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Langston Is Market <br /> 15615 Seventh Street, Lathrop, California October 5, 1995 <br /> Interim Secondary Source Removal& Monitoring Well Replacement Page: 10 <br /> 1 <br /> "ND" This indicates that, at this time, the plume probably has not migrated beyond 7th J <br />' Street <br />' 5.0 Groundwater Conditions <br /> Water samples from the newly replaced wells analyzed "ND" Well EW-1 was pumped <br /> Ary suffzslet�tly re ge Abr—sanVhn This is probably caused by the dry <br /> compacted backfill adjacent to this well which has not had time to establish itself in the <br /> water table <br /> A gradient map was prepared showing gradients with and without the EW-1 data (Figure <br />' b) At this time, it appears that the gradient is maintaining a southeasterly trend of S 46° <br /> E and is extremely flat at 0 0011 ft/ft <br /> I6.0 Conclusions <br /> This interim remedial excavation has removed the secondary source of soil contamination <br /> in the area of the former underground storage tank The de-watering of the excavation <br /> ' has significantly reduced the groundwater contamination plume <br /> Contamination was detected below the "Stockton Blue" clay in boring EW-1 No <br /> contamination was detected at this interval in any of the other borings <br /> I7.0 Recommendations <br /> 1 WBF recommends further definition of the groundwater contamination plume above the <br /> "Stockton BIue" clay (hereafter referred to as the first aquifer) east and southeast of EW- <br /> 1 <br /> Further, it is recommended that the contamination found below the "Stockton Blue" clay <br /> in boring EW-1 at 34 feet (hereafter referred to as the second aquifer) needs to be defined <br /> and a gradient direction determined before further recommendations can be made <br /> Once these activities have been completed a groundwater remediation system can be <br /> designed, installed and placed into operation <br />