Underground wall on post office site working to hold back creosote: study
Hazardous material had been seeping for decades into Saint John's Marsh Creek
An environmental study says a special underground wall installed on a contaminated Canada Post property is working to prevent the spread of toxic creosote into Saint John's Marsh Creek.
The heavy steel wall was installed in 2014 behind the Rothesay Avenue mail sorting station on property that was for decades home to a creosote plant.
The wall is known as a "Waterloo Barrier" because it was designed by researchers at Ontario's University of Waterloo to control the passage of groundwater containing contaminants like those found in creosote — a hazardous material used as a wood preservative.
The wall's joints contain a sealing material to help hold back groundwater.
Seven new groundwater monitoring wells were installed at the site in 2015 and overseen by staff from Stantec Consulting.
"The absence of measurable [contaminant] accumulations in the sheet pile wall monitoring wells and the consistent occurrence of [contaminants] in the recovery wells indicates the sheet pile cutoff wall is effective," said the December study authored by Stantec's Robert Fiander.
Health risks with exposure
An earlier 2004 report by the non-profit group ACAP Saint John, said creosote deposits in sediment on the bottom of the river itself had been recorded at levels as high as 700,000 parts per million.
"Roughly 70 per cent creosote to 30 per cent sediment. With such a high concentration of creosote, the Marsh Creek deposit could have serious health risks associated with direct contact," said that report, authored by Craig Silliphant, Tony Matthews, and Tim Vickers.
The creosote plant operated from the early 1930s until about 1970.
Sediment wasn't cleaned up
The ACAP report says creosote from fresh treated wood was allowed to seep into the ground on the site and even to drip directly into the creek from rail cars parked on a bridge spanning it.
The report said removal of the creosote in Marsh Creek "would constitute the single greatest remediation of a hazardous site in Saint John's history."
No major cleanup of the creek's sediment has been attempted.