Res 2011-037 (2) - Laserfiche WebLink

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This can also result in variability of compounds and suspended particles within the water (Goldscheider, Drew, 2007). Along with the ten scheduled events, sampling of all monitoring wells will also occur following any significant rainfall of at least two to three inches. In addition, an ISCO-6712 Portable Stormwater Sampler will be deployed at the base of an observed drainage, known as Cottonwood Creek, that runs through the Paso Robles development site towards Hunter Road (Figure 6). During a significant rain event, the sampler will begin surface water collection when a sufficient amount of water has drained through the development location and activated the liquid level actuator attached to the ISCO sampler. The device will then begin collecting 1-L water samples at programmed intervals of 6 bottles every 5 minutes, 6 bottles every 15 minutes, 6 bottles every 30 minutes, and 6 bottles every hour. Each sample collected will be analyzed for total suspended solids, nitrate, calcium, magnesium, sodium, potassium, sulfate, chloride, dissolved organic carbon, alkalinity, and conductivity at the Edwards Aquifer Research and Data Center (Table 7). In addition, a rough estimate of flow will be determined with the use of a flow meter and also the construction of a weir where samples are collected. This data will aid in the evaluation of surface runoff which may enter the aquifer as Paso Robles and the associated golf course are being constructed. In partnership with the Environmental Chemistry Lab at the A.E Wood State Fish Hatchery, Gas Chromatography Mass Spectrometry (GC -MS) and Liquid Chromatography Mass Spectrometry (LC - MS) will be used to analyze groundwater samples for compounds that a previous study found to be most frequently detected in 60% of effluent samples obtained from the City of San Marcos Wastewater Treatment Plant (Foster, 2007). These compounds, which are known or suspected endocrine disruptors, are listed in Table 4. Table 5 lists target insecticide and herbicide compounds, many of which are also known or suspected endocrine disruptors, that will also be analyzed for this study using GC -MS and LC -MS. These compounds were chosen based on their commercial availability in local stores and the inferred likelihood of their use within the Paso Robles housing development. Analysis of samples using GC -MS have been developed based on USGS analytical methods found in Open -File Report 95-181 (Zaugg, Sandstrom, Smith, 1995), and Water -Resources Investigations Report 01-4186 (Zaugg et al., 2006). LC -MS analysis will be modeled after previously developed analytical methods described by Vanderford et al., 2003. Quality Assurance Each sampling event will include the following to ensure proper quality control: lab blank, lab control spike, matrix spike for GC, matrix spike duplicate for GC, matrix spike for LC, matrix spike duplicate for LC, field blank, and sample duplicates at selected sites to indicate reproducibility. Atrazine-13C3 and Fluoranthene-dio will serve as surrogates for GC -MS experiments, and 2, 4-D-13C6 and Acetaminophen-da will be surrogates in LC -MS experiments. Each sample will be spiked with known amounts of surrogates before the extraction process to indicate the efficiency of individual sample extraction and aid in the calculation of percent recovery. In addition, a method validation will be performed to ensure success and reproducibility of analytical techniques, including extraction and elution of each sample. This will involve spiking replicates for GC -MS with all compounds to be analyzed in this chromatographic technique, as well as with the appropriate surrogates. The same will be done for LC -MS replicates. A blank for each will also be extracted and eluted with the replicate validation samples. -8-