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S E C 0 R -
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<br /> SENSTIVE RECEPTORS
<br /> A 1996 DWR survey identified 10 wells located within the survey area These wells are located
<br /> northeast to southeast of the site and are apparently utilized as cathodic protection or irrigation
<br /> wells
<br /> MONITORING AND SAMPLING
<br /> TRC's Groundwater Monitoring Report dated January 25, 2005 is included as Attachment A,
<br /> including Tables 1- 3, Figures 1 - 5, plus field data sheets and groundwater analytical reports
<br /> The site has been monitored and sampled since 2"d quarter, 1996 From 1996 to 2000 the Site
<br /> has been monitored and sampled quarterly In 2001, the site was monitored and sampled
<br /> monthly In 2002, the site was monitored and sampled bi-monthly From 2003 to the present, the
<br /> site has been monitored and sampled quarterly Currently, 11 wells (MW-1 through MW-4S and
<br /> D, MW-6S and D, MW-8D, and MW-10S,1, and D) are monitored and sampled quarterly and 9
<br /> wells (MW-5S and D, MW-7S and D, MW-8S and I, and MW-9S,1, and D) are monitored and
<br /> sampled semi-annually Samples are analyzed for TPHg, TPPH, BTEX, and fuel oxygenates
<br /> Based on the fourth quarter 2004 monitoring and sampling event (Attachment A) the maximum
<br /> TPHg and MtBE concentrations were 180 ppb (MW-1) and 550 ppb(MW-1), respectively This
<br /> represents a 96% reduction in the TPHg concentration and over 99% reduction in the MtBE
<br /> concentration from historical highs
<br /> TPHg and MtBE concentrations in groundwater continue to decline particularly in source area
<br /> • wells MWA and MW-2
<br /> Offsite wells MW-81D and MW-10S, 1, and D continue to report minor concentrations of TPHg and
<br /> MtBE
<br /> Based upon data collected during ongoing quarterly groundwater monitoring and sampling,
<br /> dissolved hydrocarbons are effectively e inea e oth laterally and vertically in the vicinity of the
<br /> site
<br /> REMEDIATION STATUS
<br /> SECOR's Quarterly Remedial Performance Summary is included as Attachments B (including
<br /> Tables B-1 - B-2, and Figures B-1 - B-3), Attachment C (Remediation Field Data Sheets), and
<br /> Attachment D (Remediation Certified Laboratory Analytical Reports and Chain of Custody
<br /> Documentation)
<br /> The ozone injection systems consist of panel mounted KVA C-SpargeTM Systems that produce 4
<br /> grams per hour (0 009 pounds per hour) of ozone The system injects to ten sparge points in
<br /> eight wells AS1 through ASS, AS7, ASB, and AS10, and nested wells AS6SID and AS9S1D
<br /> Between July 16 and September 16, 2004, the system ran for 1,025 hours, resulting in 41 percent
<br /> runtime System data is presented in Table B-1 (Attachment B) The system shut down twice
<br /> during the fourth quarter due to a circuit breaker tripping
<br /> The performance of the ozone injection system is evaluated by groundwater sampling Monthly
<br /> groundwater samples were collected from monitoring wells MW-1, MW-2, and MW-3 on October
<br /> 28, November 30, and December 30, 2004 and analyzed for total petroleum hydrocarbons as
<br /> gasoline (TPHg), benzene, toluene, ethylbenzene, and total xylenes (BTEX compounds), and
<br /> methyl tert-butyl ether (MtBE) Results of monthly groundwater sampling events are summarized
<br /> in Table B-2 Concentration versus time graphs for dissolved TPHg, benzene, and MtBE in
<br /> monitoring wells MWA, MW-2, and MW-3 are provided in Figures B-1, B-2, and B-3
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