The Mangateretere pond was the most likely pathway by which contaminated water entered the Brookvale Rd borehead 1, the Havelock North Water Inquiry heard today.
Members of a science caucus, that included scientists from Tonkin and Taylor and the Hawke's Bay Regional Council, and was formed after the hearing held in December last year, met under urgency last night to discuss three potential pathways put to them by the inquiry panel.
They agreed that there was a 78 per cent probability the contaminated water travelled from the pond, and suggested a provisional probability that the water entered the bore itself through a defect or hole in the bore casing.
Tonkin and Taylor hydrologist engineer Mr Cussins said, however, "the jury was still out" on whether the water entered through the casing or a screen in the bore, and he recommended to the panel that a short-term investigation be carried out to look into this.
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The caucus gave a 20 per cent probability to the possibility of the water travelling from neighbouring paddocks to dry well and then to bore 1, and issues remained with this theory that were difficult to explain if gland overtopping occurred.
Mr Cussins said it was agreed that the float switch worked, but there was still uncertainty as to the level of the float switch.
A third suggestion that the water entered via neighbouring paddocks to a drain and down the bore's external casing was considered only a two per cent probability.
This theory relied on tracer testings, which included dye testing to assess the potential for the water to track down the outside of the casing.
"This can now be disregarded," he said.
The inquiry will continue today hearing scientific evidence related to the contamination.