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i Additional Groundwater Investigation and Remediation Feasibility Evaluation Work Plan Stockton Center Site Authority-University Park January 25,2005 - Page 7 E 1 The drill cuttings and steam cleaning effluent will be placed in DOT-approved 557gallon drums, sealed, { labeled, and left on-site pending laboratory analyses. Condor can assist the SCSA in proper removal of the soil and water, if requested., i. 5.3 DEEP MONITORING WELL CONSTRUCTION . The deep monitoring wells will be constructed with five feet of 2-inch outside diameter,.Schedule 40, flush-threaded, machine-slotted PVC screen (slot size 0.020). The two source area/plume wells will be a installed inside the conductor casing. The up gradient well will be installed in an open hole. The monitoring wells will be installed approximately six feet into the sandy unit anticipated to be beneath the clayey/fine-grained unit interpreted from.the CPT borings, located at approximately 85 feet bgs, pending field observations during the continuous coring. A flush-threaded PVC bottom cap will be placed at the bottom of the screen sections. Blank PVC casing will be installed above the screen to the ground surface. A filter pack of#3 Monterey sand will be placed in the annular space to approximately one foot above the screen while the augers are in place. The depth of the sand in the well annulus will be monitoredwith a weighted tape measure while the sand is being placed and the augers are being gradually retracted to avoid bridging. To form a protective seal, approximately three feet of dense Baroid bentonite pellets will { be installed above the sand and allowed to settle through the water as the augers are retracted. The bentonite pellets will be allowed to hydrate at least 20 minutes. A surface seal grout mixture of Type D71 neat cement containing less than 5% bentonite solids will be pumped via a tremie pipe into the annulus and will extend from the bentonite to the. ground surface. Depending on the stability of the borehole drilled without conductor casing (up-gradient deep well), the augers may be removed before or during emplacement of the grout. The augers will be removed before emplacement of the grout in the two borings with conductor casing. The trcmie pipe will remain near the top of the bentonite seal until the pumped grout is forced to the surface. The monitoring wells will be completed with locking traffic boxes. 5.4 SHALLOW MONITORING WELL INSTALLATION PROCEDURES Three additional shallow monitoring wells are proposed for the site: One four-inch monitoring well will ± be installed in the source area to allow monitoring of groundwater beneath the source area and to allow , access for potential remediation. Two additional two-inch, down gradient monitoring wells are proposed to monitor the east and southeast lateral extent of the known contaminant plume. The monitoring well borings will be installed to approximately 55 feet bgs, depending on field conditions. No soil samples are anticipated to be collected from the borings. The proposed additional shallow monitoring well locations are shown on Figure 7(Appendix A). . ' The monitoring well borings will be advanced using 10-inch outside diameter, continuous-flight, hollow- stem auger. The hollow-stem auger and other down-hole equipment will be decontaminated between borings by steam cleaning to prevent cross-contamination. Drilling activities will be supervised by a Condor geologist in accordance with SJCEHD and CRWQCB guidelines and requirements. Drill cuttings from the monitoring well borings will be logged according to the USCS. Descriptions of soil types encountered and any other pertinent field observations will be recorded on boring logs. In addition, cuttings will be placed in a polyethylene bag and checked with a PID for the presence of hydrocarbons. All visual observations and PID measurements will be noted on the boring logs. - s k �a CONDOR