Laserfiche WebLink
1 - <br /> Ell��t <br /> 1 <br /> Mr James L Barton <br /> 1 July 12, 2004 <br /> Page 2 <br />' groundwater flow direction for Unit B was generally to the southeast, with the hydraulic gradient <br /> ranging from approximately 0 002 ft/ft to 0 004 ftlft <br />' Copies of the groundwater sampling information sheets are included as Attachment B Tabular <br /> results of recent depth to water (DTW) measurements are summarized in Table 1 Well <br /> construction details are included as Attachment C <br />' Groundwater Sampling and Analytical Results <br /> Groundwater samples were collected on April 13 through April 15, 2004 Groundwater samples <br />' were submitted to California Laboratory Services (CLS) in Rancho Cordova, California, for <br /> analyses of benzene, toluene, ethylbenzene and total xylenes (BTEX) by EPA Method 8021, <br /> total petroleum hydrocarbons as gasoline (TPHg) by EPA Method 8015 Modified, and volatile <br />' organic compounds (VOCs) by EPA Method 8260B Tabular results of recent groundwater <br /> sampling analytical results are summarized in Table 1 A summary of groundwater elevations <br /> measured to date is presented in Table 2 Cumulative groundwater sampling analytical results <br /> are summarized in Table 3 Maps depicting dissolved concentrations of TPHg and benzene in <br /> groundwater are included as Figures 5 through Figure 12 Laboratory analytical results with <br /> chain-of-custody documentation are included in Attachment D <br /> Site Conceptual Model Update <br /> In a letter dated February 8, 2002, the RWQCB requested completion of an updated Site <br /> Conceptual Model (SCM) for this site The initial SCM was submitted to the RWQCB in an EA] <br /> report titled "Supplemental Investigation Report, Problem Assessment Report, and Work Plan, <br /> Cleanup and Abatement Order No 5-00-707, Montgomery Ward Auto Service Center and <br /> t Former Unocal Site, 5400 and 5606 Pacific Avenue, Stockton, California," dated <br /> October 13, 2000 <br />' Site stratigraphy is segregated into four hydro-stratigraphic units that generally correspond to <br /> screened intervals of site wells The shallowest wells are screened in the hydro-stratigraphic <br /> unit designated as Unit A and the deepest wells are screened across hydro-stratigraphic Unit D <br />' A cross-section location map and cross sections A-A' and B-B' are included in Attachment E <br /> Second quarter 2004 analytical results are summarized on the respective cross-sections <br /> Remediation System Description <br /> The remediation system utilizes soil vapor extraction (SVE) and air sparge (AS) The SVE <br /> system is currently shut down When operational, the SVE system extracted soil vapors from <br /> 13-vapor extraction and combination wells, and four monitoring wells A thermal oxidizer <br /> provided abatement of the hydrocarbons prior to atmospheric discharge The air sparge system <br /> consists of an air compressor that forces filtered air through piping routed to 10 air sparge <br /> a points, and air sparge well AS-26 Well construction details are included in Attachment C The <br /> system layout is shown in Figure 13 <br /> J IProjects10894015098-2931FinaRReportsl2nd Qtr 04-QMR RSR12nd Qtr 04-QMR doc <br /> J 'l V � C'�1`'"t chic "IVl �'1172f1ld1.`.PI�:B< <br />