Brownfield Site Transformed for Stylish Waterside Homes Herons Reach Japanese knotweed clearance

Herons Reach is set to become a waterside development of stylish, modern properties; a heavily overgrown brownfield site made this seem unachievable, however, Wiggett Homes can now commence their construction phase in 2019 following Ebsford’s work at the site. This far-reaching project involved not only the screening of Japanese knotweed contaminated material using Ebsford’s bespoke screening equipment, but also vegetation clearance, the removal of the banking wall, removal of a concrete structure, and ultimately, the creation of a contamination-free and tidy site in just three short months.

The site posed a significant obstacle to a construction programme in the form of a large Japanese knotweed infestation; this was intertwined with the wall along the watercourse, and therefore had to be removed in its’ entirety. This aspect of the works presented further challenges, with foundation stones unexpectedly discovered, as well as a concrete structure believed to have remained from an historical mill at the site. The removal of these additional barriers lengthened the project, but were successfully overcome by the Ebsford team.

All the while, Ebsford navigated working near water, with silt curtains and sedi-mats to prevent sediment traveling down-river, as well as a nesting bird exclusion zone, and a gas main to consider during excavation works. An unexpected pocket of contamination was also encountered approximately 25 metres from the road bridge of the site; control measures were put in place for the remainder of the banking works to mitigate any further risk of contaminated substance leaking in to the river. This consisted of a spill boom (a large spill sock which spanned the river), and a secondary bund of clay-like material to keep any suspected contaminated material in place.

The screening process took four weeks to complete. The Enviroscreen 20:20 technology is a revolutionary mechanical solution for the control of Japanese knotweed. The machine took ten years to develop using experience gained from working on some of the most logistically complex construction projects ever undertaken. The system processes Japanese knotweed rhizomes through a mechanical soil separation unit; the material passes down conveyers before being passed through the screener and split into three fractions - oversized, mid-sized and fines; it is then manually picked to further remove rhizomes.

Throughout the project, 0% waste to landfill was achieved. The fines material created from the screening process is to be re-used on site – this simply must be capped with 600mm clean soils anywhere on the site. The rhizomes garnered were also prevented from creating a waste product to be disposed of – through the obtaining of an exemption from the Environment Agency, rhizomes were incinerated on site. Furthermore, other clean material generated from the screening process was re-used elsewhere on site, to raise site levels.

Ebsford saved the client approximately 50% on the traditional method of off-site disposal, with costs estimated to be above £300,000. This method would have meant a vast number of approximately 220 lorry loads needed to be removed from site, and would have had caused significant disruption for those in the residential area; the considerable carbon footprint associated with the use of wagons was also negated. Upon completion of the project, Ebsford had allowed the client to utilise brownfield land whilst reducing the sting of land preparation costs, leaving the site infestation-free for the client’s construction phase, whilst also halving traditional costs and eliminating all waste from site, mitigating considerable environmental impacts in the form of a 0% waste solution.