrow International for stage 1 and Leighs Construction for stage 2. During the course of the project, dealing with contaminated soil has been a regular occurance. From minor discoveries during drainage works to large scale remediation of entire block footprints. Each situation has required a different approach and close collaboration with numerous interested parties, all whilst the school continued to operate around us.
Example 1 – PAC Building
At the start of the demolition of the Performing Arts Centre, asbestos pipe lagging was discovered sub-floor, along with other contaminated materials and soil. This required the removal of the contaminated materials, in order to provide a clean site for the demolition work and new build. Due to the nature of the contamination and the presence of highly friable material, all work had to be conducted by hand. Over 62 tonne of contaminated material was carefully removed from the sub-floor, under controlled conditions, over a three month period.
Example 2 – Science Block
A different approach was used for the removal of contaminated soil in relation to the demolition of the Science block. MBC conducted thorough surveys of the sub-floor, well in advance of works, discovering large quantites of contaminated material. As the contaminated material was known to be present and could be stabilised in-situ, it was possible to demolish the two storey building to floor level. The timber flooring was carefully removed in sections, with removal of loose materials and services by hand.
Remediation of the ground was undertaken with an excavator, using a staged approach. MBC worked closely with the demolition contractor, contaminated land specialist and asbestos assessor to remove approximately 132 tonne of contaminated material over a three week period.
Example 3 – contaminated stockpile
Asbestos cement sheet fragments were discovered in a stockpile of excavated material that was scheduled to be sent off site as cleanfill. Unfortunately, at the time the ACM was discovered, the stockpile was 750m3 in size, with contamination scattered throughout.
Disposing of the soil as contaminated waste would have been prohibitively expensive. Fortunately, testing of the soil itself demonstrated that it was otherwise clean. MBC worked collaboratively to develop an approach to screen the soil, with the fragments being removed by MBC’s skilled operatives.
A highly systematic approach was required, with numerous screening bays and testing of each load, prior to leaving site. The end result was that the entire 750m3 stockpile of soil was able to leave site as cleanfill – a great result for the client, financially and environmentally.
