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Colorado Division of Reclamation Mining and Safety. January 6, 2011 Mr. Eric Scott 4 103-81640 2.4 Purging and Sample Collection The monitor wells were purged on September 21 and then sampled on September 27, 2010. Sampling was not performed immediately after purging because all but one of the wells (MW-1) purged dry and based on the previous water 'level recovery monitoring following pumping (Section 2.2), it was determined that several of these wells would require multiple days to produce a sufficient volume of water to fill all of the required sample bottles. All purging and sampling activities were conducted by Golder. Prior to purging, water levels were measured in all of the wells using an electronic water level indicator. Purging was then performed with a non-dedicated Grundfos Redi-flow 2 submersible pump powered by a portable generator to expedite the purging process. The water level indicator and pump were decontaminated prior to the start of this work and then again between wells using an AlconoxTm solution followed by a rinse with distilled water. The discharge tubing dedicated to each well for the pumping, described in Section 2.2, was re-used for this purging. Personnel wore new, disposable nitrile gloves to perform all purging activates. 1 Field water quality indicator parameters (pH, specific conductance, and temperature) were monitored periodically during purging activities. Purging continued until the well either purged dry or at least three well volumes were removed and the indicator parameters stabilized. Monitoring wells MW-2, MW-3, and MW-4 were purged dry. The indicator parameters at all four wells were considered stable when purging was complete. Stabilization of field parameters is defined by a change of less than ±10 percent during three consecutive readings for temperature and conductivity, and less than ±0.2 standard units for pH. Monitor well purging and sampling field data are provided on the field forms in Attachment C. The monitoring wells were sampled using new, disposable polyethylene bailers and new nylon rope. Water levels were measured in each well prior to sample collection to check that sufficient water was present to fill all of the required sample bottles. The water level indicator was decontaminated prior to the start of sampling and then again between wells using an AlconoxTm solution followed by a rinse with distilled water. Also, the initial bailer of water removed from each well was discarded. Groundwater samples were collected by pouring water from the bailer directly into the laboratory-prepared bottles, except for the samples requiring filtration prior to analysis (e.g. dissolved metals). The water to be filtered was first transferred from the bailer to a clean container. The water in the clean container was then passed through a new disposable 0.45 micron filter and into the laboratory-prepared bottles using a peristaltic pump and length of new tubing. Field parameters of pH, specific conductivity, and temperature were measured after all of the sample bottles were filled. Personnel wore new, disposable nitrile gloves to perform all sampling activities. Sample aliquots were preserved as required. Quality assurance/quality control (QA/QC) samples consisted of one blind duplicate sample (MW-20) collected at MW-4 and a field blank (MW-15). The field blank was collected by filling laboratory-prepared bottles with distilled water. Both of the QA/QC samples were analyzed for the same suite of constituents as the regular well samples. Samples were immediately placed in ice-filled coolers and shipped overnight to ACZ Laboratories, Inc. (ACZ) in Steamboat Springs, Colorado for analysis. Strict Chain-of-Custody procedures were followed throughout sample collection and shipment; copies of the Chain-Of-Custody forms are included in the laboratory reports in Attachment C. 3.0 MONITORING RESULTS AND DATA VALIDATION Water levels were measured in the wells by Golder on numerous occasions between July 30 and September 27, 2010, as described above. These water level data along with water level measurements from April 1999 through July 2000, when previous groundwater sampling was performed, were evaluated for seasonality and groundwater flow directions at the site. No distinguishable seasonal variations were observed in the data, thus the flow direction was evaluated based entirely on the 2010 measurements made by Golder. A potentiometric surface map showing the generalized groundwater flow direction for the July 30, 2010 water level measurements is displayed on Figure 3. This map suggests a general easterly groundwater flow direction. The July 30 measurements were used because these were considered to best represent static conditions. Once the pumping, hydraulic testing, and monitoring iA10\81640\0400\gwrep_ n1_06jan11\10381640 holcim gwrep_fnl-Ilr 06janl l.docx 0,,?Ider ciates