ARCHIVED REPORTS_2013 - Laserfiche WebLink

Home Browse Search

Unsaturated Zone Soil Gas The Methane concentration was zero in all wells during the 1St and 2nd Semester except SG-6,where methane was reported at 0.4% during the 1St Semester 2013 sampling event. VOCs were reported in all samples collected this year except SG-1 and SG-3 during the 1St Semester 2013. The number of VOCs reported per event varied from 15 in the first semester to 28 in the second semester. The number and type of VOCs reported does not indicate a trend. VOCs are typically not found in the groundwater. The presence of VOCs at these concentrations in the soil within the landfill property does not apparently impact groundwater. Leachate Results of leachate monitoring are consistent with past leachate monitoring events. The first semester leachate monitoring event occurred on January 23, 2013. Twenty nine different VOCs were reported during the 1St Semester 2013 sampling event. The Highest VOC concentrations reported were the Xylenes, MtBE, TBA, the benzene compounds, and Toluene. The second semester leachate monitoring event occurred on July 30,2013. Twenty Nine different VOCs were reported during the 2nd Semester 2013 sampling event. The Highest VOC concentrations reported were the Xylenes, MtBE, TBA,the benzene compounds, and Toluene. The quantities of leachate indicate that the LCRS is able to maintain the level of leachate below regulatory limits. GROUNDWATER DIRECTION AND FLOW RATE The groundwater elevations indicate that there was no groundwater gradient during the third quarter. Groundwater flow was to the southeast and northeast during fourth quarter of 2013 (Figures 3 and 4). These are unusual groundwater flow conditions, as flow is historically in a westerly direction. It appears that starting in 2009 the regional flow pattern has shifted to the south-southeasterly and sometimes to the easterly direction. This change in flow direction may be due to changes in regional agricultural groundwater pumping. The average calculated groundwater velocity in the fourth quarter is 87.53 ft/yr (Appendix G). Replacement down-gradient wells G-2A and G-5A were installed during the 2nd Semester 2013. These wells were installed deeper into the aquifer because the existing wells had gone dry. The logs for these new wells are presented in Appendix H. STANDARD OBSERVATIONS Site inspections were performed weekly this semester(Included as PDF on the CD, attached). An electronic signature on the form certifies that all observations were performed and are accurate. North County RC&SL Public Works/Solid Waste 2°"Semester and Annual 2013 Groundwater Monitoring 12 County of San Joaquin—January 25,2014