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1 <br /> ADDENDUM TO REVISED CORRECTIVE ACTION PLAN - SEPTEMBER 1997 <br /> Former CHASE CHEVROLET (Madison) Facility <br /> ' 423 North Madison Street, Stockton, California <br /> ' INTRODUCTION <br /> In accordance with the request of Mr Jeffery Setness,Advanced GeoEnvironniental, Inc (AGE) has <br /> ' prepared this addendum to the Revised Col rective Action Plan -February 1997 for the site located <br /> at 423 North Madison Street, Stockton, California <br /> 1 <br /> Due to the recent rise in ground water at the site, ground water is now in contact with hydrocarbon- <br /> impacted soil at the former location of UST No 1, rendering the previous leaching potential models <br /> and risk assessments invalid, and thereby necessitating the preparation of this addendurn to the CAP <br /> Also, additional information requested by the San Joaquin County Public Health Services - <br /> Environmental Health Division (PHS-EHD) to aid their reexamination of site remedial options has <br /> been included in this report <br /> ' ESTIMATED EXTENT OF IMPACTED SOIL <br /> The volume of impacted soil at the former location of UST No I was estimated based on analytical <br /> results from soil samples collected from probe borings GP5 through GPS Petroleum hydrocarbons <br /> NA ere detected in samples collected at depths of 10 and 15 feet in probing GPS which was advanced <br /> through the center of the fanner UST location- Petroleum hydrocarbons were not detected in samples <br /> ' collected at depths of 20 or 25 feet in probing GP5 Hydrocarbons were not detected in probings <br /> GP6, GP7 or GPS, advanced approximately 15 feet west, north and south of probing GP5, <br /> ' iespectrvely The horizontal extent of impacted soil was assumed to be laterally symmetrical A cross <br /> section showing the estimated extent of impacted soil in the vicinity of UST No 1 is illustrated in <br /> Figure 5 -Câ–ºoss Section GC' The volume of impacted soil was estimated to be approximately 150 <br /> ' cubic yards <br /> The estimated extent of impacted soil near the former location of UST No 8 was based on <br /> petioleum-like odors detected during the installation of probe borings GPI through GP4 <br /> Hydi ocarbon-like odors were noted throughout the entire depth of probing GPI to 25 feet bsg <br /> Hydrocarbon odors were noted from 10 feet to total depth of 25 feet bsg in probing GP2, advanced <br /> approximately 18 feet east of GP1 and at a depth of 25 feet bsg in probing GP4, advanced <br /> approximately 13 feet west of GP 1 Hydrocarbon odors were not detected in probing GP3, advanced <br /> apps oxrmately 15 feet south of GPI The horizontal extent of impacted soil was assumed to be fair ly <br /> ' symmeti ical laterally The vertical extent of the hydrocarbon-impacted soil was assumed to be near <br /> 30 feet bsg, based on the lowest known ground water level A cross section showing the estimated <br /> extent of impacted soil in the vicinity of UST No 8 is illustrated in Figure 6 - Cross Section D-D' <br /> The locations of cross sections C-C' and D-D' are illustrated on Figure 2 The volume of impacted <br /> soil was estimated to be approximately 750 cubic yards <br /> Ad arced GeoEn{ironmental,rtic <br /> 1 , <br />