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Surface water samples are analyzed every 5 years for the following constituents of concern <br /> (COC): <br /> • ICP Metals (26 metals) <br /> The next surface water COC monitoring is scheduled for the first semester 2014. <br /> Landfill Gas <br /> Landfill gas is monitored quarterly at monitoring points GW-9M, GW-1 OD, and East header at <br /> Landfill 1 and East or West Header at Landfill 2. Landfill gas samples were collected this <br /> semester(Table 3). <br /> Landfill gas samples are analyzed for the following field parameters: <br /> • Gas Pressure <br /> ® Methane <br /> • Carbon Dioxide <br /> Landfill gas samples taken from these sampling points are analyzed semiannually VOCs. <br /> STASTICAL ANALYSIS <br /> Groundwater <br /> Sanitas software calculations of tolerance limits for intrawell analysis call for less than 50 <br /> background observations. In cases where the total number of observations is more than 50, and <br /> there is no increasing trend, the 50 most recent observations are used to calculate intrawell <br /> tolerance limit. <br /> Concentration limits are not updated if the data contains more than 50% non-detects or if there is <br /> a statistically significant increasing trend in the data. In these cases, the concentration limit listed <br /> in the current WDRs is compared to the most recent data. <br /> At the Harney Lane Sanitary Landfill (HLSL), Concentration Limits (CLs) for statistical COCs, <br /> including general minerals and dissolved metals generally detected in background, shall be <br /> based on interwell data analysis. CLs for nonstatistical COCs, including VOCs, other organic <br /> CDCs, and dissolved metals not detected in background, shall be equal to the method detection <br /> limit (MDL). Concentration limits are updated semiannually, where possible, and were most <br /> recently updated in this semester(Table 1). <br /> Interim CLs <br /> Fourteen out of 25 dissolved metals were identified as statistical COCs, based on <br /> available historical monitoring data from upgradient well MW-1. Interim statistical CLs for <br /> r <br /> Harney Lane Sanitary Landfill 4 Department of Public Works/Solid Waste <br /> 1"Semester 2012 Groundwater Monitoring Report County of San Joaquin—July 31,2012 <br />