2012-04-25_HYDROLOGY - M2002004 - Laserfiche WebLink

Home Browse Search

INTRODUCTION Contour Consulting Engineering, LLC, (Contour) collected groundwater samples at the GCC Rio Grande, Pueblo Cement Plant, on March 20, 2012. The samples were collected to satisfy monitoring permit requirements, as stipulated by the Colorado Division of Mining Reclamation and Safety (DRMS). Quarterly sampling was initiated in 2008. Beginning in 2009, sampling was set at a semi -annual monitoring frequency. The compliance suite for the St Charles River monitoring wells now includes sulfate, total dissolved solids (TDS), radium 226, and radium 228. Sampling events previous to October 2011 included a comprehensive list of dissolved metals, anions, cations, and additional radiochemistry parameters. As part of recent semi - annual monitoring reports submitted to the Division, GCC has recommended that the reduced sampling suite would be appropriate for the site. This recommendation was based on comprehensive analysis of the results from the larger sampling suite over the sampling history for the project. Unless conditions at the site change, the new suite of monitoring parameters will be used in all future monitoring events. The previous sampling event, performed in October 2011, indicated that TDS concentrations exceeded the Numeric Protection Level (NPL) of 2,630 mg/L at wells MW -03 and MW -04. NPLs were set by the DRMS in a December 8, 2009 letter to GCC. Both TDS exceedences at wells MW -03 and MW -04 were preceded by downward trending TDS results between the October 2010 and April 2011 sampling events, and GCC noted that no upward trends were present. After reviewing the 2011 monitoring reports, DRMS submitted a letter to GCC dated February 24, 2012, indicating that, due to the TDS exceedences, another sampling event was required before March 31, 2012. The December 8, 2009 letter from DRMS to GCC states, "If an upward trend, above set limits is noted, the frequency of sampling will increase to quarterly." As of the October 2011 sampling evaluation, no upward trend was noted above the NPL TDS limit, as only one data point at each well exceeded the limit However, GCC did comply with the February 24, 2012 request, and performed sampling prior to March 31, 2012. GCC performed sampling for the currently approved suite of indicator parameters (TDS, sulfate, radium 226, and radium 228) on March 20, 2012. As the sampling was performed before March 31, 2012, this report presents findings for the first quarter 2012 sampling event. WORK PERFORMED Contour collected groundwater samples from three shallow alluvial monitoring wells (MW002, MW003, and MW004) in the vicinity of the St. Charles River. The alluvial wells represent downgradient conditions with respect to the Cement Plant operations. Deep well MWOO1A is completed in the Codell Sandstone west of the plant. This well was determined to be dry during the first quarter 2008. Approximately 4 feet of water was measured in this well during the second quarter 2008. One full bailer of very clear water was removed from the well, and then the well went dry. Similar conditions have been 2