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PIC water quality sampling

To make sure that excessive bacteria are not going into the water around Vashon-Maury Island, King County staff will sample freshwater flows from the beaches to Puget Sound. Vashon residents may see County workers obtaining freshwater samples along the beaches. County staff will only sample where there is public access to the beach or where they have permission from property owners to access private property.

From hundreds of studies and projects involving fecal coliform bacteria, the main causes of elevated levels of bacteria are often human sources. It is possible that there are inadequately designed and poorly functioning septic systems along Vashon beaches that may be contributing high fecal bacteria to Puget Sound waters. This is concerning, as untreated or poorly-treated human wastewater carries dangerous bacteria that make people sick, detergents and personal care products that harm wildlife, and excessive nutrients that can cause algal blooms.

Although waterfowl and wild animals also contribute fecal coliform bacteria, very high bacterial levels are often from humans, livestock and domestic animals. When project fecal coliform results are very high, we plan to use a systematic approach and DNA testing to confirm whether the pollution is from a human source.

King County has previously done bacterial and DNA testing of freshwater beach flows in Outer Quartermaster Harbor, as well as in numerous stream watersheds in unincorporated King County. This DNA testing has helped find and confirm pollution sources including failing septic systems and livestock waste. Bacterial and DNA testing will be used in this project to measure how clean the marine waters are and to identify any specific sources of elevated bacteria.