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0 M-10A Investigation Work Plan Addendum October 28,2011 Nestle USA,Inc.,Ripon, California from these cross sections (Figure 3 through Figure 12) and the additional data collected during the implementation of this Work Plan, to complete the characterization of COCs in the A and C Zones. M-10 Monitoring Well Nest— ECM proposes additional boring locations west and northwest of the M-10 location to complete the lateral characterization of undefined COC concentrations in the Upper and Lower A zones(Figure 3, Figure 4, and Figure 11). M-13 Monitoring Well Nest— ECM proposes additional borings between the CPT-23 and the M- 13 locations(Figure 10)to improve the characterization of COCs in the A and C zones in this area. M-28 Monitoring Well Nest and City of Ripon Supply Well MW-3— ECM proposes additional borings west of the Site along transect F-F' (Figure 8) to characterize the COCs between the Site and MW-3. Ripon Public School Well RPS-1 — ECM proposes additional boring locations between the Site and RPS-1 (Figure 10 and Figure 11) to improve the lateral characterization of CDCs in the A and C zones. 3.1 DATA COLLECTION APPROACH ECM will use CPT equipment for lithologic characterization during this investigation. The real- time soil data will be used in conjunction with Rockworksa software to prepare lithologic cross- sections in the field, allowing for field decisions regarding sampling depths for groundwater. The CPT operator will advance a second boring directly adjacent to each CPT borehole to allow ECM to collect discrete groundwater samples at each target depth using a hydropunch type sampling device. By employing these methods, ECM will identify and address data gaps in the field. The field investigation will be conducted in two phases. The first phase (Phase 1) will define the lithology and depth distribution of COC-affected groundwater in areas west, north, and south of the 2010 field investigation to a depth of 160 feet bgs. Samples will be collected and analyzed on expedited turnaround time to allow field work to progress without delay. The data collected in Phase I will be used to determine which step-out borings are necessary, and to what depths they will be drilled during the second phase of work(Phase 11). 3.1.1 Phase I Phase I of the investigation will include borings drilled immediately west of the locations drilled for CPT-28, CPT-30, CPT-23, and CPT-6, as shown on Figure 2. A boring will be advanced northwest of CPT-28. The Phase I boring locations will be drilled to depths of approximately 160 feet bgs. This depth corresponds to the C Zone where wells MW-3, RPS-1, and M-28C1 are screened. The draft downhole data logs provided upon completion of these Phase I borings (CPT-33 through CPT-37) will be used to identify the major coarse-grained units within the AS and C zones. Based on a review of the cross sections, the major coarse-grained C zone unit is generally located at 130 to 150 feet bgs. ECM will use the sampling results from Phase I CPT borings to evaluate the zone(s) of impact in the A and C zones. The results of this evaluation will be used to determine the target zones for sampling of the remaining CPT locations in the subsequent phase(s)of work. a Rockworks is a licensed product of Rockware, Inc.Geologic and GIS Software. 4