PROJECT EXAMPLE: knotweed and asbestos remediation method reduced carbon footprint
On this contract not just Japanese knotweed, but Buddleia and Asbestos were found in the contaminated ground. Using a specific method of ground remediation reduced the carbon footprint for the contractor.
Japanese Knotweed Ltd was contracted to clear Japanese knotweed and vegetation (predominantly Buddleia) from a commercial site in Yorkshire that was planned for sale. Whilst undergoing phase one of the two-phase project non-licensable asbestos was also identified in the ground. Both knotweed and asbestos were cleared from this site at the same time – saving the client time to source an asbestos removal contractor, as our team of operators were already onsite and fully licensed to handle both issues at the same time. The client swiftly received a revised quote for the additional works.
About the site
Sites that have been left for some time allow knotweed and other invasive plants to flourish. This site was formerly Bingley Police Station, which had previously been demolished and cleared. The land covered approximately 0.3 hectares, with two small patches of tarmac hard standing and the site was partially enclosed by the former stone wall of the police station. At the time of survey the land had been colonised with ruderal weeds and dense vegetation.
The perils of ignoring knotweed
Knotweed was found at two primary locations. Both sites displayed mature knotweed and evidence of last season’s knotweed (dead canes). In agreement with the client full excavation and cart-away to landfill of all hazardous soils was to be completed. But before any excavation works could begin the vegetation was flailed to ground level.
By excavating a test pit to identify the extent and depth of the knotweed, we found rhizomes extending down to 1.7m from the existing ground level making the full excavation depth, including the mound of the prior demolition material, in excess of 3.5m. This clearly showed that knotweed was present prior to demolition and was likely to have been a long-established area of growth.
A row of concrete pillars were uncovered that were clearly structural support for a boundary wall. Knotweed rhizomes were found to be growing through cracks in the concrete wall, but as we needed to keep the wall intact, these areas were instead marked for future identification. The supporting pillars would be sealed beneath a root barrier to prevent growth from any knotweed rhizomes within the wall.
Brownfield sites often contain soils contaminated with asbestos
During excavation Asbestos Contaminated Material (ACM) were spotted by the team. Soil samples of the suspected asbestos material were sent to a lab for analysis, and work was stopped pending the results of the testing.
Note: All construction works must come to a halt when asbestos or knotweed is suspected, or found on site.
Full excavation of the knotweed was completed and stockpiled ready for removal to landfill, whilst we dealt with the asbestos. All ACMs were hand-picked by our qualified team, double bagged and placed in a sealed skip ready to be removed to a licensed disposal facility. Any soils containing incidental asbestos (too small to be hand-picked) and minimal knotweed material were removed to landfill. Soils that did not contain asbestos were separated and removed as non-hazardous soils.
Future-proofing the site
A vertical root barrier was carefully installed to the site walls, making sure it molded to the pillars. Full excavation and removal of all knotweed and asbestos contaminated ground left the site clean and clear for future development. We left the ground level slightly lower than we would normally, so that potential developers would be aware of the pillars. The site is monitored for the duration of the 12 year guarantee period.
improved carbon footprint
Sorting the waste into categories on site demonstrates that we are not removing unnecessary materials to landfill. This gives us and our client a greener footprint and improves the site’s waste management record, all of which is a more environmentally sound solution.
If you’d like a quote for multi-contaminant ground removal, or you’d like us to carry out a pre-purchase or pre-commencement survey contact the team.