Toxic soil discovered in the vegetable garden of one Auckland kindergarten has been traced to soil excavated from beneath the kindergarten building itself.
Auckland City Council papers released to the Herald in April showed testing at Mt Albert's Ferndale Kindergarten had returned too-high readings for lead, arsenic and benzo-a-pyrene, a
type of hydrocarbon.
Arsenic contamination was found to be nearly 13 times the limit and lead contamination more than seven times the acceptable standard.
The lowest benzo-a-pyrene reading was 20 times above the level high enough to prompt a council investigation of a site.
Ferndale was one of nine Auckland kindergartens or early learning facilities identified as toxic, and in need of a clean-up.
It has been closed while the work takes place.
In a report to Ferndale parents earlier this month, Auckland Kindergarten Association general manager Tanya Harvey said council investigations had found the contaminated soil had been excavated from beneath the kindergarten building about five years ago.
It was mixed with fresh soil bought to the kindergarten when a vegetable garden was established in November last year.
Council had "no evidence to indicate" that the two trailer-loads of soil imported for the vegetable garden were contaminated, the letter said.
The original testing was carried out in April after a study showed an area near the kindergarten was previously used for "horticultural purposes".
The surface samples at one area found lead contamination at 2160 milligrams per kilogram of soil. The acceptable limit is 300mg/kg.
The worst-case reading for arsenic was 384mg/kg. The maximum acceptable reading is 30mg/kg.
In the letter - released to parents on May 15 and supplied to the Herald late last week - Ms Harvey said the lead and arsenic contamination had been traced to a plant nursery that earlier occupied the site.
Trace levels of DDT and Dieldrin found in soil in and around the vegetable garden supported that conclusion, she said.
Benzo-a-pyrene residue found at Ferndale was believed to have come from contaminated soil imported from a gasworks about 40 years ago.
Auckland City Deputy Mayor Bruce Hucker confirmed yesterday that remediation had been completed at all sites, including Ferndale, where final landscaping work is almost complete.
The bill for the nine-site kindy clean-up has been put at $500,000, with landscaping costs yet to be finalised, he said.
About 45 children had been given blood tests following the discovery of the toxic sites, with one youngster showing an elevated lead level. However, it is believed the child - a pupil at Barnardos Early Learning Centre at Freemans Bay - was not exposed to the lead at the preschool.
The child would be "followed up by regional health authorities", Dr Hucker said.
An Auckland City Council desktop survey identified 185 potentially toxic sites, ranging from the kindergartens - which received priority clean-ups - to industrial areas.
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