Beacon Rock is not sampled

The Washington state water quality standard provides that E.coli levels must not exceed a geometric mean value of 100 colonies /100 mL, with not more than 10 percent of all samples (or any single sample when less than ten sample points exist) obtained for calculating the geometric mean value exceeding 200 colonies /100 mL.

The EPA recommended standard provides that no single sample shall exceed 235 E.coli colonies/100mL and the geometric mean of 5 samples within 30 days shall not exceed 126 E.coli colonies/100mL. The Swim Guide will utilize the EPA standard for Washington beaches.
There is currently very limited water quality monitoring of Washington's inland swim beaches. The federal Beach Act does not cover freshwater or riverine beaches, and the State of Washington does not monitor swim beaches or recreation sites on the Columbia. Columbia Riverkeeper monitors recreation sites in the Columbia River Gorge through their Volunteer Water Quality Monitoring Program. Most sites are sampled monthly and high priority sites are sampled weekly from June-September.
The Swim Guide's safety ratings are based solely on E.coli levels. While E.coli concentration is a useful indicator of fecal contamination, there are many other potential sources of pollution that are not reflected in the Swim Guide. These include other bacteria, heavy metals, pharmaceuticals, and pesticides that may harm aquatic life. On the Columbia and other salmon rivers, high temperatures threaten fish that need cold water. If you are interested in getting involved or learning more about the Columbia River, visit www.columbiariverkeeper.org.