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Monitoring Well Installation and Destruction Report City of Stockton RWCF Page 3 11M Prior to conducting drilling activities, an on-site tailgate meeting and safety brief was conducted on April 22, 2010 with Condor representatives,RWCF personnel,and all drilling personnel in attendance.A site- specific Health and Safety Plan,prepared by Condor,and an RWCF Site Safety Plan were discussed with, 1. and presented to, all field personnel for their signatures. Prior to field activities, Condor tested several, commercially available, sand types to assess the electrical Lconductivity(EC)potential of the monitoring well filter pack. Five-day EC generation potential tests were conducted in addition to sieve analyses to determine average grain size of the various sand types. Quikrete No. 1152 All-Purpose sand was selected for use in the filter pack; test results indicated a low EC Lgeneration potential (average 466 micro-Siemens per centimeter [uS/cm]) plus an average grain size which would be less likely to pass through the well screen(slot size 0.010). L L 3.2 DRILLING PROCEDURES A Condor representative supervised the completion of four monitoring wells using hollow-stem auger drilling methods on April 22 and 23, 2010. The borings were advanced by Precision Sampling, Inc., of L Stockton,California. Monitoring well locations are shown in Figure 2,Attachment A. Drill cuttings from the borings were logged according to the Unified Soil Classification System (USCS). '` Descriptions of soil types encountered and other pertinent field observations, including detection of odors and visual staining, are recorded on the attached geologic logs (Attachment Q. Monitoring well completion details recorded on the logs include the type of well screen and casing, depth intervals of the screen, blank casing, sand pack, bentonite seals and surface seals, and the quantities of materials added to 6. the annular spaces. ! 3.3 FIELD OBSERVATIONS 6. Field observations included monitoring well boring observations and visual observations of the Site geology and are noted on the geologic logs prepared for the four monitoring well borings(Attachment Q. Soils underlying the Site appear to consist of clay-dominated sediments. No discolorations of the - - sediments or odors were noted on the geologic logs for monitoring wells MW-IS, MW-2S, MW-19, and MW-19S. 3.4 MONITORING WELL INSTALLATION PROCEDURES ` The well borings were advanced using ten-inch outside diameter, continuous-flight, hollow-stem augers. Each monitoring well was constructed using four-inch outside diameter, Schedule 40, flush-threaded, machine slotted polyvinyl chloride(PVC) screen(slot size 0.010). A flush-threaded PVC bottom cap was placed at the bottom of each well screen. Blank PVC casing was installed above the screen to the ground 6' surface. No glue or solvents were used in the construction of the wells. Monitoring well construction details are provided in Table 1, on the following page. A well construction graphic is included as part of the geologic log for each well(Attachment Q. 61 A filter pack of Quikrete No. 1152 All-Purpose sand was placed in the annular space to a minimum of one foot above the screen section while the augers were in place. The depth of the sand in the well annulus `, was monitored with a weighted tape measure while the sand was being placed and the auger was gradually retracted to minimize bridging. Following placement of the filter pack, each well was surged for approximately twenty minutes, when field conditions allowed, to settle the filter pack. Additional sand was added as necessary. V n V ILII CONDOR