Shell E&P Ireland has said it is not responsible for highly elevated aluminium levels in Carrowmore lake, the public water supply for Erris, north Mayo.
The company has also denied that it was pumping diesel from the Bellanaboy terminal site on Monday night into a stream, which feeds into the Carrowmore lake catchment. The company has acknowledged a "small" diesel leak from a generator at the site in the last few days.
Results obtained by The Irish Timesshow elevated aluminium levels in a number of tests carried out in January and February of this year on Mayo County Council's behalf for water run-off from the Bellanaboy terminal site, the Bellanaboy river and Carrowmore lake. The lake supplies drinking water to 10,000 people in Erris.
The county council warned Shell over a year ago about the risk of elevated aluminium levels, as a result of work on the site which has disturbed the "doib" or soil layer under the peat. At that time, it had a report of aluminium levels in discharge water from the site of over three times the accepted limit.
The company installed an Axonics treatment plant to deal with the problem, but "post Axonics" results dated January 31st, 2007, show aluminium levels at over 200 times the recommended World Health Organisation (WHO) maximum limit for drinking water. The recommended WHO guideline maximum limit for aluminium in drinking water is 200 micrograms per litre (ug/l).
Aluminium levels of 1714 ug/l and 406 ug/l were detected in samples from the Carrowmore lake tested at University College Hospital, Galway (UCHG), dated January 24th of this year. A similar breach of recommended aluminium levels in February 2006 was described subsequently by the local authority as a "laboratory error".
The council said last night that it was still very concerned that aluminium levels had not been reduced to agreed targets by Shell for run-off from the site, but said it was "not possible" that the elevated levels for Carrowmore lake for January 24th were caused by Shell. It said it believed it had identified the source of a "short-term problem".
Shell said that aluminium concentrations in the Bellanaboy River would consist of soil material from the catchment area and from eroding river banks, and water from Carrowmore lake is treated.
"Shell's landholding around the terminal site comprises only two per cent of the total catchment area of Carrowmore Lake and the terminal earthworks area constitutes only a small part of the site," it said.
Last week, the company dismissed as "spurious" concerns expressed by residents about a tar-like substance running off site. However, samples were taken for testing by the North Western Regional Fisheries Board. Reports of diesel being pumped off site on Monday night of this week were also denied by the company.
However, Mary Corduff, one of the residents who witnessed the diesel run-off, has disputed this. She told The Irish Timesthat when residents tried to alert Shell security, they were told there was no one on site to deal with the issue. A group of gardaí then arrived and ordered the group to "keep the road clear".
