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There have been a number of cases over the years where people have successfully sued for this sort of negligence. Your next step is to tell them that you require decontamination, and cleaning by the topdressing form, who should contact. Tell them that if they do not address this then you will sue them for the damage caused which will include any effect on your health, the costs of cleaning to ensure your water is useable, and any setback in progress to organic farming.
You chould gather evidence, such as photos, and statements from peoplw who saw this and prepare to show this to them at the appropriate time. their liability is clear. Assesing the damages will be more complex of course.
thanks for that, could you give me some information appertaining to these cases and where I might find the transcripts of them
I will give some references and some sites. The most complete database is www.nzlii.org.nz which is free. You can also use this site http://jdo.justice.govt.nz/jdo/Introduction.jsp
On spray damage see this case http://www.nzlii.org/cgi-bin/download.cgi/cgi-bin/download.cgi/download/nz/cases/NZHC/1983/8.pdf
Springwood Orchard Ltd v CCL Bins Ltd
A more recent case
Hamilton v Papakura District Council  UKPC 9 and  3 NZLR 308 where the case was lost but has much useful discussion
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