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r-- GROUNUWATER <br /> LL , TECHNOLOGY, INC. <br /> 14011lal?an!Dri+r,Suits IdO,N csY Sacramento,CA 9569I,{9tS}372.a;pQ <br /> January 27, 1992 FAX(9l6)3—j2-87R <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 rd0. 7 <br /> CHEVRON SERVICE STATION NO.9.4275 <br /> 2905 WEST BENJAMIN HOLT CRIVE <br /> r� STOCKTON, CALIFORNIA <br /> Dear Mr, Rogers: <br /> Groundwater Technology, Inc, presents this addendum to the Work Plan forAddirionalManitorfng <br /> Well Installation, C'evron Service Station No. 9-4275, 2905 W. Uenjr mm Holt Drive, Stockton, <br /> Cx/ifornia, dated:,rune 1990 (Attachment A). The original work pian 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 /> i The location of the monitoring wells <br /> 2 The frequency of soil sampling during drilling <br /> Y The construction of the monitoring wells <br /> MONITORING WELL LOCATIONS <br /> Two off-site groundwater monitoring wells will be installed to investigate the extent of dissolved- <br /> gasoline hydrocarbons to the Wrest and east of the site. The approximate locations of <br /> monitoring wells are shown on Figure 1. the <br /> SOIL SAMPLING FREQUENCY AND MONITORING WELL CONSTRUCTION <br /> As stated in the work plan, the monitoring walls 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(O.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 /> (PVC)casing and 20 feet of 0.020-inch-slotted well screen. A filter pack of No, 2112 lapis lustre <br /> S <br /> and will be placed around the well from the bottom to approximately one foot above the top of <br /> O(rires throughoul the U.S.,rar.oda and Oancas <br />