KEY POINTS:
It's the question no one seems able to answer: just who or what is putting the pee and other nasties into Piha?
The lagoon at Piha has long been one of Auckland's most favoured spots for safely cooling down over-heated children.
The shallow water and shelter from the surf beach's crashing waves make it a child-friendly option for sun and sea chasers on Auckland's West Coast.
But it is also host to levels of "faecal contamination" so high it needs weekly testings - and occasional closure.
The pollution was flagged last week by residents opposing a bid by celebrity Marc Ellis to build a cafe at Piha. They urged Auckland Regional Council commissioners considering the application to discover the source of the poo problem before allowing any more large septic tanks in the area.
Already the Waitakere City Council has carried out extensive testing to find the source of the contamination. "If there was a direct cause [of contamination] and effect, we could do something about it," said Tony Miguel, the council's group asset manager. "But without a cause, it's hard to know what to do."
Contamination theories range from bird waste, rotting algae blown in from the sea, dog leavings, and cow patties washed downstream, a city council report reads.
"The detection of human virus, although at low levels, clearly demonstrates sewage presence."
Miguel said extensive testing of septic tanks in the area - a sample of 100 out of 600 - found almost all in good condition. About 10 tanks were old, but not in such poor shape to carry the blame for polluting the lagoon.
Testing of the lagoon and upstream had failed to find a pattern to explain the occasional high levels of pollution - which would lead to warning signs being erected and the lagoon closed.
"There's no rhyme or reason to it," said Miguel.
The next round of tests is planned for February. It was hoped by comparing those to other seasonal tests, council officers could find the "cause and effect".
