Historic agrichemical use and development
If you intend to develop your land it is important to know that there are national environmental standards that you may be subject to, in addition to the Hastings District Plan.
The National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health (NESCS) is a standard you need to be aware of.
The NESCS Users’ Guide says that New Zealand has a legacy of soil contamination that is mainly associated with past practices involving storage and use of hazardous substances, and disposal of hazardous wastes. Common past activities and industries that have led to the creation of contaminated sites in New Zealand are:
- the manufacture and use of pesticides
- the production of gas and coal products
- the production, storage and use of petroleum products
- timber treatment
A more comprehensive list of activities and industries can be found on the Hazardous Activities and Industries List (HAIL) which is Appendix C of the NESCS Users Guide.
The contaminants in soil left by these activities and industries include:
- pesticides (such as DDT, DDD, dieldrin)
- metals (such arsenic, chromium, copper, lead and mercury)
- hydrocarbon compounds.
Contaminants are a problem when they are at a concentration and a place where they have, or are reasonably likely to have, an adverse effect on human health and the environment. Contaminants pose a greater risk where they are near buildings, people, water bodies and important habitats, and when they are in soil in which food is grown.
The National Environmental Standard ensures that land affected by contaminants in soil is appropriately identified and assessed when soil disturbance, change of use of land, or subdivision take place and, if necessary, remediated or the contaminants contained to make the land safe for human use.
Further information and a copy of the NESCS can be viewed at: http://www.mfe.govt.nz/land/nes-assessing-and-managing-contaminants-soil-protect-human-health/about-nes
For further information, contact the Council’s Duty Planner on 06 871 5000.
In Hastings District, testing has shown the contaminant residues are mainly arsenic, lead, copper and DDT because these agrichemicals were used extensively under government registration to control agricultural pests and diseases on horticultural land, and in glasshouses, until they were withdrawn from sale about 1975. (Some tobacco growers continued to use DDT until about 1985).
These are persistent agrichemicals that tend to bind tightly to the soil, most often in the top 10cm, and may be present in the soil as contaminant residues long after they have been applied. The more soluble arsenic may leach slowly into the groundwater. These contaminant residues may also remain in the soil near old spray sheds and in farm dumps.
Generally, commercial crops grown on this soil comply with the level of residues permitted in the Food Standards Code, because these particular contaminant residues are not taken up by most plants. The concern is that this contaminated soil may pose a human health risk when the land changes from agriculture/horticulture/glasshouses to domestic housing because then people, especially children, may be exposed to the contaminant residues through eating dirt either intentionally or unintentionally after handling or playing in dirt. Dairy and organic farming may also be restricted on this soil.
Modern agrichemicals are less persistent – they generally break down in days and weeks, therefore broad scale residues are not of concern, although modern pesticides may be of concern in “hotspot” areas created by spills or where agrichemicals are stored (spray sheds).