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GROUNDWATER MONITORING WE& NSTALLATION WORKPLAN wells. A report will then be prepared and submitted to SJCEHD detailing field activities and the results of soil and groundwater analyses. The locations of proposed groundwater monitoring wells MW-1, MW-2, MW-3, MW-4, and soil boring TP-20 are shown on Figure 3. A grab groundwater sample will be collected from soil boring TP-20 to determine the extent of MTBE cross-gradient of the former UST. Well locations are situated to monitor potential MTBE concentrations up-gradient, down-gradient, and cross- gradient of the former UST. Prior to field activities, as required by law, Underground Service two Alert(USA) will be notified for utility clearance. GROUNDWATER MONITORING WELL INSTALLATION Precision Sampling, Inc. of Richmond, California, a California licensed well driller, will be contracted by ESA for the drilling of five soil borings, and installation of the four monitoring wells. The soil borings will be installed by direct push technology using a Vibra-Push sampling rig. This rig combines percussion hammer, high frequency vibration and static push. Soil boring TP-20 will be advanced to approximately 25 feet bgs, while the other four borings will be advanced up to approximately 30 feet below ground surface (bgs) for the purposes of groundwater monitoring well installation. The field geologist well will determine final depths and +� design characteristics of each at the time of drilling based on observed subsurface conditions. The monitoring wells will consist of pre-pack wells installed within a 2.5-inch bore hole. Wells will be constructed of solid 0.75-inch diameter, schedule 40 PVC casing from 0 to 10 feet bgs, with 0.75-inch diameter schedule 40 PVC 0.010 well screen installed from 10 to 30 feet bgs. The PVC is isolated with two collars that include a bottom cap and plug. The pre-pack is constructed of 1.25-inch diameter schedule 40 PVC 0.010 well screen installed from 10 to 30 feet bgs containing number 2/12 sand filter pack material. The sanitary seal will consist of bentonite pellets (transition seal)installed above the filter pack between 5 and 10 feet bgs. The annular seal will consist of grout(neat cement) from 5 feet to 1 foot bgs within a 6" bore hole. The first five feet will be hand-augered by the driller to achieve the required monitoring well annulus. Upon completion of the well installation, a 7-inch diameter traffic-rated well box with concrete collar and locking expansion cap will be placed over the well from 1-foot bgs to the surface. A well construction diagram is provided in Figure 4. Soil boring TP-20 will be grouted to the surface following the collection of soil samples and an in-situ groundwater sample. As recommended in the San Joaquin County well standards, a minimum of 12 hours of time shall be allowed between placement of the annular seal and well development. SOIL AND GROUNDWATER SAMPLING Continuous core soil samples will be collected every five feet, at obvious changes in lithology as observed by the ESA geologist, and at the capillary fringe. Each soil sample will be sealed with end caps and Teflon, labeled and placed in a chilled ice-chest prior to transport to a state-certified �.. analytical laboratory for chemical analysis. A "Hydro-Punch" in-situ groundwater-sampling tool or other appropriate method used in conjunction with a positive displacement bailer and Environmental Science Associates 3 University of the Pacific September 25,2001 Groundwater Monitoring Well Installation Workplan b,. 200252