Officials agreed to let mercury-laden M3 waste be flushed into Belfast Lough, file reveals Some of the land on which Belfast’s newest motorway was built was so dangerously polluted that it would not just […]

Some of the land on which Belfast’s newest motorway was built was so dangerously polluted that it would not just harm human and plant life but could erode buildings – yet officials agreed that water from the construction laden with mercury end up in Belfast Lough.

Files which have just been declassified at the Public Record Office in Belfast show that in 1992 Stormont’s Department of the Environment was aware of exceptionally high pollution readings from some of the areas being excavated for the motorway bridge which spans the River Lagan, connecting north and east Belfast.

A minute of a meeting between officials on May 8 1992 to discuss the £32 million project was told by a Mr D Hamilton from Roads Service that in water at some of the sites “mercury was detected in the samples (not previously detected in the soil samples) at a level 5,000 times more concentrated than recommended”.

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The officials agreed that a long-term solution would be to have “the whole road formation sealed with impermeable membranes [meaning that] none of the contaminated groundwater could seep into the road drainage system, and therefore contamination was not a problem, long-term”.

Lead, mercury, arsenic and sulphate pollution

But there was a short-term concern about water during the construction phase.

The most seriously polluted section was in the Dalton Street area of east Belfast, the site of a former chemical works and where the M3 joins the Sydenham bypass.

A report by expert scientific consultants said that “contamination by arsenic, lead and sulphate in the Dalton Street depot is extremely heavy … contamination by lead was widespread … total sulphate values at all locations were extremely high”.

Key meeting

A draft note of a meeting between Roads Service, Water Service, environmental and scientific officials to discuss how to deal with contaminated water from boreholes at the site recorded that the Water Service had calculated that the maximum weight of mercury which could be allowed to discharge into the River Lagan – and onwards into Belfast Lough – was 5kg per day.

The Environmental Protection Division representative, Mr C Henry – who appears to have been the official raising questions about the issue – told the June 5 1992 meeting “in the worst case scenario they calculated that approximately 4.4kg/day of mercury might be discharged into the river”.

That minute was redrafted to say that “although undesirable, it would not compromise the department’s water quality objective for Belfast Lough of 0.5 ug/l due to the dilution available”.

The officials said that the possibility of reaching that situation was “extremely slight” but that in order to ensure that pollution was not worse than estimated, the levels of toxicity would have to be tested daily.

Mr Henry suggested that there could be a holding tank for the pumped water “so that if tests showed high concentrations of contamination the water flow could be stopped”. But a Roads Service official, Mr McCambley, said that even if a tank large enough to hold 24 hours’ worth of pumped water was available “it would probably be too late to stop the flow into the sewers” and therefore “documentation of tests would probably be enough”.

The meeting agreed that “the pumped groundwater during excavation can be discharged into Middlepath Street sewers, provided testing is carried out to monitor the contamination”.

Toxic waste buried where film studio now sits

Initial samples suggested far higher toxicity levels but further tests found “little contamination of the groundwater apart from that due to sulphate”. It appears to be this second set of tests – three weeks before the meeting – which led to the calculation of up to 4.4kg of mercury daily ending up in Belfast Lough.

Officials also agreed with Belfast City Council that much of the contaminated solid waste – estimated to be 2,294 cubic metres – could be dumped in what was then a landfill site but which is now being redeveloped as a business park and film studio at Belfast’s North Foreshore.

An appraisal by Ove Arup & Partners engineering consultants warned that as well as a risk to human and animal health from the toxic substances, “the contamination at the Dalton Street Depot is likely to be highly aggressive towards conventional building materials” and would require materials such as concrete and steel to be protected.

However, the engineers concluded that “the contamination discovered during the site investigation is not likely to significantly affect the construction of the road and rail links”.

It did, however, recommend that “further investigation and testing may be necessary to confirm the suitability of adjoining land for other uses”.

Two years ago a study published in the journal Nature found that the amount of mercury near the surface of many of the world’s oceans has tripled as the result of human activity.

For years, pregnant women have been warned to limit their intake of certain types of fish due to the accumulation of mercury in their flesh.