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Remediation Report - 152 East 1 lth Street, Tracy, California Page 15 site was excavated These facts point to a source of hydrocarbon release a few feet to the east of monitoring well ULT 9 Similarly, the geometry of the portion of the discus shaped distribution of hydrocarbons as it was expressed in the east and west walls section f the along remedial eBBxthat is showncavation (see he ontwo Figuoe 4} wer diagrams on Figure 6 and the cross g indicate that the source of the contaminationW�henitalcene152 togethertwith the location, type reet is on City sof Tracy property under East 11th Street and geometry of the piping that had been ion under Easnd gt 1�h Sthe teetesoymerten feet elling evidence points to a source of contamination of the property line As noted previously, the configuration sts t tie f the ergrou doped piping found ch in the remedial excavation also strongly Sugg the gasoline leaked are still present in the subsurface The projected location of the tanks is shown on Figures 2, 5 and 6 BACKFILLING OF REMEDIAL- EXCAVATION When the excavation work to remove contaminated soil from beneath the subject property was complete, a Dynapac vibratory roller with a 66-m , pad-foot drum was used to thoroughly compact the rock that had been placed beneath the water table in the bottom of the pit The compacted rock served as a foundation for compacted Caltrans Class 11 aggregate- gregate base base materia] that was used to restore remedial trucks and spread in thin�gn form layers material was discharged into the excavation from which v;ere compacted by the vibratory roller A nuclear density gauge, calibrated against a compaction test performed on a bulk sample of the Caltrans Class 1I aggregate base material according to American Society for Testing and Materials (ASTM) Procedure D1557 (Method A) was used to measure the relative density of the compacted backfill according to the procedure specified by ASTM Standard D292 In all cases, the measured density exceeded that specified in the CAP, which called for the upper 2 ft of backfill to be compacted to 95% relative density and the material from that surface layer down to the dept of the rocexcavation that be compacted to 90°o irelatiow he water table in the bottom of the remedial density The results on the compaction test performed ots on the density testingthe sample of s thatswas 11 aggregate-base material and copies oft par performed by an independent quality control inspector are compiled in Appendix D Top rovide for pumping of groundwater from beneath the affected areas of the property as had been provided for in the CAP as an adjunct to soil remediation, a pump sump had been installed in the rotk placed in the bottom uelf fuel-the storage tanks remedial that were the sourcerof�he i it had been determined that the undergroundg