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ARCADIS Ms. Amy Terrell <br /> January 29, 2014 <br /> Second NSZD Sampling Event <br /> Traps were deployed on November 4, 2013 and recovered on November 19, 2013. <br /> Based on the analytical results, NSZD occurred over an acre of land at rates ranging <br /> from approximately 1,855 to 2,665 gallons/acre/year(2,260 gallons/acre/year <br /> average). <br /> In addition, calculating the rate over the approximate LNAPL footprint (0.75 acre), <br /> NSZD occurred at rates ranging from approximately 1,391 to 1,999 gallons/0.75 <br /> acre/year(1,695 gallons/0.75 acre/year average). <br /> The higher rates observed during the fourth quarter event were expected as the <br /> warmer subsurface conditions were expected to result in an increase in microbial <br /> activity. <br /> Results Summary <br /> Based on four physical LNAPL bailing field events over four quarters of 2013, the <br /> average LNAPL bailing volume was approximately 4.7 gallons per event. <br /> Two separate CO2 flux sampling events were conducted at four on-site locations <br /> concurrent with LNAPL bailing activities. NSZD LNAPL removal rates were reported <br /> by the laboratory in units of gallons/acre/year. The laboratory rates were multiplied by <br /> the LNAPL footprint area (0.75 acre) to calculate the gallons/0.75 acre/year NSZD <br /> LNAPL removal rate. To clarify, this is the removal rate of LNAPL within the LNAPL <br /> plume footprint in gallons per year—written as gallons/0.75 acre/year. <br /> The conservative NSZD rate ranged from 754 to 1,695 gallons/0.75 acre/year, which <br /> equals an average NSZD rate of 1,224 gallons/0.75 acre/year. The 1,224 <br /> gallons/0.75 acre/year average NSZD rate would be equivalent to performing 260 <br /> physical LNAPL bailing events at an average removal volume of 4.7 gallons per <br /> event. <br /> As noted previously, it takes approximately two weeks for LNAPL to recover to 90 <br /> percent of the initial thickness at the site (ARCADIS 2010). It would take <br /> approximately 10 years of biweekly (one event every two weeks) LNAPL hand- <br /> bailing to remove the same quantity of LNAPL that is removed through NSZD <br /> attenuation in one year. This demonstrates the enormous disparity between hand <br /> bailing and natural attenuation. <br /> Page: <br /> G:1Projects\UPRR_Roseville\RC000709_Tracy Mnt Fac1lity\3_DELIVERABLES12014.01 NSZD Rpt\Tracy ca-Maint Facility_NSZD Rpt(01-29-14)doc 6/9 <br />