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Todd Del Frate • -2- <br />LYSIMETER STATUS <br />NORTH COUNTY RECYCLING CENTER AND SANITARY LANDFILL <br />According to our consultant (Shaw Environmental and Infrastructure), lysimeters could exhibit two modes of <br />failure, both of which would be indicated by the behavior of the lysimeter during sampling. <br />The first mode of failure is the separation of the tube, which would be shown by the inability to induce a <br />vacuum in the first step. As seen in the most recent data (attached), all lysimeters are able to maintain <br />significant vacuum after the vacuum is first established. Therefore, we believe that the tubes have not <br />separated. <br />The second mode of failure is plugging of the tubes or of the sampling tip itself. This failure would be shown <br />by the vacuum maintained undiminished overnight. As seen in the data, the vacuum of all lysimeters <br />significantly diminished overnight. Therefore, we believe that the sampling tubes and the sampling tips of <br />the lysimeters are not plugged. <br />Based on this analysis, we believe that the lysimeters are functioning as intended, and no corrective <br />measures are needed. <br />Secondary Leachate Sumps <br />Modules 3 and 4 are provided with a "secondary sump", that is, a second layer of containment is provided <br />below the leachate sumps at these Modules. These are, in effect, large "pan lysimeters" which can be used <br />to monitor the integrity of the sump liner. <br />Module 4 secondary sump is monitored for water accumulation quarterly, starting in January 2010. Results <br />of the monitoring indicate the primary liner is not leaking. <br />Module 3 sump has not been monitored, and is not now included in the Monitoring and Reporting Program. <br />However, the County intends to install a level measurement device similar to that now in place in the Module <br />4 secondary sump, and measure the liquid within that sump (if any) quarterly. THis data would be included <br />in the semi-annual report. <br />Workplan <br />The facilities investigated for this report were found serviceable and satisfactory. No additional work is <br />proposed beyond the installation of liquid measurement in the secondary sump of Module 3. <br />If you have any questions, please call me at (209) 468-8504. <br />Sincerely, <br />W. MICHAEL CARROLL, PE <br />Senior Civil Engineer <br />Attachments <br />WMC:sc <br />N:\1North County\Groundwater Monitoring\Repts201MDelFrate01-LysimeterEval.doc <br />c: Robert McClellon, Environmental Health Department <br />LA 63107 <br />