Wai- Intellige Frank O'Connor jineer Ernie Margetson stands at the edge of a stormwater management system on site of the new Wal-Mart in Thurlow Township. holding hundreds of thousands of cubic metres of stormwater. After two days, almost all of the dangerous substances and sediments will sink to the bottom, where they will be dredged out from time to time. The remaining water will then be fed into a deep, concrete bunker where it will be treated with a new high-tech ultraviolet light system that will kill almost all bacteria before the water carries on into the Moira River. Ultraviolet has been used as a bacteria killer for sewage effluent in Europe and North America for some years, but its use in stormwater treatment is relatively new, explained Margetson. The ultraviolet method is more costly than alternative methods -- such as relying on natural swathes of land to filter runoff -- but it best fits Wal-Mart's desire to maximize land use. One additional benefit of the ultraviolet technology chosen by Wal-Mart is it uses no extra chemicals, such as chlorine. Margetson sees the installation as a significant first step towards improving the quality of runoff water in the Quinte area. The review and approval of the stormwater works was co-ordinated through the conservation authority, which administers a stormwater quality program for the entire Bay of Quinte. The program combines the efforts of conservation authorities, the Ministry of the Environment, the Ministry of Energy and Natural Resources, and Environment Canada, through the Great Lakes Cleanup Fund.