Business discharge likely contaminant

Samples taken after wildlife died in a Marlborough stream suggest it was contaminated by organic material, or a leachate byproduct.

A business owner was told to stop discharging a liquid which was thought to have contaminated School Creek in Renwick early last month, after residents noticed a smell and an orange, oily sludge appear in the creek.

A Marlborough District Council spokesman said samples collected on April 8 returned elevated concentrations of biochemical oxygen demand (BOD) and iron.

This indicated that the initial thoughts of council investigators were accurate: the creek was impacted by an anoxic discharge, which depleted it of oxygen, and led to an iron-based bacterial growth, he said.

Samples collected further upstream, and of the suspected source of discharge, also showed elevated concentrations of BOD.

The spokesman said this suggested organic material had either been discharged directly into the waterway, or a leachate by-product from organic material had been discharged.

The ph readings measuring the acidity were below the neutral level of 7, indicating the creek and discharge were acidic in nature at these sample points, he said.

There were minor concentrations of hydrocarbons detected in samples collected from the creek adjacent to State Highway 63 but these were likely to be consistent with run-off from the road and were not of concern in relation to the events.

Another round of samples collected on May 4 showed the creek had ‘‘vastly improved’’ following rainfall, the spokesman said.

An abatement notice was issued to the business on April 8.

The business, which could not be identified while actively being investigated, was told to stop the discharge and associated activity.

The council investigation was nearing completion and would be reviewed by the Enforcement Panel. The panel would consider the level of enforcement action.