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., z <br /> .,TMro <br /> � <br /> :. .x eo»�x � >d'�� '��r•+�V'S .,,.k. 3"� `.alt 'M.' .a �:*e.��`� � �2;x� ���.i <br /> t -'m <br /> a _ <br /> k y <br /> 0_. ''u�II�� GROUNDWATER d <br /> 71�� TECHNOLOGY INC. _ <br /> TECHNOLOGY, 140I Halyard Drioe,Suite 140,West Sacramento.CA 9569L(926)37'-4700 <br /> January 27, 1992 FAX[9103 2-878] <br /> Project No. 02320 2241 <br /> Mr. Clint B. Rogers <br /> Chevron U.S.A. Inc. <br /> 2410 Camino Ramon <br /> San Ramon, CA 94583-0804 <br /> RE: WORK PLAN ADDENDUM NO. 1 <br /> CHEVRON SERVICE STATION NO.9-4275 <br /> 2905 WEST BENJAMIN HOLT DRIVE <br /> STOCKTON, CALIFORNIA <br /> Dear Mr.Rogers: <br /> Groundwater Technology, Inc.pri?rants this addendum to the Work Plan for AdditionalAfonitoring <br /> Well Installation, Chevron Service Station No. 9-4275, 2905 W. Benjamin Holt Drive, Stockton, <br /> California, dated June 1990 (Attachment A). The original work plan proposed additional site <br /> assessment consisting of the installation of two groundwater monitoring wells, collection and <br /> analyses of soil and groundwater samples, and report preparation. The following items within the <br /> work plan will be amended: <br /> K The location of the monitoring wells <br /> u The frequency of soil sampling during drilling <br /> ■ The construction of the monitoring wells <br /> MONITORING WELL LOCATIONS <br /> Two off-site groundwater monitoring wells wilbbe installed to investigate the extent of dissolved- <br /> gasoline hydrocarbons to the west and east of the site. The approximate locations of the <br /> monitoring wells are shown on Figure 1. <br /> SOIL SAMPLING FREQUENCY AND MONITORING WELL CONSTRUCTION <br /> As stated in the work plan,the monitoring wells will be installed within soil borings which will be <br /> advanced to 30 feet below grade, using a truck-mounted drill rig equipped with! 8.5-inch outside- <br /> diameter JO.D,) hollow-stem augers. Instead of continuous coring, undisturbed soil samples will <br /> be collected at five foot intervals using a 2.5-inch-O.D.by 2-foot-long split-spoon core barrel. Each <br /> monitoring well will be constructed of 10 feet of 2-inch-diameter schedule 40 polyvinyl chloride <br /> w (PVC( casing and 20 feet of 0,020-inch well screen. A filter pack of No.2/12 lapis Lustre <br /> sand will be placed around the well from the bottorn to approximately one foot above the top of <br /> Offices throughout the U.S.,Canada and Ommeas <br />