`Everyone goes walking on Sandymount Strand," says science teacher Catherine Cavendish. It was her passion for the strand - and the whole Dublin estuary - which led her to enter the recent local elections at the last minute.

A resident of Sandymount, Cavendish has been galvanised by a series of events. Late last year she discovered oil and chemicals emerging from a drain in a culvert along the strand. "It's meant to be a surface water drain, taking rainwater from the roads. But some industrial body, big or small, started using it to discharge industrial stuff. I had to make an awful row." It took several months before the pollution was halted.

She feels few appreciate the value of an estuary. "It's irreversible damage - you can't put an estuary back . . . They're the richest of all habitats, where the river meets the sea. They support the greatest biodiversity of animals, richer than the rainforests." Estuaries around the world have been seriously damaged by pollution and over-development, and she is intent on protecting Dublin from the same fate.

Cavendish was also annoyed by plans to establish a "green waste" dump in Sandymount's Sean Moore Park, next to the coast. "There was no need for that proposal - it was a hare-brained idea." Her concern was that it would upset the Brent geese, an endangered species who tend to gather in the park. The dump is not going ahead.

She is opposing the construction of a promenade along the coast, because it would obscure the old sea wall. "The wall goes from Strand Street to the Merrion Gates. Lord Fitzwilliam built it - to define his ground, I suppose . . . Imagine you were an engineer 100 years from now and you wanted to see the construction of that wall. It will have been masked. It's wiping out a particular brand of engineering that will not be repeated."

Because of these and other issues, Cavendish decided just four weeks before polling day to run in the local elections in Pembroke. "I wanted to make some kind of statement about the estuary. My election paper was just simply about the dreadful state of the place." With 262 first-preference votes she came nowhere near being elected, but is still glad she stood. "If there's something wrong, I'll go after it. And I think any further destruction of the estuary is wrong."

She is currently awaiting news on the Eastern Bypass. It is proposed that the road should include a tunnel under Sandymount Strand. "I don't think it can be done, I really don't. The geological conditions down there - it's not like digging through granite. And what are they going to do with what comes out? Millions of tonnes of mixed rock . . . That tunnel could be a ploy for land reclamation."

Cavendish can't see herself running in another election. She adds: "I'd be too old. I wouldn't have the energy."