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T <br /> • Page 1 of 2 <br /> Harlin Knoll [EH] <br /> From: Harlin Knoll [EH] <br /> Sent: Wednesday,January 02, 2008 2:51 PM <br /> To: Tim Cuellar' <br /> Subject: RE: Sierra Lumber Case No. 2 <br /> Tim: <br /> As you recommend, prepare a WP for CPT and grab soil/water sampling for review by Henderson. Also address <br /> cross contamination prevention when sampling through the source (soil and groundwater)area. <br /> As you know, the deeper on-site MWs at both Case I and Case II have historically higher groundwater elevations <br /> than the shallow on-site MWs. Please address these pressure differences in future reports. <br /> HARLIN KNOLL <br /> SAN JOAQUIN COUNTY/EHD <br /> 600 E MAIN STREET <br /> STOCKTON, CA 95202 <br /> (209)468-3442 <br /> FAX:468-3433 <br /> From: Tim Cuellar [mailto:tcuellar@advgeoenv.com] <br /> Sent: Wednesday, January 02, 2008 1:06 PM <br /> To: Harlin Knoll [EH] <br /> Subject: Sierra Lumber Case No. 2 <br /> Harlin, <br /> Earlier this morning, we had discussed preparing a work plan for replacement wells at case No. 2. <br /> However, although additional ground water monitoring wells will be necessary to assess the extent of gas- <br /> impact, I believe it is a better idea to advance a series of CPT borings, gather data, and in the report of <br /> findings, recommend locations of additional wells for lateral and vertical assessment. <br /> In reviewing previous soil and ground water data, substantial soil impact is was reported in the tank pit <br /> (MW-15)between 20 and 40 feet at concentrations around 2,000 mg/kg; additionally, Alta's boring (B-3) <br /> detected soil-impact at 20 feet at 4,960 mg/kg. Based on the vertical soil profile for the site to depths of 65 <br /> feet, it is very likely that soil and ground water are impacted at depths greater than 65-70 feet. Therefore, a <br /> CPT boring to a depth of at least 100 feet in the area of MW-15 would go a long way in helping to identify <br /> deeper lithology, migration pathways, vertical extent and in properly locating additional monitoring well <br /> screen intervals. <br /> As you know, shallow and deep ground water monitoring wells(MW-10 and MW-14)were recently <br /> abandoned; shallow well MW-10 was typically an ND well while deep well MW-14 had consistently been <br /> impacted at concentrations between 2,000 and 4,000 ug/I. I believe you may have had some concerns with <br /> this data, largely due to the soil samples being ND during the installs of MW-10 and MW-14. However, I <br /> believe the ground water data MAY have been representative of conditions at 65 feet. In reviewing the <br /> boring logs, the soil samples at deeper depths from MW-14 all had strong HC odors. Additionally, I <br /> reviewed all monitoring well purge sheets for shallow wells MWA 0 and MWA 5 and compared to that of <br /> MW-14. The field parameters (pH, EC and temp.)collected at MW-14 appeared to be representative of <br /> deeper water conditions, and consistently had lower ground water temp's and lower EC values than that of <br /> MW-10 and MW-15. Prior to installing replacement wells of MW-10 and MW-15, I believe a CPT boring <br /> further south of this area would be beneficial in identifying the vertical extent of the ground water impact. <br /> 1/3/2008 <br />