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Additional Groundwater and Agriculture Drain Monitoring Work Plan Residential Neighborhood G April 18,2005 Page 2 Consequently, Condor prepared the Additional Groundwater and Agricultural Drain Monitoring Work Plan, revised August 6, 2004, for groundwater and agricultural drainage ditch monitoring for the expanded reclamation area. In August 2004, 15 additional monitoring wells were installed. The expanded monitoring network for the additional reclamation area consisted of six pairs of very shallow and somewhat deeper wells as well as three unpaired wells (Monitoring Well Installation Report prepared by Condor dated October 7, 2004); and associated agricultural drainage ditch locations. Collection of the one-year baseline data commenced in August 2004. On September 22, 2004, a Condor representative observed that the agricultural drains for monitoring locations 8A, 9A, and 11A had been altered by construction or farming practices and were no longer usable. As an interim step, an alternative agricultural drain sample location was selected as a replacement for two sample locations that were no longer drains. A revised agricultural drain sampling plan is being submitted under separate cover for Regional Board approval. Further proposed expansion of the reclamation area has led to the development of this work plan. 3.0 MONITORING WELL DESIGN EXEMPTIONS Due to the need to monitor groundwater and agricultural drainage water near the ground surface in a flood plain area, modifications to the minimum seal thickness and to the casing height above ground specified in the State Water Well Standards and the San Joaquin County Well Standards were proposed in the August 6, 2004 work plan and are included herein. California Well Standards published by the Department of Water Resources allow for modifications to the standards. The California Monitoring Well Standards, Bulletin 74-90 (Part 1, Section 3) indicates that exemptions for unusual conditions are to be approved by the enforcing agency, the San Joaquin County Public Health Services Environmental Health Division (SJCPHS/EHD). The SJCPHS/EHD may also waive compliance to the County Well Standards under certain circumstances. The following exemptions from water well standards were approved for the previously-installed wells and must be approved by the SJCPHS/EHD for these proposed monitoring wells before drilling and installation of the wells: 1. Exemptions from the minimum surface seal thickness: The target depth of groundwater monitoring is above the depth of the specified minimum 20-foot seal thickness. Thinner seals are therefore necessary. The seal thickness for each well will be maximized within the geometric constraints of each well design. A minimum two-foot bentonite seal thickness will be placed above the screened section of each well. Overlying the bentonite seal, a surface seal of cement/bentonite grout will extend to the surface. In addition, a sloping foundation pad with a three-foot radius will be constructed to protect against ponding of surface water. 2. Exemptions from the requirement for the top of the casing to be above the 100-year flood level: Due to the location of some of the wells at the lowest points on the property(approximately sea level), it will be impractical and dangerous for personnel to conduct sampling activities if monitor wells are constructed with the casing extending to the 100-year flood level (approximately eight to ten feet above sea level). Wells located within the 100-year flood plain will be constructed with the top of the well casing four feet above ground, the maximum height appropriate for safe sampling by hand (truck access will be limited during the winter). To avoid penetration of floodwaters in the unlikely event of flooding above four feet, each well casing will be equipped with a watertight expansion cap. Watertight expansion caps are commonly used in i a CONDOR