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s <br /> 1�V Cobb EnvironmenYta,l %54Technical Sgrmic,e's _ta�_}11 <br /> IL s L ! — 1 r <br /> 4� <br /> QUARTERLY GROUNDWATER MONITORING REPQ <br /> SECOND QUARTER 1997 r [ A 'i <br /> E-Z Serve 4100878, 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 <br /> through 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 6/20/97 <br /> Wells Monitored/Sampled MW-I through MW-8 <br /> Analytes Tested TPHg, BTEX and MTBE <br /> Analytical Methods EPA Methods 8015/8020(modtfied) <br /> Laboratory Entech Analytical Labs,Inc <br /> Remarks In April the UST Cleanup Fund issued sampling protocol <br /> recommendations based on a study performed by the WSPA This <br /> recommendation,coupled by the many sampling events which <br /> preceded the second quarter 1997, has resulted in E-Z Serves decision <br /> to evaluate the suitability of the no purge method of sampling All <br /> samples collected during the second quarter utilized the no-purge <br /> method sampling <br /> GROUNDWATER MONITORING RESULTS <br /> Depth to Water 13 1 to 14 59 feet below grade <br /> . Flow Direction/Gradient Northwest at 0 0015 ft/ft <br /> SPH-welWthicknesses Not Detected <br /> TPHg concentration range <50 ppb(MW-1 through 8) <br /> Benzene concentration range <0 5ppb(MW-Ithrough 8) <br /> MTBE concentration range <5 Oppb(MW-1 through 8) <br /> Remarks Groundwater flow is generally consistent with previous measurements <br /> Groundwater dropped an average of 1 foot across the site dunng'the <br /> last quarter Wells which have historically had detectable <br /> concentrations of hydrocarbons were found to be non-detect during the <br /> Il second quarter <br /> PROTECT STATUS <br /> Third quarter monitoring will, again utilize the no-purge technique for sampling all wells It is <br /> recommended that a Risk Based Corrective Action (RBCA) report be prepared after the third quarter of <br /> sampling <br /> ATTACHMENTS• <br /> • Groundwater Elevation Contour Map <br /> • Groundwater Elevations and Analytical Results(Table 1) <br /> • ,Laboratory Report and Chain-of Custody form F ' <br /> • Groundwater Monitoring and Sampling Protocols <br /> • Gauge/Purge Calculations and Well Purging Date Sheets <br /> • Purge vs No-Purge Protocol <br /> I <br /> `1602ijTl0l, MibssslI pPxI38'80�-n16pf 02 <br /> 601-841-0995 (phone) 601-841-0810 (fax) i I' <br /> t I <br /> i <br /> i <br />