Silage surprise suspect in water woes
Silage pits on a farm near the Opihi River may have contributed to Timaru’s discoloured water woes that began in late 2021.
Environment Canterbury has confirmed in information obtained by The Timaru Herald under a Local Government Official Information and Meetings Act (Lgoima) request that it has been working with a landowner in the Waitohi area as groundwater investigations continue into the source of the high manganese levels that caused ‘‘Timaru’s water discolouration event’’.
‘‘Simultaneous to the science monitoring, we have been working with a landowner who agreed to voluntarily move some silage pits that could be a contributor to high manganese levels near the intake, as a precautionary approach,’’ Katherine Harbrow, ECan’s director operations, said.
‘‘We can’t say if the pits are definite contributors to the higher manganese levels,’’ Harbrow said.
‘‘... we will share the report on the groundwater results once finalised in July’’.
Information in the Logima documents show a conversation between ECan resource management officer Craig McLachlan and the unnamed farmer from March 10 to May 2 about shifting the silage. Removal of the silage was under way by April 5 and on April 6 the landowner said they would be able to move 30m3 per day.
By May 2 about a quarter of ‘‘the total pile was left to remove’’ but no work occurring with the farmer saying they would start again the next day.
An undated post, the final one, said ‘‘removed all but 1% of the total volume’’.
At the height of the discolouration issues, the Timaru District Council brought in tankers from December 20 to February 21 to three different locations filled with water from water supplies other than the Opihi River intakes.
The discolouration was first blamed on a mix of algae and manganese but in February 2022 the Timaru District Council’s drainage and water manager Grant Hall said test results from a laboratory had revealed that the high level of manganese was the main culprit.
‘‘The algae hasn’t continued and manganese has now been identified as the dominant cause of the discolouration,’’ Hall told The Timaru Herald on February 2.
Hall said then it would be a few months before they find the original source of the manganese.
Hall, along with council’s group manager for infrastructure, Andrew Dixon, and council’s three waters advisor, Ashley Harper, said that the higher levels of manganese had ‘‘never seen before’’, was ‘‘very odd’’, ‘‘not a common occurrence’’ and ‘‘very very strange.’’
Manganese is one of three toxic essential trace elements, which means that it is not only necessary for humans to survive, but it is also toxic when too high concentrations are present in a human body, according to Lenntech, a world-wide water treatment solutions company.