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• Page 1 of 2 <br /> Nuel Henderson [EH] <br /> From: Rick Day [day@geoconine.com] <br /> Sent: Tuesday, December 01, 2015 4:42 PM <br /> To: Nuel Henderson [EH] <br /> Cc: 'Nabaz Saieed (nabaz.saieed@tylin.com)'; FEZ(proj.320156@tylin.com) <br /> Subject: RE: Manteca Firing Range Question <br /> Attachments: image001.jpg <br /> Hi, Nuel. <br /> As lead concentrations increased,the XRF readings were lower than their corresponding total lead data with the <br /> differences between the two generally increasing with higher total lead results. I don't think there is any doubt <br /> that the berm and center of the range floor have very high lead concentrations, based on both the XRF reading <br /> and the total lead results. <br /> With this being said,the differences between the XRF readings and total lead data become decrease with the <br /> lower total lead results. <br /> If you go strictly by the equation, an XRF reading of-5 mg/kg would result in a predicted total lead <br /> concentration of 50 mg/kg and-15 mg/kg would result in a predicted total lead concentration of 135 mg/kg. <br /> However, at background sample locations BG4, BG8, and BG12,the XRF readings were higher than the total lead <br /> results (i.e.,the reason I did not use the equation to establish the lines on Figure 3). <br /> Accordingly, I used the XRF readings less than 50 mg/kg and the total lead results to estimate the STLC>5 mg/I <br /> (i.e., 50 mg/kg)and TCLP>5 mg/l (i.e., 135 mg/kg) dashed lines shown on Figure 3.The lines are dashed to <br /> indicate that the limits are approximate. <br /> With any type of remediation, I would recommend confirmation sampling during or after the remedial effort to <br /> confirm that the horizontal and vertical extents are defined. <br /> Hope this helps-let me know if you have further questions. <br /> Thanks, <br /> Rick. <br /> Richard Day, CEG, CHG I Principal/Senior Geologist <br /> GEOCON CONSULTANTS, INC. <br /> 6671 Brisa Street, Livermore, California 94550 <br /> P 1925.371.5900 ext. 401 M1925.872.5860 <br /> dav@seoconinc.com / www.eeoconinc.com / Facebook / Linkedin <br /> Bay Area - Sacramento - Fairfield - Los Angeles - Orange County - Riverside <br /> County - Palm Desert - San Diego <br /> Geotechnical Eneineerine Environmental Services Engineerine Geoloev Construction <br /> 12/16/2015 <br />