The Government had to give a $75 million (€83 million) environmental guarantee to the new owners of Irish National Petroleum Corporation (INPC) to bring about the sale of the State oil refinery.

Tosco Corporation - which itself is being taken over by US oil major Phillips Petroleum - bought the assets of INPC last July for $100 million.

Documents released under the Freedom of Information Act by the Department of Public Enterprise show that the US company sought and obtained hefty guarantees against any liabilities that might arise because of pollution from the plants.

The precise terms of the Government guarantees were not disclosed. However, a briefing document prepared for officials in advance of a briefing given by the Department to the Oireachtas Joint Committee on Public Enterprise outlines the guarantees.

The general principle was that "INPC will remain responsible for liabilities relating to pre-completion events" but that the liabilities would be limited to $75 million.

The guarantees include time limits of seven years for tax liabilities, six years for general liabilities and 12 years for "known" environmental risk and 10 years for "unknown" environmental risks.

The maximum exposure for unknown risks is $25 million. The guarantees do not cover the derelict jetty at the Bantry Bay oil storage terminal which was destroyed in the 1979 Betelgeuse disaster. The State will remain fully responsible for the jetty.

The briefing document states that "overall the sites are relatively 'clean' given the nature of the operations conducted".

But under the terms of the guarantees, Tosco Corporation is prohibited from disturbing certain areas of the INPC sites "which may have been damaged in the past".

The areas are not disclosed, but the list of documents not released by the Department indicates that a legal opinion was sought in connection with the "underfloor tank membranes".

In addition, the use to which the sites can be put in the future has also been restricted. This means that if an environment problem does arise, the State will have only to foot the bill to return the sites to their current level of contamination.

On a positive note, the document points out that the sites have been operating Environmental Protection Agency licences "with no significant issues emerging".

The document also points out that what was agreed is an improvement on Tosco's initial position "that any environment- related costs connected to events occurring while the sites were in INPC stewardship were INPC's responsibility and that no limitation on liability in either time or amount should apply".

The environmental section has been the most heavily negotiated section of the legal agreement governing the sale, according to the document.

INPC has obtained an indicative quote "which suggests that all potential liabilities under the environmental provisions can be insured" and the board of the company "strongly recommends" the insurance be taken out, according to the departmental document. The costs of the insurance policies were not released.

The document also dealt with Tosco's safety records. "Concerns have been expressed about a number of well-publicised accidents and environmental shortcomings at certain Tosco facilities in the US," it said.

"The INPC view is that these are very much the exception and that Tosco have taken prompt remedial action where deficiencies were identified.

"Even if the matter is viewed solely in commercial terms, Tosco are buying into the Irish operations for business reasons and it is decidely against their interest to compromise their investment by risking suspension of operations as a result of poor procedures," it concludes.

The document justifies the sale on a number of grounds, the main ones being that INPC could not operate on "a fully commercial standalone basis" and the sale "will also allow the State exit a commercial activity in which it need not be involved".