for many years the abattoirs located here were discharging large amounts of untreated waste into the manukau harbour. this had a detrimental effect on the ecology of the harbour, which at the turn of the 20th century had been a popular and attractive place to swim, sail, fish and gather shell fish. for most of the middle of the 20th century it was a health hazard and its shell-fish a probable source of food poisoning. since the freezing works were fully closed in 1981, the water quality has improved greatly.