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r r Surface Water Surface water is sampled at upstream monitoring point S-1 and downstream monitoring point S-2 (Figure 2) when water is present. Samples are collected after the first storm of the rainy season that produces significant flow, and quarterly thereafter when water is present. Surface water r flows are monitored semiannually for the same field and monitoring parameters as for groundwater specified above. No sampling was conducted during this monitoring period due to absence of water. Unsaturated Zone Monitoring Landfill gas is sampled at monitoring points GW-9M, GW-1 OD, and East header at Landfill 1 and East or West Header at Landfill 2. Landfill gas samples are analyzed for Gas Pressure, Methane, and Carbon Dioxide quarterly and for VOC's semiannually. VOC analysis was done during this semiannual period (Table 3). rSTASTICAL ANALYSIS Groundwater Sanitas software calculations of tolerance limits for intrawell analysis call for less than 50 background observations. In cases where the total number of observations is more than 50, and there is no increasing trend, the 50 most recent observations are used to calculate intrawell tolerance limit. Concentration limits are not updated if the data contains more than 50% non-detects or if there is a statistically significant increasing trend in the data. In these cases, the concentration limit listed in the current WDRs is compared to the most recent data. At the HLSL, Concentration Limits (CLs) for statistical COCs, including general minerals and dissolved metals generally detected in background, are based on intrawell data analysis. CLs for nonstatistical CDCs, including VOCs, other organic COCl, and dissolved metals not detected in background, shall be equal to the method detection limit (MDL). Concentration limits are updated semiannually, where possible, and were most recently updated in this semiannual period (Table 1). Interim CLs Fourteen out of 25 dissolved metals were identified as statistical COCs, based on r available historical monitoring data from upgradient well MW-1. Interim statistical CLs for these constituents have been estimated. Concentrations of the remaining 11 dissolved metals were assumed nonstatistical COCs for setting interim CLs. Revised CLs Revised CLs shall be developed for general minerals and dissolved metals once r additional background monitoring wells have been established per WDR and a sufficient amount of monitoring data have been collected for statistical determination of CLs. 1 Harney Lane Sanitary Landfill 3 Department of Public Works/Solid Waste 1"Semiannual 2014 Groundwater Monitoring Report County of San Joaquin—July 31,2014