Pandora Pond's location meant possibilities ranged from birdlife, boats dumping sewage, to industry ruminant. The council needed a faecal sample to be able to trace the source.
Staff were taking daily samples at five locations around Pandora Pond and Ahuriri Estuary - including at the Pandora Splash Zone, the Westshore Bridge, and the rail bridge - which had recently been returning clear.
"It's quite challenging for us because the pattern of contamination hasn't followed the traditional, or typical one of being associated with rainfall events," he said.
"There's no obvious source [like] an illegal discharge or accidental spill or something that may have contributed with it that fits with the timing of the samples."
The contamination has also caused changes for the long-running Tremains Triathlon event. Held next Sunday, it was to include a swim/kayak and stand-up paddleboard leg in Pandora Pond.
However, yesterday a Tremains spokeswoman said due to the contamination, triathlon organisers had decided to replace this section of the triathlon with a 2km run/walk.
"The health and safety of our competitors is the main priority for us and we believe it is in everyone's best interest to make this decision early to allow time for competitors to adjust to the new leg and/or make arrangements as necessary," she said.
"This change means that the event will be solely based from the new finish area at the Meeanee Quay Reserve. New maps of the run courses will be sent out to all competitors and available on our website. The cycle leg will remain the same."
The closure of the pond has already meant the move of a Canoe Polo Hawke's Bay tournament last weekend, and the suspension of some school activities.
Earlier this week Mr Maxwell told Hawke's Bay Today small amounts of each sample were sent for testing, with results received within 24 to 48 hours.
"If the smaller sample comes back with high bacteria readings then the larger sample is sent for faecal source tracking - which identifies if the contamination is ruminant, avian or human.
Once this returns - which can take several weeks - staff can start trying to identify the source.
"If it is avian (birdlife) there is little that can be done as the area is popular for birds. If it is ruminant (four-legged animals – sheep and cattle) then HBRC staff can investigate the possibility of stock getting access to waterways further upstream.
"If it is human then potential sewage leaks can be investigated and other potential human contamination."
-Entries for the March 11 triathlon are still open at tridentresults.com/event/190.
-Visit tremainstriathlon.co.nz for up to date information. Questions can be sent to Tremains Triathlon at Tremainstri@tremains.co.nz
