Risk reduction is primarily a matter of removing or containing the source of the risk. There are a number of alternatives for preventing exposure, including capping and paving, and these could be applied where appropriate. An analysis of the actual risks posed in particular situations would be required on a site-specific basis to determine the appropriate risk reduction method. In many instances, particularly for medium- and large-scale PCP use sites, removing the source (by excavation) does not appear to be a practicable alternative until an economic means of treatment is available.
Based on the results of the study in considering Table 4.1, the following comments address risk reduction measures in relation to landuse and the scale of PCP use,. These comments are subject to the qualifications outlined in section 5 when taking into account the interim guidelines of Table 5.1.
6.1 Ongoing sawmill/industrial use
Small-scale users
For most areas it appears that the surface could remain unpaved, given that none of the locations investigated had dioxin concentrations above the unpaved industrial criterion.
Medium-scale users
In most areas the surface could remain unpaved. The locations more likely to be contaminated should be paved and some may require a management plan to be developed.
Large-scale users
As for medium-scale sites, in most areas the surface could remain unpaved. The locations more likely to be contaminated should be paved and some may also require a management plan to be developed.
6.2 Residential use
Small-scale users
The dioxin concentrations in most areas of small-scale PCP use sites are likely to be below the residential criterion. For any particular site where it is known that the residential criterion is exceeded, these areas would need to be excavated, unless it could be guaranteed that they would be covered with paving.
Medium- and large-scale users
Most site areas are likely to be above the residential criterion, and it is unlikely to be practicable or economic to clean such sites to meet this criterion. Therefore such sites should not be allowed to have a change in land use to residential, unless there is validated clean-up to the residential criterion. In cases where un-remediated sites are abandoned, they should be fenced and secured against unauthorised occupation. A grass sward should be established and regularly maintained to minimise the run-off of contaminated sediment.
6.3 Agricultural use
Most areas of all sites where PCP has been used will have soil dioxin concentrations above the agricultural guideline value. These sites should not be allowed to have a change in use to agriculture. In cases where such sites are abandoned, they should be fenced and secured against unauthorised use. A grass sward should be established and regularly maintained to minimise the run-off of contaminated sediment.
See more on...
6. Options for risk reduction
March 2008
© Ministry for the Environment