ARCHIVED REPORTS_2012_2 - Laserfiche WebLink

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i Samples collected from the leachate sumps are analyzed for the following parameters semiannually: Temperature Total Alkalinity Electrical Conductivity (EC) Total Hardness pH Chemical Oxygen Demand (COD) Turbidity Volatile Organic Compounds (Short List) Dissolved Oxygen(DO) Chloride Redox Potential Total Dissolved Solids (TDS) Statistical Analysis of Groundwater Data The NCRC&SL has been approved to perform interwell tolerance limits (up-gradient well serves as the background). Concentration limits are updated once yearly using interwell tolerance limit methods, and were most recently updated for the first semester of 2012. Analytical results from this monitoring event were compared to the concentration limits. Concentration limits are updated where possible. If the historical data contains more than 50%non- detects, the concentration limit cannot be updated. In these cases, the established concentration limit listed in the WDRs is used for comparison. Concentration limits are updated on a yearly basis in accordance with the latest WDRs. As requested by RWQCB staff, stiff diagrams will be included in the second semester and annual report. AIL MONITORING RESULTS Groundwater Summary Groundwater was sampled on January 9, 2012. Field and Monitoring Parameters Monitoring results for the first semester sampling event of the 1st Quarter on January 9, 2012 (Table 3) indicate that the concentrations of field and monitoring parameters are below established concentration limits where limits could be established for all wells, with the exception of background well G-1 where slight exceedences for Turbidity, Sodium, Potassium, Bicarbonate Alkalinity, and Total Dissolved Solids (TDS)was reported. However, turbidity is an indicator of well function and not an indicator of landfill impact to groundwater. Groundwater elevations for the 2nd quarter 2012 show similar results (Table 4). Monitoring Parameter Concentration Limits Interwell concentration limits were established from background monitoring well G-1, as such the concentration limit exceedence for Sodium, Potassium, Bicarbonate Alkalinity, and TDS is representative of natural changes in the background conditions for the landfill and not site activities. No concentration limits were exceeded this semester in any other wells. However, since there is an North County RC&SL Public Works/Solid Waste 15'Semester 2012 Groundwater Monitoring 6 County of San Joaquin—July 26,2012