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k <br /> a <br /> Chronology <br /> Colberg Boatwork <br /> 848 Fremont, Stockton <br /> Page 2 <br /> 05/13/98 In a meeting with the responsible party and their consultant,APEX,EHD <br /> agreed to Apex's proposal to submit a plan to conduct a feasibility study for . <br /> installation of oxygen releasing compound"socks" in MW-1 through MW-3 <br /> in the area of the former gasoline tank. (ORC injection was never <br /> implemented) <br /> Apex also was to submit a mass balance calculation for the contamination in <br /> the area of the former diesel tank cluster and request"no further action <br /> needed" due to historical low concentrations in both soil and groundwater <br /> samples. Results of MW-5 and MW-6 water samples were consistently non- <br /> detect in gasoline,diesel, aromatic HC,and oxygenates after four quarters of <br /> sampling. Results of MW-4 dropped from 6,800 µg/l of diesel to 900 µ9/1 <br /> of diesel, and from 850 pg/1 to 110 ug/l of gasoline. <br /> 06/19'/98 Date of"Second Quarter 1998 Ground Water Monitoring Report and <br /> Closure Request for Former Diesel Tank Site". Apex calculated a mass of <br /> 0.88 pounds of diesel left remaining in soil and groundwater in the area of <br /> the former diesel tank cluster and recommended closure of the diesel tank <br /> location. <br /> 08/31/98 EHD letter stating that further investigation of the diesel UST area was not <br /> required at that time. <br /> 04/02/99 Date of"Mass Balance for Remaining TPH_g report.Apex calculated a <br /> mass of 0.21 pounds of TPH-g in groundwater and 3.77 pounds of TPH-g in <br /> the soil in the area of the former gasoline tank and recommended use of <br /> ORC. <br /> 05/06/99 EHD letter stating ORC not justified given the small mass calculated and <br /> requested a work plan to define the extent of the groundwater <br /> contamination. <br /> 09/29/99 An additional 5 Geoprobe soil borings SB-20 through SB-24 (numbers not <br /> sequential to previous soil boring designation) were advanced on site to <br /> collect soil and groundwater samples to delineate the extent of the <br /> contamination in the area of the former gas tank. <br /> t 02/08/00 Date of"Estimated Mass of Petroleum Constituents Remaining in <br /> Groundwater" report includes 9/29/99 work. Results of soil samples were <br /> t:; <br />