Area under treatment: over 200 sq. metres.
Technique: control of dug-out soil and cleaning off the equipment before leaving the site.
Excavation of trench was required to lay the pipes in the area occupied by Japanese knotweed. The Environment Agency recommends that all excavation works must be supervised by specialist company to prevent spread of a knotweed-containing material off-site.
Japanese knotweed was scattered sporadically across the site. The height of the canes varied from 1 to 1.5 m.
Further, there were small a couple of inches shoots visible within 0.5 m from the edge of the proposed trench.
A 1 m deep by 1 m wide trench was to be dug on the site. Ten pipes 100 mm diameter were to be laid to provide services.
Our surveyor in Japanese knotweed observed the area throughout all excavation work to make sure if Japanese knotweed is treated properly and did not leave the site.
After the trench was dug out a scrutiny of the trench was carried out by surveyor. It should be noted that the exterior of Japanese knotweed rhizomes is carrot coloured, pale orange to light yellow in colour. As during the digging, the underground parts of the plants are hardly damaged these features would be clearly seen at the edges of the trench. However, features that resemble the rhizomes of Japanese knotweed have not been found in the trench. Thus, Japanese knotweed that is present on site slightly affected the location of the trench.
After inspection of the trench the pipes have been laid inside. Our surveyor assisted to clean shoes of the workers prior to leaving the site when required to minimise the probability of spread of Japanese knotweed off-site.
When excavation was completed cleaning of the digger was carried out by our surveyor. Cleaning the equipment involved in works on sites infested with Japanese knotweed prior to leaving the site is the requirement of the Environment Agency. Photograph of the digger shows that there is a lot of soil in the track system and on the track pads that potentially may be contaminated with Japanese knotweed material.
A pressure washer was was provided by the client. The digger was moved to a distance of about two metres from the fence bordering the site. This distance is far enough to prevent from splashing washed out soil off-site and sufficiently short to leave site safely, e.g. with sufficiently low risk of being re-contaminated. The digger was risen thus leaving the gap between the track pads and ground level of about one foot. The appearance of the fragments of track pads and track system after completion of washing are illustrated below. It can be seen that the soil was carefully removed. Other external parts of the digger, e.g. bucket, cabin, etc., have also been cleaned accordingly.
After washing, the plywood was deployed under the tracks to minimise contamination during leaving the site.
The final set of photographs displays the cleaned digger prior to leaving the site safely through the plywood paths.