Laserfiche WebLink
Tim Cazier <br />February 15, 2012 <br />Page 2 <br />Your letter dated December 8, 2009 stated the following: <br />• GCC <br />Rio Grande <br />Pueblo Plant <br />"Sampling for each well will be conducted semi annually and results to be submitted <br />annually. If an upward trend above the set [NPL] limits is noted, the frequency of <br />sampling will increase to quarterly." <br />Although the October TDS results for MW -003 and MW -004 are higher than the DRMS NPL, these results <br />do not define an upward trend for these parameters. The attached December 1, 2011 Groundwater <br />Monitoring Report (Report), which was prepared by Contour Consulting Engineering (Contour), explains <br />that the TDS results obtained during the October sampling event are likely due to seasonal low <br />groundwater levels following a dry Summer with little Fall precipitation. These conditions tend to <br />concentrate dissolved chemical species, raising the level of TDS in the samples. <br />The following graph, taken from the Report, shows historical TDS levels in all wells. As shown below, <br />higher TDS levels appeared in MW -003 and MW -004 in the Fall of 2008, 2009 and 2010. TDS drops <br />markedly (especially in MW -003) in the Spring following these sampling events. <br />Please contact me if you have questions about this report. <br />Sincerely, <br />l a <br />f <br />Barbara T. Hodgson L/ <br />Environmental Manager <br />(719) 647 -6829 <br />bhodgson @gcc.com <br />z <br />