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Additional Groundwater and Agriculture Drain Monitoring Work Plan Residential Neighborhood G April 18,2005 Page 3 flood plains in San Joaquin County and are routinely approved by the SJCPHS/EHD, according to Mr. Huggins of SJCPHS/EHD. The exemptions described above are incorporated into the monitor well designs proposed in this work plan and typical well construction diagrams are included as Figures 5 and 6: 4.0 ADDITIONAL MONITOR WELL INSTALLATIONS 4.1 SITE PREPARATION The wells will be permitted through the SJCPHS/EHD. A monitor well construction permit will be completed and submitted for each parcel with a proposed monitor well. Underground Service Alert will be notified at least 72 hours in advance of the fieldwork to locate and identify underground utilities in the vicinity of the work area. 4.2 ADDITIONAL MONITOR WELLS LOCATION IDENTIFICATION The locations of the monitor wells for this additional reclamation area were chosen by a method to be consistent with previously-approved work plans and will augment the existing well locations. One up- gradient monitor well pair and two down-gradient monitor well pairs will be utilized to monitor the wastewater applied to the irrigation fields. Monitor well pairs will consist of one monitor well designed to monitor the groundwater, screened from 15 to 25 feet, and one monitor well screened from 7 to 12 feet designed to monitor applied irrigation water. Due to potential development constraints, the up-gradient wells will be placed within the reclamation area boundary. However, as noted in Figures 5 and 6, the wells are protected by a concrete pad and bollards. The placement of the pad and bollards, and the physical limitations of the equipment used to furrow the fields for irrigation, will preclude any irrigation water form being applied within approximately 10 feet of the wells. Furthermore, as the wells will be placed along the up-gradient boundary, there will be no reclamation water applied up gradient of the wells. The intent of the most down-gradient monitoring wells is to evaluate agricultural drainage and groundwater at the northern end of the northern irrigation fields. There is a concern that wells placed too closely to Old River would be influenced by Old River. We reviewed the groundwater gradients for the existing monitoring wells and determined that the gradient more than a thousand feet from Old River is on the order of 0.006 to 0.0065 feet per feet, while the gradient within a thousand feet of Old River is on the order of 0.0025 to 0.0050. The shallower gradient closer to Old River may well reflect impacts from Old River. However, Department of Water Resources data identifies the stage of Old River as between elevation 8.3 and 14.3 during the period September 1999 to July 2001, while the closest monitoring wells have had an elevation of approximately sea level. These wells are located within 10 feet of the northern perimeter irrigation drainage ditch, on the south side of the ditch. Consequently, although there may be some influence on the groundwater at these locations due to Old River, it appears to be limited. In an effort to balance the intent of monitoring the groundwater at the greatest downgradient location, while limiting the effects of Old River, we are proposing these wells be placed between 20 and 30 feet south of the Old River Levee(there is no drainage ditch along the levee in this area). 4.3 MONITOR WELL INSTALLATIONS All wells will be installed by a California Licensed C-57 contractor using the hollow stem auger drilling method, and will be supervised by a Condor geologist. A sample geologic log is provided as Figure 4. Prior to conducting drilling activities, an on-site tailgate safety meeting will be held. A site-specific health and safety plan will be discussed and presented to all personnel for their signatures. �� CONDOR