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WASTE DISCHARGE REQUIREMENTS ORDER R5-2015-0058-01 -14- <br />SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS <br />FOOTHILL SANITARY LANDFILL, INC. <br />FOOTHILL LANDFILL <br />SAN JOAQUIN COUNTY <br /> <br />four suction lysimeters, including one background lysimeter (LZ-1) installed near the <br />northeast site boundary and three detection lysimeters (LZs-2, 3, and 4) installed <br />beneath the module’s containment system. LZ-2 was installed beneath the LCRS <br />sump in the southeast corner of the module; LZ-3 was installed beneath an LCRS <br />trench in the northeast part of the module; and LZ-4 was installed beneath the base <br />liner in the southwest corner of the module. Soil pore water monitoring devices <br />installed at future LF-2 modules, beginning with Module 2, Phase A, will consist of <br />one or more pan lysimeters, including at least one pan lysimeter installed beneath the <br />module’s LCRS sump. See MRP Section A.2.a and Attachment C: Site Map. <br />No liquid has been detected in any of the lysimeters at LF-2, Module 1 since their <br />installation in 2003. This supports findings that LF-1 is the source of VOC impacts <br />detected in soil gas and groundwater at the site. <br />60. For the proposed surface impoundment, LZ-SI-1 will be used as the detection pan <br />lysimeter for the unit. The unsaturated zone monitoring system for future modules <br />shall be implemented in accordance with the operative MRP. <br />61. No leachate monitoring is conducted at LF-1(other than seep monitoring) because it <br />is unlined and is not equipped with an LCRS sump. The Discharger has been <br />conducting semiannual leachate sump monitoring at LF-2, Module 1 since 2005, <br />however. The results of this monitoring are summarized in the table below. <br /> LF-2, Module 1 <br />Leachate Monitoring Results1 <br />Constituent Average <br />Concentration <br />General Minerals mg/L <br />Chloride 208 <br />Total Dissolved Solids 1,565 <br />VOCs2 µg/L <br />1,1-Dichloroethane 4 <br />Ethyl benzene 12 <br />Methyl tert-butyl ether 96 <br />Tetrachloroethene (PCE) 2 <br />Toluene 32 <br />Trichloroethene (TCE) 3 <br />Total Xylenes 26 <br />2-butanone (MEK) 1,214 <br />4-methyl-2-pentanone 46 <br /> <br />1. Results based on semiannual LCRS sump monitoring conducted since 2005. <br />2. Listing includes most, but not all, VOCs detected in the module sumps during the monitoring period. <br />During the First Half 2014, the leachate flow rate to the sump averaged 33,600 <br />gallons per month. MRP Section D requires that the Discharger monitor leachate <br />monthly for flow rate and other field parameters and annually for landfill constituents <br />of concern.