Indicator: Fecal Coliform at Swimming Beaches
Data and Data Discussion provided by
King County DNRP
Sustainability Snapshot:
Fecal coliform, bacteria found in warm-blooded animals, originate in fresh water systems primarily from failing septic systems and animal wastes. A high concentration of fecal coliform may indicate the presence of other harmful bacteria in the water. These bacteria can cause minor skin and eye infections, gastrointestinal disorders, respiratory illness and death. If a swimming beach shows elevated concentrations of fecal coliform, the swimming area is closed.
Sustainability Trend:
Status: High bacterial counts at several beaches monitored in Lake Washington (Juanita, Magnusson Off Leash Park, Gene Coulon, and Meydenbauer) during the 2007 summer season resulted in swimming beach closures. Bacteria levels were low in Green Lake for the fifth year in a row while Lake Sammamish remained fairly consistent, with slight variability from year to year. The 2008 target and long-term outcome for swimming beaches on large lakes is that none of the testing sites violate both parts of the Washington Department of Health fecal coliform bacteria target which is a geometric mean of 200 colonies per 100 ml with no single sample exceeding 1000 colonies per100 ml.
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Percent of sampled swimming beach sites at lakes Washington, Sammamish and Green Lake, that meet state fecal standards.
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Influencing factors: Fecal coliform bacteria can enter lakes from household pets or farm animals, wildlife, stormwater runoff, untreated wastewater effluent, sewage overflows or failing septic systems. The most impacted beaches are adjacent to streams draining urbanized watersheds.
King County routinely monitors swimming beaches during the summer months to determine levels of bacterial pollution and works with Public Health - Seattle & King County to estimate relative human health risks. If bacterial counts at swimming beach testing sites are greater than 200 colonies per 100 ml of water, the beach will be temporarily closed. By matching the bacteria genetically to its source, King County scientists have identified waterfowl as the primary source of the fecal coliform contamination at many of the beaches during these times.
Priority new actions: Changes to park maintenance procedures and control of non-migratory, non-native waterfowl should reduce bacteria counts and improve the water quality at large lake swimming beaches. Efforts to identify and correct bacterial source in the urban streams that discharge adjacent to swimming beaches has begun. A Total Maximum Daily Load (TMDL) for bacteria in Thornton Creek has been started.
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The data source for this indicator comes from the King County DNRP/WLRD Major Lakes Monitoring Program.
The target indicator for fecal coliform bacteria is met when there
are less than 200 colonies per 100ml of water in any sample. This
target is based upon, but more conservative than, the Ten State
Standard which requires that the geometric mean is not greater than 200
colonies per 100 ml of water and that no single sample is greater than
1000 colonies per 100ml of water. Public Health -Seattle & King
County and the Washington State Department of Health currently use the
more stringent, Ten State Standard. When swimming beaches achieve this
standard there is less chance of being contaminated by fecal bacteria
when swimming at large lake beaches. The Ten State Standard is less
restrictive than the lake bacterial standard and may be modified in the
future to an E. coli-based standard because of regulatory changes being
considered by the U.S. Environmental Protection Agency.
Data reference: King County DNRP/WLRD Major Lakes Monitoring Program Web site http://dnr.metrokc.gov/wlr/waterres/swimbeach/default.aspx
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