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CP0057 - 2 - 15 August 2016 Stockton Charter Way Commingled Plume W. Charter Way & S. Lincoln Street Stockton, San Joaquin County • Installation of two (2) D zone monitoring wells and three (3) E zone monitoring wells southeast of existing wells SLMW-1 OD and SMW-29D, in order to assess the extent of groundwater pollution southeast of the commingled plume, and calculate flow in E zone groundwater in this vicinity. These proposed locations are off-site southeast of the Bimbo Bakeries and Former Dolly Madison properties. I concur with the tasks proposed in the Work Plan provided the following comments are adequately addressed: Five (5) groundwater zones (A through E) have been established at the Site. Wells are screened approximately 10 to 30 feet bgs in the A zone, approximately 30 to 60 feet bgs in the B zone, approximately 69 to 90 feet bgs in the C zone, and approximately 100 to 125 feet bgs in the D zone. While no E zone wells currently exist, wells SMW-34E through SMW-36E are proposed to be screened 130 to 150 feet bgs. However, prior to the establishment of the Commingled Plume, several of the Sites had established their own groundwater zones, which do not correlate to those established across the entire 4 - site area. As such, existing wells with "A", "B", "C", etc. well ID designations are not necessarily screened within the corresponding groundwater zone as established for the Commingled Plume. Proposed well MW -9B is intended to provide lateral delineation of B zone groundwater southwest of impacts observed in A zone well MW -5A. However, upon closer review, it appears that wells MW -4C, MW -5C, MW -6C, and MW -7C provide delineation within the B zone on the Chevron property. While MW -7C indicates that there is minimal pollutant migration to the southwest in the B zone on the Chevron property, wells MW -7A and MW -7B indicate that hydrocarbon impacts to groundwater are not defined in the A zone in the southwest corner of the Chevron property. As such, MW -9B should target A zone groundwater in the proposed location, and be renamed MW -9A. Please confirm installation of this well in the A zone in a Well Installation Report due by 30 January 2017. 2. Remedial well ART -7 is proposed to be constructed with the groundwater intake screened interval between 40 and 55 feet bgs. The proposed screened interval of ART - 7 is intended to target impacted groundwater observed in SMW-26B, which is screened 45 to 50 feet below ground surface (bgs). However, the construction of ART -7 will not adequately target impacted D zone groundwater observed in SMW-11-122, as requested. As SMW-11-122 is screened between 112 and 122 feet bgs, please install an additional D zone ART well in this vicinity, with similar construction to that of proposed D zone well ART -4. Please confirm installation of an additional ART well, constructed in the D zone, in the Well Installation Report due by 30 January 2017. 3. Monitoring wells installed as part of the proposed activities should be sampled during the fourth quarter 2016 sampling event, with results summarized in the fourth quarter 2016 semi-annual Groundwater Monitoring Report due by 30 January 2017. 4. A Preliminary Gantt Chart timetable was included in the Site Management Plan dated 29 February 2016. Upon completion of the well installations and boring B-30 and B-31 assessment, please provide an updated Gantt Chart in the Well Installation Report due