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t i y Ix F, N Wm. J. Hunter & Associates u - 2220 Loma Vista Dr Registered Geologists ' ` Sacramento, CA 95825 �etroleum & Mineral Appraisers J U L 0 6 1992 (916) 972-7941 ENVIRONMENTAL HEALTH FAX (916) 972-1683 PERMIVSLRVIC�S ADDENDUM TO WORKPLAN DATED NOV. 11 1991 DRILLING & SAMPLING BOREHOLES 6215 TAM D'SHANTER DRIVE STOCKTON, CA (SITE CODE 1258) July 1 , 1992 PURPOSE OF THIS ADDENDUM: The November 1991 workplan proposed to drill , log, & sample 6, 35 ' deep auger holes - 3 an Normac property & 3 on the Hammertown adjacent to the west; (refer to Plate 1 ) BRIEF REVIEW OF WORK DONEs After approval by the County EHD, work began on April 8, 1992, using Spectrum Exploration drilling equipment under the supervision of D. R. Allen, RG, of Wm. J. Hunter & Associates. Operations were performed according to the workplan, beginning on the Normac site with Borehole NCIH #3. It was taken to 36. 5 ' with soil samples taken at 15 ' , 20 ' , 25 " , 30 , & 35 ' . Refer to Figure 1 for details of soil types and sample depths. The rig then moved to Borehole NBH #1 , which was also taken to • 36.5 , and sampled at the same depths as #3; (refer to Figure 2 for details. ) Operations were discontinued for the night; the preserved soil samples were thoroughly re-iced and stored overnight. On April 9, operations recommenced at location NBH #2; it was taken to 36. 5' , and sampled at 5 feet intervals from 15 ' to bottom; Figure 3 shows soil types and sample locations. The drilling rig and equipment were then moved to the adjacent Hammertown property, and located at Borehole HBH #1 as shown an Plate II This hole was advanced to 36. 5 with soil samples taken as shown can Figure 4. The rig was then spotted at location HBH #3; the hole was taken to .36. 5 ' , with samples at 5' intervals from 15 to bottom; refer to Figure 5 for details. No odors or other evidence of contamination was noted in any of the 5 boreholes described above. The final borehole, HBH #2, was also drilled to 36. 5 ' with soil samples taken at 15 ' , 20' , 25 ' , 30 ' , & 35 ; (refer to Figure u for details. ) A petroleum hydrocarbon odor was noted in a b" thick silty, sticky blue clay at 25 feet. This appears to be correlative with the blue clay encountered in Borehole B-5 which was drilled in October, 1990. Laboratory analysis of that sample (Exhibit E, ) revealed the presence of a small amount of Benzene. The sample 1