THE Government should grade the pollution level of waterfront areas in the same way as it does beaches to enable suppliers to know where to obtain clean water for seafood restaurants, Eastern District board member Jennifer Chow Kit-bing said yesterday. Ms Chow said Kou Tong Hau in Sai Kung Country Park, the Government's proposed site for restaurant water, was too far away. Ms Chow released the results of an independent study of water quality at Causeway Bay Typhoon Shelter, which showed the absence of cholera bacteria and E-coli counts lower than the government standard. ''The samples were collected on July 22 during the rainy period,'' said Dr Richard Cheung Yun-hing of City Polytechnic, who conducted the tests on a voluntary basis. ''When storm water is being released, the water quality usually improves.'' The typhoon shelter water fared less well on other pollution indicators. Self-oxygenation, a measure of the water's ability to support life, had slipped to 0.9 milligrams per litre from 2.92 mg per litre when Dr Cheung performed the same tests two years ago. A pristine coral reef would measure about 6 mg per litre. Data showed that the shelter was three times as polluted with E-coli as Aberdeen West.