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l� <br /> 2.4 Bing and CoMpaction Testing <br /> Beginning July 23, 1990, clean, imported fill was delivered <br /> to the site for backfilling of the open excavation. The <br /> backfill material was compacted in accordance with Section 70 <br /> of the Uniform Building Code. Backfilling required an <br /> approximate total volume of 7,300 cubic yards of imported <br /> fill. The maximum dry density of the sandy gravel material <br /> used as fill was calculated to be 142.5 pounds/ft3 at an <br /> optimum moisture content of 5.0 percent. A copy of the <br /> laboratory report on the soil analysis performed by <br /> Rogers/Pacific Laboratory is included in Appendix B. <br /> Field density testing and inspections were conducted <br /> throughout the duration of the backfilling operation. <br /> A relative compaction of 90 percent was used to establish <br /> acceptable field densities of the backfill material. <br /> Backfilling of the excavated area was performed in seven <br /> lifts. The first lift was 2 feet thick to isolate water <br /> interference in the open excavation; subsequent lifts were in <br /> 12 to 14 inches in thickness. Each lift was compacted and <br /> tested as indicated in Table 2. All engineered fill was <br /> tested in accordance with ASTM methods to conform to the <br /> standards established in Section 70 of the Uniform Building <br /> Code. <br /> 3.0 PRELIMINARY GROUND WATER INVESTIGATION <br /> To assess the potential impact of hydrocarbon constituents on <br /> the ground water, and define the nature and extent of <br /> hydrocarbon constituents in the ground water, if any, a <br /> preliminary investigation was conducted. As part of this <br /> investigation, four ground water monitoring wells were <br /> installed onsite, and soil and ground water samples were <br /> collected for laboratory analysis. The monitoring well <br /> locations are shown in Figure 5. <br /> 3.1 Field rocedur_e <br /> Prior to commencement of drilling activities, Well 'Permit <br /> No. 90-841 was filed and obtained from the San Joaquin Local <br /> Health District. A copy of the permit is included in <br /> - --Appendix- D.-- - - - -- - <br /> 3.1.1 Soil Sampling <br /> On September 26, 1990,. Alton Geoscience personnel <br /> supervised the drilling of four soil borings, all of ..which <br /> were subsequently converted to ground water monitoring <br /> wells. The drilling activities were performed by West <br /> 6 <br />