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-:� �` -r`s.�e ;,�'2. deet'� � r,..�.,� � ���e rr '"''�..+..1^'' s,�a �.-� r,�'��'��i ir � ,�'�'ry i xy'�a�.r Yy ��'.� ';Y.2�i�_T. �� .��, .•`m•.��i�? _�'S <br /> - 'M ': a,ef�_*�• '�f��-�rk'4.'. ,,, a �.- _ .3'�s (rx': �."� ,�Y,Kiu .��� .�' �' ''`..�awux�..' <br /> E. <br /> September 13, 1991 <br /> Unocal Station No, 6981. S tockton, California <br /> GeoSysiems, 1991), and to construct vapor-extraction wells. "T"hc purpose of boring 13-11 <br /> near the northwest corner of the underground storage tanks is to evaluate the lateral and <br /> vertical extent of residual gasoline hydrocarbons previously detected in sail samples from <br /> beneath the dispenser islands !Applied GeoSystems, 1991). and to construct a vapor- <br /> extraction well. 'bile purpose of boring 13-12 near boring B-S is to construct a vapor <br /> extraction well. <br /> RESNA will contact Underground Service Alert at least 48 hours before drilling to delineate <br /> public utility lines at the site. Before drilling. cacti borehole will be hand-augered 3 to <br /> feet below grade. A licensed well driller will drill the soil borings and install tine wells. <br /> Soil borings will be drilled with a Ci1IG-55 (or similar) drill rig equipped with 8- and 10- <br /> inch-diameter, hollow-stem augers. Auger flights and sampling equipment will be steam- <br /> cleaned before use in cacti boring to minimize the possibility of downhole or crosshole <br /> contamination. The drilling will be performed under the guidance of a field geologist. and <br /> the earth materials will be identified using visual and manual methods, and classified <br /> according to the Unified Soil Classification System. <br /> During drilling,soil samples will be collected at -foot intervals above 55 feet and below.55 <br /> feet at 2-1/2-foot intervals, obvious changes in soil stratigraphy,and just above the ground- <br /> water surface. Samples will be collected by drilling the boring to a point just above the <br /> sampling depth and then driving the sampler, a California-modified, split-spoon sampler <br /> equipped with clean brass sleeves,into the soil through the hollow center of the auger. The <br /> sampler will be driven 18 inches with a standard 140-pound hammer dropped 30 inches. <br /> n <br /> ..._.. <br /> 38032•4W <br />