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all the soil samples will be recorded The soil sample that registers the highest concentration of organic 1 �a ,,, vapors in each borehole will normally be submitted for laboratory analysis. In the event that 10 air �l� Ss significant level of organic vapors is detected during sampling of the entire borehole, the soil sample retrieved from the interval directly above the groundwater saturated zone will normally be selected for laboratory analysis Other samples may also be submitted for analysis as described m the workplan The soil samples submitted for analysis will be transferred to laboratory-prepared containers and will , be submitted for laboratory analysis The analytical laboratory performing the analysts will possess any required regulatory agency certification A chain-of-custody record will be maintained for all the laboratory soil samples-throughout-the sampling-effort and laboratory analysts---------- Selected nalysts - `------__Selected samples may be submitted for physical analysis and for inorganic analysis to characterize the , size distribution, mineralogy, engineering, and geochemical properties of the particles Selected soil samples may also be sent to the Du Pont laboratory for in-situ biotreatment feasibility evaluation. Drilling and sampling equipment decontamination procedures will be followed to prevent cross contamination between borings and sampling intervals The drilling rig and all associated drilling equipment will be steam cleaned prior to the first boring and between each boring The split spoon sampler will be decontaminated after each sampling interval with a biodegradable deterkent scrub, potable water rinse, and a minimum of two rinses with distilled water Each boring will be grouted by tremae pipe with a cement/bentonite mixture to seal the borehole A-2 Monitoring Well Installation completion U on of the discrete soil sampling task, monitoring wells will be constructed in selected Pp g boreholes according to the geology logged A Du Pont geologist will inspect all monitoring well ' construction materials and will supervise monitoring well installation Monitoring wells will be constructed of threaded flush point, schedule 40 PVC screen and riser pipe of the specified diameter No glue or solvents will be used Factory slotted screen will be used The water level in the borings will dictate the depth of screen placement The monitoring wells will be sufficiently screened above the water table to allow the entry of lighter-than-water petroleum hydrocar- bon fuel's, if piesent-, and allow foc seasonal water elevation fluctuations Only one water-bearing unit will be intersected by the well screen of each monitoring well The annular space between the PVC well casing and the borehole will be gravel packed with a gravel -- - appropriate for the slot size of the screen The annular space will-be gravel packed to a height at least 2 feet above the top of the screen A 1- to 3-foot bentonite seal will be emplaced above the,gravel pack to prevent the direct infiltration of run-off or cement into the annular space The remainder of the annulus will be grouted by tremie pipe with a cement/bentonite mixture to the ground surface, In areas of low traffic, the monitoring wells will be completed two feet above grade and aK eel prptective 11 - " A 4005111 Rev o Du Pont Environmental Remediation Services A-2 T Pnnted on Recycled Paper 3