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River Islands <br /> We utilized hourly water level data provided by ENGEO (April 22, 2005, written <br /> communication) to calculate and contour average 2004 groundwater elevations <br /> in River Islands monitoring wells and surface water stage in Old River, San <br /> Joaquin River, and Paradise Cut. The contours show our inferred average <br /> groundwater gradients and flow directions beneath the Island (see the attached <br /> revised Figure 4). In general, groundwater elevations are influenced by irrigation, <br /> and gradients and flow directions are generally away from the center of the island <br /> as irrigation recharge discharges to the adjacent surface water features. We <br /> utilized Figure 4 (revised) to justify/revise the River Islands (Phase II) monitoring <br /> well locations and monitoring objectives. The well locations are shown on the <br /> attached Figure 6b (revised), and the monitoring objectives are summarized in <br /> Table 3 (revised) below. <br /> Table 3(revised).Construction information and 2wectives for River Islands subarea monitoring wells. <br /> Map IDScreened <br /> (Locations shown Old Well Status' Diameter Depth Interval Monitoring Objectivez <br /> in Fig. 6b) ID (inches) (feet) feet <br /> MWR-1 MW-1 E 2 21.5 5-20 Regional water levels. <br /> MWR-2 MW-2 E 2 21.5 5-20 Regional water levels. <br /> MWR-3 MW-3 E 2 21.5 5-20 Up gradient Fields 67 <br /> and 68. <br /> MWR-4 MW-4 E 2 21.5 5-20 Up gradient Fields 65 <br /> and 66. <br /> MWR-5 MW-5 E 2 21.5 5-20 Regional water levels. <br /> MWR-6 MW-6 E 2 21.5 5-20 Regional water levels. <br /> MWR-7 MW-7 E 2 21.5 5-20 Regional water levels. <br /> MWR-8 MW-8 E 2 21.5 5-20 Regional water levels. <br /> MWR-9 MW-9 E 4 221.5 5-20 Regional water levels. <br /> MWR-10 MW-10 E 2 21.5 5-20 Regional water levels. <br /> MWR-11 MW-11 E 2 21.5 5-20 Regional water levels. <br /> MWR-12 I MW-12 E 2 21.5 5-20 Re ionai water levels. <br /> MWR-23 N 4 20 10-20 Down gradient Field 68. <br /> MWR-24 N 4 20 10-20 Field 68. <br /> MWR-25 N 4 20 10-20 Down gradient Field 67. <br /> Up gradient Field 67 and <br /> MWR-26 N 4 20 10-20 68; northwest drainage <br /> ditch. <br /> MWR-27 N 4 020 <br /> 0 10-20 Field 67. <br /> MWR-28 N 4 0 10-20 Fields 65 and 66. <br /> MWR-29 N 4 0 10-20 U gradient Field 64. <br /> MWR-30 N 4 0 10-20 Field 64. <br /> MWR-31 N 4 10-20 Down radient Field 63. <br /> MWR-32 N 4 0 10-20 Down gradient Field 63; <br /> north drainage ditch. <br /> MWR-33 N 4 20 10-20 Down gradient Field 63. <br /> MWR-34 N 4 20 10-20 Field 63. <br /> 1: E=existing,and N=new. <br /> 2: Locations relative to present-day hydraulic gradients inferred from Figure 4(revised). <br /> 3: Pre-existing wells MW-13 through MW-22,which would correspond to revised map ID's MWR-13 through <br /> MWR-22,are not included as part of the River Islands monitoring well network. The locations of these wells <br /> have not been confirmed, and copies of their construction logs or permits have not been obtained. To the <br /> furthest extent possible,the wells will be located,the PVC well casing removed from the borehole, and the <br /> borehole sealed per the procedures described in Section F of the April 18,2005 monitoring plan. <br /> - 7 - <br />