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The Barton Springs Salamander Catastrophic Spill Plan describes when and how endangered salamanders would be protected or rescued should a catastrophic spill occur in the Barton Spring watershed. The best response to any particular spill depends on a variety of factors, thus an effective spill response plan requires a method to determine thresholds that will elicit each tier of salamander rescue efforts. This plan focuses primarily on developing response tiers for gasoline, since it is considered to be the most common problematic spilled material with high toxicity and the potential for very large spills., The method developed for gasoline is based on some of the most toxic and abundant concentrations of gasoline contaminants including benzene, toluene, ethylbenzene, and xylene (BTEX) predicted in Barton Springs under a range of conceivable spatial, spill volume, and spring flow conditions. A screening model to make these predictions was developed as follows. First, toxicity data and water quality criteria for the BTEX contaminants were used to derive concentration thresholds that would establish the different response tiers. Second, a method to predict BTEX concentrations at Barton Springs from a gasoline spill entering the aquifer was chosen to guide responders in selecting the appropriate response tier in an emergency event. The goal was to select a model of contaminant transport based on previous studies of karst aquifer pollutant transport and supported by available groundwater time-of-travel and flow path data for the Barton Springs Segment of the Edwards Aquifer. Results from the model must be presented simply enough to quickly determine appropriate emergency response. Several methods were tested using a variety of spill attenuation, mixing volume, averaging period, and travel time assumptions. Ultimately, a simple published regression equation was selected that was developed from dye tracing data in a number of carbonate aquifers (Worthington and Smart, 2003). The predictions from this equation were compared with empirical dye study results for the Barton Springs Edwards Aquifer and found to be a conservative estimate for all conditions corresponding to available toxicity data. Solving for the threshold BTEX values enabled the generation of simple line graphs that can be used to quickly determine which tier of salamander rescue is appropriate based on volume of spill, springflow, and distance from Barton Springs. Similar methods were also used to develop response tiers in the event of a potentially catastrophic sewage spill., since these are the most common type of spill occurring within the Barton Springs watershed. However, the large majority of sewage spills are more likely to contribute to chronic degradation of Barton Springs than pose a catastrophic threat. Open Access See Extended description for more information.
Biology, Cave Ecology, Resource Management
City of Austin Watershed Protection and Development Review Department
Turner, Martha and O'Donnell, Lisa, "Response tier development document Barton Springs salamander catastrophic spill plan" (2004). KIP Data Sets and Technical Reports. 114.