Still more than 98 per cent of fly ash has to be accounted for and has to be recovered from the site," the study noted.
Explaining how fly ash has been polluting the stretch, the study states, "Fly ash is transported as a slurry using sea water and dumped into the fly ash pond.
Leaky pipelines, leaks from fly ash ponds and accidental breaches seem to have caused the spread of fly ash over large areas of the Kosasthalai river and Ennore backwaters.
Fly ash pollution has typically and chemically altered the ecosystem."
Vegetation along the river bank near the NCTPS was found to be under heavy stress.
Water quality Water samples collected from the Kosasthalai River, backwaters and a secondary pond were found containing elevated levels of several toxic chemicals.
Borewell samples taken from Seppakkam, a village in the west of the ash pond, were found severely contaminated with copper, manganese, cadmium, mercury, selenium, lead, chromium and nickel.
Impact on marine life and vegetation Twenty samples of fishes, including fin fish, crab, prawn and oyster/mussels, were tested along with five samples of locally home-grown vegetables such as drumsticks, drumstick leaves, brinjal and ladies finger.
Selenium found in samples can affect the reproductive ability of fishes.
The panel recommended a separate study on the effect of fly ash on human health.