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Section 2 Groundwater Monitoring Well Installation 2.1 MONITORING WELL LOCATIONS AND RATIONALE The purpose of groundwater monitoring is to provide a measurement of compliance with regards to the State Antidegradation Policy and Regional Board Order 94-263, with respect to wastewater treatment and disposal activities. An effective groundwater monitoring network will provide at least one clearly "up-gradient' and a minimum of two "down-gradient'wells within the wastewater treatment and disposal areas. Furthermore, the monitoring network should be designed to allow for normal seasonal fluctuations in groundwater elevation and horizontal groundwater gradient direction,while taking into account water quality effects associated with dilution, such as wells of large diameter and/or with excessive lengths of well screens. Additional wells are sometimes required when strong seasonal changes in groundwater gradient are suspected and when hydrogeologic boundaries, or other conditions, are encountered. Such wells must be designed and located to provide representative samples of groundwater beneath the wastewater treatment, storage, and disposal sites and not create a vertical conduit for contamination of deeper groundwater. The purpose of this workplan is to augment the current monitoring network to improve the ability to spatially characterize groundwater in the vicinity of the W WTF, including the characterization of background groundwater quality, and to improve the ability to assess potential impacts from the treatment and disposal of wastewater at compliance monitoring locations. Accordingly, proposed monitoring wells PMW-7 and PMW-8 were sited such to provide an assessment of the spatial variability of groundwater not likely influenced by domestic wastewater disposal activities. The locations were chosen based on typical groundwater elevations and distance from wastewater treatment and disposal features (greater than 750 feet). Alternative, PMW-9 was sited to fill in an identified compliance monitoring gap located down gradient of the wastewater treatment ponds and adjacent to the current industrial disposal area. Figure 1 illustrates the locations of the proposed groundwater monitoring wells. 2.2 EQUIPMENT DECONTAMINATION PROCEDURES At a minimum, decontamination will comprise of a hot water pressure wash of the drilling equipment. As a precaution against cross-contamination between boreholes, the drilling equipment will be decontaminated prior to the start of drilling of the first monitoring well and between each successive monitoring well borehole. April 2007 City of Ripon Wastewater Treatment Facility 2-1 Groundwater Monitoring Well Installation Workplan