Laserfiche WebLink
Depth -to- groundwater measurements were performed at each alluvial well prior to <br />sampling. Wells were also sounded to determine total depth. The volume of standing <br />water in each well was determined. Each of the alluvial wells were purged using a new <br />disposable poly bailer. A minimum of three casing volumes was purged from each well <br />prior to sampling. Field parameters pH, conductivity, and temperature were recorded as <br />each well volume was removed. Groundwater was purged until these parameters were <br />stabilized and reproducible (typically after three or five measurement sets). <br />Water levels measured in each of the alluvial wells were the lowest recorded since routine <br />monitoring was initiated. The St. Charles River was not flowing. Water was present in the <br />river along several sections, but these sections were separated by dry streambed conditions. <br />Each of the alluvial wells has typically produced significant water while bailing, even at <br />low water conditions. For well MW003, only four inches of standing water was present in <br />the well, and each purge removed approximately 50 ml of water. Even with the <br />significantly reduced sample volume required for the new compliance suite, it took over an <br />hour to fill all required samples bottles at this well. <br />All groundwater samples were submitted to Accutest Laboratory, located in Wheatridge <br />Colorado, for analysis of TDS and sulfate. Accutest subcontracted analyses for <br />radiochemical parameters to Hazen Research laboratory, located in Golden, Colorado. <br />RESULTS AND DISCUSSION <br />Results of the October 2011 groundwater sampling are provided in Table 1. Historical <br />results for the compliance suite for all wells are shown in Table 2. Table 2 also presents the <br />average and standard deviation statistics for each parameter based on the monitoring history <br />for each well. Analytical results provided by the contract laboratories are presented in <br />Appendix A. <br />All samples were submitted for analysis of sulfate, TDS, radium 226, and radium 228. The <br />results of these analyses are discussed in the following sections. <br />General Chemistry <br />General chemistry parameters do not have primary health based standards. TDS has a <br />secondary drinking water standard of 500 mg/L. Sulfate has a secondary standard of 250 <br />mg/L. As shown in Table 2, TDS and sulfate concentrations in all three downgradient <br />alluvial compliance wells have exceeded the 500 mg/L and 250 mg/L secondary domestic <br />drinking water standard in each of the sampling events since 2003. Excess sulfate in <br />drinking water may have negative aesthetic impacts such as laxative effects. High TDS <br />makes water taste salty. None of the sulfate results exceeded the State Numeric Protection <br />Level of 1,950 mg/L for the GCC site. <br />3 <br />