A Bord Pleanála oral hearing into a proposed sewerage scheme for Arklow was told by a consultant sanitary engineer that expert opinion presented in opposition to the scheme was "totally contrary" to his experience.
The plant, originally proposed in 1993, has been held up by a number of delays, including legal actions which have challenged the works on the grounds both of its design and of its siting, beside a holiday complex.
Mr Seosamh Ó Ruairc, a civil engineer and partner in P.H. McCarthy, consulting engineers for Arklow Town Council, told the hearing that fears concerning the increased septicity of sewage, because of the distance it would have to travel to the plant (2.6km) were contradicted by experience he had had of similar such plants at Mutton Island, Galway, and Malahide, Co Dublin, and the new tertiary treatment plant at Ringsend, Dublin.
Mr Ó Ruairc added that a secondary treatment plant at Malahide adjacent to the marina was causing no problems.
Mr Ó Ruairc was supported by Prof Tom Casey, formerly professor of civil engineering at University College Dublin and now with a consultancy, Acquavara Research Ltd.
Prof Casey challenged the relevance of evidence for expected septicity at the proposed plant and contingent works given earlier at the hearing.
He said the earlier figures related to large treatment plants in Germany serving big cities, not a relatively small plant like that envisaged for Arklow.
Referring to concerns about odour emissions, Prof Casey gave the example of the waste-water treatment plant at Osberstown, Co Kildare which, like the proposed Arklow plant, is of a secondary treatment type.
Although located beside a major road, it had an "excellent" record on odour.