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rte• _ _ - :x ,Q� _ .: .x» .,.: .� .re.� ,-- '" '' ' _ y-r <br /> �i <br /> :i <br /> regarding local water well construction and use is also <br /> recommended. Monitoring well and test boring locations are <br /> shown on Plate 6. These two sampling points were selected since <br /> the fuels appeared to be concentrated in the south to southwest <br /> end of the excavated area. Also, the direction of shallow <br /> groundwater flow, from the best information currently available, <br /> is towards the west to southwest. <br /> The proposed monitoring well will need to be an estimated <br /> 100 feet deep and would be located approximately 20 feet <br /> west/southwest of the former gasoline tank location. Well and <br /> test boring locations are shown in Plate 6. A proposed <br /> monitoring well construction diagram is shown in Plate 7. The <br /> test boring and the monitoring well would be sampled every five <br /> feet after a depth of 10 feet in order to collect relatively <br /> undisturbed soils for chemical testing. Hollow stem auger <br /> methods, or approved equivalent will be used in the drilling and <br /> sampling of the well and test boring. A modified rotary/split <br /> spoon sampling system offered by a local driller is now being <br /> explored. Sampling and analysis methods patterned after State <br /> of California "LUFT" document will be utilized. Chemical test <br /> parameters will be performed in accordance with the "Tri- <br /> Regional" guidance document, which at this time is expected to <br /> be: TEPH-diesel, TPH-gasoline, BTXE, and total Lead. <br /> Extra care in the selection of screened interval in the <br /> monitoring well will be used to reduce the risk of contaminants <br /> reaching groundwater via the wellbore. It may be necessary to <br /> have a smaller than normal screened interval in order to address <br /> this concern. <br /> Drill cuttings and purged water generated in the field will <br /> be retained on-site. soils will be contained on plastic and <br /> covered. Water and drilling mud will be contained in an above <br /> ground, temporary tank (poly tank or Baker style tank) until <br /> chemical test results are completed. The disposition of the <br /> soil and mud/water will be addressed .in the "Soil Contamination <br /> Proposal" which will be completed after this field work. <br /> The workplan described above can be started immediately <br /> upon approval by San Joaquin County and/or the Regional Water <br /> -- Quality Control Board. A more detailed sampling and analysis <br /> plan and a health and safety guidelines document will be <br /> prepared prior to the start of field work. An estimated six to <br /> eight weeks may be needed to complete this work and prepare a <br /> report. Assuming a start date for field work of September 15, <br /> 1990, we anticipate completion in about late October to mid- <br /> November. At that time, we recommend that a "Soil Contamination <br /> Proposal" is submitted to the County to address the stockpile <br /> ------ ------ <br /> soils...__. supplemental---- <br /> g;----and..--possible - - . . . .... <br /> additional soil and/or groundwater contamination/remediation at <br /> +. the tank excavation site. <br /> �f <br /> 6 <br />