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City still puzzled over source of elevated bacteria levels in Bull Creek

Monday, August 9, 2010 by Mark Richardson

Think of it as CSI: Bull Creek.


Officials with the city’s Watershed Protection Department, the agency charged with keeping local creeks and other waterways clean, are still scratching their heads over just what is causing unacceptably high levels of E.coli bacteria growth in parts of Bull Creek Park. So they have ordered genetic testing to identify the culprit.


Three years after a sewage spill caused the city to begin tracking the bacteria levels in Bull Creek Park, E.coli levels in the water remain well above state-mandated levels. Biologists with Watershed Protection report that, although they have their suspicions that dogs frolicking in the water at what was formerly an off-leash park are the likely cause, they don’t have definitive proof.


Chris Herrington with Watershed Protection told the Environmental Board Wednesday night that tracing the genetic origins of the bacteria should give them some definitive answers.


“We have been taking samples of the water and testing them biweekly and posting those test results in the park for people to see,” Herrington said. “But while the tests tell us the bacteria levels are in the water, they don’t tell us where they came from.”


The city is currently negotiating an interlocal agreement with the University of Texas to perform genetic tests on E.coli bacteria samples from Bull Creek. Those tests are set to begin this month.


“That will help us determine whether the problem is coming from dogs, humans, or other animals,” Herrington said.


Bacteria levels above the state standard were first measured in Bull Creek in 2007 after city officials were alerted to a sewage spill upstream from the West Austin park. A team of city officials from Watershed Protection, the Parks and Recreation Department, and the Austin/Travis County Health Department began monitoring the health of the creek’s water but noticed that bacteria levels remained high long after the effects of the sewage spill should have abated. (See In Fact Daily, Aug. 15, 2008)


City officials responded by closing down the off-leash park for a six-month period in 2009 and then reopening the park as an on-leash area with stricter rules on pet owners cleaning up after their animals.


Herrington reported that bacteria levels were measured at 270 mpn/dL prior to closing the park, dropped to 161 mpn/dL when the off-leash park was closed, then rose back up to 230 mpn/dL. All three readings were above the Texas Commission on Environmental Quality’s standard maximum of 126 mpn/dL for E.coli in public waterways.


Herrington said that while the city has periodically tested Bull Creek for bacteria since 2003, levels remained very low until the sewage spill in 2007, when they began studying the creek more closely.


“That’s when the levels jumped up high and stayed there,” he said. Herrington quipped that the city’s efforts to fix the problem may have just made it worse. “I fear that as we began talking about this beautiful park area, we may have publicized it to a much wider group of folks than the ones who had been going there previously,” he said.

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