Successes
New Superstore
JKSL were called in to survey extensive stands of Japanese Knotweed which had gone un-noticed on a proposed new superstore development. Due to initial survey works not identifying the presence of JK, control measures had not been accounted for in the master planning of the project, no budgetary allowance had been made and no time allowance included within the already tight timescales for the works. The main contractor was also on a penalty clause of £250K per week if the opening deadline was missed.
Initial thoughts by the main contractor were based upon excavation and removal of contaminated material to a licensed tip. The cost estimate to excavate and remove the JK came to £2.8 million.
The project works were discussed with Japanese Knotweed Solutions and in close liaison with the Environment Agency alternate solutions were sought. Excavation and removal of JK contaminated material is not only highly costly but also increases the risk of cross contamination. The method is also not environmentally sound as valuable landfill is used as well as increasing road traffic with the numbers of wagons required to move the vast amount of material produced.
The superstore had been approved within sight of a residential estate and as such was subject to strict planning issues with regards to the landscape works. It was proposed to provide landscape bunding to the periphery of the site and to provide screen planting along the mound.
JKSL suggested in-situ treatment of the JK with a herbicide using both foliar applied treatment and direct injection of chemical. Dead surface growth could then be incinerated within the existing areas of contamination. Treated stands could then be carefully excavated and used as sub-soil within the bunded areas. Clean top-soil could then be placed on top of the contaminated material and screen planting incorporated in to the clean top soil. Any potential re-growth would be within landscaped areas and not within the development area – as such an ongoing maintenance plan was proposed and a ten year warranty issued.
This methodology was in line with the EA Code of Practice and cost in the region of £120K, a massive reduction in the proposed £2.8 million off site costs.
Riverside Housing Development
JKSL were called to survey extensive stands of JK on a river embankment in central Manchester. Planning permission had been granted for a riverside development of flats and townhouses adjacent to the River Irwell. Initial survey works had not identified the significant presence of Japanese Knotweed, no budgetary allowance had been made and no time allowance made for the required works.
JKSL were called in to provide detailed survey and recommendations for the works. Discussion with the local Environment Agency officer confirmed that the only approved chemical treatment would be application of a Glyphosate based herbicide which would require 2/3 applications of chemical per year over a three to five year period.
This was totally unacceptable to the developer who had based his costings upon a return on his investment within a twelve month period.
The developer was leaning towards excavation and removal of the contaminated material but had been quoted £1.6 million to have the JK taken to licensed facility. Discussions with JKSL and the local EA officer came up with an alternate strategy based on installation of root barriers along the roadway running parallel with the watercourse. This would contain the JK within the existing waterside location and allow a chemical treatment programme to be initiated whilst building works could proceed.
Root barrier and chemical treatment cost the client £60K which was a massive saving on the proposed £1.6 million off site costs. All works were strictly in line with the Environment Agency Code of Practice
Flood Alleviation Project
The Environment Agency had committed itself to a series of flood alleviation measures on a watercourse within a major conurbation. High profile flooding caused a major problem for the Agency by increasing public demand on the timescales for the work. JKSL were called in to survey JK along the watercourse and strategies for eradication were discussed.
The only chemical strategy approved by the EA is use of Glyphosate based herbicides which require repeat applications of chemical over what is quoted as a three to five year period.
JKSL have carried out detailed works to improve the efficacy of their chemical treatment and offered their experience to the EA. Works were approved and chemicals applied both in foliar applied sections and with a direct injection system. Works to date have shown a marked improvement in performance with timescales being reduced from three to five years to 12 to eighteen months for complete eradication.
