The representative of an environmental advocacy group is questioning the level of copper found in the biosolids produced at the city's Lansdowne sewage plant, saying the number makes it unsafe for application to area farmland.
Maureen Reilly of Sludge Watch, based in Toronto, notes a chemical analysis shows copper at a level of 2,400 parts per million (ppm), which she said is 200 ppm over the allowable limit in B.C., which is already high compared to Ontario and Nova Scotia.
"Natural soil would have 50 parts per million or less," she said. "So to have 2,400 is just a little over what your ordinary uncontaminated farm soils is going to contain."
Reilly said it indicates authorities are giving the city a break because concentrations of other metals and chemicals found in the material remain within the limit although still on the high side.
"What this report from the city does is say 'well, the sludge or biosolids' or whatever happy term they want to use, 'meets the other limits for land application so we're just going to say it's OK, we're just going to let [it be applied],'" Reilly said.
John Lavery of Sylvis, a consulting firm the city has hired to oversee the material's application to farmland in Salmon Valley, did not dispute the findings, which were in an analysis the firm conducted for the city.
But he also said the levels will meet standards once disked into the soil.
"Copper is managed to achieve soil concentrations that are beneficial in an agricultural context," Lavery said in an e-mail.
"Ms. Reilly indicates that an appropriate concentration in the soil would be 20 to 50 ppm. The amount in the soil post application is predicted to be 47 ppm, which falls within that range. Agricultural maximums in B.C. may be up to 150 ppm."
Reilly was also concerned about the level of mercury, which she said should be one ppm compared to four for Prince George biosolids.
Lavery responded that mercury for agriculture-grade biosolids is 15 ppm and, post-application, they're expected to be 0.06 ppm, 10 per cent of the limit under the provincial regulation.
Residents in the Wright Creek Road area in particular have been up in arms over a plan to apply about 2,400 bulk tonnes of biosolids to about 41 hectares of farmland on Pollard Road.
Attempts to deliver the material have been blockaded twice since December and the city is seeking a court injunction to prevent another one.
Reilly said there are better uses for the material, such as harvesting the methane from it and using it as a fuel.
