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including,but not limited to,sir peonit requirements,compliance monitoring,system <br /> effectiveness,VOC reduction beneath the apartments,adjacent plume control,eta <br /> 3. Installation of vapor points is confusing. The description indicates each vapor pourt will <br /> be installed to 5 feet,subcontracted to a C-57 licensed drilling company, and hand cored <br /> to five feet bgs. Clarification of vapor point installation methodology would be <br /> beneficial. <br /> 4, The Work Plan describes installation of five vapor point locations to a depth of five feet <br /> bgs. Five soil vapor point locations,with a vapor point installed at 5 feet is insufficient <br /> for system and plume monitoring. A sufficient number of vapor monitoring wells,given <br /> consideration of lateral and vertical au flow,and soil heterogeneity and plume locations, <br /> should be installed to provide evaluation of vapor flow pathways and concentrations <br /> between the SVE apartment wells,SVE excavation wells,DPS wells,and impacts to <br /> adjacent soa plumes and groundwater plumes_ integration of previously collected soil gas <br /> data,such as the Gore-Sorber data for benzene and other VOCs,as reported by Clayton <br /> (6 August 2002) should be considered during placement of vapor points. <br /> S. As reported for the L&M OU,Parcel z1 area,the presence of known and unknown <br /> underground lines were confirmed(Secor,9 January 2004)and subsequently removed <br /> (Secor, 10 Febmary 2005). By inference,underground lines are present beneath the <br /> apartments in the L&M OU,non-Parcel 2A area as a result of historic operations, <br /> including but not limited to the following: <br /> a. Underground pipelines to and from the former Standard Oil AM formerly <br /> located in the area of the northcnsteea two apaxtmentbuildings (Sanborn 1917; . <br /> Sanborn 1950;Tidewater 1961); <br /> b. Underground pipelines to the truck loading rack forrserly located in the area of <br /> the northeastern apartment building(Tidewater 1961;Sanborn 1977); <br /> • c. Underground pipelines to sad from as least 10 ASTs formedy located to the <br /> immediate northeast of the intersection of fo®er Edison Street and Main Sum <br /> beneath the apartment building at the same loradon(Sanborn 1917;Sanborn <br /> 1950);and <br /> d. Underground pipelines to and from diesel tank No.5008 founctly located to the <br /> immediate northwest of the intersection of former Flamson Street and M-= <br /> Street,beneath the sparanent building as the same location (Sanborn 1950; <br /> Tidewater 1961). <br /> Placement of vapor pmbes and air flow pathways should consider the presence of these <br /> pipelines,especially as uaaspott conduits for contaminant migration and SVE short <br /> euariting. <br /> 6. Site soils have been described as heterogeneous,these soils"...in the shallow zone <br /> predominantly coasist(ntg)of silts,silty sands, and silty gravels ranging is depths of four <br /> to ten feet bgs and organic clays,clays,high permeability silts,and lenses of sands sad <br /> poorly graded sands from depths ranging from four to ten feet bgs" (Secor,29 July 2005, <br /> pg.2). As discussed above,vapor point installation should consider betetogencity of <br /> soils,and the resultant preferential boazontal pathways(vapor transport)along more <br /> permeable soil zone& The presence of hetccogeneous soils supports the need for VOC <br /> reduction in conjunction with adequate Soil vapor coacenaation and flow evaluation to <br /> min;mire the potential fox migration oFadjacent VOC Plumes to beneath the apartment <br /> badiugs. <br /> 7. Albeit,construction of SVE wells beneath the apartments is consistent with the objective <br /> of removing volatile contaminants from beneath the apartments,the Work Plan does not <br /> Los Angeles,lderada Gita Gad Sao Diego Golden Sure Pnviroommtal <br /> • l:a:,nma,.,."_C,::o:�1.'_'xr lladpbe\1 !i <br />