Yorkshire Water is conducting environmentally friendly dye-tests off the coast of Runswick Bay today in a bid to build a greater understanding of how its sewer outfalls can impact on the quality of local bathing waters. Residents and visitors are being urged not to be concerned if they spot small plumes of red water in the sea.

The company, which is investing £110million between 2010 and 2015 as part of a multi-agency project to transform Yorkshire's beaches and bathing waters into some of the best in Europe, is monitoring how long it takes for discharges to reach the sea and the effect of underwater currents and tides.

Bathing Water Strategy Manager Lee Pitcher said the dye will have no impact on fish, birds, or other wildlife.

“The dye itself is completely inert and is not harmful in any way to plants and wildlife. Over the course of the next few days, we'll be releasing a small amount from our outfalls and then tracking where it goes. This testing is hugely beneficial as it should give us a clearer picture of how our outfalls operate and the impact they have, helping to inform our planning around £110m investment which we announced in November 2010.

Dye-testing was undertaken in Scarborough and Bridlington back in 2008, with similar work recently completed at Filey, Staithes, Runswick Bay, Sandsend, Whitby, Skipsea, Withernsea and Robin Hoods Bay.