Laserfiche WebLink
Groundwater & Surface -Water Monitoring Response Plan <br />contained benzene and trichloroethylene at concentrations exceeding the organic standard, and <br />one sample at HB -L3 contained vinyl chloride at a concentration exceeding the organic standard. <br />As specified in Regulation 41, where a background groundwater level exceeds a standard <br />established for domestic or agricultural use, the applicable standard for the parameter is either the <br />table value or the background level. Determination of whether the table value or the background <br />level applies is made considering the increased risk to public health, crops, or livestock associated <br />with the background levels; the extent of the exceedance above the table value; the degree to <br />which the pollution is deemed correctable and subject to treatment; and the economic <br />reasonableness of such treatment requirements. <br />Comparison of baseline results to surface -water standards is presented in Table 2. As shown, <br />baseline characterization results for boron and total recoverable iron concentrations in one or <br />more surface -water samples from Black Sulphur Creek exceed the stream standards. <br />The assessments will also consider the maximum allowable TDS concentration standards for <br />groundwater established by the WQCC which are based on background concentrations as <br />follows: <br />Background TDS Value (mg /L) <br />0 -500 <br />501 — 10,000 <br />10,001 or greater <br />Maximum Allowable TDS Concentrations <br />400 mg/L or 1.25 times the background level, <br />whichever is least restrictive <br />1.25 times the background value <br />No limit <br />TDS concentrations exceeded 500 mg/L in all the monitoring wells during baseline <br />characterization, with a maximum concentration of 8,340 mg /L reported for well HB -L3. <br />Therefore, within the zones monitored, the maximum allowable TDS concentration would be <br />1.25 times the background value. <br />Results of the data assessment will be used to develop specific groundwater protection procedures <br />which will be submitted to DRMS, BLM, and EPA. At a minimum, the procedures include <br />continuation of increased sampling frequency for all or a portion of the target analytes and the <br />6 <br />