Res 2011-037 (2) - Laserfiche WebLink

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Sample Collection Collection methods will be modeled after USGS ground -water collection protocols and procedures found in the USGS Open -File Report 95-399 (Koterba, Franceska, Lapham, 1995). Sampling of nine wells (Figure 6) will begin in January 2011, prior to construction of the Paso Robles housing development and associated golf course, which is believed to begin late spring to early summer, 2011. Sampling will continue on a bimonthly basis. Samples obtained prior to construction will aid in the development of an adequate baseline understanding of the water chemistry in the immediate area. Table 1 shows the estimated timeline for this project. Additional samples will be taken at each site following significant rain events of at least two, which may allow an increase in compound concentration as runoff enters the aquifer. Pre -cleaned 1-liter amber glass bottles will be used to collect water samples at each monitoring well. Water will be obtained directly from a faucet close to the well head at each site following adequate purging of each well for approximately 15 minutes to insure a representative groundwater sample is obtained. Samples will be kept on ice and transported to the Bio Assay Laboratory at the Edwards Aquifer Research and Data Center, where they will be filtered. The pH of only the samples which will be used for GC -MS and LC -MS analysis will be adjusted to 2 with concentrated sulfuric acid and stored in a refrigerator at VC until extraction, which will occur within seven days of collection. Samples collected for Ion Chromatography, total hardness, total alkalinity, total dissolved solids, and total coliform bacteria will be refrigerated a 4°C and submitted to the Edwards Aquifer Research and Data Center without adjustments to pH. Summary The development of Paso Robles will result in the placement of residential homes and a golf course over the contributing zone of the Edwards Aquifer, as well as above segments of the aquifer's crucial recharge zone where water enters the aquifer system and continues to flow in a northeastern direction (Murray, Straud, Hammond 2007; Schindel et al., 2009; Smith, Hunt, Schindel 2005). There is concern that the construction process, subsequent residential use of lawn chemicals, and the application of effluent (reclaimed wastewater) from the San Marcos Wastewater Treatment Plant on the golf course will adversely influence the water quality of surrounding areas, particularly down gradient of the site location. Contamination may occur through the introduction of excess nutrients and toxins including potential endocrine -disrupting compounds in the form of herbicides, pesticides, or residual compounds from treated effluent. These introductions could in turn severely degrade the sensitive habitats of endangered species dependent upon the Edwards Aquifer and associated springs which, in some cases, are unique to those environments. In addition, contamination of the groundwater may pose human health risks that could affect the communities that are dependent on the water for municipal and recreational purposes. This concern is based on past examples of contamination within the Edwards Aquifer. For instance, toxic metals, pesticides, and chlorinated solvents have been regularly detected in the aquifer within Bexar County (Figure 1) as a result of development; specifically spills, dumping, storm runoff, and leaks. Precise sources of contamination are often unknown, and many contaminants are detected below established levels that could impair human health. However, some wells within the area have detected contaminant concentrations that exceed required drinking water standards (Ross, Rice, 2005).