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�j URS Ms Margaret Lagorio, Supervising REHS Page 2 of 7 . San Joaquin County Environmental Health Department February 16, 2005 required during the second phase of the assessment In addition, in its letter dated October 14, 2004, SJCEHD reaffirmed its interest in defining/monitoring the eastern extent of impacted groundwater between the site and City of Lodi municipal well#1R (812 feet east of the site) ASSESSMENT ACTIVITIES AND FINDINGS Between November 20, 2004, and November 30, 2004, URS conducted the following field activities as ' part of phase I1 of the assessment i + One vertical soil boring (B-28) was advanced to first encountered groundwater on the northern �f side of Lodi Avenue, approximately 180 feet west of the site, and depth-discrete soil samples and a grab groundwater sample were collected to define the western extent of 1,2-DCA- impacted groundwater + One vertical soil boring was advanced to 70 feet bgs on the eastern side of S Cherokee Lane, and a 2-inch diameter monitoring well (MW-4) was installed to monitor the eastern extent of impacted groundwater between the site and the City of Lodi municipal well • One vertical soil boring was advanced to 105 feet bgs onsite and a 2-inch diameter deep groundwater monitoring well (MW-5) was installed in the area reporting the highest 1,2-DCA concentration to assess the vertical extent of impacted groundwater Boring locations and analytical results for each drilling event are shown on Figure 2 Cascade Drilling of Rancho Cordova, California, drilled the soil borings and installed the wells using a hollow-stem auger (HSA)-equipped drill rig with 8 25-inch, outside-diameter(OD) augers Following is a discussion of subsurface conditions, soil sampling, grab groundwater sampling, laboratory analytical methods, shallow and deep monitoring well installation, groundwater monitoring well development, sampling, and surveying, soil and groundwater analytical results, and equipment decontamination and soil cutting and wastewater disposal procedures Subsurface Conditions Recent drilling activities confirmed previously collected information about the subsurface geology at the site Soil encountered during these activities consisted of sand, silty sand, sandy silt, and silt A URS geologist logged the soils encountered according to the Unified Soil Classification System Groundwater was encountered in poorly graded sand at approximately 617 feet bgs in boring B-28, at approximately 60 5 feet bgs in groundwater monitoring well MW4, and at approximately 61 5 feet bgs in groundwater monitoring well MW-5 Boring logs are presented as Attachment B Soil Sampling Soil samples were collected from all three borings at 10-foot intervals with a modified California split- spoon sampler A portion of each sample was used for lithologic logging and for headspace screening with a photoionization detector(PID) A portion of selected samples was retained and submitted to the laboratory for analysis Each soil sample retained for chemical analysis was collected in 6-inch brass K 1WprocessUS BP ARCO\0076012004 AssessmenA760 addctional assessment report 04 doc