00:00Beaches closed, the public told to stay out of the water, and a growing effluent plume
00:07near one of Tasmania's most popular tourist sites, the Museum of Old and New Art.
00:13The environmental emergency in the River Derwent one week out from Christmas last year triggered
00:18a public health response, but how did it happen?
00:22Further up the river sits the Cadbury Chocolate Factory.
00:26It continuously creates sugary trade waste, which it treats on-site, before sending it
00:31to the Cameron Bay sewage plant near Mona.
00:34Emails and reports obtained by the ABC show how the chocolate by-product developed into
00:40a sewage crisis.
00:42On November 28, Cadbury took a key part of its on-site waste water treatment offline
00:48for replacement.
00:50In the interim, it planned to chemically treat the waste before it went to the sewage plant.
00:55By December 4, Cadbury's trade waste concentration was already exceeding TasWater's limit.
01:02It turns out Cadbury couldn't obtain a key treatment chemical until December 12.
01:08On December 13, TasWater issued a process upset notification for failure at its Cameron
01:14Bay sewage plant.
01:16TasWater didn't get monitoring data from Cadbury until December 16.
01:21By then, the trade waste had killed the bugs that are meant to treat public sewage.
01:27On December 19, TasWater issued Cadbury a breach notice, threatening to cut the site
01:32off from its sewage network.
01:35That night, a public health alert was issued, warning people to stay out of the River Derwent.
01:41In its root cause analysis, Cadbury parent company Mondelēz said it had to change its
01:46dosing when it couldn't obtain the right waste treatment chemical.
01:50It also blamed loose pipe connections and the need for manual dosing.
01:54TasWater treated the sewage with chlorine and Cadbury started land-spreading its excess
02:00trade waste.
02:01TasWater and the EPA say they are continuing to investigate the incident.
02:06Mondelēz says it's working with the regulators.
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