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momtoi ing cv em N1 CBF was detected m samples DDN and DDS (980 and 3 500 µg/l respeLtivek ) at significantlx hlUhcr concentrations than in previous and suhsegmnt monitoring events Additionally the only surface xtattr sample detections of 1AME were reported in samples DDN and DDS during the first quarter, 1999 inonitot ing event During the thud quarter monitor uig cvcnt however MTBI was detected in sample i]DN ai .t much lower concentiation ( 1 7 ug/l) and was not detected in sample DDS Ivl"I BE was detected for the third tmnt rn the sample collided t:om IDCW (1 6 µg/1) ()n DLLLI]lhel --'2 1999 ( ondoi conducted fourth quarter 1999 groundwater and surface water monitoring at the ,itc I ahoratory analytical icsults of the groundwater samples collected during the Fourth quarter 1999, monitorui`� event ��eie 4,enerally consistent with historical quarterly groundwater analytical data I3eii/ent, and total wleneS weir detccled lot the second tIML in the -roundwater sample wllected from MW-3 (Froundwatcr cli✓vation measurements collected at the site on December '' 1999, indicated that the. average depth to ,1roundWatci N,4as approximately 6 6 tcct hcloW the monitor well and surface water station measuring points I his avciage depth to water v\,as 0 1 #cet Lgreatei than measured on September 23 1999 (,totuufwater elevation e.enitouiS for Deectnber 22 1999 indicated that the ,roundwater gradient at the. SItc was gcnc.rally consistent with the, histoiical groundwater gradient rhe laboiatoty analytical surface water Sample data for the Fourth quarter, 1999, monitoring event were generally representative, of historical data, with the exception of the first quarter, 1999, data During the first quarter 1999 monitoring event, M i BI was detected in samples DDN and DDS (980 and 3,500 µg/I, respectively) at significantly higher 4onLentrations than in previous and subsequent monitoring events Additionally, the. only surface, water ,aniple dttcctrons of f AML were reported in samples DDN and DDS during the First quarter, 1999 monitoring event ]hiring the fourth quarter 1999 monitoring event, however M 1 BL was detected in samples UI)N and i)U5 at much [ower eoncentrationS (2 7 and I ti }rg/] respcctivel- On iNlarclt 17 2000 ( ondui unidueled quartcrly ground\4atei and surface, water monitoring at llerman c�c Ilclen , Marina located it VeJI[LC Island l ctry iii Stockton ( ah forma. l aboratory analytical results of the broundwatcr samples collected during the first quarter, 2000 monitoring event are generally consistent with historical quarterly groundwater anal)tical data (groundwater elevation measurements collected at the site on March 17, 2000 indicated that the average depth to groundwater was approxtmately six feet below the monitor well and island drainage channel water surface measuring points Groundwater elevation contours for March 17 2000, indicated that the groundwater gradient at the. site is generally consistent with the historical groundwatt r gradient Ilistotrcal laboratoiv analvtrcal icsults indicated that generally low concentrations of MTBE have been present in at least one of the surface water samples collected during the surface water sampling events During the first quarter, 1999 monitoring event, however MTBI; was detected in samples DDN and UDS (980 and 3,500 Fig/1, respectively) at significantly highci concentrations than in previous and subsequent monitoring events Additionally the only suitace water sample detections of TAME were reported in samples DDN and DDS during the Fist quaiter 1999, monitoring event During the first quarter, 2000, monitoring event MTBF was again detected at an elevated concentration in surface water sample DDS (4,700 Iig/l) In a lettet dated June 30 2000 Mr Rowe of the San Joaquin County Pl1S/E11D directed the submittal of a work plan amendment to modity the scope of work proposed in the above referenced work plan and work plan addendum According to Mr Rowe the w iii k plan amendment was to describe vertical character 17ation of the potential MTBE plume and be submitted by August 1 2000 ( ondot subsequently prepared the .�iatzLv Report and Adden dean to the Fork Plat dated July 24 2000 Mr Rowe approved the work plan amendment in a fared message elated August 3 2000 The installation and sampling of the soil borings described by the Work Plan,