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<br /> Semi-Annual Groundwater Monitoring and Quarterly Remediation Progress Report—First Quarter 2013 April 30,2013
<br /> Project#52.75118.2390 Page 2
<br /> Current Site Information
<br /> Historical range in depth-to-water(DTW) [feet 10.20(MW-10, 2Q06)to 32.33(MW-7, 4Q92)
<br /> ftbelow top of casing (TOC), 2Q90 to 4Q12 :
<br /> Water supply wells within a 2,000-foot radius Three wells; see Appendix A—Sensitive
<br /> and their respective direction: Receptors
<br /> Current remediation technique: None; OS offline since February 27, 2012
<br /> 2.0 Groundwater Monitoring and Sampling
<br /> 2.1 MONITORING AND SAMPLING PROCEDURES
<br /> The current monitoring well network consists of 12 wells (MW-1 and MW-3 through MW-13). As directed in a
<br /> regulatory correspondence dated July 6, 2009, the groundwater sampling schedule was modified as follows;
<br /> wells MW-3, MW-7, and MW-11 are sampled semi-annually during the first and third quarter of each year,
<br /> wells MW-6 and MW-12 are sampled annually during the first quarter of each year, and wells MW-1, MW-4,
<br /> MW-5, MW-8 through MW-10, and MW-13 are sampled biennially during the first quarter of odd-numbered
<br /> years. During First Quarter 2013, groundwater samples were collected by ATC on January 21, 2013.
<br /> CURRENT MONITORING DATA
<br /> All wells monitored; All wells sampled:MW-1,
<br /> Wells monitored and sampled: MW-3, MW-4, MW-5, MW-6, MW-7, MW-8,
<br /> MW-9, MW-10, MW-11, MW-12, and MWA3.
<br /> Monitoring and sampling date: January 21, 2013
<br /> Were SPH observed this quarter? No
<br /> A-Zone: 11.82 (MW-10)to 14.17 (MW-12)
<br /> DTW range (ft below TOC): B-zone: 12.95 (MW-6)to 13.44 (MW-7)
<br /> C-Zone: 14.68 MW-11
<br /> A-Zone:
<br /> 0.97 increase[-7.78 (1 Q13)—-8.75 (3Q12)]
<br /> Average change in groundwater elevation B-Zone:
<br /> since last event(ft): 1.34 increase [-7.73 (1 Q13)—-9.07 (3Q12)]
<br /> C-Zone:
<br /> 0.46 increase -9.50 1 Q13 —-9.96 3Q12
<br /> Groundwater flow direction and gradient A-Zone: Northeast at gradient of 0.001
<br /> (feet per foot): B-Zone: North-northwest at gradient of 0.002
<br /> C-Zone: Northeast at gradient of 0.002
<br /> 2.2 GROUNDWATER SAMPLE ANALYSIS
<br /> The groundwater samples were submitted to BC Laboratories, Inc. of Bakersfield, California, a state of
<br /> California certified lab, for analysis: gasoline-range organics (GRO) by EPA Method 8015M, benzene, toluene,
<br /> ethylbenzene, and xylenes (collectively BTEX), MTBE, TBA, di-isopropyl ether (DIPE), ethyl tert-butyl ether
<br /> (ETBE), tert-amyl methyl ether (TAME), ethanol, 1,2-DCA, and 1,2-dibromoethane (EDB), by EPA Method
<br /> 8260B.
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