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I� <br /> I•,+ , . , r S ! <br /> t 1 A <br /> t I[ I_ fi <br /> Cobb Environmental & ' Tleclhnic};a;� ervices <br /> i <br /> QUARTERLY GROUNDWATER MONITORING REPORT <br /> FOURTH QUARTER 1997 <br /> E-Z Serve#100878, 1012 W Yosemite,Manteca,CA <br /> BACKGROUND <br /> A total of eight monitoring wells(MW-1 through MW-8)have been installed, seven on-site(MW-1 through <br /> MW-6, and MW-8) and one off-site(MW-7) The extent of groundwater contamination has been <br /> delineated <br /> GROUNDWATER MONITORING FIELD ACTIVITIES <br /> Date of Field Activities 11/21/97 <br /> Wells Monitored/Sampled MW-1,2 and 5 <br /> Analytes Tested TPHg,BTEX and MTBE <br /> Analytical Methods EPA Methods 8015/8020(modified) <br /> Laboratory Entech Analytical Labs,Inc <br /> Remarks All wells were sampled using the no purge technique Additionally, <br /> MW-5 was sampled using the purge technique <br /> GROUNDWATER MONITORING RESULTS <br /> Depth to Water 14 41 to 15 94 feet below grade <br /> Flow Direction/Gradient Northwest at 0 0015 ft/ft <br /> SPH-wells/thicknesses Not Detected <br /> TPHg concentration range 240ppb(MW-2)to 25,000ppb(MW-5) <br /> Benzene concentration range <0 5ppb(MW-5)to 19ppb(MW-1) <br /> MTBE concentration range <5 Oppb(MW-1,2, and 5) <br /> Remarks Groundwater flow and depths are generally consistent with previous <br /> measurements In addition, MW-5 was sampled using both the no <br /> purge/purge technique to er aluate the effects of the purging method It <br /> appears that the results indicate relatively consistent BTEX <br /> concentrations Thus, it is concluded that the no purge technique is an <br /> effective method prior to sampling <br /> PROJECT STATUS <br /> The next quarter monitoring will again utilize the no-purge technique for sampling all wells Appropriate <br /> future courses of action are being evaluated <br /> ATTACHMENTS <br /> • Groundwater Elevation Contour Map <br /> • Groundwater Elevations and Analytical Results(Table 1) <br /> • Laboratoy Report and Chain-of-Custody form I <br /> • Groundwater Monitoring and Sampling Protocols <br /> + Gauge/Purge Calculations and Well Purging Date Sheets < <br /> • .Purge vs No-Purge Protocol <br /> I i <br /> I I i <br /> I I <br /> I <br /> 1 � <br /> I <br /> rl I rl <br /> tl <br /> I j I 'P Q Box 1602 + Tupelo Mjssi55xppt 38802--1602 f I <br /> 601-841-0995 (phonc) + 607 -841-0810 CfaY) <br /> IIl1 I I'll <br /> `! II I I '4 I I hs �klrl ��' �II If'III I u" I ¢' 1 I -0' Int II hI I' E I ' I IIF I I I I I iII n I, SII if <br />