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M i ADDITIONAL GROUNDWATER AND AGRICULTURAL DRAIN MONITORING FOR RESIDENTIAL NEIGHBORHOOD G WORK PLAN Mountain House Community Services District Groundwater and Agricultural Drainage Monitoring Plan 1.0 INTRODUCTION This is a work plan to construct additional monitor wells, identify additional agricultural drain monitoring locations, and identify additional soil sampling locations needed to satisfy requirements of California Regional Water Quality Control Board (Regional Board) Order No. 98-109, a Monitoring and Reporting Program (MRP) regarding groundwater and agricultural drainage monitoring for the Mountain House wastewater reclamation facility, prepared by Condor Earth Technologies, Inc. (Condor) on behalf of the Mountain House Community Services District (MHCSD) and Trimark Communities, L.L.C. (Trimark). The purpose of the wells, agricultural drain monitoring points, and soil sampling points is to monitor potential effects of wastewater applied to agricultural fields. The locations of the proposed monitoring wells, agricultural drain monitoring points, and soil sampling points are shown on figures in Appendix A. 2.0 SITE BACKGROUND INFORMATION Plans and specifications for groundwater monitoring wells along with locations of the agricultural drain monitoring points to monitor wastewater storage ponds IA and 1B were submitted to the Regional Board staff on June 22, 1998 by ECO:LOGIC Consulting Engineers in a written document titled Groundwater and Agricultural Drainage Monitoring Plan (MP) that was subsequently amended in a written facsimile transmitted to the Regional Board staff on June 23, 1998. Regional Board staff approved the proposed plan in a letter dated June 26, 1998. A Work Plan to construct monitoring wells according to the MP was submitted in June 1998, revised in June 1999 to accommodate a change in the location of the storage pond, and revised again in January 2001 due to changes in the borders of the reclamation area. The initial monitoring network consisted of four pairs of very shallow and somewhat deeper wells and two unpaired somewhat deeper wells (Monitoring Well Installation Report prepared by Condor dated April 23, 2001). On May 2, 2001, Condor contacted Regional Board staff regarding the shallow wells designated for agricultural drainage monitoring because these wells purged dry and did not recover adequately for sample collection during our field activities. ECOLOGIC had submitted a contingency procedure for this situation to the Regional Board, which was to designate the well "VD" (virtually dry) on monitoring report forms. This contingency was submitted prior to the Regional Board's approval of the MP. In a telephone conversation on May 4, 2001, Regional Board staff provided clarification of the approval letter dated June 26, 1998. The monitoring network was consequently expanded to include seven agricultural irrigation drainage ditch locations. The data collected during the first 12 consecutive monthly sampling events was presented in the Annual Report prepared by Condor dated February 20, 2002. Condor has since conducted annual soil sampling, semi-annual groundwater monitoring, and quarterly agricultural drain ditch monitoring with quarterly and annual reporting. The MHCSD and Trimark subsequently proposed expanding the Mountain House wastewater reclamation area to the west of Mountain House Creek, and adding additional wastewater storage ponds. n �a CONDOR