Edenvale Reserve soil contamination

The southern third of Edenvale Reserve, which has been closed for remedial work, is now open to the public. In 2003 the soil at Edenvale Reserve in Mt Eden was found to have slightly higher than usual traces of metals and hydrocarbons.

Although there was no immediate risk to park users' health, Auckland City decided to cap the contaminated soil with plastic matting and 100 millimetres of clean topsoil. The work was completed on 24 May 2004.

The area, along with the children's playground, was kept closed until now to allow the new grass to fully establish and the ground conditions to dry out and become firm.

Background

In December 2002, soil at Edenvale Reserve in Mt Eden was found to have concentrations of metals and hydrocarbons above typical background concentrations. Testing showed there were low concentrations of metals including chromium, copper, nickel and lead, and low levels of cyanide and also polycyclic aromatic hydrocarbons (PAHs), including benzo(a)pyrene. The contaminants of concern were lead and benzo(a)pyrene.

The most likely source of the metals, PAHs and cyanide is from fill materials, which appear to have been incorporated into park soil during landscaping. PAHs are formed from the burning of organic substances such as coal, oil, gas and refuse. The presence of very low concentrations of cyanide in combination with the PAHs and metals suggests the contaminants may be from gasworks waste.

The soil lead and benzo(a)pyrene levels do not present a health risk to the average park visitors. The potential for health risk occurs for extreme cases where visitors routinely ingest significantly more soil than average.

The most likely group to be at risk is a small proportion (5 per cent) of the estimated 25 per cent of children that exhibit "pica" behaviour (eating disorder), ie about 1 in 80 children. These children are typically aged between 1 and 4 years. The children would need to ingest about 200 milligrams of soil every two days for about three months (equivalent to a total of approximately 2 teaspoons) to have the potential to be at risk from the lead in soil at Edenvale Reserve.

Auckland City Council considered closing the park but tests and other research, which defined the risk levels in detail, found this was not necessary.

Practically the entire park is covered in grass, bark or playground surfacing, and the potential for direct contact with soil is minimal. The actual soil intake is likely to be significantly less than assumed in calculations because of the cover. Thus the risk to park users' health is considered negligible. However, to be conservative, Auckland City decided to undertake remedial work on the reserve.

The approach was discussed with the Regional Public Health Service, the Auckland District Health Board (ADHB), which were in general agreement.

An Assessment of Environmental Affects (AEE) was prepared. Resource consent obtained from the Auckland Regional Council and Auckland City Council. The council is looking into whether any other reserves should be investigated, based on their previous land use.