Arsenic, chromium, cadmium over permissible limits found in groundwater
A decade after the gold fields in Kolar were closed by Bharat Gold Mines Ltd. (BGML), it emerges that residents have been left with a frightening legacy: arsenic in their water.
The 4,850 million litres of water that has collected in its 75 abandoned mining shafts, creating a massive underground reservoir, has turned toxic with heavy metals, all by-products of gold mining. And now the toxins are leaching into the groundwater, the town's primary source of drinking water, finds a study by the Department of Mines and Geology.
A random water test commissioned by the Department of Minor Irrigation, which wanted to use the vast water reserve to meet irrigation needs, revealed alarming quantities of arsenic — an ingredient in rat poison — in shaft and groundwater.
The water in each of the 13 shafts tested by the Department of Mines and Geology a fortnight ago had arsenic well over the permissible limit (0.01 mg/l), with some shafts containing over 600 times the permitted amount.
Five out of eight borewell samples had arsenic over the permissible limit and three had chromium over the permissible limit. These include samples taken from schools and colleges.
Visible from the St. Joseph's Convent School, is the gigantic and rusting lift system of the Tenant Shaft, where the water sample was found to have a whopping 5.61 mg/l of arsenic.
Government authorities had not informed the school management that 0.06 mg/l of arsenic was recorded from their borewell, their only source of drinking water.
The borewell at Sri Kengal Hanumanthaiya Law College is even more toxic, with 0.10 mg/l of chromium (against the permissible limit of 0.05 mg/l), cadmium (0.03 against the permissible 0.01 mg/l) and 0.012 mg/l of arsenic.
The District Armed Reserve police quarters has recorded 0.064 mg/l of arsenic and 0.07 mg/l of chromium.
“Some of these mine shafts are 11,000 ft deep and have filled up with groundwater over a decade. The rocks crushed during mining have deposited heavy metals in the water and it was just a matter of time before the shaft water entered the groundwater,” said an official from the Department of Mines and Geology.
“It is shocking that residents have not been informed about what they are drinking,” said the official who requested anonymity, adding that the findings called for a regular analysis of the 200-odd borewells in KGF, and especially in the BGML area, before health was impacted.
It is not the first time that the State Government has considered using the mine-shaft water for the 1.5 lakh residents of KGF where groundwater has been overexploited and the only surface water, from the Bethamangala tank, is supplied twice a week.
In 2004, the Karnataka Urban Water Supply and Drainage Board chalked up a Rs. 26-crore proposal to draw water from two abandoned mining shafts to meet drinking water needs.
The proposal said that that 10 MLD of water could be accessed from the two shafts (Tenant and Okley) to meet the 11 MLD demand in KGF.
Curiously, a chemical analysis of the shaft water in 2005 concluded that the samples “do not contain heavy metals”, including arsenic.
“The only major impurity present is total dissolved solids,” said the Karnataka State Pollution Control Board report. The drinking water project has since been stalled.