Author: Taylor, Kevin M

Mapping And Analysis Of Wastewater Spills In The Barton Springs and Southern Segments Of The Edwards Aquifer
Presented for Greater Edwards Aquifer Alliance & Barton Springs/Edwards Aquifer Conservation District
Presented by Aquifer Resource Innovators [ARI]

Introduction
The Edwards Aquifer is a unique and special place to Central Texas. The aquifer serves nearly two million people with fresh water, which is used for agricultural, recreational, and personal purposes. It consists of four main zones: the contributing zone (CZ), recharge zone (RZ), transition zone, and the artesian zone. As Central Texas grows in population, the Edwards Aquifer is under increasing pressure from over-use and development. With this encroachment in and along the sensitive RZ, there is growing cause for concern regarding the future of the aquifer and the quality of the groundwater.
Pollution is a major threat to the aquifer system and its unique inhabitants. Pollution from point and non-point sources can seep into the porous limestone that characterizes the RZ of the aquifer and spoil this great natural resource. Wastewater spills make significant contributions to pollution levels in the groundwater, and can cause irreversible damage to the health of the aquifer and the people consuming its water.

Scope
Our project focused on wastewater spill s between 2007-2012 within the RZ and CZ of the Southern and Barton Springs Segments of the Edwards Aquifer TCEQ Region 11. The total area of Region 11 is comprised of ten counties, however due to a priority list provided in the Request for Proposal, we began with Travis and Hays County. We ended up adding Williamson County due to the significant area of the RZ and CZ lying in its boundaries. Figure 1 illustrates the counties and aquifer zones used in our analysis.

Scope within TCEQ Region 11
With our focus being Hays, Travis, and Williamson Counties

Sequential Maps Of Wastewater Spills within Travis County, 2007 to 2012

Data
We received an Excel document from TCEQ containing over 1,800 wastewater spill records in Region 11. From that
table we initially extracted the spills for Hays and Travis County, first by county and then by start date (2007-2012). We created new tables for both counties, and processed them by creating new columns of the full street address, city, state, zip code, spill cause and action taken for remediation. We repeated the process for Williamson County about half-way through the semester. Processing was fairly time-consuming, as much of the data contained long descriptions of the location, oftentimes without a city, and never containing a zip code. We used Google Maps and Google Earth to confirm each address location within the county.
The table at right indicates the amount of spill records we received from TCEQ and the percentage lost due to lack of geographic information or inaccurate reporting.
Methodology
After processing the data in Excel, we imported a database file (.dbf) into ArcMap in order to geocode each spill record. We used the 10.0 North American Geocode Service provided in ArcMap 10.0. Our geocoding results were impressively successful; after matching tied spills in the ‘Results’ window, we successfully matched 100% of spills in each county. This was due to: 1) some addresses only being matched by zip code, and 2) our removal of data received without any geographic information. The data loss for each county was rather significant. This is illustrated Table 1. For the points only matched by zip code in each dataset we went through the Attribute tables in order to find each point, queried the road or address given in the table, and opened an Editing session in order to place the spill in the correct spot.
Additional geoprocessing was necessary in order to complete other portions of our project, including an interactive map using Manifold 8.0, Travis sequential maps featured above, a cause of spill map, population density map, and point density map.
Results
1. Wastewater spill statistics,
This summarizes our statistical results for the 534 total wastewater spill records we successfully mapped. In a five year period, over 12 million gallons of wastewater was spilled throughout the three counties, 17.4% within the RZ.
2. Cause and Number of Spills.
This indicates spill causes by frequency with the highest number of incidents involving blockage and damaged pipes.

Data received and data mapped
County	Spill records received	Spill records mapped	Data loss (%)
Hays	113	95	15.9
Travis	422	345	18.2
Williamson	105	99	5.7

Wastewater spill statistics
Spills	Hays	Travis	Williamson	Combined
Total number	92	345	98	534
Volume (gallons)	827,820	6,920,728	4,681,086	12,429,634
Number in RZ	9	47	31	93
Percent in RZ	9.8%	13.6%	31.6%	17.4%
Volume in RZ	11,700	1,395,145	142,302	1,807,974
Number in CZ	19	21	34	73
Percent in CZ	20.6%	6.1%	34.6%	13.6%
Volume in CZ	60,100	119,750	2,812,687	3,099,237

3. Vulnerability Analysis
We initially hypothesized a correlation between wastewater spill occurrences and Municipal Utility Districts and Groundwater Conservation Districts. We hoped to pinpoint responsibility or negligence, but our data was not sufficient in this endeavor. Instead, we looked to population density overlayed by a point density analysis based on concentration of wastewater spills. In the map above one can easily interpret high levels of spills by the bright (translucent) areas . There seems to be a greater correlation of wastewater spills to cities currently growing in population and infrastructure rather than areas of the highest population density.

Final Wastewater Spill Map
With pertinent zones of Edwards Aquifer and all three counties

ARI: Katie Tritsch, Eric Schroeder, Katie Steele, Kevin Taylor
Acknowledgements: Dr. Yongmei Lu, Ryan Schuermann, Annalisa Peace, Robyn Gary, Texas State University-Geography Dept. GIS II Fall 2012