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6 2.3 Site Assessment <br />' A total of nine soil borings and six monitoring wells were installed at the site between May <br /> 1989 and May 1992 Monitoring well and soil boring locations are illustrated on Figure 2 <br />' The nine soil borings (B-1 through B-9) were drilled and sampled in May 1989 <br /> Hydrocarbons were detected in soil samples from seven of the nine bonngs Monitoring <br /> wells MW-1 through MW-3 were drilled and installed in February 1991 Total petroleum <br /> hydrocarbons (TPH as gasoline) were detected in each well during the initial sampling. In <br /> June 1991, 1.5 feet of free product was measured in MW-1 Free product has continued to <br /> be present at the site. <br />' in May 1992, three additional monitoring wells were installed at the site (MW-4 through <br /> MW-6) Petroleum hydrocarbons were detected in MW-4 and MW-6 at concentrations as <br /> great as 15,000 parts per billion (ppb, TPH as gasoline). No hydrocarbons were detected in <br /> the sample from MW-5 <br />' 2.4 Groundwater Depth and Flow Direction <br /> When the initial monitoring wells were installed in 1991, groundwater depth was <br /> approximately 25 feet Current groundwater depth at the site is approximately 35 feet <br /> Groundwater flow direction at the site has varied from northwest to southeast Current <br /> P0 groundwater flow direction is estimated to be north-northeast <br /> 2.5 Additional Soil and Groundwater Assessment <br /> Before initiation of soil or groundwater remediation at the site, the San Joaquin County <br /> Public Health Services - Environmental Health Division (PHS/EHD) required further <br /> assessment of hydrocarbon impacted soil and groundwater Details of the current <br /> investigation are summarized below. <br /> 3.0 PROCEDURES <br /> 3.1 Drilling and Sampling <br /> On December 19 and 20, 1994, four soil bonngs were drilled at the site Boring B-15 was <br /> advanced to a depth of 35 feet and backfilled in the entire depth with Poitland cement <br /> Boring B-14 was advanced to a depth of 42 feet and completed as monitoring well MW-9, <br /> boring B-16 was advanced to a depth of 44 feet and completed as MW-8, boring B-17 was <br /> advanced to a depth of 45 feet and completed as MW-7 Auger returns were placed on <br /> plastic sheeting and stored on-site Boring locations are shown on Figure 2 <br /> The borings were drilled using a truck-mounted HT-55 drill rig The drill rig and two-man <br /> �*V-1 A.&5-..,1- 4 <br /> cvs�ias-a¢nas r�.�.Qunw <br />