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CHRONOLOGY
<br /> THE CUSTOMER COMPANY
<br /> 890 NORTH MAIN
<br /> MANTECA CA
<br /> TANK#1 10,000 GALLON GASOLINE REMOVED 02-25-87
<br /> TANK#2 10,000 GALLON GASOLINE REMOVED 02-25-87
<br /> 02-25-87 2-10,000 gallon regular gasoline tanks removed under permit and guidance of PHS/EHD.
<br /> Six soil samples were taken from approximately 16' BGS. Two from each tank pit area and
<br /> two along the piping to the dispenser island. Groundwater was noted at 17' BGS. The
<br /> excavated soil was removed to Manteca Sand and Gravel for storage.
<br /> Lab results of the soil sample from the northwest end of the northern tank showed TPH as
<br /> gasoline and BTX at 1.2 ppm, 0.0188 ppm, 0.0252 ppm, and 0.0772 ppm, respectively.
<br /> EDB and total lead were not detected at detection limits of 0.010 ppm and 1.0 ppm,
<br /> respectively.
<br /> The soil sample from the northeast end of the northern tank did not detect TPH as gasoline,
<br /> BTX, EDB or total lead at detection limits of 1.0 ppm, 0.010 ppm, 0.010 ppm and 1.0 ppm,
<br /> respectively.
<br /> The soil sample obtained from the southwest end of the southern tank detected benzene at
<br /> 0.031 ppm and total lead at 1.0 ppm. All other constituents were not detected at the
<br /> detection limits noted above.
<br /> The soil sample obtained from the southeast end of the southern tank did not detect
<br /> contaminants at the detection limits noted above.
<br /> The two soil samples collected from the piping around the dispenser area detected TPH as
<br /> gasoline, BTX, and total lead at 112 ppm, 0.0113 ppm, 0.417 ppm, 1.930 ppm and 1.0 ppm,
<br /> respectively, for the south sample and 3.6 ppm, 0.0285 ppm, 0.0465 ppm, and 4.0 ppm,
<br /> respectively,for the north sample. EDB was not detected in both of these samples.
<br /> 02-26-87 Over-excavation of the former tank pit area occurred this date.
<br /> 03-02-87 Three groundwater monitoring wells are installed at the site this date. Groundwater was
<br /> encountered in the borings at 13' BGS.
<br /> 03-05-87 PHS/EHD receives telephone call from the consultant. Benzene detected in two of the three
<br /> monitoring wells installed at the site. MW#1, located south of the former tanks, showed 3.5
<br /> ppb benzene and MW#2, located north of the former tanks, showed 13.0 ppb. MW#3,
<br /> located to the northwest of the former tanks, showed nondetect.
<br /> 03-13-87 Meeting held at PHS/EHD with the RB, the RP and the consulting firm. Issues discussed
<br /> were the additional over-excavation needed in the former dispenser area, the transport of
<br /> the excavated soil to another location for aeration and the confirmation soil borings. The RB
<br /> will be the lead agency for the groundwater investigation.
<br /> 03-20-87 PHS/EHD receives phone call from person doing the over-excavation. They cannot
<br /> excavate any further to the north because of the sidewalk and there appears to still be
<br /> contaminated soil. A soil sample was taken from this area. Two other soil samples were
<br /> obtained form the west side and from the south side of the excavation. The sample results
<br /> show TPH as gasoline, BTX at concentrations of ND (detection limit???), 0.110 ppm, ND,
<br /> and 0.062 ppm, respectively, for the north sample, ND, 0.570 ppm, 0:500 ppm 1.690 ppm,
<br /> respectively, for the west sample and 31 ppm, 0.310 ppm, 1.200 ppm, and 11.30 ppm,
<br /> respectively,for the south sample.
<br /> 03-24-87 PHS/EHD receives phone call from the consultant. The soil samples show contamination.
<br /> The hard copy of these results are to be mailed to PHS/EHD.
<br /> 03-25-87 PHS/EHD receives the soil sample results from the over-excavation on 03-20-87. The letter
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