Community Garden on Contaminated Orchard Land
An urban council owns a 0.4 ha former orchard site and has leased it to a community garden trust for 18 months. The garden has 24 raised plots, 60 households on the waitlist, and an $18,000 grant for a tool shed and water tank. Soil tests taken by a university class returned lead at 180–340 mg/kg across the site. The council’s contaminated land officer says this exceeds the guideline for residential soil in some plots and advises against growing leafy vegetables in the ground. The trust has already planted winter crops in three beds. A local marae has asked to establish a māra kai on four plots to supply kaumātua with kūmara and greens. Replacing all soil in raised beds would cost about $32,000; capping and using raised beds with imported soil would cost $21,000. Testing each plot costs $450. The lease says the council must be notified of contamination ‘without delay’.
1. Explain the causes and likely effects of the lead contamination in this garden, and why the trust’s current planting plan is risky.
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Causes: lead arsenate and other lead-based sprays used in old orchards persist in topsoil; lead binds to soil and does not break down. The site’s history, not current gardening, is the main cause. Effects: lead can be ingested via soil on hands, dust, and poorly washed vegetables; leafy crops and root crops can accumulate lead, and children are more vulnerable. The trust’s winter planting is risky because three beds are in ground that may exceed the residential guideline, and the trust has not yet mapped which plots are worst. ‘Exceeds in some plots’ is not the same as ‘all safe’ or ‘all unsafe’ - uncertainty matters. The marae’s māra kai plan adds a cultural duty: food shared with kaumātua should not carry avoidable exposure. Notifying the council is a lease obligation, not an admission of fault. A defensible response separates the precautionary action (pause harvest) from the investigation (plot-by-plot testing).
2. Recommend immediate and longer-term actions. Show how you would apply precaution, kaitiakitanga, and partnership with mana whenua, and what evidence would change your mind.
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Immediate: stop harvesting and eating from ground beds; tell the council in writing; inform plot holders and the marae with the actual results; cover bare soil or keep it damp to reduce dust; keep children out of bare soil. Short term: test each plot ($450 each; prioritise the three planted beds and the four marae plots); remove or isolate the worst soil; use raised beds with imported, tested soil; grow leafy crops in containers. Longer term: apply for the $21,000 capping/raised-bed option, redirecting the $18,000 grant only if the funder agrees; co-design the māra kai with the marae so decision-making sits with mana whenua, not just consultation. Precaution: avoid claiming the garden is safe until tests and a council officer confirm it. Evidence that would change my mind: low, consistent lead levels below the relevant guideline across plots, or a validated remediation that meets the standard. Kaitiakitanga here means protecting people and soil, not abandoning the garden.