ALUMINIUM levels have been recorded up to 92 times higher than environment guidelines in creeks in west Lake Macquarie.
The creeks run into the lake, ending up in Kilaben Bay and Edmunds Bay.
Centennial Coal tested water during the past 12 months at 10 sites around Awaba, Toronto, Kilaben Bay and Rathmines, as part of its subsidence management plan for a Newstan coalmine extension.
Samples were taken in Stony Creek, Kilaben Creek, Lords Creek and Stockyard Creek.
A Centennial report said heavy metals found to have exceeded Australian and New Zealand Environment Conservation Council (ANZECC) trigger levels were aluminium, cadmium, cobalt, chromium, copper, iron, lead, manganese and zinc.
But there were ‘‘no clear sources for the high levels of pollutants’’.
A spokeswoman for the Environment Protection Authority said it would review the water-quality results outlined in the report.
‘‘Creeks and rivers in NSW frequently contain metals and other pollutants that are naturally occurring as a result of the local geology, soil types and vegetation in the area,’’ she said.
‘‘Historic land use practices such as mining, forestry, agriculture and urban uses also influence water quality.”
Associate Professor of Environmental Science Phillip Geary, of Newcastle University, said high aluminium levels were ‘‘a reason to be concerned because of the impact on the ecosystem’’.
‘‘There is a need for further investigation,’’ Professor Geary said.
‘‘Aluminium is toxic – it can cause significant problems in water. It will kill things that come in contact with it, like fish.’’
He said metals could enter the food chain and bioaccumulate in fish and marine life, posing a threat to public health. And heavy metals in the creeks end up in the lake.
Aluminium at such high levels would be from a source other than nature, possibly an old buried coal stockpile, he said.
Former Lake Macquarie council environmental officer Jim Sullivan said the Awaba tip and coalmines were also ‘‘a likely cause of heavy metals in the creeks’’.
A council statement said heavy metals did not leach from Awaba tip into the lake.
‘‘Leachate from council’s Awaba landfill is managed on site in accordance with the conditions of our EPA licence,’’ it said.
Centennial’s report said all aluminium-level samples in Kilaben Creek exceeded the recommended ANZECC trigger levels.
One sampling point in Kilaben Creek recorded concentrations 44 times higher, and aluminium levels in Stony Creek were found up to 92 times higher.
‘‘This is likely to be attributed to non-bioavailable aluminium associated with suspended sediment,’’ the report said.
‘‘High levels of aluminium seem to be a typical catchment trait of the creek waters within this area.’’
Centennial spokeswoman Katie Brassil said the subsidence management plan was ‘‘used to predict any potential surface impacts underground mining may have on an area’’.