Primary School on a Former Metal-Plating Site
A school board plans a 1,200-pupil primary school on a 2.4-hectare former metal-plating works. Soil sampling finds lead at 1,200 mg/kg and arsenic at 45 mg/kg in the top 0.5 m; groundwater is not used for drinking. The playground is designed over the former plating shop floor. Children aged 5–11 will attend, and the board wants to open in 18 months. The remediation quote for full soil replacement is high, and the board proposes a geotextile membrane and 300 mm of clean topsoil over the entire site, with raised beds in the playground. The health department must advise whether the plan is acceptable and what conditions are needed.
1. Is the proposed capping and clean soil cover acceptable for a primary school? Justify your answer and state the conditions.
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Capping can be acceptable, but not as described. The contaminants are lead and arsenic, and the critical pathway is ingestion of soil and dust by children through hand-to-mouth behavior and play. A 300 mm cover with a geotextile membrane reduces direct contact, but it is vulnerable to breaches from drainage works, planting, play equipment, and future utility trenches. The playground over the former plating shop is the highest-risk area and should be hard-surfaced or use a raised, sealed deck rather than turf.
I would require: a marker layer and visible warning barrier; a minimum cover depth supported by site-specific risk assessment, not a generic number; verification sampling of the final surface; dust suppression and air monitoring during construction; no vegetable gardens or fruit trees; sealed joints around equipment; and a legal covenant plus a school maintenance plan. Groundwater is not a drinking-water pathway here, but runoff must not pond. Without independent verification and long-term institutional controls, the plan is not acceptable.
2. Map the exposure pathways during construction and after occupancy, and explain how site design should interrupt them.
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During construction, the receptors are workers, neighbors, and future pupils. Pathways are inhalation of lead and arsenic dust from excavation, dermal contact, and ingestion from dirty hands or food. Controls include enclosed excavation, water sprays, wheel washes, air monitoring at the fence, clean changing and washing facilities, and no eating on site.
After occupancy, the main pathway is ingestion of contaminated soil or dust tracked indoors, plus inhalation of resuspended dust. Design should interrupt this at the source: keep contaminated soil under an intact cover, use hardscape and raised beds, provide shoe-cleaning and hand-washing stations at play areas and entrances, and ensure drainage does not erode the cover. Also control access to any exposed soil margins and require immediate repair of breaches. The most vulnerable are young children, especially those with pica, and pregnant women. The design should assume children will dig, fall, and put hands in mouths.
3. What post-occupancy monitoring and governance would you require?
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Require an annual cover integrity inspection by a qualified person, with photographic records and repair deadlines; surface soil and dust-wipe sampling in play areas and classrooms in the first year and then at a defined frequency; and a dust-monitoring trigger for any works. The school should hold a soil management plan that prohibits digging, garden beds, and unapproved landscaping, and requires approval before any utility trench.
The local authority should register an institutional control or covenant on the title so future owners cannot remove the cover without assessment. Include a parent information session at handover, a visible contact for concerns, and a protocol for unusual illnesses or blood lead testing if exposure is suspected. Do not rely on a one-time clearance certificate. The governance test is whether the barrier and the restrictions survive changes in school leadership, contractors, and budgets.