2014-03-20_HYDROLOGY - M1977342 - Laserfiche WebLink

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March 2014 Mill MLGW -7 Groundwater Quality Assessment ♦ 4 3.0 WATER QUALITY EVALUATION The shallow groundwater quality downgradient of the 1 -Dam TSF is monitored at POC well MLGW -7. Per the GWMP, MLGW -7 has been analyzed triannually for the indicator parameters listed in Table 1. Following the notification to DRMS, monthly monitoring of MLGW -7 was initiated in September 2013 for an expanded list also shown in Table 1. - - -- -------------..._- - - - - -- Table 1 MLGW -7 Monitoring Parameters Triannual Monitoring Parameters Iron, Dissolved Zinc, Dissolved Manganese, Dissolved pH, Field Selenium, Dissolved Specific Conductance, Field Sulfate, Dissolved Monthly Monitoring Parameters Alkalinity, Total Potassium, Dissolved Aluminum, Dissolved Sodium, Dissolved Calcium, Dissolved Sulfate, Dissolved Chloride, Dissolved Zinc, Dissolved Fluoride pH, Field and Lab Iron, Dissolved Oxidation /Reduction Potential (ORP), Field Magnesium, Dissolved Specific Conductance, Field Manganese, Dissolved Temperature, Field 3.1 HISTORICAL AND CURRENT ANALYTICAL DATA The following section presents an initial assessment of water quality sampling in MLGW -7. These results were used to develop recommendations presented in Section 4.0. • Figure 5 is a graph showing pH measurements recorded in MLGW -7 and streamflow in the Williams Fork River (Parshall station) from 1995 to 2014. The data show that PH in MLGW -7 has often been reported below 6.5 over the monitoring period of record. It is notable that pH values steadily increased from 6.4 to 7.9 between February 2001 and May 2003, which was generally a period of below average precipitation for the area. Following an above average precipitation winter (2003), AJAX Ltd ♦ 28828 Cedar Circle ♦ Evergreen, CO 80439 ♦ (303) 241 -2057 Clear Creek Associates+ 6155 E. Indian School Rd. ♦ Scottsdale, AZ 85251 ♦ (480) 659 -7131