Laserfiche WebLink
0 <br /> well documented that landfill gas contains methane, carbon dioxide, nitrogen, and trace gases. <br /> The trace gases often contain VOC's. In 1998,the County collected a sample from the deepest <br /> probe in gas well#2 and had the sample analyzed for VOC's. Results indicated the detection of <br /> eleven VOC's. Four of the eleven VOC's detected in the soil vapor have been detected in the <br /> groundwater. <br /> The County believes that landfill gas is the source of the contamination in groundwater under the <br /> Corral Hollow Sanitary Landfill. The County retained EMCON to perform an evaluation in an <br /> effort to determine the source of VOC contamination. Their evaluation(attached)concludes that <br /> landfill gas is likely the source. EMCON's conclusion is based on predictions about <br /> concentrations that could be expected if VOC's from the soil vapor were affecting the <br /> groundwater. This was accomplished using Henry's Law and the Ideal Gas Law. Please see <br /> attached report for details and calculations. <br /> The groundwater elevation in MW-5 is similar to the elevation of the deep probe within gas well <br /> #2 where the soil vapor sample was collected. In addition, gas well#2 is located along Corral <br /> Hollow Sanitary Landfill where landfill gas migration is strongest. Therefore, it is reasonable to <br /> assume that landfill gas is interacting with the shallow groundwater table. The other shallow <br /> zone groundwater monitoring wells (SB-1, MW-4)have not shown detections of VOC's <br /> historically. Accordingly, the landfill gas monitoring probes in the vicinity of MW-4 have not <br /> shown levels of migrating landfill gas. If leachate were contaminating the groundwater, it would <br /> be reasonable to assume that SB-1 and MW-4 would be affected. It appears that landfill gas <br /> migration may be restricted in some way to the south,thereby preventing gas influence on SB-1 <br /> and MW-4. <br /> PROPOSAL FOR REMEDIATION <br /> We believe that the source of VOC contamination at the Corral Hollow Sanitary Landfill is <br /> landfill gas which is migrating to the perimeter of the landfill. Therefore,the most effective <br /> means of corrective action is to install a landfill gas control system to prevent migration of VOC- <br /> 4 <br />