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r <br /> r revealed that soil and groundwater to the north of the tank cavity were impacted by gasoline <br /> compounds. Geological Technics recommended further assessment of the lateral extent of <br /> groundwater contamination No additional investigations were performed until early 1990 <br /> r2.4 Soil Excavation <br /> r In January 1990, additional soli was excavated from the former tank cavity Soil was <br /> excavated to a depth of 14 feet. Groundwater was encountered and the excavation was <br /> dewatered. The water was placed in an 8,000-gallon above ground tank and stored on-site <br /> r Between March and May 1990, all of the previously excavated soil was returned to the <br /> excavation, bringing the surface of the excavation to 7 feet below grade Subsequently, <br /> additional soil was imported and used to backfill the excavation to surface grade. The water <br /> r stored on-site in the above ground tank was released to the area of the former excavation <br /> The backfilling and discharge of purged groundwater were done without notification of the <br /> PHS/EHD, and therefore, no official documentation was available. <br /> r2.5 Monitoring Well Installation <br />' On August 19, 1993, monitoring well MW-4 was installed by GeoAudit down-gradient from <br /> MW-1 on the neighboring property, north of the site (Figure 2) Three soil samples collected <br /> sunng the drilling for MW-4 were analyzed for TPH as gasoline and diesel and BTE&X in <br /> raccordance with EPA methods 8015m and 8020, respectively <br /> Total petroleum hydrocarbons (TPH as gasoline and diesel), toluene, ethylbenzene, and <br /> xylenes were detected in soil samples from MW-4 at depths of 10 and 15 feet <br /> r2.6 Groundwater Monitoring <br /> Between 1988 and 1993, no regularly scheduled groundwater monitoring program was 1n <br /> r place It is our understanding that the monitoring wells were sampled in June 1988, January <br /> 1990 and September 1990 During each sampling, hydrocarbons were detected In MW-1, <br /> north of the tank cavity It is uncertain If any additional field work was performed between <br /> r September 1990 and February 1993. A quarterly monitonng program was initiated by <br /> GeoAudit in early 1993, with the first monitoring on February 24, 1993 <br /> I Since 1988, the depth to groundwater at the site has fluctuated from 8 5 to 12 feet <br /> Groundwater flow direction has remained between N 8° W to N 140 W This is consistent <br /> with regional trends <br /> r2.7 Re-excavation <br /> rAt the request of the PHS/EHD, the former tank cavity was overexcavated in August 1993 <br /> The excavation was expanded to approximately 40 feet by 50 feet and extended to a depth <br /> of approximately 14 feet Approximately 1,000 cubic yards of soil were removed from the <br /> rGeological Audit Services.Inc. <br /> MWARTS BEACON QRS/661 S/10 94 4 <br /> r <br />