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C indicate non-detectable VOC concentrations. At these final locations, permanent wells will ' be constructed by removing the HydropunchTM sampler, reaming the borehole to ten inches in diameter, advancing the borehole approximately 20 feet into the saturated zone, and completing well construction in accordance with State of California and San Joaquin County ' guidelines. Specific drilling, well construction, well development, sampling and analytical procedures are presented in the following sections. While the locations of the County's three EMP borehole monitoring wells described herein are immediately accessible, if additional drilling is required to define the "zero ' concentration" line, these well locations would likely be considered on properties not owned by the County or Caltrans. For these replacement wells, access agreements would need to be obtained from the property owners, and the EMP deliverable schedule would ' likely need to be revised. The County would notify the RWQCB immediately should it be necessary to revise the project schedule. 3.2 MONITORING WELL LOCATIONS AND RATIONALE As required by the Order, a minimum of three new monitoring wells are proposed to be t constructed to evaluate VOC migration in the shallow aquifer outside of the property boundary. As shown on Figure 3, wells MW -9 and MW -10 would be cross -gradient or down -gradient from the landfill, constructed to the west/northwest of existing wells MW -5 ' and MW -8. Well MW -11 would be constructed presumably upgradient of existing wells MW -5, MW -8, and SB -1, to the northeast of SR -580. The construction of these three wells will help further define groundwater flow direction and gradient of the shallow aquifer, if ' not the extent of the shallow aquifer. It is anticipated that exploratory boreholes will be drilled to depths of approximatelv 80 ' feet, with HydropunchTM samplers driven up to 20 feet into the saturated zone. Monitoring wwells-will be drilled to depths of no greater than 100 feet. Site-specific data suggest that the depth to the Corcoran Formation is approximately 50 feet, and groundwater is found ' approximately 10 to 20 feet into the Corcoran Formation. Wells will extend 20 feet past the first encountered groundwater or to the bottom of the Corcoran clay unit, whichever it encountered first. ' If VOCs are detected in samples from the initial well locations, replacement "step out" well ' locations will be considered at locations that are further beyond the locations identified on Figure 3 using the groundwater equipotential data and chemistry results to identify a direction and distance for the replacement well. If the sampling results indicate the need to construct a replacement well, then the County will provide the RWQCB with analytical data, rationale, and a plan showing the proposed location(s) of the replacement well along with a revised schedule for construction, sampling, and reporting. t ' 6 2011-0115 CHSL EMP Workplan Geo -Logic Associates Revision 1- August 24, 2011