North Shore City has a long history of commercial market gardens, orchards and glasshouses which spread north following construction of the harbour bridge.
Intensive horticulture however makes plants more susceptible to attack by numerous pests subsequently chemicals are used to protect crops. Over time this can lead to an accumulation of pesticide residues in surrounding soils.
In 2001, the Auckland Regional Council and the Auckland District Health Board undertook a sampling programme of 43 horticultural sites within the Auckland region. The results of this sampling programme were that pre 1975 horticultural activity resulted in the presence of harmful levels of chemical residues on 69 per cent of horticultural sites.
Following the receipt of this report North Shore City Council initiated a desktop study using old aerial photographs to identify any properties within North Shore City boundaries that may have been used for horticultural purposes prior to 1975.
Following the mapping of historical horticultural sites Council has undertaken testing of land that it administers (such as roads and reserves) that were historical horticultural sites. More than 400 soil samples were tested at council-owned sites across the city. Of the 67 sites previously used for horticultural purposes, only five were found to have elevated levels of horticultural spray chemicals remaining in the soil. ARC-approved remediation work is underway at all these sites, which will ensure there is no risk to public health.
Currently agreed regional guideline levels are being used as the basis for council's approach. It is understood that the Ministry for the Environment is continuing to research the introduction of national guideline levels for contaminants. Should guideline levels change then council's approach may also change if need be.