Austin Dog Lovers Unite!  Bull Creek Park is in Danger of losing it's off-leash status due to elevated e. coli levels in the water.  One factor in e. coli is the failure to responsibly clean up dog waste.  Below are materials I have received from Debra Bailey of BCDOG-Bull Creek Dog Off leash Group.  Please help in keeping Austin Weird, Green, Beautiful, Clean, and Dog Friendly!

Water quality studies along Bull Creek show high bacteria levels in the water particularly in the off-leash area of Bull Creek District Park.050100150200250300350Bull @ St.EdwardsBull @ Loop360/LakewoodBull @ DistrictParkBull above WestBullBull @ MouthMean E. coli (col/100mL)State Contact Recreation Standard

An owner or handler shall promptly remove and sanitarily dispose of feces left on public or private property by a dog or cat being handled by the person, other than property owned by the owner or handler of the dog or cat. Maximum Fine: $500

Bag it! Use the bag as a glove to scoop the waste, then turn the bag inside out and tie to seal. No mess.

1.      What is the trend of E. coli in the water?

E. coli concentrations are not changing in Bull Creek District Park based on all available non-storm to date.  E. coli concentrations are increasing at the upstream Loop 360 site, and recent samples are the highest non-storm concentrations yet measured at that site.  No regular monitoring by COA has occurred in the park since the end of the education campaign effect assessment in April 2008.

2.      What is the trend of E. coli in the sediment?  Why is sediment important?

Bacteria in sediment at the park are greater than background levels from other Bull Creek sites.  Bacteria in sediment at the park appear to be highly variable over time.  Bacteria in sediment at Loop 360 upstream of the park are increasing over time and have been greater than park sediments in last 2 sample events.  Sediment is important because it may act as a “refuge” for fecal bacteria in streams.  Re-suspension of bacteria attached to sediments may re-introduce bacteria to the water column.  Removal of sediment from the stream is not a reasonable mitigation strategy in this case. 

3.      How do these compare to other Austin creeks, especially during other dry periods?

The bacteria in sediment sampling is a new experiment for the City and has only been conducted in Bull Creek.  Thus, Bull Creek sediment bacteria concentrations cannot be compared to other Austin creeks.  In regards to E. coli concentrations in water, the long-term geometric mean for Bull District Park is worse than 65% of 117 other sites routinely monitored by COA as part of our Environmental Integrity Index.  The relative ranking of Bull District Park bacteria to other sites may not be relevant since the park currently exceeds the State of Texas contact recreation standard and people swim and wade in the creek. 

4.      What is the decay rate of E. coli in water?

Decay of bacteria are frequently modeled using first-order decay:

C_t/C_o = e^-kt  (C is concentration, t is time, k is first-order decay rate)

Decay rates are highly dependent upon temperature and exposure to sunlight.  Literature values for first-order E. coli decay rates in warm water (23ºC) are typically 0.5 day^-1.  LCRA data from Gilleland Creek suggest even higher decay rates (0.71 day^-1) but are unadjusted for temperature.  COA bacteria monitoring of Williamson Creek following a large and on-going sewage leak in Williamson Creek demonstrated a return to background concentrations within 1 week of the problem being corrected.  COA and USGS bacteria monitoring following storm events show return to background concentrations within 1-3 days.  In summary, fecal bacteria decay quickly when outside of the intestinal tract of warm-blooded animals.  

5.      What is the decay rate of E. coli in sediment?

There are no direct measurements of sediment bacteria decay that follow the same method COA has been using in Bull Creek to collect and analyze the samples.  Bacteria can remain viable in sewage sludge solids for very long periods of time, and decay in sludge is related to moisture content and temperature.  COA data has documented increases in sediment bacteria concentrations within a one week period in the absence of significant runoff events at the park. 

6.      What percent of E. coli is caused by pet waste and how much is from human waste from dirty diapers left by the creek by weekend visitors?

It is extremely difficult to directly quantify differential source contributions.  Bacterial source tracking using genetic methods would take 1-2 years and cost approximately $150,000.  A similar study in an urban Houston water body demonstrated that the largest contributor of fecal bacteria was domestic cats and dogs.   

7.      What is the measured E. coli trend since the BCDOG campaign began in May 2008?

There has been no regular COA sampling in the park since the end of the education campaign monitoring in April 2008.  The monitoring conducted following the first 2 months of the campaign did not demonstrate a decrease in bacteria in the park.  The last COA samples in the park were collected on 1 July 2008, and yielded an average concentration (129 mpn/100 mL) slightly above the contact recreation standard (126 mpn/100 mL). 

8.      What is the difference in E. coli trends between normal flow years and low flow years?

This is a complex issue, since bacteria concentrations may vary with a large number of factors.  Theoretically, reduced flows could translate to higher use intensity by wildlife and reduced dilution leading to increased bacteria concentrations.  However, COA and USGS bacteria concentrations in large undeveloped watersheds (like upper Onion Creek) during non-storm conditions do not demonstrate a relationship with flow.