Two landfill sites formerly owned by the district council are creating the highest concern in relation to contamination of Waikanae Stream.
The stream is in poor ecological condition, according to a report prepared for Gisborne District Council’s environmental planning and regulations committee.
In the report, environmental risk team leader Kate Sykes says the Waikanae Stream contaminated land investigation project has painted a picture of poor health and identified contaminants of concern in all the site investigations.
Eight sites were chosen for investigation and contaminants of concern were identified at all.
The council previously owned five of these sites.
Of greatest concern are the former landfill sites at the airport and in Innes Street.
The latter is in the industrial subdivision and has been affected by industrial and light commercial users and storage of contaminants since 1978.
While the Innes Street site is now partially owned by the council and the Department of Conservation, the report says the council has a moral responsibility to take ownership of the issues caused by its historical use as a landfill.
Both sites require remedial works to address contaminants still leaching into the stream.
There is also concern about a section of the stream by the Alfred Cox walkway, which was used as a landfill from 1957 until some time in the 1960s and may have also been influenced by a former copper chrome arsenic treatment plant between 1980 and 1994.
That area is a registered contaminated land site under the council’s Tairawhiti Resource Management Plan.
The report says the middle reach of the stream from Aerodrome Road to the Grey Street Bridge has substantially degraded water and sediment quality.
It says the benthic (sediment-dwelling) fauna is likely to only comprise pollution-resistant species such as mud crabs.
Suite of actions recommendedHeavy metals are present in the sediment indicative of the HAIL (Hazardous Activities and Industries List) activities that have occurred or are occurring along the reaches of the stream.
The downstream reach between the bridge and the stream mouth has the highest habitat value and visibly better water quality and clarity. This is probably due to the strong tidal influence and regular flushing from tidal flows.
A consultant’s report has provided a suite of recommended actions for improving the stream’s health.
The project to date has cost $197,781 of which $84,500 has been funded by the Ministry for the Environment.
There is enough funding in the current long-term plan to cover the costs of further investigation work and the resource consents needed to undertake remediation and allow for a residual discharge.
The extent of the remedial work is unknown and staff will need to reprioritise budgets.
Another application will be made to the Ministry’s contaminated site remediation fund after a previous one was unsuccessful.