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ARCADIS Mr. Eric Rapport <br /> April 21, 2011 <br /> hand held gas monitor) and VOCs (using a photoionization detector [PID])on January <br /> 17, February 11, and March 11, 2011. The results of the soil gas monitoring events <br /> are summarized in Table 7. Historical soil gas analytical data are summarized in Table <br /> 8. <br /> Written notification to the RWQCB is required if methane gas exceeds 10 percent of <br /> its lower explosive limit (10% LEL; 5,000 parts per million by volume [ppmv]). On <br /> January 17, February 11, and March 11, 2011, methane was detected at greater than <br /> 10% LEL in vapor extraction well VEW-01. ARCADIS submitted methane-exceedance <br /> notification letters to the RWQCB on January 27, February 24, and April 5, 2011. <br /> During the first quarter, the highest reading detected at VEW-01 was 10.3% methane <br /> which is 206% LEL of methane (103,000 ppmv)on January 17, 2011. <br /> Methane has not been detected in the basement of Rental Unit#1 since December <br /> 2008. It was determined that collection of Summa canister samples was no longer <br /> required due to the lack of measurable methane in the basement of Rental Unit#1. <br /> Soil gas readings and historical soil gas analytical data are summarized in Tables 7 <br /> and 8. <br /> Biosparge System <br /> The biosparge system startup was conducted by CH2M HILL on December 1, 2008. <br /> The biosparge system was shut down on August 17, 2009, with approval from the <br /> RWQCB, to evaluate the effectiveness of the system. A biosparge system pilot test <br /> was conducted on September 29 and 30, 2009 to evaluate the influence that the <br /> biosparge system has on DO in groundwater as compared to natural DO levels. This <br /> event is detailed in the Tech Memo. A figure depicting the biosparge system layout <br /> and historical biosparge system operation and maintenance data are included in <br /> Attachment 3. <br /> Consistent with previous groundwater monitoring events, the groundwater parameters <br /> (such as DO and ORP)were measured at site monitoring wells using a hand-held <br /> monitoring device. DO and ORP data are provided in Tables 9 and 10, respectively. <br /> Slope Stability Monitoring <br /> ARCADIS submitted a Notice of Termination (NOT), on behalf of UPRR, regarding the <br /> activities conducted in accordance with National Pollutant Discharge Elimination <br /> System (NPDES) General Permit No. CAS000002 (General Permit)to the RWQCB <br /> on May 21, 2010. The NOT was approved by the RWQCB in a letter to UPRR dated <br /> June 22, 2010. <br /> 1\Arcadis-us\officedatalFolsom-CA\Aproject\UPRR\RC000738-UP RR-StorrieTeliverables\QuarterlyReports120111Q1-2011VIinaltedlQ-2011StorrieStatus Rpt(4-21- Page' <br /> 11).doc 6/9 <br />