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ow" <br /> USS <br /> M N <br /> Mr. Robert McClellon <br /> January 4, 2005 <br /> Page 3 <br /> General Comment 1.Pursuant to 27 CCR 20919 and 20937,the EHD does not approve the <br /> remediation plan submitted to URS.The passive venting of landfill gas through the use of ventilation <br /> wells is not a suitable remediation for this site. <br /> Response to General Comment 1. Passive venting may not be suitable for this site. However, to assess <br /> whether passive venting is suitable, additional information is needed. We believe that the <br /> implementation of the proposed activities presented herein will allow us to obtain this information. <br /> General Comment 2.The EHD is requiring that an appropriate gas control system be planned and <br /> designed for remediation of the site as described in 27 CCR 20919 and 20937(a). <br /> Response to General Comment 2. Comment noted. An appropriate gas control system will be designed <br /> to control methane at the property boundary when the information(i.e., methane concentration,flow <br /> rate, etc.) required to design the system is collected. <br /> General Comment 3.The EHD is requiring that a revised remediation plan be submitted within <br /> fourteen (14)days of receipt of this letter. <br /> Response to General Comment 3. It is our understanding,from our meeting of December 9, 2004, that <br /> it was agreed that the revised remediation plan could be submitted to you in early January 2005. <br /> PROPOSED FIELD ACTIVITIES <br /> Additional Site Investigation Activities <br /> Additional site investigation activities are needed to assess the horizontal and vertical extents of the <br /> debris placed within the landfill and to further assess the extent of the methane plume along the <br /> northern portion of the site.We plan to conduct a geophysical survey to assess the horizontal and <br /> vertical extents of the debris placed within the landfill.To further assess the extent of the methane <br /> plume, we plan to install additional probes along the northern and western boundaries of the site. The <br /> details of the geophysical survey and additional probe installation are provided hereafter. <br /> Geophysical Survey <br /> The geophysical survey will use non-invasive surface techniques to assess the subsurface conditions at <br /> the site.Electromagnetic and electrical resistivity geophysical methods may be used. The <br /> electromagnetic method is used to measure variations in subsurface electrical conductivity. This <br /> information can be used to identify areas of buried debris. The electrical resistivity method is used to <br /> measure variations in electrical resistivity, with depth, along a profile. This information can be used to <br /> assess landfill thickness.The data collected using these two geophysical methods will be used to assess <br /> the horizontal and vertical extents of the debris placed within the landfill. The extraction wells may be <br /> relocated within an area of debris based on this information. <br /> K:\Wprocess\25532\WorldEnterprise\Remediation Plan\010405-Ltr.doc <br />