Never before has Dublin been faced with concurrent plans for two major power stations to meet its electricity needs; one in Ringsend, put forward by the ESB, and the other at Huntstown, north of Finglas, by Viridian, Northern Ireland Electricity's holding company.
Dublin Corporation is expected to grant planning permission today for the ESB's 400-megawatt project. But the environmental issues raised by the two schemes will have to be assessed separately by the Environmental Protection Agency under its licensing system.
Both schemes are intended to meet the demand for electricity, which is now growing at an unprecedented 5 per cent per year. Without additional plant, an analysis by the ESB forecasts, there will be a shortfall in generating capacity by winter 2001-2002.
With 28 per cent of the Republic's electricity market to be opened up to competition next February, at least three consortia from overseas are believed to be interested in pursuing projects here. Viridian, being already on the island, is the first to get off the starting blocks.
Last Friday Fingal County Council decided to grant planning permission to Viridian and its joint-venture partner, Cement Roadstone Holdings plc, for a 600-megawatt gas-fired power station at Huntstown, on part of the site of an extensive Roadstone quarry.
This decision is certain to be appealed by a local residents' action group, which has been campaigning vigorously against the project. Among the opponents' complaints is that its chimney stack will be only 33.5 metres high, less than half the general accepted height of power station flues.
The residents maintain that the project is totally inappropriate for a largely rural area with a dispersed residential population. But Viridian points to the fact that it is located close to an ESB switching station on the national grid and to a pipeline carrying its fuel, natural gas.
The relatively low height of the power station's flue was set to ensure that there would be no objections from Aer Rianta over its impact on Dublin Airport. An Bord Pleanala previously rejected plans for a privately run landfill site in the area on air navigation safety grounds.
According to the environmental impact statement submitted by Viridian and CRH, there would be "no significant adverse environmental impacts" from the proposed power station, which would be a combined cycle gas turbine (CCGT) plant built in two phases of 300mw each.
CCGT is much more efficient than conventional gas-fired power plants because it incorporates a steam turbine which is driven by the "waste heat" generated by the main turbine. Thus, it captures 55 per cent of the fuel's energy value nearly twice as much as the older plants.
The ESB's plan for Ringsend is also a CCGT plant, to be built on the site of the former generating station which has been closed since 1983. Over half of the buildings there are to be replaced, but the plan provides for the retention of the main buildings fronting Pigeon House Road.
The ESB lodged its plans with Dublin Corporation in early February, and since then no objections have been received. An ESB spokesman said residents in the Ringsend and Irishtown areas had been consulted and informed about the scheme.
According to the ESB's environmental impact statement, redeveloping the old Ringsend power station to provide a 400mw CCGT plant would have "no significant adverse impacts on the environment", though it does point out that the site must be decontaminated.
The "main concern" relates to some barrels of oil and bags of asbestos which were found beneath an old tennis court, as the ESB concedes. "Demolition works at the site in advance of the project will include removal and suitable disposal of buried contaminated materials," it says.
As with Viridian's project for Huntstown, the Ringsend plant would emit both nitrogen dioxides and sulphur dioxide, but at much lower levels than oil- or coal-fired generating stations. Emissions of carbon dioxide, the main greenhouse gas, would also be "very low".
However, both plants have been designed to run on gas-oil, known as "distillate", to guard against interruptions in the supply of their main fuel, natural gas. During periods when gas-oil is burned, pollution to the atmosphere would be significantly higher.
The ESB's project must also take its impact on the marine environment into account. On average, some 2,000 salmon run up the Liffey each year to spawn, and measures would be put in place to prevent these and other fish being drawn into the plant or its cooling water system.
The plume of cooling water discharged by the power station is likely to raise the temperature of receiving waters by 1.5 degrees. This "may give rise to a change in the species present in the immediate locality of the outfall, with those that favour warmer temperatures predominating". An ESB spokesman noted that the old Ringsend plant would also have discharged cooling water as does the much larger Poolbeg plant just downriver; its capacity is being extended to 980mw, making it Ireland's largest power station.
If nobody appeals against Dublin Corporation's decision on the Ringsend project, the ESB will have stolen a march on Viridian. Should the latter's project falter, however, it is likely that CRH, one of the ESB's biggest customers, would transfer its business to Viridian.
Sources close to Viridian said yesterday that it viewed the ESB's plans for Ringsend as an attempt to secure a larger share of the market in advance of deregulation next February. But the ESB insisted that the market was now growing so fast that there was "room for everyone".