Twin Rocks

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The Oregon Beach Monitoring Program (OBMP) works with the Oregon Department of Environmental Quality (DEQ) to monitor several marine and freshwater sites in the state of Oregon. Beaches are monitored on a three week rotating schedule depending upon their geographic location, previous monitoring data and test results, public input, and amount of beach use. Sites are monitored from May 21-August 31. As of 2017, the OBMP follows a Beach Action Value established with the EPA specifically for the state of Oregon. It is 130 cfu per 100ml of water. The most probable number (MPN) testing method is used to estimate the number of colony forming units (cfu) of bacteria in 100mL sample of water. That means: A beach is marked green when single sample test results show fewer than 130 MPN per 100ml of water. A beach is marked red when single sample test results show greater than 130 MPN per 10ml of water. The OBMP collects samples from multiple locations at a beach. All samples must pass for a beach to pass. If one sample fails an advisory is issued, and the OBMP collects a resample within 96 hours to determine if bacteria levels have decreased enough to lift the advisory.