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Monitoring Well Installation Report 736 E Channel Street,Stockton,CA December 15,2004 Page 4 iTable 1 Monitoring Well Construction Details Monitoring Well MW-1 MW-2 MW-3 MW-3R r Date Installed 9/23/04 9/23/04 9/24/04 10/26/04 Well Depth(ft) 47 47 47 47 _ Well Casing Diameter(in) 2 2 2 2 It - Borehole Diameter(in} 8 8 8 8 Well Screen Interval(ft) 32-47 32-47 32-47 32-47 _ Filter Pack Interval(ft} 30-47 30-47 30-47 30-47 Bentonite Seal Interval(ft) 28-30 28-30 28-30 28-30 Grout Seal Interval(ft) 0-28 0-28 0-28 0-28 1 35 MONITORING WELL MW-3 DESTRUCTION ' On October 7, 2004, a Condor technician measured the depth to water and the total depth in monitoring wells MW-1, MW-2, and MW-3 in preparation for developing the wells The technician measured the total depth in MW-3 at 38 44 feet This measurement was approximately 8 6 feet less than the expected total depth, so the technician secured the wells and returned to the office without developing the wells On October 8, 2004, a Condor geologist measured the depth to water and the total depth in MW-3 The depth to water was 36 97 feet below the top of the well casing, and the total depth of the well was 38 26 feet ® below the top of the well casing The total depth measurement indicated that the lower portion of the well screen was plugged with a foreign material The geologist used a hand auger to extract some of the material plugging the well Inspection of the material removed from the well indicated that it was cement grout The lower 8 6 feet of well screen appeared to be filled with grout, therefore The mechanism by which the grout entered the well screen was not known Condor prepared the Monitoring Well Installation Preliminary Report and Monitoring Well Destruction Work Plan, dated October 12, 2004, that described the installation of MW-3 and the discovery of grout inside the well casing In the report Condor _ recommended that monitoring well MW-3 be properly destroyed and a replacement well (MW-3R) be installed approximately 10 feet south of MW-3 In a letter dated October 21, 1004, Victoria McCartney of the SJCEHD approved the destruction of MW-3 and the installation of MW-3R Condor prepared a monitoring well destruction permit application for submittal to the SJCEHD and received the approved permit prior to initiating any fieldwork A Condor geologist was on Site on October 26, 2004, to observe the destruction of monitoring well MW-3 Victoria McCartney of the SJCEHD was also on Site to observe the well destruction The well was destroyed by V&W Drilling The well was over-drilled using 8-inch outside diameter, continuous-flight, hollow-stem auger to a depth of approximately 52 feet bgs The well boring was backfilled with a bentonite/cement (no more than five percent bentonite) grout The grout was tremied into the borehole from the bottom of the boring to the ground surface All of the removed well materials were placed in 55-gallon DOT-approved drums and left on Site pending disposal 3.6 MONITORING WELL DEVELOPMENT On November 3, 2004, monitoring wells MW-1, MW-2, and MW-3R were developed by surging and bailing the groundwater in the wells with a surge block and disposable,polyethylene bailers A total of 10 ass t g� CONDOR