The Bay of Plenty Regional Council is implementing control measures around part of the Kopeopeo Canal after recent laboratory data indicated there were elevated dioxins in stop bank surface soils.
As part of preparations for the Kopeopeo Canal Remediation Project scheduled to commence late this year, the council has contracted consultants to undertake sampling and analysis of soils on land surrounding the canal.
These investigations have revealed surface soils along the southern side of the canal between SH30 and Keepa Rd are elevated above national environment standard (NES 2012) soil contaminant standards (SCS) for rural residential land use and, in one result, just above parkland/recreational SCS.
"Due to the existing fencing in the area and the current adjoining land uses, access to the impacted area is limited and it is highly unlikely that locals have had any significant exposure to contaminants," Kopeopeo Canal Remediation Project manager Brendon Love said.
"The NES soil contaminant standards are very conservative. For a rural residential land use scenario, a 30-year exposure period and a variety of exposure pathways, including eating produce grown in dioxin-impacted soil, have been used to derive the SCS.
"This is council-owned land that adjoins the canal and has very limited public or adjoining land owner access."
Although the health risks from contact with the Gateway southside stop bank surface soils are very low, the regional council is taking the matter seriously and implementing precautionary measures to further limit access to the identified areas.
This will be achieved by replacing or improving boundary fencing along the canal, and putting up more signs advising public about the potential health risks. In the long term, the council intends to look at what future management or remediation measures are appropriate. However this work is currently outside the scope of the project to clean up sediment within the Kopeopeo Canal.
"In the meantime we have asked staff at the youth skills training centre to limit student access to the area. We are also meeting with adjoining landowners to advise them of the results and the steps we are taking to fence the affected areas including the northern side of the canal near Paroa Rd and along the canal boundary from Keepa Rd to SH30, where boundary fencing has deteriorated," Mr Love said.
"Council is committed to managing the area into the future. Further sampling and analysis is planned over the next month and this data will provide a better understanding of what long-term management or remediation options may be necessary.
"Late last year the council received results from sampling carried out along Kope Drain Road verges, and on the northern side of the canal between Paroa Rd and SH30. These results all came back very low and near background levels."
On the basis of the data currently available, it appears that the impacted area is limited to the southern side of the canal near Gateway.
"Given that the sawmill historically discharged contaminants into the Kopeopeo Canal in this area, you would expect the concentrations of dioxins in the dredge spoil placed on the canal banks to be more elevated near the discharge point," Mr Love said.
"While we accept that any dioxin-impacted material is likely to be of a concern to the community, it is fortunate that the highest concentrations are in an area with very limited public access."
The council is consulting with adjoining landowners and other community members, and feedback from this process will guide long-term remediation or management options for any dioxin-impacted material above relevant NES soil contaminant standards.