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2018 ANNUAL GROUNDWATER MONITORING REPORT FORMER KEARNEY—KPF FACILITY-STOCKTON,CALIFORNIA <br /> 4.3.1 Shallow Zone <br /> 1,1-DCE <br /> 1,1-DCE in the shallow zone has declined from a high concentration of 1400 micrograms per liter(pg/L) detected <br /> in well TP-1A in 1995 to a high of 13 pg/L in well SMW-2 in October 2018. Detections of 1,1-DCE in other shallow <br /> wells inside the Trigger Boundary did not exceed the CL of 6.0 pg/L in October 2018. <br /> PCE <br /> PCE in the shallow zone has declined from a high concentration of 280 pg/L detected in well KS-6 in 1989 to a <br /> high of 14 pg/L in well SMW-2 in October 2018. Detections of PCE in other shallow wells inside the Trigger Boundary <br /> did not exceed the CL of 5.0 pg/L in October 2018. <br /> TCE <br /> Concentrations of TCE in the shallow zone were as high as 43 pg/L in 1989. In October 2018, concentrations of TCE <br /> in all shallow zone wells sampled within the Trigger Boundary were below the CL of 2.0 pg/L,with the exception of well <br /> SMW-4(3.6 pg/L). <br /> 1,4-Dioxane <br /> The highest shallow zone concentration of 1,4-dioxane since monitoring began was measured in June 2002 in well <br /> KPS-5, at 1,800 pg/L. In the October 2018 sampling event, 1,4-dioxane was detected in monitoring wells TP-1A <br /> (2.9µg/L), SMW-1(3.5µg/L), SMW-2 (2.5µg/L), SMW-4 (6.4µg/L), and SMW-5 (5.0µg/L). <br /> 4.3.2 Intermediate Zone <br /> 1,1-DCE <br /> 1,1-DCE in the intermediate zone has declined from a high concentration of 2600 pg/L detected in well KI-3 in <br /> 1992 to a high of 6.4 pg/L in well KEW-31-1 in October 2018. Detections of 1,1-DCE in other intermediate wells <br /> inside the Trigger Boundary did not exceed the CL of 6.0 pg/L in October 2018. <br /> PCE <br /> Concentrations of PCE have declined in the intermediate zone from historical highs of between 100 pg/L and 500 <br /> pg/L to a high of 3.2 pg/L in well KEW-31J in October 2018. Detections of PCE in other intermediate wells inside the <br /> Trigger Boundary did not exceed the CL of 5.0 pg/L in October 2018. <br /> TCE <br /> Concentrations of TCE have declined in the intermediate zone wells from historical highs reaching 690 pg/L to a high of 9.2 <br /> pg/L in well KEW-3U in October 2018.TCE in wells inside the Trigger Boundary exceeded the CL(2.0 pg/L) in one other <br /> well, KEW-4U(2.5 pg/L),sampled in October 2018. <br /> D U D E K 10886-1 <br /> 16 March 2019 <br />