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V .1
<br /> Ms. Margaret Lagorio, SJCEHD November 30, 2007
<br /> Work Plan for Additional Assessment Project No. 2033-15688-01
<br /> 15688 Harlan Road,Lathrop, California
<br /> Page 3
<br /> These six soil samples were analyzed (by STL, San Francisco) for total petroleum
<br /> hydrocarbons in the gasoline range (GRO; C5-C12); total petroleum hydrocarbons in the
<br /> diesel range (DRO; CIO-C2$); benzene, toluene, ethylbenzene, and xylenes (BTEX),
<br /> methyl tertiary butyl ether (MTBE), tertiary amyl methyl ether (TAME), ethyl tertiary
<br /> butyl ether (ETBE), di-isopropyl ether (RIPE), tertiary butyl alcohol (TBA),
<br /> 1,2-dichloroethane (1,2-DCA), ethylenedibromide (EDB), volatile halogenated
<br /> hydrocarbon compounds, polychlorinated biphenols (PCBs), five LUFT metals (Cd, Cr,
<br /> Pb, Ni, Zn), and hexavalent chromium (Cr+6). Analytical results of these samples (see
<br /> Attachment D) indicated concentrations above laboratory reporting limits of only DRO,
<br /> GRO, BTEX, naphthalene, n-butylbenzene, n-propylbenzene, 1,2,4-trimethylbenzene,
<br /> 1,3,5-trimethylbenzene, Cd, Cr,Ni, Pb, and/or Zn.
<br /> On May 18, 2007, an over-excavation of the former UST area was conducted by Walton
<br /> Engineering and overseen by SJCEHD. According to SJCEHD staff field notes, soil was
<br /> excavated to a total depth of approximately 18 feet bgs. The lateral dimensions of the
<br /> over-excavation are not known. A photograph, provided by SJCEHD and taken during P;-to n
<br /> the over-excavation activities, is included in Attachment E. SJCEHD instructed City of �
<br /> Lathrop to backfill the excavation with clean soil from the site. SJCEHD field notes from US 7—
<br /> May 18, 2007 are included as Attachment F. 1�Oe4
<br /> From the over-excavation, one soil sample (called `OvEx/SOIL/11.5') and one
<br /> groundwater sample (called `OVEX/FEW') were collected and submitted to STL, San
<br /> Francisco for laboratory analytical testing. Both samples were analyzed for GRO C5-C12,
<br /> DRO CIO-C28,BTEX, MTBE, TAME, ETBE, DIPS, TBA, 1,2-DCA, and EDB (results in
<br /> Attachment G). Analytical results of the soil sample collected at a depth of 11.5 feet bgs
<br /> indicated concentrations of only DRO, benzene, and 1,2-DCA. Analytical results of the
<br /> groundwater sample indicated detectable concentrations of GRO, DRO, BTEX, TBA,
<br /> and 1,2-DCA.
<br /> On September 14, 2007, a UST Unauthorized Release (Leak) /Contamination Report was
<br /> filed by SJCEHD naming both the City of Lathrop and Mr. Dhoot as RPs
<br /> (Attachment H). On September 17, 2007, SJCEHD then issued a letter and Notice of
<br /> Responsibility to both Mr. Dhoot and to the City of Lathrop and requested the submittal
<br /> of a work plan to investigate the lateral and vertical extent of impact from the former
<br /> USTs by November 1, 2007.
<br /> SITE GEOLOGY AND HYDROGEOLOGY
<br /> Subsurface conditions in the vicinity of the site have been explored at the adjacent Joe's
<br /> Truck Plaza site at 15600 S. Harlan Road by the drilling, logging, and sampling of seven
<br /> (7) soil borings, twenty-five (25) direct-push soil borings, eight (8) cone penetrometer
<br /> test (CPT) borings, and twenty-two (22) groundwater monitoring wells screened across
<br /> K:Uoe's Truck Plaza\Work PlansUoe's Truck-SOUTH PARCEL-WP for Site Assessment 11-30-07.doc STRATUS
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